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A review of the removal of microplastics in global wastewater treatment plants: Characteristics and mechanisms

Environment International 2020 589 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count. Score: 60 ? 0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.
Weiyi Liu, Jinlan Zhang, Hang Liu, Xiaonan Guo, Xiyue Zhang, Xiaolong Yao, Zhiguo Cao, Tingting Zhang

Summary

This review analyzed data from 38 wastewater treatment plants across 11 countries to understand how effectively they remove microplastics. While treatment plants can remove the majority of microplastics from wastewater, significant quantities still pass through into waterways, and the microplastics captured in sewage sludge may re-enter the environment when that sludge is applied to farmland.

Study Type Environmental

Wastewater treatment plants (WWTPs) are considered to be the main sources of microplastic contaminants in the aquatic environment, and an in-depth understanding of the behavior of microplastics among the critical treatment technologies in WWTPs is urgently needed. In this paper, the characteristics and removal of microplastics in 38 WWTPs in 11 countries worldwide were reviewed. The abundance of microplastics in the influent, effluent, and sludge was compared. Then, based on existing data, the removal efficiency of microplastics in critical treatment technologies were compared by quantitative analysis. Particularly, detailed mechanisms of critical treatment technologies including primary settling treatment with flocculation, bioreactor system, advanced oxidation and membrane filtration were discussed. Thereafter, the abundance load and ecological hazard of the microplastics discharged from WWTPs into the aquatic and soil environments were summarized. The abundance of microplastics in the influent ranged from 0.28 particles L to 3.14 × 10 particles L, while that in the effluent ranged from 0.01 particles L to 2.97 × 10 particles L. The microplastic abundance in the sludge within the range of 4.40 × 10-2.40 × 10 particles kg. In addition, there are still 5.00 × 10-1.39 × 10 microplastic particles discharged into the aquatic environment each day Moreover, among the critical treatment technologies, the quantitative analysis revealed that filter-based treatment technologies exhibited the best microplastics removal efficiency. Fibers and microplastics with large particle sizes (0.5-5 mm) were easily separated by primary settling. Polyethene and small-particle size microplastics (<0.5 mm) were easily trapped by bacteria in the activated sludge of bioreactor system. The negative impact of microplastics from wastewater treatment plant was worthy of attention. Moreover, unknown transformation products of microplastics and their corresponding toxicity need in-depth research.

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