DIVERSION SYSTEM

TECHNICAL FIELD

The invention relates to a diversion system. In particular the present invention relates to diverting runoff from a catchment into one or more output systems.

BACKGROUND ART

When a runoff event occurs there normally is a period during which the flow is contaminated by surface material that has accumulated over the catchment surface prior to the beginning of the runoff event. This contaminated flow is commonly referred to as the first flush or sometimes the foul flush.

Where the runoff water is collected, for example in a drainage system, it can be desirable to separate the first flush from the following flow which contains relatively uncontaminated water. In such cases use can be made of a first flush device, being a device which, in principle at least, separates the first flush from the remaining flow.

A first flush device can be used, for example, where water is to be collected from a catchment for future use such as drinking, cooking, washing, or industrial use. In these instances it is preferable to separate the uncontaminated water prior to collection of the relatively clean water as this reduces substantially the amount of further processing required to render the water suitable for these uses.

First flush devices can also be used in a drainage system to divert contaminated water into a sewer system and relatively clean water into a stormwater system. In such a system the contaminated water normally flows to a sewage treatment plant where it undergoes processing prior to being released into the environment or back for future use. The stormwater system is typically vented into the

environment, usually through natural means such as streams, rivers, lakes or the sea.

In such systems it is important that only contaminated water flows into the sewer system so as not to create an unnecessary load on the treatment system by diversion of relatively clean water. Alternatively, diverting only relative clean water into the stormwater system reduces the contamination load on the environment.

A simple form of first flush device is a constant volume system, in which a chamber is used to collect the initial volume from a runoff event. A major disadvantage with constant volume devices is that they may fill before all of the contaminated water has been captured. These devices also need to be drained and cleaned of residue at regular intervals.

To understand why constant volume devices are limited in their effectiveness, it is necessary to understand the dynamics of the runoff event, such as a storm. Two key parameters with respect to first flush are the intensity and duration of the event. These tend to vary substantially during a storm and from storm to storm.

In many instances the initial period of a storm involves relatively low intensity rainfall. This tends only to remove loose surface material. Most of the surface contamination is only removed when the storm reaches a higher intensity sufficient to loosen ingrained contaminates.

During a storm that begins initially with a low intensity period, a constant volume device may well fill before the onset of the higher intensity rainfall. In such cases the more highly contaminated water overflows into the collection or stormwater system, which is an undesirable outcome.

Another form of first flush device uses a first flush valve designed to overcome the above problem by first diverting contaminated flow into a sewer or other system, and later relatively clean flow into a storage or stormwater system. Diversion of the first flush overcomes the problem with constant volume devices of them filling prior to completion of the contaminated flow.

Some first flush valve devices use a hollow container into which some of the first flush flow is diverted so that the container fills slowly with water. When the weight of water in the hollow container exceeds a certain amount it triggers the first flush valve so as to seal off the first outlet (sewer or other diversion system) with the remaining flow diverted into a second outlet (stormwater or collection facility).

First flush devices of this type suffer from the same disadvantages as the constant volume devices described above, namely the cut off occurs when a preset volume of water has been collected (in the hollow container), rather than a measurement of the rate of flow. Hence the hollow container may fill during a prolonged low intensity runoff event, potentially triggering the first flush valve prior to the onset of higher intensity runoff containing more highly contaminated water.

In an attempt to overcome this problem some other first flush devices include a rain gauge to measure the intensity of rainfall. The rain gauge is typically mounted at some point within the catchment area. Rain gauges typically require some form of computing element to measure the intensity of the rain fall at that point. They therefore require a power supply, either through connection to an electrical mains supply or a battery.

When the intensity of the rain fall, as measured by the rain gauge, exceeds a predetermined amount a signal is sent from the computing element to the first

flush valve, thus switching the flow of the runoff from a first system into a second system. In some systems the signal activates a solenoid valve attached to a mains water supply which provides the pressure to switch the first flush valve and maintain it in the new position.

While this system does use a rate measurement to switch the valve, thus overcoming disadvantages with the above devices, they still have a number of disadvantages. In particular there is no simple relationship between the measurement of the intensity of the rain fall, which is taken at a single point, and the runoff flow into the first flush device. The latter depends, among other things, on the topology of the catchment and the location of drains connected to the first flush device. Therefore there may be a considerable delay between the onset of high intensity rain and the subsequent collection of runoff into the first flush device.

Where flow into a first flush device is collected from a large catchment area, contaminated first flush water from the more distant parts of the catchment area may arrive at the first flush device much later than the contaminated flow from closer parts of the catchment. Therefore, for the first flush device to work effectively, a time delay should be built into the system to delay switching until sometime after the onset of high intensity fall. As the time delay depends on the topology, the number of collection points, their location relative to the first flow device and the area of the catchment, each installation requires separate calibration. Such calibration requires additional time and expense and adds complexity to the installation process.

Further disadvantages with this type of system include the need for a power supply and a mains water supply. Provision of either or both of these facilities, particularly in remote areas, may be a major limitation on use of these systems.

A disadvantage of all the above first flush devices is that they need to be scaled to meet the individual requirements of each catchment. Larger devices are needed to deal with the flow from larger catchment areas. Therefore a range of device sizes must be produced, adding substantially to the cost of production of the full range of devices. If one size in the product range is to be used for a range of catchment areas then some compromise in the precision of the switching point is necessary for catchments larger or smaller than the design catchment area.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised ¹ or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided a method of diverting fluid from a runoff event on a catchment area,

characterised by the steps of

(a) collecting fluid from the catchment area into a collection chamber; and

(b) allowing the fluid to flow to a diversion system; and

(c) diverting via the diversion system an initial volume of the fluid into a first outlet system; and

(d) continuing to divert fluid into the first outlet system if the flow rate of the fluid is below a pre-set rate; and

(e) subsequently diverting the fluid into a second system if the flow rate exceeds the pre-set rate.

According to another aspect of the present invention there is provided a method of diverting fluid from a runoff event on a catchment area, substantially as described above,

characterised in the additional step of

(f) re-setting the diversion system under pre-set conditions following cessation of a runoff event, so that when the next runoff event occurs steps (a) to (d) above can be implemented.

According to another aspect of the present invention there is provided an apparatus for diverting fluid from a runoff event on a catchment area, the apparatus including a collection chamber containing:

at least one inlet; and

at least one outlet to a first system; and

at least one outlet to a second system; and

a diversion system including

a flow limiter associated with the first outlet, and

a cut-off valve associated with the first outlet

characterised in that

the cut-off valve is configured to cut off fluid flowing into the first outlet when the rate of flow of fluid through the flow limiter exceeds a predetermined value.

Reference to runoff throughout this specification should be understood to refer to an amount of fluid carried off or discharged from an area over a period of time.

Runoff is generally associated with the occurrence of a runoff event. A runoff event should be understood to mean any event where fluid flows onto a surface, creating runoff. Examples of runoff events include (without limitation) showers, rainstorms, sprinkling, hosing and water blasting.

The duration of a runoff event will vary with the type of event. However, the duration of a runoff event for the purposes of this specification will be sufficiently long to include all runoff associated with the event.

For example, a storm may consist of a number of periods of rain separated by

intervals of little or no rain. The runoff event should be understood to extend from the start of the first rainfall period through to the completion of the last. Similarly, if the rainfall is associated with a passing front the runoff event should be considered to last from the first rainfall associated with the front until the end of runoff associated with rain from that front.

Typically there will be an extended period of no runoff between consecutive runoff events during which time contaminants may accumulate over the surface of the catchment.

In a preferred embodiment the fluid is water.

Runoff flows naturally under gravity towards the lowest point. Therefore the topology of the surface over which the runoff event occurs generally determines the area associated with the runoff. This is commonly called the catchment. In nature, the catchment is generally formed by hills and valleys, with the runoff typically flowing into streams and rivers and hence into lakes and/or sea.

In a preferred embodiment the catchment includes a sealed surface area.

Sealed surfaces are increasingly common in built up areas. Such surfaces include driveways, sealed yards, carparks, garage forecourts, roofs of large buildings, airport runways and tarmacs, roadways and so on.

In these situations runoff management is generally required if the normal flow over or drainage into the ground has been disrupted by the sealing or ground cover.

In a preferred embodiment the catchment includes a drainage system.

A drainage system should be understood to refer to any system of drains and conduits arranged so as to collect runoff from a catchment.

The drainage system of the present invention is connected to a diversion system.

Reference to a diversion system throughout this specification should be understood to refer to any system configured to enable runoff flow to be switched or diverted from one output system to another output system. In particular it includes any system that selectively controls runoff flow into one or more outlet systems.

In a preferred embodiment the first outlet system is a sewer system.

Reference throughout this specification to a sewer should be understood to refer to a conduit for carrying off drainage water, particularly contaminated waste water. Commonly a sewer system carries contaminated water to a water treatment plant where the contaminates are removed prior to the discharge being returned to the environment or for other uses.

Reference will be made throughout this specification to a first outlet system being a sewer. However, those skilled in the art will appreciate that the first outlet system could be connected to other means for disposal of the contaminated water, including septic tanks or settling pits, and reference to a first outlet system being a sewer only should not be seen as limiting.

In a preferred embodiment the second outlet system is a stormwater system.

Reference to a stormwater system throughout this specification should be understood to refer to a conduit for carrying off drainage water, preferably where the water does not contain a high level of contaminants. Stormwater systems generally return the runoff directly back into the environment, for example by discharge into a stream or river or other large body of water.

Reference will be made throughout this specification to a second outlet system

being a stormwater system. However those skilled in the art will appreciate that the second outlet system may be connected to other systems, for example into a reservoir or other collection system for further water treatment, and that reference to a second outlet system being a stormwater system only should not be seen as limiting. In many rural areas where there is no local water supply, runoff may be collected, for example from a roof space, and stored for future use.

The diversion system may be contained within an apparatus for diverting fluid from a runoff event on a catchment area. The apparatus includes a collection chamber which may be an enclosure having one or more inlets through which runoff from the catchment may flow into the collection chamber.

The chamber further contains at least one outlet, preferably located near the base of the collection chamber, to a first system (the sewer outlet) and at least one outlet to a second system (the stormwater outlet), as well as a diversion system.

At the beginning of a runoff event the level of water in the collection chamber is generally below the level of the outlet.

In this situation the initial runoff flows into the sewer outlet.

For a collection chamber of a given size, the rate at which the runoff water fills the collection chamber depends on the difference between the rate of flow into the collection chamber (inflow) and the rate of flow out of the collection chamber (outflow).

When the water level in the collection chamber reaches a predetermined height above the base of the collection chamber, to be referred to as the cut-off height, access to the sewer is cut off by a cut-off valve associated with the sewer outlet,

with the remaining runoff water diverted into the stormwater.

In a preferred embodiment the cut-off valve is a float valve.

Reference throughout this specification to a float valve should be understood to refer to a self regulating device which controls the supply of water into or out of a collection chamber by means of a float connected to a valve that opens or closes with a change in water level. A float valve may also be known as a ballcock.

The float valve of the current invention includes a float connected to a valve associated with the sewer outlet and configured such that when the water level in the collection chamber reaches the cut-off height the valve is closed stopping access of the water to the sewer.

Reference will be made throughout this specification to a cut-off valve in the form of a float valve. However, those skilled in the art will appreciate that other methods of closing access to the sewer when the water in the collection chamber reaches the cut-off height are possible, and that reference to a float valve only should not be seen as limiting.

For example the level of the water in the collection chamber may be sensed remotely, for example by optical means, and the valve operated when the water level reaches the cut-off height, for example by electromechanical means.

An advantage of using a float valve to regulate the flow into the sewer is that it is a self regulating mechanism in that the valve opens or closes directly in response to the water level in the collection chamber. Furthermore float valves are a well established technology, are readily available in a wide range of sizes and require very little maintenance.

A float value also has the advantage of being an entirely mechanical device. It

therefore does not require a power supply, and maintenance thus reducing cost.

In some instances it may be an advantage to use a multistage float valve. A multistage float valve may allow relatively free access to the sewer outlet during the first stage of operation, followed by a second or further stage in which the flow rate is gradually reduced until the sewer inlet is closed.

When the runoff event ceases the inflow will gradually stop. The flow in the diversion system continues to be diverted to the stormwater and the level of water in the collection chamber drops. When the water level in the collection chamber drops below the cut-off height the float valve is automatically reset to open access to the sewer in readiness for the next runoff event.

Water continues to flow out of both outlets until the water level drops to a point where it can no longer access either outlet.

A flow limiter may be used to regulate the outflow into the sewer.

In a preferred embodiment the flow limiter is a first orifice plate.

Reference throughout this specification to an orifice plate should be understood to refer to a device located inside or at the mouth of a pipe or conduit which is configured to limit the flow of fluid through the pipe or conduit.

In a typical installation, in which the outlet pipe has a circular cross section, an orifice plate may be in an annular form in which the outer diameter of the orifice plate forms a seal against the inner surface of the pipe. The diameter of the hole in the centre of the orifice plate may be chosen to provide the required reduction in flow rate.

Other forms of orifice plate may be used, for example a disc configured to seal against the inner surface of the pipe in which a plurality of holes are formed

through the disc.

Reference throughout this specification will be made to a flow limiter in the form of an orifice plate. However those skilled in the art will appreciate that any device that provides a barrier limiting flow along the outlet pipe may be fitted into an outlet and that reference to an orifice plate only should not be seen as limiting.

A major advantage of the current system is that a standard size diversion system can readily be adapted to accommodate different sized catchments, or to meet local requirements for the amount of first flush water to enter a sewer, simply by inserting a suitably sized first orifice plate into the sewer outlet.

Another advantage of using an orifice plate is that such plates are readily available in a range of sizes to fit common pipe sizes.

It is a feature of the current system that the initial runoff flow is directed into the sewer system. This requires that the runoff water cannot access the outlet to the second system, at least until such time as the float valve closes the sewer outlet.

In a preferred embodiment the collection chamber includes a partition forming a first chamber containing the inlet and the first outlet, and a second chamber containing the second outlet.

Access to the second chamber (containing the second outlet) may be restricted during the first flush flow by configuring the partition such that it encloses the second outlet and extends from the base of the collection chamber to a height not less than the cut-off height.

In a preferred embodiment the height of the partition is greater than the cut-off height and less than the height of the collection chamber.

With this configuration runoff water flows through the inlet into the first chamber from where it initially flows out through the sewer outlet. If the flow rate is sufficiently high, or the duration of the run-off event sufficiently long, the level of water in the first chamber will rise until it reaches the cut-off height, at which point access to the sewer outlet is closed off. As the inflow continues the water level within the first chamber will rise until it reaches the height of the partition following which excess water will flow over the partition into the second chamber and out through the stormwater outlet.

In alternative embodiments the partition may extend to the top of the collection chamber, with access between the first and second chambers provided by one or more openings in the partition situated at a height above the cut-off height of the float valve.

In order to reset the cut-off valve water must be allowed to flow from the first chamber into the second chamber at least until the level of water in the first chamber falls below the cut-off height.

In a preferred embodiment the first chamber is connected to the second chamber by a siphon.

Reference to a siphon throughout this specification should be understood to refer generally to a pipe or tube that is configured to allow liquid to be transferred from a container through an intermediate point that may be higher than the height of fluid in the container, to a point below the height of the liquid in the container, the flow being driven by hydrostatic pressure only.

The siphon may be in the form of a pipe extending upwards from an opening near the base of the first chamber to a height equal to or greater than the cut-off height, passing through the partition and extending back down to an opening

near the base of the second chamber.

With this arrangement the water will begin to be siphoned from the first chamber into the second chamber when the height of water in the first chamber exceeds the height of the top of the siphon.

Following the end of the runoff event, water will continue to be siphoned from the first chamber into the second chamber until the level of water in the first chamber equals the level of water in the second chamber.

The height (above the base of the collection chamber) of the open ends of the siphon may be chosen such that the siphon will continue to operate at least until the water level in the first chamber falls below the cut-off height at which the float valve resets, thus opening access to the sewer outlet.

In this way, the action of the siphon enables the cut-off valve to be reset in preparation for the next runoff event.

The time taken to reset the float valve following the end of a runoff event may be adjusted by use of a flow limiter.

In a preferred embodiment the siphon includes a flow limiter.

In a preferred embodiment the flow limiter in the siphon is a second orifice plate.

The second orifice plate is preferably inserted in the end of the siphon near the opening inside the second chamber. This allows the siphon to operate normally by allowing free access on the inlet side while restricting the flow on the outlet side.

The ability to adjust the flow through the siphon by the use of an orifice plate enables the time taken to reset the cut-off valve, and hence the diversion

system, to be adjusted.

For example in some instances a second runoff event may occur relatively soon after the end of a first runoff event. During the interval between such runoff events the surface remains effectively clear of contaminants. Therefore any further runoff from the second runoff event will consist mainly of relatively clean water which should be diverted into the stormwater.

In such instances the first flush of contaminated water does not occur. If the diversion system has already reset, relatively clean water will be diverted into the sewer system until such time as the float valve cuts the sewer outlet off. This creates an unwanted additional loading on the sewer system.

An advantage of this resetting process is that a standard siphon may be used for diversion systems located in a variety of environments, the reset time being adjusted accordingly by a selection of an appropriate flow limiter.

The diversion system and apparatus described above have a number of important advantages over prior art devices. The diversion system is purely hydro mechanical and does not require external power sources or an external pressure source (such as a water main) in order to operate. This enables the current system to be installed into any drainage system, including remote areas where access to power or water mains is not available. Further, the installation costs and construction costs are much lower as connections to power supply and mains water supply are not required.

The current diversion system uses basic, well established and ready available mechanical parts which require very little maintenance.

Another advantage of the current diversion system over the prior art devices is that the activation of the cut-off switch is determined by the flow rate of the runoff

into the collection chamber and diversion system, and not by a point measurement of rainfall intensity. The flow rate automatically accounts for any delays in the drainage system due to the distance of collection points from the diversion system and/or the topology of the catchment.

A major advantage of the current system is that a single standard sized apparatus may be used and fine-tuned to provide accurate switching and resetting for a wide range of catchments, environmental conditions, or local authority regulations, by appropriate choice of plate orifices to be fitted to the sewer outlet and the siphon.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a schematic side elevation representation of an apparatus for diverting fluid from a runoff according to one aspect of the present invention; and

Figure 2 shows a schematic plan representation of an apparatus for diverting fluid from a runoff event according to one aspect of the present invention; and

Figure 3 shows a schematic representation of the five steps of the method according to one aspect of the current invention.

BEST MODES FOR CARRYING OUT THE INVENTION

An apparatus, generally indicated by arrow (1) in Figures 1 and 2, for diverting fluid from a runoff event on a catchment includes a collection chamber (2)

containing an inlet (3) and a diversion system, generally indicated by arrow (4).

The diversion system (4) includes a cut-off valve in the form of a float valve (5), a flow limiter in the form of a first orifice plate (7), a siphon (12) and a second orifice plate (13).

The float valve (5) includes a float (16) connected to a valve (18) by a mechanical linkage (17).

The float valve (5) is associated with a first outlet which is a sewer outlet (6) connected to a sewer system (not shown).

The sewer outlet (6) includes a flow limiter in the form of a first orifice plate (7).

A partition (8) in the collection chamber (2) separates the collection chamber (2) into a first chamber (9) and a second chamber (10) as shown in Figure 2.

The first chamber (9) contains the inlet (3), the sewer outlet (6) and the float valve (5).

The second chamber (10) encloses a second outlet in the form of a stormwater outlet (11) connected to a stormwater system (not shown).

The first chamber (9) is connected to the second chamber (10) by a siphon (12).

A flow limiter, in the form of a second orifice plate (13), is located near the outlet of the siphon (12) in the second chamber (10).

The collection chamber (2) contains an access hole (14) for use during inspection or maintenance.

The collection chamber (2) also has a filter (15) into which runoff from the inlet (3) flows prior to entering the first chamber (9).

Figure 3 shows a schematic representation of the steps followed in diverting fluid from a runoff event on a catchment area.

In step (a) (details not shown in the figure) water is collected from a catchment area, typically through a drainage system which directs the runoff water to the inlet (3) of the apparatus (1 ).

In step (b) runoff water enters the collection chamber (2) through the inlet (3) and the filter (15) into the first chamber (9) containing the diversion system (4).

In step (c) the sewer outlet (6) is open so that an initial volume of runoff flows from the first chamber (9) into the sewer outlet (6).

The initial volume flowing into the sewer outlet (6) during this step depends on the difference between the inflow (rate of flow through the inlet (3)) and the outflow (rate of flow through the sewer outlet (6)). When the inflow is greater than the outflow the level of water in the first chamber (9) rises.

The initial volume is determined by the flow into the sewer outlet (6) up until the level of the water in the first chamber (9) reaches the top of the sewer outlet (6).

In step (d) the level of water is at or above the top of the sewer outlet (6) but below the cut-off height (not shown) at which the float valve (5) cuts off access to the sewer outlet (6).

In step (e) inflow is sufficiently greater than the outflow to raise the level of water in the first chamber (9) to the cut-off height. At this point the cut-off valve closes off the sewer outlet (6).

Further inflow continues to raise the level of water in the first chamber (9) until it reaches the top of the siphon (12). At this point the siphon is primed; that is the part of the siphon (12) contained in the first chamber (9) is completely filled with

water. This causes the siphon to suck water from the first chamber (9) into the second chamber (10), thus diverting the water into the stormwater outlet (11).

If ₁ as is likely, the continuing rate of inflow is higher than the rate of flow through the siphon (12), the water level in the first chamber (9) continues to rise until it reaches the top of the partition (8).

At this stage all further runoff during the runoff event flows over the partition (8) into the second chamber (10) and out of the stormwater outlet (11).

Step (f) occurs on cessation of the runoff event when no further inflow occurs. During this stage the level of water in the first chamber (9) drops due to the continuing flow through the siphon (12). Flow through the siphon (12) continues until the level of water in the first chamber (9) equals the level of water in the second chamber (10).

When the level of water in the first chamber (9) drops below the cut-off height the float (16) lowers opening the float valve (5), and thus resetting the diversion system (4) by reopening the sewer outlet (6) in preparation for the next runoff event.

A key aspect of the current invention is the selection of the size of the first and second orifice plates. The diameter of the aperture in the first orifice plate (7) limits the flow rate through the sewer outlet (6). For a given inflow into the first chamber (9) this diameter determines the first flush volume of runoff flow into the sewer outlet (6) before the water level in the first chamber (9) reaches the cut-off height at which the float valve (5) closes the sewer outlet (6).

This is a key parameter in designing the apparatus to meet the requirements for management of runoff from a catchment.

The diameter of the aperture in the second orifice plate (13) determines the flow rate through the siphon (12) and hence the time delay between cessation of the runoff event and resetting of the diversion system (4).

This resetting time will vary depending on the environmental situation pertaining at each catchment. Generally, the diversion system should not be reset until sufficient time has elapsed following the last runoff event for contaminants to accumulate over the surface of the catchment.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof of the appended claims.