title: Fate and long-term inhibitory impact of ZnO nanoparticles during high-rate anaerobic wastewater treatment.
abstract: The aim of this study was to evaluate the long-term effect of ZnO nanoparticles (NPs) on the performance of high-rate anaerobic bioreactors. Laboratory-scale upflow anaerobic sludge blanket (UASB) reactors were fed with a mixture of volatile fatty acids and exposed to either low (0.32 mg Zn L(-1)) or high (34.5 mg Zn L(-1)) concentrations of ZnO NPs. Exposure to high NP concentrations caused a rapid and permanent decline in the methane production and the removal of acetate and propionate. In contrast, a gradual and partial inhibitory response was observed in the reactor exposed to low NP concentrations. The long-term effect of the NP exposure was also evident from a decline in the specific methanogenic activity, which was more severe for the acetoclastic compared to the hydrogenotrophic methanogens. ZnO NPs were removed by 62-82% during passage through the UASB reactors. The results taken as a whole indicate that ZnO NPs cause severe inhibition of acetoclastic methanogens. Even sub-ppm levels of the nano-ZnO in the influent had a negative impact on the performance of the UASB reactor due to long-term exposure of methanogens to NPs that accumulated in the sludge bed.
authors: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, 85721 AZ, USA. Electronic address: lilaoter@email.arizona.edu.
authors: Lila
authors: L
authors: Otero-González
authors: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, 85721 AZ, USA.
authors: Jim A
authors: JA
authors: Field
authors: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, 85721 AZ, USA.
authors: Reyes
authors: R
authors: Sierra-Alvarez
mesh_terms: D000085:Acetates / Q000302:isolation & purification; D000693:Anaerobiosis; D019149:Bioreactors; D055598:Chemical Phenomena; D019605:Euryarchaeota / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D011422:Propionates / Q000302:isolation & purification; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*; D015034:Zinc Oxide / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000085:Acetates; D005232:Fatty Acids, Volatile; D011422:Propionates; D012722:Sewage; D015034:Zinc Oxide
keywords: Engineered nanomaterials; Inhibition; Methanogenesis; Toxicity; UASB