American Society of Civil Engineers

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 E-mail:, and Seyoum Gebremariam, Ph.D., (Student, Dept. of Civil and Environmental Engineering, Washington State Univ., Pullman, WA 99164.)

Journal of Environmental Engineering, Vol. 135, No. 10, October 2009, pp. 972-979, (doi:

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Document type: Journal Paper
Discussion: by Duncan Mara E-mail:    (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.

ASCE Subject Headings:
Water pollution
Water treatment
Wastewater management
Water quality