title: Efficiency and detrimental side effects of denitrifying bioreactors for nitrate reduction in drainage water.
abstract: A laboratory column experiment was conducted to test the efficiency of denitrifying bioreactors for the nitrate (NO3-N) removal in drainage waters at different flow rates and after desiccation. In addition, we investigated detrimental side effects in terms of the release of nitrite (NO2-N), ammonium (NH4-N), phosphate (PO4-P), dissolved organic carbon (DOC), methane (CH4), and dinitrogen oxide (N2O). The NO3-N removal efficiency decreased with increasing NO3-N concentrations, increasing flow rates, and after desiccation. Bioreactors with purely organic fillings showed higher NO3-N removal rates (42.6-55.7 g NO3-N m(-3) day(-1)) than those with organic and inorganic fillings (6.5-21.4 g NO3-N m(-3) day(-1)). The release of NO2-N and DOC was considerable and resulted in concentrations of up to 800 μg NO2-N L(-1)and 25 mg DOC L(-1) in the effluent water. N2O concentrations increased by 4.0 to 15.3 μg N2O-N L(-1) between the influent and the effluent, while CH4 production rates were low. Our study confirms the high potential of denitrifying bioreactors to mitigate NO3-N pollution in drainage waters, but highlights also the potential risks for the environment.
authors.affiliation: WasserCluster Lunz, Dr Carl Kupelwieser Promenade 5, 3293, Lunz/See, Austria, gabriele.weigelhofer@wcl.ac.at.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Weigelhofer
authors.forename: Thomas
authors.initials: T
authors.lastname: Hein
mesh_terms: D019149:Bioreactors / Q000382:microbiology; D003627:Data Interpretation, Statistical; D058440:Denitrification; D004323:Drainage, Sanitary / Q000379:methods*; D017752:Greenhouse Effect; D008697:Methane / Q000032:analysis; D009566:Nitrates / Q000032:analysis*; D009573:Nitrites / Q000032:analysis; D009589:Nitrogen Oxides / Q000032:analysis; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D009566:Nitrates; D009573:Nitrites; D009589:Nitrogen Oxides; D014874:Water Pollutants, Chemical; D008697:Methane