[The behavior of viruses in conventional and 2-step anaerobic-mesophilic stabilization of clarified sludge with pre- and postpasteurization]

In a pilot-plant of semi-technical scale for the digestion of sewage-sludge with two single operated reactors and five coupled reactors investigations about the influence of anaerobic mesophilic sludge digestion and pasteurisation of raw and digested sludge on viruses were carried out. Following test-viruses were used: bovine enterovirus ECBO strain LCR-4, bovine parvovirus strain "Haden" and reovirus type I. In the case of a daily addition of virus-contaminated raw sludge both ECBO-virus LCR 4 and Reovirus--with one exception--were inactivated by a conventional single stage sludge digesting process with a mean hydraulic retention time (t/R) of 20 d as well as by a two-stage digesting process with 2 d tR in the anaerobic pretreatment and 8 d tR in the main-digestion process with and without prepasteurisation of the raw-sludge. Bovine Parvovirus was inactivated completely by a single-stage sludge digesting process with 20 d tR and pasteurisation of the digested sludge. All other investigated processes did not inactivate Parvovirus completely.