Combined impacts of nanoparticles on anammox granules and the roles of EDTA and S2- in attenuation

Previous studies investigating the risk of engineered nanoparticles (NPs) to biological wastewater treatment have primarily tested NPs individually; however, limited data are available on the impact of NPs on the anaerobic ammonium oxidation (anammox) process. In this study, the toxicity of CuNPs on anammox granules was investigated individually and in combination with CuONPs or ZnONPs. Exposure to CuNPs at 5 mg g(-1) suspended solids (SS) decreased the anammox activity to 47.1 +/- 8.5%, increased the lactate dehydrogenase level to 110.5 +/- 3.4% and increased the extracellular N2H4 concentration by 16-fold but did not cause oxidative stress. The presence of CuONPs or ZnONPs at 5 mg g(-1) SS did not significantly aggravate or alleviate the toxicity of the CuNPs; however, the introduction of EDTA or S2- could attenuate the adverse effects of the CuNPs, CuONPs and ZnONPs on the anammox granules. EDTA captured Cu ions, whereas S2- shielded and deactivated Cu ions and passivated CuNPs. Therefore, our results indicated that the toxicity of NPs was dependent on the amount of active metal reaching the anammox cells. Overall, the results of this study have filled knowledge gaps and provided insights into the combined toxicity of NPs on anammox biomass. (C) 2017 Elsevier B.V. All rights reserved.