University of Oulu

Katharina Kujala, Teemu Karlsson, Soile Nieminen, Anna-Kaisa Ronkanen, Design parameters for nitrogen removal by constructed wetlands treating mine waters and municipal wastewater under Nordic conditions, Science of The Total Environment, Volume 662, 2019, Pages 559-570, ISSN 0048-9697,

Design parameters for nitrogen removal by constructed wetlands treating mine waters and municipal wastewater under Nordic conditions

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Author: Kujala, Katharina1; Karlsson, Teemu2; Nieminen, Soile3;
Organizations: 1Water Resources and Environmental Engineering Research Unit, Faculty of Technology, University of Oulu, P.O. Box 4300, FI-90014, Finland
2Industrial Environments and Recycling Unit, Geological Survey of Finland, P.O. Box 1237, FI-70211 Kuopio, Finland
3Centre for Economic Development, Transport and the Environment, P.O. Box 115, FI-87101 Kajaani, Finland
Format: article
Version: accepted version
Access: embargoed
Persistent link:
Language: English
Published: Elsevier, 2019
Publish Date: 2021-01-14


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, Ntot 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.

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Series: Science of the total environment
ISSN: 0048-9697
ISSN-E: 1879-1026
ISSN-L: 0048-9697
Volume: 662
Pages: 559 - 570
DOI: 10.1016/j.scitotenv.2019.01.124
Type of Publication: A1 Journal article – refereed
Field of Science: 1171 Geosciences
218 Environmental engineering
Funding: This study was conducted as a part of the Finnish Green Mining project MINIMAN, the SUSMIN project funded by ERA-MIN Joint Call, and projects funded by Renlund Foundation, Maa- ja vesitekniikan tuki r.y. and the Academy of Finland (project no. 287397).
Academy of Finland Grant Number: 287397
Detailed Information: 287397 (Academy of Finland Funding decision)
Copyright information: © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license