A study of seasonal effects on metal-NOM interactions and the impact of CaCO3 precipitation potentials using Visual MINTEQ, in raw and cooling water

Abstract

This paper reports on a study of calcium carbonate (CaCO 3) precipitation potentials of cooling water (CW) at Eskom power stations. It is important to understand the complexation reaction between calcium and dissolved organic carbon (Ca-DOC) because the natural organic matter (NOM) affects the precipitation potentials of CaCO 3. Secondly, it is necessary to understand the nature of the organic matter in the cooling and raw water. This study was carried out in raw and cooling water samples collected from Lethabo and Kriel power stations. These power stations obtain their cooling water from the Vaal River and Usuthu schemes, respectively. The DOC concentration in both water systems was higher in winter (little/no rainfall) as compared to spring (more rainfall). Specific ultraviolet absorption (SUVA) was calculated for the raw and cooling water for both stations. The SUVA results obtained for the raw water (RW) indicated that the NOM had a high degree of aromaticity (humic substances), whereas for the recycled CW the NOM present was found to be less aromatic.

Authors

Categories