Effects of triclosan exposure on nitrification in activated sludge, biofilms, and pure cultures of nitrifying bacteria

Abstract

Emerging contaminants, such as pharmaceuticals or personal care products, have the potential to impact many wastewater treatment processes due to their antimicrobial properties. Nitrifying bacteria initiate the nitrogen removal process in wastewater treatment, and are particularly sensitive to inhibition by these and other contaminants. The impacts of the emerging contaminant triclosan (TCS) on two common nitrifying bacteria were evaluated under multiple growth conditions. The resilience of biofilms and suspended cell cultures of the ammonia oxidizing bacterium (AOB) Nitrosomonas europaea was compared during TCS exposure. Impacts of TCS on Nitrobacter winogradskyi, a common nitrite oxidizing bacterium (NOB), were also considered. Lastly, activated sludge biofilms and suspended cells were also exposed to TCS to further evaluate impacts on nitrification. Triclosan at part per million levels was found to reduce respiration in nitrifying biofilms, and NOB were much more impacted by TCS than AOB. Interestingly, biofilms of N. europaea were just as impacted by TCS as suspended cells. Triclosan adsorbed strongly to cellular material and degradation was only observed in activated sludge at low concentrations. Altogether, TCS was found to reduce nitrification by AOB and NOB, and the results suggest that its presence at high levels in wastewater treatment is likely to have negative consequences.