Patent Application
20080008635
The present invention relates to a device and method for treatment of waste and in particular to the treatment of infectious waste from a hospital.
In the normal course of operation, hospitals generate a variety of waste which is not suitable for normal disposal. While some or most hospital waste may be harmless, it is difficult to distinguish such harmless waste from infectious waste. As a result, all of the waste from a hospital must be treated as if it may be harmful. Also, sensitivity to the handling of hospital waste has been raised as a result of AIDS and other health issues. Recently, the bird flu spread rapidly and initially was not well understood. As world travel has increased, so has the ability of infections, like the bird flu, to spread rapidly, and the need to contain outbreaks is greater than ever before. For all of these reasons, there is a need to deal properly with hospital waste.
Common methods of treating hospital waste include systems having a steam autoclave or an ethylene oxide autoclave. U.S. Pat. No. 6,726,136 for “Waste treatment plant,” describes a system including an autoclave. Other systems include incinerators. Unfortunately, incinerators may be difficult to construct and operate, and may create environmental issues. Autoclaves may also be expensive and difficult to operate. Systems including autoclaves may also require additional steps to complete disinfecting waste.
U.S. Pat. Nos. 5,425,925 and 5,656,248 for “Multi-stage infectious waste treatment system,” both assigned to the assignee of the present application, describe waste treatment systems which use grinders to grind waste into small particle size, and then soak the waste in a volatile liquid disinfectant. Unfortunately, while the systems described in the '925 and the '248 patents successfully treat most hospital waste, some hospital waste has been found to contain material, such as titanium prosthetic joints, which may jam known waste grinders. The '925 and the '248 patents are herein incorporated by reference.
U.S. patent application Ser. No. 11/190,343 filed Jul. 26, 2005 for “INFECTIOUS WASTE TREATMENT” filed by the inventor of the present patent application describes a hospital waste disposal system including a shredder which addresses many of the issues of the '925 and the '248 patents, but unfortunately, a remaining problem is a failure to shred all of the hospital waste components into small enough elements to pass through pumps and other system components. Some hospital waste, such as titanium pins, large needles, medical drills, and the like, may be bent and twisted by the shredder, but not cut or shredded into small enough pieces. In particular, these bent and twisted pins may foul or jam a pump used to advance the shredded and wetted waste through the hospital waste treatment system and may foul or jam other pumps used to circulate the liquid disinfectant. The '343 application is herein incorporated by reference.
U.S. patent application Ser. No. 11/212,009, filed Aug. 25, 2005, for “HOSPITAL WASTE TREATMENT WITH IMPROVED DISINFECTANT LIQUID PRODUCTION” filed by the inventor of the present invention, describes a hospital waste disposal system including an improved liquid disinfectant generation system, but did not address the fouling or jamming of pumps used to circulate the liquid disinfectant. The '343 application is herein incorporated by reference.
The present invention addresses the above and other needs by providing a waste treatment system which shreds waste material into small pieces and soaks the pieces in a liquid disinfectant. The system includes a feed hopper, a shredder, a wetting area, a dwell area, and a de-watering apparatus. Unprocessed waste material is dumped into the feed hopper. The feed hopper feeds the unprocessed waste material into the shredder. The shredder includes a rotor and anvil for shredding the unprocessed waste material. The shredded material falls into the wetting area where the shredded material is wetted with the liquid disinfectant to create a slurry. The wetted slurry is advanced for an additional three to four minutes of wetted time through a dwell-area before entering a de-watering apparatus. The total wetting time allows the waste material to be completely disinfected
In accordance with a first embodiment of the invention, there is provided a first apparatus for infectious waste treatment. The apparatus comprises a lift for lifting a waste container to a feed hopper which receives waste material from the waste container, a shredder for receiving the waste material from the feed hopper and shredding the waste material, a wetting area comprising a main solution tank for receiving and wetting the shredded waste material, and a dwell area comprising an auger for carrying the wetted material from the main solution tank. The shredder comprises a rotor positioned below the feed hopper, an anvil in shredding cooperation with the rotor, and a sizing screen for controlling the size of the shredded waste material. A liquid disinfectant is sprayed onto the shredded waste material in the main solution tank, and a chopper pump circulates the liquid disinfectant. The auger carries the wetted slurry from the main solution tank and provides a dwell time. A de-watering section resides at the end of the auger.
In accordance with a second embodiment of the invention, there is provided a second apparatus for infectious waste treatment. Unprocessed waste material is dumped into a feed hopper. The feed hopper feeds the unprocessed waste material into a shredder. The feed hopper includes a hopper ram for pushing the waste material into a rotor and anvil for shredding the unprocessed waste material. The shredded material falls into a wetting area comprising a treatment hopper where the shredded material is mixed with liquid disinfectant to form a slurry. The slurry material is drawn from the treatment hopper and advanced into a dwell area comprising a coil by an air operated pump, and spends three to four minutes of dwell time in the coil before entering a de-watering system. A preferred de-watering system includes a piston which compresses the waste in the de-watering system and the liquid disinfectant escapes through straining holes which filter the liquid disinfectant for re-use. The de-watered material is then dumped from the de-watering system and carried away for disposal.
The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:
Corresponding reference characters indicate corresponding components throughout the several views of the drawings.
The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims.
A first embodiment of a waste treatment system 10a according to the present invention is shown in
A radioactive material detector 13 resides in the cage 12. When the radioactive material detector 13 detects radiation in the hospital waste, the waste treatment system 10a is turned off and an alarm is sounded. An example of a suitable radioactive material detector is Micro Bomb Detector made by AI NOTL Systems Inc. in Ontario, Canada.
Continuing with
A continuous gas monitoring system 38 monitors the liquid disinfectant level in the main solution tank 18 and composition (i.e., strength) of the liquid disinfectant, and controls the generation of liquid disinfectant (see
The auger 20 is preferably a shaftless auger residing in an auger housing 21 supported by an auger strut 23 and is powered by an auger motor 22 which is preferably connected to the auger 20 through a gearbox 22a. A de-wetting area is fitted to the auger 20, wherein the liquid disinfectant used to wet the shredded waste is trapped and recirculated back into the main tank. The de-wetting area is in fluid cooperation with the auger 20 and comprises a rotatable section 26 of the auger housing 21 which may be rotationally positioned relative to the auger housing 21 at various rotations to adjust the position of a chute 24 and a fluid trap 28. If the chute 24 is pointed down, the back pressure on the flow of the wetted slurry is minimized, and the amount of liquid disinfectant removed by the fluid trap 28 is minimized. As the chute 24 is rotated away from a pointed down position, the back pressure on the flow of the wetted slurry is increased, and the amount of liquid disinfectant removed by the fluid trap 28 is increased. If the chute 24 is rotated to an upward position, the back pressure on the flow of the wetted slurry is maximized, and the amount of liquid disinfectant removed by the fluid trap 28 is maximized.
A lift 42 for lifting a waste container, for example a wheeled bin 40, to dump waste into the feed hopper 14a of the waste treatment system 10a is shown in
The lift 42 may be electrically, hydraulically, or pneumatically operated. The lift 42 preferably can lift a 95 US gallon, (360 Liter) and 65 US gallon (240 Liter) wheeled bin 40 vertically and empty its contents into the feed hopper 14a. Any containers too large to fit into a 65 US gallon wheeled bin 40 (i.e. greater than 20 inches by 20 inches) are preferably capable of being lifted by the lift mechanism. Plastic bags containing medical waste may be presented to the machine in either a 65 or 95 US gallon wheeled bin 40. The lift 42 is preferably capable of lifting up to 225 Lbs. with a cycle time of no more than 10 seconds and have its movement controlled by a Programable Logic Controller (PLC) to allow the wheeled bin 40 to be rocked and held stationery during any part of its lift cycle. The lift 42 preferably includes weight measuring in both pounds and lilograms and to an accuracy of approximately 0.5%. The lift 42 preferably includes a Geiger counter for measuring any radiation from the waste load being lifted into the machine and is preferably capable of detecting alpha beta and gamma radiation and have an operating range of mR/hr: 0.001-50.00 mR/hr (Cs-137); CPM: 0-50,000; Total: 0-60,000 counts and to a Sensitivity: 1000 cpm/mR/hr referenced to Cs-137 and Accuracy: ±10% typical; ±15% max. The lift 42 is preferably also capable of supporting European SI units (mSv/hr). Both the weighing scales and Geiger counter are preferably supplied with standard parts for calibration. A Human Machine Interface (HMI) preferably resides beside the lift 42 and is preferably capable of supporting in-put from a bar code reader, or equivalent electronic reader. The HMI is further preferably capable of supporting direct data in-put via touch screen or keypad. A mechanical barrier is preferably provided to protect the lift 42 mechanism per OSHA or OSHPD standards, to prevent anyone from accessing the lift during any part of the lift process. During lift 42 operation, the shredder is automatically operated for a predetermined period which will be software configurable. A combined bleach and fresh water (ratio 1:1) spray point, for wash-down, is be fitted to the area beside the lift mechanism. A nozzle sprays a water bleach mixture into the feed hopper 14a approximately six inches from the top of the feed hopper and is active when the lid is closed. See
A side view of a shredder 16 suitable for use with the waste treatment system 10a is shown in
A cross-sectional view of the shredder 16 taken along line 4-4 of
A cross-sectional view of the gearbox 54 taken along line 5-5 of
A side view of the main solution tank 18 suitable for use with the waste treatment system 10a is shown in
Continuing with
A bubble tank assembly 128 is partially submerged in the disinfectant liquid below the static fluid level 78a and to preferably within approximately one half inch of the bottom of the main solution tank 18, and is further described in
A second side view of the main solution tank 18 (an opposite side view from
The continuous gas monitoring system 38 measures the liquid disinfectant depth and concentration using the bubble tank assembly 128 and the gas sample tube 129 (also see
The continuous gas monitoring system 38 includes a continuous gas monitoring device which uses a diaphragm pump to provide the gas flow received through the gas sample tube 129 to a sensor. The sensor's electrical output is sent through a sensor circuit board to a digital panel meter which processes the sensor output and produces a digital readout in Parts Per Million (PPM) of the chemical levels in the liquid disinfectant. The continuous gas monitoring system 38 compares the measured gas level to the preset alarm levels and activates alarm indicators when gas levels exceed user set levels. If low gas levels are detected, a signal is sent to the liquid disinfectant generator to generate additional chlorine dioxide. If the liquid disinfectant is low, water is added to the systems. The continuous gas monitoring system 38 further includes data logging for recording data including chemical levels, fluid level, maintaining level, and kill ratio.
The static liquid level 78a (see
A detailed view of a preferred chemical manifold 112 is shown in
An overview of a second embodiment of a waste treatment system 10b according to the present invention is shown in
The shredder 16 is described in
The treatment hopper 202 has downwardly inwardly sloped sides, an access port 202a, preferably an approximately 30 gallon capacity and is preferably at least approximately 24 inches high. The liquid disinfectant is carried to the treatment hopper 202 through disinfectant feed lines 204a and 204b and mixes with the shredded waste to produce a wetted slurry. The wetted slurry is fed from the treatment hopper 202 into a first “T” 206 and is advanced by a main pump 214 through a first wetted slurry line 210a into a dwell area 218. The dwell area 218 is thus in fluid cooperation with the wetting area 202 through the “T” 206, the line 210a, and the pump 214. The wetted slurry is advanced through the dwell area 218 at a rate resulting in a sufficient dwell period between wetting and de-wetting to disinfect the wetted slurry, which sufficient dwell time is preferably between approximately three minutes and approximately four minutes. The line 210a is preferably an approximately six inch diameter line, and is preferably made from stainless steel, and preferably 316L stainless steel. Following the dwell period in the dwell area 218, the wetted slurry advances through a second wetted slurry line 210b into a de-watering system 220, wherein the de-watering system 220 is in fluid communication with the dwell area 218 through the line 210b. The line 210b is preferably similar to the line 210a and is more preferably an approximately six inch diameter line, and is preferably made from stainless steel, and more preferably from 316L stainless steel. Once in the de-watering system 220 the wetted slurry is pressed to force substantially all of the liquid disinfectant out of the wetted slurry to produce disinfected dry waste. A waste conveyor system 224 carries the disinfected dry waste away from the de-watering system 220 for disposal. A preferred waste conveyer system 224 includes an auger for transporting the de-watered waste.
The main tank 232 stores newly generated liquid disinfectant for the liquid disinfectant generation system 248 and recycled liquid disinfectant from the de-watering system 220. The tank 232 preferably has a capacity to hold approximately 250 gallons, resides at high level wherein the top of the tank 232 is preferably at approximately 7.5 feet above the floor, and the tank 232 preferably includes at least one overflow connected to a waste water tank 256 (see
A temperature probe is preferably fitted to the main tank 232 at a level where the temperature probe is always submerged in liquid disinfectant. A flow from the down-stream side on the pump 234 (P2 in
The dwell area 218 preferably has a capacity of at least approximately 14.5 Cubic Feet (approximately 110 Gallons). A preferred dwell area 218 is a coil comprising an approximately 6-inch diameter reinforced PVC hose, which is approximately 75 feet long. In general, the dwell area 218 is designed to ensure all floating waste particles are covered in liquid disinfectant (for example, remain in the slurry) for at least approximately three minutes to approximately four minutes, and is constructed of a material which is suitable for wetted parts. The length of the dwell area is thus a function of the volume pumping rate of the main pump 214, and is preferably at least the volume which the main pump 214 pumps in at least approximately three minutes to approximately four minutes. The coil configuration is preferred to reduce the floor space.
The liquid disinfectant extracted from the wetted slurry in the de-watering system 220 is filtered and passes through a de-watering system drain line 226, a de-watering system drain pump 228, and a main tank feed line 230 into the main tank 232. The liquid disinfectant may then pass through a disinfectant line 204 to a disinfectant feed pump 234 back through the disinfectant feed lines 204a and 204b and into the treatment hopper 202 to wet the shredded waste. A suitable pump 228 and/or 234 is an Iwaki Model MX-F401 supplied by Iwaki in Holliston, Mass. The main feed tank 232 is preferably positioned above the dwell area 218 to conserve floor space and provide minimum separation of system elements.
A liquid disinfectant generation system 248 is provided for generating liquid disinfectant. The liquid disinfectant generation system 248 preferably resides on top of the main tank 232.
A wheeled bin 40 ready to lift is shown in
The capacity of the feed hopper 14b is preferably 25% bigger than a 95 US Gallon bin to allow for accepting the contents of the wheeled bin 40. A 95 Gallon wheeled bin 40 is nominally H 46.1×W 27.7×D 31.6 inches. During normal operation of the waste treatment system 10b, when a wheeled bin 40 is not being emptied into the feed hopper 14a, the lid 200 is preferably closed. When medical waste is being emptied into the feed hopper 14a, the lid 200 is opened as shown in
The feed hopper 14b is preferably under a negative pressure and the exhaust is to be sized to achieve approximately 25 air changes per hour. The air intake to the feed hopper 14b is preferably filtered through a screen mesh filter and sized in order to keep air velocity below approximately 700 Ft. per minute. The air input is to be located on top of the lid 200 of the feed hopper 14b and protected from the hopper water/bleach wash down. The total volume between the closed lid 200 and an input hopper (i.e., the volume above the rotor and anvil) internal to the shredder 16 is preferably capable of holding the equivalent of two 95 US gallon wheeled bins, i.e. 24 cubic feet. A preferred Vecoplan Shredder has an input hopper capacity of 18 cubic feet which is part of the 24 cubic foot capacity. The hopper ram 290 (see
The lid 200 of the feed hopper 14b may be opened for access to the shredder 16 for the purpose of clearing jams. Preferably, a pneumatically operated cylinder 201 is provided to open the lid 200, and mechanical locks are provided to hold the lid 200 open. When closed, the lid 200 is preferably held closed by the lid latch 200a. Electrical interlocks (or switches) may fitted to the lid 200 lift mechanism 201 so that when the lid 200 is open, the electrical interlocks will prevent operation of hopper ram 290 or the shredder 16.
An internal washer comprising an automatic bleach and water wash-down spray system may be fitted internally to the top of the lid 200. The spray is preferably a one to one mix of bleach and water. The internal washer includes a wash-down (or bleach) line 288 which connects a bleach tank 286 and a fresh water source to a spray nozzle in the feed hopper 14b. The spray nozzle preferably is positioned approximately six inches down from the top of the feed hopper 14b. The bleach tank 286 may be the same tank providing bleach for generating the liquid disinfectant (see
A more detailed side view of the lid 200 is shown in
A top view of the treatment hopper 202 is shown in
A common problem encountered in known hospital waste treatment systems is the difficulty in shredding all of the hospital waste components into small elements. Some hospital waste, such as titanium pins, may be bent and twisted, but are not cut or shredded into small pieces. These bent and twisted pins may foul or jam a pump used to advance the shredded and wetted slurry through the hospital waste treatment systems. A suitable pump should be capable of processing shards of metal up to 6 inches long without jamming and pump up to 5.5 cubic feet per minute to a head of 10 Ft.
A detailed view of a main pump 214 according to the present invention, used to advance the wetted slurry through the waste treatment system 10b is shown in
An example of a suitable pump is a Saniflow VC6 manufactured by Wilden Pump in Grand Terrace, Calif. The Saniflow VC6 pump includes the vertical column, valves, pressure and vacuum source, and controller.
The displacement member 213 may be empty or may include a piston to separate the vacuum/pressure from the wetted slurry. A preferred displacing member 213 is an empty vertical member, and more particularly an empty vertical cylinder. The preferred cylinder is no more than approximately six inches in diameter, and more preferably is approximately six inches in diameter. Such empty vertical member reduces the chances of fouling the pump with debris in the wetted slurry. A compressed air source of at least approximately eight bar and 15 cubic feet per minute and a vacuum source capable of displacing at least approximately five cubic feet per minute are preferably provided for the operation of the pump 214 and other requirements of the waste treatment system 10b.
A side view of the valve 212b is shown in
A preferred pump 214 is an air operated pump generally requiring vacuum and pressure, although the pump could include a piston biased by a spring, compressed air inside the pump, or the like, and only requires vacuum or pressure. Similarly, the pump 214 could be electrically operated using a solenoid to move a piston inside the pump 214. Vacuum, if required, is preferably generated from a vacuum pump of no more than 12-inch Hg with a swept volume of no less than 6.0 CFM. Pressure, if required, is preferably no more than 5 CFM of air at no more than 120 PSI. A safety valve may be fitted on a pressure output from the pump 214 and valve release pressure is preferably adjustable in a range approximately 20 pounds to approximately 60 pounds. A flow through the safety valve is preferably pumped into the treatment hopper 202.
A mesh 213a preferably resides proximal to the top of the displacement member 213 and extends below the surface of a liquid portion of the slurry by approximately six inches when the displacement member 213 is full, acting as a strainer to prevent solid material from passing. The mesh 213a is preferably made from SS 316 L and is preferably held in place by a clamp. A stainless steel tube 217 is preferably installed in the pump cap 215 and extends approximately six inches into the displacement member 213 and is terminated externally in an electrically operated ball valve 217a. The timing of the operation of the ball valve 217a may be synchronized with the operation of the pump 214. The synchronization is to enable a sample of the liquid disinfectant to be drawn off. The sample may be used for (after dilution) measurement of the concentration of ClO2 in the liquid disinfectant (see
A preferred pump 214 operates as follows. The wetted slurry is advanced into the pump 214 from the treatment hopper 202 by opening the inlet valve 212a, closing the outlet valve 212b, and applying vacuum to the displacement member 213, thereby sucking the wetted slurry from the treatment hopper 202 into the displacement member 213. The wetted slurry is then advanced toward the dwell area 218 by closing the inlet valve 212a, opening the outlet valve 212b, applying pressure to the displacement member 213.
A separate view of the de-watering apparatus 220 and waste conveyer system 224 is shown in
The de-watering system 220 is described as follows. The de-watering system is preferably capable of processing approximately 4 cubic feet per minute with an approximately 20 second cycle time to fill with slurry, de-water, and unload de-watered waste. The de-watering system 220 is preferably capable of de-watering to meet the “Paint Filter Liquid Test”. The de-watering system 220 is preferably completely enclosed and any access points are preferably electrically interlocked to prevent system operation when an access point is open.
A cross-sectional view of the de-watering system 220 taken along line 16A-16A of
The liquid disinfectant from the de-watering system is preferably pumped by pump 228 (see
Maintenance hatches are preferably provided around the de-watering system 220 to allow access for removal of the SS sieve filter, access to conveyor 225 at all locations, and any moving parts in the de-watering system. Locations covered with liquid disinfectant are preferably fabricated out of materials suitable for tanks. Where mechanical loads are experienced the materials are preferably metal. Wetted parts are preferably SS 316 L or an approved plastic.
The de-watering system 220 may be exhausted using an exhaust pipe preferably sized for a velocity of no more than approximately 700 Feet per minute and achieving approximately 25 air changes per hour.
De-watered waste from the de-watering system 220 is preferably fed to a covered conveyer (e.g., an auger) 225 (see
A detailed view of the main tank 232 and a waste water tank 255 is shown in
A detailed view of a preferred liquid disinfectant generation system 248 is shown in
A preferred liquid disinfectant used in the water treatment system 10b is aqueous chlorine dioxide (CLO2) and a preferred liquid disinfectant generation system 248 is a chlorine dioxide generation system. The aqueous chlorine dioxide may be generated by the following chemical reaction, by means of a venturi:
NaOCl+2 NaClO2+2H3C6H5O7→2 ClO2+3 NaCl+H2O
Additionally, an anti-foaming agent is added diluted to a ratio of 1 part water to 1 part de-foaming agent. A suitable de-foaming agent is AF9010 made by GE Silicones in Wilton, Conn., or the like.
The preferred chlorine dioxide generation system is preferably at least approximately 65% efficient and preferably capable of reliably producing a concentration of ClO2 from approximately 500 PPM to approximately 1,000 PPM, and more preferably capable of reliably producing a concentration of chlorine dioxide from approximately 500 PPM to approximately 700 PPM.
The preferred chlorine dioxide generation system comprises pre-cursor containers 114a, 114b, 114c, and 114d, pre-cursor lines 110, and an eductor 250 (or venturi) for combining the pre-cursors with either water or partially depleted aqueous chlorine dioxide. The pre-cursors are supplied to the eductor 250 by a siphoning action and no pumping is required. Line 110 lengths for each pre-cursor to the eductor 250 are preferably the same to an accuracy of +/−approximately three inches. A non-return valve with a filter is provided at the containers 114a, 114b, 114c and 114d end of each line 110. The containers 114a, 114b, and 114c, and 114d contain approximately 25 percent sodium chlorite solution, a 12 to 50 percent citric acid solution, and an approximately 12.5 percent industrial clorox bleach (i.e. sodium hypochlorite) as pre-cursors for generating aqueous chlorine dioxide, and the de-foaming agent respectively. An example of a suitable eductor 250 is available from ChemCal in Grapevine, Tex. The back pressure in the water supply from the feed water tank 253 to the eductor 250 is preferably monitored by the PLC against preset limits, which limits are software configurable, by the user.
The chlorine dioxide generation is a mildly exothermic reaction and the overall process water temperature is to be monitored and controlled as follows. The feed water tank 253 may include a heater preferably comprising a thermostatically controlled heating element of at least 15 KW fitted. The temperature of the feed water is automatically controllable to predetermined limits and this is configurable within the PLC. The main tank 232 preferably includes a heating element fitted to the base of the tank with a rating of at least 15 KW. The temperature of the process water is to be automatically controllable to predetermined limits between 50 and 60° F. A cooling element is preferably installed in the main tank 232 to be capable of cooling 250 gallons of water by 10° F. in a ten minute period. The operating temperature for the system is preferably less than 60° F. (15° C.).
A preferred liquid disinfectant monitoring system 270 comprising a chlorine dioxide monitoring system is described in
A overview of liquid disinfectant flows in the waste treatment system 10b is described in
The liquid disinfectant flow from the liquid disinfectant generation system 248 may flow through a second valve V2 and a third valve V3 to the treatment hopper 202 for wetting the shredded waste material, or the liquid disinfectant from the liquid disinfectant generation system 248 may flow through the second valve V2 and to the main tank 232. The liquid disinfectant may also be provided to the treatment hopper 202 from the main tank 232 through the pump P2, valve V4, and valve V3. A second shut-off valve S2 resided between the valves V3 and V4 to allow the flow from the main tank 232 to the treatment hopper 202 to be blocked. At all times, the preferred total flow of liquid disinfectant into the treatment hopper 202 is approximately 30 gallons per minute.
The flow through the liquid disinfectant generation system 248 is selectable from either fresh water from feed water tank 253 or partially depleted liquid disinfectant from the main tank 232, which already contains liquid disinfectant but is somewhat depleted. The depleted (or used) liquid disinfectant is preferably filtered by flowing through the holes in the cylinder 221 to prevent any particle greater than approximately 0.125 inches passing through liquid disinfectant generation system 248. The liquid disinfectant is provided to main tank 232 until a predetermined level is reached. The valve V1 controls the flow into the liquid disinfectant generation system 248 and allows selection of a depleted liquid disinfectant flow from the main tank 232 or fresh water from the feed water tank 253. The liquid disinfectant is provided to the treatment hopper 202 for 15 minutes after the last wheeled bin 40 has been loaded.
The feed water tank 253 is preferably made of plastic and is capable of storing approximately 50 gallons. The tank is supplied with water from a main water supply or from a separate facility header tank. The supply of water from the feed water tank 253 is preferably regulated by a flow regulator R1 in the flow from the feed water tank 253. The feed water tank 253 is preferably covered on top and totally insulated with a minimum of approximately four inches of rock wool or fiberglass. The feed water tank 253 will be fitted with an electrical heating element. The feed water tank 253 preferably includes an overflow which is approximately one inch in diameter and is fitted a minimum of approximately four inches above the nominal water level in the feed water tank 253. The feed water tank 253 overflow is pumped to the wastewater effluent treatment tank 256. The flow regulator R1 is preferably fitted to the feed water tank 253 approximately six inches above the nominal water level. An approximately ten gallon per minute resin bed water softener may be provided in some instances to soften the water entering the feed water tank 253.
The de-watering system 220 is connected to the main tank 232 through a third pump P3 (also shown as the de-watering system drain pump 228 in
A waste water processing system 254 neutralizes and adjusts the PH of liquid disinfectant being released to a sanitary sewer. When the liquid disinfectant is aqueous chlorine dioxide, the neutralizer is preferably sodium thiosulfate (NaSO3), which neutralizes the aqueous chlorine dioxide producing a neutralized liquid. The chemical reaction exercised in the waste water processing system 254 when sodium thiosulfate is used as a neutralizer is:
5 NaSO3+2 CLO2+H2O→5 Na2SO4+2 HCL
The waste water tank 256 is connected to the main tank 232 by the waste water line 246 (see
A second water flow from the feed water tank 253 is pumped by a fourth pump P4 and through a second liquid disinfectant generation system 250a independently of the water supply to the liquid disinfectant generation system 248 to generate a second liquid disinfectant. Preferably, the second liquid disinfectant is a bleach and water mixture, and more preferably a 1:1 bleach and water mixture. The bleach may be the same bleach as used to generate the first liquid disinfectant, and the second liquid disinfectant generation system 250a may be a second eductor similar to the eductor 250, but only mixing bleach with a flow of water. A flow of the second liquid disinfectant may be provided to the waste handling section 12 to wash down waste containers, for example the wheeled bin 40, and such wash down may be automated. Additional flows of the second liquid disinfectant may be provided to the feed hopper 14b, the treatment hopper 202, and the main tank 232. The flows of the second liquid disinfectant are shown as dotted lines in
An add-on paper shredding system 260 is shown in
In an exemplar embodiment, the continuous liquid monitoring system 38 includes a special 10:1 dilution system with two peristaltic pumps, special high range sensor and flowcell assembly. The electrical control panel comprises a PLC control unit, variable frequency drives for the shreder and auger, motor starters for fan and pumps, 120VAC and 24VDC control voltage supplies. The pump control box comprises chemical concentration, receiving tank water level, main tank water level and air pressure controls, and a three light stack alarm enunciator. The operator console comprising a six inch touch screen Human Machine Interface (HMI) operator interface display, Start-Stop and Emergency Stop control operators, waste bin color detectors and weight scale. The hydraulic unit control box comprises hydraulic unit controls and position sensor junction terminal blocks.
All system functions are completely automatic and controlled by a Programmable Logic Controller (PLC) unit and the HMI display. All the operator needs to do is load the waste bin in the bin cage and press the start button on the operator console. The system will start functioning in a pre-programmed sequence. The complete process is monitored for time, water level, and chemical concentration by the PLC unit. Should any operating parameters deviate from normal, treatment is automatically halted and the control panel alerts an operator. The operation of the system can be monitored on the HMI display as explained below.
Before powering the system for the first time, the following checking steps are performed. Ensure all power cords are securely fastened (cord plugs preferably have a guide notch to prevent wrong connection of the plug to the receptacle, if a cord is unplugged, ensure that the system power is turned off, and re-plug). Check that the hydraulic unit oil level is normal. Ensure chemical containers are connected and are at least 30 percent full. Check for water leakages in the system. And lastly, ensure a water supply is present.
The waste treatment system 10 may be started by executing the following steps. Turn power on at the electrical panel (the 120VAC and 24VDC power indicator lights that are on the right side of the panel should light.) Make sure there is no alarm message on the HMI display and the 3-stack light is green. Check that the bin lift is at the extreme down position. If alarm messages are present, bring the lift down manually by using the touch buttons on the HMI display. Load the waste bin in the bin cage and make sure the cage door is firmly closed. Make sure that the E-Stop push button is released. If the green lamp on the operator console is not on, then press the Reset button. The green lamp should then turn on. And lastly, press the start button. The system will now start to run in the following sequence based on the color of the waste bin, Red=Medical waste, Grey=Cafeteria (non medical) waste. The HMI display will indicate the operating mode. If the mode must be set manually, the mode can be set on the HMI display Mode select page. The operation of the system may also be monitored on the HMI display as explained below.
An operating sequence for the waste treatment system 10 comprises the following steps. The lift will lift the waste bin and empty the contents into the hopper (there is a 5 sec delay at the top emptying position). After the bin lowers to the start position the shredder will start running. If in Medical mode, the waste particles will fall into the receiving tank located below the shredder, at the same time the receiving tank is filled with chlorine dioxide. The slurry of medical waste and chlorine dioxide is then pumped into the retention coil, where the waste will remain submerged for a minimum of 3 minutes. The waste is then pumped to the dewatering station where it is pressed and dewatered and extruded into an auger tank. The disinfected waste is then agued up and out to a compactor or waste bin. The circulation pumps will start running. The cycle time may be longer if there are hard substances in the waste. After the cycle time is over the system will stop.
The system will stop during the normal running cycle under the following conditions: water level is low or high; chemical level is low; air pressure is low; any one of the motors fault (overloading or other electrical problems); and E-Stop or Stop push button is pressed. The system will start running the cycle from the beginning when the alarm conditions are cleared and Start button is pressed.
Alarms are indicated by a bell flashing in the upper-right corner of the display when an alarm is activated. To go to the alarms screen, the alarm button on the lower right corner of all the display screens is touched. Alarms are presented in an alarm list with predefined alarm texts. The alarm list contains the latest alarms and is arranged in alarm group order according to definition, so that the latest alarms are shown at the top of the list. The number of times the alarm has been generated (if selected), the status of the alarm, the time it was activated, became inactive or was acknowledged, is shown for every alarm. Touching the acknowledge button accepts an alarm. If the alarm condition is already cleared, then the alarm message line will disappear after acknowledgment. If the alarm condition still exists, the message line will continue to display.
A method of waste treatment according to the present invention is described in
More specifically, the method for waste treatment using the second waste treatment system 10b comprises an operator loading a wheeled bin 40 containing medical waste into the waste treatment system 10b, the operator pushing a start button, the wheeled bin 40 rising from a start position and emptying the medical waste into the feed hopper 14b, lowering the empty wheeled bin 40 to the start position, shredding the medical waste into confetti like particles in a shredder and allowing the shredded medical waste to fall into a wetting area under the shredder, adding aqueous chlorine dioxide to the wetting area and wetting the shredded waste with the aqueous chlorine dioxide in the wetting area to create a slurry comprising the shredded waste material and the aqueous chlorine dioxide, pumping the slurry through a dwell area to provide a dwell time wherein the wetted slurry remains immersed in the aqueous chlorine dioxide for at least approximately three minutes to disinfect the shredded waste, advancing the slurry into a de-watering apparatus, pressing the slurry to separate the aqueous chlorine dioxide from the disinfected waste, and moving the disinfected waste for compacting or into a waste bin.
Aqueous chlorine dioxide is preferably added to the shredded waste on the following basis. The PLC will monitor the weight of wheeled bins 40 entering into the feed hopper 14b within the previous approximately five minutes. The aqueous chlorine dioxide will be added to the solution at a rate of approximately 30 gallons per minute through a number of flow nozzles. The nozzles are recessed into the sidewalls of the treatment hopper 202. An ultrasonic level sensor monitors the level of liquid disinfectant in the treatment hopper 202 and controls the operation of the shredder 16. If the level of liquid disinfectant in the treatment hopper 202 drops below a threshold, the shredder 16 is stopped until the liquid disinfectant is replenished. The sensor trigger levels are adjustable via the system PLC. The sensor installation will be in accordance with manufacturer's recommendations. The waste treatment system 10b will continue to pump liquid disinfectant into the wetting hopper 202 for at least approximately 10 minutes after the last waste bin has been loaded to the waste treatment system 10b. This period of time is software configurable.
Where feasible, the concentration of chlorine dioxide in the liquid disinfectant will be measured in solution, or if measured in gaseous state, will be based on calibrated parameters. The measurement of the concentration of chlorine dioxide in solution is preferably achieved by accurately diluting a liquid disinfectant sample to a fixed predetermined concentration of approximately one part liquid disinfectant to ten parts of fresh water. Actual chlorine dioxide concentrations in undiluted liquid disinfectant are preferably in the range of approximately 200 to approximately 1,000 PPM and the subsequent dilution will result in a chlorine dioxide concentration somewhere between 0 and approximately 100 PPM. The chlorine dioxide measuring system comprises plumbing to provide a supply of fresh water from the facility water tank 252 to all chlorine dioxide sampling outlets, a filter using standard laboratory filter paper to provide a supply of liquid disinfectant solids removed, a peristaltic pump, which has an adjustable flow rate of approximately 0.06 to approximately 0.25 gallons per hour, for metering the filtered liquid disinfectant, an adjustable flow meter with a range of approximately 7 to approximately 15 gallons per hour for metering the flow of fresh water, a static mixer for mixing the fresh water with the liquid disinfectant (the static mixer having a Reynolds number between approximately 500 and approximately 1,000) to provide a mixture, a rotameter to maintain a constant flow rate of approximately 10 to approximately 20 gallons per hour of the mixture, a chlorine dioxide sensor with a measuring range of 0 to approximately 1000 PPM for measuring the concentration of chlorine dioxide in the mixture, and plumbing to carry the mixture to the water waste tank 255 for neutralizing and disposal. Samples of liquid disinfectant are preferably taken from the Weldon Pump and the main tank 232.
A PH meter may be provided to continuously monitor the liquid disinfectant at the waste water processing system 254. The specifications for the PH meter are monitoring range preferably from 0.00 to 14.00 PH between the temperatures 0-70° C. with a resolution of 0.01 and an accuracy ±0.01 PH, calibration is to be 2 points, and the PH meter is to be suitable for interfacing with a data logger. The PH monitoring is preferably performed in the waste water processing system 254.
Temperatures within the waste treatment systems 10a and lob are preferably monitored with equipment capable of both ° F. or ° C. temperature readings, temperature range of −20° C. to +100° C., resolution of 0.1° to 1° to an accuracy of ±0.75%+1° C., and out-put suitable for data logging. The temperature monitoring is preferably performed in the main tank 232 and the waste water tank 256.
An exhaust system may be provided to extract air from around all liquid disinfectant surfaces. The exhaust system includes adjustable valves at all exhaust points to control flow. Exhaust speeds are preferably at least approximately 700 feet per minute and no more than approximately 1,000 feet per minute and the exhaust system preferably remains operational for approximately one hour after the waste treatment system has been switched off. Air is preferably extracted from the feed hopper 14b (preferably approximately 25 air changes per hour), the treatment hopper 202 (preferably approximately 6 air changes per hour), the de-watering system 220 (preferably approximately 25 air changes per hour), the main tank 232 (preferably approximately 6 air changes per hour), the waste water processing tank 255 (preferably approximately 25 air changes per hour), and all bulk chemical storage areas (preferably approximately at 6 changes per hour). Air from the exhaust system may be filtered through a wet Venturi scrubber. The air from the exhaust system is preferably released at high level to atmosphere, at least approximately 30 feet above ground level and 30 feet from the nearest building. Fan and exhaust system are preferably of plastic construction and suitable for exposure to ClO2 and rated for Zone 1 EExi EN50020 (Area of use European standard) and Class 1 Divisions 1 & 2 UL913 (Area of use US Standard). ClO2 concentration in exhaust gasses is preferably less than 0.1 PPM and is to be monitored by a suitable gas sensor. The ClO2 gas measuring system in the exhaust system is preferably capable of being calibrated and data logged.
The following general requirements apply to the waste treatment system 10b. Seals between surfaces are preferably fabricated out of FFKM (Perfluoroelastomer). These compounds contain fully fluorinated polymer chains and hence offer the excellent performance of elastomers when considering heat and chemical resistance and are for temperatures ranging from −15° C. to +270° C. Piping and tubing used in the system construction are preferably selected from Chlorinated Poly (Vinyl Chloride) (CPVC), polyvinylidene fluoride (PVDF), and PTFE (Teflon). CPVC is a thermoplastic pipe and fitting material made with CPVC compounds which are commonly used for potable water distribution, corrosive fluid handling, and fire suppression systems. CPVC may be glued using PVC schedule 80 adhesive bonded with primer. PVDF possesses the characteristic stability of fluoropolymers when exposed to harsh thermal, chemical, and ultraviolet environments. PVDF is highly resistant to oxidizing agents and halogens and is almost completely resistant to aliphatic, aromatics, alcohols, acids, and chlorinated solvents. PTFE has low friction characteristics, excellent chemical resistance, is impervious to fungi or bacteria, has high temperature stability (260C), low temperature toughness (−160C), and good weathering resistance and electrical properties. Material used for tank fabrication is preferably 316 L SS with the welds cleaned and ground back on wetted surfaces, but may be other material preferably coated with one of CPVC, PVDF, and PTFE. In general, the parts exposed to aqueous chlorine dioxide are preferably made from PVDF, PTFE, or 316 L SS. The non-wetted parts may be made from any of CPVC, PVDF, PTFE, or 316 L SS. The parts not exposed to aqueous chlorine dioxide may be made from material suitable for the material being stored.
The present invention finds industrial applicability in the field of medical waste treatment.
The present embodiments of this invention are thus to be considered in all respects as illustrative and not restrictive; the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US06/29346 | 7/26/2006 | WO | 10/26/2006 |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11212009 | Aug 2005 | US |
| Child | 11568352 | Oct 2006 | US |
| Parent | 11190343 | Jul 2005 | US |
| Child | 11212009 | Aug 2005 | US |
