There are a number of chlorinator units on the market, each
designed to meter small amounts of chlorine solution into a water supply
as the water is being used. They are roughly divided into three types:
There are three common ways to make the chlorine solution used in
disinfection: 1) dissolve calcium hypochlorate in water; 2) dissolve
sodium hypochlorate in water; and 3) bubble chlorine gas through
water.
The pump type is powered with an electric or water motor. The pump
delivers a fixed amount of chlorine solution with each discharge stroke.
The amount of chlorine delivered can be adjusted by either changing
the length of each stroke, adjusting the pump speed, or adjusting the amount
of time the pump works.
An injector-type chlorinator is also called an aspirator or a jet.
In this type, chlorine is drawn into by jet action into the water supply
system. Press the space bar to see a picture. The chlorine input is
regulated by adjusting the feed adjusting screw.
With a tablet-type chlorinator, a small amount of water is
circulated through a container of chlorine tablets and back into the delivery
line. The restricting valve forces a certain amount of water into the
container with the tablets. The amount of water allowed to circulate
determines the concentration of chlorine in the water.
The process of aeration is used for the removal of dissolved gasses,
such as carbon dioxide, hydrogen sulfide, and methane, and the addition of
oxygen necessary for the removal of iron and manganese from the water.
Oxygen entering the water will increase the corrosiveness of the water.
Aeration is not always efficient in removing taste and odor from things that
are not in the gaseous form. Also, aeration should not be used if the water
is subjected to airborne contamination.
Activated carbon filters are used for the removal of offensive
tastes and odors, color, chlorine, and certain pesticides such as DDT,
parathion, dieldrin, and lindane. Carbon filters can also remove more than
90 % of cadmium, chromium, manganese, mercury, silver, and tin, and it also
can remove turbidity.
Problems not corrected by carbon filters include: hardness; dissolved
metals such as iron, lead, manganese, and copper or chlorides, nitrates,
and fluorides; and bacteria. In fact, carbon filters may promote bacteria
growth especially when not used for a few days or when not changed at proper
intervals. Despite some manufacturers claims that carbon filters containing
silver discourage the growth of bacteria, research shows that
silver-impregnated filters do not significantly reduce bacteria growth and
may increase the silver content of the drinking water.
There are two types of activated carbon filters:
Precoat Cartridge Type
Carbon Bed Type
Activated carbon is made of specially-treated hardwood, selected
coals, and pecan nutshells all ground into a fine powder to increase
adsorptive capacity.
The length of time a filter will last depends on the concentra-
tion of impurities in the water as well as the quantity of water being
conditioned. For an average household, one filter will last from
one to three years.
Maintenance of smaller precoat cartridges consists of
replacing the entire cartridge when the water pressure starts to
lower noticeably. This pressure decrease is a result of the build-
up of material on the filter surface.
With the larger types of precoat cartridges, the filter is
removed and cleaned by washing off the dirt particles that have
accumulated. After several cleanings, and when the carbon
material has absorbed all the taste and odor it can hold, the
filter is replaced.
Maintenance of the carbon-bed filter consists of back-
washing the filter bed to remove suspended dirt from under the
filter bed. Under most conditions, more than one or two back-
washings will be required every month.
Coagulation and sedimentation is a process that causes the fine
sediment in water to collect into larger particles and settle to the bottom
of a pond, before the water reaches the filter. The addition of 12 pounds
per 7000 gallons of pond storage of powdered gypsum should cause the fine
particles to cluster (coagulate) and settle to the bottom.
Turbidity Treatment Systems (2)
A turbidity treatment system commonly consists of a screened
intake and piping for conducting the water from the intake to the first
unit of the system, a settling tank for coagulation and sedimentation, a
filter, and a storage compartment. If the turbidity is less than 40
units, the settling tank can be left out and the filter will do the whole job.
Most recommendations are that the screened intake be located
about 12 to 18 inches below the surface of the pond to take advantage of
the less turbid water.
This type of filter is used extensively for pond water
treatment. Water moves through the filter by gravity, and, as a
result, it moves through very slowly - about 27 to 75 gallons per
day per square foot of filter-bed surface.
As the water deposits dirt particles, they build up on the
surface of the sand layer and assist in the filtering action.
Although the filter becomes more effective as more material is
deposited on it, the rate of water flow through the filter
decreases.
Maintenance of the filter consists of removing the dirt
and about 1 to 1 1/2 inches of the top layer of sand when the
filtration rate becomes too slow. The time between servicings
may vary between two weeks to six months depending on the turbidity of the water and the amount of water being filtered.
Sometimes called diatomaceous- earth filters, these
filters are made from the remains of marine algae called diatoms.
When these shell-developing plants die, their shells accumulate on
the sea floor to form diatomaceous earth.
The filtering element usually consists of a cylinder of
porous called a septum. It may be made of wire cloth, plastic
fiber, or any other material that will allow water to pass
readily. A coating of diatomite-filter material is then applied
to the septum to form a precoat.
The diatomite filter removes suspended solids in the same
manner as the sand filter, but it filters greater amounts 10 to
100 times faster.
Maintenance consists of adding diatomite-filter-aid material
as the filtering action starts to slow. When the addition of the
filter aid no longer has any effect, the filter cake must be replaced. If the filter is properly sized, filter cake replacement
should not be necessary any more than about every 2 months.
The rapid-sand filter is a tank-type arrangement
containing fine sand which rests on top of a bed of coarse sand
and gravel.
The filter is connected into the delivery line from the pump
so it works under whatever pressure is developed by the pump.
The capacity of the filter is usually around 2 to 3 gallons per
minute per square foot of sand surface. Water flows through the
sand from top to bottom, so the dirt particles collect on the top
of the filter bed.
The rapid sand filter works best if the particles are few and
large. It is the least effective filter for small-sized particles,
therefore it is rarely considered appropriate for use in filtering
pond water.
The neutralizing tank is similar in appearance to the
water softener tank except it contains a bed of limestone or
marble chips. The acid in the water reacts with these materials
and gradually "eats" them until they to be replaced. This action
neutralizes the water until most of the corrosive action has been
overcome. Flow through the neutralizer should be slow to allow
the reaction to take place.
Since limestone is dissolved, water hardness will increase
slightly. This can be overcome by installing a softener just
after the neutralizer.
Maintenance consists of backwashing regularly - perhaps
weekly - to loosen and clean the neutralizing bed. Every year
the neutralizing bed should be checked and the dissolved portion
replaced.
If a chlorinator is already in place, the soda ash can be
mixed with the chlorine solution and added through the chlorinator.
If no chlorinator is in use, a chemical feeder of the same type (as
is used for chlorinators) is satisfactory for feeding in soda ash by
itself.
Feeding the soda ash directly in the well not only helps to
prevent corrosion of the piping system, as intended, but corrosion
of the casing, well screen, and pump is also avoided.
Soda ash adds no hardness to the water and has no marked
effect on water used for bathing, drinking, or clothes washing.
Soda ash does add sodium bicarbonate to the water, however.
Maintenance consists of making up the soda-ash solution.
About 1/2 pound of soda ash is added to one gallon of soft water.
It is then either fed through a feeder or dumped into the well.
It will need to be replenished about once every two weeks.
The oxidizing filter is much like a softener, but the
material inside is and oxidizing material, usually manganese-treated greensand. The manganese bed provides oxygen which causes
the iron to settle out as rust particles.
Maintenance consists of backwashing and rinsing the filter
about every week, and recharging, either then, or at longer intervals. Flow rates as high as 8 to 10 gallons per minute per
square foot of area of filter bed is recommended for backwashing.
The iron-removal filter is recharged with potassium
permanganate. The potassium permanganate is placed on top of
the tank, and the unit slowly rinsed with a down-flow of water.
This recharges the mineral filter bed with oxygen. Recharging
varies from weekly to monthly depending on the size of the filter
and the amount of iron in the water.
Hard water is caused by dissolved calcium and magnesium and has
undesirable effects on skin, hair, clothes, and water fixtures. Hard water
also causes bathtub rings, soap scum, and scale-filled pipes and water heaters.
It is a common problem throughout a large part of the United States.
Water softeners usually consist of a tank containing an
ion-exchange material such as zeolite or resin beads.
Water-softening capacity is given in terms of the number of grains of
hardness it will remove between successive regenerations.
Water softening exchanges calcium and magnesium ions with sodium
ions on the surface of an exchange resin in a tank. Sodium is released
from the resin, and calcium and magnesium go on to the resin. The water
flowing through the tank is softened as long as there are exchangeable
sodium ions available in the resin.
"Most softeners are fully automatic and require only a periodic
resupply of salt. They will automatically backwash before
regenerating to flush out accumulated sediment and iron "(7) .
The amount of sodium added to the daily diet is relatively small.
For example, suppose that the had water contains 10 grains of calcium and
magnesium. Assuming that the daily consumption of water is 1/2 gallon per
person, then the daily increase in sodium in the daily diet is 0.3 grams
(assuming 100% exchange efficiency).
Regeneration of the Softener (7)
When the available sodium ions are almost all used up, the
softener exchange resin should be regenerated. Regeneration is accomplished
by flushing brine (strong salt solution) through the exchange
material to replace the collected calcium and magnesium ions with
sodium ions. The flush brine is waste and must be disposed of
properly.
Three methods of disinfection are suggested for private water
systems: adding chlorine compounds;
heating water; or ultraviolet radiation. Before purchasing any water disinfection equipment,
consult local or state health officials concerning codes governing its use.
Disinfection by Pasteurization (2)
The water pasteurizer works under the same principle, and at the
same temperature, as the pasteurization of milk. Untreated water enters a
heat exchanger where it is heated to 150 degrees F. The water is then forced
through a heating chamber where the temperature is raised to about 161 deg. F
and maintained at that temperature for at least 15 seconds. This hot water
is then routed back by the heat exchanger where it gives up some of its heat
in heating the water that is to follow it. The water is then discharged into
the treated-water storage.
Only small amounts of water can be pasteurized at one time so the
treated water must be stored and pumped by a second pump to the points of use.
Disinfecting with Ultraviolet Light (2)
In this method, a thin layer of water is passed around a set of
ultraviolet lamps encased in a quartz sleeve. The killing action is the same
as that provided by direct sunlight in killing bacteria in open streams.
For one of these units to be effective, the water must be circulated in such
a manner as to expose every droplet of water to as much light as possible.
Also, the effectiveness decreases if there is sediment in the water,
therefore a sediment filter may need to be installed ahead of the light.
Units are available with a variety of safety devices to increase
effectiveness. These include:
An electric eye to detect when the lamp intensity gets too low;
A time delay to allow the lamp to warm up before water is run by it;
Electrical relays to insure the lamp is run with the proper amount of current;
Wipers for cleaning small particles off of the quartz sleeves
The available sizes of units vary in capacity from 22 gallons per hour
to 22000 gallons per hour.