[Zurück]

H. Schaar, R. Sommer, R. Schürhagl, P. Yillia, N. Kreuzinger:
"Microorganism inactivation by an ozonation step optimised for micropollutant removal from tertiary effluent";
Vortrag: IWA World Water Congress & Exhibition 2012, Busan, Korea; 16.09.2012 - 21.09.2012; in: "Proceedings", (2012), Paper-Nr. IWA-9088R1, 16 S.

The additional benefit of the microbicidal efficacy of an ozonation plant implemented for micropollutant removal from tertiary effluent was assessed. In addition the impact of the reduced microorganism concentration of ozonation on the biochemical oxygen demand (BOD) was studied by means of two standard methods. Since the amount of viruses and protozoa was too low to deliver representative quantitative inactivation data bacteriophage MS2 and spores of B. subtilis were dosed under controlled conditions to the effluent as surrogates for viruses and protozoa relevant for water sanitation and health. At specific ozone consumptions of 0.6 and 0.9 g O3/g DOC a 2-log CFU reduction was achieved for indigenous E. coli and enterococci and the limits of the European bathing water directive for the excellent quality of inland waters could be met. A higher removal was impeded by the shielding effect of suspended solids in the effluent, which implies the combination of ozonation with a preceding filtration step if higher microbicidal performances in terms of the inactivation of bacteria or permanent stages of bacteria and protozoa (spores, cysts, oocysts) are required. The
surrogate virus MS2 was reduced by 4-5 log while no significant inactivation was detected for B. subtilis spores. Due to their higher sensitivity compared to pathogens like parasites the faecal
indicator bacteria have only limited value for the assessment of the microbiological water quality after disinfection, which requires alternative approaches. The BOD5 measurement was not adversely
affected despite the reduced concentration of microorganisms. The intrinsic increase in BOD5 averaged 15 % at 0.6-0.7 g O3/g DOC. The impact of the projected BOD increase on the surface water quality is
generally not considered a problem but has to be assessed on a case-by-case approach.

ozonation; tertiary effluent; bacterial fecal indicators; bacteriophage MS2; Bacillus subtilis spores; biological oxygen demand