TECHNICAL FIELD

The present invention relates to waste water recycling systems, in particular but not exclusively systems for recycling used bath and shower water - so called 'grey water'.

BACKGROUND ART WO2011/158032 discloses a waste water recycling and heat recovering system. The system comprises two tanks, the larger of which is supplied with greywater, recycled greywater being supplied from the smaller of the two tanks to toilets via a pumped outlet.

DISCLOSURE OF INVENTION

According to a first aspect of the invention, there is provided:

a system for capturing and cleaning greywater and storing and supplying cleaned greywater, the system comprising:

an inlet for greywater, a first reservoir for greywater, a second reservoir for cleaned greywater and an outlet for supply of cleaned greywater, the system being configured such that the inlet feeds the first reservoir, the first reservoir feeds the second reservoir and the second reservoir feeds the outlet;

wherein the first and second reservoirs are fluidly connected via a valve configured to allow fluid flow from the first reservoir to the second reservoir but not from the second reservoir to the first reservoir.

Such an arrangement allows a head of cleaned greywater to build up in the second reservoir, e.g. to service multiple flushes of a toilet connected to the outlet. Moreover, when there is a greater head in the second reservoir than in the first reservoir, any turbulent water in the first reservoir (typically caused by greywater entering that reservoir) will not be able to enter - and disturb - the water in the second reservoir, resulting in cleaner water from the outlet supplied from the second reservoir. To the extent that potable water is supplied to top up the second reservoir (e.g. in the event of insufficient greywater input), the valve prevents that potable water from flowing into the first reservoir, thereby reducing the amount of potable water required.

The first and second reservoirs may have respective first and second drain outlets at their respective lower extremities, the system comprising a common valve to control the flow through the first and second drain outlets, the common valve being connected to the first and second drain outlets via respective first and second conduits, wherein the second conduit is configured to present a higher resistance to flow than the first conduit.

The drain outlets allow debris to be exhausted from the bottom of the reservoirs on actuation of the common drain valve. Since less debris is to be found in the second reservoir, the higher resistance to flow presented by the second conduit ensures that correspondingly less greywater is wasted from the second reservoir when the common drain valve is actuated.

The valve may be fluidly connected to the first reservoir at a level above the maximum level of debris in the first reservoir when in operation. The valve may be fluidly connected to the first reservoir at a level corresponding to about 50% to 10% of the maximum fluid level in the first reservoir, in particular about 20% of the maximum fluid level in the first reservoir. The outlet may be fluidly connected to the second reservoir at a level above the maximum level of debris in the second reservoir when in operation. The outlet may be fluidly connected to the second reservoir at a level corresponding to about 50% to 5% of the maximum fluid level in the second reservoir, in particular about 10% of the maximum fluid level in the second reservoir.

The second reservoir may comprise an inlet for water from a mains supply. The inlet may comprise a valve operable in dependence on the water level in the second reservoir.

According to a second aspect of the present invention there is provided:

a system for capturing and cleaning greywater and storing and supplying cleaned greywater, the system comprising:

an inlet for greywater, a first reservoir for greywater, a second reservoir for cleaned greywater and an outlet for supply of cleaned greywater, the system being configured such that the inlet feeds the first reservoir, the first reservoir feeds the second reservoir and the second reservoir feeds the outlet;

wherein the first reservoir comprises a heat exchanger, an overflow outlet, a drain valve, a first greywater sensor at the level of the overflow outlet and a second greywater sensor below the first greywater sensor;

the system comprising a controller configured to receive signals from the first and second greywater sensors and to open the drain valve when the level of greywater is at least equal to the level of the overflow outlet and to close the drain valve when the level of greywater is below the level of the second greywater sensor.

Such an arrangement ensures that new greywater entering the first reservoir (and which will typically have a higher temperature than the greywater already in that reservoir) is not wasted through the overflow if the first reservoir is nearly full. Rather, the bottom (cooler) portion of the greywater already in the reservoir is drained so as to make space for the new greywater, from which heat can then be extracted by the heat exchanger. The heat extraction efficiency of the system is thereby increased.

The second greywater sensor may be located at a height above the drain valve corresponding to a reservoir volume of about 20 litres and/or equal to about one third of the height of the overflow outlet above the drain valve.

The controller may be configured to delay the opening of the drain valve by a predetermined period following receipt of a signal from the first greywater sensor. The predetermined period may be at least five seconds.

The system may comprise a dispenser for dispensing biocide into the first reservoir, the controller being configured to actuate the dispenser to dispense a first amount of biocide when the level of greywater falls below the level of the second greywater sensor.

The system may comprise a third greywater sensor located below the second greywater sensor, the controller being configured to receive signals from the third greywater sensor and actuate the dispenser to dispense a second amount of biocide when the level of greywater is below the level of the third greywater sensor.

The third greywater sensor may be located adjacent the drain valve.

The second amount of biocide may be greater than the first amount of biocide. The second amount of biocide may be about four times greater than the first amount of biocide.

According to a third aspect of the present invention there is provided:

a system for capturing and cleaning greywater and storing and supplying cleaned greywater, the system comprising:

an inlet for greywater, a first reservoir for greywater, a second reservoir for cleaned greywater and an outlet for supply of cleaned greywater, the system being configured such that the inlet feeds the first reservoir, the first reservoir feeds the second reservoir and the second reservoir feeds the outlet;

wherein a wall of the first reservoir is contiguous with a wall of the second reservoir.

The contiguous walls of the first and second reservoirs result in a system that is more aesthetically pleasing, reducing the need for an additional housing.

In an embodiment, the wall of the first reservoir may be integral with the wall of the second reservoir. The two walls may be substantially planar. The two walls may lie in a vertical plane when the system is in operation.

A method of manufacturing a system according to the third aspect of the invention includes the step of providing a mould having a mould cavity configured to form both first and second reservoirs. Such a unitary, 'monocoque' approach reduces manufacturing costs. The method may comprise the step of placing moulding material in the mould cavity and rotating the mould, otherwise known as rotational moulding.

The first and second reservoirs may each comprise respective second walls lying perpendicular to respective first contiguous walls, the second walls defining a gap therebetween. The second walls may lie in respective vertical planes when the system is in operation. Such a gap may accommodate at least one fluid conduit connected with the first or second reservoir. This may make the system more compact and easier to install, as well as improving aesthetics over systems where pipework is mounted externally. The gap may accommodate a valve configured to allow fluid flow from the first reservoir to the second reservoir but not from the second reservoir to the first reservoir.

The system may comprise a housing configured to lie below the reservoirs when the system is in operation, the housing having a wall configured to lie substantially contiguous with the first contiguous walls of the reservoirs. This housing may enclose any additional system items such as pumps and pipes, thereby improving the external appearance of the system. A wall of the housing may accommodate a fluid connector fluidly connected to the inlet for greywater - such a 'bulkhead' connection also improves aesthetics as well as simplifying installation of the system.

Where the system is to be secured against an external surface (for example a vertical surface such as the wall of a room) by means of a bracket, a wall of a reservoir may comprise a recess configured to accommodate a bracket. The recess may be configured to reduce the build-up of debris on the corresponding internal surface of the reservoir. In particular, the uppermost surface of the recess may be configured to slope downwards when the system is in operation.

Moreover, the wall of a reservoir may be provided with a least one protuberance configured to engage an external surface and maintain a gap between the wall and the surface into which the remainder of the wall of the reservoir can distend without engaging the surface. In this way, inappropriate loading of the external surface is avoided.

The cross-section of the first and/or second reservoir taken in a horizontal plane when the system is in operation may have a non-unitary aspect ratio, i.e. a 'slimline' construction. The aspect ratio may be at least two. In the case of the first reservoir, the heat exchanger may comprise a tube coiled about an axis configured to lie vertically when the system is in operation, the aspect ratio of the coil about the axis being non-unitary. The heat exchanger may be attached to the reservoir by means of a mounting plate having sensors mounted thereon. Such an integrated construction may be easier to install and maintain.

According to a fourth aspect of the invention, there is provided:

a system for transferring heat from greywater to a heat sink, the system comprising: a greywater reservoir having a first heat exchanger; a heat sink having a second heat exchanger, the first and second heat exchangers being configured for transfer therebetween of a heat transfer medium;

a pump for transferring heat transfer medium between the first and second heat exchangers, wherein the system is configured to cease operation of the pump before the power consumed by the pump exceeds the rate of heat transfer from the first to the second heat exchanger.

Such a system can switch off the pump when the heat energy being obtained from the greywater no longer justifies the - so-called 'parasitic' - electrical energy consumed by the pump.

The system may be configured to operate the pump in dependence on the difference between a temperature of the greywater reservoir and a temperature of the heat sink. In particular, the system may be configured to cease operation of the pump when the temperature difference falls below a predetermined threshold. The threshold may be about 5 °C, in particular about 1 degree Celsius.

The system may be configured to cease operation of the pump after a predetermined period of continuous operation. The predetermined period may be about 37 to 40 minutes.

The system may be configured for circulation of heat transfer medium between the first and second heat exchangers. Such circulation may be effected by the pump.

The system may comprise a first sensor configured to sense a temperature of the greywater reservoir, in particular the temperature of the contents of the greywater reservoir, and generate a corresponding first signal. The system may be configured to operate the pump in dependence on the first signal.

The heat sink may be a fluid reservoir, which may be a fluid reservoir for a heating system, in particular a heating system for a building. The fluid may be water. The system may comprise a second sensor configured to sense a temperature of the heat sink, in particular the temperature of the fluid in the fluid reservoir adjacent the second heat exchanger, and generate a corresponding second signal. The system may be configured to operate the pump in dependence on the second signal.

The system may be configured to switch the pump off when the temperature of the fluid adjacent the second heat exchanger reaches the temperature at which legionella bacteria cease to be dormant, in particular when the temperature of the fluid adjacent the second heat exchanger reaches about 20 degrees Celsius.

The system may comprise a control unit configured to receive the first and second signals and control the operation of the pump accordingly.

According to the invention there is also provided a method of transferring heat from greywater to a heat sink, the method comprising the steps of:

providing a greywater reservoir having a first heat exchanger, a heat sink having a second heat exchanger, the first and second heat exchangers being configured for transfer therebetween of a heat transfer medium, and a pump for transferring heat transfer medium between the first and second heat exchangers;

operating the pump; and

ceasing operation of the pump before the power consumed by the pump exceeds the rate of heat transfer from the first to the second heat exchanger.

The method aspects of the invention can be particularlised using features of the apparatus described above.

BRIEF DESCRIPTION OF DRAWINGS

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a first embodiment of the invention;

Figure 2 is a perspective view of a second embodiment of the invention;

Figure 3 is a vertical sectional view through the embodiment of figure 2;

Figure 4 is a sectional view along line AA in figure 3;

Figure 5 is a sectional view along line BB in figure 3.

Figures 6A and 6B are detail sectional views, taken in directions F and S in figure 2 respectively;

Figures 7A, B and C are perspective, detail perspective and detail section views of an embodiment of a filter assembly;

Figure 8 is a further view of the first embodiment of the invention;

Figure 9 is a flow diagram illustrating a process of moulding the reservoirs.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to figure 1, a system 10 according to a first embodiment of the invention comprises a first reservoir 30. Greywater is fed into the first reservoir 30 from the greywater inlet 20, via a fluid filter assembly.

According to one embodiment, shown in more detail in figures 7A-C, fluid filter assembly 700 comprises a feed chute 750 that directs greywater from the inlet 20 into a tubular filter bag 720 that extends downwardly into the first reservoir 30. The filter bag 720 is held at its upper end by a filter carrier 730. The filter assembly is fluidly connected to the inlet pipe 20 by a connection pipe 740. Feed chute 750 is covered by a splash cover 710.

In an alternative embodiment, not shown, the fluid filter assembly comprises a fluid container, a filter member in the container and having a fluid inlet and a fluid outlet, wherein the fluid outlet lies above the upper extremity of the filter member when in operation. Since the outlet lies above the upper extremity of the filter member, the filter member will remain covered in biocide-containing fluid even after flow through the filter has stopped, thereby improving the hygiene of the system, particularly where no greywater enters the system for a significant period of time (e.g. when house occupants are away). 5 Referring back to figure 1, an overflow pipe 40 connected at the top of the reservoir feeds any excess water to the sewer (not shown) via purge pipe 50. As indicated at 64, any debris in the greywater sinks to the bottom of the reservoir.

A second reservoir 70 sits to one side of the first reservoir and is fed with greywater from the first reservoir at a point above the maximum level of the debris 64 (potentially about

10 50% to 10% of the maximum fluid level in the first reservoir and, as shown, about 20% of the maximum fluid level in the reservoir) by means of a non-return valve 80, e.g. the T28M-NRV in-line non-return valve with top access for cleaning from McAlpine Plumbing Products. Valve 80 allows the flow of 'cleaner' greywater having a lower debris content from the first reservoir to the second reservoir but not from the second reservoir to the first reservoir. This

15 cleaner greywater is fed for re-use (e.g. in toilet flushing) via an outlet 77 located at the bottom of the second reservoir and above the maximum level of any debris 74 that may settle at the bottom of the second reservoir (potentially about 50% to 5% of the maximum fluid level in the second reservoir and, as shown, about 10% of the maximum fluid level in the reservoir). Typically, outlet 77 is connected to a gravity-fed cistern with the option of an additional, 0 pumped outlet (not shown).

Non-return valve 80 allows a head of cleaned greywater to build up in the second reservoir, e.g. to service multiple flushes of a toilet connected to the outlet. Moreover, when there is a greater head in the second reservoir than in the first reservoir, any turbulent water in the first reservoir (typically caused by greywater entering that reservoir) will not be able to enter - and disturb - the water in the second reservoir, resulting in cleaner water from the outlet supplied from the second reservoir.

The second reservoir also has an inlet 90 for supply of potable water from a mains supply 90 via a 'ballcock' valve 95, operable in dependence on the water level in the second reservoir, to ensure that water is still available (e.g. for toilet flushing) even when there is no supply of greywater. Non-return valve 80 prevents that potable water from flowing into the first reservoir, thereby reducing the amount of potable water required.

Debris 64,74 can be dumped from the two reservoirs through respective drain outlets 65,75 connected by respective first and second conduits 66, 76 to a common dump valve 60, the first conduit having a greater diameter than the second conduit so as to present a lower resistance to flow than the second. This ensures that a greater amount of water flows through the first drain outlet than the second drain outlet, consistent with the greater amount of debris expected at the bottom of the first reservoir than the second reservoir. Dump valve 60 is periodically actuated by a controller indicated schematically at 110.

As known from WO2011/158032, the first reservoir 30 also contains a heat exchanger coil 100 for transfer of heat from the greywater to an external heat sink, for example the water tank 800 of a heating system for a building as shown in figure 8. A heat transfer medium, typically water, is circulated between the first heat exchanger 100 and a second heat exchanger 810 in the tank 800 by means of a pump 820. The circuit 880 between the two heat exchangers includes a bleed valve 890 and expansion tank 900 and well as high pressure water isolation valves 910, 920 to either side of the pump 820. Although only one heat exchanger coil 810 is shown, tank 800 may be of the 'multi-coil' variety with one or more further heat exchanger(s) arranged above the coil 810 for further heating of the water in the tank, for example to the typical hot water supply temperature of around 55 degrees Celsius, for example by means of a boiler.

The present inventors have recognized that 'new' greywater entering the first reservoir will typically have a higher temperature than the greywater already in that reservoir. To avoid such 'new' greywater going straight into the overflow when the first reservoir is full, the first reservoir is equipped with a first greywater detector 120 at the level of the overflow outlet and a second greywater detector 130 below the first greywater sensor. Controller 110 is programmed to receive signals from the first and second greywater detectors 120, 130 and to open the drain valve 60 when the level L of greywater has reached or exceeded the first detector 120 (i.e. is at least equal to the level of the overflow outlet). This drains the bottom, cooler portion of the greywater already in the reservoir until the water reaches the level of the second detector 130, at which point the valve 60 is closed. In this way, space is made for the new, hotter greywater, from which heat can then be extracted by the heat exchanger. In the embodiment shown, the second greywater sensor 130 is located at a height above the drain valve corresponding to a reservoir volume of 20 litres - in the embodiment shown, this is equal to about one third of the height of the overflow outlet above the drain valve. Moreover, the controller may be configured to delay the opening of the drain valve by a predetermined period of at least five seconds following receipt of a signal from the first greywater sensor.

The greywater is treated with biocide from a dispenser, indicated schematically at 150 in figure 1 and actuable by the controller 110 as indicated by the dashed line 150'. When the greywater in the first reservoir falls to the level of the second greywater detector 130, dispenser 150 is actuated so as to inject a quantity of biocide sufficient for the next amount of greywater that is to flow into the reservoir, i.e. the volume of water in the reservoir between the level of the second sensor 130 and the level of the first sensor 120 / overflow 40. This volume is typically 20 litres.

Controller 110 is connected to a further, third greywater detector 135 that is located at the bottom of the first reservoir, adjacent the drain outlet 65, so as to sense when the reservoir is substantially completely empty (e.g. when the system is first commissioned). In such circumstances, controller 110 actuates the dispenser 150 to inject a larger amount of biocide that is sufficient for the whole first reservoir of greywater that is to follow. The volume of the entire first reservoir up to the overflow is typically 85 litres, about four times greater than the 20 litre volume of the reservoir between the level of the second sensor 130 and the level of the first sensor 120 / overflow 40.

The system - in particular the controller - may also be configured to monitor the temperature difference between the heat transfer medium leaving the heat exchanger 100 of the system 10 and the heat transfer medium entering the further heat exchanger and to control the circulation pump in dependence on that temperature difference. In particular, operation of the circulation pump may be ceased when the temperature difference falls below a certain threshold.

Referring to figure 8, a first sensor 830 generates a signal 840 corresponding to the temperature of the contents of the greywater reservoir 30 while a second sensor 850 generates a signal 860 corresponding to the temperature of the water in the tank 800 adjacent the coil. Signals 840,860 are fed to the controller 110 which in turn controls (at 870) the pump 820, switching the pump off when the difference in temperature indicated by the two signals is less than a predetermined threshold of 5 degrees Celsius and preferably less than one degree Celsius. This ensures that the (electrical) energy consumed by the pump does not exceed the (heat) energy recovered from the greywater. Alternatively / in addition, the system can be configured to switch the pump off when the temperature of the water in the tank adjacent the coil reaches that temperature at which legionella bacteria cease to be dormant. Health and Safety Executive guidelines indicate this to be 20 degrees Celsius.

Alternatively / in addition, the system can be configured to limit the duration of continuous pump operation: a maximum duration of 37 to 40 minutes continuous operation has been found to be appropriate.

Figures 2 and 3 are perspective and sectional views of a second embodiment of a system according the invention. As in the previous embodiment, the system comprises an inlet for greywater (shown in more detail in figures 6A and 6B), a first reservoir 30 for greywater, a second reservoir 70 for cleaned greywater and an outlet 77 for supply of cleaned greywater.

Typical dimensions of the system are a width of 1000mm, a depth of 270mm and a height of 1025mm. As shown, the first reservoir 30 has a non-unitary aspect ratio of at least two - and approximately three - when viewed in horizontal cross-section, i.e. a 'slimline' construction.

Heat exchanger 100 comprises a tube 100 coiled about a vertical axis 101, the aspect ratio of the coil about the axis being non-unitary - at least two and approximately three. At its top end, the heat exchanger is attached to the reservoir by means of a mounting plate 102 having mounted thereon upper and lower greywater detectors 120,130 and a temperature sensor 140. Such an integrated construction may be easier to install and maintain.

As shown in figure 2, the front walls 31 and 71 of the two reservoirs are substantially planar, lying in a vertical plane when the system is in operation. The two walls are also contiguous, sharing a common edge 200, which results in a reservoir assembly that is more aesthetically pleasing. The need for additional housing is therefore reduced. In the particular embodiment shown, the two walls 31 and 71 are also integral, which may simplify manufacture. Indeed, as illustrated in figure 9, the two reservoirs may be rotationally moulded as a single 'monocoque' unit, by providing a mould having a mould cavity configured to form both first and second reservoirs (step 930), placing moulding material in the mould cavity (step 940), rotating the mould (step 950) and then removing the moulded reservoir from the mould (step 960).

As shown in the sectional view of figure 4, the first and second reservoirs 30,70 each comprise respective second vertical walls 32,72 lying substantially perpendicular to the first vertical walls 31,71. The second vertical walls 32,72 define between them a gap 200 in which is accommodated the non-return valve 80, mounted in a conduit 81, that interconnects the first and second reservoirs. Such an arrangement makes the system more compact and easier to install, as well as shielding unsightly pipework from view.

The system of figures 2 and 3 also has a housing 300 below the reservoirs 30,70 and having a front wall 301 that lies substantially contiguous and flush with the front walls 31,71 of the reservoirs, thereby improving the appearance of the system overall. This housing may enclose any additional system items such as pumps and pipes. The bottom wall 302 of the housing may accommodate a fluid connector fluidly connected to the inlet for greywater - such a 'bulkhead' connection also improves aesthetics as well as simplifying installation of the system.

Figure 5 shows the system of figure 3 secured to the surface 320 of a vertical wall 321 of a building by means of brackets 330, 340. The rear walls 33,73 of the reservoirs, which lie substantially parallel to the front walls 31,71, may comprise recesses (not shown) configured to accommodate such brackets. To reduce the build-up of debris on the corresponding internal surfaces of the reservoirs, the uppermost surface of the recesses may be configured to slope downwards and away from the rear walls when the system is in operation.

The rear walls 33,73 of each reservoir are also provided with a least one protuberance or raised pad 350 configured to engage the surface 320 and thereby maintain a gap (indicated by arrows 351) between the wall and the surface into which the remainder of the wall of the reservoir can distend without engaging the surface. In this way, inappropriate loading of the external surface is avoided.

Figures 6A and 6B are detail sectional views, taken in directions F and S in figure 2 respectively, of a second embodiment for controlling the treatment of the greywater with biocide from the dispenser 150.

As indicated by arrow 590, greywater from inlet 130 enters a receptacle 600, filling the receptacle up to a level at which the weight of the greywater causes the receptacle to rotate downwards about axis 610 into a second position in which the greywater flows down and out of the receptacle (as indicated by arrow 620 in respect of further receptacle 630) and in to the reservoir 30 below. In doing so, the greywater flows over a filter membrane 640 arranged on the lowermost surface of the receptacle and which removes any large debris such as hair.

Further receptacle 630 is kinematically linked to receptacle 600 such that, when receptacle 600 rotates down into its second position, further receptacle 630 rotates up into a position in which it is filled with greywater from inlet 130, the weight of that greywater subsequently driving the further receptacle downwards to empty the greywater and the receptacle 600 upwards to receive more greywater. In this way, the receptacles 600,630 reciprocate together about the axis 610 as long as there is flow through the greywater inlet 130. In the particular embodiment of figure 6B, the two receptacles share a common wall 640 that, extending radially of the axis 610, serves to direct greywater from the inlet 130 into one or other of the receptacles depending on their rotation orientation. The reciprocating motion is sensed by a sensor comprising a ferrous plate 650 arranged on the wall 670 of - and hence moving with - one of the receptacles and a magnetic sensor 660. The signal generated by the sensor 660 is then used to control the dispenser 150: as each receptacle 600, 630 will fill up to approximately the same volume before emptying, the assembly described above allows more accurate volumetric biocide dispensing (typically 85- 100 ppm) over a large range of input flows. The described assembly using receptacles is also more resistant to debris (particularly hair) of the kind typically found in greywater than other types of flow sensor, nor does it require a full pipe in order to operate accurately.

It should be understood that this invention has been described by way of examples only and that a wide variety of modifications can be made without departing from the scope of the invention.