Oxygenation Capacities of Oxidation Ditch
Rotors for Confinement
Livestock Buildings
DON  D.  JONES,  Research Assistant
DONALD  L.  DAY,  Associate Professor
JAMES C. CONVERSE, Research Assistant
Agricultural Engineering Department
University of Illinois
Urbana, Illinois
INTRODUCTION
Manure odors produced by the modern confinement rearing of livestock are
creating urban-rural fringe conflicts in many parts of the country. Intensified confinement systems produce a staggering volume of manure on a small land area. At the
present time, livestock manure production in the United States is estimated at
1.8 billion cu ft/yr (1). This is nearly 10 times that produced by the entire human
population of the United States.
To cope with the problem, researchers have concentrated a great deal of effort
toward developing a workable, odorless method of liquid waste disposal. One of the
most successful methods studied is the in-the-building oxidation ditch. Not only does
the aerobic treatment eliminate offensive and dangerous odors, but it is possible to
achieve a considerable reduction in the pollution potential of the waste. Ninety per
cent reduction in five-day BOD and 50 per cent reduction in volatUe solids are easUy
obtainable in most livestock oxidation ditches.
In order to properly design an oxidation ditch for a livestock unit, it is necessary to know the performance capabilities of an aeration rotor in a livestock manure
channel. The purpose of this paper is to present the oxygenation capacities of five
aeration rotors tested at the University of Illinois. The rotors were tested in actual
field installations with clean tap water in the ditch and the livestock removed. The
parameter studies were blade immersion, blade design, rotor speed, and gross power
requirements.
MEASUREMENT
The non-steady state method of measuring aerator efficiency was used for
these tests. The procedure followed was: 1) the dissolved oxygen (DO) was taken
out of clean water with chemicals; 2) the aerator was started with the DO of the
water equal to zero; and 3) samples were taken at various time increments and
analyzed for DO content as the DO increased.
The DO level in the water is reduced to zero by adding sodium sulfite
(Na2S03) and using cobalt chloride as a catalyst. Only 0.05 to 0.1 mg/1, of cobalt
chloride should be used since too much cobalt chloride will interfere with the
Winkler test. The sodium sulfite reacts in the following manner to reduce the dissolved oxygen level:
Na2S03+l/2 02 —*■   2Na + + S04= (1)
This equation indicates that 126 g of sodium sulfite reacts with 16 g of oxygen or a
-191 -