COMMON EFFLUENT TREATMENT PLANT PALLAVARAM, CHENNAI, INDIA
UNITED NATIONS INDUSTRIAL DEVELOPMENTORGANISATIONREGIONAL PROGRAMME FOR POLLUTION CONTROLIN THE TANNING INDUSTRY IN SOUTH EAST ASIAUS/RAS/92/120-MODEL CETPsSeptember 2001COMMON EFFLUENT TREATMENT PLANTPALLAVARAM, CHENNAI, INDIAPrepared byA. Sahasranaman, K. V. EmmanuelRegional Programme OfficeProject ManagerJakov Buljan, SIDO, UNIDO, Viennai
TABLE OF CONTENTSLIST OF SYMBOLS & ABBREVIATIONS . iii1. INTRODUCTION. 11.1. General information . 12. FEATURES OF THE CETP. 13. PROJECT PLANNING & EXECUTION . 23.1. Design . 23.2. Finance . 23.3. Implementation . 23.4. Management. 23.5. Recovery of operational cost . 34. PROCESS FLOW . 34.1. Pre-treatment in tanneries . 34.2. Treatment process . 45. CETP UNITS AND SPECIFICATIONS . 56. OPERATIONAL FEATURES . 66.1. Operational parameters . 66.2. Laboratory. 66.3. Analyses done in the laboratory. 76.4. Manpower . 86.5. Monitoring . 87. EFFLUENT CHARACTERISTICS BEFORE & AFTER TREATMENT . 88. COST OF TREATMENT . 99. UNIDO ASSISTANCE . 910. CLRI/NEERI INTERVENTIONS . 1011. UNIDO’s ASSESSMENT . 10AnnexuresAnnex 1Annex 2List & address of suppliers of equipment .Dwg. 1 : Pre-treatment units Dwg. 2: Collection & conveyance network Dwg. 3: Layout plan of the CETP .Dwg. 4: Process flow diagram of the CETP ii1112131415
LIST OF SYMBOLS & BUS :Biochemical oxygen demand, 5 daysBoard of directorsCommon effluent treatment plantChennai Metropolitan Development AuthorityChemical oxygen demandCarbon dioxideCentimetreDegree CelsiusDry solidsDayDiameterFree boardFood to micro organism ratiohour(s)Hydraulic retention timeHigh density poly ethyleneIndian RupeesKilogram(s)Kilowatt(s)Litre(s)Cubic meter (1000 litres)Milligrams per litreMinutesMixed liquor suspended solidsMixed liquor volatile suspended solidsNot detectedNumberRevolutions per minuteNegative logarithm of hydrogen ion concentrationSide water depthSludge drying bedsUS Dollar(s)Total dissolved solidsTamil Nadu Pollution Control BoardTonne (1000 kg)Totally enclosed fan cooledWattsRate of exchange: 1 US INR 46.80iii
1. INTRODUCTIONPallavaram, now a part of the CMDA and less than 3 kilometers south of Chennai airport, hasa cluster of 150 tanneries. Though it was away from residential areas when the tanneriescame up nearly a century ago, now it has become a part of the city with a substantialpopulation residing there. Density of population is quite high and land is scarce. Accordinglydesigning and creating a CETP for tanneries in this location was an absolute need and achallenge.1.1. General informationTotal number of tanneriesNumber of tanneries operating nowNumber of tanneries processing raw hides/skins to semifinished stageNumber of tanneries processing raw hides to finished leatherRaw material processedTotal production capacity of tanneries, as per design ofCETPCurrent production in the clusterNumber of tanneries doing chrome tanningNumber of tanneries processing wet blue leatherNumber of tanneries processing vegetable tanned leatherApproximate ratio of effluent from raw tanning: finishingeffluentDesigned flow rate to the CETPCurrent flow rate to the CETPCommissioning date of the CETPTotal area covered by the CETPTotal length of effluent conveyance pipelineNumber of pumping stationsTotal project cost in Indian rupees1581529143Buffalo & cow calf hides, goat& sheep skins55,000 kg/day47,000 kg/day91213110:903000 m3/day2600 m3/dayFebruary 19950.8 hectares23 km783 million2. FEATURES OF THE CETPThe CETP was the second to be commissioned for treatment of tannery effluent in TamilNadu, India. With the technical assistance of UNIDO, the CETP registered many innovativefeatures such as: Mechanically cleaned screen for removal of solidsEjector aerators in equalization tanksDiffused aeration systemBelt press filter for sludge dewateringThe CETP was designed to provide for all important units (such as equalization tank,clariflocculator, aeration tank, clarifier) in two parallel sets so that one half of the CETP onlycould be operated when it received a lower volume of effluent.1
3. PROJECT PLANNING & EXECUTION3.1. DesignThe basic design of the project was done by Enkem Engineers, Chennai. It was later modifiedby the UNIDO subcontractor, M/s. TEH-PROJEKT, Croatia, in consultation with the maincontractor selected for turnkey implementation of the project, UEM India Private Ltd., NewDelhi.3.2. FinanceThe CETP was given a total subsidy of INR 10 million by the state and the centralgovernments. The tanners contributed INR 10 million and an amount of INR 46 million wastaken as loan from Industrial Development Bank of India. UNIDO had contributed hardwareworth INR 11 million.3.3. ImplementationThe project was implemented by a company formed by the tanners of the Pallavaram area byname Pallavaram Tanners Industrial Effluent Treatment Co. Ltd. (PTIET) and UNIDO madeavailable the services of a Project Officer for its implementation.M/s. UEM India P. Ltd., New Delhi undertook the construction of the CETP on turnkey basisand implementation of collection & conveyance system was undertaken by the PTIETemploying a local contractor. Tamil Nadu Pollution Control Board was the counterpart ofUNIDO and took the overall responsibility for monitoring the implementation of the project.3.4. ManagementThe management of the CETP is done by a BoD headed by a Chairman, who is assisted by aManaging Director. The administrative head of the CETP is a qualified engineer.The organigram of the CETP as at present is as follows:Plant ManagerMechanical EngineerElectrical EngineerMechanical operator(2 nos.)ElectricalOperators (2 nos)Stores inChargeChemistJr. ChemistHelpers (3 nos)Operators-collection andConveyance – 14 nos.Junior operators(6 nos.)Casual labour (8 nos.)2
3.5. Recovery of operational costThe cost of operation and maintenance of the plant, repayment of loan with interest and otherexpenditures relating to the plant are covered by monthly contributions made by the tannermembers according to their respective production capacity.Two types of charges are being collected. The fixed cost, which covers loan repayment,salary of staff and regular maintenance expenditure etc., is charged based on the installedcapacity of the tannery @ INR 3,500 per drum per month. Additionally, a variable charge,based on actual production, is charged which varies from INR 5,000 - INR 15,000 per monthper tannery.At present, the average collection from individual tanners is in the range of INR 8,500 to INR29,000 depending on the actual production.For unforeseen expenses or new investments, special contributions are collected from themembers, pro-rata.4. PROCESS FLOW4.1. Pre-treatment in tanneries4.1.1. Chrome segregationOut of the nine tanneries processing raw hides & skins, only seven were processing raw hides/ skins during the project design. As these were all small-scale units, it was decided to have acommon chrome recovery unit (CRU) for these tanneries. Accordingly a common chromerecovery unit was installed in Arafath Leathers by UNIDO based on the design of CentralLeather Research Institute (CLRI), Chennai.The tanneries connected to the CRU made arrangement within their premises for segregationof chrome liquor and collecting it in a chrome collection tank of 3 m x 3 m x 1.5 m.4.1.2. Pre-treatment of effluent other than chrome liquorThe pre-treatment unit in each tannery consists of a grit chamber of size 1.5 m x 1.0 m x 1.0m and two coarse bar screens (MS construction) of 10 mm bar spacing. Bar racks have beenprovided for cleaning the screen manually. The grit and screenings separated are taken to aplastered floor for dewatering and for onward disposal in the sludge dumping site of theCETP. Details of pre-treatment is given in Dwg. 1 in Annex 2.4.1.3. Collection & conveyance systemEffluent from pre-treatment units is admitted into the manhole of the main collection line[HDPE pipes, diameter varying from 110 to 200 mm) that extends to a collection well bygravity. There are seven collection wells constructed in various locations of the tannerycluster. Each collection well is equipped with one coarse screen and two submersible pumpsof varying capacity (from 11 kW to 45 kW). The effluent is pumped from the collectionwells to the CETP. Details of pre-treatment is given in Dwg. 2 in Annex 2.3
4.2. Treatment processThe seven collection wells receive effluentfrom 142 tanneries, which is pumped to thereceiving sump. Eight tanneries dischargeeffluent directly into the receiving sump bygravity. The effluent collected in thereceiving sump is pumped through amechanically cleaned screen (Konicamodel, Italprogetti make) shown in figure1.Fig 1. Mechanical ScreenThe effluent then is passed through agrit chamber and collected in twonumbers of equalization tanksprovided with submerged ejectoraerators.Theejectoraeratorshomogenize the effluent, besidesoxidizing sulphides present in the raweffluent.A view of the ejector aerator is givenin figure 2.Fig 2. : Ejector aerator in the equalization tankThe equalized effluent is then pumped to the flash mixer where alum, lime andpolyelectrolyte slurry are added.The effluent thereafter enters two clariflocculators where the chemical sludge settles in thebottom. The physico-chemical treatment removes approximately 25-30% of BOD, 35-45% ofCOD and almost all chromium. The overflow from the clariflocculators is admitted into twoaeration tanks provided with fine bubble diffused aeration system which comprises of 1,200tubular membrane diffusers (Aertec make) the air supply for which is provided by 5 positivedisplacement blowers (Roots make). The biological treatment removes 90-95% of BOD and85-90% of COD. The overflow from the aeration tanks with active biological solids isadmitted into two secondary clarifiers. The settled sludge in the clarifiers is pumped back tothe aeration tank to maintain the bacteriological population. Some quantity of sludge iswasted by diversion to the sludge thickener. The overflow from the clarifiers is the treatedeffluent and it is discharged into the Adyar river through a pressure pipeline. A part of thetreated effluent is filtered using pressure sand filter and used for process applications in theCETP.The sludge settled in the primary clariflocculator is taken to a sludge well and then pumped toa sludge thickener. The thickened sludge is dewatered in a belt press filter (Italprogetti make)and a portion of the sludge is dewatered in sludge drying beds. The dewatered sludge isdisposed of in a sludge dumping site. The system is regularly operating for the past over sixyears.4
5. CETP UNITS AND SPECIFICATIONSThe layout and the process flow of the CETP is given in Dwg 3 and 4 in Annex 2.Treatment stepDescription/serviceDimension/capacityPlant design capacity3000 m3/dayPrimary treatmentCoarse screeningPumpingFine screeningGrit removalEqualisation1 no. manually cleaned screensCircular RCC receiving sump of 140m3, 3 nos. submersible pumps, 22.5kW each1 no. drum screen, Konica model,self cleaning type1 no. grit removal comprises of gritsettler, screw type grit conveyor andgrit washer2 nos. rectangular tankAeration/mixing: 4 nos ejector typepump aerator 18.5 kW eachEqualised effluent 3 nos. centrifugal pumps of 11.5 kWpumpingeachFlocculationFlash mixer with 1.5 kW agitatorChemicals: alum (Al2SO4. 16 H2O2),lime (Ca(OH)2) and anionicpolyelectrolytePrimary2 nos circular clariflocculators withsedimentationsludge scraper 12 m dia, flocculatorportion 6 m dia with comb typemechanismBiological treatmentBiological aeration 2 nos. rectangular tanks with diffusedaeration 1,200 no. retrievable typetubular diffusers (600 in each tanks)powered by 5 (3 working 2 standby)positive displacement type blowers of37.3 kW each, diffuser sleeve materialEPDMSedimentation2 nos. circular tank 12 m dia withscrapper, recycle of biological sludge:3 nos. submersible pumps 11.5 kWeachSludge treatmentDesign capacitySludge thickener15 mm bar spacingRetention time 30 minPump capacity 300 m3/h each3 mm bar spacingCapacity: 450 m3/hCapacity: 450 m3/h, retentiontime 50 seconds.Capacity 1,300 m3 each, totalretention time 21 hSpecific mixing power 28.7W/m3Capacity 125 m3/h eachCapacity 8 m3Retention time 3.8 minCapacity clarifier 300 m3,flocculator 42 m3, total retentiontime clarifier 4.8 h, flocculator40 minCapacity 2,400 m3 eachTotal retention time 1.6 daysSpecific mixing power 23.3W/m3Capacity 250 m3 each, totalretention time 4 h, pumpcapacity 125 m3/h eachAbout 1,500-3,000 tonnes DS per year1 RCC circular tank 12 m dia withCapacity 340 m3scrapper5
Sludge dewatering1 no. belt press filter Diemme make, 2m cloth width, with polymer dosing,flocculator and cake conveyor6 nos. sludge drying bedsCapacity of belt press filter 450kg DS/hTotal SDB area 960 m2Note: The addresses of suppliers may be seen at Annex 1.The dimensions of the CETP units can be seen in drawings at Annex 2.6. OPERATIONAL FEATURES6.1. Operational parametersOperational parameterChemical dosage prior to primary clarifierNutrientsDissolved oxygenFactors maintained at present200-300 ppm of alum and 600 ppm oflime. Anionic polyelectrolyte at the rate of1 ppm.No nutrient is added at present.DO level in aeration tank-1 is 1.0 mg/l andin aeration tank-2, 2.5 mg/l.Sludge re-circulationMLSS concentrationAround 55%Aeration tank-1, 3,500 mg/l and aerationtank-2, 2,200 mg/lSludge wastingApproximately 10% of the aerobic biosludgeScreenings removal and sludge withdrawal The screenings are removed once in a shift.timingSludge from primary clarifier is withdrawnonce in two or three hours.MaintenanceOiling and greasing cycleFrequency of painting15 and 20 days respectivelyOnce a yearPower consumptionTotal connected loadOperating loadCapacity of diesel generating set440 kW310 kW330 kW6.2. LaboratoryThe CETP has a laboratory, accommodated in two rooms in the first floor of theadministration building.6
Room No. 1 is generally used for the main analysis. The equipment available in this Hot air ovenFume cupboardCOD apparatusDistilled water stillElectric BunsenHeating mantleVacuum pumpBOD incubatorRefrigerator.Glass wares & ChemicalsNo. of units311123211Room no.2 is used as the instrumentation room. The instruments in this room pH meterAutomatic samplerDhona monopan balance.No. of units12116.3. Analyses done in the laboratoryVarious analyses done in the laboratory are as follows:ParameterRaw effluentpHSuspended solidsTotal otal yParameterDOMLSSMLVSSDailyDailyDailyDailyEqualised raw DailyDailyFinal yMonthlyDailyDailyDailyWeeklyWeeklyWeeklyAeration tanksDailyDailyDaily7Treated effluentDaily
6.4. ManpowerFollowing key technical personnel are available in the CETP:PersonnelPlant ManagerElectrical Engineer.Sr. ChemistChemistCivil EngineerStores in chargeQualification & experienceB.Tech. with 2 years experience in ETP managementGraduate in mechanical engineering with 6 years experienceB.Sc. Chemistry with 5 years experience in effluent testingB.Sc. Chemistry, 6 years experience in effluent testingDiploma in civil engineering with 2 years project experienceGraduate with 3 years experience in material management6.5. MonitoringFollowing is the list of log sheets presently maintained by the CETP: Pumping detailsChemical dosage and stockAeration detailsComplaints registerStore and spare parts registerMaintenance scheduleThe plant manager reviews the log sheets daily and necessary instructions for modifications inoperation and maintenance are given in consultation with chemists and other engineers.7. EFFLUENT CHARACTERISTICS BEFORE & AFTER TREATMENT(Average for the period from December 1999 to June 2001)ParameterpHSuspended /lmg/lmg/lRawAfter ,2102,955561364155,1504,810Final treatedeffluent7.2148132890524,822TNPCB norms*5.5 – 9.010030250222,100*for discharge to inland surface watersNote: The above values indicate the average during the period mentioned. During April-May 2001, somemodifications were carried out in the CETP resulting in marked improvement in the CETP performance andthe average values of COD and BOD5 after June 2001 until September 2001 were 320 mg/l and 41 mg/lrespectively.8
8. COST OF TREATMENT(Average for the period from 1 January 2000 to 30 June 2001)Cost componentCost in INRPowerChemicalsSalary & labourRepair and maintenanceLaboratory analysisSludge dewateringMiscellaneousConsents & licenseLoan repaymentOther costs (R&D etc.) lumpsumDepreciation on investmentTotalCost in US 2,030,769242,583885,8334,367,062Treatment cost per cubic meter of effluent:Treatment cost per kg of BOD removed:Treatment cost per kg of COD removed:Total treatment cost per square ft. of 18318,92793,313INR 55.3 (US 1.19)INR 41.93 (US 0.90)INR 16.67 (US 0.36)INR 0.7 - 0.9 (0.15 – 0.19 US cents)(RoE: 1 US INR 46.8)9. UNIDO ASSISTANCEBesides giving technical assistance for the design, imp
IN THE TANNING INDUSTRY IN SOUTH EAST ASIA . US/RAS/92/120-MODEL CETPs . September 2001 . COMMON EFFLUENT TREATMENT PLANT . PALLAVARAM, CHENNAI, INDIA . . Pallavaram, now a part of the CMDA and less than 3 kilometers south of Chennai airport, has a cluster of 150 tanneries. Though it was away from residential areas when the tanneries
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