Micro- and nanoplastics in wastewater treatment plants: Occurrence, removal, fate, impacts and remediation technologies – A critical review

The manifestation of microplastics (MPs) and nanoplastics (NPs) in wastewater treatment plants (WWTPs) has become a major challenge owing to their unique characteristics such as hydrophobicity, surface charges, longer molecular chain arrangement, higher specific surface area, variety of size, shape, color and functional groups. They can also act as a vector in spreading other toxic pollutants in the environment by making convoluted complexes. Therefore, in this review, the up-to-date status on occurrence and removal of MPs and NPs in WWTPs are comprehensively evaluated. The stimuli of pertinent factors on the removal of MPs and NPs in WWTPs are also elucidated. Furthermore, the sorption behavior and mechanism of MPs and NPs towards toxic pollutants are critically debated in order to inspect the genuine menaces of MPs and NPs to WWTPs performance and environment. Particularly, the impacts of MPs and NPs on the performance of different wastewater treatment processes have been critically discussed. So far, no specific treatment technology has been developed specifically to remove MPs and NPs from sewage effluents and sludge excluding the subsisting conventional treatment techniques. Hence, to fill this gap, the recent research innovations on the development of MPs- and NPs-targeted treatment technologies are critically reviewed. Regarding this, the performances, pros and cons of the proposed technologies are critically evaluated that will be helpful in developing more reliable and cutting-edge technologies to eradicate MPs and NPs from the environment. Moreover, this critical review also provides knowledge gaps/key challenges and future perspectives for scientific community to combat against MPs and NPs pollution.