JP3272714B2 - Wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a wet oxidation treatment of waste water in the presence of a catalyst to oxidatively decompose substances contained in the waste water to convert them into nitrogen, carbon dioxide, water and ash. In addition, the present invention relates to a method for detoxifying wastewater by adsorbing and removing phosphorus, and particularly to a method suitable for treating wastewater containing phosphorus.

[0002]

2. Description of the Related Art In a conventional wastewater treatment method, a chemically oxidatively decomposable substance in wastewater (the amount of which is represented by chemical oxygen demand (COD), hereinafter referred to as "COD component"). Was decomposed and released to a degree harmless to the environment. In such a treatment, what kind of element the COD component contains is not considered so much, and only the oxidation treatment is performed. As a method of treating the COD component, there are an activated sludge method and a coagulation sedimentation method which are already widely used, as well as a reverse osmosis method, an activated carbon method, a chemical oxidation method and the like as a high-order treatment method.

[0003] However, these processing methods have various disadvantages. For example, the activated sludge method requires a long time to treat wastewater, and furthermore, it is necessary to dilute the wastewater to a concentration suitable for biodegradation, so that the installation area of the treatment facility must be large. The reverse osmosis method is being put to practical use in the fields of desalination of seawater and industrial water, high-purification of tap water, and the like. However, COD components in water are simply separated by a membrane. There are many technically unsolved parts such as the life of the membrane, the method of treating the concentrated liquid produced, and the like. The activated carbon method is effective for relatively low molecular weight organic COD components such as benzene, toluene, etc.
It is inefficient for OD components, and practically difficult to apply to wastewater containing inorganic COD components that are hardly adsorbed by activated carbon. As the chemical oxidation method, there are a combustion method and a liquid phase oxidation method.However, in the combustion method, it is necessary to add fuel to a waste liquid having a small calorific value. There are many disadvantages, for example, a large amount of harmful substances such as nitrogen oxides are contained in the combustion exhaust gas and the exhaust gas needs to be treated. As the liquid phase oxidation method,
A non-catalytic liquid phase oxidation method called the Zimmerman method in which wastewater is oxidatively decomposed under high temperature and pressure is known. However, since the reaction rate is low, a COD component reduction step is required prior to discharge.

[0004] Some of the inventors have conducted intensive studies in view of the existing wastewater treatment technologies as described above, and as a result, have found it easy to operate in the presence of a specific catalyst and under specific conditions, thereby realizing a practical economy. To find a wastewater treatment method that combines
Patents have already been filed for inventions based on the findings (JP-A-63-158189, JP-A-64-47).
No. 451, Japanese Patent Application Laid-Open No. 1-218634, and the methods disclosed in these applications are hereinafter collectively referred to as "the prior invention method").

[0005]

In recent years, from the viewpoint of water quality regulation, not only oxidizing COD components but also CO
Attention has also been paid to the presence of elements contained in the D component, particularly elements that have an adverse effect on the environment, and it has come to be considered that ammonia nitrogen and phosphorus compounds need to be removed. Ammoniacal nitrogen and phosphorus compounds are the main inducers of the eutrophication phenomenon of water quality.Ammoniacal nitrogenous and phosphorus compounds contained in water released to the environment cause abnormal algae overgrowth in rivers and lakes, and red tide in the ocean. These eutrophication phenomena are a major social problem, especially in closed water bodies.

If the above-mentioned substances in the wastewater are not simply removed, but are recovered, it is possible to prevent adverse effects on the environment and to contribute to the reuse of resources.
On the other hand, according to the study of the inventors, it has been found that the wet oxidation treatment method using a solid catalyst has some problems depending on the type of wastewater. That is, when phosphorus is present in the wastewater, the phosphorus is adsorbed on the surface of the solid catalyst, the durability of the solid catalyst is reduced, and the frequency of catalyst replacement is increased, which is economically disadvantageous. Therefore, the present invention can prevent the durability of the solid catalyst for the wet oxidation treatment from being reduced even if phosphorus is present in the wastewater, and thereby a method for treating wastewater from which phosphorus is removed. The task is to provide.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted research based on the above-mentioned newly obtained findings, and have found that phosphorus is removed from wastewater before the wet oxidation treatment of the wastewater in the presence of a solid catalyst. By doing so, it has been found that both removal of phosphorus and prevention of deterioration of the catalyst can be achieved, and the present invention has been completed. Therefore, in order to solve the above-mentioned problems, the present invention relates to a method for treating wastewater in which wastewater is oxidized by contacting the wastewater with molecular oxygen in the presence of a solid catalyst and while maintaining a liquid phase, And a method for treating wastewater, wherein phosphorus contained in the wastewater is removed in advance.

[0008] The removal of phosphorus from wastewater can be carried out by various methods such as a method of insolubilizing and solid-liquid separation and a method of adsorbing on an adsorbent, but a method of adsorbing on an adsorbent is preferable. In the method of solid-liquid separation by insolubilization, it is necessary to add a chemical for insolubilization to wastewater, and it takes time for solid-liquid separation. With the method of adsorbing on the adsorbent, it is not necessary to add a chemical, and if the adsorbed phosphorus is released, the adsorbent is regenerated and the phosphorus can be recovered. Note that, here, phosphorus does not only refer to a single state, but also includes a state of a compound (including ions). The inventors have further studied and found that under wet oxidation conditions, oxides of titanium, zirconium, iron, and aluminum have a large adsorption capacity for phosphate ions, and are easy to regenerate and can recover phosphorus. Also found. In particular, it has been found that by setting the wastewater temperature to 80 ° C. or higher, adsorption inhibition by organic substances hardly occurs, and by using a hot alkali solution for the regeneration, the regeneration can be efficiently performed and the phosphorus recovery rate is also increased.

Therefore, in the present invention, it is preferable to use an adsorbent made of an oxide of at least one element selected from the group consisting of titanium, zirconium, aluminum and iron as the adsorbent. When two or more metals are used, this oxide may be a composite oxide or a mixture of oxides of each metal. Further, in the present invention, in order to adsorb phosphorus contained in the wastewater to the adsorbent, it is preferable that the wastewater is brought into contact with molecular oxygen in the presence of the adsorbent and in a state of maintaining a liquid phase. ADVANTAGE OF THE INVENTION According to this invention, when treating various wastewater containing a COD component and a phosphorus compound, the durability of a solid catalyst can be improved significantly only by adding an adsorbent before a solid catalyst. Also has the advantage that it can be collected.

The adsorbent may be used in a fixed bed type or a fluidized bed type. In the case of the fixed bed type, the shape of the adsorbent is preferably granular when the wastewater does not contain suspended matter, from the viewpoint of contact efficiency, and when the suspended matter is contained, it is preferable to prevent clogging. A honeycomb or pellet having a large porosity is preferable for this purpose,
What was shape | molded in any other shape may be used. By using a fixed bed type adsorbent, the adsorption tower and the catalytic wet oxidation tower are combined into one reactor, and the adsorbent,
The latter stage can be filled with a catalyst, which has the advantage of being economically advantageous in terms of capital investment.

The granular adsorbent has an average particle size of 1.0 to 1.0.
It is 10.0 mm, preferably 2.0 to 5.0 mm. If the average particle size is less than 1.0 mm, the pressure loss increases, and
If it is larger than 10.0 mm, the porosity may increase, leading to a decrease in the adsorption capacity. Specific surface area is 60-10
00 m ² / g, preferably 100 to 600 m ² / g.
If the specific surface area is less than 60 m ² / g, the adsorbing capacity is greatly reduced, and if it is more than 600 m ² / g, the mechanical strength of the adsorbent may be weak. As the shape of the pellet-shaped adsorbent, the average particle size is 1.0 to 10.0 mm, preferably 3.0 to 8.0 mm, and the length is 2.0 to 15.0 mm, preferably 3.0 to 10.0 mm. It is. If the average particle size is less than 1 mm or the length is less than 2 mm, the pressure loss may increase, and if the average particle size is more than 10 mm or the length is more than 15 mm, the porosity increases. The contact efficiency may decrease, leading to a decrease in the adsorption capacity.
The specific surface area of the pellet-shaped adsorbent is set in the same range as that of the granular adsorbent. As the shape of the honeycomb-shaped adsorbent, the equivalent diameter of the through hole is 2 to 20 mm, and the cell thickness is 0.1.
３3 mm and a porosity of 50-90% are preferred.
Furthermore, the equivalent diameter is 2.5 to 15 mm, and the cell thickness is 0.5 to
It is preferable that the diameter is 3 mm and the porosity is in the range of 50 to 90%. When the equivalent diameter is less than 2 mm, pressure loss is large, and clogging may easily occur due to solid content contained in water. When the equivalent diameter exceeds 20 mm, the pressure loss is reduced and the possibility of clogging is reduced, but the contact rate is reduced and the adsorption capacity is reduced. When the cell thickness is less than 0.1 mm, the pressure loss is small, and there is an advantage that the weight of the adsorbent can be reduced.
The mechanical strength of the adsorbent may decrease. If the cell thickness exceeds 3 mm, the mechanical strength is sufficient, but the pressure loss may increase. If the porosity exceeds 90%, there is an advantage that the pressure loss is reduced and the weight of the adsorbent can be reduced, but the mechanical strength of the adsorbent may decrease. If the porosity is less than 50%, the mechanical strength is sufficient, but the pressure loss may increase. In the case of the fluidized bed type, as hydrated zirconium oxide or aluminum hydroxide, or by adding a crushed adsorbent to the waste liquid,
After the adsorption of phosphorus, solid-liquid separation is performed, and the solid content is discharged out of the system. Examples of the solid-liquid separation method include gravitational sedimentation and centrifugation, and any method may be used. The adsorbent used in the present invention is produced, for example, by a production method similar to that of a conventional solid catalyst.

As the component of the adsorbent, any one may be used as long as it is composed of an oxide of one or more elements selected from the group consisting of titanium, zirconium, iron and aluminum. Since oxides of iron and aluminum may be dissolved in an acidic liquid, oxides of titanium and zirconium are preferably used. In particular, titanium and zirconium oxides of 500
It is more preferable that the calcination is carried out at a temperature of not less than ° C., since the phosphorus adsorption capacity increases with the increase of the adsorption temperature. In addition, if the adsorbent component is dissolved in the liquid under the conditions of the temperature and pressure at which the adsorption is performed, the strength of the adsorbent is reduced and it becomes difficult to reuse the adsorbent.

The reaction conditions of the phosphorus adsorbing section may be appropriately set from the temperature and pressure at which the wastewater maintains a liquid phase. Therefore, the reaction temperature must be below the critical temperature of water, and is preferably in the range of 80-370C, more preferably 100-250C. Since the inhibition of the adsorption of phosphorus by an organic substance decreases as the temperature increases, the higher the temperature, the better. However, if the temperature is too high, a correspondingly high pressure is required to maintain the liquid phase, a container which is durable against the pressure is required, and the construction cost of the apparatus may be large. For this reason, a temperature suitable for the concentration of phosphorus in the wastewater and the reaction temperature in the subsequent catalyst layer may be selected under the pressure for maintaining the liquid phase. The reaction pressure may be appropriately selected within a range where the wastewater maintains a liquid phase at a selected temperature. For example, phosphorus can be adsorbed by filling the adsorbent into a treatment tank used for ordinary wet oxidation treatment of wastewater. The supply amount of molecular oxygen during the adsorption treatment is, for example, preferably 1.0 to 5.0 times, more preferably 1.05 to 3.0 times, the chemical oxygen demand (COD) of the wastewater. The contact time between the wastewater and the adsorbent (or the residence time of the wastewater in the adsorption section) is, for example, preferably 1 to 180 minutes, and more preferably 20 to 60 minutes. Examples of the molecular oxygen include oxygen gas, ozone, and the like, and pure substances thereof may be used, but a mixture with another gas, particularly air is used.

Since the above-mentioned specific adsorbent has a large adsorptivity for orthophosphate ions, it is desirable that the phosphorus be orthophosphate ions before or immediately after the wastewater flows into the adsorption section. When a phosphorus compound, such as a phosphorus compound, which is relatively hard to be oxidized to orthophosphate ions, is contacted with molecular oxygen in the absence of a catalyst in front of the adsorption section and at a temperature and pressure at which the wastewater retains a liquid phase. Preferably, the phosphorus compound is oxidized to orthophosphate ions. The oxidation conditions here include, for example, a temperature of 8
Any pressure may be used as long as the temperature is 0 to 350 ° C. and the wastewater maintains a liquid phase. Further, hydrogen peroxide or the like may be added as an oxidation aid. The supply amount of molecular oxygen at the time of this oxidation treatment is, for example, 1.0 to the chemical oxygen demand (COD) of the wastewater.
It is preferably 5.0 times, more preferably 1.05 to 3.0 times. The time of this oxidation treatment varies greatly depending on the nature of the wastewater, and when the wastewater contains relatively hardly oxidizable phosphorus,
For example, if the state contains organic phosphorus, the treatment time is lengthened. If the state contains phosphorus which is relatively easily oxidized, for example, if the state contains metaphosphoric acid or the like, the treatment time is shortened. There is no particular limitation. By this oxidation treatment, the phosphorus compound is oxidized to orthophosphoric acid, and the easily decomposable substances among the organic substances in the wastewater are decomposed, and the organic solids are easily dissolved in the liquid.

Oxidation treatment is carried out by contacting the wastewater from which phosphorus has been adsorbed and removed as described above with molecular oxygen in the presence of a solid catalyst and at a temperature and pressure at which the wastewater maintains a liquid phase. The reaction temperature and the reaction pressure here are appropriately set, for example, within the same range as in the case of the adsorption treatment. The supply amount of molecular oxygen during this oxidation treatment is preferably, for example, 1.0 to 1.5 times the COD value of the wastewater. The contact time between the wastewater and the solid catalyst (or the residence time of the wastewater in the solid catalyst part) is preferably, for example, 6 to 120 minutes,
12 to 60 minutes is more preferred. As the catalyst used in the present invention, any catalyst may be used as long as it is a solid catalyst and has both catalytic activity and durability under the conditions of liquid phase oxidation. At least 2 selected from the group consisting of silicon and zirconium
And at least one selected from the group consisting of manganese, iron, cobalt, nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium as the catalyst B component And a catalyst containing a compound insoluble or hardly soluble in water. The ratio of the components in the catalyst is
The component A is 75 to 99.95% by weight, preferably 90 to 99.9% by weight in the form of an oxide, and the component B is 0.05 to 25% by weight, preferably 0.1 to 10% by weight in the form of a metal and a compound.
A weight percent range is appropriate. If the component B is outside the above range, the oxidation activity is insufficient, and in the case of a noble metal such as platinum, palladium and rhodium, the cost of the raw material is increased and a correspondingly sufficient effect cannot be expected.

The solid catalyst used in the present invention preferably has the composition specified as described above, and may be in the form of a separated structure such as a pellet, a granular, a ring, or a crushed type, or an integrated structure such as a honeycomb. Various things can be adopted. In the present invention, the shape and size of the solid catalyst are set, for example, in the same manner as the solid catalyst generally used for wet oxidation of wastewater. After the wet oxidation treatment in this way, the treated material is subjected to solid-liquid separation and / or gas-liquid separation as required, and then released to the environment or collected. If the adsorption removal of phosphorus and the wet oxidation treatment of the wastewater are continuously performed as described above, the phosphorus adsorbing ability of the adsorbent is reduced and breaks through. Concentration / phosphorus concentration at the entrance of the adsorption section) exceeds 0.1]. Therefore,
The supply of the wastewater is stopped once, the water is washed through if necessary, and then the adsorbent is regenerated. If necessary, the adsorbent may be replaced. Regeneration of the adsorbent is performed by desorbing phosphorus from the adsorbent. The desorption method is
Although not particularly limited, if the following method is adopted,
Without removing the adsorbent from the wastewater treatment equipment
Can be played. In other words, the alkaline solution is caused to flow and brought into contact with the adsorbent, and the adsorbed phosphorus is desorbed into the alkaline solution. The alkaline solution containing the eliminated phosphorus is appropriately collected, and can be recovered as phosphoric acid therefrom.

As the alkaline solution used for the regeneration of the adsorbent, an aqueous solution of sodium hydroxide and potassium hydroxide and an aqueous ammonia solution are preferable. Alkaline earth metal hydroxides are not preferred because alkaline earth metals may be adsorbed on the adsorbent. When the adsorbent is washed by bringing the alkali solution into contact with the adsorbent, 40 to 16
Heating to 0 ° C. (provided that the washing liquid maintains a liquid phase under pressure conditions) is preferable. If the temperature is lower than 40 ° C., the solubility of the phosphate is low. If the temperature is higher than 160 ° C., the adsorbing power of the phosphate ions to the adsorbent becomes large, so that the adsorbent cannot be sufficiently and efficiently washed. As a method for raising the temperature of the alkali solution, any method may be used. However, it is preferable to raise the temperature by heat exchange using the treated wastewater because it is economically advantageous. Regarding the concentration of the alkaline solution, the aqueous solution of sodium hydroxide and potassium hydroxide and the aqueous solution of ammonia each have a concentration of 0.1 to 5%.
It is preferable to use a normal, preferably 0.5 to 3 normal, solution. If the concentration is lower than 0.1N, the effect of washing the adsorbent is not sufficient, and if the concentration is higher than 5N, the pH of the adsorbent washing waste liquid becomes too high and a neutralization step is required. . The contact time between the alkali solution and the adsorbent is, for example, preferably 1 to 60 hours, more preferably 2 to 20 hours.

If the adsorbent is regenerated with an alkaline solution as described above, the adsorbent can be used, for example, at 90% of its initial phosphorus adsorption capacity even if the above-mentioned continuous operation is repeated, for example, 50 times.
The above is maintained. Examples of the wastewater targeted by the treatment method of the present invention include wastewater from a chemical plant, washing wastewater, and various industrial wastewaters. Phosphorus is contained in wastewater as a solute or a suspended substance, for example, as a phosphoric acid such as orthophosphoric acid and its salts, a phosphorus compound such as an inorganic phosphide and an organic phosphorus compound.

[0019]

By performing the wet oxidation treatment after removing the phosphorus from the wastewater, the phosphorus content of the wastewater is reduced and the deterioration of the solid catalyst used for the wet oxidation is prevented.
When the removal of phosphorus from the wastewater is performed by adsorbing the adsorbent, phosphorus can be recovered by desorbing the phosphorus from the adsorbent that has adsorbed phosphorus. As an adsorbent,
When an adsorbent that selectively adsorbs phosphorus, that is, an adsorbent made of an oxide of at least one element selected from the group consisting of titanium, zirconium, aluminum, and iron, phosphorus is efficiently recovered.

Before the phosphorus is adsorbed on the adsorbent, the phosphorus is easily adsorbed, that is, orthophosphoric acid is changed to increase the phosphorus recovery rate. If the desorption of phosphorus from the adsorbent is performed by flowing and contacting an alkaline solution, the adsorbent can be regenerated in the wastewater treatment device, and the adsorbent is replaced or moved for desorption. Eliminates the need.

[0021]

EXAMPLES Specific examples and comparative examples of the present invention will be shown below, but the present invention is not limited to the following examples. -Production example of adsorbent 1-Zirconium nitrate was added to titanium tetrachloride and subjected to a thermal hydrolysis reaction to form a precipitate, which was separated by filtration and washed. The obtained cake was dried, pulverized and calcined at 550 ° C. Starch and water are added to the obtained powder, mixed well, formed into pellets, dried, and refired at 550 ° C. to obtain pellets (average particle size 5.0 mm, length 6.0 mm, specific A surface area of 150 m ² / g) was obtained. This pellet was a mixed oxide of titanium oxide and zirconium oxide (molar ratio Ti: Zr = 5: 5) by X-ray diffraction and X-ray fluorescence analysis.

-Experiment 1- Using the oxide pellets obtained in Production Example 1 as a phosphorus adsorbent, an aqueous solution of orthophosphoric acid (300 ppm-P) 500
When an adsorbing experiment was performed by adding 10 g of the adsorbing material to ml, the results shown in Table 1 were obtained. In the experiment, an autoclave (trade name: Hastelloy C, manufactured by Mitsubishi Metal Corporation, content: 1000 ml) was used. After this adsorption experiment, when the component of the treatment liquid was analyzed by a chemiluminescence method, no elution of titanium and zirconium from the adsorbent was observed.

[0023]

[Table 1] The adsorbent obtained in Production Example 1 was used in the following Examples. -Example 1-Model wastewater containing 10,000 ppm of ethanol and 100 ppm of orthophosphoric acid as wastewater was treated according to the flowchart of Fig. 1. At the start of operation, valve 1
The valves 9 and 16 were open and the valves 18 and 15 were closed. First, 75 kg of wastewater sent from line 9 is pumped
/ Cm ^2, and the pressure of the air supplied from the line 10 is increased by the compressor 5, and then the wastewater is adjusted so that the ratio of O 2 / COD (oxygen amount in air / chemical oxygen demand) = 1.2. And air were mixed. This gas-liquid mixture is transferred to line 1
After preheating in the heat exchanger 4 through the
It was sent to the adsorption tower 1 filled with 0 g so that the space velocity (the volume of treated water per unit time / the volume of adsorbent; hereinafter, referred to as “LHSV”) = 2Hr ⁻¹ . The packing density of the adsorbent in the adsorption tower 1 was 1 g / ml. In the adsorption tower 1, the wastewater is further heated to 220 ° C., and at the same time, phosphorus is adsorbed by the adsorbent, and the concentration of orthophosphoric acid in the wastewater is 1 ppm.
After that, the mixture was introduced into the wet oxidation tower 2 through the line 12. The wet oxidation tower 2 contains a composite oxide of titanium and zirconium as the catalyst A component and platinum as the catalyst B component (the weight ratio of the A component and the B component is A / B = 99.
And the wastewater was further treated in the wet oxidation tower 2 by raising the temperature to 250 ° C., and the ethanol in the wastewater was decomposed.
And cooled in the heat exchanger 4 and sent to the gas-liquid separator 6. In the gas-liquid separator 6, the liquid level controller LC detects the liquid level and activates the liquid level control valve 7 to maintain a constant liquid level. The pressure controller PC detects the pressure and detects the pressure level. Was operated to maintain a constant pressure. The treated water thus obtained was stably obtained at a TOC of 10 ppm or less. FIG. 2 shows the change over time of the removal rate of phosphorus in the outlet water of the adsorption tower 1 and TOC in the outlet water of the wet oxidation tower 2 with respect to the model wastewater. As a result, the adsorbent stably adsorbed phosphorus for up to 250 hours, and no deterioration in the activity of the catalyst was observed.

The adsorption tower 1 of the apparatus used in Example 1
And the size of the wet oxidation tower 2 was as follows. Adsorption tower 1: 25 mm (inner diameter) × 1400 mmH Wet oxidation tower 2: 25 mm (inner diameter) × 1400 mmH The processing conditions in Example 1 were as follows. System pressure: 75 kg / cm ² Model wastewater flow rate: 1 liter / Hr Air supply rate: 84 Nl / Hr Adsorption section temperature: 220 ° C. Wet oxidation section temperature: 250 ° C.-Example 2 The same treatment as in Example 1 was performed. After 300 hours from the start of the operation, the operation was stopped at 300 hours, pure water was supplied from the line 9 by the pump 3 for 5 hours, and the temperature and pressure were reduced to 70 ° C. and 1 atm in the adsorption tower 1 and the wet oxidation tower 2. 3 was stopped and the supply of pure water was stopped. After that, the valves 16 and 19 are closed and the valves 15 and 18 are opened, and the 1N-NaOH aqueous solution supplied to the line 17 and heated to 70 ° C. is supplied to the wet oxidation tower 2 and the adsorption tower 1 in this order with LHSV = 0.5.
When an adsorbent washing step of circulating at Hr- ¹ and discharging from the line 20 was performed for 4 hours, 98% of the phosphorus introduced into the system was dissolved as sodium phosphate and desorbed. .

In Example 2, it is more efficient if the washing is performed only on the adsorption tower 1 and not performed on the wet oxidation tower 2. -Example 3-In Example 2, after performing the regeneration treatment of the adsorbent, in order to examine the durability of the adsorbent for re-use, the same operation as in Example 1 was performed again, and the outlet water of the adsorption tower 1 was used. When the orthophosphoric acid concentration exceeded 10 ppm (10% of the inlet concentration) (the elapsed time from the start of the supply of the model wastewater to this point was defined as breakthrough time), the inflow of the phosphoric acid solution was stopped, and Example 2 was repeated. As a result of repeating the washing step in the same manner, as shown in Table 2, the adsorbent had an initial adsorptive capacity of up to 50 times.
0% or more was maintained.

[0026]

[Table 2] Example 4 Wastewater having the composition shown in Table 3 was treated according to the flow shown in FIG.

[0027]

[Table 3] First, the pressure of the wastewater sent from the line 30 is increased to 75 kg / cm ² G by the pump 24, and the pressure of the air supplied from the line 31 is increased by the compressor 26.
D = 1.2 was mixed into the wastewater. After the gas-liquid mixture was preheated in the heat exchanger 25 through the line 32, the mixture was allowed to flow into the non-catalytic wet oxidation tower 21. In the non-catalytic wet oxidation tower 21, the wastewater is further heated to 250 ° C. to oxidize and partially decompose organic substances, and at the same time convert phosphorus in the wastewater into orthophosphate ions. It was sent to be 2 Hr ^-1 .
The adsorption tower 22 was filled with an adsorbent formed in a honeycomb shape. The shape of the adsorbent is such that the equivalent diameter of the through hole is 10
mm, a cell thickness of 1 mm, and a porosity of 83% were used. The adsorbent component was a composite oxide of titanium and zirconium (Ti / Zr molar ratio was 5/5). Phosphorus was adsorbed by the adsorbent in the adsorption tower 22 and the phosphorus concentration in the wastewater became 1 ppm or less, and was introduced into the catalytic wet oxidation tower 23 through the line 34. The catalytic wet oxidation tower 23 contains a composite oxide of titanium and zirconium as the catalyst A component and platinum as the catalyst B component (molar ratio of Ti / Zr = 7/3, weight ratio of the A component and the B component). = 99.4 / 0.
6) is charged, and the catalytic wet oxidation tower 23 is filled.
The organic matter was treated to make it harmless to carbon dioxide, water, nitrogen, etc., cooled in the heat exchanger 25 through the line 35, and sent to the gas-liquid separator 27. Gas-liquid separator 27
In the above, the liquid level is detected by the liquid level controller LC and the liquid level control valve 28 is operated to maintain a constant liquid level, and the pressure is detected by the pressure controller PC and the pressure control valve 29 is operated to maintain the constant liquid level. It was operated to keep the pressure of. The treated water thus treated had a TOC of 20 ppm or less and was obtained stably.

In the apparatus used in Example 4, the non-catalytic wet oxidation tower 21, the adsorption tower 22, and the catalytic wet oxidation tower 2 were used.
The size of No. 3 was as follows. Non-catalytic wet oxidation tower 21: 25 mm (inner diameter) x 1400 mmH Adsorption tower 22: 25 mm (inner diameter) x 1400 mmH Catalytic wet oxidation tower 23: 25 mm (inner diameter) x 1400 mmH The processing conditions in Example 4 are as follows. there were. System pressure: 75 kg / cm ² Wastewater flow rate: 1 liter / Hr Air supply amount: 84 Nl / Hr Non-catalytic wet oxidizing unit temperature: 250 ° C Adsorption unit temperature: 250 ° C Catalytic wet oxidizing unit temperature: 250 ° C Example 5 In the same apparatus as in Example 1, the adsorbent obtained in Production Example 1 was changed to commercially available γ-alumina (average particle size: 3.0 mm) to treat wastewater. The treatment conditions were the same as in Example 1 except that the temperature of the adsorption section was 40 ° C. and sodium hydroxide was added to the model wastewater to adjust the pH to 11. As a result, the TOC of the processing liquid was 10
It was obtained stably at ppm or less. As for phosphorus and aluminum, no elution was observed in the treatment liquid when the treatment liquid was measured by a chemiluminescence method.

Example 6 Starch and water are added to iron oxide powder, mixed well, formed into pellets, dried, and fired at 150 ° C. to have an average particle size of 5.0 mm and a length of 6.0 mm. Thus, a pellet-shaped adsorbent was obtained.
In the same apparatus as in Example 1, the wastewater treatment was performed by changing the adsorbent obtained in Production Example 1 to the adsorbent thus produced. The treatment conditions were the same as in Example 1 except that the temperature of the adsorption section was 40 ° C. and sodium hydroxide was added to the model wastewater to adjust the pH to 11. As a result, the TOC of the processing solution was stably obtained at 10 ppm or less after 200 hours. As for phosphorus and iron, no elution was observed in the treatment liquid when the treatment liquid was measured by a chemiluminescence method.

From the results of Examples 5 and 6, both aluminum oxide and iron oxide can be used as the phosphorus adsorbent in Examples 1 to 4 in the same manner as the mixed oxide of titanium oxide and zirconium oxide, and have the same effects. I understand. -Examples 7 to 12-Wastewater treatment was performed in the same manner as in Example 1. 300 hours after the start of the operation, the apparatus was stopped, and the adsorbent was washed by changing the temperature conditions. In the washing, pure water was flowed into the adsorption tower 1 to reach the temperature shown in Table 4, and then a 1N-NaOH aqueous solution was flowed at LHSV = 1Hr ^-1 , and the phosphorus concentration in the liquid flowing out of the adsorption tower 1 was lowered. The time until it became 1 ppm or less was measured. The results are shown in Table 4. The effluent was sampled every 0.5 hour to measure the phosphorus concentration.

[0031]

[Table 4] As shown in Table 4, when the cleaning temperature of the adsorbent was lower than 40 ° C. or higher than 160 ° C., the cleaning time was significantly increased. -Example 13-In Example 1,
The model wastewater was treated in the same manner as in Example 1 except that the temperature was changed to 100 ° C. and the pressure was changed to 5 kg / cm ² . As a result, the phosphorus concentration in the effluent from the outlet of the adsorption tower was 10 ppm or less until 70 hours after the start of inflow of the model wastewater.

[0032]

According to the present invention, the phosphorus in the wastewater is removed before treating the wastewater in the presence of the solid catalyst, so that the durability of the solid catalyst due to phosphorus does not decrease. Further, phosphorus can be recovered.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of an apparatus used for implementing a wastewater treatment method of the present invention.

FIG. 2 is a graph showing the change over time in the removal rate of phosphorus in the outlet water of the adsorption tower and TOC in the outlet water of the wet oxidation tower with respect to model wastewater in Example 1.

FIG. 3 is an explanatory diagram showing another example of an apparatus used for carrying out the wastewater treatment method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adsorption tower 2 Wet oxidation tower 3 Pump 4 Heat exchanger 5 Compressor 6 Gas-liquid separator 21 Non-catalytic wet oxidation tower 22 Adsorption tower 23 Catalytic wet oxidation tower 24 Pump 25 Heat exchanger 26 Compressor 27 Gas-liquid separator

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kunio Sano 992, Nishioki, Okihama-shi, Aboshi-ku, Himeji-shi, Hyogo Japan Nippon Shokubai Co., Ltd. (56) References JP-A-63-97300 (JP, A) JP-A-63 −236588 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 1/74 C02F 1/28 B01D 15/00 B01J 20/00

Claims (3)

(57) [Claims] 1. A wastewater treatment method in which wastewater is oxidized by bringing the wastewater into contact with molecular oxygen in the presence of a solid catalyst and maintaining a liquid phase, wherein phosphorus contained in the wastewater is previously Orthophosphate ion
Contact was removed by adsorption to the adsorbent in a down state
Come, the adsorbent which has adsorbed phosphorus, like the temperature was raised to 40 to 160 ° C.
Adsorption by flowing alkaline solution in contact
A method for treating wastewater, comprising regenerating wood . 2. An adsorbent comprising titanium, zirconium,
Claim using an adsorbent comprising an oxide of at least one element selected from the group consisting of aluminum and iron 1
The method for treating wastewater described in 1. 3. A solid catalyst comprising an oxide of at least two elements selected from the group consisting of titanium, silicon and zirconium, and manganese, iron, cobalt, nickel,
3. A water-insoluble or hardly-soluble catalyst containing at least one element selected from the group consisting of cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium. The method for treating wastewater described in 1.