This study analyzed the fate of the pesticide fipronil and its metabolites (fiproles) through a wastewater treatment train and engineered wetland. The researchers found that conventional wastewater treatment is not efficient at removing fiproles, with up to 77% of the total fiprole mass passing through treatment. While some of the parent compound fipronil may be transformed into metabolites like sulfone, the total mass of toxic fiproles reentering the environment is concerning and could impact aquatic organisms and plants that uptake the chemicals. Further research is needed to understand the ecological risks and impacts of fiprole loads discharged in treated wastewater effluent.
Removal of anionic surfactant from grey water and its comparison with chemica...
ACS Boston seminar presentation 2015
1. Samuel D. Supowit, Akash M. Sadaria, Edward J. Reyes,Rolf U. Halden
Mass balance of fipronil in a
wastewater treatment train
and engineered wetland
GLOBAL SECURITY
INITIATIVE
3. Rationale
• Fipronil is a high production chemical
• Banned for use on rice in China, 2009
• It has been banned for most agricultural uses in the E.U., 2013
3
4. 4
• Implicated in colony collapse
disorder
• Highly toxic to bees
LD50 = 1-6 ng/bee
Rationale
Compound
Procambarusa
Hyalella aztecab
Diphetor hagenib 33
OC urban
water conc.
(µg/L)
Half-life
31
LC50 (µg/L)
30
LC50
(µg/L)
30
EC50
(µg/L)
30
LC50
(µg/L)
30
EC50
(µg/L)
34
Silt
loam (d)
35
Facultative
conditions (d)
Fipronil 14.3-19.5 1.3-2.0 0.65-0.83 0.20-0.57 0.11-0.21 0.05-0.39 21±0.15 -
-desulfinyl 68.6 - - - - 0.05-0.13 - 217-497
-sulfide 15.5 1.1-1.7 0.007-0.003 - - ND >200 195-352
-sulfone 11.2 0.35-0.92 0.12-0.31 0.19-0.54 0.055-0.13 0.05-0.19 >200 502-589
a
Procambarus species were clarkii and zonangulus.
b
Values for H. azteca and D. hageni are the 95% confidence interval.
OC – Orange County, California
ND – non detect
6. Rationale
6
• Plants uptake
and translocate
pesticides
through their
xylem, providing
an indirect route
of exposure to
non-target
foragers and
pollinators
7. Rationale
7
• Plants uptake
and translocate
pesticides
through their
xylem, providing
an indirect route
of exposure to
non-target
foragers and
pollinators
8. Rationale
• Fiprole
degradate fate in
WWTPs not
assessed in
literature.
• Only one study
assessed fipronil
in influent,
effluent,
biosolids.
8
9. Background
• In a prior study, Heidler & Halden (2009)
determined 18 ± 22 % aqueous removal of
fipronil in a conventional WWTP.
• Are similarly toxic degradates formed?
9
10. Objective
• Perform a mass balance for fiproles over a
wastewater treatment train and engineered
wetland, screening for heretofore unexamined
metabolites.
– Use isotope dilution and standard addition for
quality control to produce high prec. data.
10
11. Specific Aims
1. Develop analytical methods for assessing
fiproles in WWTP matrices (influent, effluent,
sludge).
2. Design a sampling campaign in order to
determine the fate of fiproles across primary,
secondary, and tertiary treatment.
3. Perform a mass balance for fiproles over a WW
treatment train and engineered wetland.
11
12. • Fiproles are largely resistant to degradation in treatment.
Hypothesis
12
13. • Fiproles are largely resistant to degradation in treatment.
• If parent compound “disappears,” degradates form in treatment.
• Biosolids have more sulfide.
• WAS has more sulfone.
• Wetland has more amide.
Hypothesis
13
WWTP
15. ISCO 6700 and 6712
• Incremental sampling
program to
approximate flow
pattern
20 mL increments at
designated times
2.5 L composites
15
16. Experimental design
• Extraction (water)
16
1000 mL
WAS
& PS
500 mg/3 mL Strata XL 4 mL eluate x 2
LC-MS/MS
Concentrations
calculated by
both standard
addition and
isotope dilution
17. Experimental design
• Extraction (solids)
17
Surrogate
addition
Acetone
extraction
Shake Centrifuge
Solvent
switch to
hexane
Cleanup on
Florisil
Analyze by
LC-MS/MS
18. Method performance
18
Chemical
Wastewater Solids
Spiking
level
(pg/L)
MDL
(pg/L)
Relative
recovery
(%)
Absolute
recovery
(%)
Spiking
level
(pg/g)
MDL
(pg/g)
Relative
recovery
(%)
Absolute
recovery
(%)
Fipronil 100 46 116 ± 14 60 ± 14 50 19 120 ± 13 55 ± 18
-Sulfide 300 159 N/A 67 ± 13 150 144 N/A 48 ± 18
-Sulfone 200 72 N/A 101 ± 19 100 98 N/A 89 ± 32
-Amide 500 304 N/A 87 ± 22 250 88 N/A 90 ± 21
-Desulfinyl 1000 773 N/A 78 ± 15 500 242 N/A 85 ± 15
N/A ≡ Not applicable
1
Table 1. Spike levels, detection limits, and recoveries of fiproles extracted from
surrogate wastewater and sludge matrices (n = 7).
Figure 1. (Right)
Chromatograms of five
fiproles extracted from
spiked (20 ng/g nominal)
and unspiked dewatered
sludge, after cleanup on
Florisil and elution with 4
mL DCM. Primary ion
transitions are shown at
top, and secondary
(qualitative) transitions at
bottom. *Fipronil-
desulfinyl was analyzed by
GC-MS/MS.
ESI negative mode
C8 column
22. Results
22
Figure 2.
Concentrations of
fiproles in (A) WWTP
influent, (B) WWTP
effluent (wetland
influent), (C) wetland
effluent, and (D)
biosolids. Biosolids
concentrations are
normalized to 1 g dry
weight. Error bars
represent max and
min values for water
streams (n = 2), and
standard deviation for
biosolids (n = 3).
Concentration(ng/L)
WWTP influent
WWTP effluent
Wetland effluent
Biosolids
23. Results
23
Figure 3. Fiprole mass distribution in three WW streams. The most abundant congener in all three streams is fipronil.
The amide and desulfinyl degradates were not detected in these streams.
24. Results – parent compound mass balance
24
1.1 ± 0.1%
adsorbed to WAS
25 ± 3%
transformed74 ± 3% passed
through to
disinfection
basin effluent
Fipronil mass balance over treatment train Fipronil mass balance over wetland
44 ± 4%
transformed or
accumulated
56 ± 4% passed
through
Figure 4. Fipronil mass balance over treatment train from primary treatment to disinfection (left) and
engineered wetland (right).
Accounted for
by degradates
Not accounted for by
degradates
25. Results – total fiproles over treatment train
77 ± 11 73 ± 11 83 ± 24
0.09
68 ± 61.4 ± 0.003
Qx ≡ Combined flow from other treatment trains
Figure 5. Treatment train total 5-day fiprole load in mmol.
26. Results – individual fiproles
26
Figure 6. Fiprole mass loads (in mmol) in wastewater streams
over the course of five days. Direction of water flow is from
left to right, (primary influent to disinfection basin effluent).
Error bars represent high and low values from two
experimental replicates. The bars on top are enlarged
portions of the histogram on the bottom, in order to make
fipronil-desulfinyl masses visible. Fipronil-desulfinyl
concentrations are estimated, near the detection limit.
Sludge streams are omitted, as their mass contributions are
negligible (n = 2 ).
mmol
27. Results
27
Figure 7. (A) Average daily mass loads of fiproles over five
days, where error bars represent standard deviations (n =
10). (B) Daily mass loads of wetland (WL) influent and
effluent streams on days 1 and 5, respectively, where error
bars represent max/min values (n = 2); the hydraulic
retention time of the wetland was 4.7 days. The right-hand y-
axis is expressed as grams of fipronil per day.
47 ± 13% total fiprole reduction
No discernable change
30. Discussion
30
• The entire volume of AG fipronil in the U.K.
during peak use was about 124 kg/yr (273
lb/yr)
• The estimated, extrapolated discharge by US
WWTPs is 520 kg/yr (1140 lb/yr)
31. Discussion
31
While the amount of fipronil inadvertently
discharged into the environment in the form of
treated wastewater is alarmingly high, it is unclear
how wastewater contributes to the fiprole pollen
loads in angiosperms, the body burdens of aquatic
organisms, or the toxicological effects for other
non-target organisms. Further research is needed to
link the fiprole load in wastewater effluents to plant
uptake and non-target organism exposure and
effects.
32. Conclusions
•Conventional wastewater treatment is not
efficient at removing fiproles.
•Reduction in parent compound mass may
coincide with degradate formation (sulfone, in
particular).
•Total fiprole levels re-entering the environment
from wastewater treatment are toxicologically
relevant and may impact biota.
32
33. Future research needed
• Modeling uptake of fiproles in plants and food
chain
• Risk assessment needed in order to determine
ecotoxicological effects
33
34. Acknowledgements
• Dr. Rolf Halden, PI
• Dr. Arjun Venkatesan
• Akash Sadaria
• Edward Reyes
• Top secret collaborators
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