Microwave inactivation of Escherichia coli in healthcare waste.
Public healthcare wastes from the city of Ribeirão Preto, SP, Brazil, pre-sterilised in an autoclave, were inoculated with 5 x 10(5) microorganisms of the species Escherichia coli in vegetative form for microwave processing on a laboratory scale. An analysis was made of the influence of radiation exposure time (15, 25, 30 and 40 min) and power per waste mass unit (60, 80 and 100 W/kg) on the percentage of inactivation of the microorganisms at an incoming waste moisture level of 50%. The experimental results were adjusted based on Chick's law. The activation energies and the Arrhenius pre-exponential factors were determined by the least squares method. The kinetic parameters obtained allow one to predict the degree of inactivation achieved with E. coli in typical healthcare waste, based on the radiation exposure time and temperature. For example, the waste disinfection time required for the inactivation level equivalent to 4Log 10 was estimated to range from 48 to 53 min for wastes processed at 100 W/kg and at temperatures of 90-105 degrees C, respectively. Thus, under the operational conditions of the equipment currently used in Ribeirão Preto, the process of inactivation is probably ineffective, since the exposure time to radiation is only 30 min at the average power of approximately 80 W/kg.
Tonuci
L R S
LR
University of Ribeirão Preto, Post-Graduate Program in Environmental Technology, Rua José Bonifácio, 799, 13560-610 São Carlos, SP, Brazil.
Paschoalatto
C F P R
CF
Pisani
R
R
D003247:Conservation of Natural Resources; D004926:Escherichia coli / Q000528:radiation effects*; D015386:Hazardous Substances; D017744:Medical Waste Disposal / Q000379:methods*; D008872:Microwaves; D013997:Time Factors
D015386:Hazardous Substances; D017744:Medical Waste Disposal