Long-term purification efficiency of a wetland constructed to treat runoff from peat extraction

ABSTRACT

Peat extraction increases the phosphorus, nitrogen, organic matter, suspended solids, and iron concentrations in runoff, resulting in negative effects on downstream water bodies. Wetlands are commonly used as natural cost-effective solutions to mitigate these negative effects. This study analyzed changes in the quality of runoff water from peat extraction areas and the long-term efficiency of constructed wetlands. The results indicate that the quality of runoff water changed after the initial drainage and during peat extraction. Nitrogen leached at high concentrations in the early stages of peat extraction following drainage, whereas the leaching of iron and phosphorus increased after peat extraction from deeper layers. Comparison of water quality and impurities retained immediately after treatment wetland construction and 14 years later showed that the treatment wetland remained functional, with good retention capacity, over a long period.

KEYWORDS:

• Nitrogen
• peat extraction
• phosphorus
• suspended solids
• water purification
• wetland

Acknowledgments

Mr. Tommi Matela and Mr. Juha Salonen are acknowledged for sampling, the laboratory personnel, especially Mr. Mika Sarkkinen, at the Finnish Environment Institute for water analyses, and Mr. Petri Tähtinen for information on the peat extraction area. The authors would also like to thank Dr. Hannu Marttila and Dr. Anna-Kaisa Ronkanen for valuable comments on the manuscript, and Dr. Pekka Belt, Dr. Matti Mottonen, and Dr. Janne Harkonen for their support in writing this article.

Funding

This study was conducted as part of the PRIMROSE project supported by the European Union (Contract no: EVK1-CT 2000-00065). The study was also supported by the Finnish Cultural Foundation and Olvi Foundation.