Modeling and simulation of an optimal unified tank model for aeration-sedimentation processes in wastewater treatment plants

The operation of Wastewater Treatment Plants (WWTPs) depend not only on the influent characteristics and air blown into the tank, but also the design of the tank structure. In this paper, the mathematical model of the aeration tank is derived by the dynamic equations of physical and biological processes. It is aimed to obtain an effective alternative model for secondary treatment. In the conventional approach, two separate tanks are used for aeration and sedimentation processes. A Unified Tank Model (UTM) for both phases is proposed and investigated in this research. To reach the desired optimized solution, a recently introduced metaheuristic method based on whale feeding behavior, named as Whale Optimization Algorithm (WOA) is used. The dynamic model of real system behavior in the proposed conditions is observed by computer simulation. The results are examined and discussed in the cases of the conventional approach and proposed alternative model. The optimization problems based on aeration system and dissolved oxygen (DO) concentration are defined to find optimal location of the diffusers in tank which is solved using whale optimization method. The optimal design shows better DO performance compared to the conventional approach. The aeration duration and accuracy of DO variation in the proposed UTM design with WOA optimization are shown to be significantly improved. The results of optimal WOA solution in UTM design present a useful alternative with good accuracy in following the desired DO value.