Treatment Of Methanol Wastewater By Hydrolytic Acidification & Two-Stage Anaerobic Process

With the development of treatment effect, running stability, ability of resisting shock loading and automatic control mode, the application scope of anaerobic process expands continuously and shows obviously advantage in high-strength industrial wastewater treatment. However, there are some defects of single phase anaerobic reactor when treating high-strength organic wastewater with rapid changes of water quality, such as"acidification"risk. In this study, Hydrolytic Acidification & Two-Stage Anaerobic process (HATS) was developed which based on Two-phase anaerobic and SMPA theory and used External Circulation anaerobic reactor as treating unit.Early work was finished in laboratory with purpose of ehancing the process treating efficiency, running stability such as the optimizing the ecological factors. Based on these results, the pilot-test project of high-strength methanol wastewater was established. The design and operation parameter was optimized steadily which provided technological support to methanol wastewater treatment.In laboratory studies, the ethanol-type fermentation formation of hydrolytic acidification reactor was studied with seeded with anaerobic granular sludge, controlling volume loading rate, loading rate raising range, pH, etc. Test showed that reactor was quick start-up in 34d and formed the ethanol-type fermentation with controlling volume loading rate, loading rate raising type, pH, etc. The mass concentration of ethanol + acetic acid was 75.9 percent of liquid terminal products.The treatment efficiency of Two-Stage ananerobic reactor was studied with seeded with anaerobic granular sludge. Test showed that 1# reactor COD removal rate reached to 93.2% under VLR=46.78kgCOD/m3·d, HRT=5.62h. 2# reactor COD removal rate reached to 85.2%. The total COD removal rate reached to 98.9%. The Two-stage anaerobic system also presented well VFA removing ability with effluent VFA below 10mg/L.The physical properties and microbial community composition of anaerobic granule sludge seeded in hydrolytic acidification reactor was studied. And the forming way of acidizing granule sludge was also primarily explained in this paper. In hydrolytic acidification reactor, the anaerobic granular sludge transformed to acidizing granule sludge with controlling proper volume loading rate, loading rate raising type, low pH. The color of granular sludge turned from black to yellowish brown, faint yellow, cream white or caesious with preferable particle size and well settling performance which was helpful to hydrolytic acidification reactor retaining enough microbial biomass.The dominant microflora of hydrolytic acidification reactor was Brevibacterium and Spore bacteria. The dominant microflora of 1# reactor was Methanosarcina barkeri. Methanothrix soehngenii was the dominant microflora of 2# reactor. Other Methanogens also appeared, but less.The ecological factors which had effects on HATS treating efficiency was studied in this paper, such as temperature, pH values, VLR, HRT, etc. And the Optimal parameter set was determined. The kinetic model of each reactor in HATS was established and the kinetic parameter was deduced.Based on experitmental results, the pilot-test project of high-strength methanol wastewater was established and the start- up and treatment efficiency of HATS was studied. Test showed that toke granule sludge as the inoculation sludge of Two-Stage reactor, HATS accomplished the quick start-up within 50 days. The fermentation type of hydrolytic acidification reactor was mixed-fermentation. The sequence of liquid terminal products was acetic acid > propanoic acid > butanoic acid > pentoic acid. Maximum effluent VFA of hydrolytic acidification reactor was 14.6mmol/L. The low VFA concentration was related to the water quality characteristics of methanol wastewater and anaerobic stage treatment.COD removal ability of Two-stage anaerobic system increased with the enhancement of VLR. At the end of start-up period, COD removal rate of ECA reactor was about 85% and that of ECB reactor was about 80%. The total COD removal rate of Two-stage anaerobic system could arrive to 95.3～98.1%. When the influent COD of HATS was between 7000～11000mg/L, effluent COD was lower than 300mg/L.Shock loading caused by strong fluctuation of water quality did not influence the stable running of HATS. Effluent COD was always below 450mg/L, and effluent water quality was stable. The HATS presented well ability of resisting shock loading.