Contribution of surfactants and micelles to contamination and treatability of crude oil-contaminated surface water

Abstract Subsequent to an oil spill in surface water, impacts of dispersant application on water treatability and residual contamination in distributed potable water remain largely unknown. The desired outcome of dispersant application is attributable to both nonionic and anionic surfactants which reduce interfacial tension. This study evaluated the contribution of surfactants and their agglomerates, micelles, to contamination and treatability of drinking water. Both a commercial oil-spill dispersant and a formulated dispersant solution were applied in surface water, with and without crude oil, and treated by ballasted flocculation. In crude oil-contaminated surface water, the formulated dispersant was applied at two concentrations to generate surfactant monomers and surfactant micelles. Water quality degradation in the absence of crude oil was attributable to surfactants but more importantly to other organic contaminants present in the dispersant matrix. Ballasted flocculation could only handle low dispersant concentrations judging from the generated settled water quality. In the presence of crude oil, dispersant application hindered water quality and treatability due to the introduction of surfactants that were absent in surface water and whose removal was unachievable with an optimized coagulant dose for turbidity and natural organic matter removal prior to contamination. This phenomenon was of greater significance in the presence of micelles. These findings are of relevance to regulators, petrochemical and water industry professionals in their efforts to best design contingency plans for oil-spill remediation of surface water used as drinking water supply.