High Rates of Ammonia Removal in Experimental Oxygen-Activated Nitrification Wetland Mesocosms |
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Authors: | Huckleberry Palmer Marc Beutel Seyoum Gebremariam |
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Affiliation: | 1MS Student, Dept. of Civil and Environmental Engineering, Washington State Univ., Pullman, WA 99164. 2Assistant Professor, Dept. of Civil and Environmental Engineering, Washington State University, Pullman, WA 99164 (corresponding author). E-mail: mbeutel@wsu.edu 3Ph.D. Student, Dept. of Civil and Environmental Engineering, Washington State Univ., Pullman, WA 99164.
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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. |
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Keywords: | Water pollution Ammonia Water treatment Nitrification Wetlands Wastewater management Water quality |
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