Demusifiers and surfactants

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Not all desalts have surfactants or emulsifiers, but they are rare today.

The behavior of surfactants and demulsifiers is totally oposite in their nature: surfactants will tend to stabilize emulsion between hydrocarbon and water phase, while the purpose of demulsifiers is to break these bonds.
Regarding the presence of surfactants in your process stream (that has to be separated from water), you want them in as low as possible concentrations. In hydrocarbon processing industry, the most frequent surfactants are naphthenic acids.