Assessing the Sustainability of Decentralized Wastewater Treatment Systems (Dwwts’s) in the Cities of Developing Countries; Case Study: Kigali City, Rwanda

Abstract

Lack of scientific knowledge in wastewater treatment systems together with imperfect sanitation legal instruments are considered, among others, the key constraints to sustainable wastewater management systems in the cities of developing countries including Kigali city. Kigali city has increasingly shown failures of such wastewater treatment systems strictly in decentralized wastewater treatment systems. Densely populated cities of poor resourced countries like Kigali largely rely on decentralized wastewater management systems due to the absence of central sewerage systems and limited finances for the development of safe and sustainable sanitation infrastructures. Decentralized wastewater treatment systems reveals on-site sanitation systems either at individual or collective levels. This study aims to assess the sustainability of the existing collective semi-centralized wastewater treatment plants in the estates of Kigali city that are said to be in operation. The research used field observation, questionnaires, structured interviews, and laboratory tests of the analyzed parameters methods in order to protect the ecosystem and safeguard community health. The study also reviewed the influence of national ruling sanitation legal instruments in addressing development, operation and management of such decentralized wastewater treatment plants. The results of this study showed sustainability level of technical dimension at 3.77 with less sustainable status, environmental quality at 5.75 with fairly sustainable status, socio-economic status dimension at 3.53 with less sustainable status, and finally institutional and legal dimension at 3.98 with also less sustainable status. Therefore, all the weight dimensions rated the sustainability level of collective public semi-centralized wastewater treatment systems of Kigali city as Less Sustainable with 4.26 aggregate. In conclusion, the research highlighted that improved sanitation coverage doesn’t mean coverage in terms of sewerage connection proportions for wastewater collection, and the sewerage connections also does not imply wastewater treatment before being discharged.