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Autoclaving of Medical Waste – An Introduction

Autoclaving is a popular alternative medical waste treatment method in low-income countries. It is done in closed chambers where both heat and pressure are applied over a period of time to destroy all microorganisms that may be present in healthcare waste before landfill disposal. Among alternative systems, autoclaving (also known as steam sterilization) has the lowest capital costs and can be used to process up to 90% of healthcare waste and are easily scaled to meet the needs of any healthcare establishment.

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Autoclaving is an efficient wet thermal disinfection process whereby pressurized steam at a temperature of around 121°C heat infectious wastes without causing air emissions that are characterised by incineration-based processes. Moisture in medical waste increases heat transfer which effectively penetrates the waste load, thus reducing the time needed to achieve disinfection.

The growing popularity of autoclaves in the developing world is because of the fact they are less polluting that incinerators and other high-temperature thermal processes. Volatile and semi-volatile organic compounds, cytotoxic waste, mercury, other hazardous chemical waste, and radioactive waste should not be treated in an autoclave.

Segregation of different medical waste streams is essential to prevent emission of alcohols, phenols, formaldehyde, and other organic compounds in the air which may pose health risks to the autoclave operators, waste workers and hospital staff. The treated waste from an autoclave will retain its physical appearance and shredder or compactor may be used to reduce the volume. Infact, shredding infectious waste before it has been autoclaved increases the surface area exposed to the heat and steam and will lead to more complete disinfection.

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Advanced autoclaves or advanced steam treatment technologies combine steam treatment with vacuuming, internal mixing or fragmentation, internal shredding, drying, and compaction thus leading to as much as 90% volume reduction. Advanced steam systems have higher capital costs than standard autoclaves of the same size. However, rigorous waste segregation is important in steam sterilization in order to exclude hazardous materials and chemicals from the waste stream.

It is to be noted that autoclaves require a reliable source of electricity in order to maintain the pressurization and temperatures necessary to properly disinfect infectious waste.  Nowadays, hybrid or integrated autoclaving technologies are also being used in developing countries to improve heat transfer to waste, achieve more uniform heating of waste, altering the physical appearance of medical waste, and making autoclaving a continuous process.

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