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Water
Softening (Ion Exchange)
Perhaps
the most common treatment technology, softening water
by Ion Exchange has been around for over 50 years.
Ion Exchange is the process of the removal of one
ion from the water and the substitution of another.
In softening, an ion "electrically charged atom
or group of atoms" of a hardness mineral is exchanged
on a specific media for an ion of a soft mineral such
as sodium or potassium. Once the exchange media "either
polystyrene resin or silicon zeolite" is devoid
of the softer ions, it is classified as exhausted
and can longer perform ion exchange. At this time,
the water softener needs to be regenerated so that
the media can be re-saturated with the softer mineral
ions to begin another softening service cycle.
All
of this regeneration takes place automatically with
very little user maintenance required. There are several
different media and control selections to meet the
needs of different chemistries, flow rates and efficiencies
required. The key to successful softening is proper
sizing with the correct media and controls to meet
the needs of the particular project and customer.
I
am often asked why we can’t just filter out the
hardness minerals without the need for all this ion
exchange stuff. Actually, you could but the capital
and operational cost of a Nanofiltration system can
be prohibitive. Hardness minerals dissolved as ions
are extremely small. To get an idea of just how small
these ions are, we will compare them in size to a
few things. A human hair is approx. 100 microns in
diameter, a bacterium is typically between 1 to 3
microns and a hardness ion is approx. 0.00006 microns.
Pretty small.
To
learn more about Water Hardness….Click HERE.
Reverse
Osmosis
Reverse
Osmosis or "RO" as it’s sometimes referred
to, is a process of passing water across a semi permeable
membrane to separate the water from dissolved solids.
Unlike filtration, which separates solids from water
and holds onto them on a medium or surface, RO membranes
separate the water from the dissolved material by
reversing a natural process called Osmosis. Osmosis
is best described as the diffusion of ions "electrically
charged atoms" through a semi-permeable membrane
from an area of low ionic concentration to an area
of high concentration.
Using
equal amounts of salt water and distilled water as
an example, imagine a container that was separated
in the center by a membrane sheet of cellophane like
material. If you filled the left chamber with the
salt water and the right chamber with the pure water,
the level of the pure water would drop as the pure
water diffused across the membrane in an attempt to
dilute the concentration of the salt water. Consequently,
the level of the salt water would rise as molecules
of pure water joined the salt water.
That
is Osmosis.
Reverse Osmosis would take place if pressure were
applied to the salt water "concentrated"
side of the chamber. With the correct amount of pressure
"approx. 2 psi/100 PPM tds" the pure water
molecule would leave the salt water and diffuse through
the membrane to the dilute side where it could be
captured and stored for drinking water.
Reverse
Osmosis rejects ions, molecules and particles based
on their ionic charge, molecular weight and particle
size. Membrane type, water temperature, pressure and
contaminant concentration are just a few of the things
that influence removal rates. RO systems flush the
concentrated side of the membrane to drain during
water production. This flushing action keeps the membrane
surface clean as the concentrated solution is rinsed
away. Technology advancements have generated new features
such as automatic shut off valves to minimize the
water waste generated in the RO process.
Reverse
Osmosis drinking water systems are used worldwide
for the effective removal-reduction of mineral salts,
nitrates, heavy metals, protozoan parasites and many
inorganic contaminants. Aquasource small scale point
of use "pou" RO systems incorporate dual
prefiltration to protect sensitive membranes from
sediment fouling and post filtration using High Capacity
granular carbon to remove low weight organic molecules.
Aquasource also designs and installs high capacity
RO systems for daily flows up to 20,000 gallons per
day to meet the needs of commercial, industrial or
whole house residential applications.
Nanofiltration
Nanofiltration
or NF is a membrane separation process very similar
to reverse osmosis in the way it rejects ions, however
a nanofiltration membrane is more limited in the size
and molecular weight of the ions it does reject. Nanomembranes
will reject ions that are divalent and larger (i.e.
Calcium, magnesium, bicarbonate) While allowing lighter
monovalent ions (i.e. sodium, potassium, chloride)
to pass through. For this reason, nanofiltration can
be operated at lower pressures with less waste and
make membrane softening possible for commercial and
industrial uses.
Ultrafiltration
UltraFiltration
or UF is another membrane separation process that
mimics reverse osmosis but with a much larger molecular
weight cut off then either RO or NF. Like NF, UF membranes
operate at much lower pressures with less waste but
reject only large molecules (i.e. Organic Color molecules,
sugars,) and are frequently used in food and beverage
processing or as pretreatment to protect RO membranes
or other treatment equipment.
Microfiltration
Microfiltration
or MF is quite different then RO, NF or UF in that
it doesn’t separate and reject materials to a
waste stream. Microfiltration systems actually trap
particles onto the surface or within the body of the
filter. Microfiltration elements consist of various
materials and can be produced of ceramics, carbon
blocks or synthetic materials. Microfiltration is
commonly used to trap particles from 0.1 to 1.0 microns
and when properly applied can be very effective in
the removal of bacteria and protozoan cysts (i.e.
Giardia and Cryptosporidium). Because of the tiny
pore size of MF filters and the fact that they trap
and store materials, they are very susceptible to
fouling with larger particles and typically require
pre-filtration to protect them and maximize water
throughput.
Distillation
Distillation
is a method of water treatment that most duplicates
the natural process of the hydrologic cycle. Heating
water to its boiling point (212 degrees F) generates
a physical change in the water molecules to create
steam. Inorganic minerals and metals with boiling
point higher then water are concentrated and left
behind as the water vapor leaves the solution. The
water vapor in the steam is then cooled and condensed
back to a liquid form where it is collected for use.
Some organic contaminants have a boiling point lower
then water and may end up the product "distillate"
in a higher concentration and therefore may require
removal either before or after the distillation process.
Distillation has the advantage of sterilizing the
water in the boiling process but due to the energy
and time required can be more costly then other water
treatment methods. It should be noted that just boiling
water as a treatment method is not the same as distillation
and will in fact concentrate inorganic minerals and
metals.
Carbon
Absorption
Originally
performed century’s ago by passing water through
simple charcoal, it was recognized that carbon materials
made water more palatable by removing some foul taste
and odors. Specialized carbon media’s have the
ability absorb low molecular weight organic molecules
onto and within an immense structure of macro and
micro pores created when some carbon materials have
been specially treated or "activated". This
pore structure can give some carbon filtration media
an enormous amount of surface area for the organic
molecules to be absorbed and trapped. One gram of
some carbon medias can yield the equivalent surface
area of a football field!
It
is these qualities that have lead to the use of specialized
carbons for the filtration of water to remove or reduce
many volatile and synthetic organic chemicals, gasses,
sediment and even radiological contaminants in water.
The primary use of Granular Activated Carbon "GAC"
media in residential water treatment is for the removal
of chlorine and oxidized sediment formed in the chlorination
process. GAC filters are available in cartridge form,
exchange tank and automatic backwash models. AquaSource
Automatic Filters are customized with filtration media
specifically designed for each individual application.
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Oxidation/Filtration
Oxidation
is the process of converting soluble substances (i.e.
Iron, manganese, and hydrogen sulfide) into an insoluble
and filterable solid. Oxidation is accomplished by
adding an oxidant to the water such as chlorine, permanganate,
peroxide, ozone or oxygen from simple air. Oxidants
require different contact times based on the specific
chemistry of the water to perform this task successfully.
Once the substance has been oxidized to a solid or
precipitant it can be removed or reduced by the correct
filtration.
Aeration/Air
Stripping
Many
dissolved gasses and volatile organic chemicals will
leave the water and evaporate or dissipate if the
water is exposed to another gas in the correct atmosphere.
Air Stripping is the process of maximizing the exposure
of the water to a moving flow of air by spraying or
misting the water through a special media known as
packing. Misting breaks up the water into tiny droplets
to increase the surface area of the water thereby
exposing more of the water to the transport gas as
it travels through the packing. In a properly designed
Air Stripping System, dissolved gasses and many organic
chemicals will exit the water and be carried away
into the airflow. Air Strippers are normally constructed
in a tower form and can be designed to treat millions
of gallons per day.
Aeration
systems work on a similar principle as air stripping
and remove dissolved gasses by exposure to air. Oxygen
from the air is dissolved into the water and drives
the unwanted contaminant into a waste stream of moving
air that is directed away from the home or structure.
Aeration systems may either introduce air into the
water by compressing air through a bubble diffuser,
or introduce water into the air by means of specially
designed misting nozzles. AquaSource designs and builds
both air stripping and aeration systems to address
the water treatment needs of residential, commercial
and industrial applications.
AquaSource
has available a portable air stripper system to provide
pilot studies or emergency contaminant removal when
required. AquaSource residential Aeration Systems
are designed to provide both air stripping and aeration
in the same unit for superior treatment of methane,
hydrogen sulfide, radon and many volatile organic
chemicals.
Ozonation
Ozone
or activated oxygen is a powerful oxidizer that has
been used in water treatment since the early 1900’s.
Ozone gas is a highly unstable form of oxygen that
must be generated on site. When added to water
Ozone
reacts rapidly to oxidize inorganics like iron, manganese
and hydrogen sulfide. In the correct concentration,
Ozone has been proven to be very effective as a disinfectant
of water killing bacteria and protozoan cysts much
faster then conventional disinfection by chlorine
without the formation of chlorinated byproducts. New
regulations regarding chlorinated byproducts and the
rapid oxidation and disinfection properties of ozone
treatment have lead to a tremendous increase in the
recent use of this technology for Municipal drinking
and waste water as well as bottled water plants and
even private well water.
Ozone
can be generated two different ways. One is by passing
ambient air through an ultra-violet light wavelength
of 180 Nanometers "1,800 Angstrom Units".
This light energy at this wavelength converts some
of the oxygen in the air "O2" into ozone
"O3". UV generated ozonators are limited
in the concentration of ozone they produce and as
a result, are typically reserved for very small ozone
demands or applications where the water can be re-circulated
for multiple doses.
The
second and more common method of Ozone production
is CD or Corona Discharge. CD generators convert dry
air or oxygen to ozone by passing the air through
a high voltage electrical field. As the oxygen from
the air gets hit with the energy from the voltage,
many O2 molecules are separated and reconverge as
O3 or ozone. CD Ozone Generators are far more efficient
then UV Ozone Generators, typically producing ozone
concentrations from 1% to as much as 10%.
AquaSource
produces it’s own proprietary line of CD Ozone
Generation equipment for small and medium size projects
to treat from 2 to 100 Gallons per minute.
Ultraviolet
UltraViolet
or UV is a system that utilizes UV Light Bands at
a specific wavelength and contact time to kill microorganisms.
This is accomplished by passing clear water through
a chamber and exposing the organisms to the correct
UV energy for a prescribed period of time. Light waves
of 254 nanometers or 2537 angstrom units at an intensity
of 16,000 to 35,000 microwatt seconds per square centimeter
(Mw Sec/Cm2) affects micro organisms by breaking up
and re-arranging their DNA so that they are no longer
viable.
Ultraviolet
disinfection is a rapidly growing technology due to
it’s lower capital investment, ease of use and
the fact that UV energy adds nothing to the water
and doesn’t affect water’s taste or odor.
Contrary to old beliefs, recent evidence has indicated
that UV shows great promise in the disinfection of
protozoan parasites (i.e. Crypto and giardia) and
more studies are currently underway. The low cost
and ease of use of UV technology often leads to it’s
misapplication and lack of maintenance and therefore,
like any water treatment technology should be prescribed
by a professional.
Some
things commonly found in water can affect or limit
UV’s ability to disinfect. Iron, Manganese, staining
minerals hardness and turbidity (sediment and suspended
solids) can absorb or block UV energy. If the energy
is blocked or absorbed it may not get through the
water and will not disinfect properly making pre-treatment
of the water important. The energy from UV bulbs is
lost over time and most bulbs will lose up to 50 %
of their energy over 9,000 hrs or approx. 1 year.
Just because the bulb is still lit does NOT mean it
is disinfecting the water.
The
Department of Health mandates the use of control mechanisms
that confirm disinfection ability of UV when it is
used to treat public water supplies however, residential
systems are not regulated as of this time. Protective
controls that are available for UV systems include:
Manual Sleeve wipers for maintenance, UV intensity
meters, Audible and visual alarms and automatic shut
off valves to stop water flow in case of unit failure.
These controls add considerable cost to a UV unit
and for that reason, are often foregone in residential
systems.
The
AquaSource Group has installed and maintains hundreds
of Ultraviolet Disinfection Systems for use in small
community, residential and private water systems.
Chlorination
Water
chlorination has been a proven and accepted treatment
technology since the early 1900’s. It could be
said that the disinfection of drinking water by chlorination
was perhaps the most significant event affecting human
health in history. In the days before drinking water
disinfection, outbreaks of typhus, hepatitis and dysentery
killed tens of thousands in this country. Chlorine
kills bacteria by the oxidation of their cell wall
and can be compared to chopping their heads off with
an axe. Chlorine is an oxidizer and is also used to
some success in the treatment of iron, hydrogen sulfide
and nuisance bacteria. The Chlorination of a private
water system can be performed by either chlorinating
the water inside the home or right into the well itself.
Chlorination
treatment for a private water system typically consists
of A) of a chemical feed pump to move the liquid chlorine
into the water stream in proportion to water flow.
B) a solution tank to hold the mixture of chlorine
C) a properly sized detention tank to allow for adequate
contact of chlorine/water and D) proper filtration
to remove/reduce oxidized material from chlorination.
Often, the water is dechlorinated in this filter as
the chlorine has already done its work and may no
longer be needed.
Well
chlorination works on the same principal except the
chlorine is in dry tablet form or "calcium hypochlorite"
and is fed directly down the well. Well chlorination
provides some advantages in that it can protect the
water supply and pump from damage caused by slime
forming bacteria. A retention/detention tank may not
be required depending on the depth of well, quantity
and production of water. Well chlorinators are usually
easier to maintain and often require less fill ups
due to the higher strength of the chlorine.
It
should be noted that in the last decade, studies have
shown that the chlorination of water with some organic
compounds can form chlorination byproducts. These
compounds are known as trihalomethanes or THM’S
and may impose a cancer risk. Well water’s are
typically have very low in organics and THM production
is rare compared to surface waters (lakes and rivers)
that may be very high in organics.
Some
water wells in the Finger Lakes region contain organic
methane gas and should NOT be chlorinated until the
methane has been removed. Unfortunately, chlorine
in normal doses doesn’t kill everything. The
last decade has introduced us to a couple of protozoan
parasites that can be found in lakes and rivers. Cryptosporidium
and Giardia Lamblia are two bugs that are extremely
resistant to chlorination. Fortunately, properly sited,
drilled and maintained water wells are virtually immune
from these parasites.
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