Determination of the Quality of Groundwater in Mankweng, Limpopo Province, South Africa, Using the Water Quality Index

Abstract

There is a lack of groundwater quality monitoring, especially in developing countries like South Africa. This study aimed to evaluate borehole water quality. Groundwater was analysed for pH, dissolved oxygen (DO), temperature, electrical conductivity (EC), total dissolved solids (TDSs), turbidity, chemical oxygen demand (COD), nitrogen (N), sulphate (SO₄^2-), fluoride (F^-), chloride (Cl^-), calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), and sodium (Na⁺) using a multi-parameter device, spectrophotometer, turbidity meter, and inductively coupled plasma optical emission spectrophotometer. Total coliforms and <i>Escherichia coli</i> were quantified using the Colilert system. The water quality index (WQI) was calculated using the arithmetic weighting method. The parameters ranged as follows: pH (6.71-7.94), DO (2.19-7.79 mg/L), EC (379.67-1317.33 µS/cm), TDSs (190-659 mg/L), temperature (16.75-22.31 °C), turbidity (0.17-3.21 NTU), COD (9-50 mg/L), F^- (0.17-2.09 mg/L), Cl^- (36.1-184.55 mg/L), N (0.64-28.56 mg/L), SO₄^2- (27.18-112.13 mg/L), K⁺ (1.71-21.77 mg/L), Ca²⁺ (29.59-134.59 mg/L), Mg²⁺ (16.72-110.78 mg/L), and Na⁺ (38.52-170.63 mg/L). One borehole was polluted with <i>E. coli</i> (9 MPN/100 mL) and 25% were contaminated with coliforms beyond 10 MPN/100 mL. The WQI ranged from 50.430 to 190.220. The results underscore the importance of regular monitoring of groundwater.