The effect of storage and ozonation on the physical, chemical, and biological characteristics of swine manure slurries

The reduction of odor emanating from wasted swine manure is a very challenging environmental engineering problem. In an earlier work (Watkins et al., 1997), we showed the effect of ozone in reducing the odor and concentration of phenolic compounds in swine manure obtained from the pits under the slotted floors where the swine were housed. In this paper, we have expanded significantly upon the work of Watkins et al. by determining the effect of storage on the physical, chemical and biological characteristics of the swine manure slurry and whether the efficacy of ozonation is dependent upon storage time. Swine manure slurry was collected and stored, without mixing, in a fermentation reactor. This simulated the storage of the manure in the holding pits located below the swine finishing houses. A sample of slurry was collected weekly and treated with ozone to determine the efficacy of ozone in reducing the malodors of the stored samples. Results show that at an ozone dosage of I g ozone/L of slurry, ozone was very effective at reducing odors to an acceptable level, despite the observation that the malodor significantly increased during the 12 weeks of storage. The concentrations of sulfides, phenol p-cresol, p-ethylphenol and skatole were observed to decrease significantly upon ozonation. The numbers of aerobic bacteria, anaerobic bacteria, E. coli, coliform bacteria, and coliphage also were observed to decrease significantly upon ozonation. No change in the concentrations of soluble phosphate and ammonia nitrogen was observed upon ozonation at this dosage.