Optimization of Fe(II)/SPC Sludge Conditioning and Dewatering Process Based on Response Surface Methodology: Full-Scale Application

Abstract

Sludge conditioning is a crucial step in sludge dewatering aimed at minimizing excessive sludge production. The Fenton process, which harnesses oxidative radicals to dismantle extracellular polymeric substances (EPS) and microorganisms, has been unequivocally proven to enhance sludge dewaterability. However, the widespread adoption of the Fenton process is hampered by its high costs and logistical challenges in transportation. In contrast, the Fe(II)-activated sodium percarbonate (Fe(II)/SPC) process has emerged as a promising technology for sludge conditioning due to its remarkable performance and safe operation. However, limited information is available regarding the optimization of Fe(II)/SPC for sludge conditioning and dewatering at full scale. This study conducted the sludge conditioning and dewatering process within a full-scale wastewater treatment plant, utilizing the response surface methodology (RSM) to optimize the Fe(II)/SPC process. Furthermore, this study investigated its impact on sludge structure and compared the economic benefits of the Fe(II)/SPC process with other full-scale conditioning processes. The results of bound water and LDH analysis revealed that the Fe(II)/SPC process not only degraded EPS but also disrupted microbial cells, thereby releasing intracellular water. Based on the RSM results, we successfully established a polynomial prediction model to determine the optimal capillary suction time (CST) and moisture content. The optimal parameters determined through RSM were an initial pH of 3.02, Fe(II) dosage of 0.05 g/g TSS, and SPC dosage of 0.07 g/g TSS. The validation test confirmed the accuracy of the prediction results, with the conditioned sludge exhibiting a CST of 31.6 s and a moisture content of 51.47%. Furthermore, when compared to the PFS and Fenton processes, the Fe(II)/SPC process demonstrated higher economic efficiency and safety, while maintaining good dewatering performance. Overall, the Fe(II)/SPC treatment shows promise as a prospective sludge dewatering and conditioning process.