A comparative study of waste activated sludge conditioning with Fe(II)-peroxymonosulfate oxidative process

Improving sludge dewaterability is a key step of waste sludge recycling. The effect and mechanisms on two kinds of waste activated sludge (WAS) with Fe(II)-peroxymonosulfate (PMS) oxidation were compared. For WAS-A, the optimum capillary suction time (CST) and specific resistance to filtration (SRF) reduction rates were achieved (56.5% and 89.3%, respectively) with PMS 0.1 g/g TSS and Fe(II) 0.05 g/g TSS. For WAS-B, the optimal results were PMS 0.1 g/g TSS and Fe(II) 0.1 g/g TSS, and the reduction in CST and SRF was 64.6% and 90.1%, respectively. After conditioning, the particle size decreased slightly while the zeta potential increased dramatically. The proteins and polysaccharides analysis indicated the destruction in extracellular polymeric substances (EPS) and microbial cells resulted from the sulfate radicals. Microtopography showed that the original structure was changed with irregular pores formed on the surface, thus facilitating the passage of internal water and further improving the sludge dewaterability.