AU2006201865B2

AU2006201865B2 - Apparatus for the treatment of water

Info

Publication number: AU2006201865B2
Application number: AU2006201865A
Authority: AU
Inventors: Patrick Buckley; Vince Camilleri
Original assignee: BUCAM Pty Ltd
Current assignee: BUCAM Pty Ltd
Priority date: 2004-08-31
Filing date: 2006-05-03
Publication date: 2010-10-14
Anticipated expiration: 2025-08-31
Also published as: NZ554971A; AU2006201865A1; AU2006100474A4

Description

1 APPARATUS FOR THE TREATMENT OF WATER FIELD OF THE INVENTION 5 This invention relates to apparatus for the treatment of water. This invention also extends to a method for the treatment of water. This invention relates particularly but not exclusively to an apparatus for the treatment of ground water that pools when a hole in the ground is excavated, e.g. 10 acid sulphate ground water, so that this water can be discharged into the returning waters that lead ultimately back into natural waterways such as rivers and creeks. It will therefore be convenient to hereinafter describe the invention with reference to this example application. However at the same time it is to be clearly understood that the invention has a number of other applications and it is not to be limited to this 15 application. For example it could also be applied to the treatment of ground water in a domestic or home environment to improve the quality of water. This includes water that is pumped out of the ground by a spear pump. For example this water could be treated to remove undesirable components to render the water suitable for use in watering plants and the like. 20 In the specification the term "comprising" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to 25 variations on the term "comprising" such as "comprise" and "comprises". BACKGROUND TO THE INVENTION At a building site it is often necessary to excavate earth to construct basements with 30 footings and piles for the building or structure. Sometimes during basement construction water pools in the hole formed by the excavation, particularly when the lowest part of the excavation is below the level of the water table. This particularly 2 prevalent on coastal strips where the water table is higher than in inland locations. This ground water needs to be removed for the structure to be built. The raw ground water that pools in the hole is of poor quality. For example the 5 ground water may be excessively acidic and have a pH lower than six. It may also have an excessive number of particles suspended therein making it cloudy and opaque, a condition known as high turbidity. A particularly problematic form of ground water that is encountered when excavating sites is acid sulphate ground water. This water is highly acidic having a pH of less than 5 and also having a high 10 level of turbidity. Water authorities in many countries including Australia have laid down strict regulations and requirements for ground water that is discharged back into the receiving waters. These regulations require that the water have a pH of not less than 15 6. They also prescribe certain maximum levels of permissible turbidity for water. Thus it should be readily apparent that acid sulphate ground waters cannot generally be legally discharged back into the receiving waters in the form in which they are pumped out of the ground. 20 While the actual properties and condition of ground waters can vary depending on their depth and location they generally require pH adjustment to meet the standard and they also often require a reduction in turbidity. One conceivable option that could be looked at is transporting ground water away 25 from an excavation site to a disposal site by road tanker. However many sites have several ground water pumps going for 24 hours a day for 365 days a year. It would simply not be possible in any practical sense to ship this water away from the site by road tanker. 30 Another conceivable option would be to discharge the water into a municipal sewerage system. This system would then pump the water to a sewage treatment plant including settling ponds that could treat the water and then discharge it into the returning waters. However the capacity of these sewage plants to take this additional 3 water would be an insurmountable problem. The sheer volumes of water being pumped out of excavation sites as ground water at anyone time are enormous and the municipal sewerage systems could not have the capacity to cope with and process these additional volumes of water. In addition there is also the problem in many municipal areas including the Gold Coast 5 and Brisbane that sewerage infrastructure including processing plants are already overloaded. This option therefore like transporting the water away from the site is simply not a realistic option. It is therefore inevitable that the remaining option namely of treating the water at the site to 10 make it acceptable for putting it into the returning waters will need to be looked at more closely. Clearly it would be advantageous if a method and apparatus for treating the water at the site could be devised that yielded water that met the standards laid down by the water authorities. It would clearly be most advantageous if the apparatus was able to meet both the pH and turbidity requirements for water for a wide range of ground water conditions. 15 It would be advantageous if such an apparatus was transportable such that it could be shipped to one site where it was used and then when that job was complete it could be shipped to another site. By the term transportable is meant that the apparatus be transportable by road, e.g. on a truck much like a shipping container. 20 It would also be advantageous if the apparatus could record the quality of water being discharged from it during its operation. This would enable an operator to be able to demonstrate with confidence that the water that has been discharged has met the standards. 25 SUMMARY OF THE INVENTION According to one aspect of this invention there is provided a transportable apparatus for treating ground water from a ground excavation at a construction site, including: a support that is capable of being lifted off a support surface and being placed upon a vehicle for 30 transport from one location to another; a water treatment plant mounted on the support, the water treatment plant including an inlet and an outlet spaced from the inlet, and a treatment path extending from the inlet to the outlet, the treatment plant including a single water treatment tank defining a tank flow path intermediate the inlet and the outlet; and an acid/alkali addition means for adding acid or alkali to water being treated in the plant that is 35 operatively mounted on the support or the plant, the acid/alkali addition means being operatively coupled to the water treatment plant and being operable to adjust the pH of the water being treated such that the pH of water discharged from the outlet is within certain pH limits, wherein the support, the water treatment plant and the acid/alkali addition means can be lifted up at one location and transported to a site at another location as a single article in 5 an assembled form and then lowered into position on a support surface at the site ready for commissioning and use. The support may be a three dimensional container that encloses the water treatment plant including the water treatment tank. The support may also enclose the means for adding acid 10 or alkali to the water being treated in the plant. The apparatus may include lifting lugs or lifting hooks to enable the support to be lifted or lowered. In this specification the term container shall be interpreted broadly and some of the surfaces of the container can be open. That is the container need not have walls extending across its surfaces. 15 The means for adding acid or alkali may comprise an acid/alkali dosing system including an acid/alkali dosing tank and a dosing line extending from the acid/alkali dosing tank to the flow path. The dosing tank may be mounted on the support, and may be operatively coupled to the treatment plant so as to be ready for use when it arrives on site. 20 The treatment plant may include an inlet pipe portion that is upstream of the treatment tank. The inlet pipe portion may extend from an edge of the support into the treatment tank. The inlet pipe portion may have an outlet, opening into the tank interior space. The inlet pipe portion outlet may face in an upward direction so that water issuing from the inlet pipe portion is directed upward against a wall of the tank before mixing in with water in the tank. 25 The dosing system may dose acid or alkali into the inlet pipe portion at a position upstream of the tank. The treatment plant may include an outlet pipe portion that is positioned downstream of the treatment tank that extends from the treatment tank to an edge of the support. 30 The dosing system may include a pH controller for controlling the amount of acid or alkali added to the water being treated in the treatment plant. The controller may be in the form of an online controller continuously controlling the addition of acid or alkali to the water in 5 response to the measured flow rate of water passing through the treatment tank and the pH of water being treated. The apparatus may further include sensing means on the outlet pipe portion for sensing the 5 pH of water issuing from the tank continuously. The apparatus may further include means for recording the pH of water issuing from the tank sensed by the sensing means, e.g. so as to provide a historical record of the water issuing from the outlet of the treatment plant. The apparatus may further include means for removing at least some of the solid particles 10 dispersed within the water from the water while it is being treated in the plant. The means for removing at least some of the solid particles may include means for promoting settling of solids within the water being treated in the treatment plant. For example the means for promoting settling of solids may include means for adding an agglomerating agent and/or a flocculating agent to the water being treated in the tank, e.g. in the form of an agglomerating 15 agent and/or flocculating agent dosing system, that encourages particles to settle in the treatment tank. The means for removing at least some of the solid particles dispersed within the water from the water may include means for changing the momentum of water being treated as it passes 20 along the tank flow path whereby to encourage particles to settle out of the flow path due to their inertia. The means for changing the momentum of the water being treated within the tank may include a plurality of plates defining a tortuous section of the flow path through the tank, e.g. 25 three plates axially spaced apart from each other in the tank. The treatment plant may include means for facilitating removal of settled solids periodically from the treatment tank. The means for facilitating removal of settled solids from the tank may include at least one solids outlet at the bottom of the tank, and an associated solids outlet 30 pipe, and associated valve that can be selectively opened and closed, to remove settled solids from the treatment tank. The means for removing at least some of the solid particles dispersed within the water from the water may include at least one filter element that extends across the tank section of the 35 flow path between the inlet and the outlet. The means for removing some solid particles may 6 include two spaced filter elements extending across the tank section of the flow path. The tank may have a filter removal opening defined in an upper region thereof proximate to the filter element. The filter element may be able to be withdrawn from the tank through the associated opening, e.g. for cleaning or replacement thereof. 5 The support may comprises a treatment tank support portion on which the tank is mounted, and at least one auxiliary support portion including a support floor, adjacent the treatment tank support portion. The acid/alkali dosing tank may be mounted on the support floor of an auxiliary support portion, and the acid/alkali controller may be mounted on the auxiliary 10 support portion, such that both the dosing tank and the controller are accessible to an operator on the auxiliary support portion. The apparatus may further include dosing tanks of flocculating agent and/or agglomerating agent that are also mounted on the support floor of an auxiliary support portion. 15 The support may comprise a central treatment tank support portion, and one auxiliary support portion on one side of the central support portion and another auxiliary support portion on another side of the central support portion. At least one auxiliary support portion may be screened off from the outside by a wall of mesh type material to resist unauthorized access to the screened off auxiliary support portion. Optionally both auxiliary support portions may be 20 screened off to resist unauthorized access thereto. In this specification the term "container" shall be interpreted broadly to cover all forms of containers. In particular it shall not be interpreted to be limited to shipping containers. 25 The dosing system may further include a dosing pump mounted on the support for pumping the acid or alkali through the dosing line and into the tank. The online pH controller may continuously control the addition of acid or alkali to the water being treated in the treatment tank, e.g. to achieve a pH range in the outlet water of 6.0 to 9.0, preferably a pH of 7.0 to 7.9. The acid/alkali dosing system may include a plurality of said acid or alkali tanks mounted on 30 an auxiliary or end support portion of the support and each acid or alkali tank may be in the form of drum of acid or alkali having a capacity of about 200-260 litres. The means for promoting settling of solids may include a dosing system for adding flocculating agent and/or agglomerating agent to the water being treated in metered 35 quantities, e.g. including at least one supply tank of flocculating and/or agglomerating agent 7 that is mounted on the support, and a dosing line extending from the supply tank to an injection point on the tank. The means for promoting settling of solids may further include a dosing pump, and the dosing pump may be mounted on the support. 5 The dosing lines may have an injection point positioned proximate to the inlet of the tank. The dosing agent may direct the agglomerating agent into an upper region of the tank above the level of the inlet. The apparatus may include means for metering the amount of agglomerating agent that is added to the water depending on an input parameter. The amount of agglomerating agent that is added may be based on the flow rate of water through 10 the tank. The dosing system may further include a controller for controlling the amount of agglomerating agent and/or flocculating agent that is added to the water in response to the flow rate of water through the tank, and a plurality of supply tanks of flocculating and/or 15 agglomerating agent mounted on an auxiliary support portion or region of the support. The dosing pump may also be mounted on an auxiliary support portion of the support. The tanks of flocculating agent and/or agglomerating agent may be in the form of drums having a capacity of about 200-260 litres. 20 Further each auxiliary or end support portion that is screened off by a wall of mesh type material may have doors associated therewith for permitting authorized personnel to gain access to the support floor and the dosing tanks supported thereon. Typically an authorized user such as an operator will need to get access to the dosing tanks to refill them with liquid dosing agent or to replace them or to get access to the controller and dosing pumps. 25 The apparatus may include a flow meter for measuring the flow of water through the water treatment tank on a continuous basis. The flow meter may be operatively coupled to the controller of the acid or alkali dosing system. The apparatus may further include a shut-off controller that is operatively coupled to the flow meter and the dosing systems for shutting off 30 the dosing systems when the flow of water through the water treatment tank is interrupted. Further the water treatment tank, and the acid or alkali dosing system, may be broadly arranged in a single layer of single level on the support. The various components can be located in any order and are not to be limited to any particular order or sequence. 35 8 Thus the various components including the tank are ultimately supported on the support and by lifting up the support the entire apparatus can be picked up and transported on a truck by road. In one example form the support may have a similar length to a shipping container although it will typically have a height that is less than that of a shipping container. Further 5 the supports may be capable of being stacked on top of each other, e.g. in operation and also in storage between uses. Very often in use at a building site ground surface area is at a premium and more than one apparatus is required for a job. In such a case the apparatuses can be stacked on top of each other. 10 The solid removal means may comprise a plurality of said solids outlets and associated valves on the bottom of the tank. The valves associated with the solids outlets may be butterfly valves and the butterfly valves may be manually operable. The solids outlets may be spaced from each other along the longitudinal direction of the flow path. The solids removal means may further include a discharge pipe extending from each outlet to a point spaced 15 away from the bottom of the tank. Each discharge pipe may feed into a discharge main that opens out on the side of the support. The inlet pipe section or portion may comprise a curved section of pipe having a diameter of about 120-200mm, e.g. about 150 mm or 6 inches. The outlet pipe portion or section may 20 extend from the outlet of the water treatment tank to the edge of the frame of the support, and may be of the same diameter as the inlet pipe section. The controller of the acid/alkali dosing system may add an amount of acid or alkali to the water based on the flow rate of water through the tank and the approximate pH of water 25 entering the tank. The controller may be an online pH controller, e.g. a PID controller, that automatically controls the amount of acid or alkali drawn from the acid/alkali tanks, e.g. continuously, so as to achieve a pH of 6.0 - 7.9 in the water issuing from the apparatus. Thus the controller may control the pH of the issuing water continuously as distinct from periodically. These drums may be mounted on the auxiliary support portions of the support 30 adjacent the ends of the tank. If for example in one application the apparatus is being used to treat acid sulphate ground water then only alkali supply tanks will be required and acid supply tanks will not be needed. Therefore in specific applications like this it may not be necessary to have both acid and alkali 35 tanks.

9 The pH of water passing through the outlet can be recorded for the full duration of operation of the apparatus. The recording means may record the pH level as a function of time and this recorded data can then be saved, and displayed visually later on a computer screen or by 5 printing it out. This way it is able to provide a continuous record of water issuing from the tank while it is being used. This historical record could be used by a user to verify that the quality of water discharged from the apparatus complied with the regulations. The apparatus may further include means for measuring the turbidity of the water, e.g. in the 10 form of an online turbidity measuring system that continuously measures the turbidity of the water. Alternatively the turbidity measuring means may be a gauge separate from the rest of the apparatus that is used to sample the water, e.g. at time intervals. The apparatus may optionally further include a turbidity control means for controlling the 15 settling and filtration steps based on the turbidity measured by the turbidity measuring means. In addition the apparatus may include a feed conduit for coupling to the inlet pipe portion. The apparatus may further include a water feed pump, e.g. a submersible pump, for pumping water to be treated into the tank through the inlet pipe section and then through the inlet. The 20 pump may be coupled in line with the feed conduit, e.g. at an upstream end thereof. In one form the pump may be received within a well. According to another aspect of this invention there is provided an apparatus for treating ground water, the apparatus comprising: 25 a support; a water treatment tank mounted on the support, the tank having an inlet, an outlet spaced from the inlet and a flow path extending from the inlet to the outlet; 10 means for adding acid or alkali to water flowing along the flow path, that is mounted on the support, the acid/alkali addition means being used to adjust the pH of said water so that the pH of water issuing from the tank is within certain limits. 5 The apparatus, e.g. the means for adding acid or alkali to water flowing along the flow path, may include means for sensing the pH of water issuing from the outlet of the tank on an at least hourly basis. The pH of water issuing from the outlet may be sensed on at least half hourly basis. 10 The means for adding acid or alkali to water flowing along the flow path may include sensing the pH of water issuing from the outlet of the tank on a continuous basis, e.g. for the whole time that water is passing through the tank. The means for adding acid or alkali to water flowing along the flow path may also 15 include recording the sensed pH of water issuing from the outlet of the tank so as to provide a historical record of the water quality discharged from the tank for the whole duration of operation of the tank. The means for adding acid or alkali to water may include a dosing system for dosing 20 acid or alkali into the tank. The dosing system includes at least one dosing tank for acid or alkali, a dosing line extending from the dosing tank to the water treatment tank, and also a dosing pump for pumping the acid or alkali into the tank. The means for adding acid or alkali to the water may further include a control means, 25 in the form of a controller for automatically and continuously controlling the addition of acid or alkali as the case may be to the water being treated. The controller may sense the pH of water entering the tank and the volume of water entering the tank and based on that add a suitable amount of acid or alkali to bring 30 the pH of the water within the desired range.

11 The support may comprise a support surface having a central tank supporting portion on which the water treatment tank is mounted and also at least one end portion. The support may have two end portions one towards each end of the support. 5 The acid and alkali tanks may be mounted on a said end portion of the support. The apparatus may further include means for removing at least some solids from water that is passed through the water treatment tank. 10 The means for removing at least some solids from water that is passed through the water treatment tank may include promoting settling of solids in the water by adding an agglomerating agent to the tank, e.g. a flocculating agent. The means for removing solids may include a dosing system including a tank 15 containing flocculant and a dosing pump for dosing flocculating agent into the water treatment tank. The tank containing flocculant may be mounted on a said end region of the support. The dosing pump may be mounted on a said end region of the support. 20 According to another aspect of this invention there is provided an apparatus for treating ground water, the apparatus comprising: a support having a central tank supporting portion and end portions outward of the central tank supporting portion; a water treatment tank mounted on the central tank supporting portion of the 25 support, the tank having an inlet, an outlet spaced from the inlet and a flow path extending from the inlet to the outlet; and means for adding acid or alkali to water flowing along the flow path, that is mounted on the support, the acid/alkali addition means being used to adjust the pH of said water so that the pH of water issuing from the tank is within certain limits. 30 The means for adding acid or alkali to the water may include at least one acid or alkali tank and these tanks may be mounted on a said end portion of the support.

12 The apparatus may further include means for promoting settling of solids within the liquid in the form of a flocculating agent and the flocculating agent may be stored within a tank that is mounted on a said end portion of the support. 5 According to another aspect of this invention there is provided an apparatus for treating water, comprising: a support; a tank mounted on the support, the tank having an inlet, an outlet spaced from the inlet, and a flow path extending from the inlet to the outlet; 10 means for removing at least some of the solids from water flowing along the flow path mounted on the support; means for adding acid or alkali to water flowing along the flow path, that is mounted on the tank, the acid/alkali means being used to adjust the pH of said water so that the pH of water issuing from the tank is within certain limits. 15 The means for adding acid/alkali may comprise a recirculating conduit drawing water from the outlet of the tank and returning it to the inlet of the settling unit. The apparatus may also include a controller for sensing the pH of the water exiting 20 the apparatus, e.g. on a continuous basis, and in response thereto adding acid or alkali to the water in the recirculating conduit so that the water issuing from the apparatus has a pH within the range of 6.0 to 9.0, e.g. 6.0- 7.9. The means for adding acid/alkali may include any one or more of the features 25 described above according to the first aspect of the invention. The means for removing at least some of the solids from water flowing along the flow path mounted on the support may include means for promoting settling of solids within water flowing along the flow path, e.g. by agglomeration of solids with a 30 flocculating agent. The means for removing at least some of the solids from water flowing along the flow path mounted on the support may include means for filtering solids from water 13 flowing along the flow path that is mounted on the tank, e.g. by at least one filtering element extending across the flow path. The means for promoting settling of solids and the means for filtering solids from the 5 water may include any one or more of the features described above according to the first aspect of the invention. According to another aspect of this invention there is provided a method of treating ground water, the method comprising: 10 passing the water through a tank having an inlet and an outlet and a flow path extending from the inlet to the outlet; removing at least some of the particles from the water being passed through the tank while it is in the tank; adding acid or alkali as the case may be to the water to adjust its pH so that 15 the water issuing from the tank has a pH within a certain range. Thus the method comprises a combination of method steps. These include removing solids within the water, and adding acid or alkali to adjust the pH. It is important to bear in mind that the method steps can be carried out in any order. For example it is 20 not necessary that the step of removing solids be carried out before the step of adding acid or alkali. Further some of the steps may be carried out simultaneously with other steps. The step of adding acid or alkali to the water to adjust its pH may comprise adding 25 metered quantities of acid or alkali to the tank by means of a dosing system. The dosing system may inject acid or alkali into the tank proximate to the inlet, e.g. adjacent the inlet of the tank. This gives it sufficient opportunity to be fully mixed into the water before it issued from the tank. 30 The step of adding acid or alkali to the water to adjust its pH may also include controlling the addition of acid or alkali, e.g. by means of a controller, so that the 14 water being discharged from the tank has a pH in the range of 6.0 to 9.0 preferably 6.0 to 7.5 The step of controlling the addition of acid or alkali may comprise sensing the pH of 5 water entering the tank and in response to this adding an appropriate amount of acid or alkali as the case may be to water being treated in the tank. The step of controlling may also include measuring the flow rate of water passing through the tank and the pH of water entering the tank and in response thereto determining the amount of acid or alkali to inject into the tank. 10 The method, e.g. the step of adding acid or alkali to the water to adjust its pH, may include sensing the pH of water being discharged through the outlet of the tank, e.g. on a continuous basis. 15 The method may also include recording this pH of water exiting the outlet, e.g. continuously so as to preserve a record of the pH of water discharged by the apparatus. Thus method may thus include monitoring and then recording the pH of water issuing 20 from the outlet of the tank, e.g. on a continuous basis, to preserve a record for posterity. The step of removing at least some of the particles from the water may include treating the water so as to encourage at least some particles within the water to settle 25 out while it is passing through the tank. The step of causing at least some particles to settle out may comprise adding an agglomerating agent to the water causing particles to clump together and then settle under the influence of gravity. 30 The agglomerating agent may be a flocculating agent, e.g. a liquid flocculating agent.

15 The step may comprise injecting the flocculating agent into the tank by means of a dosing system, e.g. a liquid dosing system. The flocculating agent may be added to the water just before the inlet or just after the water enters the tank through the inlet. 5 The step of causing at least some particles to settle out may also comprise causing the water to undergo a change in direction when it passes through the tank. This change in direction encourages heavier particles to settle out by virtue of their inertia. The change in direction may comprise directing water entering the tank up against a 10 wall of the tank, e.g. an upper region or roof region of the tank. The step of removing at least some of the particles from the water may also include filtering the water that is passed through the tank through at least one, e.g. a plurality of filtering elements. 15 In one application the method is used to treat acid sulphate ground water which is acidic and consequently caustic soda, which is an alkali, is pumped into the tank through the dosing system to adjust the pH. 20 The method may include treating the water with a transportable apparatus that includes the tank and all other components mounted on a single support. Thus the apparatus can be transported, e.g. by road on a truck, to a site where water is to be treated. 25 The method may further include pumping raw water to be treated from a site, eg an excavation site, into the tank. The method may further include pumping water issuing from the filtration step into a storm water drainage system. According to another aspect of this invention there is provided a method of treating 30 ground water, the method comprising: passing the water through a tank having an inlet and an outlet and a flow path extending from the inlet to the outlet; 16 removing at least some of the particles from the water being passed through the tank while it is in the tank; sensing the pH of water being discharged through the outlet of the tank on a regular basis; and 5 adding acid or alkali as the case may be to the water to adjust its pH so that the water issuing from the tank has a pH within a certain range. The method may also include monitoring the pH of water issuing from the outlet of the tank on an at least hourly basis, e.g. a continuous basis. 10 The method may include recording this pH of water exiting the outlet continuously so as to preserve a record of the pH of water discharged by the apparatus. The step of adding acid or alkali may include automatically controlling the pH of water 15 issuing from the apparatus within the range of pH 6.0 to 7.5. Further the pH of water issuing from the tank may be controlled continuously. According to another aspect of this invention there is provided a method of treating water to improve its quality, the method comprising the steps of: 20 treating the water so as to encourage at least some particles within the water to settle out while it is passing through the tank; passing the water through a filter to filter out further particles; and controlling the pH of water issuing from the filtration step by sensing the pH of water being treated and in response there to adding an amount of acid or alkali as 25 the case may be to the water to maintain the pH of the water within a desired range. The settling and filtration steps may be carried out in any order. In one form the settling step is carried out before the filtration step although this need not be the case. 30 The settling step may include adding a flocculating agent to the water being treated.

17 The settling step may further include passing the water around a sharp bend so that it undergoes a rapid change in momentum thereby encouraging the particles to settle out of the water. 5 The filtration step may include passing the water to be treated through a filtration cloth, such as a geo-textile. The step of controlling the pH may include sensing the pH of water issuing from the filtration step and adding acid or alkali as the case may be. 10 The acid or alkali as the case may be may be added to water entering the tank, e.g. an upstream end or front end of the process or method. This enables it to be well mixed into the water before the water is discharged from the tank. 15 The water may be acidic, eg acid sulphate water, and alkali, e.g. caustic, may be added to the water that is treated in the apparatus to make the pH of the water more neutral. DETAILED DESCRIPTION OF THE INVENTION 20 An apparatus and method for treating ground water in accordance with this invention may manifest itself in a variety of forms. It will be convenient to hereinafter provide a detailed description of several embodiments of the invention with reference to the accompanying drawings. The purpose of providing this detailed description is to 25 instruct persons having an interest in the subject matter of the invention how to put the invention into practice. It is to be clearly understood however that the specific nature of this detailed description does not supersede the generality of the preceding statements. In the drawings: 30 Fig 1 is a schematic diagram of an apparatus in accordance with one embodiment of the invention; Fig 2 is an upper three dimensional view of the apparatus of Fig 1; 18 Fig 3 is a schematic flow sheet of an apparatus that is a variation on the apparatus in Fig 1; Fig 4 is a schematic longitudinal sectional view through a water treatment apparatus in accordance with a second embodiment of the invention, the section 5 showing some internal components of the apparatus; Fig 5 is an end view of an inlet end of the apparatus of Fig 4; Fig 6 is a three dimensional view of the inlet end of the apparatus in Fig 4; Fig 7 is an end view of an outlet end of the apparatus of Fig 4; Fig 8 is a three dimensional view of the outlet end of the apparatus in Fig 4; 10 Fig 9 is a top plan view of the apparatus of Fig 4; and Fig 10 is a schematic illustration of the water treatment apparatus in an example use. In Figs 1 and 2 reference numeral 1 refers to an apparatus for treating water' in 15 accordance with one example embodiment of the invention. The apparatus 1 comprises broadly a settling unit 2 and a filtration unit 3 coupled in line with and downstream of the settling unit 2. The apparatus also includes a pH adjustment means 5 for sensing the pH of water issuing from the filtration unit 3 and 20 in response thereto adding acid/alkali as the case may be to water entering the apparatus. In the illustrated embodiment the settling unit 2 and filtration unit 3 are formed by a rectangular tank or vessel or container 10. The tank 10 has an inlet end 11 and an 25 outlet end 12, two opposed sides 13 extending parallel to the surface of the paper on which the drawings are drawn, and a top 14 and a bottom 15. The settling unit 2 is contained within a settling portion in the left half of the tank 10 and the filtration unit 3 is contained with a filtration portion on the right half of the tank 10. The two portions are divided by a separator 20 in the form of a plate. The separator plate 20 extends 30 up from the bottom 15 of the tank 10 to a terminal end spaced below the topl4 of the tank 10.

19 The separator 20 divides the tank 10 into the settling portion which occupies about 40% of the volume of the tank 10 and the filtration portion that occupies the remaining 60% of the volume of the tank 10. This ratio of volume of settling portion to filtration portion is not fixed to this ratio. The ratio can be adjusted depending on 5 the properties of the water to be treated in any one site. To enable the ratio to be adjusted the separator may be capable of movement towards and away from an end 11 or 12 of the tank 10. The settling unit 2 in turn comprises an inlet 25 on the inlet end 11 of the tank 10 and 10 an outlet effectively formed by the space between the upper end of the separator plate 20 and the top 14 of the tank 10. The inlet 25 is suitably positioned in an upper portion or reach of the inlet end 11 of the tank 10. That is it is positioned towards the top 14 of the tank 10 on the inlet end 11. 15 A directing plate 30 extends down from the top 14 of the tank 10 to a point spaced above the bottom 15 of the tank 10 and a flow path shown generally by directional arrow 35 extends from the inlet 25 to the outlet around the end of the directing plate 30. Thus the flow path 35 flows vertically down and then turns sharply through 180 degrees and then up to the outlet. This change in direction causes a sharp change in 20 momentum of the water flowing through it and encourages particles in the water, particularly large particles to settle out. These particles will collect on the bottom 15 of the tank 10 in the settling portion. The settling unit 2 also includes a solids outlet with a removable closure 38 that permits access to the settled solids that have settled on the bottom of the tank 10 to remove them from the tank 10 from time to time. The 25 solids outlet and associated closure 38 may be located in a lower portion or reach of the inlet end 11 towards the bottom 15 of the tank 10. The separator 20 has an upper edge which forms a weir over which water passes to exit the settling unit 2 and enter the filtration unit 3. Thus the weir effectively 30 determines the level of water in the settling unit. Any water above the level of the weir flows out of the settling unit 2 and into the filtration unit 3. The separator 20 extends up about % to % of the height of the tank 10.

20 The filtration unit 3 comprises an inlet again formed by the space between the separator plate 20 and the top 14 of the tank 10 and an outlet 40 defined in the outlet end 12 of the tank 10 positioned on the outlet end 12. The outlet 40 may suitably be located about halfway up the height of the outlet wall. 5 The filtration unit 3 defines a flow path shown generally by 42 and extends from the inlet across to the outlet 40. The unit 3 includes a filter element that is a filtration cloth or filter cloth 45 extending 10 across the flow path 42 from the top 14 to the bottom 15 of the tank 10. In the illustrated embodiment the cloth is a geotube filter cloth available from CSR Industrial Water Systems Pty Ltd and the cloth has a height or length of about 1600mm and a width of about 1160 mm. As shown in the drawings the cloth 45 extends diagonally across the flow path 42 from top 14 to bottom 15 with the bottom being further away 15 from the inlet. In other words the filter cloth is not square or perpendicular to the top and bottom of the tank. This assists cleaning of the tank. The filter cloth is removable to enable it to be cleaned 20 The pH adjustment means 5 comprises a recirculation conduit 50 with an inlet 52 adjacent to the outlet 40 of the filtration unit 3 and an outlet 54 feeding into the settling unit 2, proximate to the inlet 25. The pH adjustment means 5 also includes a sensor for sensing the pH of water passing out of the filtration unit 3 and a control means in the form of a controller 56. The controller 56 responds to the pH of the 25 water issuing from the filtration unit 3 sensed by the sensor and in response there to adds acid or alkali as required to bring the pH back to a range of 6.0 to 9.0. The pH adjustment means further includes a supply tank 55 containing acid or alkali as required by the water being treated which is drawn by the controller 56 into the 30 recirculation conduit as required to bring the pH of the water into the desired range. The supply tank 55 has a supply conduit 58 that is coupled to the controller 56. The pH adjustment unit 5 also includes a water displacement means in the form of a 21 pump 59 for pumping water around the recirculating conduit 50. In the illustrated embodiment the pump 59 is positioned upstream of the controller 56. The supply tank 55 may contain acid and/or alkali in liquid form in an amount of 5 1125kg. This makes the tank 55 eminently portable which is desirable as it has to be transported onto site and moved around. Thus several such supply tanks 55 each having a weight of 1125kg of acid/alkali may be provided on the site. The tanks may be stored in a bund area on site and coupled up to the recirculation conduit 50 as and when required. The angle from the top edge of the tank 55 to the top of the bund 10 should be at least 25 degrees. The controller 56 is coupled in line with the recirculation conduit 50. The supply conduit 58 is coupled to the controller 56 and this enables the controller 56 to draw acid or alkali from the supply tank 55 into the recirculation conduit 50. The controller 15 56 responds to the sensed pH by drawing an amount of acid or alkali from the supply tank 55 and introducing it into the recycle conduit 50 where it mixes with the water passing through the recirculation conduit 50. It then gets pumped through the remainder of the recycle conduit 50 and back into the settling unit 2. 20 Thus the recycle conduit 50 draws a stream of water off the main stream of treated water issuing from the outlet 40 into the recirculation conduit 50. This water is then pumped around the conduit 50 and back into the inlet 25 and acid or alkali is added to the water in this recycle conduit 50. This is advantageous because the pH of the water issuing from the outlet 40 is sensed and the pH of the water entering the 25 apparatus 1 is adjusted. This acid/alkali is thus well and truly mixed in with the rest of the water when it issues from the apparatus. The pH adjustment unit 5 may operate automatically when there is water flowing through the tank 10 and shut off automatically when water flow through the tank 10 is 30 interrupted. A valve 60 is provided to shut off flow through the recirculation conduit 50 when the water flow through the tank is interrupted.

22 The apparatus includes means for recording or logging the pH of water issuing from the outlet of the filtration unit (not shown). This recording means may log the pH measurements so that they can they later be provided as proof or verification that the water was of the required quality. 5 The apparatus also includes means for measuring the turbidity of the water continuously or on line. Again this has not been illustrated in the drawings. The apparatus may further include manual meters for measuring the turbidity of the water. 10 In use the apparatus 1 is transported to a site, eg a building excavation site, where water has pooled and needs to be treated and removed. The apparatus 1 is transported by road to the site where it is to be used. The tank 10 has the same approximate size as a shipping container and is thus sized to be capable of being transported on a truck much like a shipping container. It can be lifted onto and off the 15 truck by means of a crane and may in fact have lifting lugs 61 provided for this very purpose. The acid/alkali supply tanks 55 which are smaller than the main tank 10 are also suitable for being transported by truck. The recirculation conduit 50 and supply 20 conduit 58 and other components are transported to the site also by road in a condition in which they are detached and separate from the tank 10. Once the apparatus 1 is on site the apparatus 1 is assembled. The recirculation conduit 50 is coupled to the filtration unit outlet 40 and the controller 56 and the recirculating pump 58. The supply conduit 58 is coupled to respectively the alkali supply tank 55 and the 25 controller 56. The assembly of the various components is simple comprising the coupling of pipes and components to each other and their positioning relative to each other and it does not take long. A water supply conduit 62 has an inlet that is placed in a pool of water to be treated 30 and an outlet feeding into the inlet 25 to the settling unit 2. A water supply pump (not shown) is coupled in line with the conduit 62 to pump water from the pool into the settling unit 2. An outlet conduit 65 is coupled to the outlet 40. The conduit 65 might be directed into a storm water drain.

23 When the water supply pump is switched on water is pumped into the settling unit 2 up to the level of the outlet with the separator 20 acting as a weir. It passes from the inlet 25 down and around the directing plate 30, and then back up to the outlet. 5 Particles, eg large particles, drop out and settle on the bottom 15 of the tank 10 in the settling unit 2. Water passes out through the outlet by overflowing the separator 20 and entering the filtration unit 3. From there it passes through the filter cloth 45 and out through the outlet 40. Particles that are above the size of the openings in the filter cloth 45 are trapped by the filter cloth 45 and accumulate on the upstream side 10 of the filter cloth 45. Thus particles are removed in both the settling and filtration steps and the turbidity of the water is lowered by these processes. After passing through the filtration unit 3 the water passes out through the outlet 40 thereof and into the outlet conduit 65. 15 Some of the water passing through the conduit 65 forms the treated water product and issues from the outlet end of conduit 65. The remainder of the water enters the recirculation conduit 50. The controller 56 senses the pH of the water and based on this introduces an appropriate amount of acid or alkali, typically alkali in the form of caustic, from the supply tank 55 into the conduit 50. This maintains the pH of water 20 passing through the outlet 40 within an acceptable range of say pH 6.0 - 9.0. Water in the recirculation conduit 50 is pumped around the recirculating conduit 50 by the recirculation pump 59. Thus alkali that enters the water via the controller 56 is mixed in with the water in the recirculation conduit 50 and then enters the settling unit 25 2 with this water when it is returned to the settling unit 2. This alkali will then be intimately mixed with the water being treated before it passes out of the outlet 40 of the filtration unit 3. From time to time it will be necessary to remove accumulated solids from the bottom 30 of the settling unit 2 and clean the filter cloth 45. To do this the flow of water into the apparatus is stopped and the pump 59 is switched off. The closure 38 is then removed to open the solids outlet and provide access to the accumulated solids.

24 These solids can be dried to a water content level below 50% water which is then suitable for landfill disposal. A common application of the apparatus is in use to treat acid sulphate ground waters. 5 Such water will be strongly acidic and thus with this treatment the supply tank 55 will contain caustic and caustic will be added to the recirculation stream 50 to help bring the pH of the water back to a range of 6-9. Fig 3 illustrates an apparatus in accordance with the second embodiment of the 10 invention. As this apparatus is structurally and functionally very similar to the apparatus in the first embodiments the same reference numerals will be used to refer to the same components unless other indicated. The following description will focus on the differences between this embodiment and 15 the first embodiment. This embodiment includes a holder 80 in the form of an open basket or container that is positioned proximate to the inlet 25 to the settling unit 2. In use a flocculating agent 82 that is a block of agglomerating material is placed in this holder 80 and the 20 water that enters the settling unit 2 is passed over it. In a preferred form the flocculating agent is an anionic flocculant in the form of a block sold in Australia under the trade name MAGNASOL. The flocculating agent may also be a liquid but a solid is preferred. 25 The block of flocculant 82 is progressively dissolved over time by the action of water passing over it. The rate of dissolution may depend on the flow rate of the water and the general condition of the water including its turbidity or hardness. The agglomerating agent 82 assists in causing the particles to agglomerate or combine together to form larger particles which are more susceptible to dropping out of the 30 stream of water particularly when it undergoes the sharp change in momentum around the directing plate 30.

25 In Figs 4 to 9 a water treatment apparatus in accordance with a second embodiment of the invention is indicated generally by the reference numeral 100. Broadly the apparatus 100 comprises a support in the form of a rectangular box 5 container 102 and a water treatment tank 105 that is mounted inside the container 102. The tank 105 is elongate with an inlet 106 at one end and an outlet 107 at the opposed end and defines a flow path 108 through its interior space from the inlet 106 to the outlet 107. 10 The apparatus 100 also includes means for promoting the settling of solids in the form of a dosing system shown generally by 111 for dosing an agglomerating agent into the water treatment tank 105. The apparatus also includes means facilitating removal of settled solids, e.g. in the 15 form of sludge from the tank, in the form of a plurality of solids outlets 112 and associated closures 114. The apparatus further includes filtering means in the form of two spaced filter elements 116 and 118 that extend across the flow path 108. Further the apparatus includes means for adding acid/alkali to water passed through the tank 102 in the form of an acid/alkali metered dosing system 119 to adjust the pH 20 of the water issuing from the tank. We now discuss each of the components above in more detail. The rectangular box container 102 that has a length that is greater than its width or 25 height. The apparatus 100 may be sized such that it has a length not exceeding 6m, a width not exceeding 2m, and a height not exceeding 2m, such that it can be lifted by a crane and that it can be loaded onto a truck. This way the apparatus 100 can be moved from one location to another by a truck travelling on the road as the need arises. Conveniently the box container 102 may have a similar length to a standard 30 shipping container although this is not essential. This size standardisation eases the transport of the apparatus from site to site as required for some of its applications.

26 The outer lines of the container 102 are defined by structural members that extend in horizontal and vertical directions as shown in the drawings. At least some of the surfaces of the container are not closed in with solid walls. Some of the surfaces are left open and others are covered with a see through mesh type material. 5 The tank 105 is received in a middle or central tank supporting portion of the box container 102. The container 102 defines inlet and outlet end portions 120, 122 that are longitudinally outward of the inlet or outlet of the tank 105 as the case may be. At the ends of the end portions 120, 122 the container 102 has a rectangular inlet end 10 and an opposed rectangular exit end. The container 102 may have support surfaces that are floors, at each of these end regions 120, 122. These support surfaces provide support for components such as drums and barrels and control equipment as will be described in more detail below. The container 102 also has doors 125, 126 on each of these ends that can be pivoted open to provide access to the 15 corresponding end region 120, 122 of the support and the end of the tank 105. The floors of the end regions 120, 122 and the surfaces of the doors 125, 126 may be covered with a mesh like material. Further the container 102 may also include lifting formations 128 for enabling the 20 container 102 to be lifted up and also lowered. The lifting formations 128 may be lifting lugs located on an upper region of the container 102. In the illustrated embodiment there are four lifting hooks 128 located towards the four corners of the container 102. 25 The tank 105 is broadly circular cylindrical and is also elongate with two opposed ends. The inlet 106 to the tank 105 is defined in one end of the tank, towards an upper edge of said one end, and the outlet 107 is defined in the opposed end of the tank 105, about midway up said opposed end of the tank. The diameter of the tank 105 is comparable to the height of the container 102. The length of the tank is quite 30 a bit less than the length of the container 102. It may be about % to % of the length of the container 102.

27 The tank 105 also includes an inlet pipe portion 130 that extends from the tank inlet 106 to the end wall of the container 102. The inlet pipe portion 130 can be coupled to a feed pipe (not shown) that feeds water into the inlet of the tank. 5 The tank 105 also includes an outlet pipe portion 132 extending from the outlet 107 to the outlet end of the container 102. This can be coupled to a discharge pipe to direct treated water away from the apparatus 100 and into a drainage system, such as a storm water drainage system. 10 The tank 105 also includes a manhole with an associated manhole cover 135 for providing a worker with access to the interior of the tank 105. As shown the manhole is conveniently positioned on the top of the tank 105. The tank also includes elongate slot openings with closures 138, again near the top of the tank. These slot openings enable filter elements (that will be described in more detail below) to be 15 removed from the tank for cleaning and the like by being lifted up out of the tank through the associated slot opening. Further the closures over the slot openings include sight glasses for enabling an operator to view the inside of the tank 105 while it is in operation. 20 The tank also includes a perforated mixing plate 110 that is mounted on the tank 105 proximate to the inlet 106 to the tank. The mixing plate 110 extends at an angle from the tank wall below the inlet diagonally upward to a point on the top of the tank spaced there from. The mixing plate is perforated with a regular array of 25 mm diameter perforations and is not unlike a plate in a heat transfer column. Thus water 25 deflected off the roof of the tank drops onto the plate, it then passes through one of the perforations and drops further into a pool of liquid in the lower half of the tank. The perforated plate helps to promote mixing of water with flocculating agent and acid or alkali within the tank. 30 The dosing system 111 comprises a supply of agglomerating agent in a drum 140 mounted on the inlet end portion of the container, a line 142 extending from the drum 140 to an agglomerating agent injection point and a dosing pump 144. The injection point is positioned on an upper region of the tank proximate to the inlet and the 28 deflector plate 110. The dosing system 111 may also have means for enabling the amount of agglomerating agent that is dosed into the tank to be adjusted by an operator. 5 The agglomerating agent may be in the form of a flocculating agent. In the illustrated embodiment a liquid flocculating agent is used. However a solid flocculating or agglomerating agent may also be used. The agglomerating agent may be an anionic flocculating agent such as that sold under the trade name MAGNASOL. 10 The two spaced filter elements 116 and 118 that extend across the flow path 108 will now be described in more detail. The purpose of the filter elements is obviously to filter out solids within the water being passed through the tank 105. The two filter elements are positioned directly beneath the elongate slot apertures described above. This enables the filter elements to be easily lifted out of the tank for cleaning 15 maintenance or the like. The tank 105 may include two longitudinally spaced internal walls 150, 152 that extend up from the bottom of the tank to a height that is about 0.25 to 0.4 of the height of the tank 105. These internal walls 150, 152 are spaced longitudinally in 20 from the inlet 106 and outlet ends 107 of the tank 105. Thus in a sense they divide the tank up into first, second and third internal compartments arranged one after another in the direction of the flow path. The first filter element 116 is mounted on the first wall 150 and extends from an upper edge of the wall to a point above the level of any water within the tank 105. That way water passing through the tank from 25 the inlet to the outlet has to pass through the filter element 116. Often the upper edge of the filter element 116 is positioned just below the top of the tank. The filter element comprises a filter cloth extending across a filter frame. The filter cloth is a polyester geo-textile and has a pore size of about 100 micron - 150 micron. 30 In the illustrated embodiment the pore size is 120 micron although this is obviously not essential.

29 The second filter element 118 is substantially the same as the first filter element 116 described above. Specifically in the illustrated embodiment the pore size of the filter cloth is the same although this obviously does not need to be the case. 5 The tank 105 also includes a solid sludge removal system for removing settled solids from the bottom of the tank 105. The removal system may comprise solid removal outlets 112 in each of the three compartments. The system also includes sludge removal pipe sections leading away from the outlets. These outlet pipe sections terminate in a single solids outlet main 156 through which all sludge issues. Each of 10 the outlet pipe sections has a said closure 114 that is a valve mounted on it that can be manually opened by an operator to open the associated solids outlet and permit sludge to pass out through it. In the illustrated version the valves are butterfly valves that can be moved between open and closed positions by a simple 90 degree tum of the valve handle. 15 The acid/alkali metered dosing system 119 for adjusting the pH of the water issuing from the tank will now be described. The system 119 comprises an acid and/or alkali supply system in the form of at least 20 one drum 160 of acid or alkali that is mounted on the support surface of one of the end regions 122, 122 of the container. There may be drums of acid or alkali 160 supported on both end regions of the container. The dosing system 119 also includes a dosing line 164 going from the drum/s 160 to an injection point/s on the tank 105 and a dosing pump 166 coupled in line with the dosing line 164. The 25 injection point/s may be located in an upper region of the tank towards the inlet, e.g. upstream of the first filter element. This provides sufficient time for the acid or alkali to be mixed in with the water before it passes out through the outlet. The apparatus also includes a Doppler flow meter 170 for measuring the flow of 30 water through the tank, e.g. on a continuous basis. The flow meter may be mounted on the inlet pipe portion and may be a supply type of flow meter. The apparatus may include a further flow meter (not shown) on the outlet pipe portion.

30 The system 199 also includes a control means in the form of a controller for controlling the amount of acid or alkali introduced to the tank. The controller senses the pH of water entering the tank by means of a pH sensor proximate the inlet (not shown) and the flow rate of water entering the tank. In response to this an amount of 5 acid or alkali is added to bring the pH within the range of pH 6.0 to 7.9. In the illustrated embodiment the controller is a PID controller. The apparatus may also include a control system (not shown) that is operatively coupled to both the flow meter and the dosing systems and which operates to shut 10 off all dosing system the moment that flow of water through the tank ceases. This has the effect of shutting off the flow of expensive dosing agents when there is no water flow through the apparatus. In use water to be treated is pumped out of the ground and into the inlet pipe portion. 15 It then passes into the tank 105 through the inlet 106. The water is directed upwardly at the roof of the tank when it enters the tank. It strikes the roof of the tank and then is deflected downwardly and then drops down into the tank. Applicant believes that the change of direction in the water caused by directing it at the roof of the tank helps to cause particles, particularly larger particles, within the water to drop out of the 20 liquid. Applicant also believes that it promotes mixing within the water. As it drops down from the roof under the influence of gravity it lands on the mixing plate 110. It then passes through the apertures in the plate and drops down into a body of water in the first internal compartment of the tank. This interferes with the 25 stream of water and causes it to drop down under the influence of gravity into the body of the tank. The Applicant has found that this apertures plate promotes mixing of the water. The water pools in the first compartment of the tank, between the inlet and the first 30 filter element 116. The agglomerating agent or flocculant dosing system 111 injects flocculant through an upper region of the tank also into the first compartment where it mixes with the water.

31 The pH dosing system 119 injects acid or alkali as the case may be into the tank. The acid or alkali is injected through an upper region of the tank into the first compartment of the tank like the flocculating agent. The amount of acid or alkali that is added is carefully metered to ensure that the pH of the water issuing from the 5 outlet has a pH within limits, say 7.0-7.8. In the illustrated embodiment the amount of acid or alkali that is added depends on the flow rate of water measured by the flow meter on the inlet pipe portion. 10 Some solids settle out of the liquid in the first compartment. The flocculating agent assists the settling process. The agent encourages particles to clump together and form bigger particles that then settle out due to gravity. When the level of water in the tank rises above the level of the wall on which the first filter element 116 is mounted then water will flow through the first filter element and into the second tank 15 compartment. The filter cloth filters out some solids from the water. Further agglomeration and settling takes place in the second compartment and more particles settle out on the bottom of the tank. The water then flows through the second filter element 118 and into the third tank compartment. 20 In the third tank compartment further mixing of the water takes place. There may also be some further agglomeration and settling out of particles in the third compartment. The water then flows out of the tank through the outlet 107 and into the outlet pipe 25 portion 132. The height of the outlet 107 determines the height of water in the tank. Generally the outlet is positioned about % of the way up the height of the tank. The outlet pipe portion is then coupled to a drainage pipe and the water drained away say down a stormwater drain. 30 As a general proposition water flows continuously into the tank and treated water is drawn continuously from the outlet. Operators can view the interior of the tank through the sight glasses 138 to check that the apparatus is functioning properly.

32 From time to time it is necessary to discharge accumulated sludge including agglomerated solids out of the solids outlets of the tank. This is done by opening the butterfly valves 114 associated with these solids outlets 112 for a time sufficient to allow the sludge to flow out of the tank. The butterfly valves are then closed. This 5 solids removal operation takes place during normal operation of the apparatus. The filter elements can also be cleaned from time to time by removing the closures over the slot apertures on the roof of the tank and then pulling the filter elements up out of the tank. The elements can be cleaned and the cloth on the element replaced 10 if necessary and then the elements are returned to the tank. The filter elements can be cleaned while the tank is in usual operation with water being pumped through the treatment tank. Generally the filter elements may be cleaned in sequence such there is always one element in the tank at any one time to effect filtering of the water. 15 Figs 7 and 8 showing the outlet end of the container shows some of the components of the dosing systems 111 and 119 and also some of the control components. On the right side are three dosing pumps for the dosing system. On the left side is a central processing means in the form of a computer. Adjacent to the computer is please supply. 20 Fig 10 is a schematic drawing showing one application envisaged for this invention. The reference numeral 200 refers to an excavated hole in the ground. Further wells shown by numeral 202 are excavated from the bottom of the hole. The ground water 25 that feeds into the wells is then pumped out of the wells by using submersible pumps. This ground water may often require treatment before it would be acceptable to water authorities to pump it down a storm water drain. This water is then pumped into an apparatus like that shown in Figs 1 or Fig 4 above 30 for treatment and indicated by numeral 100 in the drawings. This treatment removes some of the solid particles from the water and also adjusts the pH of the water by the addition of acid/alkali to adjust the pH to within acceptable limits. The water 33 discharging from the apparatus can then be put into a storm water drain where it forms part of the ground water. An advantage of the apparatus described above with reference to the drawings is 5 that it is able to be transported to a site, e.g. a construction site, where it can be used to clean water to a quality where the water can meet the requirements for it to be pumped into a storm water drainage system. Specifically it can be used to dewater a worksite allowing the treated water to be discharged directly into a stormwater reticulation network. 10 A further advantage is that it is capable of taking water of very poor quality and reducing the turbidity and acidity thereof to acceptable levels. In particular it is capable of treating acid sulphate waters which are highly acidic to a quality level where it is acceptable to pour the water down a storm water drain. The apparatus 15 described above has been able to produce water with a pH in the range of 6.0 to 9.0 and a sufficiently low level of turbidity to meet the quality standards required of water management authorities for passing the water into the storm water system. A further advantage of the apparatus described above is that it is relatively compact. 20 The settling unit and the filtration unit can easily be constructed in a tank having a size corresponding to that of a shipping container. This enables it to be transported from one site to another site on the road by truck transport. Further the apparatus is easy to assemble on site. The various components can rapidly and easily be coupled together to form the assembled apparatus. 25 A further advantage is that components used in the filter unit are readily available and can be purchased off the shelf. Similarly the dosing systems for the flocculating agent and the acid or alkali addition can also be purchased off the shelf. Further the flow meters and the control systems can be purchased off the shelf and setup to 30 control the process on this apparatus. This simplifies the manufacture of the apparatus. It also enhances the reliability of the apparatus.

34 Further the apparatus can be operated largely automatically and does not require experienced operators to run it. However from time to time accumulated solids need to be removed from the settling unit through the outlet and workers are required to do this. Further the filter cloth needs to be cleaned periodically and workers are also 5 needed to do this. One particular advantage that the apparatus has over other apparatuses is that the pH of water exiting the apparatus is measured, i.e. after the water has been treated. It is important to measure the water exiting the apparatus because this is the water 10 sent to storm water drainage. Further the acid or alkali that is added to neutralise the water is added to a water stream that is passed into the front end of the process. That is it is passed into the settling unit It will of course be realised that the above has been given only by way of illustrative 15 example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth.

Claims

1. A transportable apparatus for treating ground water from a ground excavation at a construction site, including: 5 a support that is capable of being lifted off a support surface and being placed upon a vehicle for transport from one location to another; a water treatment plant mounted on the support, the water treatment plant 10 including an inlet and an outlet spaced from the inlet, and a treatment path extending from the inlet to the outlet, the treatment plant including a single water treatment tank defining a tank flow path intermediate the inlet and the outlet; and an acid/alkali addition means for adding acid or alkali to water being treated in 15 the plant that is operatively mounted on the support or the plant, the acid/alkali addition means being operatively coupled to the water treatment plant and being operable to adjust the pH of the water being treated such that the pH of water discharged from the outlet is within certain pH limits, 20 wherein the support, the water treatment plant and the acid/alkali addition means can be lifted up at one location and transported to a site at another location as a single article in an assembled form and then lowered into position on a support surface at the site ready for commissioning and use. 25

2. A transportable apparatus according to claim 1, wherein the support is in the form of a three dimensional container that encloses the water treatment plant including the water treatment tank, and also the means for adding acid or alkali to the water treated in the plant. QU

3. A transportable apparatus according to claim 2, wherein the three dimensional container includes lifting lugs or lifting hooks to enable the apparatus to be lifted or lowered during use. 5

4. A transportable apparatus according to any one of claims 1 to 3, wherein the acid/alkali means for adding acid or alkali comprises an acid/alkali dosing system including an acid/alkali dosing tank and a dosing line extending from the acid/alkali dosing tank to the flow path, and wherein the acid/alkali dosing tank is permanently mounted on the support and is operatively coupled to the treatment 10 plant.

5. A transportable apparatus according to claim 4, wherein the treatment plant includes an inlet pipe section that is upstream of the treatment tank, and the inlet pipe section extends from an edge of the support into the treatment tank, 15 and wherein the treatment plant also includes an outlet pipe portion that is positioned downstream of the treatment tank that extends from the treatment tank to an edge of the support.

6. A transportable apparatus according to claim 5, wherein the inlet pipe 20 portion has an outlet that opens into the tank interior space, and wherein the outlet of the inlet pipe portion faces upward so that water issuing from the inlet pipe portion is directed upward against a wall of the tank before mixing in with water in the tank. 25

7. A transportable apparatus according to any one of claims 4 to 6, wherein the acidlalkali dosing system doses acid or alkali into the inlet pipe portion at a position upstream of the tank. 30

8. A transportable apparatus according to any one of claims 4 to 7, wherein the acid/alkali dosing system includes a pH controller, and wherein the pH 37 controller is in the form of an online controller continuously controlling the addition of acid or alkali to the water in response to the measured flow rate of water passing through the treatment tank and the pH of water being treated. 5

9. A transportable apparatus according to claim 8, further including sensing means on the outlet pipe portion for sensing the pH of water issuing from the tank continuously, and further including means for recording the pH of water issuing from the tank sensed by the sensing means so as to provide a historical record of the water issuing from the outlet of the treatment plant. 10

10. A transportable apparatus according to any one of claims 4 to 9, further including means for removing at least some of the solid particles dispersed within the water from the water while it is being treated in the plant. 15

11. A transportable apparatus according to claim 10, wherein the means for removing at least some of the solid particles includes means for promoting settling of solids within the water being treated in the treatment plant.

12. A transportable apparatus according to any one of claim 11, wherein the 20 means for removing at least some of the solid particles dispersed within the water from the water includes means for changing the momentum of water being treated as it passes along the tank flow path whereby to encourage particles to settle out of the flow path due to their inertia. 25

13. A transportable apparatus according to claim 12, wherein the means for changing the momentum of the water being treated within the tank includes a plurality of plates defining a tortuous section of the flow path through the tank.

14. A transportable apparatus according to any one of claims 11 to 13, 30 wherein the treatment plant includes means for facilitating removal of settled solids periodically from the treatment tank in the form of at least one solids outlet 38 at the bottom of the tank, and an associated solids outlet pipe and associated valve that can be selectively opened and closed to remove settled solids from the treatment tank. 5

15. A transportable apparatus according to any one of claims 11 to 14, wherein the means for removing at least some of the solid particles dispersed within the water from the water includes at least one filter element that extends across the tank section of the flow path between the inlet and the outlet, and wherein the tank has a filter removal opening defined in an upper region thereof 10 proximate to the filter element, and wherein the filter element can be withdrawn from the tank through the associated opening for cleaning or replacement thereof.

16. A transportable apparatus according to any one of claims 4 to 15, wherein 15 the support comprises a tank support portion for supporting the treatment tank, and at least one auxiliary support portion including a support floor, adjacent the treatment tank support portion.

17. A transportable apparatus according to claim 16, wherein the tank support 20 portion is centrally disposed on the support, and one auxiliary support portion is positioned on one side of the tank support portion and another auxiliary support portion on an opposed side of the central support portion.

18. A transportable apparatus according to claim 16 or claim 17, wherein the 25 acid/alkali dosing tank and the acid/alkali controller are mounted on one of the auxiliary support portions so that the tank and controller are accessible to an operator on the support floor of the auxiliary support portion.

19. A transportable apparatus according to claim 17 or claim 18, wherein at 30 least one of the auxiliary support portions is screened off from the outside by a 39 wall of mesh type material to resist unauthorized access to the acid/alkali dosing tank and the acid/alkali dosing system.

20. A transportable apparatus substantially as herein described in the second 5 embodiment of the specific description with reference to Figures 4 to 9.