In this study two disinfection processes were used to determine the disinfection effect of water and hospital laundry wastewater artificially contaminated with Enterococcus faecium. Different concentrations of peroxyacetic acid and different exposure times with ultraviolet radiation were tested on inoculated water and wastewater. The number of cfu after incubation on agar base was determined for each experiment. 70 mg/LPAA was sufficient to reach a 5-log10 reduction within 35 min treatment for hospital laundry waste water, whilst 5 min treatment time was reached by 110 mg/L PAA. 80 mg/L ensured a 5-log10 reduction after 15 min treatment time. For water inoculated with Enterococcus faecium 80 mg/LPAA was sufficient to reach a 5-log10 reduction within 5 min. However minimal recovery was noted and subsided after 40 min, thus proving that the hospital laundry wastewater already contained inhibitory substances shortening the necessary treatment time. Ultraviolet radiation for 1½ hours also proved to be efficient for hospital laundry wastewater with inhibitory substances preventing any dark repair after 18 hours. Thus indicating that such method could be used for laundry wastewater or similar water that is stored overnight and then reused, if scale-up and cost-effective studies prove to coincide with these results.
Enterococcus faecium, Laundry wastewater, Peroxyacetic acid, UV radiation
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