A CASE STUDY ON URBAN NON-POINT SOURCE POLLUTION CONTROL:THE HUIZHOU CHATING ECOLOGICAL REGULATION POND IN THE SHAHE RIVER BASIN OF THE DONGJIANG RIVER
To explore the seasonal efficiency of non-point source pollution in towns in South China,and deal with the low dissolved oxygen problem in the downstream tidal reach,this study took Huizhou Chating Ecological Regulation Pond(ERP)in Shahe River Basin,a tributary of Dongjiang River,as the monitoring object,and analyzed the migration and transformation process and treatment efficiency of pollutants along the river.The results showed that organic matter and phosphorus in ERP are mainly removed by sedimentation,filtration and retention,while nitrogen is mainly removed by biological nitrification and denitrification.In addition,the concentration of local dissolved oxygen in the pond is high,and the denitrification process is inhibited,resulting in NO3--N accumulation.On the whole,under the condition of 0.9％wetland/catchment area ratio,the treatment efficiency of the ERP system was stable,and the average reduction rates of COD,NH4+-N,TP and TN were 8.4％,59.3％,66.7％and 31.8％and 23.2％,52.9％,51.5％and 23.4％,respectively,in drought and rain seasons.Except for the limited removal capacity of TN and NO3--N,the other water quality indexes in the effluent complies with the Category V standard in the Environmental Quality Standard for Surface Water(GB 3838-2002),and the study can provide technical support for the control of non-point source pollution in surrounding towns.
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