Both subsurface flow and free-water surface constructed wetland systems have been used for partial treatment of manure-laden wastewater from animal production systems. Subsurface flow systems are considerably more expensive but do not breed mosquitoes. The less expensive free-water surface systems have significant mosquito production potential, which is a serious drawback, especially because of increasing concerns about emerging mosquito-borne disease organisms. Periodically draining constructed wetlands has been suggested as a method of mosquito control. To test this approach, eight free-water surface constructed wetland mesocosms (0.7 m2 each) were operated on a one-week drain/fill cycle. Simultaneously, four subsurface flow mesocosms were operated continuously, to compare nitrogen, phosphorus, and organic matter removal between the two systems. Mosquito populations (larvae, pupae, and emerged adults) were monitored in the free-water surface cells, with results demonstrating that periodic draining prevents mosquito emergence in all but high-rainfall conditions. During high-rainfall periods, supplemental drainage or chemical controls might be required to prevent mosquito emergence. Pollutant removal rates, expressed as mass removal rate per unit area, were similar for the free-water surface cells and the subsurface flow cells.
- Dairy manure treatment,
- Mosquito control,
- Nutrient removal
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