Measurement of Microbial Degradation
of Sulfonated Lignin
A. RAY ABERNATHY, Assistant Professor,
Department of Civil Engineering, Clemson College,
Clemson, South Carolina
INTRODUCTION
Disposal of its liquid wastes has long been a problem to the pulp and paper
industry. The Senate Select Committee Report(l) showed that in 1954 the water
usage for the pulp and paper mills of the United States was 1,607 billion gals. By
assuming that most of this volume is returned to the waterways and using data presented by Besselievre (2), Rudolfs (3), and McKee, et al. (4), it may be estimated
that over two million tons of lignin products are included in the five million tons
of solids discharged annually to the nation's waterways. This material constitutes
a tremendous pollutional burden upon the streams, possibly preventing plant expansion or dictating the location of new mills. However, not only do the lignin
residues add to stream pollution, but they are an enormous waste of an organic
chemical raw material of potential value.
Much of the research and development effort expanded upon the problem of
pulp mill waste has been directed at BOD reduction, fiber recovery, and avoidance
of fish kills. Biological treatment processes have shown success in the reduction
of BOD (5), yeast production (6), and alcohol fermentation (7). However, these
forms of biological treatment utilize only the carbohydrates fraction of the waste
and leave the major portion of the total organic content, i.e., lignin residues,
relatively unchanged.
One of the reasons for the small amount of work on biological decomposition
of lignin sulfonate and other lignin residues has been the problem of measuring
the effect of microbial activity upon lignin products. The structure of lignin
is not yet completely known nor is the structure of sulfonated lignin residues.
This contributes to the difficulty of measurement of lignin sulfonate concentration
before and after biological treatment. This difficulty has contributed to the confusion existing as to the biodegradability of lignin sulfonate. The following references give some idea of the diversity of methods and results in this area.
Adams and Ledingham (8) in 1942 reported that the fungus Endocnidiopbora
adiposa was found to remove ten per cent of the lignin in sulfite waste liquor in
20 days incubation. These results were based on the precipitation of calcium
lignosulfonate with napthylamine before and after incubation. These investigators
also used ultraviolet absorption for measuring the concentration of sodium lignin
sulfonate in culture media. In 1942 (9) they reported that absorption at 280 mu
decreased for incubated samples but there was no change in the absorption of controls.
Churchill (10) found that the color of paper mill waste remained constant in
a rapidly flowing stream but did decrease about 50 per cent during storage in a
reservoir.   This reduction was considered partially due to biological action.
Kroner and Moore (11) studied the removal of lignin preparations from river
water. One culture removed 76 per cent during a 24-week incubation period.
This removal was based on measurements by the Folin-Denis test.
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