Dispersant Effectiveness: Studies into the Causes of Effectiveness Variations

Abstract

Effectiveness, a key issue of using dispersants, is affected by many interrelated factors. The principal factors involved are the oil composition, dispersant formulation, sea surface turbulence and dispersant quantity. Oil composition is a very strong determinant. Current dispersant formulation effectiveness correlates strongly with the amount of saturate component in the oil. The other components of the oil, the asphaltenes, resins or polars and aromatic fractions show a negative correlation with the dispersant effectiveness. Viscosity is also a predictor of dispersant effectiveness and may have an effect because it is in turn determined by oil composition. Dispersant composition is significant and interacts with oil composition. Dispersants show high effectiveness at HLB values near 10. Sea turbulence strongly affects dispersant effectiveness. Effectiveness rises with increasing turbulence to a maximum value. Effectiveness for current commercial dispersants is gaussian around a peak salinity value. Peak effectiveness is achieved at very high dispersant quantities - at a ratio of 1:5, dispersant-to-oil volume. Dispersant effectiveness for those oils tested and under the conditions measured, is approximately logarithmic with dispersant quantity and will reach about 50% of its peak value at a dispersant to oil ratio of about 1:20 and near zero at a ratio of about 1:50.

Microbial gene functions enriched in the Deepwater Horizon deep-sea oil plume

“…They point out that spraying equipment is often preconfigured to achieve this. Some laboratory studies also support this number (Fingas et al 1995;Khelifa and So, 2009). …”

Evaluating Chemical Dispersant Efficacy in an Experimental Wave Tank: 2—Significant Factors Determining In Situ Oil Droplet Size Distribution

“…For a typical bench-scale laboratory dispersant effectiveness test (such as Fingas et al, 1995;U.S. EPA, 1996;ASTM, 2002), 120 mL of seawater in a testing flask is spiked with 0.1 mL testing oil, resulting an OWR of 1:1,200.…”

Modeling the effectiveness of oil combating from an ecological perspective – A Bayesian network for the Gulf of Finland; the Baltic Sea

“…The maximum efficiency of mechanical recovery was assumed to be dependent on the volume of oil spill, whereas the maximum efficiency of dispersants was set to 35% (see e.g. Fingas et al [49] and Fingas [50] concerning the efficiency of dispersants in brackish water). The logic of the calculation, adopted from Juntunen et al [35], is presented in Fig.…”

“…This is mainly due to the inefficiency of modern dispersants in low salinity conditions [e.g. [49,50]]. …”