4.3. How to fill a pressure filter with AFM®
In all cases it is essential that the filters are on a level concrete pad or plinth, and that the valve manifold
and pipework is supported to prevent any stress on the filter flanges.
Before the first layers of filter media are introduced via the top access port, it is best to half fill the filter
with water. This helps to prevent damage to the laterals or the nozzle distribution plate by the falling
media.
For filters with a side manhole, open the bags and gently empty the first layer onto the base of the filter
bed. The larger grades are added first, grade 3 for filters over 1m in diameter, and grade 2 for filters 1m
and smaller in diameter. See Table 1. For horizontal filters we also recommend grade 3 on the base of
the filter up to a point that is level with the laterals.
After the addition of each layer it is important to make sure the media is evenly distributed and the bed is
flat. Once all the media is in place, perform a backwash in accordance to Table 3.
After the back-wash, inspect the bed, there may be fines on top of the bed. Carefully skim the top off the
filter bed to remove the fines and any other debris that may be present that could interfere with filtration
performance. With AFM® this is never required, but with a new installation there may be debris such as
plastic shavings from the pipework and filter installation.
Dryden Aqua Ltd
Butlerfield-Bonnyrigg,
Edinburgh EH19 3JQ Scotland
Page 12 of 44
Once the filter bed has been skimmed, refit the filter lid and backwash for a period of 5 minutes, or until
the water runs clear. After the back-wash, place the filter on a rinse phase for 2 minutes. Once the rinse
phase has completed and if there is sufficient water, repeat the backwash and rinse phase for a third
time. The bed is now ready for service, however before going on-line with the network it is required to
conduct an analysis of the water in compliance with Annexe 1 if the media is being used for drinking
water.