Foreword.
"FID" are filters generally designed to remove
iron, manganese and slight turbidity to be found in well water, surface waters (rivers,
lakes, etc.).
"FID" filters are characterized by a manganese-dioxide based filtering mineral
with a powerful catalytic action which accelerates the iron and manganese oxidation
process, the flocculation of the respective precipitates, and their subsequent filtration.
The oxidation phase must already have been triggered previously by an oxidizing agent of
which a certain amount is introduced upstream of the filter. The "FID" filters
are normally equipped with a proportional chlorite of sodium feed unit including PDP-type
proportioning pumps and an impulse-emitting volumetric water meter. The first layer in
contact with the water is composed of CATALTEC 20 mineral with catalytic action in the
form of granules of an appropriate size for encouraging the oxidation-flocculation and
filtering process. The second layer is made up of silica sand with a suitable granulometry
for detaining the finer particles which might have come through the upper layer, enabling
degrees of filtration to be obtained even as high as 5 microns.
Structural features.
TANK: made from carbon steel, vertical cylinder type with
convex bottoms, complete with lower manhole, upper handrail, connections for emptying the
bottom, supporting legs and grommets for lifting.
The lower distributor is to be found inside the tank, made up of a central casin and
distribution arms with precisely sized slits, together with the upper distributor.
From the 180 model up, the tank is characterized by a lower distribution plate complete
with filtering nozzles and an additional manhole. The surface inside are subjected to SA
2.5 white-metal sandblasting and given two coast of epoxy-based paint suitable for contact
with foodstuffs. The outside is sandblasted, given a coat of primer and a
polyurethane-based finish (RAL 5015).
The hydraulic unit for the operating phases and washing of the filter, made up of n
"5 hydraulic or pneumatic valves of the type with cast iron diaphragm, nº2 flow
restrictors; nº2 brass ball valve each for the bleeding and the manual emptying of the
water in the tank; nº2 gauges placed upstream and downstream from the filter, complete
with valve on which a gauge can be fitted; pipes and pipe fittings connecting the valves
to the tank in galvanized iron. From the model 180 up, the valves are butterfly-type and
made of spheroid graphite cast iron, with a dual-effect pneumatic actuator, and the pipes
are made from weld carbon steel and treated on the valves.
The water supply intake is supplied directly from the stretch of incoming piping equipped
with on-off valve and cartridge filter. From the 180 model up, the valve is pneumatic
only; a 25 liter air compressor with a 1.1 kW single-phase 220 V - 50 Hz motor can be
supplied on request.
Choosing the "FID" filter.
The choice of the FID filter depends on the iron and
manganese content and on other characteristics of the water. The maximum rate of flow can
be taken as a reference for treating pre chlorinated water containing iron only (not
combined with organic substances) with a pH value of over 7.
When manganese only is also present, greater contact times must he allowed for,
consequently leading to lower rates of flow.
Sometimes, in certain waters with a low free oxygen content and low pH value, in order to
bring the manganese value back within the legal limits, it may be necessary to introduce a
certain amount of sodium carbonate (combined with the quantity of chlorite of sodium such
as to obtain a remaining chlorine value in the outgoing treated water of 1-2 ppm (in this
case it is advisable to use an activated carbon filter downstream). The treatment may be
incomplete if the water has a pH value of less than 7, contains hydrogen sulfide,
surface-active oils and/or grease and free carbon dioxide.
It is consequently necessary to always set up an analysis in the field (analyses of
sulfides, dissolved oxygen, CO2 and pH), and sometimes perform oxidation-flocculation
tests in order to determine the possibility of treatment.
If the water also features slight turbidity owing to other substances, etc.), The specific
rate of flow must be further restricted so as to avoid the rapid clogging of the filter
and therefore the short duration of the filtering cycle. The standard version of the
"FID" filters involves the washing of the filter with untreated water at the
rates indicated in the table; lower rates may result in the filter bed not being washed
properly.
OPERATING DATA:
- Min/max. operating pressure: 2-5 bar
- Min/max. water temperature: 5-40 °C
- Supply voltage/frequency: 220/50 V/Hz
- Power absorbed: 20 Watt
- Compressed air: 5 bar
