Enhanced Removal of Pollutants in Constructed Wetlands with Manganese Sands

Manganese (Mn) sands have been widely used in water purification due to their strong oxidation and adsorption abilities. However, there are few reports on the use of manganese sands as filler material in constructed wetlands. Based on previous studies, we speculated that the addition of manganese sands in constructed wetlands would enhance the removal of pollutants from the source water, and the resulting Mn(Ⅱ) could then be oxidized by the rhizosphere and soil microorganisms in the wetlands. To test this hypothesis, this study explored the enhanced removal of pollutants in wetlands constructed with manganese sands as substrates and Phragmites as plants, and also examined the role of Phragmites rhizosphere microorganisms in water purification. By comparing the treatment effects between the wetlands constructed with and without manganese sands (control), we found that the wetland containing manganese sands exhibited significantly improved removal of dissolved organic carbon and total nitrogen, as well as removal of ammonia nitrogen during periods of lower temperature. The 16S rRNA sequencing showed that the addition of manganese sands could increase the richness and diversity of Phragmites rhizosphere microorganisms, but had limited impacts on the microbial community structure, which might be an important factor for enhancing the water treatment performance of constructed wetlands. This study provides a new method for the technological optimization of constructed wetlands.