JP3171554B2 - Microbial carrier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microorganism carrier used for biological treatment of organic wastewater such as sewage, leachate leachate, and industrial wastewater.

[0002]

2. Description of the Related Art In the biological treatment of organic wastewater, various microorganism carriers have been put into an aeration tank for the purpose of high load countermeasures, shortening of nitrification / denitrification time, and the like. In order to complete the process in a shorter time than in the case of the above, a device is devised. Since these microorganism carriers are used in a suspended state, they have a specific gravity of about 1 and are generally cubic or spherical with a size of 3 to 7 mm, and are usually made of polyvinyl alcohol, polyethylene glycol, polyurethane, cellulose, or the like. is there.

[0003] The larger the size of the microorganism carrier, the easier it is to separate it from MLSS (activated sludge), and the more easily it is prevented from flowing out of the aeration tank. However, as described above, the size was limited to 10 mm or less, because if the size exceeds 10 mm, sedimentation is likely to occur, and even if the specific gravity difference with MLSS is small, uniform mixing with treated water is difficult. It is because it becomes.

Since the specific surface area increases as the size of the microorganism carrier decreases, the amount of adhered microorganisms can be increased and uniform mixing with treated water becomes easy. However, if it is too small, separation from the MLSS becomes difficult. For this reason, microorganism carriers conventionally used usually are particles having a specific gravity of 1.02 to 1.05 and a size of 3 to 7 mm.

[0005] As described above, regarding the size / shape of the microorganism carrier, the performance and the difficulty of sedimentation are inconsistent with the ease of separation from the MLSS. When the flow rate at the bottom of the tank is low because the water is placed at the middle depth of the tank, the usual microorganism carrier may precipitate at the bottom of the tank. In order to solve this problem, there are a method of preventing the sedimentation by increasing the amount of diffused air and increasing the flow velocity at the bottom of the tank, and a method of vertically dividing the deep tank into two parts to reduce dead water area. All of these methods have practical problems such as increased wear of the microbial carrier due to an increase in the swirling flow rate, an increase in operating costs for aeration power, and a large cost for equipment remodeling.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, can increase the amount of adhered microorganisms, facilitates uniform mixing with treated water with a small amount of aeration power, and The purpose of the present invention is to provide a microorganism carrier that can be easily separated from MLSS.

[0007]

The microorganism carrier of the present invention made to solve the above problems has a specific gravity of 1.0 to 1.1.
Characterized by a plate-like body having a thickness of 0.5 to 2 mm and a side length of 7 to 20 mm . The aspect ratio defined as the length / thickness of one side is preferably 3.5 or more. The polymeric material used can be, for example, a polyvinyl alcohol gel. In addition to the flat surface of the flat body,
A curved surface is also possible.

[0008]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an example of a plate-shaped microbial carrier, which is made of a polymer material such as polyvinyl alcohol gel and has a square shape with a side length of 7 to 20 mm, and is defined as the length / side length / thickness. The aspect ratio is set to 3.5 or more. When mechanically calculated from these values, the maximum value of the thickness is 5.7 mm. However, when the thickness is increased, the inside becomes a dead zone that does not contribute to the attachment of microorganisms. Therefore, the thickness is actually 2 mm or less. Is preferred. The most preferable thickness is 0.5 to 1.5 mm, and the aspect ratio is preferably in the range of about 5 to 100. FIG. 2 shows an example of a microorganism carrier having a curved surface, and the material, size, thickness and the like are the same as those in FIG. In addition, the curved state may be a W shape or the like in addition to the simple shape as shown in the figure, but it is necessary to be able to flutter underwater, so it is not preferable that the shape deviates significantly from the plate shape.

[0009] Such a microorganism carrier of the present invention has a greater resistance to settling in the MLSS than a conventional granular microorganism carrier, and is less likely to settle. FIG. 3 is a graph comparing the sedimentation rates of the microorganism carrier of the present invention and a conventional microorganism carrier. The thickness of the microorganism carrier of the present invention is 1.0 m
1 was prepared with a constant value of m, and the length of each side was variously changed. A cubic microorganism carrier having a side length of 5 mm was prepared as a control. The material was a polyvinyl alcohol gel having a specific gravity of 1.03.

Next, in order to confirm the fluidity of the microorganism carrier of the present invention, a test was conducted using a scale model of a deep aeration tank shown in FIG. In the model of FIG. 4, the air diffuser 2 is arranged in the middle of the tank body 1, and a vertical partition wall 3 is provided at the center in the width direction of the tank body 1. As the microbial carrier of the present invention, those having the shapes shown in FIG. 1 with various lengths and thicknesses of one side were prepared, and a cubic microbial carrier having a side length of 5 mm was prepared as a control. The material was a polyvinyl alcohol gel having a specific gravity of 1.03.

FIG. 5 is a graph showing the minimum aeration required to make these microorganism carriers flow uniformly, which is converted into a fluidizable aeration rate (amount of diffused air required for 1 hour per 1 m ^{3 of} water). Is shown. The broken line in FIG. 5 indicates the air flow rate in the scale model tank which gives the flow velocity at the bottom of the tank when the normal aeration volume is set in the full-scale deep aeration tank. Means that good flow is possible even in a full-scale deep aeration tank. As shown in FIG. 5, a material having a thickness of 2 mm or less and a length of one side in the range of 7 to 20 mm shows good fluidity.

Further, by making the length of one side of the microorganism carrier larger than that of the conventional product, the aperture when separating the MLSS and the microorganism carrier by a screen or the like can be increased. For example, when the microorganism carrier has a side of 7 mm, a screen having an aperture of 5 mm can be used. When the microorganism carrier has a side of 20 mm, a screen having an aperture of 15 mm can be used. For this reason, maintenance management work such as cleaning of clogging of the screen can be significantly reduced as compared with a conventional product in which a screen having a fine opening has to be used.

As described above, since the microorganism carrier of the present invention hardly sediments and has good flowability, the specific gravity can be made larger than that of the conventional product. That is, although the specific gravity of the conventional product had to be about 1.05 at the maximum, the fluidity of the microorganism carrier of the present invention is not impaired even when the specific gravity is about 1.1.
FIG. 6 is a graph showing the fluidizable air permeability when the specific gravity of the product of the present invention is changed. The length of one side is 20 mm and the thickness is 20 mm.
Three types of microbial carriers of 0.5 mm, 1.0 mm and 2.0 mm were used. As can be seen from the graph of FIG. 6, the microbial carrier of the present invention has good fluidity even when the specific gravity is increased to 1.1. Needless to say, the specific gravity needs to be 1.0 or more in order to prevent the floating of the microorganism carrier.

[0014]

As described above, since the microorganism carrier of the present invention hardly sediments and has good fluidity, the air permeability can be reduced as compared with the conventional product, and the aeration power can be reduced by 10 to 30.
% Can be reduced. Also, since the microorganism carrier of the present invention can take a large difference in specific gravity from MLSS,
The risk of carrier outflow in the carrier separation tank can be eliminated. Further, since the length of one side of the microbial carrier of the present invention is increased, a screen having a mesh size of 5 mm or more without clogging can be used even when the carrier is separated by a screen or the like. Moreover, since the plate-like body is used, the specific surface area contributing to the attachment of microorganisms can be increased, and a large amount of microorganisms can be supported.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a plate-shaped microorganism carrier.

FIG. 2 is a perspective view showing an example of a curved microorganism carrier.

FIG. 3 is a graph showing a relationship between a carrier size and a sedimentation velocity.

FIG. 4 is a cross-sectional view of a scale model used in an experiment.

FIG. 5 is a graph showing the relationship between carrier size and fluidizable air permeability.

FIG. 6 is a graph showing the relationship between the specific gravity of the carrier and the fluidizable air permeability.

[Explanation of symbols]

 1 tank body, 2 diffuser tanks, 3 partition walls

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 3/02-3/10 C12N 11/00-13/00

Claims (4)

(57) [Claims] 1. A high-molecular material having a specific gravity of 1.0 to 1.1, a thickness of 0.5 to 2 mm, and a length of one side of 7 to 20 m.
A microbial carrier, which is a plate-like member having a m-like shape. 2. The microorganism carrier according to claim 1, wherein an aspect ratio defined as length / thickness of one side is 3.5 or more. 3. The microorganism carrier according to claim 1, wherein the polymer material is a polyvinyl alcohol gel. 4. The microorganism carrier according to claim 1, wherein the surface is curved.