AUTOMATIC FILTERS INSTRUCTIONS MANUAL
FC/D - FAC/D
s.r.l.Milano - ITALY
Page 4 of 14
p11.02-v34.f fcd_mi-r1.doc
2. Principles of working
FC/D
and
FAC/D
series filters 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 FC/D
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 working of the system is controlled by an automatic programmer, allowing to schedule
the day and the hour of the regeneration (backwashing).
For the best working of the filter, the backwashing should be featured before the pressure
drop reaches the threshold level (1 bar - 100 kPa). According to that, it is suggested to schedule
the regeneration according to a pressure drop of 0.6÷0.7 bar (60÷70 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 FAC/D
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.
FAC/D
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.
