## 1 Introduction  
Many older operating refineries or abandoned refineries frequently contain ponds or lagoons that require remediation. Dewatering, solidification/stabilization, incineration, or oxidation are the most common technologies used to treat these sludges; however, these approaches are labor, equipment, and material-intensive [1; 2]. Frequently, cleanup of such sites may be drawn out, due to either a financially insolvent responsible party, or the site at present being within an existing operating facility, and thus RCRA (Resource Conservation and Recovery Act) closure may not be immediately required. In these instances, a method of treatment/degradation such as aerobic biodegradation, which can be slow but still effective under the proper conditions [2], may represent a desirable alternative to both the owner/responsible party and the regulatory agency. A primary challenge in applying biodegradationto oily sludge material is the significantly lower aqueous availability and biodegradation rate of the heavier hydrocarbons, including polynuclear aromatic hydrocarbons (PAHs) [2]. This research considers the use of oil dispersants and microbial consortia developed for open ocean crude oil spill treatment applied to this particular problem of oily sludge treatment via aerobic biodegradation. This treatment would occur in a more controlled and potentially engineered environment as compared to the open ocean, such as a pond or large basin. The use of surfactants or dispersant formulations, along with the addition of petroleum-degrading microbial consortia, for treatment of non-aqueous phase liquids (NAPL) such as oily sludges has been considered by others [1; 2; 3]. [PERSON] et al. [4] applied the dispersant Corexit in testing the biodegradation of a non-weathered and a weathered crude oil and determined that the active control in which the dispersant was not included indicated a greater extent of biodegradation, as compared to the test conditions that included the dispersant. [PERSON] et al. [5] found that the addition of the dispersant Corexit hindered the biodegradation of crude oil by the species _Acinetobacter_, while oil biodegradation by the species _Acinivorax_ was improved with the addition of Corexit. [PERSON] et al. [6] conducted experiments on oil dispersion at different mixing speeds (correlated to energy dissipation rates) and different mixing durations, and found that oil dispersion improved slightly with an increase in the mixing time. These cited works primarily relate to the open ocean crude oil spill management problem, rather than an engineered oily sludge biodegradation challenge. The work reported herein is an initial effort to assess dispersing and biodegradation of an oil sludge surrogate (crude oil) in a controlled laboratory setting using dispersants and microbial consortia developed and utilized in oil spill management, with the end objective being the selection of techniques for scale-up to a pond-based engineered treatment system. Other works similar to this, utilizing oil spill dispersants and microbial consortia for the purpose of oily sludge biodegradation in a controlled environment, have not been recognized by these authors. The specific objective of the research presented herein is to measure the dispersant effectiveness and biodegradation extent of the oil sludge surrogate in several laboratory-controlled environments with varying mixing intensity and scale beyond the typical small flask scale used in the literature cited above. The modeling of oil dissolution from droplets and aqueous phase biodegradation was also included as an objective. Preliminary results indicate the effectiveness in dispersing NAPL is primarily dependent on mixing intensity, and secondly on the dispersant used. The dispersant effectiveness is correlated with energy dissipation of mixing, and greater effectiveness is demonstrated with different types of impellers. Also, the mean dispersed oil drop diameter is calculated based on energy dissipation value.