Effects of peracetic acid and UV irradiation on the inactivation of coliphages in wastewater

This study aimed to determine the effectiveness of peracetic acid (PAA) on the inactivation of bacteriophages in wastewater. The possibility of utilising a shorter contact time by combining the treatment by PAA and UV irradiation was also investigated. The phages added in wastewater were exposed to UV irradiation and different concentrations of PAA. The treatment was followed by 15min with PAA and 60min with UV. In the combined treatment, PAA was first added to the wastewater and samples taken after 5 and 10min. Then UV irradiation was applied and samples taken after 1 and 2.5min. The inactivation of the DNA- and RNA-phages by UV irradiation alone for 2.5min was more than 5 log₁₀ and more than 3 log₁₀ units respectively. Peracetic acid inactivated the DNA-phage more than 6 log₁₀ units and RNA-phage about 4 log₁₀ units in 1h contact time. The same inactivation was achieved in 12.5min by PAA and UV together as by PAA alone in 1h. The turbidity of the water decreased the inactivation to some degree. The DNA-phage was clearly more sensitive to both UV irradiation and PAA than the RNA-phage.