Abstract
In this study, the reduction of phenolic compounds and other organic pollutants from greenish black (GB) and dark brown (DB)
olive mill wastewater (OMW) was investigated. Ultrasonic irradiation in combination with aerobic biodegradation was adopted
as the treatment technique. Operational parameters such as the duration of ultrasonic irradiation, ultrasonic power intensity and
ultrasonic frequency were tested to determine their effects on phenol, BOD, and COD degradations. It was found that a time
interval of 90 minutes of continuous exposure of OMW to ultrasonic field lead up to 81% degradation of the total phenol at 25°C.
In addition, the results showed that ultrasonic field affects significantly BOD of OMW. In contrast, there was no significant
dependency between COD degradation and ultrasound intensity. It was demonstrated that phenol degradation can be modelled
adequately according to first-order kinetics model with rate constant, k, of around 0.0083 and 0.0077 min-1 for (GB) and (DB)
OMW samples, respectively. In the aerobic degradation step, the COD was consumed according to Grau kinetic model. The
order of COD degradation rate, is about n=1.13 and 1.27, whereas, the Grau kinetic constant, K=0.0218 and 0.0149 h-1 for GB
and DB OMW, respectively. The maximum COD removal efficiency achieved was about 80%. It can be concluded that
sonication energy plays a significant role on enhancement the efficiency of the biodegradation of OMW by contributing
positively in the reduction of the toxic phenolic compounds.