Removal of microplastics in unit processes used in water and wastewater treatment: a review

Abstract

Many tons of micro- and nano-sized plastic particles enter the aquatic environment every year, due to increasing plastic production, with the consequent risk of microplastics contaminating our environment. Addressing this multifaceted threat requires innovative technologies that can efficiently remove microplastics from the environment. Therefore, there is an urgent need to study the efficiency of the removal of microplastics by different water and wastewater treatment technologies. After short overviewed the source, occurrence, and potential adverse impacts of microplastics to human health, we then identified promising technologies for microplastics removal, including physical, chemical, and biological approaches. A detailed analysis of the advantages and limitations of different techniques was provided. According to literature data, the performance of microplastics removal is as follows: membrane bioreactor (>99%) > activated sludge process (~98%) > rapid sand filtration (~97.1%) > dissolved air floatation (~95%) > electrocoagulation (>90%) > constructed wetlands (88%). Chemical treatment methods such as coagulation, magnetic separation, Fenton, photo-Fenton and photocatalytic degradation also show moderate to high efficiency of microplastics removal. Hybrid treatment such as the MBR-UF/RO system, coagulation followed by ozonation, adsorption, dissolved air flotation, filtration, and constructed wetlands based hybrid technologies have shown very promising results in the effective removal of microplastics. Lastly, research gaps in this area are identified, and suggestions for future perspectives are provided. We concluded this review with the current challenges and future research priorities, which will guide us through the path addressing microplastics contamination.