A plant-wide aqueous phase chemistry module describing pH variations and ion speciation/pairing in wastewater treatment process models

Flores-Alsina, Xavier, Kazadi Mbamba, Christian, Solon, Kimberly, Vrecko, Darko, Tait, Stephan, Batstone, Damien J., Jeppsson, Ulf and Gernaey, Krist V. (2015) A plant-wide aqueous phase chemistry module describing pH variations and ion speciation/pairing in wastewater treatment process models. Water Research, 85 255-265. doi:10.1016/j.watres.2015.07.014

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Author Flores-Alsina, Xavier
Kazadi Mbamba, Christian
Solon, Kimberly
Vrecko, Darko
Tait, Stephan
Batstone, Damien J.
Jeppsson, Ulf
Gernaey, Krist V.
Title A plant-wide aqueous phase chemistry module describing pH variations and ion speciation/pairing in wastewater treatment process models
Journal name Water Research   Check publisher's open access policy
ISSN 1879-2448
Publication date 2015-11-15
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.watres.2015.07.014
Open Access Status File (Author Post-print)
Volume 85
Start page 255
End page 265
Total pages 11
Place of publication London, United Kingdom
Publisher IWA Publishing
Collection year 2016
Language eng
Abstract There is a growing interest within the Wastewater Treatment Plant (WWTP) modelling community to correctly describe physico–chemical processes after many years of mainly focusing on biokinetics. Indeed, future modelling needs, such as a plant-wide phosphorus (P) description, require a major, but unavoidable, additional degree of complexity when representing cationic/anionic behaviour in Activated Sludge (AS)/Anaerobic Digestion (AD) systems. In this paper, a plant-wide aqueous phase chemistry module describing pH variations plus ion speciation/pairing is presented and interfaced with industry standard models. The module accounts for extensive consideration of non-ideality, including ion activities instead of molar concentrations and complex ion pairing. The general equilibria are formulated as a set of Differential Algebraic Equations (DAEs) instead of Ordinary Differential Equations (ODEs) in order to reduce the overall stiffness of the system, thereby enhancing simulation speed. Additionally, a multi-dimensional version of the Newton–Raphson algorithm is applied to handle the existing multiple algebraic inter-dependencies. The latter is reinforced with the Simulated Annealing method to increase the robustness of the solver making the system not so dependant of the initial conditions. Simulation results show pH predictions when describing Biological Nutrient Removal (BNR) by the activated sludge models (ASM) 1, 2d and 3 comparing the performance of a nitrogen removal (WWTP1) and a combined nitrogen and phosphorus removal (WWTP2) treatment plant configuration under different anaerobic/anoxic/aerobic conditions. The same framework is implemented in the Benchmark Simulation Model No. 2 (BSM2) version of the Anaerobic Digestion Model No. 1 (ADM1) (WWTP3) as well, predicting pH values at different cationic/anionic loads. In this way, the general applicability/flexibility of the proposed approach is demonstrated, by implementing the aqueous phase chemistry module in some of the most frequently used WWTP process simulation models. Finally, it is shown how traditional wastewater modelling studies can be complemented with a rigorous description of aqueous phase and ion chemistry (pH, speciation, complexation).
Keyword Activity correction
Ionic strength
Ionic behaviour
Dynamic pH prediction
Multi-dimensional Newton Raphson
Simulated annealing
Physico-chemical modelling
Water chemistry
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
Advanced Water Management Centre Publications
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Citation counts: TR Web of Science Citation Count  Cited 6 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 8 times in Scopus Article | Citations
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