Ecotoxicological Effects of Transformed Silver and Titanium Dioxide Nanoparticles in the Effluent from a Lab-Scale Wastewater Treatment System

Abstract

In this study, a lab-scale wastewater treatment plant (WWTP), simulating biological treatment, received 10 μg/L Ag and 100 μg/L TiO nanoparticles (NPs) for 5 weeks. NP partitioning was evaluated by size fractionation (>0.7 μm, 0.1-0.7 μm, 3 kDa-0.1 μm, < 3 kDa) using inductively coupled plasma mass spectrometry (ICP-MS), single particle ICP-MS and transmission electron microscopy. The ecotoxicological effects of the transformed NPs in the effluent were assessed using a battery of marine and freshwater bioassays (algae and crustaceans) and an in vitro gill cell line model (RTgill-W1). TiO aggregates were detected in the effluent, whereas Ag NPs (0.1-0.22 μg/L) were associated with S, Cu, Zn. Fractionation showed that >80% of Ag and Ti were associated with the effluent solids. Increased toxicity was observed during weeks 2-3 and the effects were species-dependent; with marine epibenthic copepods and algae being the most sensitive. Increased reactive oxygen species formation was observed in vitro followed by an increase in epithelial permeability. The effluent affected the gill epithelium integrity in vitro and impacted defense pathways (upregulation of multixenobiotic resistance genes). To our knowledge, this is the first study to combine a lab-scale activated sludge WWTP with extensive characterization techniques and ecotoxicological assays to study the effects of transformed NPs in the effluent.

Incidence of metal-based nanoparticles in the conventional wastewater treatment process

“…textiles, cleaning agents, personal care products), wastewater streams receive significant loads of NPs, with diverse composition and a wide range of concentrations according to predictions ( Lazareva and Keller, 2014 ;Sun et al, 2016 ). Although wastewater treatment plants (WWTP) can potentially remove over 90% of the influent load of several NPs such as Ag, SiO 2 , TiO 2 or CeO 2 ( Cervantes-Avilés et al, 2018 ;Westerhoff et al, 2018 ), it is possible that the residual concentrations of some NPs and transformation products in the effluent can affect some organisms in the aquatic ecosystems such as algae, crustaceans and fish cells on the reproduction and growth stages ( Georgantzopoulou et al, 2018 ). Since the fate of biosolids from WWTP are landfills, incineration plants and agricultural soils ( Keller and Lazareva, 2013 ;Sun et al, 2016 ;Wang et al, 2016 ), determining the NPs concentration in the sludges of secondary treatment is also relevant, and quite challenging due to high ratio of solid to liquid phases in the matrix, and the physical, chemical and biological interactions between NPs and sludge of the WWTP.…”

Occurrence and size distribution of silver nanoparticles in wastewater effluents from various treatment processes in Canada

“…The toxicity of Ag NPs on aquatic organisms could change markedly upon passing through municipal wastewater treatment plants (WWTPs), as their specific properties can be modified by physical and chemical transformations in WWTPs (Kaegi et al 2011;Bruneau et al 2016). Alterations of Ag NPs can be caused by a number of possible transformation processes such oxidation and sulphidation (Kaegi et al 2011;Kraas et al 2017;Lowry et al 2012;Georgantzopoulou et al 2018). When treated wastewater effluents are released in streams, they likely still contain Ag in dissolved, particulate, and NP forms.…”

Wastewater-Aged Silver Nanoparticles in Single and Combined Exposures with Titanium Dioxide Affect the Early Development of the Marine Copepod Tisbe battagliai

“…Environmental Science & Technology bioavailability and toxicity, yet studies investigating the combined effects of multiple NPs are very scarce 9,22,23 .…”

“…The effects of aged vs pristine NPs on the early life stage development of T. battagliai was studied over 6 days of exposure. T. battagliai was chosen as a model organism due to their importance and ecological significance in food webs, short life cycle, distinctive developmental stages, relatively high sensitivity and the relevance of epibenthic organisms to NP exposure 9 .…”