Medical Waste Disposal at
Provincial Hospitals – Western Cape
A new environmentally friendly
medical waste management strategy
CESAR ALEXANDRE
CHIEF ENGINEER
PROVINCIAL ADMINISTRATION WESTERN CAPE - DEPARTMENT OF HEALTH
ABOUT THE SPEAKER
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Mr C S Alexandre has a Masters Degree in Technology and Business Administration, M.Tech.BA.
He is a lecturer of “Project Management”, for the Masters Degree in Technology & Business
Admin., Public Management & Marketing Courses (M.Tech.BA, M.Tech.PM, M.Tech.Marketing),
& lecturer & founder of a “Project Management” course plus an “Advanced Project Management”
course, for the Centre for Continuing Education & the faculty of Business Informatics with the
Cape Technikon.
He is also a founder & lecturer of Project Management for the Cape Administrative Academy. In
December 2002 he was awarded a “Certificate of Excellence” for his outstanding contribution to
the promotion of Project Management training within the Provincial Dept. of the Western Cape.
Mr C Alexandre has previously worked for Mobil Oil Corporation and has more than 30 years
experience in Engineering, Operations, and Project Management.
ABSTRACT
Medical waste consists of all waste produced by hospitals, clinics, physicians offices, dentists offices,
funeral homes, veterinary clinics and medical and research laboratories.
Although many medical and veterinary institutions practice “universal precaution”, which means that
all materials that have come into contact with any type of body fluid are considered to be infected
WORLD HEALTH ORGANISATION, Infection Control Guidelines, indicate the most hospital waste is
no more infective than residential waste and that hospital waste disposal practices have not caused
disease in the community.
One cannot assume that all waste from a health care facility poses a risk. Currently only between 10
and 15% of medical waste is considered infectious.
Most material considered bio hazardous falls primarily into three categories: contaminated laundry,
hard and soft wastes (‘sharps’ and bandage materials), and diagnostic specimens.
The word ‘infectious’ and ‘pathological’ imply a degree of hazard and may cause unnecessary alarm,
as they are also used to describe material, which is neither human nor animal tissue.
As the SABS proposed code of practice says, in many guidelines, all waste contaminated with blood
or body fluids are classified as infectious waste.
This enormously increases the volume of waste requiring expensive handling and disposal.
Identical items of waste are disposed of from homes with no special handling or decontamination.
The identification of every patient who carries a blood borne pathogen such as Hepatitis B or Human
Immunodeficiency Virus, is both impractical and inappropriate.
The modern trend in hospital infection control is to build safe practices into all clinical procedures, the
precaution taken is dictated by the risk accompanying the procedure, not by the diagnosis.
The purpose of the paper is to analyse the nature of medical waste and its safe Handling,
(segregation, packaging, in-house transport, storage), Treatment and Disposal, as well as the new
environmentally friendly medical waste processing technology used by the Department of health,
Western Cape, which is the first in Africa and one of the most advanced technologies in the world.
Alex/Medical Waste Conference
05/2003
MEDICAL WASTE DISPOSAL AT PROVINCIAL HOSPITALS – WESTERN CAPE
A NEW ENVIRONMENTALLY FRIENDLY
MEDICAL WASTE MANAGEMENT STRATEGY
1. INTRODUCTION
Recent media attention has increased the public’s apprehension that medical wastes are not
properly controlled. The appearance of AIDS and the prospect of AIDS-contaminated medical
waste washing up on public beaches have compounded this fear, so that panic can be created by
the mere mention of the words “infectious waste” of “hospital waste”.
Is this fear justified: Certain medical wastes are more dangerous than any of the thousands of
hazardous substances disposed of by homes and industries. How are medical wastes defined?
Are all medical wastes infectious or hazardous? How are hazardous medical wastes identified,
stored, treated, and disposed of? Which medical waste management practices will ensure that
waste haulers and handlers will be protected and that the general public will not be exposed to
any risk?
The late 1980’s have witnessed a reorientating of official European Community (EC)
environmental protection policies, paralleling a deepening sense of public concern over the future
prospects for a sustainable economy and environment. Our economy and our environment are
fundamentally interrelated with nature imposing physical constraints on human production and
consumption activities. Put simply, when materials and energy are “used up” during the making
and consuming of goods and services nothing disappears, rather, everything given enough time
reappears somewhere in the environment. Unfortunately, the “useful” materials and energy that
were initially sucked into the economy are pushed out over time (to the air, water and land) as
relatively “useless” wastes of one type or another.
This large and increasing mass of redundant goods, by-products and a variety of residues must
be disposed of somehow and at a cost. The environment has a large waste assimilation
capacity, but this is not infinite. Too much waste of the wrong sort dumped without appropriate
precautions will generate significant and long pollution damage costs, including human health.
Defining hazardous waste categories to formulate rational waste management policies is an
uncertain and complex exercise. Some sources argue that the toxicity of pollution from MSW
landfill sites is indistinguishable from that of hazardous industrial waste sites. Although the
proportion of MSW that is hazardous is small, it still represents a substantial problem because of
the large volume involved.
Historically, most wastes of all categories have been disposed of via landfill sites. Only a small
percentage of waste is incinerated and an even smaller amount is incinerated at facilities with an
energy recovery capability. There is a legacy of abandoned and operational landfills containing a
variety of wastes whose exact composition is often unknown. Standards of operation,
maintenance and monitoring have been and continue to be variable; many sites probably pose
significant environmental risks. The financial costs of landfill disposal continue to be relatively
low, representing an under-pricing of the waste assimilating capacity service of the environment.
The full economic price for landfill (encompassing all relevant costs such as, for example, pretreatment and proper pollution containment measures) is much higher.
2. THE PURPOSE OF THE PAPER
The purpose of the paper is to analyse the nature of medical waste and its safe Handling,
(segregation, packaging, in-house transport, storage), Treatment and Disposal, as well as the
new environmentally friendly medical waste processing technology used by the Department of
Health, Western Cape, which is the first in Africa and one of the most advanced technologies in
the world.
3. NATURE OF MEDICAL WASTE
Medical waste consists of all waste produced by hospitals, clinics, physicians offices, dentists
offices, funeral homes, veterinary clinics and medical and research laboratories.
Although many medical and veterinary institutions practice “universal precaution”, which means
that all materials that have come into contact with any type of body fluid are considered to be
infected WORLD HEALTH ORGANISATION, Infection Control Guidelines, indicate the most
hospital waste is no more infective than residential waste and that hospital waste disposal
practices have not caused disease in the community.
One cannot assume that all waste from a health care facility poses a risk. Currently only
between 10 and 15% of medical waste is considered infectious.
Most material considered bio hazardous falls primarily into three categories: contaminated
laundry, hard and soft wastes (‘sharps’ and bandage materials), and diagnostic specimens.
The word ‘infectious’ and ‘pathological’ imply a degree of hazard and may cause unnecessary
alarm, as they are also used to describe material, which is neither human nor animal tissue.
As the SABS proposed code of practice says, in many guidelines, all waste contaminated with
blood or body fluids are classified as infectious waste.
This enormously increases the volume of waste requiring expensive handling and disposal.
Identical items of waste are disposed of from homes with no special handling or decontamination.
The identification of every patient who carries a blood borne pathogen such as Hepatitis B or
Human Immunodeficiency Virus is both impractical and inappropriate.
The modern trend in hospital infection control is to build safe practices into all clinical procedures,
the precaution taken is dictated by the risk accompanying the procedure, not by the diagnosis.
The simple presence of viable organisms does not constitute a hazard; a mechanism by which
these organisms can infect a host must coexist.
Since Hepatitis B and HIV are usually transmitted by inoculation the concern with blood alone, for
example, is misplaced.
The emphasis should more appropriately be applied to the category of clinical sharps.
Infections acquired by waste handlers are rare but almost always associated with trauma.
High priority should be toward the precaution of these injuries.
The incidence of both the wounds and accompanying infections can be reduced dramatically by
adherence to safe procedures.
Absolute elimination of all risks is impossible. A realistic goal is a reasonable degree of safety at
all times without compromising efficiency.
The safe and effective management of medical waste depends on appropriate segregation,
packaging, in-house transport, and storage procedures, and finally treatment and disposal.
Of course such appropriateness can only be achieved by all healthcare facilities having a
documented policy and procedures and the staff is properly trained.
4. EXAMPLES OF HEALTH CARE RISK WASTE
The Health Care Waste (HCW) is divided into Health Care General Waste (GCGW) and Health
Care Risk Waste (HCRW) (Medical Waste).
The purpose of HCRW management is the elimination or minimisation of the negative impact of
medical waste on humans, animals and environment.
*
The Health Care General Waste (HCGW) is the non-hazardous component of the HCWM. It
is generated during the administrative and housekeeping functions of health care facilities and
includes a number of recyclable materials.
Health Care Waste (HCW)
Health Care Risk Waste
(HCRW)
Health Care General
Waste (HCGW) *
Infectious waste:
All kinds of waste that is likely to contain pathogenic
microorganisms.
Pathological waste:
Includes parts that are sectioned from a body (Human
Anatomical Waste).
Sharps:
Includes sharp and pricking objects that may cause injury
as well as infection.
Chemical & pharmaceutical waste:
Includes all kinds of discarded chemicals, including
pharmaceuticals.
Radioactive waste:
This includes solid, liquid and gaseous waste
contaminated with radionuclides.
Cytotoxic waste:
Waste containing substances with genotoxic (affecting
genes) properties including drugs often used in cancer.
5. TREATMENT AND DISPOSAL
Disposal in a landfill site is a common method, and is appropriate for many varieties of medical
waste. (Infectious non-anatomical waste) (WHO, World Health Organisation)
If some infectious material is present in the waste transported to the landfill, the concentration of
pathogens is reduced by soil filtration. An organism passing further into the soil bed is denied the
nutrients, oxygen and other conditions necessary for survival. Certain techniques may reduce
exposure to infectious wastes. The most effective of these procedures are the segregation of
infectious loads from other loads, the visual inspection of infectious waste and the avoidance of
the direct handling of open bags, the immediate burial of infectious waste so that it is not directly
compacted on the landfill surface, and the proper personnel protective equipment by use of
employees who work on the face of the landfill.
The only special requirement for the disposal of infectious wastes in a landfill is that the wastes be
rendered unrecognisable for aesthetic reasons.
The sanitary sewer system is a safe and acceptable method of disposal for untreated bulk blood,
suctioned fluids excretions, secretions, and other infectious wastes that can be ground and
flushed into the sewer. Grinding and sewering of wastes constitutes immediate removal of the
infectious waste, eliminating storage, transport and handling costs. This method is not advised,
however, because vapours can be produced and sewer lines may become clogged. The sewer
system is designed to attenuate sewage and is, therefore, effective in attenuating infectious
agents found in blood and other body fluids. This disposal practice is allowed because sewage is
normally an infectious material. When wastes are treated in this manner, the waste should be
poured carefully to eliminate spills and the formation of vapours. The municipal sewerage
treatment system should have secondary treatment available, and the practice should meet with
the approval of all applicable local sewerage bylaws.
Incineration has traditionally been the principal method used by healthcare facilities to dispose of
anatomical and infectious non-anatomical wastes.
Over the last decade, the industry has seen a number of new medical waste processing
technologies enter the market.
Everything from micro waving to vacuum pyrolysis to steam treatment to plasma arching.
The reason for the plethor of new technologies is a result of an ever-increasing trend by countries
to phase out the use of incineration.
While incineration had been the standard of medical waste processing technology, countries are
becoming increasingly aware of the detrimental effects of incineration to stakeholders and the
environment. (Green peace recently released a report, “Incineration and Health”, that links
incineration to cancer.)
The issue with incinerators is emissions. Burning waste does not make it disappear. Depending
on the type of waste, up to 100 chemicals can be emitted into the atmosphere.
One of the common emissions from incinerators is dioxins, the toxic component of “Agent
Orange”, which was used during the Vietnam War.
Dioxins are carcinogenic, depress the immune system, and disrupt the reproductive and hormonal
systems.
Because of its effects on human health and the environment, dioxin is one of the 12 persistent
organic pollutants “Pops” that have been prioritised for immediate action under the global Pops
convention, to which South Africa is a signatories.
The Stockholm convention names incinerators as contributors to the formation of new Pops.
Medical and chemical waste incinerators are one of the largest causes of dioxin emissions.
In addition, South Africa, intends to be on the forefront in meeting the objectives set in Rio, in the
Kyoto Protocol and more recently in the United Nations Conference on Sustainable Development,
in Durban, South Africa.
The mission of any medical waste treatment technology should be three fold:
1. Render the material non-infectious and the processed waste 100% recyclable.
2. Render the material unrecognisable/un-reusable.
3. Be environmentally friendly.
Preventing circumstances in the industry, dictates that the problem of medical waste is dealt with
as a matter of collection, incineration and post incineration disposal.
However, it should address the entire spectrum from point of generation to final disposal, all within
an infectious control paradigm.
This means that the system should provide maximum security against nosocomial risks and
provide maximum safety to the health care worker, from clinician to janitor, and comprehensive intraining is provided to ensure correct use of the system, guarantees safety for the communities
and ensures zero negative environmental interfaces, i.e. be environmentally friendly.
6. WASTE MANAGEMENT SYSTEMS VS ENVIRONMENTAL HEALTH RISKS
An effective system will have to integrate waste minimisation, recycling, processing, transport and
final disposal activities.
Waste recycling is not a magic panacea for the waste generation/disposal conundrum.
Speculation about complete recycling communities and societies is both scientifically and
economically illiterate. Recycling is not an end in itself, it should not be carried out if there is no
net environmental gain – when more fuel and material usage and more pollution occur through reuse than would have occurred if new products ware made with virgin resources.
Present management systems are still largely based on a “dispose, dilute and disperse”
approach.
All the indications are that a fundamental philosophical switch is required towards a “recycle,
concentrate and contain” approach. Landfill disposal will remain an important component of the
new strategy. However, the landfill of the future will be a more costly and amore “engineered” set
of operations (in order, for example, to contain pollution on-site and recover methane gas) than it
has been in the past. The long-term objective of the overall system should not therefore be
simply the maximisation of waste recycling. What is required, and will be costly and difficult to
achieve, is a reliable, relatively low environmental risk, socially acceptable, mixed bout integrated
waste treatment, recovery and disposal system. To coil a phrase, identifying the “best practicable
environment option” for elements of the system, and more ambitiously the system itself, is the
ultimate long-term challenge for sustainable economy and society.
Given the nature of our economic system & its technological bias, it is the case that we cannot
expect to accept the material benefits of this system and enjoy zero-environmental risk founded in
zero exposure to pollution. Some sort of risk-benefit balancing process is required, in which
“acceptable” trade-offs between risk levels and the costs of reducing exposures are struck.
Environmental health risks, natural or of human origin, are an ever-present feature of human life.
As economies have industrialised, the nature of these risks has changed from past concerns over
infectious diseases, through more recent chemical and radiation exposures in the workplace, to
current worries over “environmental” (non-occupational) toxic exposures. This shift in public
health focus has inevitably meant a shift in concern away from acute illness arising promptly after
relatively high doses of toxic exposure, towards concern for delayed (perhaps years later) health
effects resulting from low dose exposure. Risk assessment (typical of hazardous waste facilities)
with respect to this latter situation can be quite an ambiguous process and will not produce the
precise answers that society seems to demand.
Waste disposal facilities in particular have suffered from the NIMBY (non in my backyard)
syndrome, with health risk perception usually at the centre of people’s concern. But why is it that
people perceive the health risks to be unacceptable when formal analysis does not confirm these
perceptions? Experts tend to use the “relative-risk” approach – the risk posed by toxic chemical
exposure from a waste site versus risks like smoking, alcoholism, poor diet, traffic accidents. On
this basis the medical waste hazard can be shown to be a relatively low risk.
Individuals, however, continue to see risks as absolutes & often involuntary, perhaps because of
misinformation & misperception. There is on the other hand a psychosocial basis for the NIMBY
syndrome. Waste facilities defined as hazardous are inherently stigmatised & therefore classed
as undesirable. Deeper and wider social concerns may also underlie local opposition, including
invasion of homelife and territory, loss of personal control, stress and lifestyle infringement, loss of
trust in public agencies and lack of accountability of the “system”. Here the waste site is merely
the catalyst of unlocking concerns about trends in society in general.
7. MEDICAL WASTE HANDLING
The safe and effective handling of medical wastes depends on appropriate segregation,
packaging, in-house transport, and storage procedures.
7.1 SEGREGATION
Health care facilities daily produce large amounts of waste, but only a small volume (about
15 %) could be considered medical waste. The medical waste must be separated from the
general waste stream to prevent the entire volume of waste from being subjected to special
treatment and handling.
Subjecting small volumes of medical waste to special treatment and disposal is more
economical than intermixing the medical waste with general refuse and treating the total
volume. Waste segregation consists of placing waste materials in their proper containers and
relies on the individual who produces the waste to separate it at the point of
generation.
Persons who are responsible for the handling and disposal of wastes are the best qualified to
decide if the waste is infectious, must be a recognised physician, veterinarian, genetic
engineer, microbiologist, nurse or laboratory technician within a health care or other facility.
The facility and regulatory bodies depend on this trained and qualified person to identify
infectious material.
7.2 PACKAGING
Proper packaging is vital to breaking the chain of events leading to disease transmission. If
the packaging of the waste is efficient, infectious agents do not have a mode of escape &,
therefore, have no access to a susceptible host. The integrity of the packaging must be
maintained throughout handling, storage, transport and treatment.
The selection of a particular type of packaging should be determined by evaluating the type of
waste being contained, appropriate colour coding alerts waste handlers to the type of waste
being handled and ensures that specific waste types undergo proper disposal.
7.3 IN-HOUSE TRANSPORT
From the point of generation, wastes are generally moved within the facility to either
intermediate or final storage areas to await disposal. While wastes are being moved, certain
practices should be followed to prevent unnecessary occupational exposures and to prevent
cross-contamination.
When loaded carts are moved through the facility, specific routes must be planned to
minimise their passage through patient care areas and other clean areas.
During the movement of hazardous materials, spills do occur despite precautionary efforts.
Faulty transfer techniques can cause minor spills involving the loss or vaporisation of small
volumes of materials, while major spills or accidents involve container rupture caused by
equipment malfunction or careless handling. The most important elements in a major spill are
common sense and a carefully prepared, well-rehearsed contingency plan. All health care
facilities must have a documented policy and procedure for managing the spill of
hazardous substances.
7.4 STORAGE
The wastes held in intermediate or final storage areas awaiting on-site disposal or transport to
the disposal site must be totally enclosed, stored away from supply rooms or food preparation
areas in an area which can be locked, and have access restricted to authorised personnel.
These requirements minimise the possibility of cross contamination between “clean” and
“dirty” areas of the facility, and restrict the accessibility of storage areas to a limited number of
staff members. Anatomical wastes should be stored no longer than one week. Although no
maximum storage time has been designated for infectious wastes, one week would be a
prudent time limit. Health care facilities should prepare a contingency plan for storage of
refrigerated waste in the event that excess wastes are produced;
incineration or
refrigeration/freezing facilities become inoperative.
8. WASTE MANAGEMENT FAILURES
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Poor segregation of waste
We have found that up to 80% of “infectious waste” consisted of cans and bottles of cool
drinks, magazines, food, CSSD sterilized paper, and other general waste.
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No clear understanding of “medical waste” and that, actually only between 10 and 15 per
cent of medical waste is considered infectious.
The words “infectious”, “pathological” and “biomedical” imply a degree of hazard and may
cause unnecessary alarm, as they are also used to describe material which is neither human
nor animal tissue.
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“Cradle to grave” protocols not available.
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No policy and procedure regarding requisitioning or rotation of stock to prevent
overstocking and lapsed expiry dates of consumables and pharmaceuticals.
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Education of the staff and public is not getting through.
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Collection of waste from the various areas is not always satisfactory.
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Lack of continuity due to rotation of staff and leave.
9. REASONS FOR WASTE MANAGEMENT FAILURES
9.1 Institutional management failure to implement:
9.1.1 Structured orientation and induction / in service education programmes that include
waste management for all categories of staff.
9.1.2 Standardised policies and procedures to prevent overstocking and lapsed expiry
dates of consumables and pharmaceuticals.
9.1.3 Clear directives related to waste minimisation and management of waste. Those to
include the monitoring of volume generated and the financial implications for each
waste stream.
9.2 Institutional management failure to enforce strict discipline and accountability for the
proper segregation of waste at the point of origin.
Half of the total expenditure on medical waste disposal, could be saved in this way.
10. RECOMMENDATIONS TO MINIMISE WASTE MANAGEMENT FAILURES
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Consumables and pharmaceuticals to prevent overstocking and lapsed expiry dates.
Minimum and maximum stock levels must be set in each section; requisitions for additional
stock should be based on these levels; expiry dates should be checked when new stock is
received; there must be a system for checking expiry dates of existing stock at required
intervals; and there must be a standardised system for the rotation of stock. There is no
policy and procedure to guide the staff related to this.
Prevention of littering. A considerable number of hours are spent on picking up litter. There
must be an adequate number of bins available for general waste, with clear signs to indicate
their position.
Plastic and other waste for recycling should separate plastic and paper for recycling and
should no longer be sent for incineration or to the landfill sites.
Strategies to improve the existing practice related to paper, cardboard and tins as many of the
staff were not aware of existing protocols.
A protocol for dealing with mercury spills should be developed and the staff educated to
become aware of the dangers and the correct method of dealing with this.
A senior member of staff at the hospital must take responsibility for ensuring that the
monitoring and reporting for each of the waste streams is completed each month.
11. CYTOTOXIC and RADIOACTIVE WASTE
Cytotoxies are highly hazardous. When using incineration, full destruction of cytotoxic
substances can only be achieved at temperatures exceeding 1,100°C. Two stage incinerators,
Pyrolytic incinerators, Retorts and Plasma furnaces with second stage or after burner temperature
of > 1,100°C and two-second-residence time are recommended.
Radioactive waste should be managed at source, separated from HCRW and not sent to the
HCRW treatment facilities. Small quantities of low-level radioactive infections waste could be
sent to Pyrolitic incinerators and Plasma furnaces.
12. HCRW TREATMENT TECHNOLOGIES
The treatment technologies more commonly used are:
 Incineration
 Chemical treatment
 Microwave treatment
 Plasma Arc
 Steam based thermal treatment
INCINERATION TECHNOLOGY
Incineration of HCRW is widely used worldwide. Incineration has been the preferred means of
treating and disposing of medical waste in South Africa. In first world countries alternative
technologies have been introduced in a drive to move away from incineration. Incineration is the
burning of waste in temperatures ranging from 800 to 1200°C. Earlier incinerators used a single
combustion chamber where HCRW is burned at temperature of between 800 and 1100°C under
high excess air conditions. This type of incinerator does not comply with current legislation.
More modern incinerators use two-stage combustion of HCRW and are supplied with gas cleanup systems. In the first chamber HCRW is pyrolysed under reducing conditions & temperatures
between 800 and 900°C. Gases from the first chamber pass into a second chamber where
incombustibles are burnt at temperatures of 1100-1200°C resulting in the formation of mainly
carbon dioxide and water. Ash produced from the incineration of HCRW is regarded as
hazardous and can be disposed into a permitted site unless the ash is de-classified.
CHEMICAL TREATMENT
Destruction of pathogens or disinfection of HCRW can be achieved by chemical treatment of
waste using chemical agents such as chlorine, formaldehyde, ethylene oxide, propylene, etc.
Waste is commonly shredded to increase exposure to the reactant. Waste is placed into a vessel
and sealed. For more effective action of the chemical reagent vacuum is drawn before pumping
the chemical into the vessel. These chemical reagents are commonly applied in their gaseous
chemicals are neutralized, filtered or scrubbed before emitted to atmosphere. Storage and
handling of chemicals by operating staff requires training and care. Chemical disinfection of
HCRW is often not as effective at killing microorganisms however; it may be an appropriate
treatment option for rural clinics with small HCRW generators. Anatomical waste and hazardous
chemical waste are not recommended for chemical treatment.
MICROWAVE TECHNOLOGY
The use of microwave energy for the destruction of HCRW is marketed as an alternative
technology to incineration. The US Occupational Safety and Health Administration (OSHA)
regard microwave energy as a non-ionizing radiation. Microwave generators emit below
10mW/cm2 of energy at a frequency of 2450 MHz. It is important not to compare the exposure
from X Ray machines with microwave generators. X-Ray machines produce ionising radiation
and can destroy human tissue operating at frequencies of 10,000GHz.
PLASMA ARC TECHNOLOGY
Plasma art technology is widely used in the metallurgical smelting industry. NASA also used it for
testing heat shields that protect space vehicles on re-entry. Plasma arc torches can produce
temperatures of between 8,000 and 20,000°C. The high temperatures in the plasma arc break
down waste or molecular structures to their elemental components. Organic compounds are
converted to fuel gas, primarily hydrogen and carbon monoxide.
Electrical energy is used to generate the plasma arc. Finely divided material is fed with the
plasma gas or through a different port into the arc. Organic materials are vaporised. Inorganic
material and metals are melted together into a molten bath, which produces lava-like chunks of
rock when cooled. The plasma process is endothermic (heat is absorbed) whereas incineration is
an exothermic reaction (heat is released). Oxygen is not directly required but it is usually
introduced in a controlled fashion to enable the production of fuel gas. By-products created in the
treatment process include:
 Solid residue – a slag that is inert and can be disposed in a conventional landfill,
 A gas stream consisting of basic molecular components.
The gas from the plasma process has to go through an environmental gas clean-up (ECG)
system to remove particulates, heavy metals, organics and other pollutants.
STEAM BASED THERMAL TREATMENT
Incineration has long been the preferred disposal method of medical waste in South Africa,
besides dumping it!!! But concerns about emission, the composition of the resulting ash and its
subsequent disposal (ash produced is regarded as hazardous and can only be disposed into a
permitted site unless the ash is de-classified, has prompted the development of cleaner, more
environmentally friendly alternatives. Such alternatives are in line with the International
Conference on Sustainable Development (UN Congress) in Durban last year.
In the Steam Based Thermal Treatment steam is used as a sterilising agent that renders HCRW
sterile to the level of a 6 log10 kill (99.9999%). The term “kill” means microbial inactivation.
Log10 kill is defined as the difference between the logarithms of number of viable test micro
organisms before and after treatment. A log10 kill of 6 is equivalent to a millionth (0.000001)
survival probability in a population or a 99.9999% reduction of the population. It is common in
steam-based technologies to shred the waste before treatment. In most recent applications
waste is shredded either during or after sterilization making the waste unrecognizable.
Steam sterilization temperatures are maintained at 95 and 150C. Increasing the temperature of
the waste to above 100C causes dehydration of the waste and a dry product. The dry, sterilised
waste leaving the sterilizer can be disposed in a normal landfill site after de-classification. In
some European countries the sterilized product is accepted at normal landfill sites without further
testing.
A common steam sterilizer is an autoclave where high temperature and pressure are used to
destroy microorganisms. Hospitals use autoclaves to sterilise instruments before and after use.
Steam under a pressure of 1 to 4 bar and temperatures of 120 to 150C is applied in a pressure
vessel to render HCRW sterile to the level of a 6-log10 kill (99.9999%).
One of the new technologies based on the Steam Thermal Treatment is the so-called ETD,
Electro Thermal Deactivation.
This process uses low frequency radio waves and an imposed high-energy field to inactivate
medical waste and destroy pathogens such as viruses, vegetative bacteria, fungi, yeast and
spores, without combusting the waste. The processed waste, with a microbial level reduced by 6
logs, can than be recycled.
The Electro Thermal De-activation process (ETD) converts the HCRW into treated
decontaminated solid waste. This process involves the pre-shredding of the waste, addition of
water, compaction of the waste and exposure to a low frequency oscillating electric field (RF unit).
The electrical energy is transferred to the waste fragments and water, which rapidly heat to
temperatures of 95 to 100C. Sterilisation of the waste occurs in the presence of steam and due
to the biological destruction caused by the 10MHz field at 50,000 volts/m. Sterilisation of the
waste takes place in an insulated fully enclosed tube offering waste a two-hour residence time.
The treated waste is cooled and compacted before disposal to a landfill site.
The entire waste shredding and sterilization process operates under vacuum. Gas drown through
the process is filtered before discharged to atmosphere. This process generates no liquid
effluent. Operating ETD plants can process up to 50 tons per day HCRW.
ETD is most effective on materials that contain polar molecules such as water, which is the major
component of microorganisms, including all human pathogens. Polar molecules have an
asymmetric electronic structure and tend to align themselves with an imposed electric field.
When the polarity of the applied field changes rapidly, the molecules try to keep pace with the
alternating field direction, thus vibrating and in the process dissipating energy as heat. The
electric field created by ETD causes high molecular agitation and thus rapidly creates high
temperatures within the microbial cell. This causes the microbial cell to rupture and die.
All of the molecules exposed to the filed are agitated simultaneously and, accordingly, heat is
produced evenly throughout the waste, instead of being imposed from the surface as in
conventional heating. This phenomenon, called volumetric heating, transfers energy directly to
the waste, resulting in uniform heating throughout the material and eliminating the inherent
inefficiency of first transferring heat from an external source to the surface of the waste and then
to the interior.
ETD uses a radio frequency that maximises the inactivation of the physical medical waste,
enabling the treatment process to kill pathogens while maintaining the temperature of the rest of
the waste below 95°C.
From the collection point, the container contents are discharged into the processing system by
automatic handling equipment, after which the containers are placed on a separate conveyor
where they are washed with detergents, disinfected and dried before being returned to service.
In the processing system, a heavy-duty size-reduction mill crushes and shreds the waste into
small particles of a relatively uniform size, which are deposited on to a sealed conveyor and
transported to the ETD. Here, the ground-up waste material and fines are mixed with a small
amount of water, compressed and extruded into the ETD tube.
The waste is then processed by the selective absorption of energy, dipolar rotation of liquid
molecules and an imposed high-energy field.
Since the ETD technology emits no pathogenic solid material, liquids or air particles, a steam of
safe solids are processed with no environmental degradation of any kind.
In the compacting room, the treated waste is delivered into a standard compactor box, reducing
the volume by as much as 85%.
The material can now either be disposed of at a general landfill site or, whenever possible
recycled.
13. CONCLUSION
Facilities that generate medical waste have a responsibility to protect their employees, waste
handlers and disposal personnel, and the general public from the potential health risks of
hazardous waste. In order to take appropriate precautions, health care facilities and other
generators of medical waste should develop and implement a medical waste management
strategy.
The properly segregated, packaged and identified waste should be safely transported within the
facility to a secure storage area. The in-house transport policy should be carefully designed to
prevent cross-contamination, unnecessary occupational or public exposure, contamination of
clean areas, spills, ruptures or other accidents. An important element of the strategy should be a
carefully prepared and well-understood contingency plan for inadvertent accidents.
Medical wastes must be properly stored in a safe, secure area to avoid contamination of public
areas before being safely removed to a final disposal facility. The medical waste management
strategy should specify alternative treatment techniques for types of infectious waste requiring
decontamination, and guidelines for the most appropriate disposal methods for each type of
medical waste or waste residue produced by the facility.
The strategy should be effectively implemented, but must not become a static, rigid policy.
Variance in the medical wastes being produced, technological changes in waste handling
equipment, regulatory guidelines, and public opinion will require frequent changes in medical
waste management strategies.
Current medical waste management practices may be improved by implementing several
precautionary measures. Occupational health and safety programmes should be developed to
protect health care workers by providing information, instruction and supervision to workers who
come into contact with medical wastes. The handling and transport of dangerous goods by a
commercial carrier should be careful and diligent, using precautions designed to protect the
employees of the carrier, the general public, and the waste disposal site. The government should
define the term “medical waste” to allow accurate figures to be reported; currently, every facility
creates its own definition or interpretation of the term.
If effective medical waste management strategies are developed and implemented by all medical
waste generators, and if precautionary action is undertaken now, medical waste will not endanger
public health or the environment in the future.
REFERENCES
1.
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3.
4.
5.
6.
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8.
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Office of Technology Assessment, Issues in Medical Waste Management: Background Paper
Theisen, E.J., “Managing Biohazardous Waste”, Hazardous Materials Management Magazine
Health and Welfare Canada, Infection Control Guidelines
Environment Canada, State-of-the-Art Report on the Management of Biomedical (Type A)
Wastes in Canada
US Environmental Protection Agency – Office of Solid Waste and Emergecy Response, EPA
Guide for Infectious Waste Management
Canadian Standards Association, Handling of Waste Materials within Health Care Facilities
Green, V.W. and Vesley, D., “Environmental Microbiology”, in: Bord, R.G., Michaelson, G.S.
and DeRoos R.L. (Eds.), Environmental Health and Safety in Health Care Facilities
Environmental Management and Health, University Press
Pearce, D.W. and Turner, R.K., The Economics of Natural Resources and the Environment,
Harvester Wheatsheaf, Hemel Hempstead, 1990
Royal Commission on Environmental Pollution, Managing Waste: The Duty of Care, HMSO,
London, 1985
Turner, R.K., “Municipal Solid Waste Management: An Economic Perspective”, in Bradshaw,
A.D., Southwood, Sir Richard and Warner, Sir Frederick (Eds.), The Treatment and Handling
of Wastes, Chapman and Hall, London, 1991.
Alex/Medical Waste Conference
05/2003