The Optimal Reuse of Reclaimed Water: A Mathematical Model Analysis

As recycling effluent from municipal sewage plants is technically a feasible way, this paper presents a mathematical model to analyze the extent to which effluent should be reclaimed for industrial use and examine the factor affecting reuse of reclaimed water. The resulting data shows that the low price of fresh water leads to reduced use of reclaimed water and impedes the investment of the effluent purification plant. A mandated regulation on the substitution rate of reclaimed water is suggested to impose on the industry. Theoretically, the optimal substitution rate as well as the water quality is determined by maximizing the total social welfare that results from the construction of conveyance channels and effluent purification plants. A case example is employed to derive the optimal substitution rate and water quality of reclaimed water. Through the numerical analysis, an effluent plant for treating 20,000 kl/day effluent with the substitution rate of 21.24 % is selected as the optimal solution.