JPH09253681A - Bacteria carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the uniform mixing with treated water and the separation from activated sludge by reduced aeration power by using a plate-shaped member composed of a polymeric material of which the specific gravity is within a specific range and made specific in the length of one side thereof as a bacteria carrier. SOLUTION: A plate-shaped member composed of a plymeric material with specific gravity of 1.0-1.1 such as a polyvinyl alcohol gel and having a square shape of which one side has a length of 7-20mm and an aspect ratio (length of one side/thickness) of 3.5 or more is used as a plate-shaped bacteria carrier. The min. air passing quantity required in the uniform fluidization of the bacteria carrier is shown in a graph in terms of a fluidization enabling air passing ratio. That is, the bacteria carrier having a thickness of 2mm or less and a length of one side of 7-20mm shows good fluidizing properties. By increasing a length of one side as compared with a conventional product, the mesh size of a screen separating activated sludge and the bacteria carrier can be made large. Since this bacteria carrier is hard to sediment and rich in fluidizing properties, even if specific gravity is set to about 1.1, fluidizing properties are not damaged.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a microbial 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 microbial carriers have been conventionally introduced into the aeration tank for the purpose of high load countermeasures, shortening of nitrification / denitrification time, etc., and MLSS (activated sludge) alone The device is designed to complete the process in a shorter time than the above. Since these microbial carriers are used in a suspended state, they are formed into a substantially cubic or spherical body having a specific gravity of about 1 and a size of 3 to 7 mm, and the material is usually polyvinyl alcohol, polyethylene glycol, polyurethane, cellulose or the like. is there.

The larger the size of the microbial carrier, the easier the separation from MLSS (activated sludge), and the easier it is to prevent runoff from 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 uniform mixing with treated water is difficult even if the specific gravity difference with MLSS is small. This is because

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

As described above, regarding the size / shape of the microbial carrier, the performance and the difficulty in sedimentation conflict with the ease of separation from the MLSS. Especially, the aeration equipment such as the deep tank aeration tank. However, when the flow velocity at the bottom of the tank is low because it is installed at the intermediate depth of the tank, the usual microbial carrier may precipitate at the bottom of the tank. In order to solve this problem, there is a method of increasing the aeration amount and increasing the flow velocity at the bottom of the tank to prevent sedimentation, a method of vertically dividing the deep tank into two and reducing the dead water area, Both methods had practical problems such as severe wear of the microbial carrier due to high swirling velocity, high operating cost for aeration power, and great cost for equipment modification.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, can increase the amount of adhered microorganisms, can easily mix uniformly with treated water with less aeration power, and The purpose is to provide a microbial carrier that can be easily separated from MLSS.

[0007]

Means for Solving the Problems The microbial carrier of the present invention made to solve the above problems has a specific gravity of 1.0 to 1.1.
It is characterized by being a plate-like body made of the above polymer material and having 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. The surface of the flat plate body may be a flat surface or a curved surface.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the 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 thickness / length / side length. The aspect ratio is 3.5 or more. When calculated mechanically from these values, the maximum thickness is 5.7 mm, but if the thickness is increased, the inside becomes a dead zone that does not contribute to the attachment of microorganisms, so the actual thickness is 2 mm or less. It is preferable. The most preferable thickness is 0.5 to 1.5 mm, and the aspect ratio is preferably in the range of 5 to 100. Note that FIG. 2 shows an example of a microorganism carrier having a curved surface, and the material, size, thickness, etc. are the same as those in FIG. The curved state may be a W shape or the like in addition to the simple shape shown in the figure, but it is necessary to be able to flutter in water, so it is not preferable that the curved shape greatly deviates from the plate shape.

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

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

FIG. 5 is a graph showing the minimum aeration amount required to evenly flow these microbial carriers, which is converted into a fluidizable aeration ratio (aeration air amount required for 1 hour per 1 m ^{3 of} water amount). It is shown. Note that the broken line in Fig. 5 is the aeration amount in the scale model tank that gives the flow velocity at the bottom of the tank in the case of a normal-scale deep aeration tank with a normal aeration amount. If it is fluidized, it means that good flow is possible even in a full-scale deep tank aeration tank. As shown in FIG. 5, those having a thickness of 2 mm or less and a side length in the range of 7 to 20 mm show good fluidity.

Further, by making the length of one side of the microbial carrier larger than that of the conventional product, it is possible to increase the opening when separating the MLSS and the microbial carrier by a screen or the like. For example, a screen having a 5 mm square opening can be used for a microbial carrier having a side of 7 mm, and a screen having a 15 mm square opening can be used for a microbial carrier having a 20 mm side. Therefore, maintenance and management work such as cleaning of clogging of the screen can be significantly reduced as compared with the conventional product in which a screen with a small opening has to be used.

As described above, the microbial carrier of the present invention is unlikely to settle and has good fluidity, so that it can have a higher specific gravity than conventional products. That is, the specific gravity of the conventional product had to be about 1.05 at the maximum, but the microbial carrier of the present invention does not impair the fluidity 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
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. As a matter of course, the specific gravity must be 1.0 or more to prevent the microbial carrier from floating.

[0014]

As described above, since the microbial carrier of the present invention is hard to settle and has good fluidity, it is possible to reduce the aeration rate as compared with the conventional product, and the aeration power is 10 to 30.
It can be reduced by about%. Further, since the microbial carrier of the present invention can have a large difference in specific gravity from MLSS,
The risk of carrier outflow in the carrier separation tank can be eliminated. Furthermore, since the length of one side of the microbial carrier of the present invention is increased, it is possible to use a screen having an opening of 5 mm or more which does not cause clogging even when the carrier is separated by a screen or the like. Moreover, since the plate-shaped body is used, a large specific surface area that contributes to the attachment of microorganisms can be obtained, and a large amount of microorganisms can be supported.

[Brief description of 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 microbial carrier.

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

FIG. 4 is a 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 aeration tank, 3 bulkheads

Claims (4)

[Claims] 1. A microbial carrier characterized by being a plate-like body having a specific gravity of 1.0 to 1.1 and having a side length of 7 to 20 mm. 2. The microbial carrier according to claim 1, which has an aspect ratio defined as one side length / thickness of 3.5 or more. 3. The microbial carrier according to claim 1, wherein the polymer material is polyvinyl alcohol gel. 4. The microbial carrier according to claim 1, which has a curved surface.