WATER FILTRATION
INTRODUCTION Water filters are used to remove microorganisms. There are some filters that have a chemical disinfectant matrix that are effective against some viruses; however, filters are not always effective in removing viruses. A combination of filtration and purification of contaminated water are recommended to ensure water safety (CDC, 2009). Filters usually have a hand pump that draws water into the filter, and they work by pumping water through an intake hose or by slow gravity flow and through a microscopic filter
Most portable filters have a prefilter on the intake tubing
that strains out harmful microorganisms. There are different
to protect the main filter. If the filter does not come with a
sizes of filters depending on what organism is to be filtered out
prefilter, a fine mesh cloth or coffee filter may be used instead.
(Backer, 2011).
Flow can be improved in a clogged filter by back-flushing or cleaning the surface of a ceramic filter to remove large particles
Most portable water filters are made of ceramic material,
trapped close to the surface (Backer, 2002).
fiber or compressed granulated activated carbon (GAC); all of these materials create irregular and complex passages to
Advantages: Water filters are easy to operate, require no
catch organisms. Depth filters have a large capacity for holding
holding time for treatment, may improve the taste and
particles, so they don’t clog as fast as single-layer membrane
appearance of water, and remove all microorganisms with the
filters do. When a filter is clogged, the water pressure increases
combination of chemical disinfections (Dvorak et al., 2009).
and forces water through the filter with the risk of possibly forcing microorganisms through it and back into the water.
mICROORGANISm SIZE AND FILTRATION (Backer, 2011) Organism
Average Size (Micrometer)
Maximum Recommended Filter Rating (Micromet Absolute)1
Viruses
0.03
Not Specified (Optimally 0.01)
Enteric Bacteria (E. coli)
0.5 X 3.0 - 8.0
0.2 - 0.4
Cryptosporidium oocyst
4.0 - 6.0
1
Giardia cyst
6.0 - 10.0 X 8.0 - 15.0
3.0 - 5.0
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EMERGENCY WATER
