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Filters
Many
types of filters are available. The specific type of filter required
depends on the problem and the degree of its severity. Basically,
filters provide some type of screening which traps the water's contaminants
as it flows through the filter. If the contaminated particles are
sufficiently large, the filter merely traps them. In other cases,a
chemical reaction may first be necessary in order to make the particles
of sufficient density to permit them to be collected on the screen.
Iron Filters
(Oxidizing Filters)
Iron
filters contain a base material coated with manganese dioxide to
convert the iron particles into insoluble form for filtration. They
are used for treatment of waters with medium concentrations of iron,
manganese, and hydrogen sulfide.
Such filters must be regenerated periodically. The units are backwashed
to remove the insoluble particles on the filter and then periodically
recharged by flushing with a potassium permanganate solution. In
many applications, a continuous feed of potassium permanganate ahead
of the filter provides effective iron and manganese removal. After
rinsing, the filter is again ready for operation. Oxidizing filters,
when used, would be placed on the water line before a softener.
Never overrun
an iron filter, as this may cause permanent damage to the filter
bed. Proper backwashing is absolutely essential. To insure recharging
of a filter on schedule, it may be advisable to plan to do it on
the same day that you recharge your softener. However, do not backwash
both units at the same time, because the water pressure may not
be sufficient for simultaneous backwashing.
If you are using
an oxidizing filter for removal of hydrogen sulfide, backwash the
unit frequently to avoid caking. Otherwise, it may show a gradual
loss of effectiveness over a period of time. Should this occur,
replace the filter material.
Turbidity
Filters
One
of the simplest filters is a unit that uses sand or ag material
as the filtering agent to strain out solid matter. These filters
remove sediment and cloudiness from water. Periodic backwashing
is necessary to remove the filtered material.
Activated
Carbon Filters
An activated carbon filter installation requires various types
of maintenance, depending on the end use of the filter. When used
for mechanical filtration alone, periodic backwashing is all that
is necessary. When used for absorbing organic tastes and odors,
however, it is necessary to replace the filter material as it loses
its effectiveness. When used for removal of excess chlorine tastes,
a portion of the carbon is consumed whenever the unit is in operation.
Under these circumstances, it may be necessary to replace the bed
periodically.
Neutralizing
Filters
These units consist of tanks filled with neutralizing agents
for eliminating acid conditions in water. They make use of limestone,
magnesia, and other proprietary materials as the neutralizing materials.
Neutralizing filters require periodic backwashing. As a portion
of the filter material is consumed in neutralizing acidity, additional
filter material should be put in the unit periodically.
Solution
Feeders
There are a wide variety of chemical feed pumps available. These
units inject corrective solutions into a water supply. Usually installed
in connection with private water systems, they provide a most satisfactory
means of proportioning solutions into the water. These chemical
feed pumps provide a means of introducing treatment solutions, such
as chlorine, into water supplies. With such equipment, keep an adequate
supply of the solution available for the tank. If using diluted
chlorine solution or permanganate, mix a fresh batch every week.
Dump out any
unused portion in the tank before pouring in the fresh batch. It
is wise to mix only enough for one week's use plus a small reserve,
because these chemicals deteriorate with the passage of time. If
using polyphosphate or soda ash in the unit, you can prepare it
in large volume, because these chemicals do not deteriorate.
Inspect your
solution tank periodically. Keep it clean at all times. When inspecting
the tank, check the lubricating oil in the unit. Some units require
replacement of the oil at specific intervals. Also, inspect the
diaphragms and check valves; clean if necessary.
It is a good
policy occasionally to check the residual of chlorine or permanganate
or the pH of the water when you use soda ash. If the proper residual
is not available, adjust the feed rate. pH and chlorine test kits
are available. If you are using permanganate, draw a glass of water
to determine whether the water is free of particles.
Periodic checking
of residuals is necessary due to seasonal changes in water quality.
Such changes, together with other variations, must be taken into
account in order for equipment to provide water of maximum quality.
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