United States
                                   Environmental Protection
                                   Agency
                 EPA/540/MR-93/508
                 April 1993
                                   SUPERFUND INNOVATIVE
                                   TECHNOLOGY EVALUATION
                                   Demonstration  Bulletin
                                                             i

                                   Mobile  Volume  Reduction  Unit

                                  U.S. Environmental Protection Agency
Technology Description:   The Volume  Reduction Unit
(VRU), which was developed by EPA, is a mobile, pilot-scale soil
washing system for stand-alone field  use in cleaning soil con-
taminated with hazardous substances. Removal  efficiencies de-
pend on the contaminant as well as the type of soil.

Soil washing is a water-based ex situ process for mechanically
scrubbing soils to remove undesirable contaminants. The pro-
cess removes contaminants from soils by either dissolving or
suspending them in the wash solution (which is  later treated by
conventional  wastewater treatment methods) or concentrating
them into a smaller volume  of soil through simple particle size
separation techniques. The concept of reducing  soil contamina-
tion through the use of particle size separation is based on the
finding that most organic and inorganic contaminants tend to bind
to fine-sized  clay and silt  particles  primarily  by physical pro-
cesses. Washing processes that separate the particles from the
coarser soil particles effectively concentrate the contaminants
into a smaller volume. The clean larger fraction can be returned
to the site for continued use.

Figure 1 provides a diagram of the typical VRU operational setup.
(Thei VRU setup at the Demonstration site was modified slightly
from this typical setup.) The basic VRU system consists of the
following subsystems:

   • Soil handling and conveying (feed soil)
   • Soil washing and coarse screening  (mini-washer and 100
    mesh screen)
                                                 Makeup Water Tank
                               Slowdown Tank
                                                                       Water Heater


                                                                           Screw Conveyor
                Carbon Drums
                                  Trommel Screen
                                  Mini-Washer

                                        Steam Boiler
       Air Compressor
                                                                                                    Grizzly
   Electric Generator
                                                                          Screened Soil Fractions
Figure 1. Typical VRU operational setup.
                                                                              Printed on Recycled Paper

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  • Hnes/floatables  gravity  separation (Corrugated  Plate
    Interceptor tank)
  • Fines flocculation/water  clarification and  solids disposal
    (ffoc tank)
  * Water treatment (10 micron fitter, liquid phase carbon
    adsorbents, blowdown tank, and water storage tank)
  * Utilities - electric generator, steam boiler, and compressed
    air unit.

Two vibrating screens continuously segregate the soil into various
stea fractions. Mini-washer overflow, containing the coarser sol-
Jds, falls onto the first screen. Solids from the first screen overflow
are gravity-fed to a recovery drum. The first screen underflow is
pumped at a controlled rate to the second screen where  it is
joined by the mini-washer underflow. The overflow from the sec-
ond screen Is gravity-fed to the same recovery drum containing
the other washed soils. The second screen underflow drains into
a tank with a mixer and is then pumped to  a Corrugated Plate
Interceptor (CPI). Three streams exit the CPI:  materials lighter
than water,  solids and washwater. Materials lighter than water
(ffoatables such  as  oil) fbw over an internal weir,  collect in a
compartment wHhin  the CPI, and drain by gravity to a drum for
treatment  and disposal. Solids are discharged by the  bottom
auger to a recovery  drum. Effluent from the CPI overflows into a
tank with a mixer to a static mixer located upstream of the floe
clarifier's mix tank.

Flocculating  chemicals such as liquid  alum  and aqueous poly-
oloclrolyte solutions  are metered into the static flash mixer tank.
The slurry overflows into the floe chamber, where bottom solids
are augured to a drum for disposal. Clarified water is pumped
from the  floe overflow tank through 10-micron filters for  fine
particle removal  and through activated carbon drums for hydro-
carbon removal to permit recycle.

Waste Applicability:  The VRU is a mobile research  unit
that was developed  for treatability studies on soils contaminated
With a wide  variety  of contaminants. It was  designed to be ex-
tremely flexible in terms of equipment and washwater additives
usod. In general, soil washing is effective on soils with a large,
coarse sand and gravel fraction contaminated with a wide range
of organic, inorganic, and reactive contaminants.
Demonstration Results: The Demonstration took place at
the former  Escambia Treating Company in Pensacola,  FL be-
tween November 5 and 13, 1992. The 26-acre facility had used
pentachlorophenol  (POP) and creosote  (polynuclear aromatic
hydrocarbons or PAHs)  to treat wood products from 1943 to
1982. The site is currently undergoing a Superfund cleanup that
is being managed by EPA Region IV.

During the  Demonstration, the VRU operated at a feed rate of
approximately 100 Ib/hr and a washwater-to-feed ratio of about
6:1. The physical condition of the washwater was modified with
various  combinations of surfactant,  caustic,  and temperature
change. Condition 1 (no surfactant and ambient pH and tempera-
ture), Condition 2 (surfactant addition and ambient pH and tem-
perature), and Condition 3  (surfactant addition, pH of 9-10 and
temperature of 150°F). A summary  of the preliminary  data is
shown in Table 1.

Table 1. Summary of Preliminary VRU Demonstration Data
Condition (%)

Average POP removal
Average PAH removal
Feed soil returned as washed soil
Mass balance of total mass
Mass balance of PCPs
Mass balance of PAHs
1
80
79
96
104
108
87
2
93
84
96
113
60
60
3
97
96
81
98
24
17
An Applications  Analysis Report and  a Technical Evaluation
Report describing the complete demonstration will be available in
the Fall of 1993.

For Further Information:

EPA Project Manager
Teri Richardson
U.S. Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7949
    United States
    Environmental Protection Agency
    Center for Environmental Research Information
    Cincinnati, OH 45268

    Official Business
    Penalty for Private Use
    $300
                                  BULK RATE
                             POSTAGE & FEES PAID
                                      EPA
                                PERMIT No. G-35
    EPA/540/MR-93/508

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