Abstract:
Communities worldwide, particularly those in developing countries, encounter challenges in providing continuous water for household consumption. This phenomenon is common in Ethiopia, particularly in the Gondar community, where access to water is intermittent. The main objective of this study is to evaluate the water quality of distribution systems in the context of intermittent supply. A total of 156 samples in two distribution zones (Selassie and Gebriel) were collected for analysis of 11 selected physicochemical and bacteriological water quality parameters in the dry and wet seasons of 2022. Simple random and purposive sampling techniques were applied for the determination of the sample point. The water quality results were compared with WHO standards. Temporal and spatial variations of water quality were analyzed using an independent sample t-test and GIS software, respectively. The Epanet software was used to simulate the free chlorine and water age dynamics in a pipeline. The results showed that pH, EC, TDS, NO2-, and NO3- in the Selassie subsystem and EC, TDS, and NO3- in the Gabriel subsystem were within acceptable limits of WHO standards for drinking water quality. However, 27.77% and 36.11% in the Selassie subsystem and 23.80% and 30.95% in the Gebriel subsystem of samples were positive for fecal coliforms and total coliforms, respectively. The physicochemical and biological parameters of the water showed highly significant variation (P ≤ 0.05) based on sampling time (seasons), except for Cl2, NO3-, fecal coliforms, and total coliforms in Selassie and Cl2, fecal coliforms, and total coliforms in the Gebriel subsystem. The Cl2 and water age model analysis results indicate spatial variations in chlorine levels across the study area and the potential impact of excessive water age on the quality of the distribution system. Depending on the tested parameters, Gondar town drinking water has deteriorated in quality, although continual testing is mandatory, including other parameters.
Keywords: distribution system, intermittent water supply, modeling, water quality,