Liquid purification or separation – Processes – Separating
Reexamination Certificate
2003-11-14
2004-11-02
Reifsnyder, David A. (Department: 1723)
Liquid purification or separation
Processes
Separating
C210S787000, C210S512100, C209S715000, C209S717000, C209S725000, C209S727000, C209S734000, C055S345000, C055S459100
Reexamination Certificate
active
06811713
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to methods and apparatus of physical separation of solids from fluids or for mixing two fluids. More specifically, the invention relates to methods and apparatus for separating solids from fluids and mixing fluids by using a ring having a plurality of grooves through which fluid passes. The methods and apparatus of the present invention are particularly suitable for use in treatment of aqueous fluids, such as water and wastewater, by dynamic separation of contaminants to be removed and by dynamic mixing of treating agents to be added as part of treatment.
2. Description of the Related Art
Commercial and industrial processes currently employ countless operations involving mixing of fluids (liquids with liquids, gases with liquids, and gases with gases) or separation of fluids or solids from other fluids
For example, excessive contaminants must be removed from the wastewater of food service institutions (restaurants, cafeterias, hospitals, etc.) before the water may be discharged. If established discharge-contamination levels are exceeded, cities and other governmental authorities may impose surcharges on the food service institutions. These surcharges increase the costs of doing business.
Typically, food service establishments are required to have grease interceptors, commonly called “grease traps,” installed in wastewater outlets with sampling wells downstream of the grease traps before the discharge enters the public sewage lines so the authorities can check the discharge from each facility. When the grease traps become full, the contaminants collected in them are removed by vacuum trucks and further treated before discharging to the public sewage.
In addition to the problem of discharging excessive contaminants to public sewage systems, animal fat rendered during the cooking process can congeal when mixed with cold water and clog up the drain lines from the kitchens to the grease traps. When this occurs, the businesses may be shutdown and typically require routing out with a rotor cutter driven by a mechanical cable to open the lines.
Some of the contaminants are destroyed in the grease traps by bacteria. When the contaminants exceed the capacity of what the bacteria can consume, they must be removed from the grease traps by vacuum trucks, or they are discharged to the public sewer, which can result in surcharges as mentioned above.
Bacteria are active only at the limited outer surface of the contaminants to be consumed as food. The bacteria produce enzymes to disperse the contaminants and increase the amount of surface, and the amount of food, available to them. A different enzyme may be required to disperse each contaminant present. When the food is available, bacteria can reproduce in large quantities in very short periods of time. Oxygen dissolved in the water drained into grease traps can become quickly depleted, and aerobic bacteria (those requiring oxygen continuously in order to survive) die. This leaves the task of consuming the contaminants to the anaerobic bacteria (those requiring the absence of oxygen in order to survive). Anaerobic bacteria are not as efficient as aerobic bacteria in consuming the contaminants, and they also produce offensive odors in the process of consuming their food. The offensive odors are prevalent around businesses with grease traps.
Feeding aerobic bacteria in the drain lines from the kitchens has been somewhat successful at either keeping the lines from clogging or increasing the intervals between the times mechanical routing is required. As soon as the aerobic bacteria reaches the grease trap with the oxygen depleted, they die.
Attempts have been made to keep the bacteria alive by bubbling air in grease traps with limited success. Bubbling air even with the finest diffusers creates a large amount of foam in the grease traps. Therefore, air injection has been largely limited to short periods of time and to smaller systems.
Air bubbles rise quickly out of the water, and the bottom of the grease traps return to an anaerobic condition almost immediately preventing the efficient aerobic bacteria from consuming the solids on the bottom of the grease trap. This limits the bubbling of air to the upper part of the grease trap. When oxygen reaches the anaerobic bacteria on the bottom of the grease trap, they die. Therefore, a periodic kill of the anaerobic bacteria on the solids settled on the bottom of the grease trap can be expected. When left for an extended period of time, the solids on the bottom of the grease trap can become packed and act as a seal to prevent oxygen from penetrating into the solids. Only floating contaminants are then consumed by the aerobic bacteria. The offensive odors are also not eliminated.
Therefore, in the food service industry, there is a need for an efficient apparatus and method that can effectively remove particles from wastewater without the problems mentioned above, e.g. incurring surcharges for unsuccessfully meeting contaminant levels, producing offensive odors, requiring the introduction of bubbling air, thus increasing costs, etc.
Another industry faced with the problem of removing contaminants from fluids is the vehicle washing industry. Water used for vehicle washing typically contains significant amounts of suspended solids, dissolved minerals, and organic materials, including oils and other hydrocarbons. Detergents and other chemicals used in the wash operation present further difficulties to the discharge problems. The wash water with the contaminants is typically drained into some type of still pool as a pit or sump. Some of the still pools function as settling basins for the suspended solids and as oil interceptors similar to the grease traps used in food processing facilities.
The water is typically reused in the washing part of the wash cycle until it becomes apparent that the quality of the vehicle wash is no longer satisfactory. Vacuum trucks are then used to remove the contaminants from the sumps and haul them away to disposal sites. Still pools are optimal breeding ground for anaerobic bacteria, which give off a strong and unpleasant odor. The offensive odors are often detected by customers, especially early in the morning when the systems have been shutdown for the night. Bubbling large quantities of air in the still pools can reduce the offensive odors.
The bubbling of air continuously can cause a foaming problem in the sumps. In addition to the offensive odors, governmental regulations may limit the amount of contaminants that can be discharged into the public sewer systems and totally prevent discharge to the environments.
Multiple attempts have been made to improve the process of separating particles from fluid. For instance, U.S. Pat. No. 5,647,977 discloses that the water from vehicle wash facilities can be completely recycled, without water discharge. However, where the cost of water is not a factor and the public sewage system can accept certain contaminants, a complete recycling system may not be cost justified. In such systems, aeration by dissolved oxygen can be used to element the foul odors without the foaming problems typically caused by continuously bubbling air in the sumps. Additional treatment to remove the suspended solids and reduce the organic materials in the sump, other than detergents, can render the water suitable for reuse in the washing part of the vehicle wash cycle, or for discharge where permitted in selected public sewage systems.
Another industry faced with the problem of separation of suspended solid particles from fluids is the water treatment industry. Typically, the solid particles are removed by settling in still pools, centrifugal separation by cyclone filters, and adding flocculating accelerators followed by clarification. Secondary filtration of the fluids often follows the bulk removal operations. The solid particles have to be concentrated and dewatered after separation for disposal. These steps may increase the time and money associated with the particle-removal operation.
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