Sustainable Valorization of Drinking Water Treatment Sludge: A Review

Among the critical stages in the drinking water treatment process is the coagulation and flocculation stage, during which a non-sustainable coagulant, such as aluminum or iron sulphate, is added to remove the dissolved and suspended components from the water. This generates a byproduct known as drinking water treatment sludge (DWTS). Alum sludge is the most commonly produced, which causes economic and environmental challenges that must be considered to bridge the gap between water treatment processes and generated sludge management. Recent research focuses on the reuse of DWTS in various fields to avoid its direct disposal and environmental impacts. This review aims to evaluate the valorization of drinking water treatment sludge as a sustainable product in a circular waste management approach, by assessing its potential to be used especially in agriculture for soil restoration and in adsorption, in attempts to evaluate the potential reuse of DWTS as a sustainable and alternative solution. Some challenges related to structure and potential ecological risks are comprehensively discussed with a focus on the crucial role of this sludge. Furthermore, techno-economic aspects were considered for assessing the technical and economic feasibility of DWTS. Research priorities and future challenges that will enable exploration and innovation in sludge reuse across many aspects were also discussed.