Potable Water, Purified Water, and Water Treatment
Processes
Potable Water can be described as all water used for human consumption that does not pose a
health danger and which is microbiologically safe and free of all pathogenic microorganisms and
bacteria associated with fecal contamination. In the United States, according to the U.S.
Environmental Protection Agency (USEPA) it is water with (0) fecal coliforms, (0) Giardia
lamblia, (0) Legionella, (0) enteroviruses. According to the World Health Organization (WHO)
Guidelines for Drinking Water Quality (2002), “E.Coli or thermotolerant coliform bacteria must
not be detectable in any 100 ml sample.” It can be produced by any method or can be naturally
occurring.
▼Does not have residual capabilities to kill microorganisms.
▼Arrow down indicates
negative
▲Conforms to regulations of the USEPA for potable water.
▲Arrow up indicates positive
▲The process does not pose health risks.
Purified water is water that complies with USEPA regulations for drinking water and has no
additional substances and no more than 0.05 mg/l of total organic carbon. It can be obtained by
distillation, ionic interchange treatment, reverse osmosis, or other appropriate processes.
▼Does not have residual capabilities to kill microorganisms.
▲The process does not pose health risks.
Ceramic Water Filter
▲Conforms to regulations of the USEPA for
The Filtron design clay filter works in two ways.
potable water.
Methods to achieve potable and/or
purified water
Distillation
Distilled water is boiled, evaporated and the
vapor is condensed. The USEPA does not have
regulations with respect to distilled water. It is
regulated through the Food and Drug
Administration (FDA). Removes bacteria,
viruses, worms, and protozoa.
▼Does not have residual capabilities to kill
microorganisms.
▲Probably conforms to regulations of the
USEPA for potable water.
▲The process does not pose health risks.
▲Removes suspended solids.
Through filtration, protozoa, helminthes, most
bacteria, and some viruses are trapped in the
pores of the filter. Through the microbicidal effects
of colloidal silver, bacteria are inactivated on
contact and are unable to reproduce. This function
also prevents growth within the filter.
There are millions of tiny colloidal silver particles
distributed throughout the filter (rather than
clumped together). Tortuosity refers to the indirect
route water is forced to take in order to pass
through the filter. And water flows downward
through the sides of the filter before dripping out
the bottom. These three things increase the
number of microbes that are trapped and that
come in direct contact with the colloidal silver, even
though some microscopic cracks and spaces in the
filter are much larger than the trapped microbes.
▼Does not have residual capabilities to kill
microorganisms.
Filtration
▲Is capable of conforming to regulations of the
This refers only to the method by which the
USEPA for potable water except for viruses.
water is treated. The quality of the water
▲The process does not pose health risks.
depends on the method of filtration. If the pores
▲Removes suspended solids.
of a filter are small enough, the filter can
produce potable water. Possibly the method of
filtration only eliminates particles that cause turbidity or only removes protozoa. There are no
regulations for filtered water. May remove bacteria, viruses, worms, and protozoa.
▼Does not have residual capabilities to kill microorganisms.
▲▼Some methods conform to regulations of the USEPA for potable water.
▲The process does not pose health risks.
▲Removes suspended solids.
Biosand Filtration
Biosand filtration is a variation of slow sand filtration. This method uses a concrete or other
container that encloses layers of fine sand, coarse sand and gravel through which water travels
slowly and collects in a pipe at the base of the filter. Removal of pathogens occurs due to a
combination of biological and mechanical processes. When water is poured through the filter, a
layer of organic material forms a biological layer at the top. Over one to three weeks,
microorganisms colonize this layer. These microorganisms consume bacteria and other
pathogens, pathogens are removed due to food scarcity, viruses become attached to sand grains,
and sediment, cysts and worms become trapped in the pores between the grains of sand. Reports
over 90% effective in removing bacteria. (Center for Affordable Water and Sanitation Technology)
▼Does not have residual capabilities to kill microorganisms.
▲▼Some methods conform to regulations of the USEPA for potable water.
▲The process does not pose health risks (when properly maintained).
▲Removes suspended solids.
Boiling
Boiling kills all pathogens including viruses, bacteria, protozoa and helminthes. Water should
come to a full boil. Recommended boiling time is three minutes at a roiling boil at sea level and
one additional minute for every 1000 meters in altitude. It’s inefficient, time-consuming and
contributes to indoor pollution and deforestation. (Center for Affordable Water and Sanitation Technology)
▼Does not have residual capabilities to kill microorganisms.
▲Conforms to regulations of the USEPA for potable water.
▲The process does not pose health risks.
▼Does not removes suspended solids.
Chlorine Disinfection
Chlorine disinfection is accomplished by adding chlorine to water in either liquid or powder
form. Bleach (sodium hypocholorite) is the most common form used. With sufficient contact
time chlorine causes chemical reaction which inactivate or kill pathogens. Organic matter,
metals and other contaminants can alter the efficiency of chlorination. It deteriorates over time
and with exposure to sunlight. With correct dosage the smell should be minimal. Chlorine is
hazardous and corrosive. It is very effective in killing bacteria and most viruses but does not
inactivate protozoa and helminth eggs. (Center for Affordable Water and Sanitation Technology)
Guide for proper chlorination of drinking water:
Concentration of
Sodium Hypochlorite
Drops per Gallon of
Clean Water
Drops per Gallon of
Dirty Water
1%
15
25
4-6%
3
5
7-10%
1
1.5
▲Has residual capabilities to kill microorganisms (except for protozoa)
▼Does not conform to regulations of the USEPA for potable water.
▼Process poses health risks.
▼Does not removes suspended solids.
Treatment with Iodine
Chemical disinfection with iodine is effective for killing all pathogens except cryptosporidium.
Cloudy water needs twice as much iodine or twice as much contact time. In cold water (below 5˚
C) the dose or time must also be doubled.
▲Has residual capabilities to kill microorganisms.
▲Conforms to regulations of the USEPA for potable water.
▼Extended use may pose health risks.
▼Does not removes suspended solids.
Solar Water Disinfection
This method uses the UV light of the sun to change dissolved oxygen into a form that acts as a
microbicide. Water is simply placed in clear plastic or glass bottles and exposed to the sun. SolAir treatment requires bright sunlight, and has been shown to be effective when ever the sun
causes a distinct shadow to be cast. Exposure to 4.5 hours of bright sunlight has been shown to
cause a thousand-fold reduction in fecal coliforms in lab tests. There is some evidence that other
bacteria and viruses may be affected also. (Anozira Water Treatment FAQ)
▼Does not have residual capabilities to kill microorganisms.
▼Does not conform to regulations of the USEPA for potable water.
▲The process does not pose health risks.
▼Does not remove suspended solids.
NOTES: