Microplastics in granular sequencing batch reactors: Effects on pollutant removal dynamics and the microbial...

Area of Science:

• Environmental Science
• Environmental Engineering
• Microbiology

Background:

• Microplastic (MP) contamination is a growing concern in aquatic environments.
• Wastewater treatment plants (WWTPs) are potential hotspots for MP accumulation.
• The impact of MPs on biological treatment processes, like granular sludge sequencing batch reactors (GSBRs), requires thorough investigation.

Purpose of the Study:

• To investigate the effects of different types and concentrations of MPs on pollutant removal in GSBRs.
• To analyze the influence of MPs on microbial community structure and function.
• To understand the interaction between MPs, biomass, and nutrient removal efficiencies.

Main Methods:

• Introduction of polyethylene (PE) and polyethylene terephthalate (PET) MPs into GSBRs at varying concentrations.
• Monitoring of chemical oxygen demand (COD), nitrogen, and phosphorus removal efficiencies.
• Analysis of microbial community dynamics using gene abundance and expression profiling (nosZ, ppk1).

Main Results:

• PET-MPs showed higher accumulation in biomass compared to PE-MPs.
• A 50 mg/L dose of PET-MP reduced COD removal by ~4% and increased P-PO4 removal by ~7%.
• Nitrogen removal decreased with increasing PET-MP dosage but increased with PE-MP dosage, affecting nosZ and ppk1 gene expression.

Conclusions:

• MP type and concentration significantly alter pollutant removal efficiencies and microbial community structure in GSBRs.
• PET-MPs can negatively impact COD removal, while PE-MPs show potential benefits for nitrogen removal.
• Findings provide crucial insights for managing WWTPs facing MP pollution and ensuring sustainable treatment processes.