Microplastics in Aquaculture Wastewater in Southeast Asia: Sources, Fate, and Treatment Technologies: A Review

This review examines microplastics (MPs) in aquaculture wastewater across Southeast Asia, focusing on sources, occurrence pathways, fate during routine farm operations, and treatment opportunities that fit regional realities. The literature shows that aquaculture wastewater behaves as a connected river-canal-estuary system, with intermittent and solids-rich discharges that create short release windows often missed by routine grab sampling. Reported MP levels range from < 1 item/L in some receiving waters to > 10 items/L in aquaculture pond waters, while fishpond sediments in Hanoi, Vietnam, have been reported at 2767 ± 240 to 2833 ± 176 items/kg dry weight. Across reviewed studies, physical capture and separation provide the most consistent control: Sedimentation-based processes show reported removal ranges of 16.5%-98.4%, retention ponds retain about 88%-95% depending on particle size, and rapid sand filtration can reach 84%-98% under tested conditions. However, credible mitigation requires treatment trains rather than single-unit solutions, because many apparent removal pathways transfer MPs into sludge, scum, and backwash. Key gaps include uneven regional data, limited wastewater/sludge evidence, and a need for harmonized operations-aligned monitoring to support technology selection and policy action at scale.