Evaluation of the physical, chemical, and biological characteristics of surface water in urban settings and its applicability to SDG 6: The case of Addis Ababa, Ethiopia

Abstract

In this study, an analysis of physicochemical and microbiological water quality parameters was carried out to evaluate the water quality status of the city from the two major reservoirs that supply drinking water to the city. Unlike most studies which only report on the water quality from the source or final treated water, this study assessed the water quality from the raw water source, the treatment plant as well as the treated water from taps. The analysis was conducted in accordance with the American Public Health Association's recommended procedures. Silica varied between 8.85–15.1 mg/l for Legedadie reservoir which is less than the stipulated limit of 25 mg/l and 72.2 to 111.77 mg/L for Gefersa. With the exception of turbidity, total phosphorus and dissolved oxygen which recorded mean values of 252.4 NTU, 2.76 mg/l and 5.46 mg/l respectively, nitrate, nitrite, ammonia, total soluble solids, total alkalinity, pH, electrical conductivity and temperature were discovered to be within the WHO permitted range with mean values of 0.36 mg/l, 0.11 mg/l, 0.067 mg/l, 0.01 mg/l, 53.13 mg/l, 8.14 mg/l, 148.9 μS/cm and 18.57 °C respectively. Total coliforms were found in all waters samples whilst faecal coliforms and Escherichia coli were recorded in the range 20–3000 CFU/100 mL. Ammonia, turbidity, pH and electrical conductivity were found to significantly influence microbial densities in the drinking water. Filtered and treated water sample recorded a 0 CFU/100 mL for faecal coliforms value which indicates that the water is in conformity to water quality standards. However, total coliforms in the range of 3000 to 5000 CFU/100 mL were found in all water samples indicating contamination hence treatment is recommended before drinking it. In contemporary times of increased urbanization and water pollution, this research will assist in the effort to provide safe water and sanitation for all city residents.