Phenolic Compound Removal in Coal-gas Wastewater by O3-IBAC

Journal of donghua University( Eng. Ed.) Vol 21, No 6(2004)Phenolic Compound Removal in Coal-gas Wastewater by O3-IBACMA Fang(马放), YANG Hai-yan(杨海燕), YANG Ji-xian(杨基先), QIN Song-yan(秦松岩), GAO Jie(高杰), XI Xin-xin(席欣欣)School of Municipal & Environment Engineering, Harbin Institute of Technology, Harbin 150090Acclimated bacteria with high ability of phenolic compound treatment plants and have been fulfilling expectationsbiodegradation were immobilized on granular activatOzone is one of the well-known strong oxidizing gases. Itcarbon to form Immobilization Bacteria Activated Carbonreacts with organic substances directly and indirectly in(IBAC). Ozone and IBAC combined process was applied to aqueous phase, The direct reaction is caused by the additiontreat coal-gas wastewater containing phenolic compoundsof ozone molecules to double bonds of organic substancesOptimum ozone dosage and contact time were determined to and the indirect reaction is the oxidation by free radicalsbe 18 mg/L and 20 min. Although pre-oxidation contributed producedgh consecutive reactions caused by thelittle to the removal of total organic carbon ( TOC ) it hydrolysis of ozone. Therefore, ozone plus IBACchanged the characteristics and structure of organic treatment for the removal of phenol was performed tosubstance in the wastewater. By using of ozone-IBAC examine the effects 5. 3treatment. when influent contained 500 mg /L cod and95 mg/L phenol, the removal rates of COD and phenol are Materials and methodshigher than 80% and 92%. After 6 months of operationclimated bacteria abundance maintained above 6. X 101 Isolation and acclimation of phenol degradingbacteriabacteria distribute evenly on the activated carbon. The long-Thirteen phenol degrading strains were isolated fromterm steady viability and high biodegradation efficiency of aerobic activated sludge. After cultivation in the flask, Removalcclimated bacteria are discussed according to the ecological efficiency of every strain was determined. Four stains that areprinePl( Pseudomonas), P2( Brevibacterium). P3( PseudomonasKeywords: ozone, IBAC, biodegradation, acclimated and P4( Bacillus were expected to be high efficiencybacteriabiodegrading bacteria with the 99. 13%, 98. 36%, 97. 9%andrespproIntroductionquickly. Then inorganic culture was dosed at an increasingquantity to promote biomass to adapt wastewater, AfterPhenolic compounds are prevalent in many industrial acclimation with alternative enrichment medium and inorganicwastewaters,especially in coal-gas industrial, where phenol culture, the biomass can be used as a starter of IBAC. Table 1compounds are major reagent during the whole production shows the composition of two kind of cultureprocess. Since they must act without changing their ownTable 1 Composition of enrichment mediumchemical structures during the whole processare veryand inorganic culturestable and can withstand adverse situation. As a resultthey are usually bio-recalcitrancy because of their chemicalEnrichment mediumInorganic culturestability and partly because of their toxicity toPhosphatic buffer2.0g/Lmicroorganisms. Wastewater containing such substance wasAmmonium nitrate0.5g/Ldifficult to be treatedIBAC treatment, which combines physical adsorptionK2HPO: 1g/LCalcium chloride 0. 025g/Lby activated carbon and biodegradation by microorgolutiongrowing in the carbon bed, is being widely applied as oneTH中国煤化工 Ide solution0.0023g1-im sulphuretof the efficient wastewater treatment technologies. IngCNMH Gutiombined processes of ozone and IBACPhenolic wastewater05 g/Ltreatments have been applied to several municipal water*Received Nov 2, 2003Correspondence should be addressed to YANG Hai-yanJournal of donghua University( Eng Ed) Vol 21. No 6(2004) 892 Formation of IBAC5 Analysis MethodAcclimated biomass liquid culture was pumped toThe concentrations of UV254, phenol in the Ibaccirculate in the IBAC column for two hours, then pump column were determined using a UV-Vis spectrolstopped for two hours interval. Sterile water was poured to (S52, Lingguang Co., China ) the iodimetry werewash activated carbon bed and carrying layer after 4employed to determine O concentration. TOChours. Clear effluent means thosecells were concentration was determined by ToC analyzer VcpNimmobilized on the activated carbon and IBAC were SSM-5 000A, Japan). DO was measured by DO meter(YSIformed. Microbe cell attached homogeneously on the 5000, YSI Incorporate, USA). The microbial populationcarbon at an average amount of 5. 6 X 10 cfu/(g carbon) in the activated carbon was enumerated by plate countinghich keep stable at the same depth of carbon bedmethoc3 Experimental installationFig. I shows the schematic diagram of reactors used in Result and discussionthe pilot-scale experiment. Reactors were made oftransparent polyvinyl columns. O contact columnRemoval of UV254 and toc by O pre-85 mm inner diameter and 700 mm height. O3 gasproduced from the ozonizer SHJ-2, China ), then wasA static beaker experiment was operated beforeintroduced with water to the bottom of o contact columncontinuously dynamic experiment to determine the optimalnd passed through metal filament filter. Two IBO3 dosage. Result indicates 18 mg/L is economic andolumns have the same volume and parameters that are efficient. Contact time between influent and O. was150 mm for inner diameter and I 500 mm high. Carrying increasing from o to 30 min to observe removal of UV254layer with 0. 2 m thickness made up of sand were fixed on and TOC by O, oxidation. As the time increasing, UV254the supporting ply. Activatedgranularityrate reached to 20% and 25% respectively and then made0.8 m thick fixed bed. Sampling ports were installed at little change Fig. 2). TOC of effluent in Fig200 mm intervals along one side wall of the reactor tefluctuating in a small range from 680 to 710 mg/L showscollect water sample and carbon sample. Wastewatertotal amount of organic materials cantfed continuously into the system from the bottom of reactor significantly and O:'s low remove efficiency of TOCwith a flow rate of 2.5 L/hUv254UV254 Removal rateFig 2 TOC change during pre-oxidation processI. &8. IBAC columns; 2. O contact column; 3. ozonizer7404.&5. water tank; 6. water pump; 7. air pumpgrams of O3-IBAC and single IBAC systeemtreatment process4 Wastewater qualityThe laboratory tests were performed using effluent ofcoal-gas wastewater treatment system that include hydrolysis-中国煤化工contact oxidation unitspond and sand filterCNMHGRaw water has a high phenolic compound concentration ata range of 100- 220 mg/L, COD value is in an average ofFig 3 TOC change during pre-oxidation process00 mg/L. The water temperature fluctuated between 20-Result of UV254 and TOC measurement proposed thatBOD/ COD ration shows poor biodegradable quality of ozone can't oxidize unsaturated constituent and aromaticJournal of donghua University( Eng. Ed.) Vol 21, No 6(2004)hydrocarbons that are difficult to degrade biologically to-+Influentinorganic completely but break the complex molecularEffluent from ozone reactorstructure to form simpler one. This partial oxidationEffluent from IBAcsufficient to render those compounds more amenable toRemoval rate by ozone reactorsubsequent unitsREmoval rate by IBAC2 Comparing study on O3 -IBAC and single800100%IBAC system笑80%conditions to identify the oxidation of O, and the effect on 2 5oo/O -IBAC and single IBAC were operated at sameIBAC. Influent introduced to two system was still taken 8400from the outlet of filter. Contact time of ozone reactor20 min as a result of first secti亠4|0%O dosage was still 18 mg/L681021416182020%2. 1 Removal of COD and phenol compoundtime(d)experIFig 4 COD removal by O3-lBAC treatment processCOD concentration of two system effluent indicatedthat COd remove efficiency of O: -IBAC process was priorInfluentto that of IBAC as shown in Fig. 4 and Fig. 5. AlthoughEffluent from IBACCOD value fell down after O pre-oxidation in O3 -IBAC-REmoval rate by IBACtreatment process, but just reduced a little. Phenolic70000an average 12% were also detected after pre-oxidation400reactor effluent were sometimes observed. In an attempt todevelop an understanding of the effectiveness of oxidative让备兽普删号20%pretreatment for a wide variety of phenolic compoundHammett constants for most compounds were introduced2468101214161820here correlated biodegradability with oxidation dosage. Itwas anticipated that significant correlations may exist withFig 5 COD removal by single IBAC treatment procesbiodegradability because electrophilic substitution is acommon biodegradation route for aromatics. It was alsonticipated that a correlation may exist with ozone dosingEffluent ft from ozone reactorfrom IBACbecause ozone is a strong, highly selective oxidant whichl20favors cycloaddition reactions across unsaturated bondsand electrophilic reactions such as with aromatic ringsBecause ozone is an electrophile, it will react readily withcompounds which are electron rich(i.e. with low Hammettconstants). Therefore, a compound which reacts morebe more able than other scavengers (i. e. oxidation by0L▲女products)to compete for ozone molecules in the aqueous024681014161820system. Hammett constant of phenol was reported to betime(d)0. 0 and phenol conversion factors was 0.42( mg/LFig 6 Phenolic compound removal bycompound per mg/L as COD). COD change in Fig 4 alsoO3-IBAC treatmentillustrate phenol were mineralized to simpler smallon+ ahorn compounds concentrationmolecular which have lower conversion factors as mg/L中国煤化 cinder the average influentCOD. It can be concluded that the subsequent 80% CODconcCNMHGthe ozone-IBAC and theremoval efficiency of IBAC in O3 -IBAC system comparing70% of single IBAC system was a result of the combination compound was noted in the ozone-IBAC process than in theof activated carbon adsorption plus biological degradationsingle IBAC process. Thus ozonation enhanced the removalof phenolbefittingly biodegradable quality of O reactor effluentJournal of donghua University( Eng Ed) Vol 21. No 6(2004) 91Influent of IBACEffluent froml BacDO consumptionEffluent from IBAC2008101214161820Fig, 7 Phenolic compound removal by single IBACtreatmen2.2 Comparing study on DOFig 9 DO change in IBAC by IBAC treatmentliving element and condition for thoseaerobic phenol removal bacteria immobilized on theelectro-accepter can promote phenol compounds biodegradableactivated carbon, plentiful DO in wastewater should be uality and make those bio-recalcitrancy easier to be utilized byassured. In this O -IBAC process, Required Do aerobic character of phenol removal microorganismconcentration should be more than 5 mg/L. doO; -IBAC has priority to single IBAC in COD removalncentration taken from inlet and first sampleenolic compound removal and DO supply. Howevertop were measured because water upflew in IBAC and dOwere consumed more along upward water flowIBAC can remove aim pollutant and get a good purificationFrom Fig.8, DO of influent and effluent were all effectivenessmore than 6.0 and 4.0 mg/L, respectively. Two curves3 Microbial ecological study of O3-IBACgap showed DO consumption were ranging from 4 to 6Ozone can act as an oxidant but also as disinfectanmg/L. It illustrated microorganism in activated carbon that can destruct cell wallleakage of cellularmaintained strong and steady activity so that high removal constituents outside of cell and damage the constituentsand stable efficiency of this treatment process were the nucleic acids of microorganism. So the researchinsured simultaneously. It can be concluded that ozone focusing on microbial ecology of activated carbon is carriednot only act as oxidant but also supply enough do to out to evaluate ozone effect on the microbial activity andbacteria on the activated carbon for the IBAC efficiency the IBAC treatment process. Result shows that theenduranceoxidization of ozone improve the biodegradability and theEffluent from ozone reactorwater,consequently acclimated bacteria utilize pollutant asEffluent from IBACsubstrate with high efficiency△ DO consumption123. 1 Abundance and species variation ofmicrobial community8Total microbial abundances of four watertaken frd. Count of是“heterotrophic bacteria showed firstly in decrease. Then annear the inlet got more intensely brush by water flow than81012interior carbon in the column: contime(d)of inlet carbon can t settle more. Due to filtering andFig 8 DO removal in IBAC by O; -IBAC treatmenton the surface of activated carbon along the upward flow,An air pump was installed in single IBAC unit to leadiV凵中国煤化工 Bacteria count on the topprovide enough Do. DO concentration of inlet wasCN MH Gasing tendency becausedetermined to be 5 mg/L and DO consumption reached to pollutants were removed gradually as water flowin4.5 mg/L in average according to Fig. 9. So once DO in Although abundance variation exited in the columnfed water was less than DO consumption, purification and microbial amount still maintained at the same scalar levelremoval efficiency can t be obtainedPlentiful do and substrate made acclimated bacteriaAs Fig 8 and Fig 9 shown, O molecular as terminational distributing homogeneouslyJournal of donghua University( Eng. Ed.) Vol 21, No 6(2004)Table 2 Engineering bacteria quantityIBAC different strataConclusionMicrobialPositionSample port(distance from top(1) Ozone cant completely oxidize organic pollutantcfu/g carbon)to inorganic but break the complex molecular structure1234form simpler one and minish molecular weight. Although8.5×103total amount of organic pollutant didn t decrease7.5×100,7msignificantly during oxidation process. Wastewater quality6.7×1became more bio-degradable and Do concentrationincreased because of ozone decompositionTable 3 Microbial species settled on activated carbon2)O3IBAC treatment process can remove organicSpeciesStraipollutant and phenolic compound with high efficiency, andenough DO concentration of IBAC influent was insuredOxygen molecular as terminal electronic accepter canBrevibactepromote pollutant biodegradation. So O.-IBAC has prioritythan single IBAC in COD removal, phenolic compoundZoogloearemoval and DO supplyTable 3 showed species and stains of bacteria attached on3) Microbial abundance on activated carbon of oactivated carbon for 6 months. Isolation and identification IBAC operating for 6 months maintained at the same scalarresult dtrated that bacteria immobilized at the level, microorganism distribute on activated carbon evenlyoperation beginning were still dominant species. HoweyAlthough wild bacteria can be adsorb on the activatedtwo new speciedidn t belongcarbon, they still cant beat indigenous bacterialavobacterium and Zoogloea, wereAcclimated bacteria still were dominant speciesbacteria,but also due to species succession of bacteria in most influential part in this treatment pra. o Ls.oinativeolate. It can be estimated that the enhanced cod(4)O.-IBAC treatment process was a combiremoval capability of the biofilm was not only due to the operation of ozone and acclimated bacteria plus activatedincrease in the COD removal capability of acclimated carbon to remove pollutant. Acclimated bacteria were thebiofilm ecosystem3.2 Mutual relationship of activated carbonReferencesand microbial community1ing, YU Xiu-e, ZHENG Ping, et al. A studon and immobilized microorganismon bioremediation of phenol-contaminated surface waterformed mutulationship Activated carbon provideJournal of Zhejiang University(Agric,& Life Sci.),1999inhabitablement where bacteria can colonize and25(4):409-413adsorb substrate that bacteria can utilize. whe[2 Armenante PM, Kafkewitz D, Lewandowaki G A, et albiodegradable ability of microorganism expanded activatedAnaerobic-aerobic treatment of halogenated phenoliccarbon servicing timecompounds[J]. Wat. Res, 1999, 33:681-692When acclimated bacteria were immobilized on [3] Brlanl Burback, Jeromei Perry. Biodegradeactivated carbon to form IBAC, Every species and strainbiotransformation of groundwater pollutant mixtures bysettled in a suitable position. Acclimation beformycobacterium vaccae. Applied and Environmentimmobilization improved those incubated bacteriaMicrobiology,l993,11(1):1025-1029adaptability to the environment with long time. After [4] vallecil lo A, P A Garcia-Encina, M Pena. Anaerobicimmobilization, those bacteria occupied fitness spatialbiodegradability and toxicity of chlorophenols. Wat. SciTech.,1999,40(8):161-168space on the activated carbon to grow as dominant species[51 YANG Ji-xian, MA Fang, ZHANG Li-qiu, LU Xing. TheWild bacteria flowing into ecosystem with influent can tfeasibility study on engineering bacteria for oil-conbeat acclimated bacteria in the competition on living spacernal of northeastand substrate utilization. So they have little possibility to中国煤化工become dominant species. According to ecologicaCNMHGIprinciple, acclimation broadened niche of incubateddy on the removal of micro-pollubacteria so that those bacteria can keep high utilizationmobilized biological activated carbon. Harbin Universityfficiency to thmutantof Civil Engineering Architecture, Ph. D