JPS6312678B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating wastewater by electrolysis, which can efficiently treat pollutants. As a general means of wastewater treatment, electrolytic treatment is performed using soluble metals such as iron and aluminum for the anode.
The metal ions generated by electrolysis capture pollutants in wastewater and coagulate them to form flocs.
Similarly, it is well known that microbubbles generated by electrolytic action are adsorbed to flocs and floated separately. However, with conventional processing equipment, it is necessary to replace worn-out electrode plates, and it is difficult to remove scale when scale adheres to the electrode plate and reduces conductivity. It was a hassle. In addition, in order to increase the effective surface area of the electrode plate, it is necessary to alternately arrange a plurality of anodes and cathodes, which leads to the problem that the structure becomes complicated and the overall size tends to increase. The present invention has been made in view of these problems, and has an object to provide a wastewater treatment method using electrolysis that is simple in construction and capable of efficiently treating pollutants. That is, the present invention provides a wastewater inlet at the bottom,
A pair of electrodes are set upright at a predetermined distance apart inside a can made of an insulating material each having a wastewater outlet at the top, and the shape is such that a gap can be formed between them that does not impede the passage of wastewater. A filler whose main component is aluminum, contains at least a few percent iron, and has an oxide film or hydroxide film formed on the surface is filled into the can, and wastewater is introduced from the inlet while applying a DC voltage between the electrodes. The wastewater is electrolytically treated while it passes through the gaps in the filler, and the pollutants are decomposed, adsorbed, coagulated, etc. and turned into flocs, which separates and floats the pollutants to the top of the can. . In this way, in the present invention, the can body is filled with a filler having an oxide film or hydroxide film formed on the surface, and the hydroxides of the component metals, such as aluminum hydroxide and iron hydroxide, are extracted from the filler. is supplied to the wastewater, and each filler reacts, greatly expanding the reaction area, so hydroxide is supplied sufficiently, and the amount of gas generated due to electrolysis increases, causing pollutants. The flocculation and floating are performed efficiently. Since the surface of the filling material is covered with an insulating film, there is no short circuit between the filling materials or between the electrodes, and sufficient contact with the wastewater passing between the filling materials is maintained to prevent reactions. promoted. Furthermore, when the filling material is consumed, there is no need for troublesome replacement work, and it is only necessary to add it from above and replenish it, making it extremely easy to handle. The floc thus obtained is scraped off at the top of the can body,
Alternatively, the particles may be removed by means such as separating and scraping using a well-known flotation separation tank. Next, the present invention will be specifically explained with reference to an illustrated embodiment. In the figure, 1 is a can body, 2 is a pair of electrodes supported by a support frame 3 at the bottom of the can body 1, 4 is a wastewater inlet provided at the bottom of the can body 1, and 5 is a waste water inlet provided at the bottom of the can body 1. A waste water outlet is provided at the top, 6 is a filling material, 7 is a scraper provided at the top of the can body, and 8 is an air supply pipe. The can body 1 is a vertically elongated cylinder with a bottom made of an insulating material such as vinyl chloride or FRP. The electrodes 2 are rod-shaped, and are erected inside the can body 1 at predetermined intervals, and are connected to a DC power source by an appropriate power supply means (not shown). As these electrodes 2, carbon-based insoluble materials such as graphite are used, and in some cases, aluminum or iron-based materials are used on the anode side. As the filler 6, one whose main component is aluminum and contains at least a few percent of iron is used, and its shape is such that a gap can be formed between each filler without hindering the passage of waste water, generally. A sphere or similar shape is suitable, and an oxide film or hydroxide film is previously formed on the surface by chemical treatment. To give a specific example, an aluminum ball called an aluminum shot, which is generally used as a deoxidizing agent for iron manufacturing, is used. This is a rounded conical cast ball with a diameter of about 25 mm and a height of about 15 mm, and is easily available and inexpensive.
It has a large surface area, allowing wastewater to pass through the gap with moderate turbulence, and its composition is 80% aluminum.
The above content is 3 to 5% iron, and also contains trace amounts of zinc, magnesium, etc., and is one of the materials suitable as a filler in the present invention. This is preliminarily treated to form a film, and then put into the can body 1 and filled inside, leaving only the top part. In such a configuration, when wastewater is sent through the inlet 4 and a DC voltage is applied to the electrode 2, while the wastewater rises through the gaps in the filler 6, pollutants in the wastewater are decomposed, reagglomerated, or Depending on the type, it may be condensed and precipitated. The chloride ions and sulfate ions present in the wastewater react with the film material on the surface of the filler 6, producing aluminum hydroxide and iron hydroxide, which progress to covalent bonding, adsorption, inclusion, etc. with the precipitates. , an insoluble floc is gradually formed, and it also reacts with hydrogen gas generated on the cathode side and oxygen gas generated on the anode side, adsorbing gases and reducing the apparent specific gravity, and the floc-formed pollutants are absorbed into the can body. It floats to the top of 1. Since the filler 6 is mainly composed of aluminum, which is an amphoteric element, the ion concentration increases around each electrode 2 due to an anode reaction or a cathode reaction, and dispersed anions and cations also move to the periphery of the electrode 2. The reaction is further accelerated. In this way, the surface of the filler 6 participates in promoting the reaction, the reaction area is expanded, and the reaction is carried out efficiently. Through these reactions, the film material on the surface of the filler 6 is consumed, but at the same time a new film is formed and hydroxide is replenished. Depending on the type of wastewater, additives may be added to the wastewater in a process before it is sent through the inlet 4. These additives are mainly salts that have the function of accelerating the above reactions by compensating for deficiencies in chlorine ions and sulfate ions. It is added accordingly to compensate for the lack of chlorine ions in wastewater.
It is necessary to select an appropriate type of additive for each wastewater through preliminary experiments. For example, in the case of organic domestic wastewater, aluminum chloride (AlCl ₃ , 6H ₂ O) or sodium aluminate (NaAlO ₃ ) is effective, and consumption of the filler 6 can be reduced by appropriate addition. The size of the can body 1 and the electrode 2 used in the present invention are relatively free, but for example, the can body 1 has a diameter of 300 mm.
mmφ, height 1m, diameter 50mmφ, length 800mm as electrode 2, electrode spacing 250mm (center distance), voltage DC 15V, current 2 to 3A, 1 ton of waste water per hour. Pollutant removal rate
It was possible to process at 80% or more. The flocs thus separated and floated to the top of the can body 1 are scraped off by a scraper 7 and taken out from the scum outlet 9, and the purified wastewater flows out from the outlet 5. A well-known rotary type scraper 7 can be used, and in the figure, 7a is a rotary blade, and 7b is a motor. In addition, if the floc recovery here is insufficient, a well-known flotation separation tank may be placed next to the outflow port 5 to ensure complete recovery, and the treated wastewater may be aerated as appropriate. It is released into the river. The air supply pipe 8 is for feeding air to give a lifting force to the flocs, and is used when the lifting force is insufficient to prevent the gaps between the fillers 6 from being clogged. As is clear from the description of the above embodiments, according to the present invention, activated hydroxide is supplied to wastewater from the filler filled in the can body, and moreover, each filler causes a reaction. Since the area is expanded, reactions against pollutants can be carried out efficiently, and a large amount of wastewater can be treated with a relatively small device. Further, in the present invention, when the filler is used up, it is only necessary to replenish the filler by adding the required amount from the top, thereby simplifying maintenance and reducing maintenance costs. Note that the amount of filler consumption is calculated theoretically using Avogatlow's law, but the actual amount of consumption varies slightly depending on the degree of pollution, additives, voltage and current, etc. The frequency of replenishment can be reduced. Note that the present invention is advantageous from the viewpoint of energy saving because the required amount of electric power is small, and operation using solar cells is also possible during the day, which also makes it possible to reduce maintenance costs. Next, examples of treatment results by the wastewater treatment method of the present invention will be shown.

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【table】 (Example 7) Oil-containing wastewater (machine oil and animal and vegetable oil emulsions) Normal hexane extract 100%

[Table] In this way, in various wastewaters, BOD,
It exhibits a removal rate of 90% or more for COD, SS, and other contained components in most cases, and also removes heavy metals (chromium, mercury, cadmium, lead, etc.) and phosphorus that are difficult to remove with normal treatment methods on average. It is possible to obtain a removal rate of over 90%.

[Brief explanation of the drawing]

The drawing is a schematic cross-sectional view of a wastewater treatment device for carrying out the method of the invention. 1...Can body, 2...Electrode, 4...Inflow port, 5...
...Outlet, 6...Filling material.

Claims (1)

[Claims] 1 A pair of electrodes are set up at a predetermined distance from each other inside a can made of an insulating material, which has a wastewater inlet at the bottom and a wastewater outlet at the top, and prevents the passage of wastewater between them. The can is filled with a filler whose main component is aluminum, contains at least a few percent of iron, and has an oxide film or hydroxide film formed on the surface, and a DC voltage is applied between the electrodes. while introducing wastewater from the inlet,
Electrolytic treatment is performed while the wastewater passes through the gaps in the filler,
A wastewater treatment method using electrolysis, characterized in that the pollutants are decomposed and floated to the upper part of the can body by decomposing, adsorbing, coagulating, etc. the pollutants and turning them into flocs.