Abstract: The invention relates to a method for treating fluid (2) resulting from hydraulic fracturing with liquid/solid separation (3), comprising the steps of: receiving the fluid in a vessel (4), such as a mixing tank or a plug flow reactor, adding a chemical mix comprising organoclay to the fluid in the vessel to reduce levels of dissolved salts and organic compounds and molecules, and to allow coagulation and flocculation to occur, adding pH-adjustment chemicals to the fluid in the vessel to reduce water hardness, adding a micaceous metal complexing agent to the fluid in the vessel to at least partially remove ionic or complexed metalloids. The invention also relates to an assembly for carrying out the method as well as a vessel to be used therein.