A system comprising a fluid treatment assembly and means for feeding the assembly with fluid to be treated and receiving treated fluid, comprising a structure (12) on which the assembly is adapted to be removably mounted, to interengage complementary connectors thereof with each other, is characterized in that it includes cooperating functional surfaces (25) formed on the assembly and the structure (12) so that they can enter into mutual contact to immobilize the assembly against movement in translation and keep the connectors interengaged with each other when the assembly is mounted on the structure (12) and to allow the assembly to be released in order to remove it from the structure (12) by exerting on the assembly an action limited to tilting it relative to the structure (12) and guided by the connectors interengaged with each other.