Natural organic matter (NOM) fractionation, identification and quantification of surface water supplied to Eskom power stations using liquid chromatography-organic carbon detection (LC-OCD)

M.Tech. (Chemistry)Abstract: The presence of natural organic matter (NOM) in water has shown an increase globally over the past 20 years due to issues such as global warming. Both drinking water quality and water treatment processes are negatively affected by increased concentrations of NOM. Problems associated with NOM in water include: (I) increase coagulant demand, (II) undesirable colour, odour and taste, (III) formation of harmful disinfectant by products (DBPs) such as haloacetic acids (HAAs) and trihalomethanes (THMs) and (IV) bacterial growth in water distribution systems. The concentration of NOM in surface water is highly influenced by seasonal variations. Seasonal variations imply new challenges in operational control for water treatment plants. To address the problems associated with NOM, it is important to understand the seasonal variations and composition of NOM. In this study NOM was characterised using techniques such as fractionation using XAD-4 and DAX-8 resins and liquid chromatography-organic carbon detection (LC-OCD). Quantification of NOM was carried out using parameters such as UV-Vis spectroscopy, specific ultraviolet absorbance (SUVA) and dissolved organic carbon (DOC). These techniques assisted with identification and quantification of NOM in surface waters that supply four of Eskom`s power stations. The water sources studied included the Vaal River, Nkomati River, Usuthu River and the Crocodile River. The pre-treatment processes (coagulation and sand filtration) at the power stations were also assessed to determine the behaviour of NOM during these processes. The results from this study indicated that the nature of NOM present in the source water varied seasonally both in composition and concentration. The SUVA254 (aromaticity) for the three sources i.e. Vaal, Nkomati and Usutu River, showed an increase in aromaticity i.e. 3.37, 3.34 and 2.04 L/(mg.m) respectively during the wet seasons (spring and summer). The DOC results for the three sources showed a similar trend to the SUVA254 values i.e. also showing an increase during the wet seasons. The Crocodile River however, showed a different trend i.e. the DOC was..