Investigation on likely effects of Ag, TiO2, and ZnO nanoparticles on sewage treatment

Because of the increasing number of applications of nanoparticles (NPs), particularly in food, personal care products, etc., these materials pose a potential threat to the environment. The performance of municipal wastewater treatment plants could be adversely affected if NPs ultimately reach these plants. In this study, the effects of silver, titania and zirconia NPs on the micro-organisms responsible for decomposition of organic matter was assessed and related to the performance of sewage treatment plants. Statistical analysis using the most probable number test demonstrated a relationship between NP concentration and parameters related to bacterial decomposition of wastewater. A sequencing batch reactor experiment demonstrated deteriorating performance of the reactor in terms of reduced chemical oxygen demand and biological oxygen demand as a function of NP concentration. The presence of NPs in influent (untreated) wastewater was found to necessitate increased hydraulic residence times to maintain the desired performance of the plant.