Filtration device

A filtration apparatus comprising:

• a filtration tank;
• a horizontally oriented layer of particulate filtration media that filters supplied raw water by passing the raw water therethrough within the interior of the filtration tank;
• and
• a screw cleansing mechanism having a cylindrical outer cylinder which is provided within the filtration tank in a vertical orientation, a spiral shaped screw located within the cylindrical outer cylinder such that a longitudinal axis of the screw is coaxial with a longitudinal axis of the outer cylinder, and a screw driving means for rotating the screw, that scrubs and cleans filtration media by rotating the screw;
• the screw being in the shape of a coil spring;
• wherein the screw defines a cylindrically shaped open interior area that extends along said longitudinal axis from an open circular aperture at a lower end of the screw to a closed upper end of the screw, and wherein a vertical side of the screw defines a helically shaped open area that fluidly connects an exterior area surrounding the screw to the open interior area of the screw, wherein the horizontally oriented layer of particulate filtration material occupies the open interior area and helically shaped open area of said screw.