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Consumers today are more aware of health concerns and the quality of the water they drink. Millions of people prefer to purchase bottled water and some even go to the extent of installing a complete water treatment in their home. This system includes the disinfection process. Disinfection which could involve chlorination, ozonation and ultraviolet irradiation, becomes the most important stage of the system when microbiological problems are present. Of the disinfection methods mentioned, ultraviolet (UV) disinfection is becoming more popular and economical than the others.
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| Chlorination:
Takes advantage of the potentials of chlorine. The use of chlorine as a
disinfectant is commonly accepted world-wide. Chlorination is a popular
choice because of its residual disinfection characteristics. Its
effectiveness is very simple to test; one needs only to measure the
residual chlorine at the point of use. If there is a sufficient level
detected, it is assume there is proper disinfection. However, peoples are
becoming more concerned about the by-products of chlorine and are looking
for alternatives. Chlorine reduces bacteria, but it also reacts with
other organic compounds producing various trihalometanes (THMS) which are
listed as probable or possible human carcinogens. Other disadvantages of
chlorination are undesirable tastes and odours, requirement of additional
equipment (such as tanks) to guarantee proper contact time, and extra time
to monitor and ensure proper concentration level. It also gives poor
disinfection performances on viruses such as enterovirus and hepatitis
A.
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| Ozonation:
Is another disinfection method . Ozone, the
greatest oxidant known, is effective as an oxidizing agent in reducing
bacteria with a relatively short exposure time. Ozone generators are used
to produce ozone gas on site, since the gas is unstable and has a very
short life. These generators, must be installed and monitored cautiously,
because high concentration levels of ozone will oxidise and deteriorate
all downstream piping and components. With ozone systems, residual
disinfection can be achieved, but the residual must be removed with an
off-gas tank to ensure homeowners are not exposed to ozone gas, which is a
strong irritant. High levels of ozone are extremely harmful especially in
enclosed or low-ventilation areas. Ozone forms highly carcinogenic
by-products at high bromide levels such as bromate, broform, dibromeacetic
acid, and others. This, in fact is becoming an even bigger concern with
drinking water disinfection. In commercial applications, UV equipment has
to be installed to remove ozone residuals prior to critical filtration or
point of use. Furthermore, ozone equipment is very costly compared to
other disinfection methods.
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UV disinfection: Although seemingly new to the average end-user, the use of ultraviolet (UV) light as means of water disinfection has been a proven process for many years. The UV method of disinfection is now widely recognised by governments in many countries. In addition , as the concern of chemical contamination increases, many companies have accepted UV as a viable water treatment option. Used by leading companies around the world, UV disinfection is trusted to provide microbiologically pure water without the unwanted effects of alternative treatments. Health authorities are becoming increasingly aware of the benefits of UV disinfection especially the fact that it does not use chemicals.
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