Treatment of methanol wastewater with two-stage and two-phase anaerobic process

Journal of Harbin Instiue of Technology (New Series)， Vol. 17, No. 1, 2010Treatment of methanol wastewater with two-stage andtwo-phase anaerobic processHAN Hong-jun, MA Wen -cheng韩洪军,马文成(School of Municipal and Environmental Engineering, Harbin Insitute of Technology, Harbin 150090, China, han13946003379@ 163. com)Abstract: The two-stage and two-phase anaerobic process (TSTP) composed of hydrolytic acidifcation reactor ,first-order and second-order extemal circulation anaerobie reactors ( EC )wastewater. Test results show that TSTP process is quick start-up in 51 d, and the maximum VFA of hydrolyticacidification reactor efluent reaches 876 mg/L. Under the condition of volume loading of 6.56 kgCOD/m’● d,COD removal rate of the frst-order EC reactor is about 85% , and under the condition of volume loading of 1. 02kgC0D/m’●d, COD removal rate of the second-order EC reactor is about 50%. When the inlow COD ofTSTP process is between 7000 - 11000 mg/L, its efluent COD is lower than 600 mg/L. In the biological con-version process of methanol into methane , the production of acetic acids as an intermediate product can be ig-nored and the direct produetion of methane from methanol is predominant.Key words: methanol wastewater; two stage and two-phase anaerobic process (TSTP) ; extemal circulation an-aerobic reactor ( EC); hydrolytic acidification reactorCLC number: X703. 1Document code: AArticle ID: 1005-9113(2010)01 0065-05Methanol wastewater is usually defined as the rff-ally changed in the range of 4000 - 20000 mg/L;nate discharged from rectifying tower in the process ofBOD3/COD > 0.42. Pollutant mainly contained smallmethanol producing or using, which contains methanol,alcohols such as methanol, ethanol, normal propyl al-ethanol, higher alcohol, higher aldehyde and some long-cohol, isopropanol, 2-butanol and some long chainchain organic compound with COD between 8000compounds as paraffin， Wastewater had single nutri-20000 mg/L and higher B/C!"- 21. At present, traditionaltional ingredient, in the absence of nutritional elementsanaerobic biological process are often adopted to treatsuch as N and P. As conditioning tank of methanol pro-methanol wastewaterl3-81 . Although in anaerobic biologi-ducing plant was small, temperature and pH value ofcal conversion process ，methanol converted into methanewastewater both fuctuated in a large range ( tempera-directly is the predominant path, there are the possibilityture: 35-65 C, pH value:5.6-8. 5).and environmental conditions of methanol being converted1.2 Treatment Process and Design Parametersinto acetic acids in anaerobic reactor. Therefore, underMethanol wastewater entered into hydrolytic acidi-higher volume loading, risk of acidification exits in tradi-fication reactor, first-order and second- order anaerobictional single stage or phase anaerobic process-.reactor in tum (as shown in Fig. 1). The unit of two-Two-stage and two-phase anaerobic processstage systerm was EC reactor as patent products ( Z[(TSTP) composed of hydrolytic acidification reactor,03157657.5). The reactor takes the way of combiningfirst-order and second- order Extermnal Circulation anae-external and internal circulation ，facilitating formationrobic reactor (EC) was adopted in the yielding test toof granular sludge. Cyclone-flow water distribution sys-treat methanol wastewater of Harbin Gasification Com-tem was used to provide well biological and hydraulicpany methanol producing plant, and treatment effectconditions. Short-distance multiple-stage three-phasewas investigated in practical operation.separator was used to enhance separating effect ofsludge. , water and gas. First-order anaerobic reaction is1 Materials and Methodscalled primary treating stage with high volume loadingand high COD removal rate, its recirculation water pos-1.1 Quality and Quantity of WastewaterQuantity of wastewater was 10 m'/b. COD gener-value中国煤化Iion is called further:YHCNMHGReceived 2008 -02 -01.Sponsored by the National Hi-Tech Research and Development Program of China ( Grant No. 2003AA601090) and Projects of Development Plan of theState Key Fundamental Research of China ( Grant No. 2004CB4185)., 65.Journal of Harbin Institute of Technology (Nev Series). Vol. 17, No. 1, 2010. Efivuentsubstance. BOD;/COD increased from 0. 42 to 0. 59.Biodegradability of wastewater enhanced greatly ( asRecirculation[shown in Fig. 2). VFA increased from 72 mg/L to 516watermg/L. Under the condition of organic matters concen-tration fluctuated greatly, COD removal rate improved②③gradually, and stayed around 23%. Sludge had been|6adapted to methanol wastewater , and naturalization fin-Methanod_ 6ished.W astewaterHydrolytie。 Reglaing Fistorder Second-orderNaturalization liquid was the same as that of hy-Aidfietion Bufe Ming EC Rector EC Reetertdrolytic acidifcation reactor. Temperature of first-orderBasinEC reactor was strictly controlled in the range of 33.51. Underwater agiator; 2. Alkeali liquor Dosing; 3. Slearm Dosing; 4. Cy-+1 C，and pH value 7.2 +0.2. Recirculation waterclone-flow water distribution system; 5. Shor-distance muliple-stagethree-phase separatorwas controlled within 30 m /h. Temperature and alka-Fig.1 Treatment process of methanol wastewaterlinity of second-order EC reactor mainly depended onmass transfer first-order EC reactor. Recirculation wa-treating stage. In the reactor with low volume loadingter was controlled within 20 m /h. The system opera-and low COD removal rate, the treatment effect is sta-ted continuously with intermittent inflow. Quantity ofble and effluent quality is good.inflow was 2 m'/h in the beginning. Then, inflowOne hydrolytic acidification reactor: carbon steelquantity was increased and inflow period was shortenedstructure, D = 5 m, H = 10 m, effective volume 176gradually.m'，and two underwater agitator are set, which are or-thogonally laid and altemately ran. One regulating buff-14. 550Influent CODer mixing basin: carbon steel structure, D = 1.2m, H12+ Efluent VFAL-450 7= 3.5 m, effective volume 3.9 m' , with pH meters and610350 pthermometer sensor device for auto control of chemicalfeed device and steam valves. EC reactors: carbon steel150 Estructure, D = 5 m,H = 16 m, effective volume 294m，with recirculation pipeline and short-distance-mul-了369121518 20tiple-stage three-phase separator on the top and cyclone-flow water distribution system at the bottom.Fig.2 The eMuent COD and VFA concentration of hydro-1.3 Inoculation Sludgelytic acidifcation reactor at start-up periodSludge of hydrolytie acidification basin came fromdehydrated anaerobic sludge in Harbin Brew House.3 days after start-up, sampled from efluent andThe volume is 30 m', SV = 75% - 80%. Sludge ofrecycle pipe of first-order and second-order EC reactor,first-order and second-order EC reactors came from re-there was lots of minute black floating -oil sludge. Theirsidual granular sludge produced by IC reactor in Brewsedimentation performance was weak , and most of themHouse. 48 m' granular sludge was added to first- -orderfloated on water surface. It showed that InoculationEC reactor and 24 m' to second-order EC reactor. SVgranular sludge gradually decomposed into flocculatingis 80% -90%，VSS/SS = 0. 53.sludge, being washed out from reactor. Only a smallpart of them was kept granular and conserved at the2 Results and Discussionbottom of reactor and their volume was less than 1/10.On one hand, for the reasons of mechanic collision in2.1 Sludge Naturalization of TSTP Systemsludge loading and unloading process and heat loss ofNaturalization liquid was mixed with some metha-transportation in winter, a great deal of strains on exte-nol wastewater and treated water, with COD betweenrior granular sludge died，sludge structure turmed relax2000 - 2300 mg/L. NH,CI, H,PO4 and NaOH wasnd rapidly fell off under hydraulic washing. On theadded into water by the proportion of COD: N:P =200other hand, granular sludge used in thtreatment of:5: 1. Temperature was control between 25 - 35 C,beer wastewaler did not adapt to methanol wastewater,and pH value 5.5 -6. 5. The reactor operated continu-which also lead to decreasing of sludge density. So thatously with intermittent inflow. Quantity of inflow was 2it ism'/h in the beginning. Then, inflow quantity was in-中国煤化工:moval rate of frst-creased and inflow period was shortened gradually.orderMHC NMH G% to around 90%，After 3 weeks operation, sampled from the bot-as shownlin rig.J. rn value uI uuuent changed in thetom. It showed that sludge turmed black with denserange of 7.0-7.3. When sampled from main reactingstructure and ffluent became limpid with less suspendarea , black and small size granular sludge appeared. It●66●Joumal of Harbin Instiue of Technology (New Series)。 Vol. 17, No. 1, 2010was about 1mm, and settled rapidly. SV is small, a-ume loading fluctuated. Hydrolytic acidification reactorround 15%. Minute bubble produced continuouslyhas weak COD removal ability, and its most importantfrom the sludge layer. COD removal rate of second-or-function is providing optimal substrate for methanogender EC reactor increased from 30% to around 50% , asand enhancing the biodegradable of wastewater.shown in Fig.4. PH value of efluent changed in therange of6.9-7.1. Because of operation in winter and50+ COD removal Tateintermittent inflow， heat quantity greatly dissipated.40+ co volume loadingTemperature of reacting area varied in the range of 26- 28C. When sampled from main reacting area,3(10sludge existed in the state of minute flocculating. It20settled slowly and SV is around 30% . Minute bubble言1was produced from sludge layer, but it was much lessthan that of the first -order EC reactor.25 30 3540 45v/e| 1.2号Fig.5 Curves of COD loading and its removal rate of hy-1.0 Edrolysis acidification reactor15000.8In addition, VFA content of hydrolytic acidifica-+ Volume loading0.6 31000- Efluent COD 304 gtion reactor effluent increased with the rising of volumeloading, but not obviously. The maximum VFA was富500.2876 mg/L. These can be related to the characters ofmethanol wastewater. According to thermodynamics/theory, there are two paths of methanol converted intoFig.3 The relationship between COD and volume loadingmethane in the biological process.of first-order EC reactor at start-up periodMethanol converts into methane directly:4CH,0H- +3CH4 +CO2 +2H20OG'。= -312 kJ/mmol、2000 EMethanol converts into acetic acids , then converts+ . Influent COD 40 只into methane:# Efluent COD 30日COD removal n城ten言4CH,OH +2CO2- +3CHCOOH +2H200日AG'。= -2. 9 kJ/ mmol5000喜CH,COOH + H20→CH, + CO2 +H2OOG'。= -31.0 kJ/ mmolAs shown in formula, methanol converting intoFig.4 The COD removal rate of second-order EC anaero-methane directly was predominant， and the path obic reactor at start-up periodmethanol- -acetic acids- methane was auxiliary anonly took place under special conditions. This was the2.2 Loading-raised Periodone reason of low VFA content in hydrolytic acidifica-When the sludge naturalization finished, the load-tion reactor efluent. In addition, the content of othering of TSTP was raised gradually with continuously in-long chain organic matter utilized by hydrolytic acidif-flow. In this period, increasing inflow quantity was acation bacteria was limit also lead to low VFA contentdopted to raise system loading with range between 1 -2of efluent.m'/h. The system ran steadily 3 - 5d after every load-As shown in Fig. 6, 51 d after start-up, TSTP ar-ing-raised. When the COD removal rate kept stable,rived to full-loading phase. The volume loading of first-the loading was raised again. To keep enough nutri-order EC reactor reached to 6. 56 kgCOD/m'●d withtional ingredient, NH,Cl and NaH2PO4 was added intoCOD removal rate 85% and the volume loading of sec-hydrolytic acidification reactor by the proportion ofond-order EC reactor reached to 1. 02 kgC0OD/m’●dCOD: N: P = 200:5: 1.with COD removal rate 50%。The total COD removalThe COD removal rate of hydrolytic acidificationrate of two-stage anaerobic system reached to 90% -reactor increased with the rising of volume loading. Fig.92.-42w COD varied be5 showed that COD removal rate increased from 18% to中国煤化工ent COD was lower27. 5% and fluctuated strongly as volume loading isingtweerfrom2. 15 to5. 93 kgCOD/m'● d. As the volume load-than:HCNM H G..ing increasing to 15. 18 kg COD/m'●d, COD removalty of first-order EC reactor increased from 20 m'/h torate kept stable as 25% and did not changed with vol-50 m'/h to emphasize the mass transfer process of or-.67●Journal of Harbin Insiue of Technology (Nee Series). Vol. 17. No. 1.2010ganie matters and reform of granular sludge, and in-2.3 Effect of Wastewater Quality Variation oncreased to 70 m'/h with hydraulic upflow rate reachingTSTP Treatment Efficiencyto4 m/h at 44 d. Although lots of light-weight floccu-61 day after fll-loading period, for the reasons oflent sludge was washed out from reactor, the COD re-accidents of condenser system in methanol producingmoval rate of firsl-order EC reactor did not fuctuateplant, lots of condenser water piped into conditioningrapidly. When sampled from the main reacting area oftank. The COD of methanol wastewater dropped rapid-reactor, black and ellipse granular sludge appearedly, and varied between 1400 - 3800 mg/L. After awith diameter between 1.5 to2.5 mm, SV 30%，set-week, problem was sttled and the COD increased to .tling rate 53 m/h. It was shown that the granular7600- 10400 mg/L rapidly. Fig. 7 showed the effectsludge with well degradation and setling ability was re-of shock loading caused by wastewater quality variationformed and the start-up of two-stage anaerobic system on TSTP.had been finished.0010585莒10士Finst-order EC COD士Second-order EC CDs5一Second-order“/loadings5607220~ . 25303540”45 50言Fig.7 Effect of Fluctuation of water quality on TSTP sys-Fig.6COD removal rate of two-stage anaerobic system attemvolume loading rising periodTSTP performed well resisting ability to shockThere were some factors for quick start-up of two-loading. Although COD remove rate of first-order ECstage anaerobic system within 51 d. 1) Inoculationreactor dropped to 65% when inlow COD rapidly in-sludge was granular sludge. Although sludge decom-creased from 1481 mg/L to 10400 mg/L, as primaryposed at beginning, the inner core of sludge existed intreating stage, it alleviated the efct of shock loadingreactor was helpful to reforming of granular sludge. 2)on whole system. In addition, large quanity of highThe separation of acidogenic phase and methanogenicactivity granular sludge existed in reactor ensured thephase provided optimum environmental conditions forsysterm adapted this variation immediately and COD re-methanogen breeding rapidly. 3) The cyclone-low wa-moval rate rise to 86% in4 d.ter distribution system and short-distance multiple-stageSecond-order EC reactor also perforned well abili-three-phase separator of EC was helpful to form granu-ty of resisting shock loading, and COD removal ratelar sludge and provided well biological and hydrauliekept around 65% . When the inlow COD of TSTP wasconditions for anaerobic reaction. 4) The higher veloc-9150 mg/L, the efluent COD of second-order EC re-ity of first-order EC reactor enhanced the hydraulicactor was as low as 442 mg/L and the COD removalscreening activity and emphasized the mass transferrate of whole system reached to 95. 16%.process of organic matters, which improved COD re-Moreover, although removal ability of organicmoval ability of first-order EC reactor. 5) The lowermatters fell down when volume loading increased rapid-velocity of second-order EC reactor was helpful toly, VFA accumulation did not take place when sam-maintain sludge washed out from former reactor, whichpled from first-order EC anaerobic reactor. Therefore ，kept enough biomass in treatment system.the decline of COD remove rate was not equivalent toAfter the fll-loading period, the recirculation wa-other wastewater anaerobic treatments, which wereter quantity of second-order EC reactor increased fromcausedd by VFA accumulation. It was because of rapid20 m/h to 40 m'/h, lots of sludge was washed out andincreasing of methanol content. It proved that directthe COD removal rate fall gradually. When the recircu-production of methane from methanol was predominantlation water quantity was adjusted to 30 m/h, the reac-was inside reactor in the anaerobic process on othertor ran steadily and blocking of water distribution systemside.did not took place. It was considered that the volume中国煤化工ound that paraffnloading of second-order EC reactor was low and the lightdissCN M H Gn sparate ou andflocculated sludge was predominant. When surface up-floatin:fYHcidification reactorward velocity increasing rapidly, lots of sludge waswhen water temperature was low. If the parafn layerwashed out, and the treatment efeet tumed bad.tumed too thick， it would cause the outlow tube.68●Jounal of Harbin Instiue of Technology (New Series)，Vol. 17, No. 1, 2010blocked. So hand-clean up the parafin layer regularlysis of wastewater from the main methanol distllation col-was necessary. It was suggested that parffin removalumns. Natural Gas Chemical Industry, 1995, 6: 31 -35.unit should be set in front of biological treatment[2] Li Weiguang. Research on Treatment and Reusing of LowConcentration Methanol w astewater. Harbin: Harbin Uni-process in future methanol wastewater treatment engi-versity of Civil Engineering and Architecture, 2000.neering design.[3] Meng Zhuo, He Yanling, Yang Shucheng. Study on metha-nol wastewater treatment by UASB reactor. China Water3 Conclusionsand Wastewater, 2006, 22(7):42 -48.[4] Zhao Hongbo. Treatment of methanol wastewater withTSTP presented well performance in the treatmentUASB process. Environmental Protection of Chemical In-of methanol wastewater. Toke granule sludge as the in-dustry, 1989, 9:6- 13.oculation sludge and accomplished the quick start-up[5] Zhao Hongbo. Some advices of methanol wastewater treat-ment by UASB settling. Water and Wastewater Design ofwithin 51 days. COD removal rate of hydrolytie acidifi-Chemical Engineering, 1998, 4:15-17.cation reactor was around 25%，and the total COD re-[6] Zhou Xuefei, Ren Nanqi. Acid resistance of methanogenicmoval rate of TSTP could reach to 90% - 92. 5%.bacteria in two-stage anaerobic process treating high con-When inflow COD of TSTP was between 7000 -centration methanol wastewater. ACTA Scientiae Circum-11000mg/L, efluent COD was less than 600 mg/L.stantiae, 2004 ,4(7) :633 - 636.At the same time , TSTP presented well ability of resis-[7] Zhou Xuefei, Ren Nanqi, Chen Manman. Treatment ofmethanol wastewaler with biological process. China Waterting shock loading when water quality fluctuated strong-and Wastewater, 2001, 17(4):50 -52. .ly. The EC reactor presented advantages such as water8] Shao Xiangwen. Treatment of High Concentration Methanoldistribution equality， well separating efect of threeWastewater Using an Anaerobic Sequencing Batch Reactor.phases and rapid formation of granule sludge. TheXi' an; Xi' an University of Architecture and Technology ,highest VFA of efluent from hydrolytic acidification re-2004.actor was 876 mg/L. Methanol in wastewater can be[9] Letinga G, Van Der Geest A T, Hobma s, et al. Anerobicused directly by methanogens bacteria, while in the bi-treatment of methanolic wastes. Water Research,1979, 13(8) :725 -737.ological process of methanol converted into methane ,the production of acetic acids as an intermediate prod-[10]Gatze L, Wilum D, Els 0. Anaerobie treatment ofwastewater containing methanol and higher alcohols. Wateruct can be ignored and the direct production of meth-Research, 1981 ,15(2):171 -173.ane from methanol was predominant.[11]Florencio L, Jenick P, Field J A, et al. Ffect of cobalt onReferences:theanaerobic degradation of methanol. Joumal of Ferenta-tion and Bioengineering, 1993, 75(5) :368 -374.[1] Zhang Juzheng, Qin Jinping, Qian Renyuan, et al. Analy-中国煤化工MYHCNMHG●69●