Section 5.    TANNERY WASTES
ODOR CONTROL AT A WESTERN MICHIGAN
TANNERY AND WASTEWATER TREATMENT PLANT
John R. Porter, Jr., Staff Engineer
Thomas A. Doane, Project Engineer
Fishbeck, Thompson, Carr & Huber, Inc.
Grand Rapids, Michigan 49506
The major sources of wastewater in leather manufacturing are the beamhouse and tan-
yard. In the beamhouse, fatty tissue, salt, dirt and hair are first removed from the hides.
These cleaning processes are followed by lime splitting (which separates the grain and flesh
layer of the hide), bating (which lowers the pH of the hide in preparation for tanning),
pickling with salt and acid (to prevent precipitation of chromium during tanning), and
degreasing. Chemicals used in the beamhouse include lime and sodium sulfide in dehairing,
lime in splitting, and ammonium salts in bating. In the tanyard, hides are tanned and re-
tanned with chromium and then finished. An average tannery wastewater stream contains
1000 mg/l BOD, 150 mg/l sulfide and 60 mg/l ammonia-nitrogen. These compounds and
degrading organic matter often produce significant odors in areas surrounding the tannery
and wastewater treatment plant.
Wolverine World Wide, Inc. is a pigskin tannery located in Rockford, Michigan, which
has received complaints about odors in the vicinity of their operations. In response to the
complaints, Wolverine retained Fishbeck, Thompson, Carr & Huber, Inc. to investigate the
problem. The investigation consisted of two segments. One segment involved pilot testing
a chemical air scrubber. The remainder of the study was comprised of an odor survey to
generate background information for an odor treatment system.
Figure 1 presents a site plan of the Wolverine tannery and wastewater treatment plant.
The chemical air scrubber was pilot tested at the raw wastewater channel, the south clarifier
which is enclosed by a fiberglass dome, and the sludge dewatering area. These sites were
selected subjectively as the three most severe odor sources in the wastewater treatment
plant. The odor survey was conducted with samples taken from all of the sites shown in
Figure 1.
AIR SCRUBBER PILOT STUDY
Study Procedure
A 7 50-cfm Pepcon scrubber was initially pilot tested at Wolverine World Wide, Inc.
from August 6 to 20, 1981. This scrubber has the following components: a brine makeup
tank, a scrubbing solution recycle system, two 100-A electrolytic cells, a 200-A/I8-V rectifier, and a blower to draw odor containing gases through the scrubbing tower.
The Pepcon scrubber was chosen for this study because it has electrolytic cells which
generate sodium hypochlorite from a brine mixture. The sodium hypochlorite is then
sprayed onto the plastic media in the scrubbing tower, trickles through the media, and
drains into a sump. The contents of the sump are recycled for regeneration in the electrolytic cells and reuse in the scrubbing tower. This cycle is continued until the scrubbing
solution is no longer reactive. At this time, the hypochlorite solution is wasted and a new
brine solution is prepared for conversion to sodium hypochlorite.
A water scrubber was placed ahead of the Pepcon scrubber during later parts of the pilot
study. This was done to determine if the quantity of sulfide gas into the Pepcon scrubber
and sodium hypochlorite consumption could be reduced by water absorption.
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