The present study examines the use of an electric field to demulsify oil-in-water (O/W) emulsions stabilized using a nonionic surfactant. First, we prepared an O/W emulsion with a low surfactant content and found that the application of an electric field promoted demulsification. The effects of the electric field intensity, droplet size, and organic solvent content on the demulsification efficiency were evaluated. The application of a high electric field was found to lead to the coalescence of droplets in O/W emulsions. However, this technique was only effective for large droplets. As the organic solvent content increased, the droplet size became larger and the demulsification efficiency improved. We investigated a combination of preconcentration and electric-field-based demulsification for wastewater treatment. Preconcentration was found to be effective for enabling the demulsification of dilute O/W emulsions.