Application Of IFAS+ Magnetic Coagulation Process In Upgrading Of Oxidation Ditch Process

This thesis takes the IFAS+magnetic coagulation process applied in the upgrading project of a sewage treatment plant in Urumqi as the research object.Starting from the actual engineering case,study the practical application of the combination of IFAS+magnetic coagulation process in the improvement of the standard,conducted a one-year water quality monitoring of the sewage inlet and outlet water quality and collected before the standard improvement（2015-2017）The water quality data of the sewage plant made a comparative study on the treatment effect of the sewage plant before and after the transformation.At the same time,the high-throughput sequencing method was also used to sample and analyze the biofilm on the activated sludge and biological filler in the aerobic section of the IFAS biological pool,and the microbial flora structure in the activated sludge and biofilm in the aerobic section was studied.Through the research on the IFAS+magnetic coagulation process applied to the sewage treatment plant in the improvement of the standard,it is expected to provide a reference for the improvement and operation management of the same sewage treatment plant.Through the analysis of the measured inflow and outflow indicators before the sewage treatment plant transformation,all reached the second-level discharge（no monitoring of TN）,measured according to the first-level A discharge standard,COD,BOD₅,SS,NH₄⁺-N and TP first-level A The compliance rates were 66.30%,53.42%,8.22%,74.25%and 22.74%,respectively.After adopting the IFAS+magnetic coagulation high-efficiency sedimentation tank process to upgrade the standard,the average effluent COD,BOD₅,SS,TN,NH₄⁺-N and TP indicators were 20mg/L,1mg/L,9mg/L,6mg/L,1.15mg/L and 0.07mg/L,all meet the Class A emission standard of"Emission Standard of Pollutants for Urban Sewage Treatment Plants"（GB18918-2002）.After half a year of operation,the effluent was stable,and samples of aerobic activated sludge and biofilm in the IFAS biological pool were taken,and the microbial flora structure was analyzed by Mi Seq Illumina high-throughput sequencing.It was found that the diversity of microorganisms in the biofilm was higher than that of activated sludge,and the dominant bacteria in the two samples were mostly microorganisms with nitrogen and phosphorus removal functions.It was found that at the phylum level,the abundance of dominant bacterial species in activated sludge and biofilms were different,but all of them the predominant phylums were Proteobacteria,Bacteroidetes,Actinobacteria,Campylobacter,Chloroflexi and Firmicutes.Seven phylums with lower species abundance were also detected in the biofilm,but they were not present in the activated sludge.The species composition varies greatly at the genera level.The dominant bacterial genera include Candidatus＿Microthrix（16.63%,2.06%）,norank＿f＿Saprospiraceae（7.68%,8.66%）,norank＿f＿Caldilineaceae（3.53%,2.11%）,unclassified＿f＿Comamonadaceae（4.33%,7.34%）,norank＿f＿Intrasporangiaceae（6.74%,1.72%）,Methylotenera（6.04%,1.10%）,Simplicispira（3.45%,3.16%）,Ferruginibacter（3.53%,2.11%）,Flavobacterium（1.51%,3.19%）,Albidiferax（2.29%,1.95%）,Rhodobacter（1.12%,0.798%）,norank＿f＿Xanthomonadaceae（0.689%,0.786%）.The genus of bacteria unique in biofilm is higher than that in activated sludge,but the species abundance is extremely low.Nitrospira and Nitrosomonas,which play a major role in nitrification,are present in biofilms and are almost absent in activated sludge.By analyzing the biofilm flora,it was found that the nitrifying functional bacteria Nitrospira（2.58%）and denitrifying functional bacteria Dokdonella（0.864%）and Dechloromonas（1.57%）were distributed in the biofilm,indicating that the IFAS biological pool is equipped with simultaneous nitrification and denitrification.Microscopic conditions.Through the above research,it is found that there is still room for optimization of the deamination capacity of this system.The method of controlling dissolved oxygen concentration and carbon-to-nitrogen ratio can be used to promote the occurrence of simultaneous nitrification and denitrification;The effect of dissolved oxygen on the environment of the pre-anoxic section;changing the water inlet method and proportion to improve the nitrogen and phosphorus removal capacity,increase the utilization rate of organic matter,and reduce the operating cost and other optimization measures.