Enhanced water quality modelling for optimal control of drainage systems under SWMM constraint handling approach

Phosphorus and nitrogen are two important nutrients to plants. Therefore, fertilizers usually used in agricultural lands hold a significant amount of phosphorus and nitrogen. Even though these two are essential for plants, they are treated as pollutants when they are contaminated to the fresh waters. Therefore, phosphorus in stormwater runoff is a concerned topic for combined sewer overflows (CSOs). Rathnayake and Tanyimboh's optimal control model was capable of handling five different water quality parameters (chemical oxygen demand, bio-chemical oxygen demand, total suspended solids, total Kjeldhal nitrogen and nitrates and nitrites) in CSOs. However, the enhanced approach is capable of integrating phosphorus concentrations into the analysis of water quality from CSOs. The new optimal control model for drainage systems was run and compared against the previous work by the author. Promising findings are illustrated from the newly developed model in controlling drainage systems.