WO2014065648A1

WO2014065648A1 - Water filtration apparatus with automatic backwash

Info

Publication number: WO2014065648A1
Application number: PCT/MY2012/000264
Authority: WO
Inventors: Moon Tuck MAK
Original assignee: Mak Moon Tuck
Priority date: 2012-10-25
Filing date: 2012-10-25
Publication date: 2014-05-01
Also published as: EP2911763A1; CN104853824B; AU2012378698B2; CN104853824A; EP2911763A4; PH12015501164A1; AU2012378698A1

Abstract

An apparatus for water filtration with an automatic and repeatable backwash comprising: a feed pipe through which unfiltered water- is supplied, a lower chamber having a feed inlet in fluid connection with said feed pipe, and a filter located in said lower chamber, an upper chamber, a means of creating a backwash when an amount of suspended solids has been trapped by said filter, and a means of halting said backwash.

Description

Water Filtration Apparatus With Automatic Backwash

FIELD OF INVENTION The present invention relates generally to a water filtration apparatus having an automatic backwash function, and more specifically to a water filtration apparatus that uses a device similar to what is known as a siphon bell to initiate an automatic backwash. BACKGROUND OF INVENTION

Today, hundreds of millions of people live in places where there is no access to adequately clean water. Industrial processes produce a huge amount of wastewater that requires treatment before it is suitable to be discharged into surface water systems. So there is a large demand for water filtration systems that cater to varied applications and requirements of size and purity of product water. What is also desired are water filtration systems that do not require much in terms of maintenance or service, so that they can be left in areas that have clean water deficiencies for a longer time without the need for skilled personnel or special tools. Another desirable feature in a water filtration system is its ability to function 24- hours daily without electricity. Many of these areas that are in need of clean water have either limited or no access to electrical power. Other desirable features are a small footprint, access to remote sites with minimum environmental impact and simplicity of installation with minimum engineering structures. Another important feature for water filtration systems is its ability to inhibit human or mechanical tampering or misuse.

One type of water filtration system that possesses many attributes mentioned in the previous paragraph is a gravity system that uses the potential energy of feed water at height to drive the water through a filter of either a media composition such as sand, or a membrane type filter, and one of the techniques used to prolong the service life of these systems is to include an automatic backwashing function into the system, so that the filters are automatically cleaned by a backwash when there is enough suspended solids and other particles trapped at the upstream side of the filter. Mak in Malaysian Patent Application No. PI2010005202 disclosed a water filter with such an automatic backwash function that uses an ejector and a system of inter-connecting pipes to initiate a siphon that creates the backwash function when a certain differential head is reached across the membranes due to suspended solids being trapped at the upstream side of the membranes. One downside to using ejector pipes is that there is a minimum height for the head that is necessary to initiate the siphon that creates the backwash. This results in an apparatus that cannot be built when the required minimum head is unavailable or too costly to provide and therefore cannot be used in numerous applications. Another downside is the requisite volume of feed water needed to initiate the siphon. This reduces the production of clean water for consumption. During drought or dry season, the reduction of feed water may also impair the effectiveness of the ejector. Furthermore, fine solids from the feed water can choke the ejector, causing it to stall.

What is needed in the art is a water filtration system that overcomes the above- mentioned disadvantages.

SUMMARY OF INVENTION

The present invention seeks to overcome the above-mentioned disadvantages by providing a water filtration apparatus that incorporates a means of automatically creating, in a repeatable fashion, a backwash that removes trapped suspended solids from an upstream side of the filter.

This invention relates to an apparatus for water filtration with an automatic and repeatable backwash function, capable of being in a filtration mode or a backwash mode. A feed pipe supplies unfiltered water to the apparatus. A filter is provided, the filter adapted to allow mainly water to pass through and to restrict suspended solids from passing through by trapping said suspended solids at an upstream side.

In a first and second preferred embodiment, the apparatus has a split chamber configuration, where a lower chamber is connected to an upper chamber located some distance above the lower chamber. The lower chamber receives one end of the feed pipe at a feed inlet located close to a bottom of the lower chamber. The filter is a membrane filter, and it is placed in the lower chamber between the feed inlet and a product opening of the lower chamber, so that the membrane filter divides the lower chamber into an upstream (before filter) side and a downstream (after filter) side. The product opening of the lower chamber is connected to a bottom side of an upper chamber via an inter-connecting pipe. The upper chamber has a product outlet for expelling filtered water to an external use. During a filtration mode, unfiltered water passes through said feed pipe into the upstream side of the lower chamber, where suspended solids contained in the unfiltered water is filtered by the filter and filtered water passes into the downstream side of the lower chamber, and subsequently into the upper chamber. There, it is expelled via the product outlet for the external use. In a third and fourth preferred embodiment, the apparatus has a tiered chamber configuration, where an upper chamber sits directly on top of a lower chamber. Typically, the upper chamber is open-bottomed and the lower chamber is open- topped. The lower chamber receives one end of the feed pipe at a feed inlet located close to a bottom of the lower chamber. The filter is a membrane filter, and it is placed in the lower chamber, where the lower chamber is joined to the upper chamber, such that the filter is sandwiched between the lower and upper chambers. In this way, the membrane filter divides the lower chamber into an upstream (before filter) side and a downstream (after filter) side flowing straight into the upper chamber. The upper chamber has a product outlet for expelling filtered water to an external use. During a filtration mode, unfiltered water passes through said feed pipe into the upstream side of the lower chamber, where suspended solids contained in the unfiltered water is filtered by the filter and filtered water passes into the downstream side of the lower chamber, and subsequently into the upper chamber. There, it is expelled via the product outlet for the external use.

In a fifth and sixth preferred embodiment, the filter is a sand or other media filter. There is an upper chamber placed above a lower chamber, and a sand or other media filter placed in the lower chamber. The lower chamber receives one end of the feed pipe at a feed inlet located close to a top of the lower chamber. The filter comprises a filter nozzle plate having a plurality of openings, into which openings are placed filter nozzles, and media such as sand resting on the filter nozzles and filter nozzle plate. This media filter is placed mid-way down the lower chamber and divides the lower chamber into an upstream side and a downstream side. Unlike the first four embodiments, the upstream side in this embodiment is in the upper portion of the lower chamber, and the downstream side is in the lower portion of the lower chamber. A plurality of inter-connecting pipes provide fluid connection between a lower part of the lower chamber and a lower part of an upper chamber, in order to deliver filtered water to the upper chamber. The upper chamber is located above the lower chamber and has a product outlet for expelling filtered water to an external use. During a filtration mode, unfiltered water passes through the feed pipe into the upstream side of the lower chamber, where suspended solids contained in said unfiltered water is filtered by the media filter and filtered water passes into the downstream side of the lower chamber, up through the inter-connecting pipes and into the upper chamber. There, it is expelled via the product outlet for the external use.

In the first, third and fifth embodiments, this apparatus provides a means of creating, automatically, a backwash when a predetermined head differential has been reached due to the amount of suspended solids trapped by the filter at its upstream side, so that filtered water flows back through the filter from the downstream to the upstream side, and in doing so removes the suspended solids from the filter upstream side. This means of creating a backwash comprises: a siphon pipe having a lower end in fluid connection with an upstream side of the filter, the siphon pipe rising up to a siphon level, where it is in fluid connection with an upper end of a siphon dropper, said siphon dropper dropping down to a lower end; a sealed casing having a first top opening in fluid connection with the lower end of the siphon dropper, a second top opening, and a bottom opening; a bell located within and at a bottom end of the sealed casing having an open bottom that encloses the bottom opening of the sealed casing, a top opening, and at least one bell entry opening at a bottom section which allows fluid communication between said bell and the sealed casing; a snorkel comprising an inverted U-shaped pipe with a higher end and a lower end, the higher end being in fluid connection with said top opening of the bell, and the lower end being in fluid communication with the sealed casing; a water trap comprising a u-shaped pipe with a higher end and a lower end; a standpipe comprising a vertical pipe with a lower end in fluid connection with said higher end of the water trap, said standpipe protruding through said bottom opening of said sealed casing, into said bell, such that a higher end of the standpipe reaches a height that is higher than said lower end of said snorkel; and a drain pipe in fluid connection with said lower end of water trap. Preferably, the standpipe has a larger diameter than the water trap, and a reducer joins the standpipe to the water trap. The sealed casing, bell, snorkel, standpipe, and water trap together form a device similar to what is known as a siphon bell. For the sake of brevity, this device will be referred to as a siphon bell in the rest of this description. An air bleeder is provided to prevent any ingress of atmospheric air into the sealed casing during the backwash mode. If air is sucked into the sealed casing when the siphon starts, the siphon will not be maintained, thus disrupting the backwash mode.

In all the above embodiments, this apparatus provides a means of halting said backwash, comprising: a siphon break line having a higher end in fluid connection with an opening of the siphon pipe at the siphon level and a lower end protruding into the upper chamber via a break line opening of said upper chamber; a cup located within said upper chamber, said lower end of said siphon break line immersed into said cup, but said lower end located higher than a bottom of said cup.

As the filter gets progressively less permeable due to suspended solids being trapped at its upstream side, a filter upstream pressure rises and unfiltered water gradually rises up the siphon pipe. As more suspended solids are trapped at the upstream side of the filter, the water level in the siphon pipe continues to rise until it reaches a predetermined head differential, which is the height of the siphon level. The water eventually flows over the siphon level, down the siphon dropper and into the sealed casing. The sealed casing starts to fill, which also fills the bell, since there are bell entry openings that allow fluid communication between the sealed casing and bell. When this water level in the sealed casing and bell submerges the lower end of the snorkel, a quantity of air will be trapped in the confines of the snorkel and an upper portion of the bell, and since air is allowed to be expelled from the sealed casing via the second top opening, the water level in the sealed casing rises quicker than the water level in the bell. The rising water level in the sealed casing causes an accordant rise in pressure in the bell. This continues until the water level in the bell reaches said higher end of the standpipe, whereupon water starts to flow into and fill said water trap via the standpipe. Eventually, the water level in the sealed casing reaches a "tipping point", when the accordant pressure in the bell is high enough to force water that has been collected in the water trap to be flushed out, thus initiating a siphon. This first causes unfiltered water to flow from the feed inlet through the backwash creating means and out via the drain pipe, in what is known as an "out to out" backwash. When a head of the feed inlet drops below that of the product outlet, filtered water from the upper chamber flows into the lower chamber, through the backwash creating means and out via the drain pipe, in what is known as an "in to out" backwash. This reverse flow through the filter removes suspended solids that have been trapped at the upstream side of the filter during the filtration mode. This backwash continues until a water level in the upper chamber falls to an upper level of the cup, whereupon a suction of a volume of water in the cup by said siphon break line drains water from the cup until air is sucked into said siphon break line, causing the siphon to break, which in turn causes the apparatus to switch back to filtration mode. In this way, a volume of water in the upper chamber between the levels of the product outlet and the upper level of the cup is referred to as the predetermined stored backwash volume for the apparatus of this invention.

In a variation of the backwash creating means described above, and embodied in the second, fourth and sixth embodiments, there is added a backwash dropper to the backwash creating means. This backwash dropper comprises a horizontal and a vertical section of pipe joined at right angles to each other with the horizontal section on top, so that the backwash dropper has an inverted L-shape. A higher end of the backwash dropper is connected to where the siphon pipe meets the siphon dropper, and a lower end is connected to where the water trap meets the drain pipe. It functions as a bypass to allow more water to flow through the backwash creating means during the backwash mode. In larger designs of the apparatus of this invention, instead of scaling up the size of the siphon bell, a relatively smaller siphon bell can be used by adding the backwash dropper to allow a volume of water to bypass the siphon bell during the backwash mode. The diameter or cross-sectional area of this backwash dropper is typically larger than that of the siphon dropper. This variation reduces the construction cost and footprint for larger apparatuses. In this variation, the air bleeder has an upper connection in fluid connection with a top opening of the siphon level, and a lower end in fluid connection with a top end of the sealed casing is provided. This air bleeder functions to prevent any ingress of atmospheric air into the sealed casing during the backwash mode. If atmospheric air is allowed to ingress into the sealed casing, the suction from the sealed casing on the siphon dropper will be impaired, and an effective backwash will not occur. A second function of the air bleeder is to suck air out of the said horizontal section of the backwash dropper. When the siphon starts, the sealed casing will become a vacuum and excess air in the horizontal section of the backwash dropper is sucked out via the air bleeder. This will induce water into flowing out the backwash dropper. In these embodiments, it is necessary to use a backwash sump at a lower end of the drain pipe.

In a second variation of the backwash creating means described in the second, fourth and sixth embodiments, it is also possible to have the backwash creating means without the u-shaped water trap, in a seventh, eighth and ninth embodiment of this invention. In this variation, the standpipe flows directly into the drain pipe. While this variation does not produce as effective a siphon as the above embodiments, it is still possible to produce a siphon. To increase the effectiveness of this variation of the backwash creating means, a funnel may be added to the higher end of the standpipe.

In all the above embodiments, an air bleed line having a higher end in fluid connection to the feed pipe at a point higher than the siphon level, and a lower end connected to a bleeder outlet of the lower chamber may be provided to allow any air that is trapped in the upstream side of the lower chamber to be expelled from the lower chamber. Trapped air in the upstream side of the lower chamber may cause the filters to be less effective and efficient. For the membrane filters, trapped air in the upstream side of the lower chamber may also cause the siphon to start prematurely, as the air may cause filter upstream pressure to rise. Also for the membrane filters, trapped air in the upstream side of the lower chamber may also cause the upper section of the filters to fail prematurely.

In all the above embodiments, there may be provided a manual means of starting the backwash. This comprises a manual bypass pipe forming a fluid connection between a downstream side of the filter and the siphon dropper and a manual bypass valve to allow manual opening and closing of said fluid connection. This manual means of starting the backwash is useful when it is desired for the operator to manually start the backwash at will.

The gravity feed used in this invention produces a low pressure at the filters, which results in suspended solids embedding to a lesser degree on the filters. This allows more thorough removal of trapped suspended solids from the filters during the backwash mode. This ultimately results in less fouling of the filters.

Other objects and advantages will be more fully apparent from the following disclosure and appended claims.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows a cross-sectional view of a water filtration apparatus using a membrane filter with lower and upper chambers in a split configuration in a first embodiment of this invention.

Figure 2 shows a cross-sectional view of a water filtration apparatus using a membrane filter with lower and upper chambers in a split configuration and with a backwash dropper in a second embodiment of this invention. Figure 3 shows a cross-sectional view of a water filtration apparatus using a membrane filter with lower and upper chambers in a tiered configuration in a third embodiment of this invention. Figure 4 shows a cross-sectional view of a water filtration apparatus using a membrane filter with lower and upper chambers in a tiered configuration and with a backwash dropper in a fourth embodiment of this invention. Figure 5 shows a cross-sectional view of a water filtration apparatus using sand or other media filters in a fifth embodiment of this invention.

Figure 6 shows a cross-sectional view of a water filtration apparatus using sand or other media filters and with a backwash dropper in a sixth embodiment of this invention.

Figure 7a shows a cross-sectional view of an enlargement of detail 62A of Figures

1 , 3 and 5, which show a device similar to what is known as a siphon bell in a first, third and fifth embodiment of this invention.

Figure 7b shows a cross-sectional view of an enlargement of detail 62B of Figures

2, 4 and 6, which show a device similar to what is known as a siphon bell in a second, fourth and sixth embodiment of this invention. Figure 7c shows a cross-sectional view of an enlargement of detail 62C of Figures 9, 10 and 11 , which show a device similar to what is known as a siphon bell in a seventh, eighth and ninth embodiment of this invention.

Figure 8 shows a cross-sectional view of an enlargement of detail 80 of Figures 2, 4, 6, 7, 8 and 9, which shows a backwash sump in a second, fourth, sixth, seventh, eighth and ninth embodiment of this invention.

Figure 9 shows a cross-sectional view of a water filtration apparatus using a membrane filter with lower and upper chambers in a split configuration in a seventh embodiment of this invention.

Figure 10 shows a cross-sectional view of a water filtration apparatus using a membrane filter with lower and upper chambers in a tiered configuration in an eighth embodiment of this invention. Figure 11 shows a cross-sectional view of a water filtration apparatus using sand or other media filters in a ninth embodiment of this invention.

DETAILED DESCRIPTION OF INVENTION

It Should be noted that the following detailed description is directed to a water filter with automatic backwash and is not limited to any particular size or configuration but in fact a multitude of sizes and configurations within the general scope of the following description.

Referring to Figures 1 and 7a, there is shown an apparatus for water filtration with an automatic and repeatable backwash function, capable of being in a filtration mode or a backwash mode, and using a membrane filter, with a lower chamber (20) and an upper chamber (50) in a split configuration in a first embodiment of this invention. There is shown a feed system (10) comprising a feed pipe (12), flow rate measuring means (13), supply inlet (14) and flow rate control means (15). Unfiltered feed water is supplied through the feed pipe (12) from a supply inlet (14) after passing through a flow rate measuring means (13) comprising a rotameter, and a flow rate controlling means (15) comprising a manual valve. The lower chamber (20) is provided with a feed inlet (212) close to its bottom, to which the feed pipe (12) is connected, such that the unfiltered water enters the lower chamber (20) via this feed inlet (212). The lower chamber is also provided with a product opening (214) close to its top. A membrane filter (30) is placed in the lower chamber (20) between the feed inlet (212) and the product opening (214), so that the filter (30) divides the lower chamber (20) into an upstream (before filter) side (21) and a downstream (after filter) side (22). The said filter (30) is adapted to allow mainly water to pass through and to restrict suspended solids from passing through. The product opening (214) of the lower chamber is connected to a bottom opening (52) of an upper chamber (50) via an inter-connecting pipe (40). The upper chamber (50) has a product outlet (54) for expelling filtered water via an outlet pipe (56) to an external use. During a filtration mode, unfiltered water passes through said feed pipe into the upstream side of the lower chamber, where suspended solids contained in the unfiltered water is filtered by the filter (30) and filtered water passes into the downstream side (22) of the lower chamber, and subsequently into the upper chamber (50). There, it is expelled via the product outlet (54) for the external use. There is a manual means of starting the backwash comprising a manual bypass pipe (90) forming a fluid connection between a lower part of the upper chamber (50) and the siphon dropper (615) and a manual bypass valve (92) to allow manual opening and closing of said fluid connection.

Still referring to Figures 1 and 7a, there is also shown a backwash creating means (60). This is a means of creating, automatically, a backwash when a predetermined differential head has been reached due to the amount of suspended solids trapped by the filter (30) at its upstream side, so that filtered water flows back through the filter from the downstream (22) to the upstream (21) side, and in this reversal of flow, removes the suspended solids from the filter upstream side. This backwash creating means (60) comprises: a siphon pipe (610) having a lower end (612) in fluid connection with an upstream side of the filter via a siphon outlet (216, 236) located close to a bottom of the lower chamber (20), the siphon pipe (610) rising up to a siphon level (611 ) where the pipe becomes horizontal, after which the pipe bends back down where it becomes a siphon dropper (615), said siphon dropper dropping down to a lower end (617); a sealed casing (620) having a first top opening (621) in fluid connection with the lower end (617) of the siphon dropper (615), a second top opening (623), and a bottom opening (622); a bell (635) located within and at a bottom end of the sealed casing having an open bottom that encloses the bottom opening (622) of the sealed casing, a top opening (636), and at least one bell entry opening (645) at a bottom section which allows fluid communication between said bell and the sealed casing; a snorkel (625) comprising an inverted U-shaped pipe with a higher end (626) and a lower end (627), the higher end (626) being in fluid connection with said top opening (636) of the bell, and the lower end (627) being in fluid communication with the sealed casing (620); a water trap (660) comprising a u-shaped pipe with a higher end (661) and a lower end (662); a standpipe (640) comprising a vertical pipe with a lower end (641) in fluid connection with said higher end (661) of the water trap (660), said standpipe protruding through said bottom opening (622) of said sealed casing (620), into said bell (635), such that a higher end (642) of the standpipe (640) reaches a height that is higher than said lower end (627) of said snorkel (625); and a drain pipe (670) in fluid connection with said lower end (662) of water trap. The standpipe (640) has a larger diameter than the water trap (660), and a reducer (650) joins the standpipe (640) to the water trap (660). The sealed casing (620), bell (635), snorkel (625), standpipe (640), and water trap (660) together form a siphon bell (62A). An air bleeder (655) having a higher end in fluid connection with the second top opening (623) of the sealed casing, and a lower end in fluid connection with the lower end (662) of the water trap is provided. This is necessary to prevent any ingress of atmospheric air into the sealed casing (620) during the backwash mode. If air is sucked into the sealed casing when the siphon starts, the siphon will not be maintained, thus disrupting the backwash mode.

There is also shown a backwash halting means (70), which is a means of halting, automatically, said backwash, comprising: a siphon break line (710) having a higher end (711) in fluid connection with an opening of the siphon pipe (610) at the siphon level (611) and a lower end (712) protruding into the upper chamber (50) via a break line opening (58) of the upper chamber; a cup (720) located within said upper chamber (50), with the lower end (712) of the siphon break line being immersed into the cup (720), but said lower end (712) located higher than a bottom of said cup (720).

Still referring to Figures 1 and 7a: During a filtration mode, unfiltered water passes through said feed pipe (12) into said lower chamber (20), where suspended solids contained in said unfiltered water is filtered by the filter (30) and filtered water passes into the upper chamber (50), where it is expelled via the product outlet (54) to an external use. As the filter (30) gets progressively less permeable due to suspended solids being trapped at its upstream side, a filter upstream pressure rises and unfiltered water gradually rises up the siphon pipe (610). As more suspended solids are trapped at the upstream side (21) of the filter (30), the water level in the siphon pipe (610) continues to rise until it reaches a predetermined head differential, which is the height of the siphon level (61 ). The water eventually flows over the siphon level (611), down the siphon dropper (615) and into the sealed casing (620). The sealed casing (620) starts to fill, which also fills the bell (635), since there are bell entry openings (645) that allow fluid communication between the sealed casing (620) and bell (635). When this water level in the sealed casing (620) and bell (635) submerges the lower end (627) of the snorkel (625), a quantity of air will be trapped in the confines of the snorkel (625) and an upper portion of the bell (635), and since air is allowed to be expelled from the sealed casing (620) via the second top opening (623), the water level in the sealed casing (620) rises quicker than the water level in the bell (635). The rising water level in the sealed casing (620) causes an accordant rise in pressure in the bell (635). This continues until the water level in the bell (635) reaches said higher end (642) of the standpipe (640), whereupon water starts to flow into and fill said water trap (660) via the standpipe (640). Eventually, the water level in the sealed casing (620) reaches a "tipping point", when the accordant pressure in the bell (635) is high enough to force water that has been collected in the water trap (660) to be flushed out, thus initiating a siphon. This first causes unfiltered water to flow from the feed inlet through the backwash creating means (60) and out via the drain pipe (670). When a head of the feed inlet drops below that of the product outlet (54), filtered water from the upper chamber (50) flows into the downstream side (22) of the lower chamber, through the filter (30), and into the upstream side (21) of the lower chamber. The water then flows through the backwash creating means (60) and out via the drain pipe (670). This reverse flow through the filter (30) removes suspended solids that have been trapped at the upstream side of the filter (30) during the filtration mode. This backwash continues until a water level in the upper chamber (50) falls to an upper level (721) of the cup (720), whereupon a suction of a volume of water in the cup (720) by said siphon break line (710) drains water from the cup (720) until air is sucked into said siphon break line, causing the siphon to break, which in turn causes the apparatus to switch back to filtration mode. In this way, a volume of water in the upper chamber between the levels of the product outlet (54) and the upper level (721) of the cup is referred to as the predetermined stored backwash volume for the apparatus of this invention. Referring now to Figures 3 and 7a, there is shown an apparatus for water filtration with an automatic and repeatable backwash function, capable of being in a filtration mode or a backwash mode, and using a membrane filter, with a lower chamber (20) and an upper chamber (50) in a tiered configuration in a third embodiment of this invention. In this embodiment, the upper chamber (50) sits directly on top of the lower chamber (20). Typically, the upper chamber (50) is open-bottomed and the lower chamber (20) is open-topped, so that when put together, they form a larger chamber. There is shown a feed system (10) comprising a feed pipe (12), flow rate measuring means (13), supply inlet (14) and flow rate control means ( 5). Unfiltered feed water is supplied through the feed pipe (12) from a supply inlet (14) after passing through a flow rate measuring means (13) comprising a rotameter, and a flow rate controlling means (15) comprising a manual valve. The lower chamber (20) is provided with a feed inlet (212) close to its bottom, to which the feed pipe (12) is connected, such that the unfiltered water enters the lower chamber (20) via this feed inlet (212). A membrane filter (30) is placed in the lower chamber (20) close to or where the lower chamber (20) is joined to the upper chamber (50), so that the filter (30) divides the lower chamber (20) into an upstream (before filter) side (21) and a downstream (after filter) side (22). The said filter (30) is adapted to allow mainly water to pass through and to restrict suspended solids from passing through. The upper chamber (50) has a product outlet (54) for expelling filtered water via an outlet pipe (56) to an external use. During a filtration mode, unfiltered water passes through said feed pipe into the upstream side of the lower chamber, where suspended solids contained in the unfiltered water is filtered by the filter and filtered water passes into the downstream side of the lower chamber, and subsequently into the upper chamber. There, it is expelled via the product outlet for the external use. There is a manual means of starting the backwash comprising a manual bypass pipe (90) forming a fluid connection between a lower part of the upper chamber (50) and the siphon dropper (615) and a manual bypass valve (92) to allow manual opening and closing of said fluid connection.

Still referring to Figures 3 and 7a, there is also shown a backwash creating means (60). This is a means of creating, automatically, a backwash when a predetermined differential head has been reached due to the amount of suspended solids trapped by the filter (30) at its upstream side, so that filtered water flows back through the filter from the downstream (22) to the upstream (21) side, and in doing so removes the suspended solids from the filter upstream side. This backwash creating means (60) comprises: a siphon pipe (610) having a lower end (612) in fluid connection with an upstream side of the filter via a siphon outlet (216) located close to a bottom of the lower chamber (20), the siphon pipe (610) rising up to a siphon level (611) where the pipe becomes horizontal, after which the pipe bends back down where it becomes a siphon dropper (615), said siphon dropper dropping down to a lower end (617); a sealed casing (620) having a first top opening (621) in fluid connection with the lower end (617) of the siphon dropper (615), a second top opening (623), and a bottom opening (622); a bell (635) located within and at a bottom end of the sealed casing having an open bottom that encloses the bottom opening (622) of the sealed casing, a top opening (636), and at least one bell entry opening (645) at a bottom section which allows fluid communication between said bell and the sealed casing; a snorkel (625) comprising an inverted U-shaped pipe with a higher end (626) and a lower end (627), the higher end (626) being in fluid connection with said top opening (636) of the bell, and the lower end (627) being in fluid communication with the sealed casing (620); a water trap (660) comprising a u-shaped pipe with a higher end (661) and a lower end (662); a standpipe (640) comprising a vertical pipe with a lower end (641) in fluid connection with said higher end (661) of the water trap (660), said standpipe protruding through said bottom opening (622) of said sealed casing (620), into said bell (635), such that a higher end (642) of the standpipe (640) reaches a height that is higher than said lower end (627) of said snorkel (625); and a drain pipe (670) in fluid connection with said lower end (662) of water trap. The standpipe (640) has a larger diameter than the water trap (660), and a reducer (650) joins the standpipe (640) to the water trap (660). The sealed casing (620), bell (635), snorkel (625), standpipe (640), and water trap (660) together form a siphon bell (62A). An air bleeder (655) having a higher end in fluid connection with the second top opening (623) of the sealed casing, and a lower end in fluid connection with the lower end (662) of the water trap is provided. This is necessary to prevent any ingress of atmospheric air into the sealed casing (620) during the backwash mode. If air is sucked into the sealed casing when the siphon starts, the siphon will not be maintained, thus disrupting the backwash mode.

There is also shown a backwash halting means (70), which is a means of halting, automatically, said backwash, comprising: a siphon break line (710) having a higher end (71 ) in fluid connection with an opening of the siphon pipe (610) at the siphon level (6 ) and a lower end (712) protruding into the upper chamber (50) via a break line opening (58) of the upper chamber; a cup (720) located within said upper chamber (50), with the lower end (712) of the siphon break line being immersed into the cup (720), but said lower end (712) located higher than a bottom of said cup (720).

Still referring to Figures 3 and 7a: During a filtration mode, unfiltered water passes through said feed pipe (12) into said lower chamber (20), where suspended solids contained in said unfiltered water is filtered by the filter (30) and filtered water passes into the upper chamber (50), where it is expelled via the product outlet (54) to an external use. As the filter (30) gets progressively less permeable due to suspended solids being trapped at its upstream side, a filter upstream pressure rises and unfiltered water gradually rises up the siphon pipe (610). As more suspended solids are trapped at the upstream side (21) of the filter (30), the water level in the siphon pipe (610) continues to rise until it reaches a predetermined head differential, which is the height of the siphon level (611). The water eventually flows over the siphon level (611), down the siphon dropper (615) and into the sealed casing (620). The sealed casing (620) starts to fill, which also fills the bell (635), since there are bell entry openings (645) that allow fluid communication between the sealed casing (620) and bell (635). When this water level in the sealed casing (620) and bell (635) submerges the lower end (627) of the snorkel (625), a quantity of air will be trapped in the confines of the snorkel (625) and an upper portion of the bell (635), and since air is allowed to be expelled from the sealed casing (620) via the second top opening (623), the water level in the sealed casing (620) rises quicker than the water level in the bell (635). The rising water level in the sealed casing (620) causes an accordant rise in pressure in the bell (635). This continues until the water level in the bell (635) reaches said higher end (642) of the standpipe (640), whereupon water starts to flow into and fill said water trap (660) via the standpipe (640). Eventually, the water level in the sealed casing (620) reaches a "tipping point", when the accordant pressure in the bell (635) is high enough to force water that has been collected in the water trap (660) to be flushed out, thus initiating a siphon. This first causes unfiltered water to flow from the feed inlet through the backwash creating means (60) and out via the drain pipe (670). When a head of the feed inlet drops below that of the product outlet (54), filtered water from the upper chamber (50) flows through the filter (30) into the upstream side (21) of the lower chamber. The water then flows through the backwash creating means (60) and out via the drain pipe (670). This reverse flow through the filter (30) removes suspended solids that have been trapped at the upstream side of the filter (30) during the filtration mode. This backwash continues until a water level in the upper chamber (50) falls to an upper level (721) of the cup (720), whereupon a suction of a volume of water in the cup (720) by said siphon break line (710) drains water from the cup (720) until air is sucked into said siphon break line, causing the siphon to break, which in turn causes the apparatus to switch back to filtration mode. In this way, a volume of water in the upper chamber between the levels of the product outlet (54) and the upper level (721) of the cup is referred to as the predetermined stored backwash volume for the apparatus of this invention.

Referring now to Figures 5 and 7a, there is shown an apparatus for water filtration with an automatic and repeatable backwash function, capable of being in a filtration mode or a backwash mode, and using a sand or other media filter, with a lower chamber (20) and an upper chamber (50) in a tiered configuration in a fifth embodiment of this invention. In this embodiment, the upper chamber (50) sits directly on top of the lower chamber (20). There is shown a feed system (10) comprising a feed pipe (12), flow rate measuring means (13), supply inlet (14) and flow rate control means (15). Unfiltered feed water is supplied through the feed pipe (12) from a supply inlet (14) after passing through a flow rate measuring means (13) comprising a rotameter, and a flow rate controlling means (15) comprising a manual valve. The lower chamber (20) is provided with a feed inlet (232) close to its top, to which the feed pipe (12) is connected, such that the unfiltered water enters the lower chamber (20) via this feed inlet (232), after passing over a weir (238). A media filter (30) is placed in the lower chamber (20). The filter (30) comprises a filter nozzle plate (32) having a plurality of openings, into which openings are placed filter nozzles (34), and media (36) such as sand resting on the filter nozzles (34) and filter nozzle plate (32). This media filter (30) is placed mid-way down the lower chamber (20) and divides the lower chamber into an upstream side (21) and a downstream side (22). In this fifth embodiment, because typical media filters restrict the flow of water to downwards during filtration mode, the upstream side (21) is in an upper portion of the lower chamber (20), and the downstream side (22) is in a lower portion of the lower chamber (20). A plurality of inter-connecting pipes (40) provide fluid connection between a lower part of the lower chamber (20) and a lower part of the upper chamber (50), each inter-connecting pipe (40) comprising a vertical pipe having a lower opening (41) at a lower part of the lower chamber and connected at a top end to a bottom opening (52) of the upper chamber in order to deliver filtered water to the upper chamber. The upper chamber (50) has a product outlet (54) for expelling filtered water via an outlet pipe (56) to an external use. To allow for ease of installation and maintenance of the filter nozzle plate (32), filter nozzles (34) and media (36), there is provided an upstream manhole (240) and a downstream manhole (242) along the walls of the lower chamber (20). During a filtration mode, unfiltered water passes through the feed pipe (12) into the upstream side of the lower chamber (20), where suspended solids contained in said unfiltered water is filtered by the media filter (30) and filtered water passes into the downstream side (22) of the lower chamber, up through the inter-connecting pipes (40) and into the upper chamber (50). There, it is expelled via the product outlet (54) for the external use. There is a manual means of starting the backwash comprising a manual bypass pipe (90) forming a fluid connection between a lower part of the upper chamber (50) and the siphon dropper (615) and a manual bypass valve (92) to allow manual opening and closing of said fluid connection.

Still referring to Figures 5 and 7a, there is also shown a backwash creating means (60). This is a means of creating, automatically, a backwash when a predetermined differential head has been reached due to the amount of suspended solids trapped by the filter (30) at its upstream side, so that filtered water flows back through the filter from the downstream (22) to the upstream (21) side, and in doing so removes the suspended solids from the filter upstream side. This backwash creating means (60) comprises: a siphon pipe (610) having a lower end (612) in fluid connection with an upstream side of the filter via a siphon outlet (236) located close to a top of the lower chamber (20), the siphon pipe (610) rising up through the upper chamber (50), out via a siphon pipe opening (59) and up to a siphon level (611) where the pipe becomes horizontal, after which the pipe bends back down where it becomes a siphon dropper (615), said siphon dropper dropping down to a lower end (617); a sealed casing (620) having a first top opening (621) in fluid connection with the lower end (617) of the siphon dropper (615), a second top opening (623), and a bottom opening (622); a bell (635) located within and at a bottom end of the sealed casing having an open bottom that encloses the bottom opening (622) of the sealed casing, a top opening (636), and at least one bell entry opening (645) at a bottom section which allows fluid communication between said bell and the sealed casing; a snorkel (625) comprising an inverted U-shaped pipe with a higher end (626) and a lower end (627), the higher end (626) being in fluid connection with said top opening (636) of the bell, and the lower end (627) being in fluid communication with the sealed casing (620); a water trap (660) comprising a u-shaped pipe with a higher end (661) and a lower end (662); a standpipe (640) comprising a vertical pipe with a lower end (641) in fluid connection with said higher end (661) of the water trap (660), said standpipe protruding through said bottom opening (622) of said sealed casing (620), into said bell (635), such that a higher end (642) of the standpipe (640) reaches a height that is higher than said lower end (627) of said snorkel (625); and a drain pipe (670) in fluid connection with said lower end (662) of water trap. The standpipe (640) has a larger diameter than the water trap (660), and a reducer (650) joins the standpipe (640) to the water trap (660). The sealed casing (620), bell (635), snorkel (625), standpipe (640), and water trap (660) together form a siphon bell (62A). An air bleeder (655) having a higher end in fluid connection with the second top opening (623) of the sealed casing, and a lower end in fluid connection with the lower end (662) of the water trap is provided. This is necessary to prevent any ingress of atmospheric air into the sealed casing (620) during the backwash mode. If air is sucked into the sealed casing when the siphon starts, the siphon will not be maintained, thus disrupting the backwash mode.

Still referring to Figures 5 and 7a: During a filtration mode, unfiltered water passes through said feed pipe (12) into said lower chamber (20), where suspended solids contained in said unfiltered water is filtered by the filter (30) and filtered water passes into the upper chamber (50), where it is expelled via the product outlet (54) to an external use. As the filter (30) gets progressively less permeable due to suspended solids being trapped at its upstream side, a filter upstream pressure rises and unfiltered water gradually rises up the siphon pipe (610). As more suspended solids are trapped at the upstream side (21) of the filter (30), the water level in the siphon pipe (610) continues to rise until it reaches a predetermined head differential, which is the height of the siphon level (611). The water eventually flows over the siphon level (611), down the siphon dropper (615) and into the sealed casing (620). The sealed casing (620) starts to fill, which also fills the bell (635), since there are bell entry openings (645) that allow fluid communication between the sealed casing (620) and bell (635). When this water level in the sealed casing (620) and bell (635) submerges the lower end (627) of the snorkel (625), a quantity of air will be trapped in the confines of the snorkel (625) and an upper portion of the bell (635), and since air is allowed to be expelled from the sealed casing (620) via the second top opening (623), the water level in the sealed casing (620) rises quicker than the water level in the bell (635). The rising water level in the sealed casing (620) causes an accordant rise in pressure in the bell (635). This continues until the water level in the bell (635) reaches said higher end (642) of the standpipe (640), whereupon water starts to flow into and fill said water trap (660) via the standpipe (640). Eventually, the water level in the sealed casing (620) reaches a "tipping point", when the accordant pressure in the bell (635) is high enough to force water that has been collected in the water trap (660) to be flushed out, thus initiating a siphon. This first causes unfiltered water to flow from the feed inlet through the backwash creating means (60) and out via the drain pipe (670). When a head of the feed inlet drops below that of the product outlet (54), filtered water from the upper chamber (50) flows into the downstream side (22) of the lower chamber, through the filter (30), and into the upstream side (21) of the lower chamber. The water then flows through the backwash creating means (60) and out via the drain pipe (670). This reverse flow through the filter (30) removes suspended solids that have been trapped at the upstream side of the filter (30) during the filtration mode. This backwash continues until a water level in the upper chamber (50) falls to an upper level (721) of the cup (720), whereupon a suction of a volume of water in the cup (720) by said siphon break line (710) drains water from the cup (720) until air is sucked into said siphon break line, causing the siphon to break, which in turn causes the apparatus to switch back to filtration mode. In this way, a volume of water in the upper chamber between the levels of the product outlet (54) and the upper level (721) of the cup is referred to as the predetermined stored backwash volume for the apparatus of this invention. Figures 2, 7b and 8 show a variation of the first embodiment described in Figures 1 and 7a above, in a second embodiment of this invention. This second embodiment is similar to the first embodiment above with the addition of a backwash dropper (68) to the backwash creating means (60). Figures 4, 7b and 8 show a variation of the third embodiment described in Figures 3 and 7a above, in a fourth embodiment of this invention. This fourth embodiment is similar to the third embodiment above with the addition of a backwash dropper (68) to the backwash creating means (60). Figures 6, 7b and 8 show a variation of the fifth embodiment described in Figure 5 and 7a above, in a sixth embodiment of this invention. This sixth embodiment is similar to the fifth embodiment above with the addition of a backwash dropper (68) to the backwash creating means (60). Referring to Figures 2, 4, 6, 7b and 8, this backwash dropper (68) comprises a horizontal (682) and a vertical section (684) of pipe joined at right angles to each other with the horizontal section (682) on top, so that the backwash dropper (68) has an inverted L-shape. A higher end of the backwash dropper (68) is connected to where the siphon pipe (610) meets -the siphon dropper (615), and a lower end is connected to an intermediate point of the drain pipe (670). The drain pipe (670) has an upper portion, from where it joins the lower end (662) of the water trap to where it joins the backwash dropper (68), and a lower portion, from where it joins the backwash dropper (68) to its lower end (671). The lower portion of the drain pipe (670) has the same cross-sectional area as that of the backwash dropper (68). The upper portion of the drain pipe (670) has, generally, a lower cross-sectional area to that of the backwash dropper (68), and a same cross-sectional area as that of the water trap (660). It functions as a bypass to allow more water to flow through the backwash creating means (60) during the backwash mode. In larger designs of the apparatus of this invention, instead of scaling up the size of the siphon bell (62B), a relatively smaller siphon bell (62B) can be used by adding the backwash dropper (68) to allow a volume of water to bypass the siphon bell (62B) during the backwash mode. The diameter or cross-sectional area of this backwash dropper (68) is typically larger than that of the siphon dropper (615). This variation reduces the construction cost and footprint for larger apparatuses. In this variation, the air bleeder (655) has an upper connection (656) in fluid connection with a top opening of the siphon level (611), and a lower end in fluid connection with a second top opening (623) of the sealed casing. This air bleeder (655) functions to prevent any ingress of atmospheric air into the sealed casing (620) during the backwash mode. If atmospheric air is allowed to ingress into the sealed casing (620), the suction from the sealed casing on the siphon dropper (615) is impaired, and an effective backwash will not occur. A second function of the air bleeder (655) is to suck air out of the said horizontal section (682) of the backwash dropper (68). When the siphon starts, the sealed casing will become a vacuum and excess air in the horizontal section (682) of the backwash dropper is sucked out via the air bleeder (655). This will induce water into flowing out through the backwash dropper.

There is shown an open-topped backwash sump (80) having a first (82) and a second (86) compartment, said compartments separated by a dividing wall (84). The dividing wall (84) is lower than an external wall (81) of the backwash sump (80). The drain pipe (670) has a lower end (671) immersed into the first compartment (82). The dividing wall (84) is provided with a drain hole (83), which allows water flow between the first (82) and second (86) compartments. The drain hole (83) is located at a height that is lower than that of the lower end (671) of the drain pipe, and has a cross-sectional area significantly smaller than that of the drain pipe (670). There is shown a drain opening (88) connected to the second compartment (86) to allow external drainage of the second compartment. This drain opening (88) is located at a height that is lower than that of the drain hole (83). The cross-sectional area of the drain opening (88) is larger than that of the drain pipe

(670) . When the apparatus of this invention is in a filtration mode, the lower end

(671) of the drain pipe is exposed, as the water level in the first compartment (82) sits at the level of the drain hole (83). As the backwash is about to start and water starts flowing down the drain pipe (670), more water flows into the first compartment (82) than the drain hole (83) is capable of draining, and the lower end (671) of the drain pipe becomes submerged in water. This creates an air-lock within the drain pipe (670) and backwash dropper (68), which prevents ingress of atmospheric air into the sealed casing (620). After the siphon starts, the sealed casing (620) sucks residual air trapped in the horizontal section (682) of the backwash dropper via the siphon dropper (615) and air bleeder (655), creating a vacuum in the horizontal section (682) thus allowing more water to flow into the horizontal section (682). The flow rate into the horizontal section (682) that has a larger diameter than the siphon dropper (615) is more than what the siphon dropper (615) is able to handle. This causes an overflow of water through the backwash dropper (68) thus initiating the full force of siphon and automatic backwash mode. After the said siphon break, and water ceases to flow down the drain pipe (670), the water level in the said first compartment (82) is gradually drained out through the drain hole (83) until it exposes the lower end (671) of the drain pipe, and cancelling off any vacuum in the said backwash dropper (68) thus preparing the apparatus for its next backwash mode.

Referring to Figures 1 through 6, and 9 through 11 , there is shown an air bleed line (16) having a higher end in fluid connection to the feed pipe (12) at a point higher than the siphon level (611), and a lower end connected to a bleeder outlet (217, 237) of the lower chamber (20) may be provided to allow any air that is trapped in the upstream side (21) of the lower chamber to be expelled from the lower chamber. Trapped air in the upstream side (21) of the lower chamber may cause the filters (30) to be less effective and efficient. Trapped air in the upstream side (21) of the lower chamber may also cause the siphon to start prematurely, as the air causes filter upstream pressure to rise.

Referring to Figures 1 through 6, and 9 through 11 , there is shown a feed system (10) comprising a feed pipe (12), flow rate measuring means (13), supply inlet (14) and flow rate control means (15). The flow rate measuring means (13) comprises a rotameter, and a flow rate controlling means (15) comprises a manual valve located along the feed pipe (12). This allows manual monitoring and control of the flow rate of feed water so that it may be restricted to operate within the design parameters of the apparatus. Referring to Figures 1 through 6, and 9 through 11 , there is shown a manual means of starting the backwash. This comprises a manual bypass pipe (90) forming a fluid connection between a downstream side (22) of the filter (30) and the siphon dropper (615) and a manual bypass valve (92) to allow manual opening and closing of this said fluid connection. This manual means of starting the backwash is useful when it is desired for the operator to manually start the backwash at will.

Referring now to Figures 7c, 9, 10 and 11 , there are shown three further embodiments that use a variation of the backwash creating means of the second, fourth and sixth embodiments in seventh, eighth and ninth embodiments of this invention. This backwash dropper (68) comprises a horizontal (682) and a vertical section (684) of pipe joined at right angles to each other with the horizontal section (682) on top, so that the backwash dropper (68) has an inverted L-shape. A higher end of the backwash dropper (68) is connected to where the siphon pipe (610) meets the siphon dropper (615), and a lower end is connected to an intermediate point of the drain pipe (670). The drain pipe (670) has an upper portion, from where it joins the standpipe (640) to where it joins the backwash dropper (68), and a lower portion, from where it joins the backwash dropper (68) to its lower end (671). The lower portion of the drain pipe (670) has the same cross-sectional area as that of the backwash dropper (68). The upper portion of the drain pipe (670) has, generally, a lower cross-sectional area to that of the backwash dropper (68). It functions as a bypass to allow more water to flow through the backwash creating means (60) during the backwash mode. In larger designs of the apparatus of this invention, instead of scaling up the size of the siphon bell (62C), a relatively smaller siphon bell (62C) can be used by adding the backwash dropper (68) to allow a volume of water to bypass the siphon bell (62C) during the backwash mode. The diameter or cross-sectional area of this backwash dropper (68) is typically larger than that of the siphon dropper (615). This variation reduces the construction cost and footprint for larger apparatuses. In this variation, the air bleeder (655) has an upper connection (656) in fluid connection with a top opening of the siphon level (611), and a lower end in fluid connection with a second top opening (623) of the sealed casing. This air bleeder (655) functions to prevent any ingress of atmospheric air into the sealed casing (620) during the backwash mode. If atmospheric air is allowed to ingress into the sealed casing (620), the suction from the sealed casing on the siphon dropper (615) is impaired, and an effective backwash will not occur. A second function of the air bleeder (655) is to suck air out of the said horizontal section (682) of the backwash dropper (68). When the siphon starts, the sealed casing will become a vacuum and excess air in the horizontal section (682) of the backwash dropper is sucked out via the air bleeder (655). This will induce water into flowing out through the backwash dropper.

In this variation, the siphon bell (62C) does not have the u-shaped water trap of the first six embodiments. The siphon bell (62C) comprises: a sealed casing (620) having a first top opening (621) in fluid connection with the lower end (617) of a siphon dropper (615), a second top opening (623), and a bottom opening (622); a bell (635) located within and at a bottom end of the sealed casing having an open bottom that encloses the bottom opening (622) of the sealed casing, a top opening (636), and at least one bell entry opening (645) at a bottom section which allows fluid communication between said bell and the sealed casing; a snorkel (625) comprising an inverted U-shaped pipe with a higher end (626) and a lower end (627), the higher end (626) being in fluid connection with said top opening (636) of the bell, and the lower end (627) being in fluid communication with the sealed casing (620); a standpipe (640) comprising a vertical pipe with a lower end (641) and a higher end (642), said standpipe protruding through said bottom opening (622) of said sealed casing (620), into said bell (635), such that said higher end (642) of the standpipe (640) reaches a height that is higher than said lower end (627) of said snorkel (625); a drain pipe (670) in fluid connection with said lower end (641) of the standpipe (640). A funnel (649) is placed at the higher end (642) of the standpipe. This funnel (649) improves the effectiveness of the siphon. In this variation, the air bleeder (655) has an upper connection (656) in fluid connection with a top opening of the siphon level (611), and a lower end in fluid connection with a second top opening (623) of the sealed casing. This air bleeder (655) functions to prevent any ingress of atmospheric air into the sealed casing (620) during the backwash mode. If atmospheric air is allowed to ingress into the sealed casing (620), the suction from the sealed casing on the siphon dropper (615) is impaired, and an effective backwash will not occur. A second function of the air bleeder (655) is to suck air out of the said horizontal section (682) of the backwash dropper (68). When the siphon starts, the sealed casing will become a vacuum and excess air in the horizontal section (682) of the backwash dropper is sucked out via the air bleeder (655). This will induce water into flowing through the backwash dropper. In this variation, as in the second, fourth and sixth embodiments, the backwash sump of Figure 8 is employed, and is placed at the lower end of the drain pipe (670).

In all the above embodiments, the water flow rate through the filter (30) during the backwash mode is at least twice that during the filtration mode.

While several particularly preferred embodiments of the present invention have been described and illustrated, it should now be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention. Accordingly, the following claims are intended to embrace such changes, modifications, and areas of application that are within the scope of this invention.

Claims

1. An apparatus for water filtration with an automatic and repeatable backwash function, comprising:

a feed pipe (12) through which unfiltered water is supplied;

a lower chamber (20) having a feed inlet (212, 232) in fluid connection with said feed pipe (12), a filter (30) located within said lower chamber and dividing said lower chamber into an upstream side (21) and a downstream side (22), said filter adapted to allow mainly water to pass through and to restrict suspended solids from passing through;

an upper chamber (50) in fluid connection with said downstream side (22) of said lower chamber (20), and a product outlet (54) for expelling filtered water to an external use;

a backwash creating means (60) when a predetermined head differential has been reached due to an amount of suspended solids trapped by the filter (30) at its upstream side (21), comprising:

a siphon pipe (610) having a lower end (612) in fluid connection with a siphon outlet (216, 236) of said lower chamber (20), said siphon pipe rising up to a siphon level (611), where it is in fluid connection with an upper end of a siphon dropper (615), said siphon dropper dropping down to a lower end (617);

a sealed casing (620) having a first top opening (621) in fluid connection with said lower end (617) of said siphon dropper (615), a second top opening (623), and a bottom opening (622);

a bell (635) located within and at a bottom end of said sealed casing (620) having an open bottom that encloses said bottom opening (622), a top opening (636), and at least one bell entry opening (645) at a bottom section which allows fluid communication between said bell (635) and said sealed casing (620);

a snorkel (625) comprising an inverted U-shaped pipe with a higher end (626) being in fluid connection with said top opening (636) of said bell, and a lower end (627) being in fluid communication with said sealed casing (620); a water trap (660) comprising a u-shaped pipe with a higher end (661) and a lower end (662);

a standpipe (640) comprising a vertical pipe with a lower end (641) in fluid connection with said higher end (661) of the water trap, said standpipe protruding through said bottom opening (622) of said sealed casing, into said bell (635), such that a higher end (642) of the standpipe (640) reaches a height that is higher than said lower end (627) of said snorkel (625);

a drain pipe (670) in fluid connection with said lower end (662) of water trap;

a means of halting a backwash (70), comprising:

a siphon break line (710) having a higher end (711) in fluid connection with an opening of said siphon pipe (610) at said siphon level (611) and a lower end (712) protruding into said upper chamber (50); and a cup (720) located within said upper chamber, and a volume of said cup immersing said lower end (712) of said siphon break line (710), and said lower end (712) located higher than a bottom of said cup (720).

2. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 1 , further comprising an air bleeder (655) having a higher end in fluid connection with a second top opening (623) of said sealed casing (620), and a lower end in fluid connection with said lower end (662) of said water trap (660).

3. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 1 , further comprising a backwash dropper (68) connected at a higher end to where the said siphon pipe (610) joins the said siphon dropper (615), and at the lower end to where the said water trap (660) meets the said drain pipe (670).

4. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 3, wherein the said backwash dropper (68) has a larger cross-sectional area than the siphon dropper (615).

5. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 3, further comprising an air bleeder (655) having a higher end (656) in fluid connection with a horizontal section (682) of said backwash dropper, and a lower end in fluid connection with said second top opening (623) of the sealed casing.

6. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 3, further comprising a backwash sump (80) adapted to submerge a lower end (671) of the drain pipe in water during a backwash mode, and to expose said lower end (671) to atmospheric air during a filtration mode.

7. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 1 , wherein the said standpipe (640) has a larger cross-sectional area than said water trap (660).

8. An apparatus for water filtration with an automatic and repeatable backwash function, comprising:

a feed pipe (12) through which unfiltered water is supplied; a lower chamber (20) having a feed inlet (212, 232) in fluid connection with said feed pipe (12), a filter (30) located within said lower chamber and dividing said lower chamber into an upstream side (21) and a downstream side (22), said filter adapted to allow mainly water to pass through and to restrict suspended solids from passing through;

a siphon pipe (610) having a lower end (612) in fluid connection with a siphon outlet (216, 236) of said lower chamber (20), said siphon pipe rising up to a siphon level (611), where it is in fluid connection with an upper end of a siphon dropper (615), said siphon dropper dropping down to a lower end (617); a sealed casing (620) having a first top opening (621) in fluid connection with said lower end (617) of said siphon dropper (615), a second top opening (623), and a bottom opening (622);

a bell (635) located within and at a bottom end of said sealed casing (620) having an open bottom that encloses said bottom opening

(622), a top opening (636), and at least one bell entry opening (645) at a bottom section which allows fluid communication between said bell (635) and said sealed casing (620);

a snorkel (625) comprising an inverted U-shaped pipe with a higher end (626) being in fluid connection with said top opening (636) of said bell, and a lower end (627) being in fluid communication with said sealed casing (620);

a standpipe (640) comprising a vertical pipe with a lower end (641) and a higher end (642), said standpipe protruding through said bottom opening (622) of said sealed casing, into said bell (635), such that said higher end (642) of the standpipe (640) reaches a height that is higher than said lower end (627) of said snorkel (625);

a drain pipe (670) in fluid connection with said lower end (641) of the standpipe (640);

a means of halting a backwash (70), comprising:

9. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 8, further comprising a backwash dropper (68) connected at a higher end to where the said siphon pipe (610) joins the said siphon dropper (615), and at the lower end to an intermediate point of said drain pipe (670).

10. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 9, wherein the said backwash dropper (68) has a larger cross-sectional area than the siphon dropper (615).

11. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 9, further comprising an air bleeder (655) having a higher end (656) in fluid connection with a horizontal section (682) of said backwash dropper, and a lower end in fluid connection with said second top opening (623) of the sealed casing.

12. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 9, further comprising a backwash sump (80) adapted to submerge a lower end (671) of the drain pipe in water during a backwash mode, and to expose said lower end (671) to atmospheric air during a filtration mode.

13. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claim 8, wherein the said standpipe (640) has a larger cross-sectional area than said drain pipe (670).

14. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claims 1 and 8, further comprising an air bleed line (16) having a higher end in fluid connection to said feed pipe (12), and a lower end connected to a bleeder outlet (217, 237) of said lower chamber (20).

15. An apparatus for water filtration with an automatic and repeatable backwash function, in accordance with claims 1 and 8, further comprising a means of manually starting said backwash mode comprising a manual bypass pipe (90) forming a fluid connection between a lower part of the upper chamber (50) and the siphon dropper (615) and a manual bypass valve (92) to allow manual opening and closing of said fluid connection.