Study On Nitrogen Removal Performance Of Low Carbon Source Urban Sewage Treated By Corn Cob Solid Carbon Source Biofilm SND

The research uses corncob as the membrane carrier of solid carbon biofilm system and external carbon source,and uses simultaneous nitrification and denitrification（SND）technology to treat low carbon to nitrogen ratio urban sewage.The experiment was conducted to compare the different pretreatment methods of corn cob under normal temperature conditions.The startup characteristics of corncob solid carbon source reactor were studied.The effects of four factors including hydraulic load,DO,influent pH and influent C/N ratio on nitrogen removal efficiency were investigated.High-throughput sequencing was used to study microbial community structure along the system.Finally,under the best working conditions,the denitrification effect of the actual sewage treated by the reactor was investigated.Research indicates:In the comparison test of different pretreatment methods of corncob.The release of corncob COD_Cr reached the highest concentration at 72h,and the COD_Cr release process satisfied the second-order kinetic relationship;the concentration of heavy metal ions in corncob leaching solution met the relevant national standards.The denitrification efficiency of corncob pretreated by NaOH was significantly improved.When the static denitrification test was stable,the nitrate removal efficiency was maintained above 90%.In the three groups of static denitrification tests,the dominant bacteria of the system are:Proteobacteria and Bacteroidetes,which play an important role in the removal of contaminants.After the system was operated for 23 days,the average removal rates of COD_Cr,NH₄⁺-N and TN were maintained at 60%,90%and 89%,respectively,indicating that the reactor system SND was successfully started.When the biofilm was examined,it was found that there was a rich biological phase on the biofilm.In the factor test,the hydraulic load is 0.045m³·m^-2·h^-1,the dissolved oxygen is 4.0±0.1mg·L^-1,and the influent pH is 8.0±0.1.The system nitrogen removal effect can meet the first-class standard of effluent quality of sewage treatment plants.Nitrogen removal and microbial community structure analysis showed that the average TN removal efficiency of the effluent was 82.37%,and there was no accumulation of NO₂^--N.The solid carbon source biofilm reactor had good denitrification effect.The high-throughput sequencing results showed that the dominant bacteria in the system were mainly Bacteroides,thick-walled bacteria and proteobacteria.The results of real-time PCR showed that AOB was mainly concentrated in the middle end of the reactor,and the rate of ammonia oxidation decreased along the course.When the solid carbon source biofilm reactor is used to treat low carbon to nitrogen ratio,the average COD_Cr removal rate is 65.41%;the average NH₄⁺-N removal rate is 78.75%;the average TN removal rate is 77.46%,and the system has good sewage treatment effect.Through the above test results,it is fully verified that the agricultural waste corn cob is a viable natural solid carbon source material and microbial membrane carrier,and the system can realize the simultaneous nitrification and denitrification process efficiently.At the same time,the process is suitable for treating the current low-carbon-to-nitrogen urban sewage,which provides a new idea for the simultaneous nitrification and denitrification of solid carbon source biofilm to treat low-carbon urban sewage.