Control strategies for wastewater treatment plants aimed to improve nutrient removal and to reduce aeration costs

Municipal wastewater treatment plants (WWTPs) are responsible for the quality of the water discharged to the emissary rivers. Besides the effluent quality, WWTPs also have to take into consideration the operational costs. Operation costs can be reduced and nutrient removal can be improved by using different control structures. In this research, three main control strategies were investigated by mathematical modeling and simulation: dissolved oxygen cascade control (DO cascade), ammonia based aeration control (ABAC) and a combination of ABAC with the control of nitrate and return activated sludge recycles. These automatic control structures are favorable from the point of view of reducing the total nitrogen effluent concentration, respectively the concentration of nitrates and nitrites in the effluent, and savings of up to 43% of aeration costs.