An oxidation ditch, a method of extended aeration, was adapted to hog confinement systems to stabilize the manure in the pits beneath the animals (Day et al. 1969). The oxidation ditch adds enough oxygen to the liquid manure so that aerobic bacteria can stabilize the waste. Carbon dioxide and water are byproducts of aerobic treatment, thus, the mixed liquor in the ditch is practically odorless. Generally, a residual dissolved oxygen (DO) concentration of 0.5 to 1.0 mg per 1 of DO is required in the ditch for the unlikited bacterial action and optimum degradation. The producer, who recycles waste back to the land, does not need complete degradation, but is interested in odor control. Since the cost of aeration is important, it is good to know whether a lower oxygen supply (less aeration) will control odors. The objectives of this study were: a) to determine if a liquid manure system can be operated with no residue of DO present and still maintain near odorless conditions, and b) to determine the amount of degradation of swine manure under such conditions.
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