>>>   HOME . : . Water Info . : . Bacteriological Safety

Bacteriological Safety

Introduction
Page 1

Above all other considerations, water to be used for cooking and drinking must be bacteriologically safe. It must contain none of the bacteria which cause diseases, such as typhoid fever and dysentery, which may be transmitted through water.

Large municipal water systems have the complex facilities and trained personnel o treat water for the destruction of "pathogens," or disease-causing bacteria, but few private water systems have these resources. Further, individual wells are often subject to unsuspected contamination. Thus, periodic bacteriological tests and preventative water treatment are recommended.

A number of devices and systems can be used to disinfect small water supplies, and each has its own advantages and limitations. Some of these methods are outlined below.

Ultraviolet systems expose the water to light from a special lamp at a specific wavelength which is capable of killing common bacteria. The system adds nothing to the water, produces no tastes or odors, and usually requires only a few seconds of exposure to be effective. Ultraviolet light, however, has no action beyond the point of application, the light penetration of water is shallow (usually only 2-3 inches), suspended solid particles and organic matter can shield organisms against the light, and the ultraviolet lamp must be cleaned frequently to insure proper exposure of the water to the light. Further, there is no simple test available to determine whether or not the system is effective.

Ozone generators are used in some systems to produce small quantities of the gas which is a very strong oxidizing agent, and is effective in killing bacteria with short exposure times. Ozone is also effective in oxidizing organic matter, iron and manganese, and produces no tastes and odors. However, the gas is so active that it must be generated at the point of use, and the equipment does not lend itself to on-off operation or variation in flow rates. Again, there is no simple test to determine whether or not the system is effective.

Several types of devices are available which feed very small amounts of silver into the water supply. Very low levels of silver are effective, and this action is powerful and long-lasting. However, relatively long contact time is necessary, a number of common substances in water interfere with the action of the silver, the silver costs are high, and overdosing can produce undesirable results, such as the discoloration of the skin. There is no simple test to determine whether or not the system is effective.

A relatively new approach is the addition of iodine to the water. This material is very effective even with relatively short contact time. However, relatively high concentrations are necessary, organic matter inhibits the action of iodine, the tastes are objectionable to some persons, iodine is not readily available, and the costs are relatively high. Its long term effects, particularly on children, are not known.

. : .

 

>>> hover over the images below to magnify

Bacteriological Safety

Coliform & E.coli Bacteria