Health Hygiene & Sanitation

Lesson 32 : Hospital Waste Management

Treatment And Disposal Technologies For Health Care Waste

Incineration, Chemical disinfection, wet and dry thermal treatment, microwave irradiation, land disposal, inertization are the methods of treatment and disposal.

1. Incineration:

Incineration is a high temperature dry oxidation process that reduces organic and combustible waste to inorganic incombustible matter and results in a very significant reduction of waste volume and weight. The process is suitable for wastes that cannot be recycled, reused or disposed off in a land fill site.



Fig 1. Simplified flow scheme of Incinerator

Waste types not to be incinerated are:

1. pressurized gas containers;
2. large amount of reactive chemical wastes;
3. silver salts and photographic or radiographic wastes;
4. halogenated plastics;
5. waste with mercury or cadmium content such as broken thermometers, used batteries and lead-lined wooden panels;
6. sealed ampules or ampules containing heavy metals



Types of incinerators

Three basic kinds of incineration technology are of interest for treating health-care waste:

1. Double chamber pyrolytic incinerators – to burn infectious health-care waste;
2. Single-chamber furnaces with static;
3. Rotary kilns operating at high temperatures, capable of causing decomposition of genotoxic substances and heat-resistant chemicals.


2. Chemical disinfection:

Chemicals are added to kill or inactivate the pathogens present. This treatment leads to disinfection rather than sterilization. Chemical disinfection is most suitable for treating liquid waste such as blood, urine, stools or hospital sewage. However solid wastes including microbiological culture, sharps etc. may also be disinfected chemically with certain limitations.

3. Wet and Dry Thermal Treatment:

Wet thermal treatment: It is based on exposure of shredded infectious waste to high temperature high pressure and is similar to the autoclave sterilization process. The process is inappropriate for anatomical waste, animal carcasses, chemical and pharmaceutical waste.

Screw-feed technology: It is the basis of a non-burn dry thermal disinfection process in which waste is shredded and heated in a rotating auger. The waste is reduced by 80 per cent in volume and by 20-35 per cent in weight. This process is suitable for treating infectious waste and sharps, but not pathological, cytotoxic or radioactive wastes.

4. Microwave Irradiation:

Most microorganisms are destroyed by the action of microwave of a frequency of about 2450 MHz and a wave length of 12.24 nm. The water contained within the waste is rapidly heated by the microwaves and the infectious components are destroyed by heat conduction.

5. Land Disposal: This method is employed when sufficient waste treatment is not possible. There are two types of disposal – land-open dumps and sanitary landfills. Health-care waste should not be deposited around open dumps so that people or animals will not come in contact with infectious pathogens.


6. Inertization: The process of "inertization" involves mixing waste with cement and other substances before disposal in order to minimize the risk of toxic substances migrating into the surface water or ground water.

   National legislation is the basis for improving health-care waste disposal practices in any country. It establishes legal control and permits the national agency responsible for the disposal to apply pressure for their implementation. The Ministry of Health and the Ministry of Environment may also be involved.

   The United Nations Conference on the Environment and Development (UNCED) in 1992 recommended the following measures;

   1. Prevent and minimize waste production
   2. Reuse or recycle the waste to the extent possible
   3. Treat waste by safe and environmentally sound methods and
   4. Dispose off the final residue by landfill in confined and carefully designed sites.