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Backwash Filter

ZeroB backwash filter is water filter that cleans themselves by regularly cleanse away impurities they have filtered from the water. ZeroB backwash filter system is particularly effective at treating specific water problems, such as iron, chlorine, or other chemical contaminants. When you need to quickly and effectively treat all of the water that comes into your home, a whole house backwash filter by ZeroB may be your best option. Our large water filters include a tank of filtering media through which water flows. The contaminants are trapped in the media, allowing clean, healthy water to flow through your home’s pipes. 

Backwash filters are large tank-style filters that get their name from the fact that they clean and renew themselves by backwashing. Backwashing consists of reversing the flow of water so that it enters from the bottom of the filter bed, lifts and rinses the bed, then exits through the top of the filter tank.

The filter bed itself is a granular substance that is usually referred to as the filter medium. Medium for filtration is numerous and varied. Common media are granular carbon, sand, garnet, anthracite, zeolite, granular manganese dioxide, and greensand.

Backwash filter system involves water treatment that encompasses water purification and sewage treatment. Backwashing through the filter media includes the intermittent use of compressed air during the process. Backwash filter systems can be operated by local programmable logic controllers (PLCs) in water treatment plants. The backwash filter cycle is triggered after a set time interval, when the filter effluent turbidity is greater than a treatment guideline or when the differential pressure across the filter exceeds a set value.

Backwash filter systems include rapid sand water filters, pressure filters, and granular activated carbon (GAC) filters. Backwash filter systems have a proprietary arrangement of pumps, valves, and filters associated with the filtration system. Slow sand filters and self-cleaning screen filters employ mechanisms other than backwashing to remove trapped particles. To keep the water treatment filters functional, they must be cleaned on a periodic basis to remove particulates. Ineffective backwashing is one of the main reasons that water treatment filters fail.

Procedure

Backwash filters involve several steps.

1) The filter is taken offline and the water is drained to a level that is above the surface of the filter bed.

2) Compressed air is pushed up through the filter material causing the filter bed to expand breaking up the compacted filter and forcing the accumulated particles into suspension.

3) After the air scours cycle, clean backwash water is forced upwards through the filter bed continuing the filter bed expansion and carrying the particles in suspension into backwash troughs suspended above the filter surface.

4) Air and water streams are simultaneously pushed upwards through the granular media followed by a rinse water wash.

5) Backwashing continues for a fixed time until the turbidity of the backwash water goes below an established value.

6) At the end of the backwash cycle, the upward flow of water is terminated and the filter bed settles by gravity into its initial configuration.

7) Water to be filtered is then applied to the filter surface until the filter clogs and the backwash cycle needs to be repeated.

Some water treatment filters use surface wash systems that break up the heavily clogged, granular media surface layer. Surface wash systems are buried in the top of the filter media or are suspended above the filter media surface. A fixed grid system of backwash filters consists of pipes with nozzles that inject jets of water into the filter material during expansion. Rotating arms use water jets to break up the blocked filter surface and to rotate a movable arm through the filter material. A surface wash step in a backwash cycle usually takes place at the beginning of the filter bed cleaning process.

Treatment

Backwash water is discharged without treatment to a sanitary sewer system or is treated and recycled within the plant. Used backwash water contains high concentrations of particulate material. Typical treatment processes include coagulation, flocculation and sedimentation. Backwash filters improve the backwash treatment process and purify the resulting poor water to make it suitable for drinking.