Nutrients and metals effects on nitrification in drinking water systems

Abstract

The activity of nitrifying bacteria in potable water systems was strongly affected by nutrient levels and the presence of certain metals. Specifically, copper (Cu) and zinc (Zn) levels > 100 μg/L and phosphate levels < 5 μg/L inhibited nitrifier activity. This research also showed that inorganic carbon has important direct and indirect effects on nitrification because inorganic carbon (0.1 mg C/mg oxidized nitrogen) was required for autotrophic nitrifier growth, but higher inorganic carbon reduced the toxicity of Cu/Zn and can increase phosphate availability to nitrifying bacteria. Different pipe materials modify nutrient availability to nitrifiers and thus either inhibit or enhance nitrifier activity. For example, orthophosphate can leach to water during corrosion of some metallic alloys but can be removed from water during corrosion of other materials.