Irradiation of Ascaris ova in sludge using an electron beam accelerator

The efficiency of sludge disinfection by irradiation was investigated using an electron beam accelerator, with the Ascaris ovum as a model. Ova suspensions prepared by worm dissection, immediately after preparation and after storage at 4 degreesC for 2 months were tested. Suspensions of ova extracted from slaughterhouse sludge were also tested. The ova were irradiated in sludge to determine, by probit analysis, the dose that inactivated 90% of viable ova. The D-10 values obtained for irradiation of residual sludge contaminated with ova depended on the source of the ova, the D-10 values were 788 +/- 172Gy for suspensions of ova extracted from slaughterhouse sludge and 1125 +/- 145Gy for suspensions freshly prepared by dissection. Ova suspensions freshly prepared by dissection were more proof against irradiation. Similarly, the D-10 value was affected by storage: 1125 +/- 145Gy for freshly produced ova suspensions and 661 +/- 45Gy for suspensions of ova stored for 2 months at 4 degreesC in deionized water. The medium in which the ova were irradiated (deionized water or sludge) also affected D-10 values, the indirect effects were smaller in samples of contaminated sludge which were rich in organic matter, with the action of the radiation being mostly direct. (C) 2001 Elsevier Science Ltd. All rights reserved.