[Use of UV radiation for the disinfection of water. IV. Microbiological studies of the UV sensitivity of different aged cells of E. faecium, E. coli and P. aeruginosa].

With a flow-through u.v. light treatment apparatus the u.v.-susceptibility of E. faecium, E. coli and P. aeruginosa in drinking water was tested. The investigations were done with cells harvested in the exponential phase of growth. One part of the suspensions was used immediately (= 0 days old cells), two other parts were stored for 5 and 7 days in sterilised drinking water in the dark at room temperature (= 5 and 7 days old cells). In either case--0 or 5 and 7 days old cells--reductions of at least 99.999% were obtained by a dosage of 25 mWs/cm2. No difference concerning the u.v.-susceptibility could be noticed between the different kind of cells of E. faecium, E. coli, and P. aeruginosa.