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index |
General Drinking Water Treatment |
| Schematic of a
surface water treatment system for drinking water. The diagram shows
pressure AFM filters, however they could equally be RGF ( Rapid Gravity
Filters). In most system there will need to be some correction of the
water chemistry. The scheme presented below gives an example of a
possible arrangement.
System specification.
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water flow through the AFM filters, 5
to 10 m3 hr-1 m2 of filter bed surface
area
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recommended filter air purge rate 90 m3
hr-1 m2 of filter bed surface area
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back-wash flow rate 40 to 60 m3
hr-1 m2 of filter bed surface area
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- RGF (Rapid Gravity Filter)
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Pressure Sand Filters |
Benefits from AFM
- Single pass filtration irrespective of the
influent water quality, negate the need to use activated carbon,
ozone or UVc
- Better performance than ultra membrane filtration
because it removes dissolved organics. Nominal filtration at 1
micron with organics removal using AFM. Absolute filtration at 0.03
micron with ultra filters but no organics removal.
- Reduce chlorine consumption by up to 80% and virtually eliminate
THM`s, applies to double filtration systems with pre-chlorination
prior to second stage filters.
- AFM does not channel so when used with good
coagulation and flocculation you have a much more effective barrier
to the passage of oocysts than is possible with sand.
- Up to 75% reduction in back-wash water, the
back-wash is predictable over years, unlike sand which has a
variable back-wash reaction.
- Public health and environmental benefits are
huge, sand filters incubate bacteria and pulses macro bacteria floc
as well as iron & manganese and other contaminants back into
the water. AFM filters are stable
- How to use AFM, it is a direct replacement for
filter sand, nothing else in the system needs to change.
- Cost, well it costs more than sand but we are
still dealing with a relatively low cost product which will give a
return in capital in under 12 months.
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