Do wetlands cause mosquito problems?
- Constructed treatment wetlands are designed to be consistently inundated allowing for a healthy population of predators including minnows and insect larvae (e.g. dragonfly) that control mosquito larvae. Mosquitoes are typically more common in areas with occasional standing water that do not support populations of predators.
How often do you have to remove the plants to remove nutrients?
- Most of the nutrient removal in treatment wetlands is done through a combination of sedimentation or conversion to gaseous forms. For phosphorus this typically means burial in wetland sediments and for nitrogen this typically means conversion to nitrogen gas and return to the atmosphere.
How often do you have to clean out a wetland?
- Treatment wetlands are typically built with sufficient freeboard to have lifespans on the order of 30 or more years before potentially requiring dry outs or sediment removal. Plant management frequency is typically based on the specific goals of the project and aesthetic preferences, but can vary from little to no maintenance up to substantial maintenance.
How do wetlands work to improve water quality?
- Wetlands work to improve water quality through a combination of mechanisms that include: sedimentation, adsorption, biodegradation/transformation, vegetative uptake, precipitation, photolysis, hydrolysis, and volatilization. Wetlands are particularly good at reducing concentrations of nutrients because of the wide range of environmental concentrations that exist within a wetland from aerobic to anaerobic which favor various chemical conversions and processes. Additionally, the turnover of vegetation within wetlands promotes the accretion of organic sediments which can bind both nutrients and other constituents such as metals or emerging contaminants.
What are the nutrient performance limits for treatment wetlands?
- Minimum achievable concentrations for nutrients in treatment wetlands can be impacted by site conditions and flows, but total nitrogen can typically be reduced to between 0.8 and 1.0 mg/L and total phosphorus can be reduced to as low as 0.01 mg/L. Both nitrate and ammonia can be consistently reduced to below detection limits in treatment wetlands.