Containers and filters for ponds or aquatic tanks

DESCRIPTION

Technical Field

The present invention relates to containers, and in particular to containers that can be used as filters that are suitable for use with ponds, aquatic tanks etc.

The containers are also suitable for use with filtration and treatment systems and also in situations where it is desirable to replicate tidal conditions such as those that may be found in seashore and tidal estuary environments.

Summary of the Invention

The present invention provides a container comprising: a housing; an inlet through which liquid is supplied to the housing at a first flow rate; and siphon means adapted to remove liquid from the housing at a second flow rate, greater than the first flow rate, when a siphon effect is established, the siphon means comprising a first substantially upright portion having an inlet end located in a cup and a second substantially upright portion having an outlet end that is lower than a base of the housing, and wherein the first and second upright portions are connected together by an overflow portion; wherein the container alternates between: (i) a filling process where the level of liquid within the housing rises, and (ii) a siphoning process where liquid is removed from the housing by the siphon means and the level of liquid within the housing falls, the siphoning process commencing when the level of liquid within the housing is sufficient to establish the siphon effect and ending when air is entrained in the siphon means through the inlet end.

The inlet is connected to a suitable liquid supply depending on the particular purposes for which the container is used. For example, liquid can be provided from a pond or aquatic tank, a storage tank or housing, or from a pressurised supply such as the mains water. Liquid can be supplied to the inlet by means of an external pump, gravity feed or at a suitable pressure from a pressurised supply. The inlet may be connected to the liquid supply or pump by any suitable piping. The liquid removed from the housing can be discarded, supplied to a suitable storage tank or housing for re-use, or, if the container forms part of a closed-loop system, returned to the liquid supply. Any suitable liquid may be supplied to the inlet, e.g. unfiltered pond or aquatic tank water, seawater, fresh water, and may include any appropriate additives or chemicals.

The first flow rate may be fixed or variable. For example, an external pump may be adjusted to select the rate at which liquid is supplied to the inlet or a pressure limiter valve may be adjusted to select the pressure at which liquid is provided to the inlet from a pressurised supply.

The inlet may optionally be configured as a spray bar (optionally a rotating spray bar) so that the liquid is distributed within the housing. However, if there is a risk that the spray bar might become clogged with particulates in the liquid then the inlet may be a simple pipe which terminates with an open mouth inside the housing.

More than one inlet may be provided. Each inlet may optionally supply liquid from a different liquid supply.

The inlet may extend through a sidewall of the housing.

The overflow portion which connects the first and second upright portions of the siphon means may extend through a sidewall of the housing.

The siphon effect is preferably established when the level of the liquid within the housing is at or about the overflow portion. Once the siphon effect has been established then it will continue until air is entrained in the siphon means. For a continuous siphon effect to be established then the siphon means must be completely full of liquid and free of air. There may be a period of time when liquid flows through the siphon means before the siphon effect is properly established, e.g. while air is forced out of the siphon means. Each siphoning process ends when air is entrained in the siphon means through the inlet end. The siphon means may optionally include a valve or other flow control means to allow a desired second flow rate to be selected. However, the second flow rate will typically be determined by the physical properties of the siphon means, e.g. the diameter of the siphon tubing, the location of elbow or return joints etc.

The cup may be free-floating in the surrounding liquid or fixed, e.g. integrally formed with, or secured to, the container. The cup may be formed by an annular collar or flange at the base of the housing or by a depression or 'well'. The open mouth of the inlet end is typically located below the annular rim of the cup so that towards the end of each siphoning process only liquid within the cup is removed through the siphon means. Each siphoning process preferably ends when the level of liquid within the cup has fallen to the extent that air is entrained in the siphon means through the inlet end. If the cup is free-floating then its lateral movement is preferably constrained by the inlet end of the siphon means. The vertical movement of a free-floating cup should preferably not be restricted by any filter material or other objects that might be in the housing. The cup and the inlet end of the siphon means may be located in a region of the housing that is separated from the remainder of the housing by a grid or wall with openings through which liquid can pass freely.

Although it is not intended that this invention should in any way be limited by theoretical observations, it is believed that the surprising reliability of the container is a result of locating the inlet end of the siphon means in a cup. It has been found that the cup guarantees that the siphon effect is broken, particularly in situations where the second flow rate is not appreciably greater than the first flow rate. The use of a cup can also help to ensure that any sediment on the base of the housing is not significantly disturbed during the siphoning process because an amount of water will be left in the container when the siphon effect is broken and the container moves to the filling process where the level of liquid within the housing rises.

The container may further include a lid for the housing which can be removed to allow access to the interior of the housing. The container may be used as a filter (e.g. for a pond or aquatic tank) and the housing may be at least partially filled with filter material. In this case the housing is preferably separated (e.g. by a grid or wall with openings through which liquid can pass freely) into an upper region which is at least partially filled with the filter material, and a lower region. The lower region is preferably devoid of filter material and contains filtered liquid which has passed through the filter material in the upper region. Any suitable filter material (bio media) can be used, e.g. Japanese matting, plastic bio media etc.

The filter may form part of a filtration or treatment system, e.g. for water purification or sewerage treatment. The filtration or treatment system may further include a pump which is connected to the inlet and which supplies unfiltered liquid from a liquid source to the housing at the first flow rate.

The present invention further provides a filter for a pond or aquatic tank comprising: a housing at least partially filled with filter material; an inlet through which unfiltered liquid is supplied to the housing at a first flow rate; and siphon means adapted to remove filtered liquid from the housing at a second flow rate, greater than the first flow rate, when a siphon effect is established, the siphon means comprising a first substantially upright portion having an inlet end located in a cup and a second substantially upright portion having an outlet end that is lower than a base of the housing, and wherein the first and second upright portions are connected together by an overflow portion; wherein the filter alternates between: (i) a filling process where the level of liquid within the housing rises, and (ii) a siphoning process where filtered liquid is removed from the housing by the siphon means and the level of liquid within the housing falls to expose the filter material to the surrounding air, the siphoning process commencing when the level of the liquid within the housing is sufficient to establish the siphon effect and ending when air is entrained in the siphon means through the inlet end. The present invention further provides a filtration or treatment method comprising the steps of: supplying unfiltered or untreated liquid to a housing at a first flow rate, the housing being at least partially filled with filter or treatment material; removing filtered or treated liquid from the housing at a second flow rate, greater than the first flow rate, by siphon means when a siphon effect is established, the siphon means comprising a first substantially upright portion having an inlet end located in a cup and a second substantially upright portion having an outlet end that is lower than a base of the housing, and wherein the first and second upright portions are connected together by an overflow portion; wherein the filtration method alternates between: (i) a filling process where the level of liquid within the housing rises, and (ii) a siphoning process where filtered or treated liquid is removed from the housing by the siphon means and the level of liquid within the housing falls to expose the filter or treatment material to the surrounding air, the siphoning process commencing when the level of the liquid within the housing is sufficient to establish the siphon effect and ending when air is entrained in the siphon means through the inlet end.

Unfiltered or untreated liquid is preferably continuously supplied to the housing, even during the siphoning process. The filtration or treatment method may be implemented using the filter or filtration/treatment systems described in more detail above.

In operation the container (or filter) continuously alternates between the filling process and the siphoning process without the need for any valves or control means. The container does not have any complicated mechanical parts that require routine maintenance or repair and instead relies on the natural establishment and breaking of a siphon effect based on the level of the liquid within the housing. During the filling process any filter material within the housing is wetted as the housing gradually fills with liquid. When the level of the liquid within the housing is sufficient to establish the siphon effect then liquid is removed from the container by the siphon means. In the case of a filter then only liquid that has passed through the filter material is removed. As the liquid passes through the filter material any particulates or pollutants are removed and the liquid is also aerated. Because the second flow rate at which the filtered liquid is removed from the container through the siphon means is greater than the first flow rate at which unfiltered liquid is continuously supplied to the container then the establishment of the siphon effect causes the housing to gradually empty. As the level of liquid falls, the filter material is exposed to the air to promote the decomposition of any removed pollutants by bacteria.

The filter material within the housing is alternately wetted and dried and the filter may therefore be referred to as a 'wet/dry filter'.

The container replicates tidal conditions such as those that may be found in seashore and tidal estuary environments. In other words, anything placed within the housing is alternately wetted and dried in a way that is similar to that caused by rising and falling tide levels. This similarity can be exploited by placing certain objects in the container that would normally require these sorts of tidal conditions. The flow rates can be selected depending on the circumstances and to achieve the desired filtration or environmental conditions within the housing. For example, the first flow rate can be selected so that the housing is filled relatively slowly so that the contents of the housing (e.g. filter material or objects that would normally require tidal conditions) are only wetted gradually and remain exposed to the surrounding air for a longer period of time. The container may be used to hold animals and plants that might normally inhabit a rocky seashore or tidal estuary environment (e.g. molluscs, seaweeds etc.) or for the curing of live rocks. In these situations, liquid can be supplied from a separate holding tank or housing by a pump and returned to the separate holding tank or housing through the siphon means. Alternatively, if a fresh supply is needed then mains water may be supplied to the inlet of the container and the used water can be discarded (e.g. to a drain) through the siphon means.

Drawings

Figure 1 is a schematic drawing of a water filter according to the present invention;

Figures 2 to 5 are schematic drawings showing the sequence of operating steps of the water filter of Figure 1 , wherein the operating steps may be described as a filling (or wetting) step (Figure 2), a siphoning (or drying) step (Figure 3) and a siphon breaking step (Figures 4 and 5).

The basic outline of a pond filter 1 according to the present invention will be described with reference to Figure 1. The pond filter 1 consists of a housing 2 made of plastics material. A water inlet 4 passes through a sidewall 6 of the housing 2 and is connected to an electric pump 8 by any suitable piping. The pump 8 supplies unfiltered water from a pond P to the housing 2 at a preselected flow rate. Siphon piping 10 is made of substantially rigid plastics tubing and provides a water outlet for the housing 2. The siphon piping 10 has a first upright portion 12 having an inlet end 14, an overflow portion 16 that passes through the sidewall 6 of the housing 2, and a second upright portion 18 that terminates in an outlet end 20 having a return or elbow. The outlet end 20 is connected to any suitable piping to return the filtered water back to the pond P. The outlet end 20 is located below a base 22 of the housing 2.

The inlet end 14 of the siphon piping 10 is located within a cup 24 that has a density greater than water.

A grid 26 divides the housing into an upper region 28 and a lower region 30. The upper region 28 is at least partially filled with a suitable filter material 32 (bio media) that cannot pass through openings in the grid 26. There is no filter material in the lower region 30.

A removable lid 34 made of plastics material can provide access to the housing to allow the filter material 32 to be changed and the interior of the housing to be cleaned.

The operation of the pond filter 1 will now be described with reference to Figures 2 to 5. Filling (or wetting) process:

Figure 2 shows the cup 24 sitting on the base 22 of the housing 2. The inlet end 14 of the siphon piping 10 is located within the cup 24. More particularly, the open mouth of the inlet end 14 is below the annular rim of the cup 24.

Unfiltered water from the pond P is pumped into the housing 2 through the water inlet 14 at a preselected flow rate. Although not shown, the water inlet may optionally be formed as a spray bar so that the unfiltered water is distributed across the filter material 32.

As the housing 2 gradually fills with water, the level of the water rises within the first upright portion 12 of the siphon piping 10.

Siphoning (or drying) process:

Once the level of the water within the housing 2 reaches the overflow portion 16 (Figure 3) then water in the first upright portion 12 will start to flow into the overflow portion and then down the second upright portion 18 to the outlet end 20. Because the outlet end 20 is lower than the base 22 of the housing 2 then once the siphon piping 10 is full of water and free of air a conventional siphoning effect is established. The siphoning effect draws filtered water from the lower region 30 of the housing 2 which has passed through the filter material 32 and returns the water back to the pond P. Once established, the siphoning effect will continue until the siphon is broken.

The flow rate of filtered water through the siphon piping 10 is greater than the predetermined flow rate of unfiltered water through the water inlet 4. The flow rate is determined by the physical construction of the siphon piping 10, e.g. the diameter of the plastics tubing. The establishment of the siphoning effect therefore causes the water level in the housing to fall as the filtered water is drawn from the lower region 30 of the housing. As the unfiltered water in the upper region 28 passes through the filter material 32 any particulates and pollutants are removed and the water is oxygenated. The filter material 32 is also gradually exposed to the air as the water level falls. It will be readily appreciated that any bacteria in the biological filter material 32 are therefore flushed and aerated as the housing 2 is alternately filled and drained so creating improved conditions for the decomposition of the removed pollutants. The filtered water that is returned back to the pond P is clean and oxygen- rich.

Siphon breaking step:

The water level will continue to fall as filtered water is drawn from the lower region 30 of the housing. Eventually, the water level will reach the annular rim of the cup 24 that is sitting on the base 22 of the housing. At this point, the remaining water in the lower region 30 is effectively divided into two parts, water that is within the cup 24 and water that is outside the cup. The surrounding water in the housing 2 does not fall appreciably below the level that is established by the annular rim of the cup 24 when it is sitting on the base 22 of the housing. Since the inlet end 14 of the siphon piping 10 is located within the cup 24 then water is drawn out of the cup by the siphoning effect. As water is drawn out of the cup 24 it starts to float in the surrounding water and will rise towards the inlet end 14 (Figure 4; including the detail view). The open mouth of the inlet end 14 is profiled with part of the rim being at an oblique angle. As the cup 24 rises it will eventually come into contact with the open mouth of the inlet end 14 (Figure 5). Once substantially all of the water has been drawn out of the cup 24 then air is entrained in the siphon piping 10 and the siphon effect is broken. The oblique angle of the rim makes sure that air can be properly entrained and prevents the cup 24 from being held against the open mouth of the inlet end 14 by any suction effect.

During both the siphoning and siphon breaking steps, water continues to be pumped into the housing through the water inlet 4. As soon as the siphon effect is broken no further filtered water is drawn through the siphon piping 10 and the housing 2 starts to fill up again. Eventually, the water level will reach the annular rim of the cup 24 that is floating next to the open mouth of the inlet end 14. The cup 24 will fill with water and because it has a density that is greater than the surrounding water it will sink to sit on the base 22 of the housing 2.

The filling, siphoning and siphon breaking steps are repeated continuously and without the need for any valves, complicated mechanical parts or the like.

The housing 2 may have any suitable volume and the flow rates at which unfiltered water is pumped into the housing and filtered water is drawn out of the housing by the siphoning effect may be selected to provide desired fill and drain times. For example, a housing having a volume of 18 litres may operate successfully with a pumped flow rate between 2500 and 4000 litres/hour taking about 4 minutes to fill and about 4 minutes to empty.

Other arrangements of the pond filter may have a cup that has a density less than the surrounding water so that it continues to float next to the open mouth of the inlet end even when the level of water within the housing is higher than its annular rim. In this arrangement the surrounding water in the housing does not fall appreciably below the level that is established by the annular rim of the cup when it is floating next to the inlet end. It is also possible for the cup to be integrally formed with the housing (e.g. in the form of an annular collar or flange at the base of the housing that surrounds the inlet end or in a depression or 'well' formed in the base).

Although the present invention has been described above with reference to a pond filter, it will be readily appreciated that the inlet can be connected to any suitable liquid source. A filter of identical construction may be used as part of a filtration or treatment system. The filter may be used to filter liquid held in any suitable container or vessel, such as an aquatic tank etc. If the filter material is removed then the housing may be filled with other objects (e.g. rocks, molluscs, seaweeds etc.) and used to replicate tidal conditions such as those that may be found in seashore and tidal estuary environments.