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7.
Run phase filtering water, performance of AFM® & sand
The fine particle retention performance of any media bed is inversely proportional to the velocity of water passed through
the filter. It is always best to operate the filter at the slowest possible flow rate to maximise performance. This is particularly
important for drinking water, especially when there may be a high concentration of cryptosporidium oocysts.
Different filtration media and sand from different countries / deposits will have a different performance. This is a function
of particle size distribution, sphericity, chemical composition and uniformity coefficient. Typically, RGF fitters operate at
6m/hr and pressure filters at 12m/hr. AFM® filters should be operated under the same conditions, however when possible,
slow the flow rate down to the slowest practical rate.
The flow rate for an AFM® filter depends upon the design of the filter and the application. For most RGF and pressure filters
the filtration velocity should be below 12m/hr. This equates to a water flow rate of 12m 3 /hr of water, for every 1m 2 of filter
bed surface area. RGF filters will be operated at a slower flow rate due to pressure head limitations, typically the water
flow velocity should be 6m/hr.
AFM® an Activated Filter Media