Mechanical/Chemical Disinfection

Chemical disinfection, primarily through the use of chlorine products, is another method to treat medical waste. The use of chlorine bleach for cleaning and disinfecting is well known and this method has been in use for many years. The mechanical/chemical disinfection process provides control and consistency to the disinfection process. The EPA identifies chemical disinfection as the most appropriate method to treat liquid medical waste. Chemical disinfection processes are often combined with a mechanical process, such as shredding or maceration, to ensure sufficient exposure of the chemicals to all portions of the waste. The disinfectant is usually combined with a large amount of water to assist with the disinfection process and to cool the mechanical equipment in the shredding process. Liquid waste treated with a mechanical/chemical disinfection process can usually be discharged into the sewer system, as long as the organization has obtained the proper sewer discharge permits from their city. Mechanical/chemical disinfection treatment devices are primarily on-site installations, rather than mobile treatment units, though these devices are available in different sizes based on the amount of waste to be treated.

Microwave

The use of microwaves to disinfect medical waste has only recently been introduced in the United States. Microwave treatment units can be either on-site installations or mobile treatment vehicles. In this type of disinfection process, the waste is first shredded. The shredded waste is then mixed with water and subjected to microwaves. The microwaves internally heat the waste, rather than applying heat externally, as in an autoclave. The heat generated in this method provides even heating over all portions of the waste, and the high-temperature steam that is generated effectively neutralizes all biologicals. The shredding operation reduces the volume of the waste by up to 80%, and the treated waste can be disposed of in a landfill. The entire process takes place within a single vessel, and the system can be operated by unskilled workers. Treatment of medical waste through exposure to microwaves is less expensive than incineration. This method is not recommended by the EPA for the treatment of pathological waste.

Irradiation

Another method used to sterilize medical equipment or waste is irradiation, generally through exposure of the waste to a cobalt source. The gamma radiation generated by the cobalt source inactivates all microbes that may be present in the waste. Dedicated sites are required for this form of treatment, as opposed to the mobile versions available for other non-incineration methods. One private company that specializes in this form of treatment shreds the treated waste after irradiation, then ships the waste to a cement kiln, where it is burned as fuel. The cost of developing a dedicated facility for this method is quite high, and therefore this method is not as widely used as other treatment methods at this time. The risk of radiation exposure by workers operating the facility, while low, is also a factor. Also, pathological waste cannot be treated using irradiation. Questions have been raised about the effectiveness of irradiation to provide consistent treatment across a batch of waste.