AU2012261524B2 - Method and system for treatment of waste - Google Patents

Abstract

- 1 The present invention is directed to a method and system for treating fats, oils and grease waste from commercial and industrial kitchens. The method involves 5 reducing the temperature of the FOG waste in the grease trap and synergistically promoting microbiological digestion of the FOG waste to reduce the amount of organic matter in the discharged effluent. c- - - -- - - -- - - - - - C>O Ii I - .-- J - - - - - - - -- - - cc c --

Description

- 1 METHOD AND SYSTEM FOR TREATMENT OF WASTE FIELD OF INVENTION The present invention relates to a method and system of treatment of fats, oils 5 and grease waste. The present invention has particular but not exclusive application for the treatment of waste from commercial kitchens, restaurants and cafes, food outlets and food courts, food manufacturers, supermarkets, shopping centers and hospitals. O BACKGROUND OF THE INVENTION Fats, oils and grease waste is produced from commercial kitchens, restaurants, cafes and the like. Fats, oils and grease waste are discharged to grease traps where the waste is trapped and evacuated before discharge through the sewage drainage system. Discharge of fats, oils and grease waste through the 5 sewage drainage systems often causes blockages and pollutes the environment into which it is discharged. Biological pollution is a serious problem as it changes the ecological equilibrium with the introduction of a contaminating organic matter. Governments impose strict regulations on the amount of fats, oils and grease waste that can be released in the sewage systems. If the amount of the fats, oils and 0 grease waste exceed the prescribed acceptable levels, the associated businesses are issued with financial penalties. To avoid discharging fats, oils and grease waste into the sewage drainage systems, waste is regularly evacuated from the grease trap and carted away. The larger the volume of the fats, oils and grease waste, more frequent is the need to have the grease traps evacuated. Higher the frequency of ?5 evacuation, higher is the cost in dealing with the fats, oils and grease waste. Consequently, there is an increasing cost associated with the treatment of fats, oils and grease waste from commercial kitchens, restaurants and cafes and the like. Businesses are faced with a dilemma that if they discharge fats, oils and grease waste into the sewage system they could be fined if the levels are higher than the 30 prescribed acceptable levels. If they regularly evacuate the grease trap, the associated costs are comparatively high. Furthermore the discharge of fats oil and grease waste through the sewage systems can cause blockages in the drainage systems and cause an increase in the level of maintenance for these drainage systems.

-2 Currently there is no satisfactory solution in treating with fats, oils and grease waste. OBJECT OF THE INVENTION 5 It is an object of the present invention to provide method and system for treating fats, oils and grease waste that overcomes at least in part one or more of the above mentioned problems. SUMMARY OF THE INVENTION 0 The present invention was developed from the understanding that the fats, oils and grease waste entering a grease trap is generally at a relatively high temperature and realizing that lowering the temperature will solidify at least part of the fats, oils and grease waste and solidified waste can be removed from the grease trap and solidifying part of the waste reduces the concentration of soluble fats, oils and grease 5 waste in the discharged effluent. With this realization, the inventors developed a method and system to reduce the temperature of the fats, oils and grease waste within the grease trap. With the reduction in temperature of the grease, oil and fat waste, the lighter oils would solidify near the top of the accumulated waste while particulate matter would combine and precipitate. The direction to solidify the fats, 0 oils and grease waste is counter to current procedures where it is desirable to keep the fats, oils and grease waste liquid to facilitate discharge from the grease trap. In one aspect the invention broadly resides in a cooling baffle positionable within a grease trap, said cooling baffle includes a continuous conduit that winds in a zigzag manner across a side of the baffle for the length of the baffle wherein the ?5 continuous conduit is adapted to passage cooled fluid through upper then to lower sections of the baffle. The conduit can be supported on the surface of the baffle side, integral with the baffle side or mounted within the baffle. Preferably the conduit is mounted within the baffle and is surrounded by fluid retained within the baffle. The fluid within the 30 baffle is preferably water. The cooling baffle preferably includes a support means for retaining the baffle within the grease trap to allow fats oils and grease (FOG) waste to pass around the baffle. In a preferred form the cooling baffle is attached to each of the opposing side walls of the grease trap.

-3 The cooled fluid is preferably water but can include refrigerant, water gycol solutions and the like. In another aspect the invention broadly resides in a system for treating FOG waste including having one or more cooling baffles as described above. Preferably, 5 the system includes cooling lines positionable about the upper internal walls of the grease trap. Preferably, the system also includes the use of microorganism inoculum for anaerobic and/or aerobic digestion and introduced to the FOG waste prior to the waste entering the grease trap and/or while the FOG waste is in the grease trap. In another aspect the invention broadly resides in a grease trap with one or 0 more of the above mentioned cooling baffles. The one or more cooling baffles are suspended to allow FOG waste to pass below the baffles. The one or more cooling baffles are preferably positioned in the grease trap to be substantially immersed in the FOG waste and form substantially separate chambers between the baffle and the grease trap walls and between the baffles where there are two or more baffles. 5 The cooling baffles can be fitted as part of a new grease trap or retro-fitted to an existing grease trap. The grease trap can preferably include one or more cooling fluid conduits that surround the upper inner walls of the grease trap. In another embodiment one or more walls of the grease trap can be fitted with cooling fluid conduits that extend 0 substantially the height of the wall. The grease trap preferably includes a refrigeration unit operationally connected to the conduits in the baffle and cooling fluid conduit lines. The FOG waste is preferably inoculated with a culture of microorganisms prior to or on entry to the grease trap. The culture of microorganisms is preferably a ?5 mixed culture of microbes that can degrade fats, oils and or grease. In one preferred embodiment, FOG waste within a chamber formed between a baffle and a grease trap wall or between two baffles is inoculated with a microorganism culture capable of aerobic digestion of oils, fats and grease. The microorganism culture is preferably a mixed culture adapted to aerobically degrade 30 oil waste. The microorganism culture is preferably supported on a suspended screen below the top of the waste level within the grease trap. The screen is preferably a mesh screen that provides sufficient surface area to expose as many of the supported microorganisms to the FOG waste substrate.

-4 The use of microorganisms to treat the FOG waste reduces the amount of organic matter in the FOG waste and substantially removes odors from the waste. The use of microorganisms to treat the FOG waste also assist in preventing blockages in the lines and in the grease trap. 5 Preferably each grease trap has a capacity between 1000 liters to 5000 litre capacity. A plurality of the aforementioned grease traps can be linked in series together where the FOG waste load is high. In another aspect the invention is a method of treating fats oils and grease 0 (FOG) waste in a grease trap including introducing FOG waste to the grease trap, said grease trap includes one or more cooling baffles where cooled fluid is circulated in each of the cooling baffles from the top of the baffle to the bottom of the baffle; cooling the FOG waste to a temperature where FOG waste near the surface 5 level substantially solidifies, particulate matter in the subsurface level precipitates and the remainder of the cooled FOG waste forms a liquid portion discharging the liquid portion of the cooled FOG waste. Preferably the solidified and precipitated portion of the cooled FOG waste is evacuated. 0 Preferably the FOG waste is treated in a continuous process where the liquid portion of the treated FOG waste is discharged at a regular rate. Preferably the temperature of the FOG waste is reduced to below 25 0 C. Preferably the FOG waste is retained in the grease trap between twenty minutes and 24 hours. Preferably the FOG waste is retained in the grease trap for ?5 approximately 1 hour. In one preferred embodiment, the temperature of the FOG waste is reduced to substantially 20 0 C and the FOG waste is retained for approximately one hour. The FOG waste is preferably inoculated with a culture of microorganisms prior to or on entry to the grease trap. The microorganisms are more preferably 30 introduced at the drain or pipe where the FOG waste is discarded from the source. Preferably the FOG waste is inoculated with microorganisms as early as possible to maximize the incubation period and increase digestion of the FOG waste. In a preferred embodiment, an inoculum of microorganisms is introduced at the drain upstream of the grease trap at regular intervals. The inoculum dose and or -5 frequency of inoculation is preferably varied depending on the composition of the FOG waste. Where there is an increased level of vegetable fats and peanut oil in the FOG waste, a larger dose of inoculum is added or a regular dose of inoculum is provided at more frequent intervals according to waste loading, waste size and trap 5 size. Preferably there are two or more cooling baffles in the grease trap. Preferably there are one or more cooling fluid conduits that surround the upper inner walls of the grease trap. Preferably the positioning of the one or more cooling baffles in the grease trap 0 enables both anaerobic and aerobic digestion of the fats, oils and grease. The various options and features combinations discussed above with respect to the grease trap aspect also apply to the method. BRIEF DESCRIPTION OF THE DRAWINGS 5 In order that the present invention can be more readily understood reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein: Figure 1 is a diagrammatic view of the preferred embodiment of the grease trap. 0 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to Figure 1 there is shown a grease trap 10 having inlets 11 and an outlet 12. The grease trap 10 is substantially rectangular and has access hatches 13 located in the roof 14 of the grease trap 10. Grease trap 10 has a ?5 uneven floor 15 where the floor section 16 near the inlets 11 is lower than the remaining floor section 17. The floor section 17 slopes downwardly towards floor section 16. There are two cooling baffles 20 mounted within the grease trap 10 and are spaced apart to provide three substantially separate chambers 21, 22, 23. There are also cooling pipes 25 surrounding the upper section 26 of the internal walls 27 of 30 the grease trap 10. Operationally associated with the grease trap is a refrigeration unit 28 that chills water that is circulated via pipes (not shown) through the cooling pipes 25 and baffles 20. The mounted baffles 20 extend downwards. There is a gap 30 formed between the end of each of the baffles 20 and the floor 15 and the gap 30 allows -6 FOG waste to pass between chambers 21, 22, 23. As the FOG waste passes from the inlets 11 to the outlet 12 and passing through chambers 21, 22 and 23, the FOG waste becomes cooler. Each of the cooling baffles 20 has an internally positioned continuous conduit 5 31 that winds across the width of the baffle 20 and for the length of the baffle 20. The continuous conduit 31 allows cooled water to pass from the top to the bottom of the baffle 20 before it returns to the refrigeration unit 28. Consequently the FOG waste near the top of the grease trap 10 is colder than the FOG waste near the floor 15 of the grease trap 10. The upper region of the FOG waste near the surface 34 0 can substantially solidify whereas the lower region of the FOG waste remains liquid. There is also a mesh screen 35 supporting a mixed microbiology culture positioned below the surface 34 of the FOG waste in chambers 22 and 23. These microorganisms facilitate aerobic digestion of the FOG waste. The lower regions of the FOG waste undergo anaerobic digestion. 5 Fats, oils and grease waste is discarded from restaurants, cafes, food courts and other food outlets into sinks and drains that lead to one or more grease traps. The grease traps temporarily retain the FOG waste which is either discharged into the sewer drains or evacuated and collected for disposal by a waste collection contractor. The grease traps can vary in size depending on the amount of waste 0 being discharged from the food outlet(s). In the preferred embodiment, FOG waste is treated as it is discarded into the drain by dosing the drain lines from near or at the drain at the sink with an inoculum of a mixed microbiological culture. In the preferred embodiment where there is a 2,000 liter grease trap 10, 650ml of inoculum is dosed every 24 hours as part of the ?5 treatment program. The inoculum contains a mixed culture of microbes at a concentration of 4x10 11 cells per ml. The inoculum includes Bacillus subtilis, Bacillus licheniformis, Bacillus pantothenticus, Bacillus aminovorans, Bacillus amyloliquiefaciens, Cellulomonas biozatae, Triobacillus versutus, Alcalagines autrophus, Enterobacter aerogenes, Pseudomonas acidovorans, Pseudomonas 30 aminovorans, Pseudomonas stuzerii, Serratia liquefaciens and Flavobacterium sp. There are commercially available inoculums such as the product sold under the trade mark DRAINSOLV that can be used to digest the FOG waste. The inoculum mixes with the FOG waste as it passes through the lines and into the grease trap 10. By introducing the inoculum as the FOG waste is discarded -7 into the lines, a longer incubation period for digestion of waste is achieved. Generally, FOG waste entering the drains is at a temperature between 30 0 C and 40 0 C. The FOG waste is in a liquid form at this temperature but starts to cool as it passes along the drainage lines. 5 The FOG waste enters the grease trap 10 via inlets 11. The baffles 20 and cooling lines 25 reduces the temperature of the FOG waste in the grease trap. There is a temperature gradient between the inlets 11 and outlet 12. While the temperature of the FOG waste near the inlets 11 is approximately 35 0 C, the temperature near the outlet is approximately 20 0 C or lower. The active reduction in temperature of the 0 FOG waste is opposite to current methods where it is desirable to maintain the FOG waste in liquid form for ease of discharge and evacuation. The reduction in temperature of the FOG waste reduces the microbiological activity of the inoculated microbes. The inoculum however, includes bacteria that are biologically active at lower temperatures and are able to degrade FOG waste at lower temperatures. 5 When FOG waste enters the grease trap 10, it enters chamber 21 formed between the baffle 20 and inlet wall 36 of the grease trap 10. The FOG waste undergoes anaerobic digestion in the lower regions of the retained FOG waste. The FOG waste passes through the gap 30 and enters chamber 22. The retained FOG waste in chamber 32 is substantially cooler. In the lower regions of chamber 22, the 0 retained FOG waste undergoes anaerobic digestion. In the upper regions of the retained FOG waste and near the surface 34 of the retained FOG waste, there is aerobic digestion of the FOG waste facilitated by aerobic digestion microorganisms supported on the mesh screen 35. At the surface 34, oils from the retained FOG waste substantially solidify and cake to form a layer across the surface 34 between ?5 baffles 20. In a similar manner, FOG waste passes through gap 30 and enters chamber 23 where there is anaerobic digestion in the lower regions of the retained FOG waste and aerobic digestion in the upper regions of the retained FOG waste. The temperature of the retained FOG waste in chamber 23 has been further reduced and is at or below 20 0 C. The oils near the surface 34 in chamber 23 substantially 30 solidify and cake. During the passage of the FOG waste from the inlets 11 to the outlet 12, the temperature of the FOG waste reduces and precipitates out of solution and falls to the floor 15 of the grease trap 10. The floor 15 of the grease trap 10 has a sloping section 17 that directs precipitants and particulates towards the lower section 16.

- 8 The precipitants and particulates are substantially collected in the lower section 16 of the floor 15. As the FOG waste passes from the inlets 11 to the outlet 12, the FOG waste remaining in liquid form clarifies because of precipitation and anaerobic and aerobic 5 digestion. Precipitation substantially results from a reduction in temperature of the retained FOG waste and/or the slowing of the movement of FOG waste within the grease trap 10. The remaining liquid portion of the retained FOG waste is discharged through the outlet 12 into the storm water drain. The discharged remaining liquid portion is effluent. 0 The liquid portion discharged through the outlet 12 contains a substantially reduced concentration of organic matter. The precipitants and particulate matter undergo an anaerobic digestion within the grease trap 10. Any matter that is not digested is evacuated from the grease trap 10. The caked waste at the surface 34 undergoes aerobic digestion and matter that is not digested can be evacuated from 5 the grease trap 10. The remaining particulate or sludge matter is pumped out of the grease trap 10. The rate of passage between the inlets 11 and outlet 12 can vary depending on the amount of FOG waste, the organic load in the FOG waste, the type of fats, oils and grease in the FOG waste, the amount of inoculum and frequency of dosage 0 of the inoculum. In the preferred embodiment the FOG waste is retained for approximately one hour in the grease trap 10. In the preferred embodiment, the frequency of the dosage of the inoculum is increased where there is a higher concentration of vegetable, peanut and seed oils. 25 Example 1 A city night club and restaurant that is open seven days a week has a kitchen that is operational from 10am to 10pm. The city night club/restaurant closes at approximately 3am. Prior to retrofitting the cooling baffles and cooling lines, the grease trap contained FOG waste with a temperature of approximately 34 0 C. The 30 FOG waste discharged from the outlet of the grease trap had a chemical oxygen demand of 15000 mg/L, total suspended solids of 14000 mg/L and total oil and grease of 16000 mg/L. After the cooling baffles and cooling lines were fitted, the FOG waste discharged from the outlet of the grease trap had a chemical oxygen demand of 4700 mg/L, total suspended solids of 1050 mg/L and total oil and grease -9 of 2600 mg/L. The use of the cooling baffles and cooling lines together with introduction and incubation of a microbiological inoculum dramatically reduced the organic matter in the discharged FOG waste. 5 Example 2 A family chain restaurant in a city suburb opened for lunch and dinner seven days a week. The restaurant was operational from 10am to 11pm, seven days a week. The restaurant had a 2000 liter grease trap which was evacuated once every two weeks (26 times per year). 0 The FOG waste discharged from the outlet of the grease trap had a chemical oxygen demand of 13440 mg/L, total suspended solids of 3930 mg/L and total oil and grease of 8900 mg/L. After the cooling baffles and cooling lines were retrofitted to the grease trap, the FOG waste discharged from the outlet of the grease trap had a chemical oxygen 5 demand of 4500 mg/L, total suspended solids of 1000 mg/L and total oil and grease of 600 mg/L. The use of the cooling baffles and cooling lines together with introduction and incubation of a microbiological inoculum dramatically reduced the organic matter in the discharged FOG waste. The frequency of evacuation of the grease trap was reduced from once every two weeks to once every eight weeks. As 0 a consequence, the cost associated with disposing the FOG waste was dramatically reduced ADVANTAGES An advantage of the preferred embodiment of the invention include is that the ?5 amount of organic matter in the FOG waste is dramatically reduced through a strategic and synergistic combination of temperature control and microbiological digestion. With the reduction in the amount of organic matter in the FOG waste, the frequency of evacuation of waste from the grease trap is reduced and the level of organic matter in the discharged effluent is reduced. There is a consequent 30 reduction in expenses when evacuation occurs less frequently and the level of organic matter in the discharged effluent is low enough to avoid government financial penalties.

VARIATIONS

- 10 It will of course be realised that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein set forth. 5 Throughout the description and claims of this specification the word "comprise" and variations of that word such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps.

Claims (14)

1. A grease trap for collecting fats, oils and grease waste including 5 one or more cooling baffles positionable within the grease trap and including a continuous conduit that winds in a zigzag manner across a side of the baffle for the length of the baffle wherein the continuous conduit is adapted to passage cooled fluid through upper then to lower sections of the baffle, said conduit is supported on the surface of the baffle side, integral with the baffle side or mounted within the baffle; o one or more cooling fluid conduits that surround the upper inner walls of the grease trap; a refrigeration unit operationally connected to the conduits in the baffle and cooling fluid conduit lines; and a screen suspended below the top level of the waste within the grease trap, 5 wherein the screen supports a microorganism culture for aerobic digestion of the waste.

2. A grease trap as claimed in claim 1 wherein a floor of the grease trap has a sloping section for collecting waste particulates and precipitants. 0

3. A grease trap as claimed in claim 1 or 2 wherein the cooled fluid is water or a refrigerant such as a water glycol solution.

4. A grease trap as claimed in any one of the preceding claims wherein the one ?5 or more cooling baffles are positioned in the grease trap to be substantially immersed in the waste and form substantially separate chambers between the baffle and the grease trap walls and between the baffles where there are two or more baffles.

5. A grease trap as claimed in any one of the preceding claims wherein the one 30 or more cooling baffles are suspended to allow waste to pass below the baffles.

6. A grease trap as claimed in any one of the preceding claims wherein an inoculum of microorganisms is introduced prior to or on entry to the grease trap. -12

7. A grease trap as claimed in any one of the preceding claims wherein an inoculum of microorganisms is introduced at a drain upstream of the grease trap and at regular intervals. 5

8. A grease trap as claimed in any one of the preceding claims wherein a plurality of grease traps are linked in series.

9. A method of treating fats oils and grease waste in a grease trap as claimed in any one of the claims 1 to 5, including 0 introducing waste to the grease trap, said grease trap includes one or more cooling baffles where cooled fluid is circulated in each of the cooling baffles from the top of the baffle to the bottom of the baffle; cooling the waste to a temperature where the waste near the surface level substantially solidifies, particulate matter in the subsurface level precipitates and the 5 remainder of the cooled waste forms a liquid portion; discharging the liquid portion of the cooled waste.

10. A method as claimed in claim 9 wherein there is an initial step of dosing the waste with an inoculum of microorganisms prior to or on entry of the waste to the 0 grease trap, the inoculum includes microbes that can anaerobically or aerobically digest the waste.

11. A method as claimed in claim 10 wherein an inoculum of microorganisms is introduced at a drain upstream of the grease trap. 25

12. A method as claimed in claim 10 wherein an inoculum of microorganisms is introduced at regular time intervals.

13. A method as claimed in claim 10 wherein a mixed culture of microorganisms is 30 introduced, said mixed culture includes one or more of the following species: includes Bacillus subtilis, Bacillus licheniformis, Bacillus pantothenticus, Bacillus aminovorans, Bacillus amyloliquiefaciens, Cellulomonas biozatae, Triobacillus versutus, Alcalagines autrophus, Enterobacter aerogenes, Pseudomonas - 13 acidovorans, Pseudomonas aminovorans, Pseudomonas stuzeri, Serratia liquefaciens and Flavobacterium sp.

14. A method as claimed in claim 9 or 10, wherein the temperature of the waste is 5 reduced to below 250C and the waste is incubated in the grease trap between 20 minutes and 24 hours prior to discharge.