Methods and systems for processing production fluid include embodiments for removal of injected chemicals from the production fluid. An embodiment of a method includes receiving production fluid from a borehole in an earth formation, the production fluid including surfactants injected into the earth formation to stimulate production of hydrocarbons therefrom. The method also includes processing the production fluid to separate the production fluid into at least an oil phase and produced water, introducing a treatment fluid from a treatment fluid source into at least one of the production fluid and the produced water, and removing the surfactants from at least the produced water. The treatment fluid includes a concentration of multivalent cations, the multivalent cations configured to reduce water solubility of the surfactants.