Effects of preozonation on anaerobic biodegradability of o-cresol

Ozone pretreatment studies of a refractory phenolic compound, ocresol, were conducted to evaluate the effects of ozonation on the anaerobic biodegradability and toxicity of the reaction products. Two types of batch studies, the biochemical methane potential (BMP) and the anaerobic toxicity assay (ATA), were performed on samples with and without preozonation. The ozonation products were well fermentable to methane after about 60% reduction in chemical oxygen demand (COD) or 32% reduction in dissolved organic carbon (DOC) was achieved by ozonation regardless of the initial concentration of o-cresol. Salicylic acid, glyoxylic acid, oxalic acid, propionic acid, acetic acid, and formic acid were the oxidation products identified. The reaction products formed in the basic pH range were more biodegradable and less inhibitory than those formed in the acid pH range. Phenol degradation was more susceptible to inhibition caused by ozonation products than was acetate utilization.