JPH06285455A - Treatment of waste liquid - Google Patents

Abstract

PURPOSE:To obtain a method for treating a waste liq. with good treating efficiency as a whole by providing a method with a distillation process for separating water and components with approximately the same b.p. as that of water or lower than that in a waste liq. and an oxidizable substance-decreasing process electrolyzing the separated components by energizing a direct current. CONSTITUTION:In the method for treating a waste liq., at first, the waste liq. is fed in a distillation tank 1, where the superheating temp. is set at 104 deg.C and water and components with approximately the same b.p. as that of water or lower than that among the components in the waste liq. are separated by means of distillation. Evaporated components are cooled and fed into an adjusting tank 2. Then, while they are fed into an electrolytic tank 3 by using a pump P, they are electrolyzed by energizing a direct current. In this process, oxidizable substances such as org. substances in the waste liq. are oxidatively decomposed by anodic oxidative reaction and odorous components in the waste liq. are almost decomposed in this process. Namely, the oxidizable substances are decomposed into carbon dioxide, nitrogen and water here in a short time by a strong oxidative action at the anode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste liquid treatment method.

[0002]

2. Description of the Related Art Water used in various industrial fields such as acid / alkali surface treatment facilities, spinning / textile products, production of marine food products and livestock food products, electroplating, photography, printing, etc. Polluted by These are finally discharged into rivers and oceans, but the water quality standards for waste liquids have been established from the viewpoint of environmental protection of rivers, etc. It is necessary to reduce the oxygen demand (COD value).

Therefore, the inventor proposed on March 1, 1993, a method for treating a waste liquid having an excellent ability to reduce the demand for chemical oxygen (Japanese Patent Application No. 5-39732). This method is a waste liquid which is an electrolyte solution or is made into an electrolyte solution by passing a direct current, and the nascent active oxygen generated thereby reacts with the oxidizable substance in the waste liquid to oxidize and decompose it. It has a processing step. According to this method, since nascent active oxygen has an extremely strong oxidizing ability, it has an advantage of being excellent in reducing the chemical oxygen demand of the waste liquid.

There are various ways in which water is contaminated. In other words, the concentration of the oxidizable substance in the waste liquid may be extremely high, or the waste liquid may contain solids. Therefore, when actually reducing the chemical oxygen demand of the waste liquid by the above treatment method, the treatment time may take an abnormally long time or the solid content may cause clogging, resulting in poor treatment efficiency. It was

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to propose a method for treating waste liquid, which has a high treatment efficiency as a whole.

[0006]

In order to solve the above problems, the present invention takes the following technical means. The method for treating waste liquid according to the present invention comprises, of the components in the waste liquid, a distillation step of separating water and a component having a boiling point which is substantially the same as or lower than the boiling point of water, and a component separated by distillation. And a step of reducing an oxidizable substance in which a direct current is applied to electrolyze.

When the component separated by the distillation is not an electrolyte solution, a step of using this as an electrolyte solution is provided.

[0008]

As a result of adopting the above means, the present invention has the following effects. In the distillation step, among the components in the waste liquid, water and components having a boiling point which is substantially the same as or lower than the boiling point of water are separated by distillation and supplied to the oxidizable substance reducing step. In other words, it is possible to remove components and solids having a boiling point higher than that of water from the components in the waste liquid and supply the components to the oxidant-reducing step.

Here, the component having a boiling point higher than that of water usually contains a high concentration of a substance to be oxidized, and the solid content is likely to become an obstacle during electrolysis. On the other hand, when a direct current is applied to the component separated by distillation in the step of reducing the oxidizable substance and electrolysis is performed, the nascent active oxygen generated thereby oxidatively decomposes the oxidizable substance in the separated component.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below with reference to the accompanying drawings. As shown in FIGS. 1 and 2,
In this example, a waste liquid treating apparatus having the following mechanism was formed. Distillation tank 1, adjustment tank 2 to which the components separated in said distillation tank 1 are sent, and sodium chloride aqueous solution supply tank 4 for supplying sodium chloride aqueous solution to said adjustment tank 2.
An electrolytic bath 3 having an electrolysis passage 30 for electrolyzing the supplied waste liquid, and a discharge mechanism 5 for atomizing the treated waste liquid after passing through the electrolysis passage 30 to the atmosphere.

In the distillation tank 1, a known band heater (not shown) is used for heating the waste liquid. In this distillation tank 1, among the components in the waste liquid, water and components having a boiling point which is substantially the same as or lower than the boiling point of the water are separated by distillation. Reference numeral 10 is a cooling unit having a known structure. In the subsequent adjusting tank 2, when the component separated by distillation is not an electrolyte solution, it is used as an electrolyte solution, and when the separated component is an electrolyte solution, it is used as an electrolyte solution having a higher electric conductivity. It is a tank. In order to more efficiently reduce the concentration of the oxidizable substance in the waste liquid in the subsequent oxidizable substance reducing step, the sodium chloride aqueous solution supplied from the sodium chloride aqueous solution supply tank 4 is mixed here. The concentration of the oxidizable substance of the waste liquid to be treated in the oxidizable substance reducing step is diluted by returning the waste liquid after passing through the electrolytic passage 30 described below to the adjusting tank 2 through the feed back route R again.

The following electrolytic passage 30 is formed in the electrolytic cell 3. Incidentally, 31 is a rectifier. As shown in FIG. 2, the electrolytic passage 30 has a cathode electrode 3 on both sides of an anode electrode 32.
3 are provided and formed between these. The electrolytic passages 30 are continuously provided (not shown). Anode electrode 32
The distance between the cathode and the cathode electrode 33 is set to about 2 mm,
The total length of the electrolytic passages 30 connected to each other is set to about 500 mm. A packing 34 is interposed between both electrodes to prevent a short circuit, and the packing 34 has a frame shape in which the inside is hollowed out leaving an externally assembled portion. The hollowed-out internal portion forms the electrolytic passage 30. A stainless steel plate 36 is provided outside the both cathode electrodes 33 via a packing 34 and a vinyl chloride plate 35.

The waste liquid flows in through a hole H penetrating below one stainless steel plate 36, passes through a hole H penetrating each of the vinyl chloride plate 35 and the cathode electrode 33, and passes through the anode electrode 3.
2 through the electrolytic passage 30 (inside the packing 34) between the cathode electrode 33 and the anode electrode 32, through the hole H penetrating above the anode electrode 32, and on the opposite surface of the anode electrode 32. Reach The same cathode electrode 33, vinyl chloride plate 35, as described above, is passed through the electrolytic passage 30 (inside the packing 34) between the cathode electrode 33 and the anode electrode 32 on the opposite surface side.
Each of the stainless steel plates 36 is discharged through a hole (not shown) passing through the lower part thereof. In this way, the anode electrode 32
A waste liquid passage is formed between the cathode electrode 33 and the cathode electrode 33.

A catalyst tank 6 for decomposing hypochlorous acid formed in the waste liquid in the electrolytic passage 30 is provided between the electrolytic tank 3 and the discharge mechanism 5. Hypochlorous acid remains in the waste liquid after passing through the electrolytic passage 30, and the hypochlorous acid becomes sodium chloride when it reacts with the nickel peroxide catalyst described below in the catalyst tank. A nickel peroxide catalyst can be used as the catalyst. For example, nickel trioxide hydrate (Ni ₂ O ₃ .
H ₂ O) alone or with nickel trioxide hydrate (Ni
₃ O ₄ . H ₂ O) and / or nickel dioxide hydrate (N
i0 ₂ . A mixture of H ₂ O) as an active ingredient can be used.

The discharging mechanism 5 is equipped with a compressor 50, and the treated waste liquid after passing through the electrolytic passage 30 is atomized and discharged into the atmosphere. Next, each step will be described. Distillation step The waste liquid is supplied to the distillation tank 1, where it is heated by a band heater and distilled. In this embodiment, the heating temperature is 104 ° C.
Then, among the components in the waste liquid, water and components having a boiling point which is substantially the same as or lower than the boiling point of water are separated by distillation. The evaporated component is cooled by a known method and supplied to the adjusting tank 2. At this stage, components and solids having a boiling point higher than that of water are removed, so that the concentration of the oxidizable substance is reduced to some extent and solids having a factor causing clogging in the electrolytic passage 30 are removed. To be done. Adjustment Step In the adjustment tank 2, the sodium chloride aqueous solution is injected from the sodium chloride aqueous solution supply tank 4 and mixed with the components separated by distillation. Oxidized Substance Reduction Step While the waste liquid is sent from the adjusting tank 2 to the electrolysis passage 30 by using the pump P, a direct current is passed through the waste liquid to electrolyze. In this process, the anodizing reaction oxidizes and decomposes the oxidizable substances such as organic substances in the waste liquid. Most of the odorous components in the waste liquid are also decomposed in this process. The waste liquid after passing through the electrolysis passage 30 is separated into two systems, and one of them is returned to the adjustment tank 2 in front of the electrolysis passage 30 through the feed back route R. The other proceeds to the next step.

Here, the substance to be oxidized is decomposed into carbon dioxide, nitrogen and water in a short time by the strong oxidizing action of the anode 32. The mechanism of such an oxidation reaction can also be explained from the known electrolytic oxidation process for industrially synthesizing phenol and quinones from benzenes. However, in this example, a complex organic matter having a considerably large molecular weight was decomposed into carbon dioxide, water, and nitrogen gas in an electrolyte solution in a short time, and the mechanism of such an oxidation reaction has recently been studied. It is considered to be due to the action of active oxygen species such as nascent active oxygen, superoxide ion, peroxide ion, hydroperoxy radical, and hydroperoxide ion in the existing electrolyte.

That is, when an electric current is applied to the electrolyte solution, a kind of low-temperature oxygen plasma-like state is generated in the waste liquid which is a liquid phase, which contains the active oxygen species and free electrons as described above. It is presumed that various oxidative reactions with organic substances cause oxidative decomposition into carbon dioxide and water via low molecular weight compounds, and ultimately only inorganic substances remain in the solution. That is, it is considered that the oxidation reaction in this step is due to the strong oxidative decomposition action of the oxygen active species in the electrode oxidation reaction. Release process The treated waste liquid after passing through the electrolytic passage 30 and decomposing hypochlorous acid in the catalyst tank 6 decomposes almost all the oxidizable substances into carbon dioxide, water and nitrogen gas, and atomizes this. Released into the atmosphere. Next, examples will be described in more detail.

The components in the waste liquid separated by distillation at about 104 ° C. in the distillation tank 1 are supplied to the adjustment tank 2. The power of the band heater used at this time was 15 kW. On the other hand, 25% sodium chloride aqueous solution is supplied from the sodium chloride aqueous solution supply tank 4 to the adjusting tank 2 at 8 cc / min,
While feeding a mixture of these into the electrolysis passage 30 with a pump P at a flow rate of 360 cc / min, a direct current 10
Flow A. The voltage at this time was 5V.

Then, the treated water in which the oxidizable substance is reduced after passing through the electrolytic passage 30 is fed back to the adjusting tank 2 on the front side of the electrolytic passage 30 at a flow rate of 240 cc / min.
And the concentration of the oxidizable substance in the waste liquid to be sent to the electrolytic passage 30 was diluted. The amount to be fed back is appropriately selected from 0 to 30 times reflux according to the COD value of the distilled waste liquid.

Then, the remaining treated water having a flow rate of 120 cc / min is decomposed in the catalyst tank 6 to remove hypochlorous acid and then treated with compressed air.
It was atomized into about 30 μm and discharged into the atmosphere. Here, the treated water after decomposition may be evaporated into the atmosphere by applying the heated exterior of the distillation tank 1. Alternatively, the water may be discharged 7 into a river without being released or evaporated into the atmosphere.

Further, the components and the solid content of the water remaining in the distillation tank 1 which exceeds the boiling point of the water were ashed by raising the temperature of the distillation tank 1 to about 600 ° C. after the completion of the oxidizing substance reduction treatment. A small amount of ash remained, which was removed from the lower valve and discarded. In addition,
Provide two evaporation tanks (not shown) for one adjustment tank, and when one side finishes distillation, start distillation on the other side and at the same time take out the residue after distillation on one side and incinerate it. By repeating this alternately, when one is performing distillation, the other can take out the residue, so that the treatment efficiency is further improved. Further, the distillation tank has a well-known wet wall type or stepped structure (not shown), and the components below the distillation tank having a large specific gravity and exceeding the boiling point of water are taken out in parallel with the distillation and taken out. The components may be incinerated. Even in this case, the processing efficiency can be further improved.

As described above, various waste liquids are steamed.
Inclusion of waste liquid before distillation, after distillation, and after passing through the electrolytic passage 30
Chemical oxygen demand (COD value), residual ash content, etc.
It was measured. Regarding the treatment of the following waste liquid,
No feed back was done. The characteristics of these waste liquids
By the way, the film development waste liquid is CO
High D value, and contains a lot of sodium sulfate and inorganic salts
It Waste liquid of photoresist intermediate synthesis is naphthalene or benzene.
Contains zen-based derivatives, sodium chloride and sodium sulfate
And about 20%. Electroless plating waste liquid is nickel
Or orthophosphoric acid (H ₃PO_Four) Etc., including about 7
%, About 6% of organic acid. Photo waste liquid is methylamino
Containing phenol / hydroquinone, etc., inorganic salt approx. 9%
contains. Printing waste liquid (press plate) and printing waste liquid (PS plate) are copied
It is the same as the true waste liquid. The results are shown in Table 1.

[0023]

[Table 1]

It can be seen that the COD value in the waste liquid after distillation is greatly reduced as compared with that before distillation. This makes it possible to more efficiently perform the COD value reduction process in the subsequent oxidized substance reduction step. According to the method of the above example, the oxidizable substance in the component separated by distillation is smoothly oxidatively decomposed in the oxidizable substance reducing step, and the component or solid content exceeding the boiling point of water is the end of the oxidizable substance reducing treatment. Since it is sufficient to further raise the temperature of the distillation tank to ash it later, there is an advantage that the processing efficiency is good as a whole.

[0025]

The present invention has the above-mentioned structure and has the following effects. The oxidizable substances in the components separated by distillation are smoothly oxidatively decomposed in the oxidizable substance reducing step, and components and solids having a boiling point higher than the boiling point of water may be treated by incineration or the like separately. It is possible to provide a method for treating waste liquid with good treatment efficiency.

[Brief description of drawings]

FIG. 1 is a system flow chart explaining an embodiment of a method for treating waste liquid according to the present invention.

FIG. 2 is an exploded perspective view illustrating the structure of the electrolytic passage of FIG.

[Explanation of symbols]

 1 Distillation tank 3 Electrolysis tank

Claims (2)

[Claims] 1. A distillation step of separating, by distillation, water and a component having a boiling point which is substantially equal to or lower than the boiling point of water among the components in the waste liquid, and applying a direct current to the components separated by distillation. A method for treating waste liquid, which comprises a step of reducing an oxidizable substance to be electrolyzed. 2. The method for treating a waste liquid according to claim 1, further comprising a step of using the component separated by the distillation as an electrolyte solution when the component is not an electrolyte solution.