AU2005279702B2 - Apparatus for the treatment of water - Google Patents

Description

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1 APPARATUS FOR THE TREATMENT OF WATER O FIELD OF THE INVENTION This invention relates to apparatus for the treatment of water. This invention N 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 is exposed by ground excavations at building sites, such that this water can be discharged directly into surface waters, including 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 application. For example it could be applied to the treatment of grey water to enable the recycling of water in a domestic environment. It could also be used for the treatment of water in an industrial environment.

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 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 build a foundation for the building or structure. Sometimes ground water forms in the ground excavation and this ground water needs to be removed for the foundations of the building or structure to be put in place.

0 The ground water is often not in a condition for it to be pumped into a stormwater reticulation system and returned to the ground water. For example O the ground water may be acidic and have a pH lower than seven. 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 level of turbidity.

Currently it is a common practice to pump this ground water into the stormwater system even though it does not meet the environmental water quality standards laid down for water to be legally discharged into the surface waters. From an environmental management point of view r it is obviously highly undesirable for acidic water having a very high level of turbidity to be discharged passed into the storm water system. Water authorities are now taking a stricter line in relation to these practices and will not allow untreated acidic water with high turbidity to be discharged into the surface waters without appropriate water treatment.

An alternative to treating the water at the site would be to pump the water into road tankers and transport it away from the site. However this option is very expensive and would not be attractive to builders and engineers for this reason.

Clearly therefore it would be advantageous if a method and apparatus could be devised for treating the water on site to improve its quality to a point where it meets the environmental standards required for it to be discharged into the surface waters without adversely affecting the water quality in the surface waters..

It would also be particularly advantageous if such an apparatus was transportable such that it could be shipped onto a site where it is to be used.

Further when that job is completed it could then be shipped to another site. By 0 the term transportable is meant that the apparatus be transportable by road, e.g. on a truck much like a shipping container.

0 SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a transportable compact apparatus for on-site treatment of ground water from a ground excavation at a construction site, which apparatus includes: a treatment tank having a ground water inlet and a treated water outlet and a flow path extending between the ground water inlet and the treated water outlet through which flow path the ground water being treated passes; a settling means for encouraging at least some particles within the ground water being treated to settle in a lower region of the tank to reduce the turbidity of the water, the treatment tank having a particles outlet for enabling settled particles to be removed from the tank; and a pH adjustment means for selectively adjusting the pH level of the ground water being treated within the tank so that treated water leaving the treatment tank is within a predetermined pH range before it is discharged from the tank through the treated water outlet, wherein both the settling means and the pH adjustment means effect treatment of the ground water within the flow path as it passes there through.

The settling means may include means for adding a flocculating agent to the ground water passing through the tank for encouraging at least some particles within the ground water passing through the tank to settle in the lower region of the treatment tank.

O The settling means may include means for adding an agglomerating agent to the ground water passing through the tank for encouraging at least some O particles within the ground water passing through the tank to settle in the lower region of the treatment tank.

N The settling means may further include at least one baffle mounted on the tank within the tank defining a tortuous flow path through the treatment tank, and the tortuous flow path changes the direction of travel of the water as it passes through the tank whereby to encourage particles within the water to settle out of the ground water being treated in the tank.

The pH adjustment means may include at least one of an acid supply tank containing acid and an alkali supply tank containing alkali, a feed pipe line extending from the supply tank directly or indirectly into the flow path, and a dosing pump mounted in line with the feed pipe line, for displacing the acid or alkali along the feed pipe line. Thus acid or alkali is drawn from the supply tank and is mixed in with ground water that is treated in the treatment tank.

The acid and alkali supply tanks may be transportable, e.g. separate from the treatment tank, and the supply tanks may be operatively connected to the treatment tank at a treatment site.

The apparatus may include a pH controller that senses the pH level of the ground water passing through the treatment tank and in response thereto selectively controls the amount of acid or alkali which is introduced to the ground water passing through the treatment tank.

The pH controller may include a pH sensor at or downstream of the treated water outlet to sense the pH level of the treated water being discharged from the treatment tank. The pH controller may be set to achieve a pH level of between 6 and 9 of the treated water being discharged from the treated water outlet of the treatment tank.

The pH controller may be set to measure the pH levels of the treated water O being discharged from the outlet for the full duration of operation of the apparatus on-site.

The pH controller may include means for visually displaying the measured pH of the treated water, e.g. measured by the pH sensor that is at or downstream of the treated water outlet. The pH controller may include means for recording the measured pH levels of the treated water, e.g. sensed by the pH sensor that is at or downstream of the treated water outlet, so that a record of the pH levels of the treated water discharged from the treatment tank over the full duration of its operation can be retained.

The apparatus may include a turbidity controller for controlling the amount of the flocculating agent and/or the agglomerating agent introduced into the ground water being treated.

By the term turbidity is meant the degree of cloudiness and opacity in the water due to the number of particles suspended in the water. A ground water having high turbidity has an excessive number of fine particles suspended therein and it is undesirable to return this water directly back into surface waters.

The turbidity controller may include a turbidity meter for sensing the turbidity level of the ground water passing through the treatment tank, which turbidity controller automatically controls the amount of the flocculating agent and/or agglomerating agent introduced to the ground water being treated in response to the sensed turbidity level.

The treatment tank may include a removable filter that is mountable inside the treatment tank. The filter may be shaped and sized to extend across the flow path such that ground water passing from the ground water inlet to the treated water outlet passes through the filter element. The filter may comprise a flexible 0 sheet of filter cloth. The flexible sheet may have openings such that particles having a size greater than 1 mm are retained on the filter cloth. In particular the O openings may be such that particles having a size greater than 0.2 mm are retained on the filter cloth.

N The particles outlet for enabling settled particles to be removed from the tank may be positioned in a lower region of the tank, and the particles outlet may be selectively opened to discharge particles from the treatment tank.

The tank may include lifting formations for enabling it to be lifted onto and off a truck by means of a crane. The apparatus may be sized and shaped to be received within a three dimensional space occupied by a standard shipping container to enable it to be mounted on a road going truck that is suitable for transporting shipping containers, and which has a crane suitable for lifting cargo containers, whereby to transport the apparatus from one site to another.

The invention also provides a process for treating ground water from a ground excavation at a construction site, the process including: displacing ground water from the ground excavation into a treatment tank positioned on the construction site, the treatment tank having a ground water inlet and a treated water outlet and a flow path defining a treatment zone extending between the ground water inlet and treated water outlet; encouraging at least some particles within the ground water to settle out in the treatment zone as the ground water passes there through; and adjusting the pH level of the ground water in the treatment zone as the ground water passes there through, so that treated water discharging from the treatment tank achieves a pH level that is within a predetermined pH range.

0 The process may include a continuous flow of ground water through the treatment zone. The treatment tank may be positioned proximate to the ground O excavation.

The process may include displacing the ground water in a single pass through N the treatment zone to form the treated water.

Encouraging at least some particles within the ground water to settle out may include adding a flocculating agent to the ground water passing through the treatment zone. Encouraging at least some particles within the ground water to settle out may include adding an agglomerating agent to the ground water passing through the treatment zone.

Encouraging at least some particles within the ground water to settle out may include changing the direction of the flow path within the treatment tank so that the water has to change direction when it passes through the tank, e.g. through a change in direction of at least 90 degrees.

Adjusting the pH level of the ground water in the treatment zone may include introducing an acid or alkali into the ground water that is passed into the treatment zone. In particular adjusting the pH level of the ground water in the treatment zone may include sensing the pH level of the ground water passing through the treatment tank and in response thereto selectively controlling the amount of acid or alkali which is to be introduced to the ground water passing through the treatment tank.

Moreover, adjusting the pH level of the ground water passing through the treatment zone may include sensing the pH level of the treated water discharging from the treated water outlet and adjusting the pH levels of the ground water to achieve a pH level of between 6 and 9 of the treated water discharging from the treated water outlet.

O The acid or alkali may be added to the water prior to its introduction to the Streatment zone, or acid or alkali may be added to the water while it is O undergoing treatment in the treatment zone.

Encouraging at least some particles within the ground water to settle out in the (Ni treatment zone may include sensing the turbidity level of the ground water passing through the treatment zone, and in response thereto controlling the amount of the flocculating agent and/or the agglomerating agent introduced into (Ni the ground water being treated.

c- The process may include filtering out, with at least one filter element, at least some of the particles within the ground water passing through the treatment tank.

The process may include monitoring the amount of particles that settle in a lower region of the treatment tank, and removing at least some of the settled particles from the treatment tank when the amount of settled particles exceeds a predetermined amount.

According to a further aspect of the invention, there is provided a method for treating ground water from a ground excavation that has been formed for receiving a structure on a construction site, the method comprising: positioning a treatment tank on a construction site having a ground excavation; displacing ground water out of the ground excavation into the treatment tank; and treating the ground water in the treatment tank to settle out some particles within the water, and adding acid or alkali to the ground water to adjust the pH of the water within the same treatment tank to achieve a pH of treated water which is within certain limits.

0 The method may include discharging the treated water from the tank into receiving waters in proximity to the excavated site.

The method may include automatically controlling the addition of acid or alkali to the ground water by a controller.

Treating the ground water to settle out some particles within the ground water may include adding a flocculating agent and/or agglomerating agent to the ground water passing through the treatment tank.

Displacing the ground water out of the excavated site into the treatment tank may include providing a pump inside the excavation and pumping the ground water from the excavation into the treatment tank.

The excavation may be made in an acid sulphate soil and alkali may be added to the ground water to raise the pH level of the ground water being treated.

The receiving waters may be storm waters passing through a storm water drain system.

According to another aspect of this invention there is provided an apparatus for treating water, comprising: a particle settling means for receiving water to be treated having means for encouraging at least some particles within the water, e.g. the larger particles, to drop out of suspension to enable these particles to be removed from the liquid; 0 a filtration means in line with the particle settling means downstream of the particle settling means having a filter element through which the water to be O treated is passed for removing further particles within the water from the water; and a pH adjustment means for adding an appropriate level of acid or alkali to the water being treated so that water issuing from the filtration unit has a pH within acceptable limits.

Thus incoming water first undergoes a particle settling step that encourages particles to settle or be knocked out of solution. Thereafter the water is filtered to remove further particles. In addition the pH of the water is sensed and in response there to an appropriate amount of acid or alkali is added to the water passing through the apparatus to reduce its acidity or alkalinity as the case may be before it issues from the apparatus.

The particle settling means may be a unit having an inlet, and an outlet, and a flow path extending from the inlet to the outlet. The particle settling unit may include means for sharply changing the momentum of the water as it passes along the flow path from the inlet to the outlet. The means for sharply changing the momentum of water may comprise a sharp change in the direction of the flow path. The change in the direction may be greater than 90 degrees, e.g.

about 180 degrees.

The particle settling unit may further include means for adding a flocculating agent or agglomerating agent to the water passing there through. This may be in the form of a flocculation holder that holds a said flocculating agent. The flocculation holder may be open to permit water to pass there through and come into contact with the flocculating agent.

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Further the means for adding a flocculating agent may also include a flocculating agent within the holder, e.g. in use. The flocculation agent may be O in the form of a solid block, e.g. a block of MAGNASOL.

The holder may be located inside the particle settling unit, proximate to the inlet (N of the settling unit. For example the holder may be positioned in proximity to the inlet such that water entering through the inlet is passed over the holder.

The settling unit may further include a solids outlet for removing settled particles from the settling unit and a removable closure mounted over the settling unit.

The solids outlet may be located in a lower region of the settling unit.

Thus from time to time the closure can be removed and solids can be physically removed from the particle settling unit through the solids outlet. The flow of water through the unit may be interrupted during the removal of the solids.

The filtration means may be a filtration unit having an inlet and an outlet and a flow path extending from the inlet to the outlet and a filter element extending across the flow path such that water passing from the inlet to the outlet has to pass through the filter element. The filter element may comprise a flexible filter element that extends across the flow path.

The filter element may be a filter cloth, e.g. a geofilter cloth or a geotube filter cloth. The warp and weft strands of the cloth may be arranged and spaced such that most of the particles in the water, including particles greater than 1 mm and more preferably particles greater than 0.5 mm, are retained on the cloth while the water passes there through.

The filter cloth may extend across the flow path transverse to the direction of the flow path. Further the cloth may be angled relative to a line orthogonal into the direction of the flow path, e.g. such that it extends diagonally from one side O of the flow path to the other. The cloth may be angled such that a lower edge the cloth is more downstream than an upper edge of the cloth.

0 The filter mesh openings may be sized between 5 1000 microns, or between 20 300 microns, preferably 100 microns.

The apparatus may include an outlet conduit extending from the outlet of the filtration unit.

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The pH adjustment means may include means for sensing the pH of water passing through the apparatus. The sensing means may sense the pH of water in the particle settling unit or the filtration unit or in the outlet of the filtration unit.

Preferably the sensing means senses the pH of water that issues from the outlet of the filtration unit. The sensing means may measure the pH in the outlet conduit downstream of the outlet of the filtration unit.

The pH adjustment means may include a pH adjustment unit including a recirculation conduit having an inlet drawing water from the filtration unit, or downstream of the filtration unit, and having an outlet returning the water to the settling unit, or upstream of the settling unit.

Preferably the inlet of the recirculation conduit is in fluid communication with the outlet conduit and draws water from the outlet conduit. Preferably the outlet of the recirculation conduit directs water back into the settling unit. The pH adjustment unit may further include a liquid displacement means for displacing water around the recirculation conduit.

The pH adjustment means may further include an acid or alkali supply. The supply may comprise an acid or alkali supply tank and a supply conduit operatively coupling the tank to the recirculation conduit.

O The pH adjustment means may further include a control means in the form of a controller responsive to the pH sensed by the sensing means to draw an O amount of acid or alkali from the supply tank into the recirculation conduit from where it is pumped through the remainder of the recirculation conduit and through the outlet of the recirculation conduit into the settling unit.

The acid or alkali may be drawn into the recirculation conduit by vacuum, by r- gravity feed or by pumping action, including pumping with a positive displacement pump.

c The controller may be an online pH controller, e.g. a PID controller that controls the amount of acid or alkali drawn from the supply tank so as to achieve a pH of 9.0 in the water issuing from the apparatus.

The pH adjustment means may include means for visually indicating the pH of water passing out through the outlet to a user or operator.

The visual indicating means may include a visual display.

The pH adjustment means may further include means for recording the pH of water passing through the outlet for the full duration of operation of the apparatus. The recording means may log the pH of water passing out of the outlet of the filtration unit over the full duration of operation of the apparatus.

The recording means may log the pH on paper or it may log the pH on an electronic storage device.

This way a record of pH of water issuing from the apparatus over the course of its operation can be produced. This can be used by a user to verify the quality of water that they discharge into a storm water drainage system complies with the regulations.

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The apparatus may further include means for measuring the turbidity of the water. The turbidity measuring means may be an online turbidity measuring O system that continuously measures the turbidity of the water while the Sapparatus is operating. Alternatively the turbidity measuring means may be a gauge separate from the rest of the apparatus that is used to sample the water.

The apparatus may further include a turbidity control means for controlling the settling and filtration steps based on the turbidity measured by the turbidity measuring means.

Conveniently the particle settling unit and the filtration unit may be formed by a tank or container having a partition dividing it up into a settling portion towards one end thereof and a filtration portion towards the other end thereof.

The tank may be a rectangular tank having two sides, a top and a bottom and inlet and outlet ends.

The partition may extend up from the bottom of the tank towards the top and terminate short of the top so as to define a gap between the terminal end of the partition and the top thereby forming said outlet of the settling unit and said inlet of the filtration unit.

The partition dividing the tank up into the settling and filtration units may comprise a substantially planar partition plate that extends up from the bottom of the tank towards the top and terminates short of the top of the container.

The tank 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 tank can be moved from one side to another by a truck travelling on the road as the need arises.

The means for changing the momentum of the water in the particle settling unit may include a directing plate extending down from the top of the tank towards O the bottom and terminating short of the bottom of the tank.

The inlet may be located on the inlet end of the tank towards the top thereof.

N The solids outlet may be located on the same inlet end of the tank as the inlet but towards the bottom of the tank.

Thus water flowing through the settling unit flows in through the inlet and is directed down towards the bottom of the tank. It then passes around the end of the directing plate and back up between the partition plate and the directing plate towards the outlet. The sharp change in direction that occurs encourages particles to settle out on the bottom of the tank proximate to the outlet. From time to time these particles can then be removed through the solids outlet.

The means for adding a flocculating agent may comprise an open container that is received within the tank and is mounted on the tank proximate to the inlet.

The open container may comprise a basket or the like that can carry a solid bar or the like of flocculating agent and water can enter into and pass through the basket.

The level of water in the particle settling unit may be the same as or higher than the height of the outlet of the particle settling unit. Thus water flows over the partition which acts as a weir retaining a certain level of water in the settling unit. The basket may be located at about the same height as the level of water in the tank.

An upper edge of the filter cloth may be attached to the top of the tank and a lower edge may be attached to the bottom of the tank. The lower edge may be positioned nearer the outlet than the upper edge which is nearer the inlet so that the filter cloth is inclined downwardly and forwardly, i.e. in the direction of flow.

Thus in a cross-sectional side view it extends diagonally from top to bottom. In O the filtration unit the water flows from the inlet to the outlet and in doing this it crosses the filter cloth. This filters out solid particles that are larger than the O openings in the filter cloth.

c, The inclination or diagonal orientation of the filter cloth encourages solids to Sdrop off the cloth onto the bottom of the tank from they can be removed, e.g.

manually. Thus they do not tend to build up on the surface of the cloth.

The acid or alkali supply tank may be located in close proximity to the primary c 10 tank, e.g. on top of the tank. The supply conduit and the recirculation conduit may be flexible.

The supply tank may be of a squat configuration to ease its transport on a truck.

For example it may have a volume of 0.5m 3 1.5 m 3 preferably 0.8m 3 1.2m 3 Thus the supply tank like the primary tank can also be easily transported on a truck. The pH adjusting unit can be detached from the tank for transport and then assembled on site.

The apparatus may further include a water feed pump for pumping water to be treated in through the inlet to the settling unit and also a feed conduit for directing water to the inlet.

According to yet another aspect of this invention there is provided an apparatus for treating water, comprising: a particle settling means for receiving water to be treated having means for encouraging at least some particles within the water to drop out of suspension to enable these particles to be removed from the water; and a pH adjustment means for adding acid or alkali to the water to be treated, the pH adjustment means comprising a recirculating conduit drawing water from downstream of the settling unit and returning it to the apparatus upstream of the settling unit, and a controller for sensing the pH of the water exiting the apparatus and in response thereto adding acid or alkali to the water O in the recirculating conduit so that water issuing from the apparatus has a pH within the range of 6.0 to N The pH adjustment means may include a water displacement means for pumping water around the recirculation conduit.

The pH adjustment means may also include an acid or alkali supply tank which is coupled to the controller for supplying acid or alkali into the recirculation conduit.

The settling unit may include any one or more of the features of the settling unit described above according to the first aspect of the invention.

According to a further aspect of this invention there is provided an apparatus for treating water, comprising: a filtration means having a filter element through which the water to be treated is passed for removing further particles within the water from the water; and a pH adjustment means for adding acid or alkali to the water to be treated, the pH adjustment means comprising a recirculating conduit drawing water from downstream of the filtration unit and returning it to the apparatus upstream of the filtration unit, and a controller for sensing the pH of the water exiting the apparatus and in response thereto adding acid or alkali to the water in the recirculating conduit so that water issuing from the apparatus has a pH within the range of 6.0 to The pH adjustment means may include a water displacement means for pumping water around the recirculation conduit.

The pH adjustment means may also include an acid or alkali supply tank which O is coupled to the controller for supplying acid or alkali into the recirculation conduit.

The filtration unit may include any one or more of the features of the filtration unit described above according to the first aspect of the invention.

According to still another aspect of this invention there is provided a method of S 10 treating water to improve its quality, the method comprising the steps of: passing the water through a settling step to cause at least some of the particles within the water to settle out; passing the water through a filtration step 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 the case may be to the water to maintain the pH of the water within a desired range.

Preferably the settling step is carried out before the filtration step.

The settling step may 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.

The method may further include adding a flocculating agent to the water being subjected to the settling step. More specifically the flocculating agent may be added to water being introduced to the settling step.

O The flocculating agent may be a solid that is exposed to water entering the settling step.

0 The filtration step may include passing the water to be treated through a filtration cloth, such as a geotextile.

The controlling step may include sensing the pH of water issuing from the r- filtration step.

S 10 The controlling step may further include adding acid or alkali as the case may be to water entering the settling step or the water undergoing the settling step.

Thus acid or alkali is added towards the front end of the process.

The controlling step may comprise drawing a recycle stream off the water issuing from the filtration step, sensing the pH of this water, and in response to this sensed pH adding a suitable amount of acid or alkali and returning the recycle stream to the settling step. The controlling step may include pumping the water in the recycle stream into the settling step or the water being fed to the settling step.

The water may be acidic, e.g. acid sulphate water, and alkali, e.g. caustic, may be added to the recirculation stream to assist in neutralizing water that is treated in the apparatus.

The method may further include pumping raw water to be treated from a site, e.g. an excavation site, into the settling unit.

The method may further include pumping water issuing from the filtration step into a storm water drainage system.

DETAILED DESCRIPTION OF THE INVENTION O An apparatus for treating 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 more than one embodiment of the invention with reference to the Saccompanying drawings. The purpose of providing this detailed description is to 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

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specific nature of this detailed description does not supersede the generality of c 10 the preceding statements. In the drawings: 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; and Fig. 3 is a schematic flow sheet of an apparatus in accordance with a second embodiment of the invention.

In Figs. 1 and 2 reference numeral 1 refers to an apparatus for treating water in accordance with one example embodiment of the invention.

In the illustrated embodiment the apparatus 1 comprises a rectangular tank or vessel or container 10. The tank 10 is divided up broadly into a settling portion 2 and a filtration portion 3 coupled in line with and downstream of the settling portion 2. The tank 10 has an inlet end 11 and an outlet end 12, two opposed sides 13 extending between the ends parallel to the surface on which the tank is mounted, and a top 14 and a bottom The apparatus also includes a pH adjustment means 5 for sensing the pH of water issuing from the filtration portion 3 and in response thereto adding acid/alkali as the case may be to water entering the apparatus.

The settling portion 2 is contained within the left half of the tank 10 and the O filtration portion 3 is contained within the right half of the tank The two portions 2, 3 are divided by a separator 20 in the form of a plate. The C separator plate 20 extends up from the bottom 15 of the tank 10 to a terminal end spaced below the top 14 of the tank Thus the separator 20 divides the tank 10 into the settling portion 2 which c 10 occupies about 40% of the volume of the tank 10 and the filtration portion 3 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 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 The settling unit 2 in turn comprises an inlet 25 on the inlet end 11 of the tank and an outlet 26 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.

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 26 around the end of the directing plate 30. Thus the flow path 35 extends vertically down and then changes direction sharply through 180 degrees and then extends back up to the outlet 26. This change in direction causes a sharp change in momentum of the water flowing through the tank 10 and encourages particles in the water, particularly large particles to settle out. These particles will collect on the bottom of the tank 10 in the settling portion 2. The settling portion 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 solids outlet and associated closure 38 may be O located in a lower portion or reach of the inlet end 11 towards the bottom 15 of the tank SThe separator 20 has an upper edge defining part of the outlet 26 past which water being treated flows to exit the settling portion 2 and enter the filtration portion 3. Water that is above the level of the upper edge can flow directly out of the settling portion 2 and into the filtration portion 3. The separator 0 10 extends up to a height that is about 2/3 to 3/4 of the height of the tank The filtration portion 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 that is a treated water outlet 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 wall at the outlet end 12. The filtration portion 3 defines a flow path shown generally by 42 and extends from the inlet across to the outlet The filtration portion 3 includes a filter element that is a filtration cloth or filter cloth 45 extending 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 1600 mm 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 from the inlet. In other words the filter cloth is not square or perpendicular to the top and bottom of the tank.

In addition to removal of solids by filtration through the filter element some settling of particles can also occur in the filtration portion 3.

The filter cloth is removable to enable it to be cleaned. A user can remove the filter cloth by lifting it out through an access opening.

The filter cloth can be removed for cleaning while ground water from a ground O excavation is being treated by the apparatus 1, in accordance with the invention. The treatment zone is defined by the flow path extending between the ground water inlet at the inlet end 11 and the treated water outlet at its outlet Send 12, through which flow path the ground water being treated passes.

Further the filter element can be omitted from the tank and settling can also take place within the filtration portion as the ground water passes there through.

c 10 Similarly mixing of acid or alkali with the water being treated can occur within the filtration portion 3 as the ground water passes there through.

In the illustrated embodiment the pH adjustment means 5 comprises a recirculation conduit 50 with an inlet 52 adjacent to the outlet 40 of the filtration portion 3 and an outlet 54 feeding into the settling portion 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 portion 3 and a control means in the form of a controller 56. The controller 56 responds to the pH of the water issuing from the filtration portion 3 sensed by the sensor and in response there to add acid or alkali as required to bring the pH back to a range of 6 to 9. Instead, the pH level of the treated water can be measured downstream and proximate the treated water outlet as it passes through the outlet conduit 65, should a user desire to isolate the recirculation conduit 50 or desire not to use it at all.

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 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 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 O 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.

SThe tanks may be stored in a bund area on site and coupled up to the recirculation conduit 50 as and when required.

The controller 56 is coupled in line with the recirculation conduit 50. The supply c 10 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 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 into the settling portion 2 where it mixes with ground water being treated in the tank 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 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 means 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 interrupted. A valve 60 is provided to shut off flow through the recirculation conduit 50 when the water flow through the tank is interrupted.

The pH controller may includes a pH sensor for sensing and recording the pH of water issuing from the outlet of the filtration unit (not shown). This controller may also record and log the pH measurements so that they can they later be provided as proof or verification that the water was of the required quality.

0 The apparatus may also include means for measuring the turbidity of the water continuously or on line. The apparatus may further include manual meters for measuring the turbidity of the water. Neither of these forms of the turbidity meters has been illustrated in the drawings.

In use the apparatus 1 is transported to a site, e.g. a building excavation site, where ground water is contained in the ground excavation site and needs to be pumped out of the ground excavation site. The tank 10 is compact to facilitate it being 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 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 treatment tank are also suitable for being transported by truck, e.g. separate from the treatment tank 10. The recirculation conduit 50 and supply 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 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 ground excavation containing ground water to be treated and an outlet feeding into the inlet 25 to the settling portion 2. A water supply pump (not shown) is coupled in line with the conduit 62 to pump water from the pool into the settling portion 2. An outlet conduit 65 is coupled to the outlet 40. The conduit 65 might be directed into a O storm water drain.

The water supply pump pumps water from the ground excavation into the settling portion 2 and fills up the treatment tank 10 to the height of the outlet of the filtration portion 3. The water passes from the inlet 25 down and around the directing plate 30, and then back up to the outlet of the portion 2. Particles, e.g. large particles, are encouraged to settle out of suspension and settle in a bottom region 15 of the tank 10 in the settling portion 2. Water passes out of the filtration portion 2 through the outlet 26 and into the filtration portion 3. From there the water being treated passes through the filter cloth 45 and out through the treated water outlet 40. Particles that are greater than the size of the openings in the filter cloth 45 are trapped by the filter cloth 45 and accumulate on the upstream side of the filter cloth In addition to filtration of the water some particles that are suspended within the ground water being treated can also settle out of the water within the filtration portion 3. Thus settling also takes place in the filtration portion 3 albeit at a lower level than the settling in the settling portion 2.

Thus particles are removed in both the settling and filtration steps and the turbidity of the water is reduced by treatment in the treatment tank 10. After passing through the filtration portion 3 the water passes out through the treated water outlet 40 thereof and into the outlet conduit 65 where it forms the treated water product that can be discharged into the surface waters.

In the illustrated embodiment some of the water enters the recirculation conduit The controller 56 senses the pH of the water in the recirculation conduit and based on this sensed pH, either alone or in combination with other readings of the pH of the water being treated and optionally also the flow rate, introduces an appropriate amount of acid or alkali, typically alkali in the form of caustic, O from the supply tank 55 into the conduit 50. This pH control acts to maintain the SpH of water passing through the outlet 40 within an acceptable range of say pH O 6.0-9.0.

Water in the recirculation conduit 50 is pumped around the recirculating conduit (N 50 by the recirculation pump 59. Thus alkali is mixed in with the treated water in the recirculation conduit 50 and then enters the settling portion 2 with this r- treated water when it is returned to the settling portion 2. This alkali is then intimately mixed in with the ground water being treated within the treatment tank S 10 10 before it passes out of the outlet 40 of the filtration portion 3.

From time to time it will be necessary to remove accumulated solids from the bottom of the settling portion 2 and clean the filter cloth 45. This can be done by an operator while the tank is in use for the treatment of water. This is possible because the tank is not pressurised. To do this the closure 38 is removed to open the solids outlet and provide access to the accumulated solids. These solids can be dried to a water content level below 50% water which is then suitable for landfill disposal.

Instead, the operation of the apparatus 1 can be interrupted while the solids are removed. To do this the flow of water into the apparatus is stopped and the pump 59 is switched off.

The filter element 45 can also be lifted out of the tank 10 for cleaning either during operation of the apparatus 1 or when the flow of water through the tank has been stopped.

A common application of the apparatus involves the treatment of acid sulphate ground waters. Such water is often 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.

O Fig. 3 illustrates an apparatus in accordance with the second embodiment of the invention. As this apparatus is structurally and functionally very similar to the O apparatus in the first embodiments the same reference numerals will be used to refer to the same components unless other indicated.

SThe following description will focus on the differences between this embodiment and the first embodiment.

This embodiment includes a holder 80 in the form of an open basket or c 10 container that is positioned proximate to the inlet 25 to the settling portion 2. In use a flocculating agent 82 that is a block of agglomerating material is placed in this holder 80 and the water that enters the settling portion 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 in the form of a liquid.

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 flocculant 82 assists in causing the particles to agglomerate or combine together to form larger particles which are more susceptible to dropping out of the stream of water particularly when it undergoes the sharp change in momentum around the directing plate An agglomerating agent in the form of a coagulant, in bar or liquid form, can also be added to the water being treated to encourage the particles to agglomerate and then settle out.

An advantage of the apparatus described above with reference to the drawings is that it is transportable and can easily and conveniently be transported to a site, e.g. a construction site, where it can be used for the treatment of ground water. Specifically the tank can be transported from one site to another site on 0 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 O assembled apparatus.

Further the apparatus described above can treat high levels of turbidity and high (acid or alkali levels to a quality where the water can meet the requirements for it to be returned directly to the surface waters without any harmful effect to the environment, e.g. it can be discharged directly into a stormwater reticulation network.

A further advantage is that the water treatment apparatus is capable of treating water of very poor quality and reducing the turbidity and adjusting the pH 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 return the water to the surface waters. The apparatus described above is capable of producing treated water having a pH in the range of 6.0 to 9.0 and a sufficiently low level of turbidity to meet the quality standards required by water management authorities for passing the treated water into the surface waters via the storm water system.

A further advantage of the apparatus described above is that it is relatively compact. The entire treatment process is carried out within a single tank having a settling portion and a filtration portion, the whole tank having a size corresponding to that of a shipping container. Further the ground water is treated in a single pass through the apparatus.

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 needed to do this.

O 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 0 treated. Further the pH of the treated water is recorded for the whole duration of the treatment process. It is particularly useful to measure the water exiting the apparatus because this is the water returned to the surface waters. Further the acid or alkali that is added is introduced to the water being treated in the settling portion. This gives it sufficient time to be fully mixed in with the water being treated before it is discharged through the treated water outlet.

c- 10 It will of course be realised that the above has been given only by way of illustrative 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 (31)

1. 2. An apparatus as claimed in claim 1, in which the settling means includes means for adding a flocculating agent to the ground water passing through the tank for encouraging at least some particles within the ground water passing through the tank to settle in the lower region of the treatment tank.
2. 3. An apparatus as claimed in claim 1 or claim 2, in which the settling means includes means for adding an agglomerating agent to the ground water passing through the tank for encouraging at least some particles within the ground water passing through the tank to settle in the lower region of the treatment tank.
3. 4. An apparatus as claimed in any one of the preceding claims, in which the O settling means includes at least one baffle mounted on the tank within the tank defining a tortuous flow path through the treatment tank, and wherein the tortuous flow path changes the direction of travel of the water as it passes through the tank and thus encourages particles within the water to settle out of the ground water being treated in the tank. An apparatus as claimed in any one of the preceding claims, in which the pH adjustment means includes an acid supply tank containing acid or an alkali supply tank containing alkali, a feed pipe line extending from the supply tank directly or indirectly into the flow path, and a dosing pump mounted in line with the feed pipe line for displacing acid or alkali from the acid or alkali supply tank into the treatment tank.
4. 6. An apparatus as claimed in claim 5, in which the acid and alkali supply tanks are transportable and capable of being operatively connected, directly or indirectly, to the flow path through the tank whereby acid or alkali is drawn from the supply tank to be mixed in with ground water that is treated in the treatment tank.
5. 7. An apparatus as claimed in any one of the preceding claims, which includes a pH controller that senses the pH level of the ground water passing through the treatment tank and in response thereto selectively controls the amount of acid or alkali which is introduced to the ground water passing through the treatment tank.
6. 8. An apparatus as claimed in claim 7, in which the pH controller includes a pH sensor at or downstream of the treated water outlet to sense the pH level of the treated water being discharged from the treatment tank.
7. 9. An apparatus as claimed in claim 8, in which the pH controller is set to achieve a measured pH level of between 6 and 9 in the treated water O discharging from the treated water outlet of the treatment tank.
8. 10. An apparatus as claimed claim 8 or claim 9, in which the pH sensor that N is at or downstream of the treated water outlet measures the pH levels of the treated water being discharged from the outlet for the full duration of operation r- of the apparatus on-site. c 10 11. An apparatus as claimed in any one of claims 8 to 10, in which the pH controller includes means for visually displaying the pH of the treated water measured by the pH sensor that is at or downstream of the treated water outlet.
9. 12. An apparatus as claimed in any one of claims 8 to 11, in which the pH controller includes means for recording the measured pH levels of the treated water, so that a record of the pH levels of the treated water discharged from the treatment tank over the full duration of its operation can be retained.
10. 13. An apparatus as claimed in any one of claims 3 to 12, which includes a turbidity controller for controlling the amount of the flocculating agent and/or the agglomerating agent introduced into the ground water being treated.
11. 14. An apparatus as claimed in claim 13, in which the turbidity controller includes a turbidity meter for sensing the turbidity level of the ground water passing through the treatment tank, which turbidity controller automatically controls the amount of the flocculating agent and/or agglomerating agent introduced to the ground water being treated in response to the sensed turbidity level.
12. 15. An apparatus as claimed in any one of the preceding claims, in which the treatment tank includes a removable filter that is mountable inside the treatment tank, the filter being shaped and sized to extend across the flow path such that ground water passing from the ground water inlet to the treated water outlet passes through the filter element. 0
13. 16. An apparatus as claimed in claim 15, in which the filter comprises a flexible sheet of filter cloth.
14. 17. An apparatus as claimed in claim 16, in which the flexible sheet has openings such that particles having a size greater than 1 mm are retained on the filter cloth.
15. 18. An apparatus as claimed in any one of the preceding claims, in which the particles outlet for enabling settled particles to be removed from the tank is positioned in a lower region of the tank, and the particles outlet can be selectively opened to discharge particles from the treatment tank.
16. 19. An apparatus as claimed in any one of the preceding claims, in which the tank includes lifting formations for enabling it to be lifted onto and off a truck by means of a crane.
17. 20. An apparatus as claimed in any one of the preceding claims, in which the apparatus is sized and shaped to be received within a three dimensional space occupied by a standard shipping container to enable it to be lifted onto a road going truck that is suitable for transporting shipping containers whereby to transport the apparatus from one site to another.
18. 21. A process for treating ground water from a ground excavation at a construction site, the process including: displacing ground water from the ground excavation into a treatment tank on the construction site, the treatment tank having a ground water inlet and a treated water outlet and a flow path defining a treatment zone extending between the ground water inlet and treated water outlet; encouraging at least some particles within the ground water to settle out O in the treatment zone as the ground water passes there through; and O adjusting the pH level of the ground water in the treatment zone as the Nground water passes there through, so that treated water discharging from the treatment tank achieves a pH level that is within a predetermined pH range.
19. 22. A process as claimed in claim 21, in which there is a continuous flow of N 10 ground water through the treatment zone.
20. 23. A process as claimed in claim 21 or claim 22, in which the ground water is displaced through the treatment zone in a single pass to form the treated water.
21. 24. A process as claimed in any one of claims 21 to 23, in which encouraging at least some particles within the ground water to settle out includes adding a flocculating agent to the ground water passing through the treatment zone. A process as claimed in any one of claims 21 to 24, in which encouraging at least some particles within the ground water to settle out includes adding an agglomerating agent to the ground water passing through the treatment zone.
22. 26. A process as claimed in any one of claims 21 to 25, in which encouraging at least some particles within the ground water to settle out includes changing the direction of the flow path within the treatment tank so that the water has to change direction when it passes through the tank. S27. A process as claimed in any one of claims 21 to 26, in which adjusting the pH level of the ground water in the treatment zone includes introducing an O acid or alkali into the ground water that is passed into the treatment zone.
23. 28. A process as claimed in any one of claims 21 to 27, in which adjusting (the pH level of the ground water in the treatment zone includes sensing the pH level of the ground water passing through the treatment tank and in response thereto selectively controlling the amount of acid or alkali which is to be introduced to the ground water passing through the treatment tank.
24. 29. A process as claimed in any one of claims 21 to 28, in which adjusting the pH level of the ground water passing through the treatment zone includes sensing the pH level of the treated water discharging from the treated water outlet and adjusting the pH levels of the ground water to achieve a pH level of between 6 and 9 of the treated water discharging from the treated water outlet. A process as claimed in any one of claims 21 to 29, in which the acid or alkali is added to the water prior to its introduction to the treatment zone, or acid or alkali is added to the water while it is undergoing treatment in the treatment zone.
25. 31. A process as claimed in any one of claims 21 to 30, in which encouraging at least some particles within the ground water to settle out in the treatment zone includes sensing the turbidity level of the ground water passing through the treatment zone, and in response thereto controlling the amount of the flocculating agent and/or the agglomerating agent introduced into the ground water being treated.
26. 32. A process as claimed in any one of claims 21 to 31, which includes filtering out, with at least one filter element, at least some of the particles within the ground water passing through the treatment tank. O 38. A method as claimed in any one of claims 34 to 37, in which displacing the ground water out of the excavated site into the treatment tank includes O providing a pump inside the excavation and pumping the ground water from the excavation into the treatment tank.
27. 39. A method as claimed in any one of claims 34 to 38, wherein the excavation is made in an acid sulphate soil and alkali is added to the ground water to raise the pH level of the ground water being treated.
28. 40. A method as claimed in any one of claims 36 to 41, wherein the receiving waters are storm waters passing through a storm water drain system.
29. 41. A transportable compact apparatus for on-site treatment of ground water from a ground excavation at a construction site substantially as herein described.
30. 42. A process for treating ground water from a ground excavation at a construction site substantially as herein described.
31. 43. A method for treating ground water from a ground excavation for receiving a structure on a construction site substantially as herein described. 33. A process as claimed in any one of claims 21 to 32, which includes monitoring the amount of particles that settle in a lower region of the treatment O tank, and removing at least some of the settled particles from the treatment tank when the amount exceeds a predetermined amount. 34. A method for treating ground water from a ground excavation that has been formed for receiving a structure on a construction site, the method comprising: S 10 positioning a treatment tank on a construction site having a ground excavation; displacing ground water out of the ground excavation into the treatment tank; and treating the ground water in the treatment tank to settle out some particles within the water, and adding acid or alkali to the ground water to adjust the pH of the water within the same treatment tank to achieve a pH of treated water which is within certain limits. A method as claimed in claim 34, which includes discharging the treated water from the tank into receiving waters in proximity to the excavated site. 36. A method as claimed in claim 34 or claim 35, which includes automatically controlling the addition of acid or alkali to the ground water by a controller. 37. A method as claimed in any one of claims 34 to 36, in which treating the ground water to settle out some particles within the ground water includes adding a flocculating agent and/or agglomerating agent to the ground water passing through the treatment tank.