Optimal Design of a Distributed Treatment System for Increasing Dissolved Oxygen in Watersheds through Self-Rotating Discs

Dissolved oxygen in water bodies is a property of major importance for sustaining aquatic life in watersheds. Because of the increasing pollution discharges in watersheds around the world, there has been a consistent reduction in the levels of dissolved oxygen. Self-rotating discs ``SRD{''} are low-cost devices that can increase the level of dissolved oxygen in watersheds. The design of SRD systems involves the determination of the number of rows of discs, spacing between discs, and flow rate to be treated. In this paper, a general optimization framework is presented to determine the optimal design of a distributed treatment system to increase the dissolved oxygen in the watersheds based on self-rotating devices. A material flow analysis model is coupled with the performance functions of the SRD. The optimization model is aimed at selecting the tributaries that require treatment, determining the flow rate to be treated, and designing the number and spacing of the SRD. The methodology is applied to a case study corresponding to the Bahr El-Baqar watershed in Egypt. The results are displayed through Pareto optimal solutions that trade off the economic and environmental objectives.