[Microplastics in wastewater treatment: current status and future trends]

Microplastics (MPs) have been detected in many ecosystems, such as the ocean, land and the atmosphere. A large number of MPs in urban sewage are trapped in the activated sludge by sewage treatment plants, but tens of thousands of MPs 'escape' the treatment and are discharged into the nature. Meanwhile, most of the MPs are transferred into the activated sludge during sewage treatment, and the sludge will be further used in agriculture, leading to secondary pollution of the MPs. Through literature research, we summarized the sources, distribution and hazards of MPs in the environment, the treatment of MPs with activated sludge, and the treatment methods of residual MPs in activated sludge, and summed up the potentials of biotechnology and synthetic biology in the genetic modification of key bacteria in activated sludge to endow them with MPs-degrading ability. The conclusion is expected to serve as a reference for optimizing the biodegradation of MPs in wastewater treatment plants.