Microwave disinfection units

Description

A microwave disinfection unit shreds hazardous waste and disinfects it with steam and microwave radiation. The waste is first shredded and then heated and moistened by a built-in steam generator to improve microwave dissipation and total heat transfer. The waste then passes through a series of computer-controlled microwaves via a screw conveyor that ensures that the temperature throughout the waste is greater than 95 degrees C for a set length of time. Microorganisms such as bacteria and fungi are killed and viruses may be deactivated by the thermal effect of the microwave radiation, rather than by the radiation itself. The disinfected waste granules are then ejected for further compaction or landfill.

Microwave disinfection units are available in stationary and mobile forms. The latter are housed in a transport container. The units have a self-sterilising programme that can be run after each day's operation.

The temperature reached in the unit is designed to be high enough to disinfect the waste but not high enough to melt plastic. In this way, noxious plastic fumes are avoided and problems with molten plastic do not occur.

Application

Microwave disinfection is particularly suited to hazardous clinical waste. Contaminated sharps, such as syringes and needles, and various pharmaceuticals and used swabs can all be disinfected by the unit. Microwave disinfection units have been shown to successfully kill Bacillus, Staphylococcus, Nocardia, Aspergillus, Giardia, and destroy polio virus and hepatitis B virus.

Microwave disinfection has two major advantages for the treatment of hazardous hospital waste: (i) the danger associated with the clinical waste can be reduced to allow reclassification as a controlled waste and landfilled accordingly; and (ii) the volume of the waste can be reduced by up to 80 %. The technique can also be applied to other solid wastes that require to be disinfected, especially in the food industry.

Sizing

A microwave disinfection unit sized to disinfect 250 kg/hour of hazardous waste would have an electrical consumption of about 50 kW. Units are also available in 150 kg/hour and 500 kg/hour sizes. Microwave disinfection units have a lower running cost than a waste incinerator, but produce substantially more waste to be landfilled.