Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2000-03-24
2001-11-13
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S620000, C210S173000, C210S767000, C210S774000, C210S799000, C210S800000, C210S787000
Reexamination Certificate
active
06315903
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of Invention.
This invention relates to a method and system for treating non-hazardous liquid waste, such as grease trap waste or raw grease grit and septage. Specifically, the invention describes a system applicable to concentrated liquid waste, such as grease trap wastewater, for removing from the water volatiles, grease, trash, solids, etc., for pre-treatment into a sewage treatment system or full treatment for direct discharge into the environment. Non-hazardous liquid waste is referred in the industry alternatively and comprises raw sewage, grease trap waste, grit trap waste, and processing waste.
2. Related Art
Food preparation, meat and food processing inherently have the byproduct of fats and grease waste. Food, grease and oils are inherent in water from processes and wash-down operations. This waste water forms an emulsion that must first pass through a grease trap, as known in the art of waste water treatment, before the outfall water is allowed to discharge into a sewer collection system. In certain smaller establishments, all sanitary sewage may likewise directed through the grease trap.
The grease trap comprises an infall pipe, which discharges the water/grease/food wastewater drainage into an underground tank capable of holding 300 to 30,000 gallons. Within the tank are barriers that trap and partially separate heavy solids (rock, grit, inorganic material such as eating utensils, personal items, etc.), floating trash (light plastics such as straws), and much of the fats, oils and grease (FOG, comprising vegetable oils, animal fat, tallow) from the food preparation/processing area drains. Periodically the grease trap becomes saturated with solids, trash and FOG's, no longer effectively trapping them, and must be drained (typically every 60-180 days) per local health regulations. A vacuum truck then drops a hose into the tank and sucks out the contents of the tank, including the floating trash, FOG/water emulsion and heavy solids. This raw liquid waste that is sucked up by the vacuum truck must then be disposed. It is this disposal to which this invention is directed, through the inventive treatment method of the raw liquid waste.
Dismissing illegal methods of disposal (dumping on open land or into a storm sewer system), there are several methods in the prior art that treat and dispose the raw waste. The oldest and simplest method is to dump the waste into an open pit, where it is mixed with ash and dirt to hydrate the mixture to form a substantially dry material, which is removed with a backhoe and placed in a landfill. This system creates a severe odor problem and takes large amounts of space in landfill areas.
Another prior art method of raw waste disposal is to dump the waste into an open pit, where it is allowed to separate by gravity. The lighter FOG is skimmed off the top, purified by a method known in the art, and recycled. The remaining concentrated wastewater is sucked out and discharged into a wastewater sewer system. The remaining bottom sludge is stabilized with flyash, removed and buried or taken to a landfill. This method likewise creates a severe odor problem, requires extensive landfill use and does not clean the water to a desired level adequate for pre-treatment requirements.
A third prior art method uses biological augmentation. In this method, microbes and surfactants are mixed with the raw waste. The surfactants break up the fat globules, allowing the microbes to surround and/or ingest the smaller pieces. Bran is often added to the mixture to provide a surface for the microbes to germinate. This process creates additional waste from the bran. Further, it has the limitation of inefficiency due to the microbes dying or becoming dormant before processing the fats, thus releasing the fats back into the wastewater causing potential blockage of the piping in the collection system. The process is expensive due to the cost of microbe replacement and maintenance (such as unclogging lines), and is difficult to regulate.
It would therefore be useful improvement of the prior art for a wastewater treatment system to remove FOG's and other solids from water from a grease trap that does not have the limitations of the prior art, including those described above.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the objectives of this invention are to provide, inter alia, a new and improved method of treating concentrated wastewater sewage that:
has a low odor;
is energy efficient;
regulated inlet flow surges for optimizing treatment processing;
cleans the water in the raw sewage to a level that is acceptable for discharge into a city sewage system or directly to the environment; and
is cost efficient.
These objectives are addressed by the structure and use of the inventive process. When the process is used in the treatment of grease trap waste, vacuum trucks containing raw grease trap waste is offloaded into a sealed pipe through a grinder/emulsifier pump. The liquid then passes through heat exchanger, which also functions as an equalization tank to mitigate inlet surges into the system, and for preheating of the raw waste before entering the main heating vessel. In this vessel, the temperature of the waste is raised to approximately 140° F., at which temperature the FOG reaches a sufficiently low viscosity where the heavy solids (such as rocks, spoons, etc.) cease to be suspended and settle out, where they are removed using a conveyor, preferably screw type.
The liquid then enters a second chamber of the heating vessel where the temperature is raised to 180° F. In this second chamber, a series of serpentine baffles de-emulsify the FOG, allowing the FOG to rise to the top of the vessel for later removal. The FOG is then drawn off with a pump, and the water and remaining suspended solids settle to the bottom of the vessel.
The water and remaining solids are pumped out and passed through the heat exchanger, where their heat is transferred to the incoming raw waste. A vibrating screen having a 200-400 mesh catches and dewaters the majority of the remaining solids. The water is then passed through a centrifuge to eliminate all remaining suspended solids in the water.
The water is then pumped into a high rate aerobic biological reactor, where the volatile organics present are reduced to acceptable concentrations for discharge into a local wastewater treatment sewer. The water then enters a holding tank, where it can be used for wash-down purposes. In this final tank, ozone or other disinfectants (such as chlorine) can be recirculated for further volatile reduction, if so desired.
If it is desired to reduce the Biological Oxygen Demands (BOD) to a level acceptable for release of the water directly to the environment (e.g. discharge into a local river), additional cycles through high rate aerobic biological reactors are taken until the BOD is acceptably low.
Other objects of the invention will become apparent from time to time throughout the specification hereinafter disclosed.
REFERENCES:
patent: Re. 31185 (1983-03-01), Greenfield
patent: 3623976 (1971-11-01), Cessna
patent: 4013516 (1977-03-01), Greenfield et al.
patent: 4040958 (1977-08-01), Rammler
patent: 4686049 (1987-08-01), Klobenzer et al.
patent: 4975195 (1990-12-01), Urbani
patent: 5098584 (1992-03-01), Leen
patent: 5545326 (1996-08-01), Petering
Barry Chester T.
Downstream Environmental, LLC
Keeling Law Firm
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