NZ565844A - Stormwater collection and underground storage and treatment using aerobic bacteria and settlement of particulates in a near hoizontal stream - Google Patents

Abstract

A water treatment apparatus (107) for treating stormwater is disclosed. The apparatus includes a substantially water impermeable treatment tank (111) installed underground and a means for treating the stormwater. The treatment tank has one or more walls forming a tubular elongate enclosure to allow a near horizontal stream of stormwater to flow through it. The treatment means primarily consists of a combination of settlement of particulates as a result of the water flow through the tank and decomposition of waste as a result of aerobic bacteria in the tank. A holding tank (105) may also be included before the treatment tank. In this case the treatment tank may (111) may encircle the holding tank. The tanks may be made up from modular pieces. There may also be a flow control means (110) to adjust the flow rate of the system (107) as well as further filtering (115) and an anaerobic bacteria treatment. A storage tank (116) can be used to hold the treated water.

Description

565844 PATENTS FORM NO. 5 Patents Act 1953 Priority Details: No. 2007900665 Date: 12 February 2007 COMPLETE SPECIFICATION WATER TREATMENT METHOD & SYSTEM WE, Stormsaver Systems Pty Ltd, an Australian company of Suite 6,895 Pacific Highway, PYMBLE NSW 2073 hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: INTELLECTUAL PROPERTY OFFICE OP N2. 26 FEB 2008 RECEIVED 565844 Received at IPONZ on 05032009 1 WATER TREATMENT METHOD & SYSTEM FIELD OF THE INVENTION The present invention relates to a method and system of treating water, in particular treating stormwater from rural and urban water catchments to provide potable or near potable water.

BACKGROUND OF THE INVENTION The pollution of creeks and streams by stormwater from rural and urban catchments has posed serious environmental issues for many years, with the dirty and silted water often causing serious environmental issues and degradation of the water quality in creeks and streams.

In addition, the ongoing drought in many countries, including Australia, has meant that the supply of water from conventional dams and other water sources (e.g. bores and desalination plants) is becoming far more difficult, expensive and non-sustainable in environmental terms. Desalination plants also have very serious environmental effects, both in terms of the carbon dioxide production related to the electricity used, as well as the effects of the high salt content at the point of discharge.

As a result, water authorities are increasingly proposing that recycled water from sewage treatment works should be used for irrigation, drinking, and domestic purposes. However, because of community concerns with the quality of the recycled water, the recycling of water from sewage treatment plants has yet to be implemented in Australia. In addition, no water supply authority has yet proposed the local collection and treatment of stormwater for domestic, or potable supply purposes.

Conventional approaches to the treatment of stormwater discharges into creeks and streams involves the construction of silt fences, silt traps and significant concrete structures that are designed to intercept and trap the major pollutants or particulate material. These systems are however not designed to clean and purify the stormwater, neither do they provide a method for use of the water as a part of the potable water supply. The silt fences, silt traps and concrete structures are also relatively complex and require significant amounts of maintenance; 565844 Received at IPONZ on 05032009 2 Similarly, conventional approaches to the recycling of water from sewage treatment plants involves the conveying of the sewage to a Central Treatment Plant where the sewage water is cleaned by a variety of mechanical devices, tanks and chemical processes. Following treatment, the treated water then needs to be redistributed to the end user by a variety of pipes and other supply systems.

This conventional approach has the serious drawback of being inherently inefficient as it involves pumping of water over long distances and mixing of the recycled water in dams and storage facilities, as well as being very costly to construct and maintain. In addition, community concerns in Australia with the quality of the treated water from sewage treatment plants has so far prevented the widespread adoption of recycling of sewage for drinking and domestic purposes.

As such, most of the present systems of water recycling can be described as large-scale engineering systems related to waste water, with a variety of structures, tanks, pumps, trickling filters and chemicals being necessary to treat and clean the water.

Further, the small scale rainwater and grey water recycling systems often advocated for installation on houses and individual structures can only address a small part of the overall water supply problem, and without appropriate regulatory supervision, can become a community health hazard.

SUMMARY OF THE INVENTION In one aspect, the present invention provides a water treatment apparatus for treating stormwater, the apparatus including a substantially water impermeable treatment tank adapted to be installed underground, the treatment tank having one or more walls forming a tubular elongate enclosure to allow a near horizontal stream of stormwater to flow therethrough, wherein the treatment tank includes means for treating the stormwater by a combination of settlement of particulates as a result of the water flow through the tank and decomposition of waste as a result of aerobic bacteria in the tank.

In a second aspect, the present invention provides a method for treating stormwater, the method including the step of causing stormwater to flow into a substantially water impermeable treatment tank installed underground, the 565844 Received at IPONZ on 05032009 3 treatment tank having one or more walls forming a tubular elongate enclosure to allow a near horizontal stream of stormwater to flow therethrough, wherein the treatment tank includes means for treating the stormwater by a combination of settlement of particulates as a result of the water flow through tank and decomposition of waste as a result of aerobic bacteria in the tank.

The treatment tank may include a plurality of stones positioned on the base of the treatment tank to mimic a natural creek bed.

In one form, there further includes an anaerobic treatment chamber having means for further treating the aerobically treated stormwater with anaerobic processes.

Allowing the stormwater to flow near horizontally through the treatment tank allows the system to be installed under parks, sportsfields and other open spaces without requiring large scale excavations. The broad shallow excavations also make the construction less costly and where difficult site conditions are encountered, for example landfill sites and sites where rock is at shallow depth, it is usually feasible to construct a broad shallow excavation where deep excavations are not possible for a variety of reasons. The treatment stream may have a small gradient to allow for gravitational water flow.

In one form, there includes a second filter for further treating the treated stormwater, which may be a sand filter, or in another form through a sand and coke filter. In another form, the second filter may include a specialised geotextile.

In yet another form, the filtration media includes passing the cleaned stormwater through a system of chlorination, or by passing the cleaned water through a membrane. The choice of final filtration media will depend upon the level of treatment and quality of water desired.

In one form, the stormwater is collected from a local area catchment. This allows existing structures and urban drainage framework to be utilised to collect the water for treatment, and allows the stormwater to be reused in the local area.

In another form, there further includes a storage tank connected to the treatment tank, for storing the stormwater prior to the stormwater entering the treatment tank. The storage tank may be formed of a plurality of modular units, and be located underground. 565844 Received at IPONZ on 05032009 4 In one form, the storage tank and treatment tank are formed of plastic materials to allow for fast and simple installation, and low cost manufacture. In another form, the treatment tank circumnavigates the storage tank when installed underground. The treatment tank and hence treatment stream can however be formed from a variety of shapes and forms and is not limited to being circumferential. Preferably, the treatment tank is formed of a plurality of modular units connected together to form the tubular elongate enclosure, for ease in installation and maintenance.

In one form, there further includes a first filter for removing gross particulate material from the stormwater prior to the stormwater entering the treatment tank.

In a preferred form, the treatment tank includes flow regulator means to control the flow rate of the stormwater through the treatment tank.

The apparatus may be installed entirely underneath a park or sportsfield such that the apparatus is substantially invisible above ground and does not inhibit normal use of the park or sportsfield. This allows the water to be collected, stored and treated in areas of higher rainfall than the area where, for example conventional dams and other water catchment structures are located. It allows the treated water to be directly pumped to provide irrigation to the park or sportsfield.

It further allows the system to be largely invisible, as the majority of the system installed underground and the surface restored to its essentially original condition.ln one form the treatment stream cleans said filtered stormwater by enabling bacteria to grow in said treatment stream to treat and purify said stormwater. This provides an environmentally friendly and low energy system of water treatment.

The present invention allows stormwater to be cleaned and used for irrigation and/or potable water supply purposes, as well as being discharged into a creek system without adverse environmental impact. Also, as the treatment system can be provided to provide water to a local area, the treated water can service a local community without requiring the transfer of water from one community or area to another. The system thus provides a natural, environmentally friendly and low energy method and system of treating and 565844 Received at IPONZ on 05032009 cleaning stormwater. The system can also be installed and implemented in a more favourable area for collection of rainfall which is typical where the water is required for use, rather than in a remote, lower rainfall area. Thus, the system does not necessarily require extensive pipework and associated pumping systems as in the prior art. Also, as the storage and treatment tanks are modular and plastic in forms of the invention, they are fast and easy to install and adaptable to almost any location and able to be of almost any size and shape.

BRIEF DESCRIPTION OF THE DRAWINGS An illustrative embodiment of the present invention will now be described with reference to the accompanying figures. Further features and advantages of the present invention will be gleaned from the accompanying description.

Figure 1 shows a schematic side view of an embodiment of the water treatment system of the present invention installed underground; Figure 2 shows schematic plan view of the embodiment of figure 1; Figure 3 shows a sectional right side view of part of the system of figure 1, showing the underground storage tank; Figure 4 shows a sectional left side view of part of the system of figure 1, showing the underground treatment tank and storage tank.

DESCRIPTION OF PREFERRED EMBODIMENT Figure 1 shows a schematic side view of the water treatment system 10.

Stormwater is produced from rain 20 falling onto land areas, streets, gutters conventional drainage systems and collector pits. The stormwater is diverted from the conventional gutters and drains to a collector pit 101, after which it is passed through a first filter 103, being a Gross Pollutant Trap, to remove particulate material. A Gross Pollutant Trap is a device that traps major, or coarse pollutants in stormwater, such as litter and course sediments. The term "Gross Pollutant Trap" is a term recognised in the art in Australia, however there are other terms used to describe similar devices, such as "Pre-cast Inline Devices", a term which is recognised in North America.

The filtered stormwater is then passed through an access chamber 109 into a temporary storage tank 105 which is installed underground, as best shown in figures 3 and 4. There may be one storage tank, or alternatively a multitude of tanks depending upon the size of the area. The storage tank 105 creates a very 565844 Received at IPONZ on 05032009 6 large near horizontal underground tank with a typical capacity of 5 to 15 ML. The tanks are preferably manufactured from recycled polypropylene or other plastics which are capable of substantial vertical and horizontal loads, and can accommodate the passing of trucks and other vehicles over the surface without damage. However, other materials such as concrete, steel or the like could be used. The tanks are preferably modular and formed of a multitude of modular cells or boxes. An example of a suitable modular storage tank available is the EcoSystems™ raintank from Water Recycle Solutions.com, and includes one or more cells forming the storage tank.

Figure 3 shows the installation of the storage tank 105 underground. The filtered water is piped from the Gross Pollutant Trap at 103 into the cells of the storage tank 105. In addition, water seeping through the ground above the tank may enter the tank, as shown by the arrows marked 106. The multitude of modular cells are stacked to the desired size to form the storage tank 105. The tank may be entirely produced off site, or alternatively the cells may be stacked together at the installation site. An impermeable membrane 121 surrounds and underlies the tank 105. Above the tank 105 are layers of geotextile 123, geogrid 125 and engineered fill 127.

The stored water is then passed through a treatment stream 107, as shown in figure 2. The treatment stream 107 is created by the water flowing at a slow rate through a treatment tank 111 which surrounds the perimeter of the storage tank 105. The treatment tank 111 is constructed of a number of modular units which are installed to create the length of treatment tank desired. The treatment tank may however incorporate just one unit if desired. The treatment stream 107 mimics the typical natural creek system and allows biological treatment of the stormwater. A plurality of stones are situated within the treatment tank 111 in order to allow this to occur. A flow regulator 110, comprising a series of sand filled modular boxes, is included along at least one portion of the treatment stream 107 to control the flow rate in the stream 107. Other forms of flow regulators may alternatively be used as desired, such as vertical plastic barriers or series of weirs.

Figure 4 shows the installation of the treatment stream 107 underground. The treatment tank 111, creating the treatment stream 107, is wrapped in an 565844 Received at IPONZ on 05032009 7 impermeable membrane 129, and is installed to circumnavigate the storage tank 105. While the treatment tank 111 is installed substantially horizontally, the depth of the treatment tank 111 underground varies around the perimeter of the storage tank 105 by installing the treatment tank or tank units on a small incline to allow a small rate of gravitational flow.

The majority of the treatment stream 107 is effectively ventilated so that aerobic conditions are maintained within the treatment stream, and to enable suitable bacteria to grow on the matrix elements of the treatment tank 111. The rate of gravitational flow through the treatment stream 107 is such that the bacteria are able to treat and purify the water as the water passes through the treatment stream 107 in a manner analogous to the flow of water in a natural creek bed.

The treatment tank 111 and hence treatment stream 107 is adjustable in both layout and treatment time to accommodate varying types of contamination and pollution of the stormwater. Generally, the stormwater will take more than one hour, and up to several days, to pass through the treatment stream 107, although the time is dependent on the conditions and the water quality. The time for passage through the treatment stream will need to be sufficient for fine sediment in the water to settle and for the bacteria to digest any harmful products and impurities so as to cleanse the water to an adequate level. In some applications, to deal with specific pollutants, the treatment stream may also include a section where anaerobic conditions are used.

The storage tank 105 is preferably installed and designed to enable pipes to be inserted so that flushing and routine maintenance can be carried out without the need to remove the tanks for cleaning and maintenance. In addition, preferably the storage tank 105 is designed and installed so the tank or individual units can be inspected using Closed Circuit Television cameras, thereby only the particular units of the tank requiring maintenance need to be removed or exhumed for repair. The design of the storage tank system may in alternate forms incorporate a horizontal skimming water flow to ensure that the storage tank 105 does not provide a breeding ground for mosquitoes and other harmful insects.

The storage tank 105 and treatment tank 111 are preferably installed underneath a park or sportsfield 113. This allows the system 10 to treat the 565844 Received at IPONZ on 05032009 8 stormwater landing in the local area, as well as the park or sportsfield area, to be then distributed to the same local area. This saves the costs and inefficiencies of conventional systems which require the water to be pumped from dams or other remote, lower rainfall, areas to the local area. It also saves the extensive pipework and associated pumping systems. It further allows simple and easy usage of the treated water for irrigation at the park or sportsfield.

As the underground storage tank 105 and treatment tank 111 are plastic and modular in the present embodiment, they can be easily and quickly installed at minimal cost, thereby allowing the tanks 105, 111 to be installed underneath a multitude of parks and sportsfields. The system is also adaptable to almost any location and is able to be of almost any size and shape depending upon the conditions and desires. Furthermore, the system is largely "invisible", and does not detract from any previous or subsequent use of an area of public park or sportsfield.

The cleaned stormwater is then passed through a second filtration media 115. The second filtration media 115 includes passing the treated water through a sand and coke filter, although a sand filter on its own may be used, which uses microbiological processes to treat the water. If necessary, the treated water is then passed through a replaceable geotextile to remove any residual hydrocarbons. The geotextile is an especially developed material that has a capacity to absorb hydrocarbons, and can be replaced as necessary. Similarly, the sand and coke filters can be replaced as necessary to ensure optimum water quality.

Once the water has passed through the above described water treatment system, it will be of near potable quality water. This treated water can then be pumped to irrigation systems and household 'non-potable' water supplies 117. An Environmental barrier tank 116 is also provided to permit ongoing monitoring of the treated water quality before discharge into the water supply system. The pump or pumps are preferably solar powered to reduce energy and environmental costs.

Where the treated and cleaned water is to be used as a potable supply, the treated water may be chlorinated in line with conventional water treatment practices to achieve potable quality water. Alternatively, the treated water can be 565844 Received at IPONZ on 05032009 9 passed through an osmotic membrane if very high quality water is required for specific purposes.

It will be appreciated that persons skilled in the art could implement the present invention in many different ways, and variations may be produced without departing from its spirit and scope. 565844 Received at IPONZ on 05032009

Claims (21)

WHAT WE CLAIM IS:

1. A water treatment apparatus for treating stormwater, the apparatus including a substantially water impermeable treatment tank adapted to be installed underground, the treatment tank having one or more walls forming a tubular elongate enclosure to allow a near horizontal stream of stormwater to flow therethrough, wherein the treatment tank includes means for treating the stormwater by a combination of settlement of particulates as a result of the water flow through the tank and decomposition of waste as a result of aerobic bacteria in the tank.

2. A water treatment apparatus according to claim 1, further including a storage tank connected to the treatment tank for storing the stormwater prior to the stormwater entering the treatment tank, wherein the storage tank is adapted to be installed underground.

3. A water treatment apparatus according to claim 2, wherein the treatment tank circumnavigates the storage tank when installed underground.

4. A water treatment apparatus according to any one of the preceding claims, wherein the treatment tank is formed of a plurality of modular units connected together to form the tubular elongate enclosure.

5. A water treatment apparatus according to any one of claims 2 to 4, wherein the storage tank is formed of a plurality of modular units.

6. A water treatment apparatus according to any one of the preceding claims, wherein the treatment tank and the storage tank are formed of plastics materials.

7. A water treatment apparatus according to any one of the preceding claims, wherein, in use, the apparatus is installed entirely underneath a park or sportsfield such that the apparatus is substantially invisible above ground and does not inhibit normal use of the park or sportsfield. 565844 11 Received at IPONZ on 05032009

8. A water treatment apparatus according to any one of the preceding claims, further including a first filter for removing gross particulate material from the stormwater prior to the stormwater entering the treatment tank.

9. A water treatment apparatus according to any one of the preceding claims, wherein the treatment tank includes flow regulator means to control the flow rate of the stormwater through the treatment tank.

10. A water treatment apparatus according to any one of the preceding claims, wherein, in use, the treatment tank is installed on an incline to allow a small rate of gravitational flow.

11. A water treatment apparatus according to any one of the preceding claims, wherein the treatment tank includes a plurality of stones positioned on the base of the treatment tank.

12. A water treatment apparatus according to any one of the preceding claims, further including an anaerobic treatment chamber having means for further treating the aerobically treated stormwater with anaerobic processes.

13. A water treatment apparatus according to any one of the preceding claims, further including a second microbiological filter for further treating the treated stormwater, the second filter consisting of one or more of a sand filter, a sand and coke filter, or a geotextile.

14. A method for treating stormwater, the method including the step of: causing stormwater to flow into a substantially water impermeable treatment tank installed underground, the treatment tank having one or more walls forming a tubular elongate enclosure to allow a near horizontal stream of stormwater to flow therethrough, wherein the treatment tank includes means for treating the stormwater by a combination of settlement of particulates as a result of the water flow through tank and decomposition of waste as a result of aerobic bacteria in the tank. 565844 12 Received at IPONZ on 05032009

15. A method for treating stormwater according to claim 14, further including the step of causing the stormwater to flow into a storage tank connected to the treatment tank for storing the stormwater prior to the stormwater entering the treatment tank, the storage tank being installed underground.

16. A method for treating stormwater according to claim 15, wherein the treatment tank circumnavigates the storage tank when installed underground.

17. A method for treating stormwater according to any one of claims 14 to 16, wherein the apparatus is installed entirely underneath a park or sportsfield such that the apparatus is substantially invisible above ground and does not inhibit normal use of the park or sportsfield.

18. A method for treating stormwater according to any one of claims 14 to 17, further including the step of causing the stormwater to flow through a first filter for removing gross particulate material from the stormwater prior to the stormwater entering the treatment tank.

19. A method for treating stormwater according to any one of claims 14 to 18, further including the step of causing the stormwater to flow through an anaerobic treatment chamber having means for further treating the aerobically treated stormwater with anaerobic processes.

20. A method for treating stormwater according to any one of claims 14 to 19, further including the step of causing the stormwater to flow through a second filter for further treating the treated stormwater, the second filter consisting of one or more of a sand filter, a sand and coke filter, or a geotextile. 565844 Received at IPONZ on 05032009 13

21. A water treatment apparatus or a method of treating stormwater substantially as herein described with reference to any one of the embodiments illustrated in the accompanying figures. STORMSAVER SYSTEMS PTY LTD BY THEIR PATENT ATTORNEYS WATERMARK PATENT & TRADE MARK ATTORNEYS