The disc filter is a really compact solution for the removal of suspended solids and its related substances, such as COD, BOD5 and phosphorus. The filter works by gravity and is installed submerged for about 60% of the diameter, within an appropriate containment tank in concrete or in stainless steel. The system is made with a series of pairs of parallel discs, which are mounted on special panels complete with filtering canvases.
The water to be treated enters directly into the central cracked cylinder, continues internally in the discs, passes through the filtering panels (from the inside to outside) depositing on the canvas the solid substances, outflows into the containment tank of the filter, and then towards the overflow of outlet. During its normal operation, there are no moving parts and therefore no wear and energy consumption The gradual clogging of the filtering canvas reduces the permeability with consequent raising of the water level upstream of the filter, until the reaching of a set level that starts automatically the cleaning phase.
The gearmotor rotates the discs and simultaneously a centrifugal pump starts to feed several pipes with nozzles, which spray filtered water on the external surface of the canvas, emerged form the water, to remove the retained solids. The rotation of the disks allows the complete cleaning of the filtering elements in a very short time. A special channel on the inside of the cylinder collects the backwash water and conveys it by gravity out of the filter.
The cleaning operation involves the lowering of the level upstream of the filter up to the achievement of another level sensor, which controls the stop of the backwashing pump and the rotation of the filter. The cycle is repeated again on the reaching of the maximum level sensor, without ever interruption of the normal filtering operation.
The main advantages of this solution, compared to a sand filter, are:
- Degree of filtration much lower (up to 6 microns)
- Compactness of machinery, while ensuring an high surface filtration
- The use of reduced water volumes for backwashing
- Lower energy costs
- Easy maintenance
- Continuous operation, even during the backwashes.
This technology is used as an integral part of the treatment process in a Partial Recovery Plant, a Zero Liquid Discharge Plant, a Primary Water Plant or a Drinking water Plant.