1. Disposition of Per- and Polyfluoroalkyl Substances During Waste Water Treatment
Jonathan P. Benskin,1,2 Michael G. Ikonomou,2 Sopida Chotwanwirach,3 Xiangjun Liao,2 Loretta Y. Li,4 John R. Grace,3 Christopher J. Lowe,5 Glenn E. Harris,5 Million B. Woudneh,1 John R. Cosgrove1
1AXYS Analytical Services Ltd., Sidney B.C., 2Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney B.C., 3Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, B.C., 4Department of Civil Engineering, University of British Columbia, Vancouver, B.C., 5Environmental Sustainability Department, Capital Regional District, Victoria, B.C.

2. Background
Per- and polyfluoroalkyl substances (PFASs) constitute a diverse class of (mostly) anthropogenic chemicals which have been used widely in commerce.
Perfluoroalkyl acids (PFAAs) have garnered the most attention due to their persistence, potential for toxicity and bioaccumulation, and elevated concentrations in humans and wildlife.
Perfluoroalkyl acids
(PFAAs)
PFOS
PFOA

3. Perfluoroalkyl acid-precursors
Background
Comparatively few data are available on the relative contribution of PFAA-precursors to PFAA concentrations measured in the environment (see reviews by Martin et al. (2010) and D’eon and Mabury (2011)).
Perfluoroalkyl acid-precursors
(PFAA-precursors)
(bio-)degradation/
(bio-)transformation
Perfluoroalkyl acids
(PFAAs)
PFOS
PFOA

4. Background
Scenarios where PFAA-precursors might be important determinants of environmental PFAA concentrations or exposure.
Urban marine sediments from False Creek, Vancouver
[∑PFOS-precursors]>[PFOS] in most locations (Benskin et al. ES&T 2012). 1 2 3 4 5 6 7 8 9 10 11 12
False Creek, Vancouver
Broughton Ref.

5. Background
Scenarios where PFAA-precursors might be important determinants of environmental PFAA concentrations or exposure.
Landfill leachate
[∑PFAA-precursors]>[PFAAs] at some time points (Benskin et al. ES&T 2012).
% composition (molar basis)
∑PFAA-precursors
∑PFAAs
% composition

6. Background
Scenarios where PFAA-precursors might be important determinants of environmental PFAA concentrations or exposure.
Waste water treatment
WWTPs have been identified as significant sources of PFAA contamination to the aqueous environment (Shivakoti et al. 2010, Sun et al. 2011, Xiao et al. 2012, many others...)
No study has systematically examined behaviour of precursors in a WWTP system.

7. Biodegradation of PAPs in WWTP sludge
Background
Scenarios where PFAA-precursors might be important determinants of environmental PFAA concentrations or exposure.
Waste water treatment-Lab biodegradation studies
Lee et al. ES&T 2010:
Biodegradation of PAPs in WWTP sludge

8. Background
Scenarios where PFAA-precursors might be important determinants of environmental PFAA concentrations or exposure.
Waste water treatment-recent data
In sludge ∑[PAPs]>>∑[PFCAs]
PFOS
PFOA
D’eon et al. ES&T 2009
8:2 diPAP

9. Objectives
To investigate time trends, phase partitioning, occurrence, and behaviour of per- and polyfluoroalkyl substances (PFASs) in a waste water treatment plant.
What proportion of PFAA-precursors remain intact following treatment?

11. Study Site
Municipal wastewater treatment plant located in Western Canada employing conventional secondary treatment.
In service since 2000.
Serves a population of 30,000.
The average annual influent flow rate is 18,150 m3/day.
Influent, effluent, primary sludge, return activated sludge and biosolids were sampled approximately every 2 weeks from August 4, 2011 to May 31, 2012.

12. RETURNED ACTIVATED SLUDGE
Schematic of Wastewater Treatment Plant
INFLUENT
MECHANICAL BAR SCREENERS
SLUDGE BLENDING AND HOLDING TANK
BELT THICKENER
LIME SILO
CLASS ‘A’ BIOSOLIDS
AERATION TANKS
PRIMARY CLARIFIERS
SECONDARY CLARIFIERS
EFFLUENT
THERMO BLENDER
PASTURIZATION VESSEL
ROTARY PRESS
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Influent enters as raw sewage
Mechanical bar screens remove particulates larger than 6 mm in diameter.

13. RETURNED ACTIVATED SLUDGE
Schematic of Wastewater Treatment Plant
INFLUENT
MECHANICAL BAR SCREENERS
SLUDGE BLENDING AND HOLDING TANK
BELT THICKENER
LIME SILO
CLASS ‘A’ BIOSOLIDS
AERATION TANKS
PRIMARY CLARIFIERS
SECONDARY CLARIFIERS
EFFLUENT
THERMO BLENDER
PASTURIZATION VESSEL
ROTARY PRESS
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Sludge-pre-settling
Solids to sludge blending and holding tank
Aqueous portion to aeration tanks

14. RETURNED ACTIVATED SLUDGE
Schematic of Wastewater Treatment Plant
INFLUENT
MECHANICAL BAR SCREENERS
SLUDGE BLENDING AND HOLDING TANK
BELT THICKENER
LIME SILO
CLASS ‘A’ BIOSOLIDS
AERATION TANKS
PRIMARY CLARIFIERS
SECONDARY CLARIFIERS
EFFLUENT
THERMO BLENDER
PASTURIZATION VESSEL
ROTARY PRESS
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Air is pumped into aeration tanks to promote aerobic conditions.

15. RETURNED ACTIVATED SLUDGE
Schematic of Wastewater Treatment Plant
INFLUENT
MECHANICAL BAR SCREENERS
SLUDGE BLENDING AND HOLDING TANK
BELT THICKENER
LIME SILO
CLASS ‘A’ BIOSOLIDS
AERATION TANKS
PRIMARY CLARIFIERS
SECONDARY CLARIFIERS
EFFLUENT
THERMO BLENDER
PASTURIZATION VESSEL
ROTARY PRESS
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Settling activated sludge is returned to the aeration tanks.
Remaining secondary sludge is thickened by the gravity belt thickener.
Supernatant is discharged to the marine environment as effluent

16. RETURNED ACTIVATED SLUDGE
Schematic of Wastewater Treatment Plant
INFLUENT
MECHANICAL BAR SCREENERS
SLUDGE BLENDING AND HOLDING TANK
BELT THICKENER
LIME SILO
CLASS ‘A’ BIOSOLIDS
AERATION TANKS
PRIMARY CLARIFIERS
SECONDARY CLARIFIERS
EFFLUENT
THERMO BLENDER
PASTURIZATION VESSEL
ROTARY PRESS
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Primary and secondary sludge are mixed in the sludge blending tanks and dewatered by rotary press.

17. RETURNED ACTIVATED SLUDGE
Schematic of Wastewater Treatment Plant
INFLUENT
MECHANICAL BAR SCREENERS
SLUDGE BLENDING AND HOLDING TANK
BELT THICKENER
LIME SILO
CLASS ‘A’ BIOSOLIDS
AERATION TANKS
PRIMARY CLARIFIERS
SECONDARY CLARIFIERS
EFFLUENT
THERMO BLENDER
PASTURIZATION VESSEL
ROTARY PRESS
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Lime is added for precipitation of both suspended and dissolved solids and heated to 70°C for 30 minutes.
The final pasteurized biosolids are used as soil amendment.

18. Sample Collection and Pre-treatment
All samples were collected in glass bottles and filtered with a glass microfibre filter (Whatman GF/B; Buckinghamshire, UK) which separated the samples into solid and aqueous portions.
Following phase separation, all samples were stored at -20°C prior to extraction.

19. Sample Extraction and Instrumental Analysis
Extraction protocols for solid and aqueous samples were adapted from EPA-821-R , 2011 with the exception that 1% NH4OH in MeOH rather than 0.3% NH4OH was used for solids extraction and SPE cartridge elution.
Analysis was carried out by LC-MS/MS using a Dionex HPLC coupled to an AB/Sciex API5000 triple quad

20. QA/QC
Initial spike/recovery experiments conducted for all matrices prior to analyzing real samples.
Samples extracted in batches of 18, which included:
1 procedural blank
1 spiked sample
1 sample analyzed in triplicate.
Exact match isotopically-labelled internal standards available for 16 PFASs.
All samples spiked with recovery standard after extraction to assess instrument response.

21. ∑PFAS Concentration Time Trends in Aqueous Samples
Concentrations fairly consistent over 10-month sampling period.
Local minima and maxima consistent among sampling sites.
May 17, 2012

22. RETURNED ACTIVATED SLUDGE
∑PFAS Concentrations in WWTP Samples-Influent
INFLUENT
CLASS ‘A’ BIOSOLIDS
EFFLUENT
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Solid Phase
Aqueous Phase

23. RETURNED ACTIVATED SLUDGE
∑PFAS Concentrations in WWTP Samples-Returned Activated Sludge
INFLUENT
CLASS ‘A’ BIOSOLIDS
EFFLUENT
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Returned activated sludge was collected after aeration and secondary clarification, and is expected to contain highly active aerobic bacteria.
Consistent with elevated concentrations of oxidation products (e.g. PFCAs, PFSAs) and intermediates (e.g. FOSAMs) present in returned activated sludge.
Solid Phase
Aqueous Phase

24. RETURNED ACTIVATED SLUDGE
∑PFAS Concentrations in WWTP Samples-Primary Sludge
INFLUENT
CLASS ‘A’ BIOSOLIDS
EFFLUENT
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
During primary clarification, no oxygen is supplied to the wastewater. Bacteria are expected to be primarily anaerobic, consistent with the lack of oxidation products (e.g. PFCAs, PFSAs) and elevated concentrations of PAPs in primary sludge.
Solid Phase
Aqueous Phase

25. RETURNED ACTIVATED SLUDGE
∑PFAS Concentrations in WWTP Samples-Effluent
INFLUENT
CLASS ‘A’ BIOSOLIDS
EFFLUENT
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Aqueous Phase
Aqueous effluent contained primarily PFSAs and PFCAs, indicative of extensive biodegradation of PFAA precursors.

26. RETURNED ACTIVATED SLUDGE
∑PFAS Concentrations in WWTP Samples-Biosolids
INFLUENT
CLASS ‘A’ BIOSOLIDS
EFFLUENT
PRIMARY SLUDGE
RETURNED ACTIVATED SLUDGE
Solid Phase
Little biodegradation of precursors was observed during the generation of biosolids, likely due to a primarily anaerobic environment from the primary clarifiers to the pasteurization vessel.

27. Summary
Overall, these data indicate that a variety of PFAAs and PFAA-precursors enter the WWTP via the influent, but primarily PFAAs are released from the WWTP in the effluent, while precursors (specifically, PAPs) are released in biosolids.
Biodegradation of precursors appears to occur primarily following aeration, likely due to the presence of aerobic bacteria.
Little biodegradation of precursors was observed during the generation of biosolids, likely due to a primarily anaerobic environment from the primary clarifiers to the pasteurization vessel.

28. Acknowledgements