GB2543369A

GB2543369A - An apparatus for treating waste water

Info

Publication number: GB2543369A
Application number: GB1604004.0A
Authority: GB
Inventors: Loughrey Nicholas; O'neill James
Original assignee: Env Products & Services Ltd
Current assignee: Env Products & Services Ltd
Priority date: 2015-10-16
Filing date: 2016-03-08
Publication date: 2017-04-19
Also published as: GB201604004D0; GB201518323D0; CN206045584U

Abstract

The apparatus comprising a reservoir 100 having at least one waste water inlet (103, figure 1) for passing waste water into an inlet region of the reservoir, at least one waste water outlet (106, figure 1) for draining waste water from an outlet region of the reservoir. Contaminants with a specific gravity less than one are able to settle on top of the waste water, at least one sensor 12 being provided on an exterior wall 2 of said reservoir at a predetermined level for determining the presence of water within the reservoir at said predetermined level adjacent the sensor without physical contact with said water, means for removing said contaminants 14 from said reservoir at or adjacent said predetermined level, and a controller 18 for controlling operation of said contaminant removal means in response to signals received from said at least one sensor when said sensor indicates an absence of water. Also disclosed is a method of operating the apparatus.

Description

An Apparatus for Treating Waste Water

FIELD OF THE INVENTION

This invention relates to a method and to an apparatus for treating waste water and in particular to an apparatus for removing fats, oils and grease (hereinafter referred to as FOG) from waste water downstream of a washing facility, such as a sink in a commercial kitchen. The apparatus may also be adapted to remove solid waste, such as food waste, from said waste water.

BACKGROUND OF THE INVENTION

Typically waste water drained from a sink in a commercial kitchen or catering facility contains grease in an emulsified state, as well as grease laden solids in suspension, typically in the form of food waste. Such contaminants can cause blockages in drainage systems and/or fouling of filtration systems or pumps within water treatment plants downstream of the drainage system.

Effluent from FOG contamination points in commercial kitchens typically originates from steam combination ovens, convection rotisserie ovens, pot sinks, pre-rinse sinks, dishwashers, canopies and the like. They have in common the use and application of hot water, typically ranging in temperature from 40° C to 85° C, for the purposes of dealing with FOG contamination, where FOG is washed away in the waste water stream from such devices.

For these reasons, depending on the country, it is often compulsory for commercial kitchen operations to fit some kind of interceptor device to collect the FOG before it enters the sewer, typically referred to as a grease trap. Additionally where FOG is a concern in the local wastewater collection system, inspection programmes have been set up to ensure that these grease traps and/or interceptors are being maintained on a routine basis.

Known grease traps range in complexity from simple settling tanks, known as "passive" grease traps, that require periodic manual intervention to pump out or otherwise remove grease, to rather complex structural arrangements that provide for automatic skimming and collection of skimmed fats, oils and grease into external containers positioned adjacent the trap assembly, commonly referred to as "automatic" grease traps or GRU (Grease Removal Units) or grease recovery units.

Passive grease traps are, in essence, simply a settling tank having a wastewater inlet at one end and an outlet at an opposite end for connection to a drain. Often baffle plates are arranged within the tank to interrupt direct flow-through of wastewater between the inlet and the outlet. Emptying grease traps is an extremely unpleasant and time consuming task. It is also difficult to know when the accumulated FOG must be removed.

Automated grease traps include automatic skimmer arrangements, typically utilising a rotating skimmer device, in the form of a disc, drum, endless belt or tube, mounted above the tank and connected to a drive arrangement to move the skimming device into and out of the waste water within the tank of the grease trap. The skimming device collects FOG from the surface of the water in the tank as it moves out of the water and is subsequently cleaned by means providing a scraping or squeezing action on the skimming device, such as wiper blades, arranged to direct the collected FOG into a collection device before the skimming device passes back into the water. The collection device is typically a separate container or reservoir located on one side of the tank. Such automated grease traps can require frequent maintenance and cleaning and can be costly.

The illicit reuse of waste grease (known as gutter oil) is a health problem in many countries, in particular in China. Therefore it is important to provide a verifiable record of the amount of FOG collected in a grease trap to ensure that it is disposed of correctly. This is generally not possible with known automated grease traps, particularly those using rotating skimmer devices. A further issue is that grease traps tend not to be regularly maintained, thus further contributing to the inefficiency of grease traps. The evidence in support of such a statement is the raft of statistics available from the drainage network companies as to the number of blockages attributable to FOG and to the service providers who clear drain blockages. The number of blockages and pollution incidents relating to fat, oil and grease are also increasing. There are approximately 200,000 sewer blockages throughout the UK every year of which up to 75% are caused by FOG. Clearing these blockages costs millions of pounds a year. Businesses also risk blocking their own drainage systems, which results in extra costs being incurred in clean-up efforts. These fat blockages can result in sewer flooding, odour problems and the risk of rat infestations, both near and beyond the affected premises. In fact, every outlet disposing of fat, oil and grease and food waste to drains is at risk of experiencing damaging and costly drainage problems In the United States, each year sewers back up annually an estimated 400,000 times, and municipal sewer overflow on over 40,000 occasions. The EPA has determined that sewer pipe blockages are the leading cause of sewer overflows, and grease is the primary cause of sewer blockages. Even if accumulated FOG does not escalate into blockages and sanitary sewer overflows, it can disrupt wastewater utility operations and increase operations and maintenance requirements.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an apparatus for treating waste water comprising a first reservoir having at least one waste water inlet for passing waste water into an inlet region of the first reservoir, at least one waste water outlet for draining waste water from an outlet region of the first reservoir, wherein contaminants, such as fats, oils and grease, having a specific gravity less than one are able to settle out on top of the waste water, at least one sensor being provided on an exterior wall of said first reservoir at a predetermined level for determining the presence of water within the first reservoir at said predetermined level adjacent the sensor without physical contact with said water, means for removing said contaminants from said first reservoir at or adjacent said predetermined level, and a controller for controlling operation of said contaminant removal means in response to signals received from said at least one sensor when said sensor indicates an absence of water.

At least one baffle may be provided between said inlet region and said outlet region of the first reservoir to provide a convoluted path for the waste water to encourage the contaminants to settle out of the waste water.

Preferably the or each sensor comprises a field effect sensor.

In one embodiment at least three sensors may be arranged in a linear array at said predetermined level on said exterior wall of said first reservoir, said controller operating said contaminant removal means only when at least two of said at least three sensors indicate an absence of water.

Said contaminant removal means may comprise a pump communicating with a contaminant inlet opening into the first reservoir at or adjacent said predetermined level. Said contaminant inlet may be located above said predetermined level such that a layer of said contaminants is maintained on top of the waste water contained within the first reservoir.

In one embodiment said controller is programmed to operate the contaminant removal means when the at least one sensor ceases to detect the presence of water at said predetermined level within the first reservoir, indicating the presence of contaminants at said predetermined level, to remove said contaminants from the first reservoir, the controller subsequently waiting for the at least one sensor to once again detect the presence of water before operating the contaminant removal means a subsequent time.

In one embodiment said controller may be programmed to initiate a contaminant removal process when the at least one sensor ceases to detect the presence of water at said predetermined level within the first reservoir, indicating the presence of contaminants at said predetermined level, said contaminant removal process comprising the steps of operating said contaminant removal means for a predetermined time period to remove a layer of contamination, such as a layer of FOG, from the first reservoir, adding water to first reservoir for a predetermined period and/or until a predetermined volume of water has been added, and repeating said steps until the at least one sensor to once again detect the presence of water, thereafter ceasing the contaminant removal process until the at least one sensor once again ceases to detect the presence of water.

The controller may be programmed to indicate a fault if the at least one sensor fails to once again detect the presence of water after a predetermined period of time or activity.

In another embodiment said controller may be programmed to check if the at least one sensor ceases to detect the presence of water at said predetermined level within the first reservoir after a predetermined period of time or at predetermined time intervals, such as once a day, and to operate the contaminant removal means when said at least one sensor ceases to detect the presence of water.

The apparatus may further comprise a second reservoir for storing a predetermined volume of water therein, said second reservoir receiving waste water from said waste water outlet of the first reservoir, means being provided for passing water from said second reservoir into said first reservoir under the control of said controller. Said means for passing water from said second reservoir to said first reservoir may comprise a pump. Said second reservoir may be provided with a drain outlet for draining waste water in excess of said predetermined volume from the second reservoir.

The controller may be programmed to operate said means for passing water from said second reservoir into said first reservoir after the contaminant removal means has been operated to remove contaminants from the reservoir, at least until the at least one sensor detects the presence of water within the first reservoir at said predetermined level, the controller being programmed to prevent operation of said contaminant removal means until he at least one sensor detects the presence of water within the first reservoir at said predetermined level.

The apparatus may further comprise a storage reservoir adapted to receive contaminants from said first reservoir via said contaminant removal means. A device may be provided for agitating the contaminants collected on top of the waste water within the first reservoir. Said agitating device may comprise one or more reciprocally or rotatably driven paddles. The controller may be programmed to operate said device for agitating the contaminants collected on top of the waste water at predetermined intervals and/or when the at least one sensor indicates the absence of water at said predetermined level within the first reservoir.

Preferably the controller is adapted to communicate with a remote location, for example to a pager or mobile phone.

The apparatus may further comprise means for removing solid waste, such as food waste, from the waste water upstream of the first reservoir. Said means for removing solid waste may comprise a strainer or filter means provided upstream of the grease trap for separating and collecting food waste from the waste water feed. The means for removing solid waste may comprise one or more filter trays, a filter drum or a filter deck for collecting solids material while passing liquid effluent to the first reservoir. In an alternative embodiment the mens for removing solid waste may comprise a compostable and/or biodegradable bag serving to filter solid waste from the waste water, the waste water draining through perforations in the bag, preferably not exceeding 4mm in diameter. A compression means may be provided for squeezing waste water out of the bags. The means for removing solid waste may incorporate heating means, such as a hot air blower.

Means may be provided for adding an additive to the separted solid waste, such as Calcium Hydroxide/Lime, to adjust the pH of the solid waste and/or deodorise the solid waste, for example by means of a pasteurisation process.

Preferably the bags and food waste content may be recycled through anaerobic digesters or composted or alternatively utilised as a renewable energy source in the co-generation of electricity and thermal energy.

The bags are preferably sufficiently robust to withstand being handles, for example thrown a distance of 5 metres onto a hard surface, without splitting and allowing the contents to spill out.

The bags may have a means for being attached to an under counter apparatus (possibly a swing out bag holder attached to a swing out door which when closed forms a seal around the bag and at the base of which will be a tun dish to collect and direct the effluent into a grease trap. The bags may be capable of being sealed with a draw string or similar.

According to a further aspect of the present invention there is provided a method of operating an apparatus for treating waste water comprising providing at least one sensor on an exterior wall of a first reservoir at a predetermined level for determining the presence of water within the first reservoir at said predetermined level without physical contact with said water, and carrying out a contaminant removal process by operating a means for removing contaminants, such as FOG, from said first reservoir at or adjacent said predetermined level when said at least one sensor indicates an absence of water at said predetermined level, indicative of the presence of contaminants at said predetermined level.

The contaminant removal process may comprise operating said contaminant removal means to remove said contaminants from the first reservoir and subsequently adding water to the first reservoir, said contaminant removal process proceeding until the at least one sensor indicates the presence of water once again.

In one embodiment said contaminant removal process may comprise the steps of operating said contaminant removal means for a predetermined time period to remove a layer of said contaminants from the first reservoir, adding water to first reservoir for a predetermined period and/or until a predetermined volume of water has been added, and repeating said steps until the at least one sensor to once again detect the presence of water, thereafter ceasing the contaminant removal process until the at least one sensor once again ceases to detect the presence of water.

Said water may be added to said first reservoir from a second reservoir adapted to receive waste water from a waste water outlet of the first reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

An apparatus for treating waste water in accordance with an embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is a schematic view of a waste water treatment apparatus in accordance with an embodiment of the present invention;

Figure 2 is a schematic view of a grease trap assembly of an apparatus for treating waste water in accordance with an embodiment of the present invention;

Figure 3 is a schematic view of a grease trap assembly of a waste water treatment apparatus in accordance with a further embodiment of the invention;

Figure 4 is a further view of the grease trap assembly of Figure 3;

Figure 5 is a schematic view of a modified waste water treatment apparatus in accordance with a further embodiment of the present invention;

Figure 6 is a schematic view of a waste water treatment appratus in accordance with a further embodiment of the present invention; and

Figure 7 is a schematic view of a waste water treatment appratus in accordance with a further embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

An apparatus for treating waste water in accordance with a first embodiment of the present invention is illustrated in Figure 1. The apparatus comprises a first section 100, comprising a food waste removal and drying process, for removing solid contamination, in particular solids food waste, from the waste water, and a second section 200, comprising a FOG removal process for removing FOG from the waste water.

The first section 100 comprises a closed chamber 102 having a kitchen effluent inlet 103 at an upper side of a first end wall 104 of the chamber. A downwardly sloping filter deck 105 having a plurality of apertures formed therein extends downwardly from adjacent the kitchen effluent inlet 103 at an upper end to terminate at a lower end adjacent a solids outlet 106 leading to a dewatering screw 108, the filter deck 105 dividing the chamber 102 into upper and lower regions, whereby material from the kitchen effluent inlet 103 passes into the upper region of the chamber 102 onto an upper end of the filter deck 105, liquid effluent passing through the apertures in the filter deck 105 to be collected in the lower region of the chamber 102, while solids material passes down the inclined filter deck 105 to exit the chamber 102 via the solids outlet 106 to enter the dewatering screw 108. A heater blower 110 may be mounted on an upper end of the chamber 102 to blow heated air through the chamber 102, from the upper region into the lower region, through the filter deck 105, to facilitate drying of the solids waste travelling down the filter screen and to blow liquid effluent through the filter deck 105. A vent 112 is provided in a lower region of the chamber 102. The vent 112 may be provided with an activated charcoal filterl 13 at the outlet thereof to prevent noxious emissions. The heat effect of the heater blower 110 also maintains any FOG in suspension in the liquid effluent while it is in the first section 100. The heat supplied to the effluent can also improve the effectiveness of FOG removal in the second section 200 of the apparatus. A heat exchanger may be provided in the chamber 102 for transferring heat to the waste liquid within the grease trap 202 of the second section 200 of the apparatus, for example by means of a heat exchange fluid, such as water.

Liquid effluent collected below the filter deck 105 in the lower region of the chamber 102 is pumped to the second section 200 via an effluent transfer pump 114 provided in an effluent transfer pipe 116.

The dewatering screw 108, having a tapered compression section, compresses and dewaters the solids waste from the solids outlet 106 of the chamber 102. The compressed and dewatered solids waste may be collected downstream of the dewatering screw 108 for subsequent treatment and/or disposal.

Liquid effluent from the dewatering screw 108 is passed into the effluent transfer pipe 116 to be pumped to the second section 200 of the apparatus. A chopper pump (not shown) may be provided upstream of the chamber 102 for chopping food and other solid waste contained within the effluent stream into consistently sized particles to reduce the risk of blockages.

The second section 200 of the waste water treatment apparatus comprise a grease trap 202 for separating FOG from the liquid effluent and a bunded storage tank 204 for collecting the separated FOG, waste water downstream of the grease trap 202 being passed to a drain 206.

The second section 200 of the apparatus for treating waste water in accordance with a first embodiment of the present invention is shown in more detail in Figure 2. The grease trap 202 comprises a first tank 2 having a waste water inlet 4 at a first end and a waste water outlet 6 at a second end, a plurality of baffles 8 being provided within the first tank 2 to provide a convoluted or sinuous flow path through the tank 2 between the waste water inlet 2 and the waste water outlet 6, such that fats, oils and grease (FOG), and any other water immiscible contaminants having a specific gravity less than one, can settle out on top of the waste water in an upper region of the first tank 2.

Preferably the waste water inlet 4 is provided in a respective end of the first tank 2 adjacent an upper region of the tank 2 such that waste water is delivered into the upper region of the tank 2. The waste water outlet 6 may be provided in an end wall of the tank 2, opposite the end wall containing the waste water inlet 4, and may be provided adjacent an upper region of the tank 2 so that only water above a predetermined level within the first tank 2 overflows out of the waste water outlet 6. A sensor array 10 is provided on a side of the first tank 2. The sensor array 10 comprises a row of non-contact water sensors 12 located on an outer wall of the first tank 2 for detecting the presence of water within the tank 2 at a predetermined level (i.e. at the position of the sensors 12). In the embodiment shown, four sensors 12 are provided in a row at said predetermined level, although it is envisaged that three or more sensors may be provided. The provision of more than one sensor reduces the risk of false readings, as will be described in more details. It is also envisaged that only a single sensor may be used, although this does not provide the advantageous fail safe benefits of providing three or more sensors, as will be described below in more detail.

In a preferred embodiment the sensors 12 of the sensor array 10 comprise field effect sensors. Field effect sensors are digital, solid-state electronic devices that can detect conductive materials such as water, without requiring direct contact with such materials. Such sensors incorporate a controller that switches its output state when the conductive target is sensed. Such sensors require no moving parts, floats, or any other mechanism to operate. When a voltage is supplied to each sensor, a low power, invisible field is created. The field emanates directly through the side wall of the first tank. When a conductive material, such as water, enters the field, the sensor detects the change and indicates an event has occurred with a corresponding output signal. Such sensors are known for use as water level sensors in numerous applications. However, contrary to expectation, in the present invention the sensors are used to determine the absence of water, indicating the presence of FOG within the tank at the level of the sensor array 10. A FOG removal pump 14 is provided in or adjacent the first tank 2 for transferring FOG and other contaminants from the first tank 2 to the FOG storage tank 204. The FOG removal pump 14 is adapted to remove FOG and other contaminants from the first tank 2 at or adjacent the the level of the sensors 12 of the sensor array 10. In one embodiment an FOG inlet communicating with the FOG removal pump 14 may be adapted to receive FOG from the first tank at a level slightly above that of the sensors 12 of the sensor array 10 so that a layer of FOG is maintained on top of the waste water, even after a FOG removal cycle has been completed. This layer of FOG may act as a thermally insulating blanket on top of the waste water, reducing heat loss from the waste water. This increases the efficiency of the FOG removal process.

Rotatable paddles 16 may be provided in an upper region of the first tank 2 which can be driven, for example by electric motors, to agitate the FOG collected in the first tank to prevent the formation of a crust or solid regions within the layer of FOG collected within the first tank 2.

The FOG storage tank 204 may comprise a bunded tank to prevent leakages and may be provided with an agitator 32, such as rotatably or reciprocably driven paddles, to prevent solidification of the grease. The FOG storage tank 204 may also be provided with sensors, such as a proximity sensor 34 in the top of the tank, for determining the level of material in the tank 204 and in particular for determining when the tank 204 is full. A system controller 18 is provided for controlling the operation of the FOG removal pump 14 based upon signals received from the sensor array 10, as will be described in more detail below. The system controller 18 comprises a programmable logic controller programmed to control operation of the paddles 16 and the grease removal pump 14 as a function of a timer and/or the signals received from the sensor array 10, as described below.

The waste water outlet 6 of the first tank may communicate with a waste water inlet 22 of a second tank, defining a buffer tank 20, adapted to hold a predetermined volume of water substantially equal to or slightly greater than the maximum volume of FOG expected to be collected in the first tank before a FOG removal operation is executed by virtue of the FOG removal pump 14, as will be described below in more detail.

The buffer tank may be fitted with a heat exchanger, capturing thermal energy. Typically waste water enters the system at a temperature of 40° C to 85° C. This energy can be used to help stop the grease from solidifying and rafting.

The buffer tank 20 has a waste water outlet 24 leading to a drain 25. A proximity sensor 26 may be provided in an upper wall or lid of the buffer tank 20 for sensing the level of water within the buffer tank. A water transfer pump 28 is provided in the bottom of the buffer tank 20 arranged to pump water from the buffer tank 20 into the first tank 2 under the control of the system controller 18.

The operation of the grease trap of Figure 2 and in particular the system controller 18 may be as follows :-

During normal operation, waste water passes into the first tank 2 via the waste water inlet 4 and overflows into the buffer tank 20, via the waste water outlet 6 of the first tank 4 and the waste water inlet 22 of the buffer tank 20, and subsequently into the drain, via the waste water outlet 24 of the buffer tank 20. During such operation, the sensors 12 of the sensor array 10 detect the presence of water in the first tank 2, indicating normal operation of the system.

As the waste water passes through the first tank 2, around the baffles 8, FOG and other water immiscible contaminants having a specific gravity less than one settle out on top of the waste water to collect in an upper region of the first tank 2. During such normal operation, the system controller 18 may be programmed to operate the stirring paddles 16, preferably intermittently at predetermined time intervals as a function of the inbuilt timer of the system controller 18, to agitate the FOG, preventing the formation of a solid crust or solid regions.

As the FOG layer builds up within the first tank 2, eventually the boundary between the waste water and the layer of FOG will reach the level of the sensor array 10. At such time, the sensors 12 will signal the absence of water, indicating the presence of FOG within the tank 2 at the level of the sensors 12, indicating that FOG removal is required.

Once at least three of the four sensors 12 of the sensor array 10 signal the absence of water, the system controller 18 will initiate a FOG removal cycle, initiating operation of the FOG removal pump 14, drawing the FOG out of the first tank and transferring it into the FOG storage tank 204. At the same time the system controller 18 may initiate operation of the stirring paddles 16.

The system controller 18 may be programmed to operate the FOG removal pump 14 for a predetermined period and/or until a sensing means indicate that all of the layer of FOG has been removed, for example by sensing that the FOG removal pump 14 is pumping air instead of FOG. At such time, the system controller 18 operates the water transfer pump 28 to pump water from the buffer tank 20 into the first tank 2. The addition of water from the buffer tank 20 into the first tank 2 raises the water level in the first tank 2 so that the sensors 12 of the sensor array 10 once again detect the presence of water within the first tank 2, thus resetting the system.

In one embodiment each FOG removal cycle may comprise operating the FOG removal pump 14 for a predetermined period of time to remove a predetermined volume of FOG from the first tank 2, thus removing a layer of FOG from the first tank 2. Subsequently the water transfer pump 28 is operated, preferably for a predetermined period of time, to pump a predetermined volume of water into the tank, approximately corresponding to the volume of FOG removed by the FOG removal pump 14. Next the cycle is repeated, operating the FOG removal pump 14 for a predetermined period of time followed by the water transfer pump 28 to remove subsequent layers of FOG, replacing the FOG with water. The controller may be programmed to add water to the first tank 2 from an alternative source after a predetermined number of cycles to avoid draining the buffer tank 20. The cycle is repeated until all sensors 12 of the sensor array 10 once again detect the presence of water, whereupon the system is reset.

The system controller 18 may be programmed to shut down the FOG removal pump 14 in the event that the level sensor 34 in the FOG storage tank 204 indicates that the FOG storage tank 204 is full. Upon such event, the system controller 18 may provide an indication of a system fault, which may be sent by SMS message to a predetermined mobile phone number to alert the person responsible that the FOG storage tank 204 must be emptied before the operation of the system can be initiated once again.

While the use of a buffer tank 20 and water transfer pump 28 is described for raising the water level in the first tank 2 to reset the sensor array 10, it is envisaged that resetting of the sensor array 10 may be achieved by the passage of waste water into the first tank 2 via the waste water inlet 4 of the first tank 2, for example from washing facilities or other systems from which the first tank 2 receives waste water, or from an alternative source of water, should the system controller determine that the buffer tank 20 is depleted.

The system controller 18 may be programmed to reset the sensor array 10 using water from the buffer tank 20, by operating the water transfer pump 28, only when the water level within the first tank 2 fails to rise to the level of the sensor array 10 within a predetermined time period by virtue of the normal passage of waste water into the first tank 2 via the waste water inlet 4.

When the sensor array 10 is reset by raising the water level within the first tank 2 until the sensors 12 of the sensor array 10 again detect the presence of water, either by pumping water form the buffer tank 20 back into the first tank 2 or via waste water entering the first tank 2 from the waste water inlet 4 or via passing water into the first tank 2 from an alternative source, the system controller 18 may send a reset signal via SMS to a predetermined mobile phone number to alert the responsible person.

Should the sensor array 10 not be reset within a predetermined period, possibly indicating failure of one or more of the sensors 12 or contamination of the first tank 2 with grease in the region of one or more of the sensors 12, a fault message may be sent by SMS to a predetermined mobile phone number to alert the responsible person and the system may be shut down.

In an alternative embodiment, illustrated in Figures 3 and 4, at least one further sensor 12A may be arranged at a higher level than the sensors 12 of the sensor array 10. The system controller 18 may be programmed to operate a separate FOG removal cycle in response to signals from the further sensor 12A. In one embodiment the controller 18 may be programmed to check if the further sensor 12A ceases to detect the presence of water at said predetermined level within the first reservoir after a predetermined period of time or at predetermined time intervals, such as once a day, and to operate the contaminant removal means when said at least one sensor ceases to detect the presence of water. Because the further sensor 12A is higher than the remaining sensors 12, the FOG at such level will be more concentrated and less mixed with waste water and air than the FOG at the level of the remaining sensors 12. Therefore the sensor 12A is less prone to false reading and thus only one sensor is required. In an alternative embodiment only the further sensor 12A may be required, the remaining sensors 12 being omitted, the position of the further sensor 12A within the concentrated and less emulsified and de-aerated layer of grease providing greater accuracy and therefore avoiding the need for multiple sensors.. A waste water treatment apparatus in accordance with a further embodiment of the present invention is illustrated in Figure 5. In such embodiment the waste water is passed through a vertically stacked arrangement of filter trays 302,304,306 housed within a chamber 300, each filter tray receiving waste water from a respective waste water outlet 308,310,312, whereby solid material, such as food waste, entrained within the waste water is separated from the waste water and retained within each filter tray 302,304,306. As with the first embodiment shown in Figure 1, a heater blower 314 is mounted on an upper end of the chamber 300 to blow heated air through the chamber 300, from the upper region into the lower region, and through each filter tray 302,304,306, to facilitate drying of the solid waste collected therein.

Waste water collected in the bottom of the chamber 300 is pumped via a water transfer pump 316 into a grease trap 400, which may be of the same type as described above in relation to the previous embodiment. A heat exchanger 320 may be provided in a lower region of the chamber 300 for heating a heat transfer fluid for transferring heat to waste water contained within the grease trap 400.

The apparatus may include sensing means, such as weighing means, for detect when the filter trays 302,304,306 require emptying/replacement.

In a further embodiment of the present invention, illustrated in Figure 6, food solids may be removed from the effluent upstream of the grease trap 400 by means of a rotational filter 500 having a rotatable filter drum 502 having an apertured cylindrical outer wall, whereby liquid effluent passes through the outer wall of the drum 502 to be passed to into the grease trap 200 while sold waste is retained within the drum can be passed out of one end of the drum 502. The solid waste may then be passed to a dewatering means, such as a dewatering screw 600, before being collected in a solid waste collection bin 620. Waste water from the dewatering screw 600 may be passed back into the body of the rotational filter 500 to be passed into the grease trap 200, by a suitable pump 602. The rotational filter 500 may be located above the grease trap 200 and the dewatering screw 600 so that separated liquid and solid waste may be passed respectively into the grease trap 200 and dewatering screw 600 under the action of gravity.

As with the previous embodiments, a buffer tank 20 may be provided downstream of the first tank 202 of the grease trap 200 from which water may be pumped back into the first tank 202 to reset the sensor array 10, as discussed above. Grease collected in the first tank 202 of the grease trap 200 may be pumped into a FOG storage tank 204 when the sensor array 10 indicate the presence of grease, under the control of a PLC controller 208, again as discussed above in relation to the previous embodiments.

Figure 7 illustrates a waste water treatment apparatus in accordance with a further embodiment of the present invention, preferably intended for use in smaller kitchens and domestic applications. A compact filtration unit 700, containing a removable strainer tray 702, is provided upstream of a grease trap 710 for collecting solid food waste in the strainer tray 702 before the waste water (containing entrained FOG) is passed under gravity into the tank 712 of a grease trap 710.

As with the previous embodiments, a sensor array 714, preferably comprising four horizontally aligned field effect sensors 716, is arranged on an exterior wall of the tank at a predetermined level for detecting the presence of FOG (in terms of the absence of water) at said predetemined level, a PLC controller 718 using this information to control a FOG transfer pump 720 to periodically pump FOG from the tank 712 of the grease trap 200 into a bunded FOG storage tank 730.

In use, waste water, for example from a sink, is passed into the filtration unit 700 to pass through the strainer tray 702, wherein solid waste, such as food waste, is collected. The waste water drains through the strainer tray 702 and passes under gravity into the tank 712 of the grease trap 710, wherein FOG separates out and settles on the upper surface of the water in the tank 702. As the FOG layer builds up a stage is reached wherein at least three of the four sensors 716 of the sensor array 714 indicate a lack of water, indicating the presence of grease at the level of the sensor array 714. This causes the controller 718 to initiate a FOG removal cycle, whereby the FOG transfer pump 720 is operate for a predetermined time period to remove a layer of FOG from the tank 712 and transfer the FOG into the storage tank 730. The FOG removal cycle is reset when the water level rises in the tank 712, either due to the addition waste water from the filtration unit 700 or from another source, until all or a majority of the sensors 716 of the sensor array 714 again detect the presence of water. An error may be registered and the system shut down if the FOG removal cycle is not reset within a predetermined period of time.

The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.

Claims

1. An apparatus for treating waste water comprising a first reservoir having at least one waste water inlet for passing waste water into an inlet region of the first reservoir, at least one waste water outlet for draining waste water from an outlet region of the first reservoir, wherein contaminants, such as fats, oils and grease, having a specific gravity less than one are able to settle out on top of the waste water, at least one sensor being provided on an exterior wall of said first reservoir at a predetermined level for determining the presence of water within the first reservoir at said predetermined level adjacent the sensor without physical contact with said water, means for removing said contaminants from said first reservoir at or adjacent said predetermined level, and a controller for controlling operation of said contaminant removal means in response to signals received from said at least one sensor when said sensor indicates an absence of water.

2. An apparatus as claimed in claim 1, wherein at least one baffle is provided between said inlet region and said outlet region of the first reservoir.

3. An apparatus as claimed in claim 1 or claim 2, wherein the or each sensor comprises a field effect sensor.

4. An apparatus as claimed in any preceding claim, comprising at least three sensors arranged in a linear array at said predetermined level on said exterior wall of said first reservoir, said controller operating said contaminant removal means only when at least two of said at least three sensors indicate an absence of water.

5. An apparatus as claimed in any preceding claim, wherein said contaminant removal means comprises a pump communicating with a contaminant inlet opening into the first reservoir at or adjacent said predetermined level.

6. An apparatus as claimed in claim 5, wherein said contaminant inlet is located above said predetermined level such that a layer of said contaminants is maintained on top of the waste water contained within the first reservoir.

7. An apparatus as claimed in any preceding claim, wherein said controller is programmed to operate the contaminant removal means when the at least one sensor ceases to detect the presence of water at said predetermined level within the first reservoir, indicating the presence of contaminants at said predetermined level, to remove said contaminants from the first reservoir, the controller subsequently waiting for the at least one sensor to once again detect the presence of water before operating the contaminant removal means a subsequent time.

8. An apparatus as claimed in any of claims 1 to 6, wherein said controller is programmed to initiate a contaminant removal process when the at least one sensor ceases to detect the presence of water at said predetermined level within the first reservoir, indicating the presence of contaminants at said predetermined level, said contaminant removal process comprising the steps of operating said contaminant removal means for a predetermined time period to remove a layer of contamination, such as a layer of FOG, from the first reservoir, adding water to first reservoir for a predetermined period and/or until a predetermined volume of water has been added, and repeating said steps until the at least one sensor to once again detect the presence of water, thereafter ceasing the contaminant removal process until the at least one sensor once again ceases to detect the presence of water.

9. An apparatus as claimed in claim 7 or claim 8, wherein the controller is programmed to indicate a fault if the at least one sensor fails to once again detect the presence of water after a predetermined period of time or activity.

10. An apparatus as claimed in any preceding claim, wherein said controller is programmed to check if the at least one sensor ceases to detect the presence of water at said predetermined level within the first reservoir after a predetermined period of time or at predetermined time intervals, such as once a day, and to operate the contaminant removal means when said at least one sensor ceases to detect the presence of water.

11. An apparatus as claimed in any preceding claim, further comprising a second reservoir for storing a predetermined volume of water therein, said second reservoir receiving waste water from said waste water outlet of the first reservoir, means being provided for passing water from said second reservoir into said first reservoir under the control of said controller.

12. An apparatus as claimed in claim 11, wherein said means for passing water from said second reservoir to said first reservoir comprises a pump.

13. An apparatus as claimed in claim 11 or claim 12, wherein said second reservoir is provided with a drain outlet for draining waste water in excess of said predetermined volume from the second reservoir.

14. An apparatus as claimed in any of claims 11 to 13, wherein the controller is programmed to operate said means for passing water from said second reservoir into said first reservoir after the contaminant removal means has been operated to remove contaminants from the reservoir, at least until the at least one sensor detects the presence of water within the first reservoir at said predetermined level, the controller being programmed to prevent operation of said contaminant removal means until he at least one sensor detects the presence of water within the first reservoir at said predetermined level.

15. An apparatus as claimed in any preceding claim, further comprising a storage reservoir adapted to receive contaminants from said first reservoir via said contaminant removal means.

16. An apparatus as claimed in any preceding claim, further comprising a device for agitating the contaminants collected on top of the waste water within the first reservoir.

17. An apparatus as claimed in claim 16, wherein said agitating device comprises one or more reciprocally or rotatably driven paddles.

18. An apparatus as claimed in claim 16 or claim 17, wherein the controller is programmed to operate said device for agitating the contaminants collected on top of the waste water at predetermined intervals and/or when the at least one sensor indicates the absence of water at said predetermined level within the first reservoir.

19. An apparatus as claimed in any preceding claim, wherein the controller is adapted to communicate with a remote location, for example to a pager or mobile phone.

20. An apparatus as claimed in any preceding claim, including means for removing solid waste, such as food waste, from the waste water upstream of the first reservoir.

21. A method of operating an apparatus for treating waste water comprising providing at least one sensor on an exterior wall of a first reservoir at a predetermined level for determining the presence of water within the first reservoir at said predetermined level without physical contact with said water, and carrying out a contaminant removal process by operating a means for removing contaminants, such as FOG, from said first reservoir at or adjacent said predetermined level when said at least one sensor indicates an absence of water at said predetermined level, indicative of the presence of contaminants at said predetermined level.

22. A method as claimed in claim 21, wherein said contaminant removal process comprises operating said contaminant removal means to remove said contaminants from the first reservoir and subsequently adding water to the first reservoir, said contaminant removal process proceeding until the at least one sensor indicates the presence of water once again.

23. A method as claimed in claim 22, wherein said contaminant removal process comprises the steps of operating said contaminant removal means for a predetermined time period to remove a layer of said contaminants from the first reservoir, adding water to first reservoir for a predetermined period and/or until a predetermined volume of water has been added, and repeating said steps until the at least one sensor to once again detect the presence of water, thereafter ceasing the contaminant removal process until the at least one sensor once again ceases to detect the presence of water.

24. A method as claimed in claim 22 or claim 23, wherein said water is added to said first reservoir from a second reservoir adapted to receive waste water from a waste water outlet of the first reservoir.

25. An apparatus for treating waste water substantially as herein described with reference to the accompanying drawings.

26. A method for treating waste water substantially as herein described with reference to the accompanying drawings.