Biological removal of methanol from process condensate for the purpose of reclamation

Journal of Entironmental Scinces Vol. 16,No. 3.pp.384- -386. 2004CON-2679/XArticle ID: 1001-0742(2004)03-0384-03CLC oumber: X701Document code: ABiological removal of methanol from process condensate for the purpose ofreclamationWANG Yan-ming'2 ，YANG Min''，ZHANG Yu'，GAO Meng-chun' ，ZHANG Jing'(1. Research Center for Eco- Environnental Sciences, Chinese Academy of Sciences, Beiing 10085., China. E-mail: yangmin@ mail. rees . ac . en;2.The Environmenlal Monitoring Center of Petro-China, Langfang 06500 , China)Abstract: The biological removal of methanol from condensate of ammonia manufacturing processes for the purposeof reclamation using contact type reactor was studied. Methanol of 60 mg/L was removed completely under an HRTof 1.12 h. Optimal inorganic nutrient dose was detemined on evaluating methanol removal performance anddehydrogenase ativities( DHA) under dfferent nutrition doses. The optimal inorganic nutrient dose only gave anincrease of conductivity of ca.10 us/cm2 in the efluent on treating synthetic condensate containing methanol of 30mg/L. The results demonstrated that biological removal of methanol was effective for the purpose of recovering themethanol-bearing condensate.Keywords: reclamation; condensate; methanol removal; biological contact reactoradded(Table 1) to a biological system to remove trace organicIntroductioncompounds from the oligotrophic rinse pure water ofA great arnount of condensate is usually produced whensemiconductor manufacturing processes ( Shibata，1987 ).carbon monoxide of composite gas is transformed in theGenerally speaking, inonganic ions should be added as litleammonia manufacturing process."condensate containsas possible because the condensate will be reused as processsome methanol( < 30 mg/L) as well as a small amount ofwater after treatment .inorganic ions ( conductivity < 20 μs/cm2 ) ( Song，2001;Table1 Composton of lnorgandc nutrldon sluton(for treating TOC ofZhu, 2002), and has been discharged as wastewater. The1 mg/L)(Shibata, 1987Unit: mg/Lcondensate, however, could be reclaimed as the high qualityNHLCI0.767 CaCh; ●2H200.001process water if methanol as well as inorganic ions wereKH,POremoved.MgsSO,●H2O0.07MnSO, -4H20Methanol is highly biodegradable， and could beFeSO, .7H200.001 ZnSO% .7H20effctively removed from wastewater with a biologicalCuSO, .5H2O0.00Al2(SO,). 14H20oxidation process. Most of the reports related to methanolremoval, however, are limited to wastewater containing highThe objective of this study is to establish a biologicalconcentration melhanol( Wu, 1998; Irene， 1999; Zhao,contact oxidation system forecovering condensate1989). Biological activated carbon( BAC) process has beencontaminated with methanol. Operational conditions as wellsucessfully used for the removal of trace organic pollutantsas necessary nutrient dose were determined on syntheticlike isopropanol, methanol, etc. from used pure water.condensate wastewater.When the BAC process is applied to the treatment ofcondensate ，however, frequent backwash is required because1 Materials and methodsof the fast growth of bacteria under the relatively high1.1 Materialsconcentration of methanol. In this case, the endurance ofFig.1 shows the schematic diagram of the biologicalactivated carbon will become a big challnge( Miller, 1978;ceramic contact reactor used in this study. A polyacrylateSong, 2001).column (132 cmx5 cm ID) was used as the reactor, and aBiological ceramic contact reactors, on the other hand,granular ceramic bio-carier ( Zibo Biocarrier Company，have been successfully used to remove low concentration ofShandong Province) with a diameter of 2- -4 mm was flled inorganic pollutants and ammonia as a pretreatment method inthe reactor to give an efective height of 80 cm， Thedrinking water treatment ( Fang，1995). The ceramic bioexperimental setup was installed in a thermostat room (20士cariers would be much better than activated carbon in terms中国煤化工of endurance. For treating condensate with a biologicalEpared by dslsvingpropermethod, however, addition of inorganic ions is necessary toYHC N M H Gade into deionized water.keep activities of microbes. Inorganic nutrition salts wereSeed sludge was taken from an activated sludge plant treatingFoundation item: The National High-Toch R&D Program(863) d China (No. 2002AA601310); # Crresponding suhorNo.3Biological removal of methanol from process condensale for the purpose of reclamation85Efluentfrom the bottom on the twenty-fth day and were examined byEM. A reference blank of carrier was also taken before themicroorganisms were inoculumed .2 Results and discussion2.1 Performance of the contact reactorThe reactor was operated under 2 methanolconcentrations for 50 d following startup, and variations ofmethanol and TOC are shown in Fig. 2. Steady removal ofGas- 9+1口methanol was achieved shortly after the startup of the reactorbecause inoculation of seed sludge acclimated to methanol.Influcent.8*Residual methanol began to be detected when the infuentconcentration was increased to 60 m/L. MethanolFig.I Experimental sketch of biological contact columndisappeared again from the efluent 3 d later, indicating thatthe bio-system was very stable for methanol removal .methanol- bearing wastewater. Stock inorganic nutrition saltsolution was prepared using chemicals of reagent grade.1.2 Analytical methods首50Methanol analysis was conducted on a gas chromatograph员46(9A, Shimadzu Co.，Japan) with a flame ionisation detector(FID) and a chromosorb 101 column(60- -80, 2 mx西复20+ Efluentmm). The carrier gas(N2) flow was 80 ml/min， and theinjection temperature was 250C. The TOC was measured101520253035404550using a TOC-500 analyzer( Shimadzu Co., Japan) . Microbes2:+[afluent)n bio-carriers were examined by SEM ( Model S-570,士EfluentHitachi, Japan) . The dehydrogenation activities (DHA) of当2(microbes were measured on a spectrophotometer ( 722S,Shanghai Analytical Instrument Co.， China) at 490 nm2 10according to a reference ( Chung，1989). All of the otheranalysis was conducted according to the Standard Methods ofWater and Wastewater Monitoring of China (1998).05101520233035404550,d1.3 Experimental methodsThe contact bioreactor was aerated for 1 d withoutFig.2 Variations of (a) mehanol; (b) TOCinlows of wastewater fllowing addition of 6.75 g seedsludge. Then, the synthetic condensate was introduced intoAs shown in Fig. 2b, a residual TOC between 2.0 andthe system at a flow rale of 30 L/d，which was equivalent to2.5 mg/L was successively detected under steady conditions.an HRT of 1.12 h. The methanol concentration in theNo other organic components except methanol were used forinfluent was about 32 mg/L during the first 33 d, and thenpreparation of synthetic condensate. So，the TOC in theincreased to 60 mg/L. The inorganic nutition solution waefluent was the products of microbial metabolic activities,added to the influent in a dose to TOC ratio equivalent to theand efractory to biodegradation. However, it seems that thesame of that used by Shibata ( Shibata，1987 ). Samplesefluent TOC was not in proportional to the infuent methanolperiodically taken from the efluent were centrifugedconcentration as showm in Fig. 2b.immediately to remove the biomass, and then refrigerated at2.2 Effects of inorganic nutrition dosage4C for methanol and T0C analysis.Microbes could not live without the existence of properInorganic nutrition solution was prepared according toamount of inorganic nutition, and so the inorganic nutitionprevious studies(Table 1; Shibata， 1987), and the optimalsolution was prepared and added to the synthetic condensate.dosage of the nutrition solution was determined using theFrom the viewpoint of pure waler production， however,previous dosage as the base( No) at an influent methanolinorganic salts are not favorable. So, the minimum dose of中国煤化工| by gadually decreaingconcentration of 32 mg/L. The performance of the reactor wasevaluated for 5- -7 d under each nutrition dose. In the sameHC N M H G value( No) proposed bytime, proper amount of bio-cariers was taken out from theShibala Snupala, 19811 In several steps, and variations ofmethanol and DHA are shown in Fig. 3.contact reactor for the determination of DHA and ss .When nutrition dose was changed from N。to N。/3, theBio-carriers were taken from the reactor at 20 cm levels86WANG Yan-ming et al .Vol. 1635曾25No 2N0/3 No2 NO3 NoV4 Nv3.◆Influent10 + ERuent0510152025303540450.12且. 5000 timnesb. 30000 times0.10Fig.4 SEM images of bio-camier section and biofim on bio-carner surface(a) 5000 times; (b) 3000 times置0.08-i 0.06Methanol in the efluent was under detection limit, and TOCin the efluent was less than 2.5 m/L under steady operationcondition,demonstrating a stable methanol removal0.02|perormance of the biological ceramic contact reactor.V。 2N%/3 N/2 Ny/3 No/4The minimum inorganie salt dose for stable methanolNutrition doseremoval was determined, giving an increase of conductivity of10 ps/cm2 in the efluent .Fig.3 Efect of (a) nutition ratio on methanol removal;(b)dose on specific DHAReferences :methanol concentration in efluent was under the dectionChung Y C, Neethling J B, 1989. Microbiul activity measurements for anaerobiesludge digesion[J]. J Water Pollut Control Fed, 61: 343- -349.limit. However, if the nutrition dose was decreased further toFangZ D, 1995. Study on the plicaion of bio-cerunie tecunique in drinkingNo14，residual methanol began to be detected in theter treatmena[D]. PHD. Thesis. Tsinghua Univerily, Beijing.efluent . The residual methanol, however, disappeared againFord D L, Leccigp G, 1966. Dehydrogenases enyme 8 a paraneter of acivatedsludge actirities[C]. Proe 21st indust waste conf. Purdue Univ.. Westthe nutrition dose was increased from No/4 to N。/3.Iofayette, Ind. 534.DHA indicates the metabolic activities of microbes to lrene P, Willi G.1999 Pllulion dynamics by methonal adition in dnitnifyigwastewater treatment plans[J]. Wat Sci Tech, 39(1): 43- -50.some extent. As shown in Fig. 3b，the specific DHA ( theMillerC w. Rice R C, 1978. Europen water teatment poctices -the promiseratio of DHA to SS) only decreased slightly with the decreaseof biological nctivated carbon[J]. Civil Eng, 48(2): 81-84.of nutrition dose from N。 to N。/3， indicating that theSatoshi M P，1997. Methanogenic fermentation and growth of granularmethanogenie sludge on a methanol- propionate mixture[J]. J of Fermentationmicrobial activities were not affected markedly under theconditions. However, the specific DHA decreased sharplyShibata M，Nakanurae K, Miyaji Y, 1987. Biological decompestio of tracewhen the nutrition ratio was decreased from N。13 to N。14,organie compounds[J]. Wat Sei Tech, 19: 417- 427.SongZ w, ChenGX, MaF e al., 2001. Slighly polluted methanol waslewaterwhich was in accordance with the above methanol removaltreatment using immobilized biological activated carbon method[J]. Urbanresult. It is clear that a nutnition ratio of N。/3 was necessaryEnvironment & Urban Ecology,14(5): 51- -54.Wu X K, 1998. The treatmet technolov of the ongance wastewater( M]. Bejing:for maintaining the stable performance of the biologicalChima Construction Industry Pr87--89system, which resulted in an increase of conductivity of ca.YangSC. PengX w.1998. The simple inodctio into tealmeat of methanol10 pus/cm in the efluent.wastewster[J]. China Nitrogenous Ferilizer, 4: 38- -39.Ye Y, 1997. The pllutio conroling measures of methanol wastewater[J}.2.3 SEM images of bioflmChemical Engineering of Oil and Gas, 26(4): 251- -255.Fig.4 shows the SEM images of bio-carrier section andZhao H B, 1989. Treatment of high-concentation methanol wastewater with one-bioflm on bio carrier surface. It is clear that the bio-carrierstep anaerobic digstion procs[J]. tCWW. (7): 914--915.Zhao H B, 1998. Application of tretment technologe for melhanol wastewater inhas a very coarse surface， which is proper for biofilmChina[J]. Environmental Prolection of Chemical Engineering， 18(3):formation. Round-shape bacteria together with some rodshape bacteria constituted the dominating microbes on bio-ZhouX F, Ren N Q, Chen M M et al.2001. The treatment example ofmethanol wastewater by biologcal methods[J]. China Water & Wastewaler,carier surface， indicating the diversity of the microbial17(6): 50-52.community .. Resarches on the pplication of中国煤化工on mhaea wuewere ei i3 ConclusionsTYHCNMHGtment, 22(7): 18- -21.Synthetic condensale containing methanol of 60 mg/L(Received for review April3, 2003. Acepted May 20, 2003)was treated with a biologicalceramic contact reactor under anHRTof 1.12 h and methanol load of 1.15 kg/(d.m' ).