Release of Nanosilver and its Behavior in Urban Wastewater

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1 Release of Nanosilver and its Behavior in Urban Wastewater Michael Burkhardt HSR University of Applied Sciences Institute of Environmental and Process Engineering (UMTEC) Rapperswil, Switzerland Rome, 19 th September 2013

Sciences Institute of Environmental and Process

2 Structure 1. General Information 2. Emissions 1. Solid and liquid waste in textile industry 2. Discharge of wastewater of industrial laundry 3. Wastewater Treatment Plant 4. Conclusions 2

3 Nanosilver Regulation Silver (AgCl, Ag 0, etc.) including nanosilver used for antimicrobial control is regulated by EU Biocidal Product Regulation (98/8/EC) Paints Application areas (product types), e.g. Disinfection (drinking water, etc.) Material protection In-can preservatives (cosmetics, etc.) Polymers Not included: medical applications Microbial growth is controlled by free silver ions (Ag + ) Laundry 3

(98/8/EC) Paints Application areas (product types), e.g. Disinfection (drinking water, etc.

4 Characteristics of Nanosilver In science, 30% of all nano-projects dealing with nanosilver (Maynard 2006) Silver Ion Exchange Silver Salt Metallic Silver Silver Form Silver Zirconium Phosphate Silver Zeolithe Silver Glass Silver Polymer Microcomposite Silver Chloride Silver Chloride Metallic Microcomposite Silver Metallic Nanosilver Size (nm) Ion Ion Ion Ion Matrix Exchange Resin Alumo Silicate Phosphate Glass Polymer Titanium Dioxide, Zeolithe - Amorphous Silicate - Size (nm) >1000 >1000 >1000 >1000 > > Struktur Dosage Form granular granular liquid liquid granular liquid liquid, granular liquid * Burkhardt et al. (2011): Entsorgung nanosilberhaltiger Abfälle in der Textilindustrie - Massenflüsse und Behandlungsverfahren. Forschungsbericht, Rapperswil, Schweiz. 4

Exchange Resin Alumo Silicate Phosphate Glass Polymer Titanium Dioxide, Zeolithe - Amorphous Silicate - Size (nm) >1000 >1000 >1000 >1000 >1000 - >1000 - Struktur Dosage Form granular granular liquid

5 Use of Silver / Nanosilver in Europe (2009) In Europe <50 t/a particulate silver in use, <4 t/a Ag for textiles (90% AgCl) Silver Products Europe(t/a) Germany (t/a) Switzerland (t/a) Silver Salts Metallic Silver Metallic Nanosilver Metalli Silver-Microcomposite Silver Ion Exchange Total Silver In reality, most products do NOT contain nanosilver 5

6 Metallic Silver 0.5 0.3 0.3 - Metallic Nanosilver 0.2 0.2 - - Metalli Silver-Microcomposite 0.3-0.

6 Silver Pathways to Aquatic Systems Release (Emission) Façade Laundry Pathways Stormwater Rainwater Infiltration Separated Separate Sewer System Combined Combined Sewer System Receiving Waters Soil Diffuse Storm Water Combined Sewer Overflow Waste Water Waste Water & Storm Water Waste Water Treatment Plant Point Sludge (Incineration) Silver may enter receiving waters diffuse or by point sources 6

Diffuse Storm Water Combined Sewer Overflow Waste Water Waste Water & Storm Water Waste Water

7 Structure 1. General Information 2. Emissions 1. Solid and liquid waste in textile industry 2. Discharge of wastewater of industrial laundry 3. Wastewater Treatment Plant 4. Conclusions 7

8 1. Silver Application in Textile Production* Fibre integration (10%) Silver Weg des Silbers Herstellung Silver Metall. Production Silber Faserherstellung Fibre Production Gewebeherstellung Fabrics Production Garnherstellung Yarn Production Textilveredlung Textiles Production Textil Consumer Endprodukt Product Fibre coating: washing or foulard-process (90%) Herstellung Silver Silberchlorid Production Weg Silver des Silbers Faserherstellung Fibre Production Gewebeherstellung Fabrics Production Garnherstellung Yarn Production Textilveredlung Textiles Coating Textil Consumer Endprodukt Product Amount and composition of waste depends on application * Burkhardt et al. (2011): Entsorgung nanosilberhaltiger Abfälle in der Textilindustrie - Massenflüsse und Behandlungsverfahren. BAFU, Bern. 8

coating: washing or foulard-process (90%) Herstellung Silver Silberchlorid Production Weg Silver des Silbers Faserherstellung Fibre Production Gewebeherstellung Fabrics Production Garnherstellung

9 Solid and Liquid Waste by Textile Application * 1. Silver production (in Europe) 1% silver as liquid (suspension) or solid (masterbatch) waste (in Europe <500 kg silver per year) Waste is disposed of to 30% in WWTP, 30% by incineration, 40% by recycling (<5 kg/a per site) High silver concentration (1-10%) 2.1 Application by fibre integration in Switzerland 4% silver as solid waste (40 g silver per year) Waste is disposed of to 80% by incineration and 20% by recycling Silver concentration <150 ppm (0.0125%) 2.2 Application by washing (laundry) in Switzerland 70% silver as liquid (wastewater, 20 kg/a) and solid (sludge, 0.7 kg/a) waste** Waste is disposed of to 85% in WWTP and 15% by incineration Silver concentration <10 ppm * Burkhardt et al. (2011): Entsorgung nanosilberhaltiger Abfälle in der Textilindustrie - Massenflüsse und Behandlungsverfahren. BAFU, Bern. ** In Switzerland application by washing has been stopped

recycling (<5 kg/a per site) High silver concentration (1-10%) 2.

10 2. Wastewater Discharge of Industrial Laundry Silver in wastewater discharged to municipal sewer system 800 Silver chloride additiv 600 Silver Silber (µg/l) :00 22:00 04:00 12:00 Time Zeit (h) (h) Silver emissions to WWTP significant (but stopped 2010) 10

600 Silver Silber (µg/l) 400 200 0 14:00 22:00 04:00 12:00 Time

11 Occurrence in Wastewater Relative Relative Silberkonzentration Silver Amount (%) (%) raw roh filterted filtriert (0.45 µm) ultrazentrifugiert centrifuged Sample Probe 11 Sample Probe 2 Sample preparation and TEM give insight to particles fate 11

12 Particulate Silver adsorbed to Cotton Fibres Sludge was disposed of in incineration plant 12

13 Silver-Transformation determined EXAFS: Extended X-ray Absorption Fine Structure (Swiss Light Source, SLS) AgCl 34 5 Ag Ag 2 S thiol-ag Rapid transformation to silver sulfide 13

(Swiss Light Source, SLS) AgCl 34 5 Ag 0 41 20

14 Structure 1. General Information 2. Emissions 1. Solid and liquid waste in textile industry 2. Discharge of wastewater of industrial laundry 3. Wastewater Treatment Plant 4. Conclusions 14

15 Fate in wastewater of WWTP Kloten/Opfikon for 60'000 inhabitant equivalent (IE) 15

16 Sampling in WWTP Secondary Treatment (Nitrification) Biology Tertiary Treatment (Sand filter) Influent Opfikon * Bar Screen Settling Tank Primary Treatment Secondary Clarifier Secondary Clarifier Biology Kloten Biology Secondary Clarifier + Digested Sludge Secondary Clarifier Biology Effluent * Discharge of silver from industrial laundry. Application stopped completely Receiving Water 16

Clarifier Biology Kloten Biology Secondary Clarifier + Digested Sludge Secondary Clarifier Biology

17 Elimination of Silver in WWTP Daily composite samples of dry weather flow Sample In (μg Ag /L) Out (μg Ag /L) Elimination Opfikon Kloten Effluent Sludge (%) Similar elimination of CeO and TiO 2 published Excellent elimination 17

(%) 1 14.0 1.9 0.54 870 94 2 18.4 1.6 0.19 860 98 3 12.3 5.3 0.08 740 99 4 12.

18 Elimination of Silver in Pilot WWTP (60 IE) Addition of metallic nanosilver (OECD NM-K 300) and silver chloride Sludge 93% Not Detected, 1% Effluent, 6% Transformation to silver sulfide Excellent elimination of silver confirmed 18

Sludge 93% Not Detected, 1% Effluent, 6% Transformation

19 Structure 1. General Information 2. Emissions 1. Solid and liquid waste in textile industry 2. Discharge of wastewater of industrial laundry 3. Wastewater Treatment Plant 4. Conclusions 19

20 Conclusions Definition of nanosize typical for ENM discussions (size matters but who cares about size?) Silver amounts / concentrations release to the aquatic environment are small (e.g. from facades, laundry) Silver is disposed of mainly in incineration plant Rapid transformation of nanosilver to insoluble silver sulfide (no antimicrobial properties) under typical environmental conditions Nanosilver exists attached to larger biosolids and sludge corresponding with 95-99% elimination in WWTP (not present as single nanoparticles) No risk of concern for aquatic organisms Nanosilver is of scientific interest, but not of environmental concern and not of main industrial interest 20

from facades, laundry) Silver is disposed of mainly in incineration plant Rapid transformation of nanosilver to insoluble silver sulfide (no antimicrobial properties)

21 What did we learn from these studies? Laboratory tests give limited insight to environmental exposure = Testing under artificial conditions (matrix, concentration) without matrix components is misleading Analytical methods for routine monitoring in waste and wastewater are lacking = Without chemical and morphological characterization results do not represent state of the art in ENM-research Main waste stream of ENM enter recycling and/or incineration plants and waste disposals ( end-of-life ) Ecotoxicology and environmental science need to collaborate (no glass house research with limited link to real world) 21

22 Acknowledgements Partner Ralf Kägi, Steffen Zuleeg, Jakob Eugster, Hansruedi Siegrist, Eawag Funding Swiss Federal Office for the Environment (FOEN), Berne, Switzerland Cantonal Office for Waste, Water, Energy and Air (AWEL), Zurich, Switzerland Literature Kägi et al. (2010): Release of Silver Nanoparticles from Outdoor Facades. Environmental Pollution, 158: Burkhardt et al. (2010): Verhalten von Nanosilber in Kläranlagen und dessen Einfluss auf die Nitrifikationsleistung in Belebtschlamm. Umweltwissenschaften und Schadstoff-Forschung (UWSF), 22: Kägi et al. (2011): Behavior of metallic silver nanoparticles in a pilot wastewater treatment plant. ES&T, 45: Burkhardt et al. (2011): Entsorgung nanosilberhaltiger Abfälle in der Textilindustrie - Massenflüsse und Behandlungsverfahren. Forschungsbericht, HSR Hochschule für Technik, Rapperswil, Schweiz. 22

23 Thank you for Attention! Michael Burkhardt HSR University of Applied Sciences Rapperswil Institute for Environmental and Process Engineering (UMTEC) Switzerland Contact: 23

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