AU2002101054A4 - Method and apparatus for the treatment of water - Google Patents

Description

WO 02/102723 PCT/AU02/00786 N, 1 O METHOD AND APPARATUS FOR THE TREATMENT OF WATER o FIELD OF THE INVENTION This invention relates to a method and apparatus for the treatment of water.

This invention relates particularly but not exclusively to a method and O apparatus for the treatment of waste water such as effluent or sewerage in a O compact plant that discharges treated water that is capable of being re-used in flushing toilets and the like. It will therefore be convenient to hereinafter describe the

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O invention with reference to this example application. However it is to be clearly understood that it is capable of broader application. For example it may also be applied to the treatment of water other than sewerage. It also need not produce water that is suitable for re-use.

BACKGROUND TO THE INVENTION Sewerage reticulation networks and the associated treatment plants are typically located wherever there are concentrations of human habitation. Sewerage contains organic waste from humans and particularly solid faecal waste and liquid urine waste. This solid and liquid waste is carried in water through a conduit system to a point at which the water is treated, eg in a sewerage plant, before being released back into the environment, eg as ground water. The solid waste comprises organic compounds made up primarily of carbon, hydrogen and oxygen with some additional amounts of nitrogen and sulphur. The objective of sewerage treatment is to degrade or breakdown the organic compounds, eg nitrogenous and phosphorous compounds, and obnoxious chemical compounds in the waste to decomposition products including CO 2 water and nitrogenous wastes. It is also to reduce the number of pathogenic organisms in the water prior to its release into the environment.

In existing sewerage plants the waste water is subjected to a series of aerobic and anaerobic unit operations to break down or degrade matter in the waste water. In addition the typical plant has a number of settling tanks for separating solid waste from water to be returned to the environment. In order to reach a consistently WO 02/102723 PCT/AU02/00786 N 2 O high level of solids removal these plants are often bulky and occupy a substantial land area. In addition the plants are capital intensive both to build and run. Further a number of difficulties have been experienced with the operation of prior art plants.

,For example fluctuating hydraulic and nutrient loads affect the degree of breakdown of organic compounds and obnoxious chemicals.

I' Clearly it would be advantageous if the process for treating this waste water

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could be simplified. It would also be advantageous if the process could be improved

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to the point where water discharged from the process could be consistently recycled, O 10 eg for use as irrigation water or toilet water, thereby to reduce overall water

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0~ consumption. An improvement in the treatment of sewerage which improved the removal of residual organic matter and pathogens from the water would have enormous benefits.

SUMMARY OF THE INVENTION According to one aspect of this invention there is provided a method of treating water containing organic matter, the method comprising the steps of contacting water with ozone gas and then allowing the ozone gas to react with organic matter within the waste to assist in breaking down or degrading organic matter within the water.

The step of contacting water to be treated may include passing the water through an ozone reactor assembly where it is brought into contact with ozone gas.

Thus ozone gas which has the ability to break down organic matter is brought into contact with the organic matter in an ozone reactor assembly.

The ozone reactor assembly may comprise a primary conduit or tubular reactor through which water to be treated is passed to bring it into contact with the ozone and a secondary tank reactor in the nature of a tank into which the water is discharged after passing through the primary tubular reactor where it has time to react with the ozone which it has contacted in the tubular reactor.

WO 02/102723 PCT/AU02/00786 Nq 3 0 Thus water is contacted with ozone in a short residence time tubular reactor O and is then discharged into the tank reactor where it is given time to react with the ozone, eg completely in the tank reactor.

The method may include passing incoming water to be treated through the tubular reactor in one direction and water that is carrying the ozone gas is passed V)through the reactor in the opposite direction (ozone carrying water). That is the

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incoming water and ozone gas travel counter-current to each other. The counter

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current flow enhances the concentration gradient which is the driver for absorption of (Ni O 10 ozone by the water.

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The ozone carrying water may contain ozone gas in the form of bubbles dispersed in the body of water.

The incoming water may be directed substantially axially through the tube and may tend towards the radially outer regions of the reactor. The ozone carrying water may flow through the tubular reactor with a flow pattern in the form of a helical spiral. The ozone carrying water may to some extent form a core occupying a relatively radially inner region of the tube.

Preferably the tubular reactor has an at least partially vertical orientation and the incoming water enters the reactor through an inlet towards a relatively upper end thereof and the ozone carrying water is introduced to the tube through an ozone carrying water inlet towards a relatively lower end thereof. Preferably both incoming water and ozone carrying water exit the reactor via the same outlet, eg which opens into the tank reactor. Typically the upper end of the reactor is closed.

Naturally the method also includes mixing ozone with water issuing from the tubular reactor to form ozone carrying water and pumping this back into the tubular reactor as said ozone carrying water that travels counter-current to said incoming water. The ozone carrying water may be drawn from the general body of water in the tank reactor and pumped into a recirculating conduit which is in fluid communication with the tubular reactor.

WO 02/102723 PCT/AU02/00786 NKI 4

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While incoming water makes an initial single pass through the tubular reactor water in the tank reactor can be circulated through the tank reactor several times.

The ozone may be introduced to the ozone carrying water by means of an injector, eg a venturi injector in the recirculating conduit downstream of the pump I' used to pump the ozone carrying water. This way a suitable amount of ozone is

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drawn in to the water where it is dispersed as small bubbles throughout the ozone

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carrying water. This provides a large mass transfer area for contact with the O 10 incoming water. The ozone concentration may be about 10 mg/l of incoming water to

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be treated.

This way the inlet water can be extensively and thoroughly mixed with ozone gas in a relatively short residence time in the single pass through the tubular reactor.

The incoming water to be treated may be retained and recirculated in the tank reactor for a considerable residence time, eg 40-80 minutes, preferably 55-65 minutes.

This gives the ozone time to react with organic compounds within the waste.

The water undergoes some gentle mixing in the tank reactor. This is due to natural convection and circulation caused by the suction of the pump. It is also caused by the discharge of water into the tank reactor.

Thus the purpose of the primary reactor zone is to bring the inlet water into contact with the ozone gas in an energy efficient manner. Thereafter it is discharged into the quieter secondary tank reactor where the ozone is given sufficient time to react more fully with the organic compounds within the water and to at least partially break down the waste.

The secondary tank reactor is typically not full with water and has a gas space or ullage space containing off-gas above the surface of the water. Naturally the gas in the ullage space contains some ozone gas by virtue of its contact with the WO 02/102723 PCT/AU02/00786 Nq 0 water. The concentration of ozone gas in the ullage space depends on its c~ concentration in the water and the phase equilibrium between liquid and gaseous phases. The amount of ozone will also be dependent on the extent to which it has reacted with organic matter in the water.

In addition to assisting to decompose organic matter, the ozone may also In assist in flocculating minerals, and also oxidising other chemical and inorganic

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0material, eg soaps and oils.

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O 10 The method may further include the step of irradiating the water with ultra-

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0~ violet radiation (UV radiation) after it has been subjected to the ozone treatment, after the ozone treatment step described above.

The step of UV treatment may comprise passing the water from the ozone reactor assembly (ozone treated water) through a UV reactor assembly where it is subjected to UV radiation to assist in breaking down further, ie completely, organic matter within the water.

The UV treatment may comprise passing the ozone treated water through a UV reactor assembly where the water is subjected to UV radiation from a UV lamp.

The UV reactor assembly may comprise a tubular reactor through which water is passed and during which passage the water is subjected to UV radiation and also a tank reactor into which the water is discharged after passing through the tubular reactor. All incoming water passes through the tubular reactor. Water may also be recirculated through the tubular reactor.

Preferably the UV lamp is at least able to provide a 99.99% kill rate of faecal colliforms at a UV transference rate of 50% that facilitates the flow therethrough of the volumetric flowrate through the pump and also the maximum expected volumetric flowrate from the ozone reactor assembly.

WO 02/102723 PCT/AU02/00786 Nq 6 O The UV treatment may also include bringing the water into contact with c~ further ozone gas when it is subjected to UV radiation The ozone gas may be generated by the UV lamp, eg at least partially.

The method may also include mixing ozone with water from the tank reactor I' and then mixing this water with incoming water from the ozone reactor assembly and

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then passing this combined stream of water through the tubular reactor and

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0subjecting it to UV radiation. Thereafter the water is discharged back into the general O 10 body of the tank reactor.

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Thus the water from the ozone reactor assembly is passed through the tubular reactor in at least a single pass where it is exposed to UV radiation and some ozone and thereafter it enters the tank reactor where it has a fairly long residence time to effect complete degradation of the water. The introduction of ozone in combination with UV radiation is found to have a synergistic effect and to enhance breakdown of the organic matter in the water.

In a preferred form the ozone is obtained from the off-gas in the ullage space of the tank reactor of the ozone reactor assembly, eg by drawing off the off-gas into a conduit and then injecting it into the UV reactor assembly.

The water from the tank reactor may be pumped by a pump through a recirculation conduit and the ozone may be mixed with the water by an injector, eg a venturi injector. The recirculated water containing ozone is passed continuously through the tubular reactor where it is exposed to UV radiation.

Small amounts of water may be discharged from the tank reactor, eg more or less continuously by means of an overflow outlet as it is replaced by water from the ozone reactor assembly.

WO 02/102723 PCT/AU02/00786 N. 7 O The method may also include regulating the amount of ozone introduced into N the recirculating water by means of a control system. The control system may be as ;Z described above with respect to the ozone reactor assembly.

The method may also include flow balancing upstream of the ozone reactor, eg a flow balancing chamber and a device that balances flow over a period of time.

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According to another aspect of this invention there is provided an apparatus

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for treating water, the apparatus including: O 10 an ozone reactor assembly comprising a tubular reactor for bringing the

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0 water into contact with ozone and a tank reactor for providing the water with an opportunity to react with the ozone.

The tubular reactor is tubular with water to be treated being passed therethrough countercurrent to water containing ozone gas.

The tubular reactor may have a vertical component in its orientation and in a preferred form is vertically extending with a lower end and an upper end. The reactor may have an inlet positioned towards the upper end thereof through which water to be treated may be pumped and an outlet towards the bottom of the reactor for directing water into the tank reactor. The reactor may have a further inlet for admitting ozone carrying water to the tubular reactor. The further inlet may be positioned towards the bottom of the reactor for directing the ozone carrying water countercurrent to the incoming water.

The tank reactor is preferably sized such that the water has a substantial residence time within the reactor to enable it to react as completely as possible with the ozone that was absorbed in the tubular reactor.

The tank reactor will be a closed reactor. The tank reactor is not filled with water and has a closed ullage space containing off gases above the water in the tank.

WO 02/102723 PCT/AU02/00786 N 8 0 O In a particularly preferred embodiment the tubular reactor is physically received within the tank reactor and occupies some of the volume of the tank reactor.

The ozone reactor assembly may include a liquid displacement means, eg a pump, for pumping water in the tank reactor into the tubular reactor and a pump conduit for conduiting water to the tubular reactor. The pump may be a submersible Spump positioned in the tank reactor towards the bottom thereof and the conduit may

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extend upwardly up through the tank reactor and then turn and enter the tubular

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reactor through the upper end thereof.

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0~ The conduit may pass downwardly through the inside of the reactor to the bottom where the further inlet opens up into the interior of the reactor.

The ozone reactor assembly also includes a means for injecting ozone gas into the conduit upstream of its entry into the tubular reactor. The injecting means may comprise an injector, eg a venturi injector, injecting ozone gas into the water that is being pumped into the tubular reactor.

The reactor assembly may also include control means for controlling the amount of ozone that is introduced into conduit. The control means may include a branch line bypassing the injector and a control valve controlling the amount of flow through the branch line.

The outlet of the tubular reactor may discharge the water into the tank reactor at a point spaced above the bottom of the tank reactor. The outlet may generally be positioned at about the height of the water level and some distance above the pump inlet.

The tubular reactor may include an outlet conduit having an open lower end and said outlet spaced some distance above the lower end, eg proximate the upper end of the conduit. The outlet may comprise a laterally extending branch of the conduit and the top of the conduit may be open.

WO 02/102723 PCT/AU02/00786 N, 9 0 0 The tank reactor may also have an outlet for discharging water therefrom. In one form the outlet is an overflow outlet that discharges water, eg more or less continuously, from the tank reactor and the ozone reactor assembly.

The tank reactor may include an outlet water conduit defining said outlet.

The outlet conduit may be as described above with reference to the tubular reactor.

0 The apparatus may further include an ultra violet (UV) reactor assembly in 0addition to the ozone reactor assembly operatively coupled to the ozone assembly o 10 downstream thereof. That is water discharged from the ozone reactor assembly is 0~ then passed through the UV assembly.

Both the ozone and UV assemblies assist in breaking down and degrading the organic compounds in the water. The two together have a synergistic effect such that water discharged from the UV assembly has been effectively treated in a very compact process.

In summary the UV reactor irradiates the water issuing from the ozone reactor assembly with UV radiation. This has produced very efficacious results in the treatment of water.

The UV reactor assembly may include a tank reactor and a tubular reactor.

The tubular reactor may include an incoming water inlet and an ozone carrying water inlet towards one end thereof and an outlet towards an opposed end thereof. The reactor may further include a UV lamp extending along at least part of the tubular reactor for radiating water passing through the reactor with UV radiation.

The UV lamp may include a central filament and a reactor wall of wavy or complex shape.

The tubular component may be physically received within the tank reactor, ie as with the ozone assembly.

WO 02/102723 PCT/AU02/00786 N 0 O In a preferred form the tubular reactor has a substantially vertical orientation with the inlets towards an upper end thereof and the outlet towards the lower end thereof.

The assembly may include liquid displacement means for displacing liquid through the tubular reactor, eg in the form of a pump and a conduit for conduiting the I water into the tubular reactor. Advantageously the pump is a submersible pump

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positioned near the bottom of the tank reactor.

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O 10 The assembly may include means for introducing ozone gas into the UV

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0 reactor assembly. The injecting means may comprise an injector, eg a venturi injector.

In a particularly preferred form the ozone containing gas is off-gas from the tank reactor of the ozone assembly. The apparatus may include a conduit extending from the ullage space of the tank reactor to the conduit of the UV assembly.

The tank reactor may include an outlet, eg for discharging treated water from the reactor. The assembly may include an outlet conduit extending up from the bottom of the reactor defining said outlet spaced above the bottom of the reactor.

The outlet is basically an overflow outlet like that for the tank reactor of the ozone assembly and thus determines the height of water in the tank reactor.

In addition the apparatus may also optionally include a settlement means, eg defining a settlement chamber, upstream of the first reactor assembly. Conveniently a septic tank may be used to perform this function. The settlement means can reduce the amount of ozone and/or UV required in the process.

An apparatus and method 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 one embodiment of the invention with reference to the accompanying 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 WO 02/102723 PCT/AU02/00786 Nl 11

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0 the invention into practice. It is to be clearly understood however that the specific C" nature of this detailed description does not supersede the generality of the preceding statements. In the drawings: Figure 1 is a schematic flow sheet of an apparatus for treating water comprising broadly an ozone reactor assembly and a UV reactor assembly; Fiur Figure 2 is a schematic cross-sectional view of the ozone reactor assembly in 0 Figure 1; and 0 Figure 3 is a schematic cross-sectional view of the UV reactor assembly in o 10 Figure 1.

0 In Figures 1 to 3 reference numeral 1 refers generally to an apparatus for treating waste water, eg sewerage containing organic matter, in accordance with an embodiment of the invention.

The ozone reactor assembly 2 comprises broadly a tank reactor 5 and a tubular reactor 6. Water passes firstly into the tubular reactor 6 and then into the tank reactor 5 and therefore the tank reactor 5 is downstream of the tubular reactor 6.

For convenience the illustrated tank reactor 5 has a broadly cylindrical configuration although clearly other shapes could also be used. The overall shape of the tank reactor 5 is short and fat. The tubular reactor 6 is contained within and received within the tank reactor The tubular reactor 6 by contrast has a long and slim tubular configuration. In the illustrated embodiment the reactor 6 is positioned in a vertically extending configuration with upper and lower ends. The reactor 6 defines an inlet 10 for influent water flowing into the reactor 6 from a feed conduit that is proximate to the upper end of the reactor. The reactor 6 also has an outlet 16 for discharging water from the tubular reactor 6 into the tank reactor spaced from the inlet 10 but also positioned towards the top of the reactor 6.

WO 02/102723 PCT/AU02/00786 N 12 O The outlet 16 is formed by a vertically extending outlet conduit 15. The outlet conduit 15 has an inlet towards the lower end thereof and extends up to the outlet 16 which is one half to two thirds of the distance up the height of the reactor 6 and preferably near the top of the reactor 6. The outlet conduit 15 has a lateral branch defining the actual outlet 16 and a vent opening at the upper end of the conduit The outlet conduit enables an overflow outlet to be provided that retains a suitable I amount of water in the reactor 6 also prevents short circuiting from the inlet to the

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outlet of the tubular reactor 6.

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O 10 A recirculating conduit 8 is positioned within the tank reactor 5 for recirculating

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0N water from the tank reactor 5 to the tubular reactor 6. The recirculating conduit 8 projects through the upper end of the tubular reactor 6 and extends down to the lower end thereof where it defines an inlet 11 into the tubular reactor 6 for the recirculating water. The recirculating conduit 8 may have a formation 12 at the end thereof for deflecting water passing from the conduit 8 into the tubular reactor 6 back up towards the top of the reactor 6. This way the recirculating water is directed upwardly through the reactor 6 counter-current to the influent water that is directed down through the tubular reactor 6.

A pump, eg a submersible pump 7, is coupled in line with the recirculating conduit 8 or pumping water though the conduit 8 and into the tubular reactor 6. An injector 9 such as a venturi injector is also mounted on the recirculating conduit 8.

The injector 9 injects ozone gas into the water passing through the recirculating conduit 8.

The recirculating conduit 8 also has a branch conduit 17 with the control valve 18 for controlling the flow rate of water passing through the conduit 8. The branch conduit 17 and control valve 18 also facilitates control of the amount of ozone in the recirculating water by variation of the fraction of water passed through the branch conduit 17.

The tank reactor 5 also has an overflow outlet 19 and an outlet conduit much like that of the tubular reactor 6. The conduit extends from an inlet towards the WO 02/102723 PCT/AU02/00786 N 13 O lower end of the reactor 5 up to the outlet 19 near the upper end of the reactor O The basic structure of the outlet conduit 20 is the same as that described above with reference to the tubular reactor 6. The purpose of the conduit 20 is to provide an overflow outlet that maintains an appropriate volume of water in the reactor 5 and also prevents short circuiting of water flow from the tubular reactor 6 to the outlet 19.

In The tank reactor 5 has a closed top at its upper end so that it is shut off from

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0the external environment. The overflow outlet 19 which effectively defines the level

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0of water in the tank reactor 5 is spaced below the top of the reactor 5. This defines O 10 an ullage space containing gasses in liquid vapour contact with the water in the tank

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0~ reactor 5. The composition of ullage gasses will be influenced by the composition of the water and will include ozone gas. The reactor 6 has a take off conduit 36 for drawing off the ullage gasses and passing them to the UV reactor assembly 3. The utilisation of the ullage gases in the reactor assembly 3 will be described in more detail below with reference to Figure 3.

The apparatus may also include a flow balancer device (not shown) upstream of the ozone reactor assembly. The flow balancer device may make use of an air driven venturi lifting device to lift air from the balancing tank to the inlet of the reactor 6. This naturally also effects a degree of initial aeration of influent water to be treated.

Referring now to Figure 3 the UV assembly 3 comprises a further tank reactor and a further tubular reactor 31 contained within the tank reactor 30. Again, the tubular reactor 31 is upstream of the tank reactor 30 in terms of water flow through the assembly 3. The assembly 3 also includes a recirculating conduit 34 for recirculating water in the tank reactor 30 back into the tubular reactor 31.

The tank reactor 30 is broadly similar in size and shape to the tank reactor 5 in the assembly 2.

The tubular reactor 31 comprises a header portion 38 and a UV radiating portion 39 operatively coupled to the header portion 38 and downstream thereof.

WO 02/102723 PCT/AU02/00786 14

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o The reactor 31 has a vertically extending orientation with the header portion 38 above the UV generating portion 39.

The header portion 38 effectively provides a chamber for mixing water that is to be introduced to the UV radiating portion 39.

I A connecting conduit 24 operatively connects the outlet of the reactor 5 to a

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feed inlet 47 to the header portion 38 of the reactor 31. Further the recirculating

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conduit 34 also directs water into the header portion 38 through inlet 48. Thus there O 10 are two inlets to the header portion 38 one of the reactor assembly 2 and the other

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0, from the recirculating conduit 34.

The UV radiating portion 39 comprises a cylindrical tube through which water is passed in a longitudinal direction. The tube has a UV radiating member positioned, eg centrally, within the tube and a transparent wall of UV reflective materials surrounding the member. The water is irradiated with UV radiation as it is passed along the tube.

The reactor assembly 3 also includes a submersible pump 33 for pumping water from the tank reactor 30 through the recirculating conduit 34. The assembly 3 also includes an injector 37 for injecting ozone gas into the recirculating water passing through the recirculating conduit 34. The injector 37 is operatively coupled to the conduit 36 connected to the ullage space of the reactor 5 shown in Figure 2.

The gasses in ullage space including ozone are drawn through the conduit 36 and then injected into the recirculating conduit 34 of the assembly 3.

The assembly 3 also includes a branch conduit and a control valve 43 for varying the amount of ozone added to the recirculating water and also for varying the flow rate through the recirculating conduit. The structure and function of this control valve and branch conduit is very similar to that described above with reference to the reactor assembly 2.

WO 02/102723 PCT/AU02/00786 N O The reactor 31 has an outlet 49 at the lower end of the radiating portion 39.

The outlet 49 is formed by a radially inwardly tapering section followed by a perpendicular turn and then a short section of reduced diameter tube that directs water laterally out of the reactor 31.

The tank reactor 30 also has an outlet conduit 40 and an overflow outlet 41 for I discharging water from the reactor 30. The outlet generally has the same structure

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and function as the outlet conduit for the reactor 5 and accordingly will not be

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0described in further detail in this part of the specification.

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0, Optionally a YOOVEE TM systems contactor may be used to agitate water pumped through the UV reactor assembly 3.

In use, influent water to be treated, eg sewerage, is fed through the feed conduit into the reactor assembly 2.

The influent water is passed through the inlet 10 into the tubular reactor 6 from where it is directed in a downward direction down through the reactor 6. In travelling downwardly through the reactor 6 this influent water is brought into contact with ozone gas carrying water from the recirculating conduit 8 moving upwardly through the reactor 6. As a result ozone gas comes into contact with the influent water. After passing through the reactor 6 in a single pass the influent water and recirculating water are discharged through the outlet into the tank reactor In the tank reactor 5 the ozone has plenty of time to react with organic matter and chemicals in the waste water and break them down. The tank reactor 5 in some respects resembles a stirred tank reactor with a reasonable amount of circulation taking place. The average residence time of water in the reactor 5 will typically be about 60 minutes. The residence time is calculated from the time an element of water enters the tank reactor 5 after the initial pass through the tubular reactor 6 until the time that it flows over the overflow outlet out of the reactor 6. The applicant has appreciated that ozone requires a reasonable length of time to react with chemicals and organic matter within the water and the tank reactor provides this time.

WO 02/102723 PCT/AU02/00786 N 16

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C The water in the reactor 5 is recirculated through the tubular reactor 6 at least once, typically several times, while it is resident within the tank reactor 5. Water that 1- is proximate to the submersible pump is drawn into the pump and then pumped around the recirculated conduit and through the tubular reactor 6.

I Water is discharged from the reactor 5 by flowing over the overflow outlet and

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0out of the tank reactor 5 on a more or less continuous basis. The overflow is caused

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by the influx of influent water into the reactor 6 which displaces water passed over O 10 the overflow outlet 19. The height of the outlet 19 determines the height of the body

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0~ of water in the reactor After it has passed out of the reactor assembly 2, the water passes into the UV reactor assembly 3. More specifically the water is passed into the tubular reactor 31 where it is mixed with ozone carrying water that is pumped into the tubular reactor 31 from the recirculating conduit 34. Water from the two sources is appropriately mixed in the header portion 38 and then passed downwardly into the UV radiating portion 39 where it is irradiated with UV radiation. UV radiation acts to progress decomposition of organic matter within the water and also other chemicals within the water. The ozone and the bubbles within the water may assist in cleaning the UV lamp as they pass through the UV radiating portion 39 of the reactor 31. This increases transference which is the rate at which UV radiation is transmitted into the water and hence the rate at which radiation/disinfection occurs. It also extends the life of the lamps.

After the water is passed through the UV radiating portion 39 of the reactor 31 it passes out of the outlet 49 and into the tank reactor 30. The water enjoys a substantial residence time of about 30 to 60 minutes within the tank reactor 30 which provides time to permit further degradation and decomposition of organic material and chemicals within the water. Water is drawn from the tank reactor 30 into the submersible pump 33 and pumped around the recirculating conduit and back into the tubular reactor 31. Each element of water in the reactor 30 will typically be recycled WO 02/102723 PCT/AU02/00786 N 17 0 O through the tubular reactor 31 at least once, typically several times, while it is resident in the tank reactor Ozone is injected through the injector 37 into the water passed through the recirculating conduit 34. As indicated above the injector 37 draws ullage gas from the ullage space in the reactor 5. The presence of ozone in the water being subjected to UV radiation appears to considerably enhance the decomposition

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process.

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O 10 Water flows over the overflow outlet 41 of the reactor 30 on a more or less

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0~ continuos basis. This is effected by the introduction of water to the reactor assembly 3 which displaces a corresponding volume of water out through the outlet 41.

Applicant has found that the water discharged from the tank reactor 30 has a very good quality and is suitable for many uses. For example in preferred forms of the invention water discharged from the UV reactor assembly may be used for watering gardens and flushing toilets.

One significant feature of the method described above with reference to the drawings is that the water in each tank reactor is recirculated through the associated tubular reactor several times. This occurs even when there is no influent water entering the reactor assemblies 2 and 3. This feature of multipass contact with both ozone and UV contributes to the production of usable water as an end product.

Applicant has found that good water quality is obtained notwithstanding considerable fluctuations in the hydraulic load and nutrient load of the influent water. Generally prior art UV systems rely on a single pass of water through a UV reactor. The difficulty with such single pass systems is that the organic matter only gets one opportunity to be irradiated with UV radiation. In a single pass system cloudy water or "cook on" material on to the lamp may mean that some of the waste matter is not subjected to UV radiation.

A further significant feature of the current application is that the UV treatment is integrated into a treatment with ozone. Immediately after the water issues from the ozone reactor it enters the UV reactor. Further ozone is mixed with the water that is WO 02/102723 PCT/AU02/00786 N18 O passed through the tubular reactor 31 where it is subjected to UV radiation. The treatment of water with ozone and also with UV has a synergistic effect. The efficacy of the method is greater than the additive effect that would be obtained by treating ,water with each of these processes separately. Applicant has also established that the use of ozone enables a lower quantity of UV radiation to be used than would otherwise be the case. Applicant has discovered that treatment with UV is enhanced I if the water has a small amount of ozone dispersed therein while it is being radiated

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with UV. The ozone undergoes rapid degradation on being subjected to UV radiation

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0which makes it highly reactive and produces an advanced oxidation effect.

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0N An advantage of a preferred form of the invention is that it provides a compact yet effective apparatus for treating sewerage. The apparatus is relatively simple and comprises two adjacent reactor assemblies and occupies only a small land area. It does not have the large setting tanks of a conventional sewerage plant.

Applicant also points out that the method described above with reference to the drawings uses lower levels of ozone gas per unit volume of water to be treated than prior art ozone processes. Applicant believes that this is achieved because the water which is brought into contact with the ozone gas in the tubular reactor has a substantially longer residence time in the tank reactor to react with the ozone. It may also be assisted by the recirculation of the water in the tank reactor back through the tubular reactor. Applicant believes that ozone gas takes a considerable amount of time to react fully with organic matter in the waste and that this method provides the time for this to occur. As a result applicant believes that its process has the effect that a large proportion of the ozone being introduced into the system is actually used to break down organic material as distinct from simply decaying without producing any decomposition reaction.

Another particularly noteworthy feature of the method described above with reference to the drawings is that water treated by this method has the surprising and unexpected ability to treat pathogens in the water after it has been discharged from the treatment plant. Preferred forms of the applicant's method produce water having high levels of dissolved oxygen typically greater than 7mg/litre and sometimes WO 02/102723 PCT/AU02/00786 19 O up to 10.5mg/litre. In addition the DO levels often persist above 9.5 for several c~ months. As far as the applicant is aware this has not been achieved with prior art processes and is a very strong diagnostic indicator of the efficacy of the treatment process.

In addition the water produced by the process contains small quantities of I' hydrogen peroxide and has a low pH typically about 3.5 to 5.0. This combination of

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very high DO, eg about 9, and low pH, eg about 3.5 to 5.0 is very unusual. The low

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0pH indicates that the water has a low surface tension and a high oxygen carrying O 10 capacity.

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Thus in preferred forms of the invention the treated water that has exited the treatment apparatus continues to undergo precipitation and oxidation. This continues to improve the quality of the water. The treated water also has a high refractive index indicating that it has certain desirable properties. Without being bound by theory the application believes that this is due to the presence of hydrogen peroxide and high levels of dissolved oxygen. It may also be due to the low surface tension of the water produced by the process.

Applicant envisages that the apparatus and method will find particular application in small communities that are relatively isolated and that require a compact and efficient sewerage treatment system. The apparatus will be particularly useful in locations such as islands and remote mining settlements where water supplies are scarce and there is an imperative to recycle water.

In addition to treating sewerage, ie black water, the apparatus and method is also suitable for the treatment of grey water. Grey water often contains matter such as body fat, soaps, lint and hair. This is particularly advantageous as this matter can pose problems if it is discharged back into the environment.

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 WO 02/102723 PCT/AU02/00786 N C 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 is herein set forth.

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Claims (36)

1. A method of treating water containing organic matter, the method comprising the steps of: contacting influent water with ozone gas and then allowing the ozone gas to react with organic matter and chemicals within the water to assist in breaking down or degrading the organic matter within the water, and then subjecting the water to ultra- 0 violet radiation (UV radiation) after it has been subjected to said ozone gas 0 contacting step. o O 0

2. A method according to claim 1, wherein the step of contacting the water with ozone gas comprises passing the influent water through an ozone reactor assembly comprising a tubular reactor and a tank reactor, and the water is brought into contact with the ozone gas in the tubular reactor and then the water is passed into the tank reactor where the organic matter has time to react with the ozone gas.

3. A method according to claim 2, wherein the influent water is contacted with ozone gas by passing it through the tubular reactor counter-current to water recirculated from the tank reactor containing the ozone gas therein.

4. A method according to claim 3, wherein the tubular reactor is orientated with at least some vertical component such that it has an upper end and a lower end, and the influent water is introduced to the tubular reactor through an influent inlet towards the upper end, and the recirculating water carrying the ozone gas is introduced to the tubular reactor through an ozone gas inlet towards the lower end.

A method according to claim 4, wherein both the influent water and the ozone gas carrying water pass out of the tubular reactor and into the tank reactor through a common outlet of the tubular reactor.

6. A method according to claim 5, wherein water recirculated from the tank reactor into the tubular reactor is pumped through a recirculating conduit from the tank reactor to the ozone gas inlet of the tubular reactor. WO 02/102723 PCT/AU02/00786 N 22 O O

7. A method according to claim 6, wherein the ozone gas is injected into the recirculating water in the recirculating conduit by means of an injector on the recirculating conduit, and wherein the ozone gas is dispersed through the water passing through the recirculating conduit as bubbles. t'

8. A method according to claim 7, wherein the amount of ozone gas that is O added to the recirculating water passing through the recirculating conduit can be O controlled by a branch conduit bypassing the injector and a control valve on the O 10 branch conduit. O

9. A method according to claim 8, wherein water in the tank reactor is drawn into the recirculating conduit and recirculated through the tubular reactor one or more times during its residence time in the tank reactor.

A method according to claim 9, wherein influent water that is discharged from the tubular reactor in the tank reactor has an average residence time in the tank reactor of 40 to 80 minutes before it is discharged from the tank reactor through a tank reactor outlet.

11. A method according to claim 10, wherein the tank reactor has a closed top spaced above the surface of the water in the tank reactor and defines an ullage space containing gases that include ozone gas that is in liquid vapour contact with the water in the tank reactor.

12. A method according to claim 1, wherein the step of subjecting the water to UV radiation comprises passing the water through a tubular reactor where it is radiated with UV radiation as it passes there through.

13. A method according to claim 12, including the step of discharging the water into a tank reactor after it has been irradiated with UV radiation in the tubular reactor so that the organic matter has sufficient time for further decomposition reactions to occur. WO 02/102723 PCT/AU02/00786 N 23 O O c

14. A method according to claim 13, wherein the step of subjecting the water to ;Z UV radiation also includes mixing the water with ozone gas when it is being passed through the tubular reactor.

A method according to claim 14, wherein water is drawn from the tank reactor In and recirculated through a recirculating conduit to the tubular reactor, and the ozone O gas is injected into the water in the recirculating conduit before it enters the tubular O reactor. o O 0

16. A method according to claim 15, wherein the tubular reactor has a substantially vertical orientation with an upstream header portion and a downstream UV radiating portion, and the water from the ozone reactor assembly is mixed with recirculated water in the header portion, and then the mixed water is passed through the UV radiating portion and into the tank reactor.

17. A method according to claim 16, wherein the ozone gas that is injected into the water in the recirculating conduit is drawn from the ullage gas in the tank reactor of the ozone reactor assembly.

18. A method according to claim 17, wherein the water in the tank reactor is drawn into the recirculating conduit and recirculated through the tubular reactor one or more times during its residence time in the tank reactor.

19. A method according to claim 18, wherein the water that enters the tank reactor from the tubular reactor has an average residence time in the tank reactor of 40 to minutes before it is discharged through a tank reactor outlet. An apparatus for treating waste water, the apparatus including: an ozone reactor assembly comprising a tubular reactor for bringing the waste water into contact with ozone gas and a tank reactor operatively coupled to the tubular reactor downstream of the tubular reactor for providing matter within the WO 02/102723 PCT/AU02/00786 N 24 0 O waste water with an opportunity to react with the ozone gas once it has been discharged from the tubular reactor; and a UV reactor assembly operatively coupled to the ozone reactor assembly downstream thereof, the UV reactor assembly including a further tubular reactor through which the waste water is passed and during which the waste water is subjected to UV radiation, and a further tank reactor operatively coupled to the I' tubular reactor downstream thereof for providing the water with a further opportunity O to decompose downstream of the tubular reactor.

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21. An apparatus according to claim 20, wherein said one tubular reactor is O 0~ oriented with an at least partially vertical component such that it has an upper end and a lower end and wherein the tubular reactor has an inlet positioned towards said upper end thereof through which waste water to be treated is introduced to the reactor and an outlet spaced therefrom through which water is discharged from the tubular reactor into the tank reactor.

22. An apparatus according to claim 21, wherein the tubular reactor has a further inlet towards the lower end of the reactor for introducing ozone carrying water from the tank reactor back into the tubular reactor, the further inlet directing said ozone carrying water into the tubular reactor in a direction that is counter-current to the flow of water discharged from said one inlet.

23. An apparatus according to claim 22, further including a recirculating conduit for recirculating water from said one tank reactor back through said one tubular reactor and an injector for injecting ozone gas into said recirculating conduit.

24. An apparatus according to claim 23, wherein the tank reactor has a closed top and is closed off from the external environment, and wherein the tank reactor defines an ullage space containing off gasses between the surface of the water and the closed top of the reactor, and the apparatus includes a conduit for drawing off the ullage gasses. WO 02/102723 PCT/AU02/00786 N 0

25. An apparatus according to claim 20, wherein said one tank reactor has an overflow outlet for discharging water from the tank reactor of the ozone reactor assembly.

26. An apparatus according to claim 25, wherein the further tubular reactor of the UV reactor assembly has a waste water inlet that is operatively coupled to the outlet I of said one tank reactor of the ozone reactor assembly by means of a connecting O conduit. O O 10

27. An apparatus according to claim 23, further including a further recirculating O 0 conduit for recirculating water from said further tank reactor into said further tubular reactor.

28. An apparatus according to claim 27, wherein said UV reactor assembly also includes an injector for injecting gas containing ozone into the further circulating conduit and connecting means for connecting the injector to the ullage space of said one tank reactor.

29. An apparatus according to claim 27, wherein the further tubular reactor of the UV reactor assembly includes a UV radiating portion along at least part of the length thereof that radiates UV radiation through water passing broadly axially through said radiating portion.

An apparatus according to claim 29, wherein the further tubular reactor, also includes a header portion upstream of said radiating portion for mixing said recirculating water and water from the ozone reactor assembly before it enters the UV radiating portion.

31. An apparatus according to claim 30, wherein said further tubular reactor has a vertically extending orientation and said header portion is at the top of the reactor and said radiating portion is at the bottom of the reactor. WO 02/102723 PCT/AU02/00786 N 26 O O

32. An apparatus according to claim 31, wherein said UV radiating portion CD N comprises an interior UV radiating member surrounded by a tube of UV reflective material.

33. An apparatus according to claim 20, wherein said further tank reactor has an overflow outlet for discharging treated water from the reactor as water is fed into the I associated reactor assembly. O O

34. An apparatus according to claim 20, wherein in each of said one and further O 10 tubular reactors is contained within and received within its associated tank reactor.

O An apparatus according to claim 27, wherein each recirculating conduit has a pump coupled in line there with for pumping water through the recirculating conduit and through the associated tubular reactor.

36. An apparatus according to claim 34, wherein each recirculating conduit includes a bypass conduit bypassing the injector and a control valve mounted in line with the bypass conduit controlling the flow rate through the recirculating conduit and the amount of ozone gas introduced for recirculating water.