Impact of microplastics on the treatment performance of constructed wetlands: Based on substrate characteristics and microbial activities

Xiangyu Yang; Qiang He; Tao Liu; Feifei Zheng; Han Mei; Mengli Chen; Gang Liu; Jan Vymazal; Yi Chen

doi:10.1016/j.watres.2022.118430

Impact of microplastics on the treatment performance of constructed wetlands: Based on substrate characteristics and microbial activities

Water Res. 2022 Jun 15:217:118430. doi: 10.1016/j.watres.2022.118430. Epub 2022 Apr 8.

Authors

Xiangyu Yang¹, Qiang He², Tao Liu², Feifei Zheng², Han Mei², Mengli Chen², Gang Liu³, Jan Vymazal⁴, Yi Chen⁵

Affiliations

¹ Key Laboratory of the Three Gorges Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Campus B 83 Shabeijie, Shapingba, Chongqing 400044, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, 400044, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² Key Laboratory of the Three Gorges Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Campus B 83 Shabeijie, Shapingba, Chongqing 400044, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, 400044, China.
³ State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
⁴ Department of Applied Ecology, Faculty of Environmental Sciences, Czech University of Life Sciences Prague,16521, Prague 6, Czech Republic.
⁵ Key Laboratory of the Three Gorges Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Campus B 83 Shabeijie, Shapingba, Chongqing 400044, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, 400044, China. Electronic address: chenyi8574@cqu.edu.cn.

PMID: 35429885
DOI: 10.1016/j.watres.2022.118430

Abstract

Presence of microplastics (MPs) in wastewater has posed a huge ecosystem risk. Constructed wetlands (CWs) can effectively intercept MPs, while with MPs accumulation the response of CWs' performance is still unclear. In order to evaluate those effects, we conducted a 370-day experiment using CW microcosms fed with different levels (0, 10, 100, and 1000 μg/L) of polystyrene (PS) MPs (diameter: 50-100 μm). Results showed that nitrogen removal efficiency was increased (by 3.9%-24.7%) during the first 60 days and then decreased (by 7.1%-41.3%) with MPs accumulating, but no obvious change in COD and TP removal was observed. From further analysis, MPs accumulation changed the biofilm composition (TOC content increased from 41.4% to 52.7%), substrate porosity (electrical resistivity increased by 1.2-2.4 folds), and oxygen mass transfer (|K_La,O2| increased from 3.5% to 18.6%). Moreover, the microbial dynamics presented a higher abundance of nitrifiers (Nitrospira and Nitrosomonas) during the 60-day experiment and a lower abundance in the last days, while denitrifiers (Thauera, Thiobacillus, and Anaerolinea) had a high relative abundance throughout the experiment, being consistent with the variation of nitrification and denitrification rates. Finally, structural equation model analysis proved that due to the changes of substrate characteristics and microbial compositions and activities, the obvious decrease in nitrification efficiency was a direct reason for the decline of nitrogen removal during 370-day MPs accumulation. Overall, our study first prove that MPs accumulation can cause a series of changes in physicochemical and microbial characteristics of substrate, and ultimately affect the nitrogen-transforming process in CWs. Although our conclusions were based on the lab-scale CWs being different from the real wetlands, we hope that the conclusions can provide the effective regulatory strategies to guide the control of MPs in the actual wetlands.

Keywords: Constructed wetlands; Microbial composition & activity; Microplastics; Nitrogen removal; Substrate characteristic.

MeSH terms

Denitrification
Ecosystem
Microplastics*
Nitrogen / analysis
Plastics
Waste Disposal, Fluid
Wastewater / analysis
Wetlands*

Substances

Microplastics
Plastics
Waste Water
Nitrogen