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Waste load allocation (WLA) is a policy-making framework that can simultaneously consider multiple objectives, such as equity, environmental violations, and economic efficiency. This study developed a WLA framework focusing on equitable perspective from Rawls' theory of justice. For this purpose, the optimal scenarios were generated by calling the Streeter-Phelps equations for river simulation with the NSGA-II optimization algorithm. In addition, equity indicators were used to improve the optimization problem based on three objective functions simultaneously: minimizing treatment costs, environmental violation, and inequity. COPRAS method was also used to select the optimized WLA scenarios. Results showed that the optimal WLA scenario based on equity can improve the practicability of WLA in river system by deriving reasonably cost-effective and environmental friendly solutions with about 70% BOD removal for polluters in Haraz basin, northern Iran. Therefore, based on three dimensional multi-objectives WLA, equity could show its potential on highlighting optimal alternatives without extreme total cost or environmental violations. [ABSTRACT FROM AUTHOR]

Variations in quality or quantity of reservoir discharges and of wastewater treatment plants (WWTP) are typical sources of uncertainty in controlling and management of river water quality downstream. This study evaluates and discusses the impacts of these operation-based uncertainties on waste load allocation (WLA) policies, like water quality trading (WQT), by Monte-Carlo simulation. For this purpose, we chose the Sefidrud River in northern Iran and developed an economic-based WLA in this area through a simulation-optimisation approach. The river with 1150 reaches is simulated by coding in MATLAB and linked to a multi-objective particle swarm optimization (MOPSO) algorithm in which the two objectives are minimisation of environmental violations and abatement costs. For uncertainty analysis through Monte-Carlo simulation, river flow and kinetic rates, dissolved oxygen (DO) at headwater, pollution loads of dischargers, and temperature are considered as primary variables. Results show that the success of WLA is mostly reliant on the DO concentration of headwater, occurrence of seasonal floods, and river aeration rate. The implications of the findings are also analysed for WQT. In particular, the above uncertainties are highlighted as possible threats for the success of discharge permit markets because polluters could be penalised or rewarded for uncertainties regardless of their pollution discharges. Consequently, effective WQT under uncertainty is likely to lead to a need for more monitoring to resolve potential disputes from uncertainties. [ABSTRACT FROM AUTHOR]

This study focuses on the challenge of using a multiple pollutant transferable discharge permit market for operating wastewater treatment plants. It uses an analytical case of Sefidrud River in Iran with two checkpoints. It shows that the operating limitations for simultaneous biochemical oxidation demand (BOD) and total nitrogen (TN) removal may convert the economically optimal waste load allocation (WLA) to a framework with lack of incentives. Therefore, water quality trading (WQT) may lose its economical advantages. In this case, a third parameter, such as dissolved oxygen is recommended as an index for assigning market interactions. In spite of economical and practical success, this approach made WLA become a more complicated and uncertain policy. It was totally concluded that using single parameter WQT is only recommended for areas with small agricultural activities or lakes. Otherwise, the integrated discharged permit and reclaimed water market is proposed instead for simultaneous BOD and TN management. [ABSTRACT FROM AUTHOR]