Highly efficient phosphorous removal in constructed wetland with iron scrap: Insights into the microbial removal mechanism

Excessive phosphorus (P) in surface water can lead to serious eutrophication and economic losses. Iron-based constructed wetland (CW) is considered as a promising solution to eliminate P effectively due to the advan-tage of low-cost. However, there is limited available information on the microbial removal mechanism of P in iron-based CW up to now. Therefore, CW with iron scrap was constructed to investigate the treatment perfor-mance and microbial removal mechanism in this study. Results showed that efficient and stable P removal (97.09 +/- 1.90%) was achieved in iron scrap-based CW during the experiment period, which was attributed to the precipitation of iron and P and improved microbially mediated P removal. Metagenomic analysis showed that microbial diversity was enhanced and phosphate accumulating organisms (e.g., Dechloromonas and Tetrasphaera) were enriched in CW with iron scrap, which explained higher P removal reasonably. In addition, the abundance of genes involved in the P starvation (e.g., phoB), uptake and transport (e.g., pstB) were enhanced in iron scrap-based CW. Enrichment analysis demonstrated that phosphotransferase pathway was also significantly up-regulated in CW with iron scraps, indicating that the energy supply of microbial P removal was enhanced. These findings provide a better understanding of the microbial removal mechanism of P in iron-based CW.

Automated summary

This study investigated the microbial removal mechanism of phosphorus (P) in an iron-based constructed wetland (CW) by constructing a CW with iron scrap. Efficient and stable P removal (97.09 +/- 1.90%) was achieved in the iron scrap-based CW, attributed to iron and P precipitation and improved microbially mediated P removal. Metagenomic analysis showed enhanced microbial diversity and enrichment of phosphate accumulating organisms in the iron scrap-based CW, explaining the higher P removal. Genes involved in P starvation, uptake, and transport were also enhanced in the iron scrap-based CW. Enrichment analysis demonstrated the up-regulation of the phosphotransferase pathway, indicating enhanced energy supply for microbial P removal. These findings provide a better understanding of the microbial removal mechanism of P in iron-based CW.