Media selection for sustainable phosphorus removal in subsurface flow constructed wetlands.
Sorption of phosphorus (P) to the bed sand medium is a major removal mechanism for P in subsurface flow constructed wetlands. Selecting a sand medium with a high P-sorption capacity is therefore important to obtain a sustained P-removal. The P-removal capacities of 13 Danish sands were evaluated and related to their physico-chemical characteristics. The P-removal properties of sands of different geographical origin varied considerably and the suitability of the sands for use as media in constructed reed beds thus differs. The P-sorption capacity of some sands would be used up after only a few months in full-scale systems, whereas that of others would subsist for a much longer time. The most important characteristic of the sands determining their P-sorption capacity was their Ca-content. Also the P-binding capacities of various artificial media were tested (light-expanded-clay-aggregates (LECA), crushed marble, diatomaceous earth, vermiculite and calcite). Particularly calcite and crushed marble were found to have high P-binding capacities. It is suggested that mixing one of these materials into the sand or gravel medium can significantly enhance the P-sorption capacity of the bed medium in a subsurface-flow constructed wetland system. It is also possible to construct a separate unit containing one of these artificial media. The media may then be replaced when the P-binding capacity is used up.
Brix
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Department of Plant Ecology, University of Aarhus, Risskov, Denmark.
Arias
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del Bubba
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D001673:Biodegradation, Environmental; D017753:Ecosystem; D004738:Engineering; D005160:Facility Design and Construction; D005374:Filtration; D019015:Geologic Sediments; D010758:Phosphorus / Q000378:metabolism*; D010944:Plants; D014872:Water Movements; D014876:Water Pollution / Q000517:prevention & control*; D018508:Water Purification / Q000379:methods
D010758:Phosphorus