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Types of Water
Filtration 2
Carbon absorption has the ability to remove unpleasant
odors and taste from water, such as that found in chlorine, in order to
improve the taste. It is one of the more popular techniques of water
treatment.
An activated carbon filter can remove various chemicals and gases. It
can also be effect against some microorganisms, although it will usually
not dissolve solids or heavy metals. Very few carbon filter systems have
the ability to remove lead, asbestos, coliform and cysts.
The two types of carbon filter systems that exist have both advantages
and disadvantages. They are granular activated carbon and solid block
carbon. They work well with a reverse osmosis system. An assortment of
carbon-based materials in a high temperature process which creates
millions of microscopic pores and fissures is the basis for activated
carbon. From 60 to 150 acres of surface area can support one pound of
activated carbon. Microscopic particles and organic molecules are
trapped into the pores, as the active surface areas adhere to or absorb
small organic molecules. An activated carbon filter has the capability
to eliminate some microorganisms and organic chemicals, such as
pesticides THMs (chlorine by-product), TCE, and PCBs. Although the
ability to remove these agents depends on the type and amount of carbon,
filter design, water flow rate, age and use of the filter, and the kinds
of contaminants that the filter has removed. This absorption process
removal depends on the size of the pores in the carbon filter and the
distribution rate of the organic molecules that pass through the pores.
The molecular weight and size of the organics determines the rate of
absorption.
Carbon removes chlorine while protecting other portions of the
purification system that may be sensitive to chlorine. Carbon is
generally used along with other treatment methods. Chloramines can
usually be removed by certain granular carbons. In order to design an
effective water purification system the position of carbon as it relates
to other elements must be considered.
The advantages to carbon absorption are that it successfully removes
dissolved organics and chlorine and it has a long life. The disadvantage
is that it can produce carbon fines.
Microporous filtration uses a hollow fiber membrane to remove carbon
fines from the carbon system and to remove bacteria and resin fragments
from the deionization system. Depth, screen and surface are the three
kinds of microporous filtration. The depth filters consist of fibers and
materials that are matted. They are condensed to create a matrix which
can hold particles by entrapping or absorbing them.
The screen filters are constructed very consistently. They work as a
strainer to keep all particles which are larger than their pore sizes on
the surface of the strainer. The surface filters are constructed from
numerous layers of fiber. These filters allow for the remaining of large
particles on the surface of the filter as the fluid passes through the
filter.
The three filters: depth, screen and surface have very diverse
functions. Depth filters are used as prefilters and provide an
inexpensive means of removing approximately 98% of solids; they also
protect the elements from clogging or foul odors. Surface filters remove
slightly more solids, about 99.99% and can be used as prefilters or
clarifying filters. The screen
filters remove the final traces of resin and carbon fines, as well as
colloidal particles and microorganisms.
The advantages of microporous membrane filtration (depth, surface and
screen) are that they can remove minerals and contaminants greater than
their pore size and their maintenance is minimal. The disadvantages are
that they will not remove inorganics which have dissolved, chemicals,
pyrogens or colloidals, and they are quite expense to use and are
replaceable.
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