uMngeni Basin Water Quality Trend Analysis for River Health and Treatability Fitness

Abstract

One of the main challenges facing the potable water production industry is deterioration of the quality of raw water. Drinking water that does not meet quality standards is unfit for consumption. Yet, this quality is a function of various factors, key among them being quality of the raw water from which it is processed. This is because costs related to potable water treatment are related to the nature of raw water pollutants and the degree of pollution. Additionally, survival of aquatic species depends on self-purification of the water bodies through attenuation of pollutants, therefore, if this process is not efficient it might result in dwindling of the aquatic life. Hence, this chapter presents spatial and temporal water quality trends along uMngeni Basin, a critical raw water source for KwaZulu-Natal Province, in South Africa. As at 2014 the basin served about 3.8 million people with potable water. Results from this study are discussed in relation to uMngeni River’s health status and fitness for production of potable water treatment. Time-series and box plots of 11 water quality variables that were monitored at six stations over a period of eight years (2005 to 2012), were drawn and analysed. The Mann Kendall Trend Test and the Sen’s Slope Estimator were employed to test and quantify the magnitude of the quality trends, respectively. Findings showed that raw water (untreated) along uMngeni River was unfit for drinking purposes mainly because of high levels of Escherichia coli. However, the observed monthly average dissolved oxygen of 7 mg/L, that was observed on all stations, suggests that the raw water still met acceptable guidelines for freshwater ecosystems. It was noted that algae and turbidity levels peaked during the wet season (November to April), and these values directly relate to chlorine and polymer dosages during potable water treatment.

The evaluation of the health status of Clarias gariepinus from the Inanda and Nagle dams in KwaZulu-Natal, South Africa.

“…pH is an indicator of acidity or alkalinity of water. Growth, metabolism and survival of aquatic organisms including fish is ideal within a pH range of 6.5 to 8.5 (Rangeti and Dzwairo 2021).…”

“…Moreover, concentrations of NH3 are generally dependent on pH and water temperature (Camargo and Alonso 2006). Moreover, elevated pH tends to convert less toxic compound ammonium (NH4 + ) into highly toxic unionized NH3 (Rangeti and Dzwairo 2021). Olaniran et al (2014) also recorded low concentrations of NH3 and not exceeding the water guideline at the uMgeni River.…”

“…Eutrophic conditions recorded in the Inanda Dam may possibly be attributed to the wastewater discharge from municipality treatment plants. Rangeti and Dzwairo (2021)…”