(417a) Analysis of the Benefit of Mixing for Oily Waste Sludge Biotreatment

The biotreatment of oily wastewaters and sludges at legacy industrial refinery and petrochemical sites can be aided by the use of adequate mixing to disperse the oily phase into small separate-phase droplets, thereby enhancing interfacial area for hydrocarbon mass transfer into the aqueous phase. The increase in dispersion effectiveness directly correlates with treatment rate of the hydrocarbons, which are sparingly soluble in the aqueous phase, where bacteria effect the biodegradation. The dispersion of the oily phase material can also be aided by the use of dispersants, while mixing also commonly assists in the aeration necessary for aerobic biodegradation. This current research studies the effect that power input and mixer device type have on the dispersion effectiveness. Mixing power per unit volume of oil-containing wastewater is a critical determinant for effective oil phase dispersion. For this reason, an analysis is conducted on how effective dispersion can be achieved over a large-area hypothetical legacy industrial oily wastewater or oily sludge pond. Different approaches, such as a sizeable number of fixed mixers or aerators versus periodic movement of fewer mixers or aerators to different sections of the pond, are used to assess the power expenditure vs effectiveness of oily waste dispersion. The results of this study may be used to assist in design of biotreatment systems for oily water ponds at legacy industrial sites.