Effect of long-term exposure to non-biodegradable and biodegradable microplastics in continuous anoxic/aerobic bioreactors: Nitrogen removal performance, microbial communities and functional gene responses

Bing Yao; Min Liu; Jin Zhang; Xuan Hu; Bin Wang; Ren-Jun Liang; Ying Chen

doi:10.1016/j.jenvman.2024.123712

Effect of long-term exposure to non-biodegradable and biodegradable microplastics in continuous anoxic/aerobic bioreactors: Nitrogen removal performance, microbial communities and functional gene responses

J Environ Manage. 2024 Dec 14:373:123712. doi: 10.1016/j.jenvman.2024.123712. Online ahead of print.

Authors

Bing Yao¹, Min Liu¹, Jin Zhang², Xuan Hu¹, Bin Wang³, Ren-Jun Liang², Ying Chen⁴

Affiliations

¹ College of Architecture and Environment, Sichuan University, Chengdu, 610065, China.
² Sichuan Science City Tianren Environmental Protection Co., Ltd, Mianyang, 621900, China.
³ Sichuan Engineering Research Center for Municipal Wastewater Distributed Treatment Technology, Chengdu, 610200, China.
⁴ College of Architecture and Environment, Sichuan University, Chengdu, 610065, China. Electronic address: cy_jhxy@scu.edu.cn.

PMID: 39675334
DOI: 10.1016/j.jenvman.2024.123712

Abstract

The environmental hazards caused by microplastics (MPs) have received widespread attention, but the effects of non-biodegradable and biodegradable MPs of long-term presence on continuously operating sewage treatment bioreactors are not well known. In this study, we investigated the effect of a representative non-biodegradable MP, polyethylene terephthalate (PET), and a biodegradable MP, polylactic acid (PLA), on the nitrogen removal performance of conventional anoxic/aerobic (A/O) process. The NH₄⁺-N removal efficiencies were suppressed to 91.7 ± 5.5% and 80.8 ± 4.1% at concentrations of 10 and 100 mg/L PLA, significantly (p < 0.05) lower than 96.3 ± 1.0% and 95.0 ± 1.5% with the presence of PET. PLA resulted in a significant (p < 0.05) decrease in adenosine triphosphate of living cells (cATP) and dehydrogenase activities. PLA enhanced redox stress and induced a series of oxidative stress reactions that were detrimental to the normal growth and metabolism of microorganisms. The relative abundance of several functional microorganisms (Nitrosomonas,Nitrospira and Ellin6067) and genes (amoA, amoB and amoC) associated with NH₄⁺-N conversion were reduced. The potential risk of biodegradable MPs to the long-term wastewater treatment process cannot be ignored and needs to be emphasized.

Keywords: Functional genes; Microbial community; Nitrogen removal; Polyethylene terephthalate; Polylactic acid.