The main aim of this work was to study the ability of an aerobically operated sequencing batch reactor (SBR) to effectively treat the wastewaters produced by a motor-oil reforming company. In fact, the most important goal was to substantially reduce the organic load of these wastewaters before their disposal to an open trench, since the currently installed wastewater treatment plant, that includes an API separator followed by physico-chemical pre-treatment and an oxidation ditch, has proved today to be completely inefficient. The wastewater to be treated was mainly composed of five different streams from various points of the motor-oil reforming plant (e.g. gas washing tanks, cooling pumps, used motor oils holding tanks, etc). The major problem faced in this work was the high organic load (about 12,000 mg COD/L) and the free and dissolved oil contained in the wastewater (around 6-7%). Moreover, two of the streams, contributing to the mixed wastewater up to 30%, were unable to sustain dissolved oxygen and unfortunately their mixing with the other three streams resulted in the same detrimental effect. Therefore, experiments were conducted using either three or all of the contributing streams. The mixed wastewater was fed to the reactor either untreated or pre-treated with ceramic membranes in order to exclude all the free and dissolved oil. The application of pre-treated wastewater with membranes to the SBR system resulted in 75.2% and 81.9% total and dissolved COD reduction, respectively.

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