Animal husbandry – Aquatic animal culturing – Fish culturing
Reexamination Certificate
1998-03-26
2002-05-07
Price, Thomas (Department: 3643)
Animal husbandry
Aquatic animal culturing
Fish culturing
Reexamination Certificate
active
06382134
ABSTRACT:
TECHNICAL FIELD
This invention relates to a fish rearing system having a water circulation system for circulating the rearing water in a fish rearing water tank, and, particularly to a fish rearing system capable of performing water quality control at a low cost by a rational combination of devices.
BACKGROUND ART
Conventionally known fish rearing system is generally comprising a water circulation system for discharging the rearing water from a discharge port provided at the bottom of a rearing water tank and re-supplying the discharged water to the rearing water tank.
Since the fish rearing system of this type is designed to rear fish in the rearing water tank, a special consideration is given to contamination of the water caused by the metabolism of fish. Thus, the heretofore proposed art has concentrated on how efficiently the water contamination can be removed within a limited space of the rearing water tank, the water circulation system and the like.
In order to improve the efficiency of the fish rearing system by removing the water contamination and regulating the rearing environment, the fish rearing system generally includes a filter device for capturing residual feed and fish feces contained in the water, an aeration device for supplying oxygen to the rearing water, an ammonium treating device for treating ammonium generated during rearing, or an ozone supplying section.
In performing water quality control of the fish rearing system, it is particularly important to control contents of salt, mineral, residual feed and fish feces, protein and ammonium, and to treat nitrogen dioxide, nitrogen dioxide, carbon oxide and oxygen which are generated during decomposition process of the above-mentioned substances. For example, it is known that ammoniac nitrogen is harmful to fish. It is observed that when the ammoniac nitrogen content in the rearing water exceeds 3 ppm, certain kinds of fish lose their eating activity sharply. Although it is known that a content of nitrogen nitrate generated during nitrifyingly decomposition of ammoniac nitrogen is not so harmful to fish, an acceptable tolerance for fish rearing is limited to the range of from 50 ppm to 500 ppm, though the tolerance depends on different kinds of fish.
Fish feces, an organic substance such as protein, and ammonium produced by a biological metabolism of fish and residual feed are particularly giving a great effect to increase water contamination, and these ill-effect elements are removed by various treatment device, or purified by the metabolism function of microorganisms which are present in the water circulation path. For an index of water contamination, the term of “biochemical oxygen demand (hereinafter referred to as “BOD”)” is generally used. The BOD represents an amount of oxygen (mg/l) dissolved and contained in the water which is consumed by proliferation activity or breathing function of bacteria which are present in the water.
For example, a nitrogen compound (ammoniac nitrogen, nitrite-nitrogen, nitrate-nitrogen), which is generated by the metabolism of fish and which is one of elements to be limited in biological production, is purified by utilizing the metabolism function of, so-called denitrification bacteria and nitrification bacteria, such as, aerobic microorganisms or anaerobic microorganisms present in the water circulation path. Ammoniac nitrogen (NH
4
—N) is biologically oxidized by nitrification of aerobic microorganisms and turned into nitrite-nitrogen or nitrate-nitrogen (NO
2
—N, or NO
3
—N), and biologically reduced further to nitrogen-oxide gas (NO
2
) or nitrogen gas (N
2
) by anaerobic bacteria. During this process, anaerobic bacteria require the presence of an organic carbon source serving as a hydrogen supply body for acquiring the energy required for biological reduction.
In the case where the metabolic function of bacteria is utilized, it is necessary that a physiological activities should be taken into consideration so that the metabolism of microorganisms can be effected under the suitable condition.
For example, in nitrification of ammoniac nitrogen (NH
4
—N), a nitrification rate reaches to about 100% when a BOD load is low, but the nitrification rate is rapidly lowered when the BOD load approaches a certain value. Further, it is known that, in denitrification of nitrite-nitrogen or nitrate-nitrogen (NO
2
—N or NO
3
—N), the higher the BOD load, the faster the denitrification speed. In other words, a value of BOD load suitable for nitrification action and a value of BOD for denitrification are the conditions contrary to each other.
Further, in this type of fish rearing system, if, for example, removal of water contaminants and regulation of the rearing environment can be effected simultaneously by a single treatment section, such a system is desirable for saving energy of the rearing system. Also, it is necessary for each treatment device to make a correction or complementary treatment of the treatment made by the other treatment section.
In view of the above-described situation, it is an object of the present invention to provide the fish rearing system capable of performing water quality control at a low cost by a rational combination of devices.
DISCLOSURE OF THE INVENTION
This invention relates to a fish rearing system having a water circulation system for discharging the rearing water from a discharge port provided at the bottom of a rearing water tank and re-supplying the discharged rearing water to the rearing water tank, characterized in that the water circulation system comprising: a trapping device for capturing residual feed and fish feces contained in the rearing water, a residual feed detecting sensor for detecting the residual feed contained in the rearing water, a denitrification device for denitrifies a nitrogen compound contained in the rearing water, a bubble surfacing device for generating bubbles by supplying air and/or ozone and removing surface active substances by capturing the generated bubbles, an ultraviolet disinfection device for disinfecting the circulating rearing water, an ammonium treating section for decomposing ammonium contained in the rearing water, and an aeration section for dissolving oxygen into the rearing water, and wherein the denitrification device is disposed at the upstream of the bubble surfacing device and in a circulation path branched out from a main circulation path.
Before effecting any/all water quality controls, it is required to provide the trapping device for capturing residual feed and fish feces contained in the water. Detection of residual feed contained in the water allows to make an adjustment of amount of feed to increase or decrease thereof. The denitrification device is required to decompose nitrite-nitrogen, which is the final product of ammonium, into nitrogen gas. The supply of air is not only desirable for regulation of the rearing environment, but the supply of air and/or ozone is effective in that it generates bubbles, and organic substances such as fatty acid and protein adhered to bubbles can be removed by capturing bubbles. The ultraviolet disinfection device disinfects germs contained in the water which cause illness to fish. This device also decomposes ozone contained in the rearing water by irradiation of ultraviolet rays. Further, the ammonium treatment device is required for performing a purification treatment of ammonium generated by physiological activities of fish and which is one of elements to cause water contamination. The aeration device is for dissolving oxygen in the water which is vital to keep the fish alive.
By disposing the denitrification device at the upstream of the bubble surfacing device as described above, an organic carbon source, which is necessary for denitrification by anaerobic bacteria, can be provided by organic substances contained in the circulating water. Therefore, this can save time and labor of adding additives to supply the organic substances required for denitrification, or even if such adding of the additives is required, it is sufficient to add a small amount of a
Gruenberg Daniel Edward
Kawaguchi Shinichiroh
Minami Akio
Morimura Shinji
Jifas Corporation
Kanesaka & Takeuchi
Price Thomas
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