A cooperative approach for waste load management in rivers

In a general river system, there are a set of pollution dischargers releasing their own produced waste load into it after an initial fractional treatment. In this paper inspired by the fact that some possible cooperation scenarios among the same single waste dischargers can lead to a more efficient quality control of the river, a new method for efficient river water quality management known as Cooperative Water Quality Management Approach was developed. The mentioned cooperation can be done through using a shared primary waste treatment process, and/or releasing the waste load into the river in an appropriate point along the river. In this approach, a sub-model embedded to a Genetic Algorithm optimization model was designed to simulate water quality of the river based on the modified Streeter and Phelps quality relations. Regarding the treatment levels of effluent dischargers, the optimization model minimizes the total waste treatment costs of the system. The model is able to calculate initial treatment levels (fractional removal percentages) and related costs for all the dischargers of the system in each single or shared waste disposing scenario. Meanwhile, the model can determine the best appropriate waste removal point for each one of the single or shared waste dischargers along the river in each disposing scenario. In this study, all waste discharging scenarios including both single and shared cooperation states among the dischargers, when the produced waste amount of each single discharger was defined, were considered by the model and optimum initial treatment levels (fractional removal percentages) and the best appropriate waste removal points for all the dischargers of the system were calculated in each scenario. Eventually, regarding the calculated costs of each waste disposing scenario, the best cooperation state was selected. The possibility of the cooperation among two or more dischargers in a river system are intimately related to financial issues, land availability, topographic condition of the river sides, effluent standards and also technical factors. The practical application of the proposed methodology was demonstrated through an actual case study of Zarjub River System located in northern part of Iran.