HK1144798B - Putrescible organic waste treatment system - Google Patents

Description

Putrescible organic waste treatment system

Technical Field

The present invention relates to a putrescible organic waste treatment system and method and to a system and method for producing a supply for producing biogas fuel.

Background

The waste disposal unit is used to comminute putrescible organic waste into a slurry or pulp for transport from the site where the comminution is performed. In the case of domestic use, the waste disposal unit may be located adjacent to a kitchen sink for preparing food.

Larger sized waste disposal units may also be used in industrial applications such as in restaurants, canteens, restaurant canteens, fruit/vegetable stores, food streets, hospitals, fast food restaurants, clubs, bakeries, and supermarkets. Such units are commonly used to grind waste into a slurry, with water added as a transport means to carry the slurry along the waste line to a waste outlet, such as a sewage system. The resulting product that is sent to the waste outlet is substantially liquid.

After treatment in the waste disposal unit, the waste slurry is typically discharged by disposal into a sewage system, thereby increasing the amount of waste that needs to be treated by the sewage system. Furthermore, there is no automatic control of the amount of water required to flush the putrescible organic waste during comminution and it is likely that excess water will be used during comminution. This of course results in a waste of the planned water, which is not environmentally desirable and costly.

Another disadvantage of disposing of putrescible organic waste in a sewage system is that no potential energy source is used. The biological waste may be digested in an anaerobic reactor to produce "biogas". Biogas is approximately 60-65% methane and can be used as a fuel source to produce electricity. The remaining slurry product may then be further processed for use as a fertilizer. At the beginning of writing, this technology has provided 22 facilities worldwide by beta garbage processing (biotechnicalsche abdallverwertung GmbH & cogg) (BTA). A problem with the use of BTA for biogas programs, for example, is that the collected biowaste feed for biogas digesters may be contaminated by inorganic materials, such as plastics, cardboard and ceramics, due to inadvertent incorporation at the site where the putrescible organic waste material is collected.

Any recitation of documents, publications, acts, devices, substances, articles, materials or the like which are included in the present specification is intended to serve as a basis for the context of the present invention. Any such description is not to be taken as an admission that any of the common general knowledge in the relevant art in the field of the invention or the subject matter forming the basis of the prior art extends to the priority date or date of the invention.

Disclosure of Invention

In a first aspect, the present invention provides a putrescible organic waste treatment system comprising:

a comminution unit adapted to substantially comminute putrescible organic waste into a pulp slurry;

a reservoir for storing the slurry from the comminution unit;

a delivery line connecting the comminution unit to the reservoir, the reservoir and the delivery line forming a closed system;

a vacuum extractor operable to depressurize the reservoir to create a reduced pressure in the transfer line and the reservoir to facilitate transfer of the slurried slurry along the transfer line from the comminution unit to the reservoir, wherein the vacuum extractor is operable to depressurize the reservoir, wherein the slurry is delivered to the comminution unit in a slurry form

The comminution unit is adapted to be connected to a water supply and comprises:

a comminution means adapted to substantially comminute putrescible organic waste into a pulp slurry; and

control means adapted to control the flow and/or volume of water supplied to the comminution unit and to control the comminution means;

wherein the control means is responsive to a load on the comminution means to control the amount of water supplied to the comminution unit to produce a waste slurry having predetermined physical characteristics.

In a preferred form of the invention, the operating parameter to which the control means is responsive is the load on the comminution means.

In a second aspect, the present invention provides a putrescible organic waste treatment system comprising:

a comminution unit comprising a rotating comminution device adapted to substantially comminute putrescible organic waste into a slurry-like slurry, the comminution unit being adapted to be connected to a water supply; and

a control device adapted to control the crushing unit;

wherein the control means is adapted to change the direction of rotation of the comminution means each time the comminution unit is operated.

In another aspect, the present invention provides a putrescible organic waste treatment system comprising:

at least one comminution unit adapted to substantially comminute putrescible organic waste into a pulp slurry;

a reservoir for storing the slurry from the at least one comminution unit;

a delivery line connecting the comminution unit to the reservoir, the reservoir and the delivery line forming a closed system,

wherein the system further comprises a vacuum evacuation device operable to depressurize the reservoir to create a reduced pressure in the transit line and the reservoir to facilitate transport of the slurried slurry along the transit line from the at least one comminution unit to the reservoir.

Drawings

Preferred exemplary embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic view of a putrescible organic waste treatment system according to an embodiment of the present invention;

FIG. 2 illustrates a control panel that may be used in the embodiment shown in FIG. 1; and is

Figure 3 shows a graph of current read by the load cell versus time during a shredding cycle.

Detailed Description

The following description is directed to preferred embodiments of putrescible organic waste treatment systems, treatment methods, and methods and systems for generating biogas fuel in accordance with the present invention. In order to facilitate an understanding of the invention, reference is made in the description to the accompanying drawings whereby the invention is illustrated in a preferred embodiment. Similar components between the embodiments are identified by the same reference numerals.

Figure 1 shows a schematic view of an embodiment of the present invention in which a putrescible organic waste treatment system 10 is shown comprising a comminution unit 12, the comminution unit 12 having an outlet 20 in fluid communication with a container in the form of a reservoir 14. The comminution unit 12 includes an internal chamber 18 for receiving perishable organic waste. The internal chamber 18 is located above the grinding unit 16, and the grinding unit 16 is used to pulverize and grind perishable organic waste. The system 10 also includes a control panel 22 for controlling the pulverizing unit 12.

The comminution unit 12 comprises comminution means in the form of a grinding unit 16, the grinding unit 16 being operable by a motor 17 to comminute putrescible organic waste into a slurry or pulp during a comminution operation. The comminution unit also comprises a mechanical brake 11 for stopping the grinding unit 16. The brake 11 communicates with a control unit in the form of a Programmable Logic Controller (PLC) 30. It will be appreciated that in alternative embodiments other comminution units may be used, such as cutting blades, the motor 17 may be internal or external to the comminution unit 12 and the brake 11 need not be provided.

A water supply 27 is also connected to the comminution unit 12 and is controlled by the PLC 30. Water from a water supply 27 is introduced into the comminution unit 12 at the inner chamber 18 from the water jets 24 and is introduced into the comminution unit 12 at the grinding unit 16 from the water jets 26.

Additional water spray inlets may be provided in the pulverizing unit 12, if desired. For example, if a pump is used to pump the waste slurry from the comminution unit 12 to the reservoir 14 (as opposed to a vacuum device as described below), an additional water inlet may be provided between the grinding unit 16 and the pump to prime the pump prior to use.

The PLC30 is programmed to receive information from the comminution apparatus regarding operational parameters of the comminution apparatus and to control the grinding unit 16 and the water supplied to the comminution unit during comminution of the perishable organic waste based on the information.

For example, the motor 17 may be equipped with a load sensor 19 for sensing the load on the motor 17 driving the comminution means. For softer waste, such as vegetable matter, the load cell 19 will only read a low load and the PLC30 will not supply a large amount of water. Conversely, for harder waste, such as bone and/or seeds, etc., the load cell 19 would read the high load and the PLC30 would supply a large amount of water to assist in shredding and transporting the shredded waste from the unit 16. Additionally, when a suitably small load is detected on the grinding unit 16, the controller 30 will interpret this as that there is no more material to be crushed and will switch off the grinding unit 16.

Finally, if it is sensed that the load on the motor 17 exceeds a predetermined value or exceeds a predetermined value for a predetermined time, the PLC30 will be programmed to interpret this as an indication that the finishing unit 16 has become sticky and should either be switched off or change the direction of rotation (as described below) in order to prevent damage to the finishing unit 16 or the motor 17.

When the PLC30 cuts power to the finishing unit 16 (e.g. at the end of a cycle or in the event of a jam/jam or some other fault), the PLC30 also operates the brake 11 to stop the rotation of the finishing unit. Although the finishing unit 16 would of course eventually stop rotating itself without power (and thus the brake 11 is not strictly necessary), by providing the brake 11 the finishing unit 16 would stop in a shorter period of time, allowing the stopping time (either due to antiquity or simply the time between cycles) to be minimised. Alternatively or additionally, dynamic braking may be used to stop rotation of the grinding unit more quickly. A simple dynamic braking device may include such a PLC 30: that is, the PLC30 turns on a dynamic braking resistor (not shown) across the armature terminals of the motor 17 when the PLC30 cuts power to the grinding unit, thereby converting the motor 17 into a generator.

By supplying water according to the load of the comminution apparatus, the PLC30 can automatically determine and increase the appropriate amount of water to ensure one or more of the following pulp characteristics are produced by the comminution unit:

specified pulp density

Range of slurry density

A specified water content; or a range of water content, flow characteristics or a range of flow characteristics.

The density, water content and flow characteristics may be selected to ensure the most efficient transport of the slurry waste material or to optimize the slurry waste material for further use. For example, further applications of the pulp waste material may be transported to a biogas plant for use in a digester for the production of biogas.

The PLC30 can be programmed to introduce a predetermined volume of water during each pulverizing cycle. A suitable volume of water per cycle may be between 2 and 5 litres, this volume being divided between the jets 24 and 26. Alternatively, the PLC30 may be programmed to vary the amount of water supplied in accordance with the load on the motor 17.

The water jets 24 and 26 are supplied by a mains water supply line 27, which mains water supply line 27 comprises an on/off control valve 28. The on/off control valve 28 is for allowing water to flow to the spout 24 in use. The outlet 20 of the comminution unit 12 is connected to the reservoir 14 via an outlet line 21.

In a preferred embodiment of the invention, the reservoir 14 is equipped with a vacuum pump 34 for depressurizing the reservoir 14. In an embodiment, waste from the shredding unit is transported through a pipe under the suction force created in the sealed reservoir 14. The vacuum pump 34 is operable to generate a negative pressure in the system, for example, up to-25 inches of mercury. To generate and maintain this pressure, the level indicator 40 in the reservoir 14 can be configured to register that the reservoir 14 is full when there is still 250 liters of empty space in the reservoir 14. Typically, each cell 12 will deliver approximately 25 liters of fluid to the reservoir 14 in each cycle. The vacuum system may be designed to provide fluid drainage from the (or each) unit to the reservoir 14 along the backbone outlet line. It is clear that for different unit devices and equipment different drainage systems, reservoirs, transfer pipes etc. are needed in order to have the ability to move the desired liquid, solid and air mixture to the reservoir.

This arrangement is particularly suitable where a plurality of separate comminution units are operating (e.g. apartment buildings or food houses) and all units fill a single common reservoir 14. The units may all be connected to the reservoir by a single backbone outlet line. Alternatively, each unit may be connected to the reservoir 14 by a separate outlet line. The PLC30 is connected to the vacuum pump to operate the vacuum pump when the pulverizing unit is operated. Alternatively, the vacuum pump may be adapted to operate on a pressure switching system.

In order to prevent an inadvertent loss of suction in this embodiment, a sealing valve 35 is provided between the comminution unit 12 and the conveyor line 21. The valve 35 is connected to the PLC30, and the PLC30 operates the valve between an open state and a closed position. In the closed state, air is substantially blocked from flowing from the pulverizing unit 12 into the outlet line 21, thus maintaining pressure in the system 10. At the appropriate time (e.g., at the beginning of the pulverizing cycle), PLC30 causes sealing valve 35 to open to draw the slurry along transfer line 21 into reservoir 14. Alternative means for conveying the waste slurry through the system are of course possible. For example, instead of the reservoir being equipped with a vacuum pump 34 to generate a vacuum for waste transport, a standard pump may be installed to pump waste from the shredder unit 12 to the reservoir 14. Suitable locations for such pumps are identified by reference numeral 34A. As mentioned above, if a standard pump is used to pump waste through the system, an additional water outlet (not shown) may also be provided to prime the pump. An additional water outlet would be advantageously connected to the mains water supply 27 via valve 28 and located between the location of the grinding unit 16 and pump 34A.

The reservoir 14 is also connected to an outlet conduit 15, said outlet conduit 15 comprising a valve 44 as shown in the figure. Preferably, the valve 44 is manually operable to enable an operator to empty the reservoir 14 independently of the comminution unit 12 and PLC 30. As discussed below, the reservoir 14 also includes a level sensor 40, the level sensor 40 for sensing the level 42 of the slurry in the reservoir 14 at any given time.

The PLC30 is capable of actuating the valve 28 to supply water to the comminution unit 12 as will be described below. The PLC30 is also connected to the control panel 22 of the system 10.

In addition to the reservoir 14, the system as described above may be included in a single unit so as to be conveniently located adjacent to a food preparation or treatment area, for example in a kitchen or food processing facility. Such a unit may be suitably dimensioned, for example dimensioned similarly to a domestic washing machine, and the control panel 22 may optionally be integrally formed therewith. Alternatively, the control panel 22 may be located adjacent to the unit. Suitable materials for forming the unit and the various components located within the unit include, for example, stainless steel, allowing for easy cleaning and decontamination when desired. In another embodiment of the invention, the reservoir 14 may be integrated within the unit for a particular application, and may be detachable so that it may be conveniently emptied.

The shredder unit 12 further includes a cover 52 that pivots about a pivot joint 53 and is used to cover the chamber 18 during operation of the shredder unit. The lid is designed to be lifted by an electronic actuator (not shown) also connected to the PLC 30. As a safety measure, the PLC30 is programmed to not allow the shredder to operate when the lid is open.

In use, the upper portion 18 of the chamber is provided with inclined walls to funnel perishable organic waste material onto the grinding unit 16. A water jet 24 (which may be one of a plurality of water jets disposed around the periphery of the upper portion 18 of the chamber) is directed towards the surface of the hopper to create a centrifugal flow of water to ensure that substantially all of the waste material is leaked onto the grinding unit 16. The grinding unit 16 pulverizes and grinds the putrescible organic waste material in the presence of water to produce a putrescible organic waste slurry.

The controller 30 is also configured to store data records regarding the shredder unit 12 and the storage 14 and to communicate with the central server using this information. The controller 30 may be programmed to upload the operational data at regular intervals, for example once a day, and may communicate with a server (again by way of example only) via a dedicated wired or wireless connection, or via a dial-up modem.

The data may include, for example:

the number and type of shredding cycles performed by the shredding unit 12

The total time that the comminution unit 12 has been operating

Load information sensed by the load sensor 19

Control operations selected by the user of the machine (as described below)

The configuration of controller 30 (e.g., communication settings, settings of grinding unit 16, settings of door 52)

Volume of water used during the comminution cycle

How the capacity of the reservoir 14 varies with each comminution cycle

Current capacity of the storage 14

Any machine failure

Such data, both operational data and statistical data, may be used to determine overall statistical information such as whether and when imminent maintenance of various components of the comminution unit 12 (e.g., the motor 17 or the grinding unit 16) may be required, when the reservoir 14 will need to be emptied, and the efficiency of the comminution unit 12 with respect to water usage.

Referring to FIG. 2, a more detailed diagram of the control panel 22 of FIG. 1 is shown. The control panel 22 includes:

a level display 22A, which displays the level of the reservoir 14;

an alarm display 22G that displays alarm information, for example, in the case where a failure such as a jam or jam is detected in the pulverization unit 12;

the solids circulation button 22B, which inputs to the PLC 30: the waste placed in the chamber 18 is substantially solid;

a mix cycle button 22C that inputs to the PLC 30: the waste placed in the chamber 18 is a mixture of solid and liquid;

the liquid circulation button 22D, which inputs to the PLC 30: the waste placed in the chamber 18 is liquid;

a stop button 22E that terminates the pulverization unit 12; and

a flush button 22F that initiates a flush cycle to flush the comminution unit 12 and the pipe work, as will be described further below.

In this example, while the user is able to manually operate the system through the control options 22B through 22F, it will be appreciated that the system may be fully or partially automated and that various sensors and controllers may be implemented in the system to at least partially control various components of the system without departing from the scope of the present invention. For example, the control panel may be limited to allow the user to only initiate a grinding cycle or a rinsing cycle. In this case, when the user selects a grinding cycle, the controller 30 will determine the appropriate amount of water to be added and the time at which the grinding unit 16 should operate (as described above) based on the sensed load of the grinding unit 16.

Referring again to fig. 1, a pulverization process according to an embodiment of the present invention is described. The lid 52 is lifted by the operator of the shredder unit 12 or automatically by the priming of the actuator device. Perishable organic waste is loaded into the chamber 18. The lid 52 is closed and the operator uses the control panel 22 to initiate operation of the shredder unit 12. A signal is sent to the PLC30 and the PLC30 initiates the grinding cycle. PLC30 activates valve 28 to supply a plug of water to chamber 18 and, if desired, grinder unit 16.

The spout 28 is located at a position on the cone to allow the fluid to travel centrifugally to ensure that the waste material is swept away from the walls of the internal chamber 18. The opening of the internal chamber 18 opens into the mill unit 16, allowing the mill unit 16 to slurry the material to a predetermined size. Valve 28 is activated for a period of time set by PLC30 using information received from load cell 19 to provide a volume of water to spray jets 24, 26 that will produce an optimal waste slurry. The operation of the grinding unit 16 itself is also controlled by the controller 30 based on the sensed load on the motor 17.

An optimal slurry density is determined to ensure that the slurry is optimal for transport to and from the storage 14. Valve 28 is a variable valve and is capable of varying the water flow between 0% and 100% of the total available water flow depending on the desired flow characteristics and the desired slurry density.

The PLC30 is also programmed to alternate the direction in which the finishing unit 16 is rotated. For example, the direction in which the grinding unit 16 rotates may be changed for each successive use of the unit. For example, the PLC30 may control the grinding unit 16 to rotate in a clockwise direction as indicated by arrow 54 for a first use, in a counterclockwise direction as indicated by arrow 56 for a second use, in a clockwise direction for a third use, and so on. This is particularly advantageous because each time the mill unit 16 is activated, residual slurry or material is removed from the mill unit 16 rather than potentially jamming and damaging the mill unit 16.

Alternatively, the PLC30 may be programmed to cause the direction of rotation of the grinding unit 16 to change when the load on the motor 16 exceeds a predetermined value or exceeds a predetermined value for a predetermined period of time. In this case, the PLC30 interprets the sensed load as an indication that the grinding unit 16 is stuck and can be released by changing the direction in which the grinding unit 16 is rotated.

To transport the waste slurry, PLC30 also activates pump 34 to depressurize storage 14 and transport the waste slurry to storage 14.

In the event that the waste for a particular cycle consists primarily of liquid or has a liquid component, such as oil, broth, juice, sauce, etc., the system 10 will selectively operate without causing the grinding unit 16 to operate while the waste is being conveyed to the reservoir 14. This liquid provides a high energy supply for cooking by the biodigester. It will be appreciated that while such liquid may be introduced into the system and added to the slurry already contained within reservoir 14, the predetermined water content or density is still maintained by adding water or alternatively by pouring out otherwise excess water.

Once reservoir 14 is filled with slurry fluid of optimal or predetermined density, the contents of reservoir 14 are periodically removed for shipment, such as by a waste delivery truck. The outlet of the reservoir 14 includes a valve 44 which is a manually operable on/off valve.

In a preferred embodiment, the waste slurry is transported to a biogas production plant which utilizes the waste slurry as a product supply to produce biogas.

In a preferred embodiment, the reservoir 14 further includes a level sensor 40, the level sensor 40 sensing a level 42 of the reservoir 14. The level sensor 40 may be, for example, a sonar device and is arranged to send a signal to the PLC30, which PLC30 then displays the level of the reservoir on the control panel 22. This allows a user of the system to remotely determine when the level of the reservoir is near full. When the waste in the reservoir 14 reaches a predetermined level, the controller 30 is programmed to indicate to the user that only a set of several grinding cycles are allowed and that the reservoir must be emptied. Once a set of several cycles has been performed (or in the event that the total capacity of the reservoir 14 is reached), the controller 30 will prevent operation of the comminution unit 12 until the reservoir has been emptied. As a safety mechanism, the controller 30 may also prevent any operation of the pulverizing unit 12 if no signal is received from the level sensor 40.

As an additional safety mechanism, the reservoir 14 may also include a float switch that communicates with the PLC30 when the reservoir 14 is full and prevents any operation of the pulverizing unit until the reservoir 14 has been emptied.

Figure 3 provides a plot of the current (read by the load cell 19) of the motor 17 during a shredding cycle. As shown in the figure, the current peaks at time 1 second (at the start of the comminution process) and gradually decreases over time as the waste passes through the grinding device 17 and is comminuted. At time 23 seconds, the current reading of the motor 17 is about 1 amp, which the controller 30 interprets as no further waste needs to be crushed and the grinding unit 16 should be switched off. As described above, the controller 30 may be programmed to add a predetermined volume of water to the pulverizing unit 12 during each pulverizing cycle, regardless of the load sensed by the load sensor 19. Alternatively, the controller 30 may be programmed to vary the amount of water added in accordance with the load on the motor 17. It will be appreciated that the system 10 may be automated to export and subsequently store waste slurry of a desired density in a storage. This ensures that excess or insufficient water is used to produce the waste slurry stored in the reservoir 14. The optimum waste slurry density should be such that a minimum amount of water is contained in the slurry to ensure comminution and transport through the pipework 20, 21, 15. This ensures that the storage 14 is able to store a maximum amount of perishable organic waste for the capacity of the storage. This ensures that the collection of perishable organic waste from the reservoir 14 is minimised, advantageously optimising the transport process.

A further advantage of the present system 10 is that it prevents putrescible organic waste from being disposed of through the sewage system, thereby reducing the load on the environment and sewage system.

Clearly, the density of the waste contained in the waste reservoir can be varied as desired, either by adding water to the waste or allowing the waste to settle and dump excess water from reservoir 14. This can be achieved by: or by allowing excess water to pass through suitable filters or baffles so that the water leaving the reservoir is sufficiently clear to enter the municipal sewage system directly without further treatment; or by having some form of simple pre-treatment reservoir through which the water passes before entering the sewage system or other treatment means. Optionally, the system may have a density control sensor located in the reservoir to evaluate whether water needs to be added to or removed from the reservoir to achieve the preferred density/fluidity characteristics to ensure that the waste hauling vehicle and system operates at optimum efficiency.

It will also be appreciated that if a filter is used with the system, inorganic materials such as plastics may be substantially prevented from entering the reservoir 14.

A further advantage of the invention is that the pulp material is essentially organic, which can be used as a supply source for producing biogas in a digester. Accordingly, the present invention allows for greater efficiency and control of the collection of putrescible organic waste at a treatment site.

It will be appreciated that a plurality of systems according to the invention may be included in, for example, a high-rise unit building or a food street, etc., in turn plumbed to a single reservoir to facilitate collection from one source. Generally, such devices work well when the transport of material is achieved via a vacuum transport line to a reservoir evacuated with a pressure-switching vacuum pump.

It will also be appreciated that when perishable organic waste is dumped in a conventional dunpster tank, it is easily mixed with other non-degradable waste and becomes worthless for further processing due to the presence of the other non-degradable waste. Moreover, the waste at least partially decays before the dunpster tank is emptied, resulting in discomfort and potential health risk issues. Waste from such dunpster tanks is dumped at the dump site, the food waste is further degraded and decayed and gives off methane gas, which is a gas determined to be responsible for part of the global warming. The invention allows energy to be generated from such perishable waste by means of a biogas digester rather than allowing the gas to heat the environment prior to combustion. The current lack of use of polymeric bags in which such perishable waste is stored and dumped at a waste dump site provides another environmental advantage. Also, bad smell of food waste degraded at a conventional waste dump site is reduced by treating such waste according to the present invention.

It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the present invention.

The foregoing describes embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims (12)

1. A putrescible organic waste treatment system comprising:

a comminution unit adapted to substantially comminute putrescible organic waste into a pulp slurry;

a reservoir for storing the slurry from the comminution unit;

a delivery line connecting the comminution unit to the reservoir, the reservoir and the delivery line forming a closed system;

a vacuum extractor operable to depressurize the reservoir to create a reduced pressure in the transfer line and the reservoir to facilitate transfer of the slurried slurry along the transfer line from the comminution unit to the reservoir, wherein the vacuum extractor is operable to depressurize the reservoir, wherein the slurry is delivered to the comminution unit in a slurry form

The comminution unit is adapted to be connected to a water supply and comprises:

a comminution means adapted to substantially comminute putrescible organic waste into a pulp slurry; and

a control device adapted to control the flow rate and/or volume of water supplied to the comminution unit and to control the comminution device,

wherein the control means is responsive to a load on the comminution means to control the amount of water supplied to the comminution unit to produce a waste slurry having predetermined physical characteristics.

2. A putrescible organic waste treatment system according to claim 1, wherein the amount of water supplied to the comminution unit is directly proportional to the load of the comminution means.

3. A putrescible organic waste treatment system according to claim 1 or 2, wherein the control means is responsive to the load of the comminution means to control the operation of the comminution means.

4. A putrescible organic waste treatment system according to claim 1, wherein the comminution means is driven by a motor and the load on the comminution means is sensed by a load sensor connected to the motor.

5. A putrescible organic waste treatment system according to claim 1, wherein the system further comprises a brake operable by the control means to brake the comminution means.

6. A putrescible organic waste treatment system according to claim 1, wherein:

the crushing device is a rotating crushing device; and is

The control means is adapted to change the direction of rotation of the comminution means.

7. A putrescible organic waste treatment system according to claim 6, wherein the control means is adapted to change the direction of rotation of the comminution means each time the comminution unit is operated.

8. A putrescible organic waste treatment system according to claim 6 or claim 7, wherein the control means is responsive to a load on the comminution means and the control means is adapted to change the direction of rotation of the comminution means if the load on the comminution means exceeds a predetermined level.

9. A putrescible organic waste treatment system according to claim 1, wherein the evacuation means is adapted to maintain the pressure in the closed system at up to minus 25 inches of mercury.

10. A putrescible organic waste treatment system according to claim 1, wherein a sealing valve is provided between the comminution unit and the transport line, the valve being operable by comminution unit control means between a closed condition in which air flow from the comminution unit into the transport line is substantially prevented and an open condition in which air and the slurry can pass from the comminution unit into the transport line.

11. A putrescible organic waste treatment system according to claim 1, wherein the system comprises a plurality of comminution units connected to the reservoir by a plurality of transport lines.

12. A putrescible organic waste treatment system according to claim 1, wherein the system comprises a plurality of comminution units connected to the reservoir by the same transport line.