Novel pretreatment technologies for sludge dewatering and dissolution: Humic acid combine with sodium percarbonate and different iron species

Large amounts of waste activated sludge are generated daily worldwide, posing significant environmental challenges. A promising sludge management method is urgently needed. This study innovatively introduces humic acid (HA) into a sodium percarbonate (SPC) sludge treatment system to enhance dewatering and dissolution processes. Therein, SPC was activated by dissolved iron (Fe(II) or Fe(III)) or solid phase iron (zero-valent iron or magnetite (Fe 3 O 4 )). Results confirmed that Fe(III)/SPC/HA could improve the dewaterability of sludge without pH adjustment, with the capillary suction time decreasing from 123.6 ± 1.32 s (control) to 58.10 ± 4.35 s, which was comparable with that of the Fe(III)/SPC at pH 3.0. Meanwhile, Fe 3 O 4 /SPC/HA significantly enhanced sludge dissolution, and the released protein and polysaccharide levels were 2.98 and 7.08 times higher than that in the control. Both Fe(III)/SPC/HA and Fe 3 O 4 /SPC/HA reduced heavy metals and pathogens in the sludge while increasing HA content in filtrates, all of which were beneficial for subsequent sludge disposal and HA recycling, offering cost-effective technologies for sludge treatment.