Seasonal Variations in Potable Water Quality of Bahawalpur City: A Comprehensive Assessment of Major Ions, Organic Matter, and Disinfection Byproducts

Industrialization and population explosion are ultimately affecting freshwater resources. Bahawalpur is a rapidly growing city in Pakistan where groundwater is the major source of drinking water. However, groundwater is also being contaminated due to various anthropogenic sources. To meet the need for clean drinking water, filtration plants have been installed throughout the city. To monitor the water quality index of the treated water, water samples were collected from the filtration plants installed by Tehsil Municipal Administration in Bahawalpur city. Different physicochemical parameters, major ions, organic matter, and disinfection byproducts (DBPs) were analysed. Both raw and chlorinated water in summer and winter season were investigated. Results revealed that all raw samples were biologically contaminated showing the presence of E. coli in all raw water samples, this justified the need for disinfection. Despite chlorination, several samples were still contaminated due to the lack of available residual chlorine in the distribution system. The carcinogenic Bromoform (27% samples) and dibromochloromethane (22% samples) surpassed the WHO permissible limits for drinking water in both seasons. Dichloroacetic acid exceeded the WHO permissible limits in 33% and 11% of samples during summer and winter, respectively. Overall, DBPs were higher during summer than winter season. Standard ultraviolet absorption at 254 nm (SUVA₂₅₄) showed that the source of organic matter was microbial except for Bohar gate and Islamic colony, where the source of water was surface water. Chlorination also affected the water chemistry in both seasons. The water quality index showed that the chlorinated water was fit for drinking in the winter season; however, 34% of samples were found unfit for drinking during summer. Monitoring of the DBPs is recommended on a regular basis, in addition to the organic matter removal from the water before chlorination. This study provides valuable information to achieve Sustainable Development Goal 6 which is for clean water and sanitation. So, this research can provide significant data to the policy makers to improve the water quality in developing countries like Pakistan.