JPH07284792A - Wastewater treatment method and wastewater treatment equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a wastewater treatment method and a wastewater treatment apparatus capable of efficiently decomposing a hardly decomposable substance in a short time. [Structure] This wastewater treatment device is a wastewater treatment device for decomposing wastewater 1 containing organic pollutants with microorganisms 2. In the wastewater treatment device, three treatment tanks 3, 4, for decomposing treatment with microorganisms 2 while circulating the wastewater 1, 5 and these treatment tanks 3,
Electrode rods 10 and electrodes 11, 12 and 13 which are disposed in Nos. 4 and 5 and which electrolyze the waste water 1 to generate bubbles, and rotating means for relatively rotating the electrode rod 10 and the electrodes 11, 12 and 13. It is characterized in that the microorganisms 2 are activated by the electric current flowing through the wastewater 1 between the electrode rod 10 and the electrodes 11, 12, 13 and the bubbles 18 are attached to the microorganisms 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment method and a wastewater treatment apparatus capable of decomposing hardly decomposable organic substances.

[0002]

2. Description of the Related Art A conventional wastewater treatment method using a conventional wastewater treatment apparatus cultivates microorganisms in a treatment tank, supplies the wastewater into the treatment tank, and causes organic contamination in the wastewater by the action of the microorganisms in the treatment tank. It is designed to decompose a substance. According to this method, the microorganisms can grow using organic pollutants as nutrient sources, decompose organic pollutants in multiple stages, and finally decompose them into gases such as carbon dioxide and ethane.

However, due to rapid progress in science and technology, many useful chemical substances have been synthesized, many kinds of chemical substances which do not exist in nature have been synthesized, and these substances are released to the natural world after use. . Organic substances such as plants and animals obtained from nature can be decomposed in a short time by the action of microorganisms existing in nature even if they are released as wastewater, or by wastewater treatment technology using such microorganisms. it can. Also, many synthetic substances can be decomposed by such microorganisms in a relatively short time.

[0004]

However, among the synthetic substances, in the case of a so-called hardly decomposable substance such as methylnaphthalene, isopropyl alcohol, tetraisopropylamine, etc., which cannot be decomposed in a short time, the microorganism is used. In the conventional wastewater treatment method, it is difficult to decompose such a persistent substance in a short time, and the microorganism has to decompose the persistent substance in multiple stages through complicated metabolic pathways. For decomposition processing, for example, 18
It took a long time of around 00 hours, and there was a problem that wastewater had to be discharged without treatment.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a wastewater treatment method and a wastewater treatment apparatus capable of efficiently decomposing a hardly decomposable substance in a short time.

[0006]

Means for Solving the Problems As a result of various studies on the decomposing action of the microorganism on the hardly decomposable substance, the present inventor has found that when the microorganism is placed in a specific environment, the microorganism is activated, It was found that even a hardly decomposable substance that requires a long time to decompose decomposes quickly in a short time.

The present invention has been made on the basis of the above findings, and the wastewater treatment method according to claim 1 is a wastewater treatment method in which wastewater containing organic pollutants is decomposed by microorganisms. A current is passed through and a magnetic field is created in the wastewater, and the microorganisms in the wastewater are activated by the current and the magnetic field.

The wastewater treatment method according to claim 2 of the present invention is a wastewater treatment method in which wastewater containing organic pollutants is decomposed by microorganisms, and an electric current is applied to the wastewater and a magnetic field is generated in the wastewater. And intermittently supplying high-pressure air into the wastewater to activate the microorganisms in the wastewater, and at the same time, to electrolyze the water in the wastewater by the electric current to generate bubbles.

The wastewater treatment apparatus according to claim 3 of the present invention is a wastewater treatment apparatus for decomposing wastewater containing organic pollutants with microorganisms, and at least decomposing it with microorganisms while circulating the wastewater. The one pair of electrodes is provided with one treatment tank, a pair of electrodes disposed in the treatment tank for electrolyzing the waste water to generate bubbles, and rotating means for relatively rotating the pair of electrodes. It is configured to activate the microorganisms by an electric current flowing through the wastewater between them and to attach the bubbles to the microorganisms.

The wastewater treatment apparatus according to a fourth aspect of the present invention is the wastewater treatment apparatus according to the third aspect, wherein the treatment tank is provided with air supply means for intermittently supplying high-pressure air into the wastewater. It is a thing.

[0011]

According to the first aspect of the present invention, when a wastewater containing organic pollutants is decomposed by microorganisms, an electric current is passed through the wastewater and a magnetic field is generated in the wastewater. Microorganisms can be activated by the electric current and magnetic field to decompose the persistent organic substances.

According to the second aspect of the present invention, when the wastewater containing organic pollutants is decomposed by microorganisms, an electric current is passed through the wastewater and a magnetic field is generated in the wastewater. Furthermore, when high-pressure air is intermittently supplied into the wastewater, the microorganisms are activated by the electric current and the magnetic field, and the shock waves of the high-pressure air stimulate the microorganisms to activate their action and decompose the hardly decomposable substances. Further, when water is electrolyzed to generate bubbles, the bubbles adhere to the periphery of the microorganisms and float in the wastewater, preventing the dissipation of the microorganisms and efficiently performing the decomposition treatment by the microorganisms. be able to.

According to the third aspect of the present invention, when the waste water containing the organic pollutant is circulated in the at least one treatment tank of the waste water treatment apparatus while being decomposed by microorganisms. In addition, when a pair of electrodes in the treatment tank are energized and the pair of electrodes is relatively rotated by the rotating means, a magnetic field is generated in the vicinity of each electrode due to energization between the electrodes, and the magnetic field acts on the microorganisms to cause the microorganisms to act. Meanwhile, air bubbles such as oxygen are generated on the surface of each electrode at the same time.
Since each electrode rotates relatively, air bubbles on the electrode surface are released into the wastewater while remaining fine, and the air bubbles rise against the flow of the wastewater. It is possible to efficiently dissociate the microorganisms by preventing the microorganisms from being dissipated by the flow of water.

According to the invention described in claim 4 of the present invention, in the invention described in claim 3, the processing tank comprises:
Since the air supply means for intermittently supplying air to the wastewater is provided, a shock wave by air pressure is applied to the microorganisms in the wastewater to stimulate the microorganisms and promote the dissolution of oxygen in the wastewater to promote the decomposition treatment of the microorganisms. can do.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in FIGS. In each figure, FIG. 1 is a configuration diagram showing an embodiment of the wastewater treatment apparatus of the present invention used in the wastewater treatment method of the present invention, and FIG. 2 illustrates the behavior of microorganisms in the wastewater treatment apparatus shown in FIG. 3 is a perspective view showing an electrode of the wastewater treatment apparatus shown in FIG. 1, FIG. 4 is a configuration diagram showing another embodiment of the wastewater treatment apparatus of the present invention used in the wastewater treatment method of the present invention, FIG. 5 is a configuration diagram showing a configuration of a main part of the wastewater treatment device shown in FIG.

Example 1 As shown in FIG. 1, the wastewater treatment apparatus of this example decomposes wastewater 1 containing organic pollutants by microorganisms 2, and three treatment tanks 3,
Three, four and five are stacked vertically, and the processing tanks are connected to each other. The bottom surface 3A of the upper processing tank 3 is formed in a cone shape with a gentle downward slope from the periphery toward the center, and an opening is formed in the center thereof. The bottom surfaces 4A and 5A of the middle and lower processing baths 4 and 5 are formed in the same manner as the upper processing bath 3, respectively, and the upper surfaces 4B and 5B of each of the processing baths 4 and 5 are formed in a cone shape with a gradual upward inclination from the periphery toward the center. And an opening is formed at the center of each of them. Organic pollutants include substances that are easily decomposed by the microorganism 2 and hardly decomposed substances that are difficult to decompose by the microorganism 2, such as methylnaphthalene, isopropyl alcohol, and tetraisopropylamine. The microorganism 2 may be an aerobic microorganism, an anaerobic microorganism, or an intermediate thereof. In this embodiment, an aerobic microorganism generally used in the activated sludge method is used.

Then, the upper processing tank 3 and the middle processing tank 4
Are connected by a cylinder 6 at each opening,
The middle processing tank 4 and the lower processing tank 5 are connected by a cylindrical body 7 at their respective openings, and three processing tanks 3, 4, 5 are connected.
Are integrated. A cylinder 8 is connected to the opening of the bottom surface 5A of the lower processing tank 5, and a discharge pipe 9 extending to the liquid level of the upper processing tank 3 is connected to the cylindrical body 8. The axes of the processing tanks 3, 4, 5 and the cylindrical bodies 6, 7, 8 are aligned with each other. Furthermore, the integrated processing tanks 3, 4,
A magnetized electrode rod 1 penetrating each shaft core in
0 is arranged, and the cylindrical magnetized electrodes 11, 12, 1 forming a pair with the electrode rod 10 are formed on the inner surfaces of the respective cylinders 6, 7, 8.
3 is attached. Electrode rod 10 and each electrode 11, 1
2 and 13 are connected to a power source 15 via a wiring 14, and the power source 15 causes the electrode rod 10 and each electrode 11, 12, 13 to be connected.
And a voltage of, for example, 5 to 40 V is applied between them and a weak current, for example, 40, through the wastewater 1 in the treatment tanks 3, 4, and 5.
A current of ˜80 mA is allowed to flow. Further, a rotating means (not shown) such as a motor is connected to the electrode rod 10 so that the electrode rod 10 is rotated in the wastewater 1 in the direction of arrow A in FIG.

The upper processing bath 3 and the lower processing bath 5 are connected by a pipe 16, and the processing bath 3 and the processing bath 5 are connected to each other through the pipe 16. Further, a pump 17 is arranged in the pipe 16, and the waste water 1 supplied to the treatment tank 3 by driving the pump 17 circulates from the pipe 16 to the original treatment tank 3 via the treatment tanks 4 and 5. Is done. Then, while the wastewater 1 is repeatedly circulated in the treatment tanks 3, 4, and 5, the microorganisms 2 act on the organic pollutants in the wastewater 1 to decompose it, and finally decompose into gases such as carbon dioxide and methane. The wastewater 1 is purified by means of the wastewater 1, and the purified treated water is discharged through the discharge pipe 9. After the drainage, the waste water 1 is automatically replenished to the treatment tank 3 so that the waste water 1 always maintains a constant amount.

Next, an embodiment of the wastewater treatment method of the present invention using the wastewater treatment equipment of the above embodiment will be explained together with the operation of the wastewater treatment equipment. First, the wastewater 1 is treated with the treatment tanks 3, 4, 5
Supplied to the inside, and the microorganisms 2 in each treatment tank 3, 4, 5 waste water 1
To make it cloudy. Then, the pH of the wastewater 1 is set to 7 in advance.
Adjusted to 9.5, and the electrode rod 10 and the electrodes 11 and 1 from the power source 15 while rotating the electrode rod 10 by the rotating means.
A voltage of 30 V is applied between the electrodes 2 and 13 and the voltage is 40 to 8 between the electrodes.
A weak current of 0 mA is applied. At the same time, the pump 17 is driven to gently circulate the wastewater 1 in the treatment tanks 3, 4, and 5 through the pipe 15 to create a downward flow of the wastewater 1 in each treatment tank 3, 4, and 5. As a result, the microorganisms 2 flow under the treatment tanks 3, 4, 5 as shown by the arrow B in FIG. 2, but most of them rise with the bubbles 18 as described later.

That is, the above-mentioned current causes the positive electrode rod 10 to move.
Oxygen gas is generated at, and hydrogen gas is generated at the-side electrodes 11, 12, and 13. At each electrode, each gas gradually grows and becomes a bubble 18. At this time, since the electrode rod 10 is rotating, the bubble 18 adhering to the electrode rod 10 is finely divided by the rotation of the electrode rod 10 into an electrode. It is released from the rod 10 and floats in the wastewater 1 and adheres to the surface of the microorganism 2. When the amount of bubbles 18 attached to the microorganisms 2 increases, buoyancy acts on the microorganisms 2 and the microorganisms 2 rise in the wastewater 1 against the downward flow thereof as shown by an arrow C in FIG. Therefore, even while the wastewater 1 circulates in the treatment tanks 3, 4, and 5, the bubbles 18 suppress the flow of the microorganisms 2 to the downstream side and make the microorganisms 2 flow back into the respective treatment tanks 3, 4, and 5 to cause the microorganisms 2 to flow. The microorganism 2 can be efficiently used for concentration and decomposition treatment of organic pollutants. Further, even if the microorganisms 2 flow from the respective treatment tanks 3, 4, 5 to the downstream side, the microorganisms 2 can be returned to the respective treatment tanks 3, 4, 5 via the pipe 9.

On the other hand, during the processing, since a voltage is applied between the magnetized electrode rod 10 and the magnetized electrodes 11, 12 and 13, a magnetic field is formed around each electrode, and this magnetic field is generated. With the current flowing between the electrodes, it acts on the microorganisms 2 to activate the microorganisms 2, selectively decomposing organic pollutants that are easily decomposed, which suppresses the selectivity of the microorganisms 2 and is a substance that is difficult to decompose with respect to the microorganisms 2. It is possible to enhance the activity of the microorganism 2 against the hardly-decomposable substance by imparting the property of decomposing the same to the microorganism 2 and acclimatizing and culturing the microorganism 2 as a microorganism 2 having a strong resistance to the decomposition of the hardly-decomposable substance. This is considered to be a phenomenon that occurs because the microorganisms 2 are stimulated by the action of an electric current and a magnetic field and their respiratory and metabolic properties are activated. Then, due to this phenomenon and conditioned culture, the transport function of the substance between the inside and outside of the cell of the microorganism 2 is enhanced, and the hardly decomposable substance is taken into the cell as a nutrient source at a speed comparable to that of other organic pollutants. Therefore, the hardly decomposable substance can be decomposed rapidly in a short time. Then, the microorganisms 2 activated in this way generate bubbles 18
Is floated up into the respective treatment tanks 3, 4, and 5, and in the respective treatment tanks 3, 4, and 5, the microorganism 2 is decomposed in combination with the dissolved oxygen from the bubbles 18 to be easily decomposed. In addition to processing, hardly decomposable substances can be decomposed in a short time like other organic pollutants which are easily decomposed, and the waste water 1 having a chemical oxygen demand of COD = 30 is used in the present embodiment. It can be decomposed by the microorganism 2. At this time, the decomposition and removal rate of the hardly decomposable substance reaches 99%, and the decomposition and removal rate in this example is remarkably improved as compared with the conventional treatment method of about 20%. In addition to the digestion of organic pollutants, the microorganisms 2 propagate due to the dissolution of oxygen gas. Here, in the case of further enhancing the decomposition treatment capability of the hardly decomposable substance by the microorganism 2, the purpose can be achieved by attaching the microorganism 2 to the carrier.

As described above, according to the wastewater treatment method of this embodiment using the apparatus of the above embodiment, the treatment tanks 3, 4,
When a voltage is applied between the electrodes 11, 12, 13 and the electrode rod 10 of No. 5, an electric current is passed between the electrode rod 10 and each of the electrodes 11, 12, 13 and a magnetic field is created in the wastewater 1 near each electrode, By activating the microorganisms 2 in the wastewater 1 by this electric current and magnetic field, the transport function of substances between the inside and outside of the cells of the microorganisms 2 is enhanced, and persistent substances are comparable to other organic pollutants. It can be taken up into cells at a rate that can be rapidly decomposed in a short time, and the decomposition and removal rate of the hardly decomposed substance reaches 99%. Therefore, in comparison with the decomposition and removal rate of the hardly decomposable substance in the wastewater treatment method using the conventional processing apparatus being around 20%, the decomposition and removal rate is remarkably improved in this embodiment. Therefore, according to the present embodiment, the installation volume of the wastewater treatment device can be significantly reduced, and the installation area can be reduced to, for example, 1/10 or less of the conventional installation volume.

Embodiment 2. Wastewater treatment apparatus 20 of this embodiment
Is connected to the side wall of a storage tank 21 that stores the wastewater 1 via a pipe 22 as shown in FIG. This piping 22
A pump 23 is disposed on the upstream side of the waste water 1, and the waste water 1 circulates between the waste water treatment device 20 and the storage tank 21 by this pump, and during this period, the organic pollutants are decomposed by the microorganisms 2 of the waste water treatment device 20. Is configured. A discharge pipe 24 is attached to the storage tank 21 at a position different from the side wall on which the wastewater treatment device 20 is attached.
The treated water of 0 is discharged from the discharge pipe 24.

Therefore, the wastewater treatment apparatus 20 of this embodiment will be described in detail with reference to FIG. Wastewater treatment apparatus 2 of this embodiment
As shown in FIG. 5, 0 is a horizontally long cylindrical processing tank 201,
Two 202 are stacked vertically. Piping portions 201A and 201B that face up and down are formed on the left and right sides of the lower processing tank 201, and pipe portions 202A and 202B that vertically face are formed on the left and right sides of the upper processing tank 202, respectively. ing. The upper and lower processing tanks 201 and 202 are respectively connected to the pipe section 2
Electrodes 203 also serving as connection pipes in 01A and 202B
Are connected by respective flanges. Further, the lids 201C and 201C are provided at both ends of the lower processing tank 201.
Are joined by bolts or the like, and these lids 201C, 2
The inside of the processing tank 201 is sealed by 01C.

The processing tank 201 has lids 201C and 20C.
The electrode rod 204 penetrates through the center of 1C via a seal member 205, and the electrode rod 204 is configured to be rotatable by a rotating means (not shown). This processing tank 2
The outer circumference of 01 and the outer circumference of both ends of the electrode rod 204 are coil 2
The coils 206A and 206B are surrounded by the gaps 06A and 206B, and the coils 206A and 206B are connected to each other by a wiring 207 to be integrated. One coil 206B
Is connected to the negative side of the power supply, and the other coil 206B
Is connected to the left end of the electrode rod 204. Also,
The + side of the power source is connected to the electrode 203 between the treatment tanks 201 and 202, and the electrode rod 204 is connected via the waste water 1 in the treatment tank 201.
A weak current flows between the coil 206 and
A magnetic field is formed inside the A and 206B, that is, inside the processing tank 201. In addition, the upper processing tank 202
Also the electrode rod 208, the seal member 209, the coil 210A,
It has 210B and wiring 211, and is configured similarly to the processing tank 201.

Further, the processing bath 2 is attached to the electrode rod 204 from the right end.
An air passage 204A reaching 01 is formed so as to pass through the axis, and the air passage 204A opens in the processing tank 201 in a direction orthogonal to the axis. This air passage 20
An air pipe 212 is airtightly connected to the opening at the shaft end of 4A. A high-pressure air source (not shown) is connected to the air pipe 212, and an electromagnetic valve 213 and a valve 214 are sequentially arranged in the air pipe 212 from the downstream side to the upstream side, and the opening degree of the valve 214 is adjusted. In the adjusted state, the electromagnetic valve 213 is intermittently opened to intermittently supply the high-pressure air from the high-pressure air source into the wastewater 1 in the treatment tank 201, and the microorganisms (not shown) in the wastewater 1 are supplied with air. It is configured to impart a shock wave. Although not shown, the electrode rod 208 of the treatment tank 202 is also provided with a similar air passage so that a shock wave of high-pressure air can be applied to the microorganisms in the treatment tank 202.

Next, one embodiment of the wastewater treatment method of the present invention using the wastewater treatment apparatus of the above embodiment will be described together with the operation of the wastewater treatment apparatus. First, the wastewater 1 is supplied into the treatment tank 201, and the microorganisms are made turbid by the wastewater 1 in the respective treatment tanks 201 and 202. Then, the pH of the wastewater 1 is set to 7-
When the voltage is adjusted to 9.5 and a voltage of, for example, 5 to 40 V is applied from the power supply to the electrode 203 and the coils 206A and 206B while rotating the electrode rod 204 by the rotating means, this voltage eventually results in the electrode rod 204 and the electrode 203. Will be applied between. Thereby, the electrode 203 and the electrode rod 20
The voltage between 4 causes a weak current of 40 to 80 mA to flow through the wastewater 1. At this time, when the pump 23 is driven, the wastewater 1 in the storage tank 21 is stored in the storage tank 21 and the processing tanks 201, 20.
2 and the wastewater 1 is circulated from the treatment tank 201 to the treatment tank 2
Make a gentle updraft to 02. At this time, the same phenomenon occurs in the processing bath 202 as in the processing bath 201.

On the other hand, the coils 206A, 206B, 210
Processing tanks 201 and 202 by the electric current flowing through A and 210B
A magnetic field is generated in the treatment tank 201, 202, as in the case of the first embodiment, because the magnetic field and the weak current in the wastewater 1 are combined.
The microorganisms therein are activated and the organic pollutants containing the hardly decomposable substance in the wastewater 1 are decomposed in the same manner as in Example 1.
At this time, the electromagnetic valve 213 is intermittently opened and closed to adjust the opening degree of the valve 214, the air pipe 212, and the air passage 20.
When high-pressure air is intermittently supplied into the processing tank 201 via 4A, this air is supplied from the air passage 204A to the processing tank 201.
A shock wave of air can be applied inside to activate microorganisms to enhance their metabolic function and oxygen can be dissolved in the wastewater 1.

As described above, according to the wastewater treatment method of this embodiment using the apparatus of the above embodiment, each electrode rod 204,
A voltage is applied between the electrode 208 and the electrode 203, and the electrode rod 20
When a current is passed between the electrodes 4, 208 and the electrode 203 and a magnetic field is created in the wastewater 1 of each treatment tank 201, 202, the microorganisms in the wastewater 1 are activated by the current and the magnetic field, and the high-pressure air is intermittently supplied. The shock wave activates the microorganism, and transports substances (metabolic function) between the inside and outside of the microorganism.
Therefore, the hardly decomposable substance can be taken into cells at a rate comparable to other organic pollutants, and the hardly decomposable substance can be rapidly decomposed in a short time. In addition, also in the present embodiment, the same operational effect as that of the first embodiment can be expected.

It should be noted that the present invention is not limited to the above-mentioned embodiments at all, and any technique included in the gist of the present invention of activating microorganisms in wastewater by an electric current and a magnetic field can be applied to the present invention. The present invention includes even those in which the respective components of (1) are appropriately designed and changed.

[0031]

According to the first and second aspects of the present invention, it is possible to provide a wastewater treatment method and a wastewater treatment apparatus capable of efficiently decomposing a hardly decomposable substance in a short time.

According to the third and fourth aspects of the present invention, it is possible to provide a wastewater treatment apparatus capable of efficiently decomposing a hardly decomposable substance in a short time.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a wastewater treatment apparatus of the present invention used in a wastewater treatment method of the present invention.

FIG. 2 is an explanatory diagram for explaining the behavior of microorganisms in the wastewater treatment device shown in FIG.

3 is a perspective view showing electrodes of the wastewater treatment device shown in FIG. 1. FIG.

FIG. 4 is a configuration diagram showing another embodiment of the wastewater treatment apparatus of the present invention used in the wastewater treatment method of the present invention.

5 is a configuration diagram showing a configuration of a main part of the wastewater treatment device shown in FIG.

[Explanation of symbols]

 1 Wastewater 2 Microorganisms 3 Treatment tank 4 Treatment tank 5 Treatment tank 10 Electrode rod 11 Electrode 12 Electrode 13 Electrode 18 Bubble 20 Wastewater treatment device 201 Treatment tank 202 Treatment tank 203 Electrode 204 Electrode 206A coil 206B coil 210A coil 210B coil

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Claims (4)

[Claims] 1. In a wastewater treatment method for decomposing wastewater containing organic pollutants by microorganisms, an electric current is passed through the wastewater and a magnetic field is generated within the wastewater, and the microorganisms in the wastewater are generated by the electric current and the magnetic field. A method for treating wastewater, which comprises activating water. 2. A wastewater treatment method for decomposing wastewater containing organic pollutants by microorganisms, wherein an electric current is applied to the wastewater, a magnetic field is created in the wastewater, and high-pressure air is intermittently supplied into the wastewater. And activating the microorganisms in the wastewater, and at the same time, electrolyzing the water in the wastewater by the electric current to form bubbles. 3. A wastewater treatment apparatus for decomposing wastewater containing organic pollutants with microorganisms, at least one treatment tank for decomposing treatment with microorganisms while circulating the wastewater, and disposed in this treatment tank. A pair of electrodes for electrolyzing the waste water to generate bubbles and a rotating means for relatively rotating the pair of electrodes are provided, and the microorganisms are activated by an electric current flowing through the waste water between the pair of electrodes. A wastewater treatment apparatus, characterized in that the bubbles are attached to the microorganisms. 4. The wastewater treatment apparatus according to claim 3, wherein the treatment tank is provided with air supply means for intermittently supplying high-pressure air into the wastewater.