JP2002233885A - Microorganism immobilization support - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microorganism immobilization support which increases the concentration of microorganisms in a treatment zone by sticking microorganisms to a molding of a synthetic resin or the like and which can effectively utilize even microorganisms sticking in the pores in the support and to provide a waste water treating method using the microorganism immobilization support. SOLUTION: In the waste water treating method, when aerobic or anaerobic waste water treatment with microorganisms is carried out, the microorganism immobilization support having flexibility and 'dustocloth wringing' effect and comprising a synthetic resin or synthetic rubber molding containing fine powder of a material which is charged with positive charges and having substantially open cells is housed in a treatment tank together with water to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microorganism-immobilized carrier and a wastewater treatment using the microorganism-immobilized carrier, particularly a synthetic resin or synthetic rubber molded article having excellent performance for increasing the concentration of microorganisms in a treatment tank. , And microbial treatment of wastewater using the same. Specifically, a carrier for microorganism immobilization effective for increasing the concentration of microorganisms in a treatment tank and a BOD removal tank, a nitrification treatment tank or a denitrification tank for efficiently removing BOD or removing nitrogen components with a compact device. Wastewater or sludge is put into a wastewater treatment tank such as a treatment tank together with wastewater or sludge to remove harmful nitrogen compounds contained in the wastewater or sludge into harmless substances. On how to do it.

[0002]

2. Description of the Related Art Generally, BOD substances are subjected to activated sludge treatment by air aeration or oxygen-enriched air as a treatment method for sewage and industrial wastewater containing BOD components and nitrogen components.
Nitrogen is also decomposed and removed, and the nitrogen component in the wastewater is similarly nitrified by activated sludge treatment in an air aeration tank, and then anaerobically denitrified. However, a method such as air aeration requires a long processing time, so that the processing equipment is generally large, and a large amount of energy is required for aeration for dissolving oxygen which also serves as stirring.

In order to make the apparatus compact, it is necessary to reduce the processing time. For this purpose, in the aerobic treatment, it is necessary to increase the concentration of activated sludge (the concentration of microorganisms) and to improve the oxygen dissolution rate. To increase the activated sludge concentration, it has been proposed to put a carrier for immobilizing microorganisms in an aeration tank, form an active microorganism layer on the surface thereof, and treat the wastewater. Also, in the anaerobic treatment for denitrification, it is necessary to increase the concentration of microorganisms effective for the denitrification reaction. For this reason, there have been many proposals for the use of a porous carrier for immobilizing microorganisms (Japanese Patent Laid-Open No. Sho 63). -209788, JP-A-2-21
1292, JP-A-3-16695, JP-A-8-173984 and JP-A-8-256773.

[0004] These methods are effective in increasing the concentration of microorganisms in the wastewater treatment zone, and have been found to be effective means for shortening the wastewater treatment time and improving the quality of treated water. However, all of these proposals merely provide a surface area for attaching microorganisms as a carrier for immobilizing microorganisms, and use of a hollow or porous synthetic resin or synthetic rubber molded article has been performed. .

[0005] When wastewater treatment is performed using such a hollow body or a porous synthetic resin or synthetic rubber molded article, there is an effect of certainly increasing the concentration of microorganisms in the treatment tank, but microorganisms are fixed during wastewater treatment. The microorganism layer attached to the inside of the hollow body or the inside of the porous pores of the carrier for
Usually, it does not work very effectively in biological treatment of wastewater due to insufficient supply of dissolved oxygen or discharge of generated nitrogen or carbon dioxide gas. Note that JP-A-8
A carrier for immobilizing microorganisms comprising a porous cellulose derivative proposed in JP-A-256773 is a foamed product obtained by forming a porous cellulose derivative into a spherical, cylindrical, hollow cylindrical or dice-like form using an epoxy compound, N-methylol. Microbial resistance is improved by using cellulose fiber treated with a compound or the like, and the above problem is solved because of its relatively flexibility, so that this is a very rational carrier for immobilizing microorganisms.

[0006] However, the carrier for immobilizing microorganisms is used for several years or more than 10 years continuously after it is once used, and is a cellulose derivative treated with an epoxy compound or the like to prevent microbial deterioration. Despite this, degradation by cellulase attack is inevitable, and further improvement is required. In particular, some chemicals used to enhance enzyme resistance inhibit microbial adhesion, and it is desirable to avoid using such an enzyme resistant agent as much as possible.

On the other hand, in biological treatment of municipal sewage, human waste effluent mainly from households and the like, and wastewater from factories or gas stations (all such effluents are referred to as “wastewater” in the present invention). Mainly BOD
(Biochemical oxygen demand) is mainly treated, so eutrophication of lakes, marshes, rivers and inland seas (bays) is progressing, and even though sewage treatment facilities are being developed and expanded, no fundamental solution has been reached. is the current situation.

Although the treatment method reduces the BOD caused by microorganisms using an activated sludge method, it has been insufficient to remove nutrients such as nitrogen compounds derived from organic compounds and phosphorus in wastewater. Lakes, rivers, and inland waters (especially in the area where red tides occur) from which wastewater from nutrient-containing wastewater treatment facilities has been discharged are in a state where phytoplankton easily proliferates, and pollution due to eutrophication is progressing.

Various methods have been employed to remove ammonia nitrogen, nitrate nitrogen and nitrite nitrogen converted from such organic nitrogen compounds, one of which is biological denitrification. There is. In this method, treatment is basically performed in a nitrification treatment tank or a denitrification treatment tank using nitrifying bacteria or denitrifying bacteria in activated sludge. That is, in the nitrification tank, organic nitrogen can be converted to ammonia nitrogen, and the ammonia nitrogen can be further converted to nitrate nitrogen or nitrite nitrogen by nitrifying bacteria having a slow growth rate.

The nitrate nitrogen and nitrite nitrogen converted in the nitrification tank are generally converted into nitrogen by denitrifying bacteria in a denitrification tank to which a hydrogen donor has been added and released to the atmosphere. In this way, nitrogen compounds are removed from groundwater and sewage. Therefore, in order to increase the processing capacity, it is necessary to use a polyurethane foam or a jelly-like polyethylene glycol derivative disclosed in JP-A-5-023684 in this nitrification tank or denitrification tank. The carrier for immobilization was charged. In addition, in order to produce useful substances such as citric acid,
In some cases, a foam of cellulose is used as a carrier for immobilizing microorganisms.

Many proposals have been made for such a denitrification method. That is, in the method using a synthetic resin or synthetic rubber molded product of a polyethylene glycol derivative disclosed in JP-A-5-023684, microorganisms must be fixed in advance to the synthetic resin or synthetic rubber molded product. However, in the case of comprehensive fixing, equipment for fixing was required, and capital investment was required. In addition, a simple fixation requires a long time for fixation. Furthermore, the synthetic resin or synthetic rubber molded product of the polyethylene glycol derivative can fix nitrifying bacteria in a nitrification treatment tank under aerobic conditions, but fix the denitrifying bacteria in a denitrification treatment tank performed under anaerobic conditions. It was difficult to make it into a versatile one and lacked versatility. When a polyurethane foam is used, it compensates for the disadvantages of the polyethylene glycol derivative in terms of being able to be used in a denitrification tank, but lacks affinity for the microorganisms and thus has a maximum denitrification when used in a denitrification tank. The speed is as low as 20 (mg-N / l-carrier / h),
No further increase in processing capacity could be expected. Also,
Cellulose foams have a remarkably short life in an environment having a high cellulolytic activity, cannot withstand several months of use, and are not suitable for various uses.

[0012]

SUMMARY OF THE INVENTION The present invention provides a synthetic resin or synthetic rubber molded article which can be effectively used for BOD removal and denitrification of wastewater in wastewater treatment. Furthermore, the concentration of microorganisms in the treatment zone is increased by selectively attaching microorganisms to the synthetic resin or synthetic rubber molded article, and the microorganisms attached in the pores of the carrier for immobilizing microorganisms can also be effectively used. An object of the present invention is to provide a certain microorganism-immobilizing carrier and a wastewater treatment method using the microorganism-immobilizing carrier.

[0013]

The present invention provides a carrier for immobilizing microorganisms, comprising: [1] a substantially open-cell synthetic resin or synthetic rubber molded article containing a fine powder of a positively charged substance;

[2] The carrier for immobilizing microorganisms according to [1] above, wherein the fine powder of the substance charged with a positive charge is mica, synthetic mica or an inorganic compound treated with a quaternary ammonium salt. The carrier for immobilizing microorganisms according to the above [1] or [2], which is an open-cell synthetic resin or a synthetic rubber molded article containing 0.1 to 10% by weight of a positively charged substance with respect to the synthetic resin. [4] The apparent specific gravity of the open-cell synthetic resin or synthetic rubber molded product is 0.05 to 0.1.
The carrier for immobilizing microorganisms according to any one of the above [1] to [3], which is a foamed molded article of [5], [5] The above, wherein the open-cell synthetic resin or synthetic rubber molded article is a granule of 3 to 30 mm. The carrier for immobilizing microorganisms according to any one of [1] to [4], [6] The foaming molded article according to any one of the above [1] to [5], which is flexible and has a wiping effect. A carrier for immobilizing microorganisms,

[7] In the treatment of aerobic or anaerobic wastewater by microorganisms, substantially open-cell synthetic resin or synthetic rubber containing fine powder of a positively charged substance together with water to be treated in a treatment tank. [8] A wastewater treatment method characterized by carrying out treatment by accommodating a microorganism-immobilizing carrier formed of a molded body, [8] the wastewater according to the above [7], wherein the aerobic wastewater treatment is removal of BOD in wastewater. Treatment method, [9] The wastewater treatment method according to [7], wherein the aerobic wastewater treatment is wastewater nitrification treatment, [10] The above [7], wherein the anaerobic wastewater treatment is wastewater denitrification treatment. And [11] an aerobic or anaerobic wastewater treatment using microorganisms, wherein a carrier for immobilizing microorganisms having an apparent volume of 2 to 50% based on the internal volume of the treatment tank is used. Any of [7] to [10] Wastewater treatment method according to solve the above problems by developing.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The wastewater to be treated in the present invention is any wastewater containing BOD, inorganic ammonia and nitrogen-containing organic matter such as domestic wastewater from general households, wastewater from factories, and wastewater from human waste treatment. . In particular, the synthetic resin or synthetic rubber molded article of the present invention can remarkably exert its effect in denitrification treatment in wastewater treatment.

The synthetic resin or synthetic rubber molded article to be used in the present invention is required to have the following properties as conditions. The synthetic resin or synthetic rubber molded article is used continuously for several years or more than 10 years, and is not affected by microorganisms in wastewater, sludge or the like or enzymes produced by the microorganisms during that period. Is easily adhered to the inside of the synthetic resin or synthetic rubber molded article, easily proliferates there, and its microbial layer works effectively in wastewater treatment. Smooth supply of wastewater and dissolved oxygen to be treated, and smooth discharge of treated wastewater and carbon dioxide gas and nitrogen gas produced by microorganisms etc. from the inside of the synthetic resin or synthetic rubber molding That

In general, there are many proposals to use a synthetic resin or synthetic rubber molded article to increase the concentration of microorganisms in a treatment tank. Although they are considered to be effective as such, the proposals so far have ignored the negative charge of microorganisms and merely provided an area to which the microorganisms attach. In the present invention, the synthetic resin or the synthetic rubber molded article itself is positively charged to improve the adhesion of microorganisms, especially aerobic bacteria such as nitrifying bacteria and nitrites, and denitrifying bacteria. The fine powder of the positively charged substance used in the synthetic resin or synthetic rubber molded article of the present invention is harmless to microorganisms, mica,
Fine powder of an inorganic compound tightly bonded to a compound charged with such a positive charge, such as synthetic mica, polyethyleneimine, and a quaternary ammonium compound, is preferred. There is no particular limitation on the particle size, but there is no problem if it is about 1 to 50 μm which does not hinder the production of the foam. Examples of such an inorganic compound include alumina, silica, and mica. Mica is particularly preferred because it coordinates (intercalates) the above compound in the crystal and binds firmly.

As the synthetic resin or synthetic rubber used for the synthetic resin or synthetic rubber molded article, the specific gravity does not cause much problem because of its high foaming degree, but a material whose actual specific gravity is slightly larger than that of water is used so as not to float. preferable. If it is light, it can be adjusted with mica or a filler. The important thing is that the material should be a synthetic resin or synthetic rubber that has no or little attack on microorganisms or enzymes.However, it is easy to manufacture open-cell foams, it has high elasticity, and it takes into consideration price. Then, in fact, polyurethane would be the best material.

The substantially open-celled foam is such that the above-mentioned microorganisms easily adhere to the inside of the synthetic resin or synthetic rubber molded article, easily proliferate there, and a layer of the microorganisms effectively works for wastewater treatment. For this purpose, the wastewater or dissolved oxygen to be treated is smoothly supplied to the inside of the synthetic resin or synthetic rubber molded article, and the treated wastewater, carbon dioxide and nitrogen produced by microorganisms and the like in the treatment are also required. The specific gravity is 0.05 to 0.5, preferably 0.01 to 0.3, and the size of the open cells is in order to meet the requirement that the gas or the like be smoothly discharged from the inside of the synthetic resin or synthetic rubber molded body. Usually, the pore diameter is 30 to 2000 μm, preferably 100 to 1000 μm, particularly preferably 100 to 50 μm.
0 μm is appropriate and is a foam mainly composed of open cells. In particular, when nitrogen gas cannot be exhausted from the inside of the synthetic resin or synthetic rubber molded body during the denitrification treatment, the synthetic resin or synthetic rubber molded body floats on the water surface and the processing capacity is greatly reduced. In order to smoothly discharge the gas from the inside of the carrier, the gas needs to be open cells. Further, with the agitation in the wastewater treatment tank, the wastewater treatment is performed while the synthetic resin or the synthetic rubber molded article itself is greatly deformed (this is referred to as “a wiping effect” in the present invention). The liquid and the gas inside the synthetic rubber molded body are exchanged.

As to the amount of the compound charged with a positive charge with respect to the synthetic resin or synthetic rubber molded product, it is considered that the larger the amount of the compound, the better the microbial adhesion can be improved. It is not preferable because the mechanical strength of the molded body is reduced. If the amount is too small, the effect of improving the microbial adhesion becomes insufficient. Charged material,
Alternatively, it is not fixed depending on the kind of the synthetic resin or the like, but is usually 0.1 to 15% by weight, preferably 0.5 to 5% by weight based on the synthetic resin or the synthetic rubber. The shape or size of the synthetic resin or synthetic rubber molded article is not particularly limited, but may be any shape such as a sphere, a cylinder, a hollow cylinder, or a die. Any size is acceptable as long as it does not pass through the synthetic rubber molded article runoff prevention screen. However, considering the ease of manufacture and the resistance of liquid and gas to the inside of the synthetic resin or synthetic rubber molded article, a cube or rectangular parallelepiped of about 3 to 30 mm is easy to use.

The carrier for immobilizing microorganisms of the present invention can be used in a BOD removal tank such as an air aeration tank or an oxygen aeration tank, an aerobic tank such as a nitrification tank, or an anaerobic tank such as a denitrification tank. It may be used in the same manner as in. The amount charged into these processing tanks is 2 to 50% by volume of the processing volume, preferably 10 to 40% by volume. When the amount is less than 2% by volume, the effect of using the carrier for immobilizing microorganisms becomes insufficient, and when the amount exceeds 50% by volume, there is no hindrance, but the effect used is saturated and does not improve.

The wastewater treatment of the present invention is particularly effective in treating wastewater containing nitrogen compounds. In the present invention, the nitrogen compound contained in the wastewater is a compound containing a nitrogen atom,
Ammonia, nitric acid, nitrous acid, etc. mainly contained in the liquid to be treated in the nitrification treatment tank or the denitrification treatment tank. In addition, proteins, amino acids, etc., which are decomposed in the aeration tank used for BOD removal, are also included. included. What is a nitrogen-containing wastewater treatment tank?
It means a treatment tank which contains nitrogen compounds and treats wastewater for the purpose of removing the nitrogen compounds. Examples of the treatment tank include a purification tank used in a water treatment plant and the like, an aeration tank used in sewage treatment, a nitrification treatment tank, a denitrification treatment tank, and the like.

The nitrification tank is used particularly in sewage treatment. Under aerobic conditions, a nitrifying bacterium or a nitrite is used by a nitrogen-containing organic compound, ammonia nitrogen, nitrite nitrogen or nitrate. A wastewater treatment tank that can be converted to nitrogen. In general, microorganisms suitable for nitrification are usually always present in wastewater treatment tanks, and this is because the supply of carbon sources, which are the nutrients of microorganisms, is cut off and the nitrification treatment tank is used to select microorganisms. Microbial groups such as nitrifying bacteria or nitrites that can be subjected to nitrification treatment are mainly concentrated. In the process, by introducing the carrier for immobilizing microorganisms containing the porous positively charged substance of the present invention, the microorganisms to be subjected to the nitrification treatment can be efficiently immobilized on the carrier, thereby increasing the processing capacity not previously available. be able to. One example of a nitrite that performs the nitrification treatment is Nitrosomonas.
s) One example of a nitrate bacterium is Nitrobacter (Nitr).
OBACTOR plays an important role in this nitrification tank.

The denitrification treatment tank is used in combination with a nitrification treatment tank in wastewater treatment, or used in the treatment of groundwater containing a large amount of nitrate groups, and is carried out under anaerobic conditions. To this end, the denitrification treatment tank is charged with the carrier for immobilizing microorganisms of the present invention, so that the denitrifying bacteria are immobilized on the microorganism immobilization carrier in the same manner as in the nitrification treatment tank, and nitric acid is converted into nitrogen gas. , To remove nitrogen compounds from the liquid to be treated.

The denitrifying bacteria include Pseudomonas (Pse
udomonas, Micrococcus (Microc)
occus), Spirlum
Genus, Achromobacter
Genus, Alcaligenes genus, Hydrogenomonas
And the genus Tiobacillus.

Further, a hydrogen donor is charged into the denitrification treatment tank at the time of treatment. For example, methanol, acetic acid, ethanol, acetone, glucose, methyl ethyl ketone, isopropyl alcohol, and the like can be used as organic substances serving as a BOD source. The hydrogen donor is to supply hydrogen for converting nitrite nitrogen or nitrate nitrogen contained in the wastewater to be treated into nitrogen gas and water. In the treatment of wastewater in the denitrification treatment tank, it is preferable to perform the treatment while stirring the treated water with a stirrer in order to achieve good contact between the microorganisms and the nitrogen compound even under anaerobic conditions and to further exert the effect of narrowing the cloth. For example, a denitrification treatment tank can be treated by providing a tubular inner cylinder at the center, and circulating and treating the treated water by an axial stirring method so as to circulate between the inner cylinder and the outside of the cylinder.

In the present invention, the liquid to be treated is treated in the order of the nitrification treatment tank and the denitrification treatment tank to remove nitrogen compounds from the wastewater to be treated. That is, the wastewater to be treated containing nitrite nitrogen or nitrate nitrogen formed in the above-described nitrification treatment tank is flowed into a denitrification treatment tank to convert nitrite nitrogen or nitrate nitrogen into nitrogen gas, and to be treated. Remove nitrogen compounds from processing solution.

In the wastewater treatment of the present invention, the wastewater to be treated flowing out of the nitrification treatment tank flows into the sedimentation tank through a sedimentation tank between the nitrification treatment tank and the denitrification treatment tank. From the wastewater to be treated to remove nitrogen compounds in the wastewater to be treated, or an aeration tank for removing BOD is installed before the nitrification treatment tank, B
The OD-reduced wastewater can be flowed into a sedimentation basin, and the wastewater to be treated in the nitrification treatment tank can flow from the sedimentation basin. Alternatively, the wastewater to be treated may be treated in the order of the denitrification tank and the nitrification tank, and a part of the wastewater treated in the nitrification tank may be circulated to the denitrification tank for treatment. Between the denitrification treatment tank and the nitrification treatment tank, treatment can be performed with a sedimentation pond interposed to remove nitrogen compounds in the wastewater to be treated.

[0030]

EXAMPLES (Example 1) A 2 liter container was kept at 20 ° C.
It was set in a warm bath and a propeller type stirrer was set. this
Put 1000 ml of sewage in a container and add
NO with thorium _Three−N to a concentration of 20 mg / L
Was. On the other hand, synthetic mica treated with a quaternary ammonium salt
% Containing polyurethane foam (apparent specific gravity: 0.0
5) is cut into 8 mm cubes to form a carrier for immobilizing microorganisms.
And use it in the denitrification reaction to fully acclimate the microorganisms.
Was. This carrier for immobilizing microorganisms is dried with an apparent volume of 2
Charge 100 ml and periodically sample
Changes in the nitrogen content of the treated water over time
Tracked. Table 1 shows the results.

(Comparative Example 1) A hollow cylindrical body having an outer diameter of 8 mm, an inner diameter of 5 mm and a length of 10 mm was molded from polypropylene containing 5% of talc, and used as a carrier for immobilizing microorganisms. This carrier for immobilizing microorganisms was also used in the denitrification reaction in the same manner as in Example 1 to sufficiently acclimate the microorganisms. The carrier for microorganisms immobilization of Example 1 was used in place of the carrier for microorganisms immobilization in the same manner as in Example 1, and the change in the nitrogen content (unit: mg / l) in the treated water was followed. Table 1 shows the results.

[0032]

[Table 1]

(Example 2) 1,000 ml of sewage is placed in a 2 liter container, and is prepared so that it can be aerated and agitated with air using a baloon. As a carrier for immobilizing microorganisms, a polyurethane foam (apparent specific gravity: 0.05) cut into an 8 mm cube containing 3% of synthetic mica containing a quaternary ammonium salt was sufficiently acclimated in advance by aeration treatment. Using. Put this carrier in the 2 liter container
0 ml is charged and sampling is performed regularly.
The change in BOD in the treated water was tracked over time. Table 2 shows the results.

Comparative Example 2 A hollow cylindrical body having an outer diameter of 8 mm, an inner diameter of 5 mm, and a length of 10 mm was molded from polypropylene containing 5% of talc, and used as a carrier for immobilizing microorganisms. This was used in advance for the BOD treatment in the same manner as in Example 2 and was sufficiently acclimated. This microorganism-immobilizing carrier was prepared in Example 2
BOD treatment was performed in the same manner as in Example 2 except that the change in BOD in the treated water was followed.
Table 2 shows the results.

[0035]

[Table 2]

[0036]

According to the present invention, microorganisms can be efficiently attached by containing fine powder of a substance charged with a positive charge,
Substantially open cells, providing a carrier for immobilizing microorganisms made of a synthetic resin or synthetic rubber having little or no biodegradability, and a method for treating wastewater using the carrier for immobilizing microorganisms, particularly in wastewater A method for removing nitrogen compounds is provided. According to the present invention, when the microorganism-immobilizing carrier is charged into a wastewater treatment tank such as a BOD treatment tank, a nitrification treatment tank or a denitrification treatment tank and stirred, microorganisms are immobilized in a large amount in the carrier. Efficiently discharges treated wastewater, produced nitrogen gas, etc., and efficiently supplies and eliminates wastewater and dissolved oxygen to the microbial layer inside the carrier for immobilizing microorganisms by the effect of squeezing the rag to increase the activity of the high-concentration microbial layer. It is possible to perform BOD treatment and wastewater treatment for removing nitrogen compounds while maintaining.

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Claims (11)

[Claims] 1. A carrier for immobilizing microorganisms comprising a substantially open-cell synthetic resin or synthetic rubber molded article containing fine powder of a substance charged with a positive charge. 2. The carrier for immobilizing microorganisms according to claim 1, wherein the fine powder of the substance charged with a positive charge is mica, synthetic mica or an inorganic compound treated with a quaternary ammonium salt. 3. The microorganism-immobilized microorganism according to claim 1, which is an open-cell synthetic resin or synthetic rubber molded product containing a positively charged substance in an amount of 0.1 to 10% by weight based on the synthetic resin. Carrier. 4. The microorganism-immobilizing carrier according to claim 1, wherein the synthetic resin or synthetic rubber molded article having open cells is a foam molded article having an apparent specific gravity of 0.05 to 0.5. . 5. The carrier for immobilizing microorganisms according to any one of claims 1 to 4, wherein the open-cell synthetic resin or synthetic rubber molded product is a granule having a size of 3 to 30 mm. 6. The microorganism-immobilizing carrier according to any one of claims 1 to 5, wherein the foamed molded article is flexible and has a wiping effect. 7. A substantially open-cell synthetic resin or synthetic rubber molding containing fine powder of a positively charged substance together with water to be treated in an aerobic or anaerobic wastewater treatment by microorganisms. A wastewater treatment method, wherein a treatment is carried out by containing a microorganism-immobilizing carrier composed of a body. 8. The wastewater treatment method according to claim 7, wherein the aerobic wastewater treatment is removal of BOD in wastewater. 9. The wastewater treatment method according to claim 7, wherein the aerobic wastewater treatment is a wastewater nitrification treatment. 10. The wastewater treatment method according to claim 7, wherein the anaerobic wastewater treatment is a wastewater denitrification treatment. 11. An aerobic or anaerobic wastewater treatment using microorganisms, wherein a carrier for immobilizing microorganisms having an apparent volume of 2 to 50% based on the internal volume of the treatment tank is used. The wastewater treatment method according to claim 1.