Next Hurdle: 1,2,3-Trichloropropane - CA-NV AWWA · A value of 0.1 lb GAC / 1,000 gallons has been...
Transcript of Next Hurdle: 1,2,3-Trichloropropane - CA-NV AWWA · A value of 0.1 lb GAC / 1,000 gallons has been...
Next Hurdle:
1,2,3-Trichloropropane
Kevin Berryhill
Agenda
1. Background
2. Origin of TCP
3. Regulations
4. Treatment Alternatives
5. Treatment Cost
Where Does TCP Come From?Notification Level established after
TCP’s discovery at the Burbank Superfund
site
“primary possible contaminating
activity appearing to be hazardous waste
sites
Where Has TCP Been Found?
Significant Impact on Rural Areas
Agricultural origin
Agriculture occurs in
rural areas
Rural areas have small
water systems
Small water systems have
no money
An Underreported Problem? California UCMR (2001 – 2003)
Prior to DLR=0.005 µg/L
Sample at source or entry point
<150 connections exempt
EPA UCMR 3 (2013 – 2015)
Systems > 10,000 people
800 representative PWSs
Sample at entry point
MRL = 0.03 µg/L
Private Wells
Laboratory Analytical Constraints
Detection Limit = 5 ng/L Equal to the notification level
7 times greater than the PHG
Specific California-approved analytical methods Sanitation and radiation laboratories purge and trap GC/MS
Sanitation and radiation laboratories liquid-liquid extraction GC/MS
EPA 504.1 (accuracy must be demonstrated by laboratory)
EPA 551.1 (accuracy must be demonstrated by laboratory)
USEPA methods 502.2 and 524.2 are not adequate for TCP
Why Regulate TCP?
Carcinogen Recognized as human carcinogen
by California
Classified as “likely to be” by the EPA
0.7 ppt health goal based on 1 in a million cancer risk
Known toxin
100% man-made Byproduct of chemical synthesis
Does not degrade naturally
Denser than water
“In wine there is wisdom,
in beer there is freedom,
in water there is TCP
-Benjamin Franklin
How is TCP Currently Regulated?
• Notification Level 0.005 µg/L (1999)
• PHG 0.0007 µg/L (2009)
• MCL 0.8 µg/L (mid-80s)
• MCL 0.6 µg/L (2005)
• MCL currently under review
TCP is not regulated by
the U.S. EPA
Regulatory Process
Draft MCL in 2014
45 day comment period
30 day administrative review
Effective within 5 months
Up to 6 months to sample
Treatment Alternatives
There is no “Best Available Technology” (BAT) for TCP
Look at what works for other VOCs Air stripping / packed tower aeration
Reverse osmosis (RO)
Advanced oxidation processes (AOP)
Granular activated carbon (GAC)
Air Stripping
The lower the Henry’s Law constant, the poorer the treatment performance
10 – 26% Removal
Chemical Molecular Weight
Henry’s Law
Constant
(atm-m3/mol)
Dibromochloropropane (DBCP) 236.2 0.0002
Methyl tertiary-butyl ether (MTBE) 88.0 0.0007
Tetrachloroethylene (PCE) 165.85 0.015
Trichloroethylene (TCE) 131.2 0.009
1,2,3-Trichloropropane (TCP) 147.43 0.0003
Reverse Osmosis
At least one operational RO treatment plant removing TCP
Bench-scale study (Fronk, Lykins & Carswell, 1990) Several membranes tested
39 to 85% rejection of TCP
Brine disposal issues
RO is a very expensive way to achieve incomplete removal of TCP
Advanced Oxidation
AOP is likely to be a technically viable treatment alternative
More viable for higher influent levels
HiPOx study (Dombeckand Borg, 2005)
Ozone
UVPeroxide
Potential AOP Byproducts
Tratnyek, P.G., V. Sarathy, and J.H. Fortuna. (2008) Fate and Remediation of 1,2,3-Trichloropropane. In Proceedings of the
Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds
Biological Treatment
Natural biodegradation is insignificant
Bacterial “directed evolution” studies are in in work.
Even superbugs could require days or weeks to act.
Granular Activated Carbon (GAC)
Granular Activated Carbon
Effective for almost all organic contaminants
Reliable
Simple
All existing TCP removal plants use GAC
Existing GAC Facilities
Existing GAC treatment facilities removing TCP include:
Alhambra, CA
Burbank Operable Unit, CA
Fresno, CA
Glendale, CA
Honolulu, HI
Kaanapali, HI
Maui, HI
Oceanside, CA
San Jerardo, Salinas, CA
Tustin, CA
GAC Vessel Configuration
Carbon characteristics
Series vs. parallel
Empty bed contact time (EBCT)
Carbon Characteristics Substrate material
Coconut
Coal (anthracite, bituminous, lignite)
Peat
Adsorption properties (iodine number, molasses number, tannin value)
Gradation, uniformity
Hardness, abrasion resistance
Empty Bed Contact Time (EBCT)
Exhausted
GAC
Mass Transfer Zone
Exhausted
GAC
Mass Transfer
Zone
Unutilized
GACUnutilized GAC
Lower
EBCTHigher
EBCT
Raw
Water
Treated
Water
minuteste)Q(gal/minu
V(gal)
Series vs. Parallel?
ExhaustedGAC
Mass Transfer
Zone
Raw
Water
Treated
Water
TCP is coming out of the filter, but
This carbon still has capacity left
TCP detected
Series vs. Parallel?
Treated
Water
ExhaustedGAC
Mass Transfer
Zone
Unutilized GAC
Treated
Water
The second vessel will allow us to more
fully utilize the carbon in the first vessel
No TCP
Lead Vessel Lag Vessel
When Do You Replace Carbon?
ExhaustedGAC
Lead Vessel Lag Vessel
Detected at 5 ng/L
Already at 0.7 ng/L
PHG?
PHG < DLR
TCP slips through monitoring
Replace carbon in lead vessel based on 50% or 75% sample port in lag vessel
Carbon Usage
Usage Rate Prediction Methods Computer modeling
Bottle point adsorption isotherms
Rapid small-scale column testing (RSSCT)
Small-scale pilot or bench studies
Full-scale testing
A value of 0.1 lb GAC / 1,000 gallons has been assumed pending a site specific water quality evaluation and testing
Chemical
Molecular
Weight
Log Octanol-Water
Partition Coefficient
(Kow)
Dibromochloropropane (DBCP) 236.2 2.43
Methyl tertiary-butyl ether (MTBE) 88.0 1.13
Tetrachloroethylene (PCE) 165.85 3.14
Trichloroethylene (TCE) 131.2 2.36
1,2,3-Trichloropropane (TCP) 147.43 2.26
Bottle Point Isotherm
Multiple bottles with
different carbon weights
added
Rapid Small Scale Column Test (RSSCT)
Most practical way to estimate carbon usage
Logistics Two 55-gallon drums of water
6 weeks
Approximately $8,500 per test
Limitations Inherent assumptions in model
Snapshot in time
Neglects biological activity
Neglects GAC bed backwashing
One batch of carbon
Apply a factor of safety!
Pilot Testing
More accurate than RSSCT
Accounts for variations in raw water quality
Captures biological effects
Long-term test (Hopefully!)
Water QualityConsiderations
TCP levels may not significantly affect carbon usage rates
Background organics may be more critical
DBCP is often found in the same well
Background TOC=
250,000 ng/L
TCP =
5 ng/L
Nitrate Spikes
Source water nitrate > 22 mg/L (as NO3)
Effect similar to chromatographic peaking
Occurs following shutdowns and backwashes
Handled by: Nitrate monitoring
Flush-to-waste
GAC Site Appurtenances
Access for delivery
Washwater disposal
Initial washing
Backwashing for head
loss reduction
Aesthetic considerations
Next Steps
Recommendations for Utilities:
Explore funding sources for construction and operation of the treatment system Factor into rates
Responsible party
Grant & SRF funding once MCL is established
Measure TOC
Compile NO3 (nitrate) data
Develop accurate production data
Consider RSSCT testing