Back-wash efficiency
100.00
90.00
80.00
70.00
60.00
50.00
40.00
30.00
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
Time in minutes for back-wash
It is essential to operate AFM® filters at the correct backwash water flow rate. Please note that we aim
for 20% bed expansion at the flow rates given in Table 3. Some filters may not be able to take the full
flow rate, in which case reduce the flow to the maximum possible without losing the media in the
backwash water.
AFM® has a 15% lower bulk bed density when compared to sand, so it is much easier to backwash.
However, some filters may be deficient with regards to backwash velocities. It is very important that
AFM® is backwashed at the correct water flow rate.
5.5.2. Air scour
Dryden Aqua Ltd
Butlerfield-Bonnyrigg,
Edinburgh EH19 3JQ Scotland
Page 21 of 44
AFM® filtration systems do not require air scour, however if air scour is applied, then it is possible to
reduce the velocity of backwash water. This is a practical solution for installation that cannot backwash at
the required water flow rate.