Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
1999-02-24
2001-02-06
Upton, Christopher (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S615000, C210S630000, C210S151000, C210S262000, C210S299000, C210S512100, C210S903000
Reexamination Certificate
active
06183643
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to denitrification of a liquid, and more specifically to a vertical, upward-flow denitrification tank.
BACKGROUND OF THE INVENTION
For at least 25 years, municipal wastewater treatment plants have been aware of the need to reduce or eliminate nitrogen compounds from their discharged effluent. Typically, they use a scheme of oxidizing ammonia to nitrate, then convert the nitrate to nitrogen gas. Microbiological processes are usually used for both steps of the process.
Since nitrate compounds are very soluble and mobile in water, they are found naturally only in arid climates. In the United States, though, nitrates are a common contaminant of groundwater in agricultural areas. Run-off from fertilized fields and from locations where animals, such as cattle, pigs and chickens, are raised in high concentration, such as dairy farms and animal feed operations, often contains enough nitrate to affect nearby water wells.
Installations to treat municipal wastes are complex systems. The several types of microorganisms employed to treat ammonia, nitrate, phosphate, and other classes of waste are generally sensitive to their environment, and do not thrive and perform their functions if conditions of Ph, oxidation or reduction potential, nutrient content, and other factors are not within the acceptable range.
Municipal sewage varies widely in these conditions. Sometimes, compounds toxic to microbial life appear suddenly. Sewage treatment plants, thus, must constantly monitor the incoming waste stream and the processes used for treatment. Technicians adjust the process conditions frequently to keep the microbial and other systems running efficiently. Failure to do so can result in release of insufficiently-treated effluent, or shutdown of the plant until the microorganisms are nursed back to health.
Municipal sewage treatment systems are made up of many tanks, covering a few acres of land. The piping, valves, access ports between tanks provide many opportunities for leaks and must be inspected daily, at least. Many of the systems require frequent backflushing and other maintenance of filters.
By comparison, agricultural well water in a given location has a simple composition, which does not fluctuate quickly. The impurities are relatively dilute and readily water-soluble.
Therefore, there has been a need for a simple nitrate removal system for rural agricultural areas that can have optimal operating conditions designed into it. Such a system should be robust, require little adjustment and maintenance, use as little electricity as possible, and be easy to transport to the site and install.
SUMMARY OF THE INVENTION
The present invention meets the need for a robust and simple nitrate treatment system for well water for agricultural use, such as drinking water for animals. In the preferred embodiment, the denitrification is accomplished within a single, vertical process tank with three process sections.
The bottom section, called the sludge section, contains an activated sludge in an anoxic, nearly anaerobic, condition. The water to be denitrified is injected into the bottom of the sludge section by nozzles, which cause the water to flow upward through the sludge in a helix. The helical flow allows slow and thorough mixing of the water to be treated with the sludge, without use of gas agitation or a stirring device. The preferred shape of the tank bottom is an inverse cone.
Water from the sludge section passes upward through a filter that retains particles in the range of 5 to 100 microns as it passes upward through a fabric filter. A flush valve just below the filter provides convenient backflushing by gravity of the filter.
An anaerobic denitrification process section, above the filter, contains an array of solid support strips coated with a film of denitrifying bacteria. These strips may contain the nutrients needed by the bacteria.
At the upper boundary of the anaerobic section, a grid of perforated pipes injects compressed air into the water. In the preferred embodiment, the water simultaneously flows upward through a biobed of aerobic bacteria on support strips similar to those below, in the anaerobic section. In this oxidation process section, the aerobic bacteria convert any odoriferous products of the anaerobic process, such as sulfides, to oxidized forms that are gaseous or non-noxious.
The treated water leaves the process tank through a pipe at the top. If it is desired to sterilize the water of introduced bacteria, the water may be directed to a final purification system. A standard biomass filter is used to remove clumps of bacteria that may have become dislodged from the support strips. A commercial ozonation device destroys living bacteria and renders the water sterile. Ultraviolet treatment could be instead, if desired. A slow sand filter, membrane cartridge, or bag filter may be used for filtration to about 2 microns.
Other features and many attendant advantages of the invention will become more apparent upon a reading of the following detailed description together with the drawings in which like reference numerals refer to like parts throughout.
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AG Tech International, Inc.
Calif Tervo
Upton Christopher
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