GB2350357A

GB2350357A - Water treatment apparatus

Info

Publication number: GB2350357A
Application number: GB9912159A
Authority: GB
Inventors: John Patrick Hynes
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-05-26
Filing date: 1999-05-26
Publication date: 2000-11-29
Also published as: GB9912159D0

Abstract

A water treatment unit comprises inlet means 1 for insertion of grey water into the unit , a coarse filter 2 to which the grey water from the inlet means 1 is fed for removing coarse particles from the water, a high pressure pump 3 to which the water from the coarse filter 2 is fed for moving the water around the unit, fine filter means 5, 6, 7 to which water from the pump 3 is fed for removing fine particles from the water, an activated carbon filter 8 for removing colour and chlorine from the water, a reverse osmosis unit 10 fed with the water from the activated carbon filter 8 for removing other waste matter from the water and outlet means 12 for supplying treated water from the reverse osmosis device 10 for for re-use. Cooler apparatus 9 and an anti-bacterial ultra-violet treatment unit 4 may be present. Particulate removal may be by cyclone or settling tanks. The reverse osmosis unit de-ionises the water.

Description

2350357 improvements in and relating to the treatment of water.

This invention relates to the treatment of water and has particular reference to the treatment of what is known as Fygrey" water for recycling. In a particular aspect of the present invention, there is provided a method and apparatus for recycling "grey" water for reuse as a potable water supply. Used water is classified either as "grey" water or as "black" water. The latter comprises sewage and it does not form a water source suitable for treatment in accordance with this invention. "Grey" water, however, comprises waste from domestic washing and bathing activities and accounts for a significant proportion of water used and treated by waste water treatment plants.

At the present time waste water, and particularly "grey" water, is treated in large sewage treatment plants principally by passing the water concerned through settling tanks to remove particulate matter and then subjecting it to treatment in a biodigesting stage in which the nitrogenous content of the water is "fixed" by conversion to nitrates and the resulting water after further treatment, e.g. by oxygenation, is then returned to the environment. Present urban waste water treatment plants do not provide water of potable quality. Waste water treatment plants, such as those commonly employed to service the needs of the urban populations, occupy a considerable amount of space and are relatively labour 1 intensive in order to deal with the volumes of waste, both "grey" water and "black" water. There is an increasing practice, in order to reduce the "load" on the natural environment, of separating the "grey" water from 5 the "black" water and treating them separately.

There is, furthermore, a considerable need in certain environments for compact and self-contained water treatment apparatus capable of converting wastewater to re-useable water and preferably to potable water. Such requirements exist in, for example, desert communities, travellers in remote places and in ships and boats. There is further a demand for the ability to desalinate seawater to potable water. At the present time these requirements are satisfied by devices such, for example, as solar stills which effectively distil pure water from the source. This is a timeconsuming and energy intensive process since the water is converted to vapour which is subsequently condensed. Furthermore, the process of distillation provides for a concentration of solids and solutes, which has to be disposed of.

It is, of course, well known and that by passing wastewater through a column of the earth approximately two metres in length, water of substantially potable quality may be obtained. The disadvantage of such a system for the purification of water is, of course, that the column of the earth rapidly becomes exhausted as to its ability to purify water supplied to it and needs to be changed frequently. Furthermore, the quality of the water is very dependent on the nature of the earth and the nature of the sub-soil from which it is obtained. Further treatment of water obtained in this way is, 2 therefore, desirable to render it safe as a potable supply.

Current water treatment systems generally fall into the category of further refining the domestic supply provided by a water supply utility in an urban area. For example, in the areas having a significantly "hard" water supply, it is common to provide a water softener in order to remove some of the calcium from the water thus reducing the tendency of pipes in the water supply system to "fur up". Furthermore, concern has been expressed at the presence of certain trace amounts of undesirable chemicals and bacteria in water such, for example, as oestrogen and e.coli. In order to deal with these it has been the practice to use either sophisticated filters or reverse osmosis equipment. Sophisticated filters require frequent maintenance while the reverse osmosis equipment is usually hard plumbed into the water supply system. There is, however, an increasing need for equipment which is relatively compact and potentially portable but which will convert "grey" water directly to a potable water supply for re circulation at a point of previous use.

According to one aspect of the present invention, 25 therefore, there is provided a method for the treatment of "grey" water which method comprises:

removing substantial quantities of particulate solids from the water treating the water to remove coloured material passing the water through a treatment means for deactivating the bacteria content and thereafter treating the water for the removal of substantial quantities of ionic material.

3 The invention further provides apparatus comprising:means for removing substantial quantities of particulate solids from "grey" water means for treating the water to remove coloured 5 material means for deactivating bacteria and de-ionising means the arrangement being such that grey water is passed through the solids removal means for removal of a substantial proportion of the solids content prior to treatment by the colour removal means and is thereafter passed to means for the deactivation of the bacterial content prior to treatment by the de- ionising means to produce potable water. 15 The removal of the particulate solids from the input of water may be effected by the use of filters or by other means such as cyclones and settling tanks. A combination of filters, cyclones or settling tanks may be employed but it is desirable to remove as much of the particulate material as possible from the "grey" water prior to removal of coloured matter or material in the water. In one aspect of the present invention, the means for removing a particulate solids material from the input water may comprise a plurality of filters which increase in fineness in the direction of water flow. In a typical arrangement in accordance with the present invention three filters may be employed; a first filter may comprises a 100 BSS mesh, a second filter may comprise a 50 BSS mesh and the third filter may comprise a 20 BSS mesh. The number and nature of the filters and component in the solids removal means will depend on the nature of the input water and its solids content. This invention is not a limited to any particular combination of filters or 4 solids extraction means. In general, however, the more solids content in the input water, the more separation steps will be required in order to reduce it to is satisfactory or acceptable level. Where there is an extensive solid content in the water it will be necessary to provide a sequence of removal steps, which remove the material in smaller size steps.

The apparatus of the present invention may be adapted by the inclusion of pump means to pass input water through the various filters under pressure. This has the advantage that sensing means and associated control means may be provided to sense the pressure differential between the two faces of any particular filter or group of filters. When the pressure differential between the upstream face and the downstream face of a filter is at predetermined level, the control means operates to provide a pressure backwash of the filter to clear the debris from the filter face. By treating the sequence of f ilters in this way., particulate debris may be substantially removed from the water stream preparatory to further processing.

The nature and extent of the filter system will, to some extent, depend on the intended purpose of the 4pparatus and process of the invention. For example, in an environment where a compact installation is required but the volumes requiring treatment are relatively small as, for example, in a boat or a vehicle, then the filtration system may be made as small and as compact as reasonably possible. Where the nature of the "grey" water is that of water that has been used mainly for domestic washing and bathing then a very compact filter system probably comprising no more than two filters would be sufficient.

The person skilled in the art will appreciate that the nature of the inlet filter system will be dependent upon the volumes of water to be treated and the environment in which the apparatus is to be used.

The removal of the coloured matter from the water undergoing treatment is preferably effected by using active carbon. The active carbon filter may be provided downstream of the means for removing the particulate material. The principal purpose of this filter is to clarify the water being treated preparatory for further processing. The filter may comprise a known filter element used for the treatment of water; in the case of a boat or a vehicle where relatively small volumes are to be treated, then one of the well-known cylindrical active carbon filters may be employed. These filters may be readily replaceable. In installations designed to treat larger quantities of "grey" water, the active carbon filters may be of much more massive construction. Optical sensing means may be provided at least downstream of the carbon filters in order to sense the degree of clarity of the water leaving the filter. When the degree of clarity of water leaving the clarifying filter is below a predetermined value; suitable indication means may be actuated to indicate that the filter requires attention.

After clarification, the water may be optionally passed through a cooler, which serves to maintain the temperature of the water and leaving the cooler to within the range on 20 degrees to 22 degrees centigrade. The cooler may be of any known design, and it may comprise an electrically driven a refrigeration unit, or simply a heat exchanger, in which water at a lower temperature is circulated to reduce the temperature of the water being 6 treated. It will be appreciated that suitable systems will be well known to the person skilled in the art. The cooling step provides a means of reducing the activity of remaining chemical and biological matter within the water being treated and this assists in conditioning and preparing the water for subsequent treatment for removal of residual biological matter and ionic species.

The means for treatment of bacteria to render it inactive is preferably ultraviolet radiation. Alpha,gamma or X radiation may also be employed but these have the disadvantage of having some degree of radiation risk associated with them. In a domestic environment, therefore, ultraviolet radiation is the preferred means of treatment of the water in order to kill or render ineffective residual bacterial matter remaining in the water. In a particular embodiment of the present invention, the water is passed through a glass tube, which is surrounded by an annular ultraviolet lamp. The water is passed through the tube under pressure but the intensity of the lamp is selected such that residual bacteria is killed or deactivated during passage through the tube.

After treatment by the ultraviolet radiation, the water is passed to a reverse osmosis treatment station in which the water is driven through a semipermeable membrane under pressure against the natural osmotic gradient. The minimum pressure employed is 100 psi but the pressure 30 will be typically 120 psi to 150 psi, although higher pressures are permissible for more rapid processing. The water leaving the reverse osmosis treatment is substantially de-ionised. 7 In a further aspect of the present invention, a pressurising pump may be provided to supply water under pressure to most or all of the preliminary filters and to the clarifying stage, the bacteria deactivating stage and the de-ionising stage. Control means may be provided for automated control of the apparatus. The control means made include sensor means for sensing the pressure drop across one or more filters. When the pressure drop is above a predetermined threshold, the operation of the apparatus is curtailed. Bypass means may be provided for back washing each filter or a group of filters with either untreated or partially treated grey water for removing the accumulated debris from each filter and discharging it to waste or to a settling tank to allow the back washed debris to settle and consolidate. After settling, the supernatant liquid may be re--passed through the apparatus for purification and clarification. When the back washing is complete and the sensors during back washed have sensed the appropriate reduction in back wash pressure, back washing is terminated and the back wash valves in the system are reset for normal operation and for the processing of the water may then continue.

In accordance with another aspect of the present 25 invention, means may be provided for flushing the inlet chamber of the reverse osmosis station. It will be appreciated that this flushing of the inlet chamber of the reverse osmosis station will preferably be conducted using a small quantity of purified water.

The control means for the apparatus in accordance with the present invention, may also incorporate sensor means for sensing the level of inlet water, pressure sensor means for sensing the system pressure overall, and second 8 level sensing means for sensing the level of output water an output receptacle, stop valve means for closing the inlet to the apparatus or for providing alternative water supply and relay means adapted to operate said stop valve either by shutting off the supply of water to the system and at the same time shutting of the pressure pump, or if an alternative water supply is available, by switching to the alternative supply. Second relay means may be provide for shutting off the high pressure pump in the event of the system pressure being sensed outside of predetermined operating limits. Further relay means may be provided for shutting down the apparatus on sensing of a high level of treated water in the outlet receptacle by second level sensor.

The control means and associated pump or pumps may be operated from a single phrase or three phrase mains supply. In the alternative, a low voltage supply may be provided for operation of pumps and control circuits.

This latter will be particularly useful in environments where compact equipment will be desirable. When used in remote areas, apparatus in accordance with the present invention may be powered by solar power in order to provide the necessary electricity for operation. In this latter case it is preferred that the solar power operates in conjunction with battery(ies) for the supply of electricity to the system.

The apparatus in accordance with the present invention is mobile and can be moved from site to site. The apparatus is comprehensive and will provide treatment for all forms of grey water. Thus, for example, a suitably sized installation in a ship at sea will be able to operate as a desalination unit without the need for distillation.

9 This will result in a considerable saving of energy compared with currently available equipment for desalination purposes. Likewise small yachts and pleasure boats at sea, on rivers or on canals will be able to draw water for treatment from the river or canal in question.

The present applicants have discovered that they are able to convert approximately 80 per cent to 97 per cent of available "grey" water to potable water, only some 10 per cent to 20 per cent being returned to the environment as "waste".

A further aspect of the present invention provides for a conditioning station at which the water is conditioned after treatment for optimum properties as a potable water supply. Typically, water treated in accordance with the process of the present invention may be substantially from of ionic species. As such the nutrient value of such water is low. The conditioning station provides for the replenishment or the optimisation of the ionic species and other properties of the water. In one embodiment, solute is added to provide the necessary mineral content for the water having regard to the intended end use. The mineral content may be added in the form of a solution using a peristaltic pump to supply a solution of known concentration of the desired ionic species to the water at a predetermined rate. In another aspect of the invention, a slow release osmotic device or osmotic pump may be employed for dosing the water prior to use. In yet another embodiment, the water may be divided so that a small quantity is treated with the desired ionic species and the said small quantity is then recombined with the bulk of treated water to produce the desired concentration of the ionic species in the combined mixture. It is preferred that the conditioning means incorporates a readily replaceable reservoir of desired species such that full conditioning of the water preparatory to final use may be achieved without the need for complex measuring and testing equipment.

Following is a description by way of example only and with reference to the accompanying informal drawings of methods of carrying the invention into effect.

In the drawings: - Figure 1 that is a diagrammatic view of the apparatus in accordance with the present invention showing the layout of the components of the apparatus.

Figure 2 is a plan view of the preconditioning treatment line of Figure 1 showing the arrangements for removal of separated waste matter.

Figure 3 is an enlarged view of the inlet tank of Figure 1.

Figure it 4 is a more detailed view of the treated water storage tank of Figure 1 Figures 5 is a circuit diagram for the control of the apparatus of Figure 1.

The apparatus in accordance with the present invention is shown diagrammatically in Figure 1, and comprises a grey water receptor tank 1 having a grey water supply 32 in the upper part of the tank, a fresh water supply 23 also in an upper part of the tank and an overflow 25. The mid part of the tank is provided with a temperature sensor 28 11 for the purpose of sensing the water temperature in water receptor tank 1. The lower part of the tank is provided with an outlet 40, which communicates with a foot or diverter valve 21. Diverter valve 21 communicates with coarse filter 2, which is adapted to remove course debris from the water supply.

The water is drawn from course filter 2 by means of a pump 3 and is then passed via a conduit to filter stations 5, 6, and 7. The filter 5 is a self cleaning filter and each of filters 5, 6, and 7 increase in fineness in the direction or flow of the treated water.

Fine filter 7 is connected with a carbon filter 8, which serves to clarify water passing therethrough.Water leaving the carbon filter 8 is then passed to a cooler 9 which serves to reduce or maintain the temperature of the water at an optimum temperature for subsequent conditioning. Typically, grey water is usually at a temperature above ambient and in these circumstances, cooling is usually necessary. Where, however, the treatment water at this stage is below ambient temperature that is to say, below a temperature of between 20 degrees centigrade and 30 degrees centigrade, then heating may be necessary to bring the water to an appropriate temperature. Where the water entering the system is at a relatively high temperature then an active cooling system will be necessary such as that provided by a small refrigeration plant. The refrigeration plant may provide cooling either directly or indirectly and the cooling means 9 may comprise a heat exchanging unit (not shown). Water leaving the heated exchange unit 9 is then passed by a conduit to an ultraviolet unit 4.

12 The ultraviolet treatment unit 4 comprises a longitudinal ultraviolet light source having a plurality of transparent conduits spiralling thereabout. The inlet to be ultraviolet treatment unit 4 terminates in a small manifold (not shown), which branches into a plurality, typically three or four conduits of relatively small cross section which are spiralled about the longitudinal ultraviolet light source. Treatment water entering the system, therefore, passes into one or more of the small section conduits and passes relatively slowly about the ultraviolet lamp to receive a dose of ultraviolet radiation sufficient such that any residual bacteria within the water being treated is killed or deactivated. At the downstream end of the light source, there is provided a further manifold which serves to reunite the plurality of small cross section conduits to a single outlet conduit 11, which leads to a reverse osmosis station 10.

The outlet, 11 bifurcates to feed two or more reverse osmosis units 10. The reverse osmosis units 10 are of standard well-known construction each containing a semipermeable membrane through which water is driven against the natural osmotic pressure by means of the pressure supplied by pump 3. As the purification process proceeds the concentration of organic and ionic residues in a chamber of the reverse osmosis unit upstream of the semipermeable membrane tends to increase. An outlet 14 is provided to this chamber in order to provide for periodic flushing of accumulated organic and ionic matter from this chamber. Water passing the semipermeable membrane is then passed by means of conduit 12 to a receptor or clean water tank 13.

13 Cleaner water tank 13 is provided with an overflow level sensor to close down the operating system in the event that the water level in the tank 13 reaches a predetermined level. The tank 13 is also provided with an inlet and pump 27 for the supply of precise doses of mineral solute typically small amounts of fluoride, chloride, potassium, sodium calcium and traces of rare earth metals. The chemistry of this dosing operation is well-known to the person skilled in the art and it does not need of further discussion here. Pump 27 it is preferably a peristaltic pump arranged to deliver the desirable solutes at the appropriate number of parts per million to the water in the tank.

Each of filters 2, 5, 6, and 7, is provided with a residue backwash outlet, each of which communicates with a waste main indicated generally at 32, see Figure 2. Each of outlets 14 also communicate with waste main 32 and material flowing into waste main 32 can either be returned to the environment, or in the case where the contamination in the grey water is only slight and the system is essentially "closed circuit", can be returned to inlet tank 1.

The system in accordance with the present invention also incorporates a bypass arrangement whereby the system may be flushed with fresh water or, when the apparatus in accordance with the invention is undergoing maintenance/backwashing, fresh or purified water from a known source may be supplied through the system. To this end, therefore, various controls are built into the grey water inlet tank 1. The fresh water supply inlet 23 is provided with a fresh water supply control valve 22. Sensor 24 is operatively connected via the electrical 14 circuit illustrated in Figure 5 to operate water supply control valve 22. Sensor 18 provides means for detecting when the inlet tank is empty. Where grey water in inlet tank 1 is high in solids content, particulate material will tend to be deposited while the water is maintained substantially stationery in the inlet tank. An increasing a layer of sediment will accumulated in the bottom of the tank and the lower part of the tank is with a sump having a sensor 16 and a dump pipe 29 incorporating a control valve 15 the arrangement being such that when the sensor 16 senses an accumulation of sedimentary material with in the sump, the controlled valve 15 is caused to open to discharge grey water and accumulated sediment from inlet tank 1.

The receptor or clean water tank 13 is provided in its upper part with an inlet 12 for the supply of treated clean water from the reverse osmosis units 14. The upper part of the clean water tank 13 is provided with a level sensor 19 for determining the maximum level of water to be permitted in the tank. When sensor 19 indicates that the clean water tank 13 is "full", the control circuit illustrated in Figure 5 operates to shut down pump 3 until the level of the water sensed by sensor 19 has fallen below the maximum Permitted level. Treated fresh water outlet 31 is provided with a stop valve and the tank is further provided with a drain cock indicated generally at 28. A sensor 26 is provided to detect the appropriate level of supplied solutes within the treated water as provided by peristaltic pump 27 The control circuit forming the subject of a Figure 5 is adapted for operation from a mains supply circuit. The mains supply provides direct supply mains supplied to pump 3, cooling unit 9, backwash means (not shown) and to the peristaltic pump 27. Each of these units is control by means of a relay C2, C3, C4, and C5 respectively and the live power supplied to each is supplied by means via fuses F2 through F 5 respectively. The circuit also provides a 12 volts supply for the control circuit and sensors for providing for control of each of the relays C 2 through C 5 respectively.

In normal operation, grey water enters the inlet tank 15 via conduit 30. Since the system is in purification mode, the pressure sensor acts to latch relay C 2 to close the circuit to activate pump 3 (see Figure 1). This has the effect or withdrawing grey water from a tank 15 via diverter valve 21 and through course filter 2. Course material and debris is removed at filter 2 and the water is then passed on via pump 3 to each of filters 5, 6, and 7. Each of these latter filters increase in fineness in the direction of waste water flow therethrough. The pressure in the system is sensed by means of a sensor and pressure relief of valve 17. Water at leaving the finest filter 7 is substantially free of non-colloidal particulate material and then passes through carbon filter 8 which serves to clarify and remove any colouring matter from the water. An optional sensor may be provided in the feed line for the water being treated at this stage in order to sense the efficiency of clarification, thereby providing an indication of the need for service or exchange of the carbon filter 8.

After clarification, the waste water is supplied to a cooler or water temperature conditioner, which cools or heats the water to a temperature within the range20 degrees centigrade to 30 degrees centigrade and typically 16 degrees centigrade to 24 degrees centigrade. After leaving the cooler, the water is then passed to the ultraviolet unit 4 in which the water is subjected to an extended exposure to ultraviolet radiation by the expedient of slowing its passage through the unit by providing an effective increase in cross-section of conduiting between the inlet and the outlet of the units. By this treatment, any residual bacterial or organic matter will be killed or rendered inactive. On leaving the ultraviolet treatment unit 4, the water passes via reverse osmosis units 10 in the manner described above, and leaves the reverse osmosis units 10 via conduit 12 into clean a water tank 13 where the treated water is further conditioned by the introduction of desirable solutes thereinto.

Sensing means may be provided in the upstream chamber of the reverse osmosis unit 10 for the purpose of detecting a build up of solutes, ionic species and residual organic matter in the chamber. When this reaches a critical level, reverse osmosis ceases and the relays are rendered operative to the effect flushing of the system to remove material via a conduit 14 to waste line 32 for discharge from the apparatus.

The cooler 9 incorporates temperature sensing means at the inlet thereto, which operates to latch or release relay C 3. The pressure of valve 17 is arranged to detect both high and low pressure in the water supply line between pump 3 and the first of the fine filters 5. When a high pressure it is detected, relay C 2 is released to stop the pump and at the same time relay C 4 is latched in to effect a backwash operation using grey water to remove debris and particular matter from the up stream 17 face of each of filters 2 through 7. The backwash period it is timed and at the end of the period the relay C 4 is released and the relay C 2 is latched to energise pump 3. The sensor 17 senses the pressure in the waste water line and if this it is above the low pressure threshold, then the backwashcycle is repeated. During be back washing cycle the system is also flushed to remove matter from the system by means of outlet conduits 14 from reverse osmosis Unit 10.

The apparatus in accordance with the present invention and in particular the embodiment specifically described above provides for a fully automated water purification system which can be conditioned to any particular level of purification. The supply of solutes for the conditioning of water in tank 13 enables control of the quality of the water for its ultimate intended purpose. Where no solute is applied, the water obtained in tank 13 is substantially deionised. It will be appreciated, therefore, by the person skilled in the art that the apparatus in the accordance with the present invention and as specifically described above, permits ultimate control of the quality of the water supplied for any particular or given purpose. Although the apparatus described above has been described on the basis of a mains power supply for the operation of the various components, it will be appreciate by the person skilled in the art that the device may be operated in its totality by means of a low voltage system such, for example, as a 12 volt supply, and that in one aspect of the invention, the necessary electrical energy made be provided by means of solar power.

18 Furthermore, the described control circuit could be replaced by any suitable circuitry and could include control by a programmed microprocessor. It has been noted in the embodiment of Figure 1 that the very basic requirements of the invention are indicated. However, provided that the basic requirements are dealt with, the additional units provided by the embodiment of Figure 2 can be present or not present depending on the use to which the treatment apparatus is put. Additionally, other treatment devices could be included in the system where particular problems occur with the water being treated. This would particularly apply where the treatment is being used to treat, for example, coolant waste for industrial applications. It will also be appreciate that while the described plant has been generally intended for use in domestic situations, the plant is equally useable in large scale water treatment and in industrial plant. one particular application which is envisaged is the treatment of sea water to render it potable.

It is also envisaged that the plant of the invention could be used for example on water to provide treated water from the sea, river, canal, lake or the like. In these circumstances, the water could be fed directly into the apparatus without the need for an inlet tank.

19 0

Claims

1. A method for the treatment of "grey" water which method comprises: subjecting the input water to a first treatment for the substantial removal of particulate solids from the water to a second treatment to remove coloured material to an optional third treatment for deactivating the bacterial content and thereafter treating the water for the substantial removal of ionic material.

2. Apparatus for the purification of grey water, which apparatus comprises: - means for removing substantial quantities of particulate solids from "grey" water means for treating the water to remove coloured material means for deactivating bacteria and de-ionising means the arrangement being such that grey water is passed through the solids removal means for removal of a substantial proportion of the solids content prior to treatment by the colour removal means and is thereafter passed to means for the deactivation of the bacterial content prior to treatment by the de-ionising means to produce potable water.

3. A method or apparatus as claimed in claim 1 or claim 2 wherein the removal of a substantial proportion of the particulate solids from the input of water may be effected by the use of filters, cyclones and/or settling tanks.

2-1

4. A method or apparatus as claimed in any preceding claim wherein the means for removing particulate solids material from the input water comprises a plurality of filters which increase in fineness in the direction of 5 water flow.

5. A method or apparatus as claimed in claim 4 wherein three or more filters are employed in which a first filter comprises an 80 to 100 BSS mesh, a second filter comprises a 30 to 50 BSS mesh and the third filter comprises a 10 to 20 BSS mesh.

6. A method or apparatus as claimed in any preceding claim including pump means to pass input water through the various filters under pressure.

7. A method or apparatus as claimed in any preceding claim wherein pressure sensing means and associated control means is provided to sense the pressure differential between the two faces of any particular filter or group of filters.

8. A method or apparatus as claimed in claim 7 including backwash means for each filter or group of filters, wherein the control means, when the pressure differential between the upstream face and the downstream face of a filter or group or filters is at predetermined level, actuates the backwash means to provide a pressure backwash of the filter(s) to clear accumulated debris from the downstream filter face.

9. A method or apparatus as claimed in any preceding claim wherein the removal of coloured matter from the water undergoing treatment is effected by passing the 1-2- water through a filter layer or bed of active carbon to clarify the water being treated.

10. A method or apparatus as claimed in claim 9 wherein optical sensing means is provided at least downstream of the active carbon layer or bed in order to sense the degree of clarity of the water leaving the filter whereby when the clarity of water leaving the active carbon is below a predetermined value, an indication is given to the effect that the active carbon layer or bed requires attention.

11. A method or apparatus as claimed in any preceding claim wherein the means for treatment of bacteria to deactivate it comprises one or more of ultraviolet radiation, alpha, gamma or X-radiation.

12. A method or apparatus as claimed in claim 11 wherein the water is passed through a glass tube, which is surrounded by an annular ultraviolet lamp where the intensity of the lamp is selected such that residual bacteria is killed or deactivated during passage of the water through the tube.

13. A method or apparatus as claimed in any preceding claim wherein deionisation is effected at a reverse osmosis treatment station in which the water is driven through a semipermeable membrane under pressure against the natural osmotic gradient.

14. A method or apparatus as claimed in claim 13 wherein the minimum pressure employed is at least 100 psi.

:23'

15. A method or apparatus as claimed in claim 14 wherein the pressure is within the range 120 psi to 150 psi.

16. A method or apparatus as claimed in any preceding claim wherein bypass is provided for back washing each filter or a group of filters with either untreated or partially treated grey water for removing the accumulated debris from each filter and discharging it to waste or to a settling tank in which latter the back-washed debris is caused or allowed to settle.

17. A method or apparatus as claimed in any preceding claim wherein the control means also comprises sensor means for sensing the level of inlet water, pressure sensor means for sensing the system pressure overall, and second level sensing means for sensing the level of output water an output receptacle, stop valve means for closing the supply of grey water and relay means adapted to operate said stop valve and/or said pressure pump.

18 A modification of the method or apparatus as claimed in claim 17 in which where an alternative water supply is available, the control means includes means for switching to the alternative water supply when the stop valve is actuated.

19. A method or apparatus as claimed in any preceding claim wherein the control means includes second relay means for shutting off the high pressure pump in the event of the system pressure being sensed outside of predetermined operating limits.

20. A method or apparatus as claimed in any preceding claim comprising further relay means for operating said 2.t stop valve or shutting off said pump on sensing of a high level of treated water in the outlet receptacle by said second level sensor.

21. A method or apparatus as claimed in any preceding claim wherein the control means and associated pump or pumps operate from a single phrase or three phrase mains supply.

22. A method or apparatus as claimed in any preceding claim wherein the control means and associated pump or pumps operate from a low voltage supply.

23. A method or apparatus as claimed in claim 22 wherein the electricity required for the control means and associated pump or pumps is generated by solar power.

24. A method as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.

25. Apparatus as claimed in claim 2 and substantially as herein before described with reference to and as illustrated in Figures 1 to 5 of the accompanying 25 drawings.