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Evaluation of a mechanical/chemical infectious waste disposal system
1Laboratoire de santé publique du Québec, Sainte-Anne-de-Bellevue, Canada.
Objectives:
The mechanical/chemical infectious waste disposal system (IWDS), model Z-5000 HC, manufactured by Medical SafeTEC Inc. (Indianapolis, Indiana) was evaluated for its ability to disinfect biomedical waste.
Methods:
The IWDS was operated with a sodium hypochlorite solution and tested with loads consisting of microbial cultures and blood. During and after processing, samples of liquid, milled solid waste, and leachate were collected to determine the efficacy of disinfection and the chemical by-products released. An inactivation factor was calculated. Aerosol emission was studied. All tests were done in triplicate.
Results:
Our results showed the expected level of disinfection (inactivation factor greater than or equal to 5 log10) for all tests carried out with Bacillus subtilis, Enterococcus faecalis, Candida albicans, and Serratia marcescens, and for most of the tests with Mycobacterium fortuitum and bacteriophages OX174 and f2. Further tests performed in the absence of blood resulted in an inactivation factor greater than or equal to 5 log10 for all tests with M fortuitum, but not for those of the milled solids with bacteriophage f2. Aerosols were found to escape the apparatus when the IWDS was operated in the absence of chlorine. The liquid effluent contained an average of 17,600, and 15 mg/l of free chlorine, chloramines, and trihalomethanes (THM), respectively. The air effluent contained 1.1 mg/m3 of total chlorine and 1.4 micrograms/m3 of THM.
Conclusions:
Under our study conditions and except for certain tests with bacteriophage f2, the IWDS reduced the microbial populations tested by a factor of 5 log10. The aerosol dispersion problem remains to be solved, and the significance of the chemical by-products released will require further investigation.