United States
Environmental Protection
Agency
Solid Waste And
Emergency Response
(OS-220)
Directive 9200.5-253FS
November 1989
oEPA Innovative Technology
BEST™ Solvent
Extraction Process
TECHNOLOGY DESCRIPTION
Solvent extraction is potentially effec-
tive in treating oily sludges and soils by
separating the media into three fractions:
oil, water, and solids. As the fractions sepa-
rate, certain contaminants are concentrated
into specific phases. For example, PCBs
concentrate in the oil fraction, while metals,
unless organically bound, accumulate in the
solids fraction. Individual phases can then
and water in the feed simultaneously solvate
with the cold TEA creating a homogeneous
mixture. As the solvent breaks the oil-
water-solid bonds, the solids are released
from the emulsion. These solids are subse-
quently removed by centrifuging, which en-
sures submicron particles are removed. The
solids are passed to a second mixing tank
where they are washed with additional sol-
vent and centrifuged a second time. The wet
solids (about 50% solids by weight) are sent
Figure 1: Schematic Diagram of a Typical BEST™
Treatment Facility
WMwTrMmMI VOOProdua
be treated more efficiently. Solvent extrac-
tion is capable of processing the oily wastes
shown in Table 1. Table 2 lists the effective-
ness of solvent extraction on general con-
taminant groups.
One type of solvent extraction, BEST1"
treatment, is a mobile solventex traction sys-
tem developed by Resources Conservation
Company (RCQ. This system uses one or
more secondary or tertiary amines [usually
trieihylamine (TEA)] to separate toxic wastes
and oils from sludges or soils. The BEST11*
technology is based on the fact that TEA is
miscibk in water at temperatures below
65°F.
A typical process diagram for the BEST*
process is shown in Figure 1. This process
begins by mixing and agitating the cold sol-
vent and sludge or soil in a mixing tank. Oil
toa dryer where the solvent is vaporized and
collected for recycling. Dry solids contain-
ing heavy metals may require further treat-
ment before disposal
The liquids from the first centrifuge,
containing the oil and water extracted from
the feed, are heated in a series of heat ex-
changers. As the temperature of the liquids
increase, the water separates from the oil-
solvent The oil-solvent fraction is decanted
and sent to a stripping column where the
solvent is recycled and the oil is discharged
forrecydingordisposal The water phase is
passed to a second stripping column where
residual solvent is recovered far recycling;
the water is typically discharged to a local
wasaswater treatment plant
Anadvmtageof RCCs brib'ty is the
modular capability, allowing on-siie treat-
Table 1
Specific Wastes Capable of Treatment
Using Solvent Extraction
RCftA L/«»rf HU**OU» Wf»t»*
• Dtedved Air Rotation (DAF) Float
• Slop OB Emubtoo Solid*
• HMt Exchanger Bundto Cleaning Sludge
• API Separator Sludge
• Tank Bottoms (L«ad«d|
Mo/»4J*Mrf H*z*rdout Wutn
• Prtmary Oll/SoUda/Waler Soparatkxi Sludges
• Secondary OiVSolid«/W«t«r Separation Sludges
•Bk^Sludgn
• Cooing Tower Sbdgee
• HFAIkglatkxi Sludge*
• Wane FCC Catalyst
• Spent Catalyst
• Stratford Unit Solution
• Tank Bottom
• Treated Clay*
Table 2
Effectiveness of Solvent Extraction on
General Contaminant Groups for
Soil end Sludge
TrMtabUlty Qraups
Hctogenaied volatile*
Hatogenated aemi-volaiila*
Non-twtogwMMd
PCB*
OtauneiFurene
Organic eyenidM
VotofemeM*
Non-vofcdemeMi
Hectlveneui
Sefl SMf* .
O
O
O
O
O
0
0
O
O
O
O
O
X
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m znt. Other advantages of the BEST™ technology include the pro-
duction of dry solids, the recovery and reuse of oil, and waste
volume reduction. BEST™ does not, however, reduce contaminant
toxicity. Furthermore, implementation can require complex engi-
neering considerations,
SITE CHARACTERISTICS AFFECTING TREATMENT
FI-ASIBIUTY
The BEST™ process is not limited by organics or oil concen-
trations. Performance, however, can be influenced by the presence
of detergents and emulsifiers, low pH materials, and reactivity of the
sludge with the solver! Other factors that affect feasibility and
actions to minimize these affects are listed in Table 3. Treatability
tests should be conducted to determine the effectiveness of the
tnatment on specific site conditions.
Tabte3
Site-Specific Crraracterlstlca and Impacts on BEST™
Ctanctwistla
FiMMfy
Prgsenee of elevated levels
ofwlatjes
Ps itide diameter greater
thin 0.25 inches
pH less than 10
Presence of high amounts
of emubifiers
^impounds thai undergo
stiong reactions under
hi jfyaflaJine conditions
Types of waste
RMSOM (Of
PofMftt
hip*
Vo latites may combine with
process so Vent
of ufwnent used in process not
capable of handbng large
patties
TEA (used in extraction
process) is weak base and win
nol exist in solvent form at pH
las than 10
Adversely affect oltater
phuse separation
Stung reactions may occur
duing treatment because of
cajstic addition
Somematenaisannot
su table for chemical extraction
(6.9^ rugny VUMM organics
and wastes cortanng mostly
toijcmetab)
Actonsto
Minimize triplets
Use an additional separation
step
Semen waste to remove large
particles or crush in a
hammerrni
DMMA — 1 * *l timtmtm turik
nase pn 01 waste wro
caustic soda
•N.
Increase quantity of solvent
Raise pH of waste with TEA
instead of caustic soda
Conduct pre-anoVor
posMreatmert
TECHNOLOGY CONSIDERATIONS
TEA is Qammabk; in the presence of oxygen, therefore, the
treatment system must be sealed from the atmosphere and operated
uri der a nitrogen blanket Also, TEA is known to be toxic to aquatic
lif: and, depending on the disposal method, may need to be removed
from the solids. Prior to treatment it is necessary to raise the pH to
grater than 10, creating an environment where TEA is stable. This
may be accomplished by adding either sodium hydroxide or TEA.
(Sodium hydroxide is more cost-effective, however. TEA is less
restive.) Itmayalsobonecessarytoaddwaterorsolventtothefeed
to create a slurry capaWe of being pumped.
Additionally, pre-treatment may require screening of the feed
to ensure that particles are all less than 0.25 inches. Because the
equipment is incapable of handling large diameter panicles, feed
may be passed through a 2-inch screen and subsequently crushed in
a 02-inch hammermill.
Further treatment of by-products may be necessary before dis-
posal. Specifically, wastewater treatment may include carbon ad-
sorption or biological treatment to remove residual organics. Chemi-
cal precipitation also may be required to remove soluble metal con-
taminants. Free water from sludge ponds may either be treated with
the sludge or may be treated separately. In addition, waste oil may
either be recycled or reused as fuel. If neither option is viable, the
oil should be tested to determine appropriate treatment, storage, or
disposal actions. Last, leachate tests should be conducted on
residual solids to determine if stabilization is necessary before
disposal. Other post-treatment alternatives for solids may include
thermal stripping, wet air oxidation, in-situ vitrification, soil wash-
ing, and/or glycolate dehalogenation.
RCC quotes the cost of treatability studies to be $4,500 for 1 kg
of non-PCB contaminated wastes and $5,500 for 1 kg of waste con-
taining PCBs. These costs include three extractions and do not
include organic analyses. Treatment costs range from $90/ton for a
large facility treating 200 tons/day to $280/ton for a small facility
treating 30 tons/day. More information about RCC can be found in
Table 4.
Table 4
BEST Vendor Information
Company
Resources Conservation Co.
Contact
PaulMcGough
Address
3006 Northup Way
Belevue, WA 98004
(206) 828-2400
Nob: BEST*" MM domtnpxj and ptitrtwl by Resourcw Conswvaliori Co.
TECHNOLOGY STATUS
The first full-scale BEST™ unit was used at the CERCLA
General Refining Site in Garden City, Georgia. Further information
is summarized in Table 5. Solvent extraction is the selected remedial
action for the Pinette's Salvage site and the F. O'Connor site, both
located in Maine; the actual process has not yet been determined.
The BEST™ process has been selected for evaluation under the
SITE Program. Formal demonstration and testing is being post-
poned until the developer has obtained funding for a demonstration
at an appropriate site.
OFFICE OF RESEARCH AND DEVELOPMENT CONTACTS
For more information regarding the BEST™ technology, con-
tact Edward Bates, U.S. EPA, Risk Reduction Engineering Labora-
tory. Cincinnati. Ohio 45268. (513) 569-7774 or FTS 684-7774.
Tables
BEST™ Status at CERCLA Sttee
SELECTS*
Region 4 • General Raining. GA
(Ramon! Adon) FVBfrFYCT
PCBs, toad in Sludge
3,700 tons
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