Eliminating non-point source pollution in a pre-dam complex system in the Tangma Reservoir,Jiangsu Province

In this study,the efficiencies of a pre-dam complex system for non-point source pollution control was investigated for the management of the Tangma Reservoir in Liyang City,Jiangsu Province.The pre-dam complex is composed of settling area(A),shallow-water area(B),deep-water area 1(C),deep-water area 2(D),surface flow wetland(E),and biological membrane purification area(F).The results showed that the pre-dam complex system under the study contributed to significant improvement in the quality of agricultural non-point source pollution flowing through the pre-dam.The removal of TN,TP,CODCr could be up to 67.2%,68.2% and 89.3%,respectively,when the retention time was 1 d.The removal efficiency was increased with increasing of retention time,while the increment was small and stable.Moreover,increased areas(E and F) could significantly improve the removals of SS,TN,TP and CODCr,particularly the smaller SS which was consisted of size less than 15μm.Furthermore,based on laboratory results,it was suggested that the retention time be 2-3 d in the Tangma project,and the system be optimized to improve the purification efficiency and high utilization of the area.