Determination of aerobic biodegradation kinetics of olive oil mill wastewater

Aerobic biological treatment was conducted for the treatment of high strength olive oil mill wastewater (OMW). Two different approaches were used for kinetic modeling of OMW biodegradation. TOC removal and CO₂–C evolution were monitored in an open and a closed bioreactor systems, respectively. Gompertz, Refractory organics plus first-order (RFO) and Chen–Hashimoto equations were applied to estimate the kinetic parameters by using the data from bioreactors. Furthermore, change in oxidation stage of carbon was monitored and temperature dependency of OMW biodegradation was investigated based on activation energy. At room temperature, 64% of TOC was removed in the open bioreactor while cumulative CO₂–C evolution was 6.32 g L⁻¹ in closed the bioreactor. Higher biodegradation efficiency and kinetic parameters were obtained at 25 °C rather than 10 °C. Gompertz and RFO equations provided better fitting with CO₂–C and TOC data, respectively. Experimental and kinetic estimations indicated that OMW constituted of approximately 30% refractory organics. The comparison of two different modeling approaches showed that kinetic modeling based on CO₂–C provided better correlation with the experimental data. Temperature coefficient indicated that biological degradation of OMW is slightly dependent on temperature.