Performance of small water treatment plants: The case study of Mutshedzi Water Treatment Plant

Abstract

The performance of small water treatment plants (SWTPs) was evaluated using Mutshedzi WTP as a case study. The majority of SWTPs in South Africa (SA) that supply water to rural villages face problems of cost recovery, water wastages, limited size and semi-skilled labour. The raw and final water quality analyses and their compliance were used to assess the performance of the Mutshedzi WTP. Electrical conductivity (EC), pН and turbidity were measured in the field using a portable multimeter and a turbidity meter respectively. Atomic Absorption Spectrometry and Ion Chromatography were used to analyse metals and non-metals respectively. The results were compared with the Department of Water Affairs (DWA) guidelines for domestic use. The turbidity levels partially exceeded the recommended guidelines for domestic water use of 1NTU. The concentrations of chemical parameters in final water were within the DWA guidelines for domestic water use except for fluoride, which exceeded the maximum allowable guideline of 1.5mg/L in August 2009. Mutshedzi WTP had computed compliance for raw and final water analyses ranging from 79% to 93% and 86% to 93% throughout the sampling period, respectively. The results from earlier studies showed that the microbiological quality of final water in Mutshedzi WTP complied with the recommended guidelines, eliminating the slight chance of adverse aesthetic effects and infectious disease transmission associated with the turbidity values between 1 and 5NTU. The study concluded that Mutshedzi WTP, though moving towards compliance, is still not producing adequate quality of water. Other studies also indicated that the quantity of water produced from Mutshedzi WTP was inadequate. The findings of the study indicate that lack of monitoring of quantity of water supplied to each village, dosage of treatment chemicals, the treatment capacity of the WTP and monitoring the quality of water treated are some of the factors that limit the performance of Mutshedzi WTP. These have been confirmed in literature to be widespread in similar WTPs in SA. It is recommended that water meters be provided and the community be advised to subsidise the cost of water supply. The study recommended that the treatments of turbidity and fluoride should form critical functions of the plant to ensure that final water for domestic use is always safe from any harmful substances or disease causing pathogens. The study concluded that the WTP only needs minor improvement to boost its efficiency with regard to the treatment of raw water. This will also ensure that the plant achieves 100% compliance for final water.