Short-term impacts of Cu, CuO, ZnO and Ag nanoparticles (NPs) on anammox sludge: CuNPs make a difference

The increasing application of engineered nanoparticles (NPs) has posed an emerging challenge to wastewater treatment processes. The short-term impacts of CuNPs, CuONPs, ZnONPs and AgNPs on anaerobic ammonium oxidation (anammox) process were investigated firstly in this study. CuONPs, ZnONPs and AgNPs up to 50 mg g(-1) suspended solid (SS) did not affect anammox activity, reactive oxygen species (ROS) production or cell membrane integrity. However, 1.25 mg g(-1) SS CuNPs significantly inhibited the anammox activity and the loads that caused 50% inhibition were 4.64 +/- 1.24 and 3.27 +/- 0.79 mg g(-1) SS for anammox granules and flocs, respectively. 5 mg g(-1) SS CuNPs caused serious accumulation of the toxic intermediate N2H4. Furthermore, CuNPs interacted with extracellular polymeric substances by specifically bonding to tyrosine or tryptophan-containing groups, C-O-C in polysaccharides and -OH in polymeric compounds. Therefore, this study calls for more attention to the risks of NPs to the anammox-based processes. (C) 2017 Elsevier Ltd. All rights reserved.