Simulation–optimization method based on rationality evaluation for waste load allocation in Daliao river

The pollution of chemical oxygen demand (COD_Cr) and ammonia (NH₃–N) in Daliao river is severe, so it is urgent to reduce COD_Cr and NH₃–N load in Daliao river through waste load allocation. In this study, simulation–optimization method based on total load allocation rationally index (TLARI) was proposed for waste load allocation. The indirect coupled model of WESC2D and WASP was used to simulate hydrodynamic and water quality of Daliao river and calculate the response relationships between waste loads and water quality of Daliao river based on the 30B3 design flow. TLARI considering the three principles of fairness, efficiency and scientifically sound was used as the optimization objective or post-evaluation index for allocating suitable COD_Cr and NH₃–N loads to each sewage outlet. However, the allocation results showed that there was no need for COD_Cr and NH₃–N loads reduction after Yingkou paper mill closed if water quality of the upstream of Daoliao river meets the water quality of Class V. That means Daliao river was seriously polluted mainly due to the upstream pollutant loads. It is concluded that coupled WESC2D and WASP model and TLARI were well used in the waste load allocation in Daliao river.