Evaluation of Filtration Technologies and Upgrade of the Filtration System at

the Cadillac Wastewater Treatment Plant

Presenter: Walid Al-Ani, P.Eng, P.E., BCEE, LEED® AP Project Manager for Stantec Consulting Michigan

Inc.

Overview of the Cadillac WWTP

Background Information

Filtration Technologies Evaluation &

Selection

Design Highlights

Construction Highlights

Post-Construction Performance

Questions and Answers

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Presentation Overview

Plant Rated for 3.2 MGD Average Daily Flow and 4.5 MGD Maximum Daily

Flow

Influent Pump Station – Screw Pumps

Equalization Basin

Preliminary Treatment

Primary Treatment

Secondary Treatment – Activated Sludge/Chemical Addition for

Phosphorous Removal

Rotating Biological Contactors

Tertiary Filters

UV Disinfection

Anaerobic Digestion

Biosolids Land Application3

Overview of the Cadillac WWTP

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Aerial View of the Cadillac WWTP

Project plan prepared in 2006 to address overall plant needs –

Requirement for seeking State Revolving Funds (SRF)

Tertiary Treatment major needs identified:

◦ Replacement of the sand filters that were nearing the end of their useful life

◦ Replacement of the sampling pumps

◦ Replacement of the samplers

Design completed in the summer of 2007

Construction completed in the early spring of 2008

Overall construction cost approximately $3,800,000

Construction cost for Tertiary Treatment Improvements approximately

$1,000,000

Construction cost for the installed filters approximately $620,000

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Background Information

Three sand filters (Hydroclear)

commissioned in 1977 Some rehabilitation work performed over

the years including replacement of filter

media, valves, and control system Deteriorating performance and extensive

backwashing necessary

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Filtration System Before Implementing Improvements

Filtration Technologies Preliminary Options

Traveling Bridge Filters

Traveling Hood Filters

Disc Cloth Media Filters

Synthetic Media Filters

Deep Sand Filters

Membrane Biological Reactors

(MBRs)

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Traveling Bridge Sand Filters Continuous downflows, automatic backwash, low head, granular

medium depth filter.

Filter bed is divided into independent filter cells.

Treated wastewater flows through the medium by gravity and exits to the clearwell plenum via a porous-plate, polyethylene underdrain.

Each filter cell is backwashed individually by an overhead traveling – bridge assembly, while the other cells remain in service.

During the backwash cycle, wastewater is filtered continuously through the cells that are not being backwashed.

Example is the US Filter Davco Products – Gravisand.8

Traveling Bridge Sand Filters

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Source Aqua-Aerobics Systems, Inc.

Traveling Hood Sand Filters

Similar to the Traveling Bridge Sand Filter.

Uses a pneumatically driven self – propelled hood instead of a conventional rail-mounted traveling bridge.

Simpler, more compact installation, lower equipment cost compared to the Traveling Bridge Sand Filter.

Example is EIMCO Water Technologies.

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Traveling Hood Sand Filters

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Source Water Online

Disc Cloth Media Filters

Filter tank contains a series of circular disk elements covered with a specialized cloth media.

The cloth media traps particulates within its interior as well as forming a particulate layer upon its outer surface.

Backwash cycle begins at a predetermined water level.

During the backwash cycle, the center tube rotates while a centrifugal pump draws filtered water through a suction header from the clean side of the filter cloth.

Examples are the Aqua-Aerobic Aqua Disks and the Kruger Hydrotech Disc Filter.

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Disc Cloth Media Filters

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Source Aqua-Aerobic Systems, Inc.

Synthetic Medium Filters Filters use highly porous synthetic medium. Porosity modified by compressing the filter medium. Wastewater flows through medium; not around

filtering medium as in conventional sand and anthracite filters.

Wastewater introduced in bottom of filter and flows upward through filter medium, which is retained by two porous plates.

Upper porous plate raised mechanically in backwash. Flow to filter continues and air introduced below lower porous plate causing medium to move in a rolling motion.

Example is Schreiber’s Fuzzy Filter.

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Synthetic Medium Filters

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Source SchreiberSource: Schreiber

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Deep Bed Upflow Continuous Backwash Sand Filters

• Wastewater introduced into bottom of filter where it flows upward through a series of riser tubes.

• Wastewater then flows upward through downward moving sand and exits filter.

• Sand particles and trapped solids are drawn downward into the suction of an airlift pipe. A small volume of compressed air draws sand, solids, and water upward.

• At the top of the airlift, the dirty slurry spills over into a central reject compartment. Sand settles and is cleaned further as it moves down through a washer.

• Example is Parkson’s DynaSand Filter.

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Deep Bed Upflow Continuous Backwash Sand Filters

Source DynaSand

Source: DynaSand

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Membrane Biological Reactors (MBRs)

• MBRs combine secondary & tertiary treatment into one process.

• Integrated bioreactor uses membranes immersed in bioreactor; re-circulated MBR in which mixed liquid circulates through a membrane module located outside the bioreactor.

• In the integrated bioreactor wastewater is drawn through the membranes using vacuum. Compressed air is used to scour the membrane surfaces.

• In the re-circulated MBR wastewater is pumped into the membranes where solids are retained inside the membranes and wastewater passes through to the outside. The membranes are backwashed systematically to remove solids.

• Examples are MBRs manufactured by Zenon, US Filter Memcor, and Envirogroup.

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Membrane Biological Reactors (MBRs)

Source: Memcor

Required performance based on NPDES effluent limitations for the summer months listed in the Cadillac WWTP permit:◦ 30-Day Average BOD5 7 mg/L◦ 30-Day Average TSS 20 mg/L◦ 30-Day Average Ammonia Nitrogen (N) 0.9 mg/L◦ 30-Day Average Phosphorous 0.5 mg/L

• Evaluation of all technologies indicated that the effluent limitation for TSS could be met.

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Evaluation of Filtration Technologies - Performance

Filter Type Budgetary Price *

Traveling Bridge Sand Filter $200,000

Traveling Hood Sand Filter $300,000

Disc Cloth Media Filter $500,000

Synthetic Media Filter $700,000

Deep Bed Sand Filter $800,000

Membrane Biological Reactor $2,400,000

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Evaluation of Filtration Technologies

Cost

* 2006 Prices – Based on equipment cost from manufacturers

Filter Type Remarks

Traveling Bridge Sand Filter Does not fit into the existing building.

Traveling Hood Sand Filter Does not fit into the existing filter footprint but may fit into existing building with structural modifications.

Disc Cloth Media Filter Fits into the existing filter footprint but requires removal of the mud well.

Synthetic Media Filter Fits into the existing filter footprint but requires removal of the mud well.

Deep Bed Sand Filter Does not fit into the existing building.

Membrane Biological Reactor Does not fit into the existing filter footprint but may fit into existing building with structural modifications. 22

Evaluation of Filtration Technologies Footprint and Required Modifications to

Existing Facilities

Filter Type Remarks Warrants Further

Consideration

Traveling Bridge Sand Filter

Does not fit into existing building

No

Traveling Hood Sand Filter

Does fit into existing filters footprint

No

Disc Cloth Media Filter Fits into existing filters footprint

Yes

Synthetic Media Filter Fits into existing filters footprint

Yes

Deep Bed Sand Filter Does not fit into existing building

No

Membrane Biological Reactor

Does not fit into existing building and is too costly

No

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Evaluation of Filtration Technologies - Summary

Filter Type

Installations in MI and other Surrounding States as of early 2007

Remarks Warrants Further

Consideration

Disc Cloth Filter Media (Aqua – Aerobic)

Several nationwide including MI

•Will not require pilot testing due to sufficient experience in MI•Site visit to Sutton Bay WWTP, MI•Conference call with Superintendent of Champagne Sanitary District WWTP

Yes

Disc Cloth Filter Media (Kruger)

One in MI one in Ravenna, OH

•May require pilot testing due to limited experience in MI•Site visit to Ravenna WWTP, OH

Yes

Synthetic Media Filter (Schreiber)

One in MI •Likely to require pilot testing due to limited experience in MI and high loading rates due to small footprint

No

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Evaluation of Filtration Technologies

Item of Comparison

Cloth Media Disc Filter (Aqua-Aerobic)

Cloth Media Disc Filter (Kruger)

Equipment Cost $547,000 $500,000

Structural Modifications

•Demolition of Mud Well•Columns and beams remain

•Partial demolition of mud well •Columns and beams remain•Significant concrete work required to accommodate open channel flows

Access Into Existing Building

•Requires demolition of building exterior wall

•Requires demolition of building exterior wall

Experience in Michigan

•Several Installations•Pilot testing not required

•One installation only as of early 2007•Pilot testing likely required

Experience at Similar Installations

Sutton Bay WWTP•In Operation since 2006•No Mechanical Problems•Good Workmanship

Urbana-Champagne Sanitary District WWTP•In Operation since 2005•Good responsiveness during construction, start-up, and post construction•Decision to install same type of filters at the larger District’s WWTP•Peak flows of 17 MGD were handled with no reported problems

Ravenna WWTP•Difficulty meeting the 2 MGD peak flow with one filter out of service•Belt supporting the discs has failed•Major rigging required for belt replacement

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Evaluation of Filtration Technologies

Decision was to adopt the cloth media filter technology (Aqua-Aerobic) based on the following:

Established experience nationwide including Michigan

Ease of Maintenance Demonstrated ability to handle peak flows Ability to meet the project’s strict milestones

since no pilot testing would be required

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Final Selection of Filtration Technology

Limitations on when construction could occur had to be established, due to the NPDES Limitations

Higher SS discharge limits allowed December 1 through April 30 (30 lbs/day on a monthly basis compared to 20 lbs/day for rest of the year)

Therefore, taking the existing filters off-line and completing installation of the new filters was allowed for December 1 through April 1

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Design Highlights Limitations

Structural integrity had to be confirmed to allow partial demolition of the walls and slab

Existing piping arrangement had to be confirmed to allow bypass of the filters to the disinfection process

Demolition of existing exterior walls had to be addressed to verify

access issues 28

Design Highlights Demolition Work

Hydraulic calculations had to be performed to ensure new filters would not be a bottleneck

Filters, piping, platforms, and controls had to be fitted into the existing space

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Design Highlights New Work

Entire work (demolition, installation, start-up, on-line) had to be completed in three months

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Construction Highlights Challenges

Access limited through existing building wall

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Construction Highlights Challenges

Filters demolished and removed

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Construction Highlights Demolition Work

All piping in gallery removed

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Construction Highlights Demolition Work

“Mud Well” slab demolished

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Construction Highlights Demolition Work

New Floor

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Construction Highlights New Work

Filter concrete support pads

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Construction Highlights New Work

New filter piping

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Construction Highlights New Work

Filters installed on concrete pads

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Construction Highlights New Work

New piping in gallery

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Construction Highlights New Work

Filters in operation

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Operation and Controls Highlights

Filter Control Panels

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Operation and Controls Highlights

Backwash and Sludge Valves

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Operation and Controls Highlights

Back Wash Cycle Back Wash Initiation:

◦ Water level exceeds specified level◦ Time interval elapses◦ Manual back wash cycle◦ High level float switch activates

Back Wash Set Points:◦ Back Wash interval, time between

automatic backwash cycles◦ Back Wash duration, wash time for

each collection manifold◦ Back Wash level, water level that

triggers a back wash cycle

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Operation and Controls Highlights

Sludge Cycle Sludge Removal Initiation:

◦ Time interval elapses◦ Back wash counts elapse◦ Manual sludge cycle

Sludge Cycle Set Points:◦ Sludge interval, time between

automatic sludge cycles◦ Backwash count, number of back

washes between automatic sludge cycles

◦ Sludge duration, duration of the sludge cycle

Filters are operating successfully and meeting the NPDES requirements

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Operation and Controls Highlights

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Questions & Answers