Grant: Strategic Projects - Group

Ammonium and nitrate contamination of groundwaters from septic field effluents, manure stockpiles, and fertilizers represents the most ubiquitous and persistent threat to water quality in rural watersheds. However, through transformation to N2 both are rendered benign. This is achieved by anaerobic ammonium oxidation, mediated though the activity of anammox bacteria. This important reaction was discovered only some fifteen years ago and is now recognized as a critical step in the global nitrogen cycle in the oceans, wastewaters and soils. Our preliminary work suggests that this reaction also occurs in groundwaters. Our objectives are to determine the occurrence of this important reaction pathway in ammonium-contaminated groundwaters, determine the isotope fractionation effects associated with the anammox reaction for its detection, and develop methods to stimulate the reaction for in-situ remediation of groundwaters. We will first research anammox reactions in impacted groundwaters (Project 1), looking at a number of sites where ammonia contamination is problematic and for which preliminary studies show conditions conducive to anammox. All will be sampled for anammox microbiological activity using complementary techniques including Polymerized Chain Reaction (PCR) and Fluorescent in situ Hybridization (FISH). Anammox strains will be then used to innoculate microcosm experiments in Project 2 to establish isotope fractionation and rates during anammox reaction. This project will examine the effect of anammox reaction on the isotopes of N and O in ammonium and nitrate as tracers. Finally, Progam 3 will develop the anammox reaction in expe- riments for a reactive barrier, where this intriguing reaction can be harnessed to attenuate ammonium and nitrate in contami- nated groundwaters.