Experimental Research On The SND Reactor Of Loofah Sponge Biofilm For Treatment Of Low Carbon And Nitrogen Ratio Domestic Sewage

The problem of low-carbon source and high-nitrogen is more and more prominent in southern China,and sufficient carbon source is an important condition for biological nitrogen removal.The effluent TN of secondary treatment can not meet the first class A standard,so it often needs advanced treatment.However,the lack of carbon source often inhibits the denitrification efficiency of microorganisms,so additional carbon source is needed.In this experiment,Loofah Sponge（LS）was used as the solid carbon source and biofilm carrier of the solid carbon source biofilm system,and the low carbon and nitrogen ratio domestic sewage was treated by simultaneous nitrification and denitrification（SND）process.The film start-up characteristics of LS biofilm SND reactor and its operation effect under different hydraulic retention time and different packing replacement ratio were investigated.The removal of nitrogen and COD_Cr in sewage by SND of LS biofilm reactor was investigated.The microbial composition in SND system of LS biofilm reactor was studied by fluorescence quantitative PCR and high-throughput sequencing technology In order to analyze the changes of microbial community structure and provide more accurate theoretical basis for the application of LS biofilm SND process in engineering practice.The main results are as follows:（1）The carbon release process of LS conforms to the second-order kinetics,and the carbon release process reaches a stable state earlier.The SND system of LS biofilm reactor was started up successfully after 22 days.The removal rates of COD_Cr、NH₄⁺-N and TN were more than 70%,75%and 65%,and the operation was stable.（2）The HRT of 12h is the best HRT.Under this HRT,the growth and enrichment of AOB,NOB and denitrifying bacteria in the system are good,and the average removal rate of TN is 70.7%.The effluent can meet the effluent standard of Grade A of WWTP.（3）In the discussion of the influence of LS replacement ratio on the system operation effect,the conclusion is drawn:when the LS replacement ratio is 40%,the system can better carry out SND denitrification,the removal effect is good,the average TN removal rate is 57.6%,the effective operation time is long,and the economic benefit is high.The abundance of denitrifying bacteria was one order of magnitude lower than that of AOB and NOB by fluorescence quantitative PCR,but the number of denitrifying bacteria increased with the operation of the reactor.（4）It could operate stably and the effect of SND was good when the SND system of LS biofilm reactor was used to treat the actual domestic sewage.The average removal rates of TN,NH₄⁺-N and CODcr were 76.2%,90.0%and 59.8%,respectively.The results of high-throughput sequencing technology show that Proteobacteria,Bacteroidetes and Planctomycetes are the dominant phyla in SND system,which play a very important role in biological treatment of wastewater.Through the above research results,it is fully verified that Loofah Sponge can be used as the external solid carbon source and microbial biofilm carrier in the biofilm SND reactor to realize the simultaneous nitrification and denitrification process,and the effect of using this process to treat the actual low carbon and nitrogen ratio domestic sewage SND is good,which provides a reference for the application of the solid carbon source biofilm simultaneous nitrification and denitrification process in the actual project Water provides a new way of thinking.