WATER DISINFECTION METHODS. Part I

There are a number of ways of purifying water. In evaluating the methods of treatment available, the following points regarding water disinfectants should be considered.

lab equipment

A disinfectant should:

  • 1. Be able to destroy all types of pathogens and in whatever number present in the water.
  • 2. Destroy the pathogens within the time available for disinfection.
  • 3. Function properly regardless of any fluctuations in the composition or condition of the water.
  • 4. Function within the temperature range of the water.
  • 5. Not cause the water to become toxic or unpalatable.
  • 6. Be safe and easy to handle.
  • 7. Be easy to determine its concentration in the water.
  • 8. Provide residual protection against recontamination.

Techniques such as filtration may remove infectious organisms from water. They are, however, no substitute for disinfection.

The following are specific methods for disinfecting water.

BOILING WATER

Place water in a container over heat. Bring it to the boiling point. Hold it at this temperature for 15-20 minutes. This will disinfect the water. Perhaps you have used this technique after a flood or when a water main has burst as an emergency aid. Boiling water is an effective method of treatment because no important water-borne diseases are caused by heat resisting organisms. Although the boiling does not remove them from the water, it does kill them and thus they will cause no illness.

How effective is boiling water?

Boiling water is an effective method to destroying bacteria and other pathogens in the water. It does not act as a filter to remove particulate matter. In fact, it does not remove anything from the water; it only destroys bacteria and pathogens such as cryptosporidia, giardia, E.coli, and typhoid. Boiling will not provide any safeguard against other things such as heavy metals, pesticides, herbicides, and pharmaceuticals. It will also not remove foul tastes and odors, so it is not recommended to depend on boiling water as the main method to purify your drinking water.

ULTRAVIOLET LIGHT

The use of ultraviolet light is an attempt to imitate nature. As you recall, sunlight destroys some bacteria in the natural purification of water. When harmful microbes are exposed to UV light rays, their nucleic acid absorbs the UV energy which then scrambles the DNA structure of the organism causing it to die. UV light is only capable of killing microorganisms such as bacteria, viruses, molds, algae, yeast, cryptosporidium, and giardia. UV light generally has no impact on chlorine, heavy metals, and other chemical contaminants. This is why a UV light is usually combined with other various types of filtration.

To assure thorough treatment, the water must be free of turbidity and color. Otherwise, some bacteria will be protected from the germ-killing ultraviolet rays. Since ultraviolet light adds nothing to the water, there is little possibility of its creating taste or odor problems. On the other hand, ultraviolet light treatment has no residual effect. Further, it must be closely checked to assure that sufficient ultraviolet energy is reaching the point of application at all times.

Characteristics of Ultraviolet Light:

Advantages: Automatic, no taste or odor, energy efficient and low contact time. One of the few affordable technologies for the home that effectively kills the majority of bacteria, viruses, and other harmful microorganisms.

Disadvantages: Low penetration power, shielding by turbidity, slime layer develops on the tube, no simple test of results, no residual effect, and ultraviolet tube gradually loses power. Also requires pre-filtration to maintain effectiveness.

With the growing number of toxic substances and the increase in sources of contamination, purified water is more important than ever for continued good health. Reverse osmosis technology is the best method of purifying your drinking water. This is the same technology used to desalinate seawater and to filter water for bottled water. Maintaining health is important to enjoying life and having the energy to continuously help others. Let us eat healthy, exercise, drink plenty of purified water and stay happy!

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