Geochemical scaling potential simulations of natural organic matter complexation with metal ions in cooling water at Eskom power generation plants in South Africa

Authors

  • GO Bosire Department of Applied Chemistry, University of Johannesburg, PO Box 17011, Doornfontein 2028 Johannesburg, South Africa
  • JC Ngila Department of Applied Chemistry, University of Johannesburg, PO Box 17011, Doornfontein 2028 Johannesburg, South Africa
  • Thabo TI Nkambule Nanotehnology and Water Sustainability Research Unit, College of Science, Engineering and Technology, University of South Africa, South Africa

DOI:

https://doi.org/10.4314/wsa.v44i4.19

Keywords:

mineral phases, PHREEQC, saturation indices, Tipping and Hurley database

Abstract

The modified database in the pH, redox equilibrium calculations code (PHREEQC) with a Tipping and Hurley database (T_H.DAT) coupled with the Windermere’s humic acid model (WHAM) was used to simulate scale formation potential in cooling water circuitry, at Eskom power generating stations in South Africa. This study reports a semi-empirical simulative approach in which organic matter fractions, metals and anions in raw and cooling water were used as modelling experimental inputs. By using the saturation index profiles of Ca2+/ Mg2+ with fulvic acid in a modified Tipping and Hurley (T_H.DAT) database, fulvate complex species such as CaFulvate, MgFulvate, and geochemical modelling predictions, mineral phases that potentially precipitate are discussed. Speciation calculations showed that the increase in fulvic acid levels decreased saturation indices of scaling metal phases due to reduced levels of Ca2+ and Mg2+ in the water. Furthermore, if the concentrations of fulvic acid are known, semi-empirical calculations using the geochemical PHREEQC code with a modified T_H.DAT are
possible. Consequently, mineral phase equilibria outputs may give an indication of how the pH and temperature is to be manipulated to optimally predict and control the incidence of scaling.

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Published

2018-10-31

How to Cite

Bosire, G., Ngila, J., & Nkambule, T. T. (2018). Geochemical scaling potential simulations of natural organic matter complexation with metal ions in cooling water at Eskom power generation plants in South Africa. Water SA, 44(4 October). https://doi.org/10.4314/wsa.v44i4.19

Issue

Section

Research paper