A Review on Microplastics Migration from Sources Through Wastewater to the Environments: Classifications, Impacts and Removal Techniques

Non-renewable microplastics are tiny (< 5 mm) synthetic polymer particles essentially of carbon and hydrogen atoms that resulted from fragmentation, degradation or production of plastic materials. These particles are emerging as worldwide pollutants with devastating impacts on the environments and the human health. This chapter provides a basic understanding of microplastics, sources, migration, impacts, removal techniques, and future projections. Microplastics originated from industrial production of plastic materials from fossil to domestic usage down to wastewater treatment systems before being discharged into the environments. In this review, microplastic pollutants were divided into three types based on environmental considerations. They include airborne, marine and terrestrial pollutants. The main air pollutants are polyethylene, polyester, and polyethylene terephthalate and circulated by wind in form of particle dust. In marine pollution, polyethylene (PE) floats on water surface and interacts with aquatic organisms, whereas denser ones sink and affects the sea floor and biota at the bottom of the sea/ocean. Terrestrial pollutants like microfiber polyesters affect the physicochemical nature of the soil and disrupting activities of microorganisms. Three major removal methods of microplastics include (i) the natural (biological) techniques, (ii) the artificial (physical and chemical) techniques and (iii) the combination techniques. Numerous studies have been directed towards the removal of microplastics from wastewater. To date, no technique has completely removed microplastics from wastewater with high level of precision and consistency. Integrated and multi-disciplinary approaches remain key for effective removal from the sources, wastewater and the environment.