AN EFFLUENT TREATMENT UNIT FIELD OF THE INVENTION

The invention relates to an effluent treatment unit. In particular, although not exclusively, the invention relates to an effluent treatment unit for anaerobic or anoxic treatment of liquid effluent before discharge from a primary treatment tank such as a septic tank or the like.

BACKGROUND TO THE INVENTION

Wastewater containing organic contaminants is commonly treated using sedimentation in what is termed primary treatment of the wastewater. In household and small business developments septic tanks and primary treatment tanks of onsite wastewater treatment systems are commonly used for this purpose. The wastewater influent separates in the tank into three distinct layers, namely a sludge layer, a liquid effluent layer and a scum layer. The sludge layer comprises settled solids which accumulate at the base of the tank. The scum layer floats on top of the liquid effluent layer. The liquid effluent layer is formed between the scum layer and the sludge layer.

The liquid effluent layer is relatively clear and may be discharged directly into an absorption field outside the tank. The liquid effluent layer does, however, include some dissolved and suspended organic contaminants. It may thus be necessary to further treat the liquid effluent before discharge from the tank to improve the effluent quality.

The quality of effluent expelled from septic tanks is expected to be regulated through future editions of AS/NZS1546:1. In order to meet or exceed the expected quality standards of treated effluent, the concentration of organic contaminants and suspended solids in the effluent may need to be reduced before being discharged from the septic tank.

One known method of removing solids from effluent is to install an outlet filter. Outlet filters are used to capture solids by acting as a barrier, preventing the passage of solids above a certain size to exit the tank. Outlet filters are known to become blocked or clogged and have not been proven to remove soluble BOD ₅ . There is a need for an improved method and system for consistently reducing organic contaminants and suspended solids from liquid effluent before discharge from a septic tank or the like. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

OBJECT OF THE INVENTION

It is an object of the invention to overcome and/or alleviate one or more of the above disadvantages and/or provide the consumer with a useful of commercial choice.

DISCLOSURE OF THE INVENTION

In one form, although it need not be the only or indeed the broadest form, the invention resides in an effluent treatment unit, the effluent treatment unit comprising:

a reactor tank:

a down-flow media region located within the reactor tank;

an up-flow region located within the reactor tank, the down-flow media region being in effluent flow communication with the up-flow region; an inlet opening formed within the reactor tank through which effluent can flow into the down-flow media region;

an outlet opening formed within the reactor tank through which effluent can flow out of the up-flow region;

a separator located within the reactor tank for separating the down- flow media region and the up-flow region; and

bacterial support media in the down-flow media region for providing bacterial residence in the down-flow media region.

The separator preferably comprises an impermeable wall in the reactor tank which partitions part of the reactor tank into the down-flow media region and the up-flow region.

The reactor tank preferably has an upper end and a lower end, the down-flow media region and up-flow region extending from the upper-end toward the lower end.

The reactor tank preferably includes a settling region below the down-flow media region and the up-flow region. The down-flow media region and up-flow region are preferably in flow communication with each other via the settling region.

The reactor tank preferably has a sloped floor above which at least part of the settling region is defined.

The impermeable wall preferably terminates short of the floor to provide a gap between the floor and the impermeable wall for effluent flow communication between the down-flow media region and the up-flow region.

The floor is preferably sloped with the lowest point located under the down-flow media region.

The impermeable wall is preferably integrally formed with the reactor tank. '

The reactor tank is preferably open-topped.

The reactor tank is preferably made of a corrosion resistant material such as polymer, fibre-glass or concrete.

The reactor tank may be adapted to be located in a primary treatment tank such as a septic tank or the like. Alternatively the reactor tank may be adapted to be located outside a primary treatment tank such as a septic tank or the like.

The bacterial support media preferably has a high surface area to volume ratio. The bacterial support media is preferably made of a corrosion resistant material.

The bacterial support media preferably comprises a number of tubes, sheets or plates, and preferably have mesh-structure walls.

The down-flow media region is preferably a passage through which effluent flows in a direction from the upper end of the reactor tank to the settling region. The bacterial support media preferably fills at least part of the passage.

The up-flow region is preferably a passage through which effluent flows in a direction from the settling region to the upper end of the reactor.

The effluent treatment unit may include bacterial support media in the up-flow region for providing bacterial residence in the up-flow region.

In another form, the invention comprises a primary treatment tank including the effluent treatment unit as defined and described hereinabove.

The effluent treatment unit may be integrally formed with the primary treatment tank.

The outlet opening of the reactor tank of the effluent treatment unit is preferably adjacent to an outlet port of the primary treatment tank. In such instances, effluent expelled from the effluent treatment unit is thus expelled from the primary treatment tank.

The reactor tank of the effluent treatment unit may be integrally formed with the primary treatment tank.

In yet another form, the invention resides in a method of further treatment of effluent, the method including:

receiving effluent, via an inlet opening, in a down-flow media region of an effluent treatment unit;

flowing the effluent downwardly through bacterial support media in the down-flow media region to digest biological matter in the effluent; and flowing the effluent upwardly in an up-flow region of the effluent treatment unit to an outlet opening of the up-flow region.

The method preferably includes flowing the effluent through a settling region between the down-flow media region and the up-flow region.

The method preferably includes displacing solids settled out of the up-flow region to a location below the down-flow media region.

The method preferably includes locating the effluent treatment unit in a primary treatment tank with the inlet opening in a liquid effluent layer of primary treated influent in the primary treatment tank.

In still another form, the invention resides in an effluent treatment unit, the effluent treatment unit comprising:

a reactor tank having an upper end and a lower end

a downwardly extending down-flow media passage located within the reactor tank, the down-flow media passage having an upper end and a lower end;

an upwardly extending up-flow passage located within the reactor tank, the up-flow passage having an upper end and a lower end, the lower end of the down-flow media passage being in effluent flow communication with the lower end of the up-flow passage;

an inlet opening through which effluent can flow into an upper end region of the down-flow media passage;

an outlet opening through which effluent can flow out of an upper end region of the up-flow passage; and

bacterial support media in the down-flow media passage for providing bacterial residence in the down-flow media passage.

The invention extends to an effluent treatment system comprising two or more effluent treatment units as defined and described hereinabove, wherein the outlet opening of one effluent treatment unit is fluidly connected to the inlet opening of an adjacent effluent treatment unit

The effluent treatment unit may be incorporated with any onsite wastewater treatment systems including, but not limited to Aerated Wastewater Treatment Systems, Recirculating Sand Filters, Wisconsin Mounds, Worm Farms and Wetland Systems.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein:

FIG. 1 shows a sectional side view an effluent treatment unit in accordance with one embodiment of the invention;

FIG. 2 shows a diagrammatic perspective view of a reactor tank of the effluent treatment unit of FIG. 1 ;

FIG. 3 shows a sectional side view of the reactor tank of FIG. 2, sectioned along section line Ill-Ill of FIG. 2;

FIG. 4 shows a diagrammatic perspective view of the bacterial support media of the effluent treatment unit of FIG. 1 ;

FIG. 5 shows a diagrammatic perspective view of the effluent treatment unit of FIG. 1 comprising the bacterial support media of FIG. 4 packed in the reactor tank of FIG. 2;

FIG. 6 shows a diagrammatic top view of the effluent treatment unit of FIG. 1 located in a septic tank; FIG. 7 shows a diagrammatic sectional side view of the effluent treatment unit of FIG. 1 located in a septic tank;

FIG. 8 shows a diagrammatic sectional side view of the flow of sewage through the septic tank and effluent treatment unit of FIG. 7;

FIG. 9 shows a diagrammatic sectional side view of the septic tank and effluent treatment unit as shown in FIG. 8, but with the effluent in the septic tank relatively stagnant; and

FIG. 10 shows a diagrammatic sectional side view of an effluent treatment system comprising a number of effluent treatment units connected back-to-back series.

DETAILED DESCRIPTION OF THE INVENTION

In this patent specification, adjectives such as first and second, left and right, top and bottom, etc., are used solely to define one element or method step from another element or method step without necessarily requiring a specific relative position or sequence that is described by the adjectives. Words such as "comprises" or "includes" are not used to define an exclusive set of elements or method steps. Rather, such words merely define a minimum set of elements or method steps included in a particular embodiment of the present invention. In the drawings, like reference numerals refer to like parts.

FIG. 1 shows a sectional view of one embodiment of an effluent treatment unit 10 in accordance with the invention. The effluent treatment unit 10 comprises a reactor tank 100, a separator in the form of an impermeable partition wall 200 within the reactor tank 100, and bacterial support media 300 packed in the reactor tank 100.

FIGs 2 and 3 show the reactor tank 100 including the partition wall 200. The reactor tank 100 has an upper end 102 and a lower end 104. The reactor tank 100 is open-topped.

The reactor tank 100 comprises a sloped floor 106 and a surrounding wall 108. The floor 106 is at the lower end 104 of the reactor tank 100. The surrounding wall 108 extends upwardly from the periphery of the floor 106. The reactor tank 100 is generally D-shaped in top-plan view. The surrounding wall 108 comprises two parallel side walls 110, an end wall 1 12, and a curved back wall 114.

An inlet opening 120 is formed in each of side walls 1 10. Liquid effluent flows into the reactor tank 100 via the inlet openings 120.

An outlet opening 122 is formed in the back wall 1 4. Effluent is discharged from the reactor tank 100 via the outlet opening 122. The outlet opening 122 is higher than the inlet openings 120.

The floor 106 is generally V-shaped in side-view. The floor 102 comprises two inwardly sloping walls 124, 126 which converge to a flat base 128 at the lowest point of the floor 106. The walls 124, 126 project at angle of approximately forty-five degrees from the base 128.

The surrounding wall 108 defines an upper part 130 of the reactor tank 100 and the floor 106 defines a lower settling region 132 of the reactor tank 100.

The partition wall 200 partitions the upper part 130 of the reactor tank 100 into a down-flow media region 202 and an up-flow region 204. The down-flow media region 202 is defined between the end wall 1 12 and the partition wall 200. The down-flow media region 202 has an upper end 210 and a lower end 212. The inlet openings 120 are formed in the side walls 1 10 at the upper end of the down-flow media region 202. The down-flow media region 202 is a passage through which effluent can flow from the inlet openings 120 to the lower end 212.

The up-flow region 204 is defined between the partition wall 200. and the back wall 114. The up-flow region 204 has an upper end 214 and a lower end 216. The outlet opening 122 is formed in the back wall 1 14 at the upper end of the up-flow region 202. The lower end 216 of the up-flow region 204 is above the sloped wall 126 of the floor 106. The up-flow region 204 is a passage through which effluent can flow from the lower end 216 to the outlet opening 122.

The partition wall 200 extends between the two side walls 110. The partition wall 200 is square relative to the side walls 110. The partition wall 200 extends vertically downward from the upper end 102 of the reactor tank 100 towards the floor 106. The partition wall 200 terminates short of the sloped wall 126 of the floor 106. A gap 206 is provided between the floor 106 and the partition wall 200.

The down-flow media region 202 is in flow communication with the up-flow region 204 by a flow passage 208 passing through the gap 206. The flow passage 208 connects the lower end 212 of the down-flow media region 202 with the lower end 216 of the up-flow region 204. The flow passage 208 passes through the settling region 132 of the reactor tank 100.

FIG. 4 shows a perspective view of the bacterial support media 300. The media 300 comprises an array of longitudinally extending tubes 302. The tubes 302 are vertically-orientated. The tubes 302 have cylindrical walls 304 of a mesh-like structure to provide ample surface area for bacterial attachment and biofilm development. The media 300 has a high surface area to volume ratio. The media 300 is adapted and dimensioned to be packed in the down-flow media region 202.

FIGs 1 and 5 show the bacterial support media 300 packed in the down-flow media region 202 of the reactor tank 100. A lower corner of the bacterial support media 300 seats against the sloped wall 124 of the floor 106. The bacterial support media 300 is sized and shaped to fill the down- flow media region 202 below the inlet openings 120. Effluent flowing through the down-flow media region 202 must flow through the media 300.

FIG. 6 shows a top view of the effluent treatment unit 10 located in a septic tank 400. FIG. 7 shows a sectional side view of the effluent treatment unit 10 located in the septic tank 400. The septic tank 400 comprises a cylindrical sidewall 402 and a floor 401. The septic tank 400 has an inlet port 404 and an outlet port 406 formed in the sidewall 402. The inlet port 404 is diametrically opposite the outlet port 406.

The effluent treatment unit 10 is located upright in the septic tank 400. The base 128 of the effluent treatment unit 10 is supported on the floor 401 of the septic tank 400. The back wall 114 of the reactor tank 100 is against the sidewall 402 of the septic tank 400. The curvature of the sidewall 402 of the septic tank 400 is the same as the curvature of the back wall 114 of the effluent treatment unit 10 so that the back wall 114 is contiguous with the sidewall 402. The outlet opening 122 in the reactor tank 100 is adjacent the outlet port 406 in the septic tank 400. An outlet tee 410 is fixed in the outlet port 406. A discharge pipe 412 of the outlet tee 410 extends through both the outlet opening 122 and the outlet port 406. An inlet tee 408 is fixed in the inlet port 404.

FIG. 8 is a sectional side view of the effluent treatment unit 10, in use in the septic tank 400. Influent wastewater containing organic contaminants from an industrial or domestic user flows into the septic tank 400 through the inlet tee 408. The flow of influent into the septic tank 400 is indicated by arrows 403. During primary treatment most solids in the influent settle as sludge 414 at the bottom of the septic tank 400. A layer of liquid effluent 416 forms on top of the sludge 414. The liquid effluent 416 includes some dissolved and suspended biological matter. A layer of scum or froth 418 floats on top of the liquid effluent 416. The scum 418 includes oil, grease and lighter solids.

The inlet openings 120 of the reactor tank 100 are within the layer of liquid effluent 416. The liquid effluent 416 in the septic tank 400 flows into the down-flow media region 202 via the inlet openings 120. The liquid effluent 416 flows through the media 300 towards the lower end 212 of the down-flow media region 202 as indicated by arrows 422. Liquid effluent 416 is forced to flow towards the outlet opening 122 by a hydraulic current pushing the liquid effluent 416 from the inlet openings 120 to the outlet opening 122. The current pushes the liquid effluent 416 through the tubes 302 of the media 300.

The media 300 has bacteria attached thereto. The bacterium grows on the media 300 as an anaerobic biomass in the form of a slime layer or biofilm. The down-flow media region 202 having the media 300 packed therein is a down-flow fixed-film digester which digests organic contaminants flowing through the media 300. The media 300 is fully submerged in the liquid effluent 416. As the liquid effluent 416 flows through the media 300, the anaerobic biomass digests both soluble and particulate organic contaminants in the liquid effluent 416. The anaerobic digestion process releases a biogas, which is mostly a mixture of methane and carbon dioxide. Anaerobic digestion of organic matter in the down-flow media region 202 is a secondary treatment of the liquid effluent 416 in the tank 400.

The secondary treated liquid effluent 416 flows along the flow passage 208 from the lower end 212 of the down-flow media region 202 to the lower end 216 of the up-flow region 204. Flow of the liquid effluent 416 through the flow passage 208 is indicated by arrows 424. The current pushes the liquid effluent 416 from the lower end 216 of the up-flow region 204 up to the outlet tee 410. The secondary treated liquid effluent 416 is expelled from the up-flow region 204 via the discharge pipe 412 of the outlet tee 410. The flow of liquid effluent 416 up the up-flow region 204 is indicated by arrows 426.

The liquid effluent 416 entering the effluent treatment unit 10 flows down the down-flow media region 202 and up the up-flow region 204. Any biological solids not digested in the down-flow media region 202 drops through the settling region 132 to the floor 106 of the reactor tank 100. The settled solids slide down the sloped wall 124 to accumulate at the base 128. Biological solids settling out of the effluent 416 in the up-flow region 204 drop to the sloped wall 126 and also accumulate at the base 128.

Flow of influent into the septic tank 400 via the inlet tee 408 is intermittent. Without inflow of influent there is no hydraulic current through the effluent treatment unit 10 and the liquid effluent 416 becomes relatively stagnant.

FIG. 9 shows the septic tank 400 and effluent treatment unit 10 when there is no influent flow into the tank 400 and the liquid effluent 416 is relatively stagnant. Biological solids 428 settled out of the down flow media region 202 and up-flow region 204 accumulate at the base 128. The Applicant envisages that rising biogas in the media 300 will cause an upward flow of effluent through the media 300 as indicated by arrows 430. The upward flow of effluent in the media 300 lifts the biological solids 428 from the base 128 into the down-flow media passage 202 and hence the media 300. Biological solids settling out of the effluent treatment unit 10 is thus reintroduced back into the media 300 for anaerobic or anoxic digestion. It will be appreciated that the base 128 is located vertically under the down- flow media region 202 and not under the up-flow region 204. The solids settled from the up-flow region 204 are thus displaced to a location below the down-flow media region 202 where the solids will be reintroduced into the media 300 for further digestion as described.

It should be appreciated that the partition wall 200 may be angled instead of the floor 106 being sloped to direct biological solids under the down flow media region 202.

The effluent treatment unit 10 provides anaerobic and/or anoxic secondary treatment of liquid effluent 416 in the septic tank 400. The effluent treatment unit 10 is adapted to reintroduce as much of the biological solids settling to the floor 106 back to the media 300 for further anaerobic digestion. The resultant secondary treated liquid effluent 416 discharged from the septic tank 400 is much clearer, of a higher quality and with reduced BOD5 when compared to the layer of liquid effluent 416 formed in the septic tank 400 by sedimentation only.

FIG. 10 shows a number of effluent treatment units 10, 12, 14 of an effluent treatment system 500 connected back-to-back in series. The effluent treatment unit 10 is the same as described with reference to FIG's 1 to 9. The effluent treatment units 12, 14 are similar to the effluent treatment unit 10, with the only difference being that the effluent treatment units 12, 14 have inlets 16 which fluidly connect to the outlet 122 of an adjacent effluent treatment unit 10, 12, 14. Biological matter in the effluent is progressively removed as the effluent flows from the one effluent treatment unit to the other. Arrows in FIG. 10 show the flow of effluent through the series of effluent treatment units 10, 12, 14.

Throughout the specification the aim has been to describe the invention without limiting the invention to any one embodiment or specific collection of features. Persons skilled in the relevant art may realize variations from the specific embodiments that will nonetheless fall within the scope of the invention. For example, the effluent treatment unit 10 may further include bacterial support media in the up-flow region 204 for providing bacterial residence in the up-flow region 204. Organic contaminants in the effluent flowing through the up-flow region 204 may thus be digested in the up-flow region before discharge from the effluent unit 10.

The effluent treatment unit 10 can be included into other types of onsite wastewater treatment systems including, but not limited to Aerated Wastewater Treatment Systems, Recirculating Sand Filters, Wisconsin Mounds, Worm Farms and Wetland Systems.

It should be appreciated that various other changes or modifications can be made without departing from the spirit or scope of the invention.