Filtering device for filtering a fluid and process for filtering a fluid

A filtering device for filtering a fluid, comprising

• (i) at least one first filter unit serving to remove substances in a first filtering step by way of a membrane filtration comprising a microfiltration and/or an ultrafiltration and/or a nanofiltration membrane, said removed substances having a molecular weight above a defined limit value, resulting in a permeate of the first filter unit mainly containing low molecular weight molecules;
• (ii) a second filter unit, disposed downstream of the first filter unit, for the treatment of the permeate of the first filter unit,
• wherein the filtering device comprises a mixing device within a receptacle containing the second filter unit,
• wherein the second filter unit comprises a filter bed comprising at least one particle filter material, the at least one filter material of the group comprising graphene and activated carbon forming a filtration bed formed from compacted particles in the form of graphene flakes and activated carbon granules;
• and
• (iii) a third filter unit, disposed downstream of the second filter unit, for the treatment of the permeate of the second filter unit, wherein the third filter unit comprises a porous membrane,
• wherein, with a view to the second filter unit, there is a void above the filter bed between the filter bed itself and any further structure which forms part of the receptacle, which receives the filter bed;
• wherein the mixing device is rotatable about a vertical axis and drive connected to a motor and wherein the rotatable mixing device;
• (a) is moveable within the receptacle in an axial direction relative to an upoer zone of the filter bed;
• (b) comprising a disc-like plate with holes and slots for passing the fluid to the filter bed;
• and
• (c) knifes extending along the axial direction from a lower surface of the plate extend into the filter bed
• wherein;
• when the filtration process is in operation;
• the rotatable mixing device is outside the filter bed with liquid between the plate and the filter bed;
• and
• the disc-like plate is configured to create additional pressure to the fluid by axial movements;
• the receptacle having fixed lateral walls and bottom, but the filtration bed being free above, so that the filtration bed can go up and down, while the disc-like plate operates as a safety catch,
• and wherein prior to starting the filtration phase, the rotatable mixing device is configured to;
• move down to have the disc-like plate close to the filter bed and the knives inside the filter bed;
• and
• rotate in order to reshape the filtration bed breaking up the filter bed when compacted
• wherein the rotatable mixing device is adapted to only mix the granules in the upper region of the filter bed thereby eliminating preferential pathways in the filter bed material which would compromise an efficient filter action.