United States
Environmental Protection
Agency
EPA/540/F-93/507
July 1993
&EFA
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Emerging Technology Bulletin
ii •
Bioscrubber
Aluminum Company of America
Technology Description: Bfofiltratfon is an established economical
air pollution control technology for removing organic contaminants from
air. The existing filters using natural media, such as peat and compost,
have been demonstrated in the field for degrading up to several
thousand ppm of contaminants. An engineered bbfilter using synthetic
media, such as activated carbon, has been developed that shows
improvements in removal efficiency, biodegradation, and space re-
quirements over existing filters.
Bbfiltratbn, in general, is the removal and decomposition of contami-
nants present in gaseous form into nonhazardous substances through
the use of microorganisms. Bfofiltratfon has been used in European
countries for wastewater treatment and odor control. The technology is
used in Germany and The Netherlands as an air pollution control
technique. An engineered bfoscrubber to digest hazardous organb
emissions from soil, water and air decontaminatfon processes was
developed under the SITE Emerging Technology Program. It contains
a unique Aluminum Company of America (Alcoa) granular activated
carbon medium which supports increased mforobial growth, enhances
bioactiv'rty, and converts diluted organics into carbon dioxide, water,
and other nonhazardous compounds. Bbregeneratbn allows constant
maximum adsorption capacity and a complete degradatbn of pollut-
ants. A schematic of the bench scale bbscrubber is shown in Figure 1.
The Alcoa bbscrubber, a carbon-based bioiittration module, addresses
the current deficiencies of composting and other naturally occurring
media-based bbfilters in the areas of pressure drop, bed requirements,
bbmass removal, and water retention. The activated carbon beds
adsorb gases onto the carbon which increases surface concentration
of contaminants and removes hydrophobia gases that would not
normally be adsorbed into the aqueous phase. These qualities result in
enhanced biodegradation of typical organb contaminants, as well as
substances (i.e., refractory compounds, fow concentration, operating
concentration fluctuations) that would not be efficiently degraded in
commercially available bbfilters.
Waste Applicability: The bfoscrubber technology removes organic
emissfons from soil, water, or air decontamination processes. It can be
utilized for treatment of streams containing trace aromatic solvents,
such as benzene, toluene, and xylene. The technology can be adapted
to treat habgenated hydrocarbons and other contaminants.
Test Results: Some problems with composting are the huge space
requirement, continual loss of effective surface area during bbmass
build up (sbthing), and inefficient bfodegradation of particularly refrac-
tory contaminants. The Alcoa bipfilter demonstrated progression over
existing commercially available filters.
Bench scale bfoscrubbers were operated continuously for more than
11 mo to treat an air stream with trace (10-20 ppm) concentrations of
toluene. Greater than 95% removal efficiency was accomplished
throughout the test period. According to the literature, the degradation
rate for toluene by existing bbfilters is 0.1-0.2 g/WP/hr for the selected
concentration. The Alcoa unit, using granular activated carbon as
media, demonstrated 40 to 80 times higher biodegradatbn rate than
existing filters; under the conditions tested, resulting in decreased
space requirement. This enhanced degradation is at least partially
attributed to the adsorption function performed by the activated carbon
medium. The active media also allows for removal of excess biomass
and prevents the compaction of the media experienced in existing
technology. This is one of the advantages of the engineered filter over
the existing compost-type filter, because compaction of the bed even-
tually develops and replacement is required in available filters. The
removal of excess bfomass accumulation in the filter also ensures
minimal pressure drop. As a result, pressure drop from excess biom-
ass was minimal (0-20 in. of water) for a flow rate of 0.5 Mers/min
during the 11-mo operation. The pressure drop did not increase
dramatically v/hen the flow rate was increased from 1 to 2 and then 4
litera/min. The pressure drop is believed to be primarily attributed to (1)
bio-mass build-up, which can be reduced via washing of the carbon,
and (2) poor flow distribution and channeling in the narrow column,
which can be eliminated in a full-scale engineered fitter. An automatic
device for bbmass removal can be designed for afield unit.
The unit was kept in a humid environment and supplemented with
inorganfo nutrients to stimulate bfogrowth. The humidified air stream
was prepared by passing pressurized house air through a Balston
cleaner/dryer (type A, BX, DX), splitting the flow into three streams
through a sparging bottle containing debnized water. An air stream
containing toluene at ca. 500 ppm was split into three streams with
individual mass fbw controllers and mixed with the humidified toluene
stream containing a target concentration of 10 ppm at room tempera-
ture,! These streams were designed as "influent" to each scrubber. The
mass transfer zone remained stationary during the entire operating
period, indicating no accumulation of contaminants and/or their meta-
bolic byproducts. To insure that toluene reductfons were due to bfo-
degradation versus carbon adsorption, the columns tested were pre-
saturated with ca 10 ppm of toluene in air prior to inoculation. The
reduction of toluene in the effluent observed immediately after start-up
was attributed to degradation by the rhbroorganisms inoculated on the
carbon support.
A portable pilot-scale bbscrubber designed and constructed based on
lessons learned from the bench-scale studies, is available for field-
Printed on Recycled Paper
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tosflog at a, hazardous waste sjte- The unit incorporates automatfc
nufcfent supply and bfomass removal systems; thus, an unattended
mod* of operaiJon can ba accomplished.
Cineihnafi, OH 45268
(513) 569-7854 Fax (S13J 569-7620
For Further InformaOon:
! Technology Developer Contact:
Naomi Bafktey
UjS, EPARfek R»ductkxi Engfn&stkig Laboratoiy
2© W*»st Marfih Luther Wng Dm»
Aluminum Company of America
1155 William Pitt Way
Pittsburgh, PA 1S238
(412)^6^3721 Fax {41! 8263720
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