Preparation of biological activated carbon (BAC) using aluminum salts conditioned sludge cake for the bio-refractory organic contaminants removal from anaerobically digested liquor

Abstract

Waste sludge management continues to pose a great challenge with the increasing development of municipal wastewater treatment. Preparation of biological activated carbon (BAC) with waste activated sludge (WAS) is a promising method which could realize the synchronous harmlessness and recycling of WAS. The chemical conditioning is an indispensable step during the high-pressure dewatering process, which may greatly affect the physicochemical properties of BAC and adsorptive performance for various contaminants. In this work, sludge cake conditioned with typical inorganic polymeric flocculants – polymeric aluminum chloride (PAC) was used to prepare BAC for anaerobically digested liquor (ADL) treatment, and the effects of hydroxyl aluminum on physicochemical properties and adsorptive performance were systematically investigated. The results indicated that hydroxyl aluminum speciation had important effects on pore structure and functional groups on the surface of BAC. In comparison with sludge activated carbon, BAC conditioned with PAC exhibited better thermal stability and contained more functional groups. Furthermore, BAC conditioned with PAC of alkalisation degrees of 0.5 and 1.5 (PAC0.5-BAC and PAC1.5-BAC) had remarkable mesoporous structure and notable adsorption capacities for organic contaminants, and the organic contaminants removal could be fitted Freundlich model better. In addition, PAC1.5-BAC performed best in removing chroma and biopolymers (humic and protein-like substances) in filtrate. In brief, this paper proposed a novel sludge carbonization process by coupling enhanced dewatering with catalytic pyrolysis to prepare efficient BAC for wastewater treatment.