Performance evaluation and factors influencing a drinking water treatment plant, Shire Indassilassie, Ethiopia

• Evaluation of turbidity removal efficiency in the water treatment plant. • Identification of critical factors limiting water treatment plant performance. • Seasonal dynamics and efficiency of slow sand filtration processes. • Operational and design challenges in Shire Town’s water treatment plant operation. • Issues impacting filtration efficiency and maintenance practices. This research assesses the efficacy of the water treatment plant in Shire Indassilassie, Tigray, Ethiopia, focusing on the slow sand filtration system. Despite the inclusion of horizontal roughing filtration and a sedimentation tank, the water treatment plant struggles with an inadequate and turbid water supply. This study evaluates the water treatment plant’s performance through field evaluation, interviews, and laboratory experiments, concentrating on major treatment processes to identify performance-limiting factors. The water source had an average turbidity of 29.70 ± 1.03 NTU in the dry season and 94.27 ± 16.71 NTU in the summer. Results indicate that horizontal roughing filtration, sedimentation tank, and slow sand filtration achieve average turbidity removal efficiencies of 42.02% ± 4.00%, 5.67% ± 3.15%, and 83.51% ± 8.75%, respectively, during the dry season. In the summer or wet season, these treatment units achieve efficiencies of 40.06% ± 3.26%, 28.17% ± 4.62%, and 77.07% ± 4.61%, respectively. Additionally, the average run times for slow sand filtration are 22 days in the dry season and 13 days in the summer. Total and fecal coliform removals were effective, except in the sedimentation tank. A one-way ANOVA confirms a significant difference in turbidity among treatment units. Factors such as fine filter sand particles causing faster clogging, pipe misconnections, inadequate cleaning practices, irregular filtration rates, air binding due to a lack of backfilling at startup, and a lack of periodic monitoring and emergency response lead to suboptimal turbidity removal and shorter slow sand filtration run times. The study underscores the need for corrective measures to address these issues, enhancing water treatment plant sustainability in the region.