Evaluation of Water Quality and Potential Scaling and Corrosion of the Water Supply Using Water Quality and Stability Indices: A Case Study of Juja Water Distribution Network, Kenya

Abstract

Drinking water quality describes the conditions for water to be accepted as suitable for human consumption. Water quality index is characterized by including in the process of assessment, water quality parameters such as physical, chemical and micro-biological. Nowadays, the management of hazardous events has become a big problem for water utilities and leads to the increase of the rate of public health risk. Availability of adequate management strategy in order to maintain good quality water has been always a challenge for water utilities. To provide a solution to the problem, one needs to think of a simple and effective tool that can be used to easily assess the quality of the water. Water Quality Index (WQI) and Water Stability Index (WSI) are known as the most reliable tools for assessing water quality and aggressiveness. This study aims at assessing the water quality and potential scaling and corrosion of the water supply in the Juja water distribution network by using WQI and WSI based on Langelier Saturation Index (LSI). Five sampling locations were selected including the treatment plant outlet and consumption points for physical, chemical and bacteriological water quality analysis and determination of WQI and WSI. It was found that 100% of the collected water samples had Calcium concentrations within the World Health Organization (WHO) and Kenya Bureau of Standards (KEBS) acceptable ranges. Additionally, 100% of the collected water samples had TDS concentrations within the WHO and KEBS acceptable ranges. However, at time, water quality parameters such as Residual Chlorine, E. coli, Alkalinity, and Turbidity were out of the WHO and KEBS standards. pH values ranged from 6.29 to 8.06 and was generally within acceptable limits. The WSI ranged between – 3.04 to – 0.99, indicating that the water is generally corrosive and may pose a risk to water quality and shorten the lifespan of the network facilities. Generally, the water from the Treatment Plant was of good quality, while at consumption points JKUAT Main Gate, JKUAT Campus, High Point, and Juja Stage had fair water quality based on the calculated WQI. There was a slight drop of the water quality associated with the low concentrations of residual chlorine, and the presence of E. coli at all the stations. The water quality therefore deteriorates in the distribution network and is corrosive throughout the system right from the treatment plant based on the WQI and WSI. The water company needs to improve on the treatment process, and relook at management strategies of the network, provide better services to consumers.