Comparative treatment efficiency and water quality index of drinking water systems in North-West Province, South Africa

Access to safe drinking water is a fundamental environmental health requirement, yet integrated assessments of treatment performance and health risks under different land-use pressures remain limited in South Africa. This study evaluated the performance of two drinking water treatment plants in Mahikeng and Klerksdorp, North-West province, representing agricultural and industrial catchments, respectively. A cross-sectional study design was employed. Physicochemical parameters were analysed using the American Public Health Association (APHA) Standard Methods for the Examination of Water and Wastewater, while microbiological quality was assessed by membrane filtration to enumerate Escherichia coli and total coliforms. Data were analysed using descriptive statistics and one-way Analysis of Variance (ANOVA), and results were evaluated against South African National Standards (SANS 241) and World Health Organisation (WHO) drinking water guidelines. Both treatment plants achieved complete microbial removal, without detectable E. coli or total coliforms, indicating effective disinfection. The water quality index (WQI) values classified treated water as moderate in Mahikeng (70–73) and good in Klerksdorp (30–35). However, physicochemical deviations were identified. Mahikeng recorded elevated turbidity (6.64 ± 9.50 NTU), electrical conductivity (183.50 ± 2.12 µS/cm), total hardness (261.94 ± 15.27 mg/L), and residual chlorine (4.14 ± 0.33 mg/L), while Klerksdorp showed an increase in total dissolved solids (491.50 ± 54.45 mg/L) with lower residual chlorine (1.50 ± 0.37 mg/L). These deviations may reduce treatment efficiency, promote microbial regrowth, and affect water acceptability. Although most of the parameters met the SANS 241 and WHO guidelines, the findings reveal system-level vulnerabilities linked to the quality of source water and the optimisation of the treatment. The study highlights the need for integrated, risk-based monitoring frameworks to ensure sustainable drinking water safety under heterogeneous environmental pressures. The Klerksdorp water treatment plant achieved a higher treatment efficiency despite poorer source water quality. The treated water from both plants was largely in accordance with WHO guidelines and SANS 241 drinking water standards. Seasonal variations had limited influence on the overall stability of treated water quality. Persistent turbidity and total hardness exceedances in Mahikeng require process optimisation. Improved source water protection and catchment management are essential for sustainable drinking water quality.