Anaerobic sludge exposures conducted at 21.5°, 37°, and 50°C produced 99.9 % G. muris cyst inactivations in 15.1 days, 20.5 hrs, and 10.7 minutes, respectively. A comparison of 99.9 % G. muris cyst inactivation times with USEPA anaerobic digestion treatment standards for land applied sludges (in 40 CFR 257) indicated that compliance with the latter would readily achieve 99.9 % G. muris cyst inactivations. Percent cyst inactivation (% I) was defined in terms of cyst concentration and cyst excystation by the following equation: %I = (1- (C)EX)100, where ‘C' was the fraction of the original cyst concentration remaining after exposure and ‘EX' was the fraction of the remaining cysts that were able to excyst. The 99.9 % Giardia cyst inactivation treatment standard of the USEPA's Surface Water Treatment Rule was adopted as a Giardia-based treatment standard for land applied sludges.
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Praagh et al. (1993) studied this question.