How do you Backwashing of Multi media filters?

To lower the amount of suspended solids (turbidity) in the incoming feed water, a Multi-Media Filter is utilized. Small particles such as silt, clay, grit, organic debris, algae, and other microorganisms make up suspended solids. High-suspended-solids incoming input water can result in a high-pressure drop, reducing the efficacy of downstream filtration equipment such as reverse osmosis membranes and ion exchange beds.

For multimedia filtration, multi-media water filters typically use three layers of media: anthracite, sand, and garnet. Because of their unique densities, these media are frequently chosen for use. The lightest filtration media per unit volume is anthracite, followed by sand, and finally garnet.

Backwashing of Multi-media filters

Large tank-style filters or backwashing water filters receive their name from the fact that they clean and renew themselves via backwashing. Backwashing a multimedia pressure vessel involves passing a significant amount of water through the filter bed at a low pressure in the opposite direction of the service flow, eliminating accumulated debris from the filter beds.The backwash involves a thorough rinsing and tossing of the medium that lasts several minutes. A normal backwash in a conventional household filter lasts roughly 10 minutes.

How is backwashing done?

The Multi Media Filter will eventually indicate a highpressure drop across the bed and/or increasing turbidity levels as it removes turbidity from the incoming feed water. As a result, cleaning the bed of the Multi Media Filter will necessitate a backwash.

Backwashing should be done when the pressure differential across the bed reaches 10 psi or when the effluent turbidity rises by 10%.The pressure drop via a 'clean' Multi Media Filter is usually between 3 and 7 psi, therefore this must be taken into account before beginning a backwash.

Optional elements can be added to improve backwashing_

1: There is hope if your filter will be subjected to mineral deposits, hard water, or sticky solids. Air scouring is an optional feature that involves adding compressed air to the first few minutes of a backwash to thoroughly stir, tumble, and fluidize the bed. For more demanding service applications, the MMF can be set to drain the vessel to half-full, then perform an air scour without flow. Finally, the solids are washed away by the backwash.

2: The usage of acid during a backwash is another alternative backwash function. Although it is quite successful at dissolving mineral deposits, it has several disadvantages, such as handling the acid and neutralizing it afterwards.

Conclusion

Backwashing your multimedia filter on a regular basis is necessary to keep your filtration system in good working order. Backwashing involves reversing water flow such that it enters from the bottom of the filter bed, lifts and rinses the bed, and then escapes from the top of the filter tank.

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