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International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.

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  1. 1. Prashant K. Lalwani, Malu D. Devadasan / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.108-112108 | P a g eReduction Of Cod And Bod By Oxidation: A Cetp Case StudyPrashant K. Lalwani *, Malu D. Devadasan ***Asst Professor in Civil Engineering Department, Ganpat University, Gujarat-384012, India** Asst Professor in Civil Engineering Department, Ganpat University, Gujarat-384012, IndiaABSTRACTThe present study is focused on aCommon Effluent Treatment Plant (CETP)located at Umaraya, District Baroda. Wastewater from about thirty five small and mediumscale industries majorly comprising of chemicalmanufacturing and pharmaceutical industries aretreated in this CETP. The incoming wastewaterwas collected and segregated into three groups asper their BOD/COD ratio. They were thenoxidized independently by two oxidants Fenton’sreagent (Fe2+/H2O2) and Sodium Hypochlorite(NaOCl) and reduction in COD and BOD wereobserved at different chlorine, H2O2, FeSO4 doses,different pH values and contact time fordetermining the optimum values. COD and BODvalues at optimized conditions for the twooxidants were compared and observed thatmaximum reduction of 64.35% and 68.57%respectively was achieved by Fenton’s reagent.The results clearly indicate that conventionalsystem should be replaced by advanced oxidationprocess and Fenton’s reagent is a suitable choice.Keywords - CETP, COD and BOD reduction,Fenton’s Reagent, Optimum Conditions, OxidationI. INTRODUCTIONDuring the last few years the concept ofCETP for the different small and medium scaleindustrial estates in the Gujarat state has developedwith a great speed. One of these CETP has beenestablished for the cluster of industries in westernside of Baroda district particularly between PadraTaluka and Jambusar Taluka. M/s EnviroInfrastructure Co. Ltd. (EICL), village Umaraya,Taluka Padra has set up a Common EffluentTreatment Plant (CETP). The plant is located onEffluent Channel Road. The CETP wascommissioned on 1st May 2000. CETP was set upto cater Small and Medium scale industries situatedin and around Padra & Jambusar Districts.These small scale industries go onexpanding and as per the market demand theychange their processes also. Therefore the compositewastewater strength on which a CETP is designed isalso getting changed in every couple of years.Because of these changes in the parameters of thecomposite wastewater it is observed that the presentCETP is not able to treat the composite effluent inan efficient manner. It may happen that the entirebiological treatment along with the primarytreatment also gets totally and /or partiallydisturbed. The study here is aimed for somemodifications in the CETP, for maintaining two ofthe important parameter COD and BOD of thetreated waste water from CETP as they do not meetthe required GPCB (Gujarat Pollution ControlBoard) disposal standards to discharge into ECP(Effluent Channel Pipe) which is a closed effluentchannel that carries the effluent to Bay of Cambay.This is achieved by oxidizing thewastewater independently by two oxidants viz.Fenton reagent (Fe2+/H2O2) and SodiumHypochlorite (NaOCl) and comparing the results ofCOD and BOD reduction between them. Suchadvanced physico-chemical processes, can takemuch higher fluctuating load and characteristics ofinlet effluent as compared to conventional biologicaltreatment methods.1.1 Field StudyAt present, there are 52 member units, outof which only 35 member industries are dischargingtheir waste water at CETP. As only 35 industries areworking the study is carried out only for compositewaste water of these industries, discharged intoequalization tank of CETP. The following Table 1shows the type of industries and their effluentcontributions.Table 1 - Category of Industries and theircontribution to the CETPSr.NoCategoryNo ofIndustriesEffluentflow(m3/d)1Chemical manufacturingindustries25 1442 Pharmaceutical industries 8 4463Glass manufacturingindustries1 104 Others 1 0.4Total flow 600.41.2 Present Condition of the CETPCETP at Umaraya is provided for treatmentof about 52 member industries. The present CETP isdesigned for 2250 m3/d of flow. The present CETPneeds modification because though the quantity offlow is very less (600.4 m3/d) than the designedcapacity, the parameters like COD, BOD, NH3-N,SS and oil & grease after final treatment comes outto be 450,150, 87.8, 484 and 25mg/L respectivelywhich do not meet the GPCB disposal standard into
  2. 2. Prashant K. Lalwani, Malu D. Devadasan / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.108-112109 | P a g eECP which are 250,100, 50, 100 and 20 mg/Lrespectively.The effluent is received from different industriesthrough a rubber lined tanker. Before the effluent isloaded in the equalization tank, the effluentparameters are measured and then only effluent isloaded in the equalization tank. From here, theeffluent is lifted to Flash Mixer. At this tank,continuous dosing of hydrated lime and AluminumSulfate (Alum) slurry is added for flocculation andcoagulation. After mixing, the effluent is transferredto Primary Settling Tank. As per original treatmentscheme (2250 m3/day), two stage Aeration followedby Secondary Clarifier treatment process wasprovided. As the present effluent quantity is veryless only one compartment of Aeration Tank is used.At tertiary treatment level, four Dual Media Filtertanks and chlorination unit is provided.Generally, conventional biologicaltreatment such as activated sludge is only able todegrade below 1000 mg/L of COD. Thus, analternative treatment or pre-treatment of thewastewater is required. There are many treatmentoptions available for the removal of pollutantssuccessfully such as stripping, carbon adsorptionand membrane process. However, due to costeffectiveness, stringent regulatory limits and processlimitations, advanced oxidation process (AOP) is aflexible technique towards enhancing the existingsystem. AOP is capable of improving thebiodegradability of complex or recalcitrantcompounds. This process is based on the chemicaloxidation technologies that use hydroxyl radical(•OH) generated in situ. The radical oxidizes theorganic and/or inorganic contaminants to produceenvironmentally friendly fragments and eventuallyto CO2 and H2O if sufficient reagents and time areallowed. There are various ways of generatinghydroxyl radical and one such method is usingFenton’s reagent. Fenton’s reaction is based on thecatalyzed decomposition of hydrogen peroxide byFerrous ions (Fe2+) to produce very reactivehydroxyl radicals [1]:Fe2++ H2O2 → Fe3++ OH-+ OH•II. MATERIALS AND METHODS2.1 MaterialsAll chemicals employed in this study wereanalytical grade. All solutions were prepared indistilled-deionized water made on each experimentalday. Glassware used in this work was soaked withHNO3 (~10%) for 24 h, and rinsed with distilled-deionized water prior to drying. A chlorine stockwas made from 12% (100ml=12mg) sodiumhypochlorite (NaOCl). Hydrogen peroxide wasprepared by using the analytical grade (30% by wt.)H2O2 as purchased. The ferrous sulphateheptahydrate (FeSO4.7H2O) was used as the sourceof Fe2+in the Fenton process. Solutions of NaOHand HCl were used for pH adjustments.2.2 Sample PreparationSampling and analysis of the raw wastewater coming from different industries was done bytaking grab sample. The waste water sample wascollected directly from tanker on approximatelyweekly basis for segregation purposes. The rawwaste water sample was first collected and analyzedfor different parameters to determine the quality ofthe incoming raw waste water and then wassegregated into three groups as per BOD/COD ratioas shown in Table 2. Segregation of effluent meansseparation as per effluent characteristics. It is a newconcept for wastewater minimization and optimizesthe operation cost [2].Table 2 - Various Industries Categorized in GroupsGroup BOD/COD Flow rateA < 0.30 480.00 m3/dayB 0.30-0.40 90.00 m3/dayC >0.40 70.00 m3/day2.3 Experimental Procedure2.3.1Oxidation by Sodium HypochloriteBatches of 100 ml volume of wastewatersample of the three groups A, B and C wereprepared. Chlorine solutions of known strength wereprepared in de-ionized water in the range ofconcentration 2, 4, 6, 8, 10 ml. The residual chlorinewas found for the different chlorine concentrationsby iodometric method. Then by using the optimumchlorine dose obtained for the three group’s residualchlorine for varying pH from 4-7 was found.Residual chlorine graph for varying chlorine dosesand pH was plotted as shown in Fig.1. Using theoptimum chlorine dose and pH range found for thethree groups, COD and BOD of the wastewater afterchlorination was determined by standard methodsand graph was plotted as shown in Fig.6. All thesamples were kept in the dark during chlorination toprevent photolysis.2.3.2 Oxidation by Fenton’s ReagentFor various batches of 100 ml volumesamples of wastewater for three groups A, B, C,COD and BOD was determined by standardmethods for varying doses of H2O2 (1,3,5,10ml) toobtain optimum dose. 1mg fixed amount of solidferrous sulfate was added to the solution and mixeduntil complete dissolution. The contact time, pH andtemperature was kept constant to 40 minutes, 7.5and 30oC respectively. Similarly the process wasrepeated for obtaining optimum pH and contact timeby using optimized H2O2 dose, pH, and contact timeas experiments proceed and keeping all otherquantities constant. The graphs of COD and BODwere plotted as shown in Fig. 2,3, 4 & 5.Then byusing all the optimized parameters obtained above
  3. 3. Prashant K. Lalwani, Malu D. Devadasan / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.108-112110 | P a g eCOD and BOD was again determined and graphwas plotted (Fig.6).Similarly, 100 ml volume sample wasprepared by mixing A, B and C group wastewaters.There initial COD and BOD was measured and thentreated with different H2O2 dose (3, 4,5ml) to obtainoptimum dose using 1mg FeSO4, 4 pH, 60 mincontact time and 32oC temperature. This processwas repeated using optimum H2O2 dose for varyingFeSO4 dose (0.5, 1, 1.5, 2mg) and graph was plotted(Fig.7). The sludge formation was 3ml.III. RESULTS AND DISCUSSIONAfter optimization of chlorination andFenton’s reaction, COD and BOD reduced for threesegregated groups of wastewater by both processescan be compared. Figures 3 and 10 shows the initialCOD and BOD level and reduced levels aftertreatment. The COD reduction during chlorinationwas 23.2%, 19.16%, 45.14% while BOD reductionwas 38.91%, 24.27%, 44.67% [3]. Whereas theCOD and BOD reduction during Fenton treatmentwas 50.86%, 49.47%, 60% and 34.55%, 49.33%,56.67% respectively. Furthermore COD and BODreduction during Fenton treatment of mixedwastewater at optimized pH, H2O2 and FeSO4dosing was found to be 64.35% and 68.57%respectively [4, 5]. The results obtained clearlyindicates that there is no significant differencebetween the COD and BOD reductions forsegregated and mixed wastewater but rather theFenton’s reagent was more effective for combinedwastewater. Thus in this case segregation conceptcannot be applied. The reduction in other parameterslike NH3-N, SS and oil & grease after treatmentwith Fenton’s reagent of mixed wastewater cameout to be 45.76%, 75.43% and 17.32% respectively.It is obvious from the above data that CODand BOD reduction was achieved maximum duringFenton’s treatment. The optimum pH, contact time,H2O2 and FeSO4 dosing was found to be 4, 60 min,4ml and 1mg respectively at temperature 32oC forthe mixed wastewater [6]. The reduction achievedby oxidation process was more than that achievedby conventional biological treatment at CETP. Itshows that the organic loading coming from thechemical and pharmaceutical industries is majorlyof non-biodegradable type. In any case 100 per centoxidation could not be achieved because all theadded oxidant molecules may not be available forthe oxidation of organic matter contributing toCOD. A portion of oxidant might have also beenused in the oxidation of some other metals (in lowconcentrations) in the sample [7].IV. CONCLUSIONFrom the above experiments we canconclude that conventional biological treatment ofthe CETP should be replaced with physico-chemicalprocess like advanced oxidation process asincoming COD value is more than 1000mg/Lmajorly consisting of non-biodegradable load. Thestudy showed that among the two oxidants SodiumHypochlorite and Fenton’s reagent, the latter is themost efficient as the maximum COD and BODreduction was observed for this oxidant.Figure 1: Residual Chlorine for varying Chlorinedoses and pH valuesFigure 2: Optimization of H2O2 dosing
  4. 4. Prashant K. Lalwani, Malu D. Devadasan / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.108-112111 | P a g eFigure 3: Optimization of pHFigure 4: Optimization of Contact TimeFigure 5: Optimization of pHFigure 6: Comparison of Chlorination and Fenton’streatment process at optimized conditions
  5. 5. Prashant K. Lalwani, Malu D. Devadasan / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.108-112112 | P a g eFigure 7: Optimum H2O2 and Iron dosing for mixedwastewaterV. ACKNOWLEDGEMENTSThe authors would like to acknowledge CETPUmaraya for the assistance rendered.REFERENCES[1] Putri F. Khamaruddin, M. Azmi Bustamand A. Aziz Omar, Using Fenton’sReagents for the Degradation ofDiisopropanolamine: Effect ofTemperature and pH, InternationalConference on Environment and IndustrialInnovation IPCBEE 12, Singapore, 2011,12-17.[2] Metcalf and Eddy, WastewaterEngineering: Treatment and Reuse (TataMcGraw-Hill, Fourth edition, 2003).[3] F. Vaezi, K. Naddafi, F. Karimi and M.Alimohammadi, Application of chlorinedioxide for secondary effluent polishing,International Journal of EnvironmentalScience & Technology, 1(2), 2004, 97-101.[4] Qingxuan Zhang and Guohua Yang, Theremoval of COD from refinery wastewaterby Fenton reagent, IEEE Conference(RSETE), China, 2011, 7974 – 7977.[5] Lech Kos, Karina Michalska and JanPerkowski, Textile Wastewater Treatmentby the Fenton Method, Fibres & Textiles inEastern Europe, 18 (4), 2010, 105-109.[6] Cláudia Telles Benatti and Célia ReginaGranhen Tavares, Fenton’s Process for theTreatment of Mixed Waste Chemicals, inDr. Tomasz Puzyn (Ed.), OrganicPollutants Ten Years After the StockholmConvention - Environmental and AnalyticalUpdate, (InTech, 2012) 247-270.[7] M. Ali Awan, Reduction of chemicaloxygen demand from Tannery wastewaterby oxidation, Electronic Journal ofEnvironmental, Agricultural and FoodChemistry 3(1), 2004, 625-628.