Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TREATMENT OF BIOMEDICAL WASTE
This invention is in the field of waste treatment and in particular in the
treatment and
disposal of biomedical waste products.
BACKGROUND
to
Within the medical field, and especially in hospital environments, controlling
the spread
of potentially pathogenic organisms is an important concern. A number of
studies have
shown that the risk of infection due to the spread of disease organisms is a
serious human
health problem. Infections can be transferred by contact with surfaces upon
which
organisms can be deposited by handling by patients or hospital staff, or by
airborne
dispersion after a cough or sneeze. The risk of infection is further
exacerbated by the
confined space of typical hospitals, and by the fact that people in hospitals
may have an
impaired ability to resist infection due to their own health problems. In some
cases as
well, the infectious organisms are sometime resistant to commonly used
antibiotics, so
called super-bugs, and so remediation of the infection through medical
intervention may
be difficult, if not impossible.
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As a result, it is common practice in modern day medical setting to take
appropriate
measures to reduce the risk of infection. Such measures include hand washing
after
contact with patients, frequent cleaning of floors, walls and furniture with
disinfecting
solutions, and the use of disposable products. The use of disposable plastic
syringes,
cutlery and beverage containers are but a few examples of products designed
for single
use in order to reduce the risk of spreading pathogens, and which through use
become
biomedical waste.
Biomedical waste also comprises such things as blood and blood products,
tissues
to resected during surgery, as well as single use items used and discarded in
the normal
course of surgical procedures. It is well-recognized that contact with human
fluids such
as blood is a significant risk factor in the spread of the human
immunodeficiency virus
(HIV) that causes the disease acquired immune deficiency syndrome (AIDS).
is It is well recognized that health hazards are posed by the handling and
disposal of
biomedical wastes, and that care must be exercised in handling such waste and
in the
disposal thereof. It is desirable and mandated in many jurisdictions that
biomedical waste
be processed, typically by incineration, to destroy pathogens. Incineration
requires
significant amounts of energy, and also releases potentially harmful
combustion products
2o into the atmosphere.
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Alternatively, chemical sterilizing solutions can also be used to destroy
pathogens in
biomedical waste. These chemicals, being themselves toxic, pose added risks to
those
whose responsibility it is to handle biomedical wastes, as well as a risk to
the
environment upon their disposal.
Ozone is also well known as having disinfecting properties, and is well known
as a
sterilizing agent in certain applications. Ozone is considered very safe as
evidenced by
the approval of the U.S. Food &, brag Administratio n for use ir~ treating
food products.
Ozone is a chemically active radical species of oxygen, commonly produced by
ionization of either air or pure oxygen. Unlike conventional disinfecting
chemicals,
ozone does not form hazardous disinfectant by-products that are harrriful to
the
environment or are toxic to animals and humans. Once ozone has fully reacted
with
substances in water or air, excess gas decomposes quickly to normal oxygen and
is
reabsorbed into the atmosphere. Commercial ozone generators are available
which
economically produce significant amounts of ozone.
The use of ozone in the disposal of biomedical waste is disclosed in a number
of prior art
patents. United States Patent Numbers 5,078,965 and 5,116,574 to Pears on
disclose
grinding the waste and adding water to create a slurry over a fluidized bed,
and then
bubbling ozone up through the slurry. The systems disclosed in United S tates
Patent
Numbers 6,494,391 to Mosenson and 5,820,541 to Berlanga Barrera similarly add
water
to the ground waste, and add a disinfectant such as ozone, to the mixture.
United States
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Patent Number 5,520,888 to Berndt uses a slush or slurry of waste and ice-
containing
ozone to sterilize medical waste.
Largely for reasons of economy, present waste practices in hospitals and the
like include
segregation of waste into general waste and biomedical waste with the
biomedical waste
being processed as such, and the general waste being processed as ordinary
garbage and
taken to landfills and disposal sites with no treatment. Typically, biomedical
waste must
be packaged ar~d transported accordi ng to strict regulations in or~3er to
move same from
the source, such as a hospital or the like, to off site processing.
to
Such segregation is subject to human error, and as well general waste is often
in contact
with biomedical waste prior to segregation. Further such segregation lengthens
the time
between creation of the biomedical waste and treatment thereof. Pathogens
therefore
have an extended time in which to multiply prior to treatment, thereby
increasing the
number of pathogens that the treatment process must inactivate. As well, waste
management personnel are exposed to these pathogens during the common manual
separation of biomedical waste from general waste.
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SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus for the
treatment of
biomedical waste that overcomes problems with current methods of biomedical
waste
treatment and disposal.
The invention provides, in a first embodiment, an apparatus for processing
solid
biomedical vaaste. The apparatus comprises a waste input container ha«ing an
input
opening in a top thereof and an output opening in a bottom thereof. An input
door is
l0 operative to close and substantially seal the input opening, and an output
door is
operative to close and substantially seal the output opening. A shredder is
mounted under
the output opening and is operative to shred waste to a desired maximum size.
A
processing chamber is located under the shredder such that, when the output
door is open,
solid waste deposited in the waste input container passes through the output
opening and
through the shredder, and shredded waste drops into the processing chamber. A
sealable
discharge opening is provided in the processing chamber. An ozone gas source
is
connected to the processing chamber and is operative to direct ozone gas into
the
processing chamber, and an ozone indicator is operative to indicate a
concentration of
ozone gas present in an atmosphere inside the processing chamber. A chamber
exhaust is
2o selectively operative to exhaust the atmosphere from the processing
chamber, and a
hopper exhaust is selectively operative to exhaust the atmosphere from the
waste input
container.
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The invention provides, in a second embodiment, a method for processing solid
biomedical waste. The method comprises providing a shredder above a
substantially
sealed processing chamber; maintaining a selected concentration of ozone in an
ozone
rich atmosphere inside the processing chamber during shredding at a level
sufficient to
sterilize the biomedical waste; feeding waste into the shredder and operating
the shredder
to shred the waste to a desired maximum size, and allowing shredded waste to
fall
~h_rnugh tlZ~ Oz~??le rich atmosphere inside t_he processing cha_~r!ber and
keeping the Waste
in the processing chamber for a length of time sufficient to sterilize the
biomedical waste
to at the selected concentration of ozone; and exhausting the ozone rich
atmosphere from
the processing chamber and removing sterilized waste.
The present invention uses gaseous ozone in a simple system that does not
require the use
of slurries as in the prior art. A considerable level of automation can be
provided by the
inclusion of sensors and control mechanisms. The sensors operate to provide
information
about ozone levels in the processing chamber, or to indicate when the hopper
is full or
when the treatment process is complete and another batch of material can ~e
safely added
to the processing chamber.
2o The present invention provides an apparatus that is relatively simple and
easy to install
and which is relatively inexpensive to operate, and allows for substantially
automated and _
continuous treatment of biomedical waste. Biomedical waste treated with the
apparatus
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will be essentially free from pathogens, and as such safe for disposal in
municipal
landfills and the like. The apparatus for practicing the method of the
invention is simple
and economical, such that same could be installed in a hospital or like source
of
biomedical waste and all waste could be processed therein. Chemicals and
pharmaceuticals would still require separation, however these wastes are not
presently
considered general waste suitable for conventional disposal in any event.
DESCRIPTION OF THE DRAWINGS:
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:
Fig. 1 is a perspective schematic view of an embodiment of the invention for
the
treatment of biomedical waste;
Fig. 2 is an exploded perspective view of the embodiment of Fig. 1;
Fig. 3 is a schematic side view of the embodiment of Fig. 1;
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_g_
Fig. 4 is a schematic side view of an alternate embodiment of the invention,
showing in particular a waste cart lifting and dumping mechanism.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:
The present invention provides a waste processing apparatus 100 for processing
b?omedzCal waste, Such that the processed waste is sterilized to ar~ extent
SiiffiClent fOr
disposal in sites such as sanitary landfills. In the illustrated embodiment of
Figs. 1 - 3,
to the apparatus comprises a waste input container, illustrated as a hopper 1
into which
untreated waste is placed though an input opening provided by the open top of
the hopper
1.
The hopper 1 includes an input door 3 operative to close and substantially
seal the input
opening provided by the open top of the hopper 1 to prevent the escape of air
from the
hopper 1. The level of waste in the hopper 1 can be visually monitored, or an
indicator 7
can be provided to inform the operator of the waste treatment system that the
hopper is at
maximum capacity by activating a visible or audible warning or a combination
of the
two. The apparatus may further comprise a lift 2, such as hydraulic or
mechanical lift,
2o which is operative to lift waste carts and like containers up to the input
opening in the top
of the hopper 1, and the contents dumped into the hopper 1 without the need
for manual
handling of the waste carts.
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An output door 9 is provided in the bottom of the hopper 1 and is opened to
allow the
waste to move from the hopper 1 into the processing chamber 5. The apparatus
includes
a shredder 11, which shreds and grinds the waste material as it passes from
the hopper 1
into the chamber 5. Shredding and grinding exposes increased internal areas of
the waste
to the ozone, increasing the effectiveness of the sterilizing effects of the
ozone. A screen
retains the waste in the shredder 11 until the shredded waste pieces are below
a
minim>?m size, at which time they can pass through ts~:e screen 10 and into
the processing
chamber 5.
to
While many types of shredders could provide satisfactory shredding, one
suitable
shredder is Model STQ-50 Four Shaft Industrial Shredder manufactured by Shred-
Tech
of Cambridge, Ontario, Canada. The Shred-Tech shredder includes a screen such
that the
waste passes around the shredder until it is small enough to pass through the
screen.
The shredder 11 and screen 10 combine to allow only pieces of waste smaller
than about
2 - 3 centimeters across to drop from the shredder into the processing chamber
5.
In operation the hopper 1 is filled and the input door 3 is closed. An ozone
generator 15
is operated to inject ozone gas into the atmosphere inside the processing
chamber 5 until
2o the concentration of ozone reaches a desired level, contemplated to be
between 100 parts
per million (ppm) and 10,000 ppm. Time and ozone concentration are related in
that
inactivating a given number of pathogens requires less time at higher ozone
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concentrations. For example, where it is required to expose a pathogenic strip
to an
atmosphere with a concentration of 10,000 ppm for 3 minutes to kill the
pathogens, it will
be required to expose the same strip to a concentration of 100 ppm for 300
minutes to kill
the same pathogens.
Ozone sensors 19 in the processing chamber 5 are connected to indicators on a
control
panel. An operator can control the concentration of ozone in the atmosphere
inside the
pr'JCeSsiiag Ch?.u'Iiber 5 by C3ntrOiilitg the atWOi;u'2t Of l?izone
li"3~eCted Illt(5 t'fle Chan ~l7et~ J'
from the ozone generator 15. Conveniently, the ozone generator 15 may be
adapted to
to use either commercially available portable compressed air or oxygen
cylinders, or where
available, piped in hospital breathing air or oxygen, as the oxygen source 17.
Some
commercially available ozone generators also have the ability to extract
oxygen from
ambient air for ozonation, and as such do not require any special oxygen
supply. Such
devices would be readily adaptable to the apparatus 100.
When the desired ozone concentration in the atmosphere is achieved, the output
door 9 in
the bottom of the hopper 1 is opened to allow the materials to move from the
hopper 1
into the shredder 11 and then into the processing chamber 5. A pusher
mechanism 6 is
provided in the hopper 1 that can pivot as schematically shown in the phantom
lines in
2o Fig. 3 to force waste through the output door 9 and into the shredder 11.
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As the waste is shredded to a size sufficiently small to pass through the
screen 10 it falls
through the ozone rich atmosphere in the processing chamber 5, and is thus
exposed to
the sterilizing effects of the ozone. As the waste falls into the chamber, the
pieces pile up
on the bottom of the processing chamber 5, and ozone rich air is present in
the spaces
between the pieces in the pile. Once the contents of the hopper 1 have been
shredded and
have dropped into the processing chamber 5, the output door 9 can be closed if
desired,
and the waste pile can be retained in the sealed processing chamber 5 for the
time
calculated to be required to satisfactorily sterilize the waste by
inactivating tl'le biGlGgiCai
organisms that may be present in the waste material.
to
The length of treatment time can be varied, such that different types or
quantities of
pathogens that may be present in waste, and which may be more or less
resistant to
inactivation, can be effectively inactivated during the ozone sterilization
process. Based
on known studies, it will be readily determinable as to what combinations of
time and
ozone concentration will be appropriate to achieve the goal of the process to
inactivate
substantially all pathogens that may be present in the waste. The outputs from
sensors
and the timer and other desired controls may be included in a control panel
31,
conveniently placed for use by an operator. Control of the ozone concentration
and
treatment time could be automated.
Sealing the processing chamber 5 prevents the release of ozone rich air into
the
surrounding atmosphere. As ozone is toxic to humans, controlling the release
of ozone
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by the apparatus is important to ensure the safety of the operator, or those
who may
happen to be in the area of the apparatus while it is in operation.
The waste processing apparatus 1 can further comprise an agitator 13 in the
processing
chamber 5 if it is found to be required or desirable, depending on the waste
being
processed and the process steps being used. For example if some waste is
present in the
processing chamber prior to the introduction of ozone into the atmosphere in
the
processing chamber, ti~:e agitator 13 ~t.~ill Lift that waste and drop same
through fee czone
rich atmosphere to ensure contact with ozone during the treatment process.
to
It is contemplated that introducing moisture into the atmosphere of the
processing
chamber 5 could be beneficial in aiding penetration of ozone into the shredded
waste. A
water source could spray water into the processing chamber 5, or a steam
source 33 could
be connected to the processing chamber 5 to add moisture.
In the illustrated embodiment a disposal container 23 has a filling opening
releasably
attached and sealed to the discharge opening 21 in a wall of the processing
chamber 5.
Means such as conveyors or the like are provided to move shredded waste from
the
processing chamber 5 through the discharge opening 21 into the disposal
container 23.
2o Conveniently the means can be provided by a mechanism analogous to a trash
compactor
comprising a substantially upright wall located in the processing chamber 5
opposite the
discharge opening 21, and an actuator operative to move the wall toward the
discharge
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opening 21 and push the shredded waste through the discharge opening 21 and
into the
disposal container 23. Thus several batches can be processed in the processing
chamber
and pushed into the disposal container 23.
5 As ozone is a toxic substance, exhausts are provided in the processing
chamber 5 and
hopper 1. In Fig. 2, the exhausts comprise filters 25, 35 containing
CaruliteTM or a like
substance operative to break ozone down into oxygen, and vacuum vents 27, 37
mounted
on and connected to the processing chamber 5 and hopper I. The filters 25, 35
break
down ozone and the vacuum vents 27, 37 are connected to a vacuum source that
can be
activated to draw the ozone rich atmosphere from the processing chamber 5 and
hopper 1
through the filters 25, 35 and out to an exterior atmosphere where the
remaining ozone
will be dispersed. A heater may be added to increase the effectiveness of the
filters 25,
35. It is contemplated that the filters 25, 35 may not be required if the
venting area is not
near people.
Because the output door 9 at the bottom of the hopper 1 is open during
shredding, high
levels of ozone are present in the hopper after the waste material has been
emptied
therefrom. Thus when all waste from the hopper 1 has been shredded into the
processing
chamber 5, and the output door 9 at the bottom of the hopper 1 has been
closed, the
hopper 1 is exhausted prior to opening the input door 3 by operating the
vacuum source
through vent 37. Once the ozone has been vented from the hopper 1, the input
door 3 can
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be opened and further waste added, and the output door 3 re-closed and sealed,
and the
output door 9 then opened and the shredding process repeated.
In the illustrated embodiment this process can be repeated until such time as
the disposal
container 23 is full. Since the processing chamber 5 is in open communication
with the
interior of the disposal container 23 through discharge opening 21, the
atmosphere inside
the disposal container has substantially the same ozone concentration as the
atmosphere
in the processing eharnber 5. Thus the waste is exposed to ozone from the time
it enters
the shredder until the disposal container is full and the ozone exhausted
prior to removal.
to This period can last up to several days in many applications. For best
results the
atmosphere has the chosen high ozone concentrations prior to waste entering,
all waste in
the processing chamber 5 or disposal container 23 is at all times fully
exposed to ozone as
it piles up and as it is pushed into the disposal container, and as it rests
in the disposal
container.
Once full, the disposal container 23 can be removed and replaced with another
empty
disposal container 23. The full disposal container can be transported to
disposal sites
such as a sanitary landfill, and the contents, now sterilized, can be disposed
of without
fear of harm to either humans or the surrounding environment.
An alternate embodiment of a waste processing apparatus 150 for processing
biomedical
waste is schematically illustrated in Fig. 4 comprising a hydraulic lift 102
which is
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operative to lift waste carts 155 and like containers from substantially floor
level adjacent
to the apparatus 150 up to the input opening in the top of the hopper 101, and
dump the
-contents into the hopper 1 without the need for manual handling of the waste
carts. The
lift 102 engages a front portion 157 of the waste cart 155 and is linked by
arms 159 to the
input door 103. The input door 103 is opened by hydraulic cylinders 161. As
the input
door 103 moves up to the open position OP, the arms 159 pull the cart 155 up
to the
inverted dumping position DP such that waste is emptied into the hopper 101.
When the
in_p~t d~nr ~lpgeg~ ~P .art 155 ie _rPtyPd tn flrJpr ie'rel,
to The waste processing apparatus 100, 150 are relatively simple and
economical, such that
same could be located at a source of biomedical waste, such as a hospital or
the like, and
such that un-segregated waste containing both biomedical and general waste
could be
shredded and processed therein, removing the problems associated with
segregating the
waste. The time between creation of the biomedical waste and treatment could
thus be
reduced, and handling of the waste would not be necessary. Errors in
segregation, and
exposure of personnel to pathogens would be reduced as well, along with
packaging and
transport concerns.
The foregoing is considered as illustrative only of the principles of the
invention.
2o Further, since numerous changes and modifications will readily occur to
those skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in
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structure or operation which may be resorted to are intended to fall within
the scope of
the claimed invention.
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