Surfactant-enhanced biodegradation of crude oil sludge in sequencing batch reactor: effect of surfactant concentration, oil loading rate and number of cycle per day

Abstract

Biological treatment has been proposed to treat crude oil sludge but it is often restrained by the limited availability of hydrocarbons present in the sludge due to their poor solubility in aqueous phase. The way to overcome this problem is to use surfactant to increase solubilization of the hydrocarbons and enhancing their bioavailability to degrade microorganisms. In this research, two units of sequencing batch reactors (SBR) were used for study the biodegradation of crude oil sludge obtained from Bangkok Public Company Limited. The solubilization experiment was first studied to improve the biodegradation efficiency, polyoxyethylene sorbitan monoleate (Tween 80), a nonionic surfactant was selected to enhance the solubilization of the crude oil sludge. The optimum surfactant concentration was found to be 0.2% w/v. The oil loading was examined to find the optimum oil loading by using surfactant concentration at 0.1% w/v and the result showed that at oil loading 1 kg/m3d provided the highest removal efficiency. Then the effect of number of cycle per day of SBR operation was studied, when the number of cycle per day increased, the removal efficiency decreased. When changing the surfactant concentration to 0.2% w/v, the result showed that the highest removal efficiency provided at 1 cycle per day of SBR operation as high as 80%