Health-care waste treatment technologies included in this database
The products included in this database include disinfection technologies and ancillary equipment such as needle or hub cutters, grinders and shredders. Companies which provide waste treatment services are not included.
Information has been gathered from internet searches, direct contact with companies and literature sources. All suppliers referred to in other sources have been checked and reassessed as part of the process.
- Steam based technologies
- Dry heat technologies
- Chemical based technologies
- Shredders and grinders
- Syringe and needle destroyers
Steam based technologies
Steam-based technologies include autoclaves, microwaves, frictional heating and continuous steam-based treatment. These rely on of steam, either at atmospheric or high pressure, to inactivate pathogens.
Autoclaves are the most commonly used of these technologies and are by far the most numerous in this inventory. These offer several advantages, especially in the low resource environment. Firstly, almost every health care facility already has autoclaves, so their engineers are familiar with them and consequently are able to operate and maintain them more easily than other technologies. In addition, it is easier to find local suppliers who can provide technical support and spare parts at need. Autoclaves are available in many different sizes, applicable to almost every situation.
Many companies offer autoclaves specifically for medical waste, and wherever possible, these are preferred. These are usually vacuum models which pump air out to enhance steam penetration and improve disinfection. Automatic control also helps ensure consistent operation. Autoclaves and other disinfection technologies should be validated at installation to make sure that the chosen operating cycle is satisfactory. Thereafter, routine testing will ensure no deviation from safe operation. The UNDP guidelines for routine challenge testing of medical waste autoclaves, or a similar procedure should be used.
Dry heat technologies
Dry heat technologies, like steam based technologies, operate at temperatures between 100 and 180ºC, though without the agency of steam, dry heat technologies generally operate at higher temperatures than steam technologies. Above 180ºC, chemical alteration and, ultimately, combustion, can occur, creating the hazardous byproducts that the Stockholm Convention exists to eliminate.
Chemical based technologies
Chemical based technologies mostly use chemical disinfectants. These are problematic as they will produce toxic effluents. Many of the disinfectants are proprietary, so it is not possible to understand the impacts they are likely to have on the environment. For this reason, most chemical technologies are excluded from this inventory. Two exceptions are ozone treatment and alkaline hydrolysis.
Ozone is a strong gaseous disinfectant and can be generated on site, avoiding the need to transport and store it. It does have to be handled carefully and workplace exposure prevented as it is harmful, but the ozone molecule consists of three oxygen atoms, and any excess left will rapidly degrade to the more stable molecule, with two atoms, which is the form normally found in the air.
Alkaline hydrolysis uses sodium or alkaline hydroxide at high temperature and pressure to destroy tissues. This can include wastes from the operating theatre or samples from the laboratory as it can also break down the formaldehyde they are often stored in. It is also proven to destroy prion waste. Alkaline hydrolysis produces an effluent with a high pH and high BOD but can be discharged to sewer after neutralisation, subject to the normal consents.
Alkaline hydrolysis is also capable of destroying chemicals such as pharmaceuticals, but more research is needed on this subject.
Shredders and grinders
Shredders and grinders, including vial crushers, are an important support technology. They reduce the volume of waste, make it unrecognisable, and prevent unauthorised reuse. Shredding before disinfection is not recommended because, although it increases the surface area of the waste and can make treatment easier, it can create an aerosol of infectious particles. In addition, should a shredder or grinder break down with infectious material in it, it could represent a hazard for maintenance personnel. Some of the more complex machines incorporate an internal shredder, which can be disinfected as part of the process. Other than that, shredding and grinding should take place after disinfection.
The use of syringe and needle destroyers varies from country to country. They can have safety benefits because around 10-20% of needle stick injuries occur during disposal. They also reduce the amount of space that syringes take up in the container, increasing the efficiency of the process. There are several different types, either electrically or mechanically operated. Hub cutters remove the needle from a syringe and also cut off the tip which prevents the syringe being reused. This is particularly important in some countries, where there is an illicit trade in used medical devices, including syringes, which unscrupulous waste handlers waste and repackage to sell to the unwitting.