52    FIELD-PILOT RESULTS OF STYRENE BIODEGRADATION
USING BIOFILTRATION: A CASE STUDY
A. Paul Togna, Manager, Air Toxics Program
George J. Skladany, Manager of Technology Applications
James M. Caratura, Senior Project Manager
Sam Frisch, Senior Process Engineer
Envirogen, Inc.
Princeton Research Center
Lawrenceville, New Jersey 08648
INTRODUCTION
In this study, treatment of styrene-contaminated air discharged from a fiberglass spray booth
operation was investigated using a field-pilot biofilter containing 30 ft3 of packing. The length of the
testing program was approximately four months, from November, 1992 through February, 1993. The
testing program was designed primarily to evaluate biofilter efficiency as a function of vapor residence time so that an economic evaluation of biofiltration for styrene removal from this process
stream could be prepared. Of equal importance to the design team was the response of the biofilter to
rapid changes in contaminant concentration, discontinuous daily and weekly plant operation, and
extended periods of plant shutdown.
BACKGROUND
Styrene is one of the 189 hazardous air pollutants listed under Title III of the 1990 Clean Air Act
Amendments (CAAA). The CAAA require a 90 percent reduction in hazardous air pollutant releases
by the year 2000. Styrene is used in a number of manufacturing operations, and transfer of this
compound to plant air typically occurs during drying operations at ABS and polystyrene plastics
manufacturing facilities. In 1990, an estimated 400 million pounds of suspected carcinogens were
released into the environment; styrene, dichloromethane, and trichloroethylene were the three major
chemicals discharged.1 But while dichloromethane and trichloroethylene are known to contaminate
soil, water, and air, a recent review of the environmental fate of styrene has shown that air is the
major source of styrene exposure.2
Biofiltration is a process that utilizes microorganisms immobilized in the form of a biofilm layer on
a porous filter substrate such as compost or peat. As a contaminated vapor stream passes through the
filter bed, pollutants are transferred from the vapor phase to the biolayer and are oxidized, forming
carbon dioxide and water. Biofiltration has been used for many years in Germany, The Netherlands,
the United Kingdom, Japan, and to a limited extent in the United States for odor control (H2S, etc.),
but the use of biofilters to degrade more complex air toxic emissions from chemical plants has
occurred only within the last few years. Vapor-phase biological treatment systems are rapidly gaining
acceptance as a cost-effective abatement technology for the treatment of volatile organic compounds
(VOCs) and air toxics released from industrial manufacturing facilities. Biological degradation of
styrene has been demonstrated by a number of investigators,3'4 and removal of styrene from air using
biofiltration has been demonstrated at both the bench5,6 and pilot scales.7
PILOT SYSTEM DESCRIPTION
Biofilter System
A conceptual diagram showing the major features of Envirogen's field-pilot biofilter system is
shown in Figure 1. The total flow of vapor through the spray booth stack was approximately 13,000
to 18,000 cfm. A blower was used to supply a small slip stream (15 to 120 cfm) of the total spray booth
discharge through a 3" diameter pipe running from the roof discharge point to the humidifier located
48th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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