A literature review shows that more than 500 compounds occur in wetlands, and also that wetlands are suitable for removing these compounds. There are, however, obvious pitfalls for treatment wetlands, the most important being the maintenance of the hydraulic capacity and the detention time. Treatment wetlands should have an adapted design to target specific compounds. Aquatic plants and soils are suitable for wastewater treatment with a high capacity of removing nutrients and other substances through uptake, sorption and microbiological degradation. The heavy metals Cd, Cu, Fe, Ni and Pb were found to exceed limit values. The studies revealed high values of phenol and SO4. No samples showed concentrations in sediments exceeding limit values, but fish samples showed concentrations of Hg exceeding the limit for fish sold in the European Union (EU). The main route of metal uptake in aquatic plants was through the roots in emergent and surface floating plants, whereas in submerged plants roots and leaves take part in removing heavy metals and nutrients. Submerged rooted plants have metal uptake potential from water as well as sediments, whereas rootless plants extracted metals rapidly only from water. Caution is needed about the use of SSF CWs (subsurface flow constructed wetlands) for the treatment of metal-contaminated industrial wastewater as metals are shifted to another environmental compartment, and stable redox conditions are required to ensure long-term efficiency. Mercury is one of the most toxic heavy metals and wetlands have been shown to be a source of methylmercury. Methyl Hg concentrations are typically approximately 15% of Hgt (total mercury). In wetlands polycyclic aromatic hydrocarbons (PAH), bisphenol A, BTEX, hydrocarbons including diesel range organics, glycol, dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCB), cyanide, benzene, chlorophenols and formaldehyde were found to exceed limit values. In sediments only PAH and PCB were found exceeding limit values. The pesticides found above limit values were atrazine, simazine, terbutylazine, metolachlor, mecoprop, endosulfan, chlorfenvinphos and diuron. There are few water quality limit values of these compounds, except for some well-known endocrine disrupters such as nonylphenol, phtalates, etc.
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Research Article|
January 01 2012
Organic and metallic pollutants in water treatment and natural wetlands: a review
K. Haarstad;
1Bioforsk Soil and Environment, N-1432 Ås, Norway
E-mail: [email protected]
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H. J. Bavor;
H. J. Bavor
2Water Research Laboratory, University of Western Sydney, Hawkesbury, Locked Bag 1797, Penrith, New South Wales 2751, Australia
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T. Mæhlum
T. Mæhlum
1Bioforsk Soil and Environment, N-1432 Ås, Norway
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Water Sci Technol (2012) 65 (1): 76–99.
Article history
Received:
April 14 2011
Accepted:
August 23 2011
Citation
K. Haarstad, H. J. Bavor, T. Mæhlum; Organic and metallic pollutants in water treatment and natural wetlands: a review. Water Sci Technol 1 January 2012; 65 (1): 76–99. doi: https://doi.org/10.2166/wst.2011.831
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