Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 14, 755-766, 2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
20 Feb 2017
Aquatic macrophytes can be used for wastewater polishing but not for purification in constructed wetlands
Yingying Tang1,*, Sarah F. Harpenslager1,a,*, Monique M. L. van Kempen1, Evi J. H. Verbaarschot2, Laury M. J. M. Loeffen1, Jan G. M. Roelofs2, Alfons J. P. Smolders1,2, and Leon P. M. Lamers1 1Department of Aquatic Ecology and Environmental Biology, Institute for Water and Wetland Research, Radboud University, P.O. Box 9010, 6500 GL Nijmegen, the Netherlands
2B-Ware Research Centre, Radboud University, P.O. Box 6558, 6503 GB Nijmegen, the Netherlands
acurrent address: School of Biological and Chemical Sciences, Queen Mary University, London, UK
*These authors contributed equally to this work.
Abstract. The sequestration of nutrients from surface waters by aquatic macrophytes and sediments provides an important service to both natural and constructed wetlands. While emergent species take up nutrients from the sediment, submerged and floating macrophytes filter nutrients directly from the surface water, which may be more efficient in constructed wetlands. It remains unclear, however, whether their efficiency is sufficient for wastewater purification and how plant species and nutrient loading affects nutrient distribution over plants, water and sediment. We therefore determined nutrient removal efficiencies of different vegetation (Azolla filiculoides, Ceratophyllum demersum and Myriophyllum spicatum) and sediment types (clay, peaty clay and peat) at three nutrient input rates, in a full factorial, outdoor mesocosm experiment. At low loading (0.43 mg P m−2 d−1), plant uptake was the main pathway (100 %) for phosphorus (P) removal, while sediments showed a net P release. A. filiculoides and M. spicatum showed the highest biomass production and could be harvested regularly for nutrient recycling, whereas C. demersum was outcompeted by spontaneously developing macrophytes and algae. Higher nutrient loading only stimulated A. filiculoides growth. At higher rates ( ≥  21.4 mg P m−2 d−1), 50–90 % of added P ended up in sediments, with peat sediments becoming more easily saturated. For nitrogen (N), 45–90 % was either taken up by the sediment or lost to the atmosphere at loadings  ≥  62 mg N m−2 d−1. This shows that aquatic macrophytes can indeed function as an efficient nutrient filter but only for low loading rates (polishing) and not for high rates (purification). The outcome of this controlled study not only contributes to our understanding of nutrient dynamics in constructed wetlands but also shows the differential effects of wetland sediment types and plant species. Furthermore, the acquired knowledge may benefit the application of macrophyte harvesting to remove and recycle nutrients from both constructed wetlands and nutrient-loaded natural wetlands.

Citation: Tang, Y., Harpenslager, S. F., van Kempen, M. M. L., Verbaarschot, E. J. H., Loeffen, L. M. J. M., Roelofs, J. G. M., Smolders, A. J. P., and Lamers, L. P. M.: Aquatic macrophytes can be used for wastewater polishing but not for purification in constructed wetlands, Biogeosciences, 14, 755-766, doi:10.5194/bg-14-755-2017, 2017.
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Short summary
Aquatic macrophytes can be used for wastewater polishing but not for purification. At a low nutrient loading M. spicatum and A. filiculoides performed equally well for P removal, whereas at loads ≥ 22 mg P m−2 d−1, A. filiculoides removes P more efficiently. We provide an easily applicable method to select efficient macrophytes species for wastewater polishing, which is essential for decision support in water management using constructed wetlands for nutrient removal by plant harvesting.
Aquatic macrophytes can be used for wastewater polishing but not for purification. At a low...