Operating parameters
AFM® filtration performance will depend upon the operating parameters. It is important to use good
quality filters, we recommend filters in compliance to the German DIN standard. The follow represent the
optimum filter bed operating conditions.
range
notes
Bed depth AFM® 1200mm 1800mm Bulk bed density 1.25 to 1
Run phase water
flow 5 m/hr 15 m/hr The slower the flow rate the better the performance
0.2 0.4 Back-wash water
flow >45m/hr <60m/hr Back-wash for 5 minutes or until the water runs clear.
Air purge not required
Rinse phase
duration 5
minutes Or until water
runs clear It takes a few minutes for the bed to stabilize after a
back-wash
Running pressures
(differential)
Standard ratios of media, typically 10-15% grade 3,
10-15% grade 2 and 70-80% grade 1. Grade 0 is not
used for this application.
Filter grades
Back-wash
frequency / per
week
Do not exceed 0.4 bar differential
1
7
Air purge is not required, but may be used to reduce
back-wash water consumption.
Meeting the standard
AFM® makes it much easier to achieve low concentrations of phosphate in the product water. AFM®
performance is confirmed by IFTS to be much better than sand or any other similar media by a factor of 1
log in removing sub 5-micron particles. AFM® is sustainable and uses a lower applied concentration of
chemicals.
If it is a requirement to achieve very low concentration of total phosphate it may be necessary to adjust
the following parameters;
1. Reduce run phase flow velocity
2. Increase ferric concentration
3. Increase bed depth
Dryden Aqua Ltd
Butlerfield-Bonnyrigg,
Edinburgh EH19 3JQ Scotland
Page 39 of 44
Reducing run phase water flow rate or increasing bed depth are operational parameters. We
recommend filter bed depth in accordance to DIN, which is between 1200 and 1400 for mechanical
filtration application. Phosphate removal it is also mass balance adsorption reaction so increasing bed
depth to 1800 can be an advantage.