Using wetlands for water quality improvement

Introduction to treatment wetlands

Wetlands, whether naturally occurring or designed for treatment purposes, have an incredible ability to improve water quality through filtering and breakdown of nutrients, pesticides and other pollutants. Vegetated treatment wetlands have been used to treat wastewaters worldwide for over 50 years and have been proposed as a best management practice for water quality improvement in the Moro Cojo, Elkorn Slough and Salinas Valley watersheds (Vymazal, 2010; Habitat Restoration Group, 1996; ABA consultants, 1989).

Constructed Wetlands

Constructed treatment wetlands (CTWs) are categorized by vegetation, hydrology and flow direction and may be arranged as single stage or multi-stage hybrid systems (Vymazal, 2007; Vymazal 2010). To enhance water treatment capabilities, treatment wetlands are planted with multiple types of vegetation and water retention times and flow rates into wetlands are managed to optimize biological processes removing pollutants from waters (García-Lledó, 2011; Thullen et al, 2005; Poe et al, 2003; Beutel et al, 2009). Treatment wetlands can also be constructed to enhance wildlife habitat while adhering to local food safety and pest management measures.

For More information on one of CCWG's treatment wetlands, click here

Considerations

Things that are important to consider when designing treatment wetlands include

  • Nitrogen species (ammonia, nitrate, nitrite) and relative concentrations in incoming water
  • Are there pesticides?
  • Is there heavy metal contamination?
  • Size of the watershed and volume of water to be treated in relation to residence time in wetland
  • Soil chemistry and properties (i.e. clay, sandy, porosity)
  • Food safety guidelines for adjacent farmlands
  • Maintenance required for upkeep    
    • Pumping water into ponds or gravity fed
    • Weed removal/vegetation restoration/erosion control       
    • Will plants be harvested for nitrogen removal or left to become carbon as leaf litter?

How Treatment Wetlands Work

how wetlands work