Nitrate-N removal rate variabilities in floating treatment wetland mesocosms with diverse planting and carbon amendment designs

Authors: MESSER, TIFFANY - University Of Kentucky; Miller, Daniel; LITTLE, HELEN - University Of Nebraska; OATHOUT, KENNETH - University Of Nebraska

Submitted to: Ecological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2021
Publication Date: 10/4/2021
Citation: Messer, T.L., Miller, D.N., Little, H., Oathout, K. 2021. Nitrate-N removal rate variabilities in floating treatment wetland mesocosms with diverse planting and carbon amendment designs. Ecological Engineering. https://doi.org/10.1016/j.ecoleng.2021.106444.
DOI: https://doi.org/10.1016/j.ecoleng.2021.106444

Interpretive Summary: Although floating treatment wetlands (FTWs) improve water quality, remove pollutants from lakes, and are simpler to implement than traditional treatment wetlands, design options are limited. This study determined nitrate removal rates in two FTW vegetation designs using rush species or more diverse species mixes and evaluated the effects of barley straw and coffee grounds carbon amendments on nitrate removal. FTWs using diverse species compared to just rush species removed nitrate at more than twice the rate of rush. Carbon amendments, however, had very little effect. Including diverse wetland species should be promoted in FTW design while alternative methods to add carbon amendments to FTWs mats should be further explored.

Technical Abstract: Floating treatment wetlands (FTWs) are an innovative wetland design to passively improve water quality and remove pollutants from lakes with limited infrastructure modification or construction as compared to traditional treatment wetlands. However, design recommendations remain limited. Therefore, the objectives of this study were: 1. Determine NO3-N removal rates in two FTW vegetation designs and 2. Evaluate NO3-N removal performance in FTW designs with carbon amendments. Three nutrient FTW mesocosm experiments were conducted in a greenhouse during the summer of 2019, where nitrate-N removal was assessed. Two FTW plant designs (rush species and diverse species) and three carbon conditions (no amendment, spent coffee grounds, and barley straw) were assessed. FTW vegetation design (rush versus diverse) was found to have significant (P < 0.05) effects on nitrate-N removal with diverse FTW removing nitrate-N at more than twice the rate of rush FTW (1.81 and 0.75 mg N L-1 d-1, respectively. However, impacts of nitrate-N removal following carbon amendments was minimal with either coffee grounds or barley stray amendment compared to no amendment controls (0.73, 1.09, and 0.79 mg N L-1 d-1, respectively. Diverse wetland species should be considered in FTW design while alternative methods to add carbon amendments to FTWs mats should be further explored.