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[ FS301 ] [ FS401 ] [ FS401P ]
Why do I need RO
Water ?
Reverse Osmosis (RO) - Advanced Water Treatment
A Multipurpose Tool For Producing High Quality Water
Summary: Most aquarium hobbyists have seen ads for RO filters online, in magazines or in catalogs. But what did they take away from viewing such ads other than prices and promises of purer water and a healthier aquarium? The intent of this article is to provide further clarification on several of them.
In the natural world, objects frequently have more than
one purpose. For example, a Damselfish comes to a sudden
stop in the water with its pelvic fins flared downward
which makes it easier for the fish to slow. A Goby comes
to rest on the bottom and the shape of its pelvic fins
enable it to cling to a rock more securely. The pelvic
fins in both examples are homologous structures but they
clearly perform separate functions. Similarly, in the
equipment-filled world of the aquarium hobby, the
reverse osmosis (RO) filter is a tool that is also
capable of performing multiple functions. The intent of
this article is to provide further clarification on
several of them. A reverse osmosis filter is undoubtedly
a useful piece of equipment to own, but before you
purchase one you first need to decide what you need it
to do.
Most aquarium hobbyists have seen ads for RO filters
online, in magazines or in catalogs. But what did they
take away from viewing such ads other than prices and
promises of purer water and a healthier aquarium? The
expense alone of buying an RO filter demands that you do
your homework before purchasing one. The fact is that
not all filters are equal and ads alone are just too
little information to go on. You need to decide which RO
filter is correct for your particular application. The
general design of most RO filters is basically the same
but the filter cartridges and membranes that come with
the various models differ greatly and these are the
items that make up the majority of the price of an RO
unit. So, the replacement parts are an expense you
should consider prior to your purchase of an RO unit
because not all the filter cartridges that come
pre-installed in an RO filter unit may suit your needs.
And replacing them unnecessarily or prematurely is a
costly lesson that can be easily avoided with a little
planning.
RO Unit Components
Before we discuss choosing a unit, a brief discussion on
the various components of an RO filter may be helpful.
RO units usually consist of several individual filters
placed in series. Each individual filter is referred to
as a "stage". The placement of the individual filter
cartridges on RO units may differ according to the
manufacturer but the general path of the water through
the filters remains the same.
The water begins its journey at the source, for example
a pipe under you kitchen sink. It is then pre-filtered
through one or two cartridges that remove substances
that could damage the RO membrane (which is the most
expensive element of the RO unit). The first is usually
a sediment cartridge that removes particulate matter
that could clog the membrane. The second is a chlorine
pre-filter. The chlorine or chloramines used to
disinfect municipal waters damage some types of RO
membranes (particularly the TFC - thin film composite
type), so it is necessary to remove such chemicals prior
to the water reaching the surface of the membrane. (The
carbon filter also removes heavy metals and many
chemical pollutants). Once the water is pre-filtered it
is ready to be pushed through the membrane itself. This
is accomplished through back pressure, hence the name
"reverse osmosis". The pressure is created by a small
part called a Mini flow restrictor, which is connected
to the waste water line.
The most common configuration of stages (in order of
water flow) is sediment, carbon, carbon, RO. (as our
FS401) The presence of two carbon filters demonstrates
how important it is to remove chlorine and chloramines.
Drinking water units often have a final carbon filter
for polishing the water and many aquarium units have a
de-ionization filter for the final stage (RO/DI units).
RO membranes alone are not capable of removing 100% of
the impurities from the source water, so a de-ionization
cartridge is placed at the end to filter out most of the
remaining traces.
RO Unit Function and Performance
The back pressure produced forces some of the water
through the membrane and allows the rest to pass by into
the waste water line. Depending on several variables,
anywhere from about 1 to 6 gallons of waste water are
produced for every 1 gallon of filtered water collected.
The waste water serves two important purposes in an RO
filter. It flushes away the substances extracted from
the source water and it produces the very back pressure
that allows the filter to operate.
The primary influences on the type of RO filter unit you
will want to purchase will most likely be geography and
geology, because where you live invariably determines
what type of water comes out of your tap. For instance,
USA cities that receive municipal water from the
Mississippi River usually have very hard tap water.
Cities in Southern California have the same problem.
Water is the universal solvent, so rivers pick up all
kinds of substances as they travel through geologically
rich areas. For the home aquarist this can be a bane.
Very hard water (high in minerals like calcium and
magnesium) is often incompatible with breeding
freshwater fish that are native to very soft waters.
(Examples are Discus, Cardinal Tetras, and Corydoras
Catfish). This difficulty leads many aquarists to
finally buy an RO filter.
Choosing an RO Unit
If reducing the hardness of the water is enough, this
can be accomplished with a 3-or-4 stage RO filter units.
These units are economical and are sufficient to filter
water for an aquarium system that is relatively
undemanding. The output rate on most of these units is
low (around 50 gallons per day or less), and the water
may test from 10 to 20 parts per million of dissolved
solids, certainly good enough to soften up any liquid
rock that may come out of your tap! But there are other
more expensive 4-stage units (RO/DI units) that are
capable of filtering larger amounts of water and
reducing the dissolved solids level to about 10 parts
per million. When deciding which filter in this category
best suits your needs, it is important to know the
sediment level of your tap water and how the water is
treated by your local municipality. Water that
originates from rivers can have high levels of
particulate matter, so the size of the sediment
pre-filter and carbon block filter on your RO unit will
affect the unit’s performance, and determine how often
you will need to replace the individual filter
cartridges.
If you live in a rural or agricultural area your main
source of water may be a well. Ground water is typically
a hard water source, and in addition it is easily
contaminated by local runoff from agriculture and
industry. It is therefore not uncommon for a well to be
a soup of unpleasant substances that affect water
quality. Although it may be certified perfectly
palatable for human consumption, the water may fall
short in being suitable for keeping aquarium fish.
Pollutants such as nitrates, phosphates or heavy metals
may be a problem for your fish. In this case, an RO
filter equipped with 4 or 5 stages might be helpful in
eliminating these substances. It is worth considering
doubling up on chemical filtration by having two carbon
pre-filter stages, and a de-ionization filter at the end
to polish the water to a high purity.
Lessening the growth of algae is the goal of many
aquarium hobbyists and utilizing an RO filter for this
purpose is now a common practice. Excess algae growth is
part of the freshwater and marine aquarium hobbies
alike. It is becoming more common for local water
authorities to treat tap water with orthophosphates in
order to prevent corrosion and scale formation in pipes.
Unfortunately, this phosphate overload strikes
freshwater aquariums with the plague of planktonic
algae, turning clear water to green pea soup. In marine
aquariums, high phosphate levels are even more
problematic especially when corals are being kept.
Excess organic chemicals have a deleterious effect on
the growth many captive invertebrates. Alleviating the
situation with RO water is simple as long as the correct
filter elements are used.
Algae growth is connected to nutrients like iron,
nitrogen, silica, as well as the previously mentioned
phosphate. Most of these elements are very effectively
removed by RO, except for excessive Phosphate. If the
source water is high in phosphate, a de-ionization stage
on the RO filter may be required to reduce it to
reasonable levels. If you decide on an RO unit with a
de-ionization stage, you might want to consider running
a second de-ionization cartridge in series. Single DI
filters must be changed before they are completely
exhausted (indicated by change in color). Running two
de-ionization cartridges together is actually more
effective because of the increased contact time the
water has with the resin, and it saves resin since the
first DI cartridge can be run until it is completely
exhausted since the second will continue to work. When
the first cartridge is exhausted, the second can be
moved to the first position and a fresh cartridge placed
second. This way the RO water produced will always be of
the highest quality for your battle against the dreaded
algae growth.
Capacity
When choosing an RO unit, think carefully about the
rating of the membrane. Membranes are rated in gallons
per day. However, the rated output can only be achieved
under ideal conditions of water pressure and
temperature. Most residential water is too cold and at
too low of a pressure to even come close to the rated
output. For example, a membrane rated at 35 gpd may in
fact only produce 10 to 15 gpd. So, anticipate how much
water you intend to use per week or month and purchase
an RO unit with a membrane rated higher than what you
require. A membrane will last for years, so replacing
one prematurely because it is underperforming is a waste
of money. Excess water from your RO unit can always be
stored in a plastic garbage can, but if you are ever
caught in a situation in which you need to make large
water changes in your aquarium, it can be a long wait
for your RO unit to produce enough water.
RO units are versatile household appliances; they can be
setup to produce water for an aquarium system as well as
drinking water for a family. And ideally, the waste
water can be redirected from going down the drain and
used for watering a garden, washing clothes or even
washing a car. Aquarists at all levels of experience can
benefit from the investment in a good reverse osmosis
system! Start Using One today and your animals will
thank you tomorrow!