Treatment of olive mill wastewaters by ozonation, aerobic degradation and the combination of both treatments

The degradation of the pollutant organic matter present in olive oil mill w astewaters (OMW) is carried out by a single ozonation, a single aerobic deg radation, and the combination of two successives steps: an ozonation follow ed by an aerobic degradation, and an aerobic degradation followed by an ozo nation. In both single processes, the removal of this contaminant load is f ollowed by means of global parameters which are directly related to the con centration of organic compounds in those effluents: chemical oxygen demand and total aromatic and phenolic contents. In the ozonation, an approximate kinetic study is performed which leads to the evaluation of the apparent ki netic constants for the aromatic reduction, k(A) In the aerobic degradation , the kinetic study is conducted by using the Grau model, which is applied to the experimental data, and leads to the determination of the kinetic par ameters of this model, K-2 and n. In the combined processes, a higher COD g lobal reduction is obtained by the successive stages, and an improvement in the removal of the organic material during the second treatment of both pr ocesses due to the pretreatment conducted is also observed. This enhancemen t is shown by an increase of the kinetic parameters (K-2 and n in the aerob ic degradation of the pre-ozonated wastewaters; the apparent constant k(A) in the ozonation of the wastewaters preliminary fermented aerobically), in relation to the values obtained for them in the single processes carried ou t at the same operating conditions. (C) 1999 Society of Chemical Industry.