Disposal of Wastes irom
Small Abattoirs*
Robert E. Stiemke
Professor of Sanitary Engineering
The Pennsylvania State College
Much work has been done in the past on the development of satisfactory methods of treatment of liquid wastes from large- and small-
sized meat-packing plants. For many such plants waste-treatment works
have been constructed and are operated successfully. The methods of
treatment include standard and high-rate trickling filtration, activated
sludge, and chemical treatment. Such plants, when properly designed
and under good operating conditions, have been reported to produce
a satisfactory effluent. The literature is replete with information concerning the treatment of packing-plant waste for the larger plants;
therefore, since this paper specifically concerns small slaughterhouses,
treatment works for larger plants will be dismissed without further
emphasis.
It is estimated that 30 to 35 percent of all the nation's slaughtering
is done in small establishments having a capacity of less than 40 hog
units per day. (A hog unit means one hog, calf, or lamb killed. One
steer or beef is equivalent to two and one-half hog units.) Some small
abattoirs discharge their wastes to a municipal or other public sewer,
in which case the responsibility for providing treatment rests with the
municipal sewage-treatment plant. Others, having no access to a public
sewer, discharge their wastes directly to streams or must provide their
own treatment facilities. The high strength of the waste, its deep color
and foul odor when partially decomposed, make it an objectionable
pollutant, especially when discharged to a small stream, which is the
case in many instances. It has a BOD population equivalent of about
18 per hog unit.
In Pennsylvania it is necessary, in order to comply with the order
of the Sanitary Water Board under the authority of the Clean Streams
Program legislation, for all abattoirs to provide treatment. Such treatment as is provided at some of the small plants at present is confined
largely to septic tanks or cesspools.   These are recognized as being in-
* Photographs and drawings in this paper are by courtesy of The Pennsylvania
State College.
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