Treatment And Utilization Of Methanol Wastewater

Methanol is main pollutant in some specific wastewater or exists in wastewater as an intermediate product of organic decomposition under certain conditions.There are several industrial wastewater containing methanol,for instance,the condensate water from coal gasification plants,wastewater from pulp and paper industry,potato starch production plants and leachate from landfill sites.In addition,various laboratory testing instruments,such as liquid chromatography,are also a way to discharge methanol waste liquid.The toxicity of methanol has a great impact on the human nervous system and blood system.Methanol can be biodegraded under both aerobic and anaerobic conditions.The aerobic biodegradation rate of methanol is obviously faster than that of anaerobic biodegradation.However,due to the strong volatility of methanol,about 12%of methanol will be volatilized into the air during the aerobic process,which will transfer the organic pollution from water to the air.Therefore,aerobic treatment is not the best choice.Methanol has a complex anaerobic biodegradation pathway,it can be directly converted to methane by methylotrophs（methylotrophic methanogens）,or it can be converted with bicarbonate to acetate by acetogens,and the acetate can be metabolized by acetoclastic methanogens.In addition,methanol can also be converted to H₂ and CO₂,which can be used by hydrogenotrophic methanogens and/or acetogens to form methane and acetate,respectively.The direct methanogenesis is thermodynamically more favorable among all degradation pathways,while the other two pathways are metabolized through H₂ and acetate,respectively.Compared with the direct methanogenesis,the other two pathways have certain disadvantages.The acetate pathway requires the addition of bicarbonate,and the syntrophic pathway is difficult to enrich the corresponding functional bacteria.Methanol degradation is more efficient when methanol is directly consumed by methylotrophic methanogens.In this paper,anaerobic activated sludge is operated in batch mode and treated with simulated methanol wastewater.The anaerobic degradation of methanol can achieve excellent methanol removal without the addition of bicarbonate,and the p H range is6.0-7.0.The main research results include:（1）By adding 100 mg/L Vancomycin,the microbes stopped the hydrogenesis and acetogenesis process,so that methanol was no longer degraded by acetate and hydrogen pathways.However,the degradation rate of methanol did not decrease after adding vancomycin,which was slightly increased from 61.07(mg TOC·L^-1·h^-1)to 69.50.In the control group,the degradation of methanol was not affected by the cut-off of the hydrogenesis and acetogenesis process,indicating that the main degradation pathway was direct methanogenesis metabolized by methylotrophic methanogens.The possible reason for the acceleration of reaction was that vancomycin blocked the acetate pathway,and eliminated the accumulation of acetate,which alleviated the toxic effect of acetate on the methanogenesis process.（2）The addition of sodium bicarbonate in the acclimation stage increased the p H of the anaerobic system,which changed the microbial community in the anaerobic system,and finally led to the enhancement of the acetate degradation pathway of methanol.About 67%of methanol was converted to acetate and then metabolized to methane through acetate.However,the enhancement of acetate pathway did not accelerate the overall anaerobic degradation rate of methanol.On the contrary,the anaerobic degradation rate decreased to 16.77(mg TOC·L^-1·h^-1),which was 3.64 times lower than that of the control group.Therefore,in the anaerobic degradation of methanol,there is no need to add sodium bicarbonate to adjust the p H of the anaerobic system,and the direct conversion from methanol to methane is more efficient.（3）Waste methanol can also be used as a carbon source for denitrification.Compared with glucose,a traditional carbon source,methanol can be used by microorganisms more quickly.When methanol was added as carbon source,the total nitrogen removal rate k=4.53[(mg·L^-1)^0.55·h^-1],and when glucose was added as carbon source,k=1.36[(mg·L^-1)^0.55·h^-1].The denitrification rate with methanol as carbon source was 3.3 times higher than that with glucose as carbon source.