Disposal refers to the long-term placement of waste or treated waste. It is almost always off-site - away from where the waste is generated - and usually involves burial underground. We do not classify putting waste in storage containers on site as a form of disposal.

Validating sterilization

How do you know if the treated waste is safe for disposal? Sterilization is a process where all living microbes are destroyed, removed or inactivated.

waste disposal Heat treatment processes often use a "time and temperature" criteria. These rest on laboratory validation of the effectiveness of the treatment. In the validation process samples of waste are subjected to a temperature for a given time (and sometimes with a certain oxygen content in the atmosphere.) If analysis of the samples treated in the laboratory this way shows it is safe for disposal, the operating conditions – residence time and temperature – regulators write these conditions into the operating permit and the conditions become a target for the operators of the treatment.

The second and more rigorous treatment validation is the spore test.

Spore Tests

Biological indicators are preparations of specific microorganisms (usually bacteria) that have a known survival/die response to a sterilization processes. These indicators are used to determine the level of performance of sterilization equipment and to establish sterilization has likely occurred.

Biological indicators can be used to ensure that products are sterile in their final containers. They also are employed to ensure the sterilization of materials and equipment that are used in aseptic processing. They can also be used as a means of evaluating autoclave sterilization cycles and the quality of processes employed to decontaminate aseptic clean-room environments or isolators.

Spore-forming bacteria are the microbes most often used as biological indicators, as these microorganisms are hardier and resist sterilization better than most microflora. One form of biological indicator involves addition of spores to a carrier; a package encompasses the carrier to maintain shape. Another form is a biological indicator that includes a spore suspension inoculated into or on a representative unit of the material that is meant to be sterilized.

Waste management engineers employ the concept of a process challenge device (PCD). These devices are designed to be a stand-in for a larger sterilization system. The PCD is a small and disposable device that acts as a canary in a coal mine. It is overly sensitive. If the PCD shows microorganisms can survive, it means the larger unit may not be up to snuff.

PCDs are placed in the sterilizers in the place that provides the greatest challenge to sterilant penetration. PCDs play an important role in the monitoring of sterilization processes. When spores are killed in a test pack that corresponds to the greatest challenge to the process, it can be inferred that the other items in the load were likely sterilized.

Monitoring spore strips are typically sold in packs. The price for a pack of 100 spore strips is usually between $200-$600. The size of a spore strip also varies, typically ranging between 4 and 8 inches.

Biological indicators are currently the most effective way of assessing whether an environment is sterile or not. It is likely that in the near future enzyme indicators will replace biological indicators, as they are thought to provide a higher level of accuracy.

More on sterilization.

Sanitary landfills

Sanitary landfills are a staple of the waste disposal system in the United States and many countries. The idea is that the waste will stay in the landfill and hence not harm the environment until it has degraded to a sufficient level that it is safe. The engineering of these landfills is pretty well worked out now. A plastic liner or liners underlies the waste. Waste is deposited in layers and soil from the local area is put on top of the waste. Then another layer of waste goes on top of the soil and another layer of soil on top of that. Different landfill designs employ different numbers of layers. The shape of the deposit discourages waste and leachate from migrating away from the landfill. The plastic liner and configuration of the layers provides "hydrogeological isolation," so leachate (water that has flowed through the waste) does not enter the aquifer and general groundwater in the area.

Most sanitary landfills also have on-site staff, vertical vents to prevent build-up off off-gas, and monitoring of air emissions. We have another page on landfills for disposal of medical waste.

Recycling medical waste into compost or fertilizer

conpost synbolMunicipalities across the country have embraced recycling programs and some even have city-run composting services, which pick up compostable material from residences. Regulated medical waste (e.g. infectious or biohazardous waste) is not recycled or composted and there is no movement to start doing so. This type of waste is a small fraction of society’s overall waste stream and the protocols needed to ensure safety have not been developed and probably will not be developed. There is little economic reason to recycle or compost biohazardous waste.

However, the carcasses of dead animals are often disposed of alkaline hydrolysis, and the result of that process can be used as fertilizer,

Also, large facilities like hospitals can and do institute compost collection programs for non-hazardous, non-regulated waste, such as waste from kitchens.

Procedures for disposing of dead animals.

Treatment of Pharmaceutical Waste