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Tender 12000123-HD-48002 Annexure-1, Page No.1

Annexure-I

IETP Process - BASIS OF DESIGN

EFFLUENT SEGREGATION & COLLECTION

Following Collection and segregation philosophy is adopted for various effluent generated in refinery.

The refinery has two sections, viz., Fuel refinery (FR) and Lube refinery (LR). Refining of crude is a complex

process, which involves physical separation of products on the basis of difference in their boiling points. This is

achieved in the primary operations like atmospheric distillation units and vacuum distillation units. Secondary

processing units include catalytic cracking of low value heavier hydrocarbon products to yield lighter hydrocarbon

products and lube refining processes such as solvent extraction, solvent de-waxing and solvent de-asphalting.

Finally, product treatment is done in order to maintain product quality conforming to required standards.

One of the most pertinent aspects in the design of any effluent treatment plant is the effluent collection scheme.

A segregated system of collection not only makes the refinery operations easier but also makes control on the

effluent quality more effective. For effective operation of biological section of the ETP, sea cooling water streams

shall never be allowed to enter into the ETP feed network.

Effluents from the different refinery units are segregated depending upon the stream quality to achieve optimum

sizing of specific treatment sub-systems, thereby reducing the overall costs of installation and operation of the

treatment plant. The principal contaminants in different streams include the following:

Stream Description Principal Contaminants

Process (Oily) Effluents Oil, BOD/COD, TSS, Phenols, Sulfides

Spent Caustic Sulfides, Phenols, BOD/COD, Oil

Contaminated Rain Water Oil, BOD/COD, TSS

Sanitary Waste BOD, TSS

After reviewing the existing effluent collection system, various modifications have been proposed in the same.

NEW INTEGRATED ETP FEED STREAMS

The following effluent streams are to be routed to the new Integrated ETP for treatment:

Process Streams

Following Streams from process area have been considered as a part of process streams:


Stripped / Un-stripped sour water from GFEC-SWS (Sour Water Stripper)

Stripped / Un-stripped sour water from DHDS – SWS (Sour Water Stripper)

Sour water from existing FCCU

Spent caustic streams from existing refinery units

Spent caustic streams from GFEC units

Catch basin water & Spent caustic streams from NMP-I/II/III

FR/FRE flare seal drum & flare K.O. drum

LR flare seal drum & PDA K.O. drum

Tank farm drains

Miscellaneous streams from FR/FRE

Miscellaneous streams from LR/LRE

Effluent from proposed LOBS project

ATF Wash Water

Hexane-NMP ejector condensate water

The above stream are routed to new Integrated ETP.

Non-Process Streams

The non-process effluent mainly consists of the following:

1. Floor washes

2. Gland cooling water

3. Cleaning / washing of units

4. Boiler blow down


These non-process effluent streams other than boiler blow down are also be treated in the new Integrated ETP

during dry weather flow conditions, whereas the same shall be treated in the existing API bays over and above

the design capacity of the new Integrated ETP during wet weather flow condition.

Contaminated Rain Water

No separate system exists in the refinery to divert Contaminated Rain Water (CRW). In view of this, contaminated

and un-contaminated rainwater along with various other effluent streams (including floor washes, leakages /

spillages, pump gland leaks, laboratory drains / washings, canteen waste, sampling drains, etc.) are to be routed

to the dirty water sewer (DWS) / oily waste sewer (OWS) system as per existing philosophy. During dry weather

flow conditions, these streams are to be treated in the new Integrated ETP. However, during wet weather flow

conditions, these streams along with contaminated / un-contaminated rain water are to be treated in the existing

API separators for oil recovery over and above the design capacity of the new Integrated ETP.

COOLING WATER STREAMS

For sustainable operation of any effluent treatment plant, it is of utmost concern that salt water shall never be

allowed to mix with the effluent streams. An ETP (conventional or advanced) cannot handle salty effluent which

has TDS more than 5000 ppm on a sustained basis. In case of HPCL-Mumbai Refinery, the predominant sea

cooling water streams, which enters the existing gravity sewer network leading to ETPs/API shall be diverted to

as per the following philosophy.

FR / FRE / LEU coolers back-flushing waste

Sea cooling water back-flushing and draining (to MAT) wastes from various coolers of FR/FRE are presently being

diverted to the dirty water sewer. All these back-flushing and draining wastes to be routed to storm water sewer

(SS) with a connection to clean water sewer (CWS) so that the operator may decide to route the back-flushing

waste either to SS or to CWS depending on the oil leakage observed. Necessary piping works for diversion of

these streams to SS/CWS has been considered under the scope of this project.

LR/LRE coolers back-flushing waste

Sea cooling water back-flushing and draining (to MAT) wastes from various coolers of LR/LRE are presently being

diverted to the oily waste sewer (OWS). All these back-flushing and draining wastes shall be collected in a

common header and shall be routed to the new API separators proposed at the inlet section of the Skim pond.

Necessary piping works for diversion of these streams has been considered under the scope of this project.

DHDS / SRU coolers back-flushing waste


Sea cooling water back-flushing and draining (to MAT) wastes from various coolers of DHDS/SRU are presently

being diverted to the dirty water sewer. CWS does not exist in this area. All these back-flushing and draining of

identified Cooler shall be connected to SWC only which exists on the west side of the unit.

SANITARY EFFLUENT

Exiting sanitary lines to Imhoff tank within new Integrated ETP battery limit are to be re-routed to make space

available for the new Integrated ETP.

A new package treatment plant has been envisaged to treat sanitary effluent and new administration building

canteen waste. Treated sanitary effluent shall be disposed off to sea with a provision to further treat in biological

section of new Integrated ETP in case of non-availability of sufficient feed to the new Integrated ETP.

SUMMARY OF EFFLUENTS TO BE TREATED IN NEW INTEGRATED ETP

A brief description of the effluent streams to be treated in the proposed new Integrated ETP along with their

proposed routing to new Integrated ETP is given in the previous sections. Summary of these effluent streams and

their design flow is given below:

Sr.

No.

Effluent Stream Design Flow

(m3/h)

Basis

1. Stripped / Un-stripped sour water from GFEC /

Existing units

120* Note-1

2. Stripped / Un-stripped sour water from DHDS 17* Note-2

3. Sour Water from Existing FCCU 12* Note-2

4. Spent Caustic (GFEC streams) 2* GFEC design basis

5. Spent Caustic from PC-D-200 Drum:

Existing streams (1.75 m3/h)

HM unit boot water (1.5 m3/day)

FR/FRE stabilizers boot water

ATF caustic bubbler effluent

Rock salt filter entrained water

3 Note-2

6. Effluent from ATF Effluent Tank: 5 Note-2


ATF Wash Water (1.25 m3/hr)

Hexane-NMP ejector condensate water (3 m3/h):

Note-6

7. Effluent from P-175 Sump:

Catch basin water from NMI-I, II & III (3 m3/h-1 m3/h

from each unit)

LR flare seal drum & PDA K.O. drum (2 m3/h)

FR/FRE flare seal drum (2 m3/h)

7 Note-2

8. Spent caustic from New Spent Caustic Collection

Drum NMP-I, II & III Spent Caustic Streams)

1 Note-2

9. Miscellaneous non-process effluent streams from

DWS-ETP Feed Pit:

Floor washes (by non-salty water), Leakages/spillages

and Pump gland leaks (25 m3/h)

Desalter desludging waste (5 m3/h)

Tank Farm drains (5 m3/h)

Lab drains / washing & Slop oil from storm water oil

catchers (5 m3/h)

Sampling drains (1 m3/h)

Contaminated rain water (not included in design

capacity of the new Integrated ETP and to be treated

in the existing API separators)

41 Note-3

10. Miscellaneous non-process effluent streams from

new LR/LRE Floor wash API separator:

Floor washes (by non-salty water),

leakages/spillages and pump gland leaks (20 m3/h)

Tank Farm drains (5 m3/h)

Canteen waste (1 m3/h)

27 Note-3


Sampling drains (1 m3/h)

Contaminated rain water (not included in design

capacity of the new Integrated ETP and to be treated

in the new LR-API separators

11. Crude Tank Drains from LR/LRE ETP Feed Pumps 30 Note-3

12. Effluent from Proposed LOBS project 7 Note-2

13. Sanitary Effluent – 21 m3/h and New Admin Building

Canteen waste – 4 m3/h (to be mixed at inlet of the

biological section of the new Integrated ETP after

treatment in the new Sanitary Effluent Treatment

Package)

25 Note -3

14 Oily Effluent Streams (excluding spent caustic and

sanitary effluent )

Additional Design Margins (10%)

TOTAL

266

26.6

292.6

300 (say)

Note 2

15 Treated Sanitary Effluent & New Admin Building

Canteen Waste

25 Note 2

16 Spent Caustic Streams 6 Note 2

*These effluent to be routed to the New Integrated ETP under ongoing GFEC project. No new routing is

envisaged for these streams under the new Integrated ETP project.

Notes:


Refer Design Basis for GFEC – Sour Water Stripper

These figures are based on operating data furnished by HPCL.

Design basis for various flows shall be as follows.

Basis for FR/FRE/LEU/DHDS/SRU/GFEC Floor Wash Flow Rates:

Location No. of

Operating

Hoses

Average Flow Rate

(m3/hr)

Operating Hours

(Hr)

Total Flow

(m3/day)

FR 12 6 2 144

FRE 6 6 2 72

LEU 4 6 2 48

DHDS/SRU 6 6 2 72

GFEC 6 6 2 72

Miscellaneous 10 6 2 120

Total Floor Wash Flow (m3/day) 528

Average Floor Wash Flow (m3/hr) 22

Average Floor Wash Flow Considered (m3/hr) 25

Basis for LR/LRE Floor Wash Flow Rates:

Location No. of Operating

Hoses

Average Flow Rate

(m3/hr)

Operating Hours

(Hr)

Total Flow

(m3/day)


LR 15 6 2 180

LRE 10 6 2 120

Miscellaneous 10 6 2 120

Total Flow (m3/day) 420

Average Floor Wash Flow (m3/hr) 17.5

Average Floor Wash Flow Considered (m3/hr) 20

Basis for Sanitary Effluent Flow Rates:

Number of persons = 1500 (HPCL personnel) + 500 (Additional)

Average Effluent (as per Sewage Manual) = 250 liter /day / person

Total Sanitary Effluent = 2000 x 250 / 1000 x 24 =20.8 m3/hr

Total Sanitary Effluent Considered = 21 m3/hr

Basis for New Admin Building Canteen Waste Flow Rates:

Number of persons = 1500

Average Effluent = 50 liter/day/person

Total Canteen Effluent = 1500 x 50 / 1000 x 24 = 3.2 m3/hr

Total Sanitary Effluent Considered = 4 m3/hr

Basis for LR Canteen Waste Flow Rates:


Number of persons = 1500

Average Effluent = 50 liter/day/person

Total Canteen Effluent = 500 x 50 / 1000 x 24 = 1.0 m3/hr

Total Sanitary Effluent Considered = 1m3/hr

Basis for New Crude Tank Drains

Capacity of one Crude Tank = 90,000 m3

BS&W (Average) = (1.0 - 0.05) % = 0.95%

Water to be drained from Each Tank = 855 m3/day

Average Crude Tank Drains = 35.6 m3/hr

ETP to be designed for the following capacity:

Oily effluent streams ( 300 m3 / Hr)

Spent caustic streams ( 6 m3 / Hr)

Sanitary effluent streams, for which New Sanitary effluent treatment package is proposed. (25 m3 / Hr)

RAW EFFLUENT CHARACTERISTICS

The effluent to be treated in the new Integrated ETP can be broadly classified as:

Oily effluent streams

Spent caustic effluent streams

Sanitary effluent streams


A. OILY EFFLUENT STREAMS

Oily effluent streams from various parts of the refinery is collected and routed to the Battery Limit of ETP for

treatment.

Design Flow (Oily Effluent Streams): 300 m3/hr

Parameter Concentration

Temperature 25 Deg C

pH 5.5 – 9.0

Oil 1000 - 20000

Total Suspended Solids 200

BOD @ 270C, 3 Days 1000

COD 1700

Total Sulphide as S 235

Phenols 100

Total Dissolved Solids 5000

Organophosphate as PO4 10

Conductivity, micro mho/cm 9000

M Alkalinity as CaCO3 2000

Calcium Hardness as CaCO3 190

Magnesium Hardness as CaCO3 2380


Chlorides as Cl 300

Sulphates as SO4 830

Nitrate + Phosphate as PO4 + NO3 78

Ammonia as NH3 90

Iron as Fe 1


Total Silica as SiO2 25

Reactive Silica as SiO2 22.5

SDI Out of Range

KMnO4 consumption at 370 C 10

All other Metals Traces

All units are in mg/l except pH or as specified.

Notes :

The New IETP will be designed for maximum TDS Load of 5000 mg / lit.

Free Oil handling units will be designed for maximum oil of 20,000 ppm.

For Emulsified Oil, units will be designed for 500 mg/l.

Free and emulsified portion to be considered at 80% and 20% respectively for normal oil conc of 1000 mg/l in the

raw effluent stream.

Total Sulphide levels also include Mercaptant.


B. SPENT CAUSTIC STREAMS

Spent caustic streams from refinery units will be stored within IETP battery limit before feeding to the New IETP

at controlled rate for the treatment of its high sulfide concentration and other contaminants. The treatment

envisaged for this stream is Oxidation by Hydrogen peroxide treatment.

Design flow: 6 m3/hr


pH 13.6

Oil & Grease 200


Total Suspended Solids 2200

BOD27 deg. C, 3 days 25000

COD 60000

Total Sulfides (as S) 6500

Phenols 2000

Mercaptans 5

Sodium Thiosulphate 9%

Sodium Carbonate 11.5%

Crystallates 0.5%

Sulphates 400

Ammonical Nitrogen 25

Total Dissolved Solids 125000


C. SANITARY EFFLUENT

Sanitary waste from the refinery complex and canteen effluent from the canteen of New Admin Building will be

routed to a sanitary effluent treatment package unit. The quantity and quality of sanitary waste will be as under.


Design flow: 25 m3/hr


BOD 200

COD 400

TSS 200

All units are in mg/l .

TREATED EFFLUENT CHARACTERISTICS


A. Treated Effluent Characteristics AT PLANT OUtLET

The treated effluent will be of fresh water quality and will be recycled as D.M. plant feed / Floor wash water

network. It should meet the following design parameters.

SR.NO. PARAMETER CONCENTRATION

1 pH 6.7 - 7.8

2 Turbidity 1.0 NTU

3 Total Suspended Solids 1.0

4 Total Dissolved Solids 120

5 Total Cation/Total Anion as CaCO3 100

6 BOD BDL

7 COD 3

8 KmnO4 value @ 100 degree C 5

9 Oil & Grease NIL

10 MO-Alkalinity as CaCO3 66.0

11 Chloride as Cl 30

12 Sulphate as SO4 17

13 Total Silica as SiO2 1.0



Effluent from the plant, if required to be disposed off, will meet the quantitative and qualitative limits of

parameters stipulated in Minimal National Standards (MINAS-Refineries) as given below:

SR. NO. Parameter Limiting value for

concentration (mg/l,

except for pH)

Limiting value for

quantum (kg/1000

tonne of crude

processed, except for

pH)

Averaging Period

Parameters to be monitored daily: grab samples for each shift with 8-hours interval.

1. pH 6.0 – 8.5 - Grab

2. Oil & Grease 5 2 -do-

Parameters to be monitored daily: composite sample (with 8-hours interval) for 24-hours flow

weighted average.

3 BOD3 days 27 deg.C, 15 6 24-hours

4. COD 125 50 -do-

5. SS 20 8 -do-

6. Phenols 0.35 0.14 -do-

7. Sulphides 0.5 0.2 -do-

8. CN 0.2 0.08 -do-


Parameters to be monitored once in a month: composite sample (with 8-hours interval) for 24 hours

flow weighted average.

9. Ammonia as N 15 6 -do-

10. TKN 40 16 -do-

11. P 3 1.2 -do-

12. Cr (VI) 0.1 0.04 -do-

13. Total Cr 2.0 0.8 -do-

14. Pb 0.1 0.04 -do-

15. Hg 0.01 0.004 -do-

16. Zn 5.0 2 -do-

17. Ni 1.0 0.4 -do-

18. Cu 1.0 0.4 -do-

SR. NO. Parameter Limiting value for

concentration (mg/l,

except for pH)

Limiting value for

quantum (kg/1000

tonne of crude

processed, except for

pH)

Averaging Period

19 V 0.2 0.8 -do-

Parameters to be monitored once in a month: grab samples for each shift with 8-hours interval.

20. Benzene 0.1 0.04 Grab

21. Benzo (a)

Pyrene

0.2 0.08 -do-

B. RAW & TREATED EFFLUENT CHARACTERISTICS AT SBR INLET & OUTLET

The following is the quality and quantity of Raw and Treated effluent characteristics for the SBR unit.


SR. NO. PARAMETER CHARACTERISTICS (MG/L)

RAW EFFLUENT

TREATED EFFLUENT

1 Flow (m3 / hr) 300 300

2 BOD 27 deg @ 3 days 1000 ≤20

3 COD 1700 ≤100

4 Sulphides 50 ≤30

5 Phenols 100 ≤20

6 Suspended Solids 100 ≤10

7 Total Nitrogen 115 ≤10

8 Ammonical Nitrogen 74 ≤2

9 Phosphorous 10 ≤1

10 Oil and Grease 10 ≤10

C. TREATED EFFLUENT CHARACTERISTICS AT MBR OUTLET

The following is the quality and quantity of Raw and Treated effluent characteristics for the MBR unit.

SR. NO. PARAMETER

UNIT INFLUENT EFFLUENT

Flow m3 / hr 300 300

Raw water Temperature Deg. 25 (minimum) NA


(Note 1) Centigrade 35 (maximum)

BOD3 days 27 deg.C mg/l 100 < 5

COD mg/l 200 < 20 (Note 2)

Oil (max) mg/l 10 < 5 (Note 3)

TSS mg/l 20 < 3

Phenols mg/l 50 < 0.35 (Note 4)

Sulphides mg/l 40 < 0.5 (Note 5)

Total Nitrogen mg/l 35 < 7.0 (Note 6)

Phosphorous mg/l 3 < 3.0

Minimum Alkalinity (Note 7) mg/l 2000 NA

TDS mg/l 5,000 NA

SDI - NA < 3.0

pH - 7 – 8 6 – 8.5

Cyanide mg/l 1.0 < 0.2 (Note 7)

Note 1 : Minimum raw water temperature has been assumed to be 25 deg. Centigrade.

Note 2 : An effluent COD < 20 mg/l is achievable if the non-biodegradable portion of influent COD is < 20

mg/l.

Note 3: Oil present in the raw water should not be free oil. The effluent value is achievable if oil present is

biodegradable in nature.

Note 4: The effluent value is achievable if phenols present are biodegradable in nature.

Note 5: It is assumed that Sulphides are all in metal form and there is not H2S present.


Note 6: We have designed to achieve TN<7 mg/L. This effluent can be achieved based on the following

assumptions

Influent TN to MBR: 35 mg/L

TN in suspended form: 10 mg/L. It is assumed that this concentration will be maintained in suspended form and

will be rejected by the membrane system.

TN in soluble form: 25 mg/L. It is assumed that influent TKN: 15 mg/L and NO3-N: 10 mg/L

Maximum non-biodegradable content of soluble TN: 0.5 mg/L

Note 7: The effluent value is achievable if cyanide present are biodegradable in nature.

Note 8: Alkalinity of 2,000 mg/L in the influent.

Note 9: Maximum TDS value of 5,000 mg/L in the influent.

D. TREATED EFFLUENT CHARACTERISTICS AT RO OUTLET

SR.

NO. PARAMETER INFLUENT EFFLUENT

1 pH 7 6.7 - 7.8

2 Turbidity --- ≤1.0 NTU

3 Total Suspended Solids <5 1.0

4 Total Dissolved Solids 5000 120

5 BOD <5 BDL


6 COD

<20 BDL

7 Oil & Grease Nil BDL

8 Total silica as SiO2 25 <1


E. TREATED CHARACTERITICS OF SANITARY EFFLUENT

SR.NO. PARAMETER

CONCENTRATION

1 Flow, m3/hr 25

2 BOD, mg/l < 10


3 TSS, mg/l < 20

F. EQUIPMENT DESIGN PHILOSOPHY

Overall water recovery from the plant – 65% (min.) based on design conditions

Hydraulic Turn Down requirements - 30%

On stream factor – Plant should be able to operate round the year

PRINCIPLES OF TREATMENT


The wastewater contains pollutants that can be seen from the data presented under the design specifications,

which require different types of treatment to reduce their presence in the effluent to acceptable levels.

The processing scheme has broadly following types of treatment:

Physical Treatment

Chemical Treatment

Biological Treatment

Tertiary Treatment

Sludge Treatment

VOC Treatment

Sewage Treatment

The major operations involved in these processing scheme are:

Free Oil Removal

Emulsified Oil Removal


Sulphide Treatment

Biological Treatment

RO Treatment

Sludge Thickening & Centrifugation

Bio-Remediation

VOC Treatment

Sewage Treatment

The principles of the above operations are described below:

A. FREE OIL REMOVAL

Oil & grease in the wastewater can be present in essentially two main forms namely “FREE OIL” and “EMULSIFIED

OIL”. During transit of the oil contaminated water, various factors such as flow turbulence, temperature, presence

of other chemicals breaks the oil in smaller globules. The fraction of oil that under quiescent conditions can

coalesce and separate from the water phase due to the gravity differential of the two phases is termed as FREE

OIL. Generally, oil globules of above 60 micron are removed by API Oil Separators and less than 60 micron by TPI

Oil separators.


a. API Oil Separator

The separation of oil from water by gravity differential is based on the rise rate of oil globules. Since the oil

globules present will have varying sizes,for practical purposes the design is based on the rise rate of globules

having a diameter of 60 microns. The separation basins are designed to have low velocity (0.6 m/s) and minimum

cross or eddy currents, and sufficient retention time to permit the globule to coalesce and rise to the surface.

During its upward travel to the surface, particles coalesce to form a film of oil, which is mechanically skimmed and

recovered.

b. TPI Oil Separator

The current trend is to satisfy the increased separating area requirements by providing a number of stacked

plates. Thus, the separating surface area is increased vertically. The area is further increased by selecting

corrugated plates. The plates are located one on top of the other at specific distance from one another. The

entire plate pack is placed in a tank at an approx. angle of 45 degrees. Hence the unit is called as “Tilted Plate

Interceptor (TPI)”. The wastewater enters the plates either parallel to corrugations in “Counter Current Flow” or

at right angles to the corrugations in “Cross Flow” under laminar flow conditions. The short distance between the

inclined plates is now the only distance over which the oil globule has to rise before it is intercepted and

separated from the water. Due to the laminar flow conditions the separated oil globules coalesce into large

droplets and gradually rise to the surface. The film formed on the surface is then skimmed off through slotted

pipes.

B. EMULSIFIED OIL REMOVAL

An intimate, two - phase mixture of two immiscible liquids with one phase dispersed as minute globules in the

other phase is defined as an EMULSION. In the case of refinery wastes, the oil phase is intimately dispersed in the

water phase. Various factors contribute to the stability of this dispersion. The minute globules are stabilized by an

interfacial film or stabilizing agent such that the globules do not coalesce and do not respond to gravity settling. A

major factor contributing to the formation and stability of emulsions is the electrical charge carried by the

emulsified particles. In general, globules of oil in an oil-water emulsion may be broken by an electrical current or

by electrolytes supplying a sufficient concentration of effective ions which neutralize the surface charges on the

emulsified oil globules, permitting them to coalesce into larger globules.


Dissolved Air Flotation (DAF) is a process commonly used in refineries to remove emulsified oil and suspended

solids from gravity separator effluent. The process involves pressurizing the influent to DAF Unit and then

releasing the pressure, which creates minute bubbles that float suspended and oily particulates to the surface.

The floated material is collected by a mechanical froth skimmer.

If a significant portion of the oil is to be emulsified, chemicals are used for breaking the emulsion and enhancing

the separation. Chemicals normally used are Aluminum/ Iron salts and polyelectrolytes.

D. SULPHIDE TREATMENT

Sulphur is an inherent impurity in most crude oils, and its concentration depends on the source of the crude.

During the crude refining process, this impurity is separated from the product and discharged as a liquid effluent.

During the processing step the sulphur is converted to sulphide. The sulphides present in the effluent may be in

the form of free sulphides or as hydrogen sulphide depending on the pH of the stream. These compounds are

toxic in nature and need to the treated / removed prior to disposal of the effluent.

Sulphides are removed by chemically oxidizing them to elemental Sulphur or Sulphate using strong oxidising

agents such as Hydrogen Peroxide (H2O2), Ozone & Chlorine. In view of its various advantages, Hydrogen

Peroxide is normally the preferred chemical.

The reactions involved are as under:-

Acidic Range / Neutral Conditions

In acidic range and neutral conditions, sulphides in the effluent are mostly present in the form of H2S. The H2O2

reacts with H2S to give products of oxidation – water and elemental sulphur as shown below:


H2O2 + H2S 2 H2O + S

(Stoichiometrically 1.06 kg of H2O2 is required for 1 kg of sulphide)

Alkaline Range

In alkaline range, sulphides present in the effluent are generally in the form of Na2S. The H2O2 reacts with Na2S

to give end products as water and Na2SO4 (relatively harmless and impose no oxygen demand), as shown below.

4 H2O2 + Na2S Na2SO4 + 4 H2O

(Stoichiometrically 4.25 kg of H2O2 is required for 1 kg of sulphide.)

E. BIOLOGICAL TREATMENT

Organic matter, phenols, residual sulphides, non-recoverable oil and hydrocarbons contribute to the effluent’s

Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). BOD is indicative of the quantity of

oxygen required to biologically stabilize the organic matter present in the waste water, while the COD indicates

the oxygen requirement for oxidizing the organic matter by a strong chemical in an acidic medium, at elevated

temperature. In order to stabilize the organic matter, biological treatment of waste water is to be accomplished

by aerobic digestion of the organic matter. Most modern effluent treatment plants (ETP) in refineries employ

Sequential Batch Reactor (SBR) followed by Membrane Bio Reactor (MBR) systems for treatment of organics.

Sequential Batch Reactor (SBR)


in Sequential Batch Reactor system a Cyclic Activated Sludge Treatment (C-Tech) technology is used. It provides

highest treatment efficiency possible in a single step biological process. The C-Tech system is operated in a batch

reactor mode. This eliminates all the inefficiencies of the continuous processes. A batch reactor is a perfect

reactor, which ensures 100% treatment. Two or more modules are provided to ensure continuous treatment. The

complete process takes place in a single reactor, within which all biological treatment steps take place

sequentially as described below.

STEP 1: Fill-Aeration (F/A)

STEP 2: Settlement (S)

STEP 3: Decantation (D)

These phases in a sequence constitute a cycle, which is then repeated. During the period of a cycle, the liquid

volume inside the Reactor increases from a set operating bottom water level. During the Fill- Aeration sequence

mixed liquor from the aeration zone is recycled into the Selector. Aeration ends at a predetermined period of the

cycle to allow the biomass to flocculate and settle under quiescent conditions. After a specific settling period, the

treated supernatant is decanted, using a moving weir Decanter. The liquid level in the Reactor is so returned to

the bottom water level after which the cycle is repeated. Solids are wasted from the Reactor during the decanting

phase.

The C-Tech system selected is capable of achieving the following:

1. Removal of Organics

The effluent free from free oil & emulsified oil shall be taken up for Biological treatment for the removal of

organics, nitrogen and phosphorus. The activated sludge bio system is designed using Cyclic Activated Sludge

Technology which operate on extended Aeration activated sludge principle for the reduction of carbonaceous

BOD, Nitrification, Denitrification as well as phosphorous removal, using energy efficient fine bubble membrane

diffused aeration system, with automatic control of oxygen uptake rate, resulting in 20–30% power savings. The

practice of manipulating activated sludge reaction environments to obtain maximum nitrogen and phosphorous

removal has been optimized, using cyclic activated sludge technology, by co-current nitrification denitrification

mechanism. In its simplest form, the sequences of fill, aeration, settle and decant are consecutively and

continuously operated all in the same tank, allowing up to 30-40% space saving. No secondary clarifier system is

required to concentrate the sludge in the reactor. The return sludge is recycled and the surplus sludge is wasted

from the C-Tech basin to the Bio sludge sump.


2. Nitrification

Any oxidation must be coupled with reduction, and oxygen satisfies this requirement in the aerobic

microorganisms. Extended Aeration system, with high c values, ensures uniform nitrification performance.

Nitrification results from the oxidation of ammonia present in the sewage by Nitrosomanas to nitrite and the

subsequent oxidation of the nitrite to nitrate by Nitrobacter. The nitrifying organisms are strict aerobic

autotrophes and use carbon source present in the sewage, in the presence of oxygen, maintained at 2 mg/l in the

SBR to avoid oxygen limitation. The nitrification of ammonia can be represented as given below:

Nitrosomonas + 2 NH4+ + 3O2 ---------> 2 NO2- + 2 H2O + 4 H+ + New Cells

Nitrobactor + 2 NO2- + O2 ----------------> 2 NO3- + New Cells

The diffused aeration system is sized so that sufficient oxygen is provided for carbonaceous treatment, sludge

stabilisation, nitrification and maintaining the DO at the specified level of 2 mg/l, taking into account the

reduction in oxygen demand due to denitrification. The capacity of diffused aeration in each SBR basin will be

sufficient to ensure good mixing conditions during Fill Aeration phase of the cycle of operation.

3. Denitrification

The wastewater enters the Selector zone in the front end of the SBR, where anoxic conditions are maintained.

Part of the wastewater along with return sludge from the aeration SBR basin is recycled here, using RAS Pumps.

With the incorporation of biological Selector there is no need for an Anoxic – Mixing sequence and is therefore

replaced by a simple Fill – Aeration sequence. As the microorganisms meet high BOD, low DO condition in the

Selector zone, natural selection of phosphate accumulating microorganisms and floc-forming microorganisms

takes place. This is very effective in containing all of the known low F/M bulking microorganisms and eliminates

the problems of bulking and surface foaming. Also, due to the anoxic conditions in the Selector zone,

denitrification and phosphorous removal occurs by co-current nitrification & Denitrification. Complete

nitrification and denitrification pathways take place with nitrification taking place external to the activated sludge

flocs and denitrification taking place within the interior of the flocs. This denitrification pathway is not bound to

the absence of dissolved oxygen in the liquid phase but requires diffusion of nitrate into the anoxic parts of the


floc with a probable use of stored intracellular carbon or adsorbed organic carbon for denitrification. During

anaerobic conditions, all phosphorous that is released to the liquid phase is totally contained within the bio solids

layer. Biological denitrification in the Selector zone by recycling of mixed liquor from aeration zone requires

nitrification of all ammonical nitrogen in the incoming wastewater in the aeration zone. This requirement of plant

design is met by operating the SBR under Extended Aeration Process with higher C values, which ensure co-

current nitrification and denitrification in the aeration zone.

Denitrification releases nitrogen which escapes as an inert gas to the atmosphere, while the oxygen released stays

dissolved in the liquid and thus reduces the oxygen input needed for the aeration.

4. Carbonaceous BOD Removal

The aeration zone of SBR is provided with diffused aeration to oxidize the organic matter including phenol, by

Extended Aeration Process. An extended aeration activated sludge process operates in the endogenous

respiration phase of the growth curve where the microorganisms are forced to metabolize their own protoplasm

without replacement, since the concentration of food available is at a minimum. During this phase, the nutrients

remaining in the dead cells diffuse out to furnish the remaining cells with food. This system has been developed

for application where minimum solids production is desirable. Less solids production is achieved by using a larger

fraction of the entering organic material for energy rather than for synthesis. This means that more oxygen will be

consumed per unit mass of organic material removed.

The activated sludge process is capable of converting most organic wastes to more stable inorganic forms or to

cellular mass. In this process, the soluble and colloidal organic material is metabolized by a diverse group of

microorganisms to carbon dioxide and water. At the same time, a sizable fraction of incoming organic matter is

converted to cellular mass that can be separated from the effluent by settling.

Activated sludge comprises a mixed microbial culture wherein the bacteria are responsible for oxidizing the

organic matter, while protozoa consume the dispersed un-flocculated bacteria and rotifers consume the

unsettled small bio-flocs in the treated wastewater, performing the role of effluent polishers.

The utilization of substrate by a bacterial cell can be described as a three-step process:


1. The substrate molecule contacts the cell wall.

2. The substrate molecule is transported into the cell

Metabolism of the substrate molecule by the cell. However, as the bacteria require the molecule in the soluble

form, colloidal, spherically incompatible molecules, which cannot be readily biodegradable, have to be first

adsorbed to the cell surface and then broken down or transformed externally to transportable fractions by

exoenzymes or wall-bounded enzymes. The organic matter will be utilized by the bacteria resulting in cell

synthesis and energy for maintenance.

The following reactions best describe the organic utilization by the aerobic bacteria:

Oxidation

COHNS + O2 + Bacteria ---------> CO2 + NH3 + Other End Products + Energy

Synthesis

COHNS + O2 + Bacteria -----------> C5H7O2N (New Bacterial Cell)

Endogenous Respiration

C5H7O2N + 5O2 --------------> 5CO2 + NH3 + 2H2O + Energy

Nutrients available in the wastewater or from external source of supplements cater to the nutrient requirements

of the aerobic microorganisms and to enhance the activity of the aerobic microbes. In addition to the nutrient

requirements, the aerobic microbes require oxygen to sustain their microbial activity. Oxygen also functions as a

terminal electron acceptor in the energy metabolism of the aerobic heterotrophic organisms indigenous to the


activated sludge process. In other words a portion of the organic material removed is oxidized to provide energy

for the maintenance function and the synthesis function.

5. Phosphorous Removal

The key to Phosphorous removal is exposure of microorganisms to alternating aerobic and anaerobic conditions.

The alternating condition stresses the microorganism to uptake higher concentration of dissolved phosphorous,

from the effluent thereby reducing the Phosphorous level in the effluent. This phenomenon is called as Enhanced

Phosphorous Uptake. Phosphorous is also used by the microorganism for cell maintenance, synthesis, energy

transport and is also stored for future requirements.

Hence in C-Tech system, the removal of phosphorous from the wastewater is accomplished by the enhanced

phosphorous uptake rate and consumption of P for the cell growth with selector/aeration compartments.

6. Sulphides Removal

The removal of sulfides from the wastewater is accomplished during the Fill-Aeration phase in the aeration zone

of C-tech, by oxidation with oxygen present in the diffused air.

The oxidation of sulphides is represented as:

S2- + O2 SO2

7. Phenol Removal

Phenol is a complex organic matter. This can be oxidized in aerobic biological system with acclimatized biological

environment. Ideal treatment conditions such as maintenance of DO levels, good settling sludge, higher SRT, good

process control, etc. will further enhance the phenol removal. C-Tech system provides ideal conditions of

biological environment for phenol degradation.


Process Microbiology

Bacteria are the most important type of microorganisms concerned with organics removal. There are

essentially two types of microbes in terms of metabolism, namely, Heterotrophs and Autrotrophs. Heterotrophic

bacteria utilize organic material as a source of carbon and energy, while Autotrophic bacteria generally

depend on the oxidation of inorganic compounds such as NH3 and H2S for energy requirements, and utilize

CO2 or carbonates or bicarbonates, as a carbon source (eg. Nitrifying and Sulfur oxidizing bacteria).

All microbial species in the activated sludge process utilize oxygen as the final electron acceptor in the oxidative

biochemical reaction. For certain species, presence of oxygen is absolutely essential, without which they would

die out. These are called `Obligate Aerobes'. However, there are many bacterial species which utilize oxygen

under aerobic conditions, but in the absence of oxygen switch over to a fermentative or anoxic metabolic

route. This class of microbes are called “Facultative Anaerobes”.

Bacterial genera most frequently occurring in activated sludge are as follows:- Pseudomonas,

Flavobacterium, Achromobacter, Chromobacterium, Azotobacter, Micrococcus, Bacillus, Alcaligenes,

Arthrobacter, Acinetobacter, Mycobacterium, Nocardia, Lophomonas, Escherichia, Zoogloea. Activated

sludge also frequently contains undesirable filamentous organisms: Sphaerotilus, Thiothrix, Beggiatoa,

Geotrichum, Nocardia, Microthrix. These organisms are associated with `Sludge Bulking', where the

activated sludge has poor thickening and settling characteristics.

Protozoa and Rotifiers The protozoa act as polishers of the effluents from biological waste treatment

processes by consuming bacteria and particulate organic matter. Various types of protozoa may be

present, namely, amoeba, flagellates, ciliates (both stalked and free swimming). Rotifers are multi-cellular

organisms. They are also effective in consuming dispersed and flocculated bacteria and particulate organic

matter. As in the case of protozoa, their presence in an effluent indicates a highly efficient and stabilized

aerobic biological process.

Physical Characteristics of Activated Sludge


Visually activated sludge from sewage treatment has a light brown colour. However, in the case of industrial

waste treatment the colour of the activated sludge could vary depending on the waste being treated. For

example, activated sludges in the treatment of coal carbonization effluents have a very dark colour (almost

black). Well stabilized sludges appear to be well flocculated, with rapidly settling flocs leaving a clear

overflow. The activated sludge has a musty odour in the case of sewage treatment. This odour, however, may

be not apparent in the case of treatment of industrial effluents having a strong odour of their own.

Factors Affecting the Process

Numerous factors influence the performance of the activated sludge process. Some of the factors are:-

- Variability in Waste Water Flow and Quality

- Sludge Retention Time (SRT)

- Hydraulic Retention Time (HRT)

- Organic Loading (F/M ratio)

- Macronutrient (Nitrogen and Phosphorus) Levels

- Mixed Liquor Suspended Solids (MLSS) concentration

- Mixing and Aeration Intensity/Pattern

- Mixed Liquor Temperature

- Mixed Liquor pH Value

- Mixed Liquor Dissolved Oxygen levels

- Influent Waste concentrations

Characteristics of sludge


Membrane Bio Reactor (MBR)

Based on the process requirements and influent characteristics, a Modified Ludzack-Ettinger (MLE) process was

selected for MBR system.

This design consists of the influent being fed into an anoxic zone followed by an aerobic zone. Nitrate formed in

the aerobic and membrane zones, is recycled back to the anoxic zone where it is denitrified. Having the anoxic

zone as a first zone, allows for maximum influent BOD utilization for denitrification (maximized the C:N ration).

The effluent of the SBR treatment will be collected in an MBR feed tank where submersible pumps will transfer

wastewater into the Bioreactor Splitter Box. Wastewater is combined with the recycled mixed liquor from the

membrane trains and is equally distributed into two biological trains. Supplemental carbon will be added in the

Splitter Box should the influent carbon be insufficient for the biological process. Sodium hydroxide and antifoam

agents will be added if required. A bypass of the SBR is included should the influent to the MBR be deficient in

nutrients which will affect the biological process.

Mixed liquor flows through each biological process train by gravity from the anoxic to the aerobic zone and into

the Bioreactor Collector Channel. Foam and scum are collected in a foam trap located at one end of the overflow

channel via a motorized downward opening gate. Dry-pit centrifugal pumps will transfer foam, scum and waste

activated sludge to the sludge handling facility.

Mixed liquor recirculation pumps will transfer mixed liquor from the Bioreactor Collector Channel into the

Membrane Tank Splitter Channel. Mixed liquor flows by gravity into (4) parallel ZeeWeed® membrane tanks via

partially submerged sluice gates, which are designed to ensure equal flow distribution to all the membrane tanks

and same water level in all tanks. The mixed liquor overflows to the Membrane Tank Collector Channel and it

flows by gravity to the Bioreactor Splitter Box where it is combined with the influent before entering the anoxic

zones.

Clean water is withdrawn from the mixed liquor through the membrane using a dedicated permeate pump and is

discharged to a common collector header discharging to the Treated Effluent Tank for RO feed. Permeate will be

used from this tank for backpulsing and cleaning the membranes.

The system is completed with membrane tank drain pumps. These pumps are common to all membrane trains

and will drain the membrane tanks when required.


F. REVERSE OSMOSIS

The treated effluent after Membrane Bio Reactor is taken for the tertiary treatment. The tertiary treatment

mainly consists of Reverse Osmosis System.

The Reverse Osmosis (RO) unit essentially works at the molecular level. It separates the molecular impurities from

the water thus making one stream rich in salt molecules and other stream lean in salts thus reducing the TDS and

silica of the water.

Process of Reverse Osmosis:

Osmosis is a natural process involving fluid flow across a membrane, which is said to be ‘semi-permeable’. A semi-

permeable membrane is selective in that certain components of a solution, usually the solvent can pass through,

while others, usually the dissolved solids cannot pass through it. Its chemical potential determines the direction of

solvent flow, which is a function of pressure, temperature and concentration of dissolved solids. In case pure

water is available on both sides of a semi-permeable membrane at equal pressure and temperature, no resultant

flow can occur across the membrane, as the chemical potential is equal on both the sides. However, if any soluble

salt is added on one side of the membrane, the chemical potential of the water on that side is reduced. The

osmotic flow from the pure water on one side to the salt solution on the other side will occur across the

membrane until equilibrium of solvent chemical potential is restored.

The Thermodynamic requirement for osmotic equilibrium is that the chemical potential of the solvent be the

same on both sides of the membrane. No such condition is imposed on the solute, since the membrane prevents

its passage. The Equilibrium State occurs when the pressure differential on the two sides is equal to the osmotic

pressure, a solution property that is independent of the membrane.

The application of external pressure to the solution side, which equals the osmotic pressure, will also accomplish

equilibrium. A further increase in pressure will increase the chemical potential of the water in the solution and

will cause a reversal of the osmotic flow towards the pure water side which is at a lower solvent chemical

potential relative to the solution. This phenomenon is termed as Reverse Osmosis and is the basis for a process to

desalinate water without phase change.


Reverse Osmosis System:

The treated water from MBR is further polished into RO plant to get the product water which can be use as feed

to DM plant, floor wash etc.

In order to prevent the precipitation of the salts on reject side, an antiscalant is added at the inlet of the cartridge

filter, which will result in inhibition of scales. Furthermore Sodium bisulfite shall be dosed to remove free chlorine

present in the feed water. Presence of free chlorine in the feed water will irreversibly damage the RO

membranes. 30 - 33 % HCl acid is also continuously dosed inlet of the cartridge filter to adjust the pH of the feed

water.

Micron cartridge filter is provided in order to remove micron size particles, which is additional safety. Water is

then pumped using high-pressure pumps through R.O. module for removal of TDS. Reverse Osmosis module

consists of thin film composite Polyamide Membranes. On continuous running the R.O. membranes get fouled

with fine colloids, bacterial debris or some times carbonate scales. These need to be removed and cleaned from

the surface of the membrane. For each type of flocculant, there is a recommended chemical cleaning procedure,

which is convenient to perform with CIP system.

The permeate from the RO plant is then stripped into degasser tower for reduction of CO2 in water.

Degasser Tower is filled with PP packing rings. Air is forced from the bottom of the tower by Centrifugal Blowers,

while the water flows down through the packed bed of PP rings. The carbonic acid present in the water splits up

into carbon dioxide gas and water.

This carbon dioxide gas is stripped off and escapes from the top of the tower. The degassed water is collected in

the degassed water tank and is pumped further for polishing.

The RO treated water will be pumped for reuse as DM plant feed (in DHDS and GFEC units) and floor wash. The

RO treated water will also be used in suck back tank.


G. SLUDGE THICKENING AND CENTRIFUGE OPERATION

Biological sludge generated from SBR & MBR is thickened for volume reduction. Thickening is done by gravity belt

thickener and then dewatered by centrifuge operation. Polyelectrolyte is used to increase efficiency of the

centrifuge operation. The dewatered sludge send for further treatment and secured landfill.

The oily & chemical sludge generated from API, TPI Oil Separators, DAF, RO & DM plant is thickened in a gravity

thickener. The thickened sludge is dewatered by centrifuge operation. Polyelectrolyte is used to increase

efficiency of the centrifuge operation. The dewatered sludge is send to bioremedation unit for further treatment.

H. BIOREMEDATION

The Bioremediation process is a biological method to reduce the Total Petroleum Hydrocarbon (TPH) level in the

oily sludge to make it suitable for non hazardous land fill site.

The process involves biological processing of the oily sludge in a confined Bioreactor using specially designed

bacterial columns and advanced fermentation methods to degrade the petroleum hydrocarbon in the sludge

producing a non hazardous sludge with very low level of hydrocarbon. The TCLP analysis of the remediated sludge

is within US EPA guideline for land fill in a non hazardous site.

The Bacterial mass is naturally selected and acclimated with a careful blend of nutrients and surfactants. The

reactor conditions promote growth of highly active microbial population which rapidly converts the TPH into

carbon dioxide and water.

The contents of the bio reactor are closely monitored for temperature, pH, aeration intensity and nutrients. Each

batch is treated for approximately 10-15 days after which the bioremediated sludge is removed from the reactor

using discharge pumps.


I. VOC TREATMENT

Recently, several environmental regulations have been enacted that require industries to limit gaseous and

aqueous emissions containing Volatile Organic Compounds “VOC’s”. These new laws have greatly increased the

number of regulated VOC’s and expanded the categories of emissions from industrial facilities. For example,

reduction of VOC gaseous emissions is now made mandatory under new Environmental Pollution Act and all the

new facilities are now being asked through No objection certificate to adopt VOC control and treatment

measures. This also requires a reduction of the emission of Hazardous Air Pollutants (HAP’s), many of which are

VOC’s and regulate the levels of VOC’s in both air emissions and wastewater. This regulation also requires the

control of "fugitive" VOC’s from processing units. A significant number of VOC's have also been added to the TC

(Toxicity Characteristic) Rule, which is part of the hazardous waste regulations. In addition, chemical-specific

effluent limitations are being added to wastewater standards. These are extremely stringent and apply to a large

number of VOC's.

In response to the need to find cost-effective ways of reducing VOC’s emissions, many industrial initiatives have

occurred. These initiatives have led to the realization that pollution prevention provides the most comprehensive

and efficient strategy for reducing VOC’s emissions. Furthermore, it has been realized that any successful

pollution prevention strategy should address management and technical concerns. For example, management

concerns addressed within a corporate pollution strategy are reduced liability, improved corporate image within

the community, and reduced uncertainty relative to waste shipments from the company to some disposal party.

Examples of technical concerns are waste reduction process efficiency, economics of recovery and recycle of

wastes, and energy efficiency.

Within the past decade, significant academic efforts have been devoted to the development of systematic tools

and robust design methodologies that could be incorporated within a corporate pollution strategy to allow the

systematic development of environmentally acceptable process designs. These tools and methodologies are

designed to address the technical and, in many cases, the management concerns of a company with respect to

their corporate pollution strategy. Prior to presenting the systematic tools and design methodologies that have

been developed for use in designing VOC separation systems, several pollution prevention terms should be

defined. Additional information on these definitions can be found in Noyes (1993) and Freeman (1990). The

following is a brief discussion of these terms. In addition following figure is included as a hierarchical

representation of these definitions.


Pollution Prevention Waste Minimization

Source ReductionToxic Chemical

Use SubstitionRecycling

Use or Reuse Reclamation

A Hierarchical Representation of Pollution Prevention Definitions

Pollution Prevention Definitions as Used by the Environmental Protection Agency

Waste : Non-product outputs of processes and discarded products,

regardless of the environmental medium impacted.

Pollution Prevention : “Industrial pollution prevention” and pollution prevention refer to

the combination of source reduction and toxic chemical use

substitution. It does not include any recycling or treatment of

pollutants. It also does not include substituting a nontoxic product

made with nontoxic chemicals for a nontoxic product made with

toxic chemicals.

Waste Minimization : Current RCRA definition indicates that waste minimization refers to

source reduction and recycling activities, but does not include

treatment and energy recovery activities.

Recycling

: Recycling techniques are categorized as use, reuse and reclamation

techniques. These techniques allow potential waste materials to be

put to a beneficial use rather than going to treatment, storage or

disposal.

Use or Reuse

: Use and reuse involves the return of a potential waste material

either to the originating process as a substitute for an input material,

or to another process as an input material.


Reclamation

: The recovery of a useful or valuable material from a waste stream is

referred to as reclamation.

Source Reduction : Source reduction is any practice that :

Reduces the amount of any hazardous substance, pollutant, or

contaminant entering any waste (pollutant) stream or otherwise

released into the environment prior to recycling, treatment, and

disposal.

Reduces the hazards to public health and the environment

associated with the release of such substances, pollutants, or

contaminants.

This term also includes:

Equipment or technology modifications

Process or procedure modifications

Reformulation or Redesign of products

Substitution of raw materials

Improvements in housekeeping, maintenance, training or inventory

control

Toxic Chemical Use

Substitution

: This term refers to the replacement of toxic chemicals with less

harmful chemicals.

Toxic Use Reduction

: Source reduction activities whose intent is to reduce, avoid or

eliminate the use of toxic substances in processes and/or products.

VOC Separation Systems for Gaseous Wastes

Several technologies exist that can be used for recovery & treatment of VOC’s from gaseous wastes. The most

widely used technologies for recovering VOC’s from gaseous wastes are liquid absorption using heavy


oils/hydrocarbons, activated carbon adsorption, and condensation using coolants/refrigerants. In addition,

recently developed membrane-based technologies can be used in conjunction with one of the above technologies

to improve system efficiency and/or overall operating.

The activated carbon adsorption system is considered for the control and treatment of VOC based on the merit of

the system and techno-economic superiority on other systems.

Activated Carbon Adsorption

Description

VOC gaseous emissions flow into the top or bottom of an adsorption column, filled with porous

activated carbon, & is distributed throughout the carbon bed.

Two adsorption processes exist, temperature-swing adsorption (TSA) and pressure-swing adsorption

(PSA). Temperature-swing adsorption is the approach commonly used for VOC recovery and the

process description, advantages, and disadvantages listed in this section correspond to the

temperature-swing adsorption process.

Carbon adsorption beds can be fixed or moving, with respect to the carbon. For moving beds, the flow

of activated carbon is countercurrent to the flow of the gas; however, fixed beds are more common in

industry.

The VOC is adsorbed onto the surface of the activated carbon and onto the surface of the pores. At

some point the carbon becomes saturated with VOC and loses its capacity for additional adsorption.

This results in the concept of “breakthrough” where significant quantities of VOC become apparent in

the gas stream exiting the adsorption process. When this occurs the carbon must be regenerated for

re-use or replaced with virgin carbon.

Multiple fixed beds are generally employed so that as one or more beds are adsorbing at least one bed

can be regenerating. Regenerating a bed of activated carbon typically involves the direct injection of

steam, hot nitrogen or hot air to the bed which causes VOC to release from the carbon & exit the bed

via a vapor or condensate stream. The regenerated stream, containing a higher concentration of the

VOC than the original wastewater stream, is subsequently condensed. If the VOC is immiscible in

water, the condensate will form an aqueous layer & a solvent layer that can be separated using a

decanter. If the VOC is miscible in water, additional distillation can be used to further separate the VOC


& water.

“VOC-free” gas exits the adsorber after contacting the activated carbon.

Advantages

A widely used technology with well established performance levels.

Can achieve high recovery efficiencies (90-98%).

Can be used for a wide range of gas flow rates (100-60,000 cfm).

Can handle a wide range of inlet VOC concentrations (20-5,000 ppm).

Can efficiently handle fluctuations in gas flow rates and VOC concentration.

Disadvantages

VOC having high adsorption heats (typically ketone)can cause carbon bed fires.

Carbon attrition properties (permanent bonding of small quantities of VOC through each adsorption

cycle) requires the periodic replacement of carbon with virgin or reactivated carbon. Spent carbon may

need to be disposed of as a hazardous waste depending on the VOC(s) adsorbed.

Carbon efficiency decreases for high humidity (>50% r.h.) air streams.


Activated Carbon AdsorbersVOC Gaseous Waste

Clean Air

Adsorption Mode

Steam or Hot Nitrogen

Regeneration Mode

Condenser

Decanter

To Atmosphere

or Carbon Adsorber

Recovered VOCRecycled or Sent to Distillation

Water EffluentDischarged or Sent to

Air or Steam Stripping

Vapor

Liquid

A Schematic Representation of a Carbon Adsorption Process for VOC Gaseous Wastes

J. SEWAGE TREATMENT

1. Screening

This is the first unit operation encountered in sewage treatment plants. A screen is a device with openings,

generally of uniform size, that is used to retain coarse solids found in wastewater. A screen with parallel rods or

bars is called a Bar Rack or Bar Screen. These devices are used to protect downstream equipment such as pumps,

lines, valves etc from damage and clogging by rags and other large objects. The important criteria involved are

effluent velocity and hydraulic head loss through the bar screen, which increases with clogging of the screen.

2. Biological Treatment

The “Dorr Completreator” unit is provided for removal of organics from sewage. The Completreator is a complete

on site sewage treatment plant, specifically designed to accommodate all treatment facilities viz. contact

chamber, digestion chamber, stabilization chamber, clarifier mechanism as well as chlorination chamber in a

single tank installation.


The Dorr Completreator Aeration plant employs the contact stabilization complete mixing flow sheet to provide

treatment for domestic waste. The raw sewage is aerated and completely mixed by high efficiency aeration grids.

The aerated influent is directed to the clarifier where the sludge settles. The settled sludge from the clarifier is

transferred to the stabilization chamber and digestion chamber by a sludge recirculation pump. The aerobic

digestion chamber overflows to the stabilization chamber. The stabilization chamber in turn overflows to the

contact chamber to mix with incoming raw sewage.

Any floating scum, which collects on the contact chamber, is carried into a launder, which runs the full width of

this chamber. The clarifier is kept clean of scum by a continuous mechanical skimmer, which also collects the

scum from the contact chamber and then pumps it for disposal into aerobic digester with the help of sludge

recycle pumps.

The “Dorr Completreator” has the following advantages:

This compact unit considerably reduces the land area required.

The erection costs are extremely low as compared to conventional plants.

It needs very little maintenance and supervision.

The Dorr Recirculation system eliminates the danger of bad smell and fly nuisance.

The plant can be located in the Hotel / Residential Premises, and hence it is unnecessary to install a long and

expensive sewer system.

The plant can be augmented in future by providing additional units.

The treated sewage from the clarifier is disposed to sea or can be routed to SBR inlet.


PROCESS DESCRIPTION

Refer P & ID -A1-2070846 -601-1123 to 1141.

The detailed process scheme is as described below.

Oily effluent from various units gravitates to the existing API Separators (601-API-1001 A/B/C). Free floating oil

from all API Separators is removed by the installed oil skimmers, and gravitates to the Wet Slop Oil Sump (601-TK-

1050). The settled oily sludge is periodically withdrawn by gravity, and collected in the Oily & Chemical Sludge

Sump (601-TK-1045). The overflow from all the API units flows by gravity to the TPI Separator (601-TPI-1001

A/B/C).

In the TPI Oil Separators (601-TPI-1001 A/B/C), the effluent flows counter-currently downwards through the

corrugated plate pack. The residual free oil fraction separates in the plates and collects at the water surface in the

TPI unit, while the clarified waste passes down through the plate pack and overflows via the overflow launder

.The free floating oil collected at the TPI separator water surface removed by slotted pipe oil skimmer and

diverted to Wet Slop Oil Sump (601-TK-1050) by gravity while the settled sludge is withdrawn periodically and

transferred to the Oily & Chemical Sludge Sump (601-TK-1045).

From TPI separator the effluent gravitates to the Flash Mixing Tank (601-TK-1001 A). Hydrochloric acid (HCl) and

Caustic is dosed in the Flash Mixing Tank (601-TK-1001 A) for pH adjustment by HCl Solution Dosing Pumps (601-

P-1019 A/B/C) and Caustic Solution Dosing Pumps (601-P-1022 A/B/C) respectively. FeCl3 is also dosed by FeCl3


Solution Dosing Pumps (601-P-1033 A/B) for demulsification of emulsified oil present in the effluent. Hydrogen

peroxide (H2O2) is added as required in the flash mixing tank for removal of sulphide in the effluent by means of

H2O2 Dosing Pumps (601-P-1017 A/B/C/D). Flash Mixing Tank Agitator (601-AG-1001 A) is provided in the Flash

Mixing Tank (601-TK-1001 A ) for proper mixing of all these chemicals with the effluent.

The effluent from Flash Mixing Tank (601-TK-1001 A) is gravitates to Flocculation Tank (601-TK-1002 A). The

deoiling polyelectrolyte solution is dosed in the flocculator by DOPE Solution Dosing Pumps (601-P-1023 A/B) for

flocculation of the demulsified effluent. Flocculation Tank Agitator (601-AG-1002 A) is provided in the

flocculation tanks for proper mixing and flocculation.

The effluent then gravitates to DAF Tanks (601-TK-1004 A/B). A side stream of clarified effluent from the DAF unit

is pumped by means of the DAF Recycle Pumps (601-P-1002 A/B/C) to Saturation Vessel (601-V-1001) into which

air is supplied under pressure from the DAF Air Compressors (601-K-1001 A/B). Air dissolves at high pressure in

this side stream, which is then allowed to enter the DAF unit via a pressure release valve, along with the main

flocculated effluent stream. On sudden release of pressure in the side stream effluent to atmospheric pressure,

the excess dissolved air in the over saturated effluent precipitates out as very fine air bubbles, which attach with

the free oil globules and flocculated solids in the main effluent stream and carry them to the surface as floating

sludge froth. The froth from DAF is removed periodically by means froth skimmer and flows by gravity to Wet Slop

Oil Sump (601-TK-1050). Settled solids are withdrawn periodically from the DAF underflow and diverted to Oily &

Chemical Sludge Sump (601-TK-1045) by gravity. The effluent from DAF overflow gravitates to pH Adjustment

Tank (601-TK-1005).

In the pH Adjustment Tank (601-TK-1005) based on requirement Hydrochloric acid (HCl) and Caustic is dosed for

pH adjustment by HCl Solution Dosing Pumps (601-P-1019 A/B/C ) and Caustic Solution Dosing Pumps ( 601-P-

1022 A/B/C) respectively. DAP & Urea Solution is dosed as required in the pH adjustment tank by Nutrient

Solution Dosing Pumps (601-P-1024 A/B). DAP & Urea are added as a source of Nitrogen 'N' & Phosphorous “P”

which are macro nutrients required for growth of microorganisms in biological systems. The effluent from pH

adjustment tank pumped to Sequential Batch Reactor – C Tech (056-SBR-1001) by SBR Feed Pumps (601-P-1003

A/B/C).

The C-TECH – System is operated in a batch reactor mode, which eliminates all the inefficiencies of the continuous

processes. A batch reactor is a perfect reactor, which ensures 100% treatment. Three modules are provided to

ensure continuous treatment. The complete process takes place in a single reactor, within which all biological

treatment steps take place sequentially.


No additional settling unit / secondary clarifier is required.

The complete biological operation is divided into cycles. Each cycle is of 3-6 hrs duration (6 hours as design basis),

during which all treatment steps take place.

Explanation of cyclic operation:

A basic cycle comprises:

Fill-Aeration (F/A)

Settlement (S)

Decanting (D)

These phases in a sequence constitute a cycle, which is then repeated.

A Typical Cycle

During the period of a cycle, the liquid is filled in the C Tech Basin up to a set operating water level. Aeration

Blowers are started for aeration of the effluent. After the aeration cycle, the biomass settles under perfect

settling conditions. Once Settled the supernatant is removed from the top using a DECANTER. Solids are wasted

from the tanks during the decanting phase.

These phases in a sequence constitute a cycle, which is then repeated.


A Typical C Tech Cycle

C Tech Components:

The C Tech system comprises the following features,

Flow Equalisation

C-TECH CAN HANDLE FLOW FLUCTUATION

Biological Selector zone

ENSURES NO FOAMING AND BULKING PROBLEMS


Dissolved Oxygen Control to automatically control and optimise power consumption

ENSURES 20 - 30% POWER SAVINGS.

Co Current Nitrification and De nitrification, Phosphorous removal

PROVIDES NITROGEN AND PHOSPHOROUS REMOVAL TO REMOVE NUTRIENTS MAKING THE WATER SAFE FOR

WATER DISCHARGE

Decanter assembly in Stainless steel equipped with VFD to automatically control rate of decanting based on input

feed condition.

ENSURES NO CORROSION, LONG EQUIPMENT LIFE, NO MAINTENANCE

Diffusers for Aeration

OUTLET

INLE

T

DECANTER SELECTOR

AERATION

GRID

RAS/SAS PUMPS


HIGHEST AERATION AND OXYGEN TRANSFER EFFICIENCY

Return sludge (RAS) recycle and Surplus sludge (SAS) pumps for sludge wasting from reactor only

REDUCES SPACE REQUIREMENT. NO SECONDARY CLARIFIER IS USED WHICH DRASTICALLY REDUCES CIVIL COST

AND CONSTRUCTION COST

PLC unit for complete automatic cycle control and operation

REDUCE MANPOWER COST. COMPLETE OPERATION CAN BE HOOKED TO CENTRAL CONTROL DESK.

Equalization tank

In refinery effluent where wide fluctuations are expected in the feed quality, it is very critical to provide an

equalization tank, which can normalize all input variations. This equalization facility has been provided inbuilt

within the C Tech basins.

Typically, for treating wastewaters with characteristics as mentioned in the inlet analysis, a Hydraulic detention

time of 36 to 40 hours is sufficient for C-Tech. However, we have provided 42.2 Hours detention time considering

additional 2.2 hours to cater to fluctuating load conditions. In effect, the Equalization tank is built into the C-Tech

basin.

The C-Tech basin has a fixed volume (for containing the biomass) and a variable volume (for containing the

effluent to be treated). This variable volume is designed such that it can hold fluctuating flow rates. In effect, this

volume acts like a equalization tank. C-Tech can absorb shock loads, as it is a batch process. Every batch is

completely treated and then discharged.


The C-Tech system can take variable flow rate ranging from 30% to 100% of design flow.

Biological SELECTOR zone

The incorporation of a biological SELECTOR in the front end of the C-TECH- Systems distinguishes it from most of

the technologies. The raw effluent enters the SELECTOR zone, where ANOXIC MIX conditions are maintained. Part

of the treated effluent along with return sludge from the aeration basin is recycled in here, using RAS pumps. As

the microorganisms meet high BOD, low DO condition in the SELECTOR, natural selection of predominantly floc-

forming microorganisms takes place. This is very effective in containing all of the known low F/M bulking

microorganisms, eliminates problems of bulking and sludge foaming. This process ensures excellent settling

characteristics of the bio sludge. SVI of treated effluent of less than 120 is achieved in all seasons.

A coarse bubble aeration grid is provided in the selector to agitate sludge initially at the beginning of each cycle.

This operation is done for few minutes in each cycle through PLC controlled auto valve.

Also due to the anoxic conditions in the SELECTOR zone, Denitrification and phosphorous removal occurs in case

the Ammonical nitrogen and phosphorous levels are high in the effluent.

The instrument and control philosophy of selector zone is as follow:

Selector zone receives flow from the inlet channel. A motorized gate opens automatically as soon as the tank is

ready for next fill cycle based on timer settings. Once the filling is started, RAS pump starts automatically and

sludge recycle starts. There is no any speed control of the pump. It is again a timer controlled function linked to

time sequence of basin operation. When the filling period is over, RAS pump also stops. In the present case, the

sludge recycle is maintained at 2.16 times feed flow.

Another function in selector is operation of selector air valve. The selector air valve is opened during the start of

the aeration cycle for a preset time (which can be adjusted through HMI). During the settling and decanting

operation, the selector valve is in continuously open position.


Dissolved Oxygen Control

The C Tech process uses measurement of dissolved oxygen (DO) levels in the basin to enhance treatment

efficiency and optimise power consumption. The DO concentration in the basin is continuously monitored using a

DO sensor. Once DO level is measured in the basins, a variable frequency drive automatically alters the aeration

blower rpm to maintain desired DO levels in the basin. This methodology provides a true in-basin method for the

efficient use of energy.

Decanter Assembly

The clean supernatant is removed from the basin using a Decanter assembly complete in stainless steel

construction. During decanting there is no inflow to the basin. The moving weir DECANTER is motor driven and

travels slowly from its “park” position to a designated bottom water level. Once the Decanting phase sets in, the

decanter automatically lowers to the required bottom level. Variable frequency drives are provided to control the

rate of movement of the Decanters.

VFD in decanter controls and adjusts the speed of the decanter as per system requirements. During aeration and

settling phase, decanter is stationed at PARK position. At the start of the decanting period, decanter moves up to

few centimetres above Top Water Level (TWL) at maximum speed so that the time taken is minimum. As soon as

it reaches TWL (sensed by float switch attached to decanter), it moves down at specified speed till it reaches

Bottom Water Level (BWL). During decanting, it moves at very slow speed to achieve desired decanting rate.

After the required level of supernatant is removed the Decanter is returned to its “park” position through reversal

of the drive. The basin is now ready for the next cycle to begin.

Operational Simplicity - Fully PLC based intelligent control


The complete C-Tech plant operation is controlled automatically through a PLC system, which is a major factor in

reducing operating costs. This also prevents malfunctioning of the various set process parameters within the

plant. All key functions like, RAS, sludge wasting, aeration intensity, cycle time control, decanting rate etc are

automatically controlled without operator intervention as well as data logged. Complete historical records of

plant operation are available on touch of a button. All interlocks are shown in the P&I drawing.

The effluent from pH adjustment tank pumped to Sequential Batch Reactor – C Tech (056-SBR-1001) by SBR Feed

Pumps (601-P-1003 A/B/C). Based on the cyclic operation one of the Inlet Gate (GT-3001, 3002, 3003) will open

and effluent will be filled in one of the SBR Tank (601-SBR-1001 A/B/C). SBR Air Blower (601-K-1002 A/B/C/D/E/F)

will start and air will be introduced in the SBR Tank (601-SBR-1001 A/B/C) in which effluent is being filled. Also the

respective Return Sludge Pump (601-P-1004 A/B/C) will start and will recirculate the biosludge near the inlet.

After the set time interval, the aeration will stop in the SBR Tank (601-SBR-1001 A/B/C) which is under Fill &

Aeration Mode and settling will start. Also respective Return Sludge Pump (601-P-1004 A/B/C) will stop. At the

same time the Inlet Gate (GT-3001, 3002, 3003) of another SBR Tank (601-SBR-1001 A/B/C) will open and effluent

will be filled in this tank. Aeration will start in this tank and also respective Return Sludge Pump (601-P-1004

A/B/C) will start. After the set time interval for settling, the treated effluent from SBR Tank (601-SBR-1001 A/B/C)

will be decanted at the outlet launder by SBR Decanter Mechanism (601-P-1036 A/B/C). The cyclic operation - Fill

& Aeration, Settling and Decanting will continue and effluent will be treated continuously.

For detailed operation of SBR system (C-Tech), refer process operating manual of C-Tech submitted by SFC

Environmental Technologies Pvt. Ltd.

The treated effluent from SBR System (601-SBR-1001) is collected in MBR Feed Tank (601-TK-1034). It is then

pumped to Membrane Bio Reactor (MBR) System (601-MBR-1001).

The effluent of the SBR treatment will be collected in an MBR feed tank where submersible pumps will transfer

wastewater into the Bioreactor Splitter Box. Wastewater is combined with the recycled mixed liquor from the

membrane trains and is equally distributed into two biological trains. Supplemental carbon will be added in the

Splitter Box should the influent carbon be insufficient for the biological process. Sodium hydroxide and antifoam

agents will be added if required. A bypass of the SBR is included should the influent to the MBR be deficient in

nutrients which will affect the biological process.

Mixed liquor flows through each biological process train by gravity from the Anoxic Zone (601-TK-1042 A/B) to the

Aerobic Zone (601-TK-1043 A/B) and into the Bioreactor Collector Channel. Foam and scum are collected in a


foam trap located at one end of the overflow channel via a motorized downward opening Weir Gate (GT-3301).

Foam/Was Pumps (601-P-1038 A/B) will transfer foam, scum and waste activated sludge to the sludge handling

facility.

Mixed Liquor Recirculation Pumps (601-P-1037 A/B/C) will transfer mixed liquor from the Bioreactor Collector

Channel into the Membrane Tank Splitter Channel. Mixed liquor flows by gravity into (4) parallel ZeeWeed®

Membrane Tanks (601-TK-1044 A/B/C/D) via partially submerged Sluice Gates (GT-3101/3102/3201/3202), which

are designed to ensure equal flow distribution to all the membrane tanks and same water level in all tanks. The

mixed liquor overflows to the Membrane Tank Collector Channel and it flows by gravity to the Bioreactor Splitter

Box where it is combined with the influent before entering the anoxic zones.

Clean water is withdrawn from the mixed liquor through the membrane using a dedicated MBR Permeate Pump

(601-P-1039 A/B/C/D) and is discharged to a common collector header discharging to the RO Feed Collection Tank

(601-TK-1007). Permeate will be used from this tank for back pulsing and cleaning the membranes by Backpulse

Pumps (601-P-1006 A/B).

The system is completed with membrane tank Drain Pumps (601-P-1040 A/B). These pumps are common to all

membrane trains and will drain the membrane tanks when required.

The membrane net flux is the most important parameter when designing a membrane filtration system. The

selection of conservative membrane flux depends on a number of factors including the minimum operating

temperature, flow rates, and assumed sludge characteristics. Our flux selection is based on design curves

developed from years of experience from full scale operating MBR plants under different conditions.

The membrane design for HPCL MBR consists of four (4) membrane trains with three (3) cassettes per train, each

cassette having 40 modules and each module having 31.59 m2 of surface area. This corresponds to 3,790.8 m2 of

membrane area installed per train and a total of 15,163.2 m2 of membrane area installed in the four (4) trains.

Each cassette has a maximum capacity of 48 modules, which means that a 16.7% spare space is included within

the installed cassettes. This percentage is within the range of our typical design (15-20% spare space).

Carbon Source Dosing Pumps (601-P-1041 A/B) will add a carbon source (i.e. methanol) to the Bioreactor Splitter

Box should the influent carbon be insufficient for denitrification.

Antifoam Dosing Pumps (601-P-1042 A/B) will add antifoam agents (approved by GEWPT) to the Bioreactor

Splitter Box should it be required.

A pH transmitter is located on the permeate collector header for monitoring purposes. As per specifications,

analyzers for silica, conductivity and TOC are also installed on the permeate collector header. A common

turbiditymeter is installed on the permeate collector header. A solenoid valve arrangement allows the

turbiditimeter to monitor each train and the common discharge.


An SBR Bypass line is included in the design should the biological process require it. This by-pass provides

flexibility to the operation of the system as the influent wastewater might be deficient of nutrients affecting the

MBR biological process. The by-pass will provide nutrients to the system to maintain the biomass.

The two biological trains are identical. Each biological train is designed with two Anoxic Zone (601-TK-1042 A/B)

and two Aerobic Zone (601-TK-1043 A/B). Each anoxic zone has a dedicated Submersible Mixer (601-SM-1001

A/B) to ensure homogeneous mixed liquor, maximizing denitrification and alkalinity recovery.

From the anoxic zones, the mixed liquor flows to the aerobic tanks which are equipped with one (1) independent

fine bubble aeration grid that supplies oxygen necessary for the biological process as well as keeps the mixed

liquor fully mixed. The dropleg on each aeration grid is equipped with a motorized valve which allows aeration to

be cycled between zones. Process aeration is provided by a common group of positive displacement Process

Aeration Blowers (601-K-1003P D/E/F) completed with variable frequency drives. The air flow rate can be

regulated to control the DO level in the aerated zones. On each process train, the second aerobic zone has a

Dissolved Oxygen probe.

The mixed liquor flows by gravity from the aeration basins to the Bioreactor Collector Channel through partially

submerged gate valves to allow foam to pass.

The foam and scum are collected in the Foam/WAS Tank (601-TK-1053) located at one end of the Channel via a

motorized downward opening Weir Gate (GT-3301). Foam, scum and waste activated sludge are removed from

the system via Foam/Was Pumps (601-P-1038 A/B).

The mixed liquor is transferred to the Membrane Tank Splitter Channel via Mixed Liquor Recirculation Pumps

(601-P-1037 A/B/C) with a design flow rate of 5 times the influent flow (5Q).

The mixed liquor flows from the Channel into four (4) identical ZeeWeed® membrane trains. Each train is

equipped with partially submerged weir manual Sluice Gates (GT-3101/3102/3201/3202) which are designed to

ensure equal flow distribution and same water level in all Membrane Tanks (601-TK-1044 A/B/C/D. To protect

the membrane cassettes, a deflector plate is installed on the inlet of each tank.

Each train is designed with a dedicated MBR Permeate Pump (601-P-1039 A/B/C/D) (variable speed). The

permeate pump will generate a slight vacuum that draws water from the mixed liquor through the membranes.

Permeate flowrate demand is based on the influent flow with trim to the level in the bioreactor via control loops

in the programmable logic controller (PLC).

Since the membrane system operates under a slight vacuum, there will be a tendency for dissolved air to be

released from the water. In order to prime the permeate system, an ejector system (per membrane train) is

provided which incorporates the use of compressed air.

The permeate pumps discharge the treated water into a common collector header that discharges into the RO

Feed Collection Tank (601-TK-1007). Backpulse water will be from this tank. Chemicals for membrane cleaning

(i.e. sodium hypochlorite and citric acid) will be directly injected into the permeate header. Sodium Hypochlorite

Dosing Pumps (601-P-1027 A/B) and Citric Acid Dosing Pumps (601-P-129 A/B) are provided for the same.


In order to maintain and chemically clean the membranes, permeate is used for backpulsing the membrane

trains. A common pair of Backpulse Pumps (601-P-1006 A/B) is used to service all membrane trains.

Membrane aeration is provided by a common group of air scour blowers. MBR Membrane Aeration Blowers (601-

K-1003M A/B/C) will discharge to a common air supply header leading to the membrane tanks. Each membrane

train is designed with two air headers in order to cycle air within each train via cyclic air valves.

The membrane tanks are drained by Drain Pumps (601-P-1040 A/B) that discharge to the Membrane Tank

Collector Channel.

The activated sludge flows by gravity to the Membrane Tank Collector Channel which terminates in a pipe that

recirculates the combined mixed liquor to the head of the bioreactor. The recirculated mixed liquor flow rate will

be 4 time the influent flow rate.

Common cleaning chemical dosing pumps with dedicated installed standby units are used to service all

membrane trains.

Membrane Cleaning Requirements

Cleaning is necessary to ensure a smoothly operating MBR. ZeeWeed® modules are based on a hollow fibre

geometry which is more versatile as cleaning can be carried out quickly, easily, and automatically.

GEWPT incorporates a multi-level approach to maintaining membrane performance in every MBR system. We

offer several cleaning strategies for membranes that ensure optimum permeate production with a minimum

investment in time and resources. The cleaning systems included for HPCL Refinery MBR System incorporate fully

automated processes such as relaxation, backpulsing, maintenance cleaning and recovery cleaning. The cleaning

methodology is very flexible and the system can be optimized to reduce the frequency of chemical cleaning based

on site specific conditions.

During normal operation, the GEWPT system is operated with a repeated filtration cycle, which consists of a

production period (permeation) followed by a relaxation or backpulse period. ZeeWeed® MBR systems have the

unique capability to operate in either relaxation or backpulse mode. Under normal conditions the system is

operated in relaxation mode, whereas during start-up or under conditions of poor sludge filterability the system

can be operated in backpulse mode. Details of the filtration cycle with relaxation and backpulse are provided

below.

The membrane filtration system, including membranes, headers and mechanical equipment is sized to produce

the design net flow rates under all operating scenarios.

Relaxation


While operating in relax mode, the MBR Permeate Pump (601-P-1039 A/B/C/D) for each train is stopped

sequentially for a short period of time (30-45 sec) every 12-15 minutes to allow air scouring of the membrane

without permeation. No chemical or permeate is used during relaxation mode.

Process Flow Schematic – Relaxation Mode

Backpulse or Backwash

Under certain fouling conditions or when experiencing poor sludge characteristics, the ability to backpulse is

essential to maintaining a clean membrane. This feature allows for flexible and reliable system performance

during unexpected influent or process operating scenarios. Applying the backpulse cleaning option is one of the

simplest methods to ensure that immersed membranes retain optimum permeability throughout all operating

conditions.

Backpulsing involves reversing the flow through the membranes to slightly expand the membrane pores and

dislodge any particles that may have adhered to the membrane fibre surface. An entire membrane train is

backpulsed at a time using permeate stored in the RO Feed Collection Tank (601-TK-1007) with no addition of

chemicals.

For HPCL Refinery MBR System design, the Backpulse Pumps (601-P-1006 A/B) will provide the reverse flow at low

pressures.

An optimized backpulse cleaning schedule can ensure that the plant benefits from:

High membrane permeability;

Efficient plant operation with minimal downtime;

Reduced frequency of chemical cleans;

Lower consumption of cleaning chemicals.


Process Flow Schematic – Backpulse Mode

Maintenance Clean

Sodium hypochlorite is used to oxidize organic foulants and citric acid to remove inorganic scaling.

For this project, maintenance cleaning is recommended up to once per week using sodium hypochlorite and once

per week using citric acid.

The maintenance cleaning procedure incorporates the following features;

Fully automated and the frequency is set by the operator;

Performed without draining the membrane tank;

< 1 hour duration per clean per train

Based on the site specific requirements, cleaning procedures can be modified to obtain effective cleaning and

maximize chemical savings.

Recovery Clean


Recovery cleaning is required to restore the permeability of the membrane once the membrane becomes fouled.

A recovery clean should be initiated when permeability declines to less than 50% of initial stable permeability.

This will generally occur when the trans-membrane pressure (TMP) consistently exceeds 4-5 psi (vacuum) under

normal flow conditions. The recovery cleaning procedure consists of a chemical backpulse sequence, followed by

a chemical soak period. The cleaning chemical concentrations typically used to soak the membranes are sodium

hypochlorite (NaOCl) for the removal of organic foulants and citric acid for the removal of inorganic foulants.

For inorganic cleaning the acid soak concentration should have a pH between 2.5 – 3. Based on an influent

alkalinity of 1,730 mg/L as specified on table 1.2, citric acid will not be sufficient to reduce the pH to the target.

Therefore, addition of a strong acid, i.e. hydrochloric acid (HCl) is required. The amount of HCl required depends

solely on the water quality and it is not possible to determine. The process for adding this strong acid is fully

manual:

Dose citric acid to a concentration of 2,000 mg/L

Operator to measure pH in cleaning solution.

If pH > 2.5-3.0, add HCl manually to the tank

Aerate for 1 min to mix the acid and measure again

Repeat steps until desired pH is reached

Key features of the recovery cleaning procedure for ZeeWeed® membrane filtration system are:

Fully automated and initiated by the operator;

Cleans all membrane cassettes in a train at the same time;

Recommended up to four times per annum

Requires moderate chemical concentration

Spent cleaning chemicals will be neutralized with mixed liquor

For detailed process operation of MBR system refer Process Operating Manual of MBR system submitted by GE

Water & ZENON Membrane.

The treated effluent from MBR system outlet is RO system. The RO permeate from RO system is recycled back to

main process plant for reuse and RO rejects are disposed to sea.


Reverse Osmosis Plant:

Osmosis is a natural process involving fluid flow across a membrane, which is said to be ‘semi-permeable’. A semi-

permeable membrane is selective in that certain components of a solution, usually the solvent can pass through,

while others, usually the dissolved solids cannot pass through it. Its chemical potential determines the direction of

solvent flow, which is a function of pressure, temperature and concentration of dissolved solids. In case pure

water is available on both sides of a semi-permeable membrane at equal pressure and temperature, no resultant

flow can occur across the membrane, as the chemical potential is equal on both the sides. However, if any soluble

salt is added on one side of the membrane, the chemical potential of the water on that side is reduced. The

osmotic flow from the pure water on one side to the salt solution on the other side will occur across the

membrane until equilibrium of solvent chemical potential is restored.

The Thermodynamic requirement for osmotic equilibrium is that the chemical potential of the solvent be the

same on both sides of the membrane. No such condition is imposed on the solute, since the membrane prevents

its passage. The Equilibrium State occurs when the pressure differential on the two sides is equal to the osmotic

pressure, a solution property that is independent of the membrane.

The application of external pressure to the solution side, which equals the osmotic pressure, will also accomplish

equilibrium. A further increase in pressure will increase the chemical potential of the water in the solution and

will cause a reversal of the osmotic flow towards the pure water side which is at a lower solvent chemical

potential relative to the solution. This phenomenon is termed as Reverse Osmosis and is the basis for a process to

desalinate water without phase change.

The treated effluent from MBR is further polished into RO plant to get the product water which can be use as feed

to DM plant, floor wash etc.

The treated effluent from MBR is collected in RO Feed Collection Tank (601-TK-1007). The effluent then pumped

to Cartridge Filters (601-CF-1001 A/B/C/D) by Cartridge Feed Pump (601-P-1007 A/B/C). In order to prevent the

precipitation of the salts on reject side, an antiscalant is added at the inlet of the cartridge filter by Antiscalant

Dosing Pumps (601-P-1028 A/B), which will result in inhibition of scales. Furthermore sodium bisulphite shall be

dosed by Sodium Bisulphite Dosing Pumps (601-P-1030 A/B) to remove free chlorine present in the feed water.

Presence of free chlorine in the feed water will irreversibly damage the RO membranes. HCl acid if required is also

dosed inlet of the cartridge filter to adjust the pH of the feed water by Acid Dosing Pumps –RO (601-P-1020 A/B).


Micron cartridge filter is provided in order to remove micron size particles, which is additional safety. These

Cartridges are disposable type and should be replaced if differential pressure across cartridges approaches pre-

specified level.

The cartridge filter outlet is pumped to two stages Reverse Osmosis Train 1/2/3 (601-RO-1001 A/B/C) by high

pressure RO Feed Pumps (601-P-1008 A/B/C) for removal of TDS. In order to have flux balancing between two

stages inter stage Turbocharger (601-TC-1001 A/B/C) is provided between RO stage I & stage II.

Reverse Osmosis module consists of thin film composite Polyamide Membranes. On continuous running the R.O.

membranes get fouled with fine colloids, bacterial debris or some times carbonate scales. These need to be

removed and cleaned from the surface of the membrane.

The permeate from the RO plant is then stripped into Degasser Tower (601-DG-1001) for reduction of CO2 in

water.

Degasser Tower is filled with PP packing rings. Air is forced from the bottom of the tower by Centrifugal Blowers,

while the water flows down through the packed bed of PP rings. The carbonic acid present in the water splits up

into carbon dioxide gas and water. The reaction is as follows:

H2CO3 H2O + CO2

This carbon dioxide gas is stripped off and escapes from the top of the tower. The degassed water is collected in

the Permeate Water Storage Tank (601-TK-1009) and then treated water is pumped to DM Plant/Floor Wash by

Treated Water Transfer Pumps (601-P-1031 A/B/C). The pH of the treated water is maintained by dosing NaOH in

the RO permeate after degasification.

RO Membrane Fouling & Prevention

Fouling is the accumulation of foreign materials from feed water on the active membrane surface and/or on the

feed spacer to the point of causing operational problems. The term fouling includes the accumulation of all kinds


of layers on the membrane and feed spacer surface, including scaling. More specifically, colloidal fouling refers to

the entrapment of particulate or colloidal matter such as iron flocs or silt, biological fouling (biofouling) is the

growth of a biofilm, and organic fouling is the adsorption of specific organic compounds such as humic substances

and oil on to the membrane surface.

Scaling refers to the precipitation and deposition within the system of sparingly soluble salts including calcium

carbonate, calcium sulfate, etc.

Pretreatment of feed water must involve a total system approach for continuous and reliable operation. For

example, an improperly designed and/or operated clarifier will result in loading the sand or multimedia filter

beyond its operating limits. Such inadequate pretreatment often necessitates frequent cleaning of the membrane

elements to restore productivity and salt rejection. The cost of cleaning, downtime and lost system performance

can be significant.

The proper treatment scheme for feed water depends on:

Feed water source

Feed water composition

Application

The type of pretreatment system depends to a large extent on feed water source (e.g., Industrial wastewater).

Industrial wastewaters have a wide variety of organic and inorganic constituents. Some types of organic

components may adversely affect RO membranes, inducing severe flow loss and/or membrane degradation

(organic fouling), making a well-designed pretreatment scheme imperative.

Scaling of RO membranes may occur when sparingly soluble salts are concentrated within the element beyond

their solubility limit. For example, if a reverse osmosis plant is operated at 50% recovery, the concentration in the

concentrate stream will be almost double the concentration in the feed stream. As the recovery of a plant is

increased, so is the risk of scaling.


Due to water scarcity and environmental concern, adding a brine (RO concentrate) recovery system to increase

recovery has become more popular. To minimize precipitation and scaling, it is important to establish well-

designed scale control measures and avoid exceeding the solubility limits of sparingly soluble salts. In an RO

system, the most common sparingly soluble salts encountered are CaSO4, CaCO3, and silica. Other salts creating a

potential scaling problem are CaF2, BaSO4, SrSO4, and Ca3(PO4)2.

Most natural surface and ground waters are almost saturated with CaCO3. The solubility of CaCO3 depends on

the pH, as can be seen from the following equation:

Ca2 + + HCO3 H+ + CaCO3

By adding H+ as acid, the equilibrium can be shifted to the left side to keep calcium carbonate dissolved.

CaCO3 tends to dissolve in the concentrate stream rather than precipitate. This tendency can be expressed by the

Langelier Saturation Index (LSI) for brackish waters and the Stiff & Davis Stability Index (S & DSI) for seawaters. At

the pH of saturation (pHs), the water is in equilibrium with CaCO3.

The definitions of LSI and S & DSI are:

LSI = pH – pHs (TDS < 10,000 mg/L)

S & DSI = pH – pHs (TDS > 10,000 mg/L)

To control calcium carbonate scaling by acid addition alone, the LSI or S & DSI in the concentrate stream must be

negative.

Acid addition is useful to control carbonate scale only.


Scale inhibitors (antiscalants) can be used to control carbonate scaling, sulfate scaling, and calcium fluoride

scaling. There are generally three different types of scale inhibitors: sodium hexametaphosphate (SHMP),

organophosphonates and polyacrylates.

Organophosphonates are more effective and stable than SHMP. They act as antifoulants for insoluble aluminum

and iron, keeping them in solution. Polyacrylates (high molecular weight) are generally known for reducing silica

scale formation via a dispersion mechanism.

Polymeric organic scale inhibitors are also more effective than SHMP. Precipitation reactions may occur, however,

with negatively charged scale inhibitors and cationic polyelectrolytes or multivalent cation (e.g., aluminum or

iron). The resulting gum-like products are very difficult to remove from the membrane elements. Hence dosage

rates on all antiscalant needs to be carefully selected in consultation with antiscalant manufacturers during

operation of the plant. Overdosing should be avoided. Make certain that no significant amounts of cationic

polymers are present when adding an anionic scale inhibitor.

Colloidal fouling of RO elements can seriously impair performance by lowering productivity and sometimes salt

rejection. An early sign of colloidal fouling is often an increased pressure differential across the system.

The source of silt or colloids in reverse osmosis feed waters is varied and often includes bacteria, clay, colloidal

silica, and iron corrosion products. Pretreatment chemicals used in a clarifier such as aluminum sulfate, ferric

chloride, or cationic polyelectrolytes are materials that can be used to combine these fine particle size colloids

resulting in an agglomeration or large particles that then can be removed more easily by either media or cartridge

filtration. Such agglomeration, consequently, can reduce the performance criteria of media filtration or the pore

size of cartridge filtration where these colloids are present in the feed water. It is important, however, that these

pretreatment chemicals become incorporated into the agglomerates themselves since they could also become a

source of fouling if not removed. In addition, cationic polymers may co precipitate with negatively charged

antiscalant and foul the membrane. Several methods or indices have been proposed to predict a colloidal fouling

potential of feed waters, including turbidity, Silt Density Index (SDI) and Modified Fouling Index (MFI). The SDI is

the most commonly used fouling index. The guideline is to maintain SDI15 at <3 is recommended.

CIP system is provided for cleaning of RO membranes. This system is consists of RO Cleaning Solution Tank (601-

TK-1011), RO Clean-up Pumps (601-P-1016 A/B) and Cartridge Filters (601-CF-1002 A/B). Based on the

requirement acid or caustic solution is prepared in Cleaning Solution Tank (601-TK-1011) by transferring required

amount of acid or caustic by Conc. HCl Unloading /Transfer Pumps (601-P-1018 A/B) and Caustic Lye Unloading /


Transfer Pumps (601-P-1021 A/B). Then the solution is pumped to RO Train by RO Clean-up Pumps (601-P-1016

A/B) through Cartridge Filters (601-CF-1002 A/B).

Refer RO Process Operating Manual submitted by Aqua Tech Systems for detailed process operation of RO

system.

Spent Caustic Effluent Treatment

Spent caustic effluent is collected in Spent Caustic Storage Tank (601-TK-1003 A/B). It is pumped to Flash Mixing

Tank (601-TK-1001 B) by Spent Caustic Pumps (601-P-1001 A/B). In the flash mixing tank if required HCl is added

for pH corrections by HCl Solution Dosing Pumps (601-P-1019 A/B/C ). Also H2O2 is added for removal of sulphide

from spent caustic effluent by H2O2 Dosing Pumps (601-P-1017 A/B/C/D).. Flash Mixing Tank Agitator (601-AG-

1001 B) is provided in the tank for proper mixing of H2O2 & HCl . The effluent is then gravitates to Flocculation

Tank (601-TK-1002 C) in which DOPE is added if required. Flocculation Tank Agitator (601-AG-1002C) is provided

for proper mixing of DOPE with the effluent by DOPE Solution Dosing Pumps (601-P-1023 A/B). The treated spent

caustic effluent is either discharged to sea for disposal or can be diverted to DAF Tanks (601-TK-1004 A/B) based

on the quality of treated spent caustic effluent.

Sludge Treatment

The biosludge from SBR and MBR is collected in Biosludge Sump (601-TK-1047) and transferred to Biosludge

Thickener (601-ST-1002) by Biosludge Transfer Pump (601-P-1011 A/B). In the thickener feed DWPE (Bio) Solution

is added by DWPE (Bio) Solution Dosing Pumps (601-P-1026 A/B) to enhance the thickening of sludge. Belt

Cleaning Pump (601-P-1048) is provided for cleaning of belt of gravity belt thickener. The thickened biosludge

from thickener underflow collected in Thickened Biosludge Sump (601-TK-1048 A/B) which is provided with

Thickened Biosludge Sump Agitators (601-AG-1004 A/B) for uniform mixing of thickened sludge. It is then pumped

to Dewatering Biosludge Centrifuge (601-G-1002) by Thickened Biosludge Transfer Pump (601-P-1012 A/B). In the

centrifuge solid liquid separation take place. Polyelectrolyte is dosed at centrifuge inlet by DWPE (Bio) Solution

Dosing Pumps (601-P-1026 A/B) to enhance the solid liquid separation. Solid cakes from centrifuge discharge are

collected in a trolley and then send to further treatment / secure landfill. The centrate from centrifuge is collected

in a Supernatant Sump (601-TK-1049) and then transferred to API inlet by Supernatant Transfer Pump (601-P-

1013 A/B).


The sludge from TPI, API, DAF and LR/LRE and drains from Flash Mixing Tanks, Flocculation Tanks is collected in

Oily & Chemical Sludge Sump (601-TK-1045). It is then pumped to Oily & Chemical Sludge Thickener (601-ST-

1001) by Oily & Chemical Sludge Transfer Pump (601-P-1009 A/B). In the thickener feed DWPE (Oily) Solution is

added by DWPE (Oily) Solution Dosing Pumps (601-P-1025 A/B) to enhance the thickening of sludge. The

thickened sludge is withdrawn from thickener underflow and collected in Thickened Oily & Chemical Sludge Sump

(601TK-1046 A/B. Thickened Oily & Chemical Sludge Sump Agitators (601-AG-1003 A/B) are provided in the sump

for uniform mixing of sludge. The sludge is then pumped to Dewatering Oily & Chemical Centrifuge (601-G-1001)

by Thickened Oily & Chemical Transfer Pump (601-P-1010 A/B). In the centrifuge solid liquid separation take

place. Polyelectrolyte is dosed at the centrifuge inlet by DWPE (Oily) Solution Dosing Pumps (601-P-1025 A/B) to

enhance the solid liquid separation. Solid cake from centrifuge discharge is send to Bioremediation Unit. Solid

cake from centrifuge discharge is collected in a trolley and then sends to further treatment / secure landfill. The

centrate from centrifuge is collected in a Supernatant Sump (601-TK-1049) and then transferred to API inlet by

Supernatant Transfer Pump (601-P-1013 A/B).

The wet slop oil from API, TPI & Spent Caustic Storage Tanks is collected in Wet Slop Oil Sump (601-TK-1050). It is

then transferred to Wet Slop Oil Storage Tank (601-TK-1010 A/B) by Wet Slop Oil Transfer Pump (601-TK-1014

A/B). LP/MP Steam is injected in Wet Slop Oil Sump as well as in Wet Slop Oil Storage Tank for separation of Oil.

Oil from Wet Slop Oil Storage Tank (601-TK-1010 A/B) is pumped to Refinery Slop Oil Tank by Dry Slop Oil Transfer

Pump (601-P-1015A/B).

Bio-Remediation

The treatment scheme for the bio-remediation of oily sludge is as follow:


The treatment scheme consists of following treatment units:

Oily Sludge sump

Bioreactor Feed pumps

Bioreactor Tanks with air diffuser system

Air blowers

Nutrient Feed tank

Surfactant Feed tank

Acid/Alkali Feed tank

NUTRIENTS

SURFACTANT

ACID/ALKALI

AIR

BIO-REMEDIATED

SLUDGE FOR

DISPOSAL TO NON

HAZARDOUS LAND

FILL SITE

BIO-

REACTOR

SLUDGE SUMP


Oily sludge generated from existing units of ETP- II and skim pond is collected in Oily Sludge Sump (601-TK-1052).

Characteristics of the sludge such as pH, TPH, TSS & Temperature are measured for pre-conditioning the sludge

before feeding it into Bioreactor (601-R-1037 A/B) by Bioreactor Feed Pumps (601-P-1045 A/B). Acid/Alkali is

added in bioreactor if required to keep the pH near neutral. Acid Feed Tank (601-TK-1038) and Alkali Feed Tank

(601-TK-1039) are provided for the same. Measured quantity of nutrients and surfactants are also added in

bioreactor. Nutrient Feed Tank (601-TK-1040) and Surfactant Feed Tank (601-TK-1041) are provided for the same.

Then the sludge is thoroughly mixed by recirculation using the feed pump.

The treatment in the bio-reactor is a batch process. There are two bio-remediation reactors provided. After pre-

conditioning, the oily sludge from the storage sump is pumped into the reactor. Required quantity of inoculum is

already present in the reactor (from the previous batch). For the first batch, required quantity of inoculums in the

form of fresh bacterial culture also needs to be added in the feed sump.

After filling the bio-reactor with required quantity of sludge and other chemicals, the contents are thoroughly

aerated using positive displacement Air Blowers (601-K-1006 A/B/C). A coarse bubble aeration system is installed

at the bottom of the reactor. This coarse bubble aeration system consists of air header and laterals with holes.

Aeration supplies required quantity of oxygen to bacteria and ensures degradation of oil in the sludge. The

process may take around 10 to 15 days.

After the treatment, sludge meets the outlet standards of US EPA for non hazardous landfill sites. The same

Bioreactor Feed Pumps (601-P-1045 A/B) can be used to withdraw sludge from the bio-reactors and pump to

disposal point.

During the degradation process, the bio-reactor requires minimum monitoring. Regular preventive maintenance

shall be made for blowers, etc. Flushing of lines prior and after feeding/discharge of sludge is required.

Refer Bio-remediation Process Operating Manual submitted by EWT Enviropro Water Tech for detailed process

operation of bio-remediation system.

VOC System


Facilities are provided for Handling of Volatile Organic Compounds (VOC) in terms of their collection from oil-

handling units, routing to centralized VOC handling and control facilities to meet the VOC emission norms as per

statutory standards.

Carbon adsorption system is considered for the control of VOC based on the merit of the system and techno-

economic superiority on other systems as narrated in previous sections. The VOC has been estimated based on

the USEPA model for estimation of VOCs. System design / sizing calculations have been done based on the VOCs

estimated from the USEPA model and the breathing losses or displacement losses account for the volume

entering the VOC control system or due to volatility of the compound.

The VOC Control System consists closed loops of vents, carrying pipes, valves, ID fans, flame arrestors, carbon

filters and a vent to take out the VOC stripped air from the system. System is designed for compactness &

minimization of operation cost by putting up the VOC Control unit in the vicinity where VOC emissions are

generated.

The system is designed to accommodate the estimated flow rates and concentrations of the system, meet the

emission requirement of minimum 90% capture rate, and minimize pressure drop. The quantity of Carbon used

may vary based on actual operating conditions.

Carbon use rate is estimated based on the compounds present as identified. It is very difficult to estimates the

concentrations of various compounds that may appear at a particular time as refinery operations are diversified in

nature. Their concentrations may not necessarily be able to be specified in the incoming stream and the same are

estimated using chemical formulas and EPA guidelines/programs/model. As a precautionary note, it is

emphasized that this data is estimated only and actual operation will vary and may require operational

adjustments.

Another area of concern of the carbon adsorption system is that a high concentration level of some VOCs may

cause the carbon to generate heat on the bed since the adsorption is an exothermic reaction. This heat may

eventually build into a fire. Therefore the quantities of VOC’s in the dilution air need to remain below the Lower

Explosive Limit (LEL) to avoid the risk of fire. It may be necessary to use a LEL monitor or other device as

suggested to meter the level of VOC’s and add dilution air as necessary. As a design precaution, water quenching

and temperature measurement at the adsorption system are envisaged.


The presence of higher concentrations of VOCs that may be present will shorten the life of the carbon beds.

Carbon needs replenished when the adsorption level drops below 90%. The main unit that is considered to be the

largest source of VOC is API separators. It has been observed that in a waste water treatment plant, VOC

emanating from API accounts for the Majority of the total VOC emissions from the ETP. The design of the system

uses the oil as the primary air borne VOC since the oil is taken as 100% on the liquid phase on top of the water.

The balance of VOCs is minor concentrations in comparison and consumes low levels of carbon.

For better safety, Thermocouple connections are provided in the carbon bed. The pipe length are optimized for

best plant layout and system is distributed in such a way that a balanced flow achieved in each of the sub-system.

The diameter is sized to maintain a good design velocity at full flow.

The VOC control system design provides the following benefits:

The system is designed to meet emission control requirements.

Low air pressure drop thus low operating cost

ID fans are designed to keep the flow rate in the pipe as required for the estimated concentration of VOC and well

below of LEL to improve safety of the system.

System flexibility to handle normal and minimum flows, pressures and temperatures. Field adjustment may be

required.

VOC emanating from API Separators (601-API-1001 A/B/C), TPI (601-TPI-1001 A/B/C), Flash Mixing Tank (601-TK-

1001 A/B), Flocculation Tank (601-TK-1002 A/B/C), Slop Oil Tank (601-TK-1050) and DAF Tank (601-TK-1004) is

collected by pipelines and send to Activated Carbon Filters (601-ACF-1001 A/B/C) through Flame Arrester (601-

FA-1002). Also VOC emanating from Slop Oil Storage Tanks (601-TK-1010 A/B) are fed by ID Fans (601-K-1007 A/B)

to the pipeline of above units through Flame Arrester (601-FA-1001). Volatile Organic Compounds are adsorbed

on the activated carbon surface and the outlet of activated carbon filters is vent off to atmosphere through Vent

Stack (601-VS-1001) by using ID Fans (601-K-1008 A/B). Hydrocarbon gas detectors are provided at the inlet and

outlet of Activated Carbon Filters.


Refer VOC Process Operating Manual submitted by IIT, Roorkee for detailed process operation of VOC system.

Chemical Dosing & Handling Systems

HCl Dosing System

Concentrated HCl is unloaded from Acid Tanker to Conc. HCl Storage Tank (601-TK-1013) by Conc. HCl

Unloading/Transfer Pumps (601-P-1018 A/B). Service water and treated effluent is stored in Service Water Tank

(601-TK-1042) located above chemical house. The service water from this tank is taken into HCl dosing tanks for

dilution of HCl to about 10%. Conc. HCl is then transferred to HCl Solution Dosing Tanks (601-TK-1014 A/B) by

Conc. HCl Unloading/ Transfer Pumps (601-P-1018 A/B). The HCl Solution Dosing Pumps (601-P-1019 A/B/C) are

provided for dosing of HCl into pH Adjustment Tank (601-TK-1005), Flash Mixing Tanks (601-TK-1001 A/B) at a

controlled rate . Provision is also made to recycle the HCl solution from HCl dosing pumps to HCl dosing tanks.

Acid Solution Dosing Pumps-RO (601-P-1020 A/B) are provided for dosing acid at the inlet of Cartridge Filter (601-

CF-1001 A/B/C/D). Also Conc. HCl is transferred to RO Cleaning Solution Tank (601-TK-1011) by Conc. HCl

Unloading /Transfer Pumps (601-P-1018 A/B).

Caustic Dosing System

Caustic Lye is unloaded from Caustic Tanker to Caustic Lye Bulk Storage Tank (601-TK-1015) by Caustic Lye

Unloading / Transfer Pumps (601-P-1021 A/B). Caustic lye is transferred to Caustic Solution Dosing Tanks (601-TK-

1016 A/B) by Caustic Lye Unloading / Transfer Pumps (601-P-1021 A/B). The service water from Service Water

Tank (601-TK-1042) is taken into Caustic dosing tanks for dilution of caustic to about 10%. The Caustic Solution

Dosing Pumps (601-P-1022 A/B/C) are provided for dosing of caustic into pH Adjustment Tank (601-TK-1005),

Flash Mixing Tanks (601-TK-1001 A) and MBR System at a controlled rate . Provision is also made to recycle the

caustic solution from caustic dosing pumps to caustic dosing tanks. Also Caustic Lye is transferred to RO Cleaning

Solution Tank (601-TK-1011) by Caustic Lye Unloading / Transfer Pumps (601-P-1021 A/B).

DOPE Dosing System


DOPE Dosing Tanks (601-TK-1017 A/B) with DOPE Dosing Tank Agitators (601-AG-1006 A/B) are provided for

preparation of DOPE solution. The service water from Service Water Tank (601-TK-1042) is taken into the dosing

tank so that the agitator’s blades are submerged in the water. Agitator is started and the required quantity DOPE

is added slowly into the tank. The service water is added up to the overflow nozzle. Agitators are stopped after

about 1-2 hrs. The DOPE solution is dosed into the Flocculation Tanks -601-TK-1002 A/B/C) by DOPE Solution

Dosing Pumps (601-P-1023 A/B).

DWPE (Oily) Dosing System

DWPE (Oily) Dosing Tanks (601-TK-1019 A/B) with DWPE (Oily) Dosing Tank Agitators (601-AG-1008 A/B) are

provided for preparation of DWPE solution. The service water from Service Water Tank (601-TK-1042) is taken

into the dosing tank so that the agitators blades are submerged in the water. Agitator is started and the required

quantity DWPE (Oily) is added very slowly into the tank. The service water is added up to the overflow nozel.

Agitators are stopped after about 1-2 hrs. The DWPE (Oily) solution is dosed into the Oily & Chemical Sludge

Thickener (601-ST-1001) and Dewatering Oily & Chemical Sludge Centrifuge (601-G-1001) by DWPE (Oily)

Solution Dosing Pumps (601-P-1025 A/B).

DWPE (Bio) Dosing System

DWPE (Bio) Dosing Tanks (601-TK-1020 A/B) with DWPE (Bio) Dosing Tank Agitators (601-AG-1009 A/B) are

provided for preparation of DWPE solution. The service water from Service Water Tank (601-TK-1042) is taken

into the dosing tank so that the agitators blades are submerged in the water. Agitator is started and the required

quantity DWPE (Bio) is added very slowly into the tank. The service water is added up to the overflow nozel.

Agitator is stopped after about 1-2 hrs. The DWPE (Bio) solution is dosed into the Bio Sludge Thickener (601-ST-

1002) and Dewatering Bio Sludge Centrifuge (601-G-1002) by DWPE (Bio) Solution Dosing Pumps (601-P-1026

A/B).

FeCl3 Dosing System


FeCl3 Solution Dosing Tanks (601-TK- 1026 A/B) with FeCl3 Solution Dosing Tank Agitators (601-AG-1015 A/B) are

provided for preparation of FeCl3 solution. The service water from Service Water Tank (601-TK-1042) is taken

into the dosing tank so that the agitator blades are submerged in the water. Agitator is started and the required

quantity FeCl3 is added slowly into the tank. The service water is added up to the overflow nozel. Agitator is

stopped after about 1-2 hrs. The FeCl3 solution is dosed into the Flash Mixing Tank (601-TK-1001 A) by FeCl3

Solution Dosing Pumps (601-P-1033 A/B).

Nutrients Dosing System

Nutrients Solution Dosing Tanks (601-TK1018 A/B) with Nutrients Solution Dosing Tanks Agitators (601-AG-1007

A/B) are provided for preparation of nutrients solution. The service water from Service Water Tank (601-TK-1042)

is taken into the dosing tank so that the agitator blades are submerged in the water. Agitator is started and the

required quantity Nutrients (DAP & Urea) is added slowly into the tank. The service water is added up to the

overflow nozel. Agitator is stopped after about 1 hrs. The nutrients solution is dosed into the pH Adjustment Tank

(601-TK-1005).

H2O2 Dosing System

H2O2 is unloaded from the H2O2 tanker to H2O2 Storage Dosing Tanks (601-TK-1012 A/B) by H2O2 Unloading

Pumps (601-P-1023 A/B). The H2O2 is dosed into the Flash Mixing Tanks (601-TK-1001 A & B) by H2O2 Dosing

Pumps (601-P-1017 A/B/C/D).

Sodium Hypochlorite (NaOCl) Dosing System

Sodium Hypochlorite Dosing Tank (601-TK-1021) is provided for preparation of NaOCl solution. The service water

from Service Water Tank (601-TK-1042) is taken into the dosing tank and required quantity of NaOCl (approx

10.8%) is added manually into the tank. The service water is added up to the overflow nozzle. The diluted NaOCl

solution is dosed by Sodium Hypochlorite Dosing Pumps (601-P-1027 A/B) to the membrane installed in MBR

Tanks during cleaning step of MBR system operation.


Citric Acid Dosing System

Citric Acid Dosing Tank (601-TK-1023) is provided for preparation of citric acid solution. The service water from

Service Water Tank (601-TK-1042) is taken into the dosing tank and required quantity of citric acid (approx 50%) is

added manually into the tank. The service water is added up to the overflow nozzle. The diluted citric acid

solution is dosed by Citric Acid Dosing Pumps (601-P-1029 A/B) to the membrane installed in MBR Tanks during

cleaning step of MBR system operation.

Carbon Source Dosing System

Carbon Source Dosing Tank (601-TK-1035) is provided for preparation of carbon source (methanol) solution. The

service water from Service Water Tank (601-TK-1042) is taken into the dosing tank and required quantity of

methanol is added manually into the tank. The service water is added up to the overflow nozzle. The diluted

methanol solution is dosed by Carbon Source Dosing Pumps (601-P-1041 A/B) to the Bioreactor Splitter of MBR

System.

Antifoam Dosing System

Antifoam Dosing Tank (601-TK-1036) is provided for preparation of Antifoam solution. The service water from

Service Water Tank (601-TK-1042) is taken into the dosing tank and required quantity of liquid antifoam is added

manually into the tank. The service water is added up to the overflow nozzle. The antifoam solution is dosed by

Antifoam Dosing Pumps (601-P-1042 A/B) to the Bioreactor Splitter of MBR System.

Sodium Bisulphite Dosing System

Sodium Bisulphite Dosing Tanks (601-TK- 1024 A/B) with Agitators (AG-013 A/B) are provided for preparation of

Sodium Bisulphite solution. The service water from Service Water Tank (601-TK-1042) is taken into the dosing

tank so that the agitator blades are submerged in the water. Agitator is started and the required quantity Sodium

Bisulphite is added slowly into the tank. The service water is added up to the overflow nozzle. Agitator is stopped

after about 1-2 hrs. The Sodium Bisulphite solution is dosed into the inlet of Cartridge Filter (601-CF-1001

A/B/C/D) by Sodium Bisulphite Dosing Pumps (601-P-1030 A/B).


Antiscalant Dosing System

Antiscalant Dosing Tanks (601-TK- 1022 A/B) with Agitators (AG-011 A/B) are provided for preparation of

Antiscalant solution. The service water from Service Water Tank (601-TK-1042) is taken into the dosing tank so

that the agitator blades are submerged in the water. Agitator is started and the required quantity Antiscalant is

added slowly into the tank. The service water is added up to the overflow nozzle. Agitator is stopped after about

1-2 hrs. The Antiscalant solution is dosed into the inlet of Cartridge Filter (601-CF-1001 A/B/C/D) by Sodium

Bisulphite Dosing Pumps (601-P-1030 A/B).

Sanitary Waste Treatment

Sanitary effluent is collected in Sanitary Sewage Sump (601-TK-1051). The raw sewage is then pumped to a

Completreator (601-CT-1001). Completreator is a complete on site sewage treatment plant, specifically designed

to accommodate all treatment facilities viz. Bar Screen Chamber (601-BS-1001), Digestion Chamber (601-TK-

1028), Stabilization Chamber (601-TK-1029), Contact Chamber (601-TK-1030), Secondary Clarifier (601-CL-1033)

and Treated Sanitary Waste Tank (601-TK-1031) in a single tank installation.

The incoming raw sewage is passed through Bar Screen Chamber (601-BS-1001) where floating (suspended)

material will be removed. The raw sewage is then aerated and completely mixed by high efficiency aeration grids

in Digestion Chamber (601-TK-1028), Stabilization Chamber (601-TK-1029), Contact Chamber (601-TK-1030). The

air is supplied to aeration grids by Air Blowers (601-K-1005 A/B). The aerated influent is directed to the Secondary

Clarifier (601-CL-1033) where the sludge settles. The settled sludge from the clarifier is transferred to the

stabilization chamber and digestion chamber by Sludge Recycle Pump (601-P-1035 A/B). The aerobic digestion

chamber overflows to the stabilization chamber. The stabilization chamber in turn overflows to the contact

chamber to mix with incoming raw sewage. The floating scum in clarifier is collected in sum pit and recycled back

to digestion chamber by recycle pumps. The treated sewage from clarifier overflows to Treated Sanitary Waste

Tank (601-TK-1031). Treated sewage is send to SBR system or disposed into sea by Treated Sewage Transfer

Pump (601-P-1049 A/B).


INSTRUMENTATION & CONTROL PHILOSOPHY

Running/stop indications of all drives (motors, agitators. etc.) are provided in the control room. A dedicated

PC/PLC based control system has been envisaged for the ETP and the same is housed in a Control Room located in

the Chemical House building within the IETP area. For all types of tanks/sumps/pits, Non Contact type SMART

Radar type Level Transmitters (including the interface level) are used as primary level measurement device and


for secondary level measurement, mechanical float operated gauges are provided. Switching action will be in PLC.

Level transmitter will be used for local & control room level indication and for tripping purposes (including low &

high levels alarms in the control room). Switching will be in PLC.

Incoming and Outgoing Lines

Suitable type of flow measurement systems (orifice type for fluids without solid particles and magnetic type for

fluid with solid particles) with local and control room indication along with recording and totalizing facilities (in

Control Room) are provided on incoming effluent feed (pressure lines) & utility lines (except instrument air &

drinking water), and outgoing lines (e.g. treated effluent, slop oil, etc.) with PG and double block valves with a

spectacle blind provision at IETP battery limit.

The following are flow transmitters are provided on the incoming and outgoing lines.

Sl no

Tag No. Type of Instrument Service

1. 601-FIT-2301 Magnetic Type Flow transmitter 8" Line from Crude Desalter FR /FRE

2. 601-FIT-2302 Magnetic Type Flow transmitter 8" Line from Sour water stripper -GFEC

3. 601-FIT-2303 Magnetic Type Flow transmitter 4" Line from LR units

4. 601-FIT-2304 Magnetic Type Flow transmitter Effluent from ATF effluent transfer Pumps

5. 601-FIT-2305 Magnetic Type Flow transmitter Effluent from P-175 Sump

6. 601-FIT-2306 Magnetic Type Flow transmitter Effluent from DWS ETP feed pumps

7. 601-FIT-2307 Magnetic Type Flow transmitter Effluent from LR/LRE floor wash pumps

8. 601-FIT-2308 Magnetic Type Flow transmitter Effluent from new LR/LRE ETP feed pumps

9. 601-FIT-2309 Magnetic Type Flow transmitter

Common Header of spent caustic lines coming

from OSBL area.


10. 601-FIT-2310 Magnetic Type Flow transmitter Sludge from LR/LRE sludge pumps

11. 601-FIT-2311 DP Type flow transmitter Service water header from B/L

12. 601-FIT-2312 DP Type flow transmitter LP steam from B/L

13. 601-FIT-2313 DP Type flow transmitter Plant air header from B/L

14. 601-FIT-2316 Magnetic Type Flow transmitter Spent caustic from CR-LPG units (GFEC)

15. 601-FIT-2317 Magnetic Type Flow transmitter Spent caustic from NHTISOM / NHTCCR (GFEC)

16. 601-FIT-2318 Magnetic Type Flow transmitter Spent caustic from PC-D-200 pumps

17. 601-FIT-2319 Magnetic Type Flow transmitter

Spent caustic from NMPI / NMP II/NMP III spent

caustic pumps

18. 601-FIT-2401 Magnetic Type Flow transmitter Oily effluent from units to API separators.

19. 601-FIT-2501 DP Type flow transmitter

Treated water transfer pump (601-P-1031-A/B)

header

Sanitary Sewage Sump (601-TK-1051) & Raw Sewage Transfer Pumps (601-P-1034 A/B)

The sump is provided with Non Contact SMART Radar type Level Transmitter (LT 2901), secondary level

measurement device Level Indicator (LI-2902), with local & control room indication, high/low alarms in control

room and interlocks to trip the Raw Sewage Transfer Pump (601-P-10330 A/B) at low-low level. Downstream of

these pumps, there is Magnetic Type Flow Transmitter (FIT-2901) with local and control room indication along

with totalizing facilities in Control Room.

Secondary Clarifier (601-CL-1033)

The clarifier drive mechanism has been provided with a Torque Indication (TQSH 2903) as well as interlock for

high torque alarm and drive motor auto trip.


Treated Sanitary Waste Tank (601-TK-1031)

The tank is provided with a Level Transmitter (LIT 2902) and indicator controller with local and control room

indication. Also provided with high and low level alarm in the control room as well as interlock for auto trip of

Treated Sewage Transfer Pump (601-P-1049 A/B) at low-low level in the tank.

Treated Sewage Transfer Pump (601-P-1049)

Orifice Type Flow Transmitter (FIT-2903) has been provided in the pump discharge line with local and control

room indication and also totalizing facility.

DAF System - DAF Tank (601-TK-1004 A/B), Saturation Vessel (601-V-1001), Recycle Pumps (601-P-1002 A/B/C) &

Air Compressor (601-K-1001 A/B)

Magnetic Type Flow Transmitter (FIT-2403 & FIT-2404) with local & Control Room Indication with associated

piping are provided at a suitable point to help measure and control (by means of the pressure regulating valve or

manually by globe valve) the recycle flow to individual compartments of the Flotation Tank. Air supply line to

Saturation Vessel is provided with air filter, air supply pressure gauge, pressure regulator, pressure gauge

(downstream of Pressure regulator), and Flow Indicator (FI-2405) for local indication, check valve, etc. as required

to ensure the required quantity of air taken to the system. Saturation Vessel is provided with safety relief valve,

pressure gauge, Level Gauge (LG-2404), and Level Transmitter (LIT-2403) with corresponding high/low alarms. A

solenoid valve is provided on the air supply line to saturation vessel and the solenoid valve will be auto activated

by the level in the vessel to close at low level and open at high level. Pressure regulating valve is installed near the

inlet to the Flotation Unit.


pH Adjustment Tank (601-TK-1005) & Biological Feed Sump

It is ensured that appropriate quantity of the acid/caustic is dosed in the pH adjustment tank in relation to adjust

pH of the effluent. On-line pH Analyzer (AE-2403) and auto pH-Adjustment facility is provided for the same which

will control the dosing rate of acid/caustic by variation in dosing pump speed (VFD Control). Biological feed sump

is provided with Non Contact SMART Radar type Level Transmitter (LIT-2404), secondary level measurement

device - Level Indicator (LI-2403), local & control room indication, high/low alarms in control room and interlocks

to trip tank agitator and SBR Feed Pumps at low level.

Permeate Water Storage Tank (601-TK-1009) and Treated Water Transfer Pumps (601-P-1031 A/B/C)

Permeate Water Storage Tank (601-TK-1009) is provided with Non Contact SMART Radar type Level Transmitter

(LIT 3702), secondary level measurement device –Level Indicator (LI-3702), local and control room indication,

high/low alarms in control room and interlocks to trip the Treated Water Transfer Pumps (601-P-1031 A/B/C) at

low low level and at high level, RO Train (601-RO-1001 A/B/C) in service will proceed to standby.

MBR Feed Tank (601-TK-1034) & MBR Feed Pumps (601-P-1044 A/B/C)

The tank has been provided with Level Transmitter (LIT-2501), local and control room indication, high and low

level alarms in control room and interlocks to trip the MBR Feed Pumps (601-P-1044 A/B/C) at low level in MBR

Feed Tank (601-TK-1034) and also trip pump at high high level in MBR Bioreactor Collector Basin.

Wet Slop Oil Sump (601-TK-1050) & Wet Slop Oil Transfer Pumps (601-P-1014 A/B)

Sump is provided with Non Contact SMART Radar type Level Transmitter (LIT-2608), secondary level

measurement device- Level Indicator (LI-2608), local & control room indication, high/low alarms in control room

and interlock to trip the Wet Slop Oil Transfer Pumps (601-P-1014 A/B) at low level in the Wet Slop Oil Sump (601-

TK-1050).

Slop Oil Storage Tanks (601-TK-1010 A/B) & Dry Slop Oil Transfer Pumps (601-P-1015 A/B)


Tanks are provided with Non Contact SMART Radar type Level Transmitters (LIT-2609 & LIT-2610), secondary level

measurement device -Level Indicator (LI-2609 & LI-2610), local & control room indication, high/low alarms in

control room and interlocks to trip Dry Slop Oil Transfer Pumps (601-P-1015 A/B) at low level in tank. Interface

(oil-water) Level Indicators (LIT-2611 & LIT-2612) are also provided in the tanks with local & control room

indication and low level alarms. After holding the tank contents for sufficient time, water can be drained from

bottom (through drain valve) and upon receiving the interface low-level alarm, drain valve will be closed and

thereafter dry slop will be pumped to the offsite refinery slop oil tank. Tanks are provided with Temperature

Indicators (TI-2609 & TI-2610) for local & control room indication. High/Low temperatures will also activate

corresponding alarms in the control room. A flow measuring device -Flow Transmitter (FIT-2602) is provided in

the discharge line of the Dry Slop Oil Transfer Pumps (601-P-1015 A/B) with flow indication local and at control

room along with recording cum totalizing facility is provided at Control Room for measuring the dry slop

transferred to offsite slop oil tank at the refinery.

Oily & Chemical Sludge Sump (601-TK-1045), Oily & Chemical Sludge Pumps (601-P-1009 A/B) and Oily & Chemical

Sludge Thickener (601-ST-1001)

Sump is provided with Non Contact SMART Radar type Level Transmitter (LIT-2601), local & control room

indication, high/low alarms in control room and interlocks. Low level in the Oily & Chemical Sludge Sump (601-TK-

1045) will auto trip Oily & Chemical Sludge Pumps (601-P-1009 A/B). A local Temperature Indicator (TI-2601) is

provided in the sludge sump. Oily & Chemical Sludge Thickener (601-ST-1001) is provided with running indication

of the motor in the control room. A Torque Switch (TQSH-2610) is provided with high alarm in control room with

corresponding interlock to trip thickener mechanism at high torque level.

Thickened Oily & Chemical Sludge Sumps (601-TK-1046 A/B), Thickened Oily & Chemical Sludge Pumps (601-P-

1010 A/B) and Dewatering Oily & Chemical Sludge Centrifuge (601-G-1001)

The thickened underflow sludge from Oily & Chemical Sludge Thickener (601-ST-1001) is collected in Thickened

Oily & Chemical Sludge Sumps (601-TK-1046 A/B). The agitator in the sump followed by Pumps (after allowing

sump contents to be agitated) will be started manually. Sumps are provided with Non Contact SMART Radar type

Level Transmitters (LIT-2602 & LIT-2603), secondary level measurement device -Level Indicators (LI-2602 & LI-

2603), local & control room indication, high/low alarms in control room and interlocks. Low level in sump will

auto trip the Thickened Oily & Chemical Sludge Pumps (601-P-1010 A/B) and Agitators (601-AG-1003 A/B) in the

sump. The dewatering centrifuge has instrumentation interconnection with the Thickened Sludge Pumps. In the

event of Thickened Oily & Chemical Sludge Pumps (601-P-1010 A/B) trips, the Dewatering Oily & Chemical Sludge


Centrifuge (601-G-1001) will also trip simultaneously (after a specified time lag). In case the centrifuge trips, the

thickened sludge pump (centrifuge feed) should trip. Local Temperature Indicators (TI-2602 & TI-2603) are also

provided in the Thickened Oily & Chemical Sludge Sumps (601-TK-1046 A/B).

Bio Sludge Sump (601-TK-1047), Bio Sludge Pumps (601-P-1011 A/B) and Bio Sludge Thickener (601-ST-1002)

Sump is provided with Non Contact SMART Radar type Level Transmitter (LIT-2604), local & control room

indication, high/low alarms in control room and interlocks. Low level in the Bio Sludge Sump (601-TK-1047) will

auto trip Bio Sludge Pumps (601-P-1011 A/B). A local Temperature Indicator (TI-2604) is provided in the sludge

sump.

Thickened Bio Sludge Sumps (601-TK-1048 A/B), Thickened Bio Sludge Pumps (601-P-1012 A/B) and Dewatering

Bio Sludge Centrifuge (601-G-1002)

The thickened bio sludge from Bio Sludge Thickener (601-ST-1002) is collected in Thickened Bio Sludge Sumps

(601-TK-1048 A/B). The agitator in the sump followed by Pumps (after allowing sump contents to be agitated) will

be started manually. Sumps are provided with Non Contact SMART Radar type Level Transmitters (LIT-2605 & LIT-

2606), secondary level measurement device -Level Indicators (LI-2605 & LI-2606), local & control room indication,

high/low alarms in control room and interlocks. Low level in sump will auto trip the Thickened Bio Sludge Pumps

(601-P-1012 A/B) and Agitators (601-AG-1004 A/B) in the sump. The dewatering centrifuge has instrumentation

interconnection with the Thickened Sludge Pumps. In the event of Thickened Bio Sludge Pumps (601-P-1012 A/B)

trips, the Dewatering Bio Sludge Centrifuge (601-G-1002) will also trip simultaneously (after a specified time lag).

In case the centrifuge trips, the thickened sludge pump (centrifuge feed) should trip. Local Temperature

Indicators (TI-2605 & TI-2606) are also provided in the Thickened Bio Sludge Sumps (601-TK-1048 A/B).

Supernatant Sump (601-TK-1049) & Supernatant Transfer Pumps (601-P-1013 A/B)

Sump is provided with Level Transmitter (LIT-2607), secondary level measurement device- Level Indicator (LI-

2607), local & control room indication, high/low alarms in control room and interlock to trip the Supernatant

Transfer Pumps (601-P-1013 A/B) at low level in the Supernatant Sump (601-TK-1049). A Flow Transmitter (FIT-

2601) is provided on the discharge line of these pumps.


Bulk Chemicals Storage Tanks & Pumps

Liquid chemicals required in bulk quantities such as Hydrogen Peroxide, Con HCL, Caustic Lye are stored in

Storage Tanks. Each tank is provided with Non Contact SMART Radar type Level Transmitter, secondary level

measurement device, local & control room indication, high/low alarms in control room and at low level & high

level in the tank the Unloading/Transfer Pumps will trip in case of Con HCl & Caustic Lye. In case of Hydrogen

Peroxide, at low level in the tank Dosing Pumps will trip and at high level in the tank Unloading Pumps will trip.

The pump discharge is provided with Flow element-transmitter for indication with recording cum totalizing facility

at the control Room. Local flow indicator is also provided. The tag numbers of various instruments are as follows.

Storage Tank Level Transmitter Level Indicator Unloading/Transfer

Pumps

Flow Transmitter

H2O2 Storage Tank (601-

TK-1012 A/B)

LIT-2803 & LIT-

2804

LI-2805 & LI-

2806

601-P-1032 A/B FIT-2801

Con HCl Storage Tank (601-

TK-1013)

LIT-2701 LI-2711 601-P-1018 A/B FT-2714

Caustic Lye Storage Tank

(601-TK-1015)

LIT-2708 LI-2712 601-P-1021 A/B FT-2715

All Chemical Solution Dosing Tanks & Pumps

For chemical solution dosing tanks, two (2) Nos. level measurement instruments is provided for each tank.

Primary level measurement instrument is a Non Contact type SMART Radar type Level Transmitter whereas

secondary level measurement instrument is level gauge. Level transmitter is to be used for local & control room

level indication and for tripping purposes (auto trip of dosing pumps and agitators) including low & high levels

alarms in the control room. Switching will be in PLC. All the dosing pumps have in built pressure safety relief

valves at their respective discharge lines. The tag numbers of various instruments are as follows.

Dosing Tank Level Transmitter Level Indicator Dosing Pumps Flow Indicator


H2O2 Storage Tanks (601-TK-1012

A/B)

LIT-2803 & LIT-

2804

LI-2805 & LI-

2806

601-P-1017 A/B

601-P-1017 C/D

FI-2802

FI-2803

HCl Dosing Tanks (601-TK-1014

A/B)

LIT-2702 & LIT-

2703

LG-2701 & LG-

2702

601-P-1019 A/B/C

601-P-1020 A/B

FI-2706, FI-2707 &

FI-2708

FI-3702

Caustic Dosing Tanks (601-TK-1016

A/B)

LIT-2709 &

LIT-2710

LG-2707 & LG-

2708

601-P-1022 A/B/C

601-P-1051 A/B

FI-2711, FI-2712 &

FI-2713

FI-3705

DOPE Dosing Tanks (601-TK-1017

A/B)

LIT-2704 &

LIT-2705

LG-2703 & LG-

2704

601-P-1023 A/B FI-2703, FI-2704 &

FI-2705

DWPE (Bio) Dosing Tanks (601-TK-

1020 A/B)

LIT-2706 &

LIT-2707

LG-2705 & LG-

2706

601-P-1026 A/B FI-2701 & FI-2702

DWPE (Oily) Dosing Tanks (601-TK-

1019 A/B)

LIT-2711 &

LIT-2712

LG-2709 & LG-

2710

601-P-1025 A/B FI-2709 & FI-2710

FeCl3 Dosing Tanks (601-TK-1026

A/B)

LIT-2806 &

LIT-2807

LG-2803 & LG-

2804

601-P-1033 A/B FI-2804

Nutrients Dosing Tanks (601-TK-

1018 A/B)

LIT-2801 &

LIT-2802

LG-2801 & LG-

2802

601-P-1024 A/B FI-2801

NaOCl Dosing Tank (601-TK-1021) LIT-3501

LG-3501 601-P-1027 A/B FI-3501

Citric Acid Dosing Tank (601-TK-

1023)

LIT-3502

LG-3502 601-P-1029 A/B FI-3502

Carbon Source Dosing Tank (601-

TK-1035)

LIT-3503

LG-3503 601-P-1041 A/B FI-3503

Antifoam Dosing Tank (601-TK- LIT-3504 LG-3504 601-P-1042 A/B FI-3504


1036)

Sodium Bisulphite Dosing Tank

(601-TK-1024 A/B)

LIT-3704 & LIT-

3705

LG-3703 & LG-

3704

601-P-1030 A/B FI-3704

Antiscalant Dosing Tank (601-TK-

1024 A/B)

LIT-3706 & LIT-

3707

LG-3705 & LG-

3706

601-P-1028 A/B FI-3703

On-line Analyzers

The following on line analyzers are provided to monitor the pollutant concentrations at various stages of

treatment.

Oil : API Separator Overflow Line to TPI Unit (AE-2408)

: SBR Feed Pump Discharge Line to SBR Tank (AE-2409)

pH : Flash Mixing Tank A outlet (AE-2401)

: Flash Mixing Tank B outlet (AE-2402)

: pH Adjustment Tank outlet (AE-2403)

: Outlet of MBR (AE-3401)


: Cartridge Feed Pump Discharge Line (AE-3601)

: Discharge Header of Treated Water Transfer Pumps (AE-3701)

TOC (BOD & COD) : pH Adjustment Tank outlet (AE-2410)


DO : Each compartments of SBR Aeration Tank (DOE-3001/2/3) : MBR Aeration Tank (AE-3301)

Turbidity : Outlet of MBR (AE-3405)


Conductivity : SBR Feed Pump Discharge Line (AE-2404)



: Outlet of each RO Skid (AE-3608/9/10)

Silica : Outlet of MBR (AE-3402)

: At R O skid -multi channel (AE-3611)

Sulphide : TPI Separator Overflow line to Flash Mixing Tank (AE-2405)

: SBR Feed Pump Discharge line to SBR Tank (AE-2407)

: Spent Caustic Stream Flocculation Tank Outlet (AE-2406)

ORP : Cartridge Feed Pump Discharge Line (AE-3603)


SDI : Cartridge Feed Pump Discharge Line (AE-3607)

Above analyzers are provided with indication cum recording facility at the control Room along with local

indication.

Gas Detectors

Following gas detectors are provided:

Hydrocarbon (HC) : At Inlet & Outlet of ACF (AE-4101 & AE-4102)

Hydrogen Sulphide (H2S) : Near DAF unit (GDIT-2401& GDIT-2402)

Carbon Monoxide (CO) : Outlet of ACF (AE-4103)

Above gas detector are provided with indication cum recording facility at the control Room along with local

indication with Alarm (both locally & Control Room) for exceeding preset values. The Instruments are selected as

per the specific application and sensors to be suitably located. All specifications provided as recommended by the

respective Instrument manufacturer for the specific model proposed.

GENERAL

All pumps have Pressure Gauge (PG) on their discharge lines. The pressure gauges on all slop oil, sludge and

chemical services are of diaphragm type.

All motors have their running indication in PLC.


All motors have local start / stop facility. The motors having interlock facility will have local / remote selector

switch , auto/manual switch is located on auxiliary console in control room, start/stop push buttons and selection

of main/standby switch in control room to facilitate remote operation.

All required start/stop push buttons, selector switches, etc. for operation of various equipment is through soft

keys.

In case a motor is already running, there should not be a stoppage due to mode change over from local to remote

and vice-versa. This is equally applicable for mode change over from auto to manual and vice-versa.

For all pumps/blowers acting on interlocks/program, if the running pump/blower fails, the standby pump/blower

will start automatically. However, manual override arrangement for the same is also be available. All

pumps/blowers are interchangeable.

At no point of time both the operating and standby pumps/blowers will run together in auto mode.

In case of more than two pumps, provision of alarm is made only for the highest cut-in level and not for

intermediate cut-in levels, unless otherwise specified. In auto mode removal of high level signal would not cause

stoppage of the running pump. All pumps are interchangeable and start will depend on the liquid level in the

sump, i.e. as the level in the sump rises, pumps to correspondingly get activated.

Effective Liquid Depth of units will be considered between levels corresponding to Lowest Water Level and

Highest Water Level. Flooded suction requires that lowest switch level will not be lower than the elevation of

discharge flange of pump.

All sumps and pumps are provided with appropriate instrumentation for alarms and auto operation (start/stop) of

pumps with respect to preset levels.

No direct level switches are used in the ETP. Instead level transmitters are used for all sumps and other tanks.

These transmitters are connected to PLC system and software switches shall be generated for interlock/alarm.


No direct process switches are used. Instead level transmitters are used for all sumps and other tanks. These

transmitters are connected to PLC system and alarms will be generated.

Refer attached instrumentation list for details for various instruments and tag numbers.

The instrumentation & control philosophy of SBR, MBR, Bioremediation and VOC system is given in the respective

systems process operating manual.


PROCESS CONTROL

Once the plant has been stabilized at full load it is important to maintain the operating parameters in a manner

such that the plant produces a treated effluent meeting the desired treated parameters on a consistent basis.

The plant is designed for a load of pollutants as specified in design specifications. However, excess load in terms

of various parameters can affect the performance of the plant. Hence, the values specified in the chapter ‘design

specifications’ should be considered as alarm limit for operating parameters.

Process control involves maintaining all process operating conditions that were stabilized during the stabilization

process. It also involves taking corrective measures as and when the feed conditions change. Further, the

operation and efficiency of the treatment process are best monitored in the laboratory. The analytical data

generated in a laboratory provides data for the evaluation of the incoming waste, performance of the plant and

the course of corrective action for a given problem. Always update and ensure that the spares are available at site

to handle any breakdown at any time. Thus the process control is a two step function involving control based field

observation and those based on laboratory inputs.


1. Field observations

2. Laboratory control

FIELD OBSERVATIONS

The following important points will need attention during regular plant operation:

API SEPARATOR & TILTED PLATE INTERCEPTOR (TPI)

- Check and control oil levels by regular operation of the oil skimmer.

- Ensure that the oil flows freely through the pipes into the slop oil tank.

- Withdraw sludge at regular intervals so that sludge does not build up in the tank, and at the same time, the

sludge withdrawn is not unnecessarily dilute, leading to a dilute centrifuge feed.

- At least once a day flush the underflow lines with steam, air, service water to prevent clogging of lines.

- If required, flush the plate packs with a water jet to remove any material clogged between the plates. This must

be done very carefully to avoid damage to the Plate Pack sheets.

DISSOLVED AIR FLOTATION


Check the overflow quality and regulate chemical dosing.

Ensure that saturation line pressure is maintained at 4 -6 Kg / cm2.

Maintain a uniform measured air flow and recycle flow to the Air Saturator.

Regulate the air discharge rate in accordance with the oil and solids load to achieve optimal oil/solids capture.

Periodically check all flow rates, make sure they haven’t significantly varied from the initial set points.

Withdraw the settled sludge at regular intervals to prevent build up in the system.

Check the overflow and regulate chemical dosing as required.

The suction strainers of the FeCl3 and DOPE pumps need to be cleaned regularly to ensure smooth operation of

the pump.

The preparation of FeCl3 and DOPE should be an attended operation to prevent overflow of tanks and waste of

utility.

SECONDARY CLARIFIER (COMPLETREATOR)

Ensure that the return sludge pumps and rake mechanisms are operated continuously.


Accumulation of the sludge in the clarifier can lead to serious problems such as septicity of the sludge and floating

in the clarifier, high solids in overflow.

Launders should be cleaned regularly to prevent build up of sludge and growth of algae.

THICKENER

Ensure continuous operation of the rake mechanism.

In case of the Bio Sludge Belt Thickener, the speed of the belt should be adjusted to ensure adequate dewatering

of the feed slurry.

Maintain adequate dosing of Dewatering Polyelectrolyte (DWPE) to ensure maximum sludge compaction.

Adequate dosing rate of DWPE is especially essential for the Bio Sludge Belt Thickener to ensure rapid dewatering

of the slurry on the belt.

Ensure regular operation of the underflow sludge pumps.

Accumulation of the excess sludge in the thickeners may lead to serious problems such as overloading of the rake

drive and choking of the underflow pipe, and septicity of the sludge.

Check regularly the underflow solids concentration.


Launders should be cleaned regularly.

CENTRIFUGE

Check the suspended solids levels in the centrate and moisture content of the centrifuge cake. Improvements

may be possible by varying the dose of polyelectrolyte, and the feed rate to the unit. Periodically conduct

laboratory jar tests to fix the DWPE dosage required.

If centrifuge shows severe vibration when being started or in running condition, it could be due to bearing

problem, improper anti vibration pads or due to accumulation of solids in the unit. In this case stop the feed

immediately and thoroughly flush the centrifuge with water.

Centrifuge should be kept clean by proper flushing with water prior to shutdown.

CHEMICAL DOSING SYSTEM

- Regularly check the stock of dosing chemicals required to ensure availability at all times.

- Make note of the all dosing tank levels regular intervals.

Check all dosing pumps for proper discharge and adjust stroke length according to requirements.

Regularly flush out the dosing tanks .Clean the strainers at pump suction as and when required.


SPENT CAUSTIC STREAM

- Operation should regularly monitor the level of H2O2 Storage Tank, ensure availability of chemical and to avoid

dry running of pumps.

Operator should keep regular check on operation and dosing rate with respect the sulphide concentration in the

influent and effluent.

In case of emptying of these tanks, operator should follow standard refinery practice.

LABORATORY CONTROL

Sampling

The reliability of the results of wastewater sample depends upon the proper collection of a truly representative

sample from the large volume of wastewater streams. The sample after collection should be transported to the

laboratory in a well preserved condition so that it will represent fairly, accurately the waste in its original state.

The sample may be grab or composite depending upon the requirement and extent of monitoring required.

Grab sample represents the conditions that exist at the time of collection of the sample since they do not indicate

average conditions. This data generally should not be used for final reporting purposes. Grab samples are useful

whenever abnormal discharge is observed or suspected at sampling points. This sampling method is also adopted

for measurement of parameters where the analysis has to be done immediately such as pH, turbidity, dissolved

oxygen, sulphide, etc.


Composite sample are the average samples collected over specified period and at specified intervals.

Consideration should be given to the duration of the sampling period, which will be dictated by the operating

conditions of the processing units of the main plant.

Method of Sample Collection

Samples are collected for plant operation controls. They should be collected in a suitable sampling bottle with

tight cover.

Interpretation of Laboratory Results

This is one of the most difficult tasks before the plant personnel. Since the main objective of the analysis are

directed towards prevention and control and then proper operation and maintenance of plant. Proper

interpretation of the analytical data should be the prime responsibility of the Plant In-Charge.

Preferably daily, the analytical data in respect of each source of samples has to be examined to determine degree

of conformity or deviation of the prescribed standard for influent and effluent. In case of vast deviation the

corrective action should be initiated by Plant In-Charge.

LABORATORY SAMPLE SCHEDULE


OM&S Daily Effluent Water Samples:

SN Sample Qty. Time Hrs. Tests

1. API Separator O/L

(FR)

0.5 Lit. 0600,1800 pH, Oi l& Grease, Free Cl2 ppm

2. Mahul Catcher O/L 0.5 Lit. 0600 pH, Oil & Grease, Free Cl2 ppm

3. Oil Catcher

oppositeTk-259

0.5 Lit. 0600 pH, Oil & Grease, Free Cl2 ppm

4. CPP Nallah Outlet 0.5 Lit. 0600 pH, Oil & Grease, Free Cl2 pp

IETP: Daily Samples

SN. Sample Quantity Time Tests

1. API Feed inlet 2 x 1 Lit

0900

pH, O&G, TSS, Sulphide, BOD, COD & Phenol

2. pH tank outlet 2 x 1 Lit 0900

pH,O&G, Sulphide, TSS, BOD, COD & Phenol

3. SBR Outlet 2 x 1 Lit 0900 O&G, TSS, BOD, COD, Sulphide & Phenol

4. SBR Aeration tank 1 Lit 0900 MLSS

5. MBR Aeration tank 1 Lit 0900 MLSS

6. MBR Outlet 2 x 1 Lit 0900 pH, O&G, TSS, BOD, COD & Sulphide

7. RO Outlet (permeate) 2 x 1 Lit

0900 pH, O&G, TSS ,BOD ,COD, Turbidity, Total Silica, TDS

8. Reject 2 x 1 Lit 0900 pH, O&G, TSS ,BOD ,COD, Sulphide, Phenol, TDS

9. Spent Caustic Inlet 0.5 Lit 0900 pH & Sulphide

Note: 1) BOD sample to be collected in 2 BOD bottles only

2) O&G sample to be collected in separate bottle


IETP: Weekly Samples

SN Sample Qty. Day Tests

1. API Feed inlet 1.0 Lit Monday TDS

2. pH tank outlet 1.0 Lit Monday TDS

3. Spent caustic O/L 2 x 1.0 lit Monday pH,Sulphide

4. SBR Aeration tank 1 x 2.0 lit. Monday MLVSS

5. MBR Aeration tank 1 x 2.0 lit. Wednesday MLVSS

6. Completreater O/L 1 x 2 Lit Tuesday pH, O&G, TSS ,TDS,BOD&COD

TROUBLE SHOOTING

In any process operation system upsets occurred due to various reasons. In ETP, these upsets could be due to

changes in the incoming wastewater or inadequate process controls. Whenever plant upsets occur, the first step

is to identify the cause for the upset. Subsequent, corrective measures then become simpler and meaningful.

Some of the common problems, their causes and possible solutions are discussed below:

API OIL SEPARATOR


Problem

Slippage of oil or poor performance of unit due to –

- Unit hydraulically overloaded.

- Non uniform overflow of effluent.

Excessive oil in the influent.

Accumulation of excess sludge at the bottom of unit.

Irregular free slop oil withdrawal.

Solution

Hydraulic overloading in the unit will reduce the retention. Maintain an average uniform flow in the specified

range of flow rate.

Check and ensure the overflow weir is not clogged to ensure uniform overflow of effluent throughout the length

of the overflow launder.

Increase oil skimming from upstream unit operations.

Withdraw the settled sludge and floating free slop oil on a regular basis.

TILTED PLATE INTERCEPTOR (TPI)

Problem


Slippage of oil or poor performance of unit due to –

- Unit hydraulically overloaded.

- Non uniform overflow of effluent.

Accumulation of excess sludge at the bottom of unit.

Plate packs are partly clogged.

Irregular free slop oil withdrawal.

Solution

Hydraulic overloading in the unit will reduce the retention. Maintain an average uniform flow in the specified

range of flow rate.

Check and ensure the overflow weir is not clogged to ensure uniform overflow of effluent throughout the length

of the overflow launder.

Regularly carefully clean the plate packs of adhering oily sludge solids by using a water jet. This would increase

the settling area to the maximum and prevent short-circuiting through the plates.

Check that packing between plate pack and TPI unit wall is intact. Replace packing material wherever required.

Withdraw the settled sludge and floating slop oil on a regular basis.


DISSOLVED AIR FLOTATION (DAF)

Problem

Turbulence is evident at influent end of flotation basin due to excess undissolved free air with the recycle air

stream.

Solution

Reduce the air flow rate to the saturation vessel or increase the flow rate of the recycle stream. In case the

recycle stream flow rate cannot be increased and the same quantum of dissolved air is required, then the airflow

rate to the saturation vessel may varied by varying the system pressure by means of the Air Filter Regulator (AFR)

so that the solubility of the air increases resulting in consequent a correspondingly larger amount of precipitated

air.

Check and ensure that the set liquid levels are maintained in the saturation vessel. In case the saturator level goes

so low that the saturator is completely empty, then free air from saturator will pass into the DAF unit.

Problem

Insufficient air supply due to -

Clogging of air line.

Malfunction of AFR.

Malfunction of air compressor.

Solution


Check for malfunctioning of the regulating valve and air compressor. Refer the service manual for air filter

regulating valve and air compressor.

Problem

Excessive oil or solids carry over in overflow.

Causes

Inadequate chemical dosing.

Inadequate quantum of precipitated air.

No uniform overflow of effluent.

Improper operation of skimmer.

Size of air bubbles is not uniform or too large /small.

Saturation system is not working properly.

Excessive sludge accumulation at the bottom.

Solution

Check the dosing system and readjust the dosing as per requirements. Repeat lab jar tests to check/confirm

chemical dosages for FeCl3 /DOPE.

Adjust the air quantity & pressure and recycle pump flow rate to ensure adequate quantity of precipitated air and

ensure air bubble size is proper for effective oil/solids capture at the operated effluent flow rates.


Regularly check that the liquid levels in the saturator are maintained at the desired range. Too high liquid level

could result in the saturator packing media getting submerged resulting in reduced mass transfer of air into the

effluent. Too low level could result in the saturator vessel getting completely empty cause free air to enter the

DAF resulting in turbulence in the unit.

Improper desludging leads to accumulation of sludge at the tank bottom, which decomposes over a period of

time. The decomposed solids being light in weight and will get carried into the overflow. Regulate the frequency

of underflow withdrawal.

Check the skimmer operation.

Problem

Scum too thick on the surface of DAF Tank.

Solution

Operate the skimmer regularly and remove the scum.

Problem

Air rotameter reading drops.

Causes

- Malfunction of AFR.

- Malfunction of rotameter.


- Air compressor malfunction.

Solution

Check and correct malfunction of AFR.

Check the performance of the air compressor: Ensure the required pressure is achieved.

Ensure the rotameter is functioning properly.

CENTRIFUGE

Problem

Chokage in centrifuge.

Causes

Feed slurry consistency is high.

Fluctuation in feed flow.

Improper flushing of centrifuge.

Loose ‘V’ belts.

Sudden failure of fluid coupling.

Solution


The centrifuge feed pump and DWPE dosing pump to be switched off. Check feed solids consistency.

Actuate the flushing system.

The centrifuge to be switched off after getting clear centrate (about 15 minutes).

Ensure the proper cleaning of the centrifuge by getting clear water from solid outlet. If water is not clear, restart

the centrifuge and again flush it with flushing liquid. If required clean the inlet pipes in the centrifuge as per

instructions of centrifuge supplier.

Check belts & fluid coupling.

Problem

Severe vibration.

Causes

Chokage in centrifuge.

Failure of bearings or antivibration pads.

Misalignment of motor and equipment.

Solution

Dechoke the centrifuge by adequate flushing of the centrifuge and clean the inlet pipes in the centrifuge as per

instructions of centrifuge supplier.


Check bearings and antivibration pads.

Check alignment of motor.

Problem

Output solid consistency is not satisfactory.

Causes

Feed slurry consistency less than specified level.

Feed slurry flow is more.

DWPE dose is not adequate.

DWPE solution strength is not proper

Solution

Check feed slurry solids and increase the concentration to the specified range.

Reduce feed flow.

Check DWPE dose by jar test. Adjust dosing rate based on required dose and solids flow rate.

Check DWPE solution preparation procedure details.


Problem

High suspended solids in centrate.

Causes

Choking of centrifuge by solids.

High solids consistency in feed slurry.

High feed slurry rate.

DWPE dose is not adequate.

DWPE strength is not proper.

Solution

Flush the centrifuge to remove accumulated solids.

Check feed slurry solids and decrease the concentration to the specified range.

Reduce feed flow rate.

Check DWPE dose by jar test. Adjust dosing rate based on required dose and solids flow rate.

Check DWPE solution preparation procedure details.


Spent Caustic Treatment

Problem

High sulfide contain in the treated effluent.

Solution

Check sulfide & pH. High pH at inlet could be due to draining of spent caustic in OWS in process units.

Conduct laboratory jar test and adjust the dose of H2O2. As per stoichiometric, 4.25 Kg of H2O2 is required for 1

Kg of sulphide.

COMPLETREATOR

Problem

Poor Organic (BOD/COD) Removals.

Causes

Inadequate biomass (MLVSS) concentration.

Improper recycle of return sludge.


Organic /Volumetric overloading.

Inadequate air supply – Low Dissolved Oxygen (DO) levels.

Solution

Check the MLSS/MLVSS values at regular intervals and adjust sludge wastage rates to achieve the desired

specified values.

Ensure return sludge is being recycled continuously.

Check the BOD/COD levels and match with specified values. Ensure unit is not highly overloaded volumetrically.

Check dissolved oxygen values in various aerobic compartments are positive (0.5 - 2.0 mg/l DO are normal values

encountered in an aerobic system). Ensure air blowers are functioning properly.

Problem

High suspended solids level in clarifier overflow.

Causes

High volumetric flow rate.

Bulking of bio sludge

Accumulation of bio sludge in clarifier due to inadequate sludge recycle rate.

Solution


Ensure that system is not grossly overloaded volumetrically.

Bulking of bio sludge can be taken care by bleeding off sludge / chlorination of return sludge.

Adequately desludge the clarifier to remove accumulated sludge.

PLANT SHUTDOWN

Effluent treatment plants are generally not shutdown completely in view of their essentiality from the

environmental angle as under no circumstances effluent can be discharged without treatment. However, at times,

shutdown may be required due to non-availability/ breakdown of equipment for which the following operations

are suggested:

In case of breakdown of API Oil Separators or downstream equipment, by-pass the equipment.

In case of breakdown of the equipment downstream of API Oil Separators or excessive receipt of influent, the

excessive influent may be diverted to guard ponds if provided or release from the refinery. This operation shall

require clearance from Plant In-Charge .

In case of shutdown of Biological systems, keep air blowers running. Biological sludge recirculation pump should

also be kept running for survival of the microbes.

In case of shutdown of Sludge Thickeners, keep sludge scraping mechanism running.

Before shutdown of Centrifuges & Centrifuge Feed Pumps, flushing is must.


SAFETY SYSTEM

Safe operating practices are an important aspect of plant operation and proper safety instructions must be laid

out and scrupulously followed. This becomes especially significant when handling inflammable and corrosive

materials. Some of the important safety considerations are highlighted below.

The plant area to be kept clean and free of spillage.

Proper precautions must be taken while doing maintenance work of equipments especially equipments handling

oil.

While preparation of chemical solutions, safety gloves & goggles must be worn.

Safety gloves & goggles must be worn while collecting samples.

Safety showers must be checked at regular interval for proper operation.

Chemical splashes must be immediately washed with copious quantity of water. Seek medical aid if necessary.

Contact with the effluent must be avoided as far as possible. However, if contact is unavoidable, ensure that

hands are washed with soap.


Standard safety procedures to be followed while handling electrical equipments.

EMERGENCY HANDLING

The most likely emergency situations are:

1. Oil spillage

2. Fire

1. Oil spillage - Oil spillage may occur due to accidental overflow/ leakage of equipments.

Action

Isolate the equipment & take action to arrest leakage.

Clean plant area with water.

Oil recovery to be started at Final Oil Traps (‘Effluent Leaving Refinery’) to avoid oil escape from the refinery.

Inform Shift In-Charge & Plant In-charge.

2. Fire

Action

Immediately take action to stop the fire with the fire safety equipments (suitable for type of fire) available at site.


Inform Fire Station.

Inform Shift In-Charge & Plant In-charge.

GAS EMISSION DETECTION SYSTEM

In the ETP, there are mainly two types of hazardous gases, namely hydrocarbon vapors and hydrogen sulphide

gas.

A gas detection system has been installed for the safety of plant and operating personnel.

Following gas detectors are provided:

Hydrocarbon detector - Near OWS Sump

H2S detectors - Minimum 2 Nos. in the vicinity of DAF unit (Main treatment chain)

Above gas detector are provided with indication cum recording facility at the control Room along with local

indication with Alarm (both locally & Control Room) for exceeding preset values. The Instrument are selected as

per the specific application and sensors to be suitably located. All requirements including (Shed, Environment,

etc.) is provided as recommended by the respective Instrument manufacturer for the specific model proposed.

In case of alarm goes off, the area should be immediately evacuated of all the operating personnel. The cause of

alarm to be investigated and remedial action should be initiated as per standard procedures.

Slop Oil & Sludge Generation- Design basis

The IETP consists of various treatment processes, which yields a number of products as listed below: -


1. Slop Oil

2. Oily Sludge

3. Chemical Sludge

4. Bio Sludge

5. Treated effluent

The above units are produced in the following units:

1. API separator (601-API-1001 A/B/C)

2. TPI separator (601-TPI-1001 A/B)

3. DAF unit (601-TK-1004 A/B)

4. SBR(601-SBR-1001)

5. MBR(601-MBR-1001)

The quantity of products from the above units is as follows:

A. SLOP OIL

1. From API separator (601-API-1001 A/B/C)

Unit Inlet Outlet

Flow m3/hr 300 300

Free Oil (Nor/Max.) mg/L 800/19500 400/975

Emulsified Oil (Nor/Max) mg/L 200/500 200/500


Total Oil (Nor /Max.) mg/L 1000/20000 600/1475

Free oil removed at Max. Oil Content = 18525 mg/L (133380 kg/day)

At 20 % consistency, Volume Of

Wet Slop Oil At. Max. oil Content = 133380/ (200)

= 666.9 m3/day

= 27.79 m3/hr.


Free oil removed at Normal Oil Content = 400 mg/L (2880 kg/day)

At 5% consistency, Volume of

Wet Slop Oil at Normal oil Content = 28800/ (50 )

= 57.6 m3/day

= 2.4 m3/hr.

2. From TPI separator (601-TPI-1001 A/B)

Unit Inlet Outlet

Flow m3/hr 300 300

Free oil (Nor /Max.) mg/L 400/975 15/50

Emulsified Oil (Nor/Max) mg/L 200/500 200/500

Total Oil (Max.) mg/l 600/1475 215/550

Free oil removed at Max. Oil Content = 925 mg/L (6660 kg/day)

At 5% consistency, Volume Of

Wet Slop Oil At. Max. oil Content = 6660/ (0.05 X 1000)

= 133.2 m3/day

= 5.55 m3/hr.

Free oil removed at Nor. Oil Content = 385 mg/L (2772 kg/day)

At 5% consistency, Volume of


Wet Slop Oil at. Nor. oil Content = 2772/ (50)

= 55.44 m3/day

= 2.31 m3/hr.

3. From DAF flotation tank (601-TK-1004 A/B)

Unit Inlet Outlet

Flow m3/hr 300 300

Free oil mg/L 50 5

Emulsified Oil mg/L 500 5

Total oil mg/L 550 10

Suspended mg/L 20 10

Solids


Total oil removed at Nor. Oil Content = 540 mg/L (3888 kg/day)

At 3% consistency, Volume Of

Wet Slop Oil At. Nor. oil Content = 3888/ (30)

= 129.6 m3/day

= 5.4 m3/hr.

Total Slop oil Generated at Max. Oil Content = 27.79+5.55+ 5.4

(ISBL) = 38.74 m3/hr

Total Slop oil Generated at Nor. Oil Content = 2.4 + 2.31+ 5.4

(ISBL) = 10.11 m3 / hr


B. OILY SLUDGE

1. From API separator (601-API-1001 A/B/C)

Unit Inlet Outlet

Flow (Nor.) m3/hr 300 300


Solids

Suspended Solids removed in API = 140 mg/L (1008 kg/day)

At 1.5% sludge consistency

Sludge generation = 1008/15

= 67.2 m3/day

= 2.8 m3/hr

2. From TPI separator (601-TPI-1001 A/B/C)

Unit Inlet Outlet

Flow (Nor.) m3/h 300 300


Solids


Suspended Solids removed in TPI = 40 mg/L (288 kg/day)



= 19.2 m3/day

= 0.8 m3/h

Total oily sludge @ 1.5 % consistency = 2.8 + 0.8

= 3.6 m3/h


C. CHEMICAL SLUDGE

From DAF tank (601 -TK-1004 A/B)

Unit Inlet Outlet

Flow (Nor.) m3/hr 300 300


Solids

Suspended Solids removed in DAF = 10 mg/L (72 kg/day)



= 4.8 m3/day

= 0.2 m3/h

Sludge due to precipitation of Fe(OH)3

FeCl3 dosing = 30 mg/L

Chemical mass balance:

FeCl3 + 3NaOH Fe (OH) 3 + 3NaCl

1. 107

FeCl3 dose per day = 30/1000 x 300x24

= 216 kg/day

Fe (OH) 3 sludge generated = 107/162.5 x 216


= 142.23 kg/day

Sludge flow rate @ 1.5 % consistency = 9.48 m3/day

= 0.4 m3/hr.

Total Chemical sludge = 0.2 + 0.4 m3/h

= 0.6 m3/h

Total Oily and Chemical sludge generated = 3.6 + 0.6

(ISBL) = 4.2 m3/h

Total oily & chemical sludge dry solids : 1008 + 288 + 72 + 142.23

(ISBL) : 1510.23 Say 1511 kg/d

Total oily & chemical sludge generated

(ISBL + OSBL) : 8.4 m3/h

Total oily & chemical sludge dry solids : 3023 kg / day

(ISBL + OSBL)

Thickened Oily & chemical Sludge from : 3023/ (50 x 1.05)

the thickener as 5 % solids & Sp. Gr. Of 1.05 = 57.58 m3/ day = 2.4 m3 / h

(Feed to Centrifuge)

Solids in Thickener supernatant (0.1%) : (8.4-2.4) x 1000/1000

= 6 kg/hr = 144 kg/day


Actual solid loading to Centrifuge : 3023 – 144 = 2879 kg/day

Solid capture in centrifuge (97%) : 2792.63 kg/day

De watered sludge from centrifuge as 20 % : 2792.63 / (200 x 1.1)

Solids and Sp. Gr. Of 1.1 = 12.69 m3/day =0.53 m3 / h

Supernatant from Oily and Chemical sludge thickener = 201.6– 57.58

= 144.02 m3/day

Supernatant from Oily and Chemical sludge Centrifuge = 57.58 – 12.69

= 44.89 m3/day


D. BIO SLUDGE

Bio sludge from SBR

Bio sludge generated in SBR = 1872 kg/day based on BOD load of 7200 kg/day

However, the SBR is followed by MBR where the inlet BOD concentration will be 100 mg/l viz. BOD

load of 720 kg/day.

Hence, the biological sludge generated in SBR considering BOD removal of 6480 kg/day:

BOD removed from SBR : 1000 – 100 = 900 mg/l

Considering sludge wasting rate of

0.26 kg/kg of BOD removed,

Bio sludge wasted : (900/1000) x 300 x 24 x 0.26

=1684.8 kg/day

At 0.8 % consistency,

Sludge generation rate : 1684.8 / 8 = 210.6 m3/day

= 8.78 m3/hr

Bio sludge from MBR

BOD removed from MBR : 100 – 5 = 95 mg/l


As per BEP of MBR(R2)

Bio sludge wasted : 341.2 kg/day

At 0.8 % consistency,

Sludge generation rate : 341.2 / 8

= 42.6 m3/day

= 1.78 m3/h

Bio sludge from Sanitary Treatment

Sludge generated from sanitary treatment

Package @ 0.8 % consistency : 3.75 m3/d (30 kg/day)

= 0.16 m3/h

Total Bio-Sludge generation rate = 8.78 +1.78+ 0.16

( At 0.8 % consistency) = 10.72 m3 / h

(2058 kg /d)

Solid capture rate in GBT (96%) : 1975.9 kg/d

Thickened Bio Sludge from : 1975.9/50/1.05 = 37.63 m3/ day

GBT as 5 % solids & Sp. Gr. Of 1.05 =1.57 m3 / hr

(Feed to Centrifuge)

Solid capture in centrifuge (97%) : 1916.62 kg/day


De watered sludge from centrifuge at 20 % : 1916.62/1.1/200 = 8.71 m3/day

Solids and Sp. Gr. Of 1.1 = 0.36 m3 /h

Supernatant from Bio-sludge thickener = 257.28–37.63 = 219.65

m3/day

minuscule

Supernatant from Bio-sludge Centrifuge = 37.63 – 8.71

= 28.92 m3/day

Total Supernatant quantity from Bio sludge and Chemical sludge de-water

= ( 144.02+44.89+219.65+28.92)

= 437.48 m3/day


Chemical Consumption at IETP

Chemicals used and their application

Sr No

Chemical & concentration for rated feed

Pumps Application/Purpose

1 Acid (HCL) 10%

601-P-1019 A/B/C & 601-P-1020 A/B.

Used for neutralization/Flash Mixing Tank/PH adjustment Tank & RO permeate dosing.

2 Alkali (NaOH) 10%

601-P-1022 A/B/C

Used for Neutralization/Flash Mixing Tank/PH adjustment Tank & permeate water PH adjustment.

3 Hydrogen Peroxide (H2O2) 50%

601-P-1019 A/B/C

Used for oxidation of sulphides to sulphates in flash mixing tank of oily and spent Caustic treatment.

4 FeCl3

601-P-1033 A/B

Used as flocculant in flash mixing tank of oily effluent chain.

5 DOPE 0.5%

601-P-1023 A/B

Used as de-emulsifier in flocculant tank for emulsified oil removal.

6 UREA & DAP 0.1%

601-P-1024 A/B

Used in PH adjustment tank for nutrients.

7 DWPE (Oily + Bio) 0.5%

601-P-1025 A/B 601-P-1026 A/B

For Dosing in Chemical/& Oily & Bio sludge thickener and dewatering centrifuge.

8 Methanol 10%

601-P-1041 A/B

Used in MBR as a carbon Source for growth of Microbes.

9 Anti-form 10%

601-P-1042 A/B

Used in MBR for Foam Control

10 Citric Acid 50%

601-P-1029 A/B

Used for Cleaning of MBR Membranes.

11 Sodium hypochlorite (NaOCL) 11%

601-P-1027 A/B

Used for Cleaning of MBR Membranes.

12 Antiscalant 6%

601-P-1028 A/B

Used for RO Scale Controls.


13 Sodium Bi-sulphite 5%

601-P-1030 A/B

Used in RO to remove free chlorine.

Chemical dosage at IETP

Sr No

Chemical Dosage Consumption Unit Purity of chemical available

% of solution prepared

1 DOPE 5ppm 36 Kg/day 100 0.5

2 DWPE (Oily) 2.0 kg/T of dry solids

6.046 Kg/Day 100 0.5

3 DWPE (Bio) 2.5 kg/T of dry solids

4.940 Kg/day 100 0.5

4 DAP (Note-1) BOD:P(100:1) 384 Kg/day 80 10

5 Sodium Bisulphite 5 ppm 36 Kg/day 80 5

6 Urea (Note-1) BOD:N(100:5) 631 Kg/day 100 10

7 Citric Acid Note 2 3784 Litres/Year

50 ---

8 Sodium Hypo-chloride

Note 3 3242 Litres/Year

10.8 ----

9 Anti-Foam 2 ppm 15.16 Litres/Day

100 10

10 Anti-Scalant 5.55 ppm 40 Litres/Day

100 6

11 H2O2 Sulphides:H2O2 (1:4.25)

16014 Litres/Day

50 __

12 HCL 35 788 Litres/day

100 10

13 NaOH 25 418 Litres/Day

100 10


14 Methanol 20 ppm 180 Litres/Day

100 10

15 FeCl3(anhydrous) 30ppm 216 Kg/day 100 10

Notes:

I. Sufficient Quantity of N&P are available in the raw effluent and hence normally

nutrient dosing will not be required. A dosage of 100:5:1 of BOD:N:P has been

considered to calculate the DAP and urea consumption during startup of the plant.

For Stabilized plant a dosage of 350:5:1 of BOD:N:P has been considered for DAP &

urea consumption.

II. For maintenance cleanning of Citric acid dosa is 2000ppm and for recovery clean

citric acid soaking concentration is 200ppm.

III. For maintenance cleanning of NaOCL dose is 200ppm and for recovery clean citric

acid soaking concentration is 1000 ppm.

annexure-i - hpcltenders.hpcl.co.in/tenders/tender_prog/tenderfiles/5546/tender... · annexure-i...

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