title: Governing factors affecting the impacts of silver nanoparticles on wastewater treatment.
abstract: Silver nanoparticles (nanosilver or AgNPs) enter municipal wastewater from various sources, raising concerns about their potential adverse effects on wastewater treatment processes. We argue that the biological effects of silver nanoparticles at environmentally realistic concentrations (μgL-1or lower) on the performance of a full-scale municipal water resource recovery facility (WRRF) are minimal. Reactor configuration is a critical factor that reduces or even mutes the toxicity of silver nanoparticles towards wastewater microbes in a full-scale WRRF. Municipal sewage collection networks transform silver nanoparticles into silver(I)-complexes/precipitates with low ecotoxicity, and preliminary/primary treatment processes in front of biological treatment utilities partially remove silver nanoparticles to sludge. Microbial functional redundancy and microbial adaptability to silver nanoparticles also greatly alleviate the adverse effects of silver nanoparticles on the performance of a full-scale WRRF. Silver nanoparticles in a lab-scale bioreactor without a sewage collection system and/or a preliminary/primary treatment process, in contrast to being in a full scale system, may deteriorate the reactor performance at relatively high concentrations (e.g., mgL-1levels or higher). However, in many cases, silver nanoparticles have minimal impacts on lab-scale bioreactors, such as sequencing batch bioreactors (SBRs), especially when at relatively low concentrations (e.g., less than 1mgL-1). The susceptibility of wastewater microbes to silver nanoparticles is species-specific. In general, silver nanoparticles have higher toxicity towards nitrifying bacteria than heterotrophic bacteria.
authors.affiliation: Department of Civil and Environmental Engineering, University of Missouri, Columbia, MO 65211, USA. Electronic address: czxr9@mail.missouri.edu.
authors.forename: Chiqian
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Civil and Environmental Engineering, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Hu
authors.affiliation: College of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China.
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.affiliation: Department of Civil and Environmental Engineering, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Shashikanth
authors.initials: S
authors.lastname: Gajaraj
mesh_terms: D001419:Bacteria / Q000187:drug effects*; D053768:Metal Nanoparticles; D012834:Silver / Q000494:pharmacology*; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000382:microbiology*
chemical_list: D012834:Silver; D062065:Wastewater
keywords: Adaptability; Biological treatment; Functional redundancy; Microbial community; Municipal wastewater; Reactor configuration; Silver nanoparticles; Toxicity