Study On The Combined Process Of Sulfate Reduction And Mixotrophic Desulfurization Denitrification For Wastewater Treatment

With the rapid development of China's economy,industries such as mining plants,tanneries and chemical plants produce large amounts of wastewater,which contains high concentrations of sulfides,sulfates5 nitrates,nitrites and organic carbon.These contaminants which are discharged to natural water bodies are harmful to ecological environment and human health.Because of this,the comprehensive treatment of such wastewater is of great significance.In this research,sulfate reduction and mixotrophic desulfurization-denitrification were used to remove sulfate,organic compounds and nitrogenous compounds in wastewater simultaneously.The sulfate reduction reactor and mixotrophic desulfurization-denitrification reactor were connected in series to form a series process.The influent parameters and hydraulic residence time were adjusted to analyze the simultaneous removal rules of carbon,nitrogen and sulfur;The activated sludge in the desulfurization-denitrification reactor in series process was collected,and the bacteria were isolated,purified,identified and the functions of bacteria were analyzed;The upflow anaerobic reactor with a sleeve was designed,and the sulfate reduction reaction and mixotrophic desulfurization-denitrification reaction were placed in the same reactor to form an integrated process.The simultaneous removal rules of carbon,nitrogen and sulfur were investigated;The activated sludge samples from the inner sleeve region,outer sleeve region and cross region of the integrated reactor were extracted,and the microbial community characteristics were analyzed by high-throughput sequencing method,and the metabolic characteristics of microorganisms were analyzed together with the degradation characteristics of various pollutants,so as to clarify the simultaneous removal mechanism of carbon,nitrogen and sulfur.The main research results are shown as follows:(1)The simultaneous removal of sulfate,organics,nitrate and nitrite was realized by the series process of sulfate reduction and desulfurization-denitrification,and the removal efficiencies reached 94.1%,97.7%,99.1%and 94.0%,respectively.Among them,sulfate was first converted to sulfide,and its conversion efficiency reaches 97.5%,and sulfide was finally oxidized to elemental sulfur.Nitrites and nitrates were reduced to nitrogen.(2)The functional bacteria in desulfurization-denitrification part of series processing were separated and purified.24 strains were obtained,among which 1 strain of bacteria had strong ability to degrade sulfide and nitrate and had higher homology with Ciceribacter thiooxidans.This strain of bacterium could degraded S2-and NO3-for 100%and 98.3%in 48 hours.This result confirmed the effectiveness of the integrated process in simultaneous removal of sulfur and nitrogen from the perspective of functional microbes.(3)The sulfate reduction reaction and mixotrophic desulfurization-denitrification reaction were put into the same reactor to form an integrated process.The upflow anaerobic reactor with a sleeve was started up to realize the simultaneous removal of sulfate,organics and nitrogen compounds,with the removal efficiencies of 84.5%,99.3%and 99.5%,respectively.(4)The microbial community structure in the integrated process was analyzed,and the microorgahisms in the activated sludge were classified by phylum.The relatively high abundance phylum mainly included Proteobacteria,Bacteroidetes,Chloroflexi,Firmicutes and Synergistetes.The genera with relatively large abundance in sulfate reduction unit were Desulfobacter,Thermovirga,unidentified Anaerolineaeea,Fastidiosipila and Desulfuromonas.The abundances were 14,4%?17.9%,9.6%?14.1%6.5%?8.3%,4.0%?6.2%and 2.7%?2.5%,respectively.All these bacteria had the function of the sulfate reducing or anaerobic fermentation,which were correspond to the higher efficiency of sulfate.The genera with relatively large abundance in mixotrophic desulfurization-denitrification unit were Thiovirga,Thauera,Pseudomonas and Fastidiosipila and their abundance were 6.7%?10.6%,4.7%?8.3%,1.9%?3.8%and 3.2%?5.8%,respectively.All these bacteria had the function of autotrophic desulfurization-denitrification or heterotrophic denitrification,corresponding to the high removal efficiencies of nitrogen and sulfur.