A method for treating a process water from a bitumen recovery process in order to obtain carbon dioxide from the process water, which method includes lowering the pH of the process water, thereby causing carbon dioxide to evolve from the process water as evolved carbon dioxide gas. The evolved carbon dioxide gas may be collected and compressed, and water vapour associated with the evolved carbon dioxide gas may be separated from the evolved carbon dioxide gas. After the carbon dioxide has been obtained from the process water, the process water and the water vapour separated from the evolved carbon dioxide gas may be recycled back to the bitumen recovery process. The evolved carbon dioxide gas may be stored for future use or sale. The method may also include heating the process water in order to reduce the solubility of carbon dioxide in the process water.