The ultraviolet way of purifying consists of several wavelengths; the most prevalent one is visible to the human eyes, while some are called narrow band wave lengths that are invisible to the human eyes. The ultraviolet gamut includes wavelengths from 2000 to 3900 Angstrom units (?). One unit is one ten billionth of a meter. This spectrum is generally divided into three basic sections:

Long wave ultraviolet water purification: This wave length range is 2950 to 3900 ?. Having a little germicidal value, long wave UV rays occur naturally in sunlight.

Middle-wave ultraviolet Rays: The middle-wavelength range - 2950 to 3250 ? - is also found in sunlight. It is popular for its sun-tanning effect and germicidal action with sufficient exposure.

Short wave Ultraviolet: Having a wave length of 2000 to 2950 A, this process provides the major germicidal effectiveness of all ultraviolet wavelengths. This technique is most extensively used to raze bacteria, virus, mold, spores, etc. Short-wave ultraviolet is usually done by converting the electrical energy in a mercury vapor lamp, because the earth's surface screens out any sunlight radiation below 2950 ?.

Mercury Vapor or Germicidal Lamp is the main apparatus through which the short wave length ultraviolet energy is passed to purify the water. An electric arc is there in a sealed special glass tube. The arc is heated by the emanation of the electrical energy; this in turn will vaporize the small amount of mercury in the tube. The mercury after being vaporized gets ionized and provides the UV radiation in the electric semicircular wire. Turbid water should be filtered before UV purification to allow the transmission of an adequate amount of UV energy. A 5-micron filter is advisable here.

UV Water Purifier Design

1.The different parts of the chamber should be unique in design and should be interchangeable.

2.Sight Port ensures visual monitoring of lamp operation and operates the adaptation to the electronic monitor device.

3.There should be a single lamp in each chamber; it gives much more productivity than the multi-lamp-in-single-chamber.

4.A protective quartz sleeve must be there with the higher lamp temperature required for 2537 ? radiation. This protection is generally required to maintain the lamp temperature and radiation yield.

5.Flow controls, UV light bulb monitor, electronic water shut-off valves, mechanical wiper and alarms, must be associated to provide continuous operation without the operator guidance.
Water having purified in this way is totally safe for drinking as well as for other purposes.