Alternative Cleanup
Methods for
Chlorinated VOCs
Getting beyond pump and treat
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Soil Vapor Extraction



Vacuum is applied through extraction
wells
Creates a pressure gradient that
induces gas-phase volatiles to be
removed from soil
Also is known as:
 in
situ soil venting
 in
situ volatilization
 enhanced
3/10/2016
W. Fish, PSU
 soil
volatilization
vacuum extraction
fishw@eas.pdx.edu
Jump to first page
Soil Vapor Extraction
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Soil Vapor Extraction




Works only in the vadose
(unsaturated) zone
Typically used with shallow extraction
wells (5-10 ft)
Has been used as deep as 300 ft
Extraction wells can be either vertical
or horizontal
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
SVE: Applicability

Target contaminant groups:
 Volatile
compounds (chlorinated or
not)
 Fuels


(especially lighter fractions)
Will not remove heavy oils, metals,
PCBs, or dioxins
Can promote in-situ biodegradation
of low-volatility organic compounds
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
SVE: Limitations




Low permeability soil or high degree of
saturation requires higher vacuums
(increasing costs)
Heterogeneous subsoils may require
large screened intervals to get even
flows of vapor
Reduced removal rates when soil is
highly sorptive (high organic content)
Off-gases may require treatment
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
SVE: Possible Improvements



Impermeable cap on soil surface can
improve removal rates (but not always
that effective)
Horizontal wells may be efficiently laid
in trenches; can improve removal
De-watering by pump drawdown can
expose more unsaturated zone
(especially with floating LNAPLs)
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
SVE: Performance



Has worked well at many sites, but
often find lower removal rates, higher
costs than expected
Site-specific pilot study needed to
establish feasibility and fine tune the
design
Intermittent (pulsed) extraction can
improve efficiency be allowing vapor
levels to build up between pulses
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
SVE: Pulsed Operation
120
No-pump interval
100
80
60
VOC
40
20
17
15
13
11
9
7
5
3
1
0
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Air Sparging




Air is injected through wells into a
contaminated aquifer
Air traverses horizontally and
vertically through the soil column
Creates an in-situ air stripper
Usually used in conjunction with
SVE to capture contaminant-rich
vapors
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Air Sparging
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Air Sparging: Applicability


As with any stripping system,
limited to volatile compunds
(VOCs) and light components of
fuels
Can double as a source of oxygen
to stimulate biodegradation of
hydrocarbons
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Air Sparging: Limitations




3/10/2016
W. Fish, PSU
Physics of air-flow in saturated
zone poorly understood
Preferential channels can “short
circuit” much of the air, by-passing
much of the contaminated zone
Contaminated air may escape the
capture zone of SVE system
In heterogeneous aquifer only the
porous zones will get much air
flow; little removal from less
permeable layers
fishw@eas.pdx.edu
Jump to first page
Air Sparging: Performance




Has been used successfully at
many sites
But still very hard to generalize
from that experience
Hard to say why it is working in
some cases
Not very effective if there is
extensive DNAPL free-product
below the sparging zone
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Enhanced Biodegradation



Microbes can degrade most pollutants
But rate can be VERY slow if they lack
proper conditions
Groundwater often lacks what they
need:
 “electron
acceptors” (like oxygen)
 nutrients (N, P, K, trace elements)
 co-metabolites (for chlorinated cmpds)
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Enhanced Biodegradation

SOLUTION (?): Inject materials that
microbes need to degrade
contaminants
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Examples:
 Add
oxygen via sparging
 Add oxygen via hydrogen peroxide
 Add alternate electron acceptor
(nitrate that substitutes for oxygen)
 Micro nutrients
 Hydrogen-releasing compounds
(for reductive dehalogenation)
3/10/2016
fishw@eas.pdx.edu
Jump to first page
Enhanced Biodegradation
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
E.B.: Limitations




3/10/2016
If heterogeneous, very difficult to deliver
the nitrate or hydrogen peroxide evenly
Safety precautions when handling
hydrogen peroxide
Concentrations of H2O2 > 100 to 200 ppm
is inhibiting to microorganisms
A groundwater circulation system must be
created so contaminants don’t escape
from zones of active biodegradation
Many states prohibit nitrate injection

W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Regenesis Corp.


Mfr of proprietary solid-phase
products for enhancing
biodegradation
ORC: Oxygen Release Compound
(patented Mg peroxide)
 Stimulates

aerobic breakdown)
HRC: Hydrogen Release
Compound (poly-lactate gel)
 Stimulates
3/10/2016
W. Fish, PSU
reductive dechlorination
of chlorinated solvents
fishw@eas.pdx.edu
Jump to first page
Regenesis ORC: Case Study




3/10/2016

Service station in Wisconsin,
underground storage tank (UST)
leakage
Contaminants: Gasoline, BTEX
and MTBE
Treatment: ORC Slurry Injection
Soil Type: Loose to medium to
course grain sand
Project Cost: $16,150 (ORC Only)
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Regenesis ORC: Case Study



UST was removed along with some
of the contaminated soils
Residual soil and groundwater
contamination remained in source
area.
Continuing groundwater plume
contained MTBE up to 800 ppb and
BTEX concentrations ranging up to
14,000 ppb
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page


ORC slurry was applied into the
source area via Geoprobe® injection
A total of 1,700 pounds of ORC
powder were injected in a slurry
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
ORC: Slurry Injection Method
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
ORC Injection Scheme
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Regenesis ORC: Results
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Regenesis ORC: Results


Both BTEX and MTBE were
apparently degraded by > 99.9 %
within 10 months of ORC application
Post-treatment monitoring throughout
a complete hydrogeologic cycle,
showed no significant rebound in
contaminant concentrations
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
ORC: Reputed Savings

Compared with Air Sparging plus Vapor
Containment
Site
Oklahoma
California
Alabama

3/10/2016
W. Fish, PSU
AS/SVE
$158,000
180,000
99,000
ORC
Savings % Savings
$46,000 $112,000
70%
80,000 100,000
55%
26,000
73,000
74%
“All values were derived independently
by the sites’ consultants. The costs are
full systems costs with the objective of
site closure.” [Regenesis]
fishw@eas.pdx.edu
Jump to first page
Permeable Reactive Barriers



A permeable “barrier” zone is
placed across front of contaminant
plume
Contaminant can passively flow
into barrier
Chemical or biological reactions in
barrier destroy or otherwise
remove contaminants from water
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Permeable Reactive Barriers
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Permeable Reactive Barriers




3/10/2016
Most common material used are
zero-valent (metallic) iron (ZVI)
ZVI removes chlorines from
chlorinated solvents
Chemistry not completely
understood but it certainly works
Also interest in ion-exchange
barriers (for metals, etc.) and
biological barriers (zones of
enhanced bacteria)
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
PRBs: Limitations




Passive treatment walls may lose their
reactive capacity, requiring replacement of
the reactive medium.
Passive treatment wall permeability may
decrease due to precipitation of metal salts
Depth and width of barrier.
Limited to a subsurface lithology that has a
continous aquitard at a depth that is within
the vertical limits of trenching equipment.
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page
Natural Attenuation


Not an “action” but a methodology
for closing out a site safely with no
further action
We’ll discuss this more in
Wednesday’s lecture
3/10/2016
W. Fish, PSU
fishw@eas.pdx.edu
Jump to first page