Toward achieving sustainable management of municipal wastewater sludge in Egypt: The current status and future prospective

Over the past 4 decades, the increasing amounts of excess sludge from municipal wastewater treatment plants (WWTPs) represent a challenge toward achieving the sustainability of the drinking water and sanitation sector in Egypt, resulting in a serious environmental pollution due to the uncontrolled use of non-stabilized sludge. Here, we report a comprehensive overview on the current situation of excess sludge production, management, and disposal in Egypt. Owing to the technologies used for wastewater treatment in Egypt that mainly consist of activated sludge based-technologies, about 2.1 million tons of dry solids is produced annually. The majority of WWTPs in Egypt lack proper sludge stabilization facilities, except for the WWTPs in high living standards governorates (e.g., Cairo, Alexandria, and Giza). Therefore, about 85% of the non-stabilized sludge is improperly disposed and directly used for agricultural purposes. Despite the importance of managing the use of non- and/or partially-treated sludge, especially for agricultural purposes, the national legislations for sludge disposal/reuse in Egypt are incomplete and, in practice, they are not reinforced. In order to evaluate the most sustainable scenario for sludge management in Egypt, a qualitative decision-support system (DSS) was used. The DSS framework was refined and estimated, based on several evaluating categories, and used to guide the decision process towards achieving sustainable management of municipal wastewater sludge in Egypt. The results reveals that "sludge-to-energy" through anaerobic digestion is the most sustainable scenario for sludge disposal and management in Egypt. The anaerobic digestion-based technology seems to offer advantages of interest at affordable costs, such as the production of renewable energy, stabilized soil conditioners, and fertilizers for agricultural purposes.