期刊
SCIENCE OF THE TOTAL ENVIRONMENT
卷 662, 期 -, 页码 559-570出版社
ELSEVIER
DOI: 10.1016/j.scitotenv.2019.01.124
关键词
Passive treatment; Removal kinetics; Mine emissions; Nitrogen load; Recipient water body
资金
- ERA-MIN Joint Call
- Renlund Foundation
- Maa- ja vesitekniikan tuki r.y.
- Academy of Finland [287397]
- Academy of Finland (AKA) [287397, 287397] Funding Source: Academy of Finland (AKA)
Nitrogen (N) loads from municipal and mine wastewater discharges typically increase N concentrations in recipient water bodies which should get more attention especially in cold-climate regions. This study compared N removal efficiency of six constructed wetlands (CWs) treating mine waters and three CWs polishing municipal wastewater. There were clear impacts of point source N loading to recipient water bodies in all cases studied and >300-fold increase in N was seen in some cases. First-order N removal coefficient was determined for seven of these CWs. All CWs studied were observed to remove N efficiently during the warm growing season but the amount of N released increased significantly during the cold season. Although some year-round purification was achieved by both peat-based and pond-type CWs, removal of nitrate + nitrite-N((NO3- + NO2-)-N) was low during winter. The first-order N removal coefficient varied from 4.9 . 10(-6) to 1.9 . 10(-3) d(-1) and showed that peat-based CWs were slightly more efficient in N removal than pond-type CWs. However, purification efficiency was steadier and higher for pond-type CWs, as lower hydraulic load or longer water residence time compensated for purification performance. Pond-type CWs showed mean removal efficiency of 59% and 46% for ammonium-N (NH4+-N) and (NO3- + NO2-)-N, respectively, whereas peatland-type CWs had lower removal efficiency for NH4+-N (mean of 26%) and in many cases negative removal for (NO3- + NO2-)-N. Correlation analysis revealed no clear, systematic relationship between temperature and N removal. However, in some CWs the highest correlation was between temperature and (NO3- + NO2-)-N, reflecting lower denitrification rate at lower temperature. More than 50% removal was found to require a hydraulic load below 10 mm d(-1). In order to achieve 70% of NH4+-N removal, N-tot load lower than 75 g m(-2) year(-1) and a residence time longer than 80 d are needed in CWs in cold-climate regions. (C) 2019 Elsevier B.V. All rights reserved.
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