Performance and microbial community features of tidal-flow biochar-amended constructed wetlands treating sodium dodecyl sulfate (SDS)-containing greywater

Abstract

A large quantity of surfactants (e.g., sodium dodecyl sulfate (SDS)) are discharged along with greywater especially during the COVID-19 pandemic, while information on the treatment of surfactant-containing greywater using eco-friendly constructed wetlands (CWs) and the impact of surfactants on CW systems has rarely been reported. In the present study, lab-scale CWs amended with a biochar substrate and operated in tidal flow (TF) mode were used to treat SDS-containing greywater. The results showed that the biochar-amended CWs removed NH4+-N significantly better (18.2–37.9%) than the gravel-only CWs (2.5–24.6%) but removed phosphorus (P) and COD less efficiently, and the feeding of SDS at 50 and 100 mg/L led to a notable decrease in N removal. TF not only notably improved the pollutant removal performance but also effectively eliminated SDS stress in the CWs (NH4+-N removal of 67.1–72.1%). Mean SDS removal efficiencies of 75.3–79.3% were obtained in the CWs. TF mode altered the microbial community structure and metabolic pattern and enhanced the abundance of functional bacteria related to N and P removal in the CWs. The bacterial community shifted considerably with SDS feeding, resulting in higher species diversity and more intensive co-occurrence network relationships. TF-CWs filled with composite substrates are highly feasible and promising for the treatment of SDS-containing greywater.