This invention relates to a drinking water supply system. More particularly, this invention relates to a drinking water supply system which effectively filters out contaminants. DESCRIPTION OF THE PRIOR ART

Water is essential to all known forms of life. There are millions of people worldwide suffering from water poverty. It is difficult for some of these communities of people to obtain affordable and sustainable drinking water supply that is sufficiently clean. The availability of a water delivery service may seem like a solution. However, this is usually not affordable for low-income households. Besides that, the limited coverage of water delivery services may not reach remote communities.

Communities living in areas with no utility service provider for water supply will have to resort to natural sources of water. For example, the direct collection and use of rainwater for domestic purposes. Natural sources of water normally require treatment before it is safe for drinking.

The simplest and most primitive way to collect rainwater is by providing a tank with a wide opening for catching rainwater in an open area. There have been many initiatives to improve the water quality collected from rainwater collection systems. Rainwater collection tanks have either built-in filters or have extensive piping systems leading to filters. However, the pores of such filters are coarse and are not small enough to trap disease-causing bacteria and viruses. The filtered water from these rainwater collection systems is therefore not suitable for drinking. Water Filters Australia Pty Ltd is an example of a company that sells rainwater filter kits which can filter contaminants in rainwater up to a size of 15μιη. Such a filter pore size will not eliminate small waterborne viruses such as the polio virus, which is 15nm in size. A more efficient way to collect rainwater is by collecting rainwater drained off roof surfaces. Rainwater collected in roof gutters are directed to a rainwater collection system. However, such rainwater will also carry accumulated fallen leaves, insects, dust and even decomposed bacteria-riddled organic matter into the collection system. Unwanted organic matter in the rainwater will result in unclean water and cause a buildup at the base of collection tanks which will result in blockage of outlet taps. To maintain the usage capacity of such a rainwater collection system, a first-flush diverter system to remove the initial flow of the rainwater containing unwanted matters has been devised by companies such as RainHarvest Systems, LLC.

Although improved water quality will be observed if a flush diverter is implemented, the filters of rainwater collection systems usually get clogged up quickly. Ambient dust, smoke and debris can be dissolved in rainwater before it enters the collection systems. The life of a filter is highly dependent on incoming water quality. Frequent maintenance is required otherwise filters will not operate at full capacity. This is not desirable nor practicable for communities in rural remote areas.

All the prior rainwater collection systems described above does not provide water that is suitably clean and safe for drinking without the need for further treatment.

Cascade Designs, Inc.'s Platypus Gravityworks provides filters that utilize the force of gravity to filter raw water to produce drinking water. The Platypus Gravityworks filter device comprises a siphon tube with a filter in the middle, and water reservoir bags at opposite ends of the tube. Raw water will be scooped into one water reservoir bag and that bag will have to be placed at a higher position than the other water reservoir bag at the opposite end. Gravity will force water through the filter and the filtered water will flow into the reservoir bag at the opposite end. The disadvantage of this device is that the filter unit provided only has a pore size of 0.2μιη. The filter will not be able to eliminate most disease-causing waterborne viruses, bacteria, protozoa and other microorganisms. Correct orientation and positioning of the water reservoir bags are essential before filtering can take place. The reservoir bags have a small capacity and thus, are only able to filter water for few people at any given time. Users of the device are also required to search for appropriately clean raw water to be used with the device. This is again not desirable and not ideal for large communities in remote areas.

The LIFESAVER® bottle by Lifesaver Systems Ltd filters out contaminants of up to 15nm from raw water and is able to remove all bacteria, viruses, cysts, parasites, fungi and all other microbiological waterborne pathogens. The LIFESAVER® bottle comprises a filter cartridge bearing filter membranes having a minimum pore size of 15 nm. Due to this small pore size, it is not possible for water to be filtered through solely by action of gravity and human intervention is required. A user will have to use a hand pump to draw water through the filter. The LIFESAVER® jerrycan operates similarly as the LIFESAVER® bottle. The LIFESAVER® bottle and jerrycan, published as UK patent no. 2 443 608 B and UK patent no. 2 473 256 B, are effectively pressurized vessels. The hand pump is highly susceptible to damage from everyday use. Any leakage to the pressurized vessels via a faulty hand pump or the threaded covers will reduce the effectiveness of the filters. These devices are not suitable for use by young children and the elderly since it requires significant physical strength to operate the hand pumps to filter raw water. Users are also required to search for sufficiently clean raw water source to be used with the device.

The LIFESAVER® Ml tank by Lifesaver Systems Ltd has a larger water reservoir in comparison to the bottle or jerrycan but operates on the same principle, i.e. utilization of a 15nm pore size filter but requiring a pressurized enclosed atmosphere for forcing water through the filter. Being a pressurized vessel, it also faces the same problems as the LIFESAVER® bottle and jerrycan. Having internal pressure pumps requires frequent maintenance of the Ml system and this is undesirable especially for remote rural communities. The Ml system which does not have any features that allow the tank to be drained and flushed for cleaning is easily clogged up quickly by sediments present in the collected raw water. To remove the accumulated sediments at the bottom of the Ml system, the user will have to manually clean the Ml system by turning it upside down to allow the sediments to flow out of the system. This is not practical as the Ml system is a large vessel. The Ml system also does not have features to remove taste and odour of the treated water rendering the treated water to have an unpleasant taste and odour.

This invention thus aims to alleviate some or all of the problems of the prior art. SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, there is provided a drinking water supply system comprising a receiver module for receiving raw water and a filter module capable of storing water. The filter module has a filter cassette containing filter membranes of a minimum pore size of 15nm. The filter cassette is disposed horizontally within the filter module and there is an outlet for expression of filtered drinking water. The filter module is disposed below the receiver module. The position of the filter module relative to the receiver module and the weight of stored water within the filter module enables filtering of water through the filter cassette solely by action of gravity to produce drinking water. The present invention enables utilisation of local natural sources of raw water to provide drinking water. The pores of the filters of the present system having a minimum pore size of 15nm enables filtering out even the smallest waterborne viruses, such as the polio virus. The water from the drinking water supply system of the present invention is safe for human consumption without requiring any further treatment. With the system of this invention the filtration of raw water occurs automatically without the need for a pressurized vessel or human intervention of any kind. Due to the configuration of the receiver module and filter module of the drinking water supply system of this application, the magnitude of gravitational force acting on the raw water within the system is sufficient to force water through the pores of the filter. Since the filter is built-in, no extensive piping network is required.

In an embodiment, the receiver module may further comprise a diverter for flushing out of the system a predetermined amount of raw water before filtration commences. The diverter may be a float valve. Alternatively, the diverter may be a sink valve. The incorporation of a diverter for flushing out of the system the initial flow of raw water prevents the drinking water supply system from being clogged up easily by unwanted organic or inorganic matter. As a result, less frequent maintenance of the filter (and the system) is required. In a further embodiment, the receiver module may further comprise a filter lid mesh for preventing large particles from entering the system. Large organic or inorganic matter such as rubbish, leaves, insects and small organisms can be prevented from entering the drinking water supply system. In a different embodiment, the receiver module may further comprise a filter for filtering incoming raw water before it is filtered by the filter cassette. The filter may be a reticulated foam filter having a pore size of 127 ppcm to 254 ppcm (50 ppi to 100 ppi), or a woven polypropylene membrane filter having a minimum pore size of lOOnm and a vertical configuration extending along the height of the filter module. The filter may be of uniform or differing pore sizes. The pre-filtering performed at this juncture enables better quality of water to be filtered by the filter membranes of the filter cassette. This aids in prolonging the life of the filter membranes and decreases the accumulation of sediments in the filter module.

In a further embodiment, the filter module may comprise a plurality of filter cassettes. The filter cassettes may be aligned parallel to one another. In a preferred embodiment, the filter membranes of the drinking water supply system may comprise hydrophilic membranes. The filtering efficiency of the drinking water supply system can be improved by use of hydrophilic membranes which enables only water to pass through but not air. In a different embodiment, the filter membranes within the filter cassette may have a uniform pore size.

In another embodiment, filter membranes of differing pore sizes may be used within a filter cassette. Such membranes may be arranged within the cassette such that the membranes are of progressively smaller pore size towards the centre of the cassette. This is advantageous because the filter membranes with the smallest pores are centrally located and hence, better protected.

In a further embodiment, the filter cassette may be coupled to the outlet for the expression of drinking water directly after completion of filtration.

In a further embodiment, the filter module may further comprise a water level gauge indicator. In a preferred embodiment, the base of the filter module may be funnel-shaped for the accumulation and easy drainage of sediments. The filter module may further comprise a drainage valve at the bottom end of the funnel-shaped base for release of sediments. Built-up sediments at the bottom of the filter module can be simply removed by activating the drainage valve. Again, this is a one-step action that can be performed directly by the user.

In an embodiment, the receiver module or filter module may further comprise an overflow channel.

In a further embodiment, the receiver module and/or filter module may comprise a multilayer wall.

The wall of the receiver and/or filter modules may be incorporated with an antimicrobial additive. This is to prevent bacteria and other microbial growth on the inner surfaces of the drinking water supply system. The system is built to have long-lasting antimicrobial effect as the antimicrobial additive is not applied as a coating which can be easily scrapped off but is incorporated into the wall. In an embodiment, the receiver module and filter modules may be separable.

In a preferred embodiment, the receiver module and filter module may be provided to be of a configuration to permit nesting of a plurality of receiver modules and filter modules for easy transportation and storage. The receiver module and filter modules may further comprise threaded concentric sections to optimize nesting capability.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated, although not limited, by the following description of embodiments made with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of the drinking water supply system according to an embodiment of the present invention.

Figure 2 shows a top view of the drinking water supply system according to an embodiment of the present invention. Figure 3 shows a left side view of the drinking water supply system according to an embodiment of the present invention.

Figure 4 shows a right side view of the drinking water supply system according to an embodiment of the present invention.

Figure 5 shows a cross sectional view of a back view of the drinking water supply system according to an embodiment of the present invention.

Figure 6 shows a cross sectional view of a side view of the drinking water supply system according to an embodiment of the present invention.

Figure 7 shows the flush diverter of the receiver module of the drinking water supply system according to an embodiment of the present invention. Figure 8 shows a cross sectional view of a side view of the filter cassette of the drinking water supply system according to an embodiment of the present invention.

Figure 9 shows an image of a particle affixed to the outer filter membranes of the drinking water supply system according to an embodiment of the present invention.

Figure 10 shows an image of a perspective view across the surface of the filter membrane of the drinking water supply system according to an embodiment of the present invention. Figure 11 shows a backwash control valve located within the water outlet of the drinking water supply system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

The drinking water supply system of this invention mainly comprises a receiver module 10 and a filter module 20. As shown in Figure 1, the receiver module 10 is disposed above the filter module 20 which has a relatively vertical configuration. The drinking water supply system of this application enables filtering of water through filter membranes of a very small pore size solely by action of gravity. The vertical configuration as shown in Figure 1 is ideal, but is not a system requirement. Although the vertical configuration concentrates the force of gravity to aid in forcing water through the pores of the filter, it is the position of the filter module 20 relative to the receiver module 10 and weight of stored water within the filter module 20 that enables the filtering of water solely by action of gravity.

The drinking water supply system 1 is generally a hollow tank comprising an assembly of the receiver module 10 and filter module 20. The filter module is disposed below the receiver module. Raw water enters the system via the receiver module 10, flows to and is filtered through the filter module 20 and expressed through an outlet 40.

The receiver module 10 may be of any suitable shape and generally comprises a chamber 12 with an inlet 11 for entry of raw water into the system, as shown in Figures 2 and 7. The inlet 11 may preferably be located at the top of the receiver module 10. There may be more than one inlet. A filter lid mesh may be provided over the opening of the inlet 11.

The inlet 11 of the receiver module 10 provides an entrance for raw water to enter the system. For rain harvesting applications, where gutters and downpipes are available, a filter mesh lid covering or attached to the inlet 11 can easily be coupled with the gutter downpipes. This is for filtering coarse materials from raw water to prevent large particles such as rubbish, leaves, insects and small organisms from entering the system. Additional inlet(s) 11 may be provided in the receiver module 10, when the system is adapted to receive raw water from rivers, gravity feed systems or rainwater harvesting farms. For example, a compression fitting inlet with High Density Polyethylene (HDPE) Pipe connected to an external gravity feed system. The compression fitting inlet may be connected to an inline sediment pre-filter 19, as shown in Figure 3, which traps coarse sediments from raw water sources.

Optionally, a diverter may be provided in the receiver module chamber 12 to divert the flow path of incoming raw water. Firstly, the diverter directs a predetermined volume of incoming raw water into the receiver module chamber 12. Subsequently, it diverts further incoming raw water to the filter module 20. The diverter may be installed directly beneath the inlet 11 of the receiver module 10. Adjacent to the diverter, a filter may be provided along the flow path which directs water to the filter module 20. Preferably, when the system is coupled to downpipes, the receiver module 10 may further comprise a diverter in the chamber 12 for flushing out of the system a predetermined amount of incoming raw water before filtration commences.

The diverter is particularly important if the source of raw water entering the system is from an open conduit along which water flows, for example, roof gutters. Such open conduits often times have accumulated bacteria-laden fallen leaves, insects, small animal carcasses, animal droppings or even decomposed matters. The initial flow of raw water would carry these contaminants into the system. Generally, a pre-determined amount of water, for example, the first 25L of water should be flushed out. This flush diverter may be executed in various ways. Once the predetermined volume of "dirty" raw water has been directed into the chamber 12 of the receiver module 10, the diverter will divert subsequent incoming "clean" raw water to the filter module 20.

For example, as shown in Figure 7, the diverter may be a float valve comprising a floating body 13, a valve 14 and a valve guide 15 located in the chamber 12 of the receiver module 10. The floating body 13 may be a ball and the valve may be an opening. The valve guide 15 provides an ascending channel for the floating body 13 to move towards the valve 14. The floating body 13 may be disposed in the valve guide 15. As the water level rises in the chamber 12, the floating body 13 floats in the valve guide 15 towards the valve 14. Once the chamber 12 is full, the floating body 13 rests at and closes the valve 14 thus, directing subsequent flow of raw water to the filter module 20. A flush valve 16 is provided to flush out the contents of the chamber 12 after a rainfall. This prepares the receiver module 10 of the drinking water supply system 1 to re-set and start operating again.

Alternatively, the diverter may be a sink valve (not shown) comprising a suspended body in the chamber of the receiver module and a valve which may be an opening at the base of the chamber. The suspended body is adapted to receive raw water and hangs off a shaft and the valve opening is directly disposed beneath the suspended body. The valve opening may directly lead to a drain. The initial flow of dirty raw water will enter the drain via the valve opening. As incoming raw water enters the chamber and flows through the valve opening, the suspended body will receive raw water and will descend. The suspended body will eventually rest on the valve and this results in the valve being closed, thus, directing subsequent flow of incoming clean raw water to the filter module 20. When the flow of raw water ceases, the water in the suspended body will slowly drain out by way of evaporation and slowly be retracted to its originally suspended position. This prepares the receiver module to re-set and start operating again. The receiver module 10 may function as a "lid" to the filter module 20. The receiver module 10 may be provided to be integral with the filter module 20 or separately provided from the filter module 20.

To prevent the system from being clogged up quickly, the raw water which is to be diverted to the filter module 20 from the receiver module 10 may be pre-filtered before it is filtered by the filter cassette 30.

A filter may be provided horizontally in the receiver module 10 along the flow path of incoming raw water for pre-filtering the raw water before it is filtered by the filter cassette 30. The filter may be removable and thus replaced from time to time. Any suitable filter may be used such as a reticulated foam filter, sand filter or ceramic filter. These filters may preferably have a pore size of about 127 ppcm to 254 ppcm (50 ppi to 100 ppi) for filtering coarse debris and contaminants. Alternatively, a filter 25 may be disposed vertically extending along the height of the filter module 20 as shown in Figure 5, for pre-filtering the raw water before it is filtered by the filter cassette 30. The filter 25 is connected to the receiver module along the flow path of incoming raw water by connecting pipes, and is a hollow tube sealed at its ends. The side wall of the tube comprises a filtering media which may be made of any type of suitable material, preferably woven polypropylene membrane material. As incoming raw water fills the hollow tube, water within the hollow tube passes through the pores of the filtering media. The filtering media may have a minimum pore size of lOOnm. The filtering media may have a uniform pore size or progressively smaller pore size towards the exterior of the hollow tube. The bottom end of the hollow tube is connected to a filter drainage valve. When the filter drainage valve 26 is open, a differential pressure is created and water from the filter module 20 will push trapped sediments and accumulated sediments out of the filter 25. The filter module 20 may be of any suitable shape and generally comprises a hollow tank. The filter module 20 preferably has a height greater than its width with a generally vertical configuration which aids in concentrating the force of gravity to force water through the pores of the filter. The vertical configuration is ideal, but not a system requirement to enable the filtering of water through the pores of the filter. As shown in the embodiment of Figures 1, 3, 4, 5 and 6, it can have an upright hollow body with a funnel-shaped base 21. The upright hollow body may comprise threaded concentric sections to enable nesting of the module in transport whilst protecting its inner surface.

The filter module 20 contains a filter cassette 30 horizontally disposed across the width of the upright hollow body and preferably located above the funnel-shaped base 21, as shown in Figure 6. Having horizontally disposed filter cassettes 30 increases the filter surface area since the entire length of the filter will be submerged in water. More than one filter cassette 30 may be provided. When a plurality of filter cassettes 30 is provided, they may be aligned parallel to each other. Each filter cassette 30 will be able to produce up to 1,000,000 litres of water at a flow rate of up to 8 litres per minute. The filter cassette 30 may be replaced after producing 1,000,000 litres of water or every 2 years. The filter cassette 30 may comprise of a front section 31 and back section 35. The front section 31 is adjacent to the outlet 40 of the system. The back section 35 extends backward from the front section 31. The filter cassettes 30 are shown in Figure 8. The back section 35 may comprise at least three concentric layers of filter, i.e. outer layer, intermediate layer and inner layer. The outer layer of the filter cassette 30 comprises a first layer of foam filter 36 having a pore size of about 5μιη. The first layer of foam filter 36 is followed by the intermediate layer which is a second layer of foam filter 37 having a pore size of about Ιμιη. The outer and intermediate layers trap sediment and particles in the water initially absorbed by the filter. The foam filter may also be coated with an anti-bacterial formula to combat microbial growth. The inner layer of the filter cassette 30 comprises a layer of activated carbon 38 which removes contaminants such as Arsenic, Fluoride, Chlorine, volatile organic compounds and dissolved gases from the water rendering it safe, which also removing taste and ordour. The activated carbon 38 may be from Atmospheric Collection Technology's Nano-Carb™.

The layers of the filter cassettes 30 may be bonded together by any suitable material such as an epoxy resin. The front section 31 of the filter cassette 30 mainly contains filter cartridges 32 having filter membranes of a minimum pore size of 15nm at a log 7 Microbiological Reduction. The filter cartridges 32 are preferably aligned parallel to one another within the filter cassette 30. The outer layer of filter from the back section 35 may extend to the front section 31 of the filter cassette 30. Thus, water may be absorbed throughout the entire length of the filter cassette 30 and may pass through the outer layer, intermediate layer and inner layer of filters prior to passing through the filter cartridges 32.

Unlike normal filters that are incapable of distinguishing between air and water and, hence, filter air and water simultaneously, the filter membranes in the filter cartridges 32 used in the present system are preferably hydrophilic membranes which has an affinity to water and will readily filter water instead of air. This avoids the occurrence of air pockets within the filter cartridges 32 and enables expression of only water from the system during each operation session. The filter membranes of the present system are preferably of identical composition. The filter membranes are basically a blend of plastics that are extruded from hydrophilic hollow fibre tubes. The pore size of the filter membranes used in the system of this invention has a minimum pore size of 15nm. The filter membranes may be of uniform pore size or of different pore size. Preferably, the filter membranes are of differing pore sizes and arranged within the filter cartridges 32 such that the membranes are of progressively smaller pore sizes towards the centre of the filter cartridges 32. Figure 9 shows a particle affixed to the outer filter membranes. The pore sizes are small but the pore sizes of the inner filter membranes are even smaller. The progressively smaller pores of the filter membranes towards the centre of the filter cartridges 32 provides a depth filter for the trapping of progressively smaller particles as water flows through the filter membranes. This is advantageous because the final filter membranes with the smallest pores are disposed in the centre of the filter cartridges 32 and hence, are better protected. This increases the life span of the filter membranes. Figure 10 shows a perspective view across the surface of the filter membrane. It can be seen that the pores are abundant.

The filter module 20 acts as a storage facility for storing water and only supplies drinking water when required. The filter cassettes 30 may be directly coupled to the outlet 40 for the expression of drinking water. This guarantees that the expressed drinking water is free from contaminants at the point of consumption. A tap may be installed exterior to the drinking water supply system to control the opening and closing of the outlet 40. The filter module 20 may further comprise a backwash control valve 41 to create a reverse flow of water through the filters to push out sediments trapped in the filter layers and membranes in the filter cassette 30. The backwash control valve 41 is shown in Figure 11. During a backwash operation, the flow of water is reversed so that it rinses the filter membranes, foam layers and activated carbon layer to flush out trapped sediments within the filter pores in the filter cassette 30. The backwash control valve regulates and limits the pressure exerted to the filter layers and membranes while it is subjected to a periodic backwashing practice up to about 48 kPa (7psi). This is a simple to use feature that allows the user to maintain the drinking water supply system without the need for external technical support. It is not necessary to provide the backwash control valve as an integral part of the system and it may only be installed onto the system during maintenance.

The filter module 20 may be additionally equipped with a water level gauge indicator 18 which indicates the water level in its tank. The presence of a water level gauge indicator 18 helps users manage the stored water in the system more efficiently. Any type of water level gauge indicators 18 may be used with the present system. For example, a clear plastic tube which is connected externally to the filter module 20 with one end fitted to the base of the filter module 20 and the other end fitted to the top of the filter module 20, containing a float. In this type of water level gauge indicator, water in the system will flow into the tube and the float at the surface of the water indicates the water level in the filter module 20.

The water level indicator 18 may also be colour coded to represent water level conditions in the system. For example, green represents a good water level and water can be used freely, yellow represents low water level and users have to be cautious in withdrawing water from the system and red depicts that water is scarce and users should stop withdrawing water from the system. As raw water is stored locally within the present system, there will inevitably be sediments present inside the system. The filter module 20 of the present system preferably has a funnel-shaped base 21 for the accumulation and easy drainage of sediments from the system. A drainage valve 22 positioned at the bottom end of the funnel-shaped base 21 enables easy complete drainage and flushing out of sediments from the present system. The draining and flushing of sediments may be executed at any time. However, a waiting period of about at least an hour is required for sediments to settle at the base of the system if a backwash has just been completed.

The receiver and filter modules 10, 20 of the present system may be constructed using the multilayer co-extrusion technology which enables the walls of the modules to be produced in multilayers. In the co-extrusion process, a plurality of sheets are pressed together to form an integral piece. Each individual sheet maintains its original properties although combined with other sheets in a single piece. Therefore, the inner walls and the outer walls of the present system may have different physical and chemical properties allowing for system-design flexibility.

The walls, particularly the inner walls of the present system may be preferably incorporated with an antimicrobial additive. Any type of suitable antimicrobial additive may be incorporated in the construction of the walls. The antimicrobial additive serves to prevent growth of harmful bacteria on the surface of the system's internal walls. The incorporation of the antimicrobial additive in the construction of the walls provides a permanent antimicrobial effect as compared to having an applied coating of antimicrobial additive.

In the present embodiment, the antimicrobial additive is a combination of organic and inorganic compounds, such as polyethylene (carrier), sorbic acid, citric acid anhydrous, cupric sulphate, titanium dioxide and propylene glycol. The positively charged ions of the inorganic compounds bind with the microorganisms and cause their enzymes to break down. As a result, the microorganisms are unable to reproduce and eventually die out. The organic compounds give the disruptive effect on the membrane of microorganisms which results in interference with the uptake of nutrients through the membrane and also prevents cell division.

The filter module 20 may optionally further comprise an overflow channel which is normally in an opened configuration. When the water level in the filter module 20 reaches its maximum capacity, excess water will be discharged via the overflow channel to the nearest drain or discharge location via any connecting piping assembly.

The receiver modules 10 and filter modules 20 of the drinking water supply system may be separately provided. The receiver and filter modules 10, 20 may be of any suitable shape and configuration. Preferably, both modules are of a corresponding shape to enable nesting of the modules. Nestability will allow easy transport and delivery of the modules.

According to the embodiments of the system shown in the accompanying drawings, both the receiver module 10 and filter module 20 have a generally cylindrical shape. It is ideal for the modules to be cylindrical as this will result in the weight of the water being centralized within the system and thus enhancing the action of gravity on the water, aiding in more efficient filtration. However, the present system will function even if the receiver and filter modules 10, 20 are of other polygonal shapes since the force of gravity will still act on the water regardless of the shape of the drinking water supply system of the modules. Furthermore, the filter module 20 preferably having a vertical configuration also centralizes the weight of stored water within the system.

The drinking water supply system of the present invention has a large capacity for storing water. The gravitational weight of the large volume of stored water generates sufficient pressure naturally to enable filtering of water through filter membranes of a very small pore size. A minimum operating head pressure of 2.9kPa is sufficient to effectively filter water through a filter of a pore size of 15nm and achieve a steady minimum flow of filtered drinking water. Filtered drinking water may still flow out of the system, however, at a much slower flow rate when the operating head pressure is below 2.9kPa. The minimal pressure of 2.9kPa is not sufficient to force water through the 15nm filter pores of the filter membranes. Drinking water flowing out of the system when the system is having an operating head pressure below 2.9kPa is water which has already been filtered through the 15nm filter membranes but yet to flow out of the filter cassettes.

The drinking water supply system of this invention functions in a repeating continuous series of operations. The present system is an independent system which does not require human intervention to produce drinking water. It is adapted to automatically harvest natural raw water, for example, rain water, with the operational series of the system beginning when it starts to rain and ends when the rain stops. In use, raw water will firstly flow into the receiver module 10. A predetermined amount of raw water, such as the first 25L of raw water, carrying large contaminants may be diverted and trapped within the chamber 12 of the receiver module 10. Once the chamber 12 is full, the diverter subsequently directs raw water to the filter module 20. The contaminated raw water in the chamber 12 is left in the chamber 12 until the end of the present series of operations. After rainfall, the water in the chamber 12 of the receiver module 10 may be drained out via the flush valve 16. The flush valve 16 may be manually released at any time before the beginning of the next raining session. Once the chamber 12 of the receiver module is empty the series of operations may be repeated again. Before raw water enters the filter module 20, it may be pre-filtered. When a user opens the outlet via the tap, raw water will be forced through the filter membranes and flow out of the tap. The filtered drinking water may be consumed as it is. Conventional filtering devices having filter with small pores are generally tightly enclosed and requires the use of a pump to compress air and water in the enclosed device to force water through the filter. There are also filters with pumps to create a differential pressure within the filter to force water through the filter bed. In general, a difference in pressure at the outgoing and incoming end must be created to force water through filters having small pore sizes. However, the present system is designed to maximize and utilise the force of gravity which generates natural pressure to force water through the filter. A minimum operating head pressure of 2.9kPa creates a force great enough to pull water through the filter having a pore size of 15nm without a pump. The pores of the filters are so small that it filters out even the smallest waterborne viruses, such as the polio virus. The flow rate of filtered drinking water from the filter module 20 will decrease once it is at half capacity. Water may still be able to be filtered through and flow out of the filter module 20 until a water level slightly above the filter cassette 30. When water reaches slightly above the filter cassette 30, the weight of the volume of water stored at this minimal capacity is not sufficient to create a magnitude of gravity force great enough to push water through the filter. When the volume of water is at minimal capacity, water which has entered the filter cassette 30 will remain in the filter cassette 30 until the next operation. This potentially allows the filter membranes to be kept soaked at all times, thus, enabling the membranes to be longer lasting. All directional statements such as front/forward, back/rear, top, bottom, lateral, inward, outward, made herein are relative to the orientation of the present system after assembly.

As will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its scope or essential characteristics. The present embodiments are, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within therefore intended to be embraced therein.