Comparative applications of bioreactor and shake-flask systems in the laboratory treatment of oily sludge

Abstract

This study investigates the remediation efficiencies of a locally fabricated bioreactor system and a shake-flask system, using samples of oily sludge with varying concentrations of NPK fertiliser. Hydrocarbon removal efficiency of 46% and 24.2% was recorded for the stirred slurries containing 15- and 0-g NPK, respectively, in the bioreactor; whereas values of 40.1%, 33.2% and 18.9%, respectively, were obtained for the shaken flasks containing 0.3-, 0.113- and 0-g NPK at the end of this study. Corresponding values of 26% and 11.8% were obtained for the unstirred slurries; as well as 21.9%, 23.1% and 14.3% for the unshaken flasks. Nutrient amendment was shown to enhance the rate of oil removal in the following order: 0.2% NPK > 0.075% NPK > no NPK. However, the combined effects of nutrient addition and agitation proved to be the most effective treatments as confirmed by gas chromatography. pH and temperature values obtained were generally in optimal range (6.5–8.5 and 29–31°C, respectively). This preliminary investigation shows the potential utilisation of NPK in large-scale bioremediation of soils contaminated by oily sludge, using a well-stirred bioreactor system.