Study On The Treatment Of Low Carbon Source Wastewater And Its Microbial Community Dynamics In Small Towns By Bioaugmentation And Solid Carbon Sources

At present,most of the urban sewage treatment plant emission standards for water quality implementation of the discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002)level of B standard.With the improvement of the national pollutant emission reduction requirements,all sewage treatment plants are facing a more stringent standard(A level standard)requirements,ammonia and other indicators are also included in the control standards.Aiming at the long-term existence of low-carbon source,low-sludge activity and low microbial abundance of small-scale urban sewage treatment plant,a combination of natural solid carbon sources and bioaugmentation(nitrifying bacteria,denitrifying bacteria and aerobic denitrifying bacteria)combined to deal with low-carbon source wastewater.Using Illumina Miseq to analyze the microbial community structure and its dynamic changes of small test experiment sludge and experiments of corn cob,fiber ball and sludge before and after experiment.The COD,NH4+-N and TN indexes of water quality were monitored in the laboratory experiment and field test.In order to observe the treatment effect of low carbon source wastewater in small towns,the combination of bioaugmentation agent and carbon source of corncob was used to simulate the actual operation state of Linjiang wastewater treatment plant in Kaixian by using a small scale CASS reactor.The results showed that the biodegradation rates of NH4+-N and TN were increased by 26.33% and39.18%,respectively.The effluent concentrations of COD,NH4+-N and TN were up to level A in the whole experiment.The experimental group and the control group of sludge samples were detected by 31 kinds of bacteria,including Proteobacteria,Bacteroides,Saccharibacteria,Chlorobi,Chloroflexi and Firmicutes as the main bacteria,Chlorobi,Saccharibacteria,Proteobacteria relative abundance difference is relatively large.The relative abundance of ?-Proteobacteria,?-Proteobacteria,?-Proteobacteria,?-Proteobacteria,?-Proteobacteria and CFB-group were 66.55% and 62.85%,respectively,and were dominant in the sludge samples.The relative abundance of the Nitrosomonas,Nitrosomonadaceae uncultured and Nitrospira accounted for the total number of bacteria in the experimental group and the control group by 1.39% and 1.12%,respectively.There were 20 species of denitrifying bacteria,accounting for the total number of bacteria in the experimental group and the control group by 15.37% and 14.18%,respectively.The denitrifying bacteria of Thauera,Halomonas,Xanthomonadales uncultured,Thiobacillus and Hydrogenophilaceae uncultured are the common advantages of the experimental group and the control group.The microbial community richness and diversity of the sludge can be improved by adding the bioaugmentation agent and the solid carbon source,and the dominant bacteria can exist in the system for a long time.In order to optimize the structure of aerobic denitrifying bacteria,three aerobic denitrifying bacteria were screened from the soil of the river.The three strains were Klebsiella variicola,Acinetobacter sp.and Sphingobacterium sp.,which were Gram-negative bacilli.Nitrate was used as the sole nitrogen source to detect the denitrification ability.The three strains had the best denitrification ability in the logarithmic growth phase,and the nitrate removal rate was above 85%.K.variicola had nitrite accumulation at the end of the incubation period,and A.sp.and S.sp.had no such phenomenon.The best C/N of K.variicola,A.sp.,S.sp.were 9,12 and 12,respectively.The optimum temperature of K.variicola and A.sp.were 30?~40? and 30?~35?,respectively.The denitrification capacity of S.sp.achieve the best at the temperature of about 25?.When the DO(dissolved oxygen)was 2.7mg/L~ 7.6mg/L,the degradation rate of nitrate was above 94%,and the degradation ability of nitrite was increased with the increase of DO.When DO is greater than 2.7 mg/L,the nitrate degradation rate of A.sp.is above 83%.The nitrate degradation rate of S.sp.is above 84% when DO is greater than 5.4 mg/L.In the course of culture,A.sp.and S.sp.did not appear obvious nitrite accumulation.In the field test stage,the influent of Linjiang wastewater treatment plant showed obvious characteristics of low carbon nitrogen ratio.By adding solid carbon source and bioaugmentation agent to the reaction tank,the degradation rate of NH4+-N and TN was increased by 5.33% and 9.58% compared with the same period last year,and the average concentration of effluent reached level A standard.Twelve phylums were detected from corncob and fiber ball samples,including Proteobacteria,Bacteroidetes,Firmicutes,Actinobacteria,Acidobacteria,Nitrospirae and so on.The average relative abundance of Proteobacteria,Bacteroidetes and Firmicutes accounted for more than 10% of the total bacteria.At the beginning of the experiment,the relative abundance of Proteobacteria,Bacteroidetes and Firmicutes in corncob and fiber ball were different.With the progress of the experiment,the relative abundance difference between the corncob and the fiber sample was gradually reduced.?-Proteobacteria,?-Proteobacteria and CFB-group were the dominant microflora in corncob and fiber samples,and the relative abundance of flora in the corncob samples was higher than that of the fiber samples at each time.The average abundance of Nitrosomonas and Nitrospira was 0.41% and 1.28%,respectively,for the total number of autotrophic nitrifying bacteria.At the same time,13 species of denitrifying bacteria were detected in the samples.The average abundance of denitrifying bacteria was 11.68% and 8.43% of the total number of bacteria in corncob and fiber ball samples,respectively.Where Thauera and Dechloromonas are their common dominant denitrifying bacteria.By adding the bioaugmentation agent to the reaction tank,the relative abundance of the target microbial flora in the reaction tank was increased from 3.99% to 15.03%.The relative abundance of aerobic denitrifying bacteria such as Pseudomonas,Acinetobacter and Sphingobacterium increased from 0.02% to 1.55%.The bioaugmentation denitrification bacteria can be stable in the reaction tank for a long time,which can effectively improve the relative abundance of the target microbial flora and improve the system to improve the denitrification performance.