DEVELOPMENT OF ANAEROBIC TREATMENT PROCESS
FOR WASTEWATERS CONTAINING HIGH SULFATES
Meint Olthof, Vice President
William R. Kelly, Project Engineer
Duncan, Lagnese, and Associates, Inc.
Pittsburgh, Pennsylvania 15237
Jan Oleszkiewicz, Professor
Department of Civil Engineering
University of Manitoba
Winnepeg, Manitoba
Canada R3T 2N2
Harold G. Weinreb, Engineer
W. R. Grace and Company
New York, New York 10036
INTRODUCTION
Over the past several years, much attention has been paid to anaerobic treatment of high strength
waste streams. In all this research the presence of sulfates has been considered to be a nuisance. The
sulfate reducing bacteria (SRB) reduce sulfates to the sulfides that create a toxic environment for the
methane forming bacteria (MFB). Furthermore, the sulfides in the gas are considered to be a nuisance
causing potential corrosion problems and resulting in undesirable sulfur oxide releases. The work
that will be presented in this paper presents the development of a process called "BIOSULFIX" that
degrades the organics and forms a valuable byproduct in the form of sodium bisulfide.
This process can adequately take care of the sulfides that are formed by the SRB. At the same
time the environment in the bioreactor is such that the MFB can also perform. The type of organics
and ratio of organics to sulfates in the waste will determine the ratio of hydrogen sulfide and methane
in the gas formed.
This paper will present results of three applications of the "BIOSULFIX" process. The potential
commercial applications for this process are numerous. There are a large number of high strength
(BOD) industrial waste streams that are unsuitable for direct methane digestion because of the high
sulfate concentration. For such situations it is possible to use the SRB to oxidize the organics while
at the same time produce useful sulfur products. Another application is for sulfur recovery from
gypsum sludges from power plants and the phosphoric acid fertilizer industry in the presence of
organic waste such as undigested municipal sewage sludge.
BACKGROUND INFORMATION
The SRB's can be found in nature in several locations. First of all they propagate in river and
estuary sediments where the presence of organics and sulfates allow the SRB to grow. Furthermore,
they can be found in municipal sewage. Most anaerobic digesters of municipal treatment plants have
a certain amount of SRB's. There has been a lot of research conducted on the microbiology of these
organisms. Originally, it was thought that they were only able to oxidize organics to acetic acid. With
time, however, it was discovered that there are SRB's that can oxidize the organics all the way to
C02 and H20. The types of organics that can be totally oxidized by the SRB's include compounds
such as: lactic, propionic, acetic and amino acids, sugars, alcohols, cheese whey, organic material
containing waste streams from industry, and municipal sewage sludge. Also, hydrogen gas can be
used by the SRB's in their metabolism. The first stage in the anaerobic digestion process is the degradation of large organic molecules to the smaller fatty acids. The SRB bacteria then oxidize the low
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