Anthracite Filter Media is often used to produce a multi-media filter.
This has several advantages over a single media filter:-
- Increased filtration rates
- Longer filter run times
- Reduced backwash water consumption
The bed of anthracite placed on top of the sand layer provides the
filter with:-
- Larger grain particles on the surface of the filter which delays
the pressure drop across the filter.
- A larger reservoir in which the floc may be held before
backwashing.
- A prefilter for sand filter below.
The grade of anthracite filter media is chosen so that it has a
similar backwash expansion as the sand below it. This is important
to prevent losses of anthracite during backwashing.
Below are some examples of filters
Single Media Filter
| Media |
Grade |
Depth |
Bulk
Density |
| Sand |
0.50 - 1.00mm
|
850 mm |
1.56
t/m3 |
| Gravel |
6.30 - 13.6mm |
150 mm |
1.60
t/m3 |
Duel Media Filter
| Media |
Grade |
Depth |
Bulk
Density |
| Anthracite |
1.18 - 2.36mm |
600mm |
0.74
t/m3 |
| Sand |
0.60 - 1.18mm |
600mm |
1.56
t/m3 |
| Gravel |
6.30 - 13.6mm |
150mm |
1.60
t/m3 |
Triple Media Filter
| Media |
Grade |
Depth |
Bulk
density |
| Anthracite |
1.18 - 2.50mm |
400 mm |
0.74
t/m3 |
| Sand |
0.60 - 1.18mm |
400 mm |
1.56
t/m3 |
| Garnet |
0.30 - 0.60mm |
150 mm |
2.10
t/m3 |
| Garnet |
1.40 - 2.36mm |
75 mm |
2.10
t/m3 |
| Gravel |
6.20 - 13.6mm |
150 mm |
1.60
t/m3 |
|
