ABSTRACT: The present paper aims at determining the status of surface water quality by applying the treatability index for the raw water in four water treatment plants (WTPs), namely Vaalkop, Klipdrift, Wallmansthal, and Cullinan. These plants are based in South Africa. Sampling was conducted from July 2011 to June 2018 (7 years). The collected water samples were analysed on monthly basis over the specified period. Three Hundred and thirty six (336) water samples were collected and analysed. The Treatability Index (TI) was calculated for twenty-one physicochemical and microbial parameters, which include pH, conductivity, chloride, sodium, potassium, hardness, alkalinity, precipitation potential, turbidity, colour, E. coli, organic carbon, chlorophyll, nitrite, ammonia, nitrates, phosphate, ir
