LEE, Timmy (17/308 Pitt Street, Sydney, NSW 2000, AU)
WOODLEY, Paul, Stair (13-2 Merdu Idaman, Jalan SerojaKg Sungai Kaya Ara, Petaling Jaya, Selangor Darul Ehsan, 47400, MY)
LEE, Timmy (17/308 Pitt Street, Sydney, NSW 2000, AU)
| CLAIMS 1. A kitchen wastewater treatment device for removing oil, fat and grease from kitchen wastewater, the device comprising: a mechanical filter (3) to filter out solid matter from the raw wastewater; and a vessel having an internal baffle plate (6) that extends upwardly from a base of the vessel, to divide the vessel into a primary chamber (25) and a secondary chamber (26); wherein the mechanical filter is removably mounted to a housing disposed above the primary chamber (25), the housing having an inlet (1) for the raw wastewater, whereby in use the wastewater flows from the inlet (1), through the filter (3) and into the primary chamber (25), and then passes therefrom into the secondary chamber (26) by rising up over the baffle plate; and wherein secondary chamber comprises a discharge riser pipe (9) having an inlet (10) open at the bottom of the secondary chamber for extracting wastewater with reduced oil, fat and grease; and a holding chamber for temporary storage of oil, fat and grease separated from the wastewater, the holding chamber having a floating skimmer (12, 13, 14) adapted to float on the oil, fat and grease layer that forms in the vessel whereby any oil, fat and grease entering into the holding chamber through the skimmer is isolated from the surrounding wastewater and may be extracted outside of the device through a hose (17). 2. A kitchen wastewater treatment device according to Claim 1 , wherein the mechanical filter (3) comprises a mesh screen. 3. A kitchen wastewater treatment device according to Claim 2, the mesh screen is inclined to the horizontal. 4. A kitchen wastewater treatment device according to any one of Claims 1 to 3, wherein the mechanical filter is fitted to a drawer (2) that is slidably insertable into the said housing. 5. A kitchen wastewater treatment device according to any one of the preceding claims, wherein the wall of the holding chamber comprises a flexible bellows (13) that permits the skimmer to adjust in height according to the level of said oil, fat and grease layer. 6. A kitchen wastewater treatment device according to any one of the preceding claims, wherein the height of the internal baffle plate (6) is at least one half of the full liquid height in the vessel during normal operation. 7. A kitchen wastewater treatment device according to any one of the preceding claims, wherein the vessel includes a return inlet (21 ) for feeding treated wastewater back to the primary chamber (25). 8. A kitchen wastewater treatment device according to Claim 7, the return inlet is connected to one or more return nozzles (34) located at the bottom of the primary chamber (25). |
FIELD OF THE INVENTION
The invention relates to a device and method for the treatment of kitchen wastewater. As used herein, the term "kitchen wastewater" refers to wastewater collected from the drains of sinks in the kitchens of such places as cafes, restaurants, bars, eateries, coffee shops and the like. The solids material thus comprises mainly food materials of the kind left on plates and dishes to be cleaned after being roughly scraped clean before washing.
BACKGROUND OF THE INVENTION
Kitchen wastewater containing large amounts of fine waste food materials and fat, oil and grease is a major contributor to the problems being faced by local authorities. When this waste material and in particular the fat, oil and grease enter storm water or sewerage piping systems, it causes blockages to these systems and sewers to overflow, also creating problems for sewerage and wastewater treatment plants. Contamination by fat, oil and grease poses a major threat to the global environment. There is a need for a simple and cost effective solution to remove these contaminants to allow clean water discharge to public sewers, storm water drains, wastewater and sewerage treatment plants, inland waterways, seas and oceans. The invention aims to meet this need.
United Kingdom patent GB-A-0125212 describes an apparatus for recovering greasy or fatty refuse and like matter from kitchen wastewater or like water from sinks, baths, or factories in which the level of the liquid in a settling chamber is regulated by means of a float. The floating grease is discharged through a valve or valves at or near the normal level of the liquid. A certain amount of liquid is always maintained in the chamber by arranging the discharge opening at a certain height above the bottom of the settling chamber. The liquid admitted from a waste pipe flows to a space between a vertical partition near one end wall and that end wall which then passes into the settling chamber proper either through an opening or openings in the partition. A certain amount of liquid is always maintained in the settling chamber proper by providing another partition near the opposite end wall of a tank. The floating grease may be drawn off through the above-mentioned one or more valves, at suitable intervals.
SUMMARY OF THE INVENTION
The treatment device of the invention allows small food particles and any other miscellaneous solids material to be removed from a flow of kitchen wastewater and for fat, oil and grease contained in the flow of kitchen wastewater to be trapped.
In one aspect, the invention provides a kitchen wastewater treatment device for removing oil, fat and grease from kitchen wastewater having a mechanical filter to filter out solid matter from the raw wastewater. A vessel has an internal baffle plate that extends upwardly from a base of the vessel and divides the vessel into a primary chamber and a secondary chamber. The mechanical filter is removably mounted to a housing disposed above the primary chamber. The housing has an inlet for the raw wastewater, whereby in use the wastewater flows from the inlet, through the filter and into the primary chamber, and then passes into the secondary chamber by rising up over the baffle plate. The secondary chamber has a discharge riser pipe with an inlet open at the bottom of the chamber for extracting wastewater with reduced oil, fat and grease, and a holding chamber for temporary storage of oil, fat and grease separated from the wastewater. The holding chamber has a floating skimmer adapted to float on the oil, fat and grease layer that forms in the vessel whereby any oil, fat and grease entering into the holding chamber through the skimmer is isolated from the surrounding wastewater and may be extracted outside of the device through a hose.
The small food particles as well as small miscellaneous solids material can be removed from the mechanical filter and disposed of. On the other hand, the trapped fat, oil and grease may be removed periodically using a mobile pump installed or brought to the area where device is used and pumped to a separator device that separates oil, fat and grease from water. A suitable separator device is that described in Malaysian patent MY-125745-A and US patent US-B2-7160450. The separated oil, fat and grease would then be discharged from the separator device (Counter Flow Cyclonic Separator) to a collection container and the wastewater with fat, oil and grease removed may be allowed to flow back to the treatment device of the invention. Such an operation of connecting a separator device may be performed as often as necessary (for example, daily, weekly, etc.) according to the amount of waste oil, fat and grease generated at the usage site. The collected oil, fat and grease may be transported off site for sale and/or further use or processing.
The mechanical filter may comprise a mesh screen. The mesh screen is suitably inclined to the horizontal to prevent or reduce clogging with the solids material. The angle of inclination may be about 5 degrees or more from the horizontal.
The mechanical filter may be fitted to a drawer that is slidably insertable into the housing of the vessel. This enables easy removal and replacement of the filter using the drawer handle. In an embodiment, the wall of the holding chamber comprises a flexible bellows that permits the skimmer to adjust in height according to the level of the oil, fat and grease layer. The bellows is suitably made parachute materials such as polyester. However, any other flexible, non-porous material may equally be used.
The height of the baffle plate is at least one half of the full liquid height in the vessel during normal operation. The full liquid height is determined by the horizontal liquid discharge pipe.
The vessel suitably includes a return inlet for feeding treated wastewater back to the primary chamber. This allows for feedback of clarified wastewater from a connected separator device in the above-described operation for removal of the trapped oil, fat and grease.
The return inlet may be connected internally of the vessel to one or more return nozzles located at the bottom of the primary chamber. This provides the advantage that the formation of the air bubbles through the nozzles speeds up the process of bringing the small entrained particles of fat, oil and grease to the top surface in both primary and secondary chambers thus providing a more efficient separation process within the two chambers.
In another aspect, the invention provides a method of treating kitchen wastewater as disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more clearly understood from the following description of preferred embodiments thereof, when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims.
In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views.
Fig. 1 is a perspective view of a kitchen wastewater treatment device for removing oil, fat and grease from kitchen wastewater with its cover removed; and
Fig. 2 is a perspective view of a kitchen wastewater treatment device showing the manner in which the device may be connected to a separator device and collection container, with the wastewater with fat, oil and grease removed allowed to flow back to the treatment device.
DETAILED DESCRIPTION OF THE EMBODIMENTS
A detailed embodiment of the treatment device includes a rectangular vessel into which is designed a series of stages to remove the various contaminants, these being solid waste food particles and other solid waste which may find its way from kitchen sinks and dish washers. This solid material is first removed by a sliding drawer mechanical filtration system mounted on an upper portion of the device, above the main vessel body, where the wastewater enters. The wastewater is passed through the drawer which has a fine mesh screen to the bottom and here the solid waste contaminants are trapped for removal. The wastewater containing the fats, oils and grease is allowed to pass through the drawer screen and drop into a collection vessel being the main body of the device. In the main body area the fats, oils and grease are allowed to disengage from the wastewater and rise and float to the top surface of the wastewater contained within the main body vessel.
The direction of flow of the wastewater is along the longest length of the main body vessel. This allows more residence time for the wastewater within the device to allow for separation of the fats, oils and grease. Part way along the length of the main body is an internal baffle plate that rises vertically from the bottom of the vessel to at least one-half, and in this embodiment about two-thirds, of the full liquid height. The full liquid height is determined by the horizontal liquid discharge pipe described later. The baffle forms two chambers within the device main body area, these being a primary chamber and a secondary chamber. The wastewater containing the fats, oils and grease is required to pass over the baffle plate from the first chamber to the second chamber as the wastewater travels from one end to the opposite end of the main vessel. Thus, the residual fats, oils and grease are forced to the liquid top surface by the baffle plate, which assists in the separation of the fats, oils and grease contained within the wastewater to float on the liquid top surface.
At the opposite end of the main body to the inlet, there is a discharge pipe set at a suitable height from which the wastewater can exit to sewer or storm water drain. However the discharge pipe is designed in such a way that the discharge pipe rises vertically from a position at a suitable dimension from the bottom of the vessel so that there is a gap created between the vessel bottom and the inlet of the vertical discharge pipe. Therefore, only wastewater from the bottom most area within the main body can pass to the vertical discharge pipe and this wastewater has no or minimal fats, oils and grease as this has now been collected on the top liquid surface within the main body and is not allowed to enter the vertical discharge pipe. The fats, oils and grease become trapped on the liquid top surface. Within the main body area and within the secondary chamber is positioned a floating skimmer device which is set so that fats, oils and grease can be withdrawn from the top surface through the inside of a floating skimmer head to a bottom suction chamber. This chamber is connected to the outside of the main body by means of a pipe which allows the fats, oils and grease to be removed with a quantity of the wastewater by a non- emulsifying pump and pumped to a fat, oil and grease separator. A suitable separator is that described in Malaysian patent MY-125745-A and US patent US patent US-B2- 7160450. Here, the fat, oil and grease are separated and discharged from the separator whilst the wastewater with fat, oil and grease removed flows back to the return inlet connection of the treatment device.
Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 illustrates, in a perspective view, a kitchen wastewater treatment device in which kitchen wastewater containing small food particles and other solid waste as well as fat, oil and grease is fed from the kitchen sink or dishwasher to the device and enters at the wastewater inlet 1 which is sized to suit the required flow rate from the kitchen sink. The wastewater passes through the inlet pipe 1 and exits to flow into a removable slide in drawer screening device 2 that is mounted within a housing located at an upper portion of the device. The drawer is fitted with a suitable sized mesh screen 3 on the bottom of the drawer to separate and trap within the drawer any fine solid food particles or other small entrained solids material that needs to be removed from the wastewater flow. The mesh screen can also be applied to one or more sides of the drawer to also act as a screen to remove the fine solid food particles or other small entrained solids material. The drawer 2 is angled at a small inclination such as five degrees or more from the horizontal to allow any trapped fine food particles or other small entrained solids material to flow to the lowest point of the drawer 2 to maintain areas of the bottom and sides of the screen 3 free of fine solid food particles or other entrained material. The drawer which is removable by handle 24 runs on drawer slides 4.
Wastewater containing the fats, oils and grease but without any fine solid food particles or small entrained solids material passes through the screen mesh 3 into primary chamber 25 which is designed and sized to allow separation of the fats, oils and grease contained within the wastewater. These fats, oils and grease coalesce together within primary chamber 25 and float to the wastewater top surface where they become a fat, oil and grease layer 11. As wastewater enters primary chamber 25 from the discharge of the mesh screen 3, the level within the primary chamber rises. This increase in volume allows the wastewater in primary chamber 25 to flow to secondary chamber 26. However any fat, oil and grease at a low level in the wastewater within primary chamber 25 is forced upwards towards the wastewater top surface as the wastewater flows upwards to pass over baffle plate 6 where the fat, oil and grease recombine and coalesce with the fat, oil and grease layer 11 which in turn moves into secondary chamber 26. Fat, oil and grease are prevented from exiting the device by virtue that the fat, oil and grease remain as a floating layer 11 within the primary and secondary chambers 25 and 26 that is prevented from exiting the secondary chamber 26 as it is trapped by the outlet riser pipe 9. Wastewater with fat, oil and grease removed at the bottom of secondary chamber 26 is allowed to exit in the space between the secondary chamber bottom 27 and the inlet to the outlet pipe 9 through opening 10 in the outlet pipe 9. The wastewater with fat, oil and grease removed rises vertically in outlet pipe 9 until it reaches a pipe junction point where the wastewater with fat, oil and grease removed is made to change direction and flow horizontally to outlet pipe 7 where it now exits the device.
A holding chamber has a floating skimmer 12 adapted to float on the oil, fat and grease layer that forms in the secondary chamber and a flexible bellows 13 which permits the skimmer to adjust in height according to the level of said oil, fat and grease layer. Fat, oil and grease which is trapped within the device as layer 11 can be removed through the floating skimmer head 12. Removal can be accomplished by connecting hose 17 to the leak proof snap-in hose connector 16 and to the inlet of non-emulsifying pump 18, and connection hose 28 to the leak proof snap connector 21 and de-oiled wastewater outlet 29 of the Counter Flow Cyclonic Separator 19 which is described in Malaysian patent MY-125745-A and US patent US-B2-7160450. Referring to Fig. 2, a non-emulsifying pump 18 (meaning a pump which can pump oily liquid without causing it to form an emulsion) when operating and pumping draws liquid through the floating skimmer head 12 and as the volume of fat, oil and grease as well as wastewater reduces in the internal area of the floating skimmer it loses buoyancy and the flexible bellows 13 allows the floating skimmer head to sink and more fat, oil and grease as well as wastewater flow into the floating skimmer head which passes into the suction cup 14 and on through connection hose 17 to the pump 18. The skimmer head 12, bellows 13 and suction cup 14 define a holding chamber that collects the skimmed oil, fat and grease. The skimmer head and suction cup are suitably made of a moulded plastics material, especially polypropylene while the bellows 13 are suitably made of polyester which is a flexible material that permits the skimmer 12 to adjust in height according to the level of the oil, fat and grease layer. In one embodiment, parachute material was used for the flexible bellows. From the pump 18 fat, oil and grease together with wastewater flows to the separator 19 as previously described and the concentrated fat, oil and grease are discharged from the separator 19 through fat, oil and grease outlet 30 and collected in the fat, oil and grease collection drum 31. Wastewater with the fat, oil and grease removed flows from the separator outlet
29 through connection hose 28 and leak proof snap connector 21 and on through down pipe 33 within the primary chamber 25 to one or more return nozzles 34 located at the bottom of chamber 25 where it rejoins the wastewater containing fat, oil and grease within the chamber 25. Wastewater which has had the fat, oil and grease removed and exits from the separator 19 through exit pipe 29 entrains air through a vent pipe opening 35. The air and wastewater with fat, oil and grease removed are mixed together while flowing through pipeline 29 and hose 28. This allows the formation of small air bubbles within the wastewater with fat, oil and grease removed, and this mixture passes through leak proof snap connector 21 and down pipe 33 where it exits into chamber 25 through nozzles 34. The result is that the small air bubbles as they rise to the top surface of the wastewater in chamber 25 carry small entrained particles of fat, oil and grease to the top surface in both chambers 25 and 26 thus speeding up and providing a more efficient separation process within chambers 25 and 26.
In use, a removable cover 23 is fitted over the top of the vessel to cover the portion not covered by the filter housing. The main vessel, baffle and cover are suitably made of moulded plastics material such as polypropylene.
The present embodiment is designed to fit under a sink unit to serve the drainage from two adjacent sinks. However, a device in accordance with the invention can be scaled to a size to suit the application of the user. The invention may also be embodied in many ways other than those specifically described herein, without departing from the scope thereof.
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