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Ozone disinfection Resistant microorganisms

Deactivation of resistant microorganisms

The last decennia protozoa, such as Cryptosporidium Parvam and Giardia Lambia, have caused a large number of epidemics in the United States and Great Britain through drinking water [28,29,30]. In many cases, drinking water did comply with bacteriological quality standards. Consequentially to resistance of Cryptosporidium Parvum and Giardia Lambia in the environment and their resistance to disinfectants, direct purification of surface water much comply to very strict quality demands.
Protozoa spread through the environment rapidly as (oö)cysts (spores), which live longer and are more resistant to disinfectants than bacteria or viruses. In general, Cryptosporidium Parvum causes larger problems for drinking water treatment than Giardia Lambia does. Cryptosporidium Parvum is 4 – 5 µm in size, which makes it difficult to remove by conventional filtration [6]. Giardia Lambia is 8 – 14 µm in size, which makes it easier to remove by conventional filtration than Cryptosporidium Parvum [30]. Moreover, when drinking water or swimming pool water is treated by means of conventional chlorination, Cryptosporidium Parvum is insufficiently deactivated [28]. Alternative treatment methods, such as ozone and UV disinfection, appear to have the ability to deactivate the oocysts sufficiently [28,30].