Harnessing sewage sludge to remove high organic loads through biosorption

Biosorption is a physicochemical process in which pollutants bind to biological materials, enabling biomass to be used as a natural, accessible and environmentally friendly biosorbent. Highly loaded wastewater, particularly leachate from waste management systems, contains very high concentrations of organic matter and therefore requires efficient, sustainable and resource‑oriented treatment approaches. This study investigates the valorisation of sewage sludge as a biosorbent for the removal of organic pollution from leachate with an initial chemical oxygen demand of 12,868 mg O₂/L. Biosorption was tested at sludge concentrations ranging from 1 to 6 g/L. The maximum removal efficiency achieved was 30.0%, and the biosorption capacity of the activated sludge was 649 mg/g, confirming the strong biosorption potential of sludge due to its floc structure, active EPS matrix and diverse functional groups. The Temkin isotherm model provided the most accurate description of biosorption equilibrium (F = 0.971).