The advantages of UV disinfection are well-known, for example, there are no by-products, the taste and smell of the water remains neutral, UV radiation is non-corrosive and very effective against parasites and protozoa.
The discovery that UV inactivates Cryptosporidium parvum oocysts has given greater emphasis to the role of UV. Its applications extend beyond potable water to municipal waste water, swimming pools, water features, industrial cooling circuits and industrial process water.
However, an important criterion is the method of generation of UV. There are two main types of UV lamp - low pressure and medium pressure. The low pressure lamp disrupts the DNA in the cell and prevents cell reproduction. Unfortunately, the other proteins and enzymes are not destroyed. The proteins and enzymes are capable of repairing the DNA, particularly in the presence of light, so that disinfection is not complete.
Medium pressure lamps, on the other hand, destroy proteins, DNA and enzymes, so that disinfection is complete. The table below gives a summary of the performance of the two types of lamp.
An indication of the UV spectral emission curves of the two types of lamp are shown in the diagrams below.