Nitrogen Removal Efficiency Of Sulfur Autotrophic Denitrification System With Limited Carbon Electron Donor Intervention Impact Study

At present,the main problem faced by sewage treatment plants in the treatment process of low C/N domestic sewage is that the TN removal rate is very low,and the TN concentration in the effluent is generally higher than the national "Level A" discharge standard.The secondary treatment water of sewage treatment plants often needs more advanced treatment technology,which significantly increases the cost of sewage treatment.Based on the deep denitrification technology of sulfur autotrophic denitrification,this study proposes an innovative sulfur autotrophic denitrification system with limited carbon electron donors,which is expected to solve the problems of the current heterotrophic denitrification filter such as low TN removal rate,COD secondary excess,high operating cost,and large sludge yield.It provides strong technical support for the implementation of special emission limit standards in some environmentally sensitive areas.In this study,three packed bed reactors(R1 reactor: heterotrophic denitrification reactor;R2 reactor: sulfur autotrophic reactor with limited carbon electron donor involvement;R3 reactor: sulfur autotrophic reactor)were designed,and the anaerobic activated sludge from Beijing Gaobeidian wastewater treatment Plant was used as the inoculated sludge.Taking heterotrophic denitrification system and sulfur autotrophic denitrification system as reference,based on the sulfur autotrophic denitrification system with efficient denitrification,the effect of limited carbon electron donor intervention on the nitrogen removal rate of sulfur autotrophic denitrification was explored.The contents of this study mainly include the following aspects:(1)In phase I(start-up phase),the influence nitrate concentration of R1 reactor,R2 reactor and R3 reactor was 15 mg/L,and the empty bed contact time(EBCT)was gradually reduced from 5h to 0.5h to complete the rapid start-up of the reactor.Then,in order to show the differences between the treatment effects of each reactor,the nitrogen nitrate concentration in the effluent of the reactor was gradually increased from 15mg/L to 45mg/L in stage II(acclimatization stage).In the stable operation,the average nitrate degree of the effluent of R1 reactor is 43.00mg/L,indicating that only a small part of the external carbon source provides electrons for the heterotrophic denitrification reaction.The nitrate concentration of the effluent of R2 reactor and R3 reactor are 11.75 and 11.87mg/L,respectively,indicating that the external carbon source has almost no effect in the reactor.Or the additional carbon source inhibits the progress of the sulfur autotrophic denitrification reaction,which is different from the previous research results.Observing the reactor,the packing appears to aggregate into blocks,which is called packing compaction in this paper.Therefore,it is speculated that the additional carbon source causes packing compaction,reduces the effective action volume of the packing,and inhibits the progress of the sulfur autotrophic denitrification reaction.Therefore,in stage III,the backwashing frequency was enhanced from once a day to twice a day.The effluent nitrate and nitrogen concentrations in R1,R2 and R3 reactors were 39.09,11.67 and 11.34 mg/L,respectively,and the effluent nitrous nitrogen concentrations were 2.73,1.44 and0.10mg/L,respectively.The decrease of nitrate and nitrogen concentration in R1 reactor indicates that the compaction can be effectively removed by increasing the backwashing frequency.Reasonably,the backwashing frequency(stage IV)was increased again to 4 times a day.At this time,the effluent nitrate and nitrogen concentrations were 37.08,3.21,11.50 mg/L,and the effluent nitrous nitrogen concentrations were 3.42,0.18,0.17 mg/L,respectively.The NO3 / N concentration of the effluent from R2 reactor was 8.29 mg/L lower than that from R3 reactor,and the NO3 / N concentration of the effluent from R2 reactor reached the Sanitary Standard for Drinking Water(GB5779-2006),which indicated that the addition of sodium acetate could improve the denitrification rate of the sulfur autotrophic denitrification reactor.(2)Reveal the mechanism of inhibition of denitrification effect after limited carbon electron donor intervention in the process of sulfur autotrophic denitrification:In order to explore the reasons for the above phenomenon,the pressure loss in each area of each reactor,ATP on the surface of the filler,biological structure characteristics and extracellular polymeric substances(EPS)were analyzed.The experimental results show that the involvement of limited carbon electron donor increases the EPS in the reactor system,the filler is cemented,and the filler is cemented,and the dead zone will form.The denitrification reaction was inhibited,resulting in unsatisfactory denitrification effect.(3)After the three reactors R1,R2 and R3 were in stable operation,microbial samples were extracted by using the fillers of each module of the reactor,and the microbial community structure and species abundance were studied.Analysis of16 Sr DNA high-throughput sequencing results showed that the microbial diversity in the system was significantly reduced after the addition of carbon source,and the abundance of unclassified＿f＿Comamonadaceae in the sulfur autotrophic denitrification system was increased by the addition of sodium acetate.