Chlorine and its derivatives are no longer regarded as acceptable disinfectants of water because of compounds they form with organic material in water. These compounds have been proved to be mutagenic and carcinogenic to man. Alternative disinfectants like UV radiation and ozonization are regarded as less harmful disinfectants of microorganisms in water.

In the present study the effect of UV radiation alone and together with hydrogen peroxide, and ozone treatment on the inactivation of coliphages in tap water were studied. Two phage types, DNA- and RNA-phages were seeded into tap water and exposed to these disinfectants in batch experiments. The inactivation of phages was determined as a reduction of phage titer as a function of contact time.

Disinfection with ozone proved to inactivate coliphages more rapidly than UV light or UV light together with hydrogen peroxide (H2O2). After two minutes exposure time the reduction in phage titer was from 6 to 8 log units with ozone while with UV light or UV with H2O2 the reduction was from three to four log units.

According to these results ozonization seemed to be more efficient disinfectant than UV light radiation.