Biological Waste Disposal
Biological agents are assessed before being placed in the appropriate waste stream.
> Departmental responsibilities
> Types of biological waste
> Deactivation and disposal of biological waste
> Disinfectant effectiveness
> Ultraviolet light
The UCL waste streams are managed by Estates who have produced the UCL Clinical Waste Procedures.
All departments must have a hazardous waste plan which ensures waste produced by the department is identified and managed before entered into the waste stream.
Types of biological waste
Biological Waste can include the following:
- Infectious waste - wild type microorganisms or materials containing pathogens
- Genetically Modified Organism waste - the class of the GMO will determine the waste route
- Offensive waste - not infectious and does not contain any pharmaceutical or chemical substances. Examples are sterilised masks, gowns and other PPE or hygiene waste such as nappies
- Plasters and similar waste-dressing from non-infectious wounds (dentistry and fracture clinics) have their own waste stream
- Waste medicines - this depends on the risk posed by the medicine – cytotoxic and cytostatic medicines are separated from other medicines
- Sharp and related waste - depending on the type of contamination
- Anatomical waste - depends on whether the agent is infectious and if it has been chemically preserved
For more information refer to Laboratory waste web page.
Deactivation and Disposal of Waste
There are a range of options available for the inactivation and disposal of biological waste. The main methods used are through chemical disinfection, heat treatment through autoclave and incineration or UV.
Before disposing of biological agents, the following factors need to be considered and assessed:
- The amount of agent
- The medium that the agent is in
- The infectious nature of the agent
- The treatment of the agent before entry into the waste stream
- Any other hazards e.g. toxic chemicals or radiation
Disinfection is not the same as sterilisation and is subject to many variables that may cause failure to adequately decontaminate material. It is best used to reduce the infectious hazard associated with small quantities of liquid or solid waste accumulated during laboratory activities and for the decontamination of surfaces and equipment.
Chemical disinfectants should be selected with regards to the situation in which they will be used, and biological agents may be present. Do not assume all disinfectants will deactivate all microorganisms.
Disinfection procedures should detail suitable concentrations, contact times and applications. For hazard group 3 and Class 3 GMOs disinfectants must be validated for the infectious agent being handled. Where practicable the number of different disinfectants should be restricted to a minimum to avoid mistakes in application.
Disinfection is reliant on the following factors:
- The disinfectant must be able to deactivate the biological agent that needs to be deactivated
- The right concentration needs to be made for disinfectants that have to be made fresh
- Disinfectants need time to be effective always adhere to the disinfection times
Factors that can have a negative effect on the effectiveness of disinfectants:
- Concentration of contaminant
- Concentration of disinfectant
- Type of disinfectant
Disinfectants and effectiveness
This section provides information on the effectiveness of various types of disinfectant and provides information on their hazards, limitations and use.
- Hypochlorites e.g. Presept
The table below shows the effectiveness of the hypochlorite based disinfectants at deactivating microorganisms.
Microorganism Effectiveness Fungi Recommended Vegetive bacteria Recommended Mycobacteria Variable Spores Variable Lipid Viruses Recommended Non lipid viruses Recommended TSEs Recommended
Inactivated by organic matter, corrosive to some metals, may cause damage to rubber, not compatible with cationic detergents. Working solutions need to be changed daily and do not autoclave.
Corrosive in concentrated forms. Irritant in dilute. Releases chlorine gas on contact with acids, releases bis chloromethyl 3 ether, a carcinogen, on contact with formalin or formaldehyde.
1000ppm for general surface disinfection of benches and equipment.
- Peroxygen compounds e.g. Virkon
The table below shows the effectiveness of the peroxygen compound based disinfectants at deactivating microorganisms.
Microorganism Effectiveness Fungi Recommended Vegetive bacteria Recommended Mycobacteria Not Suitable Spores Variable Lipid Viruses Recommended Non lipid viruses Recommended TSEs Not Suitable
Corrosive to some metals, (releases hypochlorous acid), but less than hypochlorite. Can be inactivated by organic matter.
Powder form is an irritant when making up solutions. Harmful if inhaled swallowed or absorbed through the skin or eyes and skin.
Due to its wide spectrum of activity, Virkon is suitable for a wide range of applications in routine bacteriology, virology and cell culture laboratories. The powder can be used to treat spills.
- Accellerated Hydrogen Peroxide (AHP) e.g. Oxivir TB
The table below shows the effectiveness of the peroxygen compound based disinfectants at deactivating microorganisms.
Microorganism Effectiveness Fungi Recommended Vegetive bacteria Recommended Mycobacteria Recommended Spores Variable Lipid Viruses Recommended Non lipid viruses Recommended TSEs Not Suitable
Incompatible with rubber, some plastics, aluminium, copper, zinc, brass. Check product label for incompatibilities.
Do not mix with concentrated bleach products.
Due to wide spectrum of activity, AHP is suitable for a wide range of applications in routine bacteriology, virology and cell culture laboratories. Contact time is typically 1 min, but could be more or less depending on the pathogen, thus check product label. Most products use 0.5% hydrogen peroxide which will break down to water and oxygen. High concentrations are typically needed to be effective against spores
- Alcohol e.g. 70% Ethanol
The table below shows the effectiveness of the alcohol based disinfectants at deactivating microorganisms:
Microorganisms Effectiveness Fungi Variable Vegetive bacteria Recommended Mycobacteria Variable Spores Not suitable Lipid Viruses Recommended Non lipid viruses Not suitable TSEs Not suitable
Poor penetration of organic matter and should only be used on physically clean surfaces.
Flammable, irritant to eyes nose and throat at high airborne concentrations may cause drowsiness or dizziness.
Surface disinfection of clean surface, electrical equipment should be disconnected from the mains before treating.
- Quaternary Amine Compounds e.g. Chemegene HLD4
The table below shows the effectiveness of the Quaternary Amine Compound based disinfectants at deactivating microorganisms:
Microorganisms Effectiveness Fungi Variable Vegetive bacteria Recommended Mycobacteria Not suitable Spores Not suitable Lipid Viruses Recommended Non lipid viruses Variable TSEs Not suitable
Inactivated by protein and some plastics, not compatible with anionic detergents. Inactivated by soaps and organic matter.
Non-toxic, however many are classified as skin, eye, respiratory and GI irritants may degrease skin on prolonged contact. Incompatible with Phenols.
General surface disinfectant, spillages and discard jars. Follow manufactures in instructions for appropriate dilutions.
- Chlorine dioxide e.g Tristel Jet
The table below shows the effectiveness of the chlorine dioxice based disinfectants at deactivating microorganisms:
Microorganisms Effectiveness Fungi Recommended Vegetive bacteria Recommended Mycobacteria Recommended Spores Recommended Lipid Viruses Recommended Non lipid viruses Recommended TSEs Not suitable
Trisel is an aqueous solution of chlorine dioxide and requires activation before use
Not skin or respiratory sensitiser or irritant. Hazards may vary depending on composition, check SDS
Surface disinfection, spills and discard jars where spores or resistant bacteria -e.g. mycobacteria may be present
Autoclaves are used to treat waste to render it non-infectious before transporting to a licenced incinerator. This ensures that infectious waste is safe to transport on the public highway.
Autoclaves work by generating steam at high temperatures such as 121oC under pressure. The steam penetrates the waste to kill any viable pathogens. There can be many different cycles for different agents and for liquid waste as well as solid waste. This is determined by risk assessment. Information should be available on what cycle to run and why, including information on how to load the autoclave to ensure the materials are efficiently autoclaved. People generating waste that needs autoclaving should ensure that steam can penetrate the waste by not sealing autoclave bags and bottles. If the steam cannot penetrate the load, it can not be assured that the waste has been deactivated.
The location of an autoclave will be determined by risk assessment and the level of hazard of the biological agent used. Where higher hazard material is handled the autoclave may be in the laboratory or suite (e.g. in CL3 areas), For lower hazard material the autoclave will be in the building for biological agents in hazard group 2 and Class 2 materials.
Autoclaves are pressure systems and come under the Pressure Safety Systems Regulations (PSSR) which means they are subject to statutory testing. All autoclaves need to be asset registered to ensure they under --autoclaves should undergo a through inspection for insurance as well as validation and calibration by a competent person to ensure autoclaves are safe and effective in their operation. There should be an appointed person for pressure systems who is the first point of contact for new and existing pressure systems, such as autoclaves to ensure they are included in annual statutory testing and have maintenance plans in place.
Validation of an autoclave can be through a 12 point thermocouple test to ensure the autoclave reaches and maintains the temperature of the cycle being validated. Other methods include Bowie Dick and Helix tests provide an indication of steam penetration but doesn't confirm a successfull cycle. However if these tests fail the autoclave should not be used until a competent person has confirmed the autoclave is operational.
Insurance and through inspections information can be found in Crimson, whilst maintainance information can be found in Planet.
Be aware that some material may not be suitable for autoclaving e.g. radioactive material or toxic chemicals
Incinerators are facilities with a constant flame that burns waste and high temperatures to destroy the waste. This waste disposal route is used for low hazard biological waste and is also used to dispose of carcasses. For guidance on the packing of waste for incineration can be found on the Laboratory waste page. Different bags are required for transporting different types of waste off campus.
Incinerators do not need to present in the building, and risk assessments should cover how waste will be packed to travel to the incinerator or what other disposal arrangements are in place. Some licensed incinerators convert waste to power.
Ultraviolet light is a form of non-ionising radiation. Based on wavelength the UV spectrum can be split into 3 different bands UV-A, UV-B and UV-C.
UV-C can be used for germicidal purposes to kill or inactivate microorganisms.
There are a number of factors that influence the effectiveness of UV-C sterilisation.
- Exposure: microorganisms need direct contact with UV-C for kill or inactivation of a microorganism. Dust and dirt can shield microorganisms which means that inactivation is not achieved.
- Temperature: the optimum temperature output of UV-C is 25oC-27oC outside this range the effectiveness is reduced
- Humidity: adversely affects UV. A relative humidity above 70% reduces the germicidal properties of UV.
- Cleanliness of UV light: dust and dirt can block the UV. UV lights should be cleaned weekly
- Age of UV lights: with increasing age the germicidal properties of UV will reduce over time. Periodic monitoring of the UV output will ensure efficiency.
UV light also has health implications. Over-exposure can lead to erythema, photokeratitis and or conjunctivitis. UV exposure is known to increase the risk of developing skin cancer.
Last updated: Tuesday, January 17, 2023
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