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Annex 2 AFM® for the tertiary treatment of Waste water
AFM® is used for the tertiary treatment of wastewater in gravity flow of pressure filters. AFM® has many benefits over sand
filtration, which include the following;
• AFM® does not biofoul, coagulate or experience transient channelling
• Predictable and repeatable performance
• Turbidity and TSS reduction better than 90%
• Perfect for ferric removal as such AFM® is also very good at removing phosphate and arsenic
• Many priority chemicals such as herbicides are hydrophobic and are adsorbed onto sub 10 micron particles. AFM®
will remove 97% of all particles down to 4 microns, independent confirmation by IFTS
• Should never need to be replaced
Operational criteria
range
Bed depth AFM®
500mm
notes
2000mm
Typical bed depth is 1200mm with 200mm of 1 to 2mm anthracite on
top of the bed
Run phase water flow
1 m/hr 20 m/hr
0.1 0.5
Back-wash water flow >50m/hr 60m/hr
Rinse phase duration 5 Or until water
minutes runs clear
4 40
Running
pressures
The slower the flow rate the better the performance
Do not exceed 0.5 bar differential
(differential)
Back-wash for 5 minutes, or until the water runs clear. Air purge not
required
Back-wash frequency /
It takes a few minutes for the bed to stabilize after a back-wash
Depends upon solids load in wastewater
hours
Water quality
Ideally the dissolved oxygen level should be above 2mg/l or redox
potential above 300mv entering the AFM® filter bed
TYPE OF FILTER
RGF sand filter
with sand
Pressure filter
with sand
Moving
bed
sand filter with
sand
Drum filter 10
micron
Disc Filter
10 micron
Ring Filter 10
micron
AFM® Pressure
filter
SS. (mg/l)
Performance
%
inlet
7.14 outlet
2.2 69 Turbidity
Performance
ntu
%
inlet outlet
3.5
2.23
36 8.18 3.82 53 5.87 4.76 18 22311 18023 19 4.96
7.08 3.82 46 2.13 1.79 16 14067 10307 26 5.4
14.66 7.33 50 7.16 3.88 45 56712 38460 32 3.23
5.6 3.1 44 2.22 2.06 7 30450 21138 30 2.12
7.41 3.98 46 3.01 3.17 9447 7761 17 2.5
10.60 0.89 96% 2.98 0.24 92 % 23000 10000 58 % 3.59
bacteria Performance % inlet
outlet
23120.0 12300.0 46 Filtration
Velocity
m3/m2/h
1.2