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Toxicity And Fate Of Inorganic Nanoparticles In Wastewaters: A Potential Risk To Wastewater Systems?

Congress: 2015
Author(s): FLORIAN MALLEVRE, Camille Alba, Craig Milne, Simon Gillespie, Thomas Aspray, Teresa Fernandes
School of Life Sciences, NanoSafety Research Group, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, UK1, Lille 1 University, Science and Technology, Villeneuve d’Ascq 59650, France2, Scottish Water, Juniper House, Heriot-Watt Research Park, Edinburgh EH14 4AP, Scotland, UK 3

Keyword(s): Sub-theme 11: Key vulnerabilities and security risks,
AbstractFlorian Mallevrea,*, Camille Albab, Craig Milnec, Simon Gillespiec, Teresa F. Fernandesa, Thomas J. Aspraya
a School of Life Sciences, NanoSafety Research Group, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, UK
b Lille 1 University, Science and Technology, Villeneuve d'Ascq 59650, France
c Scottish Water, Juniper House, Heriot-Watt Research Park, Edinburgh EH14 4AP, Scotland, UK
* Corresponding author:

Introduction. The extensive and poorly regulated use of nanoparticles (NPs) in the last ten years has raised concern regarding their potential adverse effect on the environment, leading to the emergence of nanoecotoxicology.1,2 Today, the release of NPs in wastewaters is evident,3,4 however the risk of those emergent contaminants in such complex matrices is still poorly understood,in part due to a lack of appropriate methodologies.5,6 Despite growing knowledge around the toxicity of various NPs to a diverse range of microorganisms,7 there is limited evidence to draw conclusive statements about the behaviour (i.e. toxicity and fate) of NPs on microorganisms in real wastewaters.5,8
The main aim of this work was therefore to investigate the ecotoxicity of selected fresh and aged inorganic NPs on a model wastewater bacterium Pseudomonas putida in real crude and final wastewaters from different wastewater treatment plants (WWTPs). Observed behaviours were then analysed alongside physicochemical and microbiological wastewater parameters via multivariate (e.g. principle component) analysis.
This work thus provide insights in methodology for water/wastewater research related ecotoxicology and complementary information about the behaviour of NPs in wastewaters. Practical and fundamental information will be therefore proposed for a further understanding of potential risks of representative inorganic NPs to wastewater systems.

Methods and Materials. The experimental procedure included the assessment of the ecotoxicity of representative NPs (i.e. from the OECD) spiked in different wastewater samples via a high throughput bioluminescent methodology conducted using the switch-off Pseudomonas putida BS566::luxCDABE bioreporter based approach in 96-well plate as previously reported.9 Ag NM-300K, ZnO NM-110 and TiO2 NM-104 NPs were considered. Real urban wastewater samples were collected from February to July 2014 from four distinct WWTPs in the central belt of Scotland and used in the 24 h after collection. Both crude (CW: influent or untreated) and final (FW: effluent or treated) wastewater samples were tested for each site. Briefly, bacteria were exposed to 0 - 200 mg L-1 of NPs in CWs or FWs and the emitted luminescence evolution monitored in a kinetic mode for 2 h at 28 °C. Assays were performed with both fresh and aged NPs. For ageing, stock suspensions of NPs in CWs and FWs were stored in the dark at 4 °C alongside the wastewater samples for two months and tested in weeks 0, 1, 2, 4 and 8. Toxicity results (i.e. derived IC50 values at selected time points) were then related to a comprehensive list of wastewater characteristic parameters via multivariate analysis, as well as NP characterisation in wastewaters. Considered wastewater parameters were: biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonia, sulphide, chloride, silver, pH and total plate count. Considered NP analyses were: dynamic light scattering (DLS), UV-visible spectrophotometry (UV-vis) and atomic absorption spectrophotometry (AAS).

Results and Discussion. Results showed that Ag NM-300K NPs were more toxic in final than crude wastewater from four distinct WWTPs. Multiple wastewater physicochemical characteristics (e.g. BOD, COD, TSS, ammonia, sulphide, chloride, total plate count) correlated with toxicity; however no conclusive site effect was drawn. Fate of NPs was assessed by the study of NP ageing impact to toxicity in wastewater. Ag NM-300K NPs exhibited significantly reduced toxicity with ageing in CWs. Toxicity of Ag NPs was mainly attributed to released-ions, as previously discussed in artificial wastewater simulating effluent elsewhere.9 The decrease of toxicity in CWs, then with ageing, was attributed to occurring aggregation and complexation phenomena in this complex matrix more likely diminishing the eventual availability of Ag ions. ZnO NM-110 and TiO2 NM-104 NPs were not found to be toxic in either FWs or CWs; assays of ageing were consequently not pursued. The toxicity of tested inorganic NPs was found in the mg L-1 range, whereas currently modelled or measured environmental concentrations of such NPs in wastewaters generally are below the µg L-1 range. In addition, speciation based studies, with Ag NPs notably, have proposed that NPs would more likely accumulate in the biosolids and therefore not even pass the primary treatment process, limiting therefore their impact to subsequent WWTP processes and downstream water environments.10,11 Reported results therefore suggest low toxicity of various representative inorganic NPs to microorganisms in real wastewaters, CWs especially, as well as the further decrease of toxicity with ageing.

Conclusions. In regards to herein reported fate and toxicity of aged and non-aged NPs in real crude and final wastewaters from different WWTPs, as well as the literature addressing the speciation of NPs in wastewaters or their actual concentrations in such environmental matrices, it suggests probable low adverse effect of tested representative inorganic NPs on wastewater systems. Offering better predict behaviours of NPs based on real wastewater characteristics, the presented information and approach should assist the wastewater industry in the risk mitigation and management of such emerging contaminants.
Given the ease of use of the reported methodology it has potential further value in ageing experiments over different timescales, contaminants and matrices.

Keywords. Wastewater system; Nanoparticle; Toxicity; Fate; Ageing; Pseudomonas putida. 1. Marcoux, M., Matias, M., Olivier, F., and Keck, G. (2013) Review and prospect of emerging contaminants in waste - Key issues and challenges linked to their presence in waste treatment schemes: General aspects and focus on nanoparticles. Waste Management, 33, pp. 2147-2156.
2. Karhu, A., and Ivask, A. (2012) Mapping the dawn of nanoecotoxicological research. Accounts of chemical research, 46, 3, pp. 823-833.
3. Kaegi, R., Voegelin, A., Ort, C., Sinnet, B., Thalmann, B., Krismer, J., Hagendorfer, H., Elumelu, M., and Mueller, E. (2013) Fate and transformation of silver nanoparticles in urban wastewater systems. Water Research, 47, pp. 3866-3877.
4. Gottschalk, F., Sun, T. Y., and Nowack, B. (2013) Environmental concentrations of engineered nanomaterials: review of modeling and analytical studies. Environmental Pollution, 181, pp. 287-300.
5. Eduok, S., Martin, B., Villa, R., Nocker, A., Jefferson, B., and Coulon, F., (2013) Evaluation of engineered nanoparticle toxic effect on wastewater microorganisms: Current status and challenges. Ecotoxicology and Environmental Safety, 95, pp. 1-9.
6. Klaine, S. J., Alvarez, P. J. J., Batley, G. E., Fernandes, T. F., Handy, R. D., Lyon, D. Y., Mahendra, S., McLaughlin M. J., and Lead, J. R. (2008) Nanomaterials in the environment: behaviour, fate, bioavailability, and effects. Environmental Toxicology and Chemistry, 27, 9, pp. 1825-1851.
7. Bondarenko, O., Juganson, K., Ivask, A., Kasemets, K., Mortimer, M., and Kahru, A. (2013) Toxicity of Ag, CuO and ZnO nanoparticles to selected environmentally relevant test organisms and mammalian cells in vitro: a critical review. Archives of Toxicology, 87, 7, pp. 1181-1200.
8. Duester, L., Burkhardt, M., Gutleb, A. C., Kaegi, R., Macken, A., Meermann, B., and von der Kammer, F. (2014) Toward a comprehensive and realistic risk evaluation of engineered nanomaterials in the urban water system. Frontiers in Chemistry, 2, 39, pp. 1-6.
9. Mallevre, F., FernandesT. F., and Aspray T. J. (2014) Silver, zinc oxide and titanium dioxide nanoparticle ecotoxicity to bioluminescent Pseudomonas putida in laboratory medium and artificial wastewater. Environmental Pollution, 19, 5, pp. 218-225.
10. Ma, R., Levard,C., Judy, J. D., Unrine, J. M., Durenkamp, M., Martin, B., Jefferson, B., and Lowry, G. V. (2013) Fate of Zinc Oxide and Silver Nanoparticles in a Pilot Wastewater Treatment Plant and in Processed Biosolids. Environmental Science & Technology, 48, pp. 104-112.
11. Impellitteri, C. A., Harmon, S., Gune Silva, R., Miller, B. W., Sheckel, K. G., Luxton, T. P., Schupp,D., and Panguluri, S. (2013) Transformation of silver nanoparticles in fresh, aged, and incinerated biosolids. Water Research, 47, 12, pp. 3878-3886.

2011 IWRA - International Water Resources Association - - Admin