title: Long-term effects of copper nanoparticles on wastewater biological nutrient removal and N2O generation in the activated sludge process.
abstract: The increasing use of copper nanoparticles (Cu NPs) raises concerns about their potential toxic effects on the environment. However, their influences on wastewater biological nutrient removal (BNR) and nitrous oxide (N(2)O) generation in the activated sludge process have never been documented. In this study the long-term effects of Cu NPs (0.1-10 mg/L) on BNR and N(2)O generation were investigated. The total nitrogen (TN) removal was enhanced and N(2)O generation was reduced at any Cu NPs levels investigated, but both ammonia and phosphorus removals were not affected. The mechanism studies showed although most of the Cu NPs were absorbed to activated sludge, the activated sludge surface was not damaged, and the released copper ion from Cu NPs dissolution was the main reason for TN removal improvement and N(2)O reduction. It was also found that the transformation of polyhydroxyalkanoates and the activities of ammonia monooxygenase, nitrite oxidoreductase, exopolyphosphatase, and polyphosphate kinase were not affected by Cu NPs, whereas the decreased metabolism of glycogen and the increased activities of denitrification enzymes were observed. Further investigation revealed that Cu NPs increased the number of denitrifiers (especially N(2)O reducing denitrifiers) but decreased nitrite accumulation. All these observations were in correspondence with the enhancement of TN removal and reduction of N(2)O generation.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China. yg2chen@yahoo.com
authors.forename: Yinguang
authors.initials: Y
authors.lastname: Chen
authors.forename: Dongbo
authors.initials: D
authors.lastname: Wang
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Zhu
authors.forename: Xiong
authors.initials: X
authors.lastname: Zheng
authors.forename: Leiyu
authors.initials: L
authors.lastname: Feng
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009609:Nitrous Oxide / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; D003300:Copper; D007770:L-Lactate Dehydrogenase; D009609:Nitrous Oxide