Automated Pig Wastewater Treatment
and Effluent Recycle
E. PAUL TAIGANIDES, Professor of Agricultural Engineering
C. ROLAND MOTE, Research Associate
RICHARD K. WHITE, Assistant Professor
Agricultural Pollution Control Research Laboratory
Agricultural Engineering Department
The Ohio State University
Columbus, Ohio 43210
INTRODUCTION
Success of the large confinement units being built today by the nation's pork producers
often hinges on the waste handling and treatment system incorporated into the operation. A
successful waste handling and treatment system must minimize labor requirements, be
economical to build and maintain, and process the waste in a manner compatible with the
local environment. A system which appears to have good potential for meeting the waste
handling and treatment requirements of the nation's pork producers was built on the
Research Farm of the Botkins Grain and Feed Company in 1971 and has been operated as a
demonstration project for two years.
HANDLING OF WASTE
The treatment plant receives all the waste produced in a 500 head capacity swine
growing and finishing barn. Pigs are brought into the barn at about 40 pounds and taken
out for marketing at about 220 pounds. During their stay in the barn, the pigs are in pens
equipped with a dunging channel across the back. One of the channels is a two inch deep by
three foot wide exposed gutter which the pigs have access to. The other four dunging
channels are four feet deep and are covered with slats. As long as the proper population
density is maintained in the pens and the feeder is located near the front, the pigs will
defecate in the gutter or on the slats. The movement of the pigs forces the solid waste
through the cracks in the slatted floor and into the channel below.
Removal of the waste from the building is accomplished by periodically flushing each
dunging channel with water. The flushing is performed automatically by siphon flush tanks
installed at the end of each channel. Figure 1 is a schematic of the flush tank. The size of the
bell and trap is designed so that flushing occurs when the tank is nearly full. Frequency of
flushing is controlled by the flow rate of water into the tank.
Tanks on three of the channels have a capacity of 190 gallons and a fourth tank has a
270 gallon capacity. During the two year operation of the system, the time between flushes
for each channel has varied from 30 minutes to two and one half hours. The various flushing
frequencies have produced no significant differences in the quality of the environment
inside the barn. The pigs are always clean and there is never any strong manure odor.
TREATMENT OF WASTE
Figure 2 is a schematic of the treatment plant. The slurry of animal waste and flush
water from the dunging channels flows into a sump from which it is pumped at a 75 gpm rate
to a commercial, non-corroding stationary screen. The screen is 18 inches wide and is
composed of bars placed with a 40 mil spacing. Solids removed by the screen drop into the
solids treatment unit. The liquid effluent from the screen goes into an oxidation ditch where
the dissolved and suspended organic matter is decomposed by aerobic microorganisms.
A commercial cage rotor, 27 inches in diameter and five feet six inches long is installed
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