Liquid purification or separation – Processes – Treatment by living organism
Patent
1987-10-06
1990-04-17
Spear, Frank
Liquid purification or separation
Processes
Treatment by living organism
2105001, 210615, 210621, 210630, 210906, 423331, B01D 1500
Patent
active
049178024
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a method for treating waste water such as animal urine, home waste water and sewage, which provides easy and efficient removal of organic substances, nitrogen and phosphorus.
2. Background Art
Organic waste water such as animal urine, home waste water and sewage causes eutrophication of lakes and inland seas, which can result in generation of green and red algae. Heretofore, a variety of treatment methods for the organic waste water, such as an activated sludge method, tricking filters, and a rotating biological contactor, have been proposed, and submerged filters have been often used in view of the installation area, efficiency of treatment, and maintenance.
In the dipping filter bed method, an aerobic filter bed tank is filled with a contact material, and waste water is introduced in the tank and aerated, thereby producing biomembranes on the surface of the contact material, and the waste water is cleaned by the function of microbes in the biomembranes. The contact material used in the submerged filters includes gravel, plastic pieces, and honeycomb tubes.
The submerged filters can remove organic substances, but are not sufficient to remove nitrogen compounds, and phosphoric acid and phosphates (hereinafter referred to as phosphorus), and discharging the treated water into a closed water area results in eutrophication, which leads to a major damage to the fisheries. Therefore, when organic wastes are treated by the submerged filters, separate denitrification and dephosphorization are required.
For the purpose, a biological denitrification method is normally used in combination with the submerged filters. In the biological denitrification method, an anaerobic filter bed tank is provided after the aerobic filter bed tank of the submerged filters, in which NO.sub.2.sup.- --N and NO.sub.3 ---N coming from NH.sub.4 +--N through oxidation by the action of nitrification bacteria in the aerobic filter bed tank are reduced into N.sub.2 gas by the action of denitrification bacteria under an oxygen-free condition. To obtain a sufficient effect of the denitrification, the oxidation of NH.sub.4 +--N into NO.sub.2 ---N and NO.sub.3 ---N, or nitrification, must be sufficiently carried out in the aerobic filter bed tank of the submerged filters. However, the pH value in the aerobic filter bed tank decreases with progress of nitrification, and a neutralization with an alkali is required for the aerobic filter bed tank, which results in a complex control and a complicated structure of facilities with an increase in cost due to the use of chemicals.
Heretofore, a dephosphorization has been performed after the denitrification. Dephosphorization methods include a flocculation/precipitation method which uses metal salts such as salts of calcium, aluminum and iron to remove phosphorus in the form of metal phosphates, and a crystallization method which removes phosphorus by crystallizing it as hydroxyapatite in an alkali region in the presence of calcium. Either method requires a separate dephosphorization system or a separate dephosphorization tank.
As described above, to treat organic waste water, three steps including the removal of organic substances (submerged filters), denitrification and dephosphorization are indispensable at present. An example of such a treatment process for organic waste water will now be described with reference to FIG. 17. Referring to FIG. 17, organic waste water is primarily treated in a screen sand precipitation basin 01 and a vibrating sieve 02 to remove suspended substances and precipitates. The primarily treated waste water is diluted with water in a dilution tank 03, and then treated in an aerobic tank 04 using the submerged filters to remove organic substances and for sufficient nitrification while adjusting the pH value with an alkali agent. The treated waste water is added with methanol and agitated in an agitation tank 05, and then subjected to denitrification in an anaerobic tank 06. The denitrogenated waste water is treated in a
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Fukaya Yukio
Hatano Kazuyuki
Sainohira Kazuhiro
Drodge Joseph
Onoda Autoclaved Light Weight Concrete Co., Ltd
Spear Frank
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