An alternative treatment process for upgrade of petroleum refinery wastewater using electrocoagulation

本资料包含pdf文件1个，下载需要1积分

：! l3) ：丝 ：竺DOI l0.1007/sl2182-013-0291-4421An alternative treatment process for upgrade ofpetroleum refinery wastewater using eleCtr0c0agulati0nDhorgham Skban Ibrahim ，-，M ohan Lathalakshmi ，AppusamyMuthukrishnaraj and Natesan Balasubramanian 术Department of Chemical Engineering，AC Tech Campus，Anna University，Chennai 600025，IndiaDepartment of Petroleum Engineering，Colege of Engineering，University of Baghdad，Iraq◎China University ofPetroleum(Beijing)and Springer-Verlag Berlin Heidelberg 2013Abstract：An electrocoagu1ation treatment process was developed for treatment and upgrade ofpetroleum refinery e珂uent(wastewater)，instead of the conventiona1 methods，which can consume higheramounts of chemicals and produce larger amounts of sludge.The efect of the operation parameters，suchas current density，initial pH，anode material，anode dissolution，energy consumption and electrolysistime.on treatment eficiency was investigated.The experimental results showed that the e用uent can beefectively treated under optimal conditions.Fourier transfc)ITn infrared(FTIR)analysis of the efHuent，and scanning electron microscopy(SEM)coupled with energy dispersive analysis of X-rays(EDAX)of the sludge produced，revealed that the unwanted pollutants can be eliminated.The electrocoagulationtreatment process was assessed by using the removal eficiency of chemica1 oxygen demand(COD)，totalsuspended solids(TSS)，and the general physicochemical characteristics of wastewater，and the resultsshowed that the electrocoagulation is an efhcient process for recycling of petroleum wastewater；it isfaster and provides better quality oftreated water than the conventional methods。

Key words：COD/TS S reduction，electrocoagu1ation，petroleum refinery efl uent，recycle，sludgeanalysis。

1 IntroductionPetroleum refining is an essentia1 step in convertingcrude oil into useful products through a series of processesrDiyauddeen et al，201l；Yavuz et al，20lO).Usuallyabout240.340 L of water is consumed when processing of a barre1of crude oil(Diyauddeen et a1 20 1 21 and huge amounts ofwastewater are generated during these processes rabout 70.90percent of the water supplied to the petroleum refinery comesout as wastewater).鼢 stewater generated by petroleumrefineries is characterized by high concentrations of aliphaticand aromatic petroleum hydrocarbons，which usually havedetrimenta1 and harmfu1 effects on plant and aquatic 1ife.aswel as ground water sources fWake，2005).Fortunately，ahigh proportion of wastewater generated by the petroleumrefinery can be recvcled/reused.The remaining wastewaterafter a combination of treatment stepswould be reduced tothe allowable limit.in accordance with the internationa1regulations，before the wastewater can be discharged(Prather，1 970).Fig.1 shows the water balance in a typical petroleumrefinery。

A number of criteria have been suggested for evaluatingCorresponding author.email：nbsbala###annauniv.eduReceived October 27，2012a particular technology for upgrading refinery wastewater，including(IPIECA，20l0)：·The ability to achieve the required product waterspecifcation；·Simple equipment，ease of operation，and flexibility；·Minimum processing time；·Reduced capital and operating cost；and·Lesser space requirement。

In recent years.there has been an increasing interest in theapplication of electrochemical coagulation in the treatmentand purification of industrial wastewater.The treatment ofpetroleum refinery e用uents by electrochemical coagulationhas been reported by a number of researchers，supporting thetechnical feasibility of the process(Abdelwahab et al，2009；E1.Naas 2010：E1.Naas et al，2009：Martinez.Delgadilloet al，20 l 0；Ylng，2007).It consumes less chemicals withlow sludge production.In addition.the electrochemicalcoagulationprocess required less time to reach the standardlimit for recycling water than other conventional methods(Mohan et al，2007).Electrocoagulation is an electrochemicaltechnique，which generates the coagulant in situ by anodicdissolution，and subsequently produce meta1 hydroxideshaving a considerable sorption capacity.Simultaneouslya cathodic reaction allows for pollutant removal either by422 Pet.Sci.(2013)10：42l-430Fig.1 Schematic diagram of the typical water usage in a petroleum refinery(modifed from IPIECA，20lo)deposition on the cathode or by flotationfrom evolutionof hydrogen at the cathode](Balasubramanian andSrinivasakannan.2010、.Electrocoagulation is efi cient inremoving suspended solids oi1 and grease metal，colloidalsolids，particles，and soluble inorganic pollutants fromaqueous medium，by introducing highly charged polymericmetal hydroxide species to facilitate agglomeration orcoagulation(Bukhari，2008；Khemis et al，2005).In thepresent work，it is proposed to use electrOcoagulation as analternative treatment process to treat petroleum wastewater，and recycle it in vital utilities of the Chennai PetroleumCorporation Limited(CPCL)refinery，India.Today CPCLis the largest refinery corporation in south India.with aninstalled refining capacity Of 10.5 MMTPA or 28.760 m /day，generating 1 2.500 m /day of wastewater.Reprocessing andreuse of refinery effluent and city sewage is widely adoptedin CPCL.The liquid efluent generated in the refinery，and thecity sewage purchased from the Chennai Metro Water Supplyand Sewage Board(CMWSSB).was recycled with the use ofthe followintechnologies：· Free and emulsified oil removal by the AmericanPetroleum Institute(API1 separator，followed by Tilted PlanedInterceptor(TPI)separator，and dissolved air flotation unit forthe removal of dissolved oil；·Bio.Chemica1 Oxygen Demand rBOD1 removal by usingthe activated sludge process and attached film process：·Removal of bacteria by chlorination；·Removal of suspended solids by multimedium filter；·Removal of colloidal particles by the use of ultra-fl1tration technology；·Removal of dissolved solids by the use of reverseosmosis technology。

Fig.2 shows a simplified oPtion which can beimplemented at the refinery，for the purpose of recyclingof wastewater.This option includes a number of processes。

such as the API separator for the removal/recovery of freeoil；electrocoagulation as the physico.chemical treatment forthe remova1 of sulphides.emulsified oil.and heavy metals；biological treatment through the biological reactor；and apolishing treatment through the adsorption column。

The e1ectrOcOa2ulation treatment process was assessedby using the removal emciency of chemica1 oxygen demand(C0D)，total suspended solids(TSS)，hazardous compounds，and pollutant elements.The effe cts of different parameters。

1ike pH，current density，electrolysis time，and anode material，on the electrochemical coagulation eficiency were studied.Inaddition，the anode dissolution，the energy consumption，andthe sludge characteristics were also studied。

Fig.2 A schematic representation ofthe integrated system for recycling/reuse ofpetroleum refinery wastewate(1)API separal品(2)E1ectrocoagulation reactor，(3)Equalization tank，(4)Biological reactor，(5)Adsorption column and(6)Product tank426 Pet.Sci.(2013)10：42l-430was found to be the optimum for the removal Of COD.andTSS.using a mild steel anode.The仃eatment e伍ciency wasaffected by the current intensity and anode materia1.As thecurent density decreased，the time needed to achieve similarefnciency increased.and the increase in the current densityincreased the cost of the treatment.However，as the cost ofthe process required is determined by the consumption of theelectrode and the elec仃ical energy，one may use an optimumvalue of curent density for eficient treatment at minimumcost。

3.2 Effect ofpHFig.6 shows the eflfect Of the initial PH of efi uentonthe percentage of COD removal，and the final PH after onehour of the reaction period.using mild steel and aluminiumanodes，at optimum curent density.It can be seen that thepercentage Of COD remova1 was low in the case of thealkaline and acidic medium.The COD removal was highwhen the pH was between 6 and 8 for both the anodes.Forthe basic pH f 1 01 medium，about 70% of COD removal，andfor the acidic pH f4)medium，about 56% of C0D removal，was achieved.The maximum percentage of COD removalwas about 90% when the original pH value of the emuentwas unaltered，for the mild steel anode.Also the PH of the0 c口>oE0d)ooonitial pH of efluent-r-△ - c口CuFig-6 variati0ns in the percentage of COD remoVaJ and final pH.，with 81 initial pH using mild steel and aluminium anodes at 9 mA/cm2current density and 60 min treatment timeelectrolyte changed during the process；this change dependson the initia1 pH value and the anode material(Kobya eta1.2003).An inverse response of the pH value with timeduring the electrOcOagu1atiOn process was observed.Thus，the cathodic reduction of H，O and hydrogen evolution wouldresult in an increase in the pH value as given in Eq.(1)，whereas.the formation of different aluminium/iron speciesby the combination of the electrodissolved ions and hydroxylions.and the oxidation of water at the anode，leads to adecrease in the pH value as given in Eqs.(2)to(4)(Chen，2004)。

2H2O(1)2e- H2(g)2OHiaq)A1 )3H2O(1- AI(OH)3(。)3Haq)(1)(2)Fe )2OH[aq) Fe(OH)2(s) (3)4Fe 1 0H2O(1)02(aq)- 4Fe(OH)3(。)8Haq) (4)3.3 Specific energy consumptionThe specifc energy consumption(SEC)(kWh/kg of CODremoved)was expressed as folows(Un et al，2009)：SEC UIt(Cf-C，)x1000 (5)where，U is the voltage(V1，1 is the current(A)，f is theelectrolysis time(hr)，V is the volume of the efluent(m )，Gis the initial COD concentration(kg/m )，and c，is the COD - concentration at time t(kg/m )。

The SEC increases with an increase of the curent density。

The SECs at low charges were close to each other for bothmild steel and aluminium f5 kWh/kg).and increased withrising current density with some difference for both theanodes(25 kWh/kg for aluminium anode and 30 kWh/kgfor mild steel anode).This is because at the beginning ofthe process the electrode surface is smooth，and the currentsupplied is directly proportional to the amount of metal iongeneration.The proportiona1 rate of metal ion generationdecreased during the process，and the excess current was usedto heat the solution，resulting in a reduction in the percentageC0D of removal and an increase in the SEC。

Fig.7 shows the variation of the specific energyconsumption wim electrolysis time for aluminium and mildsteel anodes，at a current density of 9 mm/cm and at pH 8.Itcan be seen that the SEC increased with the increase of theelectroly sis time.About 1 5 kW h/kg was required to remove88% Of C0D within 40 min.using mild stee1 as the anode。

whereas 20 kW h/kg was required to remove 82% of C0Din one hours time，using aluminium as the anode.Beyond40 min of electrolysis time，only a progressive formationof surplus flOCS was observed.with an increase in thetreatment cost without further COD remova1.A similar resultwas reported by Panizza and Cerisola(20l01.Therefore。

the treatment time of 40 min was selected as the optimum.量E- n)ESpecifc energy consumption，kWh/kg∞ o∈o口ooFig.7 Variations in the specific energy consumption with electrolysistime and COD removal using mild steel and aluminium anodes at 9mA/cm current density∞ ∞ 加 ； 加 佃 OPet.Sci.(2013)10：421-430 429stretching vibrations of alkenes and alkynes at 2，1 00 cmand 2，356 cm～and sulphur containing groups at 1，38 1 and1.399 cm .Some of the hazardous components disappearedduring treatment using mild steel as an anode(Fig.1 3(c))；ie peaks at 617cm～，730 cm～，1，381 cm～，2，100 cm and2.356 cm～.The reason for this is due to the fact that in theelectrocoagu1atiOn process，different types of pollutants aredestabilized by the hydrolysis of the ferrous ions to fo·rmmonomeric hydroxide and polymeric hydroxide complexes，which collide and drag the pollutants down with them。

纾西ereas when aluminium was used as anode the removal ofthese hazardous compounds was 1ess effective compared tomild steel as mentioned earlier(Fig.1 3(b11W ave number，cm-Fig.1 3 FTIR spectmm of the raw and treated efluent after 60 min ofthe electrocoagulation process(a)Before treatment，(b)and(c)after treatment using aluminium andmild steel anodes，respectively4 ConclusionsExperiments were caried out for upgrading the petroleumrefinery effluent by the e1ectro-coagulation process。

under various operating conditions.The physicochemicalcharacteristics of petroleum he applied current，type of anode and initial pH during theelectrOcoagulation treatment.An optimum COD removalof 87% was observed under experimenta1 conditions of aninitial PH of 8，curent densit7 of 9 mA/cm ，using mild steelas an anode.The energY consumption and anode dissolutionwere l 5 kWh/kg and 622 mg/dm respectively.within 40min of treatment time.The FTIR。EDAX and SEM analysesconfirmed that the unwanted pollutants were largely removedwith the mild steel anode.Also.the results depicted that thedesign parameters of the efnuent after electro coagulationwere better than the influent at the reclamation plant.ofthe CPCL refinery.It can be concluded from these results。

that electrocoagulation is a promising technique to recyclepetroleum refinery wastewater。

AcknowledgementsDhorgham Skban Ibrahim gratefuly acknowledges thefinancial support from the Ministry of Higher Educationand Scientitic Research.Iraq.Also，the authors gratefullyacknowledge the help rendered by the team of the CPCL-Manali，Chennai，India，for providing the petroleum effluentand details about the refinery。

ReferencesAbdelwahab O.Amin N K and E1-Ashtoukhv E-S Z.Electrochemica1removal of phenol from oil refinery wastewater，J.Hazard.Mater。

2009.163：711.716Balasubramanian N and Srinivasakannan C.ElectrOcOagu1ation/electroflotation-fundamentals.present and future perspectives。

in：Kuai S and Meng J(Eds.).Electrolysis：Theory，Types andApplication.New York：Nova Science Publishers.Inc.2010.1-17Bukhari A A.Investigation of the electro-coagulation treatment processfor the remova1 of total suspended solids and turbidity frommunicipal wastewate Bioresour.Techno1.2008.99：9 14.92 1Cafiizares M artinez F.Jim6nez C.Siez C.et a1.Coagulation andelectrocoagulation of oil.in-water emulsions.J.Hazard.Mater.2008。

151：44-5lChen G.Electrochemical technologies in wastewater treatment Sep。

Purif Techno1.2004.38：ll-4lC0INDS/4/1 98 1-82.Minimal National Standards Oil Refineries.CentralBpard for the Prevention and Control of Water Pollution New Delhi。

India.1982Diyauddeen B H.Abdul Aziz A R and Daud W M A W Oxidativeminera1isation of petroleum refinery efi uent using Fenton.1ikeprocess.Chem.Eng.Res.Des.2Ol2.90：298-308Diyauddeen B H.Daud W M A W and Abdul Aziz A R.Treatmenttechnologies for petroleum refinery efltuents：A review.Proce.Safe。

Environ.Protec.20l1.89：95-1O5Drouichea N，Aoudja S，Hecini M，et a1.Study on the treatment ofphotovoltaic wastewater using electrocoagu lation：Fluoride removalwith aluminium electrodes-Characteristics of products.J.Hazard。

Mater.2009.169：65.69Drouichea N，Gha仃0ur N.Lounici H.et a1.Electrochemical treatmentof chemica1 mechanical polishing wastewater：removal of fluoride-sludge.characteristics-operating cost.Desalination.2008.223：l 34。

142E1-Naas M H.Elecocoagu lation for the treatment ofpetroleum refinerywastewater.Hydrocarb.W0rld.2O10.5r1、：11.13E1-Naas M H。Al-Zuhair S，A1.Lobaney A.et a1.Assessment ofelectrocoagulation for the仃eatment ofpetroleum refinery wastewateLJ.Environ.Manage.2009.91：18O.185IPIECA(Intemational Petroleum Industry Environmental ConservationAsSOCiation).Petroleum refining water/wastewater use andmanagement.Operations Best Practice Series，London，UK.2010Khemis M，Tanguy G，Leclerc J P，et a1.E1ectrocoagulation for thetreatment of oiI suspensions-relation be een the rates of electrodereactions and the e衔cieney of waste remova1.Proce.Safe.Environ。

Protec.2005.83(B1、：50.57Kobya M，Can O T and Bayramoglu M.Treatment oftextile wastewatersby electrocoagu1ation using iron and aluminum electrodes.J。

Hazard.Mater.2003.Bl00：163-178Lahnsteiner J and Mita1 R.Reuse and recycling of secondary emuentsin refineries employing advanced multi-barier systems.Wat.Sci。

Tech.20l0.62f81：1813.1820Linares-Hernfindez I，Barrera.Diaz C，Bilyeu B，et a1.A combinedelect1OcOagu1atiOn-e1ectrOoxidation treatment for industria10/o. o亡 #毛 ∞亡BJL430 Pet.Sci.(2013)10：421-430wastewater.J.Hazard.Mater.201O.175：688.694Manning F S and Snider E H.Environmenta1 assessment data base forpetroleum refining wastewaters and residuals.Technical report data。

ADA.0klahoma.1 983Mainez.Delgadilo S A.Morales.Mora M A and Barcel6.Quintal I D。

Electrocoagulation treatment to remove polutants from petroleumrefinery wasteWater.Sustain.Environ.Res.2010.20r4 ：227-23 1Meas Y Ramirez A J，Villalon A M，et a1.Indus仃ial wastewaters treatedby electrocoagulation.Electrochim.Acta.2010.55：8165-8171Mohan N.Balasubramanian N and Ahmed Basha C.Electrochemica1oxidation of textile wastewater and its reuse.J.Hazard.M ater。

2007.147：644.65 lPanizza M and Cerisola G.Applicabilitv of electrochemical methods tocarwash wastewaters for reuse.Part 2：Electrocoagulation and anodicoxidation integrated process.J.Electroana1.Chem.2010.638：236-240Prather B V Advanced treatment of petroleum refinery wastewater byautoxidation.Water Polut.Contro1 Federat.1 970.42f41：596.603Sengi1 IA and Ozacar M .Treatment of dairy wastewaters byelectrocoagulatiOn using mild steel electrodes.J.Hazard.Mater。

2006.B137：1197.1205Un U T，Koparal A S and Ogutveren U B.ElectrOcOagulation ofvegetable oi1 refinery wastewater using aluminum electrodes.J。

Environ.M anage.2009.90：428.433Wake H.Oil refineries：a review of their ecological impacts on theaquatic environment.Estuat.Coast.ShelfSci.2005.62：131-140Yang C L.Electrochemical coagulation for oily Water demulsifcation。

Sep.Puri"rechno1.2007.54：388.395Yavuz Y.Koparal A S and 0itveren U B.Treatment of petroleumrefinery wastewater by electrochemical methods.Desalination.2010。