Presentation on theme: "PROF. ARUNABHA MAJUMDER Emeritus Fellow"— Presentation transcript:
1 Appropriate Effluent Treatment System for Dyes and Dye-intermediates Industries PROF. ARUNABHA MAJUMDEREmeritus FellowSchool of Water Resources EngineeringJadavpur UniversityandEx-Director-ProfessorAll India Institute of Hygiene and Public Health, Kolkata
2 BackgroundDyes and dye- intermediates Industries: Designated as ‘ Special Red’ Category IndustryAs 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.
3 Fabric dyeing is carried out by either in continuous or batch process. In the continuous dyeing process, the dye is transferred to the fabric by passing the fabric across roller which are partially submerged in the dye solution.A batch dyeing of fabric is often accomplished in atmosphere or pressure backs or in jet dyeing machines. The majority of knitted fabric are batch dyed, using a variety of processes.
4 Salient features of the dyeing process with different classes of dyes Direct dyesBasic dyesVat dyesSulphur dyesDeveloped dyesNapthol dyesMetal Complex dyes
5 Dyeing ProcessesDirect 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 easy to apply without any mordants. The colors produced are stable and are fast to light.Basic dyes: These are salts of colored base and require an acid mordant such as tannic acid, tartaric and acetic acids. These dyes 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 waste streams and other process chemicals are generated during the process.
6 Contd.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 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 neutralize the excess acid.Sulfur dyes: These contain sulfur compounds and are applied together with a suitable reducing agent like sodium sulfide followed by oxidation.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 and HCl. Next the stable form of the color is developed on the fiber by the action of beta napthol.
7 Contd.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 is at first treated with beta-napthol and then diazotised with sodium nitrite and HCl. A hot soap and soda bath is used.Metal complex dyes: In the case of certain types of cotton fabrics and synthetic textiles like nylon and polyester, dyeing process is carried out by depositing inside the fibre complex salts of iron and chromium. 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 application of wash and wear permanent press and water repellant and flame retardant finishes.
8 General Characteristics of dye house waste water pH to 10.5TDS – 3180 mg/lSuspended Solids (SS) 380 – 950 mg/lBOD – 820 mg/lCOD – 2000 mg/l
10 Primary TreatmentBy the process of coagulation- flocculation and sedimentation, color, colloidal, suspended and settleable solids are removedFlush mixing for 60 to 90 secSlow mixing for 20 to 25 minutesDetention time in PC : 150 minBOD and COD reduction: 45 to 65 %
11 Secondary Treatment Bio-reactor with Conventional or Extended aeration Detention time:Conventional : 6 hrs to 10 hrsExtended Aeration : 12 hrs to 24 hrs(18 to 36 hrs)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 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 optimum MLSS in the reactorRegular Sludge wasting is compulsory and must be regularBOD and COD removal in Secondary treatment: 85-95%Regular monitoring and surveillance
12 Tertiary Treatment Filtration options Sludge Management Sand and GravelActivated Carbon-sand-gravelUltra-filtrationNano-filtrationCeramic Membrane FiltrationReverse osmosisSludge ManagementSludge dewateringSludge thickeningSludge drying bed
13 Effluent Treatment Plant Performance Effluent treatment plant performance depends on:Proper wastewater neutralization through uniform mixing in the equilization tankOptimization of coagulant and flocculant dosage based on treatability studies.Proper dosing by providing dosing tank instead of manual operation.Regular de-sludging from Primary Clarifier and Secondary ClarifierBuild up of design MLSS concentration in the A.T of biological treatment processReplacement of media in the tertiary treatment column.
14 Schematics of Advanced Treatment System RejectsMultigradeFilterUFPUFPermeatesumpPSecondaryEffluentPermeateRORejects
16 Case Study: Common Effluent Treatment Plant (CEPT) for proposed Garment and Textile Park, Maheshtala Total Unit: 292Unit handling 225 kg/day = 159Unit handling 450 kg/day =138Water requirement for 159 units 225 kg/day X 50 lts/kg X 159= lts/dayWater requirement for 138 units = 450 kg/day X 50lts/kg X 138= lts/day
17 Case Study: Common Effluent Treatment Plant (CEPT) for proposed Garment and Textile Tank, Maheshtala (Contd.)Industrial water requirement= lts/dayAdding 7.5 % extra, Industrial Waste Water= lts/dayWaste Water generation (90% of Water requirement)= 4.80 MLDDomestic sewage generation= 0.20 MLDETP design capacity= 5.0 MLD
18 Characteristics of raw wastewater for different dying units Average Characteristics of UnitsSl. NoParametersUnit IUnit IIUnit IIIAverage1pH184.108.40.206.732COD mg/L55491510258313BOD mg/L2704705524314TSS mg/L300280220267
19 Unit Design 1. Volume of Equalization Tank = 834 m3 Size = 26 m X 13 m X 3 m2. Chemical mixing flush TankDetention time = 120 secSize = 3 m X 2.5 m X 1.5 mChemical to be added:Alum = 300 mg/LPAC = 150 mg/LLime = 60 mg/L
21 Aeration Tank (Baffeled-4.5m wide) ( 2 Nos ) Length = 18.7 mBreath = 16.4 mDepth = 3.5 mDetention time = 8hrsF/M ratio = 0.24MLSS = 3000 mg/LSurface aerator = 4 HPDiffused Aeration System : In addition
22 Secondary Clarifier ( 2 Nos ) Diameter = 13 mDepth = 3 mDetention time = 3.16 hrsSurface over flow rate = 3.16 hrsSludge Thickener ( 2 Nos )Gravity thickener with Continuous flow typeTwo thickeners of 2 m diameter and 3 m depth are to be providedVacuum filter ( 2 N0s )Two vacuum filters to operate at 10 kg/m2/hrLand Requirement to treat 5 MLD effluent : 4500 sq.m.( 500 sq.m/MLD)
24 ConclusionThe ETP for treatment of dye effluent need to be designed on the basis of treatability test atleast in bench scale level.Both chemical and biological treatment are to be carried at bench scale levelChemical doses are to be finalised as per raw effluent qualityThe bio-reactor is to be stabilized with specific biomass in dye effluentDesign F/M ratio, MLSS, MLVSS, D.O, sludge wasting, return sludge etc. are to be maintained during operation of ETP
25 Conclusion( Contd.)Wastewater quality monitoring and surveillance are to be carried out regularlyTertiary treatment with different filtration system may be adopted as per requirementProper housekeeping should be maintained in the ETPThe Plant Operators / Supervisors must be trained