April 2022 Webinar - Constructed Wetlands for (Waste)water Treatment

Speaker: Jan Vymazal
The non-point source pollution is a global problem affecting the safety of drinking water supply and aquatic habitats. Pollutants originating from agricultural runoff and drainage include sediment, nitrogen, phosphorus, pesticides, pathogens, salts, trace elements and dissolved organic carbon. However, the major problem is represented by elevated concentrations of nitrate. Wetlands can act as filters removing particulate material, as sinks accumulating nutrients, or as transformers converting nutrients to different forms such as gaseous forms of nitrogen. The ability of natural wetlands to retain nitrogen from freshwaters was recognized and reported since the 1970s. The use of constructed wetlands to remove nitrogen from agricultural drainage waters was first proposed during the late 1980s.
The current webinar will focus on the use constructed wetlands and vegetated drainage ditches to treat agricultural drainage waters in the Czech Republic. The experiments were carried out at various locations in the Czech Republic during the years 2014-2021. Both surface and subsurface flow constructed wetlands were built. In addition, naturally vegetated drainage ditch was valuated as well. The results revealed very high removal for nitrate with average values about 1000 kg N/ha yr for surface flow system and about 6000 kg N/ha yr for subsurface flow systems. The addition of woodchips proved to be effective as drainage waters in the experiments were rather poor in organics. The results obtained during the experiments are in a good agreement with results reported from other countries. Subsurface flow constructed wetlands are more effective for nitrate removal due to prevailing anoxic/anaerobic conditions in the filtration bed.
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