Study On Bio-enhanced Treatment Technology Of Discontinuous Flow Rural Wastewater

Aiming at a series of problems caused by the large change of sewage discharge and frequent cut-off in rural areas,this study is committed to building a discontinuous flow biological enhanced treatment system of rural sewage coupled with sludge fermentation.This system builds a fermentation system on the basis of traditional AAO.The sludge fermentation liquid is mixed with the secondary effluent of the biological system,and the mixed liquid is used as the supplementary water for the system when the flow cutoff occurs.Under the condition of cut-off flow,the self-sufficiency of biological treatment substrate and the efficient and stable removal of pollutants can be realized,which provides ideas for the practical treatment of rural sewage.The main research results of this paper are as follows.（1）The influences of the working conditions with the cut-off time of 4h,8h,12h and16h on the strengthening system were analyzed and compared.The mixture of sludge fermentation liquid and secondary effluent was used as the system water intake to supplement the carbon source during the cut-off period.The energy efficiency of nitrogen and phosphorus removal and sludge activity of the bio-enhanced treatment system under different working conditions were explored.Through the detection of nitrification rate,denitrification rate,phosphorus release and phosphorus uptake rate and the change of dissolved organic matter,the operation mechanism of the strengthening system was studied.The results show that the bio-enhanced treatment technology can continuously maintain the nitrogen and phosphorus removal capacity of the biological system when the flow is cut off.With the increase of the cut-off time,the ability of the system to remove pollutants was strengthened.The system effluent COD,NH₄⁺-N,and TN can all meet the limits of the first-class A standard,the effluent TP can meet the first-class B standard limit,and the system sludge activity was good.（2）In order to further verify the effectiveness of bio-enhanced treatment technology in dealing with discontinuous flow of rural sewage,a device with an effective volume of10.24 m³ and an influent flow rate of 0.3-0.5 m³/h was built in the town-level area for practical application research.The research focuses on the nitrogen and phosphorus removal performance,sludge activity and microbial population structure of bio-enhanced treatment system in practical applications.The results show that the COD,NH₄⁺-N and TN of the effluent from the system can meet the limits of the first-class A standard when the non-continuous flow rural sewage was treated by the bio-enhanced treatment technology.By increasing the daily sludge discharge,the effluent TP of the system can meet the limit of the first-class B standard,and the sludge activity of the system was good.（3）In order to study the effect of biological enhanced treatment technology on microbial population structure,through high-throughput sequencing,the diversity of microbial populations in the enhanced system and the growth of various functional bacterial genera were studied under different working conditions.The results showed that the dominant bacterial phylum in the bioaugmentation system was Proteobacteria,with an average relative abundance of 29.22%in different periods of cut-off time.Microbial population diversity was good.During the 4h,8h,12h,and 16h periods of cut-off,the relative abundances of Denitratisoma were 0.93%,0.86%,0.98%,and 0.73%,respectively.The relative abundances of Thauera were 0.57%,0.50%,0.59%,and 0.43%,respectively.Compared with the stable operation of the AAO system,it was improved.Nitrobacter and Phosphorus can also maintain a certain relative abundance.The overall functional bacteria in the system were active.Bio-enhanced treatment technology can maintain the system microbial diversity and the activity of functional bacteria in the event of cut-off.