There are several filters available for granular media filters. Some of them are mentioned below:
- Upflow filters
- Cell filters
- Automatic backwash filters
- Horizontal and radial filters
- Membrane filters
Type 1: Cell filters: A normal filter can be built to a maximum fixed size if the whole filter bed is to be backwash at the same time. If it is possible to backwash the filter bed in small sections then the filter shell can be larger. If the filter bed is divided by walls, then it is possible to backwash the bed in small sections. The filter bed should be divided just above the bed the filter floor so that we can place the hood over the section to get backwashed. The hood is placed on a Four-legged base of casks (gantry) that runs on rails along the top of the filter’s main sidewalls. Civil engineering cost required for this method has been reduced after applying this approach but on the other hand, mechanical engineering cost has increased a lot if it is compared to a large number of filters of equivalent total filtration area.
Type 2: Automatic Backwash filters: As the disposits get collected in the filter bed, the more difficult it becomes to flow through the bed. With the help of an outlet valve, we can keep the flow constant. The outlet valve is opened alternatively to provide less resistance to flow through it to compensate for the increased resistance to flow through the bed. By applying this method, we can keep the water level constant above the media. The flow through the filter remains relatively constant as the level of water keeps on increasing above the bed. Sometimes, commercial grease trap and septic tanks denver are also used, and for their treatment drain cleaning denver co is used.
Type 3: Horizontal and Radial filter:
- Horizontal filters – Instead of flowing the water in an upward or downward direction through the filter bed, it can flow horizontally across through the bed. If the filter bed is placed inside a rectangular tank then the speed of filtration remains constant along the length of the filter. We can filter the backwashed hydraulically if needed. Horizontal filters are also used as clarifiers when the filters are used after filling them with pebbles.
- Radial filters – A radial filter is simply a horizontal filter but in this case, the width of the filter bed keeps on increasing in the direction of flow. The speed of filtration gradually decreases as the water flows through the filter media which makes it more efficient to remove the particles.