JPH0734909B2 - Electric levitation device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technology for treating industrial wastewater, and more particularly to a technology effective when applied to the treatment of organic wastewater using an electric levitation method.

[Prior Art] Industrial wastewater treatment methods are roughly classified into biological treatment methods and physicochemical treatment methods. Organic wastewater is mainly treated by (1) activated sludge method and (2) catalytic oxidation method. , (3) Biological treatment methods such as disk aeration method are used. However, the biological treatment method is 0.5 kg of water for 1 kg / day of treated BOD.
To 1 m ³ / day, since it requires air quantity 50 Nm ³ / day, facility area, that there is a drawback that requires enormous expenses such as facilities costs have been pointed out.

On the other hand, physicochemical treatment methods include (1) coagulation and precipitation method,
(2) pressure levitation method, (3) electric levitation method, (4) adsorption method,
(5) There is a reverse osmosis method and the like. Among these treatment methods, the adsorption method and the reverse osmotic pressure method are used to treat wastewater treated by a biological treatment method or the like to a higher degree. The coagulation-sedimentation method is used for treating wastewater containing heavy particles and containing no oil. Since the pressurized flotation method can efficiently remove SS, BOD, COD, oil, etc. in high-concentration wastewater, it can be used alone as a pretreatment for biological treatment or when water quality control values are not so strict. There is. The electro-levitation method is a process in which organic wastewater is introduced into an inorganic reaction tank and a polymer reaction tank, a part of hydrophilic substances and hydrophobic pollutants in the wastewater are aggregated to form flocs, and the wastewater with flocs is floated. It consists of a process of leading to the tank and associating the flocs with electrolytic gas bubbles to float, and a process of leading the floating flocs to the flotation separation tank and removing them by a schema.Similar to the pressure flotation method, SS, BOD in highly concentrated wastewater, CO
It has the advantage that D, oil, etc. can be removed efficiently.
The electric levitation method has the following advantages over the pressure levitation method.

(1). No noise is generated because no compressor or pressure pump is used.

(2). Since the pressurized water is not used, the flotation tank can be downsized. Moreover, since a pressurized water production apparatus is not required, the entire equipment can be downsized.

(3). By varying the electrolysis current, it is possible to easily increase / decrease and control fine electrolysis gas bubbles.

(4) As secondary effects of electrolysis, hypochlorite gas and chlorine gas as by-products can reduce BOD and COD and can be decolorized.

The wastewater treatment device using the electric levitation method is described in JP-A-62-38286 and JP-A-2-21994.

[Problems to be Solved by the Invention]

The electric levitation method is an excellent wastewater treatment method having many advantages as described above, but the conventional wastewater treatment equipment using this electric levitation method has the following practical problems. As a result, it is rarely used for the treatment of organic wastewater.

(1). Since the density of the electrolytic gas bubbles in the flotation tank is low, the association of the electrolytic gas bubbles with the flocs becomes insufficient,
A large amount of flocs that are not associated with each other is generated to cause a carryover phenomenon. In addition, the electrolytic gas bubbles are separated and dispersed from the flocs that have once floated, and the flocs are likely to reprecipitate.

(2). When the wastewater guided to the floating tank passes between the electrodes,
Since crosslinks are easily formed by the flocs, an electrical short circuit occurs and an accident occurs in which the generation of electrolytic gas bubbles is stopped.

(3). Due to the structure of the flotation tank, it is difficult to clean the electrodes and remove the scale, and the SS removal efficiency decreases over time.

(4). Due to the occurrence of flocs due to carryover, the removal efficiency of BOD and COD decreases.

An object of the present invention is to provide an electric levitation device suitable for use in organic wastewater treatment, by improving the above-mentioned problems of the effluent treatment device using the electric levitation method (hereinafter, simply referred to as an electric levitation device). .

[Means for Solving the Problems]

The following is a brief description of the outline of the typical invention disclosed in the present application.

The electric levitation device of the present invention comprises a reaction tank for forming flocs by causing a flocculant to act on the wastewater to be treated, a levitation tank for floating the flocs by associating the flocs with electrolytic gas bubbles, and a partition for the levitation tank. An electric levitation device comprising a separation tank disposed adjacent to each other to separate the flocs from the wastewater to be treated, and a schema for removing the flocs, wherein the flocs formed by the reaction tank are supplied to the flotation tank. Forming a floc inlet on the side wall of the flotation tank, raising the electrolytic gas along the side wall from a lower side than the floc inlet, and a floc rising flow along the side wall; An electrode for forming a self-cleaning convection that descends along the partition wall and an entrained convection that flows from the partition wall side toward the flock rising flow is positioned below the flock inlet port. Characterized in that attached to the lower portion of the side wall.

A backflow prevention plate for preventing backflow of electrolytic gas bubbles is provided at the flock inlet, and a flock inflow tank having a guide wall is provided between the reaction tank and the floating tank.

[Action]

Since the electrolytic gas rises along the side wall of the flotation tank and the flock inlet is formed on the side wall, the floc flowing into the floating tank can be brought into contact with the high-density electrolytic gas. In addition, since self-cleaning convection that descends along the partition wall facing the side wall is formed, the surface of the electrode is always kept clean by the self-cleaning convection after almost all the flocs are removed, and an electrical short circuit in the electrode is prevented. Occurrence can be prevented. Then, in the flotation tank, since convection that entrains the flocs above the electrodes from the partition side is formed in the flotation tank, flocs that could not associate with the electrolytic gas are entrained in this convection and re-float on the electrode, The flocs are prevented from entering the self-cleaning convection, and the flocs do not settle below the electrodes.

Hereinafter, the present invention will be described with reference to examples.

[Embodiment] FIG. 1 is a view showing a main part of an electric levitation apparatus according to this embodiment.

The organic wastewater to be treated is first introduced into the inorganic reaction tank 3 through the wastewater inlet 2 provided at one end of the electric levitation apparatus 1.
The inorganic reaction tank 3 is filled with an inorganic coagulant having a predetermined concentration, and a part of the hydrophilic substance in the organic wastewater to be treated coheres to form flocs. The inorganic reaction tank 3 is provided with a stirring means for stirring the treated organic waste water, a pH sensor for measuring the pH of the waste water, and the like as required.

The flocs formed in the inorganic reaction tank 3 are introduced into the polymer reaction tank 4 together with the organic wastewater to be treated. A polymer flocculant having a predetermined concentration is injected into the polymer reaction tank 4, and the hydrophobic pollutants in the organic wastewater to be treated cohere to form flocs. A stirring means for stirring the organic wastewater to be treated is installed in the polymer reaction tank 4 as needed.

The flocs formed in the inorganic reaction tank 3 and the polymer reaction tank 4 are the floc inflow tank 5 together with the organic wastewater to be treated.
And is introduced into the floating tank 6. The flock inflow tank 5 is provided with a guide plate 7 for uniformly introducing the flocs into the floating tank 6.

An electrode 8 is disposed below the side wall 6a of the flotation tank 6, and flocs and organic wastewater to be treated are floated above the electrode 8 through a floc inlet 9 formed in the side wall 6a. It is introduced into the tank 6. The electrode 8 has a structure in which a plurality of anodes and cathodes are alternately opposed to each other, and hydrogen gas bubbles generated from the cathodes by electrolysis of water float up through the gap between the anodes and the cathodes. Convection (A) as shown in FIG.
That is, the self-cleaning convection that descends toward the bottom surface of the floating tank 6 along the partition wall 20 is formed. As described above, in the electric levitation device 1 of the present embodiment, the floc inlet 9 is arranged immediately above the electrode 8 and the flocs introduced into the flotation tank 6 through the floc inlet 9 immediately contact the high density hydrogen gas bubbles. Most of the flocs are associated with hydrogen gas bubbles as soon as they are introduced into the flotation tank 6 and rise along the side wall of the flotation tank 6 due to their buoyancy. Between the side wall where the electrode 8 and the flock inlet 9 are arranged and the partition wall 20 facing the side wall, as shown in FIG. Since entrained convection is formed, the remaining flocs that did not associate with hydrogen gas bubbles immediately after being introduced into the flotation tank 6 are also entrained in this convection (B) and re-float at the electrode 8 to associate with hydrogen gas bubbles. To do. A backflow prevention plate 10 is provided in the flock inlet 9.
Is provided to prevent a part of the flocs floating in association with the hydrogen gas bubbles from flowing back to the flocks inlet port 9. As described above, all the flocs introduced into the levitation tank 6 are associated with the hydrogen gas bubbles on the electrode 8 to float, and the convection (A) formed on the side and below the electrode 8 contains the flocs. Therefore, the electrode 8 is cleaned by the self-cleaning convection that does not contain much flock, and the flock is not clogged in the gap between the electrodes 8.

The flocs associated with the hydrogen gas bubbles and floated are guided to the separation tank 11 together with the wastewater, and then separated from the wastewater by the schema 12 provided above the separation tank 11, and the sludge discharge port 13
Is discharged to the outside through. Since the above flocs contain a large amount of hydrogen gas bubbles, they have a low water content and therefore a small volume. On the other hand, the effluent that has been clarified by removing the flocs is discharged to the outside through the treated water separation pipe 14 and the treated water discharge port 15.

Next, a method of cleaning the electrode 8 of the electric levitation device 1 will be described with reference to FIG.

In order to clean the electrode 8, the drain valve 16 provided at the bottom of the levitation tank 6 is opened to remove the drainage in the levitation tank 6, and then the cleaning solution (for example, the electrode 8 is immersed in the levitation tank 6). 5%
Hydrochloric acid aqueous solution) is injected to remove the scale attached to the surface of the electrode 8. In the electric levitation apparatus 1, the electrode 8 is arranged below the levitation tank 6, so that a small amount of cleaning liquid is required.

Next, the analytical values of the organic wastewater (seafood processing wastewater) treatment carried out using the electric levitation apparatus 1 are shown in Tables 1 to 3 below.

[Effects of the Invention] The effects obtained by the typical ones of the inventions disclosed in this application will be briefly described as follows.

(1). Since the flocs can be efficiently associated with the electrolytic gas bubbles, the BOD and COD removal efficiency is significantly improved.

(2). Since the electrode cleaning and scale removal can be performed easily, the removal rate of SS is greatly improved.

(3). According to the above (1) and (2), it is possible to treat the organic wastewater by the floating device alone. When used as a pretreatment for biological treatment, the load of biological treatment can be significantly reduced.

(4). Since the flocs are not contained in the waste water passing between the electrodes, it is possible to prevent an accident in which the generation of electrolytic gas bubbles is stopped due to the short circuit of the electrodes.

(5). The volume of the flotation tank and the separation tank can be reduced. In addition, the electrode capacitance can be reduced.

(6). Since the content of hydrogen gas bubbles in the floating flocs is high, the content of flocs becomes low, and the sludge volume can be reduced.

(7). Due to the above items (5) and (6), expenses (initial cost, running cost) such as equipment area and facility cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part showing an electric levitation device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional part of an essential part for explaining an electrode cleaning method of this electric levitation device. 1 ... Electric levitation device, 2 ... Drainage inlet, 3 ... Inorganic reaction tank, 4 ... Polymer reaction tank, 5 ... Flock inflow tank, 6
...... Floating tank, 7 ... Guide plate, 8 ... Electrode, 9 ... Flock inlet, 10 ... Backflow prevention plate, 11 ... Separation tank, 12 ... Schema, 13 ... Sludge outlet, 14 ... … Treated water separation pipe, 15
…… Treatment water outlet, 16 …… Drain valve.

Claims (3)

[Claims] 1. A reaction tank in which a flocculant is caused to act on wastewater to be treated to form flocs, a flotation tank in which the flocs are associated with an electrolytic gas bubble to float, and the flotation tank is adjacent to the flotation tank through a partition wall. An electric flotation device comprising a separation tank arranged to separate the flocs from the wastewater to be treated, and a schema for removing the flocs, wherein a floc flow for supplying the flocs formed by the reaction tank to the flotation tank. An inlet is formed on the side wall of the flotation tank, and the electrolytic gas is raised from below the flock inlet along the side wall to increase the flow rate of the floc along the side wall, and along the partition wall facing the side wall. The electrode for forming self-cleaning convection that descends toward the bottom surface of the flotation tank and entrained convection that flows from the partition side toward the floc rising flow below the floc inlet. Electric levitation device, characterized in that attached to the lower portion of the side wall is positioned. 2. The electric levitation device according to claim 1, wherein a backflow preventing plate for preventing backflow of electrolytic gas bubbles is provided at the floc inlet. 3. The electric levitation device according to claim 1, wherein a floc inflow tank having a guide wall is provided between the reaction tank and the levitation tank.