The sequencing batch reactors were developed to treat the actual wastewater from ethylene
glycol/ethylene oxide producing industry. Four identical reactors with total and effective liquid volumes of 9
and 7 L were operated respectively in parallel. Laboratory experiments were conducted with different organic
loadings of 500, 1000, 1500 and 3000 g-COD/m3.day and the performance of the reactors was studied under different sludge ages of 10, 20 and 30 days, the kinetic constants at optimal operational conditions were also determined. According to the results, the efficient removal of COD was 79.5 and 83.5% (SRT = 20 days) and 86% (SRT = 30 days) for SBR 1 and 2 respectively (OLR = 0.5 to 1 kg-COD/m3.day) with required reaction time of about 17 h. In order to reach the COD removal efficiencies over 86% at higher OLR values, the researchers required longer reaction periods about 34.5 h for SBR 3 and 4. However, the SRT values have no significant effects on the performance of SBR 1 and 2 at the aeration times greater than 22.5 h while in the case of reactors 3 and 4, with an increase on SRT at all aeration times, the COD removal efficiency increased. It is concluded that the system used in the present study could show an acceptable stability and performance in the treatment of the wastewater containing high concentrations of organic matters especially from EO/EG industries.