A generalised chemical precipitation modelling approach in wastewater treatment applied to calcite
Article
Article Title | A generalised chemical precipitation modelling approach in wastewater treatment applied to calcite |
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ERA Journal ID | 4694 |
Article Category | Article |
Authors | Kazadi Mbamba, Christian (Author), Batstone, Damien J. (Author), Flores-Alsina, Xavier (Author) and Tait, Stephan (Author) |
Journal Title | Water Research |
Journal Citation | 68, pp. 342-353 |
Number of Pages | 12 |
Year | 2015 |
Place of Publication | United Kingdom |
ISSN | 0043-1354 |
1879-2448 | |
Digital Object Identifier (DOI) | https://doi.org/10.1016/j.watres.2014.10.011 |
Web Address (URL) | https://www.sciencedirect.com/science/article/pii/S0043135414007064?via%3Dihub |
Abstract | Process simulation models used across the wastewater industry have inherent limitations due to over-simplistic descriptions of important physico–chemical reactions, especially for mineral solids precipitation. As part of the efforts towards a larger Generalized Physicochemical Modelling Framework, the present study aims to identify a broadly applicable precipitation modelling approach. The study uses two experimental platforms applied to calcite precipitating from synthetic aqueous solutions to identify and validate the model approach. Firstly, dynamic pH titration tests are performed to define the baseline model approach. Constant Composition Method (CCM) experiments are then used to examine influence of environmental factors on the baseline approach. Results show that the baseline model should include precipitation kinetics (not be quasi-equilibrium), should include a 1st order effect of the mineral particulate state (Xcryst) and, for calcite, have a 2nd order dependency (exponent n = 2.05 ± 0.29) on thermodynamic supersaturation (σ). Parameter analysis indicated that the model was more tolerant to a fast kinetic coefficient (kcryst) and so, in general, it is recommended that a large kcryst value be nominally selected where insufficient process data is available. Zero seed (self nucleating) conditions were effectively represented by including arbitrarily small amounts of mineral phase in the initial conditions. Both of these aspects are important for wastewater modelling, where knowledge of kinetic coefficients is usually not available, and it is typically uncertain which precipitates are actually present. The CCM experiments confirmed the baseline model, particularly the dependency on supersaturation. Temperature was also identified as an influential factor that should be corrected for via an Arrhenius-style correction of kcryst. The influence of magnesium (a common and representative added impurity) on kcryst was found to be significant but was considered an optional correction because of a lesser influence as compared to that of temperature. Other variables such as ionic strength and pH were adequately captured by the quasi-equilibrium description of the aqueous-phase and no further kinetic corrections were required. The baseline model is readily expandable to include other precipitation reactions. For simple representations, large values for kcryst with n = 2 (or n = 2 or 3 for other minerals, as appropriate) should be selected without corrections to kcryst. Where accuracy is required (e.g., in mechanistic studies), machine estimation of kcryst should be performed with robust process data and kcryst should at least be corrected for temperature. |
Keywords | physico–chemical modelling, minerals precipitation, calcite, acid–base titration, equilibrium, kinetics |
ANZSRC Field of Research 2020 | 401102. Environmentally sustainable engineering |
Public Notes | Files associated with this item cannot be displayed due to copyright restrictions |
Byline Affiliations | University of Queensland |
Technical University of Denmark, Denmark | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q52v4/a-generalised-chemical-precipitation-modelling-approach-in-wastewater-treatment-applied-to-calcite
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