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Inadequate water quality exacerbates global water resources scarcity. Hence, water quality of the river basin is increasingly perceived as a global obstacle to sustainable development because of the limited water carrying capacity. Efficient waste load permits (WLPs) allocation plays a critical role in enhancing water quality by controlling the emission cap. Considering transboundary water pollution and transaction among regions, a bi-level objective model is proposed to analyze the WLPs allocation based on the node-arc method. Motivated by alleviating regional development differences, the watershed management committee concentrates on equitable distribution of WLPs to regions. Furthermore, regional authorities focus on how to guarantee the maximum economic development and balance the WLPs emissions from the municipal, industrial, and agricultural sectors. Practicality and efficiency of the constructed model is demonstrated by applying it to Tuojiang River Basin. Through the analysis of the results, three management recommendations are proposed for Tuojiang River: strengthening the prevention of agricultural non-point source pollution, sticking to the cooperation between upstream and downstream regions, and speeding up the construction of sewage environmental tax system. The results illustrate that as the proposed method can control the total amount of sewage, it could provide decision-making references for the amelioration of water environment.

As the management of wastewater emission permits in watershed has become a growing worldwide concern, a substantial challenge has been created in balancing the social stability, economic construction, and ecological function. Therefore, the equitable and efficient allocation of wastewater emission permits in watershed integrating sustainability is vital for environmental management. Considering the wastewater discharge permits transaction between subareas, a multi-objective model is proposed to analyze the allocation of wastewater emission permits in a watershed. The first objective function is to maximize the allocation equity using the environmental Gini coefficient, and the second is to maximize the economic efficiency for the sustainable development of a watershed as the constraint. In this study, the trade-off between the equity and economic efficiency of allocation is balanced. A case study of the Tuojiang River Basin in China is conducted to demonstrate the feasibility, rationality and practicality of the model. The multi-principle and multi-objective allocation model was found to be more reliable and feasible than the previous models, indicating that the equity and efficiency should be balanced to mitigate the water scarcity and deteriorating water quality when managing the basin, and trading is an effective measure for ensuring the equity.

The treatment of airport sewage has posed many novel challenges because of its huge impact on the surrounding environment. This paper proposes a multi-objective decision model to optimize the scale design and process selection of sewage treatment plants in airports. In this model, we consider the conflict among the process cost, environmental protection, and benefits of recycled water. In addition, the uncertainty in influent concentration and passenger throughput is also incorporated. Airport sewage treatment has its own unique features, such as the concentration of airport sewage is higher than that of ordinary urban sewage, the change in passenger throughput impacts the volume of the airport sewage treatment, and the utilization rate of the entire sewage treatment plant must be higher than or equal to 70%. Only in this case can the airport sewage treatment plant pass the acceptance test. The Tianfu International Airport, the largest civil transportation hub airport project in southwestern China, is used to prove the efficiency of the proposed model. Finally, some significant insights are suggested for the design of wastewater treatment plants in airports.