title: Effects of macrophytes and external carbon sources on nitrate removal from groundwater in constructed wetlands.
abstract: Several microcosm wetlands unplanted and planted with five macrophytes (Phragmites australis, Commelina communis, Penniserum purpureum, Ipomoea aquatica, and Pistia stratiotes) were employed to remove nitrate from groundwater at a concentration of 21-47 mg NO3-N/l. In the absence of external carbon, nitrate removal rates ranged from 0.63 to 1.26 g NO3-N/m2/day for planted wetlands. Planted wetlands exhibited significantly greater nitrate removal than unplanted wetlands (P<0.01), indicating that macrophytes are essential to efficient nitrate removal. Additionally, a wetland planted with Penniserum showed consistently higher nitrate removal than those planted with the other four macrophytes, suggesting that macrophytes present species-specific nitrate removal efficiency possibly depending on their ability to produce carbon for denitrification. Although adding external carbon to the influent improved nitrate removal, a significant fraction of the added carbon was lost via microbial oxidation in the wetlands. Planting a wetland with macrophytes with high productivity may be an economic way for removing nitrate from groundwater. According to the harvest result, 4-11% of nitrogen removed by the planted wetland was due to vegetation uptake, and 89-96% was due to denitrification.
authors.affiliation: Department of Environmental Engineering and Health, Chia-Nan University of Pharmacy and Science, Tainan, Taiwan, ROC. yflin@ms12.hinet.net
authors.forename: Ying-Feng
authors.initials: YF
authors.lastname: Lin
authors.forename: Shuh-Ren
authors.initials: SR
authors.lastname: Jing
authors.forename: Tze-Wen
authors.initials: TW
authors.lastname: Wang
authors.forename: Der-Yuan
authors.initials: DY
authors.lastname: Lee
mesh_terms: D001673:Biodegradation, Environmental; D018533:Biomass; D002244:Carbon / Q000494:pharmacology; D017753:Ecosystem; D056890:Eukaryota / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D013045:Species Specificity; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*
chemical_list: D009566:Nitrates; D014874:Water Pollutants, Chemical; D002244:Carbon