University of Oulu

K. Heikkinen, A. Karppinen, S.M. Karjalainen, H. Postila, M. Hadzic, M. Tolkkinen, H. Marttila, R. Ihme, B. Kløve, Long-term purification efficiency and factors affecting performance in peatland-based treatment wetlands: An analysis of 28 peat extraction sites in Finland, Ecological Engineering, Volume 117, July 2018, Pages 153-164, ISSN 0925-8574,

Long-term purification efficiency and factors affecting performance in peatland-based treatment wetlands : an analysis of 28 peat extraction sites in Finland

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Author: Heikkinen, K.1; Karppinen, A.1; Karjalainen, S.M.1;
Organizations: 1Finnish Environment Institute (SYKE), P.O. Box 140, FI-00251 Helsinki, Finland
2Water Resources and Environmental Engineering Research Unit, P.O. Box 4300, FI-90014 University of Oulu, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 0.7 MB)
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Language: English
Published: Elsevier, 2018
Publish Date: 2020-04-13


Peatland-based treatment wetlands that purify incoming water by means of natural physical, chemical and biological processes belonging to the peatland ecosystem are widely used at Finnish peat extraction sites. They can comprise either undrained or drained overland flow areas (OFAs or DOFAs), with the OFAs representing the best available technology (BAT) for peat extraction. We analyse here the long-term treatment performance of these OFAs and DOFAs and factors affecting this performance. Data on 14 OFAs and DOFAs in different parts of Finland were taken from the extensive long-term environmental pollution control databases. Nearly half of these wetlands had been monitored for at least 4 years and seven for 8–23 years. The results indicated that peatland-based treatment wetlands purify drainage water as efficiently as other natural treatment wetlands on soils in general, the common challenge being phosphorus retention. Iron was also efficiently retained. The average reductions were highest in OFAs with good hydraulic function, and these also showed long-term water protection performance. An important factor affecting purification efficiency was the hydraulic loading rate. Important system design elements in this regard were the size of the wetland in relation to its catchment area, its gradient, the length of the water flow route within the wetland, and the efficient flow area of the wetland. The results regarding the latter two design elements strongly indicate that not all the areas potentially suitable in DOFAs for water purification are yet being used efficiently.

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Series: Ecological engineering
ISSN: 0925-8574
ISSN-E: 1872-6992
ISSN-L: 0925-8574
Volume: 117
Pages: 153 - 164
DOI: 10.1016/j.ecoleng.2018.04.006
Type of Publication: A1 Journal article – refereed
Field of Science: 218 Environmental engineering
Funding: The study was supported by Nordic Centre of Excellent BIOWATER (An integrating nexus of land and water management for a sustainable Nordic bioeconomy), the LIFE + Environment Policy and Governance project LIFEPeatLandUse (Quantification and valuation of ecosystem services to optimize sustainable re-use for low-productive drained peatlands), the peat extraction company Vapo Oy and the Finnish Environment Institute.
Copyright information: © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license