49    TREATMENT OF CS2 AND H2S VAPORS BY BIOFILTRATION
Yonghua Yang, Research Engineer
A. Paul Togna, Manager, Air Toxics Program
George Skladany, Manager, Technology Applications
Envirogen, Inc.
Princeton Research Center
Lawrenceville, New Jersey 08648
INTRODUCTION
Considerable amounts of hydrogen sulfide (H2S) and carbon disulfide (CS2) are emitted into the
atmosphere by various industries. Industrial processes producing H2S include petroleum refining,
rendering, wastewater treatment, paper and pulp manufacturing, food processing, and the treatment
of "sour" natural gas and other fuels. Industries emitting CS2 include the manufacture of viscose
rayon, cellophane, carbon tetrachloride, flotation agents, and cellulose food casings. H2S is also
frequently found in CS2 waste streams in various concentrations.
At normal conditions, H2S is a colorless, flammable gas and CS2 is a colorless, flammable, and
volatile liquid. Both H2S and CS2 are highly toxic and odorous. H2S and CS2 are extremely hazardous
compounds which are human poisons when ingested, absorbed through the skin, and inhaled.
According to the Occupational Safety and Health Administration (OSHA), the maximum concentrations allowed in the workplace are 4 ppmv and 10 ppmv for CS2 and H2S, respectively. The National
Institute for Occupational Safety and Health's (NIOSH) ceiling level for both compounds is 10 ppm
for 15 minutes.1 The odor threshold levels are 4.7 and 7.7 parts per billion by volume (ppbv) in air for
H2S and CS2, respectively.2 The rotten-eggs odor of H2S may be noticeable miles away from the
emission source and is often the main component of odor complains. In addition, the U.S. EPA has
classified CS2 as one of the 189 hazardous air pollutants listed under Title III of the 1990 Clean Air
Act Amendments (CAAA). The discharge of these compounds must be reduced by 90% before the
year 2000.
H2S and CS2 are traditionally treated by absorption, adsorption, and incineration. These methods,
however, are either expensive or inefficient, especially for treating dilute waste gas streams with
contaminant concentrations of less than 1% (10,000 ppmv). Recently, alternative biological methods
are attracting attention due to their ability to overcome many of the process and economic limitations
associated with physical/chemical treatment technologies. One promising biological treatment
method is biofiltration.
Biofiltration was first developed in the 1950s for controlling odor emissions.3 Since then, this
technology has been developed to treat volatile organic compounds (VOCs) and other inorganic
compounds. Removal efficiencies of greater than 90% and 99% have been frequently reported for
many VOCs and reduced sulfur compounds, respectively.4"8 Biofiltration depends on physical,
chemical, and biological processes for its success. At the present time, biofiltration systems cannot be
designed, or system performance guaranteed, based on standardized data alone. The design parameters needed for an economical full-scale system must be determined on a case-by-case basis through
bench-scale and/or pilot-scale studies.
Although biofilters have been used for the treatment of municipal wastewater odors (mainly H2S)
for many years, its application in the chemical industries for treating high concentrations of H2S is
less frequent. Information concerning the use of biofiltration to treat CS2contaminated vapors is even
more limited. From an industrial perspective, it would also be desirable to have data regarding the
simultaneous biological treatment of CS2 and H2S.
ENVIROGEN has conducted a series of studies in order to investigate the feasibility of using
biofiltration to treat H2S and CS2 alone, or in mixtures. This work was performed to determine design
and operating parameters as well as to identify and solve potential operating problems that may occur
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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