Study On Water Quality Adaptive Control Technology Of Haihe River Main Stream Combined With Target And Capacity Control

Due to the impact from shortage of natural runoff and the sluice control of dam,the Haihe River main stream has become a typical artificial water level controlled slow-flow and stagnant landscape river.In recent years,a series of water environment and landscape problems have occurred e.g.water quality deterioration after rainstorm,algal bloom burst.The Water Pollution Control Action Plan(referred to as"Water Ten")issued by the State Council in 2015 sets the overall requirements and major objectives for the prevention and control of water pollution in rivers and lakes including the Haihe River main stream.As the most important landscape river and reserve water source in Tianjin,the water quality maintenance and improvement of the Haihe River main stream will be an important part of the work of"Water Ten"in Tianjin.Thus the Haihe River basin urgently needs to be studied and formulated a scientific and reasonable load control scheme for the basin pollution source(point source and non-point source)based on the water quality of the section.Based on the GIS technology,the Haihe River main stream is divided into four control units:the confluence section,the upstream section,the middle section and the downstream section.Water pollution load input and water environment capacity of both the point source and non-point source were calculated in terms of the diversion period(April to November)and non-water-diversion period(December to March).Moreover,the control plan for controlling the water quality of the section is proposed,with the hope to provide technical support for the improvement of the water environment.The main research contents and results of this studies are as follows:(1)Based on pollution sources investigation in recent years,the river pollution input in the Haihe River main stream was calculated.The calculation result data showed that the downstream section of the Haihe River owns the highest total pollutant input:COD_Cr2518.07 t/a,NH₃-N380.32 t/a,TN638.10 t/a,and TP31.51 t/a.The non-point source pollutant input of COD_Cr,NH₃-N,TN and TP are the highest in the middle reaches of the river,which are 5633.44 t/a,141.75 t/a,328.48 t/a,86.87 t/a.The non-point source pollution input formed by storm runoff is the most important contribution source of non-point source pollution into river load.(2)By applying one dimensional model and reservoir model,calculation model of water environment capacity for the Haihe River main stream was established.During the water diversion period,the ideal water environment capacity of COD_Cr,NH₃-N,TN and TP in the Haihe River main stream is 36477.07 t,935.89 t,833.81 t,97.92 t,respectively,due to the fixed external water input.To ensure the water quality permit standard,the pollution load reduction should reach 27.8%,84.87%,90.96%,23.17%for the confluence section,the upstream section,the middle section and the downstream section,respectively.In the non-water diversion period,the ideal water environment capacity of COD_Cr,NH₃-N,TN and TP in the Haihe River main stream is 415.98 t,10.44 t,0.44 t,2.09 t,respectively.The point source pollution input load far exceeds the ideal water environment capacity.To ensure the water quality permit standard,the pollution load reduction should reach 94.18%,96.49%,89.61%and96.81%,for the confluence section,the upstream section,the middle section and the downstream section,respectively.(3)Taking the total capacity control as the core,this study puts forward the total emission control requirements with the adaptive management scheme for the Haihe River main stream.The adaptive management of water quality target of the Haihe River main stream mainly includes five stages,such as problem identification,scheme design,scheme implementation,monitoring and evaluation,and scheme adjustment.In particular,in management practice,the results of scheme implementation should be monitored and evaluated in a timely manner,and the water quality improvement objectives and specific scheme should be adjusted in time through feedback.The water quality improvement of the Haihe main stream should focus on the reduction of exogenous nutrient load through engineering/management measures.And the water system interconnection,ecological remediation,and algae bloom emergent treatment should be also considered.The water quality adaptive management plan for the Haihe River main stream,has been adopted by the Tianjin Ecological Environment Bureau.It is applied in the second part of the?Tianjin Water Pollution Prevention and Control Work Plan?to assist in the formulation of pollution discharge and urban living pollution control programs.