Farm constructed wetlands for nutrient recovery

Farm Constructed Wetlands (FCW) is a type of Nature Based Solution (NBS) which can be used for retaining and reducing nutrient concentrations in water affected by agriculture. Phosphorous (P) is mainly retained by sedimentation of particles to which P tends to be adsorbed. Nitrogen (N) is mainly retained through biochemical processes (denitrification) in bacteria which convert mineral N to gas which returns to the atmosphere. Nutrients are also taken up by plants growing in the wetland, or accumulated in the soil. The objective of FCW for nutrient retention is to reduce the eutrophication effects of agricultural drainage water or water affected by agriculture on downstream watercourses, lakes and sea.

Another potential benefit of FCW is the possibility for managing the flow of water through farmland. Wetlands can thus be used to save water in order to use it for irrigation when needed, and to provide temporary storage during intensive rain events in order to reduce peaks and associated downstream problems. 

The innovative aspect of FCW for nutrient retention is the fact that it is an NBS which provides a number of ecosystem services as beneficial side effects, and that it can deal with variable flows typical of agricultural drainage water, also managing variable fluxes of different contaminants.