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1 Center for Process Engineering and Technology, Department of Chemical and Biochemical Engineering, Technical University of Denmark 2 Department of Chemical and Biochemical Engineering, Technical University of Denmark 3 CAPEC-PROCESS, Department of Chemical and Biochemical Engineering, Technical University of Denmark 4 Lund University 5 Ghent University 6 University of Girona 7 Université Laval 8 Illinois Institute of Technology 9 Department of Environmental Engineering, Technical University of Denmark 10 Lund University 11 Ghent University 12 University of Girona 13 Illinois Institute of Technology
The objective of this paper was to show the potential additional insight that result from adding greenhouse gas (GHG) emissions to plant performance evaluation criteria, such as effluent quality (EQI) and operational cost (OCI) indices, when evaluating (plant-wide) control/operational strategies in wastewater treatment plants (WWTPs). The proposed GHG evaluation is based on a set of comprehensive dynamic models that estimate the most significant potential on-site and off-site sources of CO2, CH4 and N2O. The study calculates and discusses the changes in EQI, OCI and the emission of GHGs as a consequence of varying the following four process variables: (i) the set point of aeration control in the activated sludge section; (ii) the removal efficiency of total suspended solids (TSS) in the primary clarifier; (iii) the temperature in the anaerobic digester; and (iv) the control of the flow of anaerobic digester supernatants coming from sludge treatment. Based upon the assumptions built into the model structures, simulation results highlight the potential undesirable effects of increased GHG production when carrying out local energy optimization of the aeration system in the activated sludge section and energy recovery from the AD. Although off-site CO2 emissions may decrease, the effect is counterbalanced by increased N2O emissions, especially since N2O has a 300-fold stronger greenhouse effect than CO2. The reported results emphasize the importance and usefulness of using multiple evaluation criteria to compare and evaluate (plant-wide) control strategies in a WWTP for more informed operational decision making. © 2013 Elsevier B.V.
Science of the Total Environment, 2014, Vol 466-467, p. 616-624
Benchmarking; Carbon dioxide; Clarification; Decision making; Global warming; Model structures; Process control; Sustainable development; Water quality; Greenhouse gases
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