Treating pathological and anatomical waste

Pathological and anatomical wastes include everything from lab cultures and stocks to donated blood to tissue excised for testing or to remove disease. Anatomical waste is a subtype of pathological waste, being materials that are recognisably human, such as an amputated limb.

Some of this waste, such as placentas from healthy mothers or expired blood may not be infectious, but unless it status is known, it is treated as though it were.

The most appropriate treatment can depend on cultural factors as well as practical ones. For example, in some places it is traditional to bury the placenta in the grounds of the home. Similarly, in some cases an amputated limb may be buried or cremated in the same way as a dead person, and in others it is regarded as waste to be disposed of. These considerations should come first unless there is a risk of disease transmission.

Lab cultures and stocks are the most dangerous of these wastes and should be autoclaved as close to their source as possible, ideally in the microbiology department itself. Tissue digesters can also be used for this and indeed any type of pathological waste, but these are far more expensive and less widely available than autoclaves.

Many low income countries rely on placenta pits to dispose of pathological waste. These rely on a combination of natural chemical and biological decomposition processes. They can be perfectly effective if they are well designed and constructed, but may not be suitable for urban areas, close to water sources or where the groundwater is near to the surface.

Where there is an adequate sewage treatment system- even a well-functioning septic system, it is possible to dispose of some types of pathological waste to sewer. Blood and placentas are the most likely candidates for this route; placentas need to be fed into the sewers through a macerator. These can be autoclaved first as a precautionary measure, but this is not essential provided that proper measures are taken to prevent splashing or aerosolization of infected material.

Finally, biodigestion is a possibility for pathological wastes such as placentas. This technology is widely used for agricultural waste and can be adapted for healthcare settings. As a bonus, this disposal method also generates biogas which can be used as a fuel.

Essential modifications for biodigesters in healthcare settings include making sure that there is a sufficiently long residence time to kill all pathogens and ensuring that the slurry is properly dealt with. More research is needed to establish ideal procedures for this technology. Until then, a residence time of 90-100 days for human materials is recommended. Slurry should not be used as a fertiliser, as is common with agricultural biodigesters. Instead, it can be diverted directly to sewers without any need for further handling.


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