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Granular Filtration
Granular Filtration

Granular filtration is a popular choice of pretreatment for most reverse osmosis and ion exchange systems. This is usually done in a two-step setup, the first one being multimedia filtration and the second activated carbon filtration. In multimedia filtration, sand, anthracite, or a combination of both is used to remove any suspended solids from the water to be treated. This is followed by activated carbon filtration, where instead of anthracite, activated carbon is used to employ adsorption of chlorine and organic carbon. 

In some cases, carbon is also used to remove odor. In both cases, however, the media beds are placed on top of pebbles that would support the media and prevent it from carrying over to the next unit operation.

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A multimedia filter is a recommended pretreatment method for RO and ion exchange setups. It is suggested when the Silt Density Index (SDI) value is greater than 3 or when the turbidity is greater than 0.2 NTU. There is no... (More)

In sand filters, backwashing is done at a flow rate higher than the feed flow. This is to allow the media bed to loosen and suspended solids to detach from the media and flow out of the vessel.

It is... (More)

(1) Was there some downtime in the plant? We have to be careful with tolerating stagnant water as this is a potential breeding ground for microorganisms. Maximum downtime should only be 2 days. Activated carbon is more susceptible to microorganism... (More)

Yes, through hot water disinfection.
1. The media bed is first backwashed
2. Water is recirculated about the tank for 30 minutes, while heating up to 203ᵒF using a heat exchanger
3. Water maintained at 203ᵒF is allowed to continue... (More)