Electrodialysis: An application for the environmental protection in shale-gas extraction

Water is one of the resources used to fracture the host formation and retrieve the trapped gas during the process of shale-gas extraction. A portion of the injected water, which is known as flow-back water, is recovered during the initial extraction of the gas. The main characteristic of flow-back water is the very high concentrations of dissolved solids (e.g. calcium, sodium, and chloride), which renders its treatment highly challenging for most existing treatment methods. An alternative for onsite treatment (or pre-treatment) and recycling of the flow-back water is electrodialysis. The method is based on an electrically assisted membrane process for separation of salts from the solution. In this study, the efficiency of the electrodialysis for desalination of flow-back water was investigated at the laboratory scale using samples of flow-back water from the Marcellus shale-gas formation.