Hydroclave High Level of Sterilization
The Hydroclave was thoroughly tested by the University of Ottawa, Department of
Microbiology and Immunology, with the following results:
6 log spore reduction was achieved at 132° C and only 15 minutes of
treatment time. At this level the waste is considered "sterile".
No correlation between load size, water content and sterilizing levels was found. This
means that all the waste is always equally sterilized , regardless of
The researchers found the Hydroclave "highly suitable" for the treatment
of infectious waste.
The Ontario Ministry of Health noted that "the data would indicate that
the Hydroclave is capable of sterilizing biomedical waste after 15
minutes and 132° C.".
The Ontario Ministry of Environment/Energy agreed that: "waste which
is treated to this degree is deemed to be sterilized and can be disposed
of as municipal waste at a municipal landfill site".
The protocol for the testing was submitted to the Ontario Ministry of
Health. Once the approval was given, the testing was conducted according
to the submitted protocol, at the Kingston General Hospital, on the
prototype Hydroclave vessel between October 1995 and November 1995.
The biological indicators used were the Bacillus Stearothermophilus and Bacillus Subtilis var. niger at population levels
of 4 log10, 5 log10, 6 log10. Although a 4 log10 reduction is acceptable
for the treatment of biomedical waste, the Hydroclave achieved a 6 log10
reduction (sterility) which is well beyond the capability of other non-incinerative
treatment methods using the same treatment time.
The concluding remarks from the University of Ottawa report state
"the Hydroclave appears to be highly suitable for the treatment of
biomedical waste and can achieve an inactivation of microbial load
of 106 equivalent of B. Stearothermophilus within 30 minutes @ 121°
C. or within 15 minutes @ 132° C. Although the cycle time may be
able to be shortened even further @ 132° C., 15 minutes is a
relatively practical time frame and a shorter exposure may be