The use of ozone to reduce the concentration of malodorous metabolites in swine manure slurry

A pilot-scale ozonation system was constructed and operated to reduce the m alodours emanating from fresh and stored swine manure slurry. The concentra tions of; the malodorous bacterial metabolites (phenol, p-cresol, p-ethylph enol and skatole) found in the liquid fraction of the manure slurry were fo und to increase during three weeks of storage. The fresh and stored manure slurry was ozonated at dosages of 0.25, 0.5, 0.75 and 1.0 g/l. Ozonation el iminated these metabolites from the manure slurry. On the contrary, no usef ul decrease in the concentration of all the above metabolites was observed after treatment with either nitrogen or oxygen. The odour intensity of the manure slurry was also significantly reduced (P < 0.05) after ozonation at a dosage of 0.5 g/l. In contrast, neither stripping with nitrogen nor oxida tion using oxygen had a significant effect on the odour acceptability of th e mature. The use of hydrogen peroxide and ozone did not offer additional b enefit over that obtained with ozone alone. Within the range of 14-25 degre es C, temperature had no effect on the efficiency of ozonation. The ozonate d manure did not regain its original malodour after one month of storage su bsequent to ozonation. (C) 1999 Silsoe Research Institute.