Experimental Study On Treatment Of Rural Domestic Sewage By Anaerobic Contact-Tidal Flow Wetland Integrated Device

Aiming at the ecological environment pollution problem of decentralized rural domestic sewage,this paper conducts a dynamic treatment experiment on rural domestic sewage through the combination technology of anaerobic contact reactor and tidal flow wetland.Combined with the enhanced removal effect of zero-valent iron on anaerobic contact reactor,it discusses the feasibility of anaerobic contact-tidal flow wetland combination integrated device to treat rural domestic sewage and the strengthening effect and mechanism of key control factors,providing technical support for the improvement of rural ecological environment.The main research results obtained are as follows:?1?For the anaerobic pretreatment unit,the optimal hydraulic retention time is 6h.Under this condition,the COD_cr influent concentration is 100-375mg/L,and the average removal rate of COD_cr and SS in the anaerobic reactor reaches 30%and 35%respectively.,to achieve a better pre-processing effect.After the anaerobic pretreatment unit enters the stable period,the average removal rate of COD_cr added to the iron powder is 35%,which is 7%higher than that of the uncoated iron powder.Compared with the control group,there is no phosphorus removal effect.The average removal rate of powder to TP is about 16%,and the addition of iron powder has an effect on phosphorus removal.?2?Three groups of tidal flow wetlands with different fillers had good removal effects on COD,ammonia nitrogen and total nitrogen pollutants.Total zeolite group had the best removal effects on COD?average removal rate was 76.2%?,ammonia nitrogen?average removal rate was 86.6%?and total nitrogen?average removal rate was 77.9%?,especially on ammonia nitrogen and total ammonia,which were obviously better than zeolite+volcanic rock group and zeolite+ceramsite group,but the three groups had the best removal effects.Apart from the good effect of physical adsorption in the early stage,the effluent concentration of total phosphorus after stable operation is on the high side,and the removal effect of total phosphorus is not ideal.Tidal flow wetland can effectively improve the oxygen environment in the matrix,and the highest dissolved oxygen in the nearest U?60cm?water can be increased to about 2.5 mg/L.The removal of organic matter in wetland system is mainly in the middle and upper layers of the wetland where the oxygen environment is better.The removal rate of organic matter can reach more than 80%.The removal rules of ammonia nitrogen and total nitrogen are similar.The removal efficiency of ammonia nitrogen is higher in the middle and upper layers,which can reach 97%.The complete removal of ammonia nitrogen is almost realized.The removal effect of phosphorus is weak in the whole process,and phosphorus release phenomenon exists.?3?Under the optimal process conditions(the hydraulic retention time of the anaerobic reactor is 6h,and the hydraulic load of the full zeolite substrate tidal flow wetland is 0.32m·3m^-2d-1),the contact reaction/empty bed is controlled to be 8h:8h,and the combined process is continuously and stably operated for more than 3 months.During the test,the influent concentration of COD_cr was 100mg/L?375mg/L,the influent concentration of NH4+-N was 8 mg/L?25 mg/L,the influent concentration of TN was 24mg/L?45mg/L,and the influent concentration of TP was 3mg/L-5.5mg/L.The average removal rates of COD_cr,NH4+-N,TN,and TP by the combined process were 86.3%,87.6%,77.9%and 12%,respectively.?4?Through the analysis of Shannon index at different points of three groups of different substrates,the diversity of bacterial communities in three groups of different wetland substrates is relatively rich,and the diversity of ceramsite medium substrate and zeolite lower substrate communities is relatively high.Eight dominant phyla were detected in the zeolite substrate experimental group of wetland system.Proteobacteria is the first dominant phyla in the zeolite substrate microbial flora.Microorganism diversity strains detected in zeolite substrate experimental group of wetland system are mainly divided into 15 genera,and functional bacteria genera with higher abundance such as Nitrospira,Nirosomonas,Hydrogenophaga and the like are found at the genus level.