A bi-level multiobjective optimization model for waste load allocation in rivers

It is often difficult to apply existing waste load allocation (WLA) models to management institutions at all levels of the river basin because the existing WLA models do not consider the principles of fairness and efficiency at each management level of the basin. The implementation of environmental protection tax law has also greatly impacted WLA. This paper proposes the bi-level multiobjective allocation model under an environmental protection tax law to solve the WLA problem for different management levels. The upper allocation targets the minimal environmental Gini coefficient and the minimal unit pollutant emission cost. The impact of the environmental protection tax is also considered. The targets of the lower-level allocation are the maximal industrial output value and the minimal unevenness of reduction rates. The proposed model was applied to the case of the Wei River basin, and the results demonstrated that the bi-level multiobjective allocation model could solve the problem of WLA under an environmental protection tax law. Each level of the bi-level multiobjective allocation model considers the principles of fairness and efficiency to distribute the load in the basin, thereby offering a better reference for decision-makers at both levels.