title: Plant-wide modelling of phosphorus transformations in wastewater treatment systems: Impacts of control and operational strategies.
abstract: The objective of this paper is to report the effects that control/operational strategies may have on plant-wide phosphorus (P) transformations in wastewater treatment plants (WWTP). The development of a new set of biological (activated sludge, anaerobic digestion), physico-chemical (aqueous phase, precipitation, mass transfer) process models and model interfaces (between water and sludge line) were required to describe the required tri-phasic (gas, liquid, solid) compound transformations and the close interlinks between the P and the sulfur (S) and iron (Fe) cycles. A modified version of the Benchmark Simulation Model No. 2 (BSM2) (open loop) is used as test platform upon which three different operational alternatives (A1, A2, A3) are evaluated. Rigorous sensor and actuator models are also included in order to reproduce realistic control actions. Model-based analysis shows that the combination of an ammonium ( [Formula: see text] ) and total suspended solids (XTSS) control strategy (A1) better adapts the system to influent dynamics, improves phosphate [Formula: see text] accumulation by phosphorus accumulating organisms (XPAO) (41%), increases nitrification/denitrification efficiency (18%) and reduces aeration energy (Eaeration) (21%). The addition of iron ( [Formula: see text] ) for chemical P removal (A2) promotes the formation of ferric oxides (XHFO-H, XHFO-L), phosphate adsorption (XHFO-H,P, XHFO-L,P), co-precipitation (XHFO-H,P,old, XHFO-L,P,old) and consequently reduces the P levels in the effluent (from 2.8 to 0.9 g P.m-3). This also has an impact on the sludge line, with hydrogen sulfide production ( [Formula: see text] ) reduced (36%) due to iron sulfide (XFeS) precipitation. As a consequence, there is also a slightly higher energy production (Eproduction) from biogas. Lastly, the inclusion of a stripping and crystallization unit (A3) for P recovery reduces the quantity of P in the anaerobic digester supernatant returning to the water line and allows potential struvite ( [Formula: see text] ) recovery ranging from 69 to 227 kg.day-1depending on: (1) airflow (Qstripping); and, (2) magnesium ( [Formula: see text] ) addition. All the proposed alternatives are evaluated from an environmental and economical point of view using appropriate performance indices. Finally, some deficiencies and opportunities of the proposed approach when performing (plant-wide) wastewater treatment modelling/engineering projects are discussed.
authors.affiliation: Division of Industrial Electrical Engineering and Automation, Department of Biomedical Engineering, Lund University, Box 118, SE-221 00, Lund, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Solon
authors.affiliation: CAPEC-PROCESS Research Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-2800, Kgs. Lyngby, Denmark.
authors.forename: X
authors.initials: X
authors.lastname: Flores-Alsina
authors.affiliation: Advanced Water Management Centre, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Kazadi Mbamba
authors.affiliation: Water Research Group, Department of Civil Engineering, University of Cape Town, Rondebosch, 7700, South Africa.
authors.forename: D
authors.initials: D
authors.lastname: Ikumi
authors.affiliation: Department of Biosystems Engineering, Ghent University, Coupure Links 653, B-9000, Gent, Belgium.
authors.forename: E I P
authors.initials: EIP
authors.lastname: Volcke
authors.affiliation: BioEngine, Department of Chemical Engineering, Université Laval, Québec, QC, G1V 0A6, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Vaneeckhaute
authors.affiliation: Water Research Group, Department of Civil Engineering, University of Cape Town, Rondebosch, 7700, South Africa.
authors.forename: G
authors.initials: G
authors.lastname: Ekama
authors.affiliation: modelEAU, Département de Génie Civil et de Génie des Eaux, Université Laval, Québec, QC, G1V 0A6, Canada.
authors.forename: P A
authors.initials: PA
authors.lastname: Vanrolleghem
authors.affiliation: Advanced Water Management Centre, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Batstone
authors.affiliation: CAPEC-PROCESS Research Center, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-2800, Kgs. Lyngby, Denmark.
authors.forename: K V
authors.initials: KV
authors.lastname: Gernaey
authors.affiliation: Division of Industrial Electrical Engineering and Automation, Department of Biomedical Engineering, Lund University, Box 118, SE-221 00, Lund, Sweden. Electronic address: ulf.jeppsson@iea.lth.se.
authors.forename: U
authors.initials: U
authors.lastname: Jeppsson
mesh_terms: D010710:Phosphates / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry; D014865:Waste Disposal, Fluid; D062065:Wastewater
chemical_list: D010710:Phosphates; D010758:Phosphorus; D012722:Sewage; D062065:Wastewater
keywords: Benchmarking; Control strategies; Multiple mineral precipitation; Nutrient removal; Physico-chemical modelling; Struvite recovery