Preparation and Dewatering Performance Evaluation of CPAD Sludge Conditioner: From Small Scale to Pilot Scale

This study aimed to develop a novel sludge conditioner (CPAD) based on carboxymethyl chitosan (CTS) to address the low efficiency of municipal sludge dewatering. CPAD was prepared by grafting acrylamide (AM) and dimethyldiallylammonium chloride (DADMAC) onto CTS, resulting in a honeycomb-like porous structure, and its flocculation and dewatering performance were validated through laboratory and pilot-scale tests. The novelty of CPAD lies in its combination of the environmental friendliness of natural polymers and the high efficiency of synthetic polymers, significantly reducing the specific resistance to filtration (SRF) and moisture content of sludge. Experimental results showed that at a pH of 6 and a CPAD dosage of 3 kg/t dry sludge (DS), the SRF of the sludge decreased by 90.15%, and the moisture content decreased by 11.85%. Under pilot-scale conditions, with a filtration pressure of 1.2 MPa and a filtration time of 90 min, CPAD reduced the sludge moisture content to 59.3%. Additionally, CPAD effectively neutralized the sludge's electronegativity, reduced electrostatic repulsion between particles, promoted sludge particle bridging and aggregation, and lowered the chemical oxygen demand (COD) and total organic carbon (TOC) of the filtrate as well as the sludge viscosity. This study provides new insights and technical support for developing low-cost, efficient, and environmentally friendly sludge conditioners. Summary: CPAD promotes sludge particle aggregation and reduces sludge viscosity. The mud cake produced by CPAD were environmentally friendly. Sludge conditioner CPAD is nontoxic and harmless and does not cause secondary pollution. CPAD can effectively reduce the moisture content of sludge cake.