Wastewater Treatment Plant Operation: Simple Control Schemes with a Holistic Perspective

S. Revollar, R. Vilanova, P. Vega, M. Francisco and M. Meneses
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S. Revollar: Informatics and Automatics Department, University of Salamanca, 37008 Salamanca, Spain
R. Vilanova: Dept. Telecommunications and Systems Engineering, School of Engineering Universitat Autonoma Barcelona, 08193 Barcelona, Spain
P. Vega: Informatics and Automatics Department, University of Salamanca, 37008 Salamanca, Spain
M. Francisco: Informatics and Automatics Department, University of Salamanca, 37008 Salamanca, Spain
M. Meneses: Dept. Telecommunications and Systems Engineering, School of Engineering Universitat Autonoma Barcelona, 08193 Barcelona, Spain

Sustainability, 2020, vol. 12, issue 3, 1-28

Abstract: In this paper, a control approach for improving the overall efficiency of a wastewater treatment plant (WWTP) is presented. It consists of a cascaded control system that uses a global performance indicator as the controlled variable to drive the plant to operating conditions that satisfies trade-offs involved in the WWTP operation, improving the global performance of the plant. The selected global performance indicator is the N/E index that measures the ratio between the amount of nitrogenated compounds eliminated (kgN) and the energy (kWh) required to achieve that goal. This index links the variables of the activated sludge process with the energy consumed in the whole plant, thus the control strategy takes actions based on plantwide considerations. An external Proportional Integral (PI) controller changes the DO set point according to the N/E index and the basic dissolved oxygen (DO) control scheme in the activated sludge process follows this reference changes varying the aeration intensity. An outer loop with an event-based controller is used to compute the index values when the DO concentration is driven to excessively low limits, preventing long operation periods in this undesirable condition. Simple proportional integral controllers (PI) are used to adapt the strategy to the automation systems available in WWTPs. The implementation in the Benchmark Simulation Model 2 (BSM2) demonstrates the potential of the proposed approach. The results show the possibilities of the N/E index to be used as an indicator of global performance of WWTPs. It provides a link between water line objectives and energy consumption in the whole plant that can be exploited to introduce plantwide considerations in alternative control strategies formulated to drive the plant to operating conditions that optimize the overall process efficiency.

Keywords: wastewater treatment plants; environmental costs; PID control; plantwide control; hierarchical control strategies (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (9)

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