Assessment of variation in treated water quality and linkage to possible intrusion of contaminants in makindye division, Kampala, Uganda

Abstract

Good drinking water quality is essential for human well-being. However, water quality in the distribution network tends to be affected at points of leakages through intrusion by pathogens. Maintenance of water tanks also tends to be very irregularly undertaken. The study was carried out through field surveys and data collection. This study aimed at assessing the extent to which the variation in treated water quality could be linked to possible intrusion of contaminants. Makindye Division, Kampala, Uganda was selected as the case study. The study had three specific objectives including: i) assessment of temporal variation in water quality parameters, ii) investigating variation of water quality parameters in space, and iii) determining the possibility of intrusion of contaminants along distribution networks. The research utilised both primary and secondary data for the distribution and storage tanks. With help of the Cochran formula, a sample size was obtained. For primary data, Samples were collected utilizing both Insitu and laboratory measurements for both direct connections and storage tanks. A questionnaire was also used to obtain data from the selected households and direct connections with analysis done in Excel. In objective 1, Turbidity was found to increase with time from 2015 to 2019 at a rate of 0.l45NTU per year. The highest turbidity values were obtained in 2018. Colour increased at a rate of l. l 8PtCo per year. Residual chlorine for the period 2015-2018 had an increasing trend at a rate of 0.0247mg/l/yr and was found highest in 2018. The month of March recorded the highest residual chlorine while the month of May recorded the lowest residual chlorine. pH was found to fall within the standard limits of 6.5 - 8.5. However, over the period 2015 to 2019, pH exhibited a decreasing trend at a rate of -0 .032 per year. In objective 2, the mean values of turbidity in water sampled from direct connections and storage tanks were 0.76±0.38NTU and 5.96±3.8NTU respectively. The average colour of water from the direct connections was 8±4.lPtCo while that of the storage tanks had 57±20.5 PtCo. Colour of water from the direct connections and storage tanks showed significant differences with p = l .74333E-l 0. The mean of residual chlorine in water sampled from direct connections was found to be 0.56±0. l 6mg/I while that from storage tanks was 0.25±0.13mg/1. Using the t-test, these mean values were found to be significantly different (p<0.05). In objective 3, the number of people who do not clean their tanks in the study area was found to be 58% of the study population. Those who clean their water storage tanks after one year or six months was found to constitute 43% of the sampled water users. Water storage tanks which are not cleaned or regularly maintained can be a potential source of contamination of water at consumer points. There was a significant difference (p<0.05) between the water quality in the distribution network and at draw off points for most of the parameters attributed to factors like; approximate of drainage systems (35%), toilets (30%), garbage pits (25%) and main road (48%). The number of leakages in the study area between 2016 and 2019 was found to be 4852 which exhibited a positive trend at a rate of 42 leakages per year. Whereas the significant difference (p<0.05) between water in the storage tanks and direct connection draw offs could have been due to leakages, none routine cleaning of storage tanks and the use storage tanks without covers. Kawuku and Soya villages were the most affected areas in terms of water quality distributed to them and this could be attributed to the connection on the dead end of the pipes. Leakage monitoring and management should be prioritized with constant sensitization of water users on how to clean tanks and maintain good water quality. Key words; Trend, water quality, water pollution, pipe leakages, water contamination.