Enhanced removal of microplastic fibres using aluminium and chitosan-based coagulants assisted with microbubble technology

Microplastic (MP) pollution has emerged as a threat to drinking water quality, where fibres are the dominant type of MPs found in drinking/wastewater treatment plant influents. The potential of MP removal through conventional treatment has not been vastly studied. Accordingly, this study investigates the removal of MP fibres using two-hybrid methods: coagulation-flocculation followed by sedimentation (CFS); and coagulation-flocculation combined with flotation using microbubbles (CFm) in the presence of two different water matrices, deionised water (DI) containing surfactants and DI water in the presence of humic acid (HA). A typically used Aluminium-based coagulant (AlCl 3 .6H 2 O) and a green-based coagulant, Chitosan, were employed and their microfibre removal efficiencies were compared with the aid of turbidity measurements. The results in the HA-simulated water matrix, the CFS treatment with the AlCl 3 .6H 2 O coagulant achieved the highest MP removal rate of 88.46 %. In contrast, Chitosan was most effective during the CFm treatment in the same water matrix, with a removal rate of 78.30 % and a 5 mg/L coagulant concentration. These results demonstrate that Chitosan has the potential to achieve high MP fibre removal with less coagulant dosage in different water matrices. • Polyester microplastic (MP) fibre removal was studied. • Coagulation-flocculation-sedimentation (CFS)/microbubble introduction (CFm) were tested. • AlCl 3 .6H 2 O and Chitosan coagulants were tested at varied conditions in both systems. • AlCl₃.6H₂O in CFS achieved 88.46 % turbidity removal at pH 7. • Chitosan outperformed in CFm, removing 78.30 % turbidity at pH 4.