Assessing the Effects of Silver Nanoparticles on Biological Nutrient Removal in Bench-Scale Activated Sludge Sequencing Batch Reactors

Abstract

Consumer products such as clothing and medical products are increasingly integrating silver and silver nanoparticles (AgNPs) into base materials to serve as an antimicrobial agent. Thus, it is critical to assess the effects of AgNPs on wastewater microorganisms essential to biological nutrient removal. In the present study, pulse and continuous additions of 0.2 and 2 ppm gum arabic and citrate coated AgNPs as well as Ag as AgNO3 were fed into sequencing batch reactors (SBRs) inoculated with nitrifying sludge. Treatment efficiency (chemical oxygen demand (COD) and ammonia removal), Ag dissolution measurements, and 16S rRNA bacterial community analyses (terminal restriction fragment length polymorphism, T-RFLP) were performed to evaluate the response of the SBRs to Ag addition. Results suggest that the AgNPs may have been precipitating in the SBRs. While COD and ammonia removal decreased by as much as 30% or greater directly after spikes, SBRs were able to recover within 24 h (3 hydraulic retention times (HRTs)) and resume removal near 95%. T-RFLP results indicate Ag spiked SBRs were similar in a 16s rRNA bacterial community. The results shown in this study indicate that wastewater treatment could be impacted by Ag and AgNPs in the short term but the amount of treatment disruption will depend on the magnitude of influent Ag.

Facile Synthesis of Silver Nanoparticles Decorated Magnetic-Chitosan Microsphere for Efficient Removal of Dyes and Microbial Contaminants

“…Since the silver nanoparticles (AgNPs) exhibit broad spectrum antimicrobial activity, decoration of AgNPs on magnetic-chitosan nanomaterial may lead to the formation of a novel antifouling nanomaterial. 34,35 Nevertheless, the formation of stable AgNPs requires flammable organic solvents and toxic reducing agents, which triggers environmental and safety issues. 36,37 Development of an environmentally benign facile synthesis process is thus, a prerequisite to prepare silver nanoparticle decorated magnetic chitosan nanomaterial for cost effective and efficient water purification.…”

Critical review of the influences of nanoparticles on biological wastewater treatment and sludge digestion

“…One important function of WWTPs is to achieve nitrogen and phosphorus removal, thus previous studies concerning the potential influences of NPs on wastewater treatment primarily focused on their risks to biological nutrient removal (Alito & Gunsch, 2014;Huang et al, 2014;Jeong et al, 2012;Liang et al, 2010). Usually, bacteria related to nitrogen removal are found to be more sensitive than polyphosphate accumulating organisms at the same nanoparticle concentration (Chen et al, 2012b;Zheng et al, 2011a).…”

Examining relationships between total silver concentration and Sil silver resistance genes in domestic wastewater treatment plants

“…) as well as the broad ecological impacts of AgNPs in a WWTP context (Colman et al . ; Alito and Gunsch ; Gwin et al . ), there are currently little data on the prevalence of silver resistance genes in the environments associated with the life cycle of AgNPs, most notably WWTPs and soil environments other than mines.…”

“…Silver-resistant bacteria have mostly been identified in environments where silver toxicity might be expected to select for resistance such as in hospitals, soil around mines and industrial water catchments (Silver 2003). However, while there have been many studies exploring the impact of AgNP physical and chemical properties on their toxicological potential (Gorka et al 2015; Le on-Silva et al 2016) as well as the broad ecological impacts of AgNPs in a WWTP context (Colman et al 2013;Alito and Gunsch 2014;Gwin et al 2017), there are currently little data on the prevalence of silver resistance genes in the environments associated with the life cycle of AgNPs, most notably WWTPs and soil environments other than mines.…”