Principles Of Working; Quartz-Sand Filters Fcd; Activated-Carbon Filters Facd - Nobel FCD 05 Instruction Manual

2.

PRINCIPLES OF WORKING

FCD, FACD and FCD series filters (on versio DT, DT-DUAL, DP and DP-DUAL) are used for
water treatment for residential and industrial applications as well. All the materials are food
grade and approved for drinking water.
2.1.

Quartz-sand filters FCD

The filtration through a sand media is a mechanical process that allows to remove suspended solids
(even of small dimensions) from water.
The slower is the linear flow (speed of water trough the filtering bed), the better is the filtration action.
During the process, as the filtering bed traps the suspended particles, as filtration action increases,
since the trapped solids works the same way of a filtering bed!
But it also increases the resistance of the filtering bed against the water flow; so the pressure drop
between inlet and outlet increases as well.
The maximum allowed pressure drop is 1 bar (100 kPa), after that it is required to backwash the
filtering bed.
The purpose of the backwashing is to re-built the filtering bed efficiency, by removing the solids
trapped during service; it is featured by a counter-flow of water through the filtering bed.
The programmer allows to set the regeneration at the scheduled days and time; for DP and DP-DUAL
models, regeneration can also be set to start when the max allowable value of pressure drop is reached.
For the best working of the filter, the backwashing must be featured before the pressure drop
reaches the threshold level (1 bar - 100 kPa).
During regeneration the water supplying is completely inhibited by means of a membrane valve
mounted on the outlet line.
2.2.

Activated-carbon filters FACD

Filtration through a bed of activated carbon is the process that allows to remove organic matters and
chlorine from water.
The lower is the flow rate, the better is the filtration action.
FACD series filters are designed and sized for chlorine removal. The expected life of activated-carbon
used as de-chlorination (chlorine removal) is very long; it works as chemical reduction of chlorine to
chloride ion.
Activated carbon action is not selective in removing the substances contained in water and crossing
the filtering bed: hence, it removes also the organics the water contains, if any.
Therefore, it could happen that the filtering bed is exhausted or clogged by the trapping of substances
contained in water, even if the purpose of treatment was not the removal of these substances, but just the
de-chlorination.
Furthermore, it could happen that the filtering bed releases some of the substances previously trapped
in higher concentration than before.
Since it is quite impossible to forecast the exhaustion of the activated carbon bed, or to monitor the
exhaustion itself, with current instrumentation, the utilization of an activated carbon filter must be strictly
avoided without adequate pre-treatments, like quartz-sand filtration, chlorination, etc.
Whether raw water contains organics and/or is biologically polluted, FACD series filters CANNOT be
used without written authorization by NOBEL Technical Department.
The activated-carbon bed also works as a mechanic filter same way of quartz-sand bed.
Although this working should be avoided, it can happen that the pressure drop of activated-carbon bed
reaches a value of 1 bar (100 kPa); in this case the backwashing of the filtering bed is required.
The programmer allows to set the regeneration at the scheduled days and time; for DP and DP-DUAL
models, regeneration can also be set to start when the max allowable value of pressure drop is reached.
For the best working of the filter, the backwashing must be featured before the pressure drop
reaches the threshold level (1 bar - 100 kPa).
It is recommended to run the regeneration only when it is strictly required: the backwashing causes
the mixing of the bed and could displace the higher layers of activated carbon (most polluted) from the
top to the bottom of the column.
During regeneration the water supplying is completely inhibited by means of a membrane valve
mounted on the outlet line.
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s.r.l.Milano - ITALY
INSTRUCTIONS MANUAL AUTOMATIC FILTERS
FCD-FACD-FFD /DT /DP /DT-DUAL /DP-DUAL
Page 4 of 23 r.4
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