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<p>This study evaluates the valorisation of wastewater treatment plant (WWTP) grit, a largely overlooked residue, as a partial replacement for construction sand in mortar bricks. Grit from four Costa Rican WWTPs was characterised, showing substantial variability in moisture, organic matter, granulometry and physical properties. After washing and sanitisation, mortar cubes were produced at different substitution levels. At 30% sand replacement, 28-day compressive strength reached 16.9&#xa0;MPa, meeting ASTM C270 Type S requirements for mortar cubes. Higher substitutions reduced strength and workability, consistent with high absorption, low density and residual organics. An economic analysis indicated up to 5.9% cost savings at 30% due to reduced sand consumption and avoided landfilling. A life cycle assessment (LCA) of 0%, 15% and 30% scenarios showed environmental benefits, including a 45% reduction in global warming potential and improved freshwater eutrophication, mainly from avoided sand extraction and grit disposal. Trade-offs were observed for human carcinogenic toxicity and stratospheric ozone depletion linked to chlorine-based sanitisation. Overall, controlled recovery and valorisation of WWTP grit offers a feasible circular-economy route for the sanitation and construction sectors.</p>

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Circular reuse of WWTP grit in mortar bricks: performance, cost, and environmental assessment

  • 期刊论文

  • 发表日期：

    2026年5月22日

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  • Erick Centeno Mora,
  • Mauricio Alpízar Murillo

摘要

This study evaluates the valorisation of wastewater treatment plant (WWTP) grit, a largely overlooked residue, as a partial replacement for construction sand in mortar bricks. Grit from four Costa Rican WWTPs was characterised, showing substantial variability in moisture, organic matter, granulometry and physical properties. After washing and sanitisation, mortar cubes were produced at different substitution levels. At 30% sand replacement, 28-day compressive strength reached 16.9 MPa, meeting ASTM C270 Type S requirements for mortar cubes. Higher substitutions reduced strength and workability, consistent with high absorption, low density and residual organics. An economic analysis indicated up to 5.9% cost savings at 30% due to reduced sand consumption and avoided landfilling. A life cycle assessment (LCA) of 0%, 15% and 30% scenarios showed environmental benefits, including a 45% reduction in global warming potential and improved freshwater eutrophication, mainly from avoided sand extraction and grit disposal. Trade-offs were observed for human carcinogenic toxicity and stratospheric ozone depletion linked to chlorine-based sanitisation. Overall, controlled recovery and valorisation of WWTP grit offers a feasible circular-economy route for the sanitation and construction sectors.