A variety of systems for recovering and purifying rainwater to produce potable water are known in the prior art though those generally available on the market only provide non-potable water. The systems generally have a system of physical filtration, such as sand, to remove particulate matter and a system of disinfection, for example chemical treatment, to kill bacteria. One known system, described in UK Patent Application number 2,038,307A, includes a first filter to remove particles from the water, possibly a carbon filter to improve the appearance of the water and a purification filter using chemical or UV treatment to disinfect the water and make it suitable for drinking. The systems generally have a restricted flow rate depending on the slowest flow rate of the filters in the system.

Known systems are complicated to set up and use and once in situ cannot easily be moved to another site.

A further problem with known systems is that the filtration of particles from the water is often carried out using fibre or mesh filters. These tend to clog up very quickly and have to be replaced often, which is inconvenient and costly.

An object of the invention is to provide a compact, cheap and effective water processing unit.

The invention provides a water processing unit comprising : a water inlet, for inputting water to the water processing unit;

at least one primary filter having an inlet connected to the water inlet and at least two outlets; at least two secondary filters in parallel, each having an inlet connected to one of the primary filter outlets and an outlet ; a disinfection unit having an inlet connected to the outlets of the at least two secondary filters and an outlet; and a potable water outlet connected to the disinfection unit outlet.

Preferably the primary filter comprises a further outlet for enabling water that has been partially filtered but not disinfected to be extracted for use in flushing toilets and other applications in which it is not necessary to have the water disinfected.

The primary filter removes particulate matter from the water. Preferably the primary filter comprises a series of coils through which the water flows, with no particles larger than the gaps between the coils being able to pass through. Preferably the filter is of the type referred to as a zero gravity filter. Preferably the water processing unit further comprises a backwashing mechanism to flush water back through the filter to clean it periodically. Preferably the unit comprises a further outlet for the backwash water. Advantageously the backwashing mechanism may be activated automatically at set time intervals or when set amounts of water have flowed through the unit. Preferably the primary filter is automatically backwashed on activation of a pressure switch when the filter requires cleaning. Alternatively the backwashing mechanism can be activated by an operator.

Advantageously the primary filter filters to at least 50um. Preferably water exiting the primary filter has been filtered to between lopm and

25pm. If the filtration rating of the primary filter is greater than about 50, um the operation of the secondary filters may be affected. However, if the filtration rating of the primary filter is less than about 10pm the flow through rate of the water will be too slow for practical use.

The filtered water from the primary filter is separated into at least two parallel channels that flow to the secondary filters. The parallel arrangement of the secondary filters enables the flow through of the processing unit to be increased without reducing the effectiveness of the filters.

Preferably the secondary filters are carbon filters to remove colours, odours and organic matter from the water. Preferably the filters comprise granulated carbon. Advantageously the filters comprise cellulose activated carbon. Preferably the carbon comprises granulated carbon which itself has a filtration rating of the order of 10pm.

Preferably the carbon filters are replaceable. In a household rainwater processing unit, it has been found that the carbon filters will need to be replaced once or twice a year but this depends on the quantity and the input quality of the water being processed.

If a faster flow through of water is required and the aesthetic cleansing of the water is not so important then the secondary filters advantageously may comprise coil (zero gravity) filters. In this arrangement, the primary filter may advantageously comprise a filter that filters to 50jus, for example, and the secondary filters may advantageously comprise filters that filter to 25pm, for example.

The water exiting from the parallel secondary filters is then fed into the disinfection unit.

Preferably the disinfection unit comprises an ionisation purifier. In ionisation purifiers, the water is treated electrically to destroy bacteria : Preferably the unit comprises a silver particulate ionisation purifier.

Advantageously silver and copper ions are used, which has the further advantage that a residue is left in the water that continues to provide a disinfection effect after the water has left the processing unit. It is important that the flow-through is regulated to ensure that the correct amount of ions enters the water. Advantageously flow-control valves are provided to regulate the flow-through of water through the disinfection unit. Ionisation purifiers are"environmentally friendly"compared with other types of disinfection units as no chemicals have to be added.

Additionally such units can be made particularly compact.

Advantageously the disinfection unit is replaceable.

In some circumstances it may be advantageous to use another type of disinfection unit such as ultraviolet, ozone or chemicals such as chlorine.

These units generally have disadvantages in size, complexity, operation, or in the chemicals that are required. These types of unit also have high maintenance requirements, with the associated high costs of carrying out such maintenance.

In a first preferred embodiment, the water processing unit of the invention comprises: a water inlet, for inputting water to the water processing unit;

at least one primary filter comprising a zero gravity filter and having an inlet connected to the water inlet and at least two outlets; at least two secondary filters comprising carbon filters and being arranged in parallel, each having an inlet connected to one of the primary filter outlets and an outlet ; a disinfection unit comprising an ionisation purifier and having an inlet connected to the outlets of the at least two secondary filters and an outlet; and a potable water outlet connected to the disinfection unit outlet.

In a second preferred embodiment, the water processing unit of the invention comprises: a water inlet, for inputting water to the water processing unit; at least one primary filter comprising a zero gravity filter having a first filtration rating to filter out particles of greater than a first selected size and having an inlet connected to the water inlet and at least two outlets; at least two secondary filters comprising zero gravity filters having a second filtration rating to filter out particles of greater than a second selected size, the second selected size being smaller than the first selected size, and being arranged in parallel, each having an inlet connected to one of the primary filter outlets and an outlet; a disinfection unit comprising an ionisation purifier and having an inlet connected to the outlets of the at least two secondary filters and an outlet; and a potable water outlet connected to the disinfection unit outlet.

Preferably the water processing unit further comprises an enclosed housing, with the primary filter, the secondary filters and the disinfection

unit being contained within the housing and the housing having a water inlet and at least one water outlet. Preferably the housing comprises a lid. Preferably the lid is arranged to connect the water inlet to the primary filter, the primary filter to the secondary filters, the secondary filters to the disinfection unit and the disinfection unit to the water outlet.

Preferably the lid comprises channel means to transfer water between the elements.

Preferably the water inlet to the housing feeds water into the primary filter at the top of the filter such that water flows down the outside of the filter and then up through the middle of the filter. Advantageously the water inlet feeds the water into the primary filter at an angle to enable a more efficient filtration rate to be achieved for the filter.

The outlet of water from the unit depends on the requirements for the use of the water. If the water is only required for flushing toilets or washing clothes, for example, the water does not need to be fully treated and the water can be drawn out of the unit from an outlet directly from the primary filter. This enables a much higher flow through of water to be achieved than is possible if all the water has to pass through the whole unit, whatever the final use. Water that is required for drinking, for example, is processed through the whole unit and is drawn out of the unit from the outlet from the disinfection unit.

A particular advantage of the water processing unit of the invention is that it provides filtration and disinfection within one purposely-designed unit.

The unit is capable of processing small flows of water (for example, about up to 20 litres/minute) to potable water quality. Previous systems provide much larger flows and are better suited to municipal or commercial

treatment works, as opposed to private water supplies like those for which it is principally intended will be supplied by the unit of the invention.

For flows larger than 20 1/min, water processing units of the invention can be placed in parallel to each other to increase flow. This has the further advantage that flow does not need to be disrupted whilst one unit is being maintained.

The water processing unit of the invention integrates a number of pods within one unit and is compact and small (for example it can be approximately 300mm x 300mm x 300mm) in comparison to prior art water processing units. The invention provides a single unit housing all the components for filtration.

The unit of the invention has been designed to operate with low running costs, requiring only occasional replacement of the activated carbon filters, normally about twice per year. Other filters used with the unit are stainless steel filters, which can be automatically backwashed. In contrast, prior art systems use replaceable or throw-away disposable filters, which are increasingly considered to be environmentally unfriendly and in n addition, increase operational and running costs.

Other prior art units including such equipment as membrane technology or reverse osmosis require high pressure to operate effectively. The unit of the present invention operates under low pressures of approximately 1-2 Bar and therefore does not need large pumping equipment.

Prior art equipment that utilises disinfection methods such as chemical (chlorine), ozone or UV have a number of disadvantages. Chlorine is

chemical disinfection that is difficult to control and requires expensive dosing equipment, ozone is difficult to control and unstable, both being more suited to municipal treatment works. UV treatment, although it can be suited to small units, is not effective at destroying both bacteria and viruses and is only effective at destroying bacteria if one can be sure that no particles are shielding bacteria and that there is no slime build up on the UV tube; additionally UV tubes require costly maintenance and degrade in quality (kill rate) over time. The preferred embodiments of the unit of the invention utilise ionisation disinfection which, as well as suiting the compact unit, is simple to control, effective at destroying both bacteria and viruses and has simple and low cost maintenance. The use of ionisation is preferred to chemical treatment, which is not considered to be environmentally friendly.

The invention also provides a water reclamation and processing system in which water is collected from, for example the roof of a structure, such as a building, stored in a tank, processed through a water processing unit and supplied to outlets as a potable water supply and a non-potable water supply. A water reclamation and processing system in accordance with the invention comprises: water collection means; a storage tank; a pump ; a pump inlet filter ; a water processing unit comprising a water inlet, for inputting water to the water processing unit, at least one primary filter having an inlet connected to the water inlet and at least two outlets, at least two secondary filters in parallel, each having an inlet connected to one of the primary filter outlets and an outlet, a disinfection unit having an inlet

connected to the outlets of the at least two secondary filters and an outlet, and a potable water outlet connected to the disinfection unit outlet ; and at least one water outlet.

Preferably rainwater is collected from the roof of a structure and is fed through a pre-tank filter, to remove any debris, into the storage tank.

Preferably the water is fed in through an inlet calmer so as not to disturb any sediment in the water tank. Preferably the water is pumped out of the storage tank when it is required through a pump inlet filter.

Preferably the pump inlet filter comprises a suction filter on the pump inlet. Advantageously this comprises a floating filter which floats near the surface of the water. The use of a floating filter limits disturbance of the natural biofilm layer that forms at the bottom of the tank and which acts to naturally reduce bacteria and cloudiness in the water.

Preferably sensors are provided to indicate how much water is held in the tank and advantageously the supply automatically switches to a mains water supply if there is insufficient water in the tank.

Advantageously the system operates on demand, for example when a tap is turned on. Preferably the pump is switched on on demand and, advantageously the system further comprises a pressure vessel to ensure that water is under pressure in the system to enable an instant supply of water to be provided.

The water is pumped from the tank through a water processing unit in accordance with the first aspect of the invention. Partial filtration is provided for toilet flushing, for example, and full filtration and disinfection is provided for a supply of potable water.

The invention will now be described, by way of example only, by reference to the accompanying drawings, of which: Figure 1 shows a schematic plan view of a water processing unit according to a first aspect of the invention; Figure 2 shows a schematic side view of the water processing unit shown in Figure 1; Figure 3 shows a plan view of a water processing unit and housing according to the invention ; Figure 4 shows a cross sectional view from the top of a lid of a housing according to Figure 3; and Figure 5 shows a schematic view of a water reclamation and processing system according to a second aspect of the invention.

As shown in Figures 1 and 2, a water processing unit 1 comprises a housing 2 enclosing a primary filter 3, a pair of secondary filters 4a, b and a disinfection unit 5. Reclaimed water, such as rainwater or stream water, is fed into the unit 1 through an inlet 6, into the primary filter 3.

The primary filter 3 comprises a zero gravity filter having a series of coils 7 through which the input water flows. The water exits the primary filter 3 at outlet 8 and passes through channels 9a, b to the secondary filters 4a, b. A non-drinking water outlet 10 is provided from the primary filter 3 for water for uses such as toilet flushing.

The water flow from the primary filter outlet 8 is split substantially equally between the two channels 9a, b and flows to inlets lla, b to the secondary filters 4a, b. The secondary filters 4a, b contain granulated carbon 12 and are arranged in parallel. For optimum operation of the processing unit 1, the water flow passes through both secondary filters

4a, b but in certain circumstances it may be desirable to shut off or remove one of the secondary filters and in this case the water will be directed to flow through only the other filter.

The water flows out of the secondary filters 4a, b via outlets 13a, b, through channels 14a, b and into the disinfection unit 5 through inlet 15.

The disinfection unit 5 comprises an ionisation purifier having a source of silver and copper ions 16. An electricity supply 17, for example a mains electricity supply, provides power to the disinfection unit 5. The purified and disinfected water is then extracted from the system via an outlet 18 to be provided to a tap 37 for use as drinking water or as required.

The unit 1 also includes a backwash outlet 19 for water used for backwashing filter 3 to be outlet from the unit.

Figure 3 shows the unit 1 in the housing 2 and Figure 4 shows a cross- sectional view of a lid 100 of the housing 2, as arranged for operation. In use, the lid 100 is fitted to the top of the housing 2. Water is fed into the housing 2 through the inlet 6 and to the primary filter 3. The water flows down the coils 7 in the filter 3 and up through the centre 101. It then flows through channels 9a, 9b in the lid 100 and into the secondary filters 4a, 4b at their respective bases 102a, 102b. The water flows up through the carbon 12 secondary filters 4a, 4a and out of the respective tops 103a, 103b and via a channel 14a, 14b, 104 in the lid 100 to the disinfection unit 5. The filtered and disinfected water may then flow out of the system from outlet 18. The non-drinking water outlet 10 from the primary filter 3 allows water which has only had a basic filtering carried out on it to be used for washing and so on. This outlet 10 also provides

an outlet for backwashing water which is fed via inlet 105 through the primary filter 3 when cleaning is required.

As shown in Figure 5, a water reclamation and processing system according to a second aspect of the invention comprises primarily a water storage tank 20 and a water processing unit 1, as described with reference to Figures 1 to 4. Rainwater falling on the roof 21 of a structure 22 runs into gutters 23 and is fed via downpipes 24 through a pre-tank filter 25, to remove debris, to the storage tank 20. The water enters the storage tank 20 through an inlet diffuser or calmer 26 so as not to disturb any sediment at the base of the tank 20. Sensors 27 in the tank 20 provide an indication of the amount of water in the tank and information relating to this amount is fed to a control unit 28 associated with the processing unit 1. If there is insufficient water in the tank 20, the system is automatically switched to a standard mains supply 29, which provides a backup in the event that there is insufficient rainfall to supply the needs of the household.

A pump 30 pumps water from the tank 20 to the processing unit 1 for purification. The pump 30 has an inlet 31 with a suction filter 32 to prevent debris being drawn into the pump 30. A float 33 keeps the inlet 31 near the surface of the water so that the action of pumping water out of the tank 20 does not disturb the natural biofilm that forms at the base 34 of the tank 20. This biofilm naturally reduces bacterial and cloudiness in the water and thus it is advantageous to retain it in the tank 20.

A tank overflow 35 allows water to run off through a back pressure flap 36 if the tank 20 gets too full. The back pressure flap 36 ensures that water cannot flow back into the tank 20 via the overflow outlet 35.

When a tap or other outlet 37a, 37b, 38a, 38b, 38c, 38d is turned on in the structure 22, the system switches on the pump 30. A pressure vessel 39 ensures that water under pressure is already in the system to ensure an instant supply to the tap or other outlet and the pump 30 pumps water from the tank 20 to the processing unit 1, as described with respect to Figures 1 to 4. Water to toilets, washing machine or other appliances or outside taps 38a, 38b, 38c, 38d comes from outlet 10 of the unit 1 and potable water to the interior taps 37a, 37b comes from the outlet 18 of the unit 1.

Any overflow from the filters in the unit 1 or the pre-tank filter 25 can flow out through an outlet 40. Back pressure flap 41 ensures that the overflow water cannot flow back into the system.

The water processing unit according to the invention has many advantages. The combination of the elements of the unit combined with their arrangement in the unit provide an effective water processing unit that can be supplied as a single unit and which is compact, convenient and relatively cheap. The user does not have to join the separate elements together but is provided with an effective and easy-to-use unit that allows the user various different options depending on their requirements.

The arrangement of the unit with a primary filter feeding to two secondary filters in parallel enables a higher flow through rate to be obtained than in prior art water processing systems. The water processing unit and reclamation and processing system of the invention can be used to process any source of relatively clean water such as rainwater, stream water and some household water.