Feasibility of improving wastewater sludge dewaterability by combination of cationic polyacrylamide and synthetic fibers for resource utilization

• The combination of CPAM and PP achieves sludge MC of 65.88% • CPAM and synthetic fibers improved sludge filtration through adsorption bridging and enhanced rigidity. • Sludge calorific value exceeded 6676 kJ∙kg -1 after treated by optimal combination. As a by-product of wastewater treatments, sewage sludge possesses great value but its high moisture content impedes the resource recovery. Chemical conditioners are required prior to mechanical dewatering, and they are important in dewatering operations. On the other hand, synthetic fibers have good compression properties and can help sludge to build qualified sludge cake in mechanical dewatering process. In this study, we investigated the synergistic effects between CPAM and synthetic fibers, which could improve the wastewater sludge dewaterability and resource utilization. The sludge water content decreased from 96.2% to 65.9% after conditioning with the combination of CPAM at 1 mg∙g -1 DS combined with PP at 0.15 g∙g -1 DS. The combination of CPAM and fiber increased the zeta potential of sludge from -12.5 mV to -5.12 mV and decreased the compressibility coefficient of sludge cake from 1.13 to 0.89, achieving the effect of destabilizing the system and enhancing the rigidity of sludge cake. EPS analysis showed that the association of CPAM with fiber acted as an aid to dewatering mainly through the disruption of TB-EPS. In addition, the dry basis calorific value (35%) reached 6676 kJ∙kg -1 , indicating the feasibility of subsequent resource utilization. In conclusion, this study provided a new method and its underlying theory for deep sludge dewatering and wastes reutilization.