Control of Ammonium Ion and Biochemical Oxygen Demand in Wastewater using Eigen-pair Placement and Loop-wise Control

In this paper, the control of two environmental parameters namely, ammonium ion (AI) concentration and biochemical oxygen demand (BOD<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf>) is presented in the secondary treatment of a wastewater treatment process (WTP). The system model is derived from the standard activated sludge model 3 2N of a WTP. The control of AI and BOD<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> is achieved by manipulating the recycled sludge flow rate and the air flow rate. The control scheme consists of an eigen-pair placement (EP) followed by a loop-wise proportional integral (PI) control. The EP takes care of the cross-coupling in the system. Then the decoupled system is controlled by the PI controllers for each loop. The performance of the proposed method is verified by numerical simulation. The results reveal that the proposed method successfully tracks the reference and rejects the disturbance. The proposed control strategy outperforms several reported works.