Interactions of high-rate nitrate reduction and heavy metal mitigation in iron-carbon-based constructed wetlands for purifying contaminated groundwater

Lixia Jia; Hai Liu; Qiang Kong; Ming Li; Shubiao Wu; Haiming Wu

doi:10.1016/j.watres.2019.115285

Interactions of high-rate nitrate reduction and heavy metal mitigation in iron-carbon-based constructed wetlands for purifying contaminated groundwater

Water Res. 2020 Feb 1:169:115285. doi: 10.1016/j.watres.2019.115285. Epub 2019 Nov 5.

Authors

Lixia Jia¹, Hai Liu², Qiang Kong³, Ming Li¹, Shubiao Wu⁴, Haiming Wu⁵

Affiliations

¹ College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi, 712100, PR China.
² State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China.
³ College of Geography and Environment, Shandong Normal University, Jinan, 250014, PR China.
⁴ Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, 8000C, Denmark. Electronic address: wushubiao@gmail.com.
⁵ College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi, 712100, PR China; Department of Bioscience, Aarhus University, Aarhus, 8000C, Denmark. Electronic address: haimingwu14@nwsuaf.edu.cn.

PMID: 31722275
DOI: 10.1016/j.watres.2019.115285

Abstract

Groundwater, as the most important drinking water source in arid regions of China, has been polluted seriously by accumulated nitrate and heavy metals. An economic alternative with capacity of simultaneous mitigation of nitrate and heavy metals is urgently needed. This study explored the incorporation of iron scraps and biochar into constructed wetlands (CWs) for enhancing purification performance and investigated interactions of effective nitrate reduction and heavy metals mitigation. The results showed that nitrate reduction performance could reach 87% in iron and carbon-based (Fe-C) CWs through Fe-C micro-electrolysis process, with lower nitrous oxide (N₂O) emission (4.6-11.75 μg m^-2 h^-1) due to the complete denitrification process. Moreover, efficient heavy metals mitigation of 75-97% total chromium (Cr) and total lead (Pb) was obtained from Fe-C systems. However, the occurrence of heavy metals (Cr and Pb) in the influent posed an adverse impact on nitrate removal with the reduction rate of 19-43%. Biochemical characteristics of wetland plants indicated that the plants also suffered from the stress which induced from heavy metals. Overall, although the addition of iron and biochar in CWs enhanced nitrate and heavy metals removal in low carbon groundwater, further investigation is still needed to reveal the complex relationships between the removal of nitrate and heavy metals in CWs.

Keywords: Constructed wetlands; Groundwater; Heavy metals; Iron-carbon micro-electrolysis; Nitrate removal.

MeSH terms

Carbon
China
Groundwater*
Iron
Metals, Heavy*
Waste Disposal, Fluid
Water Pollutants, Chemical*
Wetlands

Substances

Metals, Heavy
Water Pollutants, Chemical
Carbon
Iron