Influence of non-prescription pharmaceuticals on pond sediment nitrification

With the growing number of pharmaceuticals entering aquatic environments, there is increased concern with respect to their influence on aquatic organisms.  Human and animal pharmaceuticals that enter waterways are generally not removed in wastewater treatment plants and thus have become ubiquitous in most freshwater ecosystems.  We studied the influence of four common non-prescription pharmaceuticals (ibuprofen, caffeine, nicotine, and acetaminophen) on the bacterially-mediated process of nitrification.  Nitrification is a fundamental process associated with nitrogen transfer in the natural environment as well as in the wastewater treatment process to remove ammonium.  To simulate both the natural and wastewater treatment environment we tested nitrification response to pharmaceuticals at both ambient nutrient concentrations and elevated ammonium concentrations.  Mean and maximum concentrations previously documented in aquatic ecosystems were tested.  We found that regardless of concentration magnitude, acetaminophen inhibited nitrification rates whereas both concentrations of nicotine tested stimulated nitrification.  Across all pharmaceutical treatments, ammonium amendments significantly decreased nitrification rates and there as an interaction between pharmaceutical treatment and ammonium amendment.  In general, abundant ammonium similar to wastewater conditions yielded less influence of pharmaceuticals on nitrification rates whereas experiments more representative of natural ecosystems yielded a stronger nitrification response to pharmaceutical treatments.  These data demonstrate that trace organic pollutants, such as pharmaceuticals, may significantly change microbial activity in both natural and wastewater environments.