Several methods of treatment are available from
our Engineering department, for specific projects. Selection of the most
effective method depends on the water analyses, treated flow, and other local
conditions as specified in our Questionnaire.
In the past, the usual Public Health stand was more-less where there are two or
more people drinking from the same source, it has to be chlorinated. Finally,
this attitude is changing thanks to greater awareness of the health hazards
associated with the use of Chlorine to disinfect drinking water – see the
Chlorine section at www.the-ozone-store.com . While drinking water should be
free from disease causing pathogens, it should also be free from disease causing
In order to assure disease free drinking water, the U.S. EPA finalized (in June
1989) a set of procedures for community water treatment systems called: SURFACE
WATER TREATMENT RULE (SWTR). Although the laws covering this SWTR are not
compulsory in other countries, there are advantages to using the data
accumulated in the United States where more money is available for research. In
1. All water supplies obtained from surface water, or ground water under the
direct influence of surface water, must be disinfected to remove or inactivate
Giardia Lambda, and Cryptosporidium at least 99.9% (3 Log) and viruses to at
least 99.99% (4 Log).
2. In conjunction with proper filtration the level of further disinfection may
be reduced to 0.5 Log.
3. Inherent in the rules for disinfection are the CT tables. CT constant
describes the time required for disinfection to certain levels at given
parameters of pH, temperature, concentration of a particular disinfectant, and
its contact time. For instance:
• For 3 log Giardia disinfection:
Chlorine at 2 ppm for 100 min while Ozone is sufficient at 0.4 ppm for 2.4 min.
• For 0.5 log Giardia disinfection (after proper filtration):
Chlorine at 2 ppm for 8.5 min while Ozone is sufficient at 0.4 ppm for 0.4 min.
• For virus inactivation to 4 log:
Chlorine at 2 ppm for 2 min while Ozone is sufficient at 0.4 ppm for 1.5 min.
Chlorine and Ozone have served communities for nearly a century. 100 years ago
ozone was too expensive and the ozone generation equipment not very reliable. At
that time chlorine was cheap and its side effects unknown. Yet, because of
chlorine's bad taste, and because of its terrible reputation as a WWI poison
gas, after WWII ozone was already favored by many European cities. Today
technology has made ozone generators relatively inexpensive and reliable.
It has been concluded in many studies that heart disease, cancer, and asthma are
directly linked to the disinfectant by-products called TRIHALOMETHANES (THMs)
and Halo-Acetic Acids. As 1000s of kinds of organic molecules may be present in
water, there are also 1000s of Chloro-organics THM by-products formed when these
organics react with chlorine. Each of them ever tested shows carcinogenic
effects. The ultimate choice is Ozone.
When in contact with any organic molecule Ozone will start oxidizing by
attacking the carbon-hydrogen bonds, and will continue on through a chain of
reactions ending off with harmless CO2 gas (Carbon Dioxide). The actual Ozone
system design is based on the water tests and on the existing hydraulics layout.
Water source may also contain inorganic oxidable compounds such as Iron,
Manganese, Sulfur, Arsenic…. All of them can be removed with Ozone directly, or
in combination with filtration. Once all contaminants have been eliminated,
residual Ozone reacts with any microorganism (bacteria, virus, or fungus),
destroying by rupturing the cell membrane. Ozonation also adds dissolved oxygen
to the water supply. In many countries, 10 mg/l of oxygen is required to meet
drinking water quality standards.
Typical surface water contains organic compounds which result mainly from the
decay of vegetative matter. These organic compounds are mostly in the form of
Humic and Fulvic acids. Removal of organic compounds by precipitation requires
low doses of Ozone in the presence of polyvalent metal ions such as Calcium,
Iron, & Aluminum. The oxidation process leads to compounds with organic acids on
either end of the molecules. These further react with the metal ion and form
flocks that can be filtered out. This process will remove 50-85% of the organic
contamination. After filtration the water is again subjected to Ozone in order
to kill the remaining pathogens which may be present.
After ozonation, the treated water is passed through a filter. Even if it is
necessary (in larger distribution systems) to chlorinate, this organics-free
water would require only about 0.2 ppm of chlorine to maintain sterilization
through sometimes questionable distribution lines. Due to non-existence of
organic compounds after ozonation, THMs are not being formed and the low free
chlorine residual will dissipate when water is left in a fridge for a couple of
Another very serious concern with surface water sources is the presence of
Giardia and Cryptosporidium. These protozoa live in the intestines of infected
wild animals, and surface water supplies are contaminated from their feces. In
British Columbia, Canada, 60% of all water-borne disease outbreaks in the last
decade were attributed to Giardia. It is therefore essential to address this
organism when offering a complete water treatment package.
For proper and the most economical water treatment we propose:
• Pre-treatment with Ozone to remove organics and to precipitate iron, manganese
and Hydrogen Sulfide. Here we supply enough ozone also for reaching the
disinfecting levels of ozone residual in order to eliminate all pathogens.
• Followed by filtration to remove the flocks of organic material.
• Depending on the size of the distribution network, either re-ozonation or a
chlorine residual of 0.2 ppm. It has been experienced that in communities up to
about 1000 houses the distribution is usually in good shape or easy to repair,
and secondary chlorination is not needed, if the same procedures are followed as
if chlorinated. This is to take bacteria test-samples from all branches each
three month. If there is zero bacteria count, no chlorination is required. The
best results are when the reservoir is maintained at 0.03 mg/l residual ozone.
This level is not a concern when supplied to the houses. Once in a few years the
distribution can be shock-treated in organized event with larger amounts of
ozone while by-passing the reservoir. This method is much safer then
shock-treatment with chlorine bleach of course as accidental drinking of water
with even very large amounts of dissolved ozone does not posses any threat to
Treatments involving ozone will leave desirable levels of dissolved oxygen in
the treated water. It naturally happens to be that oxygen provides 90% of water
superior taste. The oxygen content in water is important as it enters the
digestive system where oxygen from breathing does not enter, thus supporting
friendly aerobic digestion and preventing pathogenic fermentation process. This
is why in Europe a minimum of 10 mg/l of dissolved oxygen is required in the
public drinking water supplies.
The cost of the finest quality drinking water system will be inversely
proportional to the number of people using the system. Generally speaking, a
system supplying about 1000 people could be about ~ $350 per household for the
capital expenditure. The average annual operating cost would be ~ $50 per
household. The numbers will vary based on the source water quality and
elevations. Presently, the cost of installing this high quality water system for
a single household is anywhere between $3,000 to $14,000 — and even the higher
amount may still be less than drilling a new well. It is much less expensive
where communities get organized and willing to spend much less per household
with centralized ozone treatment.