In the first two years of operation a nitrogen removal efficiency of 53% and a high average elimination rate of 1,000 g N m−2 yr−1 could be observed for a two-stage vertical flow (VF) constructed wetland (CW) system. The two-stage system consists of two VF beds with intermittent loading operated in series, each stage having a surface area of 10 m2. The first stage uses sand with a grain size of 2–3.2 mm for the 50 cm main layer and has a drainage layer that is impounded; the second stage sand with a grain size of 0.06–4 mm and a conventional drainage layer (with free drainage). The two-stage VF system was designed for and operated with an organic load of 40 g COD m−2 d−1 (i.e. 2 m2 per person equivalent). Data from the following years of operation showed that from the third year nitrogen elimination increased and stabilized. The median values of the nitrogen elimination rate in the first five years of operation have been 3.51, 2.76, 4.20, 3.84 and 4.07 g N m−2 d−1, the median value of the last three years being 3.8 g N m−2 d−1 and 1,380 g N m−2 yr−1, respectively, and the nitrogen removal >60%. It can be assumed that the vegetation as well as the biofilm development in the two-stage VF CW system plays the major role for the enhancement of the nitrogen elimination rate.
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Research Article|
September 01 2011
Long-term behaviour of a two-stage CW system regarding nitrogen removal
Guenter Langergraber;
1Institute for Sanitary Engineering and Water Pollution Control, University of Natural Resources and Life Sciences, Vienna (BOKU), Muthgasse 18, A-1190 Vienna, Austria
E-mail: guenter.langergraber@boku.ac.at
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Alexander Pressl;
Alexander Pressl
1Institute for Sanitary Engineering and Water Pollution Control, University of Natural Resources and Life Sciences, Vienna (BOKU), Muthgasse 18, A-1190 Vienna, Austria
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Klaus Leroch;
Klaus Leroch
2ÖKOREAL GmbH, Carl Reichert-Gasse 28, A-1170 Vienna, Austria
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Roland Rohrhofer;
Roland Rohrhofer
2ÖKOREAL GmbH, Carl Reichert-Gasse 28, A-1170 Vienna, Austria
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Raimund Haberl
Raimund Haberl
1Institute for Sanitary Engineering and Water Pollution Control, University of Natural Resources and Life Sciences, Vienna (BOKU), Muthgasse 18, A-1190 Vienna, Austria
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Water Sci Technol (2011) 64 (5): 1137–1141.
Article history
Received:
July 22 2010
Accepted:
August 26 2010
Citation
Guenter Langergraber, Alexander Pressl, Klaus Leroch, Roland Rohrhofer, Raimund Haberl; Long-term behaviour of a two-stage CW system regarding nitrogen removal. Water Sci Technol 1 September 2011; 64 (5): 1137–1141. doi: https://doi.org/10.2166/wst.2011.332
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