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 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 cause jamming. The '925 and the '248 patents are herein incorporated by reference.
The present invention addresses the above and other needs by providing a waste treatment system which grinds waste material into small pieces and soaks the pieces in a liquid disinfectant. The system includes a hopper, a grinder, a main solution tank, and an auger conveyer. Unprocessed waste material is dumped into the hopper. The hopper feeds the unprocessed waste material into the grinder. The grinder includes a rotor and anvil for grinding the unprocessed waste material. The ground material falls into the main solution tank where the ground material is wetted with the liquid disinfectant. The wetted waste is carried from the main solution tank by the auger, and spends an additional two to three minutes of wetted time on the auger conveyer before entering a de-watering section. The total wetting time allows the waste material to be completely disinfected.
In accordance with one aspect of the invention, there is provided an apparatus for infectious waste treatment. The apparatus comprises a lift for lifting a waste container to a hopper, a hopper for receiving waste material from the waste container, a grinder for receiving the waste material directly from the hopper and grinding the waste material, a main solution tank for receiving and wetting the ground waste material, and an auger for carrying the wetted material from the main solution tank. The grinder comprises a rotor positioned below the hopper, an anvil in grinding cooperation with the rotor, and a sizing screen for controlling the size of the ground waste material. A liquid disinfectant is sprayed onto the ground waste material in the main solution tank, and a chopper pump circulates the liquid disinfectant.
In accordance with another aspect of the invention, there is provided a method for treating hospital waste. The method includes pouring waste material into a hopper, providing the waste material to a grinder, grinding the waste material in the grinder, wetting the ground waste material with a liquid disinfectant, and carrying the wetted waste material on an auger for between two and three minutes.
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 waste treatment system 10 according to the present invention is shown in
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. The auger 20 further includes a fluid trap 28 where the liquid disinfectant used to wet the ground waste is trapped and recirculated back into the main tank. A rotatable section 26 of the auger housing 21 may be rotationally positioned relative to the auger housing 21 at various rotations to adjust the position of a chute 24. If the chute 24 is pointed down, the back pressure on the flow of the ground waste 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 ground waste 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 ground waste is maximized, and the amount of liquid disinfectant removed by the fluid trap 28 is maximized.
A lift 42 for lifting a waste container 40 to dump waste into the hopper 14 of the waste treatment system 10 is shown in
A side view of a grinder 16 suitable for use with the waste treatment system 10 is shown in
A cross-sectional view of the grinder 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 10 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
In an exemplar embodiment, the continuous gas monitoring system 38 includes an electrical control panel, a pump control box, and an operator console. The electrical control panel comprises a PLC control unit, variable frequency drives for the grinder and auger, motor starters for fan and pump, 120VAC and 24VDC control voltage supplies. The pump control box comprises chemical pumps, chemical concentration, reservoir tank water level and air pressure controls, and a three light stack alarm annunciator. The operator console comprising a six inch touchscreen 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 sensors junction terminal blocks.
All system functions are completely automatic 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 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 in to the hopper (there is a 5 sec delay at the top emptying position). The shredder, auger and HEPA fan will start running. If in Medical mode, the circulation pumps will start running. The lift will lower the waste bin. The hopper door will close. If in Medical mode, the chlorine dioxide generator will start pumping chemicals into the system based on the chemical concentration set point adjusted on the chemical concentration controller. The shredder will continue to run based on the pre-programmed cycle time. The cycle time maybe 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
While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.