Upcycling of Lychee Seed Powder-Coagulated Wastewater Sludge into Sustainable Construction Product: A Green Circular Innovation

Abstract

Greywater surfactants affect ecosystems and water quality [1]. This study investigated the use of LS powder as a surfactant-removal coagulant in synthetic wastewater. In jar testing, with 3 g/L, pH 8, and a mixing speed of 140 RPM for quick mixing and 40 RPM for slow mixing, followed by 1 hour of sedimentation, turbidity was reduced by 77.08% and surfactant removal was 66.75%. SEM, XRD, EDX, FTIR, zeta potential, confocal microscopy, and contact angle measured LS characteristics. For LS, the total protein content was 179.48 μg/g and the total carbohydrate content was 590 μg/g. Response Surface Methodology optimized parameters: dose 3.58 g/L, pH 6.86, and 46.33 minutes used in a novel clariflocculator. Sludge was transformed into eco-friendly paver blocks to replace traditional cement blocks and promote a circular economy. This study shows that LS powder is a cost-effective, efficient, and ecologically friendly coagulant for sustainable building and wastewater treatment.