Water Softeners
What is a water softener?
The idea of a water softener is simple. The calcium and
magnesium ions in the water are replaced with sodium ions.
Since sodium doe not penetrate out in pipes or react badly
with soap, both of the problems of hard water are eliminated.
To do the ion replacement, the water in the house runs
through a bed of small plastic beads or through a chemical
matrix called Zeolite. The beads of Zeolite are covered
with sodium ions. As the water flows past the sodium ions,
they swap places with the calcium and magnesium ions.
Eventually, the beads or Zeolite contain nothing but calcium
and magnesium and no sodium, at this point they stop softening
the water. It is then time to regenerate the beads of
Zeolite.
Regeneration involves soaking the beads or Zeolite in
a stream of sodium ions. Salt is Sodium Chloride, so the
water softener mixes up a very strong brine solution and
flushes it through the Zeolite or beads (this is why you
load up a water softener with salt). The strong brine
displaces all the calcium and magnesium that has built
up in the Zeolite or beads and replaces it again with
sodium. The remaining brine plus all the calcium and magnesium
is flushed out through a drainpipe. Regeneration can create
a lot of salty water- something like 25 gallons (95 litres).
What sort of salt could I use for my water softener?
For water softening, three types of salt are generally
sold: -
Rock salt
Solar salt
Evaporated salt
Rock salt as a mineral occurs naturally in the ground.
It is obtained from underground salt deposits by traditional
mining methods. It contains between ninety-eight and ninety-nine
percent sodium chloride and a water insolubility level
of about 0.5-1.5%, bring mainly calcium sulphate. Its
most important component is calcium sulphate.
Solar salt as a natural product is obtained mainly through
evaporation of seawater. It contains eighty five percent
sodium chloride. It has a water insolubility level of
less than 0.03%. It is usually solid in crystal form and
sometimes solid in pellets.
Evaporated salt is obtained through mining underground
salt deposits of dissolving salt. The moisture is then
evaporated, using energy from natural gas or coal. Evaporated
salt contains between 99.6 - 99.99% sodium chloride.
Rock salt contains a lot of matter that is not water-soluble.
As a result, the softening reservoirs have to be cleaned
much more regularly. Rock salt is cheaper than evaporated
salt and solar salt, but reservoir cleaning may consume
a lot of time and energy.
Solar salt contains a bit more water-insoluble matter
than evaporated salt. When one makes a decision about
which salt to use, consideration should be given to how
much salt is used, how often the softener need a cleanout,
and the softener design. Is salt usage is low; the products
could be used alternatively. If salt usage is high, insoluble
salts will build up faster when using solar salt. Additionally,
the reservoir will need more frequent cleaning. In that
case, evaporated salt would be recommended.
It is generally not harmful to mix salts in a water softener,
but there are types of softeners that are designed for
specific water softening products. When using alternative
products, these softeners will not function well. Mixing
evaporated salt with rock salt is not recommended as this
could clog the softener reservoir. It is recommended that
you allow your unit to go empty of one type of salt before
adding another to avoid the occurrence of any problems.
Salt in usually added to the reservoir during regeneration
of the softener. The more often a softener is regenerated,
the more often salt needs to be added. Usually water softeners
are checked once a month. To guarantee a satisfactory
production of soft water, the salt water should be kept
at least half-full at all times.
Before salt starts working in a water softener, it needs
a little residence time within the reservoir since the
salt is dissolving slowly. When one immediately starts
regeneration after adding the salt to the reservoir, the
water softener may not work according to standards. When
water softening does not take place, it could also indicate
softener malfunction or a problem with the salt that is
applied.
What is a simplex water softener?
A simplex water softener consists of one vessel containing
ion exchange resin. Once the iron exchange resins are
exhausted, the water softener will go into the regeneration
sequence. During the regeneration sequence that takes
about two hours, there will be no water passed through
the softener to service. If the water softener is time
controlled, it is possible to set the regeneration time
to 3am when there is usually no requirement for water.
If the water softener is a water meter controlled unit,
it is more difficult to gage what time the water softener
will regenerate. If a continuous supply of softened water
is required, it is advisable to install a duplex water
softener.
What is a duplex water softener?
A duplex water softener consists of two vessels containing
ion exchange resin, once the first column of resin has
exhausted and goes into regeneration, the second column
goes into service. This maintains soft water to service
at all times. Duplex water softeners are usually water
meter controlled but in some cases, duplex water softeners
can be time clock controlled.
What is water-softening resin?
During the softening process, water is passed through
a column of ion exchange resin. The calcium and magnesium
ions present in the water are exchanged on the resin beads
for an equivalent amount of sodium ion. The softened water
exiting the water softener is significantly higher in
sodium than the raw water. This basically is “The
ion exchange process”.
The exchange of hardness for sodium is not perfect or
complete. A small amount of ‘hardness’ usually
passes through the softener in the treated water. However,
testing of the softened water discharging from a properly
operating softener unit for hardness at this stage will
usually not detect the trace amount of hardness. Eventually,
more and more hardness will escape in the water and can
be detected using a normal hardness test kit. At some
stage, it will be necessary to rejuvenate or regenerate
the resin so that the quality of the softened water can
be maintained at the required standard.
Regeneration of the resin is achieved by passing a solution
of salt (Brine or Sodium Chloride) through the resin to
displace the calcium and magnesium ions that have been
taken up by the resin beads from the water. The sodium
from the brine replaces the calcium and magnesium ions
on the resin. When this process is complete, the resin
can be used again for softening water.
Generally, the more efficiently the brine is used, the
more efficiently the hardness is displaced from the resin.
For more demanding applications such as softening boiler
water, more brine needs to be used. This is to minimise
the amount of resin that is left on the resin when the
softener is brought back into service. If insufficient
brine is used, hardness leakage from the softener will
be higher.
Water softening resin selection
A variety of ion exchange resins can be used for water
softening. They are the heart of the water softener. When
hard water that contains calcium and magnesium (the primary
hard water constituents) passes through a bed of resin,
calcium and magnesium are removed from the water. Together
these impurities are referred to as the total hardness
(TH) of the water.
Depending on the accuracy needed, the water hardness
can be tested by trillion or by the simpler dropper bottle
test. The result for the total hardness test can be as
either parts per million (PPM) of hardness, or grains
per gallon (GPG) or even milligrams per litre (MD/L),
and usually expressed as Calcium Carbonate (CaCO3). (Grains
per US Gallon x 17.118 = parts per million).
Household water containing less than 1 grain per gallon,
or (17.1ppm total hardness as CaAo3) is generally considered
to be soft water. However, water for industrial or commercial
use (e.g.- boiler feed water or other more demanding applications)
may require the water hardness to be reduced to less than
1ppm total hardness.
In both cases, similar softening processes can be used.
To achieve the lower lever of total hardness required
for the industrial application, the design for the industrial
and commercial units is likely to be more stringent.
In addition to removing hardness from water, ion exchange
resins will also remove soluble iron from the water. It
is therefore important to test water for presence and
quality of soluble iron. Standard resins are generally
limited to a maximum of 3ppm of soluble iron. The resin
can be applied to remove a higher amount of iron providing
steps are taken to ensure iron fouling does not occur.
Iron fouling could occur by removal of the iron before
the water has been fed through the resin or by applying
a resin-cleaning chemical during the regeneration process.
What is ion exchange?
Most common ion exchange systems use a Zeolite resin
bed and simply replace unwanted ions (Ca 2+ and Mg 2+)
with benigin (soap friendly) sodium or potassium ions.
This is the common water softener. A more rigorous type
of ion exchange swaps hydrogen (H+) ions for unwanted
cations and hydroxide (OH-) ions for unwanted anions.
The result is H+ + OH- - > H 2 O. this system is recharged
with hydrochloric acid and sodium hydroxide. The result
is essentially deionised water.What is a brine tank?
The brine tank is a tank in which the salt is held and
mixed in order to produce a brine solution for the water
softener to regenerate.
What are the advantages of having a domestic
water softener?
Along with the obvious advantages that softened water
has upon a household (less need for soaps and chemicals,
healthier hair and skin, protection of water using equipment)
there are also some great advantages that could in turn
save money.
Having soft water saves you money. When your water is
soft, you can use much less soap and fewer cleaning products.
Your budget will automatically reflect the savings.
Your plumbing will last longer. Hard water can cause
a build up of scales from a build up of mineral deposits.
Over time, pipes can clog, water flow can diminish and
water pressure can be reduced. This doesn’t happen
with soft water. Soft water is low in mineral content,
therefore doesn’t leave deposits in the pipes.
Your hot water heater will last longer. Scale and lime
build up created by minerals will not occur if your water
is soft. This concludes to a prolonged life of your hot
water heater. Another advantage is that by preventing
deposits in your hot water heater, it will cost approximately
20% less to heat the water that your family will use.
At the end of a year, these savings can really add up.
Most water using appliances will last longer. From your
coffee pot to your humidifier, soft water inhabits a build
up of minerals and adds life to these products.
What is softened water?
Softened water is water that has a low calcium and magnesium
content. Water hardness usually means less than 100 ppm
or 6 grains, also water that has gone through a water
softener. Pools and spas should never be filled with soft
water from a softener. Water with less than 100 ppm of
hardness should be increased to a minimum of 150 to 200
ppm using calcium chloride
What is hard water?
We call water ‘hard’ if it contains a lot
of calcium or magnesium dissolved within it. Domestically,
hard water causes TWO problems.
It can cause scale to form in the inside of pipes, water
heaters kettles and so on. The calcium and magnesium precipitate
out of the water and sticks to things. Eventually, pipes
can become completely clogged.
It reacts with soap to form a sticky scum and therefore
reduces soaps ability to form lather.
To correct all the problems of hard water, it is essential
to either filter the water by distillation or reverse
osmosis. These processes will remove the calcium and magnesium
from the water. The outcome of this would be achieving
a production of soft water. An alternative option is filtration.
Although affective, filtration would be extremely costly
to use throughout the household on a regular basis.
What else will a water softener remove?
Water softeners will remove nearly all the calcium and
magnesium from the raw water during the softening process.
Softeners will also remove up to 10 ppm of iron and manganese.
Water supplies with high levels of iron and manganese
(greater than 10 ppm) may need pre-treatment to prolong
the lifespan of a water softener.
How long will water softeners last?
A quality water softener, such as the softeners available
from Industrial Water Equipment LTD can last for tens
of years. However, it is usual to replace the ion exchange
resins within the water softener once they have been exhausted.
This is usually between 4 and 7 years, depending on the
incoming water hardness and other variable factors.
Do water softeners need to be serviced?
It is usual to have water softeners serviced once a year
for domestic water softeners and twice a year for industrial
water softeners.
How can the operation of a water softener be
tested?
There is wide range of water hardness kits are available
from Industrial Water Equipment LTD.
Disinfection treatment explained
Under certain conditions when contaminated water sources
in particular are being fed to ion exchange systems the
resins may become fouled either with bacteria or algae.
Where contamination of resin beds is observed one of the
following procedures can be considered:
Peracetic acid
Peracetic acid, a derivative of hydrogen peroxide, displays
a very wide bandwidth of attack against microbes.
Research has shown that peracetic acid will be used to
an ever-increasing degree in the field of human medicine
due to its bacterial, fungicidal, spo-ricidal and anti-virus
action.
Because of the wide spectrum of attack peracetic acid
has been shown to be very suitable as a wide bandwidth
disinfectant for deionsers. (Result of work done by Degussa
Technical Applications Department in conjunction with
Chemiewerk Homburg).
Using a peracetic acid solution of strength 0.2% (in water,
with a reaction time of one hour), -a slime concentration
of 104 -1 05/ml- including mould-was reduced to almost
zero. The short rinsing time after using peracetic acid
is of importance (typically about 45 minutes or 10-15BV).
In addition to the excellent disinfection action, peracetic
acid (according to experiments) has a minimal effect on
the ion- exchange properties of cation or anion resins.
If peracetic acid is used as a disinfectant the following
procedure should be followed for both cation and anion
resin:-
Ensure anion resins are fully exhausted as peracetic acid
performs best at a pH below 8.
Make up one bed volume (BV)* of peracetic acid solution
containing 0.2% peracetic acid.
Inject 1 BV of disinfectant at a flow rate of SBV/h, with
displacement discharged to drain.
When all the peracetic acid has been injected close all
valves and retain the disinfectant for at least ONE HOUR
to soak the resin and pipe work.
Carry out a displacement rinse using raw water for at
least 60 at 5BV/h, followed by a fast flush for 30 minutes.
Regenerate the resins once and return the unit to service.
Formaldehyde
If formaldehyde is to be used as disinfectant the following
procedure should be followed:-
Make up 3BV* of formaldehyde solution containing 0.5%
formaldehyde. Commercial formaldehyde (called formalin)
contains 40% formaldehyde and should therefore be diluted
approximately 80 times. Alternatively arrange the regenerant
injection system to provide a solution of injection strength
0.5%. The ion exchange plant manufacturer will provide
advice as to how this can be accomplished.
Inject 1 BV of disinfectant at a flow rate of 5BV/h discharging
to drain.
If possible, drain down the unit to a level about SOmm
above the resin surface.
Inject a second BV of disinfectant at the same rate and
retain in the unit for a period of at least eight hours
and preferably in the unit overnight. Formaldehyde should
be detectable by smell at any drain valve.
Flush the unit to drain using raw water until no formaldehyde
is detectable at the drain by Schiffs Test.
Regenerate the resins TWICE (double regeneration) and
return the unit to service.*1 BV = 1 litre per litre of
resin.
Sodium hypochlorite
Availability
The most convenient packout of sodium hypochlorite is
in the form of small carboys/containers.
Preparation
For resin sterilisation a 1% available chlorine solution
should be used. This is obtained by diluting the commercially
available hypochlorite.
Treatment Procedure
The column should be regenerated with brine before treatment
in order to convert all resin to the exhausted form (a
double or triple regeneration is often required). It should
be ensured particularly that cation resin is fully exhausted
before treatment so that there is no possibility of production
of chlorine gas.
The minimum volume of solution required to treat the bed
is 3 bed volumes (i.e. 3 times the resin volume installed
in the unit).
The first bed volume should be passed through the bed
at normal regeneration flow rate or approximately 4 bed
volumes per hour (4BV/h).
A portion of the second bed volume should be retained
in the bed, but for no more than 2 hours.
The third bed volume should be passed through the bed
at the same rate as the first bed volume.
The sodium hypochlorite should now be displaced at a rate
of approximately 4BV/h with softened water and then rinsed
thoroughly to drain to remove any trace of sodium hypochlorite.
At least 8-10 bed volumes will be required. The resin
should be triple regenerated before returning to service.
Caution
It should be noted that this form of treatment may cause
slight decrosslinking of the resin matrix and therefore
frequent treatments are not advised. The procedure is
not recommended for phenolic, polycondensation, and chelate
resins.
In the case of anion resins, the oxidising effect of
the sodium hypochlorite is on the amine groups and therefore
disinfection in sodium hypochlorite should only be considered
in extreme cases and then only on a once off basis.
Please note:
Suitable safety precautions should be taken when using
sodium hypochlorite and drains into which the waste is
discharged should be free from acids or other chemicals
that may react adversely with the dilute hypochlorite
discharge.Iron and magnesium explained
Introduction
Iron can be present in several different forms in water.
For example in the case of un-aerated borehole water iron
can be present in the ferrous state (Fe++) but on oxidation
it is converted into the ferric form (Fe+++).
Iron can also be complexed with organic matter; in which
case it is present as an anionic complex.
Normally iron present in the ferric state is removed by
cation resin operated either in the sodium or hydrogen
forms.
In the case of hydrogen form cation resin representing
the first stage of a demineralisation system the iron
is removed from the water but eluted on regeneration with
mineral acid. With softening resin the situation is different,
as the ion exchange resin removes the iron from the water
but the regeneration procedure using brine does not elute
the accumulated iron from the resin during the regeneration
cycle. Consequently the iron accumulates on the resin
from cycle to cycle and steadily causes progressive iron
fouling.
In the case of iron being present as organo/iron complexes
the complex is present as an anion and is therefore removed
from solution by the anion resin.
Because the anion resin is being regenerated with caustic
soda, whilst the organic matter may be substantially removed
each regeneration cycle, the iron is retained on the resin.
The accumulation of iron on the resin causes the anion
resin to become iron fouled.
It is recommended that where the iron content of water
is higher than 0.5ppm some form of pre-treatment is used
in order to reduce the iron level down to less than 0.1
ppm.
Remedial Action
Cation Resin
When using sulphuric acid constantly while iron is present
in the feedwater some accumulation of iron on the resin
might take place causing a reduction in performance.
In these cases, treatment with hydrochloric acid should
be considered providing the internal construction of the
units and attendant pipe work make this possible.
In the case of accumulation of iron on Base Exchange softening
resin, again either hydrochloric acid or sodium dithionite
treatment may be considered.
Sodium dithionite treatment
Sodium dithionite is a powerful reducing agent and when
applied to an iron fouled resin bed will reduce any ferric
iron present to the soluble ferrous form. Thus the bed
can be freed from iron during a normal aqueous cycle.
We would recommend the following procedure for applying
the sodium dithionite to a resin bed: -
The sodium dithionite should be added to water (and not
the reverse) so as to form a 4% solution.
Caution should be shown when mixing the sodium dithionite
because strong fumes of an obnoxious nature are evolved
during the mixing process. Sufficient solution should
be mixed so that when applied to the resin bed there is
sufficient to fully immerse the whole of the resin. The
resin should be agitated so that the sodium dithionite
solution is evenly distributed throughout the bed.
Air should not be used for agitation purposes, as this
will tend to oxidise the sodium dithionite.
The dithionite should be allowed to remain in contact
with the resin bed for a minimum of 3 hours but 6 hours
if possible.
After this period drain and rinse the unit thoroughly
in a down flow fashion after pressuring the unit and then
backwash for a full 30 minutes in order to remove any
extraneous matter.
After this last procedure the unit should be regenerated
in the normal way prior to it being returned to service.
Because of the relative instability of sodium dithionite
solution a method utilising sodium tripolyphosphate has
been found to be even more effective than using sodium
dithionite alone.
In this instance the solution should be made up of 2%
sodium dithionite 2% sodium tripolyphosphate. The resultant
solution retains its iron removal power for a period of
up to sixteen hours because of its greater stability.
In instances where a preventive procedure may be considered
we would recommend the addition of a 1 gram of sodium
dithionite to every 100 grams of sodium chloride used
during the regeneration sequence.
However, we would emphasise that the same precaution should
be taken in both the preventing of oxidation of the sodium
dithionite by addition immediately prior to brine injection
and also in the method of addition to brine solution.
The general characteristics of sodium dithionite together
with the precautionary procedures are as follows: -
Characteristics of sodium dithionite
Sodium dithionite will decompose under the influence
of heat or moisture. For this reason sodium dithionite
should be kept in sealed watertight containers and stored
in a cool dry place. Under such conditions this material
can be stored over a pro- longed period with negligible
loss in activity. Care should be exercised in handling
sodium dithionite since, on contact with water; this product
decomposes quite rapidly forming gases that can ignite
spontaneously.
For this reason Sodium Dithionite is classified as a flammable
solid and is shipped under the appropriate caution label.
Because of the above mentioned, any material which is
spilled should be promptly cleaned up and the site washed
with copious amounts of water. Partially used containers
represent a definite fire hazard.
When fighting a sodium dithionite fire the burning material
should be deluged with water since too little water may
be worse than none at all. Carbon dioxide and dry fire
extinguishers are valueless since the product provides
for its own oxygen for combustion.
Caution
Full details of the recommended procedure for storing
and handling sodium dithionite should be obtained from
the supplier and these recommendations strictly adhered
to so as to ensure full compliance with local Health and
Safety Regulations.
Hydrochloric acid treatment
In many instances it is not possible to treat softening
resins with hydrochloric acid in situ because of the materials
of construction of the softening unit.
However, where it is possible, 6% hydrochloric acid should
be utilised and three bed volumes applied retaining the
middle bed volume in contact with the resin for a period
in excess of two hours (warming to 40'C is beneficial).
The resin should then be regenerated twice with 10% brine
solution, before putting back into service.
Organic fouling explained
Introduction
It is well known that anion resins are susceptible to
fouling by the humic and fulvic acids sometimes found
in surface waters. These organic species, because of the
relatively large molecular weights, become trapped within
the resin matrix (to a greater or lesser degree depending
upon the resin) and specific procedures have to be employed
to cause recovery of the original ion exchange properties
of the resin.
The symptoms of organic fouling include long rinse requirements,
poor capacity and, in the case of strong base resins,
higher silica leakage.
Treatment
The most common forms of treatment involve the use of
brine solution; the procedure is as follows: -
The resin should be treated at the end of the normal exhaustion
cycle.
Three bed volumes of 10% w/v brine solution containing
2% w/v caustic soda should be prepared.One bed volume
should be introduced into the ion exchange unit at a flow
rate not exceeding 2 BV's per hour followed by a second
bed volume -this second bed volume should be retained
in the unit for as long as possible, but at least 4 hours.
Some agitation, if possible, should be employed periodically
throughout the retention period.
At the end of the retention period the last bed volume
of brine should be passed through the resin at a rate
of 1 BV per hour and the resin thoroughly rinsed with
clean water until free from brine.
The resin should be subject to at least two complete regeneration
cycles before being put back on line.
N.B. Brine at minimum 35°C should be employed or preferably
as high as 60°C so as to produce a better organic
elution effect.
Iron/Organic Complexes
This subject is covered to some extent in the section
on iron fouling.
Occasionally the presence of iron is detected on the anion
resin. This can arise from an iron/organic complex being
present in the raw feed water. In these cases, it is advisable
to consider treatment of the anion resin with 6% hydrochloric
acid immediately after the brine treatment.
The procedure that should be followed is similar to that
given for brining. It is extremely important that all
traces of hydrochloric acid are removed from the unit
before introduction of the caustic soda regenerant.
It is important to ensure that the materials of construction
are suitably resistant to hydrochloric acid.Which minerals
cause water hardness?
The most common are magnesium, manganese and calcium
Why is hard water a problem?
For many uses, hard water is not a concern, although
there are equally as many scenarios that hard water would
be become an issue. One problem is the reaction soap has
with hard water. The reaction causes the soap to form
a scum that can result to all sorts of problems. One of
which is the scum not washing off your body properly,
resulting in clogged pores. This could then lead onto
skin irritation, especially if the service user already
suffers from skin irritations such as eczema. Another
problem that occurs with the use of hard water is the
prevention of soaps to create a lather, hard water tries
to prevent this process, therefore service users end up
using twice as much soap, whether is be washing the car,
washing clothes or washing themselves. The obvious problem
to this is that it is not cost effective.
Can Industrial Water Equipment test my water?
Yes, please see water analysis link
What should be done if water is found to be hard?
Although considered a luxury, treating water that is
not above 3GPG hard is not necessary. It will provide
extra comfort when bathing or shaving but the cost of
the instillation will not be saved from the running of
the system. On the other hand, water that is found to
be over 3 GPG would benefit from receiving treatment from
a water conditioner. This is because the effects of the
hard water being softened would be extremely noticeable.
Another advantage is that the savings that the water conditioner
would generate would cover the cost of the installation.
What should I look for in a water conditioner?
Firstly you need to determine the required volume of
the water conditioner and the resin. You need to ensure
that the resin will be enough for your daily water usage.
The average water usage for a household is 87 gallons
per day per person. Another thing to look for in a water
conditioner is the method in which you want to recharge
the unit. There are several options. The most common of
which is to recharge by a time clock. This method relies
upon a calculation of how much water you are going to
use throughout a day, then the information will be programmed
into the timer resulting in the timer knowing when it
needs to recharge. It will be set to recharge at a certain
day or certain time of day. In theory this works, but
any changes to your routine can result in wasted salt
and water or running out of softened water. |
Water Softener related videos - view the latest information online.
If you live within a hard water area of the UK then your whole family could benefit from a domestic water softener.