Mechanism of microplastics effects on the purification of heavy metals in piggery effluents by microalgae

Huimin Wang; Longzao Luo; Binghua Yan; Shuang Luo

doi:10.1016/j.envpol.2024.124028

Mechanism of microplastics effects on the purification of heavy metals in piggery effluents by microalgae

Environ Pollut. 2024 Apr 25:351:124028. doi: 10.1016/j.envpol.2024.124028. Online ahead of print.

Authors

Huimin Wang¹, Longzao Luo², Binghua Yan¹, Shuang Luo³

Affiliations

¹ College of Environment and Ecology, Hunan Agricultural University, Changsha, 410128, China.
² School of Chemistry and Environmental Science, Shangrao Normal University, Shangrao, 334001, China.
³ College of Environment and Ecology, Hunan Agricultural University, Changsha, 410128, China; Centre for Water Technology (WATEC) & Department of Biological and Chemical Engineering, Aarhus University, Universitetsbyen 36, 8000, Aarhus C, Denmark. Electronic address: shuangluo@hunau.edu.cn.

PMID: 38677456
DOI: 10.1016/j.envpol.2024.124028

Abstract

Microalgae is an effective bioremediation technique employed for treating piggery effluent. However, there is insufficient study on how the presence of microplastics (MPs) in wastewater affects the ability of microalgae to remove heavy metals from piggery effluent. This study aims to investigate the influence of two prevalent heavy metals found in piggery wastewater, Cu²⁺ (2 mg/L) and Zn²⁺ (2 mg/L), on their removal by microalgae (Desmodesmus sp. CHX1) in the presence of four types of MPs: polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene terephthalate (PET). The results revealed that smaller particle size MPs promoted chlorophyll accumulation, while larger particles inhibits it. Additionally, higher concentrations of MPs promoted chlorophyll accumulation, while lower concentrations inhibited it. As for heavy metals, the presence of microplastics reduced the removal efficiency of Cu²⁺ and Zn²⁺ by Desmodesmus sp. CHX1. The highest inhibition of Cu²⁺ was 30%, 10%, 19%, and 16% of the control (CK), and the inhibition of Zn²⁺ was 7%, 4%, 4%, and 13%, respectively, under the treatments of PE, PVC, PP and PET MPs. Furthermore, Desmodesmus sp. CHX1 can secrete more extracellular polymeric substances (EPS) and form heterogeneous aggregates with MPs to counteract their pressure. These findings elucidate the impact of MPs on microalgae in bioremediation settings and offer useful insights into the complex relationships between microalgae, MPs, and heavy metals in the environment.

Keywords: Heavy metals; Microalgae; Microplastics; Piggery wastewater.