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MACKAY INFRASTRUCTURE ALLIANCE

WP004 – NEBO ROAD WATER TREATMENT PLANT

Functional Description Specification (formerly known as Control Philosophy)

28 May 2010

MACKAY INFRASTRUCTURE ALLIANCE WP004 – NEBO ROAD WATER TREATMENT PLANT Functional Description Specification

Revision D

MACKAY INFRASTRUCTURE ALLIANCE Mercury House, 1st Floor, 38 Wellington Street PO Box 2084, Mackay QLD Australia 4740 T: +617 4961 9000 F: +617 4953 2599

DOCUMENT STATUS

REV NO. REASON FOR AMENDMENT SECTION NO. PREPARED BY APPROVED BY DATE

A For Review R. Cabalse D. Maguire 15.09.09

B Issued for Tender R. Cabalse D. Maguire 24.09.09

C Updated for finalised P&IDs, document modified to become FDS

A. Sneyd A. McFadyen 19.04.10

D Updated from review workshop comments

A. Sneyd G. Thorne

A. McFadyen 28.05.10

E Amendments to control for HL PSTN 11.4 L.Taylor G. Grima 23.06.2010

APPROVALS

REV NO. POSITION APPROVAL STATUS NAME SIGNATURE DATE

E Project Manager Issued for Approval G. Grima

E Program Alliance Manager Issued for Approval C. Davies

E Manager – Infrastructure Delivery – Water and Waste Services

Issued for Approval L. Jamieson


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TABLE OF CONTENTS

1 SCOPE ....................................................................................................................................................... 1

2 DEFINITIONS ............................................................................................................................................. 1

3 ACRONYMS ............................................................................................................................................... 2

4 RELATED DOCUMENTS ............................................................................................................................. 3

5 TREATMENT PLANT OPERATION .............................................................................................................. 4 5.1 Introduction .................................................................................................................................................... 4 5.2 Water Treatment Process Overview ............................................................................................................... 4

6 OPERATIONAL PHILOSOPHY ..................................................................................................................... 6 6.1 Control Systems .............................................................................................................................................. 6 6.2 River Water and Initial Treatment .................................................................................................................. 7 6.3 Bore Water and Initial Treatment ................................................................................................................... 9 6.4 Filter Inlet Channels and Rapid Gravity Filters ................................................................................................ 9 6.5 Final Water Conditioning and Delivery ......................................................................................................... 10 6.6 Sludge Handling System ................................................................................................................................ 12 6.7 Dosing Systems ............................................................................................................................................. 14

7 CONTROL PHILOSOPHY ..........................................................................................................................18 7.1 General .......................................................................................................................................................... 18 7.2 Operator Adjustable Set-Points .................................................................................................................... 19

8 RIVER WATER TREATMENT ....................................................................................................................19 8.1 River Water Feed System .............................................................................................................................. 19 8.2 River Water Quality Monitoring .................................................................................................................... 24 8.3 River Water Inlet Works – Chemical Dosing Systems ................................................................................... 24 8.4 River Water Dosing Tank ............................................................................................................................... 25 8.5 Clarifiers ........................................................................................................................................................ 27 8.6 River Water Filters......................................................................................................................................... 33

9 BORE WATER TREATMENT .....................................................................................................................48 9.1 Filters 1-4 Feed Source Selection .................................................................................................................. 48 9.2 Bore Water System ....................................................................................................................................... 50

10 COMMON FILTERED WATER TREATMENT .............................................................................................57 10.1 Clearwater Well ............................................................................................................................................. 57 10.2 Filtered Water Chemical Dosing .................................................................................................................... 57

11 TREATED WATER STORAGE AND PUMPING WATER ..............................................................................58 11.1 Balance Tanks ................................................................................................................................................ 58 11.2 Mt Pleasant Reservoir ................................................................................................................................... 60 11.3 Mt Oscar Reservoir ........................................................................................................................................ 61 11.4 Treated Water Pumping (High Lift Pump Station) ........................................................................................ 62

12 SLUDGE HANDLING SYSTEM ..................................................................................................................65 12.1 Washwater Tank ........................................................................................................................................... 66 12.2 Sludge Thickener ........................................................................................................................................... 69 12.3 Thickened Sludge System .............................................................................................................................. 72


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12.4 Centrifuge System ......................................................................................................................................... 75

13 CHEMICAL DOSING SYSTEMS .................................................................................................................79 13.1 Potassium Permanganate ............................................................................................................................. 79 13.2 Caustic Soda Dosing ...................................................................................................................................... 85 13.3 Powder Activated Carbon (PAC) Dosing ........................................................................................................ 87 13.4 Aluminium Chlorohydrate (ACH) Dosing ....................................................................................................... 88 13.5 Polymer Dosing and Batching ....................................................................................................................... 91 13.6 Sludge Thickener Polymer System ................................................................................................................ 99 13.7 Chlorine Dosing ........................................................................................................................................... 105 13.8 Sodium Silicofluoride Dosing ....................................................................................................................... 108

14 MAIN POWER SUPPLY ..........................................................................................................................109 14.1 Power Under Normal Condition .................................................................................................................. 109 14.2 Partial Power Failure 1 - Existing TX1 is out Service .................................................................................... 111 14.3 Partial Power Failure 2 - New TX2 Is Out Service ........................................................................................ 113 14.4 Partial Power Failure 3 - New TX3 is out Service ......................................................................................... 114 14.5 Complete Power Failure - New TX2, TX3 and Existing TX1 Are Out Service ................................................ 116

TABLE INDEX Table 8-1 Clarifiers Flow Valves .................................................................................................................28 Table 8-2 Clarifiers Step and Transition .....................................................................................................30 Table 8-3 Stage 1 River Filters Flow Valves ...............................................................................................34 Table 8-4 Stage 1 River Filter Instruments ................................................................................................34 Table 8-5 Stage 2 Inlet River Filters Flow Valves .......................................................................................39 Table 8-6 Stage 2 Outlet River Filters Flow Valves ....................................................................................39 Table 8-7 Stage 2 River Filters Instruments ...............................................................................................40 Table 9-1 Stage 1 Bore Filters Flow Valves ................................................................................................55 Table 9-2 Stage 1 Filter Instruments ..........................................................................................................56 Table 13-1 River Water KMNO4 Dosing .......................................................................................................81 Table 13-2 Bore Water KMNO4 Dosing ........................................................................................................83 Table 13-3 Caustic Soda Dosing ...................................................................................................................85 Table 13-4 River Water Dosing Tank PAC Dosing ........................................................................................88 Table 13-5 River Water ACH Dosing.............................................................................................................89 Table 13-6 Clarifier Aid Polymer Dosing ......................................................................................................93 Table 13-7 River Filter Aid Polymer Dosing .................................................................................................95 Table 13-8 Bore Filters Aid Polymer Dosing – Bore Mode ..........................................................................96 Table 13-9 Bore Filters Aid Polymer Dosing – River Mode ..........................................................................97 Table 13-10 Sludge Thickener Polymer Dosing ...........................................................................................100 Table 13-11 Centrifuge Feed Polymer Dosing .............................................................................................103 Table 13-12 Clear Water Chlorine Dosing ...................................................................................................106 Table 13-13 Clear Water Fluoride Dosing ....................................................................................................108 Table 14-1 Field Sensing Devices at Normal Condition .............................................................................110 Table 14-2 Field Sensing Devices at Partial Power Failure 1 .....................................................................112 Table 14-3 Field Sensing Devices at Partial Power Failure 2 .....................................................................113 Table 14-4 Field Sensing Devices at Partial Power Failure 3 .....................................................................115 Table 14-5 Field Sensing Devices at Complete Power Failure ...................................................................116


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APPENDICES

APPENDIX A Drive Control Philosophy

APPENDIX B VSD Drive Control Philosophy

APPENDIX C Duty Standby Changeover Control Philosophy

APPENDIX D Proposed Future Dumbleton Weir Control Philosophy

APPENDIX E River Water Chemical Dosing Matrix


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1 SCOPE

Mackay Regional Council requires the existing Nebo Road Water Treatment Plant (WTP) to be upgraded to meet the planned future requirements up to the year 2026. This requires the plant to be upgraded to have a design capacity of 75 ML/d, to be supplied from the river. Due to the criticality of this WTP to the region it shall be required to be in operation during the upgrade of the control system upgrade.

The plant control system requires upgrading to update and extended the current programmable logic controller (PLC) and supervisory control and data acquisition (SCADA) functionality. Some items of equipment currently using relay logic are nearing the end of their useful life and are to be replaced with PLC control.

This document describes the control and operational philosophy of the Nebo Road Water Treatment Plant and its associated plant items. The operation of the river water pumping system and associated valves, located at Dumbleton Weir, is not within the scope of this document. However this plant shall be required to be incorporated into the Nebo Road WTP SCADA control system.

Provision for future upgrades is nominated in this document and shall be included in the water treatment plant control system.

This document is to enable the existing Nebo Road Water Treatment Plant to be upgraded. The following list is indicative of the new equipment systems to be installed:

• PAC Dosing;

• Caustic Soda dosing;

• Fluoride dosing;

• Additional polymer vendor dosing units; and

• Dewatering system including but not limited to washwater tank, sludge thickening process, and sludge dewatering and removal of waste product.

Please note: For further detail on the upgrade refer to section 4 Related Documents - 004-7032-E-Electrical Scope of Works.

For detail on the project interfaces refer to Mackay Infrastructure Alliance (MIA) specification 004-7032-E-Electrical Scope of Works.

2 DEFINITIONS

The definitions listed below have the following meaning given throughout this document.

Main PLC Shall mean the programmable logic controller (PLC) in the main control room and its associated I/O modules and associated remote located flex I/Os.

SCADA/HMI system

Shall mean the SCADA/HMI system as an interface to the Operators for monitoring and control.

Control system Shall mean the PLC and SCADA/HMI system comprised of the PLC hardware and software, communications network, power supplies, PC hardware, SCADA software, HMI hardware and software, RTU, paging equipment, hardwired control logic and


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miscellaneous hardware.

Caustic Soda Shall mean Sodium Hydroxide (NaOH)

3 ACRONYMS

Acronym Definition

ACB Air circuit breaker

ACH Aluminium chlorohydrate

AIT Analysing indicating transmitter instrument

AS Australian standard

BT Balance tank(s)

CD Chemical dosing

CPU Central processing unit

CV Conveyor

CWST Clear water storage tank

DC Direct current

DB Distribution board

DF Dewatering facility

DOL Direct-on-line motor starting method

EPA Environmental protection agency

FIFO First in first out

FIT Flow indicating transmitter

FP Filter process

FV Flow valve

GPO General purpose outlet

HLPS High lift pump station

HMI Human machine interface

IEC International electrotechnical commission

I/O Input/output

LAN Local area network

LCS Local control station

LIT Level indicating transmitter

L&SP Light and small power

LOLO Last in last out

LS Limit switch

MCC Motor control centre

MIA Mackay Infrastructure Alliance


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Acronym Definition

ML Mega litres

MSWB Main switchboard

PD Non submersible pump

P&ID Piping and instrumentation drawing

PAC Powder activated carbon

PC Personal computer

PE Pressure element

PFR Phase failure relay

PID Proportional, integral and derivative controller

PIT Pressure indicating transmitter

PLC Programmable logic controller

PU Submersible pump

PV Process variable

RCD Residual current device

RGF Rapid gravity filter

RTU Remote terminal unit

SCADA Supervisory control and data acquisition, and is a category of software application programs for process control which gathers real time data from remote locations in order to monitor and control remote equipment and conditions

SLD Single line diagram

TK Tank

TWL Tank water level

UPS Uninterruptible power supply

UTP Unshielded twisted pair

VA Volt Amps

VSD Variable speed drive

WIT Weight indicating transmitter

WTP Water treatment plant

WWT Wash Water Tank

4 RELATED DOCUMENTS

Other documents which are related and must be used in conjunction with this document are:

• Standard Specification 004-7032-E-SE001 Electrical Installations;

• Standard Specification 004-7032-E-SE006 Electrical Commissioning;

• Standard Specification 004-7032-E-SE009 Fibre Optic Cable Installation;

http://knowledgemgt/Lists/Document%20Repository/Attachments/395/SE001_Electrical%20Installations.doc

http://knowledgemgt/Lists/Document%20Repository/Attachments/395/SE001_Electrical%20Installations.doc


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• Standard Specification 004-7032-E-SE022 Small Enclosures Technical Specification;

• Standard Specification 004-7032-E-SE024 Variable Speed Drives;

• Standard Specification 004-7032-E-SE033 Control System Specification;

• Standard Specification 004-7032-E-SE055 Preferred Electrical Equipment List;

• Standard Specification 004-7032-E-SE059 Metal Clad Switchboards and Enclosures;

• Standard Specification 004-7032-E-SE062 Site Conditions;

• 004-7032-E-Electrical Scope of Works;

• 004-7032-E-Equipment List; and

• 004-7032-E-Indicative I/O list.

5 TREATMENT PLANT OPERATION

5.1 Introduction The Nebo Road Water Treatment Plant is located approximately 3 km south-west of the Mackay CBD and will be capable of producing 75 ML/day of water to the people of Mackay. Raw water is sourced from the Dumbleton Weir on the Pioneer River and/or ground water which is accessed through local bores. Typically, approximately 90% of the source water is pumped from the weir with the remaining 10% from the bores.

The river water is fed from any of four raw water pumps at Dumbleton Weir via two raw water mains through to coagulation, clarification, and filtration (with filter aid polymer). The bore water can be fed from any of eight bores (and two low lift bores not currently operational) via pre-chlorination, aeration, potassium permanganate oxidation (with lime for pH adjustment) and filtration (with filter aid polymer). The filtered water from the two plants is combined in the clear water well before chlorination, fluoridation and pH adjustment and storage in three balance tanks. Six high lift pumps then pump the treated water through the reticulation to Mt Pleasant Reservoir and on to Mt Oscar Reservoir (via the Mt Oscar Pump Station).

The WTP is in the process of being upgraded with additional chemical dosing facilities, a raw water dosing tank and new wastewater and sludge handling system. In addition the bore water filters are being incorporated (optionally) into the river water treatment plant.

The site will employ PLC’s for automation of processes where sequencing and task iteration occur. In addition to the PLC automatic control, information from the site’s network of sensors will allow the Operator to monitor alarm states, apply trending to historical logs and facilitate report generation. The philosophies of flexibility, safety and reliability are key to the design of the Nebo Road Water Treatment Plant’s design and operation.

5.2 Water Treatment Process Overview The completed Nebo Rd WTP will consist of:

River Water Train • At Dumbleton Weir:

http://knowledgemgt/Lists/Document%20Repository/DispForm.aspx?ID=394




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− Raw water pumping

− Raw water early warning turbidity monitoring at Dumbleton Weir.

• At WTP:

− Raw water turbidity monitoring

− Raw water flow monitoring

− pH adjustment using caustic soda

− Oxidation with potassium permanganate

− PAC Dosing

− Contact tank

− Coagulation with ACH

− Polymer dosing

− Clarification

− Flow monitoring

− Polymer dosing

− Filtration through dual media filters.

Bore Water Train • Raw water flow monitoring.

• Pre-chlorination for algae control in the aeration basin and additional oxidation.

• Aeration for removal of free carbon dioxide and any volatile compounds.

• pH adjustment using lime (change to caustic soda).

• potassium permanganate dosing for oxidation of manganese;

• Filtration through dual media filters.

Combined Trains • Filtered water storage for backwashing.

• Fluoridation.

• pH adjustment with lime (change to caustic soda).

• Disinfection through chlorination.

Treated Water Storage • Balance tanks.

• High lift pumps.

• Mt Oscar reservoir.

• Mt Pleasant reservoir.

Sludge Handling System • Waste washwater collection.


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• Sludge thickening from waste washwater tank.

• Thickened sludge storage.

• Dewatering of sludge via centrifuges.

• Removal of dewatered sludge.

6 OPERATIONAL PHILOSOPHY

6.1 Control Systems

6.1.1 Cascade Flow Control Fully automated flow control through the WTP from demand at the reservoirs through the WTP to raw water pump control is required in the future. This component of the control upgrade will be considered as a separate exercise subsequent to the current works. However all control system modifications to be implemented in this phase of the project should be compatible with this future requirement.

Key points of automatic cascade control for future operation are proposed as follows:

a) Level in Mt Pleasant Reservoir to control HL pumps – selection and operation of pumps, VSDs on some pumps, possible diurnal level set point target range in reservoir.

b) Level in Balance Tanks controlling Dumbleton Weir Pumps (and bore pumps) – selection and operation of pumps, VSDs on some pumps – start and stop of WTP to be included.

c) Continuous constant rate flow of WTP for as long as possible is preferred with flow rate ramping for flow increases.

d) Plant flow rate to be manually set by operators.

e) Pump and WTP protection needs to be considered and what interlocks are required to protect them.

6.1.2 Process Variations With normal RW quality the WTP can run on normal coagulation (as is current operation) with ACH dosing into the new mixer after the dosing tank with polymer dosed downstream prior to clarification and possible filter aid polymer dosing as well.

When longer flocculation time is required, because of cooler raw water or possibly elevated organics levels, then ACH can be dosed prior to the dosing tank with polymer either into the middle or at the end of the dosing tank for improved flocculation. This option may also become normal operation if it leads to improved settling in the clarifiers.

After storm events when raw water alkalinity is suppressed then caustic soda may also be required to raise the alkalinity – however this needs to be balanced against the associated pH increase.

When soluble manganese is present in the raw water then potassium permanganate (possibly with caustic dosing to raise the pH to between 7 and 8) would be dosed prior to the dosing tank with ACH dosed at the end of the tank and polymer prior to clarifier. It is also possible to dose ACH to the middle of the dosing tank if less oxidation contact time is required.


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When organic contaminants such as taste and odour compounds, algal toxins or pesticides/ herbicides are present in the raw water then PAC would be dosed at the front of the WTP with ACH dosed at the end of the dosing tank and subsequent polymer. PAC dosing should also be considered in conjunction with algae management and incident management protocols.

If both manganese and organic contaminants are present then permanganate would be dosed up front with PAC at the end of the dosing tank followed by ACH and polymer.

The process selection will be by the operator for these options.

6.1.3 Chemical System Operation All chemical systems will be flow proportional controlled with the flow signal supplied from the most appropriate flow meter to adjust motor VSDs.

In addition caustic soda (pre and post) will be pH trimmed by an online pH meter.

Chlorine dosing will be trimmed by an online chlorine residual analyser with a relatively short feed back time preferred of around 5 minutes after well mixed chlorine dosing. Another analyser on the water exiting the balance tanks would be used for monitoring only.

Other chemical dose changes will generally be manual stroke adjustment.

6.1.4 Clarifiers Operation Clarifier operation and control includes operator adjustable blowdown frequency and period with the option to use the online turbidimeter to automatically shut off the valves.

6.1.5 Filters It is preferred that all filters automatically backwash initiated on operator set turbidity, head loss or time. Automatic backwash capability already exists in WTP however only headloss to initiate filter wash process automatically is available.

6.1.6 Waste Washwater System This is a new system to be installed to manage the waste products for the existing filter backwash, existing clarifier blowdown and new centrifuge dewatering facility.

6.2 River Water and Initial Treatment Raw water from Dumbleton Weir is pumped to the WTP where it can be dosed with, caustic soda ACH and polymer and, if required, PAC and/or potassium permanganate upstream and downstream of the river dosing tank prior to settling in the two clarifiers. The water from the clarifiers is then dosed with a polyelectrolyte (polymer) before being filtered by the eight river water sand filters.

6.2.1 Inlet Works River water from the Dumbleton weir is lifted to the treatment plant by four (4) high flow river pumps to the inlet works. An early warning turbidity monitoring system will be added to the raw water pump station.

The raw water travels to the WTP via two mains. The inlet works brings raw water into the treatment plant and applies the first stage of chemical dosing.


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The inlet works is designed to add flexibility to dosing by having two (2) chemical dosing options. They are as follows:

• Potassium permanganate; and

• Caustic soda.

6.2.2 River Water Dosing Tank The river water dosing tank is designed to add flexibility to dosing by having multiple dosing points for different raw water conditions and process requirements. They are as follows:

• Pre-dosing tank mixer allowing dosing of ACH, polymer or PAC;

• Dosing tank direct to centre baffle wall diffuser allowing dosing of ACH or polymer; and

• Post- dosing tank outlet mixer allowing dosing of ACH, polymer or PAC.

The dosing tank may fulfil the following functions depending on chemicals dosed as follows:

• Flocculation if caustic soda/ ACH / polymer dosed upstream;

• Oxidation if caustic soda/ potassium permanganate dosed;

• Organic adsorption if PAC dosed upstream; and

• No process if no chemicals dosed upstream and ACH/ polymer dosed downstream.

A combination of these processes is also possible through the various chemical dosing combinations available.

The tank is continuously monitored by the SCADA system. Water height is determined by an ultrasonic sensor mounted above the tank and two (2) level switches are installed within the normal water level range to physically determine the low water level and high water level. An emergency overflow is provided and the chemical dosing stops if high high level is reached.

The mixer’s speed is also operator adjustable controlled via the SCADA system.

6.2.3 Clarifiers and Sedimentation The process of removing the flocc occurs in the two (2) clarifiers. Each clarifier receives the flocculated water from the river water dosing tank and allows sedimentation to occur. The clarifiers can be operated independently of each other.

The flocculated water enters the clarifier via the flocculation chamber, and then slowly flows out and upward; the supernatant decants over the launder weir. The settled flocc descends to the clarifier’s base and into the sludge hoppers.

The settled sludge is captured within the nine (9) hoppers of each clarifier. Pneumatic valves on the hopper outlet open in a co-ordinated periodic system to blow down sludge that has accumulated. Blowdown is a PLC controlled process and is initiated by a timer mechanism. The Operator of the plant can adjust the timer set point of the blowdown process and thus allow the blowdown sequencing for each of the hoppers to occur less or more frequently. He can also adjust the period of each blowdown or the blowdown period can be controlled by online turbidimeter.

The Operator can run blowdown process manually via the SCADA/HMI displays or locally at the valves.

Clarifier blowdown and filter backwash are prevented from occurring simultaneously.


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6.3 Bore Water and Initial Treatment Raw water from the bores is pumped to the WTP where it (may be pre-chlorinated) and is aerated and then dosed with potassium permanganate and caustic soda to oxidise the manganese. A polyelectrolyte (polymer) is added to the inlet of the four bore water gravity filters. While the normal flow of bore water maintains a processing path designed for bore water characteristics, it is possible to open a valve on an interconnector pipe allowing bore water to flow to the river water dosing tank and for it to be processed within that system.

6.3.1 Bore Water Aeration Bore water is lifted to the treatment plant by eight high flow bore pumps to the inlet works. Bore water enters the aeration basin directly from the bore pumps. An array of nozzles showers the water into the aeration basin. This process reduces any volatile organics and carbon dioxide and dissolves oxygen into the water for oxidising organics and iron/manganese.

The aerated water is collected from the aeration basin and is delivered to the aeration basin collector. Excess water that may accumulate in the aeration basin due to fault or blockage may be delivered to the overflow system. The aeration basin collector also has an overflow trough that makes it possible to divert overflow water to the storm water drain.

Once aerated, the bore water is piped to the relift pump well within the filter channels.

6.3.2 Relift Tank Bore water from the aeration basin enters the relift tank where caustic soda and potassium permanganate is added for manganese removal. The oxidised water is lifted to the filter channel via Archimedean screw pumps. Flows through the filters are controlled by the PLC through a position monitored and controllable butterfly valves.

6.4 Filter Inlet Channels and Rapid Gravity Filters Following the pre-treatment processes to the water treatment plant’s source water, both the river water and bore water reach their designated filter inlet channels where the water is dosed with polyelectrolyte (polymer) as a filter aid. The two (2) inlet channels in stage 1 are now able to be fed with river water for added water treatment flexibility.

If selected, bore water can be mixed into the feed water for processing.

6.4.1 Filter Inlet Channels Clarified river water enters the stage 1 and stage 2 filter inlet channels where the flows through the filters are controlled by the PLC through position monitored and controllable butterfly valves.

• Stage 1 filters are controlled via their inlet channel ultrasonic level detector; and

• Stage 2 filters are controlled via their individual filter pneumatic bubbler level control.

It is also possible to deliver river water from the clarifiers to the bore filters delay tank. This allows the Nebo Road WTP to process 100% river water through all of its available rapid gravity filters.

6.4.2 Rapid Gravity Filters Rapid gravity filters use a granular media to remove flocc. Rapid gravity filters must be cleaned frequently, typically daily, by scouring the media with air then backwashing with treated water and


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channelling the resulting waste washwater to the waste water treatment processing. All the filters are monitored on the SCADA/HMI displays.

River Water Filters There are eight (8) river water filters as follows:

• Four (4) river plant stage 1 filters – single filter cells (filters 5-8); and

• Four (4) river plant stage 2 filters – double filter cells (filters 9-12).

The four double filters results in 12 individual filter cells in total. The river water filters can operate in one of the following states:

• Offline;

• Online filtering; and

• Online backwash.

Bore Water Filters There are four (4) bore water filters as follows:

• Four (4) stage 1 filters – single filter cells (filters 1-4).

The bore water filters can be operated in the following states:

• Offline;

• Online filtering bore water;

• Online filtering river water;

• Online filtering mixed bore/river; and

• Online backwash.

Backwashing The process of backwashing is performed to clean every filter for re-use and to remove the accumulated flocc. Clean water is pumped in the reverse direction through each filter and the output flows to the wastewater tank for sludge processing. The Clearwater well serves as the backwash holding tank and provides the clean water needed for the backwash processes.

Air is used to scour the filters to remove trapped solids and the water treatment chemicals that can adhere strongly to the filter media.

Backwashing will be inhibited in the event that the Clearwater holding tank is low on water. The water level monitoring and backwash pump control are all handled by the SCADA system.

The backwashing process across every filter cell is fully automated by the SCADA system. All filter units for the water treatment plant use a common backwash pump and air blower. This results in only one (1) filter being backwashed at any one time.

6.5 Final Water Conditioning and Delivery The filtered water is stored in the Clearwater storage tank where it is dosed with caustic soda at the outlet weir and downstream with chlorine and fluoride, prior to entering the three balance tanks. A water splitter tank distributes water to the balance tank and also provides the location for sampling for testing


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within the laboratory. Water from the balance tanks is distributed within the Mackay water reticulation system via the high lift pumping station.

6.5.1 Clearwater Storage Tank The Clearwater storage tank buffers the volume of filtered water and holds it to provide a supply of clean water for the filter backwash processes.

Water is accepted into the Clearwater storage tank through two (2) inlet channels. Clearwater inlet channel 1 accepts water from the stage 1 rapid gravity filters. Clearwater inlet channel 2 accepts water from the stage 2 rapid gravity filters. The tank water temperature is constantly monitored via an installed temperature sensor and a low water level switch is provided.

The water runs into an overflow trough to which caustic soda is dosed for final pH adjustment of the water prior to chlorination and fluoridation.

Two (2) non-submersible backwash pumps take water from the Clearwater tank. Each pump unit is independently isolated with gate valves and monitored with inline flow switches. The pump motors are controlled by the PLC and the pump rotation speed is sensed and transmitted to the PLC by a speed indicator controller. The out flow of the backwash pumps join together and pass through a venturi before passing through a PLC controlled pneumatically actuated butterfly valve.

The outflow from the Clearwater storage tank is via a magflow pit. The magflow pit houses accurate flow meters that transmit rate of flow signals to the PLC and to the fluoride dosing system. The magflow pit is also the location for the chlorine and fluoride dosing.

6.5.2 Balance Tanks The balance tanks are the water flow buffers to the Mackay water network and house the fully treated and prepared water for consumption.

The tanks have the following capacities:

• Tank 1: 2.27 ML;

• Tank 2: 2.27 ML; and

• Tank 3: 4.5 ML.

Immediately prior to entering the balance tanks, treated water enters into the distribution splitter pit. From here, a range of sampling and quality assurance tasks take place. Two (2) sample pumps lift water out of the pit and deliver sample water to the fluoride analyser, chlorine analyser and the pH analyser which are located in the water testing laboratory. A sample / reference water supply is also provided to the analysers from downstream of the high lift pump station.

The outflow from the distribution splitter pit feed each of the three balance tanks. Balance tank 1 and balance tank 2 normally operate as a paired couple with open interconnections. As such, only one level meter is installed and is located in balance tank 1. These two tanks can be decoupled by the use of isolation gate valves should maintenance or cleaning be required.

Balance tank 3 employs its own water level detection. An interconnecting pipe from balance tank 1 permits the movement of water for storage by balance tank 3. While a connecting pipe allows the flow of water from the splitter tank to balance tank 3, it is not used as the inlet water short circuits to the outlet without mixing.

Each balance tank has an adjacent overflow pit.


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6.5.3 High Lift Pumps A series of six high lift pumps transfer treated water from the balance tanks to both Mt Pleasant Reservoir and the reticulation system. A flowmeter monitors the high lift flow rate, providing continual monitoring on SCADA in addition to a high lift flow set point and high and low flow alarm set points.

Automated pumping control shall be incorporated based on Operator adjustable reservoir level set-points. The Operator shall be able to configure the level set-points, such that the set-points will be associated with a timeframe to enable peak/off-peak control and ensure the reservoirs water is cycled through to ensure there is not a chemical dead band in the reservoir. In this operation mode the Operator selects the level set-point and the Main PLC controls the duty cycle and speed of the pumps to best achieve the required set-point.

All available pumps will be set in priority order queue by the Operator on the SCADA/HMI displays. The pump will be brought on line by the pump scheduler logic to match the queried flow rate.

6.6 Sludge Handling System The sludge handling system is designed to remove the solids from the wastewater, which are removed from site by skip bins. The supernatant water is discharged to Kaliguil lagoon for recycling (irrigation). The wastewater collection point at the start of the sludge handling system is the Washwater tank. The collected wastewater is then thickened in the sludge thickening tank and the sludge is dewatered in the centrifuges.

6.6.1 Washwater Tank The Washwater tank collects all the wastewater the treatment plant produces. It receives wastewater from the following:

• Settled sludge from the clarifier hoppers;

• Waste Washwater from the filter backwash cycle;

• Overflow from the thickened sludge tank;

• Overflow from the sludge thickener tank; and

• Wastewater from the centrate tank including discharge from the centrifuges.

A submersible mixer within the Washwater tank is used to blend wastewater and minimise settling. Three (3) submersible pumps lift the mixed wastewater to the sludge thickener tank. The lift pumps operate in the following manner:

• Pump 1: DUTY;

• Pump 2: DUTY / ASSIST; and

• Pump 3: STANDBY.

All pump motors are able to be both locally and PLC monitored. As the sludge leaves the Washwater tank it is monitored for pressure in each pipe. All three (3) pipes have individual butterfly valves for isolation and control after which they combine supplies to be sent to the sludge thickener tank.

The flow rate of the pre-treated sludge to the sludge thickener tank is measured with a magnetic flow meter.

Emergency overflow from the Washwater tank will discharge to Kaliguil Lagoon.


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Settled sludge from the clarifier hoppers may bypass the Washwater tank via a dedicated pipe if required by the Operator. This pipe routes the already dense sludge from the hoppers directly to the thickened sludge transfer tank.

6.6.2 Sludge Thickener Tank Thickening of the sludge from the Washwater tank is promoted by the direct addition of polymer from the sludge thickener polymer dosing system. The sludge thickener tank also uses a high torque, low rpm rotary rake to maintain movement in the tank and to facilitate the thickening process by concentrating the sludge as it settles and move it towards the central sump for pumping.

The polymer dosing system is a packaged product from an external vendor and receives a permission to operate from the site PLC. This package is also monitored by the site PLC.

The clean supernatant from the thickening process is discharged to Kaliguil Lagoon.

The sludge collected in the bottom of the thickener is piped to the thickened sludge tank. Two (2) pipe channels are used for the transport of thickened sludge and flow control is achieved with a gate – diaphragm valve combination.

6.6.3 Thickened Sludge Tank Thickened sludge is dumped from the sludge thickener to the thickened sludge tank, and is then pumped from there to the centrifuge system by duty/ duty / standby thickened sludge pumps. Polymer dosing occurs during transfer, to further thicken the sludge and optimise the performance of the centrifuges.

There are three (3) thickened sludge pumps installed. These are pumps located in the thickened sludge tank and operate in a duty / standby / duty-assist configuration. Where possible, the two (2) duty pumps are dedicated to a centrifuge each while the standby pump remains idle. Manual re-configuration of pumping circuits is required to circumvent a pump fault.

The duty thickened sludge pump operates when the thickened sludge tank level is above a start (high) level set point. The thickened sludge pump will stop when the level in the thickened sludge tank falls below the stop (low) set point, or the thickened sludge tank low level switch is activated.

A thickened sludge tank high level set point inhibits sludge dumping from the sludge thickener tank. This level will be set during commissioning, and will be such that a sludge dump does not cause the level to rise to the flood level. A thickened sludge tank high level switch also inhibits sludge dumping.

Thickened sludge flow is measured by the thickened sludge flowmeter. High and low flow alarms are triggered if the transfer flow rate falls outside the operational range. A low flow fault will trigger a pump fault and duty change. It will also raise a thickened sludge low flow fault alarm. A high flow fault will raise an alarm to alert the operator to the condition. This indicates that the transfer rate is excessive. The wastewater flow rate is manually adjusted via the thickened sludge regulating valve.

6.6.4 Sludge De-Watering and Disposal Three (3) centrifuges dewater the thickened sludge from the thickened sludge pumped to the system. Initially only two (2) centrifuges will be installed, the third centrifuge being installed at a later date.

Under normal conditions, a single centrifuge is capable of treating the full thickened sludge volume. Only during higher solids loading events will the system require two (2) centrifuge systems to operate.

The operator selects whether one duty centrifuge only is required (normal water quality conditions) or two duty centrifuges are required (poor water quality conditions).


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When a single centrifuge only is required, they operate in a duty / standby mode, whereas when two centrifuges are required, they operate in a duty / duty arrangement.

Isolation ball valves govern the flow of thickened sludge to a centrifuge. These open and close as required to enable thickened sludge to flow to the duty centrifuge(s). The centrifuges are stand-alone vendor packaged units complete with control panel. They include all controls and monitoring required for automatic operation, with SCADA interface for provision of remote ON-OFF signals and output of system health / fault signals.

Thickened sludge is discharged to a conveyor system, which transports the dewatered sludge to skips located external to the building. When a skip is full the Operator can traverse the conveyor arm to the next empty bin, allowing the full bin to be trucked offsite for disposal. Conveyer slewing is a local manual operation only to ensure safe operation of the equipment.

Centrate is returned to a centrate tank for disposal.

6.6.5 Centrate Handling The centrate tank receives all the waste liquids from the sludge dewatering processes. The sources of centrate are from:

• Thickened sludge pump station bund;

• Centrifuge No. 1;

• Centrifuge No. 2;

• Centrifuge No. 3 (Future);

• Sludge dewatering building drain pit;

• Sludge bin area pit No. 1; and

• Sludge bin area pit No. 2.

The centrate tank transfers the liquid to the wastewater tank via two (2) pumps in a duty and duty/standby configuration. Level of centrate is accurately measured with four (4) level switches at the following level points:

• Centrate level High;

• Centrate level High High overflow event is imminent;

• Centrate level Low; and

• Centrate level Low Low at the near pumping dry point/pump inhibits.

A paired couple of gate valves control the flow of centrate from the centrate pumps to the Washwater tank.

6.7 Dosing Systems

6.7.1 Potassium Permanganate (KMnO4) Potassium permanganate is a strong oxidant that does not generate toxic by-products and has disinfectant and deodorising properties. Oxidation breaks down organic materials converts metals such as iron and manganese to their particulate form for subsequent coagulation.


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The required river water potassium permanganate dose rate set point is entered into SCADA. The dose required will be determined by the operators and will be proportional to the soluble manganese concentration of the raw water.

The potassium permanganate dosing system will operate when the following conditions are satisfied:

• The river water plant is in operation;

• The river water flow rate is greater than 20l/s;

• The potassium permanganate dosing system is selected to operate; and

• The potassium permanganate dosing system is available and online.

If the potassium permanganate dosing system is selected to operate but is not available due to any system fault, an alarm will be raised and the system will not run.

The potassium permanganate dosing system is located at Nebo Road WTP, the potassium permanganate dosing location options are:

• River water inlet mains (downstream of the caustic soda dosing point); and

• Bore water relift tank.

An ‘Automatic / Manual / off‘selection is provided on SCADA for potassium permanganate dosing pumps 1 & 2.

A potassium permanganate ‘1-2 / 2-1’ duty/standby selector switch is provided on SCADA. Automatic transfer to the standby pump is required on detection of a duty pump failure or potassium permanganate flow fault, as detected by both the potassium permanganate flowmeters which are located after the potassium permanganate dosing pumps.

6.7.2 Caustic Soda (Sodium Hydroxide) Caustic soda is a strong alkali that provides pH and alkalinity adjustment.

When caustic soda dosing is selected to operate the required caustic soda dose rate set point is entered into SCADA. The dosed river water pH set point is also entered and caustic dosing will be automatically controlled to achieve this set point.

The caustic soda dosing system will operate when the following conditions are satisfied:



• The caustic dosing system is selected to operate; and

• The caustic soda dosing systems is available and online.

If the caustic soda dosing system is selected to operate but is not available due to any system fault, an alarm will be raised and the system will not run.

Caustic soda dosing occurs at:

• The inlet mains, up stream of all other chemicals;

• The bore water relift tank; and

• The outlet weir of the filtered water tank.


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Dosed water pH meter #1 will be an immersed unit located at the inlet to the dosing tank, whereas dosed water pH meter #2 will be a side-stream unit located between the two clarifiers, drawing sample water from the dividing tee where feed water divides to each clarifier. Dosing may also be performed at the outlet of the tank.

6.7.3 Powdered Activated Carbon (PAC) The addition of the powdered activated carbon adsorbs organic contaminants such as taste and odour compounds, algal toxins and pesticides/herbicides.

When PAC dosing is selected to operate from the river water chemical selection matrix, the required river water PAC dose rate set point is entered into SCADA.

The PAC dosing system will operate when the following conditions are satisfied:


• The river water flow rate is greater than 20L/s;

• The PAC dosing system is selected to operate; and

• The PAC dosing system is available and online.

If the PAC dosing system is selected to operate but is not available due to any system fault, an alarm will be raised and the system will not run.

The PAC dosing location options are:

• River water dosing tank – Inlet; and

• River water dosing tank – Outlet.

When called to operate, the PAC batching and dosing system will operate automatically from the vendor-provided PLC. The required PAC feed rate (kg/hr) is calculated in the WTP PLC based on the operator adjustable PAC dose rate set in SCADA and the river water flowrate, as measured by the river water feed flowmeter. The resulting PAC feed rate value is transmitted to the PAC PLC, and the PAC system then automatically provides this feed rate.

6.7.4 Aluminium Chlorohydrate (ACH) ACH is used in the water treatment process as a coagulant within the water treatment process.

When ACH dosing is selected to operate from the river water chemical selection matrix, the required river water ACH dose rate set point is entered into SCADA.

The ACH dosing system will operate when the following conditions are satisfied:

• The river water plant in operation;


• The ACH dosing system is selected to operate; and

• The ACH dosing system is available and online.

If the ACH dosing system is selected to operate but is not available due to any system fault, an alarm will be raised and the system will not run.

The ACH dosing location options are:

• River water dosing tank – inlet;


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• River water dosing tank – midpoint; and

• River water dosing tank – outlet.

An ‘Automatic / Manual / off‘selection is provided on SCADA for ACH Dosing Pump 1 & 2.

An ACH ‘1-2 / 2-1’ duty/standby selector switch is provided on SCADA. Automatic transfer to the standby pump is required on detection of a duty pump failure or ACH flow fault.

6.7.5 Polymer (Polyelectrolyte) Polymer is used as flocculation aid (prior to clarification) and as a filter aid and to assist in sludge thickening and dewatering. It assists in the agglomeration of flocc and subsequent settling of larger denser particles and in its adsorption of fine flocc onto the filter media. It also assists in conglomerating flocc for thickening/ dewatering.

Polymer is dosed into the water treatment process through three (3) independent systems. These are for dosing to the following WTP components:

• River water dosing tank and pre-clarifiers;

• Inlet channels for the filters;

• Sludge thickener using an independent vendor package; and

• Centrifuges using an independent vendor package.

The operation philosophy for the site controlled system for the clarifiers and filter is detailed below.

The flocculation aid polymer dosing system will operate when the following conditions are satisfied:



• The polymer dosing system is selected to operate; and

• The polymer dosing system is available and online.

If the polymer dosing system is selected to operate but is not available due to any system fault, an alarm will be raised and the system will not run.

The polymer dosing location options are:

• River water dosing tank – multiple dosing locations;

• Clarifier inlet mains; and

• Filter inlet channels.

An ‘Automatic / Manual / Off’ selection is provided on SCADA for polymer dosing pump 1 & 2.

A polymer ‘1-2 / 2-1’ duty/standby selector switch is provided on SCADA. Automatic transfer to the standby pump is required on detection of a duty pump failure or clarifier aid polymer flow fault, as detected by the clarifier aid polymer flowmeter.

The vendor packages dosing systems accept sensor inputs and employ and independent PLC for their dosing processing. They are, however, given a permission to operate signal from the site’s main PLC.

The Sludge Thickener Polymer Batching System is a Vendor package unit complete with PLC and control panel. For operation it is dependent on the transfer of dirty wash water from the WWT to the sludge thickener tank.


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The Centrifuge Feed Polymer Batching System is a Vendor package unit complete with control panel and PLC. This system, when enabled, injects polymer in to the thickened sludge being transferred from the Sludge Thickener tank to the Centrifuges. This operates whenever thickened sludge transfer is in progress.

6.7.6 Chlorine and Fluoride Dosing Chlorination and fluoridation occur downstream of the Clearwater storage tank.

Chlorine is housed in the chlorine drum room where a maximum of two (2) drums of chlorine are connected to the dosing system. Each of the connected drums is on weight scales to monitor their available capacity and each connected drum has its temperature maintained by a storage drum heater.

For personnel safety a chlorine gas detector is installed with the output signal being transmitted to the PLC for continuous monitoring.. Chlorine gas detection is also installed within the chlorine dosing room and the output signal is transmitted to the PLC for continuous monitoring. If chlorine gas is detected by either unit, a site wide evacuation alarm is activated by the PLC.

The chlorine dosing system delivers accurate doses of chlorine to an incoming flow of service water via two (2) chlorinators. The chlorinators are monitored with flow indicators, pressure switches and speed indicator controllers.

The fluoridation system is a proprietary unit with an independent operation philosophy as required by the Queensland Fluoridation Guidelines. It runs its own PLC and receives external signals to determine appropriate dosing. This includes the resultant from the fluoride analyser which is located in the water testing lab. The fluoridation system operates independently up to the point where overall permission to operate is granted by the water treatment plant’s PLC.

7 CONTROL PHILOSOPHY

7.1 General Operators shall be provided with all necessary plant data such as alarms, trending, historical, current plant and process data (e.g. water quality, flow rates, etc.) to enable them to make to an informative decision to operate the plant.

The Operator has the option of selecting river water and/or Bore Water for the treatment process. The Operator’s selection at the Supervisory Control and Data Acquisition (SCADA) / Human Machine Interface (HMI) system activates the appropriate changeover valves to enable the selected treatment process to proceed. Refer to Section 9.1 for further information.

The Operator starts and stops the River Pumps at Dumbleton Weir as needed to balance the water into the plant with the outgoing consumption rate. The required plant flow rate is set to approximately balance the prevailing consumption rate. The Operator decides the required flow rate based on the selected level of the in-service BT. This maintains acceptable levels at the Nebo Road BT and Mt Pleasant Reservoir.

The Operator can select either BT No. 1 & 2 or BT No. 3 from SCADA/HMI as the River Pump control, as well as for monitoring of the current stored volume on site. BTs 1 & 2 are manifold together with a common level transmitter monitoring the level in BT 1 & 2 and a dedicated level transmitter monitoring the level in BT 3.


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Normally, BT 1 & 2 Level Transmitter will be selected for control due to the typical flow arrangement for BT 3. BT 3 Level Transmitter shall be selected if BT 1 & 2 is out of service e.g. maintenance cleaning or failure of the BT 1 & 2 Level Transmitter.

When the level in the selected BT drops, an alarm is initiated to alert the Operator to increase flow into the plant. An Operator adjustable (SCADA/HMI) BT High level set-point is provided to indicate an alarm to the Operators to monitor, reduce or stop the flow into the plant. This alarm set-point applies to the selected BT Level Transmitter.

When a High-High level or a Low-Low level is detected at a selected BT, an alarm will be initiated for Operator action.

The control philosophy for all drives including variable speed drives (VSD) and Duty/Standby changeover of drives are covered in Appendix A, B and C. The drive control philosophy shall apply to all drives including pumps, fans, mixers and other motor drives. The VSD control philosophy shall also apply to all VSD drives. Further, the Duty/Standby changeover philosophy shall apply to all drives that are configured as Duty/Standby or Duty/Duty/Standby.

The local HMIs will provide for monitoring and control of all batching and dosing within the WTP.

7.2 Operator Adjustable Set-Points All Operator Adjustable set-points shall have an upper and lower limit for User input that shall stop equipment from being damaged. The upper and lower limit shall not be adjustable on SCADA/HMI displays. Changes to Operator adjustable set-points shall be logged locally as an event.

The following rules shall be adhered to when allowing Operators to configure level set-points:

1. Users shall not be able to configure the Duty Stop Level below the height of the Low Level float switch (if installed).

2. Users shall not be able to configure the Duty start Level above the height of the High Level float switch (if installed).

3. Users shall be prohibited from configuring the Duty Start Level below the Duty Stop Level.

4. At a three pump station, users cannot set the Duty 1 Start Level higher than the Duty 2 Start Level, nor the Duty 2 Stop Level lower than the Duty 1 Stop Level.

5. Users shall not be able to set the Duty Start Level higher than 300 mm below the 100% Level.

8 RIVER WATER TREATMENT

8.1 River Water Feed System Reference P&ID drawing:

• 004-7032-I-5003 Rev. 2 (INLET WORKS).

Overview Dumbleton Weir is currently under review to be upgraded at a later date. From initial discussions the raw water pumps at the weir will be upgraded and continue to be able to operate in an automated system that will require the installation of new instruments and VSD control of the pumps.


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The four (4) river water pumps located at Dumbleton Weir (at the Pioneer River) pump water to the Nebo Road WTP via two separate mains. The two water mains diverge at the river water header pipe-work at Dumbleton Weir.

On the inlet to Nebo Road WTP each main is isolated by a separate electric/pneumatic open/close control valves FV11006 and FV11005 that finally control the respective flow valves FV11003 and FV11002. FV11003 and FV11002 isolate the water main following a pump cycle as the system can drain due to the level of the water main relative to the treatment plant.

Monitoring and control at Dumbleton Weir is achieved by the Main PLC at the WTP. The Main PLC interfaces with the master RTU at the WTP which maintains a radio telemetry link to a slave RTU at Dumbleton Weir.

Operation and Control Control of the pumps from the Main PLC and SCADA/HMI is achieved using a radio telemetry system. Dumbleton Weir currently has three operation modes, these are:

• Remote auto mode – controlled from WTP;

• Remote manual mode – controlled from WTP; and

• Local manual mode – controlled from Dumbleton Weir.

The existing control and operation of the river water pumps and valves will remain unchanged for the duration of construction at the WTP; however allowances will need to be made to incorporate the changes made at Dumbleton Weir raw water pumping station. For the Dumbleton Weir future proposed sequences refer to Appendix D.

The Operator has limited monitoring capability at Dumbleton Weir and currently undertakes regular site inspection to ensure the equipment is operating correctly.

The four river water pumps are as follows:

• Pump 1 – 500 L/s, this pump cavitates (out of pump curve), and is not used unless absolutely required;

• Pump 2 – 470 L/s, but can be reduced to 350 L/s by throttling discharge valve;

• Pump 3 – 350 L/s, but can be reduced to 220 L/s by throttling discharge valve; and

• Pump 4 – 630 L/s.

The Operators currently swap between pumps, if necessary, to achieve the required average throughput. The pumps are started by one of the three modes as stated above.

The Operator can select Open/Close/Auto from the SCADA/HMI for river valves 1 & 2 individually. When Auto is selected, the valve will open or close as controlled by the pump sequence.

FV11003 and FV11002 can be opened or closed manually from a local control station. Solenoid valves FV11006 (for FV11003) and FV11005 (for FV11002) at the water extraction points are controlled from the Main PLC.

When the selected BT level rises above the alarm set-point, the Operator is required to control the flow rate or shut down the pumps manually.

Only two (2) out of four (4) river water pumps will be used as the Duty Pumps. This process is currently under investigation and an allowance for VSD control of the pumps shall be made.


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Start Permissive The start sequence includes starting the pumps against the closed valve and then opening the respective control valve and checking for open limit.

When power is restored at the treatment plant after power failure, the system shall not restart automatically but has to be re-started by the Operator.

Start Sequence 1. Duty Pump selection to achieve flow rate set point is selected/entered in WTP SCADA (this can

occur at any stage).

2. Start command from WTP.

3. Start Duty pump.

4. Signal sent for Duty pump running.

5. Valves ramp open on delivery line (normal operation speed).

6. Signal sent from Dumbleton Weir for valves opening to WTP.

7. Valves ramp open inlet works of WTP (normal operation speed).

8. Signals sent to WTP SCADA to confirm all valves are fully open.

9. Sequence completed.

Stop Sequence and Interlock Expected normal stop sequence:

1. Stop command from WTP.

2. Valves ramp closed on delivery line (normal operation speed).

3. Duty Pump Shutdown.

4. Signal sent from Dumbleton Weir for valves closing to WTP.

5. Valves ramp closed inlet works of WTP (normal operation speed).

6. Signal sent to WTP to confirm all actuators are fully closed.

7. Signal sent from Dumbleton Weir to confirm Duty Pump stopped to WTP.

8. Sequence completed.

The following events cause the raw river water pumps to stop:

• If either river valves for delivery and termination line are closed during pump operation or fail to open correctly:

− Complete normal stop sequence.

• River water Pumps failed to run (i.e. none of river water Pumps 1 – 4 ‘Running’ feedbacks from the telemetry system are active during pump operation):


• River water flow rate falls below 20 L/s during river water plant operation:


• High-high turbidity alarm triggered at Dumbleton Weir:


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− ‘High-High Turbidity Alarm’ signal sent to WTP


• Communication (heart beat signal) lost on the RTU, the pumps are shutdown by the local RTU if the communication is not re-instated after five minutes and the Main PLC indicates a ‘Communications Failure’ alarm:

− Where communications are lost the pump station shall continue operating for set ‘Communications Lost Duration’ timer (Operator adjustable and expected to be 5 minutes). Timer to be set no longer than the maximum operational time of the UPS

− Once timer is exceeded go to ‘Normal operation – stop process’

− The ‘Communications Lost Duration’ timer should be reset every time the heartbeat is received. This restarts the timer at zero again and prevents it reaching its timeout value.

• WTP rapid stop command – Nebo Road WTP:

− Rapid stop command received from WTP

− All chemical dosing on river feed, inlet works and river dosing tank at Dumbleton Weir and Nebo Road WTP to shut down

− Ramp down Duty VSD (emergency ramp down speed duration)

− Valves ramp closed on delivery line (emergency operation speed)

− Signal sent from Dumbleton Weir for valves closing to WTP

− Signal sent to WTP to confirm all actuators are fully closed

− Signal sent from Dumbleton Weir to confirm VSD stopped to WTP

− Sequence completed.

• Emergency stop – Dumbleton Weir:

− Emergency stop command sent to WTP

− Ramp down Duty VSD (emergency ramp down speed duration – this may require instantaneous power disconnection depending on which emergency stop is used)

− Valves ramp closed on delivery line (emergency operation speed– this may require instantaneous power disconnection depending on which emergency stop is used)



− Chemical dosing in WTP shall stop according to their flow set-points

− Sequence completed

− Emergency stop shall only be where the emergency stop button on the LCS of the running drive is activated.

• Power failure at Dumbleton Weir/Pumps stop, valves cannot close:

− ‘Dumbleton Weir Power Failure’ signal sent to WTP

− Valves ramp closed inlet works of WTP (normal operation speed)

− Signal sent to WTP to confirm status of all actuators.


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• Power restored:

− ‘Dumbleton Weir Power Healthy’ signal sent to WTP

− Valves ramp closed on delivery line (normal operation speed)




− ‘Dumbleton Weir System Available’ signal sent to WTP

− Wait for start signal from WTP.

Monitoring and Indication Open and closed limit switches are provided on both river water valves FV11003 and FV11002. FV11003 and FV11002 send open and close status to its local control station and to the SCADA/HMI for monitoring.

Surge pipe overflow flow switch (LSH20501) is wired to the Main PLC input. The input shall be used for a SCADA/HMI status display only.

The following information from Dumbleton Weir is displayed in the SCADA:

1. Instruments:

− Turbidity

− Flow (multiple instruments).

2. Pump status.

3. Actuator status.

4. Remote/off/local selection.

Alarm Status The open or close command and general valve fail alarm will be used to determine whether a ‘Failed to Close’ or ‘Failed to Open’ alarm will be raised on the corresponding valve. ‘Failed to Open’ and ‘Failed to Close’ alarm time set-points shall be displayed and can be adjusted by the Operator from the SCADA/HMI system. If both valves fail to open, a ‘River Water Feed System Failed’ alarm will be raised.

At the existing surge tower the level switch LSH20501 monitors the level and sends a Level High alarm to the SCADA/HMI.

An allowance for alarm status from Dumbleton Weir is required for, but not limited to the following:

1. Instruments:

− Turbidity

− Flow (multiple instruments)

− Power monitoring

− Other.

2. Pump status.

3. Actuator status.

4. Loss of communications (heart beat signal).


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8.2 River Water Quality Monitoring Reference P&ID drawing:

• 004-7032-I-5002 Rev. 0 (DUMBLETON WEIR).

• 004-7032-I-5003 Rev. 2 (INLET WORKS).

Stop Condition and Interlock A High-High Turbidity alarm generated by an analyser indicating transmitter (AIT11001) will automatically shut down the Dumbleton Weir Pumps, and the river water plant thereby preventing unacceptable raw water filling the entire feed system and compromising the treatment process.

Monitoring and Indication Raw water turbidity is monitored at the new Dumbleton Weir turbidity meter (AIT11001) and also by the raw water turbidity meter at the river inlet works (AIT11005).

The analogue turbidity signal from Dumbleton Weir (AIT11001) and the river inlet works (AIT11005) are displayed in the SCADA/HMI.

Alarm Status A High Turbidity alarm (AIT11001) is activated if the turbidity exceeds an Operator adjustable High Turbidity set-point for an Operator adjustable duration at the SCADA/HMI system. This provides an early warning to alert the Operator to a deteriorating feed water quality.

A High-High Turbidity alarm (AIT11001) is activated if the turbidity exceeds an Operator adjustable High-High Turbidity set-point at the SCADA/HMI system for an Operator adjustable duration. The Operator can adjust the time delay setting for the High and High-High Turbidity alarms at the SCADA/HMI system.

An analyser fail alarm for Turbidity Analysers (AIT11001 and AIT11005) shall be indicated on the SCADA/HMI system.

8.3 River Water Inlet Works – Chemical Dosing Systems Reference P&ID drawing:

• 004-7032-I-5003 Rev. 2 (INLET WORKS).

• 004-7032-I-5004 Rev. 2 (NEW RIVER WATER DOSING TANK).

• 004-7032-I-5005 Rev. 2 (CLARIFIER NO.1).

Overview The following chemicals can be dosed in the inlet works of the river water dosing tank:

• Potassium permanganate (KMnO4); and

• Caustic soda.

For detail on the chemical dosing process refer to the appropriate chemical section.

Operation and Control The Operator selects from the SCADA/HMI the chemicals required from a river water chemical selection matrix with the required dose rates, and the dosed river water pH Operator adjustable set-point


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(associated with AIT29501). The Operator also selects the required chemical dosing/injection point locations from the following options:

• River water inlet mains (KMNO4 and caustic soda); and

• Clarifier Inlet Mains (caustic soda only).

Flow indicating transmitter (FIT29531) from the river water line will have an Operator adjustable high and low flow alarm set-points.

Stop Condition and Interlock KMNO4 will be inhibited from dosing into the river water inlet system where the pH is outside of the KMNO4 operation range.

Monitoring and Indication The following instruments provide monitoring and indication locally and at the SCADA/HMI displays:

• Flow indicating transmitter (FIT29531) from the river water line monitors the flow and volume.

Raw river water is sent to the laboratory via the existing river water dosing tank sample pump (PD29505) for analysis.

Alarm Status The following devices will send High and Low flow alarms to the SCADA/HMI;

• Flow indicating transmitter (FIT29531) from the river water inlet line; and

• pH indicating transmitter (AIT29501) on the outlet to the RWDT.

8.4 River Water Dosing Tank Reference P&ID drawing:

• 004-7032-I-5003 Rev. 2 (INLET WORKS).


Overview The new river water dosing tank includes the following chemicals which are used according to the prevailing water quality conditions and chemical dosing regimes:

• Polymer dosing;

• PAC Contact (with PAC dosing); and

• Flocculation (with ACH dosing).


The dosing location options are selected by the Operator via the SCADA/HMI. The options include:

• River water dosing tank – inlet;

• River water dosing tank – midpoint;

• River water dosing tank – outlet; and

• Clarifier inlet mains.


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The River Water Dosing Tank is baffled to prevent short-circuiting, and two (2) high energy river water dosing tank mixers (MX29501 and MX29502) provide the required level of agitation for the specific roles.

When the RWDT is bypassed, generally for maintenance, the flow transmitter FIT29531 shall not have any water flow. Under this situation the Operator shall select the RDWT to bypass mode and the river water plant inlet flow shall be calculated using the summation of flow transmitters (FIT29241 and FIT29231) at the outlet of the clarifiers. The selection of RWDT bypass mode shall affect the automated selection for chemical dosing from the Chemical Dosing Matrix in Appendix E.

Please note: PAC dosing system will be moved to Dumbleton Weir once the upgrade at the Dumbleton Weir raw water pump station is complete.

Operation and Control The river water dosing tank flow, mixers and chemical dosing is controlled from the Main PLC and SCADA/HMI.

The two (2) mixers can be controlled manually at a local station.

Dosing control flow valves at the River Water Dosing Tank (TK29501) are controlled from the Main PLC (for details refer to the relevant dosing system). Flow indicating transmitter (FIT29531) from the river inlet works) LSH29502 and LSL29503) and level switches and transmitter (FIT29501) at the river water dosing tank provide respective flow and level controls to the Main PLC.

pH analyser transmitter (AIT29501) at the new River Water Dosing Tank will have an Operator adjustable low and high alarm set-points.

The Main PLC logic determines the dosing tank mixers to start and the appropriate Operator adjustable speed set-point to the respective dosing mixer speed controllers. The speed set-point is based on the chemicals being dosed and their respective dosing points as selected on the river water Chemical Dosing Point Selection Matrix.

Refer to Appendix E for the river water Chemical Dosing Point Selection Matrix.

Start Permissive A mixer sequence shall start when the following conditions are satisfied:

• River water plant is operating or start sequence initiated;

• River water plant flow ≥ 20 L/s;

• Mixer drive available;

• Lsh29502 and lsl29503 alarms are not activated;

• Flow reading from fit29531 is within operator adjustable set-point range; and

• Level reading from lit29501 is within operator adjustable set-point range.

Start sequence is initiated when all start permissive and start conditions are satisfied.

Stop Condition and Interlock Level alarms from the level switches (LSL29503 and LSH29502), level transmitter (LIT29501) and raw river water flow less than 20 L/s will stop the affected running mixer.


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Level switch LSH29502 alarm will indicate an imminent overflow event is about to occur and shut down all dosing in the river feed, inlet works and river water dosing tank. This will initiate a rapid stop command – Nebo Road WTP action, as per River Water Feed System section.

Monitoring and Indication The following instruments provide local and SCADA/HMI display:

• High and Low river water Dosing Tank level switches (LSH29502 and LSL29503) and level transmitter (LIT29501);

• Analyser transmitter (AIT29501) monitors ph at the New River Dosing Tank; and

• Flow indicating transmitter (FIT29531) from the river water line monitors the flow for local and SCADA/HMI display.

Alarm Status The River Water Dosing Tank’s level switches and level transmitter will raise an alarm when a low or high level is detected and display at the SCADA/HMI.

An analyser transmitter (AIT29501) at the new River Water Dosing Tank will send low and high alarm status to the SCADA/HMI and the pH levels will be indicated locally.

8.5 Clarifiers Reference P&ID drawings:



• 004-7032-I-5007 Rev. 2 (WASHWATER TANK).

• 004-7032-I-5009 Rev. 2 (THICKENED SLUDGE TANK).

• 004-7032-I-5013 Rev. 1 (FILTER INLET CHANNELS).

Operation and Control The Clarifiers are controlled from the Main PLC and SCADA/HMI.

The operation of the Clarifiers includes the blowdown process as described in the succeeding section.

The following dosing and sampling valves are controlled from the Main PLC and SCADA/HMI:

• FV29113 – Clarifier polymer dosing line; and

• FV29123 – Clarifier caustic soda dosing line.


Motorised valves MV24101 and MV29240 are controlled and monitored locally and at the SCADA/HMI. The position of these valves is trimmed by the operator using the SCADA/HMI to progressively open or close the valve to reach a desired value of flow through flow meters FIT29231 and FIT 29241 respectively.

Stop Condition and Interlock The filter stage inlet valves are controlled in order to minimise the risk of an RWDT overflow.


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In order to avoid a clarifier & RWDT back-up or overflow event, the control of valves MV29240 and MV24101 shall be interlocked such that both valves cannot be modulated away from the 100% open position at the same time.

For example:

• Where flow to the stage 1 filters 1-8 is to be trimmed then MV29240 is modulated away from 100% open only if MV24101 is fully open and vice-versa;

• Where flow to stage 2 filters 9-12 is to be trimmed then MV29240 is modulated away from 100% open only if:

− In stage 1 filters 1–4 river or mixed mode, MV29240, FV29213 and FV15601are fully open

− In stage 1 filters 1–4 bore mode, MV29240 and FV29213 are fully open and FV15601 is fully closed.


• Analyser transmitters (AIT29312 and AIT29412) monitor the turbidity at the existing clarifier sludge pits; and

• Flow meters (existing venturi FIT29231 and new magflow FIT29241) monitor the flow going to the filter inlet flow.

8.5.1 Clarifier Blowdown

Operation and Control Clarifier blowdowns are automated using nine (9) pneumatically actuated blowdown valves through pilot solenoids on each of the two (2) clarifiers.

Table 8-1 Clarifiers Flow Valves

Clarifier No. 1 Clarifier No. 2

Pilot solenoid Blowdown valve Pilot solenoid Blowdown valve

FV29161 FV29191 FV29261 FV29291

FV29162 FV29192 FV29262 FV29292

FV29163 FV29193 FV29263 FV29293

FV29164 FV29194 FV29264 FV29294

FV29165 FV29195 FV29265 FV29295

FV29166 FV29196 FV29266 FV29296

FV29167 FV29197 FV29267 FV29297

FV29168 FV29198 FV29268 FV29298

FV29169 FV29199 FV29269 FV29299

The blowdown valves will open for a period sequentially once a blowdown sequence has been initiated.

An Operator adjustable Clarifier Blowdown Interval Timer (one for each clarifier) will trigger the blowdown of an individual clarifier. The Clarifier Blowdown Interval (i.e. the period of time between


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blowdown on an individual Clarifier) will be an operator adjustable set-point on the SCADA/HMI. This timer will be overridden by the Filters Backwash Blocking Timer, which will inhibit the Clarifier blowdown when a Filter backwash is in progress. This is to minimise the amount of blowdown/backwash water entering the WWT.

An Operator adjustable Clarifier Blowdown Duration set-point at the SCADA/HMI determines Clarifier Blowdown Duration (i.e. the period of time that each of the nine (9) individual Clarifier Blowdown Valves are opened for each Clarifier). The Operator will be given the option to change the blowdown period, as determined by a Clarifier Blowdown Turbidity Set-point, via a adjusting the set-point on the SCADA/HMI for the turbidity meter on the blowdown line.

An Operator adjustable Clarifier blowdown blocking timer will be adjustable at the SCADA/HMI and start once the clarifier blowdown inhibit elapses. This timer is to be used in conjunction with the permanent 30 minute clarifier blowdown inhibit to allow an adjustable delay between backwash and blowdown processes. the permanent 30 minute clarifier blowdown inhibit starts once the filter backwash sequence has finished.

The Operator can select Auto/Manual/Off at the SCADA/HMI for each of the Clarifier Blowdown valves. In Auto mode, the valve is controlled by the Clarifier Blowdown sequence. In Manual mode, the valve is taken out of automatic sequence, is bypassed and the Operator can open or close the valve from SCADA/HMI.

The blowdown valves can be operated locally, bypassing the Main PLC control, from the local control station via the pilot solenoids.

Monitoring and Indication The turbidity at the Sludge Pits (via AIT29312 and AIT29412) from the river plant are monitored and indicated locally and at the SCADA/HMI display.

The flow to Filter Inlet Flow is monitored by flow indicating transmitters FIT29231 and FIT29241 for the local and SCADA/HMI displays.

All blowdown valves for Clarifier 1 and Clarifier 2 provide open and closed status monitoring and indication for local and SCADA/HMI displays.

Alarm Status The turbidity at the Sludge Pits will send alarms to the SCADA/HMI.

All blowdown valves for Clarifier 1 and Clarifier 2 for failure to operate will send alarms to the SCADA/HMI.

Sequence Start Permissive A Clarifier blowdown sequence shall start when the following conditions are satisfied:

• River water plant is operating;

• Clarifier blowdown interval set-point elapses;

• Other clarifier is not performing a blowdown;

• Level in the WWT is below the operator adjustable clarifier blowdown inhibit level set-point during normal operation;


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• Level in the test is below the operator adjustable clarifier blowdown inhibit level set-point during the WWT bypass operation;

• Filter backwash blocking timer is not inhibiting the blowdown; and

• For auto blowdown sequence to operate, at least one valve shall be required to be in auto mode.


Sequence Run Condition If the level in the WWT rises above the Operator adjustable Clarifier Blowdown Inhibit Level (High) set-point during the Clarifier Blowdown sequence, the blowdown will continue.

Sequence Stop Condition However once the Clarifier Blowdown Duration Timer elapses, the sequence will halt until the level falls below the Clarifier Blowdown Inhibit Level (high) set-point again.

A blowdown will immediately halt by closing the open valve if the level in the WWT rises above the Operator adjustable Clarifier Blowdown Halt Level (High-High) set-point via LIT58100. The sequence will halt until the level falls below the Clarifier Blowdown Inhibit Level (High) set-point again.

Sequence Step Action and Transition Conditions The clarifier 1 blowdown sequence operates as follows (clarifier 2 blowdown sequence is the same but instead checks for the status of Clarifier 1 as a permissive to start):

Table 8-2 Clarifiers Step and Transition

Step Description of Step/Transition

1 Open Clarifier 1 Blowdown Valve 1 if valve is selected to Auto AND

WWT level < Inhibit level

Else Go to Blowdown Valve 2 (Step 6).

Transition Condition

• Clarifier 1 Blowdown Valve 1 open limit switch detected, Go to Next Step • Fault condition - Valve fail to open (valve fault), an alarm is raised, valve trip to manual,

sequence Go to next blowdown valve.

2 Start Clarifier Blowdown Duration Timer.


• Clarifier Blowdown Duration Timer elapses, Go to Next Step OR

• WWT Level > Clarifier Blowdown Halt level, Go to Next Step.

3 Close Clarifier 1 Blowdown Valve 1.


• Clarifier 1 Blowdown Valve 1 close limit switch detected AND WWT Level < Inhibit Level, Go to Step 6

• Fault condition - Valve fail to Close within 10 sec. (valve fault), an alarm is raised,

4 Wait for level inhibit release


• Restart Clarifier 1 Blowdown Valve 1 sequence, Go to Step 1 OR • Inhibit release timed out, raise alarm, Go to Next Step.

5 Pause sequence


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• Operator to select Clarifier 1 Blowdown Valve 1 to manual mode AND • Operator to bypass Clarifier 1 Blowdown Valve 1, Go to Step 6 OR

• Operator to continue Clarifier 1 Blowdown Valve 1, Go to Step 1

6 Open Clarifier 1 Blowdown Valve 2 if Valve is selected to Auto

Else Go to Blowdown Valve 3 (Step 11).


• Clarifier 1 Blowdown Valve 2 open limit switch detected, Go to Next Step • Fault condition - Valve fail to open (valve fault), an alarm is raised, valve trip to manual,

sequence Go to next blowdown valve. OR

7 Start Clarifier Blowdown Duration Timer.


• Clarifier Blowdown Duration Timer elapses, Go to Next Step OR • WWT Level > Clarifier Blowdown Halt level, Go to Next Step.

8 • Close Clarifier 1 Blowdown Valve 2


• Clarifier 1 Blowdown Valve 2 close limit switch detected AND WWT Level < Inhibit Level, Go to Step 11

• Fault condition - Valve fail to Close within 10 sec (valve fault), an alarm is raised, Go to Step 10

9 Wait for level inhibit release


• Restart Clarifier 1 Blowdown Valve 2 sequence, Go to Step 6 OR • Inhibit release timed out, raise alarm, Go to Next Step.

10 Pause sequence


• Operator to select Clarifier 1 Blowdown Valve 2 to manual mode AND • Operator to bypass Clarifier 1 Blowdown Valve 2, Go to Step 11 OR • Operator to continue Clarifier 1 Blowdown Valve 2, Go to Step 6

11 Continue sequence, until all nine (9) Clarifier Blowdown Valves sequence steps have been completed.

1x Close Clarifier 1 Blowdown Valve 9.


• Clarifier 1 Blowdown Valve 9 close limit switch detected, Go to Last Step • Fault condition - Valve fail to Close within 10 sec (valve fault), an alarm is raised, Go to Step 1z

1y Wait for level inhibit release


• Restart Clarifier 1 Blowdown Valve 2 sequence, Go to Step 1x OR • Inhibit release timer exceeds, raise alarm and move valve to manual mode, Go to Last Step.

1z Pause sequence


• Operator to select Clarifier 1 Blowdown Valve 9 to manual mode AND • Operator to bypass Clarifier 1 Blowdown Valve 9, Go to Step 11 OR

• Operator to continue Clarifier 1 Blowdown Valve 9, Go to Step xx

Last Step Start Clarifier Blowdown Interval Timer

END OF SEQUENCE

The following four steps shall be inserted to replace Step 2 and Step 7 ‘Start Clarifier Blowdown Duration Timer’ when blowdown bypass timer mode is selected.


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Xa Open WWT bypass valve (FV74153) to thickened sludge tank and close (FV58103)


• Turbidity > bypass start set-point, Go to Next Step OR • Thickened Sludge tank Level < Clarifier Blowdown Halt level, Go to Next Step Else go to Step Xc

Xb Start WWT Blowdown Bypass Duration Timer.


• WWT Blowdown Bypass Duration Timer elapses, Go to Next Step OR

• Thickened Sludge tank Level > Clarifier Blowdown Halt level, Go to Next Step.

Xc Close WWT bypass valve (FV74153) to thickened sludge tank and open (FV58103)


• Turbidity < blowdown stop set-point, Go to Next Step OR • WWT Level > Clarifier Blowdown Halt level, Go to Next Step.

8.5.2 Staged Clarifier Blowdown

Operation and Control From the SCADA/HMI, the Operator shall be able to select a bypass of the WWT. The bypass will allow the Clarifier blowdown water to pass directly to the Thickened Sludge Tank. Two (2) actuated valves in the sludge line divert the flow to either the Thickened Sludge Tank or the WWT. When sludge is selected to flow to the Thickened Sludge Tank, the valve (FV58103) will close and valve (FV74153) will open.

When bypass is selected by the Operator on the SCADA/HMI, the blowdown can be selected to work on either the timer per valve or turbidity in the line. However, when blowdown path is to the WWT, the system works on a timer base only to provide a longer purge. If WWT bypass is selected by the Operator, the above clarifier blowdown sequence and the blowdown duration can be selected to blowdown bypass turbidity mode or blowdown bypass timer mode, where the condition for proceeding to the next blowdown valve will be determined by Operator selected turbidity set-point on the SCADA/HMI.

8.5.3 Clarifier Blowdown Interlock and Blowdown Blocking Timer Control

Operation and Control The frequency of Clarifier Blowdown is entered at the SCADA/HMI by the Operator. Clarifier blowdown is performed at least twice daily.

Blowdowns can only occur on one clarifier at a time. The clarifier requiring blowdown is therefore placed into a sequential first-in first-out (FIFO) queue. Clarifiers in this queue are blowdown sequentially according to their place in the queue.

The following conditions shall inhibit Clarifier from blowdown:

• Stage 1 filter backwash:

− When Stage 1 Filter Backwash Sequence in Wash Stage 3 and Wash Stage 4, i.e. when the Backwash Pump is running

− Inhibit Clarifier blowdown by a further 30 minutes to the Clarifier blowdown blocking time after the Backwash Pump has stopped (in wash stage 5).

• The Stage 2 filter backwash:


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− When stage 2 filter backwash sequence in Wash Stage 3 and to Wash Stage 5, i.e. when the backwash pump is running

− Inhibit Clarifier blowdown by a further 30 minutes to the Clarifier blowdown blocking time; after the Backwash Pump has stopped (in Wash Stage 7).

8.6 River Water Filters Reference P&ID drawings:

• 004-7032-I-5063 Rev. 0 (RIVER PLANT STAGE 1 FILTER NO. 5).




• 004-7032-I-5055 Rev. 0 (RIVER PLANT STAGE 2 FILTER NO. 9 INLET).

• 004-7032-I-5056 Rev. 0 (RIVER PLANT STAGE 2 FILTER NO. 9 OUTLET).







• 004-7032-I-5007 Rev. 2 (WASHWATER TANK).


Overview Eight (8) river water Filters are as follows:

• Four (4) River Plant Stage 1 Filters – single filter cells (Filters 5-8); and

• Four (4) River Plant Stage 2 Filters – double filter cells (Filters 9-12).

The presence of four (4) double filters actually results in 12 individual filter cells in total.

Each filter can be in one of the following states:

• Offline (out of service);

• Online Filtering (in service); and

• Online Backwash (in service).

Filter Aid Polymer Dosing is provided to enhance the filterability of the flocculants that carry over from the Clarifiers.

8.6.1 Stage 1 Filters

Operation and Control The routine operation of the filters will be under the automatic control of the Main PLC and SCADA/HMI.


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In normal operation, filters are backwashed due to operator intervention, high head loss or elapsed time. Backwashes can only occur on one filter at a time. Filters requiring backwash are therefore placed into a sequential first-in first-out (FIFO) queue. Filters in this queue are backwashed sequentially according to their place in the queue.

If a filter requires backwashing due to high turbidity it will take priority in the wash queue.

An ‘In Service’ filter is defined as a unit that is in filtration or backwashing.

An ‘Out of Service’ filter is defined as a unit that has been removed from service e.g. all filter inlet valves and outlet valves are closed, for maintenance or as a result of a fault and is unavailable for filtration.

Individual filters may be taken ‘Out of Service’ either manually or as a result of certain fault conditions.

Stage 1 Filter Consoles Eight (8) single filters, including Stage 1 River Filters No. 5-8, are currently controlled from four (4) filter console units. Each of these units currently has local indication and manual control within each filter console.

Remote automatic and manual control is provided by the Main PLC and SCADA/HMI system. Automatic PLC control of the Filter Backwash sequence can be initiated by the Operator from a button on the console or SCADA/HMI.

The Stage 1 Filter flow valves in the tables below are controlled from the Main PLC via a pneumatic valve.

Table 8-3 Stage 1 River Filters Flow Valves

Description Filter No. 5 Filter No. 6 Filter No. 7 Filter No. 8

Inlet Valve FV74501 FV74601 FV74701 FV74801

Dirty Backwash Outlet Valve FV74561 FV74661 FV74761 FV74861

Air Scour Valve FV74511 FV74611 FV74711 FV74811

Air Vent Valve FV74581 FV74681 FV74781 FV74881

Backwash Inlet Valve FV74551 FV74651 FV74751 FV74851

Outlet Flow Control Valve FCV74525 FCV74625 FCV74725 FCV74825

A level indicating transmitter (LIT15802) is installed to measure the water level in the River Filter Inlet Channel. This instrument is used for the Inlet Channel and Filter Outlet Flow Control of their respective filters.

A selected control band within the analogue level signal range will be configured within the Main PLC to linearly represent the desired set point filter flow rate range. The top of the level control band represents the maximum desired set point filter flow rate and the bottom represents zero set point flow.

All flow controllers will be identically configured (i.e. all filters will be operating to a common set point to ensure equal flow division). High and low channel level alarms will also be generated from the analogue level signal.

The following Stage 1 Filters instruments provide level, turbidity, differential pressure and flow controls to the PLC.

Table 8-4 Stage 1 River Filter Instruments


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Instrument Type Filter No. 5 Filter No. 6 Filter No. 7 Filter No. 8

Differential pressure PDT74571 PDT74671 PDT74771 PDT74871

Level switch LSL74501 LSL74601 LSL74701 LSL74801

Turbidity analyser AIT74533 AIT74633 AIT74733 AIT74833

Flow transmitter FIT74523 FIT74623 FIT74723 FIT74823

Backwash Queue Entry Permissive for Stage 1 Filters During normal service the filter will enter the Wash Queue under the following conditions:

• If the differential pressure transmitter in Stage 1 Filters detect a high differential pressure across the filter bed for a period in excess of the preset time, a high head loss signal is set;

• Operator selects filter to be backwashed;

• Hours operated since last backwash timer (operator adjustable set-point) is exceeded; and

• If the turbidity transmitter in Stage 1 Filters detects high turbidity from the output of the filter bed for a period in excess of the preset time, a high turbidity alarm signal is sent to SCADA and the filter is pushed to the top of the backwash queue.

Please note that a filter that is pushed to the top of the backwash queue due to high turbidity shall follow the same FIFO philosophy with regards to other filters that have generated a high turbidity alarm and entered the backwash queue i.e. they will enter at the top of the queue below the other filter that is in the queue due to the high turbidity alarm.

Stage 1 Filters Backwash Sequence The filters have the following wash stages:

1. Drain down.

2. Air scour.

3. Air venting.

4. High rate backwash.

5. Filter refill and media settling.

6. Slow start.

Stage 1 Sequence Start Permissive A filter backwash sequence shall start when the following conditions are satisfied:

• River water plant is operating;

• A filter is not running through a manual backwash process;

• Required filter # is at the top of the wash queue;

• A clarifier is not currently performing a blowdown;

• Level in the wwt is below the operator adjustable filter backwash inhibit level set-point;

• Filter # is not offline;

• For auto backwash sequence to operate, the filter shall be required to be in auto mode;


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• All filter # associated valves have not initiated an alarm;

• A air scour blower is available to operate; and

• A backwash pump is available to operate and not inhibited from the cwst low level.


Wash Stage 1: Drain Down (tags refer to the tables above) Drain Down Level

• When a filter enters a wash sequence:

− The ‘Filter No. # in Filtration Mode’ signal shall be removed

− Set ‘Filter No. # Washing’ and ‘Filter No. # Drain Down’ signals will be set at SCADA/HMI.

• Start ‘Drain Down Failure’ timer.

• The Filter No. # Inlet Valve shall close. The valve is set up to open or close over a set duration of time finalised during previous commissioning of the filters.

• Confirm that the Filter No. # Inlet Valve is closed within a preset time period.

• The Filter No. # Outlet Flow Control Valve shall continue to operate as previously described (flow control) in conjunction with the Common Filter Inlet Channel level. This shall allow the filter to drain down.

• When Level Switch is reached:

− The Filter No. # Outlet Flow Control Valve will close

− The Filter No. # Dirty Backwash Valve will open

− Filter No. # Air Scour Valve will open.

Wash Stage 2: Air Scour • When the Filter No. # Outlet Flow Control Valve is confirmed closed and the Filter No. # Dirty

Backwash Valve is confirmed as opened, and the Filter No. # Air Scour Valve is confirmed opened, the Main PLC will determine if there is sufficient volumetric capacity in the Dirty WWTs (based on LIT). If there is insufficient capacity a ‘Dirty WWT Available Time’ timer will start. If the timer expires prior to sufficient capacity being available an alarm will be raised. This alarm condition will not prevent continued progress of the Wash Sequence when sufficient capacity becomes available.

• When sufficient volumetric capacity in the Dirty WWTs is confirmed, send signal requesting Air Scour Blower operation

• Confirm an Air Scour Blower running signal within a preset time.

• When Air Scour Blower running signal is confirmed start ‘Filter Air Scour Time’ timer.

• When the ‘Filter Air Scour Time’ timer expires:

− Shut down the blower

− Close signal sent to Filter No. # Air Scour Valve

− Open signal sent to Filter No. # Air Vent Valve.

Wash Stage 3: Air Venting


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• When Filter No. # Air Scour Valve is confirmed closed and Filter No. # Air Vent Valve is confirmed opened, start a ‘Filter Venting Time’ timer and the ‘Backwash Delay Time’ timer.

• Start Backwash pumps and run on low rate set-point with filter # backwash inlet valve closed.

• Open signal sent to common backwash valve.

Wash Stage 4: High Rate Backwash • When the ‘Filter Venting Time’ timer expires, close Filter No. # Air Vent Valve. Note: Backwash is

permitted during venting if timers are appropriately set, additionally failure of the Filter No. # Air Vent Valve to be confirmed closed will not inhibit progress of the wash sequence.

• When the ‘Backwash Delay Time’ timer expires send signal to request a Backwash flow, and start the ‘High Rate Flow Totaliser’.

• When common backwash valve is confirmed open:

− Open filter # backwash inlet valve

− Ramp up backwash pump to backwash set-point.

• Confirm ‘Backwash Flow Established’ signal is present within a preset time.

• When the totalised Backwash flow is reached (nominally set between 3 and 5 filter bed volumes - Operator adjustable value), the Backwash Pumps will be stopped.

• When the Backwash Pumps are confirmed as stopped:

− Close the Filter No. # Backwash Inlet Valve

− Close Filter No. # Dirty Backwash Outlet Valve

− Close Common Backwash Valve.

Wash Stage 5: Filter Refill and Media Settling • When Filter No. # Backwash Inlet Valve and Filter No. # Dirty Backwash Outlet Valve are

confirmed closed, open Filter No. # Inlet Valve and start ‘Media Settling Time’ timer.

• Main PLC to check that Filter No. # Inlet Valve closed signal is removed.

• When ‘Media Settling Time’ timer expires allow next stage to proceed.

Wash Stage 6: Slow Start • When the Filter No. # Inlet Valve is confirmed opened; the outlet flow (Filter No. # Outlet Valve)

from the filter is gradually increased by ramping the PLC PID flow controller set point from zero at a preset ramp rate (10 m3 to 100 m3 / hour/minute).

• When the actual flow equals the inlet channel level derived set point the ramp adjustment is stopped and the inlet channel derived set point is applied to the PLC PID flow controller and the ‘Filter No. # Washing’ signal is removed. The next filter at the top of the Wash Queue will be permitted to start the Wash sequence.

Stage 1 Filters Wash Sequence Stop Condition Should the wash sequence fail for any reason, the respective filter shall attempt to be Isolated (shutdown).

During a wash sequence when a filter is put ‘off-line’ the flowing steps shall occur:


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• Raise an alarm i.e. ‘filter no. 1 isolation initiated’;

• Stop air scour blower if running;

• Stop backwash pump(s) if running;

• Close inlet valve if open;

• Close outlet flow control valve if open;

• Close air vent valve if open;

• When the backwash pump(s) is/are confirmed not running, close the backwash inlet valve if open and close dirty backwash outlet valve if open;

• When air scour blower is confirmed not running, close air scour valve if open; and

• Raise condition ‘filter no. 1 isolation successful’ or ‘filter no. 1 isolation not successful’ as applicable.

If the Isolation has been successful, filters can continue to enter the Washing Sequence as required. If a preset number of successive filters have an ‘Isolation Initiated’ signal e.g. 4 No., an ‘Excessive Filters Isolated’ alarm shall be raised and no further filters will be permitted to enter a wash sequence until the preset number is manually reset at SCADA/HMI.

If the isolation is not successful, the Main PLC shall determine if any further filters can enter the wash sequence by reference to the filter faults, backwash and air scour inhibits.

When a filter is in filtration a Fault is defined as the following:

• Filter No. # Inlet Valve failure or not opened;

• Filter No. # Outlet Valve 1 failure or closed;

• Filter No. # Outlet Flow Control Valve failure or closed;

• Filter No. # Backwash Inlet Valve failure or not closed;

• Filter No. # Dirty Backwash Outlet Valve failure or not closed;

• Filter No. # Air Scour Valve 1 failure or not closed;

• Filter No. # Level instrument failure; and

• Filter No. # Loss of Head instrument failure.

Monitoring and Indication The Stage 1 filter flow valves MV29240, FV29213 and those in Table 4 provide open and close status locally and to the SCADA/HMI display

The Stage 1 filter instruments in Table 5 monitor each existing river plant filters local panel and SCADA/HMI display.

Each differential pressure transmitter continuously monitors the total loss of head across each individual filter bed. The Operator can disable a high loss of head signal from initiating a wash via SCADA/HMI to allow instrument calibration.

Alarm Status The Stage 1 filter flow valves MV29240, FV29213 and those in Table 4 send a general operation fail alarm on a fail to open or close status to the SCADA/HMI.


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The Stage 1 river filter instruments in Table 5 send alarm status to the SCADA/HMI, except the flow transmitters.

If more than a preset number of filters exhibit high loss of head from a differential pressure transmitter at any time then an alarm is initiated, e.g. ‘Three Filters High LOH’.

8.6.2 Stage 2 Filters

Operation and Control The routine operation of the filters will be under the automatic control of the PLC / SCADA.

There are four (4) Stage 2 river water Rapid Gravity Filters, designed to remove small quantities of residual solids carried over from the upstream process stage.

In normal operation, if a filter requires backwashing due to operator intervention, high head loss or elapsed time it will remain on line until all other filters higher up the wash queue have been backwashed.

If a filter requires backwashing due to high turbidity it will take priority in the Wash Queue.

An ‘In Service’ filter is defined as a unit that is in filtration or backwashing.

An ‘Out of Service’ filter is defined as a unit that has been removed from service e.g. all filter inlet valves and outlet valves are closed, for maintenance or as a result of a fault and is unavailable for filtration.

Individual filters may be taken ‘Out of Service’ either manually or as a result of certain fault conditions.

Stage 2 Filter Consoles The routine operation of the filters will be under the automatic control of the Main PLC and SCADA/HMI.

Four (4) double filters are currently controlled from two (2) filter console units. Each of these units currently has local indication and manual control within each filter console.

Remote automatic and manual control is provided by the Main PLC and SCADA/HMI system. Automatic PLC control of the Filter Backwash sequence can be initiated by the Operator from a button on the console or from the SCADA/HMI displays.

The Stage 2 Filter flow valves in the tables below are controlled from the Main PLC via a pneumatic valve.

Table 8-5 Stage 2 Inlet River Filters Flow Valves



Outlet Flow Valve FV74121 FV74221 FV74321 FV74421



Table 8-6 Stage 2 Outlet River Filters Flow Valves




Outlet Flow Valve FV74131 FV74231 FV74331 FV74431


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The following Stage 2 Inlet and Outlet Filters instruments provide level, turbidity controls to the Main PLC.

Table 8-7 Stage 2 River Filters Instruments

Instrument Type Inlet/Outlet Filter No. 9 Filter No. 10 Filter No.11 Filter No. 12

Level switch Inlet LSL74101 LSL74201 LSL74301 LSL74401

High level switch Outlet LSH74102 LSH74202 LSH74302 LSH74402

Low level switch Outlet LSL74103 LSL74203 LSL74303 LSL74403

Turbidity analyser Outlet AIT74133 AIT74233 AIT74333 AIT74433

Differential pressure Inlet PDT74171 PDT74271 PDT74371 PDT74471

Filter Level Control and Filter Outlet Flow Control There is one pneumatic bubbler installation per 2nd stage filter, which maintains the water level in the Filter based on the pressure required to produce an air bubble. The bubble pressure is amplified via a pneumatic relay, which in turn supplies a variable pressure (0 to 10 psi) to the respective Filter Outlet Flow Control valve pneumatic positioning actuator.

There is no PLC control during the normal operation of the filters. The PLC and the local control desk can open and close the Filter Outlet Flow Control valve via digital signals to solenoid valves that supply full control pressure the positioning actuator to open the valve fully or vent to close the valve.

All flow controllers will be identically configured.

Backwash Queue Entry Permissive for Stage 2 Filters During normal service the filter will enter the Wash Queue under the following conditions:

• If the differential pressure transmitter in Stage 2 Filters detect a high differential pressure across the filter bed for a period in excess of the preset time, a high head loss signal is set;

• Operator selects filter to be backwashed;

• Hours operated since last backwash timer (operator adjustable set-point) is exceeded; and

• If the turbidity transmitter in Stage 2 Filters detects high turbidity from the output of the filter bed for a period in excess of the preset time, a high turbidity alarm signal is sent to SCADA and the filter is pushed to the top of the backwash queue.

Please note that a filter that is pushed to the top of the backwash queue due to high turbidity shall follow the same FIFO philosophy with regards to other filters that have generated a high turbidity alarm and entered the backwash queue i.e. they will enter at the top of the queue below the other filter that is in the queue due to the high turbidity alarm.

Stage 2 Filters Wash Sequence The filters have the following wash stages.

1. Drain down.

2. Air scour cell 1.


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3. Air scour cell 2.

4. Settle.

5. Backwash cell 1.

6. Backwash cell 2.

7. Filter refill and media settling.

8. Slow start.

Sequence Start Permissive Refer to the Stage 1 Filters backwash sequence – Sequence start permissive.

Wash Stage 1: Drain Down (tags refer to Stage 2 Filters tables) Filter Level is measured by level switch with the following:

• When a filter enters a wash sequence:

− the ‘Filter No. # in Filtration Mode’ signal shall be removed

− Set ‘Filter No. # Washing’ and ‘Filter No. # Drain Down’ signals will be set at SCADA/HMI.

• Commence ‘Drain down Failure’ timer.

• The Filter No. # Inlet Valve shall close. The valve is set up to open or close over a set duration of time finalised during previous commissioning of the filters. .

• Confirm that the Filter No. Inlet Valve is closed within a preset time period.

• The Filter No. # Outlet Flow Control Valve shall continue to operate as previously described (flow control); this shall allow the filter to drain down.

• When the inlet Level Switch is reached:

− the Filter No. # Outlet Flow Control Valve will close

− the Filter No. # Dirty Backwash Valve will open

− Filter No. # Cell 1 Air Scour Valve will open

− Filter No. # Cell 2 Air Scour Valve will remain closed.

Wash Stage 2: Air Scour Cell 1 • When the Filter No. # Outlet Flow Control Valve and the Outlet Valves are confirmed closed, and

the Filter No. # Dirty Backwash Valve is confirmed as opened, and the Filter No. # Air Scour Valve is confirmed opened the PLC will determine if there is sufficient volumetric capacity in the Dirty Washwater Tanks (based on LIT58100). If there is insufficient capacity a ‘Dirty Washwater Tank Available Time’ timer will start. If the timer expires prior to sufficient capacity being available an alarm will be raised. This alarm condition will not prevent continued progress of the Wash Sequence when sufficient capacity becomes available.

• When sufficient volumetric capacity in the Dirty Washwater Tanks is confirmed, send signal requesting Air Scour Blower operation.


• When Air Scour Blower running signal is confirmed start ‘Filter # Cell 1 Air Scour Time’ timer.


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• When the ‘Filter # Cell 1 Air Scour Time’ timer expires:


− Close Filter No. # Cell 1 Air Scour Valve

− Open Filter No. # Cell 2 Air Scour Valve.

Wash Stage 3: Air Scour Cell 2 • Confirm:

− Filter # Cell 1 Air Scour Valve is confirmed closed

− Filter # Cell 2 Air Scour Valve opened.

• PLC will send signal requesting Air Scour Blower operation.


• When Air Scour Blower running signal is confirmed start ‘Filter Air Scour Time’ timer.

• When the ‘Filter # Cell 2 Air Scour Time’ timer expires:


− Close Filter No. # Cell 2 Air Scour Valve.

Wash Stage 4: Settle • When Filter No. Air Scour Valve is confirmed closed and the blower confirmed stopped start the

‘Backwash Delay Time’ timer.

• Start Backwash pumps and run on low rate set-point with filter # backwash inlet valves closed.


Wash Stage 5: Cell 1 High Rate Backwash • When the ‘Backwash Delay Time’ timer expires:

− Send signal to request a Backwash flow

− Start the ‘High Rate Flow Totaliser’.


− Open filter # cell 1 backwash inlet valve


• Confirm ‘Backwash Flow Established’ signal is present within a preset time, signal from the relevant MCC.

• When the totalised Backwash flow is reached (nominally set between 3 and 5 filter bed volumes - operator adjustable value), the Backwash Pumps will be stopped.


− Close the Filter No. # Cell 1 Backwash Inlet Valve




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Wash Stage 6: Cell 2 High Rate Backwash • Start Backwash pumps and run on low rate set-point with filter # backwash inlet valves closed.



− Open filter # cell 2 backwash inlet valve


• Filter Outlet Valve and send signal to request a Backwash flow, and start the ‘High Rate Flow Totaliser’.

• Confirm ‘Backwash Flow Established’ signal is present within a preset time, signal from the relevant MCC.

• When the totalised Backwash flow is reached (nominally set between 3 and 5 filter bed volumes - operator adjustable value), the Backwash Pumps will be stopped.


− Close the Filter No. # Cell 2 Backwash Inlet Valve



Wash Stage 7: Filter Refill and Media Settling • When Filter No. # Backwash Inlet Valve and Filter No. # Dirty Backwash Outlet Valve are

confirmed closed, open Filter No. # Inlet Valve and start ‘Media Settling Time’ timer.

• Main PLC to check that Filter No. # Inlet Valve closed signal is removed.

• When ‘Media Settling Time’ timer expires allow next stage to proceed.

Wash Stage 8: Slow Start • When the Filter No. # Inlet Valve is confirmed opened, the level in the filter is allowed to rise until

the high level is achieved at which point the Filter No. # Outlet Valve is opened.

• On confirmation the outlet valves are open the PLC will release the control of the Outlet Flow Control via the pressure solenoid valves. The outlet flow from the filter is gradually increased by the pressure applied to the air bubbler system.

• When the actual flow equals the set point derived from the total flow equally shared between the 2nd stage filters in service, the ‘Filter No. Washing’ signal is removed. The next filter at the top of the Wash Queue will be permitted to start the Wash sequence.

Monitoring and Indication The Stage 2 inlet filter flow valves in Table 6, motorised valve MV24101 and the Stage 2 outlet filters flow valves in Table 7 provide local and SCADA/HMI display indicating open and close status.

The Stage 2 River filters instruments in Table 8 monitor each existing river plant filters local panel and SCADA/HMI display.



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Alarm Status The flow valves in the Stage 2 inlet filters flow valves, Stage 2 outlet filters flow valves (tables 6 and 7) and motorised valve MV24101 send alarms on a fail to open or close status to the SCADA/HMI.

The Stage 2 River Filters instruments in Table 8 send alarm status to the SCADA/HMI.


8.6.3 Air Scour Blower Control Reference P&ID drawing:

• 004-7032-I-5018 Rev.0 (BLOWERS).

Overview The Filter Air Scour system comprises two (2) blowers (BL63101 and BL63201). Each blower package comprises inlet silencer and filter, motor driven blower, pressure relief and unloading valves, and outlet silencer.

The fixed speed blowers shall operate in a Duty/Standby regime. In general, the blowers shall operate in conjunction with the RGF wash sequence. The blowers shall be called to operate during the following Wash Stages:

• Stage 1 filters – Wash Stage 2; and

• Stage 2 filters – Wash Stage 2 and Wash Stage 3.

Operation and Control The blower BL63101 and BL63201 can be started and stopped manually via push buttons located on the local filter control desk and from the SCADA/HMI.

The Operator can select the Air Scour Blower to either Duty or Standby. The Duty/Standby drives shall operate as per the Drives and Duty/Standby control philosophy in Appendix C.

The blowers are started and stopped by the Main PLC as part of the automatic Filter Wash Sequence. A ‘Running’ signal is passed to Filter Wash sequence, if the ‘Running’ signal is not maintained in accordance with the Filter Wash sequence the Standby Air Scour Blower shall be requested to operate during the next Filter Wash.

The air blowers shall perform this mode of control if a filter is in Wash Stage 2 (Stage 1 filters) and Wash Stage 2 and Wash Stage 3 (Stage 2 filters) of the wash sequence. Under this control the duty blower shall start upon receipt of the ‘Perform Air Scour’ signal from the filter wash control. The duty blower shall be required to run for the Operator adjustable ‘Filter Air Scour’ time period. Once this time period has expired the filter wash sequence shall enter Wash Stage 3: ‘Air Venting’ for Stage 1 filters or Wash stage. The blower shall then stop.

If the duty air scour blower starts, and 10 seconds later (fixed time interval) a low or no flow signal is registered with the Main PLC, the following shall occur:

• The duty blower shall shut down;

• The existing standby blower shall start;

• Running standby blower status shall be changed to duty; and


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• The faulted blower shall be pushed to manual and an alarm sent to the scada/hmi displays it indicate air scour blower failed to operate correctly.

Start Permissive The blowers shall require all filter back wash permissives (refer to Stage 1 and Stage 2 backwash sequence start permissive) and blower availability

Stop Condition and Interlock Automatic filter washing (including blowers) will be inhibited by any of the following conditions:

• Respective filter service selection is in the Manual position;

• Respective filter has a fault;

• An air scour blower is not available;

• Back wash pump(s) is/are not available;

• Air scour inlet valves are not closed for all other filters that are selected for automatic control;

• Backwash inlet valves are not closed for all other filters that are selected for automatic control;

• WWT high level alarm activated; and

• Clearwater Storage Tank low level alarm activated.

In event that the required air flow is below the required flow set-point, the Duty Air Scour Blower will stop and the standby Air Scour Blower shall start.

Blowers can be stopped manually at a local control station (emergency stop or LCS stop) and by the Main PLC (fault stop, sequence stop, manual stop through SCADA)

Monitoring and indication A flow transmitter (FIT63111) monitors the flow from the Air Scour Blower and provides indication locally and to the SCADA/HMI.

Alarm status When air is below the required flow set-point an alarm shall be initiated and displayed in the SCADA/HMI to warn the Operator that there is a problem with the respective Air Scour Blower and start the standby blower and changes its status to duty. The flow transmitter FIT63111 sends flow alarm to the SCADA/HMI.

8.6.4 Filter Backwash Reference P&ID drawing:

• 004-7032-I-5014 Rev. 2 (TREATED WATER AREA - CLEARWATER STORAGE TANK).

Overview Filter wash is also referred as backwash.

Treated water for the backwashing of the filters is drawn from the Clearwater Storage Tank (CWST) TK52001.

Operation and Control


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Two (2) variable speed backwash pumps (PD52001 and PD52011) operate under the control of the Main PLC to provide clean water to a filter during the backwash sequence. The pumps operate on a duty/standby basis. One (1) pump operates to meet the requirements of the high rate backwash. Each pump will operate under Main PLC control to achieve the high rate set point.

The Backwash valve (FV52010) is controlled by a pilot solenoid (FV52013) and can be actuated via local control station or SCADA/HMI.

Manual Control The pumps and backwash valve FV52010 can be started and stopped via push buttons and controls located on the local control panel.

Automatic Control Backwash pump control (PD52001/PD52011)

The variable speed pumps shall operate in a duty/standby regime.

In general, the backwash pumps shall operate in conjunction with the filter wash sequence. The pumps shall be called to operate during the following wash stages (see below for further details):

• Stage 1 filters:

− Wash Stage 3 – ‘Air Venting’

− Wash Stage 4 – ‘High Rate Backwash’.

• Stage 2 filters:

− Wash Stage 4 – ‘Settle’

− Wash Stage 5 – ‘Backwash Cell 1’

− Wash Stage 6 – ‘Backwash Cell 2’.

The duty pump’s speed shall be controlled by the Main PLC, to achieve and maintain desired flow rate applicable to the wash stage. The backwash flow shall be measured using flow meter FIT52010.

The Operator can select the backwash pumps to either duty or standby at the SCADA/HMI. The duty/standby drives shall operate as per the drives and duty/standby control philosophy in Appendix C. Starting and stopping of the backwash pump is controlled from the filters backwash sequences as per existing filters backwash sequences.

Backwash Pumps Backwash Control

The backwash pumps shall perform this mode of control if a filter is in the ‘Backwash’ stage of the wash sequence. Under this control the duty pump is required to operate and the pump shall start on receipt of the Backwash Signal from the filter backwash control.

A PID loop control shall then switch to Auto and the loop algorithm shall modify the pump speed in order to maintain the desired backwash flow set-point. This set-point should decrease as temperature (TT52001) decreases due to the increase in viscosity, to reach the optimal backwash flow rate.

The backwash pump shall perform this control until the desired Backwash Flow set-point has been reached. Failure to achieve the flow-rate shall abort the wash sequence and an alarm raised on SCADA/HMI.

Totalising of the Backwash Flow shall commence at the start of the Backwash stage.


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PID Loop Control The backwash control employs an individual PID loop to control the speed of the backwash pump. Two (2) separate set-points shall be automatically entered into the PID loop algorithm depending on the particular mode of control being undertaken. The Process Variable (PV) of the loop shall be the measured value of backwash flow meter FIT52010.

In general, if the pump set is not operating due to pump failure, instrument failure or an inhibit on pumping then the associated PID loop shall be switched to Manual mode of operation. The loop shall only be switched back to Auto mode when conditions exist permitting the pump to operate.

Start Permissive In event that the required backwash flow is below the required flow set-point, the Standby Backwash Pump shall start.

Stop Condition and Interlock Automatic filter washing will be inhibited by any of the following conditions:

• Respective filter service selection is in the Manual position;

• Respective filter has a fault;

• Air scour blower(s) is/are not available;

• Backwash pump(s) is/are not available;

• Air scour inlet valves are not closed for all other filters that are selected for automatic control;

• Backwash inlet valves are not closed for all other filters that are selected for automatic control;

• WWT high level alarm activated; and

• Clearwater Storage Tank low level alarm activated.

The pumps PD52001 and PD52011 shall be inhibited if an overflow is detected at the dirty WWT inlet by level switch LSH58101.

If level switch LSL52001 indicates a low level in Clearwater Storage Tank then the backwash pump is stopped.

Monitoring and Indication Backwash flow transmitter FIT52010 monitors the flow from the backwash pumps and provides local and SCADA/HMI displays.

Backwash valve FV52010 provides open or closed status locally and to the SCADA/HMI display.

The Main PLC shall monitor the Washwater flow and display the instantaneous value on the SCADA/HMI. During the Backwash stage the flow shall be monitored. If the measured flow, while in Backwash, exceeds the Backwash High Flow set-point for a period of time (60 seconds) then an alarm shall be raised on the SCADA/HMI.

During the Backwash stage the Main PLC shall totalise the flow by taking the instantaneous flow and flow duration to totalise the volume of water. The accumulated flow shall be displayed at the SCADA/HMI and used to determine the end of the Backwash stage (see above). The totalised flow shall be reset at the end of the associated RGF wash sequence.


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Flow transmitters (new magflow FIT52031 and existing venturi) connected to the BT line provides flow and the new magflow also provides volume indication locally and status display at the SCADA/HMI.

The following instruments provide SCADA/HMI display:

• Temperature transmitter TT52001 monitors the temperature at the existing Clearwater Storage Tank; and

• Low level switch LSL52001 monitors the level in the tank.

Alarm Status When clean water in the CWST is below the required low level switch (LSL52001) an alarm shall be initiated to warn the Operator that there is a problem with the Duty Backwash Pump.

If the measured flow for Backwash, exceeds the Backwash High Flow set-point for a period of time (60 seconds) then an alarm shall be raised on the SCADA/HMI.

Failure to operate shall cause the Backwash Valve (FV52010) to generate a general alarm to the SCADA/HMI.

The following instruments will provide signals for alarm to the SCADA/HMI:

• Two (2) flow switches at the CWST outlet FS52032 and FS52033 to the BT lines;

• Flow switch FS52002 at the Backwash Pump No.1;

• Flow switch FS52012 at the Backwash Pump No. 2; and

• Level switch LSL52001 when sending a low level signal.

9 BORE WATER TREATMENT

9.1 Filters 1-4 Feed Source Selection Reference P&ID drawing:



Overview As part of the Nebo Road WTP upgrade, the current Bore Filters (Stage 1 Filters 1-4) will be converted to treat either Bore Water or river water. This will be achieved by new interconnecting feed pipe work, pneumatically actuated valves and control logic.

Operation and Control Stage 1 and Stage 2 river water feed electric actuated valves (MV29240 and MV24101) from the clarifiers can be controlled locally via local control station or via the SCADA/HMI.

The selection of either Bore Water or river water as the feed source for Filters 1-4 is made by the Operator at the SCADA/HMI.

The clarifier to filter stage 1 connection valves are actuated by solenoid valves FV15602 and FV29214 to operate their respective flow valves FV15601 and FV29213.


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The Operator can set the operation of Filters 1-4 to either Auto or Offline mode:

• In Auto mode, the operation of the Delay Tanks changeover valves will depend on the Filters 1-4 feed water selection (river water or Bore Water); and

• In Offline mode, the feed water to Filters 1-4 is shut off. However, the WTP can still operate in river water mode. In river water mode, the river water is directed to Filters 5-8 and Filters 9-12 but not to Filters 1-4.

When Filters 1-4 feed source is selected to Bore Water mode, the Filters 1-4 will start operating in accordance with the current control philosophy for Bore Water Filters operation.

9.1.1 Filters 1-4 River Water Mode

Operation and Control When the Filters 1-4 operation is selected to Auto mode and feed water for the Filter 1-4 is selected to river water mode, the following shall occur:

• Clarifier to filters 1-4 connection valve FV15601 shall open, feeding river water to Delay Tank 1 (TK15701), then to Filters 1-4;

• Relift duty pump (PD15501 or PD15502) shall shut down;

• Clarifier to filters 5-8 connection valve FV29213 shall remain open, feeding river water to Delay Tank 2 (TK15801), then to Filters 5-8; and

• Bore water operation shall shutdown and disable.

Please note: The control philosophy for river water trough level control for Filters 1-4 will be same as the existing river water trough level control for Filters 5-8, however operating independently. In river water mode, the control philosophy for Filters 1-4 outlet flow control shall be the same as for existing Filters 5-8 outlet flow control, however operating independently.

Stop Condition and Interlock When the Operator select the Filter 1-4 to offline from river water mode, the Filters 1-4 and the Filters 1-4 Filter Aid Polyacrylamide Dosing System will cease operation, irrespective of whether the river water mode start conditions are satisfied.

9.1.2 Filters 1-4 Bore Water Mode

Operation and Control When the Filters 1-4 operation is selected to automatic and feed water for the Filters 1-4 is selected to bore water, the following occurs:

• Clarifier to filters 1-4 connection valve FV15601 shall close;

• Relift duty pump (PD15501 or PD15502) shall start, feeding bore water to Delay Tank 1 (TK15701), then to Filters 1-4;

• Clarifier to filters 5-8 connection valve FV29213 shall remain open, feeding river water to Delay Tank 2 (TK15801), then to Filters 5-8; and

• River water operation shall shutdown the feed to filters 1-4 if the Mixed River/Bore Water Mode is not selected. In Mixed River/Bore Water Mode, the valve FV15601 shall remain open, feeding river water to Filters 1-4 via Bore filters Delay Tank (TK15701).


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The relift pumps can be started by an Operator locally using a local control station or the SCADA/HMI system.

Start Filter Permissives A bore filter operation sequence shall start when the following conditions are satisfied:

• Bore water plant is operating, including flow ≥ 20L/s;

• Bore water mode is selected;

• Filter is not ‘offline’. This shall include filters put ‘offline’ due to head loss alarm and waiting to undergo backwash sequence;

• Bore filter # associated valves have not initiated an alarm; and

• The filter is not undergoing backwash sequence.

Start filter sequence is initiated when all start permissive and start conditions are satisfied.

When the flow meter (FIT29241) detects a flow ≥ 20 L/s, the following will be initiated:

• Filters 1-4 will commence operation (as per current Filters 1-4 control philosophy); and

• Filters 1-4 Filter Aid Polyacrylamide Dosing System commences operation as described in river water filters operation.

Filters 1-4 receive clarified river water in line with the other twelve filters. Filters 1-4 then commence operation in river water mode when the river plant start conditions are satisfied.

The bore plant commences operation in accordance with the current control philosophy.

Stop Condition and Interlock Filters 1-4 are set to offline from bore water mode, Filters 1-4 and all other bore plant systems will cease operation including caustic soda or KMNO4 dosing systems, irrespective of whether the Bore Mode Start conditions are satisfied.

Monitor and Indication The clarifier to river filter connection valves (FV15601 and FV29213) shall provide open or closed status locally and via the SCADA/HMI displays.

Alarm Status If any of the clarifier to river filter connection valves (FV15601 and FV29213) failed to open or close, an alarm will be raised for the related valve.

If any of the relift pumps failed to operate, an alarm will be raised for the related pump.

9.2 Bore Water System Reference P&ID drawing:

• 004-7032-I-5012 Rev. 0 (EXISTING AERATION BASIN).


• 004-7032-I-5015 Rev. 2 (TREATED WATER AREA – BALANCE TANK).


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Operation and Control Filters 1-4 online operation sequence will remain unchanged and the existing sequence shall be retained. A series of eight (8) Bore Pumps convey water from the bore field to the Bore Water Plant, via the Aeration Basin. Bore Pumps are controlled via the radio telemetry system and are manually started by the Operator. The Bore Pumps are not started automatically.

The Bore Water Plant flow rate depends on the number of operating Bore Pumps that can only be varied by starting or stopping one (1) or more Bore Pumps.

Start Permissive A bore filter operation sequence shall start when the following conditions are satisfied:

• Bore water pumps are available and/or running;


• Bore water feed mode is selected;

• At least one filter is not ‘offline’. This shall include filters put ‘offline’ due to head loss alarm and waiting to undergo backwash sequence;

• A bore water associated valve has not initiated an alarm;

• Relfit pumps are available and not initiated an alarm;

• Caustic soda dosing system is available;

• KMNO4 dosing system is available; and

• BT level < WTP start level.

Start filter sequence is initiated when all start permissive and start conditions are satisfied.

When selected to automatic, the operating sequence of Filters 1-4 (whether in River Mode or Bore Mode) will start operating when the level in the Operator selected BT Duty system falls below the WTP Start Level set-point. If any critical system is unavailable, an alarm will be raised and Filters 1-4 will not commence operation.

When power is restored at the treatment plant after power failure, the system will not restart automatically and will require to be re-started by the Operator.

Stop Condition and Interlock When the selected BT level rises above the WTP Stop Level set-point, all the bore water feed pumps will stop.

The following events will also cause the bore pumps to stop:

• Bore pumps failed to run (None of Bore Water Pumps 1 – 8 ‘Running’ feedbacks from the telemetry system are active during pump operation);

• Bore water flow rate falls below 20L/s during bore water plant operation;

• WTP has a power failure (for ≥ 10 minutes);

• Change of Filters 1-4 feed source to river water.

Monitoring and Indication Relift pumps running shall be indicated locally and to the SCADA/HMI displays.


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An existing bore water venturi flowmeter (FIT15031) provides flow monitoring and indication locally and to the SCADA/HMI.

A pH analyser transmitter (AIT15701) shall monitor the water pH in the bore water inlet channel (TK15701) and indicate locally and on the SCADA/HMI displays.

The pH analyser shall send an analyser alarm to the SCADA/HMI.

Alarm Status If a bore pump fails to start following a command, a ‘Failed to Start’ alarm for that bore pump is initiated. If all bore pumps fail to start an alarm shall be generated.

If the existing bore water venture flowmeter (FIT15031) fails to operate a general alarm shall be sent to the SCADA/HMI.

9.2.1 Bore Water Oxidation System – Relift Tank Reference P&ID drawings:


• 004-7032-I-5024 Rev. 2 (POTASSIUM PERMANGANATE (KMnO4) DOSING PUMPS).

Overview Aerated bore water gravitates into the Relift Tank. KMNO4 is dosed into the bore water to oxidise dissolved manganese for removal in the filtration process.

For detail on the KMNO4 batching and dosing system refer to the Chemical dosing section.

Operation and Control The KMNO4 dosing is controlled by running the dosing pumps. It is not controlled by a solenoid valve.

Stop Condition and Interlock The Relift Tank Low Level Switch LSL15501 will stop the Relift Pumps if it is running to prevent dry-running of the pumps inhibiting any pump to start.

Monitoring and Indication A Relift Tank low level sensor LSL15501 monitors the low water level in the Relift Tank and automatically starts and stops the Duty Relift Pump.

Alarm Status A Low Relift Tank level switch will initiate an alarm if the levels fall outside the normal operating range.

9.2.2 Bore Water Caustic Soda Dosing – Relift Tank Reference P&ID drawings:

• 004-7032-I-5031 Rev. 2 (BORE WATER CAUSTIC SODA DOSING).

• 004-7032-I-5003 Rev. 2 (INLET WORKS).

Overview


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Caustic soda is dosed in this location to control pH. It is dosed into relift tank and the relift pumps assist in mixing the caustic soda with the bore water.

For operation detail on the caustic soda batching and dosing system refer to the Chemical dosing section.

Operation and Control The caustic soda dosing is controlled from the Main PLC and SCADA/HMI.

The caustic soda dosing point is controlled by the solenoid valve FV66348.

Stop Condition and Interlock Related To Relift Tank The following will shut down the caustic dosing in the relift tank:

• Bore water within pH Operator adjustable high and low set-points;

• Bore pumps failed to run (None of Bore Water Pumps 1 – 8 ‘Running’ feedbacks from the telemetry system are active during pump operation);

• Bore water flow rate falls below 20L/s during bore water plant operation;

• WTP has a power failure (for ≥ 10 minutes);

• Change of Filters 1-4 feed source to river water;

• All filters are ‘offline’. This shall include filters put ‘offline’ due to head loss alarm and waiting to undergo backwash sequence.

• A bore water associated valve has initiated an alarm; and

• Relift pumps are not available and initiated an alarm.

9.2.3 Relift Pumping Reference P&ID drawing:


Overview Two (2) Relift Pumps (PD15501 and PD15502) transfer dosed bore water from the Relift Tank to the inlet chamber. These pumps are Archimedes Screw type pumps that transfer water present at the screw intake – therefore the pump flow rate always equals the bore water flow rate without the need for variable speed drives.

Caustic soda and KMNO4 dosing shall occur in the relift tank using the pumps to assist with mixing.

Operation and Control The Relift Pumps are controlled from the Main PLC, SCADA/HMI and local control station.

The Operator can select each Relift Pump to Auto, Manual or Off with the SCADA/HMI. The Operator can select Pump No.1 or Pump No.2 to duty.

Relift Tank Low Level Switch (LSL15501) provides level and sequence control to the Main PLC. The Start and Stop levels are filtered by delay timers linked to LSL15501 to prevent unnecessary starting and stopping of the pumps.

Start Permissive


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The relift pump operation shall start when the following conditions are satisfied:

• Bore water pumps are available and/or running;


• Bore water feed mode is selected;

• At least one filter is not ‘offline’. This shall include filters put ‘offline’ due to head loss alarm and waiting to undergo backwash sequence;

• A bore water associated valve has not initiated an alarm;

• Relift pumps are available and not initiated an alarm;

• Relift Tank level rises above the Relift Tank Low Level Switch (LSL15501) by an Operator’s adjustable time delay period;

• Caustic soda dosing system is available;

• KMNO4 dosing system is available; and

• BT level < WTP start level.

Start pump sequence is initiated when all start permissive and start conditions are satisfied.

Stop Condition and Interlock The Relift Tank Low Level Switch (LSL15501) will trip the running pump and will inhibit the operation of the Relift Pumps.

The relift pumps will go through the normal shutdown procedure if FV15601 fails to close correctly.

The relift pumps will continue to operate if FV15601 is open and Mixed River/Bore water mode otherwise the pumps will go through normal shutdown procedure.

Alarms Failure of the relift pumps to start or stop shall generate a fail to start or fail to stop alarm to the SCADA/HMI displays. A Operator adjustable delay timer (0-120 seconds) shall be used to ensure that repeated stopping and started does not occur.

9.2.4 Delay Tanks Reference P&ID drawing:


Overview The existing delay tanks (stage 1) and flow splitter (stage 2) shall not be changed from the existing control philosophy.

Polymer is dosed into the stage 1 delay tanks and stage 2 flow splitter.

Operation and Control The analyser transmitter AIT15701 at the existing bore filter delay tank, level transmitter LIT15802 to the existing river plant and the bore plant transmitter LIT15702 provide control signals to the Main PLC. These levels are used to modulate the stage 1 filter outlet valves in order to maintain a set level in the existing Stage 1 delay tanks.


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Monitoring and Indication Analyser transmitter AIT15701 at the existing bore filter delay tank (TK15701) monitors the pH level and provides local and SCADA/HMI display.

Level transmitter LIT15802 from the existing River Plant and Level transmitter LIT15702 from the existing Bore Plant provide signals for the local and SCADA/HMI displays.

Alarm Status The analyser and level transmitters send alarms status to the Main PLC and SCADA/HMI.

9.2.5 Bore Water Filters Reference P&ID drawings:


• 004-7032-I-5067 Rev. 0 (STAGE 1 FILTER NO. 1).




Overview Four (4) Stage 1 Filters have single filter cells (Filters 1-4).

The control and monitoring of these filters is the same as that for the river water filters – refer to Section 8.6 for full operating descriptions.

Operation and Control Note: all filters use the same common backwash pumps and air blowers. Therefore only one (1) filter can be in backwash at any given time. This will occur automatically through SCADA/HMI.

Eight (8) single filters, including Stage 1 Bore Filters No.1-4, are currently controlled from four (4) filter console units. Each of these units currently has local display and manual control within each filter console. Remote automatic and remote manual control is provided by the Main PLC and SCADA/HMI system. Automatic PLC control of the filter sequence can be initiated by the Operator from a button on the local control station or on the SCADA/HMI display.

The Stage 1 filters 1 – 4 flow valves in the tables below are controlled from the Main PLC via a pneumatic solenoid valve.

Table 9-1 Stage 1 Bore Filters Flow Valves





Air Vent Valve FV75181 FV75281 FV75381 FV75481




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A level indicating transmitter (LIT15702) installed to measure the water level in the Bore water Inlet Channel. This instrument shall be used for the Inlet Channel and Filter Outlet Flow Control of their respective filters.

The following Stage 1 Filters instruments provide level, turbidity, flow and head loss controls to the Main PLC.

Table 9-2 Stage 1 Filter Instruments

Instrument Type Filter No. 1 Filter No. 2 Filter No. 3 Filter No. 4

Differential pressure PDT75171 PDT75271 PDT75371 PDT75471

Level switch LSL75101 LSL75201 LSL75301 LSL75401

Turbidity analyser AIT75133 AIT75233 AIT75333 AIT75433

Flow transmitter FIT75123 FIT75223 FIT75323 FIT75423

Queue Entry Permissive During normal service, if the differential pressure transmitter in Stage 1 detects a high differential pressure across the filter bed for a period in excess if the preset time, a high head loss signal is set. The filter will then enter the wash queue.

Monitoring and Indication The Stage 1 filter flow valves MV29240, FV15601 and those in Table 9 provide local and SCADA/HMI display indicating open and close status.

The Stage 1 filter instruments in Table 10 monitor each existing bore plant filters and provide indication to each local panel and to the SCADA/HMI.


Alarm Status The Stage 1 Filter flow valves in Table 9 send alarms on a fail to operate (open or close) status to the SCADA/HMI.

The Stage 1 Filter instruments in Table 10 send alarm status to the SCADA/HMI, except the flow transmitters.


Stage 1 Filters Wash Sequence The backwash sequence of these filters is the same as the stage 1 filters 5-8 backwash sequence. For further details refer to Stage 1 River Filters section.


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10 COMMON FILTERED WATER TREATMENT

10.1 Clearwater Well Reference P&ID drawing:

• 004-7032-I-5014 Rev. 2 (TREATED WATER AREA - CLEARWATER STORAGE TANK).

Overview Filtered water from both the river water System and the Bore Water System combine in the Clearwater Well. Filtered water overflows this tank and passes to the Balance Tank (BT) network. The Clearwater Well also serves as a backwash and service water holding tank.

The following chemicals can be dosed in the clear water storage tank:

• Caustic soda (in CWST);

• Chlorine dosing (injection point in pipe work to BTs); and

• Fluoride dosing (injection point in pipe work to BTs).

Operation and Control For detail on the Backwash pumps refer to the Filter Wash section.

For detail on the above chemical dosing systems refer to the Chemical Dosing section.

Stop Condition and Interlock A low level switch (LSL52001) inhibits the backwash pumps from starting. This will also trip any running pumps and inhibit the backwash sequence from starting until the low level switch is deactivated and the water level is above the required low level.

Monitoring and Indication A new temperature transmitter (TT52001) monitors the temperature of the filtered water. The temperature is displayed at the SCADA/HMI for determining:

• Backwash flow rate (the optimal backwash flow rate should decrease as temperature decreases, due to the increase in viscosity).

Alarm Status Low level switch (LSL52001) will raise an alarm to SCADA/HMI.

10.2 Filtered Water Chemical Dosing Reference P&ID drawing:

• 004-7032-I-5015 Rev F (TREATED WATER AREA - BALANCE TANK).

Overview Filtered water passing from the Clearwater Well to the BT network undergoes post dose alkali (caustic soda) dosing for pH correction, chlorine disinfection and dosing of fluoride.


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The chlorine and fluoride is injected into the filtered water pipe between the Clearwater Well and the Distribution Splitter Pit, as close to the Clearwater Well as practicable.

The caustic soda is injected into the back end of the clear water storage tank.

The treated water tested as a side-stream unit drawing sample water via two (2) sample pumps (PD52111 and PD52121) from the Distribution Splitter Pit.

Splitter Pit New Sample Pump (PD52121) draws water for the Fluoride analyser in the Laboratory.

Splitter Pit Existing Sample Pump (PD52111) draws water for the chlorine and pH analyser located in the filed at the distribution splitter pit (TK52101).

For operation detail on the caustic soda, chlorination and fluoride systems refer to the Chemical dosing section.

Start Permissive When the filtered water flow rises above a minimum flow rate (nominally 50 L/s, Operator adjustable) post dose alkali and chlorination systems, and fluoridation system (set at 100 L/s) operate.

Stop Condition and Interlock For detail on the stop conditions and interlocks refer to the appropriate dosing system under the Chemical Dosing section.

11 TREATED WATER STORAGE AND PUMPING WATER

Treated water is pumped from the BT to the distribution system by four (4) High Lift Pumps connected in parallel. These pumps transfer water from Nebo Road WTP to the Mt Pleasant Reservoir, with a portion of the transferred water entering the reticulation system en route. Water then gravitates from Mt Pleasant Reservoir to Mt Oscar Reservoir, with water feeding the reticulation system from both reservoirs.

11.1 Balance Tanks Reference P&ID drawing:

• 004-7032-I-5015 Rev 2(TREATED WATER AREA - BALANCE TANK).

Overview Three (3) BTs (TK53001, TK53101 and TK53201) receive all treated water from the WTP prior to distribution. The capacities of TK53001 & TK53101 are 2.27 ML, while TK53201 has a capacity of 4.5 ML (9.0 ML total peak capacity). The maximum water depth in the tanks is 4.2 m, with overflow at 4.3 m.

Operation and Control The preferred operating regime is to see a significant rise and fall in the levels in the BT over the course of a day. These levels ensure that a significant turn-over of water occurs eliminating short-circuiting and dead-spots where major chlorine residual decay can occur. Furthermore, a minimum 30 minute contact time is required prior to discharge. At a peak flow rate of 75 ML/d, this corresponds to 1.56 ML.


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Currently, plant Operators achieves this level change by manually adjusting the High Lift transfer rate and the plant feed flow rate from Dumbleton Weir. Several changes are performed daily on the basis of the prevailing demand, time of day and Operator experience.

Monitoring and Indication A common level transmitter (LT53001) located in BT No.1 provides continuous monitoring over the water level both in BT No1 and 2. These tanks are directly coupled giving equal rise and fall indication.

A dedicated level transmitter (LT53201) in BT No.3 monitors its level. Due to a restriction on flow into BT No.3, the level in this tank is not always equal to that in the other two (2) tanks. This occurs because inflow to BT No.3 is from BT No.1 via a 300 mm scour pipe rather than the originally intended 980 mm inlet pipe from the flow splitter pit. The original inlet pipe was located too close to the outlet pipe, allowing short-circuiting to occur in this tank, and therefore providing the conditions for a significant chlorine residual decay.

The PLC shall monitor BT level transmitters rate of change versus time to identify a malfunctioning device. A delay timer (Operator adjustable 0 to 600 seconds) shall be used to stop nuisance alarms from being generated.

LT53001 in BT1 shall be chosen as the primary device with LT53201 in BT3 the secondary. LT53201 will change state to primary on failure of the LT53201. The Operator shall be able to select which device shall be the primary instrument.

When LT53201 is selected to primary an alarm shall be generated.

Water is drawn from the Existing Distribution Splitter Pit (TK52101) by existing and new sample pumps (PD52111 and PD52121). Sample pump PD52121 provides water to the Laboratory for:

• Fluoride analysis.

Sample pump PD52111 provides water to the following field mounted analysers:

• Chlorine analysis.

• pH analysis.

These analysers provide local and SCADA/HMI display.

Provision shall be made for future devices LSL53002 and LSH53003 for BT1 and LSL53202 and LSH53203 for BT3 to monitor for level transmitter failure and provide backup alarms.

Alarm Status High and Low Level Alarm set-points are provided for each of the BT level transmitters and displayed at the SCADA/HMI. Failure or malfunction of the level transmitters shall initiate and alarm to the SCADA/HMI displays.

Provision shall be made for low and high level alarms for future devices LSL53002 and LSH53003 for BT1 and LSL53202 and LSH53203 for BT3 and to monitor for level transmitter failure.

The final water chlorine and pH analysers include Operator adjustable high and low residual alarms.

The fluoride analyser sends concentration data to the PLC and alarms are generated and sent to the SCADA/HMI. For detail on this system refer to the Fluoride dosing section under Chemical dosing.


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11.2 Mt Pleasant Reservoir Reference P&ID drawing:

• 004-7032-I-5016 Rev. F (HIGH LIFT PUMP STATION).

Operation and Control The preferred operating regime is to see a significant rise and fall in the level in the Mt Pleasant Reservoir over the course of a day to ensure a significant turn-over of water occurs. Operators report that the Mt Pleasant Reservoir level varies between 6.0 – 9.4 m, with 3.0 m the minimum allowable level (1.5 m results in no water in higher parts of Mackay). The capacity of Mt Pleasant Reservoir is 54.46 ML, corresponding to the TWL of 9.6 m, and this equates to 5.673 ML/m. Therefore, a rise and fall of 3.4 m/d equates to 19.3 ML.

Currently plant Operators achieve this level change by manually adjusting the High Lift transfer rate, with several changes performed daily on the basis of the prevailing demand, time of day and Operator experience. The previous day’s demand is a strong indicator of what the current days demand would be unless rain or other significant events impact on demand.

Stop Condition and Interlock When the communication (heart beat signal) is lost on the RTU, the HLPS pumps are shutdown by the Main PLC if the communication is not re-instated after a set duration (5-60 minutes) and the Main PLC indicates a ‘Mt Pleasant Reservoir Communications Failure’ alarm.

1. Where communications are lost the pump station shall continue operating for set ‘Communications Lost Duration’ timer (Operator adjustable between 5-60 minutes and expected to be 5 minutes). Timer to be set no longer than the maximum operational time of the UPS.

2. Once timer is exceeded shutdown the high lift pumps feeding the Mt Pleasant reservoir.

3. SCADA will generate a Mt Pleasant reservoir communication failure alarm

4. If the Mt Pleasant reservoir communication failure alarm is not acknowledge in a preset time at the WTP SCADA, then the Mt Pleasant reservoir communications failure alarm is escalated and dialled out to the appropriate personnel.

5. The ‘Communications Lost Duration’ timer should be reset every time the heartbeat is received. This restarts the timer at zero again and prevents it reaching its timeout value.

6. When a High Lift Pump is selected to local the communications failure alarm shall not inhibit the pump from running.

Monitoring and Indication A level transmitter monitors the level in the Mt Pleasant Reservoir, and transmits this signal back to Nebo Road WTP via telemetry.

Provision shall be made for future devices Low and high level float switches to monitor for level transmitter failure and provide backup alarm signals back to Nebo Road WTP via telemetry.

The level in the Mt Pleasant Reservoir will be displayed in the SCADA/HMI.

Alarm Status High and Low Level Alarm set-points are provided in the SCADA/HMI to alert the Operator to an irregular level allowing them to take the appropriate corrective action.


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Provision shall be made for low and high level alarms for the future float switches and to alarm for level transmitter failure.

On RTU communications failure between Mt Pleasant reservoir and the WTP a ‘Mt Pleasant Reservoir Communications Failure’ alarm is displayed at the WTP SCADA/HMI displays. If this alarm is not acknowledged it shall be escalated and dialled out to the appropriate personnel.

11.3 Mt Oscar Reservoir Reference P&ID drawing:


Operation and Control The preferred operating regime is to see a significant rise and fall in the level of the Mt Oscar Reservoir over the course of a day to ensure that a significant turn-over of water occurs. The capacity of Mt Oscar Reservoir is 13.01 ML, corresponding to the TWL of 6.86 m, and this equates to 1.897 ML /m.

Since Mt Oscar Reservoir is fed by gravity, this storage is monitored by Operators but no actual controls, other than high and Low level alarms, are provided.

Stop Condition and Interlock When the communication (heart beat signal) is lost on the RTU, the HLPS pumps are shutdown by the Main PLC if the communication is not re-instated after set duration (5-60 minutes) and the Main PLC indicates a ‘Mt Oscar Reservoir Communications Failure’ alarm.

1. Where communications are lost the pump station shall continue operating for set ‘Communications Lost Duration’ timer (Operator adjustable between 5-60 minutes and expected to be 5 minutes). Timer to be set no longer than the maximum operational time of the UPS.

2. Once timer is exceeded shutdown the high lift pumps feeding the Mt Oscar reservoir.

3. SCADA will generate a Mt Oscar reservoir communication failure alarm

4. If the Mt Pleasant reservoir communication failure alarm not acknowledge in preset time at WTP SCADA, then the Mt Oscar reservoir communications failure alarm is escalated and dialled out to the appropriate personnel.

5. The ‘Communications Lost Duration’ timer should be reset every time the heartbeat is received. This restarts the timer at zero again and prevents it reaching its timeout value.

6. When a High Lift Pump is selected to local the communications failure alarm shall not inhibit the pump from running.

Monitoring and Indication A level transmitter monitors the level in the Mt Oscar Reservoir, and transmits this signal back to Nebo Road WTP via telemetry.

Provision shall be made for future devices Low and high level float switches to monitor for level transmitter failure and provide backup alarm signals back to Nebo Road WTP via telemetry.

The level in the Mt Oscar Reservoir will be displayed in the SCADA/HMI.

Alarm Status


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High and Low Level Alarm set-points are provided in the SCADA/HMI to alert the Operator to an irregular level, and allow them to take the appropriate corrective action.

Provision shall be made for low and high level alarms for the future float switches and to alarm for level transmitter failure.

On RTU communications failure between Mt Pleasant reservoir and the WTP a ‘Mt Pleasant Reservoir Communications Failure’ alarm is displayed at the WTP SCADA/HMI displays. If this alarm is not acknowledged it shall be escalated and dialled out to the appropriate personnel.

11.4 Treated Water Pumping (High Lift Pump Station) Reference P&ID drawing:


• 004-7032-I-5017 Rev. B (HIGH LIFT PUMP STATION - DISCHARGE).

Overview The pumps can be selected to ‘Remote/Off/Local’ via a selector switch on the switchboard. Under normal operating conditions the selector switch shall be in the Remote position with level sensors at Mt Pleasant Reservoir controlling the pumps. Operators may configure the start stop levels, tariff policy selection, the pumps mode (Duty or Standby) or minimum pump speed through the touch screen interface or at the SCADA host.

Once Local is selected, the operator has full local control (via local pushbuttons) which disables the Nebo Rd WTP PLC and SCADA from automatically starting the associated pump. In local mode, hardwired protections (overloads etc) are still available. Level protection (draining balance tanks or overfilling Mt Pleasant Reservoir) is not active in this mode. When a pump is out of service for any reason, the selector switch shall be set to Off locally and prohibited from starting. When Remote mode is selected, the operators have full control of the pump station via the SCADA. The operators can select to run pumps manually or automatically via SCADA.

A hardwired interlock prevents more pumps than the hydraulic design can manage running at the same time. No more than three pumps shall be permitted to run at the High Lift Pump Station at the same time.

The control of the pumps is overseen by a tariff policy selection which determines the maximum number of pumps that are permitted to operate at different times of the day (peak/off-peak).

The Mt Pleasant Reservoir has a Kingfisher RTU which monitors the reservoir level via a level transmitter. Future provision is required for the reservoir to have backup float switches for low and High High level control. If High Lift pumpstation pumps run in automatic mode and communications is lost (heartbeat) between Mt Pleasant Reservoir and Nebo Rd WTP or the High High float is activated, then the pumps should stop.

Operation and Control The six (6) High Lift Pumps (PD53101, PD53201, PD53301, PD53401, PD53501 and PD53601) are controlled from the Main Plant PLC. Automated pumping control shall be incorporated based on Operator adjustable reservoir level set-points. The Operator shall be able to configure the level set-points, such that the set-points will be associated with a timeframe to enable peak/off-peak tariff control and ensure the reservoirs water is cycled through to ensure there is not a chemical dead band in the reservoir.


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In this operation mode the Operator selects the level set-point, the tariff policy and the Main PLC controls the duty cycle and speed of the pumps to best achieve the required set-point.

All available pumps will be set in priority order queue by the Operator by assigning a duty preference (Duty 1, Duty 2 and Duty 3) on the SCADA/HMI displays. Pumps not selected for duty shall be placed in the queue as standby pumps.

The duty 1 pump shall start and stop at the duty 1 start and stop level, duty 2 pump shall operate between the duty 2 start and stop levels and the duty 3 pump shall operate between the duty 3 start and stop levels. The remaining three pumps if available will be standby in case one of the selected duty pumps fail.

The duty 1 pump shall start and run at minimum speed (typically 50%). This configurable parameter shall be defined by the operator through the SCADA/HMI displays. Whilst the level in Mt Pleasant Reservoir remains above the configured start level, the duty 1 pump shall continue to operate at minimum speed until the stop level is reached. When the stop level is reached the duty pump shall be stopped. If the level at Mt Pleasant Reservoir decreases below the duty 1 pump start level, the duty 1 pump speed shall be varied (increased) once per minute in order to run proportional to the incoming flow. At an operator configurable level, the duty 1 pump shall be running at maximum speed.

If the reservoir level continues to decrease and the duty 2 start level is reached, the duty 1 pump shall continue to run at maximum speed and the duty 2 pump shall be started at minimum speed. If the level at Mt Pleasant Reservoir continues to decrease and falls below the duty 2 start level, the speed of duty 2 pumps shall be varied once per minute in order to run proportional to the incoming flow. At an operator configurable level both duty pumps shall be running at maximum speed. If the reservoir level increases to the duty 2 pump stop level, the duty2 pump shall stop and the duty 1 pump will continue until the duty 1 pump stop level is reached at minimum speed.

The operation of duty 3 pump will be similar in theory to the duty 1 and 2 pump operation described above.

Should the duty pump fail to run for any reason, an alarm shall be raised and the standby pump brought into operation.

For detail on the VSD operation and duty cycle philosophy please refer to Appendices B & C.

Level transmitter (LIT54502) in the existing High Lift Pump Station dry well will control the sump pumps (PU54501 and PU54502) to remove excess water from the dry well.

The operational philosophy with 3 duty pumps above is overseen by a policy selection. Even if the pump is requested to start, the policy may lock it out until the correct conditions are met. Nebo Rd WTP is on Ergon Tariff 43 with peak times between 0700 – 2300 Monday to Friday and Off-Peak at all other times. The way tariff 43 is structured, it is advantageous to maximise pumping during off-peak hours. Taking demand into account, the operators are given three policy options for automatic pumping. The policies are below:

Policy Number Off-Peak (Max available Pumps) Peak (Max available Pumps)

1 2 1

2 3 2

3 3 3


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Start Permissive The high lift pump automatic sequence shall start when the following conditions are satisfied:

• BT1 or BT3 low-low level switch is not activated;

• Low level alarm (Operator adjustable set point) on the selected BT is not activated;

• At least one high lift pump is set to remote and healthy and available;

• High level alarm (Operator adjustable set point) at Mt Oscar is not activated;

• High level alarm (Operator adjustable set point) at Mt Pleasant is not activated;

• High-High level switch at Mt Oscar is not activated (future provision);

• High-High level switch at Mt Pleasant is not activated (future provision);

• High level switch (LSH54501) for HLPS dry well is not activated;

• Communications with Mt Oscar RTU is healthy; and

• Communications with Mt Pleasant RTU is healthy.


A high lift pump shall be able to be started in local manual when the pump is healthy. For this situation the Operator shall be required to monitor safety related concerns for the BTs, reservoirs or HLPS.

Stop Condition and Interlock The high lift pump automatic sequence shall stop and be inhibited when a minimum of one of the following conditions are satisfied:

• BT1 or BT3 low-low level switch is activated The Operator can bypass this inhibit by running the High Lift Pumps in local mode to enable cleaning or maintenance in the BTs;

• Low level alarm (Operator adjustable set point) on the selected BT is activated. The pump inhibit will not be released until the Low-Low and Low level alarms are no longer active;

• All high lift pumps are not set to remote and/or not healthy and/or not available;

• High level alarm (Operator adjustable set point) at Mt Oscar is activated;

• High level alarm (Operator adjustable set point) at Mt Pleasant is activated;

• High-High level switch at Mt Oscar is activated (future provision);

• High-High level switch at Mt Pleasant is activated (future provision);

• High level switch (LSH54501) for HLPS dry well is activated;

• Communications with Mt Oscar RTU is not healthy; and

• Communications with Mt Pleasant RTU is not healthy.

Where Duty pump flow rate is below the Main PLC set-point for duration of 5 minutes the Duty pump shall be shut down, forced to remote local mode and alarmed. A standby pump or combination of pumps will be moved to Duty and replace the tripped pump.

A high level alarm at either Mt Oscar or Mt Pleasant reservoirs will stop and inhibit the running of the high lift pumps until the reservoir levels are below the Operator adjustable reservoir level set point.


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Monitoring and Indication Piping in the existing High Lift Pump includes incoming and outgoing pressure indicators for local monitoring.

Flow meters (FIT53521 and FIT53522) monitor the high lift pumps flow rate for local and SCADA/HMI display.

A high level switch (LSH54501) will monitor the level in the existing High Lift Pump Station dry well.

Level transmitter LIT54502 provides a signal to the Main PLC and SCADA/HMI for monitoring of the HLPS sump and control of the sump pumps.

An additional Final Water Fluoride Analyser (AIT52103) monitors the fluoride residual of the treated water entering the BT and the distribution system - sample drawn off from the high-pressure side of the High Lift Pumps. This provides continual online monitoring of the fluoride residual exiting the Nebo Rd WTP.

This analyser provides local and SCADA/HMI display.

Alarm Status The following alarms shall be sent to and displayed at the SCADA/HMI displays:

• High Lift Pump Flow set-point (Operator adjustable) and High and Low Flow Alarm Set-points;

• Activation of The High Lift Pump Station dry well High level switch (LSH54501);

• High level alarm (Operator adjustable set point) at Mt Oscar is activated;

• High level alarm (Operator adjustable set point) at Mt Pleasant is activated;

• High-High level switch at Mt Oscar is activated (future provision);

• High-High level switch at Mt Pleasant is activated (future provision);

• Communications with Mt Oscar RTU is not healthy;

• Communications with Mt Pleasant RTU is not healthy; and

• Sump pump (PU54501 and PU54502) generate a general alarm.

The High Lift Pumps will generate alarms and send them to the SCADA/HMI displays based on the type of fault that occurs. The minimum alarms for the motor and VSD shall include:

• Motor not available;

• motor over temperature;

• bearing over temperature;

• motor control system not healthy; and

• VSD not healthy.

12 SLUDGE HANDLING SYSTEM

A HMI is located at the Dewatering Building for the monitoring and control of the Sludge Handling System. The HMI will also provide plant monitoring overview of critical items and alarms status.

The sludge handling system shall have the capacity to operate 24 hours a day, 7 days a week.


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The centrifuge and dewatered sludge collection system shall only be permitted to operate, as stated above, when the WTP has an Operator on site to initiate and monitor the centrifuge and dewatered sludge handling system

12.1 Washwater Tank Reference P&ID drawing:

• 004-7032-I-5007 Rev. H (WASHWATER TANK).

• 004-7032-I-5008 Rev. G (SLUDGE THICKENER TANK).

Overview The wash water tank (WWT) periodically receives waste flows from the Clarifier Blowdown and Filter Backwash processes.

Three (3) Washwater Transfer Pumps (PU58201, PU58211 and PU58221) are installed with Pump No.1 as Duty, Pump No.2 as Duty/Assist and Pump No. as Standby to transfer the liquid to the Sludge Thickener Tank (TK58301).

A submersible mixer (MX58100)is used to stop solids from settling out in the Washwater Tank (TK58101).

The Washwater Tank can be bypassed for the clarifier blowdown process.

12.1.1 Tank and Tank Mixer

Operation and Control WWT Mixer (MX58100) operates continuously when the Washwater System is enabled by the Operator and the WWT level (LIT58100) exceeds a Mixer Inhibit Level set-point (Operator adjustable on SCADA/HMI).

The mixer (MX58100) can be operated locally at a LCS.

The level transmitter (LIT58100) at the WWT and flow transmitter (FIT58201) provide level and flow control via data sent to the Main PLC.

Level switches (LSH58101, LSL58102 and LSLL58103), transmitter (LIT58100) provide mixer control via signals sent to the Main PLC.

Start Permissive The mixer operation shall start when the following conditions are satisfied:

• WWT Level (LIT58100) is above the mixer inhibit level set-point;

• WWT level is within the level band of operation;

• Low level switch LSL58102 is deactivated; and

• Low low level switch LSLL58103 is deactivated.


Mixer Inhibit Level will have a built-in hysteresis and a time delay filter to prevent unnecessary starting and stopping.

Stop Condition and Interlock


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If the WWT level is below the Mixer Inhibit Level set-point or LSL58102 or LSLL58103 is activated, the Mixer will stop to prevent Mixer mixing air into the WWT or damaging the mixer.

Clarifier blowdowns are inhibited if the level (LIT-58100) in the WWT exceeds a Blowdown Inhibit Level set-point (Operator adjustable). This prevents a Clarifier blowdown from starting if there is insufficient capacity in the WWT to accept the full blowdown volume.

When the level in the WWT (LIT58100) exceeds a Backwash Alarm set-point, the backwash sequence will not commence.

The Clarifier blowdowns and Filter backwashes shall stop on WWT High Level Switch (LSH58101).

Monitoring and Indication The level of the WWT is monitored by level switches (LSH58101, LSL58102 and LSLL58103) and a level transmitter (LIT58100) with local and SCADA/HMI display.

A flow indicating transmitter (FIT58201) monitors the flow and indicates locally and to the SCADA/HMI displays.

Alarm Status If there is insufficient capacity in the WWT to accept the full backwash volume when a Filter Backwash is initiated, i.e. when the level in the WWT (LIT-58100) exceeds a Backwash Alarm set-point, an alarm will indicate that the WWT is in danger of overflowing.

Two (2) Backwash Alarm set-points are available at the SCADA/HMI, one (1) for a single filter and the other for a double filter which requires more tank volume to handle the additional backwash flow.

WWT High Level Switch (LSH58101) shall initiate an alarm to warn the Operator that an overflow is imminent.

An alarm will be initiated when flow is detected via flow switch (FS58191) on the overflow to the Kaliguil Lagoon.

12.1.2 Wash Water Transfer Pumps

Operation and Control Washwater transfer is an automatic operation.

The three (3) Washwater Pumps (PU58201, PU58211 and PU58221) are controlled from the Main PLC according to the Duty/Standby control philosophy.

The pumps will operate in a Duty1 /Duty2 /Standby configuration. These are submersible pumps located in the WWT. The Washwater Transfer Pumps transfer Washwater to the Sludge Thickener based on the WWT Duty1 and Duty2 Start and Stop Level Operator adjustable set-points.

The Operator can select any WWT Transfer Pumps to Duty1/Duty2/Standby at the SCADA/HMI, however the main PLC shall also provide the choice of using a designated duty cycle. When the WWT Level (LIT58100) reaches the Duty1 Start Level, the Duty1 Pump VSD controller will be energised if the Duty1 Pump is selected to Auto.

Level switches (LSH58101, LSL58102 and LSLL58103), transmitter (LIT58100) and pressure switches (PS58204, PS58214 and PS58224) provide pump control via signals sent to the Main PLC.


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The Duty1 Pump speed demand signal to VSD controller is normally set to a minimum speed (nominally 50%) unless the Operator entered a different value at the SCADA/HMI. This will continue until the WWT level reaches above the Duty2 Start Level or drops below Duty1 Stop Level.

If the level in the WWT increases above the Duty1 Start Level the Duty 1 Pump speed will be varied once per minute in order to run proportional to the incoming flow, to a maximum speed at a level just below the Duty2 Pump Start Level.

When WWT Level reaches the Duty2 Start Level, the Duty1 pump shall drop from maximum speed to the lowest minimum speed defined for both Duty Pumps, and the Duty2 Pump shall be started at this same speed. Note: Whilst an Operator can set different minimum speeds for each pump, the two pumps shall always operate at the same speed. This will continue until the WWT level drops below Duty2 Stop Level.

If the level in the WWT increases above the Duty2 Start Level the Duty Pumps speed will be varied once per minute in order to run proportional to the incoming flow, to a maximum speed set by the Operator for both pumps running.

When there is a need to carry out a clarifier purge under low flow, the Operator will manually adjust the Duty1 Pump Speed at the SCADA/HMI to the required WWT Transfer Flow Rate. The light sludge conditions are best performed at a lower thickener rise rate.

When WWT Level drops below the Duty2 Stop Level, the Duty 2 Pump will stop and the Duty 2 VSD controller de-energised. Duty1 pump shall ramp up to maximum speed and then be proportionally controlled by the tank level.

When WWT Level drops below the Duty 1 Stop Level, the Duty 1 Pump will stop and the Duty 1 VSD controller de-energised.

In event of Duty 1 or Duty 2 Pump trip, the Standby Pump will start (VSD controller energised). The Standby Pump will operate at maximum speed (default speed) unless Operator enters a different value at the SCADA/HMI. The tripped Duty 1 and/or Duty 2 Pump will be forced to Manual. The Standby Pump will take over the function of Duty 1 or Duty 2 Pump as appropriate.

For detail on the VSD operation and duty cycle philosophy refer to Appendices B & C.

Note: For automatic sequencing of the pump Start/Stop based on WWT Levels, the required pumps must be selected to Auto.

Start Permissive The pump operation shall start when the following conditions are satisfied:

• WWT Level (LIT58100) reaches the Duty# Start Level;

• WWT level is within the level band of operation;

• Duty# Pump is selected to Auto;

• Low level switch LSL58102 is deactivated;

• Low low level switch LSL58103 is deactivated; and

• Pressure switch for the respective pump is deactivated.


Stop Condition and Interlock The pump operation shall stop when any of the following conditions are satisfied:


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• WWT Level (LIT58100) reaches the Duty# Stop Level;

• WWT level is below the level band of operation;

• Duty# Pump is selected to manual while pump is running in Auto;

• Low low level switch LSL58103 is activated;

• Pressure switch for the respective pump is activated; and

• Turbidity from AIT58333 is above the turbidity level set point.

Stop pump sequence is initiated when any of the above conditions are satisfied.

The pumps will be inhibited until low level switch LSL58102 is deactived.

If one of the pressure switches (PS58204, PS58214 and PS58224) are activated the associated pump shall be shut down and switched to manual. The Operator shall be required to manually operate the pump or change back to Auto mode. This may cause all three pumps to trip if there is a blockage further along the pipeline.

Turbidity from AIT58333 is above the turbidity level set-point at the overflow of the sludge thickener tank, shall stop the WWT transfer pumps and inhibit them from running in Auto, The transfer pumps shall be required to be run in remote manual or local by the Operator until the turbidity level drops below the turbidity level set-point. This will then remove the inhibit on the Auto operation of the transfer pumps.

Monitoring and Indication The Wash water transfer pumps and pressure switches are monitored and provide indication back to the SCADA/HMI.

Alarm Status The following alarms will get initiated and sent to the SCADA/HMI display:

• Washwater Transfer Pump 1 (PU58201) failure to operate;

• Activation of pressure switch (PS58204) indicating a pipe line blockage;





• Flow transmitter (FIT58201) will initiate a low flow alarm; and

• Washwater at duty2 start level and duty1 pump not at maximum speed.

If the level in the WWT reaches the Duty 2 Start level while operating in a Clarifier purge condition, an alarm will be initiated to prompt the Operator to take actions. The Operator can either increase the Duty 1 Pump Speed to increase the flow rate or to discontinue with the low flow clarifier sludge operation.

12.2 Sludge Thickener Reference P&ID drawings:

• 004-7032-I-5007 Rev. H (WASHWATER TANK).



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• 004-7032-I-5009 Rev. H (THICKENED SLUDGE TANK).

Overview Washwater is pumped to the Sludge Thickener from the WWT. Polymer Dosing (if enabled) occurs during wash water transfer to further thicken the wash water and sludge. This encourages faster settling in the Sludge Thickener Tank and minimises sludge dump volumes.

A continuous operating sludge rake pushes the settled thickened sludge into the sump, discharging sludge under gravity from the bottom of the Sludge Thickener Tank (TK58301) to the Thickened Sludge Tank (TK58401).

Operation and Control Polymer Dosing occurs automatically when the Polymer Batching System is placed on line and at least one (1) Washwater Transfer Pump is running. The Washwater flow measured by flow meter (FIT58201) must also be greater than the set flow rate.

De-sludging of the Sludge Thickener is an automatic operation and is performed periodically. A Sludge Dump Interval set-point (0 – 60 minutes), Operator adjustable on SCADA/HMI) governs the period between sludge dumps.

A Sludge Dump Duration set-point (0 – 60 seconds, Operator adjustable on the SCADA/HMI) governs the length of time that the Sludge Dump Valves (FV58312 and FV58322) remain open. The sludge dump operation will not start until the Thickened Sludge Tank level drops below the Operator adjustable inhibit high level set-point.

The sludge dump valves (FV58312 and FV58322) are actuated via pilot solenoids and will have Auto/Manual/Off selection on the SCADA/HMI. When the valve is selected to Auto, the de-sludging operation will be automatic. Automatic operation is disabled when the Operator selects the valve to Manual. This allows the Operator to carry out the de-sludging operation manually.

A turbidity analyser transmitter (AIT58333) at the overflow of the sludge thickener tank, to Kaliguil Lagoon, provides turbidity monitoring and control to the Main PLC. A high turbidity set-point (Operator adjustable) shall be used to notify the Operator that remedial action is required to reduce the turbidity of the outflow to Kaiguil Lagoon and stop WWT transfer in Auto mode into the Sludge Thickener tank.

In general, as the sludge rake is in continuous operation, the rake shall able to be started and stopped via local LCS or remote manual on the SCADA for maintenance purposes.

Start Permissive The automatic de-sludging operation starts when the following conditions are satisfied:

• Either of the sludge dump valves (FV58312 or FV58322) are available;

• Valve(s) is/are selected to Auto;


• Sludge Dump Interval timer has finished ; and

• TST below inhibit high level set-point.

De-sludging sequence is initiated when all start permissive and start conditions are satisfied.

The sludge rake does not have any start permissives.


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Stop Condition and Interlock Polymer Dosing ceases if no Washwater Transfer Pump is running or washwater less than a pre-determined level.

De-sludging shall stop when the Sludge Dump Duration timer has finished.

De-sludging will be inhibited (the Sludge thickened Dump Valve(s) will be forced closed) when Thickened Sludge Tank reaches a High level (LSH58403) or the Sludge Thickener Tank activates a low level switch (LSL58302)..

The sludge rake shall be stopped when the over-torque switch is activated. This shall be used to notify the Operator that intervention is required to remove a possible obstruction that has stopped the rake.

Monitoring and Indication A Sludge Thickener Low Level Switch (LSL58302) monitors for a fault with the sludge dump system. Since the thickener operates at overflow level, a Low level will only be present if no inflow occurs while dumping continues as usual. Low level also results if the dump mechanism is releasing too much sludge either due to inappropriate settings or a valve fault.

Analyser transmitter (AIT58333) at the sludge thickener tank overflow monitors the turbidity for local and SCADA/HMI display.

Alarm Status The following alarms, when initiated, are sent to the SCADA/HMI:

• Sludge Thickener Scraper (SCP58301) fault will occur on over-torque (YA58301) or general failure to operate;

• Sludge Thickener Low level switch(LSL58302) is activated for 30 seconds;

• Sludge Thickener High level switch (LSH58303) is activated for 30 seconds. This indicates that the decant is about to over flow back into the Washwater Tank (TK58101);

• Sludge Thickened Dump Valve (FV58312 or FV58322) fails to operate (open or close); and

• Turbidity from AIT58333 is above the high turbidity level set-point (at the sludge thickener tank overflow to Kaliguil Lagoon), and will initiate a high turbidity alarm.

12.2.1 Supernatant Collection and Disposal

Overview Sludge Thickener supernatant disposal occurs whenever the level in the Sludge Thickener is at the decant level.

No other equipment is associated with this system and supernatant gravitates directly to Kaliguil Lagoon.

A take-off with manual valve supplies water to the Botanic Gardens.

Monitor and Indication An additional overflow is provided for levels exceeding the normal decant level for the cases of a blocked decant line. This goes to the WWT as this indicates a problem with the decant process.

Alarm Status


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As described above, a High level alarm switch will indicate the level has risen and is approaching an overflow event.

12.3 Thickened Sludge System Reference P&ID drawings:


• 004-7032-I-5009 Rev. H (THICKENED SLUDGE TANK).

Overview Thickened sludge is dumped from the Sludge Thickener Tank to the Thickened Sludge Tank. The sludge is then pumped to the Centrifuge System by dedicated Sludge Pumps, one (1) per centrifuge.

Polymer Dosing (if enabled) occurs during transfer, injected into the line midway on the pipe to the centrifuge to further thicken the sludge and optimise the performance of the Centrifuges.

Three (3) Thickened Sludge Pumps with Pump No.1 (PD58401) on Duty, Pump No.2 (PD58411) on Standby and Pump No.3 (PD58421) on Duty/Assist are located on a slab outside the Thickened Sludge Tank.

A VSD driven continuous operation mixer (MX58402) is in the thickened sludge tank to keep the solids in suspension.

Operation and Control The centrifuges are linked to their dedicated pumps with the Operator initiating the centrifuge start under normal conditions.

If a failure of pumps and centrifuges results in the available pumps not matching the available centrifuges, the system will indicate that the centrifuges cannot be started normally. In this situation the Operator will need to select the components from the available pumps and centrifuges. To do this the Operator will need to select a manual start pop-up screen which will indicate as follows:

• The available pumps and centrifuges will be indicated by normal colour convention. From this information the Operator will decide which valves to set for the desired flow paths;

• The Operator will need to locally configure the valves in the field to suit the available valves;

• The valve and flow path status can be confirmed on screen after selection. An allowance shall be made within the SCADA for all the manual inter-connecting valves (eight in total) to have limit switches installed. Where the limit switches are not installed the operator shall be able to confirm his manual selection on the SCADA to assist with pump operation;

• If required, the Operator can alter the valve configuration if the initial selection did not match the available equipment;

• The valves will be interlocked to the valve configuration and available centrifuges. A correct valve switching profile will enable the permissive for a particular pump to start;

• The valve interlock will prevent a centrifuge from starting unless a flow path from an available pump has been established; and

• The flow meter selected for flow monitoring will be dependent on the inter-connecting valves matrix.

The following service water supply line pneumatic valves are controlled from the Main PLC :


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• Pilot solenoid FV68003 actuates Centrifuge No. 2 service water pneumatic valve (FV68002);

• Pilot solenoid FV68013 actuates the Split to Centrifuge No. 1 and No. 2 service water pneumatic valve (FV68012); and

• Pilot solenoid FV68023 actuates Centrifuge No. 1 service water pneumatic valve (FV68022).

Level transmitter (LIT58400) at the thickened sludge tank and flow meters (FIT58401 and FIT58421) on the two (2) centrifuge lines provide respective level and flow monitoring and indication locally and to the Main PLC.

Start Permissive The Thickened Sludge Mixer MX58402 is a continuous operation mixer. When it has stopped it will only start when the Operator selects it to start and the low level switch LSL58402 is not active.

The automatic pump operation shall start when the following conditions are satisfied:

• The respective dedicated centrifuge is running and healthy;

• The dewatered sludge handling system associated with the dedicated centrifuge is running and healthy;

• Valve and flow path is confirmed on SCADA;

• Pump(s) is/are selected to Auto;

• TST level is within the level band of operation;


• Low low level switch LSL58401 is deactivated; and

• Pressure switch for the respective pump is deactivated.


For remote manual, once the centrifuge indicates back to the SCADA/HMI that it is running and healthy, the Operator can start the dedicated pump which will be indicated on the screen.

Stop Condition and Interlock The automatic pump operation shall stop when any of the following conditions are satisfied:

• The respective dedicated centrifuge is not running and/or not healthy;

• The dewatered sludge handling system associated with the dedicated centrifuge is not running and/or not healthy;

• Valve and flow path is not confirmed on SCADA;

• Pump(s) is/are selected to manual;

• TST level is above the level band of operation;

• low level switch LSL58402 is activated;

• low low level switch LSL58401 is activated; and

• Pressure switch for the respective pump is activated.



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A Low level alarm (LAL58402) at the Thickened Sludge Tank stops the running of the Thickened Sludge tank Mixer.

The valves will be interlocked to the valve configuration and available centrifuges. A correct valve switching profile will enable the permissive for a particular pump to start.

The valve interlock will initiate a normal shutdown procedure where a centrifuge runs without feedstock and the Feedstock Fail Duration timer finishes, unless a flow path from an available pump has been established.

Monitoring and Indication The thickened tank pumps and mixer are monitored and indicated to the SCADA/HMI displays.

Thickened Sludge flow is measured by the Thickened Sludge flow meters (FIT58401 and FIT58421) on each sludge line with local and SCADA/HMI display.

Thickened Sludge tank level is monitored by a level transmitter (LIT58400) with local and SCADA/HMI display.


• Thickened Sludge Low-Low level switch (LSLL58401) is activated for 30 seconds;

• Thickened Sludge Low level switch (LSL58402) is activated for 30 seconds;

• Thickened Sludge High level switch (LSH58403) is activated for 30 seconds. This indicates that the tank is about to over flow back into the Washwater Tank (TK58101);

• Thickened Sludge Pump 1 (PD58401) failure to operate;






• Thickened Sludge Mixer (MX58402) failure to operate;

• Centrifuge 1 Flow transmitter (FIT58401) will initiate a high or low flow alarm. High and low flow alarms are triggered if the transfer flow rate falls outside maximum and minimum values (set during commissioning) for 30 seconds;

• Centrifuge 2 Flow transmitters (FIT58421) will initiate a high or low flow alarm. High and low flow alarms are triggered if the transfer flow rate falls outside maximum and minimum values (set during commissioning) for 30 seconds;

• Dilution service water flow valves (FV68002, FV68012, FV68022 and FV68032) failed to operate (open or close); and

• Dilution service water supply flow switches (FS68002, FS68012 and FS68022) will initiate a low flow alarm when the associated service water flow valve is signalled to open.


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12.4 Centrifuge System Reference P&ID drawing:

• 004-7032-I-5010 Rev. H (SLUDGE DEWATERING).

Overview Three (3) centrifuges dewater the thickened sludge from the thickened sludge pumped to the system. Initially only two (2) centrifuges will be installed, the third centrifuge being unavailable and installed at a later dates.

Under normal conditions, a single centrifuge is capable of treating the full thickened sludge volume. Only during the highest solids loading events will the systems two (2) centrifuge systems operate.

Dewatered sludge is discharged to a conveyor system that loads the skips. The skips are trucked offsite for disposal when full.

Centrate is returned to a Centrate Tank (TK57001) for return to the WWT by fixed speed sump pumps.

Operation and Control The Centrifuges are individual vendor package units complete with their own PLC and HMI for local control and monitoring. An interface to the Main PLC and SCADA/HMI will be provided for each local HMI for remote control and monitoring including system status, faults, critical events and alarms via Ethernet communications and a fibre backbone.

The Operator selects one (1) centrifuge to operate (normal water quality conditions) or two (2) centrifuges to operate (poor water quality conditions). When a single centrifuge is only required, they operate in a Duty /Assist/Standby mode. When two (2) Centrifuges are required, they are operated independently. Duty selection is performed by the Operator on screen.

Polymer is dosed in the thickened sludge prior to entering the centrifuges. The flow valves from Centrifuge Polymer Dosing System (FV65065 and FV65055) are controlled from the Main PLC.

Stop Condition and Interlock The centrifuges operate independent of the status of the Washwater Transfer System and Supernatant System.

The respective centrifuge will be inhibited by the Main PLC when an alarm is generated by the centrifuge dedicated dewatered sludge conveyor system.

Where the thickened sludge pumps fail to operate the centrifuges will not be allowed to run for a continuous Feedstock Fail Duration set-point (operator adjustable between 0-60 minutes, this does not include the start up time of the centrifuge).

Monitoring and Indication The SCADA/HMI monitors the status of the Centrifuges via the signal status coming from the Vendor PLCs.

Alarm Status The individual vendor PLCs will generate a fault signal when a centrifuge fails to operate and send the alarm to the SCADA/HMI display


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12.4.1 Dewatered Sludge Collection System Reference P&ID drawing:


Overview Each of the two (2) Centrifuges transfers the dewatered sludge cake via two (2) dedicated discharge conveyors (CV56111 and CV56211). The discharge conveyors then feed two (2) dedicated incline conveyors (CV56113 and CV56213) outside the sludge dewatering building. These conveyors discharge into five (5) bins placed on the ground below the conveyor discharge. The incline conveyors have slew motors which enable the Operator to slew the conveyors to select which bin each conveyor feeds into.

Skip bin three is common to both centrifuge conveyor systems.

Selection of the bin is to be performed by the Operator standing in the bin area where the conveyors and bins can be monitored. The selection operation is to be from a local control panel via the site SCADA system.

There are currently two methods of sludge delivery that may be utilised. These are either belt or screw conveyors.

Where a belt conveyor is used, A recognized belt cleaning system is required. There shall be measures designed into the belt conveyor to eliminate the possibility of sludge material adhering to the drive or snub pulleys and thereby introducing tracking or traction issues associated with the conveyor. Machine guarding to the appropriate Australian Standard shall be complied with.

On Incline conveyors, an anti run-back device shall be fitted if required to prevent a fully laden conveyor being able to reverse in the event of a power failure, unless the drive train prevents this occurrence.

Where a screw conveyor is used it shall be enclosed with suitable covers such that access to the auger is prevented except by mechanical means under direct supervision.

The protection devices of either screw or belt conveyors shall adhere to AS 1755-2000.

Conveyors will be provided with the Supplier’s standard protective devices relative to the specific size and type of conveyor. Conveyor protective devices include the following:

1. Motor stators will incorporate thermistors to monitor the temperature of each phase winding. Thermistor relays will be supplied and installed by others

2. Belt tracking and tensioning systems shall be provided. 3. Emergency stops and Lanyards will be provided 4. Torque and slip detection switches will be fitted.

A weight measurement system shall be incorporated into the conveyor system to enable accurate weight measurements for the controlling the filling of the skip bins.

ON HOLD – TO BE VERIFIED ON AWARD OF SLUDGE HANDLING SYSTEM

Operation and Control The Operator will manually position the respective skip bins (BN56121, BN56122, BN56123&BN56223, BN56221 and BN56222) and the Operator shall manually (via LCS) drive the conveyors to the selected positions, if the adjacent conveyors are clear and the skip bin position switches show that the bin is correctly aligned. The screen will show the configuration of the two (2) conveyors over the respective bins.


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When the Sludge Skip 90% alarm has been raised the Operator shall:

• Shut down the respective thickened sludge pump;

• Wait for the centrifuge to clear its current feedstock;

• Verify that the conveyor system is not registering out put from the centrifuge;

• Shut down the conveyor system;

• Operate the slew conveyor into the operator selected position via the local control station;

• Restart the conveyor;

• Restart the thickened sludge pumps; and

• The dewatering process will continue.

Stop Condition and Interlock If the skip bin position switches (ZS56121, ZS56122, ZS56123 & ZS56223, ZS56222 and ZS56221) are not activated, correctly positioned, the slew conveyor will be inhibited from utilising that skip bin position. A manual override of this interlock will only be available when the slew conveyor is run by the Operator at the local control station.

Both slew conveyors will be inhibited from using Skip Bin 3 at the same time.

Start Permissive The slew of the conveyors is an Operator driven function. It shall be the Operators decision on whether to pause the dewatering process during conveyor slew process. The slew start permissives shall be finalised once the conveyor system selection is finalised.

An emergency stop will inhibit the both conveyor systems from start or running until the emergency stop inhibit is locally deactivated.

Monitoring and Indication The skip bin position switches (ZS56121, ZS56122, ZS56123 & ZS56223, ZS56222 and ZS56221) indicate locally if the skip bins are correctly positioned.

The dewatered sludge weight measurement system shall provide local and SCADA/HMI displays. It is anticipated that the load cells on the discharge conveyors (WT56111 and WT56211) along with the discharge conveyor speed shall be used to indicate the amount (weight) of dewatered sludge that has been discharged into the respective skip bins.


• Centrifuge conveyor system 1:

− Conveyor (CV56111) drive fail to operate

− Conveyor (CV56111) drive torque overload from torque switch (YS56111)

− Conveyor (CV56111) emergency stop activated

− Sludge skip bin 90% full from load cell (WT56111)


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− Sludge skip bin 100% full from load cell (WT56111). Under continued operation the skip bin is about to overflow and require manual removal of skip contents to enable the skip bin to be safely removed from site




− Conveyor (CV56113) slew drive (M56114) fail to operate

− Conveyor (CV56113) slew drive (M56114) torque overload from torque switch (YS56114)

− Centrifuge conveyor system 1 emergency stop activated.

• Centrifuge conveyor system 2:




− Sludge skip bin 90% full from load cell (WT56211)

− Sludge skip bin 100% full from load cell (WT56211). Under continued operation the skip bin is about to overflow and require manual removal of skip contents to enable the skip bin to be safely removed from site




− Conveyor (CV56213) slew drive (M56214) fail to operate

− Conveyor (CV56213) slew drive (M56214) torque overload from torque switch (YS56214)

− Centrifuge conveyor system 2 emergency stop activated.

Please note: the emergency stop function shall include the LCS emergency stop and/or the conveyor safety system (which shall include safety lanyards).

12.4.2 Centrate Disposal System Reference P&ID drawing:

• 004-7032-I-5011 Rev. G (CENTRATE TANK).

Operation and Control Centrate from the centrifuges, skip bin area pits, thickened sludge pump station bund and Dewatering building drain pit gravitates to a centrate sump in front of the dewatering building.

Two (2) sump pumps (PU-57001 and PU-57011) are installed in the sump as Duty/Standby with selection on the SCADA/HMI and auto-changeover if the Duty pump fails.

The centrate sump pumps can be operated via the local control stations or the SCADA/HMI system.

Start Permissive


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During normal operation (auto mode), Centrate fills the sump until the high level switch (LSH57003) is reached which then starts the Duty pump.

The Duty pump stops when the low level switch (LSL57002) is reached.

Stop Condition and Interlock When the low level switch (LSL57002) is activated the sump pumps will be inhibited from operating.

Due to the low volumes anticipated the centrate tank shall operate independently and not be inhibited by the backwash and/or blowdown sequences.

Monitoring and Indication The centrate sump pumps and associated level and flow switches are monitored locally and on the SCADA/HMI displays.

Alarms The following alarms, when initiated, are sent to the SCADA/HMI:

• Centrate sump Low-Low level switch (LSLL57001) is activated;

• Centrate sump High-High level switch (LSHH57004) is activated;

• Centrate Sump Pump 1 (PU57001) fails to operate;

• Centrate Sump Pump 1 (PU57001) low flow switch (FS57001) is activated;

• Centrate Sump Pump 2 (PU57011) fails to operate; and

• Centrate Sump Pump 2 (PU57011) low flow switch (FS57011) is activated.

13 CHEMICAL DOSING SYSTEMS

13.1 Potassium Permanganate

13.1.1 Batching System Reference P&ID drawing:

• 004-7032-I-5003 Rev. G (INLET WORKS).

• 004-7032-I-5023 Rev. G (POTASSIUM PERMANGANATE (KMnO4) BATCHING SYSTEM).

• 004-7032-I-5024 Rev. J (POTASSIUM PERMANGANATE (KMnO4) DOSING PUMPS).

Operation and Control The potassium permanganate Batching System is controlled from the Main PLC and SCADA/HMI.

The following flow valves are controlled from the Main PLC:

• FV66802 - from service water line to the existing KMnO4 Day Tank;

• FV66811- from existing Batch Tank to the existing potassium permanganate pump line;

• FV66821 - from existing KMn04 Day Tank to existing potassium permanganate pumps and new dosing pumps; and


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• FV65621 - from dosing pumps to the WTP inlet works dosing point.

The following can be controlled from a local control station or SCADA/HMI and PLC:

• Mixer MX66801; and

• Mixer MX66821.

The existing VSD operated dosing pumps (PD66831 and PD66841) can be controlled from the Main PLC and local control stations.

The new dosing pumps (PD66851 and PD66861) will be controlled from the Main PLC and local control stations.

Start Permissive When called to operate, the potassium permanganate Batching System is started from the Main PLC and SCADA/HMI.

The KMNO4 batching system operation shall start when the following conditions are satisfied:

• Vendor package batching system is available, this shall include the transfer system;

• The mixers are available;

• The high level float switch LSH66802 and LSH66822 are deactivated; and

• The KMNO4 bund level alarm is deactivated.

Start batching sequence is initiated when all the above start permissive and start conditions are satisfied with at least on of the following:

• Level switch low alarm (LSL66803) in batch tank 1 OR

• Level switch low alarm (LSL66823) in batch tank 2 is activated OR

• At least one of the level transmitters in the day tanks have activated the Operator adjustable Start Batching Sequence set-point.

Stop Condition and Interlock The respective mixer in the Batch Tanks TK66801 and TK66821 at the potassium permanganate batching system will be stopped when a low level is detected via low level switch LSL66803 and LIT66801 for Batch Tank 1 TK66801, and low level switch LSL66823 and LIT66821 for Batch Tank 2 TK66821.

The vendor package batching system shall be stopped from filling the respective batch tank where the high level float switch LSH66802 and LSH66821 are activated.

A warning from the LIT66801 and LIT66821 shall be provided to notify the operator that the mixers or batching system is about to be interrupted. The warning high and low levels shall be Operator adjustable set-points entered into the SCADA/HMI displays.

Monitoring and Indication The Main PLC and SCADA/HMI monitors the operation of the potassium permanganate Batching System.

Alarm Status If the potassium permanganate Dosing System is selected to operate but is not available due to any system fault, alarms will be sent to the SCADA/HMI for Operator intervention.


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These alarms will be initiated and sent to SCADA/HMI:

• Batch tank 1 (TK66801):

− Exceeding level indicating transmitter alarm (LIT66801) set-point

− Level switch high alarm (LSH66802)

− Level switch low alarm (LSL66803)

− Mixer drive alarm (MX66801).

• Batch tank 2 (TK66821):

− Exceeding level indicating transmitter alarm (LIT66821) set-point

− Level switch high alarm (LSH66822)

− Level switch low alarm (LSL66823)

− Mixer drive alarm (MX66821).

• KMNO4 tank bund (TK66891) level alarm (LS66891).

13.1.2 River Water Dosing System Reference P&ID drawings:



Overview The potassium permanganate dosing occurs at the:

• WTP inlet works dosing point (FV65621 controlled by SCADA/HMI).

Operation and Control The potassium permanganate dosing is controlled from the Main PLC and SCADA/HMI.

When potassium permanganate dosing is selected to operate, the required river water potassium permanganate dose rate set-point is entered at the SCADA/HMI.

The potassium permanganate dosing options are as follows:

Table 13-1 River Water KMNO4 Dosing

Flow paced Required potassium permanganate Delivery Rate (mg/s) = river water Flow Rate (L/s) x river water potassium permanganate Dose Rate set-point (mg/L)

A potassium permanganate Duty/Standby Selector for dosing pumps is provided at the SCADA/HMI. Automatic transfer to the Standby pump is initiated when Duty pump failure or potassium permanganate flow fault is detected by a potassium permanganate flow switch.

The required potassium permanganate Delivery Rate (mg/s) is used by the PID controller as the potassium permanganate delivery rate set-point. The PID controls the speed of the dosing pump by using the measured flow rate to maintain the required dosing set-point.

An Auto/Manual selection is provided at the SCADA/HMI for potassium permanganate dosing controller pop-up.


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In Auto mode, the dosing controller controls the pump dosing rate to the required delivery rate set-point. In Remote Manual, the Operator can adjust delivery rate (i.e. indirectly varying the dosing pump speed) at the SCADA/HMI. The transfer from Auto to Manual and visa versa shall be bumpless.

The Operator can also select Auto/Manual/Off for each of the dosing pumps. The two (2) dosing pumps can also be operated manually from a local control station.

Start Permissive In event of failure of the Duty dosing pump, the Standby dosing pump is automatically started and continues to control the dosing flow rate to maintain the dosing set-point.

The potassium permanganate dosing system shall Auto Start when the following conditions are satisfied:

• River water plant is in operation;

• River water flow rate is greater than 20l/s (refer to chemical dosing matrix in appendix e for appropriate fit to use as reference flow);

• Potassium permanganate dosing system is selected to operate;

• River water potassium permanganate dosing system is available;

• River caustic soda dosing system is available; and

• Day tank level is above the operator adjustable dosing pump inhibits level set-point.

Start dosing sequence is initiated when all start permissive and start conditions are satisfied

Stop Condition and Interlock If the river water potassium permanganate dosing system is selected to operate but is not available due to any system fault the system will not run.

The river water potassium permanganate Dosing System shall be inhibited when a minimum of one of the following conditions are satisfied:

• River water plant is not in operation;

• River water flow rate is less than 20l/s (refer to chemical dosing matrix in appendix e for appropriate fit to use as reference flow);

• Ph in the river water dosing tank less than the river water low ph set-point;

• River water potassium permanganate dosing system is not selected to operate;

• River water potassium permanganate dosing system is not available; and

• River water caustic soda dosing system is not available.

Monitoring and Indication Level and pressure monitoring and indication are displayed locally.

The speed of the pumps is monitored at the SCADA/HMI.

The level of batch tanks TK66801 and TK66821 and the common KMNO4 pump pressure relief tank TK66831 are monitored at the SCADA/HMI.

Alarms Status


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An alarm will be sent to the SCADA/HMI when the duty dosing pump has failed. If the potassium permanganate dosing system is selected to operate but is not available due to any system fault, alarms will be sent to the SCADA/HMI for Operator intervention.

An alarm will be sent to the SCADA/HMI for:

• High and low levels of batch tanks TK66801 and TK66821;

• The common KMNO4 pump pressure relief tank TK66831 level (LA66831); and

• KMNO4 dosing pumps low flow switches FS66855.

13.1.3 Bore Water Relift Tank Dosing Reference P&ID drawings:

• 004-7032-I-5013 Rev. H (FILTER INLET CHANNELS).


Overview Potassium permanganate is dosed directly into the Relift Tank (manual control valve), and mixes under ambient flow conditions.

Operation and Control The potassium permanganate dosing is controlled from the Main PLC and SCADA/HMI.

When potassium permanganate dosing is selected to operate, the required Bore Water potassium permanganate Dose Rate set-point is entered into SCADA/HMI.

The potassium permanganate dosing options are as follows:

Table 13-2 Bore Water KMNO4 Dosing

Flow paced Required potassium permanganate Delivery Rate (mg/s) = Bore Water Flow Rate (L/s) x Bore Water potassium permanganate Dose Rate set-point (mg/L)

The required potassium permanganate delivery rate (mg/s) is used by the PID controller as the potassium permanganate delivery rate set-point.

An Auto/Manual selection is provided at the SCADA/HMI for potassium permanganate dosing controller pop-up. In Auto, the dosing controller controls the pump dosing rate to required delivery rate set-point. In Manual, the Operator can manually adjust delivery rate (i.e. indirectly varying the dosing pump speed) at the SCADA/HMI.

The Operator can also select Auto/Manual/Off for each of the drives. The two (2) dosing pumps can also be operated manually from a local control station.

Note: A Bore Water High pH Set-point may currently stop the potassium permanganate system and prevent it from running. If so, this should be disabled since higher pH values result in more efficient manganese oxidation. The High pH alarm set-point should be set to detect an overdosing problem with the ACH system, and not inhibit the KMnO4 dosing system from operating.

Start Permissive In event of failure of the duty dosing pump, the standby dosing pump will automatically start up and continue to control the dosing flow rate to dosing set-point.


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The bore water potassium permanganate Dosing System shall Auto Start when the following conditions are satisfied:

• Bore water plant is in operation;

• Bore water flow rate is greater than 20l/s (refer to chemical dosing matrix in appendix e for appropriate fit to use as reference flow);

• Ph in the delay tank greater than the bore water low ph set-point;

• Level in the relift tank greater than the relift tank low level switch;

• Bore water potassium permanganate dosing system is selected to operate;

• Bore water potassium permanganate dosing system is available; and

• River water caustic soda dosing system is available.

Start dosing sequence is initiated when all start permissive and start conditions are satisfied.

Stop Condition and Interlock If the bore water potassium permanganate dosing system is selected to operate but is not available due to any system fault the system will not run.

The bore water potassium permanganate Dosing System shall be inhibited when a minimum of one of the following conditions are satisfied:

• Bore water plant is not in operation;

• Bore water flow rate is less than 20l/s (refer to chemical dosing matrix in appendix e for appropriate fit to use as reference flow);

• Ph in the delay tank less than the bore water low ph set-point;

• Level in the relift tank lower than the relift tank low level switch;

• Bore water potassium permanganate dosing system is not selected to operate;

• Bore water potassium permanganate dosing system is not available; and

• Bore water caustic soda dosing system is not available.

Monitoring and Indication The speed of the pumps is monitored locally and displayed at the SCADA/HMI.

Alarm Status An alarm is initiated indicating that the duty dosing pump has failed and the standby dosing pump has started.

An alarm will be sent to the SCADA/HMI when the duty dosing pump has failed. If the potassium permanganate dosing system is selected to operate but is not available due to any system fault, alarms will be sent to the SCADA/HMI for Operator intervention.

An alarm will be sent to the SCADA/HMI for

• High and low levels of batch tanks TK66801 and TK66821;

• The common KMNO4 pump pressure relief tank TK66831 level (LA66831); and

• KMNO4 dosing pumps low flow switches FS66835.


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13.2 Caustic Soda Dosing Reference P&ID drawings:

• 004-7032-I-5030 Rev. G (CLEARWATER CAUSTIC SODA DOSING).

• 004-7032-I-5031 Rev. G (BORE WATER CAUSTIC SODA DOSING).

• 004-7032-I-5032 Rev. G (RIVER WATER TANK CAUSTIC SODA DOSING).


• 004-7032-I-5005 Rev. H (CLARIFIER No.1).

• 004-7032-I-5012 Rev. G (EXISTING AERATION BASIN).


• 004-7032-I-5014 Rev. F (TREATED WATER AREA - CLEARWATER STORAGE TANK).

Overview Caustic soda dosing location options selected by the Operator via the SCADA/HMI are:

• Clearwater storage tank (FV52122 – new dosing point);

• Relift Tank (FV66348 – new dosing point);

• Inlet works (FV66776 – new dosing point); and

• Clarifier Inlet Mains (FV29123 – new dosing point).

Operation and Control The caustic soda dosing is controlled from the Main PLC and SCADA/HMI.

When caustic soda dosing is selected to operate (typically this will be enabled at all times by the Operator), but only when the treated water pH is less than the Treated Water pH set-point.

The required caustic soda dose rate set-point and the pH set-point are entered into SCADA/HMI by the Operator for each of the following areas;

• Filtered clear water;

• Raw bore water; and

• Raw river water.

The caustic soda dosing options are as follows:

Table 13-3 Caustic Soda Dosing

Flow paced Required Caustic Soda Delivery Rate (mg/s) = Treated Water Flow Rate (L/s) x Filtered Water Pre Caustic Soda Dose Rate set-point (mg/L)

Flow paced with pH trim

Required Caustic Soda Delivery Rate (mg/s) = Treated Water flow rate (L/s) x Filtered Water Pre Caustic Soda Dose Rate set-point (mg/L) x pH Trim Factor Note: the pH Trim Factor is calculated by a PID control loop on the basis of the Treated Water pH Analyser and the Treated Water pH set-point. The pH Trim Factor is limited by Operator adjustable (SCADA/HMI) trim percentage (typically 20%, i.e. 0.8 ≤ pH Trim Factor ≤ 1.2).

Start Permissive


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When called to operate, the caustic soda dosing is started from the Main PLC and SCADA/HMI dependant on the pH set-point entered in to the SCADA/HMI.

The appropriate caustic dosing system operation (Clear water, River or Bore) shall start when the following conditions are satisfied for the respective dosing system:

• The level indicators in the tank have not activated the Operator adjustable Inhibit Start Pumping Sequence set-point;

• water flow rate is ≥ 20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• Caustic soda dosing system is selected to operate in SCADA / HMI;

• Caustic soda pumps are available; and

• River water caustic soda flow switch alarm (FS66773) has not been activated when dosing valve (FV66776) is open.


Stop Condition and Interlock Respective low flow alarm to the, Clearwater Storage Tank (FIT52031), Bore Water Aeration basin (FIT15031) and River Water Dosing Tank (FIT29531) will stop the respective dosing pumps.

The caustic dosing system operation shall be inhibited when a minimum of one of the following conditions are satisfied:

• The level indicators in the tank alarm is activated the Operator adjustable Inhibit Start Pumping Sequence set-point;

• Caustic soda pumps are not available;

• water flow rate is ≤ 20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• River water caustic soda flow switch alarm (FS66773) has been activated when dosing valve (FV66776) is open;

• Dosing pump is running and a Low Flow alarm is generated with the respective dosing point valve is indicated open.;

• Potable water low flow switch alarm (FS66275) for Clear water caustic soda has been activated when dosing valve (FV66272) is open;

• Potable water low flow switch alarm (FS66375) for Bore water caustic soda has been activated when dosing valve (FV66372) is open; and

• Potable water low flow switch alarm (FS66475) for River water caustic soda has been activated when dosing valve (FV66472) is open.

Monitoring and Indication For the caustic soda storage system, level transmitter LIT66201 at the caustic soda Tank No.1 (TK66201) will monitor and indicate for local and SCADA/HMI displays.

For the clear water caustic soda dosing, flow meter FIT66241 will monitor the flow for local and SCADA/HMI display. The speed and torque of the Clearwater Caustic Soda Dosing Pump No.1 (PD66221) and No. 2 (PD66231) are also monitored at the SCADA/HMI.


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For the bore water caustic soda dosing, a flow meter (FIT66341) monitors the flow for local and SCADA/HMI display. The speed and torque of the Caustic Soda Dosing Pump No.1 (PD66321) and No.2 (PD66331)are also monitored at the SCADA/HMI.

For the river water tank caustic soda dosing, a flow meter (FIT66441) monitors the flow for local and SCADA/HMI display. The speed and torque of the River Water Tank Caustic Soda Dosing Pump No.1 (PD66421) and No.2 (PD66431) are also monitored at the SCADA/HMI.

Alarm Status These alarms will be initiated and sent to SCADA/HMI:

• The level transmitter (LIT66201) at the Caustic Soda Tank No1 will send a Low level alarm;

• Flow meter (FIT66241) will send Low and High Flow alarm for the Clearwater Caustic Soda Dosing for Operator intervention due to dosing point valve or dosing pump failure;

• Flow meter (FIT66341) will send Low and High Flow alarm for the Bore Water Caustic Soda Dosing for Operator intervention due to dosing point valve or dosing pump failure;

• Flow meter (FIT66441) will send Low and High Flow alarm for the River Dosing Water Tank Caustic Soda Dosing for Operator intervention due to dosing point valve or dosing pump failure;

• Caustic soda bund (TK66293) level alarm (LS66293);

• Use of the safety shower or eyewash station (ES66281) as detected by flow switch FS66285; and

• Water pressure failure for the safety shower or eyewash station (ES66281) as detected low pressure switches PS66284.

13.3 Powder Activated Carbon (PAC) Dosing Reference P&ID drawing:

• 004-7032-I-5004 Rev. K (NEW RIVER WATER DOSING TANK).

• 004-7032-I-5034 Rev. F (PAC DOSING SYSTEM).

Overview The PAC dosing location options are selected by the Operator via the SCADA/HMI. The options include:

• River water dosing tank – inlet (FV65712 - normally open); and

• River water dosing tank – outlet (FV65722 - normally closed).

Operation and Control The PAC Dosing is controlled from a Vendor package PAC PLC with interfacing signals to and from the Main PLC and SCADA/HMI.

The required PAC Delivery Rate (mg/s) is calculated in the Main PLC based on the operator adjustable PAC dose rate set-point at the SCADA/HMI and the river water flow rate, as measured by the river water feed flow meter.

The resulting PAC Delivery rate value is transmitted to the PAC PLC. The PAC System then automatically provides this delivery rate.

The PAC dosing options are as follows:


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Table 13-4 River Water Dosing Tank PAC Dosing

Flow paced Required PAC Delivery Rate (mg/s) = River Water Flow Rate (L/s) x River Water PAC Dose Rate set-point (mg/L)

Start Permissive When called to operate at the SCADA/HMI through a start signal from the Main PLC, the PAC Batching and Dosing System will then be started from the vendor provided PLC.

The PAC Dosing System can be started when the following conditions are satisfied:

• river water plant is in operation;

• river water flow rate is ≥ 20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• PAC dosing system is selected to operate in SCADA / HMI;

• PAC dosing system is available; and

• Dosing point solenoid valves on the river water dosing tank (FV65712 and FV65722) have not registered an alarm.


Stop Condition and Interlock If the Vendor package PAC Dosing System is selected to operate but is not available due to a system fault, the system will not run.

If the dosing point valves fail to operate the dosing system will be inhibited from operating.

Monitoring and Indication The Main PLC and SCADA/HMI monitors the operation of the PAC Dosing System via an Ethernet communication link to the PAC local PLC.

Alarm Status If the PAC dosing system is selected to operate but is not available due to any system fault, alarms will be sent to the SCADA/HMI for Operator intervention.

An alarm state will occur and be sent to the SCADA/HMI upon:

• PAC dosing bund (TK65784) level alarm (LS65784);



13.4 Aluminium Chlorohydrate (ACH) Dosing Reference P&ID drawing:



• 004-7032-I-5020 Rev. H (ALUMINUM CHLOROHYDRATE (ACH) DOSING).


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Overview The ACH dosing location options are selected by the Operator via the SCADA/HMI. The options include:

• River water dosing tank – inlet (FV65322 – ACH Dosing Point no. 1);

• River water dosing tank – midpoint (FV65332 – ACH Dosing Point no. 2); and

• River water dosing tank – outlet (FV65342 – ACH Dosing Point no. 3).

The dosing point at the Clarifier inlet mains is only able to be operated manually at the valve.

Operation and Control The ACH Dosing is controlled from the Main PLC and SCADA/HMI.

An Auto/Manual selection shall be provided at the SCADA/HMI for ACH dosing on a controller pop-up. In Auto, the dosing controller controls the pump dosing rate to required delivery rate set-point. In Manual, the Operator can manually adjust delivery rate (i.e. indirectly varying the dosing pump speed) from SCADA/HMI.

The two (2) dosing pumps (PD65311 and PD65312) can also be operated manually from a local control station.

When ACH Dosing is selected to operate, the required river water ACH dose rate set-point is entered into SCADA/HMI.

The ACH dosing options are as follows:

Table 13-5 River Water ACH Dosing

Flow paced Required ACH Delivery Rate (mg/s) = River Water Flow Rate (L/s) x River Water Pre ACH Dose Rate set-point (mg/L)

The Required ACH Delivery Rate (mg/s) is used by the PID controller as the ACH Delivery Rate set-point. The PID controls the speed of the dosing pump by using the measured flow rate to maintain the required dosing set-point.

Start Permissive In auto mode, in event of failure of the Duty dosing pump or ACH flow fault, as detected by the ACH flow meter, the Standby dosing pump is automatically started up and continues to control the dosing flow rate to dosing set-point. When in manual mode the dosing pump will stop, an alarm will be generated and dosing will not re-commence until the Operator intervenes and starts the standby dosing pump.

The ACH dosing system shall automatically start when the following conditions are satisfied:


• River water flow rate is ≥20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• ACH dosing system is selected to operate; and

• ACH dosing system is available.




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The ACH dosing system shall automatically stop or be inhibited when a minimum of one of the following conditions are satisfied:


• River water flow rate is ≤20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• ACH dosing system is not selected to operate;

• ACH dosing system is not available;

• ACH dosing point valves fail to operate correctly identified via existing dosing flow transmitter reading low flow and pumps running, or pumps not running and flow transmitter reading a flow input, or common pressure relief tank level element (LE65132) is activated;

• ACH dosing pumps not available; and

• ACH system is in Manual mode.


• Level transmitters (LIT65301 and LIT65311) monitor the level of the existing ACH Tank No.1 and No.2; and

• ACH pump No.1 and No.2 (PD65311 and PD65312) send status speed to SCADA/HMI for monitoring and control.

Other monitoring and indication for level and pressure are provided locally.

Alarm Status If the ACH dosing system is selected to operate but is not available due to a system fault, an alarm will also be sent to the SCADA/HMI for Operator intervention.


• A dosing pump has failed to operate;

• Dosing point valve has failed to operate via ach pressure relief valves back filling the common pressure relief tank and activating the level element (le65312) will indicate no dosing flow and possible dosing point valve failure;

• Lit65301 and lit65311 at the existing ach tank no.1 and no.2 are activated upon operator adjustable high and low set-points;

• Use of the safety shower or eyewash station (es65371) as detected by flow switch fs65375;

• Water pressure failure for the safety shower or eyewash station (es65371) as detected low pressure switch ps65374;

• Use of the safety shower or eyewash station (es65381) as detected by flow switch fs65385;

• Water pressure failure for the safety shower or eyewash station (es65381) as detected low pressure switch ps65384; and

• Activation of the level element (le65312) for the common ach pump pressure relief tank tk65312.


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• Where an ach alarm that generates a stop condition or interlock is not acknowledge in preset time at wtp scada, then the associated alarm is escalated and dialled out to the appropriate personnel.

13.5 Polymer Dosing and Batching

13.5.1 Existing Filter and Clarifier Polymer Batching System Reference P&ID drawing:

• 004-7032-I-5021 Rev. G (POLYMER DOSING).

Overview This polymer batching system provides polymer for the Filter and Clarifier dosing systems.

Operation and Control The batching system is activated on a start command from the Main PLC. The Main PLC receives the level status of the polymer holding tank via a low level switch (LSL67026).

The following polymer batching components can be controlled via manual or automatic operation mode on the SCADA/HMI or controlled locally at the local control stations:

• Existing hopper polymer conveyors SCR67001 and SCR67011;

• Polymer batch tank mixers MX67006 and MX67016;

• Hopper blower pumps BL67002 and BL67012;

• Service water flow valves FV67005 and FV67015; and

• Pneumatic valves FV67008 and FV67018 to the diaphragm pumps.

The level switches at the existing Polymer Batch Tanks No.1 and No.2 and Holding Tank No.1 provides sequence control to the Main PLC. The level switches indicate the following:

• Low-Low level switch (LSLL670x5) is used to indicate batching tank is empty and to shut down the pneumatic transfer pump;

• Low level switch (LSL670x6) is used to shut down and inhibit the respective batch tank mixer; and

• High level switch (LSH670x7) is used to indicate that:

− the batch tank is full and ready for transfer

− Need to close the respective batching service water valve

− Batching system is paused awaiting permission to transfer contents.

Start Permissive The batching system shall Auto Start when the following conditions are satisfied:

• The service water valves have not initiated an alarm;

• Polymer holding tank level switch (LSL67026) is activated;

• Polymer batch system 1 has not initiated any alarms;

• Polymer batch system 2 has not initiated any alarms; and


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• Polymer dosing area bund (TK65094) level alarm (LSH65094) is not activated.

Start batching sequence is initiated when all start permissive and start conditions are satisfied. If there is a fault on one of the polymer batch systems the other polymer batching system shall not be inhibited from operating.

Stop Condition and Interlock A stop condition and/or inhibit shall be created if any of the alarm status conditions below occur.

Alarm Status If the Batching System are selected to operate but are not available due to a system fault, an alarm will be sent to the SCADA/HMI for Operator intervention.


• Activation of polymer hopper 1 (HO67001) level alarm from LT67002;

• Activation of polymer hopper 2 (HO67011) level alarm from LT67012;

• Activation of screw conveyor 1 (SCR67001) drive fault alarm MA67001;

• Activation of screw conveyor 2 (SCR67011) drive fault alarm MA67011;

• Activation of hopper blower 1 (BL67002) drive fault alarm MA67002;

• Activation of hopper blower 2 (BL67012) drive fault alarm MA67012;

• Activation of mixer 1 (MX67006) drive fault alarm MA67006;

• Activation of mixer 2 (MX67016) drive fault alarm MA67016;

• Activation of polymer dosing area bund (TK65xxx) level alarm (LSxxx);

• Activation of Batch Tank 1 (TK67005) Low-Low level (LSLL67005), Low level (LSL67006) and High level (LSH67007) alarm;

• Activation of Batch Tank 2 (TK67015) Low-Low level (LSLL67015), Low level (LSL67016) and High level (LSH67017) alarm;

• Activation of Holding Tank 1 (TK67025) Low level (LSL67026) and High level (LSH67025) alarm; and

• Batch tank pneumatic transfer pumps fail to operate. This shall be identified by the start command to the pilot solenoid and a failure for the low level switch in the holding tank to deactivate after an Operator adjustable set-point (0-180 seconds).

13.5.2 Clarifier Aid Polymer Dosing Reference P&ID drawing:




• 004-7032-I-5025 Rev. G (CLARIFIER POLYMER DOSING SYSTEM).

Overview Polymer dosing location options selected by the Operator via the SCADA/HMI are:


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• River water dosing tank – inlet (FV65267 – Polymer Dosing Point no. 1);

• River water dosing tank – midpoint (FV65277 – Polymer Dosing Point no. 2);

• River water dosing tank – outlet (FV65287 – Polymer Dosing Point no. 3); and

• Clarifier Inlet Mains (FV29113 – new dosing point).

Operation and Control The polymer dosing pumps (PD65251and PD65261) and batching system shall be control from the Main PLC and SCADA/HMI.

When clarifier aid polymer dosing and batching is selected to operate, the required river water polymer dose rate set-point is entered into SCADA/HMI.

The polymer dosing options are as follows:

Table 13-6 Clarifier Aid Polymer Dosing

Flow paced Required Clarifier Aid Polymer Delivery Rate (mg/s) = river water Flow Rate (L/s) x river water Clarifier Aid Polymer Dose Rate set-point (mg/L)

A Polymer Duty/Standby selector is provided on SCADA/HMI.

The required Polymer Delivery Rate (mg/s) will be used by the PID controller as the Polymer Delivery Rate set-point. The PID controls the speed of the dosing pump by using the measured flow rate to maintain the required dosing set-point.

An Auto/Manual selection is provided at the SCADA/HMI for polymer dosing. In Auto mode, the dosing controller controls the pump dosing rate to the required delivery rate set-point. In Manual mode, the Operator can manually adjust the delivery rate (i.e. indirectly varying the dosing pump speed) from SCADA/HMI.

The Operator can also select Auto/Manual/Off from the SCADA/HMI for each of the pumps. The two (2) dosing pumps (PD65251 and PD65261) can also be operated manually from a local control station.

A flow valve (FV65272) on the un-chlorinated water supply line is controlled from the Main PLC.

Start Permissive Automatic transfer to the Standby pump is required on detection of a Duty pump failure or Polymer flow fault, as detected by the Polymer flow meter.

In event of the failure of the Duty dosing pump, the Standby dosing pump is automatically started up and continues to control the dosing flow rate to the dosing set-point.

The Clarifier Aid Polymer Dosing System shall Auto Start when the following conditions are satisfied:


• River water flow rate is ≥20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• Clarifier Aid Polymer Dosing System is selected to operate;

• Clarifier Aid Polymer Dosing System is available;

• Polymer holding tank level switch (LSL67026) is not activated; and

• The polymer dosing point valves have not initiated an alarm.


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Stop Condition and Interlock If the polymer dosing and the batching systems are selected to operate but are not available due to any system fault, the system will not run.

The Clarifier Aid Polymer Dosing System shall stop or be inhibited when a minimum of one of the following conditions are satisfied:


• River water flow rate is ≤20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• Clarifier Aid Polymer Dosing System is not selected to operate;

• Clarifier Aid Polymer Dosing pumps are not available;

• Polymer holding tank level switch (LSL67026) is activated; and

• The polymer dosing point valves have initiated an alarm.

The polymer system will not automatically start when it is selected to manual.

Monitoring and Indication The dosing system provides monitoring information for alarms to the Main PLC via the remote I/O.

Level, pressure and flow monitoring and indication are provided locally.

Alarm Status If the Clarifier Aid Polymer Dosing System is selected to operate but is not available due to a system fault, an alarm will be sent to the SCADA/HMI for Operator intervention.


• Duty dosing pump has failed; and

• Activation of Holding Tank 1 (TK67025) Low level (LSL67026) and High level (LSH67025) alarm.

13.5.3 Filter Aid Polymer Dosing Reference P&ID drawings:



• 004-7032-I-5022 Rev. G (POLYMER DOSING PUMP STATION).

Overview The Operator selects the required chemical dosing/injection point locations from the following options:

• Existing Bore Filters Stage 1 No. 1-4 Inlet Channel;

• Existing River Filters Stage 1 No. 5-8 Inlet Channel; and

• Existing River Filters Stage 2 No. 9-12 Flow Splitter.


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The batching system supplies the dosing/injection points as stated above and the clarifier aid polymer dosing pumps.

Operation and Control The Filter Aid Polymer Dosing and Batching is controlled from the Main PLC and SCADA/HMI.

When Filter Aid Polymer Dosing is selected to operate, the required Filter Aid Polymer Dose Rate set-point is entered into SCADA/HMI.

The polymer dosing options are as follows:

Table 13-7 River Filter Aid Polymer Dosing

Flow paced Required Filter Aid Polymer Delivery Rate (mg/s) = Filter Feed Flow Rate (L/s) x Filter Aid Pre Polymer Dose Rate set-point (mg/L)

Start Permissive Automatic transfer to the Standby pump is required on detection of a Duty pump failure or Polymer flow fault, as detected by the Polymer flow meter.

In event of the failure of the Duty dosing pump, the Standby dosing pump is automatically started up and continues to control the dosing flow rate to the dosing set-point.

The Filter Aid Polymer Dosing System shall Auto Start when the following conditions are satisfied:


• River water flow rate is ≥20 L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• Filter Aid Polymer Dosing System is selected to operate;

• Filter Aid Polymer Dosing System is available;

• Polymer holding tank level switch (LSL67026) is not activated; and

• The polymer dosing point valves have not initiated an alarm.


Stop Condition and Interlock If the polymer dosing systems is selected to operate but is not available due to a system fault, the system will not run.

The Filter Aid Polymer Dosing System shall stop or be inhibited when a minimum of one of the following conditions are satisfied:


• River water flow rate is ≤20 L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• Filter Aid Polymer Dosing System is not selected to operate;

• Filter Aid Polymer Dosing pumps are not available;

• Pressure switch PS675x4 is activated. This will identify a valve that has failed to open or a potential pipeline blockage;


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• Polymer holding tank level switch (LSL67026) is activated; and

• The polymer dosing point valves have initiated an alarm.

The polymer system will not automatically start when it is selected to manual.

Monitoring and Indication The dosing system provides monitoring information for alarms to be sent to the Main PLC via the remote I/O.

Level, pressure and flow monitoring and indication are provided locally.

Alarm Status If the Filter Aid Polymer Dosing System is selected to operate but is not available due to a system fault, an alarm will be sent to the SCADA/HMI for Operator intervention.


• Duty dosing pump has failed;

• Pressure switch PS675x4 is activated. This will identify a valve that has failed to open or a potential pipeline blockage;


• Activation of the level element (LE65231) for the common Polymer pump pressure relief tank TK65231.

13.5.4 Filters 1-4 Filter Aid Polyacrylamide Dosing Reference P&ID drawings:



• 004-7032-I-5022 Rev. G (POLYMER DOSING PUMP STATION).

Overview The filters 1-4 Filter Aid Polyacrylamide Dosing location is at the discharge of the Delay tank (TK15701).

Operation and Control This dosing system operates during either bore or river mode treatment. Any change to the required dose rate needs to be made manually by the Operator at the SCADA/HMI.

The Coagulant dosing options are as follows:

Bore Mode Operation When Bore Mode and the Filter Aid Polyacrylamide Dosing are selected to operate, the required Filters 1-4 Filter Aid Polyacrylamide Dose Rate set-point is entered into SCADA/HMI.

The required polyacrylamide dosing option is:

Table 13-8 Bore Filters Aid Polymer Dosing – Bore Mode


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Flow paced Required Filter Aid Polyacrylamide Delivery Rate (mg/s) = Bore Water Flow Rate (L/s) x Filters 1-4 Filter Aid Polyacrylamide Dose Rate set-point (mg/L)

River Mode Operation When River Mode and the Filter Aid Polyacrylamide Dosing are selected to operate, the required Filters 1-4 Filter Aid Polyacrylamide Dose Rate set-point is entered into SCADA/HMI.

The required polyacrylamide dosing option is:

Table 13-9 Bore Filters Aid Polymer Dosing – River Mode

Flow paced Required Filter Aid Polyacrylamide Delivery Rate (mg/s) = Filters 1-8 river water Feed Flow Rate (L/s) ÷ 2 x Filters 1-4 Filter Aid Polyacrylamide Dose Rate set-point (mg/L)

Start Permissive

Bore Mode The Filters 1-4 Filter Aid Polyacrylamide Dosing System shall Auto Start when the following conditions are satisfied:

• Filters 1-4 are selected to Bore Mode operation;

• bore water flow rate is ≥20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• pH in the Relift Tank exceeds the bore water low pH set-point;

• A Relift Pump is operating;

• level in the Relift Tank exceeds the Relift Tank low level switch set-point;

• Filters 1-4 Filter Aid Polyacrylamide dosing system is selected to operate;

• Filters 1-4 Filter Aid Polyacrylamide dosing system is available; and

• Dosing set-point manually entered into SCADA/HMI.


River Mode The Filters 1-4 Filter Aid Polyacrylamide Dosing System will Auto Start when the following conditions are satisfied:

• river water Plant is in operation;

• Filters 1-4 are selected to River Mode operation;

• Filters 1-8 river water Feed Flow Rate is ≥20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• Filters 1-4 Filter Aid Polyacrylamide dosing system is selected to operate;

• Filters 1-4 Filter Aid Polyacrylamide dosing system is available; and

• Dosing set-point manually entered into SCADA/HMI.



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Stop Condition and Interlock If the Filters 1-4 Filter Aid Polyacrylamide Dosing System is selected to operate but is not available due to any system fault the system will not run.

Bore Mode The Filters 1-4 Filter Aid Polyacrylamide Dosing System shall stop and/or be inhibited from operating when a minimum of one of the following conditions are satisfied:

• Filters 1-4 are selected to River Mode operation;

• Bore water flow rate is ≤20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• pH in the Relift Tank is below the bore water low pH set-point;

• A Relift Pump is not operating or available;

• Level in the Relift Tank is below the Relift Tank low level switch set-point;

• Filters 1-4 Filter Aid Polyacrylamide dosing system is selected not to operate;

• Filters 1-4 Filter Aid Polyacrylamide pump system is not available;

• Pressure switch PS675x4 is activated. This will identify a valve that has failed to open or a potential pipeline blockage; and

• Dosing set-point is not manually entered into SCADA/HMI.

River Mode The Filters 1-4 Filter Aid Polyacrylamide Dosing System shall stop and/or be inhibited when a minimum of one of the following conditions are satisfied:

• River water Plant is not in operation;

• Filters 1-4 are selected to Bore Mode operation;

• Filters 1-8 river water Feed Flow Rate is ≤20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• Filters 1-4 Filter Aid Polyacrylamide dosing system is not selected to operate;

• Filters 1-4 Filter Aid Polyacrylamide dosing pumps are not available;

• Pressure switch PS675x4 is activated. This will identify a valve that has failed to open or a potential pipeline blockage; and

• Dosing set-point is not manually entered into SCADA/HMI.

Alarm Status Filter Aid Polyacrylamide Dosing System will be raised an alarm if a system fault occurs when filters 1-4 operate.


• Duty dosing pump has failed;

• Pressure switch PS675x4 is activated. This will identify a valve that has failed to open (manually closed) or a potential pipeline blockage;


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• Activation of the level element (LE65231) for the common Polymer pump pressure relief tank TK65231.

13.6 Sludge Thickener Polymer System

13.6.1 Sludge Thickener Polymer Batching Equipment Reference P&ID drawings:

• 004-7032-I-5026 Rev. G (SLUDGE THICKENER POLYMER DOSING SYSTEM).

Overview The Sludge Thickener Polymer Batching System is a stand-alone unit complete with PLC and control panel. This unit includes a vacuum loader and hopper, volumetric screw feeder, dissolver and ejector, batching tank with mixer, day tank and level switches.

Operation and Control A Sludge Thickener Polymer System, when enabled, doses polymer into the Washwater being transferred from the WWT to the Sludge Thickener Tank. This operates whenever a transfer from the WWT to the Sludge Thickener tank is in progress.

This system is automatic and self-contained but requires signals to and from the Main PLC to operate. The system is monitored by Main PLC and plant statuses are displayed at the SCADA/HMI.

The system can continue to batch and operate even with polymer Low Level Switch is active since the polymer usage is extremely slow. The remaining contents of the hopper will last several days. Even if the polymer runs out, no mechanical damage to any equipment will result.

Polymer batch concentration is set by adjusting the polymer feed duration appropriately to achieve the desired concentration. This is determined from the polymer feed rate from the screw conveyor, the batch volume and the required concentration. When the required polymer feed rate is determined, the value is manually entered in to the small keypad on the front of the Polymer Batching System control panel. The Operator must also manually enter the specified polymer concentration at the SCADA/HMI to determine the required Polymer Dosing Pump speed correction.

Start Permissive The Sludge Thickener Polymer Batching System is a standalone system and is started from the vendor provided PLC from monitoring the vendor polymer holding tank. The Vendor PLC shall notify the Main PLC that batching is in progress.

The polymer dosing area bund (TK65094) level alarm (LSH65094) is not activated.

Stop condition and Interlock If Sludge Thickener Polymer System is selected to operate but are not available due to any system fault, the system will not run.

The polymer dosing area bund (TK65094) level alarm (LSH65094) is activated. This shall stop and inhibit the batching system from operating. It shall not inhibit the dosing pumps.


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Monitoring and Indication A polymer batching output signal is taken from the Polymer Batching System local control panel to the Main PLC.

Alarm Status If a fault occurs with the Polymer Batching System, the vendor package PLC will raise an alarm and send it to the SCADA/HMI.

A polymer Low Level Switch is located in the polymer powder hopper. If a low powder level is detected, an alarm will be raised at the HMI interface of the vendor local control panel as well as at the SCADA/HMI.

13.6.2 Sludge Thickener Polymer Dosing Pump System Reference P&ID drawings:


• 004-7032-I-5026 Rev. G (SLUDGE THICKENER POLYMER DOSING SYSTEM).

Operation and Control Duty/ Standby sludge thickener Polymer Dosing Pumps (PD65151 and PD65161) are provided.

The stroke length of the Polymer Pumps can be set at the Main PLC and SCADA/HMI. The stroke should only be adjusted while the pump is running. Failure to observe this may result in mechanical damage to the pump. Both pumps must be set with the same stroke after which the pump stroke parameter can be manually entered at the SCADA/HMI, on a pump control pop-up window. The pump speed will then be automatically adjusted according to flow rate, dose rate and stroke to provide the required chemical dose rate.

The operating modes for the Sludge Thickener Polymer System are as follows.

Table 13-10 Sludge Thickener Polymer Dosing

Off Duty pump does not operate.

Online flow pace Dilution water solenoid valve and WWT Polymer Dosing valve open. Duty pump starts and the signal to the Duty dosing pump is: Pump Speed Signal = Washwater Transfer Flow (L/s) × Sludge Thickener Feed Polymer Dose Rate (mg/L) × polymer concentration (%) (obtain from polymer batching system) × constant. The constant is determined at commissioning, while the dose rate is Operator adjustable.

When the Sludge Thickener Polymer Dosing System starts operating, the Sludge Thickener Polymer Dosing Valve (FV58241) opens. The required drive speed is calculated according to the formula above, this signal is sent to the drive VSD, which in turn runs the pump at the required speed.

Start Permissive When called to operate, the Thickening Polymer Dosing Equipment is started from the vendor provided PLC via a Start signal from the Main PLC.

The Main PLC will send the start signal to the vendor package PLC only when a Washwater transfer pump is about to be given the start signal or is operating.


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The sludge thickener polymer dosing system shall Auto Start when the following conditions are satisfied:

• The start permissives for a dirty wash water transfer between the WWT and the sludge thickener tank are satisfied and flow is registered form FIT58201;

• Sludge Thickener Polymer Dosing System is selected to operate;

• Sludge Thickener Polymer Dosing pumps are available;

• Sludge Thickener Polymer Dosing vendor package system has not generated an alarm;

• The polymer common pressure relief tank (TK65151) level element (LE65151) has not been activated;

• The polymer dosing point valves have not initiated an alarm;

• Communications between the vendor PLC and the Main PLC are healthy; and

• Sludge thickener polymer dosing system is selected to Auto mode.


Stop Condition and Interlock The sludge thickener polymer dosing system shall stop and/or be inhibited from running when a minimum of one of the following conditions are satisfied:

• The start permissives for a dirty wash water transfer between the WWT and the sludge thickener tank are not satisfied;

• Sludge Thickener Polymer Dosing System is not selected to operate;

• Sludge Thickener Polymer Dosing pumps are not available;

• Sludge Thickener Polymer Dosing vendor package system has generated an alarm;

• The polymer common pressure relief tank (TK65151) level element (LE65151) has been activated; and

• Auto start shall be inhibited when sludge thickener polymer dosing system is selected to manual mode.

Where communication between the vendor PLC and the Main PLC fail, the vendor package shall stop dosing, initiate an alarm and change to manual mode. The Operator shall be required to run the dosing system from the vendor package LCS. When communications is restored the Operator shall be required to select Auto mode to re-instate automatic operation.

Monitoring and Indication The Main PLC and SCADA/HMI monitors the operation of the Washwater Thickening Polymer Dosing via an Ethernet communication link to the batching plant local PLC.

The vendor package PLC shall the following signals to the Main PLC and the SCADA/HMI displays:

• Batching sequences started;

• Polymer product level is low and requires extra feedstock;

• Dosing rate of pumps;

• Pump availability; and

• Mode of operation – manual or auto.


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Alarm Status If the dosing pumps fail to operate an alarm will be initiated and sent to the SCADA/HMI.

An alarm will be initiated if the common polymer pressure relief tank TK65151 level element (LA65151) is activated.

An alarm shall be initiated to indicate a dosing point valve operation failure or potential dosing line blockage and sent to the SCADA/HMI when the valve is selected to open and the polymer common pressure relief tank (TK65151) level element (LE65151) has initiated an alarm

13.6.3 Centrifuge Feed Polymer System

Centrifuge Feed Polymer Batching Equipment Reference P&ID drawing:

• 004-7032-I-5027 Rev. G (CENTRIFUGE POLYMER DOSING SYSTEM).

Overview A Centrifuge Feed Polymer System, when enabled, injects polymer in to the thickened sludge being transferred from the Sludge Thickener to the Centrifuges. This operates whenever thickened sludge transfer is in progress.

The Centrifuge Feed Polymer Batching System is a Vendor package unit complete with control panel and PLC. This unit includes a vacuum loader and hopper, volumetric screw feeder, dissolver and ejector, batching tank with mixer, use tank and level switches.

Operation and Control The Vendor package system requires signals to and from the Main PLC to operate although the system is monitored by SCADA/HMI.

A polymer low level switch is located in the polymer powder hopper. If a low powder level is detected, the Operator must then refill the hopper. The system continues to batch and operate even with this switch is active. This indicates the polymer usage is extremely slow and the remaining contents of the hopper will last several days. If the polymer runs out, no mechanical damage to any equipment will result.

Polymer batch concentration is set by adjusting the polymer feed duration appropriately to achieve the desired concentration. This is determined from the polymer feed rate from the screw conveyor, the batch volume and the required concentration. When the required number of seconds of polymer feed is determined, it is manually entered in to the small keypad on the front of the polymer batching system control panel. The Operator must then enter the specified concentration at the SCADA/HMI so that the required pump speed correction can be determined.

Start Permissive The Centrifuge Feed Polymer Batching System is a standalone system and is started from the vendor provided PLC from monitoring the vendor polymer holding tank. The Vendor PLC shall notify the Main PLC that batching is in progress.

The polymer dosing area bund (TK65094) level alarm (LSH65094) is not activated.



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If Centrifuge Feed Polymer System is selected to operate but are not available due to any system fault, the system will not run.

The polymer dosing area bund (TK65094) level alarm (LSH65094) is activated. This shall stop and inhibit the batching system from operating. It shall not inhibit the dosing pumps.

Monitoring and Indication The Main PLC and SCADA/HMI monitors the operation of the Centrifuge Polymer Dosing via an Ethernet communication link to the batching plant vendor PLC.

A polymer batching output signal is taken from the Polymer Batching System control panel to the Main PLC.

Alarm Status If a fault occurs with the Polymer Batching System, the vendor package PLC will raise an alarm and send it to the SCADA/HMI.

A polymer Low Level Switch is located in the polymer powder hopper. If a low powder level is detected, an alarm will be raised at the HMI interface of the vendor local control panel as well as at the SCADA/HMI.

13.6.4 Centrifuge Feed Polymer Dosing Equipment Reference P&ID drawing:



• 004-7032-I-5027 Rev. G (CENTRIFUGE POLYMER DOSING SYSTEM).

Operation and Control Duty/Duty/ Standby Centrifuge Feed Polymer Dosing Pumps (PD65051, PD65061 and PD65071) are provided.

The stroke length of the Polymer Pumps must be set manually at the pump by the Operator. The stroke should only be adjusted while the pump is running. Failure to observe this may result in mechanical damage to the pump. Both pumps must be set with the same stroke after which the pump stroke parameter is manually entered at the SCADA/HMI, on a pump control pop-up window. The pump speed will then be automatically adjusted according to flow rate, dose rate and stroke to provide the required chemical dose rate.

The operating modes for the Centrifuge Feed Polymer Dosing System are as follows:

Table 13-11 Centrifuge Feed Polymer Dosing

Off Duty pump does not operate.

Online flow pace Dilution water solenoid valve and at least one (1) Centrifuge Polymer Dosing Valve open. Duty pump starts and the signal to the Duty dosing pump is: Signal = Thickened Sludge Transfer Flow × Centrifuge Feed Polymer Dose Rate (mg/L) × polymer concentration (%) (obtain from polymer batching system) × constant. The constant is determined at × constant. The constant is determined at commissioning, while the dose rate is Operator


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adjustable.

The motor pumps (PD65051, PD65061 and PD65071) are controlled by the Main PLC, and it can also be manually controlled at a local a switch and at a local control station.

When a thickened sludge pump runs, the Polymer Dosing valve for the pump will open. As flow is established, the Dilution Water Low Flow Switch changes state, indicating dilution water flow. When flow is detected, the Duty Centrifuge Feed Polymer Pump commences operation. The required drive speed is calculated according to the formula above, and this signal is sent to the drive VSD, which in turn runs the pump at the required speed.

Start Permissive When called to operate, the Centrifuge Feed Polymer Dosing Equipment is started from the vendor provided PLC via a Start signal from the Main PLC.

The Main PLC will send the start signal to the vendor package PLC only when a thickened sludge transfer pump is about to be given the start signal or is operating.

The Centrifuge Feed polymer dosing system shall Auto Start when the following conditions are satisfied:

• The start permissives for a dirty wash water transfer between the thickened sludge tank and the centrifuge are satisfied and flow is registered on the respective flow transmitter;

• Centrifuge Feed Polymer Dosing System is selected to operate;

• Centrifuge Feed Polymer Dosing pumps are available;

• Centrifuge Feed Polymer Dosing vendor package system has not generated an alarm;

• The polymer common pressure relief tank (TK65151) level element (LE65151) has not been activated;

• The polymer dosing point valves have not initiated an alarm;

• Communications between the vendor PLC and the Main PLC are healthy; and

• Centrifuge Feed polymer dosing system is selected to Auto mode.


Stop Condition and Interlock The opening Centrifuge Polymer Dosing Valves (V58402, V58412 & V58422) is interlocked with their respective Thickened Sludge Pumps.

The Centrifuge Feed polymer dosing system shall stop and/or be inhibited from running when a minimum of one of the following conditions are satisfied:

• The start permissives for thickened sludge transfer between the thickened sludge tank and the Centrifuge Feed are not satisfied;

• the stop and interlock conditions for the centrifuge feed system are satisfied;

• Centrifuge Feed Polymer Dosing System is not selected to operate;

• Centrifuge Feed Polymer Dosing pumps are not available;

• Centrifuge Feed Polymer Dosing vendor package system has generated an alarm;

• The polymer common pressure relief tank (TK65151) has been activated;


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• Auto start shall be inhibited when Centrifuge Feed polymer dosing system is selected to manual mode; and

• Dilution water low flow switches (FS68002, FS68012 and FS68022) is activated and one (1) of the respective polymer dosing pumps is running.

Where communication between the vendor PLC and the Main PLC fail, the vendor package shall stop dosing, initiate an alarm and change to manual mode. The Operator shall be required to run the dosing system from the vendor package LCS. When communications is restored the Operator shall be required to select Auto mode to re-instate automatic operation.

Monitoring and Indication The Main PLC and SCADA/HMI monitors the operation of the Centrifuge Feed Polymer Dosing System via an Ethernet communication link to the batching plant local PLC.

The vendor package PLC shall the following signals to the Main PLC and the SCADA/HMI displays:

• Batching sequences started;

• Polymer product level is low and requires extra feedstock;

• Dosing rate of pumps;

• Pump availability; and

• Mode of operation – manual or auto.

Alarm Status If the dosing pumps (PD65051, PD65061 and PD65071) fail to operate an alarm will be initiated and sent to the SCADA/HMI.

If the dilution water low flow switches (FS68002, FS68012 and FS68022) is detected and one (1) of the respective polymer dosing pumps is running, an alarm will be raised.

An alarm shall be initiated to indicate a dosing point valve operation failure or potential dosing line blockage and sent to the SCADA/HMI when the valve is selected to open and the polymer common pressure relief tank (TK65151) level element (LE65151) has initiated an alarm

13.7 Chlorine Dosing Reference P&ID drawing:

• 004-7032-I-5029 Rev. G (POST CHLORINE DOSING).


Overview The Chlorine Dosing injection point is in the filtered water pipe between the Clearwater Well and the Distribution Splitter Pit, as close to the Clearwater Well as practicable.

One Treated Water Chlorine Analyser will be a side-stream unit, drawing sample water from the Distribution Splitter Pit as described in section 10.2 filtered water chemical dosing – overview.

The other Treated Water Chlorine Analyser will be a side-stream unit, drawing sample water from water network after High lift pumps station.


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The selection of the primary analyser for chlorination control shall be selected on SCADA/HMI.

Operation and Control Currently the Chlorine system is a standalone system.

Currently when filtered water Chlorine Dosing is selected to operate, the Chlorine Dosing System is monitored locally and sampling for Chlorine is done manually in the laboratory.

An allowance shall be made for the chlorine system to be monitored and controlled by the main PLC.

The Chlorine Dosing options are as follows:

Table 13-12 Clear Water Chlorine Dosing

Flow paced Required Chlorine Delivery Rate (mg/s) = Treated Water Flow Rate (L/s) x Filtered Water Pre Chlorine Dose Rate set-point (mg/L)

Flow paced with chlorine residual trim

Required Chlorine Delivery Rate (mg/s) = Treated Water flow rate (L/s) x Filtered Water Pre Chlorine Dose Rate set-point (mg/L) x Chlorine Residual Trim Factor Note: the Chlorine Residual Trim Factor is calculated by a PID control loop on the basis of the Treated Water Chlorine Analyser and the Treated Water Chlorine Residual set-point. The Chlorine Residual Trim Factor is limited by Operator adjustable (SCADA) trim percentage (typically 20%, i.e. 0.8 ≤ Chlorine Residual Trim Factor ≤ 1.2).

Chlorine residual trim only

Required chlorinator output (%) = Chlorine Residual-Only Trim Factor Note: the Chlorine Residual-Only Trim Factor is calculated by a PID control loop on the basis of the Treated Water Chlorine Residual Analyser and the Treated Water Chlorine Residual set-point. This permits disinfection to continue in the absence of a flow signal, and would typically only be enabled during such rare circumstances.

Start Permissive When called to operate, the Chlorine Dosing is started locally at a LCS.

The Chlorine Dosing System shall be allowed to be started by an Operator when the following conditions are satisfied:

• The water treatment plant is in operation;

• Filtered Clearwater flow rate is ≥20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow);

• Chlorine Dosing System is selected to operate;

• Chlorine Dosing System is available;

• The CWST level switch is not activated; and

• The existing chlorine leak alarm for the drum room and/or the dosing room are not activated.

Start dosing sequence is initiated when the Operator selects the dosing rate and starts the process. The above conditions shall be indicated on the SCADA/HMI to enable the Operator to run the chlorine dosing system correctly.

An allowance shall be made to incorporate the start permissives into an Auto mode.

Stop Condition and Interlock Currently the existing chlorine system is run manually as an independent system.


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An allowance shall be made to incorporate the following to facilitate an auto mode control function:

• If the Chlorine Dosing System is selected to operate but the system has faults or active interlocks, the Main PLC will initiate a stop command to the affected running valves;

• If either of the two chlorine leak alarms (AIT66104 & AIT66121) are activated, the Main PLC will initiate an alarm on the SCADA/HMI and sound an audible alarm to warn personnel of the hazard. It shall be the Operators decision on whether to provide a stop command to affected running valves and start to shut down the WTP or to keep operating;

• The Chlorine Dosing System shall be stopped and/or inhibited when a minimum of one of the following conditions are satisfied:

− The water treatment plant is not in operation

− Filtered Clearwater flow rate is ≤20L/s (refer to Chemical dosing matrix in Appendix E for appropriate FIT to use as reference flow)

− Low flow switch (FS52023) is activated

− Chlorine Dosing System is not selected to operate

− Chlorine Dosing System is not available

− The CWST level switch is activated

− The dosing point valves have initiated an alarm

− The existing chlorine leak alarm for the drum room and the dosing room are activated.

Monitoring and Indication A Treated Water Chlorine Analyser monitors the treated water chlorine residual after Chlorine Dosing and prior to entering the BT System and the other residual chlorine analyser samples water from the water network after High lift pumps station. These units shall be operated in a duty/standby philosophy for the control of the chlorination of the treated water. For example: the Operator selects the primary device and if that analyser fails, the other analyser shall change state to become the primary analyser for control of the chlorination system.

Provision shall be made to provide continual online monitoring of the treated water chlorine residual (both units) and Operator adjustable High and Low Chlorine Residual alarm set-points at the SCADA/HMI.

An allowance shall be made such that the following devices shall monitor and indicate to the SCADA/HMI displays:

• Load cells (WT66101) for Chlorine stage drum 1 (TK66101);

• Load cells (WT66102) for Chlorine stage drum 2 (TK66102); and

• An Operator adjustable chlorine drum low level warning shall be indicated to the SCADA/HMI to notify the Operator that one of the Chlorine Drums is close to empty.

Alarms When the two chlorine leak alarms (AIT66104 & AIT66121) are activated, an alarm signal with be sent to the Main PLC and SCADA/HMI displays.

High and Low Chlorine Residual alarms will be activated and sent to the SCADA/HMI when the adjustable set-points have been exceeded. This shall be to initiate an Operator intervention. Where the alarm is not


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acknowledge in preset time at WTP SCADA, then the associated alarm is escalated and dialled out to the appropriate personnel.

An allowance shall be made to incorporate Alarm indication for the Chlorinators and service water valves.

13.8 Sodium Silicofluoride Dosing Reference P&ID drawing:

• 004-7032-I-5033 Rev. F (FLOURIDE DOSING SYSTEM).


Overview The Fluoride Dosing System is supplied as a vendor package.

Please Note: This package has been installed and commissioned in December 2009 to meet the Queensland Fluoride Code. Hence the existing control systems should be utilised for this upgrade.

The Fluoride Dosing injection point is at the filtered water pipe between the Clearwater Well and the Distribution Splitter Pit, as close to the Clearwater Well as practicable.

Operation and Control The Fluoride Dosing System is controlled by a vendor PLC with interfacing signals to and from the Main PLC and SCADA/HMI.

SCADA/HMI monitoring of the Fluoride System is provided in accordance with the Queensland Fluoride Code.

The Fluoride Dosing options are as follows:

Table 13-13 Clear Water Fluoride Dosing

Flow Paced Required Fluoride Delivery Rate (mg/s) = Treated Water Flow Rate (L/s) x Filtered Water Pre Fluoride Dose Rate set-point (mg/L).

Flow paced with pH Trim

Required Fluoride Delivery Rate (mg/s) = Treated Water flow rate (L/s) x Filtered Water Pre Fluoride Dose Rate set-point (mg/L) x pH Trim Factor. Note: the pH Trim Factor is calculated by a PID control loop on the basis of the Treated Water pH Analyser and the Treated Water pH set-point. The pH Trim Factor is limited by Operator adjustable (SCADA) trim percentage (typically 20%, i.e. 0.8 ≤ pH Trim Factor ≤ 1.2).

Start Permissive When called to operate, the Filtered Water Fluoride Dosing is started from the vendor provided PLC.

This dosing system was recently installed and commissioned. The existing start permissives shall be used.

Stop Condition and Interlock In event of a Main PLC power failure, the Fluoride Dosing Pumps shall stop.

This dosing system was recently installed and commissioned. The existing start stop conditions and interlocks shall be used.


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Loss of communications with the Main PLC will not shut down the fluoride dosing system as the vendor package controlling this system is directly linked to the vendor package.

Loss of communications shall shut down and inhibit the fluoride dosing system where the fluoride concentration levels cannot be sent to the vendor package PLC.

Monitoring and Indication A Treated Water Fluoride Analyser monitors the treated water fluoride concentration prior to entering the BT System. This provides continual online monitoring of the treated water fluoride concentration and Operator adjustable high and low fluoride alarm set-points on the SCADA/HMI.

This dosing system was recently installed and commissioned. The existing start devices shall be monitored and indicated on the SCADA/HMI displays.

Alarms An alarm shall be raised and sent to the SCADA/HMI for any of the following:.

• A low flow alarm shall be raised from FS52032 and FS52033 and sent to the SCADA/HMI;

• A high level alarm shall be raised by the PLC from the analogue input of the Fluoride analyser;

(Where the above alarms are not acknowledged in a preset time at WTP SCADA, then the associated alarm is escalated and dialled out to the appropriate personnel.)

• Fluoride dosing area bund (TK659xx) level alarm (LS659xx);



14 MAIN POWER SUPPLY

Reference Drawings:

• 004-7032-E-4000 Rev. E MAIN SWITCHBOARD, SLD, SHEET 1.

• 004-7032-E-4001 Rev. E MAIN SWITCHBOARD, SLD, SHEET 2.

• 004-7032-E-4005 Rev. D FILTER PROCES MCC, SLD, SHEET 1.

• 004-7032-E-4006 Rev. D FILTER PROCES MCC, SLD, SHEET 2.

• 004-7032-E-4010 Rev. D DEWATERING MCC, SLD.

• 004-7032-E-4015 Rev. D DEWATERING BUILDING DB.

• 004-7032-E-4020 Rev. D.NEW CHEMICAL DOSING MCC, SLD.

14.1 Power Under Normal Condition Under normal condition the existing 500kVA TX1 and new 1MVA transformers TX2 and TX3 and are supplying power to all processes and equipment.

A portable generator is not on site and not connected.


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The main power supply points at the WTP include the following:

• Main Switchboard A, B & C

− High Lift Pumps

− Pump No. 1 (375kW) with VSD, existing pump





− Pump No. 6 (200kW) with VSD, existing pump.

− Active Harmonic Filter

− HLPS lighting and small power DB (DB1)

− UPS distribution board (DB2)

• Filter Process MCC;

• Dewatering Facility MCC;

• Low Lift (Bore System Feeder) DB; and

• New Chemical Dosing MCC.

Local Monitoring and Control The ACBs including the Bus-tie shall be equipped with local indication such as an open/close status. A lamp connected to PFR shall be installed at the load side of Q2-TX1, Q2-TX2 and Q2-TX3 for local failure indication.

PLC and SCADA Monitoring The ACBs shall be fitted with field sensing devices connected to the PLC for reading data and detecting status signals. The table below details the field sensing devices, type of connection and data/signals to send to the PLC.

A single line diagram mimic shall be configured in a SCADA screen to display the status of the field signals as read from the PLC. The PMC data shall be sent to the SCADA/HMI to be archived and trended.

Table 14-1 Field Sensing Devices at Normal Condition

Description Connection to PLC Data/signals to PLC

PMC at the line side of Q1-TX1 serial volts, amps, pf



PFR at the load side of Q2-TX1 hardwire No loss power supply



PMC at the load side of Q1-G1 serial volts, amps, pf


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ACB signals at Bus-Tie 1 (built-in) serial closed

ACB signals at Bus-Tie 2 (built-in) serial closed

ACB signals at Q2-TX1 (built-in) serial closed



Surge diverter at Q3-TX1 hardwire no fault



In addition, the following WTP MCCs send signals to the PLC and SCADA/HMI for monitoring of status and displaying for critical events and alarms:

• Filter Process MCC – surge diverter, PFR;

• Dewatering Facility MCC – surge diverter, PFR;

• New Chemical Dosing MCC – surge diverter, PFR; and

• Dewatering Building DB– surge diverter, PFR.

14.2 Partial Power Failure 1 - Existing TX1 is out Service The first partial power failure condition is when the existing TX1 is temporarily out of service while the new TX2 and TX3 are active and the portable generator is still unavailable.

During this condition the following processes and equipment are still supplied from TX2 and TX3:

• High Lift Pump:

− Pump No. 5 (220kw) with VSD (duty1 pump), only under interim configuration

− Pump No. 6 (200kw) with VSD (duty2 pump), only under interim configuration

− Pump No. 4 (80kw) and 3 (90kw) with VSD (standby pumps), only under interim configuration.

• HLPS lighting and small power DB (DB1);

• UPS distribution board (DB2);



• Dewatering Building DB;


• Chemical Dosing MCC.

Under ultimate configuration the three (3) High Lift Pumps (90kW, 2x335kW with VSD will be temporarily out of power while the Bus-Tie 1 is still open.

Local Monitoring Q2-TX1 ACB will indicate an opened/tripped status. A lamp connected to PFR will be activated to indicate a phase failure and send a loss of supply signal to the SCADA/HMI. The three (3) pumps will indicate a stop status at each LCS.


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Local Control Bus-Tie 1 ACB needs to be closed manually to allow supply of power from the new TX2. This shall be interlocked as stated on note 2 of electrical drawing 004-7032-E-4000 Rev E.

PLC and SCADA Monitoring The field sensing devices in the Table 25 will send data and status signals to the PLC. Partial power failure 1 fault signals shall be logged and displayed in the SCADA/HMI alarm system. These alarms require operator acknowledgement before activating any equipment after power has been restored to normal.

The partial power failure 1 data and status of the field sensing devices shall also be indicated in the single line diagram display in a SCADA screen. The data and signal status can also be archived and trended.

Table 14-2 Field Sensing Devices at Partial Power Failure 1

Description Connection to PLC Data/Signals to PLC SCADA Alarms

PMC at the line side of Q1-TX1 serial volts, amps, pf (faulty) Yes

PMC at the line side of Q1-TX2 serial volts, amps, pf (no fault)


PFR at the load side of Q2-TX1 hardwire Loss of power supply Yes

PFR at the load side of Q2-TX2 hardwire no fault


PMC at the load side of Q1-G1 serial volts, amps, pf (no fault)

ACB signals at Bus-Tie 1 (built-in) serial Open -> close Open to close status


ACB signals at Q2-TX1 (built-in) serial Opened/tripped Yes

ACB signals at Q2-TX2 (built-in) serial status


Surge diverter at Q3-TX1 hardwire status Yes, if faulty



PLC Control and Interlock The PLC logic shall be programmed to suppress all the Low level alarms generated from the high lift pumps during partial power failure 1. The PLC may also need to be programmed to reset any sequence logic involving the any of the high lift pumps.

If the pump 5 (200 kW + VSD) is currently running, any of the other three (3) high lift pumps shall be inhibited to start after Bus-Tie 1 has been manually closed. If there are no pumps running, the PLC interlocking logic shall be activated automatically to allow only one (1) pump running at any time during this partial power condition. The PLC logic shall also be programmed with a delay timer which starts on restoration of power. This timer will provide a delay to ensure power stability before pumps can be started and to stop unnecessary starting and stopping of the pumps.


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14.3 Partial Power Failure 2 - New TX2 Is Out Service The second partial power failure condition is when the new TX2 is temporarily is out of service while the new TX3 and existing TX1 is active and the portable generator is still on Standby.

During this condition the following processes and equipment still take power from TX1:

• High Lift Pumps:


− Pump No. 2 (80kW) with VSD existing pump.

• Active Harmonic Filter.

The following processes and equipment will be temporarily out of power while the Bus-tie 1 or 2 is still open:








Local Monitoring Q2-TX2 ACB will indicate an opened/tripped status. A lamp connected to PFR will be activated to indicate a phase failure and send a loss of supply signal to the SCADA/HMI. The 200kW pump will indicate a stop status on its LCS.

Local Control Bus-Tie 1 or Bus-Tie 2 ACB needs to be closed manually to allow supply of power from the new TX3 or existing TX1. The UPS supplying the 24V DC control power DB2 shall automatically activate while the Bus-Tie 1 or Bus-Tie 2 is still open. After the Bus-Tie 1 or Bus-Tie 2 has been manually closed, the UPS shall deactivate and DB2 will be supplied from the new TX1.

PLC and SCADA Monitoring The field sensing devices in the table below will send data and status signals to the PLC. Partial power failure 2 fault signals shall be logged and displayed in the SCADA/HMI alarm system. These alarms require operator acknowledgement before activating any equipment after power has been restored to normal.



Field Sensing Devices Connection to PLC Data/Signals to PLC SCADA Alarms


PMC at the line side of Q1-TX2 serial volts, amps, pf (fault) Yes


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PFR at the load side of Q2-TX2 hardwire fault Yes







Bus-Tie 1 ACB (built-in) serial/hardwire Open -> close

PLC Control and Interlock The PLC logic shall be programmed to suppress all the Low level alarms generated from the 200kW pump and other affected equipment during partial power failure 1. The PLC may also need to be programmed to reset any sequence logic involving the any of the High Lift Pumps.

If more than one of the other three (3) Pumps is currently running, the PLC logic shall automatically stop the other pump(s) running leaving only one (1) pump active. The PLC interlocking logic shall be activated automatically to allow only one (1) pump running at any time during this partial power condition.

The PLC logic shall also be programmed with a delay timer so that any pump cannot be started right after the power is restored to its normal condition.

14.4 Partial Power Failure 3 - New TX3 is out Service The third partial power failure condition is when the new TX3 is temporarily is out of service while the new TX2 and existing TX1 is active and the portable generator is still on Standby.

During this condition the following processes and equipment still take power from existing TX1 and new TX2:

• High Lift Pumps:


− Pump No. 2 (80kW) with VSD existing pump.

• Active Harmonic Filter;








The following processes and equipment will be temporarily out of power while the Bus-tie 2 is still open:


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• High Lift Pump:

− pump No. 5 (220kW) with VSD (duty1 pump), only under interim configuration

− pump No. 6 (200kW) with VSD (duty2 pump), only under interim configuration

− pump No. 4 (80kW) and 3 (90kW) with VSD (standby pumps), only under interim configuration.

Local Monitoring Q2-TX3 ACB will indicate an opened/tripped status. A lamp connected to PFR will be activated to indicate a phase failure and send a loss of supply signal to the SCADA/HMI.

Local Control Bus-Tie 2 ACB needs to be closed manually to allow supply of power from the new TX2. The UPS supplying the 24V DC control power DB2 shall automatically activate while the Bus-Tie 2 is still open. After the Bus-Tie 2 has been manually closed, the UPS shall deactivate and DB2 will be supplied from the new TX2.

PLC and SCADA Monitoring The field sensing devices in the table below will send data and status signals to the PLC. Partial power failure 2 fault signals shall be logged and displayed in the SCADA/HMI alarm system. These alarms require operator acknowledgement before activating any equipment after power has been restored to normal.



Field Sensing Devices Connection to PLC Data/Signals to PLC SCADA Alarms


PMC at the line side of Q1-TX2 serial volts, amps, pf (fault)

PMC at the line side of Q1-TX3 serial volts, amps, pf (no fault) Yes



PFR at the load side of Q2-TX3 hardwire fault Yes







Bus-Tie 1 ACB (built-in) serial/hardwire Open -> close

PLC Control and Interlock


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The PLC logic shall be programmed to suppress all the Low level alarms generated from the pumps and other affected equipment during partial power failure 3. The PLC may also need to be programmed to reset any sequence logic involving the any of the High Lift Pumps.

If more than one of the other three (3) Pumps is currently running, the PLC logic shall automatically stop the other pump(s) running leaving only one (1) pump active. The PLC interlocking logic shall be activated automatically to allow only one (1) pump running at any time during this partial power condition.

The PLC logic shall also be programmed with a delay timer so that pumps cannot be started until power stability has been verified.

14.5 Complete Power Failure - New TX2, TX3 and Existing TX1 Are Out Service Complete power failure condition is when the new TX1 and TX2 are both out of service and the all the processes and equipment are affected.

A Standby portable generator needs to be sized, supplied and energised to supply the following:

• 1x335kW pump (ultimate configuration);

• Backwash process;

• Chemical dosing;

• Ups site power db; and

• Dewatering facility.

Local Monitoring All ACBs affected will indicate an open/faulty status and all lamps connected to PFRs will be activated to indicate a failure. The pump stop/fault status will be displayed at each LCS.

Local Control Bus-Tie 1 ACB needs to be closed manually to allow supply of power to the 335kW pumps from the portable generator. The UPS supplying the 24V DC control power DB2 shall automatically activate while the generator has not been energised. Once the generator is energised, the UPS shall deactivate and DB2 will be supplied from the generator.

PLC and SCADA Monitoring The field sensing devices in table below will send data and status signals to the PLC. Complete power failure fault signals shall be logged and displayed in the SCADA alarm system. These alarms require operator acknowledgement before activating any equipment after power has been restored to normal.

The complete power failure data and status of the field sensing devices shall also be indicated in the single line diagram display in a SCADA screen. The data and signal status can also be archived and trended.

Table 14-5 Field Sensing Devices at Complete Power Failure

Field Sensing Devices Connection to PLC Data/signals to PLC SCADA Alarms




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Field Sensing Devices Connection to PLC Data/signals to PLC SCADA Alarms





PMC at the load side of Q1-G1 serial volts, amps, pf (faulty) Yes

ACB signals at Bus-Tie 1 (built-in) serial Open -> close Yes

ACB signals at Bus-Tie 2 (built-in) serial close/no fault Yes




Surge diverters at Q3-TX1 hardwire status Yes, if faulty



PLC Control and Interlock The PLC logic shall be programmed to suppress all the Low level alarms generated from all the pumps and other affected equipment during complete power failure. The PLC may also need to be programmed to reset any sequence logic involving the any of the High Lift Pumps.

The PLC interlocking logic with a delay timer shall be activated automatically to only allow the 335kW pump to run once the generator is energised.

Reference P&ID drawings/diagrams:

Drawing No. Title Revision

004-7032-I-5000 PROCESS FLOW DIAGRAM 0

004-7032-I-5001 LEGEND 1

004-7032-I-5002 DUMBLETON WEIR 0

004-7032-I-5003 INLET WORKS 2

004-7032-I-5004 NEW RIVER WATER DOSING 2

004-7032-I-5005 CLARIFIER NO. 1 2

004-7032-I-5006 CLARIFIER NO. 2 2

004-7032-I-5007 WASHWATER TANK 2

004-7032-I-5008 SLUDGE THICKENER TANK 1

004-7032-I-5009 THICKENED SLUDGE TANK 2

004-7032-I-5010 SLUDGE DEWATERING 1

004-7032-I-5011 CENTRATE TANK 2

004-7032-I-5012 EXISTING AERATION BASIN 0

004-7032-I-5013 FILTER INLET CHANNELS 1


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004-7032-I-5014 TREATED WATER AREA - CLEARWATER STORAGE TANK 2

004-7032-I-5015 TREATED WATER AREA - BALANCE TANK 2

004-7032-I-5016 HIGH LIFT PUMP STATION 2

004-7032-I-5017 HIGH LIFT PUMP STATION – DISCHARGE 1

004-7032-I-5018 BLOWERS 0

004-7032-I-5020 ALUMINUM CHLOROHYDRATE (ACH) DOSING 2

004-7032-I-5021 POLYMER DOSING 0

004-7032-I-5022 POLYMER DOSING PUMP STATION 0

004-7032-I-5023 POTASSIUM PERMANGANATE (KMnO4) BATCHING SYSTEM 1

004-7032-I-5024 POTASSIUM PERMANGANATE (KMnO4) DOSING PUMPS 2

004-7032-I-5025 CLARIFIER POLYMER DOSING SYSTEM 2

004-7032-I-5026 SLUDGE THICKENER POLYMER DOSING SYSTEM 1

004-7032-I-5027 CENTRIFUGE POLYMER DOSING SYSTEM 2

004-7032-I-5029 POST CHLORINE DOSING 0

004-7032-I-5030 CLEARWATER CAUSTIC SODA DOSING 2

004-7032-I-5031 BORE WATER CAUSTIC SODA DOSING 2

004-7032-I-5032 RIVER WATER TANK CAUSTIC SODA DOSING 2

004-7032-I-5033 FLOURIDE DOSING SYSTEM F

004-7032-I-5034 PAC DOSING SYSTEM 1

004-7032-I-5050 MASS BALANCE A

004-7032-I-5055 RIVER PLANT STAGE 2 FILTER NO. 9 INLET 0

004-7032-I-5056 RIVER PLANT STAGE 2 FILTER NO. 9 OUTLET 0







004-7032-I-5063 RIVER PLANT STAGE 1 FILTER NO. 5 0




004-7032-I-5067 BORE PLANT STAGE 1 FILTER NO. 1 0





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004-7032-I-5071 CLEARWATER INLET CHANNEL 0

004-7032-I-5072 FILTER WASHWATER COLLECTION PITS 1

004-7032-I-5073 RIVER PLANT STAGE 2 FILTER PNEUMATICS 0


Revision D

APPENDIX A Drive Control Philosophy


Revision D

1. At the Switchgear MCC • When the switchgear selector switch is selected to the Off position, the drive cannot be operated

locally from the switchgear (Start/Stop Push Button) as well as from SCADA/HMI.

• When the switchgear selector switch is selected to the Manual position, the drive can be operated locally from the switchgear (Start/Stop Push Button) but not from SCADA/HMI.

• When the switchgear selector switch is selected to the Auto position, the drive cannot be operated locally from the switchgear (Start/Stop Push Button). The drive can only be operated remotely from SCADA/HMI.

• Operation of the Emergency Stop Push Button will stop the drive irrespective of the position of the switchgear selector switch.

• Similarly, any hardwired trip (i.e. Over temperature (Thermistor Relay), moisture in stator (Moisture in stator relay) etc.) will stop the drive whether in Manual or Auto. The drive will remain in trip state until the responsible trip relay is reset.

2. Remote Control (SCADA/HMI/PLC) • Remote control is enabled when the switchgear selector switch is in the Auto position.

• When in remote control, the starting and stopping of the drive is via the SCADA/HMI/PLC. Remote control has three (3) modes of operation, Remote Auto, Remote Manual and Off. These modes are selectable from the SCADA/HMI.

• When Remote Auto is selected from SCADA/HMI, the starting and stopping of the drive is controlled by PLC logic (i.e. from a sequence step to start the drive, demand start/stop from the process). Drive will only start if there is permissive for it to start and the interlock is ok (process conditions allow it to start). The starting and stopping of drive is via drive control logic. Operator manual start/stop from SCADA/HMI is inhibited.

• When Remote Manual is selected from SCADA/HMI, the starting and stopping of the drive is manually initiated by the Operator from the SCADA/HMI. The Operator can start/stop the drive providing permissive to start or stop is available (normally, this is no stop permissive required for stopping drives). In this mode, automatic control of the drive is inhibited. However, in conditions where the plant process requires the drive to trip, a protection trip signals will trip the drive even in Remote Manual.

• When Remote Off is selected from SCADA/HMI, the remote starting and stopping of drive is inhibited.

3. Permissive to Start Drive The drive can only start if the following permissive are available. Typical examples are as follows:

• Isolator Closed

• Motor Temperature Normal

• Motor Seal Healthy (for submersible drives only)

• No Moisture in Stator (for submersible drives only)

• Bearing Not Over Temperature

• Soft Starter (or VSD) Healthy

• Enabled by process conditions (as require).

• Once the drive has started, the permissive signals are not required to maintain drive run.


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4. Protection Trip In event of abnormal process condition, (for example, Tank level LOLO) a protection trip signal is generated, the drive control logic will trip the drive irrespective of the mode selected (Remote Auto/ Remote Manual). A drive trip will automatically force the drive selection to Remote Manual.

• The faulty drive will be inhibited from starting until the fault condition is cleared and the fault alarm is reset.

5. Alarms • All drives fault conditions will be alarmed on the SCADA/HMI.

Note: The Auto, Manual and Off selection in SCADA/HMI as reference in this document refer to Remote Auto, Remote Manual and Remote Off respectively.


Revision D

APPENDIX B VSD Drive Control Philosophy


Revision D

1. At the Switchgear MCC • When switchgear selector switch is selected to the Off position, the VSD cannot be started locally

from the switchgear (Start/Stop Push Button) as well as from SCADA/HMI.

• When switchgear selector switch is selected to the Manual position, the VSD can be started locally from the switchgear (i.e. using the Start/Stop Push Button) but not from SCADA/HMI.

• The VSD must be Ready, VSD Not Inhibited and VSD Healthy to enable the drive to Start in Local.

• When switchgear selector switch is selected to Auto position, VSD cannot be started locally from the switchgear (i.e. using the Start/Stop Push Button). The VSD can only be operated remotely from SCADA/HMI.

• Operation of the Emergency Stop Push Button will stop the drive and de-energise the VSD irrespective of the position of the switchgear selector switch.

• Similarly, any hardwired trip signals (i.e. Over temperature (Thermistor Relay), moisture in stator (Moisture in stator relay) etc.) will trip the drive and de-energise the VSD irrespective of Manual or Auto selection. The VSD will remain in trip until the responsible trip relay is reset from the VSD local control panel.

2. From the VSD Local Control Panel • When selected to Auto from the VSD local control panel, the speed control of the VSD is

determined by external speed demand signal from the Main PLC.

• When selected to Manual from the VSD local control panel, the VSD speed output can be manually adjusted from the VSD local control panel. Operator can raise and lower the drive speed using the local panel keypad. External speed demand input is disabled.

3. Remote Control • Remote control is enabled when the switchgear selector switch is in the Auto position.

• When in remote control, the starting and stopping of the VSD is via SCADA/HMI/PLC. Remote control has three (3) modes of operation, Remote Auto, Remote Manual and Remote Off. These operating modes are selectable from the SCADA/HMI.

• When Remote Auto is selected from SCADA/HMI, the starting and stopping of the VSD is controlled by Main PLC control logic. VSD can only be started if permissive is available. Manual operation from SCADA/HMI is inhibited.

• When Remote Manual is selected from SCADA/HMI, the starting and stopping of the VSD is manually initiated by the Operator from the SCADA/HMI. The Operator can operate the VSD providing the permissive is available (normally, there is no permissive required for stopping the VSD). In this mode, the automatic control of the VSD is inhibited. However, in conditions where the plant protection logic requires the VSD drive to trip, the drive protection logic will trip the VSD and de-energise the drive even in Remote Manual.

• When Remote Off is selected from SCADA/HMI, the remote operation of the VSD is inhibited.

4. VSD Drive Speed Control • The speed of a VSD drive can be controlled in two (2) ways:

− manual speed adjustment from the VSD local control panel

− external speed set point to the VSD controller from the Main PLC.

• The VSD controller must be selected to Auto mode (from VSD local control panel) to enable it to accept external speed set-point for the control the drive speed. Once the VSD controller is started, the VSD controller will control the drive speed to the external speed set-point.


Revision D

• From SCADA/HMI, the Operator can set the PID controller to Manual and vary the drive speed via the PID speed controller pop-up. The PID controller can be selected to Auto or Manual. In Auto, the PID controller will control the drive speed in order to control the process variable to match the process set-point. The PID controller output is connected to the VSD external speed set-point via serial link.

5. Duty/Standby changeover • Duty/Standby Changeover of VSD is as per Duty/Standby control philosophy.

• The speed demand signal from the PID controller is connected to both the Duty and Standby VSD Drives. Only the active drive (Duty or Standby drive, depending on the status of the Duty/Standby logic) will be started. Only the active drive will respond to the PID speed demand signal.

6. Permissive to Start Drive • The VSD drive can only start if the following permissive are available. Typical examples are as

follows:

− Motor Available

− Isolator Closed

− Motor Temperature Normal

− Motor Seal Healthy (for submersible drives only)

− No Moisture in Stator (for submersible drives only)

− Bearing Not Over Temperature

− VSD Healthy

− Enabled by process conditions (as require).

Once the drive has started, the permissive signals are not required to maintain drive run.

7. Drive Protection Trip • In event of abnormal process condition, (for example, Tank level LOLO) a protection trip signal

connected to the drive control logic will trip the VSD drive irrespective of the mode selection (Remote Auto/ Remote Manual). A VSD drive trip will automatically force the drive selection to Remote Manual.

• The faulty VSD drive will be inhibited from starting until the fault condition is cleared and the fault alarm is reset.

• The following drive fault shall trip the VSD drive.

− Motor Temperature abnormal

− Motor seal not healthy (for submersible drives only)

− Moisture in stator (for submersible drives only)

− Bearing over temperature.

− Fault can be reset either from the SCADA/HMI or from the MCC except for motor bearing over temperature.

• Reset for VSD fault (e.g. overload trip) is at the VSD local control panel.

8. Alarms • All VSD drive fault conditions will be alarmed on the SCADA/HMI.

Note: The Auto, Manual and Off selection in SCADA/HMI as reference in this document refer to Remote Auto, Remote Manual and Remote Off respectively.


Revision D

APPENDIX C Duty Standby Changeover Control Philosophy


Revision D

1. General A pushbutton shall be supplied on the HMI to enable or disable Duty Rotation. If disabled, the duty sequence will remain unchanged until manually altered. Therefore, a pump set as Duty by an Operator will remain on Duty until either a failure has occurred, or an Operator changes the pump to Standby. If enabled, Duty Rotation shall be configured for either:

a) Alternating; or

b) Timed.

If configured for Alternating, rotation shall occur every 24 hours. Timed Rotation shall allow each pump to be configured for a set number of run hours, after which rotation shall occur. The timed settings for each pump do not need to be identical, with the intention to ensure multiple pumps are not due for service, or reach their end of life at the same time. By entering a value of zero (0) in each Time Setting, pumps will rotate Duty at the completion of each pump cycle.

Selection of either Alternating or Times modes (or the associated numeric fields), shall be available via the local HMI or Host SCADA.

In addition to the regular Duty Rotation of Pumps, the Standby Pump (if available) shall be brought into operation should a Duty Pump be:

1. Switched Off;

2. Switched to Manual;

3. Inhibited; or

4. Faulted;

In this instance the Pumps Mode shall be changed immediately to reflect the situation.

2. Two (2) Drives Duty/Standby control • The Operator can select any drive to be the Duty drive or let the PLC control the duty cycle. The

non Duty drive will automatically becomes the Standby. Only the drive that is selected to Remote Auto can be selected to Duty.

• When the process logic initiated a start of the required drive, the drive that is selected to Duty will start if it is selected to Remote Auto.

• In event that the Duty drive failed to start when called upon or when the Duty drive goes into fault, the Standby drive will start if it is selected to Remote Auto. A Duty drive failed alarm as well as Standby drive start alarm will be initiated.

• The changeover of the Duty to Standby drive in event of Duty drive fault/process abnormal condition will change the Duty/Standby selection status.

• While the Duty drive is in service and the process conditions call for the Standby drive to start (for example, flow low), the Standby drive will start. However, the Duty drive will continue to run.

• At a two pump station, when Duty is rotated, the Standby Pump becomes the Duty Pump, and the Duty Pump is now the Standby Pump.

3. Three (3) Drives Duty/Duty/Standby control • All drives are available; the Operator can select any drive to Duty1 and Duty2. The last drive will

automatically become the Standby drive. Only the drive that is selected to Remote Auto can be selected to Duty1, Duty2 or Standby.

• When the process logic calls for a drive to start, the drive that is selected to Duty1 will start if it is selected to Remote Auto,


Revision D

• If Duty1 drive failed to start, then the drive that is selected to Duty2 will start if selected to Remote Auto. The failed Duty1 drive will be forced to Remote Manual. In this situation, the Duty2 drive will behave like a Duty1 drive and the Standby drive will becomes Duty2 as well as Standby drive even though the SCADA/HMI Duty1/Duty2/Standby drives selection has not changed.

• Starting and stopping of drives should not change the Duty1/Duty2/Standby selection statuse. The status change will only occur as per the requirements of the Alternating or Timed or changed by the Operator.

• If Duty2 drive failed to start, then the drive that is selected to Standby will start if selected to Remote Auto. The failed Duty2 drive will be forced to Remote Manual.

• With only Duty1 drive in-service and the process condition (for example, flow low) require a second drive to start in order to maintain correct process condition, then the process logic will initiate Duty2 drive to start.

• All drives tripped will be alarm.

• Under normal duty rotation the Standby Pump becomes the Duty 1 Pump, the Duty 1 Pump becomes the Duty 2 Pump and the Duty 2 Pump converts to the Standby Pump.

Note: The Auto, Manual and Off selection in SCADA/HMI as reference in this document refer to Remote Auto, Remote Manual and Remote Off respectively


Revision D

APPENDIX D Proposed Future Dumbleton Weir Control Philosophy


Revision D

Overview Dumbleton weir shall be upgraded to an automated three (3) or four (4) pump VSD driven station.

Future Planned Operation and Control Dumbleton Weir shall maintain the three operation modes, these shall be:

• Remote auto mode – controlled from WTP;

• Remote manual mode – controlled from WTP; and

• Local manual mode – controlled from Dumbleton Weir.

Only two (2) out of four (4) river water pumps will be used as the Duty Pumps. This process is currently under investigation and an allowance for VSD control of the pumps shall be made.

Start Permissive The start sequence includes starting the pumps against the closed valve and then opening the respective control valve and checking for open limit.

When power is restored at the treatment plant after power failure, the system shall not restart automatically but shall be re-started by the Operator.

Start Sequence Expected normal start sequence:

• Flow rate set point is selected/entered in WTP SCADA (this can occur at any stage);

• Start command from WTP;

• Ramp up Duty VSD to flow rate set point (normal ramp up speed duration);

• Signal sent for VSD running at flow rate set-point to WTP SCADA;

• Valves ramp open on delivery line (normal operation speed);

• Signal sent from Dumbleton Weir for valves opening to WTP;

• Valves ramp open inlet works of WTP (normal operation speed);

• Signals sent to WTP SCADA to confirm all valves are fully open; and

• Sequence completed.

Expected bleed line start sequence:

• Flow rate set point is selected/entered in WTP SCADA (this can occur at any stage);

• Start command from WTP;

• Ramp up Duty VSD to flow rate set point (slow ramp up speed duration);

• Signal sent for VSD running at flow rate set-point to WTP SCADA;

• Valves ramp open on delivery line (normal operation speed);

• Signal sent from Dumbleton Weir for valves opening to WTP;

• Bleed line process signalled from WTP SCADA to start;

• Bleed line process complete signal sent to WTP SCADA;

• Valves ramp open inlet works of WTP (normal operation speed);

• Signals sent to WTP SCADA to confirm all valves are fully open; and


Revision D


Stop Sequence and Interlock Expected normal stop sequence:

• Stop command from WTP;

• Ramp down Duty VSD (normal ramp down speed duration);

• Valves ramp closed on delivery line (normal operation speed);

• Signal sent from Dumbleton Weir for valves closing to WTP;

• Valves ramp closed inlet works of WTP (normal operation speed);

• Signal sent to WTP to confirm all actuators are fully closed;

• Signal sent from Dumbleton Weir to confirm VSD stopped to WTP; and


The following events cause the raw river water pumps to stop:

• If either river valves for delivery and termination line are closed during pump operation or fail to open correctly:


• River water Pumps failed to run (i.e. none of river water Pumps 1 – 4 ‘Running’ feedbacks from the telemetry system are active during pump operation):


• River water flow rate falls below 20L/s during river water plant operation:


• High-high turbidity alarm triggered at Dumbleton Weir:

− ‘High-High Turbidity Alarm’ signal sent to WTP


• Communication (heart beat signal) lost on the RTU, the pumps are shutdown by the local RTU if the communication is not re-instated after five minutes and the Main PLC indicates a ‘Communications Failure’ alarm:

− Where communications are lost the pump station shall continue operating for set ‘Communications Lost Duration’ timer (Operator adjustable and expected to be 5 minutes). Timer to be set no longer than the maximum operational time of the UPS

− Once timer is exceeded go to ‘Normal operation – stop process’

− SCADA will generate a communication failure alarm

− Communication failure alarm not acknowledge in preset time at WTP SCADA, then the communications failure alarm is escalated and dialled out to the appropriate personnel

− The ‘Communications Lost Duration’ timer should be reset every time the heartbeat is received. This restarts the timer at zero again and prevents it reaching its timeout value

− When the Dumbleton Weir pump station is selected to local the communications failure alarm shall not inhibit the pumps from running.

• WTP rapid stop command – generated by Nebo Road WTP:


Revision D

− rapid stop command received from WTP

− All chemical dosing on river feed, inlet works and river dosing tank at Dumbleton Weir and Nebo Road WTP to shut down

− Ramp down Duty VSD (emergency ramp down speed duration)

− Valves ramp closed on delivery line (emergency operation speed)





• Emergency stop – generated by Dumbleton Weir:

− Emergency stop command sent to WTP

− Ramp down Duty VSD (emergency ramp down speed duration – this may require instantaneous power disconnection depending on which emergency stop is used)

− Valves ramp closed on delivery line (emergency operation speed– this may require instantaneous power disconnection depending on which emergency stop is used)



− Chemical dosing in WTP shall stop according to their flow set-points


Emergency stop shall only be where the emergency stop button on the LCS of the running drive is activated.

• Power failure at Dumbleton Weir/pumps stop, delivery valves cannot close:

− ‘Dumbleton Weir Power Failure’ signal sent to WTP

− Valves ramp closed inlet works of WTP (normal operation speed)

− Signal sent to WTP to confirm status of all actuators

− SCADA will generate a Dumbleton Weir power failure alarm

− Dumbleton Weir power failure alarm not acknowledge in preset time at WTP SCADA, then the communications failure alarm is escalated and dialled out to the appropriate personnel.

• Power restored at Dumbleton Weir:

− ‘Dumbleton Weir Power Healthy’ signal sent to WTP






− Wait for Operator initiated start signal from WTP


Revision D

− Where the pump station is inactive for greater than 24 hours, the pump station shall only be allowed to remotely start using the bleed line start sequence.

• Power failure at Nebo Rd WTP/termination valves at the water treatment plant cannot close:

− ‘Nebo Road WTP Power Failure’ signal sent to SCADA

− Ramp down Duty VSD (normal ramp down speed duration)



− Signal sent to WTP to confirm all delivery status of all actuators


− SCADA will generate a Nebo Road WTP power failure alarm

− Nebo Road WTP power failure alarm not acknowledge in preset time at WTP SCADA, then the communications failure alarm is escalated and dialled out to the appropriate personnel.

• Power restored at Nebo Road WTP:

− ‘Nebo Road WTP Power Healthy’ signal sent to WTP SCADA

− Valves ramp closed on termination line (normal operation speed)




− Wait for Operator initiated start signal from WTP

− Where the pump station is inactive for greater than 24 hours, the pump station shall only be allowed to remotely start using the bleed line start sequence.

Monitoring and Indication Open and closed limit switches are provided on both river water valves FV11003 and FV11002. FV11003 and FV11002 send open and close status to its local control station and to the SCADA/HMI for monitoring.

Surge pipe overflow flow switch (LSH20501) is wired to the Main PLC input. The input shall be used for a SCADA/HMI status display only.

An allowance shall be made for the display of the following information from Dumbleton Weir:

1. Instruments:

− Turbidity (installed as part of Nebo Road WTP upgrade)



− Pressure

− Position

− Other.

2. Pump status.

3. Actuator status.


Revision D

4. Remote /off/local selection.

5. Emergency stop status.

6. Access door status.

Alarm Status The open or close command and general valve fail alarm will be used to determine whether a ‘Failed to Close’ or ‘Failed to Open’ alarm will be raised on the corresponding valve. ‘Failed to Open’ and ‘Failed to Close’ alarm time set-points shall be displayed and can be adjusted by the Operator from the SCADA/HMI system. If both valves fail to open, a ‘River Water Feed System Failed’ alarm will be raised.

At the existing surge tower the level switch LSH20501 monitors the level and sends a Level High alarm to the SCADA/HMI.

An allowance for alarm status from Dumbleton Weir is required for, but not limited to the following:

1. Instruments:

− Turbidity (installed as part of Nebo Road WTP upgrade)



− Pressure

− Position

− Other.

2. Pump status.

3. Actuator status.

4. Remote /off/local selection.

5. Emergency stop status.

6. Access door status.


Revision D

APPENDIX E River Water Chemical Dosing Matrix


Revision D

River Dosing Tank Chemical Matrix Chart

In and around the river dosing tank are several different chemical dosing locations, which have been based on certain river water quality.

During normal operation all plant flow will flow through the river dosing tank and all the associated chemical will us the flow signal generated by FE29531 for proportional flow control. When the river dosing tank is bypassed, the proportional flow control signal is generated from the summation of all filter outlet flows.

The following tables represent the most common conditions, which the operator will be confronted with:

Refer to P&ID’s 004-7032-5003, 5004 & 5005 for valve locations.

Normal Conditions <50 ML/d

Normal Conditions >50 ML/d

pH Monitoring

RDT Mixer

KMnO4 NaOH POLYMER PAC ACH

Valve Number

FV29

507

FV29

507

MV2

9501

MV2

9502

FV65

621

FV66

776

FV29

123

FV65

267

FV65

277

FV65

287

FV29

113

FV65

712

FV65

722

FV65

363

FV65

322

FV65

332

FV65

342

Open○ Close●

● ○ ● ○ ● ● ● ● ● ○ ● ● ● ● ● ● ○

pH Monitoring

RDT Mixer


Valve Number

FV29

507

FV29

507

MV2

9501

MV2

9502

FV65

621

FV66

776

FV29

123

FV65

267

FV65

277

FV65

287

FV29

113

FV65

712

FV65

722

FV65

363

FV65

322

FV65

332

FV65

342

Open○ Close●

● ○ ○ ○ ● ● ● ● ● ○ ● ● ● ● ○ ● ●


Revision D

Normal Conditions <50 ML/d Alternative

High Manganese River Conditions

High Taste and Odour River Conditions

pH Monitoring

RDT Mixer


Valve Number

FV29

507

FV29

507

MV2

9501

MV2

9502

FV65

621

FV66

776

FV29

123

FV65

267

FV65

277

FV65

287

FV29

113

FV65

712

FV65

722

FV65

363

FV65

322

FV65

332

FV65

342

Open○ Close●

● ○ ● ● ● ● ● ● ● ○ ● ● ● ● ● ○ ●

pH Monitoring

RDT Mixer


Valve Number

FV29

507

FV29

507

MV2

9501

MV2

9502

FV65

621

FV66

776

FV29

123

FV65

267

FV65

277

FV65

287

FV29

113

FV65

712

FV65

722

FV65

363

FV65

322

FV65

332

FV65

342

Open○ Close●

● ○ ● ○ ○ ○ ● ● ● ○ ● ● ● ● ● ● ○

pH Monitoring

RDT Mixer


Valve Number

FV29

507

FV29

507

MV2

9501

MV2

9502

FV65

621

FV66

776

FV29

123

FV65

267

FV65

277

FV65

287

FV29

113

FV65

712

FV65

722

FV65

363

FV65

322

FV65

332

FV65

342

Open○ Close●

● ○ ○ ○ ● ● ● ● ● ○ ● ○ ● ● ● ● ○


Revision D

High Taste and Odour with High Manganese River Conditions

River Dosing Tank Bypassed

pH Monitoring

RDT Mixer


Valve Number

FV29

507

FV29

507

MV2

9501

MV2

9502

FV65

621

FV66

776

FV29

123

FV65

267

FV65

277

FV65

287

FV29

113

FV65

712

FV65

722

FV65

363

FV65

322

FV65

332

FV65

342

Open○ Close●

● ○ ● ○ ○ ○ ● ● ● ○ ● ● ○ ● ● ● ○

pH Monitoring

RDWT Mixer


Valve Number

FV29

507

FV29

507

MV2

9501

MV2

9502

FV65

621

FV66

776

FV29

123

FV65

267

FV65

277

FV65

287

FV29

113

FV65

712

FV65

722

FV65

363

FV65

322

FV65

332

FV65

342

Open○ Close●

○ ● ● ● ● ● ● ● ● ● ○ ● ● ○ ● ● ●