High Rates of Ammonia Removal in Experimental Oxygen-Activated Nitrification Wetland Mesocosms

by Huckleberry Palmer, MS Student; Dept. of Civil and Environmental Engineering, Washington State Univ., Pullman, WA 99164.,
Marc Beutel, (corresponding author), Assistant Professor; Dept. of Civil and Environmental Engineering, Washington State University, Pullman, WA 99164, mbeutel@wsu.edu,
Seyoum Gebremariam, Ph.D., Student; Dept. of Civil and Environmental Engineering, Washington State Univ., Pullman, WA 99164.,

Serial Information: Issue 10, Pg. 972-979

Document Type: Journal Paper

Discussion: Mara Duncan (See full record)

Abstract: While constructed treatment wetlands are very efficient at polishing nitrate from secondary effluent, they are much less effective at removing ammonia. A key factor that limits ammonia oxidation via biological nitrification in vegetated wetlands is low levels of dissolved oxygen. This study evaluated the effectiveness of side-stream oxygenation to enhance ammonia removal in replicate surface-flow experimental mesocosms containing wetland sediment and plants (Typha spp.). Mesocosms had a water volume of 29.5 L, a hydraulic retention time of 5 days, and a hydraulic loading rate of 4.3 cm/d, and were loaded with synthetic secondary effluent contain 10 mg-N/L of ammonia. Relative to nonoxygenated controls, oxygenation increased ammonia removal rates by an order of magnitude. Areal removal rates increased from 40 mg-N/m2/d to 450 mg-N/m2/d, concentration removal efficiency increased from 10 to 95%, and area-based first-order removal rates increased from <2 m/year to 50–75 m/year. Ammonia removal rates in oxygenated mesocosms were 2- to 4-fold higher than rates reported for full-scale constructed wetlands treating secondary effluent. Results show that oxygen-activated nitrification wetlands, a hybrid of conventional oxygenation technology and wetland ecotechnology, hold promise in economically enhancing rates of ammonia removal and shrinking the wetland area needed to polish ammonia-dominated secondary effluent. Further study is needed to confirm that oxygenation can promote high rates of ammonia removal at the field scale.

Subject Headings: Ammonia | Wetlands (fresh water) | Oxygen | Effluents | Hydraulic loads | Dissolved oxygen | Field tests | Loading rates |

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