Anaerobic-Aerobic Treatment of
Spent Vegetable Tan Liquors from a
Sole Leather Tannery
J. DAVID EYE, Professor
JOHN G. ALDOUS, Research Assistant
Environmental Health Engineering
University of Cincinnati
Cincinnati, Ohio
INTRODUCTION
The increased emphasis on water pollution control by governmental agencies
and the general public has prompted the tanning industry to initiate an intensive
research program for finding acceptable means for treating the water borne wastes
stemming from tanning operations. Because of the relatively unfavorable economic position of the sole leather industry the basic criteria for a satisfactory
waste treatment system include: a low capital investment; low operating costs;
simplified operating procedures; flexibility in operation; small land usage; and
performance capability commensurate with effluent requirements.
While these goals will be difficult to achieve in their entirety for wastes as
complex as those derived from sole leather (vegetable) tanneries, recent research
has demonstrated that it is possible to formulate a treatment scheme that approaches these requirements. Detailed studies on the volumes and characteristics
of the wastes discharged from sole leather tanneries show that about 75 to 85 per
cent of the major pollutants are contained initially in only 20 to 30 per cent of
the total waste volume (1, 2). The remaining waste waters are comprised mainly
of rinse waters which are not grossly polluted. The two waste streams of greatest
concern are the lime-sulfide liquors from the hair loosening process and the spent
vegetable tans from the tanning operation.
The treatment procedures utilized in this study consisted of separation of the>
waste streams, pretreatment of the individual waste fractions to the degree required and biological treatment of the blended, pretreated wastes in a stratified
anaerobic-aerobic lagoon.
SOURCES AND CHARACTERISTICS OF TANNERY WASTES
The waste waters used in this study were obtained from the Virginia Oak
Tannery of Luray, Virginia. While the exact tanning procedure followed will
vary from plant to plant the basic steps are illustrated in simplified form in
Figure 1.
The volume of waste water discharged from the tannery varied from 450 to
590 gal/hide (9. 0 to 11. 7 gal/lb of finished leather) which is slightly higher than
normally found for sole leather tanneries (3). The pollutants include soluble and
suspended lime, sulfides, soluble proteins, hair, grease, particles of flesh, chlorides, bacterial inhibitors, wetting agents, manure, enzymes, inorganic salts and
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