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During the process of shale gas extraction, water is one of the resources used in order to fracture the formation and retrieve the trapped gas. A portion of the injected water is recovered during the initial extraction of the gas, which is known as flow-back water. Flow-back water was found to contain very high concentrations of dissolved solids (e.g. calcium, barium, magnesium, chloride, and iron), which renders its treatment highly challenging for most of the existing treatment methods. Electrodialysis is an alternative for onsite treatment (or pre-treatment) and recycling of the flow-back water, which has gained more attention in recent years. The method is based on an electrically assisted membrane process for separation of salts from the water. In this study, the efficiency of the electrodialysis as a desalination process for flow-back water was investigated in the laboratory scale using samples of flow-back water from the Marcellus shale gas formation. The preliminary findings indicated a removal of total dissolved solids of between 35% to 90%.

In the domain of shale gas extraction, water is used during the process of fracturing the shale in order to retrieve the gas trapped in the formation. A portion of the injected water is recovered during the initial extraction of the gas, which is known as flow-back water. Electrodialysis is an alternative for onsite treatment (or pre-treatment) and recycling of the flow-back water, which has gained more attention in recent years. The method is based on an electrically assisted membrane process for separation of salts from the water. Flow-back water has very high concentrations of dissolved solids (e.g. calcium, barium, magnesium, and iron) and electrodialysis is highly susceptible to these cations and has great potential to be used as a desalination process in such aggressive environment. In this study, the efficiency of the electrodialysis as a desalination process for flow-back water was investigated using samples of flow-back from Marcellus shale wells in the laboratory scale. The preliminary findings in the experimental evaluation of the method indicated a removal of total dissolved solids of more than 90%.