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

Weiyi Liu; Jinlan Zhang; Hang Liu; Xiaonan Guo; Xiyue Zhang; Xiaolong Yao; Zhiguo Cao; Tingting Zhang

doi:10.1016/j.envint.2020.106277

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

Environ Int. 2021 Jan:146:106277. doi: 10.1016/j.envint.2020.106277. Epub 2020 Nov 20.

Authors

Weiyi Liu¹, Jinlan Zhang¹, Hang Liu¹, Xiaonan Guo¹, Xiyue Zhang¹, Xiaolong Yao², Zhiguo Cao³, Tingting Zhang⁴

Affiliations

¹ Department of Environmental Science and Engineering, Research Centre for Resource and Environment, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China.
² Department of Environmental Science and Engineering, Beijing Technology and Business University, Beijing 100048, People's Republic of China.
³ School of Environment, Henan Normal University, Xinxiang 453007, People's Republic of China.
⁴ Department of Environmental Science and Engineering, Research Centre for Resource and Environment, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China. Electronic address: zhangtt@mail.buct.edu.cn.

PMID: 33227584
DOI: 10.1016/j.envint.2020.106277

Abstract

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^-1 to 3.14 × 10⁴ particles L^-1, while that in the effluent ranged from 0.01 particles L^-1 to 2.97 × 10² particles L^-1. The microplastic abundance in the sludge within the range of 4.40 × 10³-2.40 × 10⁵ particles kg^-1. In addition, there are still 5.00 × 10⁵-1.39 × 10¹⁰ 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.

Keywords: Environmental toxicity; Fate; Meta-analysis; Microplastics; Wastewater treatment technology.

Publication types

Research Support, Non-U.S. Gov't
Review

MeSH terms

Environmental Monitoring
Microplastics
Plastics
Waste Disposal, Fluid
Wastewater / analysis
Water Pollutants, Chemical* / analysis
Water Purification*

Substances

Microplastics
Plastics
Waste Water
Water Pollutants, Chemical