Assessment of surfactant removal capacity and microbial community diversity in a greywater-treating constructed wetland

Abstract

Surfactants are among the main chemical contaminants in greywater (GW) and can cause severe health issues in humans and aquatic organisms. We assessed the performance of a multistage constructed wetland system (EvaTAC) for GW treatment and capacity of the microbial community in linear alkyl benzene sulfonate (LAS) biodegradation. Physicochemical analyses were performed over 497 d, and biomass samples were collected for high-throughput DNA sequencing. The system was predominated by anaerobic conditions and received an average chemical oxygen demand (COD) and LAS of 374 and 32 mg·L⁻¹, with removal rates of 66% and 43%, respectively. A positive correlation between COD and LAS suggested COD as a design parameter for LAS removal. We identified microbial genera participating in hydrolysis, fermentation, syntrophy, acetogenesis, methanogenesis, surfactant degradation, and sulphate reduction. Among the 15 surfactant-degrading genera, Pseudomonas was predominant. Community richness and diversity indices were comparable between subsystems, with a slight decrease in diversity observed towards the outlet. Among the LAS degraders, Rhodopseudomonas palustris had the highest relative abundance of operational taxonomic unit (OTU)s in all samples and the highest richness in the anaerobic chamber. The patterns in microbial community composition and environmental conditions suggest that LAS biodegradation occurred throughout the EvaTAC system.