Using Fe(III)-coagulant-modified colloidal gas aphrons to remove bio-recalcitrant dissolved organic matter and colorants from cassava distillery wastewater

Efficient removal of bio-recalcitrant dissolved organic matter (DOM) and colorants is essential for discharging or reusing the distillery wastewater. The present work adopted a novel microbubble system - Fe(III)-coagulantmodified colloidal gas aphrons (CGAs) in flotation as tertiary treatment of the bio-chemically treated cassava distillery wastewater. Approximately 93% of bio-recalcitrant color and around 79% of dissolved organic carbon (DOC) were removed at the initial pH of 9.0 and 7.1, individually. The modified CGAs exhibited strong ability of complexation and electrostatic attraction of the polyanions of DOM and colorants. But the 1-10 kDa DOM was found to be resistant to the CGA capture. Compared with directly dosing coagulant, the Fe(III)-coagulantmodified CGAs consumed similar to 47% and similar to 21% less coagulant to achieve the optimum decoloration efficiency and DOC removal, respectively. In the flotation with Fe(III)-coagulant-modified CGAs, the coagulant-dosing system could be omitted while the coagulant utilization was improved.