Disinfection By-Product Formation Catalyzed by Nanoparticles in Wastewater Effluents

Engineered nanomaterials (ENs) are rapidly increasing in consumer products and therefore there is a need to understand their environmental impacts. A significant portion of consumer based ENs will be disposed to wastewater treatment plants (WWTPs) and subsequently released to the environment. Prior to discharge, WWTP effluent is commonly disinfected, with the potential to form disinfection by-products (DBPs) when chlorine reacts with natural organic matter (NOM). DBPs may impact aquatic life and may also be a concern for municipalities employing wastewater reuse. The purpose of this study was to assess the potential for ENs to catalyze DBP formation. Four nanoparticles (silver, titanium dioxide, ceria, and nano zero valent iron) were spiked into two distinct WWTP secondary effluents at 20 mg/L and subject to UV and chlorine disinfection regiments, both individually and sequentially. Trihalomethane (THM) production was determined using headspace gas chromatography with an electron capture detector. Silver nanoparticles (Ag-NPs) were found to result in increased THM production at 20 mg/L and in a follow-up experiment at 1 mg/L relative to controls containing no nanomaterials or ionic silver as an analog. Given that ENs are commonly employed as catalysts, this study highlights the need to further examine the ability for ENs to catalyze unfavorable reactions en route to the environment.