title: Long-term effect of metal oxide nanoparticles on activated sludge.
abstract: This study evaluated the influence of metal oxide nanoparticles (NPs) (Ag2O, TiO2) and their mixture on activated sludge for 180 days. When tested, a mixture of NPs at 1 and 10 mg/L had greater impact than individual NPs, in which maximum reduction in chemical oxygen demand (COD) elimination (76.3%) was observed after 150 days for 1 mg/L (500 mg/L COD concentration) and after 180 days (70.2%) for 10 mg/L (250 mg/L COD concentration). TiO2had higher inhibition on COD reduction than Ag2O NPs at 1 and 10 mg/L. An antagonistic effect was observed in which the combination of individual NPs had a greater effect than a mixture of NPs. Reduction in COD elimination was found to be dependent on NP type and concentration (p < 0.05). Further, metal ion concentration was higher in sludge than supernatant irrespective of NPs, while microscopic analysis showed the presence of NPs inside activated sludge. Among NPs tested, the concentration of Ti4+ion was greater in sludge than in the Ag+ion, thus indicating that TiO2has a greater affinity than Ag2O NPs. All three factors (NP type, NP concentration, organic concentration) play a significant role in imparting COD removal (p < 0.05). Future studies are required to quantify NP concentration to minimize NP effect on plant performance.
authors.affiliation: Department of Civil Engineering, Indian Institute of Technology, New Delhi, India E-mail: arunku@civil.iitd.ac.in.
authors.forename: Baranidharan
authors.initials: B
authors.lastname: Sundaram
authors.affiliation: Department of Civil Engineering, Indian Institute of Technology, New Delhi, India E-mail: arunku@civil.iitd.ac.in.
authors.forename: Arun
authors.initials: A
authors.lastname: Kumar
mesh_terms: D053768:Metal Nanoparticles / Q000633:toxicity*; D008670:Metals / Q000633:toxicity*; D010087:Oxides; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D014865:Waste Disposal, Fluid / Q000379:methods*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D008670:Metals; D010087:Oxides; D012722:Sewage; D014874:Water Pollutants, Chemical