污水管网内污染物去除动力学分析及模拟OA

This study investigated the removal characteristics of key pollutants in sewer networks and their impact on the influent carbon-to-nitrogen(C/N,calculated as COD/TN)of the wastewater treatment plants(WWTPs).The distribution of the C/N in source wastewater was characterized by sampling at sewage discharge outlets.Using an adjustable sewer network research and validation system at the Kunshan Water Environment Treatment Research Base,pollutants removal over 144 h was monitored under high-and low-velocity conditions(0.491 m·s-1 and 0.089 m·s-1,respectively).COD and total nitrogen(TN)removals were fitted using pseudo-first-order kinetics.Combined with user discharge water-quality data,C/N variations within the sewer network were simulated.The results indicated that the effluent C/N was dependent upon the user type and discharge time.Pilot-scale experiments demonstrated that removal rates for COD(including SCOD and PCOD),five-day biochemical oxygen demand(BOD5),and suspended solids(SS)over 144 h were all approximately 80%,with higher removal observed under low-flow conditions.In contrast,the system exhibited an inferior removal efficiency for TN,NH3-N and TP in general.Kinetic fitting results demonstrated that the COD removal rate constant exceeded that of TN,and both decreasing at higher flow velocity(kCOD=0.016 7 h-1,KTN=0.002 9 h-1 at low velocity;kCOD=0.012 7 h-1,KTN=0.002 0 h-1 at high velocity).Simulations based on the average mass concentration of actual source pollutants indicated that the time required for the C/N to decline to the denitrification threshold(4.50)was 12.24 h under high velocity and shortened to 9.49 h at low velocity.These findings showed that a higher flow velocity effectively retarded the decline of the C/N.Therefore,regulating the sewer flow to shorten the hydraulic retention time of wastewater is crucial for maintaining a suitable C/N in the terminal sewage and ensuring the denitrification efficiency at WWTPs.