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Addition of iron materials for improving the removal efficiencies of multiple contaminants from wastewater with a low C/N ratio in constructed wetlands at low temperatures

Zhao, Zhimiao, Xu, Chenglong, Zhang, Xiao, Song, Xinshan
Environmental science and pollution research international 2019 v.26 no.12 pp. 11988-11997
Thauera, Thiobacillus, bacteria, carbon, carbon nitrogen ratio, chemical oxygen demand, chromium, constructed wetlands, copper, denitrification, heavy metals, ion exchange, iron, kinetics, microbial communities, nitrates, nitrogen content, operating costs, pollution control, temperature, wastewater, wastewater treatment
Constructed wetlands (CWs) are widely used in wastewater treatment. Wastewater generally contains multiple contaminants. In this study, CWs were applied to treat wastewater with a low COD/TN ratio and containing heavy metals. Iron-based material was added in CWs to enhance the treatment efficiency. The contaminant removal efficiency was positively correlated with the dosage of iron-based material. Considering the operation cost, we added 1 g of iron-based material in CW and realized the multi-contaminant removal efficiency after 4-day treatment at low temperature: 99.51% of Cu(II), 87.22% of Cr(VI), 65.62% of TN, and 60.23% of COD. Microbial community analysis and kinetic analysis predicted that the removal mechanism involved ion exchange and microbial denitrification. Specific bacteria were found in CWs with iron-based material, such as Thiobacillus spp. and Thauera spp., indicating that the nitrate removal in the denitrification process was triggered by carbon sources and that Fe²⁺ worked as both the electron donor and the adjuster of the abundances of specific bacteria. The addition of iron-based material into CWs was a green option to improve the pollutant removal performance.