Utilization of Water Treatment Sludge in Construction Materials
Summary
Water treatment sludge, a by-product of drinking and wastewater purification processes, is increasingly recognised as a valuable resource for the construction sector. Composed predominantly of silica, aluminium and iron hydroxides alongside minor calcium and trace heavy metals, this residue can be processed to serve as a supplementary cementitious material, aggregate substitute or soil stabiliser. Advances in thermal activation, notably calcination, unlock pozzolanic reactivity by transforming amorphous phases into reactive aluminosilicates, thereby reducing the demand for Portland cement and lowering carbon emissions. When incorporated into mortars or concrete mixes, water treatment sludge can enhance durability, resistance to biogenic corrosion and long-term strength development, while offering a circular-economy solution to waste management. Challenges remain in standardising sludge pre-treatment protocols, controlling potential contaminants and optimising mix designs for diverse construction applications, from rendering mortars and structural concrete to ceramic products. Global research efforts are addressing these gaps to establish safe, economically viable and environmentally sustainable pathways for large-scale sludge valorisation.
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Utilization of Water Treatment Sludge in Construction Materials publication trend
The graph below shows the total number of articles in utilization of water treatment sludge in construction materials across all publications each year (not limited to Nature Index journals).
Technical terms
Water treatment sludge (WTS): Residual solids generated during drinking or wastewater treatment, rich in metal hydroxides and siliceous compounds.
Supplementary cementitious material (SCM): A non-cement binder, often pozzolanic, used to partially replace Portland cement in concrete or mortar.
Pozzolanic reactivity: The ability of an amorphous siliceous or aluminous material to react with calcium hydroxide in the presence of water, forming cementitious hydrates.
Calcination: Thermal treatment of sludge to remove organic matter, dehydrate hydroxides and induce phase transformations that enhance reactivity.
Geopolymer: An inorganic polymeric binder formed by alkali activation of aluminosilicate materials, offering an alternative to Portland cement.
References
- Valorisation of alum sludge to produce green and durable mortar. Waste Disposal & Sustainable Energy (2022).
- Feasibility of Using Calcined Water Treatment Sludge in Rendering Mortars: A Technical and Sustainable Approach. Sustainability (2019).
- Valorization of Municipal Waterworks Sludge to Produce Ceramic Floor Tiles. Recycling (2018).
- Physico-chemical characterization of sludge from a unit water drinking production. MATEC Web of Conferences (2012).
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