Two Rapid Enhanced Flushing NAPL Recovery Methods

1
Two Rapid Enhanced Flushing NAPL Recovery
Methods  James A. Jacobs (Environmental
Bio-Systems, Inc.), Lief Nelson (Worley Parsons
Komex) and Jim Begley (inVentures Technologies of
Canada)
Abstract
Gas Mass Transfer

EBS Biosolvent Actions To Remove Heavy Free
Product (Diesel, Motor Oil, Hydraulic Oils,
Bunker-C Oils, Heavy Oils) 1. Dissolves
petroleum and lowers viscosity 2. Decreases
adhesion to grain surfaces 3. Reduces density of
weathered oil, allowing recovery by HVDPE 4.
Consolidates the oil into floating globules and
patches for easier recovery 5. Enhances the
biodegradation of the residual petroleum
hydrocarbons
Lab and Field Tests
Two Rapid Enhanced Flushing NAPL Recovery
Methods Rapid free product removal of
hydrocarbons and solvents has been a major
challenge over the past three decades of
remediation. Long-term product only or
pump-and-treat systems are commonly used for
removal of NAPLs. Failing rapid removal of free
product allows for long-term dissolution around
the edges of the NAPL, providing a continuing and
unabated source of dissolved groundwater
contamination. Two different enhanced flushing
methods have been developed within the past two
years to rapidly remove gasoline free product
from within an aquifer. Recovery Method 1
involves a field trial in Ontario, Canada.
Supersaturated Water Injection (SWI) technology
was used with carbon dioxide saturated water
injection for controlled mobilization of VOCs to
the water table for collection with soil vapor
extraction (SVE) or dual phase extraction where
NAPL was present. In the SWI process, water was
supersaturated with CO2 in a patented gas-liquid
mass transfer system. The saturated water was
injected into an aquifer test cell were a 200
liter hydrocarbon mixture had been placed forming
a residual NAPL zone. CO2 bubbles nucleated at
the targeted area of the aquifer. The rising CO2
bubbles contact with VOC NAPL ganglia in the
saturated zone and cause volatilization of the
VOCs into the vapor phase and mobilization of
NAPL trapped in pores. Extraction and
reinjection wells were used to recirculate the
CO2 saturated water.. The CO2 is distributed by
flowing water resulting in effective gas
distribution followed by heterogeneous bubble
nucleation and continuous growth of gas bubbles
in situ. A gas saturation front developed which
expanded laterally and vertically towards the
water table. VOCs mobilized to soil gas were
extracted with a SVE system. Results indicated a
significant proportion of VOCs were removed by
SVE.   Recovery Method 2 was performed at a
former tank pit at a northern California
containing used hydraulic oil that was trapped
beneath the saturated zone. Recovery Method 2
used a two-step flushing process which included
high-pressure air injection and biosolvent
injection to thin and mobilize the heavy oil,
which was measured up to 41 cm in height in one
well. The high-pressure air injection and
biosolvents were used with high-vacuum extraction
to recover both the used hydraulic oil and the
biosolvent. The final stage separated the heavy
oil from the unspent biosolvent and groundwater.
Over 11 barrels of free product were removed and
a similar volume of biosolvent was recovered
during the one week process. Site closure is
imminent. These two remedial methods show rapid
removal of free-product that was trapped within
the pore spaces of the saturated zone.    
Recovery of 100 of residual hexane by CO2
Supersaturated Injection in lab scale experiment
in 65 minutes
Air and EBS Biosolvent injection left) at up to
600 psi With high vacuum dual phase extraction
(HVDPE) Removes the used hydraulic oil (right)
As an example of gas mass transfer into water,
oxygen (O2) mass transfer chart above shows flow
rates and water flow. Other gases such as carbon
dioxide (CO2) have been used as well.
SWI Process with CO2
EBS Biosolvent Flushing
Below left, 200 L of hydrocarbon (mixture of
pentane, hexane and Soltrol) existing as residual
NAPL in the saturated zone (enclosed cell in the
sand pit at Borden, Ontario. Field experimental
process (right)

• SAN FRANCISCO CASE TREATMENT USED HYDRAULIC OIL
  IN SATURATED GRAVELS
• Air/Biosolvent delivery/extraction system
• High pressure compressed air injected to
  dislodge the submerged heavy oil from pore
  spaces
• Injected 300 gal EBS Biosolvent at 200-600 psi
• 20 hp liquid ring vacuum pump used to extract
  oil, EBS Biosolvent and groundwater. Recovered
  550 gal heavy oil removed from pit
• 480 gal of EBS biosolvent/water mixture
  recovered
• 7,790 gal groundwater extracted and treated
  with carbon and discharged to sanitary sewer

Treatment Technology
CASE 1 FREE PRODUCT REMOVAL USING CO2 FLUSHING
(gPRO System)
.
A CO2 bubble growing by mass transfer from the
injected supersaturated aqueous phase.
CASE 2 FREE PRODUCT REMOVAL USING EBS
BIOSOLVENT FLUSHING

1. EBS Biosolvent not an emulsion
2. Aggressive polar solvent with oxygen.
3. Breaks through weathered product (heavy oil,
   crude oil, bunker C oil, diesel, kerosene. Not
   for gasoline.
4. Mixture of EBS Biosolvent and petroleum mixture
   is cohesive and a fuel.

Lift draws the CO2 bubbles upward.
Upper left panel, gPRO mass transfer module with
iSOC? gas delivery tool on right (same
technology), gPRO module in lower left panel.
Right panel shows gPRO demo unit with pump,
controller, high-pressure mass transfer unit.
Collection of used hydraulic oil (left).
Extraction of oil using HVDPE (right)
Discussion
CASE 1 CO2 Flushing for Free Product Removal
Pilot Testing at Several Sites CASE 2 EBS
Biosolvent Flushing for Free Product Removal
Site Status (3/2/08) Site Closure granted early
2008, well abandonment planned. CONTACTS James
Jacobs, Environmental Bio-Systems, Inc., 707 View
Point Road, Mill Valley, CA 94491 USA, Tel
415-381-5195 jimjacobs_at_ebsinfo.com
www.ebsinfo.com   Leif Nelson, Worley Parsons
Komex Suite 100, 4500 16th Ave. NW, Calgary,
Alberta, T3B0M6 Canada, Tel [phone]
leif.nelson_at_worleyparsons.com   Jim Begley,
inVentures Technologies of Canada,
www.isocinfo.com Tel [phone]
jim.begley_at_inVentures.ca    EBS Biosolvent is
available from Environmental Bio-Systems,
Inc. gPROHP System developed by inVentures
Technologies, Inc.
EBS Biosolvent Flushing Event 4/15/06 \/

Mobilization of NAPL ganglia for recovery
LIFT The CO2 bubbles as they nucleate in the
target area, the contaminants dissolve in the
more soluble CO2 bubbles. Then the CO2 bubbles
with dissolved contaminant inside are lifted to
the surface, where they are removed by soil vapor
extraction.
gPROHP System Schematic - Control
Data of free product thickness in RW-4 shows
reduction on 4/15/06.