considerations for large and small presentation overview
TRANSCRIPT
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Considerations for large and small utilities for addressing emerging
contaminants from upstream sources
Detlef KnappeProfessor of Civil, Construction, and Environmental Engineering
North Carolina State University([email protected])
Students and post-doc: Elisa Arevalo, Amber Greune, Catalina Lopez-Velandia, Mei Sun
Funding: National Science Foundation, NC Water Resources Research Institute,
NC Urban Water Consortium
Freshwater in the North Carolina Coastal Plain, New Bern, NC, February 16, 2016
Presentation Overview
• Upstream sources
• The Universe of Chemicals
• Example contaminants of concern
– Bromide
– 1,4-Dioxane
– Perfluoroalkyl substances
• Implications
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Increasing Reliance on Surface Water and Associated Water Quality and Treatment Challenges
Central Coastal Plain Capacity Use Area Trends 2007 2014
Population 198,362 219,966
Surface Water Sources (mgd) 13.4 21.8
Groundwater Source (mgd) 12.1 4.0
Drinking Water Derived from Surface Water (%) 52.5 84.6
Shift to surface water introduces new drinking water quality and treatment challenges:• Disinfection (pathogens in surface water)• Disinfection by-product formation (higher total organic carbon concentration, bromide
discharges from power plants and industries)• Unregulated contaminants
Shift to surface water also occurring outside of the CCPCUA. For example, Lower Cape Fear River Water and Sewer Authority provides water to:• Pender County Utilities• Brunswick County• Cape Fear Public Utility Authority
Upstream Sources• Point sources
– Municipal wastewater treatment plants• Industrial wastewater inputs• Landfill leachate• Coal ash leachate• Coal/oil/gas extraction
wastewater
– Industrial wastewater treatment plants
– (Coal-fired) power plants
• Non-point sources– Urban stormwater– Agricultural runoff– Land application sites for wastewater treatment plant biosolids– Contaminated groundwater discharge– Dry and wet deposition of air pollutants
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Bromide (Br -)
http://www.epa.gov/eg/steam-electric-power-generating-effluent-guidelines-2015-final-rule
http://www.heddels.com/dictionary/sulphur/
Bromide is a precursor for disinfection by-products (DBPs)
• Cl2 + H2O HOCl + H+ + Cl-
• HOCl + Br- HOBr + Cl-
• DOM + HOCl + HOBr trihalomethanes (THMs) + haloacetic acids (HAAs) + …
http://water.usgs.gov/edu/pictures/color-tannin-sediment.jpg
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Trihalomethanes (THMs)
• ChloroformMolecular weight = 119.4 g/molOne-in-a-million cancer risk: -
• BromodichloromethaneMolecular weight = 163.8 g/molOne-in-a-million cancer risk: 0.6 mg/L
• DibromochloromethaneMolecular weight = 208.3 g/molOne-in-a-million cancer risk: 0.4 mg/L
• BromoformMolecular weight = 252.7 g/molOne-in-a-million cancer risk: 4 mg/L
Drinking water standard:S THMs 80 mg/L
Effect of bromide concentration on THM speciation
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THM
Mo
le F
ract
ion
Raw Water Bromide Concentration (mg/L)
CHCl3 BDCM DBCM CHBr3
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Bromide Impact on THM Compliance
• Bromide reacts with HOCl to form HOBr
• HOBr shifts speciation to brominated DBPs
• Bromine weighs 2.25x chlorine….so shift towards brominated DBPs leads to higher DBP mass concentrations
Quarter 3, 2003
(Raw Bromide = 50 µg/L)
Quarter 3, 2012
(Raw Bromide = 106 µg/L)
µmol/L µg/L Percent µmol/L µg/L Percent
Chloroform 0.44 53 68% 0.21 25 27%
Bromodichloromethane 0.11 18 23% 0.20 32 34%
Dibromochloromethane 0.03 7 9% 0.14 29 31%
Bromoform 0 0 0% 0.03 7 8%
TTHM 0.58 78 100% 0.57 93 100%
Bromide and SpeciatedTHM data for 4th quarter of 2013
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TTH
M C
on
cen
trat
ion
(mg/
L)
TTHM - Madison TTHM - Eden
Scrubber placed into service
Dan River, NC• Wet flue gas desulfurization
scrubber went online in 2008• No baseline bromide data• 2011 bromide levels in Dan
River at Eden reached 430 μg/L
Eden, NC:• <20% brominated
THMs in 2006• >95% brominated
THMs in 2011
Bromide Management Considerations
• Advocate for discharge limits on bromide (e.g. work with AWWA, contact DEQ)
• Manage hydraulic residence time in clearwell– Sufficient contact for disinfection
– Limit excessive contact to control DBP formation
• Install tank aeration systems to strip out THMs in clearwell and/or storage tanks
• Chloramination can help with compliance of existing DBP regulations, but need to carefully manage– Nitrification in distribution system
– Potential lead corrosion problems
– Formation of nitrosamines and other N-DBPs
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1,4-Dioxane
1,4-Dioxane – Background Information
• Sources
– Solvent stabilizer (declining, mostly GW pollution)
– Industrial solvent
– By-product of manufacturing processes involving ethylene oxide
• EPA’s Third Unregulated Contaminant Monitoring Rule (UCMR3)
– Detected nationwide in 11.6% of 32,740 drinking water samples
– 6 of the 12 highest concentrations occurred in NC (all derived from Cape Fear River water)
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1,4-dioxane cancer risk
• Likely human carcinogen (EPA IRIS database)
• Lifetime consumption of drinking water containing
– 0.35 mg/L = 1:1,000,000 excess cancer risk
– 3.5 mg/L = 1:100,000 excess cancer risk
– 35 mg/L = 1:10,000 excess cancer risk
• Comparison with disinfection by-products
– Bromodichloromethane: 0.6 mg/L = 1:1,000,000 risk
– Dibromochloromethane: 0.4 mg/L = 1:1,000,000 risk
• NC Surface Water Supply Standard (WS I – WS IV): 0.35 mg/L
• Standard violated in vast stretches of the Haw, Deep, and Cape Fear Rivers
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1,4
-Dio
xan
e C
on
cen
trat
ion
(µ
g/L
)
Date
RawWater
TreatedWater
1,4-Dioxane is not Removed in Conventional Water Treatment Plants
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Avg. raw: 8.8 µg/LMax. raw: 36 µg/LAvg. treated: 8.7 µg/LMax. treated: 31 µg/L
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-Dio
xan
e C
on
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trat
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)
Date
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TreatedWater
Avg. raw: 2.8 µg/LMax. raw: 5.3 µg/LAvg. treated: 2.6 µg/LMax. treated: 4.6 µg/L
Pittsboro Fayetteville
0.35 μg/L 0.35 μg/L0
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-Dio
xan
e C
on
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(μ
g/L
)
Date
Raw Water
Treated Water
1,4-Dioxane is Partially Oxidized by Ozone
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0.35 μg/L
Avg. raw: 3.8 µg/LMax. raw: 7.7 µg/LAvg. treated: 1.2 µg/LMax. treated: 2.1 µg/L
Ozone oxidized 67% of influent 1,4-dioxane
Wilmington
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• Miscible in water and essentially non-volatile
• Effectiveness of treatment processes– Not removed by conventional treatment
– Poorly adsorbed by activated carbon
– Only partially removed by reverse osmosis membranes
– Permanganate – very slow kinetics
– Ozone is somewhat effective (via hydroxyl radical generation)
– Among established treatment processes, advanced oxidation processes (O3/H2O2, UV/H2O2) may be the only effective treatment option
1,4-Dioxane – Treatability1,4-Dioxane Management Considerations
• Advocate for enforcement of existing NC stream water quality standard (0.35 mg/L)
• Advanced oxidation processes may offer a viable treatment option, but expensive
• A biological treatment option is showing promise in the research stage
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Perfluoroalkyl Substances (PFASs)
Non-stick coatings
Grease- and oil- resistant coatings for paper products
Water repellent fabrics
Stain-resistant coatings for fabrics, carpets, and leather
Aqueous film forming foams
Perfluoroalkyl substances (PFASs) are organic compounds in which all C-H bonds are replaced with C-F bonds.
Perfluorocarboxylic acids (e.g. perfluorooctanoic acid,
PFOA or C8)
Perfluorosulfonic acids (e.g. perfluorooctane sulfonate,
PFOS)
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PFASs have long half-lives in humans
• Half-lives in humans
– PFOA: 3.8 years
– PFOS: 5.4 years
– PFBS: 4 months
• Toxicokinetic differences for PFOA
– 17-19 days in mice
– 4 hours in female rats
To protect the public from adverse health effects, health based guidelines have been established.
EPA Provisional Health Advisory(subchronic exposure)
PFOS: 200 ng/L
C8: 400 ng/L
Health-based guidance level, New Jersey(chronic exposure)
C8: 40 ng/L
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UCMR3 Data for NC (October 2015 status)
Compound EPA Method
MRL, mg/L
NC Detects
Perfluorooctanesulfonic acid (PFOS)
537 0.04 7 (max. 90 ng/L)
Perfluorooctanoic acid (PFOA) 537 0.02 9 (max. 30 ng/L)
Perfluorobutanesulfonic acid (PFBS)
537 0.02 0
Perfluorohexanesulfonic acid (PFHxS)
537 0.03 5 (max. 110 ng/L)
Pefluoroheptanoic acid (PFHpA) 537 0.01 26 (max. 50 ng/L)
Perfluorononanoic acid (PFNA) 537 0.09 0
18 out of 145 PWSs that submitted samples had detects (12.4%)
Land application of biosolids in watershed of a NC drinking water reservoir
PFOS = 720 ng/L
PFOA = 1020 ng/L
PFOS = 500 ng/L
PFOA = 966 ng/L
PFOS = 65 ng/L
PFOA = 109 ng/L
PFOS = ND
PFOA = ND
Data from A. Lindstrom, USEPA, RTP
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PFAS Occurrence in CFR WatershedPFAS Concentrations in
Haw River at Bynum (Pittsboro source)
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PFA
S C
on
cen
trat
ion
, ng
/L
PFHpA
PFOA
PFNA
PFBS
PFHxS
PFOS
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PFOS Concentrations can Exceed EPA’s Public Health Advisory Level
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PFO
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trat
ion
, n
g/L
Public Health Advisory Level
Potential Sources:1. Industrial Wastewater2. Landfill Leachate3. Land Application of Biosolids
No measurable PFAS removal by conventional and advanced treatment
PFAS Concentration (ng/L)
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C/C
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Bed Volumes
TOC
UV254
C6
C8=PFOA
PFBS
PFHxS
PFOS
GAC Adsorption Effective for PFAS Control
Water: Settled OWASA water spiked with PFASs
GAC: Norit 1240EBCT: 7 minutes
PFAS Management Considerations
• Advocate for control of upstream sources
– NPDES discharges
– Test biosolids prior to land application
– Manage runoff from fire fighting (training) activities
• Install GAC adsorber
– Monitor TOC removal
– DBP precursor removal is an added benefit
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Thank you!
Questions:
Wastewater percentage in Haw River at Bynum (Pittsboro Intake)
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rce
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tew
ate
r
Stre
amfl
ow
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D)
Streamflow at Pittsboro Percent of flow from WWTPs
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Bromide Concentrations and Streamflow (Haw River at Bynum)
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Bro
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/L)
Me
an D
aily
Dis
char
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t3 /s)
Mean Daily Discharge
Bromide (ug/L)
2013 Data
TTHM Levels in Wilmington, NC Trend with Bromide Concentrations in Cape Fear River Source
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Bro
mid
e (
mg
/L),
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Cx1
00
(m
g/L
)
TTH
M (
mg
/L)
Site 1 TTHM Bromide Post-filter TOC (x100)
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What do we know?
• Regulated contaminants (known knowns)
• Unregulated contaminants on our radar (known unknowns)
• The universe of chemicals (unknown unknowns)
?
MajorityofChemicalsNotTestedBeforeEnteringtheMarketUnknown unknowns
Woodruff, T. Identifying Cumulative Exposures to Chemicals in Pregnant Women –
Non-targeted Screening of Environmental Chemicals. PPTOX IV, Boston, MA, Oct. 26-29, 2014.
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How safe are new chemicals?
Precautionary
principle:
"When an activity raises
threats of harm to
human health or the
environment,
precautionary measures
should be taken even if
some cause and effect
relationships are not
fully established
scientifically."