AU2004200072B1 - The treatment of wastewater - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 P/D00011 Regulation 3.2 Original Complete Specification Standard Patent Invention Title: THE TREATMENT OF WASTEWATER The following statement is a full description of this invention, including the best method of performing known to me: Title of the Invention The Treatment of Wastewater Field of the Invention This invention relates to the treatment of wastewater. More particularly, this invention relates to a wastewater treatment system, a method of treating wastewater and to a filtration device.

Backgqround to the Invention The treatment of domestic wastewater for households that are not connected to a sewage reticulation system has for many years been by the use of septic tanks and greywater tanks.

Both septic tanks and greywater tanks rely on the use of naturally occurring organisms to break down waste matter into effluent and solids which are separated from the effluent by sedimentation. In order to facilitate this process, the tanks include baffle members that enhance sedimentation and inhibit the flow of suspended solids into an effluent outlet.

Thus, usually, the inlet of the tank is positioned on one side of the tank and the outlet on an opposite side. It will be appreciated that a flow of wastewater occurs from one side to the other side. Accordingly, the baffles are positioned to extend across this flow path, thus enhancing the capture of waste solids in the wastewater and allowing the organisms to break down the waste solids into a form in which they can settle on a bottom of the tank into sludge that can be physically removed at a later stage, usually with a suitable suction apparatus.

It has been found that the effluent from such a system, when working properly, has a suspended solids content of 200 to 300 ppm. Since filtration is not used with such a system, certain of the suspended solids can incorporate faecal solids which are hazardous as they contain pathogens, such as e-coli.

As is known in the field of wastewater treatment, the biological oxygen demand (BOD) is known as the amount of oxygen used for biochemical oxidation by a unit volume of water at a given temperature and for a given time. Thus, BOD is an indication of the degree of organic pollution in water. It has been found that a conventional septic tank discharges effluent that has a BOD of between 200 ppm and 300 ppm.

Many municipal authorities have determined that such faecal and BOD counts are too high. Accordingly, it has been a requirement for new households in such municipal areas to install wastewater treatment systems that achieve lower suspended solids content and lower BOD. These systems are known as Aerated Wastewater Treatment Systems or AWTS's.

An AWTS is configured to carry out the following processes: Primary sedimentation.

Anaerobic biological treatment.

Aerobic biological treatment.

Secondary sedimentation or clarification.

Disinfection.

Final effluent holding for irrigation.

In order to achieve this, the AWTS has an anaerobic chamber in which the primary sedimentation and anaerobic processes take place. It is usually a two-compartment chamber with predetermined flow and sedimentation capacities depending on the envisaged use.

An aerobic chamber is located downstream of the anaerobic chamber and serves to stabilize the output from the anaerobic chamber. Aeration in this chamber is provided by diffused air, mechanical aeration, percolation through fixed media or by rotating biological contacts.

A secondary sedimentation or clarifying chamber is located downstream of the aerobic chamber to remove settled solids and floating scum passing from the aerobic chamber. This component can have a number of features such as suction pipes to balance the system and a sludge hopper to allow the settled solids to be removed.

A disinfection chamber is positioned downstream of the clarifying chamber and is used to disinfect the effluent from the clarifying chamber. The generally accepted disinfecting agent is chlorine.

Alternatively, or in addition, the AWTS includes an irrigation chamber to receive effluent from the clarifying chamber. An irrigation pump is provided to ensure a suitable rate of discharge from the irrigation chamber.

The AWTS can achieve a BOD (biochemical oxygen demand) of 20 ppm and a suspended solids (SS) count of 30 ppm.

Applicant has found that the AWTS often loses efficiency when placed under even a slight operational overload. This can cause the BOD and SS counts to rise to levels that are the same as the traditional septic and greywater tanks described above.

Furthermore, an AWTS is generally a relatively expensive apparatus, particularly when compared with the traditional septic or greywater tank. This is clear from a consideration of the above description.

The Applicant has conceived the present invention to address the problems associated with the septic or greywater tank and the AWTS.

In this invention, the Applicant proposes to make use of one or more filtration membranes.

Membrane filters have been used for solid-liquid separation in activated sludge (oxygenated sludge containing micro-organisms). Filtered liquid from the membrane filter submerged in the activated sludge vessel is extracted via a tube that connects the membrane filter to a suction pump. Various disadvantages are associated with such suction pumps when used in this format. These include high cost, regular breakdown, excessive electricity consumption and regular maintenance requirements.

In order to address these disadvantages, liquid head pressure has been used as an alternative to a suction pump for driving liquid to be filtered through one or more membrane filters. In this case, liquid to be filtered is stored above the activated sludge vessel. However, as is known, such membrane filters require a substantial amount of pressure to achieve filtration and the liquid head pressure is not always sufficient to achieve filtration.

Further, air entrained in the liquid to be filtered is also required to pass through the membrane filter. Thus, a discharge filtered liquid tube is connected to an uppermost position of the membrane filter to ensure that air is not trapped in the membrane filter. It follows that this configuration may require a treatment vessel that is unacceptably tall.

Summary of the Invention According to a first aspect of the invention, there is provided a wastewater treatment system that includes a vessel into which wastewater can be received, the vessel having a floor and a wall; a cover unit that is mountable on the wall to close the vessel, the cover unit having a support member that covers an opening of the vessel and a closure that is mounted on the support member to define an enclosure, the closure being removable to permit access to the enclosure; a gas displacement device that is positioned in the enclosure; a gas diffuser that is positioned proximate the floor and is connected to an outlet of the gas displacement device; a filtration device that is positioned above the gas diffuser, the filtration device having at least one filtration membrane so that the, or each, filtration membrane is exposed to gas from the gas diffuser, the filtration device including at least one outlet connected to a suction pump so that filtrate can be drawn from the vessel via the filtration device; a disinfection unit that is positioned in the enclosure and is in fluid communication with the, or each, outlet and the suction pump, to disinfect the filtrate; and a flow control arrangement operatively positioned with respect to the vessel to control the flow of wastewater into and out of the vessel.

The, or each, filtration membrane may have a retention rating of between 0.1 and 0.4 microns.

The filtration device may include a support structure that defines at least one filtration zone, the, or each, filtration membrane being positioned on the support structure to bound a respective filtration zone.

The support structure may define at least one gas outlet and at least one filtrate outlet in fluid communication with the, or each, filtration zone such that, when the support structure is in an operative condition, the at least one gas outlet is positioned above the at least one filtrate outlet.

In particular, the support structure may define an air outlet and a filtrate outlet, with the air outlet being positioned in an operatively upper region of the support structure and the filtrate outlet being positioned below the air outlet.

The support structure may be a frame on which the filtration membranes are positioned.

The flow control arrangement may include a float switch arrangement that is positioned in the vessel. The float switch arrangement may be connected to the suction pump to control a level of wastewater in the vessel.

The disinfecting unit may be positioned downstream of the suction pump. The disinfecting unit may be an ultraviolet disinfecting unit.

The vessel may be partitioned so that the vessel defines a treatment chamber and a treated water chamber, an outlet of the suction pump being in fluid communication with the treated water chamber.

The apparatus may include a primary tank into which untreated wastewater is received, the primary tank being in fluid communication with the vessel.

According to a second aspect of the invention, there is provided a method of treating wastewater, the method including the steps of: directing wastewater into a vessel; drawing the wastewater through a filtration device to generate a flow of filtrate; generating a supply of diffused gas to impinge on the filtration device; and subjecting the filtrate to a disinfecting process, wherein the steps of drawing the wastewater through the filtration device and subjecting the filtrate to a disinfecting process are carried out in an integral apparatus.

According to a third aspect of the invention, there is provided a filtration device that includes a support structure that defines at least one filtration zone, the support structure further defining at least one gas outlet and at least one filtrate outlet, the outlets being in fluid communication with the, or each, filtration zone such that, when the support structure is in an operative condition, the at least one gas outlet is positioned above the at least one filtrate outlet, which is positioned so that the filtrate is gravity-fed from the, or each, filtration zone; and at least one filtration membrane that is positioned on the support structure to bound a respective filtration zone.

The, or each, filtration membrane may have a retention rating of between 0.1 and 0.4 microns.

The support structure may define one air outlet and a one filtrate outlet.

The support structure may be a frame on which the filtration membranes are positioned.

According to a fourth aspect of the invention, there is provided an apparatus for filtering a liquid, the apparatus including a vessel in which liquid to be treated is stored; a filtration device positioned in the vessel, the filtration device including a support structure that defines at least one filtration zone, the support structure further defining at least one gas outlet and at least one filtrate outlet, the outlets being in fluid communication with the, or each, filtration zone such that, when the support structure is in an operative condition, the at least one gas outlet is positioned above the at least one filtrate outlet, which is positioned so that the filtrate is gravity-fed from the, or each, filtration zone; and at least one filtration membrane that is positioned on the support structure to bound a respective filtration zone; a gas outlet conduit in fluid communication with the at least one gas outlet that is positioned above the at least one filtrate outlet; a filtrate outlet conduit in fluid communication with the at least one other opening; and an agitating mechanism that is positioned in the vessel to agitate the liquid on an outside of the filtration device to inhibit the build up of detritus on the filtration device.

According to a fifth aspect of the invention, there is provided a method of filtering a liquid across a filtration device that includes a support structure that defines at least one filtration zone, the support structure further defining at least one gas outlet and at least one filtrate outlet in fluid communication with the, or each, filtration zone such that, when the support structure is in an operative condition, the at least one gas outlet is positioned above the at least one filtrate outlet and at least one filtration membrane that is positioned on the support structure to bound a respective filtration zone, the method including the steps of displacing the liquid across the filtration device; 7a removing filtrate from the filtration device at the, or each filtrate outlet; and removing gas from the filtration device at the, or each, gas outlet.

The invention is now described, by way of example, with reference to the accompanying drawings.

Brief Description of the Drawings In the drawings: Figure 1 shows a schematic side view of a first embodiment of a wastewater treatment system, in accordance with the invention.

Figure 2 shows a schematic side view of a second embodiment of a wastewater treatment system, in accordance with the invention.

Figure 3 shows a schematic side view of a third embodiment of a wastewater treatment system, in accordance with the invention.

Figure 4 shows a schematic side view of a fourth embodiment of a wastewater treatment system, in accordance with the invention.

Figure 5 shows a schematic side view of a fifth embodiment of a wastewater treatment system, in accordance with the invention.

Figure 6 shows a schematic side view of a sixth embodiment of a wastewater treatment system, in accordance with the invention.

Figure 7 shows a schematic plan view of a seventh embodiment of a wastewater treatment system, in accordance with the invention.

Figure 8 shows a schematic side view of the wastewater treatment system of Figure 7.

Figure 9 shows a schematic plan view of an eighth embodiment of a wastewater treatment system, in accordance with the invention.

Figure 10 shows a schematic side view of the wastewater treatment system of Figure 9.

Figure 11 shows a schematic sectioned side view of a filtration device, in accordance with the invention.

Figure 12 shows a schematic sectioned front view of the filtration device of Figure 11.

Figure 13 shows a schematic side view of an apparatus, in accordance with the invention, for filtering liquid.

Figure 14 shows a schematic side view of a ninth embodiment of a wastewater treatment system, in accordance with the invention.

Figure 15 shows a schematic side view of a tenth embodiment of a wastewater treatment system, in accordance with the invention.

Figure 16 shows a schematic side view of an eleventh embodiment of a wastewater treatment system, in accordance with the invention.

Detailed Description of the Drawings In the drawings, reference numeral 10 generally indicates a first embodiment of a wastewater treatment system, in accordance with the invention.

The system 10 includes a vessel 12. The vessel 12 has a floor 14 and a wall 16. The vessel 12 can be of any suitable size, depending on the envisaged amount of wastewater to be treated. Further, the vessel 12 may be of a plastics material, such as HDPE or polypropylene, a fibreglass-based material or a corrosion-resistant metal.

The vessel 12 has an inlet, indicated schematically at 18, that is connected to a source of wastewater, in the form of either greywater or blackwater.

A cover unit 22 is positioned on the wall 16 to close the vessel 12. The cover unit 22 has a support member 24 that spans the wall 16. A cover member or cover 26 is positioned on the support member 24 to define an enclosure 34.

A filtration device 20, also in accordance with the invention, is positioned in the vessel 12 a certain distance above the floor 14. The filtration device 20 includes a number of filtration membranes having a retention rating of between 0.1 and 0.4 micron. In this embodiment, instead of the filtration device 20, the filtration device can be selected from a range of commercially available filtration devices, depending on the operational requirements of the system The filtration device 20 has an outlet, indicated at 28, which is connected to a suction pump 30 with a suitable conduit or hose 32. The suction pump 30 is positioned on the support member 24 in the enclosure 34. In these drawings, the outlet 28 is positioned on an operatively upper end of the filtration device 20. However, as will be seen below with reference to figures 11 to 13, the outlet 28 can be positioned on a lower end of the filtration device 20 while an air outlet is positioned on the upper end. It will be appreciated that, in this case, a naturally occurring head of pressure can be sufficient to feed water from the vessel 12, thereby obviating the need for the suction pump An air diffuser 36 is positioned beneath the filtration device 20 to bubble air through the filtration device 20. The air diffuser 36 is connected to an air blower 38 with a suitable conduit or hose 40. The air blower 38 is also positioned on the support member 24, in the enclosure 34.

The bubbles from the diffuser 36 serve to dislodge solids that may cling to the membrane filters. The air also serves to facilitate oxidation of the solids that cling to the membrane filters, thereby enhancing the organic breakdown of the solids.

It will be appreciated that a level of wastewater in the vessel should be strictly controlled. This will ensure that the membrane filters are not exposed to the atmosphere, thereby enhancing their life, and that overflow does not occur. Thus, the system 10 includes a flow control arrangement 42 to control the flow of wastewater into and out of the vessel 12.

The flow control arrangement 42 includes an electronic control unit 44 that is mounted on the support member 24 in the enclosure 34. The arrangement 42 includes a float switch 46 that is connected to the control unit 44. The float switch 46 is configured to generate a signal when a level of wastewater in the vessel 12 reaches a predetermined low level (indicated at 50), above the filtration device and when the wastewater reaches a predetermined high level (indicated at 52). The control unit 44 is connected to the suction pump 30 and to an inflow pump or inlet valve (not shown) which controls the flow of wastewater into the vessel 12. The control unit 44 is configured so that, when the float switch 46 generates the low level signal, the control unit 44 switches off the suction pump 30 and switches on an inflow pump or opens an inlet valve. On the other hand, when the float switch 46 generates the high level signal, the control unit 44 switches off the inflow pump or closes the inlet valve and switches on the suction pump An outlet conduit 54 is connected to the suction pump 30 to direct treated wastewater out of the vessel 12. A disinfecting unit 56 is positioned in the outlet conduit to disinfect the treated wastewater. The disinfecting unit 56 is in the form of an ultraviolet disinfecting unit.

The suction pump 30 is connected to a pressure gauge 150 so that an operator can simply remove the cover 26 and check the gauge 150 to ascertain whether or not the filtration device 20 is blocked.

The cover unit 22 is detachably arranged on the vessel 12 with a suitable fastening arrangement. Thus, an operator can simply lift the cover unit 22 from the vessel 12, gaining direct access to the filtration device 20 for maintenance purposes. Thus, the system 10 is modular. Further, the cover 26 is also detachable from the support member 24 to permit the operator to gain ready access to the components in the enclosure 34.

In use, operation of the suction pump 30 serves to draw the wastewater through the filtration device 20. At the same time, the bubbles from the air diffuser 36 serve to dislodge solids from the filtration members so that the solids are circulated in the vessel. The bubbles also serve to enhance oxidation of the solids.

In Figure 2, reference numeral 60 generally indicates a second embodiment of a wastewater treatment system, in accordance with the invention. With reference to figure 1, like reference numerals refer to like parts, unless otherwise specified.

The system 60 includes a vessel 62 that has a dividing wall 64 that extends from the floor 14 to divide the vessel 62 into a treatment chamber 66 and a treated water storage chamber 68.

The treated water storage chamber 68 is in fluid communication with the outlet conduit 54 to receive treated water. An immersion pump 69 is positioned in the treated water chamber 68 to pump treated water from the chamber 68 for, for example, irrigation or recycling.

In Figure 3, reference numeral 70 generally indicates a third embodiment of a wastewater treatment system, in accordance with the invention. With reference to Figures 1 and 2, like reference numerals refer to like parts, unless otherwise specified.

The system 70 includes a tank 72. The tank 72 has a dividing wall or baffle 74 that defines a primary sedimentation chamber 76 and a secondary sedimentation chamber 80 in the tank 72. An inlet 82 is mounted on the tank 72 to be in fluid communication with the primary sedimentation chamber 76.

The baffle 74 has an opening 272 defined therein to permit wastewater in the primary sedimentation chamber 76 to flow into the secondary sedimentation chamber The vessel 12 is positioned in the primary sedimentation chamber 76. An airlift or submersible pump 274 is positioned in the secondary sedimentation chamber 80 to pump the wastewater into the vessel 12. The vessel 12 is positioned in the tank 72 so that the cover unit 22 extends from the vessel 12. A ground level is indicated by 78.

Thus, as can be seen, the cover unit 22 extends above the ground level 78.

The outlet conduit 54 is in fluid communication with a treated water storage tank (not shown) so that water discharged from the vessel 62 can be stored.

In Figure 4, reference numeral 140 generally indicates a fourth embodiment of a wastewater treatment system, in accordance with the invention. With reference to Figures 1 to 3, like reference numerals refer to like parts, unless otherwise specified.

The system 140 indicates how the system 10 can be used with a conventional septic tank, indicated at 142.

The septic tank 142 is a concrete moulding with a central baffle 144 that divides the septic tank 142 into a primary sedimentation chamber 146 and a secondary chamber 148 that receives wastewater from the primary sedimentation chamber 146. Thus, heavy solids are inhibited from entering the secondary chamber 148.

The system 10 is positioned in the secondary chamber 148, with the inlet 18 in fluid communication with the secondary chamber 148. Thus, the system 10 is able to filter the water in the secondary chamber 148. As before, the cover unit 22 extends from the septic tank 142 to allow access to the vessel 12, by simply removing the cover unit 22.

It will thus be appreciated that the system 10 can very easily be used to upgrade an existing conventional septic tank by simply mounting the system 10 in the septic tank.

It will readily be appreciated that the system 10 can also be mounted outside of the septic tank where necessary.

In Figure 5, reference numeral 90 generally indicates a fourth embodiment of a water treatment system, in accordance with the invention. With reference to Figures 1 to 4, like reference numerals refer to like parts, unless otherwise specified.

'%AeMrnflSflwm' 14 The wastewater treatment system 90 includes a primary tank 92. A baffle 94 is positioned in the primary tank 92 to divide the primary tank 92 into a primary sedimentation chamber 95 and a secondary sedimentation chamber 96. An opening 276 is defined in the baffle 94 to permit wastewater to flow into the secondary sedimentation chamber 96.

An inlet conduit 106 is mounted in a wall 108 of the tank 92 in fluid communication with the primary sedimentation chamber 95. The inlet conduit 106 is T-shaped to allow for wastewater to be siphoned into the tank 92 as a level of wastewater in the tank 92 drops below a high level 278.

A biological filter 98 is positioned in the chamber 96. An outlet conduit 100 is positioned in the chamber 96 and extends through a wall of the tank 92. The outlet conduit 100 is in the form of a T-shaped conduit, with one end of an arm 102 defining an inlet for biologically treated water and the other end of the arm 102 being positioned above the baffle 94 to act as a vent to permit the treated water to enter the inlet. The arm 102 is in fluid communication with a leg 104 that extends through the wall 108. The leg 104 is positioned at a low level 280 so that wastewater stops flowing from the tank 92 at the low level 280.

A treated water storage tank 110 is positioned in the tank 92 and, in particular, in the primary sedimentation chamber 95, to extend from a roof 126 of the tank 92. The tank 110 is a discrete component and its contents are not exposed to the contents of the sedimentation or biological treatment chambers 95, 96.

A submersible pump 112 is positioned in the tank 110 to pump water from the tank 110 for irrigation or non-potable household use.

The system 90 includes a secondary tank 114. The secondary tank 114 has a baffle 118 that divides the secondary tank 114 into a primary chamber 120 and a secondary chamber 122. An opening 282 is defined in the baffle 118 to permit water to flow from the primary chamber 120 to the secondary chamber 122.

The secondary tank 114 has an inlet 116 that is in fluid communication with the outlet conduit 100 and the chamber 120, via the leg 104.

A filtration tank 124 is positioned in the unfiltered water chamber 120 to extend from a roof 128 of the secondary tank 114. The filtration tank 124 defines a volume 130 in which the vessel 12 of the system 10 is received with the cover unit 22 being accessible from outside the secondary tank 114, as shown in dotted lines. The inlet 18 is in fluid communication with the water chamber 122 so that unfiltered water can be pumped into the vessel 12 and through the filtration device 20, as described earlier, via a submersible or airlift pump 132.

The outlet conduit 54 is in fluid communication with the treated water storage tank 110.

In this embodiment, depending on the application, the cover unit (here indicated at 134) can be positioned on the roof 128.

As can be seen in the drawings, the tanks 92, 114 are structurally similar. It follows that this facilitates fabrication of the system In Figure 6, reference numeral 160 generally indicates a sixth embodiment of a wastewater treatment system, in accordance with the invention. With reference to Figures 1 to 5, like reference numerals refer to like parts, unless otherwise specified.

The system 160 is particularly suited for the treatment of greywater. The system 160 includes a greywater tank 162. The tank 162 can, for example, be moulded from a plastics material such as HDPE or polypropylene.

A baffle 284 is positioned in the tank 162 to divide the tank 162 into a primary sedimentation chamber 286 and a secondary sedimentation chamber 288. An opening 290 is defined in the baffle 284 to permit grey water to flow from the primary sedimentation chamber 286 to the secondary sedimentation chamber 288.

A treatment vessel 164 is positioned in the tank 162 to extend from a roof 166 of the tank 162. Thus, an annular volume 180 is defined about the treatment vessel 164.

An inlet conduit 168 is mounted in a wall 170 of the tank 162. A foraminous conduit 172 is mounted on the inlet conduit 168 and is in fluid communication with an overflow pipe 174 that leads to a sewage system. The inlet conduit 168 is positioned at a high water level, indicated at 176. Thus, greywater enters the annular volume 180 via the foraminous conduit 172. If the greywater reaches the high water level 176, the greywater then enters the sewage system via the overflow pipe 174.

A feed conduit 178 is interposed between the secondary sedimentation chamber 288 and the treatment vessel 164. The feed conduit 178 has an inlet 182 and a vent 184, both positioned in the secondary sedimentation chamber 288. The vent 184 is positioned above the high water level 176, while the inlet 182 is positioned below a low water level, indicated at 186.

The feed conduit 178 has an outlet 188 that is positioned in the treatment vessel 164 above a high water level, indicated at 190, of the treatment vessel 164. A return overflow pipe 192 is interposed between the treatment vessel 164 and the primary sedimentation chamber 286 so that, if the water in the treatment vessel 164 moves above the high water level 190, the water flows back into the primary sedimentation chamber 286 via the pipe 192.

An airlift pump 194 is positioned in the secondary sedimentation chamber 288. On operation of the airlift pump 194, air pressure above the high water level 176 is increased and the greywater is driven into the inlet 182 to emerge in the treatment vessel 164.

Suitable flotation or level switches are connected to the airlift pump 194 so that, when the greywater reaches the high water level 176, the airlift pump 194 is activated and when the greywater reaches the low water level 186, the airlift pump is deactivated.

Further flotation or level switches are positioned in the treatment vessel 164 so that the airlift pump 194 is activated when a low water level 196 in the treatment vessel and the high water level 176 are reached and is deactivated when the high water level 190 and the low water level 186 are reached.

Instead of the airlift pump 194, a submersible pump can be used, an outlet of the submersible pump being connected to the inlet 182 of the feed conduit 178.

The vessel 12 is positioned in the treatment vessel 164 to treat the greywater pumped into the treatment vessel 164. The outlet conduit 54 is connected to a recycling vessel 198 that receives the treated greywater. A suitable pump 292 is in fluid communication with the recycling vessel 198 to pump the treated greywater from the vessel 198 for non-potable use.

It will thus be appreciated that the system 160 provides a means whereby greywater can be recycled for non-potable domestic use.

In Figures 7 and 8, reference numeral 200 generally indicates a seventh embodiment of a water treatment system, in accordance with the invention. With reference to Figures 1 to 6, like reference numerals refer to like parts, unless otherwise specified.

The system 200 includes a cylindrical concrete tank 202, which could be an existing septic tank.

A baffle 204 is positioned diametrically in the tank 202, to define a primary sedimentation chamber 206 and a treatment chamber 208. A filtration receptacle 210 and a storage receptacle 212 are positioned in the treatment chamber 208.

The vessel 12 is received in the filtration receptacle 210. The inlet 18 is in fluid communication with the treatment chamber 208. Thus, once primary sedimentation has taken place, the wastewater can be fed into the vessel 12.

The outlet conduit 54 is in fluid communication with the storage receptacle 212 so that treated wastewater can be stored in the receptacle 212.

In Figures 9 and 10, reference numeral 220 generally indicates an eighth embodiment of a water treatment system, in accordance with the invention. With reference to Figures 1 to 8, like reference numerals refer to like parts, unless otherwise specified.

The system 220 includes the system 10. The inlet 18 is connected to an outlet pump 222 of an existing Aerated Wastewater Treatment System (AWTS) 224. As set out in the background of the invention, AWTS's are well known. Therefore the AWTS 224 will not be described in any detail.

The outlet conduit 54 is connected to a treated water storage tank 226, via a flow meter 228.

In figures 11 and 12, reference numeral 230 generally indicates a filtration device, in accordance with the invention. The filtration device 230 is suitable for use with the system 10 and can be understood to mean the filtration device 20 described above.

The filtration device 230 includes a support structure in the form of a frame 232 that defines a filtration zone 234.

The filtration device 230 includes a pair of opposed filtration members 236 that are mounted on the frame 232 to bound the filtration zone 234.

The frame 232 defines two outlets in the form of an air outlet 238 and a filtrate outlet 240. Both the air outlet 238 and the filtrate outlet 240 are in fluid communication with the filtration zone 234. The air outlet 238 is positioned at an uppermost end 242 of the frame 232 and the filtrate outlet 240 is positioned at a lowermost end 244 of the frame 232.

It will be appreciated that the frame 232 both supports and protects the filtration members 236. Further, the frame 232 serves to entrain air towards the air outlet 238 at the uppermost end 242 of the frame 232.

In figure 13, reference numeral 250 generally indicates an apparatus, in accordance with the invention, for filtering a liquid. In particular, the apparatus 250 is suitable for filtering wastewater such as grey- or blackwater. With reference to figures 11 and 12, like reference numerals refer to like parts, unless otherwise specified.

The apparatus 250 includes a vessel 252 in which the wastewater to be filtered is fed, via an inlet pipe 254. The filtration device 230 is submerged in the wastewater.

The vessel 252 is filled to a level 256 resulting in a pressure head that provides the necessary pressure to drive the wastewater through the filtration device 230 and out through the filtrate outlet 240 and a filtrate conduit 258.

The filtrate conduit 258 is connected to the filtrate outlet 240 so that filtrate can be fed, via a control valve 260 out of the filtration zone 234. The control valve 260 is used to ensure that the level 256 does not drop below a certain position 262 which would be detrimental to the operation of the apparatus Solids accumulated in and on the pores of the filtration device 230 are typically washed out by turbulence. Creating currents and bubbles in the vessel 252 proximate the filtration device 230 induces this turbulence. In order to achieve this, a diffuser 264 is positioned beneath the filtration device 230. The diffuser 264 is connected to an air blower 266 via an air pipe 268. Bubbles created by the diffuser 264 move up and over the filtration device 230 to dislodge solids that may have collected on the filtration device 230.

Within the filtration zone 234, air that is entrained in the wastewater rises upwardly towards the air outlet 238. An air tube 270 is connected to the air outlet 238 so that the air can be expelled from the apparatus 250.

The inventor has surprisingly found that by separating the air outlet 238 and the filtrate outlet 240, a shorter vessel 252 can be achieved. Further, backpressure and turbulence in the filtration zone 234 are reduced or eliminated, thus improving liquid flow and reducing liquid head height requirements.

The apparatus 250 may include a plurality of the filtration devices 230, which can all be in fluid communication with a common air outlet and a common filtrate outlet.

Further, a plurality of air outlets and filtrate outlets can be defined by the frame 232 of each filtration device 230 to enhance filtration efficiency.

Instead of using the flat membrane filtration devices 230, a plurality of hollow fibre membranes can be employed and mounted within a frame having an upper end and lower supports. In this regard, the hollow fibre membranes typically extend vertically between the supports in use, with air leaving via the upper support and liquid leaving via the lower support. Waste liquid passes across and into, and is filtered by the hollow fibre membranes in the usual manner.

In figure 14, reference numeral 300 generally indicates a ninth embodiment of a water treatment system, in accordance with the invention. With reference to the preceding figures, like reference numerals refer to like parts.

The system 300 is similar to the system 70. However, instead of the system 10 being positioned in the tank 72, the system 60 shown in figure 2 is positioned in the tank 72.

In figure 15, reference numeral 302 generally indicates a tenth embodiment of a water treatment system, in accordance with the invention. With reference to the preceding figures, like reference numerals refer to like parts.

The system 302 is similar to the system 140 shown in figure 4. However, instead of the system 10 being positioned in the tank 142, the system 60 shown in figure 2 is positioned in the tank 142.

An airlift or submersible pump 312 is positioned in the secondary sedimentation chamber 148 to pump water into the vessel 62.

In figure 16, reference numeral 304 generally indicates an eleventh embodiment of a water treatment system, in accordance with the invention. With reference to the preceding figures, like reference numerals refer to like parts.

The system 304 includes a conventional, two-tank septic tank system that comprises a primary sedimentation tank 306 connected to a secondary sedimentation tank 308 in a conventional manner. An airlift or submersible pump 310 is positioned in the secondary sedimentation tank 308 to pump the wastewater to the system In each embodiment of the wastewater treatment system, there is provided a means whereby a large proportion of suspended solids can removed from wastewater. This includes dangerous suspended solids such as faecal coliform which, to date, cannot be removed with an AWTS as described in the background to the invention.

A particular advantage of the invention is that the cover unit 22 contains all the control components, together with the air blower 38, the suction pump 30 and the disinfecting unit 56. Thus, all these components are able to be removed from the vessel 12 in a single operation to permit a user to gain access to the filtration device for replacement or maintenance. Further, by simply removing the cover 26, a user can gain access to the enclosure 34 for maintenance or replacement of the components in the enclosure 34.

A further advantage is the fact that the system 10 can simply be "dropped" into a conventional septic tank substantially to enhance operation of the septic tank. This is extremely useful, given that the majority of households that do not have municipal sewage services use conventional septic tanks.

Applicant has found that the system 10 can produce effluent with a suspended solids count of less than 1 ppm, a BOD of less than 5 ppm and zero faecal count. This is clearly a substantial improvement on AWTS's, which generally produce a suspended solids count of around 30 ppm and a BOD of around 30 ppm.

22 Still further, Applicant submits that the system 10 is very simple to manufacture, using readily available components. As such, the Applicant envisages that the system 10 will be of lower cost than AWTS's currently available.

Of particular importance is the fact that the system 10 allows for recycling domestic water in non-potable applications. The filtration is sufficient to remove faecal coliform.

Thus, the recycled water is sufficiently clean for safe domestic use. It will be appreciated that this can provide a substantial saving in water use.

Claims (23)

1. A wastewater treatment system that includes a vessel into which wastewater can be received, the vessel having a floor and a wall; a cover unit that is mountable on the wall to close the vessel, the cover unit having a support member that covers an opening of the vessel and a closure that is mounted on the support member to define an enclosure, the closure being removable to permit access to the enclosure; a gas displacement device that is positioned in the enclosure; a gas diffuser that is positioned proximate the floor and is connected to an outlet of the gas displacement device; a filtration device that is positioned above the gas diffuser, the filtration device having at least one filtration membrane so that the, or each, filtration membrane is exposed to gas from the gas diffuser, the filtration device including at least one outlet connected to a suction pump so that filtrate can be drawn from the vessel via the filtration device; a disinfection unit that is positioned in the enclosure and is in fluid communication with the, or each, outlet and the suction pump, to disinfect the filtrate; and a flow control arrangement operatively positioned with respect to the vessel to control the flow of wastewater into and out of the vessel.

2. A wastewater treatment system as claimed in claim 1, in which the, or each, filtration membrane has a retention rating of between 0.1 and 0.4 microns.

3. A wastewater treatment system as claimed in claim 1 or 2, in which the filtration device includes a support structure that defines at least one filtration zone, the, or each, filtration membrane being positioned on the support structure to bound a respective filtration zone.

4. A wastewater treatment system as claimed in claim 3, in which the support structure defines at least one gas outlet and at least one filtrate outlet in fluid communication with the, or each, filtration zone such that, when the support structure is in an operative condition, the at least one gas outlet is positioned above the at least one filtrate outlet.

A wastewater treatment system as claimed in claim 4, in which the support structure defines an air outlet and a filtrate outlet, with the air outlet being positioned in an operatively upper region of the support structure and the filtrate outlet being positioned below the air outlet.

6. A wastewater treatment system as claimed in any one of claims 3 to 5, in which the support structure is a frame on which the filtration membranes are positioned.

7. A wastewater treatment system as claimed in any one of the preceding claims in which the flow control arrangement includes a float switch arrangement that is positioned in the vessel, the float switch arrangement being connected to the suction pump to control a level of wastewater in the vessel.

8. A wastewater treatment system as claimed in any one of the preceding claims, which includes the suction pump that is positioned in the enclosure.

9. A wastewater treatment system as claimed in any one of the preceding claims in which the disinfecting unit is positioned downstream of the suction pump.

A wastewater treatment system as claimed in any one of the preceding claims in which the vessel is partitioned so that the vessel defines a treatment chamber and a treated water chamber, an outlet of the suction pump being in fluid communication with the treated water chamber.

11. A wastewater treatment system as claimed in any one of the preceding claims, which includes a primary tank into which untreated wastewater is received, the primary tank being in fluid communication with the vessel.

12. A method of treating wastewater, the method including the steps of: directing wastewater into a vessel; drawing the wastewater through a filtration device to generate a flow of filtrate; generating a supply of diffused gas to impinge on the filtration device; and subjecting the filtrate to a disinfecting process, wherein the steps of drawing the wastewater through the filtration device and subjecting the filtrate to a disinfecting process are carried out in an integral apparatus.

13. A filtration device that includes a support structure that defines at least one filtration zone, the support structure further defining at least one gas outlet and at least one filtrate outlet, the outlets being in fluid communication with the, or each, filtration zone such that, when the support structure is in an operative condition, the at least one gas outlet is positioned above the at least one filtrate outlet, which is positioned so that the filtrate is gravity-fed from the, or each, filtration zone; and at least one filtration membrane that is positioned on the support structure to bound a respective filtration zone.

14. A filtration device as claimed in claim 12, in which the, or each, filtration membrane has a retention rating of between 0.1 and 0.4 microns.

A filtration device as claimed in claim 13 or 14, in which the support structure defines one air outlet and one filtrate outlet.

16. A filtration device as claimed in any one of claims 13 to 15, in which the support structure is in the form of a frame on which the filtration membranes are positioned.

17. An apparatus for filtering a liquid, the apparatus including a vessel in which liquid to be treated is stored; a filtration device positioned in the vessel, the filtration device including a support structure that defines at least one filtration zone, the support structure further defining at least one gas outlet and at least one filtrate outlet, the outlets being in fluid communication with the, or each, filtration zone such that, when the support structure is in an operative condition, the at least one gas outlet is positioned above the at least one filtrate outlet, which is positioned so that the fitrate is gravity-fed from the filtrate outlet; and at least one filtration membrane that is positioned on the support structure to bound a respective filtration zone; a gas outlet conduit in fluid communication with the at least one gas outlet that is positioned above the at least one filtrate outlet; a filtrate outlet conduit in fluid communication with the at least one filtrate outlet; and an agitating mechanism that is positioned in the vessel to agitate the liquid on an outside of the filtration device to inhibit the build up of detritus on the filtration device.

18. A method of filtering a liquid across a filtration device that includes a support structure that defines at least one filtration zone, the support structure further defining at least one gas outlet and at least one filtrate outlet in fluid communication with the, or each, filtration zone such that, when the support structure is in an operative condition, the at least one gas outlet is positioned above the at least one filtrate outlet and at least one filtration membrane that is positioned on the support structure to bound a respective filtration zone, the method including the steps of displacing the liquid across the filtration device; removing filtrate from the filtration device at the, or each filtrate outlet; and removing gas from the filtration device at the, or each, gas outlet.

19. A new wastewater treatment apparatus substantially as described herein with reference to the accompanying drawings.

A new method of treating wastewater, substantially as described herein.

21. A new filtration device, substantially as described herein, with reference to the accompanying drawings. 27

22. A new apparatus for filtering a liquid, substantially as described herein, with reference to the accompanying drawings.

23. A new method of filtering a liquid, substantially as described herein. Dated this 3 0 th day of March 2004 By my patent attorneys Eagar Buck