Experimental Study On The Treatment Of Initial Rain Runoff Pollution In Baoding City By Artificial Rapid Infiltration System

At present,rainfall runoff pollution has become one of the main factors causing urban water environment pollution,especially the initial rainfall runoff pollution seriously affects the water quality of urban inland rivers.The Fu River flows through Baoding City and Xiong’an New Area,and finally injects into Baiyangdian,which is one of the rivers with water entering the precipitation all year round,and its water quality has a direct impact on the quality of Baiyangdian water environment,so it is of positive significance to carry out research on the characteristics analysis and control technology of rainfall runoff pollution in Baoding City to improve the water environment quality of the Fu River and Baiyangdian.The artificial rapid infiltration system is a low-cost,effective and simple management technology for rainfall runoff pollution purification.Based on the investigation and analysis of the characteristics of rainfall runoff pollution in Baoding,the feasibility of using artificial rapid infiltration system to treat the initial rainfall runoff pollution in Baoding was investigated,and research on filler screening,parameter optimization,purification law and purification capacity restoration was carried out.The pollution characteristics of rainfall runoff from different functional areas in Baoding were investigated and analyzed,and different types of functional areas,such as residential areas,commercial areas and factory areas,were selected for the study.The COD concentrations in the initial rainfall runoff from residential,commercial and factory areas were 24～625mg/L,16～552mg/L，32～784mg/L;NH4+-N concentrations were 1.95～11.12mg/L,2.40～15.60mg/L,1.35～12.52mg/L;TN concentrations were 2.31～It is concluded that the rainfall runoff in Baoding City is seriously polluted and direct discharge will have a greater impact on the water quality of the receiving water bodies.The filtering media of the artificial rapid percolation system were selected,and the static adsorption test was carried out by choosing green zeolite,clay vitriol and oyster shell as fillers.The adsorption capacity of the three fillers for NH4+-N was green zeolite>clay ceramic pellets>oyster shell in descending order;the adsorption capacity of TP was oyster shell>clay ceramic pellets>green zeolite in descending order;the adsorption capacity of COD was green zeolite>clay ceramic pellets>oyster shell in descending order.A pilot study of artificial rapid infiltration system for the pollution purification of primary rainfall runoff in Baoding was conducted,and two artificial rapid infiltration systems with different filler combinations were used to treat primary rainfall runoff.The results showed that the removal rates of COD,NH4+-N,TN and TP could reach 92.27%and 95.12%,76.13%and 80.32%,76.31%and 75%,68.95%and 77.20%for system 1#and 2#respectively after 30 days of operation of the two systems,which proved that the system had better purification effect on the pollution of initial rainfall runoff.The parameters of the artificial rapid infiltration system were optimized by changing three operating conditions of wet-to-dry ratio,hydraulic load and hydraulic load cycle.The optimal operating parameters of the artificial rapid infiltration system were determined as wet-to-dry ratio 1:3,hydraulic load 2m/d,and hydraulic load cycle 12h.In order to further improve the feasibility of the artificial rapid infiltration system in practical engineering,the removal pattern of pollutants along the system and restart test research were investigated.The test results showed that most of COD,NH4+-N and TP were removed in the upper layer of the filler,and the removal of TN was mainly concentrated in the lower filler section of 110～150cm.After the artificial rapid infiltration system was restarted after one month of drying,it was concluded that both systems could recover the removal capacity of major pollutants in rainfall runoff faster,but the addition of oyster shells and clay pellets could make the system recover the removal capacity of pollutants faster and better.This study shows that the artificial rapid infiltration system has a good purification effect on the primary rainfall runoff pollution in Baoding City,which provides a theoretical basis for the practical application of the artificial rapid infiltration system to treat the primary rainfall runoff pollution in Baoding City.