JPH042232B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for immobilizing nitrifying bacteria used in a biological water treatment method for purifying human waste, sewage/waste water, municipal water, or raw water for tap water. [Prior art and its problems] The mainstream of biological water treatment technology is the activated sludge method, and the method for removing nitrogen from water is nitrification-denitrification activated sludge, which combines the multiple biological effects of activated sludge. Law is becoming mainstream. In the nitrification-denitrification method, the ammonia nitrogen contained in water is converted into nitrite, nitrite, and
Or a nitrification process that oxidizes to nitrate nitrogen,
It consists of a denitrification process in which these oxidized nitrogen is reduced to nitrogen gas by facultative anaerobic heterotrophic bacteria called denitrifying bacteria. In other words, for the nitrification-denitrification method to work efficiently, these two steps must be combined efficiently, but autotrophic cells such as nitrifying bacteria have an extremely slow growth rate compared to heterotrophic bacteria. In the current nitrification-denitrification method, the nitrification step is the rate-limiting process. That is, enhancement of nitrification capacity is desired. In addition, conventional biological treatment methods such as activated sludge method
This technology was originally used to purify organic wastewater such as human waste, sewage, and wastewater, but today it is also being applied to purify the raw water taken by washing plants that supply the tap water we drink every day. However, the activated sludge method cannot be applied to purify such relatively low level polluted water, so the biofilm method is applied. Requirements for biological treatment of water supply raw water are ()BOD,
Reduction of COD, () Removal of ammonia nitrogen,
There are a wide variety of methods, including () the removal of trihalomethane precursors and () the removal of off-flavors such as musty odors, but the most demanding at this stage is the removal of ammonia nitrogen. In this case as well, ammonia nitrogen is oxidized by nitrifying bacteria, as described above, but the concentration of ammonia contained in raw water is extremely low compared to sewage and wastewater, and at most it is 2 to 3 mg-N. /, and is often around 1 mg-N/. In this way, when nitrifying bacteria are used to purify raw water, the nitrifying bacteria are placed in an environment where the concentration of ammonia, which is a substrate, is extremely low. This applies not only to nitrifying bacteria but also to microorganisms in general, but the growth rate and specific activity of microorganisms are usually controlled by a hyperbolic function type expressed by Monod's empirical formula with respect to substrate concentration, and as the substrate concentration decreases, They will decline. That is, in the water supply field, there are seemingly contradictory demands such as high nitrification activity at low ammonium concentrations. As mentioned above, the demands placed on nitrifying bacteria are extremely high, and various efforts and ideas have been proposed to increase the nitrifying capacity, but no effective means have been established so far. On the other hand, recently, as a new water treatment technology,
Immobilized microorganisms are attracting attention and various studies are being conducted. The immobilized microorganism method is a technology that has been developed mainly in the fermentation industry, and is a method that stabilizes microbial reactions and increases efficiency by combining microorganisms with water-insoluble elements using physicochemical means. .
As simple substances, polymer compounds such as alginic acid, κ-carrageenan, and photocrosslinkable resins are mainly used, and the microorganisms perform the reaction while being enclosed within the gel composed of these polymer compounds. [Object of the Invention] An object of the present invention is to utilize the immobilized microorganism method to stabilize and increase the efficiency of nitrification, and to overcome various problems related to ammonia nitrogen removal. [Structure of the Invention] Many researchers have investigated the application of the immobilized microorganism method to nitrifying bacteria, but it has been concluded that this method is generally effective in stabilizing nitrification. ing. However, when we applied this method to the removal of ammonia nitrogen from raw water water, the nitrification ability was only about the same as that of the conventional biofilm method, and the main reason for this was: This was thought to be due to the extremely low concentration of ammonia nitrogen, which is the substrate. Therefore, in order to develop an immobilized microorganism method that can carry out a highly efficient nitrification reaction even in a low ammonia concentration range, we have conducted extensive studies and as a result, we have arrived at the present invention. The present invention is a method for immobilizing microorganisms, which comprises comprehensively immobilizing a group of microorganisms including nitrifying bacteria and an adsorbent capable of adsorbing ammonia in a gel composed of a polymer compound. As the adsorbent used in the present invention, any adsorbent having ammonia adsorption ability, such as natural zeolite, zeolite, and synthetic zeolite, can be used. Further, the field of application of the present invention is not limited to water containing ammonia at a low concentration, but may also be water containing ammonia at a high concentration. Next, the present invention will be explained in more detail based on examples. [Example] Water from Lake B, where eutrophication has become a problem in recent years, was used as the experimental water. NH ₄ ⁺ −N contained in the water of Lake B is 0.1 to 2.3 mg/year throughout the year.
The BOD was in the range of 2 to 5 mg/. In some cases, (NH ₄ ) ₂ SO ₄ was added to Lake B water to adjust the ammonia concentration. The experiments were conducted using immobilized microorganisms containing an adsorbent produced according to the method of the present invention (referred to as A series), immobilized microorganisms containing no adsorbent (referred to as B series), and adsorbent itself to which microorganisms were attached. Three series of fluidized bed biofilm methods (referred to as C series) were used as the medium. The reaction tank used had an effective volume of 50, and air was sucked in from the lower end of an air lift tube placed in the center of the reaction tank, thereby supplying oxygen and mixing inside the tank. Separation of the immobilized microorganisms and the medium to which the microorganisms were attached was performed by sedimentation separation using gravity in a separation section adjacent to the reaction tank. In addition, raw water was supplied continuously and temporarily. Water temperature and pH were not particularly adjusted, but the water temperature was in the range of 13°C to 29°C and the pH was in the range of 6.9 to 8.5. The nitrifying bacteria used as seed bacteria were nitrite bacteria (Nitromonas europaca ATCC 19718) and nitrate bacteria (Nitrobocter agilis ATCC 14123), which were cultured in a medium with the composition shown in Tables 1 and 2 below.

【table】

[Table] Autoclaved.

[Table] Autoclaved.
Next, a method for producing immobilized microorganisms will be described. (a) Manufacturing method of A: 300g of sodium alginate, 1g of nitrite bacteria
(wet weight), 1 g of nitrate bacteria (wet weight), clinobutyrolite ((Ca, Na ₂ ) as adsorbent)
[Al ₂ Si ₇ O ₁₈ ]・6H ₂ O, a type of natural zeolite)
Mixture 10 containing 200g of powder (dry weight)
was dropped into a 0.1 MCaCl ₂ solution under stirring through a nozzle with a diameter of 2 mm to obtain an immobilized microorganism 20 (bulk volume) composed of a spherical calcium alginate gel with a diameter of 3 to 5 mm. (B) Manufacturing method of B: 300g of sodium alginate, 1g of nitrite bacteria
(wet weight), after mixing 1 g (wet weight) of nitric acid bacteria, it was dropped into the 0.1MCaCl ₂ solution under stirring through a nozzle with a diameter of 2 mm, and was composed of a spherical calcium alginate gel with a diameter of 3 to 5 mm. Immobilized microorganisms 20 (bulk volume) were obtained. (C) Regarding C: As a medium for adhesion of nitrifying bacteria, particle size is 0.3 to 0.5 mm.
granular clinobutyrolite was used. The amount of clinobutyrolite is 20 in bulk volume.
As seed bacteria, the same amounts of nitrite bacteria and nitrate bacteria as in (a) and (b) were introduced into the tank together with cributyrolite at the start of the experiment. A summary of the experimental results is summarized in Table 3.

〔Effect of the invention〕

The present invention skillfully combines the ammonia adsorption ability of the adsorbent and the ammonia oxidation ability of the nitrifying bacteria, thereby producing excellent effects not found in conventional methods. It is believed that this invention will continue to be widely accepted as a biological water treatment method for sewage/wastewater, human waste, municipal water, or tap water sources.

Claims (1)

[Claims] 1. A method for immobilizing microorganisms, which comprises comprehensively immobilizing microorganisms including nitrifying bacteria and an adsorbent capable of adsorbing ammonia in a gel.