Evaluation of operational challenges and technological performance of wastewater treatment plants in Addis Ababa

Rapid urban expansion has led to increased wastewater generation and mounting pressure on existing wastewater treatment plants This study presents a comprehensive evaluation of selected wastewater treatment plants (WWTPs) in Addis Ababa, with a particular focus on operational efficiency, technological deployment, and institutional and financial challenges. A mixed-method approach was adopted, integrating quantitative data from plant operations with qualitative insights derived from stakeholder interviews and on-site observations. The assessment covered key treatment technologies including the Activated Sludge Process (ASP), Upflow Anaerobic Sludge Blanket Reactor (UASBR), and Membrane Bioreactor (MBR), whose performances were evaluated against national effluent discharge standards. MBR systems were found to be predominantly utilized in decentralized treatment facilities, representing 81.8% of such installations, whereas UASBR technology was mainly employed at the central municipal plant. A significant positive correlation was identified between plant treatment capacity and workforce size, with higher-capacity facilities necessitating more personnel. Operationally, 89.1% of the surveyed WWTPs had functional treatment stages, while 10.9% were non-operational. Key operational challenges included equipment malfunctions, poor sludge management, odor emissions, influent flow rate fluctuations (reported in 86.4% of facilities), and limited hydraulic or treatment capacity (64.5%). Financial constraints, reported by 70% of respondents, and low levels of community awareness (20.9%) further impeded effective WWTP operation. These findings underscore the critical need for strategic investment, institutional capacity building, stakeholder engagement, and policy reform to enhance the sustainability, resilience, and long-term performance of wastewater treatment infrastructure not only in Addis Ababa but also in other urban centers facing similar developmental and environmental challenges.