a device for preparing a nutritional composition by supplying water to ingredients provided to the device includes a pump connected to an integrated or external water supply , and a water discharge head designed for providing water to a cartridge containing ingredients for interaction between water and the ingredients in the cartridge . the pump and the water discharge head are in water communication via a water flowpath , and the pump can supply water under pressure through the water flowpath the device includes a rigid filter assembly having at least one antimicrobial filter membrane and filter enclosing member . the filter assembly and the filter enclosing member are complementary configured such that the filter assembly is insertable into the filter enclosing member across the water flowpath in a fluid tight manner before the water discharge head , and is removable from the filter enclosing member .