Appropriate Effluent Treatment System for Dyes and Dye- intermediates Industries PROF. ARUNABHA MAJUMDER Emeritus Fellow School of Water Resources Engineering.

Appropriate Effluent Treatment Appropriate Effluent Treatment System for Dyes and Dye-System for Dyes and Dye-intermediates Industries intermediates Industries

PROF. ARUNABHA MAJUMDER

Emeritus Fellow

School of Water Resources Engineering

Jadavpur University

and

Ex-Director-Professor

All India Institute of Hygiene and Public Health, Kolkata

Dyes and dye- intermediates Industries: Designated as ‘ Special Red’

Category Industry

As per Industrial siting (Locational) Policy for West Bengal, Special red

Category Industries cannot be permitted to be operated in municipal areas

falling under Kolkata Metropolitan Area (KMA).

Dyes and Dye-intermediates Industries are restricted / prohibited within the

belt of 10 km radius around the periphery of the Leather Complex at

Bantala.

Background

Fabric dyeing is carried out by either in continuous or batch Fabric dyeing is carried out by either in continuous or batch

process.process.

In the continuous dyeing process, the dye is transferred to the In the continuous dyeing process, the dye is transferred to the

fabric by passing the fabric across roller which are partially fabric by passing the fabric across roller which are partially

submerged in the dye solution.submerged in the dye solution.

A batch dyeing of fabric is often accomplished in atmosphere A batch dyeing of fabric is often accomplished in atmosphere

or pressure backs or in jet dyeing machines. The majority of or pressure backs or in jet dyeing machines. The majority of

knitted fabric are batch dyed, using a variety of processes.knitted fabric are batch dyed, using a variety of processes.

Direct dyesDirect dyes Basic dyesBasic dyes Vat dyesVat dyes Sulphur dyesSulphur dyes Developed dyesDeveloped dyes Napthol dyesNapthol dyes Metal Complex dyesMetal Complex dyes

Direct dyes: These dyes are neutral and are used for dyeing of cotton Direct dyes: These dyes are neutral and are used for dyeing of cotton

textiles on account of its natural affinity to this class of dyes, which are textiles on account of its natural affinity to this class of dyes, which are

easy to apply without any mordants. The colors produced are stable easy to apply without any mordants. The colors produced are stable

and are fast to light.and are fast to light.

Basic dyes: These are salts of colored base and require an acid Basic dyes: These are salts of colored base and require an acid

mordant such as tannic acid, tartaric and acetic acids. These dyes mordant such as tannic acid, tartaric and acetic acids. These dyes

impart very bright colors to the fabrics. Soluble oil and soda ash are impart very bright colors to the fabrics. Soluble oil and soda ash are

also used in the final stages of dyeing with basic dyes. A number of also used in the final stages of dyeing with basic dyes. A number of

waste streams and other process chemicals are generated during the waste streams and other process chemicals are generated during the

process.process.

Vat dyes: This group of dyes are fast dyes and are not water soluble, but are rendered soluble by Vat dyes: This group of dyes are fast dyes and are not water soluble, but are rendered soluble by

strong reducing agents like sodium hydrosulphite. In this process the cloth is immersed in a vat strong reducing agents like sodium hydrosulphite. In this process the cloth is immersed in a vat

containing the dye, dilute acid and sodium hydrosulphite and then exposed to oxidation in containing the dye, dilute acid and sodium hydrosulphite and then exposed to oxidation in

presence of an oxidizing agent. This is followed by scouring with a dilute alkaline solution to presence of an oxidizing agent. This is followed by scouring with a dilute alkaline solution to

neutralize the excess acid.neutralize the excess acid.

Sulfur dyes: These contain sulfur compounds and are applied together with a suitable reducing Sulfur dyes: These contain sulfur compounds and are applied together with a suitable reducing

agent like sodium sulfide followed by oxidation.agent like sodium sulfide followed by oxidation.

Developed dyes: These are colors which are produced on the fiber. At first the color is directly Developed dyes: These are colors which are produced on the fiber. At first the color is directly

applied on the fabric and is converted into an unstable azodye by the addition of sodium nitrite applied on the fabric and is converted into an unstable azodye by the addition of sodium nitrite

and HCl. Next the stable form of the color is developed on the fiber by the action of beta napthol.and HCl. Next the stable form of the color is developed on the fiber by the action of beta napthol.

Napthol dyes: In this process the color is developed by a reversal of the Napthol dyes: In this process the color is developed by a reversal of the

sequence of operations of the dyeing with developed colours, the cloth sequence of operations of the dyeing with developed colours, the cloth

is at first treated with beta-napthol and then diazotised with sodium is at first treated with beta-napthol and then diazotised with sodium

nitrite and HCl. A hot soap and soda bath is used.nitrite and HCl. A hot soap and soda bath is used.

Metal complex dyes: In the case of certain types of cotton fabrics and Metal complex dyes: In the case of certain types of cotton fabrics and

synthetic textiles like nylon and polyester, dyeing process is carried out synthetic textiles like nylon and polyester, dyeing process is carried out

by depositing inside the fibre complex salts of iron and chromium. by depositing inside the fibre complex salts of iron and chromium.

Depending on the quantity of the metal salts and various shades khaki Depending on the quantity of the metal salts and various shades khaki

colour can be produced. Metallic salts are also used as catalysts for the colour can be produced. Metallic salts are also used as catalysts for the

application of wash and wear permanent press and water repellant and application of wash and wear permanent press and water repellant and

flame retardant finishes.flame retardant finishes.

General Characteristics of dye General Characteristics of dye house waste waterhouse waste water

pHpH 6.3 to 10.56.3 to 10.5 TDSTDS 680 – 3180 mg/l680 – 3180 mg/l Suspended Solids (SS)Suspended Solids (SS) 380 – 950 mg/l380 – 950 mg/l BODBOD 320 – 820 mg/l320 – 820 mg/l CODCOD 750 – 2000 mg/l750 – 2000 mg/l

Effluent Treatment processEffluent Treatment processCoagulant

/Lime/flocculant

Recycle/Reuse

Final Effluent

1 2 3

4

1. Screen2. Equilisation Tank3. Flush Mixer4. Primary Clarifier5. Bio-reactor/AT6. Secondary Clarifier7. Sump8. Active Carbon Filter9. Sludge dewatering10. Sludge thickener11. SDB

5

67

8

Filter

91011

Primary TreatmentPrimary Treatment

By the process of coagulation- flocculation and By the process of coagulation- flocculation and

sedimentation, color, colloidal, suspended and sedimentation, color, colloidal, suspended and

settleable solids are removedsettleable solids are removed

Flush mixing for 60 to 90 secFlush mixing for 60 to 90 sec

Slow mixing for 20 to 25 minutesSlow mixing for 20 to 25 minutes

Detention time in PC : 150 minDetention time in PC : 150 min

BOD and COD reduction: 45 to 65 %BOD and COD reduction: 45 to 65 %

Bio-reactor with Conventional or Extended aerationBio-reactor with Conventional or Extended aeration

Detention time: Detention time:

ConventionalConventional : 6 hrs to 10 hrs: 6 hrs to 10 hrs

Extended AerationExtended Aeration : 12 hrs to 24 hrs(18 to 36 hrs): 12 hrs to 24 hrs(18 to 36 hrs)

Aeration System: Combined system of diffused and surface aeration. Additional Aeration System: Combined system of diffused and surface aeration. Additional

oxygenation capacity of the aerators in the tune of 30% to 40% need to be oxygenation capacity of the aerators in the tune of 30% to 40% need to be

considered. D.O of 1.0 to 1.5 mg/l is to be maintained in the Reactor.considered. D.O of 1.0 to 1.5 mg/l is to be maintained in the Reactor.

Return Sludge Pump: at least 3 (three) pumps are necessary for maintaining Return Sludge Pump: at least 3 (three) pumps are necessary for maintaining

optimum MLSS in the reactoroptimum MLSS in the reactor

Regular Sludge wasting is compulsory and must be regularRegular Sludge wasting is compulsory and must be regular

BOD and COD removal in Secondary treatment: 85-95%BOD and COD removal in Secondary treatment: 85-95%

Regular monitoring and surveillance Regular monitoring and surveillance

Filtration optionsFiltration options

– Sand and GravelSand and Gravel

– Activated Carbon-sand-gravelActivated Carbon-sand-gravel

– Ultra-filtrationUltra-filtration

– Nano-filtrationNano-filtration

– Ceramic Membrane FiltrationCeramic Membrane Filtration

– Reverse osmosisReverse osmosis

Sludge ManagementSludge Management

– Sludge dewateringSludge dewatering

– Sludge thickeningSludge thickening

– Sludge drying bedSludge drying bed

Effluent treatment plant performance depends on:Effluent treatment plant performance depends on:

Proper wastewater neutralization through uniform mixing in the Proper wastewater neutralization through uniform mixing in the

equilization tankequilization tank

Optimization of coagulant and flocculant dosage based on treatability Optimization of coagulant and flocculant dosage based on treatability

studies.studies.

Proper dosing by providing dosing tank instead of manual operation.Proper dosing by providing dosing tank instead of manual operation.

Regular de-sludging from Primary Clarifier and Secondary ClarifierRegular de-sludging from Primary Clarifier and Secondary Clarifier

Build up of design MLSS concentration in the A.T of biological treatment Build up of design MLSS concentration in the A.T of biological treatment

processprocess

Replacement of media in the tertiary treatment column.Replacement of media in the tertiary treatment column.

Schematics of Advanced Treatment SystemSchematics of Advanced Treatment System

PMultigrade

Filter

UF

Rejects

UFPermeate

sumpSecondary

Effluent

P

RO

Rejects

Permeate

1.1. Activated Sludge process (Conventional)Activated Sludge process (Conventional)

2.2. Trickling FilterTrickling Filter

3.3. Rotating biological ContactorRotating biological Contactor

4.4. Extended AerationExtended Aeration

5.5. Aerated LagoonAerated Lagoon

6.6. UASBUASB

7.7. UFAF / HFAB / UAFBUFAF / HFAB / UAFB

Case Study: Common Effluent Treatment Plant Case Study: Common Effluent Treatment Plant (CEPT) for proposed Garment and Textile Park, (CEPT) for proposed Garment and Textile Park,

MaheshtalaMaheshtalaTotal Unit: 292Total Unit: 292

Unit handling 225 kg/dayUnit handling 225 kg/day = 159= 159

Unit handling 450 kg/dayUnit handling 450 kg/day =138=138

Water requirement for 159 unitsWater requirement for 159 units 225 kg/day X 50 lts/kg X 159225 kg/day X 50 lts/kg X 159= 1788750 lts/day= 1788750 lts/day

Water requirement for 138 units = 450 kg/day X 50lts/kg X 138Water requirement for 138 units = 450 kg/day X 50lts/kg X 138= 3105000 lts/day= 3105000 lts/day

Case Study: Common Effluent Treatment Plant Case Study: Common Effluent Treatment Plant (CEPT) for proposed Garment and Textile Tank, (CEPT) for proposed Garment and Textile Tank,

Maheshtala (Contd.)Maheshtala (Contd.)Industrial water requirementIndustrial water requirement

= 4893750 lts/day= 4893750 lts/day

Adding 7.5 % extra, Industrial Waste WaterAdding 7.5 % extra, Industrial Waste Water= 5260781 lts/day= 5260781 lts/day

Waste Water generation (90% of Water requirement)Waste Water generation (90% of Water requirement)= 4.80 MLD= 4.80 MLD

Domestic sewage generationDomestic sewage generation= 0.20 MLD= 0.20 MLD

ETP design capacityETP design capacity= 5.0 MLD= 5.0 MLD

Characteristics of raw wastewater for Characteristics of raw wastewater for different dying unitsdifferent dying units

Sl. No Parameters Unit I Unit II Unit III Average

1 pH 9.5 9.2 10.5 9.73

2 COD mg/L 554 915 1025 831

3 BOD mg/L 270 470 552 431

4 TSS mg/L 300 280 220 267

Average Characteristics of Units

Unit DesignUnit Design1. Volume of Equalization Tank1. Volume of Equalization Tank = 834 m= 834 m33

Size = 26 m X 13 m X 3 mSize = 26 m X 13 m X 3 m

2. Chemical mixing flush Tank2. Chemical mixing flush Tank

Detention time Detention time = 120 sec= 120 sec

Size Size = 3 m X 2.5 = 3 m X 2.5 m X 1.5 mm X 1.5 m

Chemical to be added:Chemical to be added:

Alum Alum = 300 mg/L= 300 mg/L

PACPAC = 150 mg/L= 150 mg/L

LimeLime = 60 mg/L= 60 mg/L

Primary Clarifier ( 2 Nos )Primary Clarifier ( 2 Nos )

DiameterDiameter = 14 m= 14 m

DepthDepth = 3.5 m= 3.5 m

Over flow rateOver flow rate = 25 m= 25 m33 /m /m22/day/day

Detention timeDetention time = 4.2 hrs= 4.2 hrs

Weir loading rateWeir loading rate = 57.32 m= 57.32 m33/m/day/m/day

Aeration Tank (Baffeled-4.5m wide) ( 2 Nos )Aeration Tank (Baffeled-4.5m wide) ( 2 Nos )

LengthLength = 18.7 m= 18.7 m

BreathBreath = 16.4 m= 16.4 m

DepthDepth = 3.5 m= 3.5 m

Detention timeDetention time = 8hrs= 8hrs

F/M ratioF/M ratio = 0.24= 0.24

MLSSMLSS = 3000 mg/L= 3000 mg/L

Surface aeratorSurface aerator = 4 numbers@10 HP= 4 numbers@10 HP

Diffused Aeration System : In additionDiffused Aeration System : In addition

Secondary Clarifier ( 2 Nos )Secondary Clarifier ( 2 Nos )

DiameterDiameter = 13 m= 13 m

DepthDepth = 3 m= 3 m

Detention timeDetention time = 3.16 hrs= 3.16 hrs

Surface over flow rateSurface over flow rate = 3.16 hrs= 3.16 hrs Sludge Thickener ( 2 Nos )Sludge Thickener ( 2 Nos )

Gravity thickener with Continuous flow typeGravity thickener with Continuous flow type

Two thickeners of 2 m diameter and 3 m depth are to be Two thickeners of 2 m diameter and 3 m depth are to be provided provided

Vacuum filter ( 2 N0s )Vacuum filter ( 2 N0s )

Two vacuum filters to operate at 10 kg/mTwo vacuum filters to operate at 10 kg/m22/hr/hr

Land Requirement to treat 5 MLD effluent : 4500 sq.m.( 500 sq.m/MLD)Land Requirement to treat 5 MLD effluent : 4500 sq.m.( 500 sq.m/MLD)

ConclusionConclusion

The ETP for treatment of dye effluent need to be designed The ETP for treatment of dye effluent need to be designed on the basis of treatability test atleast in bench scale level.on the basis of treatability test atleast in bench scale level.

Both chemical and biological treatment are to be carried at Both chemical and biological treatment are to be carried at bench scale levelbench scale level

Chemical doses are to be finalised as per raw effluent Chemical doses are to be finalised as per raw effluent qualityquality

The bio-reactor is to be stabilized with specific biomass in The bio-reactor is to be stabilized with specific biomass in dye effluentdye effluent

Design F/M ratio, MLSS, MLVSS, D.O, sludge wasting, Design F/M ratio, MLSS, MLVSS, D.O, sludge wasting, return sludge etc. are to be maintained during operation of return sludge etc. are to be maintained during operation of ETPETP

Conclusion( Contd.)Conclusion( Contd.)

Wastewater quality monitoring and surveillance Wastewater quality monitoring and surveillance are to be carried out regularlyare to be carried out regularly

Tertiary treatment with different filtration system Tertiary treatment with different filtration system may be adopted as per requirementmay be adopted as per requirement

Proper housekeeping should be maintained in Proper housekeeping should be maintained in the ETPthe ETP

The Plant Operators / Supervisors must be The Plant Operators / Supervisors must be trained trained

THANK YOUTHANK YOU