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