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- Title
Silver Sulfidation in Thermophilic Anaerobic Digesters and Effects on Antibiotic Resistance Genes.
- Authors
Bojeong Kim; Miller, Jennifer H.; Monsegue, Niven; Levard, Clément; Yanjuan Hong; Hull, Matthew S.; Murayama, Mitsuhiro; Brown Jr., Gordon E.; Vikesland, Peter J.; Knocke, William R.; Pruden, Amy; Hochella Jr., Michael F.
- Abstract
Physical and chemical transformations and biological responses of silver nanoparticles (AgNPs) in wastewater treatment systems are of particular interest because of the extensive existing and continually growing uses of AgNPs in consumer products. In this study, we investigated the transformation of AgNPs and AgNO3 during thermophilic anaerobic digestion and effects on selection or transfer of antibiotic resistance genes (ARGs). Ag2S-NPs, sulfidation products of both AgNPs and AgNO3, were recovered from raw and digested sludges and were analyzed by analytical transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS). TEM and XAS revealed rapid (⩽20 min) Ag sulfidation for both Ag treatments.Once transformed,Ag2S-NPs (as individualNPs or anNP aggregate) persisted for the duration of the batch digestion. The digestion process produced Ag2S-NPs that were strongly associated with sludge organics and/or other inorganic precipitates.Ag treatments (up to 1,000mgAg/kg) did not have an impact on the performance of thermophilic anaerobic digesters or ARG response, as indicated by quantitative polymerase chain reaction measurements of sul1, tet(W), and tet(O) and also intI1, an indicator of horizontal gene transfer of ARGs. Thus, rapid Ag sulfidation and stabilization with organics effectively sequester Ag and prevent biological interactions with the digester microbial community that could induce horizontal gene transfer or adversely impact digester performance through antimicrobial activity. This finding suggests that sulfide-rich anaerobic environments, such as digesters, likely have a high buffer capacity to mitigate the biological effects of AgNPs.
- Subjects
SILVER; PRECIOUS metals; SULFIDATION; CHEMICAL reactions; DRUG resistance in bacteria
- Publication
Environmental Engineering Science, 2016, Vol 33, Issue 1, p1
- ISSN
1092-8758
- Publication type
Article
- DOI
10.1089/ees.2015.0226