|Humenik, Frank - NC STATE UNIV., RALEIGH|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 5, 2000
Publication Date: N/A
Technical Abstract: Constructed wetlands are an alternative to anaerobic treatment lagoons because they are low-cost, passive systems that provide effective nitrogen removal. Ammonia volatilization has not been considered a major problem in constructed wetlands because of their neutral pH, but that has never been experimentally verified. The objective was to quantify ammonia volatilized dfrom constructed wetlands treating swine wastewater. The constructed wetland system consisted of two parallel sets of wetland units loaded with wastewater at rates between 25 and 50 kg N/ha/day. One set of wetland units was planted with rushes/bulrushes and the other set was planted with cattails/bur-reed. On these wetlands, ammonia volatilization was measured with a steady-state, open-enclosure method. The enclosure consisted of inlet and outlet flow-conditioning sections, each with a variable-speed fan, and a tunnel-shaped working section that covered the experimental plot. Gas-washing bottles containing acid were used to sample gases flowing into and out of the enclosure. Average ammonia volatilization rates ranged from 3 to 4 kg NH3-N/ha/day. Results indicated that from 6 to 11% of the N load was lost from the wetlands as a result of volatilization.