Structural characterization of modified straw combined with CPAM conditioned sludge filter cake and analysis of its structure-performance relationship with sludge dewatering performance

In previous studies on the enhancement of sludge dewatering technology, limited attention has been given to investigating changes in the pore structure of sludge cake, and the impact of water migration channels within the sludge cake on dewatering performance has not been considered. In this study, a correlation between sludge dewatering performance and the alteration of the sludge cake structure was established, and the factors influencing sludge dewatering efficiency through changes in the pore network structure within the sludge cake was analyzed. In this study, municipal sludge was conditioned via three methods: cationic polyacrylamide (CPAM), modified straw fiber (MF), and a combination of CPAM and MF. The results indicated that the combination of CPAM and MF notably enhanced the sludge dewatering performance, achieving an 86.19 % reduction in CST and a 48.83 % decrease in SRF. By employing CT to reconstruct the sludge cake, a three-dimensional model of both the sludge cake and its pore network was developed, facilitating a more intuitive analysis of the structural alterations occurring in the sludge cake before and after conditioning. The CPAM+MF conditioning method yielded the best results, with the sludge porosity increasing to 47.8 %, the total number of pores reaching 1305, and the number of pore throats reaching 3298. Following CPAM+MF conditioning, the number of pore channels increased by 341.4 %. Further analysis of the compressibility of the conditioned sludge was conducted through a consolidation experiment, which revealed that the compression coefficient of the sludge was reduced by 62.60 % after CPAM+MF conditioning.