Research On Combined Process Of UBF/Multi-Layered Biological Tricking Filter/Constructed Wetland For Rural Dispersed Livestock Wasterwater Treatment

China is a great country of livestock and poultry breeding.Although the proportion of large-scale farming has been increasing in recent years,traditional garden-style dispersed breeding farming is still prevalent.Traditional treatment processes are not suitable for the treatment of this kind of wastewater while the wastewater is small scale,fluctuating and difficult to collect.A sewage treatment system with combined process of UBF/multi-layered biological-tricking filter/constructed wetland was used to treat rural dispersed livestock wastewater,and the contaminant removal efficiency of combined process was investigated.With the experimental data,the optimal running conditions are obtained which can provide the experiences for continued treatment tasks.The study shows that:1.The UBF/multi-layered biological-tricking filter/constructed wetland combined process had excellent performance on treating rural dispersed livestock wastewater.Under the condition of HRT（UBF）,hydraulic load and HRT（constructed wetland）at 30 h,0.42 m³/（m²·d）,5 d and 35 mJ/cm² respectively while the concentration of influent isρ(COD_Cr)=760¹448mg·L^-1,ρ（TN）=155.21⁴75.67mg·L^-1,ρ（NH₃-N）=90.0³01.93 mg·L^-1,ρ（TP）=3.16¹9.67 mg·L^-1,the mean removal rate of COD_Cr,TN,ammonianitrogen and TP were achieved 87.50%,71.79%,77.03%,91.17%respectively,meet the Discharge standard of pollutants for livestock and poultry breeding.2.When the HRT of UBF was controlled at 24h,30h,36h,the average removal rate of COD_Cr reduced with the extension of HRT,while the TN,ammonianitrogen,TP have no direct relation to HRT.Considering construction investment and operation management,select the optimal hydraulic retention time for 24 h.3.While the hydraulic load was controlled at 0.42 m³/（m²·d）,biological-tricking filter reached the best removal efficiency,the average removal rate of COD_Cr,ammonianitrogen and TP were 72.15%,57.25%,49.66%respectively.The removal rate of TN reached the highest under the condition of hydraulic load at 0.66 m³/（m²·d）,the average removal rates were 26.03%.Because of the/multi-layered biological-tricking filter for TN removal effect was not obvious,considering removal optimization of COD_Cr,ammonianitrogen and TP,selected the 0.42 m³/（m²·d）as the optimum hydraulic load condition.4.While the HRT was controlled at 5 d,constructed wetland reached the best removal efficiency,the average removal rates of COD_Cr,TN,ammonianitrogen and TP were 59.82%,60.30%,71.70%and 90.86%respectively.5.While the reflux ratio was controlled at 1:1,the sysytem reached the best removal efficiency,the average removal rates of COD_Cr,TN,ammonianitrogen and TP were 88.18%,65.24%,81.04%,91.92%respectively.So adopting high reflux ratio can obviously enhance the removal efficiency for system.6.The concentration of total E.coil in dispersed livestock wastewater can reach up to 400000 MPN/100mL,which had reduced to 2000¹7000MPN/100 mL after combined process.Under the condition of uv dose of35 mJ/cm²,the concentration of total E.coil in Ultraviolet sterilization effluent did not exceed 15 MPN/100mL,met the emission standards.