A shallow constructed wetland combining porous filter material and Rotala rotundifolia for advanced treatment of municipal sewage at low HRT

Water scarcity is a worldwide problem. Recycled municipal wastewater is considered a useful alternative to the conventional types of water resources. In this study, a shallow constructed wetland (SCW) with porous filter material and Rotala rotundifolia was used for advanced municipal sewage treatment. The wetland without plant was set as the control ( SCWC). The pollutant removal performance of the system at different hydraulic retention times (HRTs) was investigated. The diversity of the microbial community was analyzed, and the fate of nutrients, mainly N and P, in the system was discussed. Results showed that SCW was efficient in pollutant removal. Effluent concentrations of chemical oxygen demand (COD), total phosphorus (TP), and ammonium nitrogen -(NH4+-N) were 15.0-23.6, 0.19-0.28, and 0.83-1.16 mg/L, separately, with average removal efficiencies of 61.2%, 46.3%, and 88.1% at HRT 18 h, which met the requirements of type IV water set by the environmental quality standards for surface water in China. The richness and evenness of the bacterial community were significantly higher in the plant- rooted SCW. They increased along with the system. The dominant genera in the system were phosphate-solubilizing bacteria, nitrifying bacteria, and denitrifying bacteria. The P in the influent mainly flowed to the substrate and plant. At the same time, most N was removed by nitrification and denitrification. These findings suggested that the SCW could remove pollutants from the municipal sewage effluent and meet the standard requirement at low HRT.

Automated summary

Water scarcity is a global issue, and recycled municipal wastewater has been considered as an alternative solution. This study utilized a shallow constructed wetland with porous filter material and Rotala rotundifolia for advanced municipal sewage treatment. The results showed that the wetland efficiently removed pollutants from the effluent and met the standard requirements. The presence of plant roots significantly increased the richness and evenness of the bacterial community, with phosphate-solubilizing bacteria, nitrifying bacteria, and denitrifying bacteria being the dominant genera.