JPH0724482A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To highly purify a waste water at a low cost by treating the waste water containing a metal or metallic compound and an organic material under a high pressure to make the metal or metal compound insoluble and after that, solid-liquid separating and oxidizing or oxidation decomposing the liquid portion. CONSTITUTION:The waste water is supplied into a line 8 by pressurizing by pump 3 and after mixed with air supplied from a oxygen containing gas supply line 9 and pressurized by a compressor 5, is introduced into a heat exchanger 2 and after the temp. is raised, is introduced into a wet oxidation reactor 1 through the bottom. The primary treated solution by the wet oxidation is cooled in the heat exchanger 2 and is introduced into a tank 14 through a gas-liquid separator 4. And the primary treated solution with the pressure opened is introduced into a solid-liquid separator 15 to solid-separate. Next, the obtained treated solution pressurized by a pump 33 and mixed with the air pressurized by a compressor 35 is introduced into a heat exchanger 32 and after the temp. is raised, is introduced into a catalytic wet oxidation reactor 31 to oxidize or oxidation-decompose the organic material.

Description

Detailed Description of the Invention

[0001]

Industrial field The wastewater may contain both a metal or a metal compound (hereinafter sometimes referred to as an inorganic substance) and an organic substance depending on its origin. The present invention relates to equipment for efficiently purifying wastewater in such a case.

[0002]

2. Description of the Related Art Typical examples of wastewater containing both inorganic and organic substances are chemical plant equipment, plating industry equipment, leather manufacturing equipment, metal industrial equipment, metal mining equipment, food manufacturing equipment, pharmaceutical manufacturing equipment, Waste water discharged from textile industry equipment, paper pulp industry equipment, dyeing dye industry equipment, electronics industry equipment, machinery industry equipment, printing plate making equipment, glass manufacturing equipment and the like can be mentioned. However, these are merely representative examples, and it is apparent from the gist of the present invention described below that the application target of the present invention is not limited by these examples.

As the inorganic substance, Fe, Cr, C
o, Cu, Mn, Ag, Sn, Pb, Bi, Ni, Z
In addition to heavy metals represented by n, Cd, Hg, As, Tl, Sb, Mo, W, etc. or their compounds, Al, C
There are a, Mg, Ti, P, Si and the like or compounds thereof, and the organic substances include toluene, ethanol, acetic acid and the like, as well as organic phosphorus compounds, organic halogen compounds, organic silicon compounds, nitrogen-containing organic compounds and the like. Is also included.
The former must be purified, for example, from the viewpoint of toxicity, and the latter, for example, from the viewpoint of exhibiting a high COD (chemical oxygen demand) value and being involved in environmental pollution.

Examples of the purification treatment technology include biological treatment method, combustion method, dry method of heating and evaporation, oxidation method using chlorine-based chemical agent, electrolytic oxidation method, hydrogen peroxide-ferrous iron salt method, ozone oxidation. Method, coagulation separation removal method by addition of inorganic or organic coagulant, adsorption separation separation method using activated carbon, inorganic adsorbent or organic polymer material, reverse osmosis method using membrane, electrodialysis method and ultrafiltration method Are known.

[0005]

However, the above-mentioned various methods are in great need of improvement as described below. For example, (1) biological treatment method, coagulation separation removal method, adsorption separation removal method, electrodialysis method, reverse osmosis membrane method, ultrafiltration method,
The hydrogen peroxide-ferrous iron salt method, the ozone oxidation method, etc. are difficult to carry out a purification treatment by themselves to a sufficient level. (2) Combustion method, dry solidification method, electrolytic oxidation method, ozone oxidation method Method, adsorption separation removal method, reverse osmosis membrane method, electrodialysis method, ultrafiltration method, etc. have high treatment costs, and (3) combustion method, dryness method, coagulation separation removal method, adsorption separation removal method, etc. There was a problem such as generation of substances that would later become secondary pollution. The present invention has been made in view of such circumstances, and it is possible to highly purify wastewater without generating a substance that causes secondary pollution, and to operate at a relatively low cost. It is an object of the present invention to provide a wastewater treatment method which is possible and has good facility maintainability.

[0006]

The gist of the present invention is to treat wastewater (excluding photographic processing wastewater) under high pressure to insolubilize or mainly insolubilize mainly the inorganic substances in the wastewater. Step, solid-liquid separation step in which the solid-containing liquid discharged from the first oxidation step is decompressed and introduced to perform solid-liquid separation, and the solid-content removing liquid from the separation step is introduced to remove the catalyst under high pressure. It exists in that it is configured so as to mainly include a second oxidation step of oxidizing or oxidatively decomposing an organic substance in the presence thereof.

[0007]

The present inventors have researched a new wastewater treatment technology which does not have the above-mentioned problems, and have completed the invention described in Japanese Patent Application No. 4-348393 for the treatment of photographic treatment wastewater. Although the content of the invention of the patent application was directed only to the photographic processing waste liquid, the present invention was found to be applicable to other waste water containing both an inorganic substance and an organic substance, and the present invention has been completed.

The first oxidation step in the present invention is carried out mainly for insolubilizing or sparingly insolubilizing the inorganic substance in the wastewater. This first oxidation step is carried out under high pressure, but it is particularly preferable to supply a gas serving as an oxygen supply source at 140 to 370 ° C. (more preferably 180 to 30 ° C.).
Wet oxidation treatment at a temperature of 0 ° C.) and a pressure at which the treated wastewater maintains a liquid phase. The processing pressure and the processing temperature are appropriately selected according to their correlation.

By the reaction in the first oxidation step, silver,
Inorganic substances such as iron and aluminum produce water-insoluble or sparingly soluble solid substances (sometimes represented by a scale in this specification) such as oxides, hydroxides and inorganic salts, and are precipitated from wastewater. Incidentally, silver or the like may be deposited as silver chloride or the like, and may be deposited in a state of being adsorbed by an insolubilized compound or the like. Elements other than the above, such as phosphorus, silicon, calcium,
Magnesium and the like are also converted into water-insoluble or sparingly soluble substances, or are adsorbed and deposited on other deposited scales, but these elements can become catalyst poisons to the catalyst used in the second oxidation step described later. Since they are substances, their removal in this first oxidation step and the subsequent solid-liquid separation step is evaluated as a purposeful phenomenon which is well positioned as a position in the whole system of the present invention. The pressure of the suspension generated in the first oxidation step is once released, and then the solid-liquid separation is performed in the solid-liquid separation step to remove the solid content (solid-liquid separation step).

As the solid-liquid separation type adopted in the solid-liquid separation treatment device, various types such as sedimentation separation treatment, centrifugal separation treatment, filtration separation treatment, etc. can be adopted, but are not particularly limited. It is effective to carry out a filtration separation treatment which has a relatively short time required for solid-liquid separation and has high separation performance.
Further, in this case, although not particularly limited, examples of the filtration separation treatment include a leaf filter system, a Schenk filter system, a Nutsche system, a filter press system and the like.

The filter cloth used at this time is selected from nylon, polyester, polypropylene, acrylic resin, saran, fluorocarbon, rayon, glass fiber felt, wire mesh, various porous filter bodies, etc. in consideration of operating temperature and filtration pressure. It is desirable to select and use the optimum one. Further, depending on the particle size, it is preferable to perform precoating or body feeding using a filter aid. For example, when the particle size is 2 μm or less, precoating, or precoating and body feeding is performed, and when the particle size is 2 to 50 μm, filtration is performed as it is, or the same procedure as when the particle size is 2 μm or less. On the other hand, when it exceeds 50 μm, filtration is performed as it is, and the scale is adjusted to several pp at the outlet.
It is recommended to perform filtration so as to keep it below m.

In the solid-liquid separation treatment device, a coagulant, a coagulant aid, etc. may be added as necessary to increase the treatment speed and the separation efficiency. As the aggregating agent and the aggregating auxiliary agent, conventionally known ones can be used and are not particularly limited. However, since water-soluble inorganic flocculants and flocculation aids may cause catalyst poisoning in the next second oxidation step, and their use is often limited, organic polymer flocculants may be used, It is preferable to use an organic substance or a water-insoluble inorganic aggregation aid. The solid matter collected in this solid-liquid separation treatment step has a significantly small amount of organic matter, particularly high molecular weight organic matter, even after the coagulation separation removal method and the adsorption separation removal method. It is also easy to treat the solid matter.

Next, the solid content removing liquid discharged through the solid-liquid separation step is supplied to the second oxidizing step under high pressure, and mainly organic substances in the solid content removing solution are oxidized or oxidatively decomposed. This oxidation or oxidative decomposition is a catalytic reaction under high temperature and high pressure, preferably under the supply of a gas serving as an oxygen supply source, 1
It is carried out at a temperature of 40 to 370 ° C. (more preferably 180 to 300 ° C.) and a pressure at which the treated wastewater maintains a liquid phase.

As described above, by performing the catalytic wet oxidation treatment using the catalyst in the second oxidation step, organic matter and inorganic CO
The component D and the like are oxidized and oxidatively decomposed to be converted into lower molecular weight organic substances, inorganic salts, carbon dioxide gas, water, ash and the like, and the waste water is far more purified than in the first oxidation step. It should be noted that the wet oxidation reaction tower in the second oxidation step does not matter whether it is a single-tube type or a multi-tube type, depending on the components and amount contained in the wastewater.
The single pipe type and the multi-pipe type may be used alone or in combination, and the components contained in the wastewater may be treated separately and under conditions suitable for the treatment.

If there are many inorganic substances to be removed,
Alternatively, if the concentration of the inorganic substances to be removed is not reduced to a sufficient concentration after the solid-liquid separation removal (solid-liquid separation step) after the wet oxidation treatment (first oxidation step) for other reasons, before the wet oxidation treatment In addition, it is also possible to remove it by using a conventional method for purifying inorganic substances such as an activated carbon, an adsorption separation removal method using an inorganic adsorbent or an organic polymer material, and an electrodialysis method. Similarly, after performing wet oxidation treatment (first oxidation step) and solid-liquid separation removal (solid-liquid separation step), the conventional purification method for heavy metals and harmful substances is used to further remove heavy metals and harmful substances. You may choose to

The two-step oxidation process of the present invention will be described in more detail below. First, the wet oxidation step, which is the first oxidation step, mainly treats inorganic substances, but it also oxidizes and oxidizes and decomposes other pollutants such as organic substances and inorganic COD components in the wastewater, thereby lowering the molecular weight of organic substances. , CO2, inorganic salts, carbon dioxide, water and ash can be converted to partially purify COD of wastewater. Therefore, when the inorganic substance in the wastewater forms a compound with the organic substance and is dissolved in the wastewater, the organic substance in the wastewater may be simultaneously oxidized or oxidatively decomposed during the first oxidation step. It is particularly effective in removing inorganic substances and organic substances from wastewater. That is, when the inorganic substance and the organic substance are dissolved in the wastewater as a chelate complex or the like, the chelating agent is decomposed and the inorganic substance is liberated in the first oxidation step. Therefore, the inorganic substance or the like is likely to be deposited as a solid substance which is insoluble or hardly soluble in water and is easily removed. It is also possible to fill the first oxidation reaction tower with a filler such as metal or ceramic to improve stirring of liquid and gas.

The catalyst used in the subsequent wet oxidation step, which is the second oxidation step, is any catalyst as long as it is a solid catalyst and has both activity and durability under the conditions of liquid phase oxidation. May be used, and examples thereof include catalysts containing titanium, iron, aluminum, silicon, zirconium, activated carbon or the like, and preferably oxides of titanium, titanium-zirconium, titanium-iron or the like are used. These catalysts may contain a second component in addition to the above components (hereinafter referred to as the first component).

The second component is at least one metal such as manganese, cobalt, nickel, tungsten, copper, cerium, silver, platinum, palladium, rhodium, gold, iridium or ruthenium, or a component thereof. Can be used. This catalyst is the first
For the component 75 to 99.95% by weight, the second component 25 to
The ratio is preferably 0.05% by weight. In addition, various shapes of the catalyst can be adopted and are not particularly limited. An adsorption tower filled with an inorganic adsorbent may be provided in front of the second oxidation reaction tower to appropriately prevent poisoning of the catalyst by an inorganic substance that has not been sufficiently removed. The inorganic adsorbent is not particularly limited, but is preferably an oxide containing titanium such as titanium, titanium-zirconium, or titanium-iron.

The treatment amount of waste water in the first oxidation step can be increased when the treatment temperature is high, and conversely, it is small when the treatment temperature is low. As an example, when the processing temperature is 270 ° C., the space velocity is 0.5 / hr to 5
/ Hr is preferred. When the processing temperature is 180 ° C,
/ Hr to 1 / hr is preferable. Space velocity 5 / at 270 ° C
When it exceeds hr and when the space velocity exceeds 1 / hr at 180 ° C., the treatment efficiency decreases, and conversely, when the space velocity is less than 0.5 / hr at 270 ° C. and space velocity less than 0.1 hr / at 180 ° C. Is not preferable because the treated amount of waste water decreases, the equipment becomes excessive, and the reaction efficiency exceeds the appropriate range.

Therefore, the higher the treatment temperature is, the better the treatment efficiency is, and the treatment speed can be increased, so that the reaction apparatus can be downsized. However, the treatment pressure becomes high, which makes maintenance difficult and COD in the wastewater. When the concentration is low, it becomes difficult to maintain the temperature in self-sustaining operation. On the other hand, when the processing temperature is low, the processing efficiency is low, but the processing pressure is low, which facilitates maintenance and the like.

If the treatment efficiency of the COD component is increased more than necessary in the first oxidation step, the heat source for maintaining the temperature in the second oxidation step and performing the self-sustaining operation becomes insufficient. For this reason, it is preferable that in the first oxidation step, the generated solid matter and the like are sufficiently precipitated and the COD treatment efficiency is suppressed to such an extent that they can be sufficiently separated and removed in the solid-liquid separation step. C in the first oxidation step
The treatment efficiency of the OD component is not particularly limited and may be appropriately selected depending on the case, but is generally 20% to 80%.

The amount of processing liquid supplied to the second oxidation step is
As in the case of the first oxidation step, the number can be increased when the processing temperature is high, and conversely, the number can be decreased when the processing temperature is low. Generally, space velocity is 0.1 / hr
˜5 / hr, more preferably 0.5 / hr˜3
/ Hr is preferred. This is because when the space velocity exceeds 5 / hr, the processing efficiency decreases, and when the space velocity is less than 0.1 / hr, the processing amount decreases and the equipment becomes excessive.

The oxygen supply source gas (hereinafter sometimes referred to as oxygen-containing gas) in the present invention means a gas containing oxygen or ozone. When a gas such as ozone or oxygen is used, it can be appropriately diluted with an inert gas or the like before use. Air is preferably used, but in addition to these gases, an oxygen-containing gas, which is a waste gas generated from another plant, can be appropriately used.

The amount of the oxygen-containing gas used in the first oxidation step can be appropriately selected depending on the concentration of waste water. In this case, the amount of oxygen required for completely decomposing the COD component of waste water into water, carbon dioxide, inorganic salts, and other ash is 0.5
˜5 times, more preferably 1.0 to 3 times. When it exceeds 5 times, unnecessary oxygen is supplied, and when it is less than 0.5 times, the amount of oxygen required is insufficient and the purification of waste water becomes incomplete. It should be noted that the range of 0.5 to 1.0 times is inadequate as the amount of oxygen, but it is one of the effective means when it is desired to secure the COD in the second oxidation step which is the next treatment.

The oxygen-containing gas in the second oxidation step is, similarly to the above, 0.5 to 5 times, and more preferably 1.0 to 3 times the required oxygen amount. When it exceeds 5 times, the oxygen is excessively supplied, and when it is less than 0.5 times, the required amount of oxygen is insufficient and the purification of the wastewater becomes incomplete. Further, the range of 0.5 to 1.0 times is inadequate as the amount of oxygen, but since the treatment efficiency of COD is usually less than 100%, the supplied oxygen is not used 100% and remains in the end. In such a case, even if the amount of oxygen supplied is less than 1 time in accordance with the actual processing efficiency, the COD processing efficiency does not deteriorate so much.

Inorganic substances treated according to the present invention include heavy metals, as well as aluminum, phosphorus, silicon, magnesium and calcium. The heavy metal, for example, cadmium, nickel, cobalt, manganese, copper, zinc,
Examples include silver, iron, chromium, tin, lead, mercury, arsenic, bismuth, thallium, antimony, molybdenum, and tungsten. The state of these metals is not particularly limited, and, for example, elemental ions or complex ions of the above-mentioned various metals, organometallic compounds and the like can be treated. Among these heavy metals, lead, cadmium, nickel, cobalt, mercury, iron, copper, zinc, chromium, manganese, and silver are particularly effective.

The concentration of heavy metals or harmful substances in the wastewater treated in the present invention is not particularly limited as long as the total of these is 1 mg / liter or more, but 10 mg / liter to 100 g in the wastewater. It is effective when the amount is contained in 100 μg / liter, and more effective is 100 mg / liter to 50 g / liter.
When it exceeds 100 g / liter, the solubility of the gas containing oxygen in the waste water is drastically changed and the reaction is hindered. Further, when the content of these is relatively small, less than 100 mg / liter, the treatment can be performed by using other treatment methods, and the merit of the treatment method of the present invention is reduced.

The concentration of COD in the waste water is effective when it is contained in the range of 1 g / liter to 200 g / liter, and more effective is 5 g / liter to 150 g.
g / liter. When the concentration of COD exceeds 200 g / liter, the heat of oxidation of COD becomes extremely large, which makes it difficult to control the processing apparatus. If it is less than 1 g / liter, the heat of oxidation of COD is small, and in such a case, even if a heat exchange device is used as an auxiliary equipment to recover heat, it becomes difficult to independently operate the wet oxidation treatment device by this heat. It is a thing. In such a case, there is no problem in the wet oxidation itself, but when performing the treatment, a separate heat supply device is required, which is relatively disadvantageous in terms of energy consumption. Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these descriptions.

[0029]

【Example】

<Embodiment 1> FIG. 1 is a schematic view showing an apparatus of a method for treating wastewater according to the present invention. In the figure, 1 is a wet oxidation reaction tower used in the first oxidation step. 8 is a wastewater supply line,
The supplied wastewater is boosted by the wastewater supply pump 3.
Reference numeral 9 denotes an oxygen-containing gas supply line, the oxidation-containing gas is pressurized by the compressor 5, and is introduced into the gas-liquid mixture supply line 10 together with the pressurized waste water. Reference numeral 11 is a primary treated water line for conducting the primary treated water from the wet oxidation reaction tower 1,
A heat exchanger 2 exchanges heat between the gas-containing wastewater (gas-liquid mixture) and the primary treated water heated in the reaction tower 1. Reference numeral 4 is a gas-liquid separator, 12 is a gas discharge line for discharging a gas component from the gas-liquid separator, and 7 is a pressure control valve for controlling the pressure of the gas-liquid separator 4. 13 is a liquid component from the gas-liquid separator 4 (1
A primary treated water discharge line for deriving the secondary treated water liquid content and solid matter suspension content), and a liquid level control valve 6 for controlling the liquid level of the gas-liquid separator 4. 14 is a primary treated water tank, 15
Is a solid-liquid separation treatment device used in the solid-liquid separation process, and 16 is a secondary treated water tank for storing the liquid component (secondary treated water) discharged from the solid-liquid separation treatment device 15.

38 is a secondary treated water supply line, 33 is a secondary treated water supply pump for increasing the pressure of the secondary treated water from the line 38, 39 is an oxygen-containing gas supply line, and 35 is air from the line 39. A compressor 40 for increasing the pressure is a gas-liquid mixture supply line for conducting a mixture of the secondary treated water and the oxygen-containing gas. Reference numeral 31 is a catalytic wet oxidation reaction tower used in the second oxidation step, 41 is a tertiary treated water line for leading the tertiary treated water from the reaction tower 31, and 32 is a heat exchanger. Three
4 is a gas-liquid separator, 42 is a gas discharge line for discharging the gas component from the gas-liquid separator 34, 37 is a pressure control valve for controlling the pressure of the gas-liquid separator 34, 43 is a gas-liquid separator 34 A treated water discharge line for discharging a liquid component (treated water), and a liquid level control valve 36 for controlling the liquid level of the gas-liquid separator 34.

Next, the operation of the first embodiment will be described. The wastewater used for the treatment of this example is chromium 4
A liquid of 50 mg / liter and aluminum 30 mg / liter was used. And the TOC (organic carbon) of the wastewater
Was 15.5 g / liter and COD _Cr was 48.0 g / liter. First, send wastewater from the wastewater supply line 8,
90 at a flow rate of 2 liters / hr by the wastewater supply pump 3
The pressure was fed up to kg / cm ² G. On the other hand, after the air supplied from the oxygen-containing gas supply line 9 is pressurized by the compressor 5, the waste water is added to the waste water at a ratio of O ₂ / COD _Cr (oxygen content in air / chemical oxygen demand) = 2.0. Mixed. The temperature of this gas-liquid mixture was raised by the heat exchanger 2. Then, it was introduced into the wet oxidation reaction tower 1 (empty tower) from below and subjected to wet oxidation treatment at a treatment temperature of 260 ° C. (first oxidation step). After that, this primary treated water was cooled by the heat exchanger 2 and allowed to flow into the gas-liquid separator 4. The space velocity of the wastewater at this time is 2.0 / hr.
Met.

In the gas-liquid separator 4, the liquid level controller LC detects the liquid level, the liquid level control valve 6 is operated to maintain a constant liquid level, and the pressure controller PC is used.
The pressure of the gas-liquid separator 4 was detected by, and the pressure control valve 7 was actuated to maintain a constant pressure. Next, the pressure of the primary treated water from the gas-liquid separator 4 was released and stored in the primary treated water tank 14, and then introduced into the solid-liquid separation treatment device 15 for solid-liquid separation (solid-liquid separation step). The above-mentioned wet oxidation treatment and solid-liquid separation treatment were continuously performed for 500 hours.

The secondary treated water which is the liquid content (solid content removing liquid) obtained by the solid-liquid separation treatment is subjected to inductively coupled high frequency plasma emission spectroscopy. Also, the contents of chromium and aluminum were measured. Also, TOC and CO
D _Cr was measured. The result is chromium less than 1 mg / liter, aluminum less than 1 mg / liter, TOC
The concentration was 6.9 g / liter and the COD _Cr concentration was 18.5 g / liter. The TOC treatment efficiency was 55% and the COD _Cr treatment efficiency was 61%.

Subsequently, the secondary treated water is supplied to the secondary treated water supply pump 33 at a flow rate of 1 liter / hr for 90 kg.
The pressure was fed up to / cm ² G. On the other hand, the air supplied from the oxygen-containing gas supply line 39 is supplied to the compressor 3
After pressurizing at 5, the mixture was mixed with the secondary treated water at a ratio of O ₂ / COD _Cr = 1.2. This gas-liquid mixture is used as a heat exchanger 3
The temperature was raised at 2 and introduced into the catalytic wet oxidation reaction tower 31 from below. The reaction tower 31 is filled with 1 liter of a catalyst (0.4% by weight of platinum) composed of titanium-zirconium composite oxide and platinum. 2 in the reaction tower 31
The secondary treated water was subjected to catalytic wet oxidation treatment at a treatment temperature of 260 ° C. (second oxidation step). After that, the water to be treated (third treated water) was cooled by the heat exchanger 32, and was made to flow to the gas-liquid separator 34. The space velocity of the secondary treated water at this time was 1.0 / hr.

In the gas-liquid separator 34, similar to the above,
The liquid level controller LC detects the liquid level and detects the liquid level control valve 36.
The liquid level is maintained by the pressure controller PC
The pressure was detected by and the pressure control valve 37 was operated to maintain a constant pressure. The above catalyst wet oxidation treatment is 5
It was carried out continuously for 00 hours. Regarding the liquid content of the tertiary treated water derived from the gas-liquid separator 34, that is, the final treated water, TO
The C and COD _Cr were measured.

The result is TOC 1.6 g / liter, C
The OD _{Cr was} 4.3 g / liter. The TOC treatment efficiency was 77% and the COD _Cr treatment efficiency was 77%. Therefore, in Example 1, the treatment efficiency calculated from the first wastewater to the final treatment liquid was TOC 90%, COD _Cr
It was 91%. From the above, it can be seen that the present Example 1 is an excellent wastewater treatment method.

<Embodiment 2> As the treatment apparatus in Embodiment 2, the treatment apparatus shown in FIG. 1 is used, and as waste water to be treated,
Copper 180 mg / liter and phosphorus 25 mg / liter, TOC 12.5 g / liter, COD _Cr 42.
The one used was 0 g / liter. By the same operation as in Example 1, the wet oxidation treatment (first oxidation step) and the solid-liquid separation treatment (solid-liquid separation step) were continuously performed for 1000 hours.

The conditions of the wet oxidation treatment (first oxidation step) are as follows:
Waste water flow rate 0.5 liter / hr, waste water space velocity 0.
5 / hr, O ₂ / COD _Cr = 3.0, processing pressure 9 / kg
/ Cm ² G, the treatment temperature was 160 ° C. As a result of analyzing the obtained secondary treated water, copper 1 mg / liter or less and phosphorus 1 mg / liter or less, TOC 8.6 g / liter and COD _Cr 24.5 g / liter, TOC
The treatment efficiency was 31%, and the treatment efficiency of COD _Cr was 42%.

Subsequently, a catalytic wet oxidation treatment (second oxidation step) was continuously performed for 250 hours on the secondary treated water by the same operation as in Example 1. As the catalyst, 1 liter of the same titanium-zirconium composite oxide as in Example 1 and platinum catalyst (0.4% by weight of platinum) was used.
The conditions of the catalytic wet oxidation treatment are as follows: flow rate of secondary treated water 0.5 liter / hr, space velocity of secondary treated water 0.5 / hr, O ₂
/ COD _Cr = 1.5, the treatment pressure was 9 kg / cm ² G, and the treatment temperature was 160 ° C.

As a result of analysis of the final treated water obtained, TO
C was 2.7 g / liter, COD _{Cr was} 7.5 g / liter, and TOC treatment efficiency was 69% and COD _Cr treatment efficiency was 69%. Therefore, in Example 2, the treatment efficiency calculated from the initial waste water was TOC 78%, COD _Cr
It was 82%. From the above, it can be seen that Example 2 is an excellent purification method.

<Third Embodiment> FIG. 2 shows a third embodiment according to the present invention.
2 is a schematic view showing the apparatus of FIG. In the figure, the parts given the same symbols as in FIG. 1 indicate the same or corresponding parts, and 44 is an adsorption tower,
It is provided in front of the catalytic wet oxidation reaction tower 31. As wastewater, lead 75mg / liter, calcium 35mg /
TOC 15.4 g / liter, COD _{Cr in} liters
Using 53.8 g / liter, the wet oxidation treatment (first oxidation step) was continuously performed for 500 hours under the following conditions by the operations of the same first oxidation step and solid-liquid separation step as in Example 1 above. And a solid-liquid separation treatment (solid-liquid separation step).

The condition of the wet oxidation treatment is that the flow rate of wastewater is 1.0.
Liter / hr, space velocity of wastewater 1.0 / hr, O ₂ /
COD _Cr = 1.2, the treatment pressure was 75 kg / cm ² G, and the treatment temperature was 250 ° C. The analysis results of the obtained secondary treated water were as follows: lead 1 mg / liter or less, calcium 4 mg / liter, TOC 5.8 g / liter, COD _Cr 16.
7 g / liter, TOC treatment efficiency 62%, COD
_{The Cr} treatment efficiency was 69%.

Next, regarding the secondary treated water, FIG.
The catalytic wet oxidation treatment was continuously carried out for 500 hours using the catalytic oxidation treatment apparatus equipped with the adsorption tower 44 shown on the right side. 1 liter of a catalyst composed of titanium-iron composite oxide and ruthenium (ruthenium: 1.5% by weight) was used as a catalyst, and 0.5 liter of titania was used as an adsorbent. The condition of the catalytic wet oxidation treatment is that the flow rate of the secondary treated water is 1.0 liter /
hr, space velocity of secondary treated water 1.0 / hr, O ₂ / CO
D _Cr = 1.1, treatment pressure 75 kg / cm ² G, treatment temperature 250 ° C.

The analysis results of the final treated water thus obtained were calcium 1 mg / liter or less, TOC 0.96 g / liter and COD _Cr 2.7 g / liter, TOC treatment efficiency 83%, COD _Cr treatment efficiency 84%. Met. Therefore, the TO calculated from the first wastewater in Example 3
The C treatment efficiency was 94%, and the COD _Cr treatment efficiency was 95%. From the above, it can be seen that the third embodiment is an excellent purification method.

<Comparative Example 1> FIG. 3 is a view showing a catalytic wet oxidation treatment apparatus. In the figure, the parts given the same reference numerals as those in FIG. 1 indicate the same or corresponding parts. In Comparative Example 1, the first oxidation step and the solid-liquid separation step were not performed, and the second oxidation step
Only the oxidation step, ie catalytic wet oxidation, was applied to the wastewater. The waste water used for the treatment was the same as that used in Example 1, and the treatment conditions were the same as those of the catalytic wet oxidation treatment in Example 1 except that O ₂ / COD _Cr = 2.0. As a result, after about 450 hours, the catalytic wet oxidation reaction tower 3
No. 1 was blocked and no further processing was possible.

<Comparative Example 2> FIG. 4 is a diagram showing a continuous wet oxidation treatment apparatus and a catalytic wet oxidation treatment apparatus, in which the same reference numerals as those in FIG. 1 indicate the same or corresponding portions. In Comparative Example 2, the first oxidation step (wet oxidation treatment) and the second oxidation step (catalyst wet oxidation treatment) were continuously performed without performing the solid-liquid separation step. The same wastewater as that used in Example 1 was used, and the treatment conditions were as follows: wastewater flow rate 1.0 liter / hr, wastewater (or wet oxidation treatment liquid) space velocity 1.
0 / hr, O ₂ / COD _Cr = 2.0, processing pressure 90 kg
/ Cm ² G, the treatment temperature was 260 ° C. As the catalyst, 1 liter of the same catalyst composed of titanium-zirconium composite oxide and platinum (0.4% by weight of platinum) as in Example 1 was used. As a result, in about 350 hours, the catalytic wet oxidation reaction tower 3
No. 1 was blocked and processing could not be performed.

As can be seen from the above Comparative Examples 1 and 2, the second
The cause of clogging of the wet oxidation reactor or deterioration of the catalyst due to the formation of scale by adsorbing harmful substances or heavy metals on the catalyst used in the oxidation step is the first oxidation step and It can be excluded by performing a solid-liquid separation step.

[0048]

As described above, the wastewater treatment method of the present invention is
This is an excellent purification method for wastewater as compared with conventional treatment methods, and the wastewater purified by the treatment method of the present invention can be directly discharged into a river. In addition, biological treatment or chemical treatment may be carried out as a post-treatment. When such post-treatment is carried out, heavy metals and harmful substances are removed from the wastewater in advance, and COD components and the like are considerably reduced, and they remain. Since the COD components and the like are decomposed into substances that are very easily decomposed in biological treatment and chemical treatment, the burden on the biological treatment equipment or the chemical treatment equipment becomes very small. Further, in the wastewater treatment method of the present invention, since the site is small and the device is compact,
Compared to the case where conventional wastewater treatment equipment, such as biological treatment equipment and combustion treatment equipment, is used, the treatment equipment is smaller, the treatment process is simplified, and capital investment and
It is also advantageous in terms of running cost.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus of a wastewater treatment method according to first and second embodiments of the present invention.

FIG. 2 is a diagram showing an apparatus of a wastewater treatment method according to a third embodiment of the present invention.

FIG. 3 is a diagram showing a catalytic wet oxidation treatment apparatus according to Comparative Example 1.

FIG. 4 is a view showing a continuous wet oxidation treatment apparatus and a catalytic wet oxidation treatment apparatus according to Comparative Example 2.

[Explanation of symbols]

 1 Wet Oxidation Reaction Tower 2,32 Heat Exchanger 3,33 Pump 4,34 Gas-Liquid Separator 5,35 Compressor 8 Wastewater Supply Line 9,39 Oxygen-Containing Gas Supply Line 14 Primary Treated Water Tank 15 Solid-Liquid Separation Equipment 16 Secondary treated water tank 31 Catalytic wet oxidation reaction tower 38 Secondary treated water supply line 44 Adsorption tower

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C02F 9/00 D 7446-4D 503 G 7446-4D C 7446-4D (72) Inventor Kunio Sano Hyogo 1 992 Nishikioki, Akihama, Aboshi-ku, Himeji, Japan Inside the Japan Catalysis and Catalysts Research Institute Co., Ltd. (72) Inventor Takehiro Takashima 1 992 Nishikioki, Akihama, Aboshi-ku, Himeji, Hyogo Prefecture

Claims (1)

[Claims] 1. A method for treating wastewater containing a metal or a metal compound and an organic substance (excluding photographic processing wastewater), wherein the wastewater is mainly treated under a high pressure to insolubilize or prevent the metal or the metal compound. A first oxidation step of solubilizing, a solid-liquid separation step of decompressing and introducing a solid-containing liquid discharged from the first oxidation step to perform solid-liquid separation, and a solid content removal liquid from the solid-liquid separation step Then, a method for treating wastewater, which comprises a second oxidation step of mainly oxidizing or oxidatively decomposing an organic substance in the presence of a catalyst under high pressure.