JP3372921B2 - Wastewater treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying wastewater. More specifically, the present invention relates to a method for efficiently treating wastewater containing an organic compound having 2 or more carbon atoms and / or a nitrogen compound by combining an oxidation treatment step and a reverse osmosis membrane treatment step.

[0002]

2. Description of the Related Art Conventionally, as a means for treating wastewater,
Although a method of oxidizing and decomposing organic substances and nitrogen compounds in wastewater by oxidation treatment has been implemented, it was not possible to sufficiently oxidize and decompose persistent organic substances and nitrogen compounds. For example, when a wet oxidation treatment is used, a method has been proposed in which the wastewater subjected to the wet oxidation treatment is concentrated using a reverse osmosis membrane, and the concentrated liquid is subjected to the wet oxidation treatment again to improve the purification action. As such a method, for example, in Japanese Patent Laid-Open No. 1-262993, the wastewater is subjected to wet oxidation treatment for the purpose of suppressing NOx-N production in the reaction tower, and the acid component in the treated wastewater is treated by using a reverse osmosis membrane. There has been proposed a method of concentrating and mixing this concentrated liquid (non-permeated liquid) with wastewater so as to be subjected to an oxidation step, and adjusting the pH of the wastewater to 7. However, in the reverse osmosis membrane used in this method of concentrating the acid component, although the acid components having pH of 1 to 3 can be concentrated in the reverse osmosis membrane, acetic acid almost permeates the reverse osmosis membrane. For this reason, the permeate contained oxides such as acetic acid, and the wastewater was not sufficiently purified.

"Development of wastewater recycling technology by a wet oxidation method using a catalyst" (water production technology, Vol. 16, N.
o. 3, P13-24 (1990)) describes a method of treating treated water obtained by subjecting waste water to wet oxidation treatment using a polyether-based or polyvinyl alcohol-based reverse osmosis membrane. Reverse osmosis membranes such as polyethylene series including polyethylene oxide series and polyethylene imine series, cellulose acetate series, polyvinyl alcohol series, and polyether series have high separation performance (exclusion rate) for acid components with a molecular weight of 100 or more. Although present, the rejection of acid components having a molecular weight of less than 100 is low, and organic acids such as acetic acid having a small molecular weight cannot be sufficiently captured. for that reason,
It was necessary to further subject the permeate to a purification step such as methane fermentation to treat acetic acid and the like.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and an object thereof is a treatment obtained by subjecting waste water to an oxidation treatment step and oxidizing and / or decomposing it. It is an object of the present invention to provide a method for treating wastewater which enables a liquid to be separated into a treatment liquid containing an oxide such as an organic substance and a treatment liquid containing almost no oxide by a reverse osmosis membrane.

[0005]

Means for Solving the Problems The wastewater treatment method of the present invention which has solved the above problems is a solid catalyst for oxidizing and / or decomposing wastewater containing an organic compound and / or a nitrogen compound having 2 or more carbon atoms. In a method for treating wastewater by subjecting it to a wet oxidation treatment step using, a treatment liquid obtained through the wet oxidation treatment step is treated with a polyamide-based composite membrane (reverse osmosis membrane) having a high desalination rate. The gist is to separate into a reverse osmosis membrane non-permeate and a reverse osmosis membrane permeate.

At this time, all or part of the non-permeate may be subjected to an oxidation treatment step together with the waste water, or all or part of the non-permeate may be subjected to an organic acid and / or ammonia recovery step. May be. At this time, it is recommended that the pH of the treatment liquid treated with the reverse osmosis membrane be 4 or more.

In the present invention, it is recommended to use a polyamide composite membrane as the reverse osmosis membrane.

In the present invention, it is preferable to employ a wet oxidation treatment as the oxidation treatment step, and it is desirable to perform the wet oxidation treatment under heating and pressure.

The impermeable liquid obtained by the method of the present invention contains at least one of organic acid and ammonia,
Further, these active ingredients contained in the non-permeate can be subjected to a recovery step.

Further, it is also effective to subject a part of the treatment liquid and / or a part or all of the permeated liquid obtained through the oxidation treatment step to the oxidation treatment step together with the waste water.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of various studies conducted by the present inventors on a method for purifying wastewater, it was found that organic acids (acetic acid and the like) and ammonia and other oxides contained in the treatment liquid after the oxidation treatment step were If treated with a reverse osmosis membrane having a high desalination rate, it can be concentrated and contained in the non-permeate, and the permeate becomes highly purified treated water containing almost no oxidizable substances. I found that.

That is, in the treatment method of the present invention, wastewater, especially wastewater containing an organic compound and / or nitrogen compound having 2 or more carbon atoms, is oxidized and / or decomposed (hereinafter abbreviated as “oxidation / decomposition”). The treatment solution obtained through the oxidation treatment step and the treatment solution obtained through the oxidation treatment step are treated with a reverse osmosis membrane having a high desalination rate to remove organic acid and / or ammonia in the non-permeate. It has one feature in the concentration.

The type of wastewater treated in the present invention is not particularly limited, and for example, various industrial plants such as chemical plants, electronic parts manufacturing equipment, food processing equipment, metal processing equipment, metal plating equipment, printing plate making equipment, and photographic equipment. From the power generation facilities such as thermal power generation and nuclear power generation, and any wastewater containing organic compounds and / or nitrogen compounds having 2 or more carbon atoms is included. Specifically, wastewater from EOG manufacturing facilities, alcohol manufacturing facilities such as methanol, ethanol, and higher alcohols, especially aliphatic carboxylic acids such as acrylic acid, acrylic acid esters, methacrylic acid, and methacrylic acid esters and their esters, or terephthalic acid. , Terephthalic acid ester and other aromatic carboxylic acids or organic substance-containing wastewater discharged from the process for producing aromatic carboxylic acid esters is exemplified. Further, waste water containing nitrogen compounds such as amine, imine, ammonia and hydrazine may be used. It may also be domestic wastewater such as sewage or night soil. Or dioxins and freons, diethylhexyl phthalate,
Wastewater containing harmful substances such as organic halogen compounds such as nonylphenol and environmental hormone compounds may be used.

Examples of the oxidation treatment step adopted in the present invention include wet oxidation treatment, supercritical oxidation treatment, ozone oxidation treatment, oxidation treatment using hydrogen peroxide, and oxidation treatment using perchlorate. Oxidation treatment using nitrous acid, oxidation treatment using ultraviolet light, oxidation treatment using electrolysis, and biological treatment and combustion treatment are also included, but wet oxidation treatment is particularly recommended.

Hereinafter, a method of treating wastewater using the treatment apparatus of FIG. 1 will be described. FIG. 1 is a schematic view showing an embodiment of a processing apparatus when a wet oxidation treatment is adopted as one of the oxidation treatment steps, but the apparatus used in the present invention is not intended to be limited to this.

Waste water containing an organic compound and / or nitrogen compound having a carbon number of 2 or more supplied from the waste water supply source is supplied to the waste water tank 18 through the waste water supply line 6. Further, a non-permeated liquid described later may be supplied to the drain tank 18 through the concentrated liquid return line 19, but the non-permeated liquid may be supplied to the waste water at an arbitrary position and mixed,
Further, the drainage tank 18 may not be provided.

The wastewater subjected to the oxidation treatment step may be prepared by previously using a reverse osmosis membrane to concentrate the organic compound having at least 2 carbon atoms and / or the nitrogen compound contained in the wastewater into the impermeable liquid. At this time, a reverse osmosis membrane having a high desalination rate used after the wet oxidation treatment described later can be used.

Waste water is sent from the waste water tank 18 to the heater 3 from the waste water supply pump 5. The space velocity at this time is not particularly limited and may be appropriately determined depending on the processing capacity of the reaction column, but normally, the space velocity per reaction column is 0.1 hr ^−1.
~10hr ^-1, more preferably 0.2hr ^-1 ~5h
It is recommended to adjust r ^-1 , more preferably 0.3 hr ^{-1 to 3} hr ^-1 . Space velocity is 0.1 hr
If it is less than ^-1 , the amount of wastewater treated decreases, and an excessive amount of equipment is required. On the contrary, if it exceeds 10 hr ^-1 , oxidation and decomposition treatment of wastewater in the reaction column becomes insufficient.

The wet oxidation treatment which can be used in the present invention can be carried out under the presence or absence of an oxygen-containing gas, but if the oxygen concentration in the waste water is increased, the waste water in the reaction tower will be discharged. Since it is possible to improve the oxidation / decomposition efficiency of the oxides contained therein, it is desirable to mix an oxygen-containing gas into the wastewater.

When the treatment is carried out in the presence of the oxygen-containing gas, the oxygen-containing gas is introduced from the oxygen-containing gas supply line 10 and the pressure is increased by the compressor 9, and then the waste water is heated by the heater 3.
It is advisable to mix it into the wastewater before it is supplied to.

The oxygen-containing gas that can be used in the present invention is not particularly limited as long as it is a gas containing oxygen molecules and / or ozone, and may be pure oxygen, oxygen-enriched gas, air, or the like, or peroxide. Hydrogen water or oxygen-containing gas generated in other plants may be used. Among these, it is recommended to use air from the economical point of view.

The supply amount of the oxygen-containing gas is not particularly limited, and an amount effective for enhancing the ability of oxidizing and decomposing the oxides in the waste water may be supplied. The supply amount of the oxygen-containing gas can be appropriately adjusted by providing the oxygen-containing gas flow rate control valve 11, for example. The supply amount of the oxygen-containing gas is preferably 0.5 to 5.0 times, more preferably 0.7 to 3.0 times the theoretical oxygen demand of the oxidizable substance in the waste water. Recommended. If the supply amount of the oxygen-containing gas is less than 0.5 times, the oxide to be oxidized is not sufficiently oxidized / decomposed and remains in a relatively large amount in the treatment liquid obtained through the wet oxidation treatment, and the reverse osmosis membrane is present. The burden on the reverse osmosis membrane in the treatment process increases. Further, even if oxygen is supplied more than 5.0 times, the oxidation / decomposition processing capacity is saturated.

In the present invention, the "theoretical oxygen demand" is the amount of oxygen required to oxidize and / or decompose the oxides in the waste water into nitrogen, carbon dioxide, water and ash. .

In many cases, the theoretical oxygen demand of the oxides in the waste water can be determined by the chemical oxygen demand (COD (Cr)).

Next, the waste water sent to the heater 3 is preheated and then supplied to the reaction tower 1. The temperature of the wastewater in the reaction tower is also affected by other conditions, but when heated to a temperature above 370 ° C., high pressure must be applied to keep the wastewater in the liquid phase state, and therefore In addition, the heating temperature is preferably 270 ° C. or lower, more preferably 230 ° C. or lower, still more preferably 170 ° C. or lower, because the equipment size becomes large and the running cost increases. On the other hand, if the temperature of the wastewater is less than 80 ° C, it becomes difficult to efficiently oxidize and decompose the oxides in the wastewater, so heating to 100 ° C or higher is preferable, and 110 ° C or higher is more preferable. desirable.

The time of heating the wastewater is not particularly limited, and the wastewater preheated as described above may be supplied into the reaction tower, or the wastewater may be heated after being supplied into the reaction tower. Of course, a heat source such as steam may be supplied to the wastewater.

In the wet oxidation method used in the present invention, the number, type, shape, etc. of the reaction towers are not particularly limited, and a single reaction tower or a plurality of reaction towers used in a usual wet oxidation treatment can be used. For example, a single-tube reaction tower or a multi-tube reaction tower can be used. When a plurality of reaction towers are installed, the reaction towers may be arranged in series or in parallel depending on the purpose.

As a method for supplying the wastewater to the reaction tower, various forms such as gas-liquid upward cocurrent, gas-liquid downward cocurrent, gas-liquid countercurrent can be used, and these methods can be used in two or more ways. You may combine.

When a solid catalyst is used for the treatment in the reaction tower,
This is desirable because it is possible to improve the efficiency of the oxidation / decomposition treatment of organic compounds and nitrogen compounds contained in the wastewater, and to lower the treatment temperature in the reaction column as compared with the case where no solid catalyst is used. The solid catalyst that can be used in the present invention is not particularly limited, but for example, manganese, cobalt, nickel, copper, cerium, silver, platinum, palladium,
A solid catalyst containing at least one selected from the group of rhodium, gold, iridium and ruthenium is recommended. The content of these elements is not particularly limited, but the solid catalyst preferably contains 0.01 to 25% by mass, and more preferably 0.05 to 10% by mass. In addition to the above elements, titanium,
It is desirable to contain at least one selected from zirconium, aluminum, silicon, iron and activated carbon.

The shape of the above solid catalyst is not particularly limited, and it can be used in any shape such as pellet, sphere, granule, ring or honeycomb.

When the wet oxidation treatment is used, several kinds of the above solid catalysts may be used. When a plurality of reaction towers are used, a reaction tower using the solid catalyst and a reaction tower not using the solid catalyst are combined. However, the method of using the solid catalyst is not particularly limited.

In addition to these solid catalysts, various packings, internal crops, etc. may be incorporated in the reaction tower for the purpose of stirring gas / liquid, improving contact efficiency, reducing gas / liquid drift. .

On the other hand, if the temperature of the wastewater is too high, the wastewater becomes a gas state in the reaction tower, so that organic substances, inorganic substances, etc. may adhere to the surface of the catalyst to deteriorate the activity of the catalyst. Therefore, it is recommended to apply pressure to the inside of the reaction tower so that the waste water can maintain the liquid phase even at high temperature. Further, it is desirable that a pressure adjusting valve is provided on the exhaust gas outlet side of the wet oxidation treatment apparatus and the pressure is appropriately adjusted according to the treatment temperature so that the waste water can maintain the liquid phase in the reaction tower. For example, the processing temperature is over 80 ℃,
When the temperature is lower than 95 ° C., the waste water is in a liquid phase even under atmospheric pressure, and may be under atmospheric pressure from the viewpoint of economy, but it is preferable to pressurize it in order to improve treatment efficiency.
When the treatment temperature is 95 ° C or higher, the wastewater is often vaporized under atmospheric pressure.
When the temperature is lower than 0 ° C, the pressure is about 0.2 to 1 MPa (Gauge), the processing temperature is 170 ° C or higher, and when the temperature is lower than 230 ° C, the pressure is about 1 to 5 MPa (Gauge), and the processing temperature is 230 ° C or higher. It is desirable to apply a pressure of more than 5 MPa (Gauge) and control the pressure so that the waste water can maintain the liquid phase.

Oxidized substances in the waste water are oxidized and decomposed in the reaction tower. In the present invention, "oxidation and decomposition treatment" means oxidative decomposition of acetic acid into carbon dioxide and water, and acetic acid into carbon dioxide. And methane decarboxylation decomposition treatment, urea and ammonia and carbon dioxide hydrolysis treatment, ammonia and hydrazine nitrous gas and water oxidative decomposition treatment, dimethyl sulfoxide ash such as carbon dioxide, water and sulfate ions Oxidation and oxidative decomposition treatment, oxidization treatment of dimethyl sulfoxide to dimethyl sulfone or methanesulfonic acid, and the like are exemplified.
Various oxidation and / or oxidation treatments such as carbon dioxide, water, ash, etc. decomposition, decomposition treatment to reduce the molecular weight of hardly decomposable organic compounds and nitrogen compounds, or oxidation treatment
It also means to include decomposition.

In the treatment liquid obtained through the wet oxidation treatment, a non-decomposable organic compound of the oxidant is often reduced in molecular weight and remains. Often, low molecular weight organic acids, especially acetic acid, remain as the compound. In addition, when there are many nitrogen compounds as oxidants in the waste water, ammonia often remains in the treatment liquid obtained through the wet oxidation treatment, and particularly when the wet oxidation treatment is performed without using a solid catalyst. A large amount of ammonia can be left in the treatment liquid after the wet oxidation treatment.

The waste water that has been oxidized and decomposed in the reaction tower is taken out from the treatment liquid line 12 and, if necessary, the cooler 4
After being appropriately cooled by, the gas-liquid separator 13 separates it into a gas and a liquid. At this time, it is desirable that the liquid level controller LC is used to detect the liquid level and the liquid level control valve 15 controls the liquid level in the gas-liquid separator to be constant. Or without cooling the wastewater that has been oxidized and decomposed,
Alternatively, as shown in FIG. 3, it may be cooled to some extent by the cooler 34, then discharged through the pressure control valve 44, and then separated into gas and liquid by the gas-liquid separator 43.

Here, the temperature in the gas-liquid separator is not particularly limited, but since the carbon dioxide is contained in the wastewater oxidized and decomposed in the reaction tower, for example, the temperature in the gas-liquid separator. To raise carbon dioxide in the drainage,
Alternatively, it is desirable that the liquid after being separated by the gas-liquid separator be subjected to a bubbling treatment with a gas such as air to release carbon dioxide in the liquid.

The liquid (treatment liquid) obtained by separation in the gas-liquid separator 13 is then treated with a reverse osmosis membrane having a high desalination rate to form a non-permeation liquid containing an oxide and a non-permeation liquid. It is separated into a permeate containing almost no oxide. The temperature of the treatment liquid supplied to the reverse osmosis membrane is preferably 40 ° C. or lower in order to maintain the durability of the reverse osmosis membrane. To control the temperature of the treatment liquid, a cooler 4 may be provided to cool the treatment liquid before attaching the treatment liquid to the gas-liquid separator 13, or a heat exchanger (not shown) or a cooler (not shown) may be provided after the gas-liquid separation. ) May be provided to cool the processing liquid.

In carrying out the wet oxidation treatment used in the present invention, a heat exchanger may be used as a heater and a cooler, and these may be used in an appropriate combination.

The treatment liquid supplied to the reverse osmosis membrane is an MF membrane,
You may use various filtration facilities, such as a UF membrane, and perform a solid-liquid separation process previously, and then process with a reverse osmosis membrane.

In the wastewater treatment method according to the present invention, when the treatment liquid obtained through such wet oxidation treatment or other oxidation treatment is treated with a reverse osmosis membrane having a high desalination rate, It is possible to capture and concentrate the organic acid (acetic acid and the like) and / or the nitrogen compound (ammonia and the like) contained in the non-permeated liquid.

It is desirable that the oxide to be contained in the treatment liquid obtained through the oxidation treatment step is mainly an organic acid and / or ammonia, preferably 30 mass% or more, more preferably 50 mass% or more. It is more preferable that the treatment liquid contains 70% by mass or more.

The amount of oxides contained in the treatment liquid is, for example, TOD, ThOD, COD (Cr), COD (M
n), TOC, BOD, total nitrogen, or the measured value of a specific component.

In the present invention, a "reverse osmosis membrane having a high desalination ratio" means a pressure of 1.47 MPa (Gauge), a pH.
The desalination rate (exclusion rate) is 98.0% or more, more preferably 99.0% or more, and further preferably 99.5% with respect to a 0.15% NaCl aqueous solution under the condition of 6.5 and a temperature of 25 ° C. It is a reverse osmosis membrane showing the above, and has high separation performance for organic acids having a molecular weight of less than 100, such as acetic acid (exclusion rate 60%).
Or more, preferably 70% or more, and more preferably 80% or more), and examples of such a reverse osmosis membrane include polyamide-based and aliphatic-based including cross-linked polyamide-based and aromatic polyamide-based. Amine condensate type and heterocyclic polymer type reverse osmosis membranes are exemplified, and in particular, polyamide type reverse osmosis membranes such as crosslinked polyamide type and aromatic polyamide type are recommended because they have high separability from organic acid and / or ammonia.

Cellulose acetate type, polyethylene type,
Reverse osmosis membranes having a low separation performance (exclusion rate of less than 60%) for organic acids having a molecular weight of less than 100, such as acetic acid, such as polyvinyl alcohol-based and polyether-based reverse osmosis membranes, have a high desalination rate. Is not preferable.

As the membrane form of the reverse osmosis membrane, various membrane forms such as an asymmetric membrane and a composite membrane can be used. Among them, the composite membrane is particularly recommended. In the present invention, the polyamide-based composite membrane is used as the reverse osmosis membrane. Is recommended.

The membrane module of the reverse osmosis membrane used in the present invention is not particularly limited, and may be, for example, a flat membrane module, a hollow fiber module, a spiral module, a cylindrical module, a pleated module, or the like. In particular, a spiral type module having a large membrane area of the module and suitable for making the apparatus compact is desirable.

The amount of the treatment liquid supplied to the reverse osmosis membrane is not particularly limited, and the treatment liquid obtained through the wet oxidation treatment may be wholly or partially applied to the reverse osmosis membrane.

When the treatment liquid obtained through the oxidation treatment step is separated (treated) into a non-permeate liquid and a permeate liquid by a reverse osmosis membrane, organic acids and / or ammonia contained in the treatment liquid are organic acids. If it is a salt or an ammonium salt, the separation performance of the reverse osmosis membrane will be improved, and more non-permeate can contain oxides such as organic acid salts and ammonium salts. It contains almost no and is highly purified.

As a method for converting an organic acid into a salt, it is desirable to add an alkali metal ion and / or an ammonium ion.

The added alkali metal ion and / or ammonium ion ionically bonds with the organic acid contained in the treatment liquid to form an organic acid salt, and the molecular size increases, so these oxides of the reverse osmosis membrane are oxidized. Separation performance (rejection rate) is improved. In addition, the organic acid becomes negatively charged by the addition of alkali metal ions and / or ammonium ions, and electrostatic repulsion occurs with the reverse osmosis membrane having a negative charge, so that the separation performance of the reverse osmosis membrane is improved.

In FIG. 1, an alkali supply line 8 is provided for addition to the wastewater, but alkali metal ions and / or
Further, the addition position of ammonium ions is not particularly limited, and alkali metal ions and / or ammonium ions may be added to the treatment liquid after the oxidation treatment step, as long as they are added to the treatment liquid to be supplied to the reverse osmosis membrane. Good. At this time, the content of alkali metal ions and / or ammonium ions is 5 relative to the total amount of organic acids contained in the treatment liquid.
It is desirable to add it in an amount of 0 mol% or more because the separation performance of the reverse osmosis membrane can be further enhanced.

As a method for converting ammonia into salt,
Although it is preferable to add an organic acid and / or an inorganic acid, it is preferable to add an inorganic acid such as sulfuric acid because the organic acid reduces the purification performance of waste water.

The added organic acid and / or inorganic acid ion-bonds with ammonia contained in the treatment liquid to form an ammonium salt, which increases the molecular size. Therefore, the separation performance of these reverse osmosis membranes against these oxides is increased. Is improved.

The addition position of the organic acid and / or the inorganic acid is not particularly limited as in the case where the organic acid is made into a salt.
At this time, the separation performance of the reverse osmosis membrane can be further enhanced by adding an organic acid and / or an inorganic acid so as to have a content of 50 mol% or more based on the total amount of alkali components contained in the treatment liquid.

Further, when an organic substance is contained in the oxidation treatment step of the nitrogen compound, a carbonate is produced by the oxidation / decomposition treatment and ammonia can be converted into an ammonium salt.

It should be noted that the pH of the treatment liquid when treating with a reverse osmosis membrane
Is 4 or more, the separation performance of the reverse osmosis membrane is further improved,
The rejection rate of the reverse osmosis membrane with respect to the oxide is increased, and the purifying property of the obtained permeate can be dramatically improved.

When the organic acid content in the treatment liquid is high, it is desirable that the pH is adjusted to preferably pH 4 or higher, more preferably pH 5 or higher, still more preferably pH 6 or higher. If the pH exceeds 9, the separation performance of the reverse osmosis membrane often decreases, so the upper limit of the pH of the treatment liquid is preferably pH 9, more preferably pH 8, and further preferably p.
It is H7.5.

Further, when the ammonia content in the treatment liquid is high, it is desirable to adjust the pH to preferably 4 or higher, more preferably pH 5 or higher, still more preferably pH 6 or higher. Since the separation performance of the osmotic membrane is reduced, it is recommended that the pH is preferably 9 or less, more preferably pH 8 or less.

According to the wastewater treatment method of the present invention, the organic acid (and / or organic acid salt) and / or ammonia (and / or ammonium salt) is trapped in the non-permeate. Part or all of this non-permeate may be returned directly or indirectly to any position in the wastewater oxidation treatment step. For example, it may be directly returned to the wastewater before being subjected to the oxidation treatment step, or may be supplied to the wastewater from an arbitrary position and subjected to the oxidation treatment step.

It is desirable to circulate the non-permeated liquid in the oxidation treatment step and oxidize / decompose again so that the circulated oxide can be almost completely oxidized / decomposed.
At this time, part or all of the non-permeate may be treated by biological treatment such as methane fermentation, or may be subjected to other wastewater treatment such as combustion treatment or chemical treatment, depending on the purpose or purpose. They can be combined and combined freely. The amount of non-permeate liquid subjected to such treatment is more concentrated than the case where no reverse osmosis membrane is used, and the treatment can be performed with higher efficiency and at lower cost.

Further, part or all of the non-permeation liquid may be subjected to a step of recovering the active ingredient contained in the non-permeation liquid, such as organic acid or organic acid salt and / or ammonia or ammonium salt. The recovery method at this time is not particularly limited, for example, a method of recovering by direct distillation, a method of extracting an organic acid using an organic solvent, and then a method of dehydrating and desolvating the extract by distillation to recover the organic acid. Known collection methods such as the above can be used.

When the wastewater is treated by the method for treating wastewater according to the present invention, the reverse osmosis membrane can separate the non-permeate containing the oxide and the permeate containing almost no oxide. Further, since the permeate contains almost no oxidizable substances and is highly treated purified water, it is possible to carry out industrial water and domestic water without performing the acetic acid treatment step which has been conventionally performed such as biological treatment. Can be reused as Further, the treated water obtained by subjecting the permeated liquid to a high-level purification treatment can also be used as pure water.

Further, in the method according to the present invention, a part of the treatment liquid obtained through the oxidation treatment step and / or a part or the whole of the reverse osmosis membrane permeate is directly returned to the waste water before being subjected to the oxidation treatment step. Alternatively, the effluent may be supplied to the effluent from any position of the effluent supply line and subjected to the oxidation treatment step. For example, when the treated liquid and / or the permeated liquid obtained through the oxidation treatment step is used as the diluting water for the wastewater, the TOD concentration and the COD concentration of the wastewater can be reduced. Alternatively, the permeate can be used as water for diluting the salt concentration of the waste water.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples do not limit the present invention, and any modification may be made without departing from the spirit of the above and below. Included in the range.

[0066]

EXAMPLES Example 1 Using the apparatus shown in FIGS. 1 and 2, a wet oxidation treatment was adopted for the oxidation treatment step, and the treatment was carried out for 500 hours under the following conditions. Wet oxidation treatment has a diameter of 26 mm and a length of 300
A cylindrical reaction tower 1 of 0 mm was used, and titania and platinum were used as solid catalysts in the interior, and the platinum content was 0.1.
0.8 liter of mass% catalyst was charged. The wastewater used for the treatment is the wastewater discharged from the aliphatic carboxylic acid and aliphatic carboxylic acid ester production process, which contains alcohol,
It contained a large amount of organic compounds having 2 or more carbon atoms such as aldehydes and carboxylic acids. The COD (Cr) of drainage is 35
The g / l and pH were 2.8. The wastewater did not contain alkali metal ions, ammonium ions, or inorganic salts.

(Oxidation treatment step) The above-mentioned wastewater supplied through the wastewater supply line 6 and a non-permeated liquid described later are mixed in the wastewater tank 18, and the wastewater supply pump 5 is used to flow at a flow rate of 2.4 liter / h. After pressure feed, 2 in heater 3
Waste water heated to 00 ° C. was supplied from the bottom of the reaction tower 1. Further, air is supplied from the oxygen-containing gas supply line 10 and the pressure is increased by the compressor 9, and then O ₂ / COD (Cr) (oxygen amount in supply gas / chemical oxygen demand amount of waste water) = 1.1.
The oxygen-containing gas flow rate control valve 11 was used to control the flow rate so that the oxygen-containing gas was mixed into the waste water before the heater 3. In the reaction tower 1, the treatment was performed in a gas-liquid upward cocurrent flow. In the reaction tower 1, the wastewater was kept at 200 ° C. by using the electric heater 2 to carry out oxidation / decomposition treatment, and the obtained treatment liquid was treated liquid line 12
And was sent to the gas-liquid separator 13 to separate gas-liquid. In the gas-liquid separator 13, the liquid level controller LC detects the liquid level, and the liquid is discharged from the liquid level control valve 15 so as to maintain a constant liquid level. Further, the pressure control valve 14 detected the pressure with the pressure controller PC and controlled so as to maintain the pressure of 2.45 MPa (Gauge). COD (Cr) of the treatment liquid obtained through the wet oxidation treatment is 2.6 g / liter, pH 3.0.
And 92% of all TOC components were acetic acid.

(Reverse Osmosis Membrane Treatment Step) This treatment liquid was further applied to a reverse osmosis membrane treatment apparatus 20 as shown in FIG.
The amount of non-permeate liquid was controlled so as to be about ⅕ of the amount of treatment liquid treated by the reverse osmosis membrane. As the reverse osmosis membrane, a polyamide-based composite membrane (desalination rate (exclusion rate) for 0.15% NaCl aqueous solution)
99.5%) was used. The COD (Cr) of the permeate obtained by treatment with the reverse osmosis membrane was 1.1 g / liter, and the COD (Cr) of the non-permeate was 8.4 g / liter. Then, 95% of the non-permeated liquid was supplied to the drain tank 18 from the concentrated liquid return line 19. In addition, a treatment liquid obtained by subjecting the treatment liquid obtained through the wet oxidation treatment to sodium hydroxide to change the pH of the treatment liquid was subjected to a reverse osmosis membrane treatment step, and the COD (Cr) concentration of the obtained permeate I checked. Results are shown in FIG.

Comparative Example 1 (Reverse Osmosis Membrane Treatment Step) The treatment liquid after wet oxidation treatment (COD (Cr) 2.6 g / liter) obtained in Example 1 was subjected to a reverse osmosis membrane treatment. The reverse osmosis membrane treatment step was performed in the same manner as in Example 1 except that a cellulose acetate-based membrane (desalination rate (exclusion rate) of 95% with respect to 0.15% NaCl aqueous solution) was used as the reverse osmosis membrane. . The reverse osmosis membrane could hardly separate the organic matter, and the resulting permeate had CO
D (Cr) was 2.3 g / liter, and a sufficient separation result could not be obtained.

Example 2 (Oxidation treatment step) A wet oxidation treatment was carried out in the same manner as in Example 1 except that the aqueous sodium hydroxide solution was supplied from the alkali supply line 8. The supply amount of the sodium hydroxide aqueous solution was controlled so that the pH of the treatment liquid after the wet oxidation treatment was about 6. The COD (Cr) of the obtained treatment liquid was 3.0 g / liter, and 93% of all TOC components was acetic acid. Further, Na was contained in an amount of about 1.5 mol times with respect to acetic acid.

(Reverse Osmosis Membrane Treatment Step) The obtained treatment solution was subjected to the same reverse osmosis membrane treatment step as in Example 1. COD (Cr) of the obtained permeated liquid is less than 0.1 g / liter,
The COD (Cr) of the non-permeate was 15 g / liter. Then, 95% of this non-permeated liquid was mixed with the wastewater through the concentrated liquid return line 19.

Comparative Example 2 (Reverse Osmosis Membrane Treatment Step) The treatment liquid (CO 2) obtained in Example 2 was used.
Treatment with D (Cr) 3.0 g / liter as a reverse osmosis membrane using a polyvinyl alcohol membrane (desalination rate (exclusion rate 93% against 0.15% NaCl aqueous solution)) It was subjected to the same reverse osmosis membrane process as in Example 1 except that the pressure was 1.96 MPa (Gauge). The COD (Cr) of the obtained permeated liquid was 2.6 g / liter, and almost no organic matter could be removed by this reverse osmosis membrane.

Example 3 Using the same reaction tower as in Example 1, a wet oxidation treatment was carried out for 500 hours. 0.8 liter of a catalyst containing titania and platinum as main components as a solid catalyst and a platinum content of 0.5 mass% was filled in the reaction tower 1. The wastewater used for treatment was discharged from the power generation facility and contained ammonium sulfate, sodium ions and carbonate ions. The ammonia concentration in the waste water was 2.2 g / liter and the pH was 7.8. The amount of evaporated solid matter in the waste water was 15 g / liter.

(Oxidation treatment step) This waste water and a non-permeated liquid which will be described later are mixed in a waste water tank 18 and pressure-fed at a flow rate of 0.8 liter / h by a waste water supply pump 5, and then 160 ° C. by a heater 3. It was heated to the bottom and fed from the bottom of the reaction tower 1.
Further, air was introduced from the oxygen-containing gas supply line 10, pressurized by the compressor 9, and then supplied to the waste water before the heater 3 so that O ₂ /COD=2.0. In the reaction tower 1, the temperature of the waste water was kept at 160 ° C. by using the electric heater 2 and subjected to oxidation / decomposition treatment, then cooled to 30 ° C. by the cooler 4 and sent to the gas-liquid separator 13 for gas-liquid separation. At this time, the pressure is detected by the pressure controller (PC), and 0.9 MPa
It was controlled in the same manner as in Example 1 so as to maintain the pressure of (Gauge). The ammonia concentration of the obtained treatment liquid is 0.5
It was 3 g / liter and pH was 7.1.

(Reverse Osmosis Membrane Treatment Step) This treatment liquid was supplied to the reverse osmosis membrane treatment apparatus 20 so as to maintain a pressure of 4.9 MPa (Gauge). The amount of non-permeated liquid was controlled to be about 1/3 of the amount of treated liquid applied to the reverse osmosis membrane. The reverse osmosis membrane is a polyamide composite membrane (0.15% N
A desalination rate (exclusion rate) of 99.5% was used for the aCl aqueous solution. Ammonia concentration of the obtained permeate is 0.01 g
/ L and the ammonia concentration of the non-permeate was 1.6 g / L. 80% of the non-permeate was mixed with the wastewater through the concentrate return line 19.

Example 4 Using the apparatus shown in FIGS. 3 and 4, wet oxidation treatment was performed under the following conditions for 500 hours. The reaction tower 31 has a diameter of 2
A cylindrical one having a length of 6 mm and a length of 3000 mm was used, and 1.3 liters of a catalyst containing activated carbon and platinum as main components as a solid catalyst and a platinum content of 0.2% by mass were filled therein.
The wastewater used for the treatment was solvent-based wastewater containing a large amount of alcohols such as ethyl alcohol and propyl alcohol. The COD (Cr) of the waste water was 30 g / liter and the pH was 7.1. The wastewater did not contain alkali metal ions, ammonium ions, or inorganic salts.

(Oxidation treatment step) The above-mentioned wastewater sent from the wastewater supply line 36 was mixed with the non-permeated liquid described later in the wastewater tank 48. The waste water was pressure-fed at a flow rate of 1.3 l / h by a waste water supply pump 35, heated to 120 ° C. by a heater 33, and then supplied from the upper part of the reaction tower 31. Further, an aqueous sodium hydroxide solution was mixed with the waste water from the alkali supply line 38 using the alkali supply pump 37. The supply amount of sodium hydroxide was controlled so that the pH of the treatment liquid after the wet oxidation treatment was about 6.5. Further, air is supplied from the oxygen-containing gas supply line 40, the pressure is increased by the compressor 39, and then O ₂ / COD (Cr) =
The flow rate was controlled by the oxygen-containing gas flow rate control valve 41 so as to be 0.7, and was supplied to the waste water before the heater 33. In the reaction tower 31, the treatment was carried out in a gas-liquid downward cocurrent flow. Also the reaction tower 3
In No. 1, the electric heater 32 is used to control the temperature of the drainage to 120
Oxidation / decomposition treatment was carried out while keeping at ℃. The treated wastewater was cooled to 80 ° C. by the cooler 34 through the treatment liquid line 42, and discharged under pressure from the pressure control valve 44. The discharged gas-liquid was sent to the gas-liquid separator 43 for gas-liquid separation. The pressure control valve 44 detects the pressure with the pressure controller PC,
The pressure was controlled so as to maintain a pressure of 9 MPa (Gauge).
The COD (Cr) of the obtained treatment liquid was 9.1 g / liter, and 95% of all TOC components was acetic acid.

(Reverse Osmosis Membrane Treatment Step) The obtained treatment liquid was supplied to the reverse osmosis membrane treatment step 50 so as to maintain a pressure of 2.9 MPa (Gauge). Further, the treatment was performed so that the amount of the non-permeated liquid was about 1/3 of the amount of the processing liquid supplied. As the reverse osmosis membrane, a polyamide-based composite membrane (demineralization rate (exclusion rate) 99.7% with respect to 0.15% NaCl aqueous solution) was used.
The permeated liquid obtained had a COD (Cr) content of less than 0.1 g / liter, and the non-permeated liquid had a COD (Cr) content of 28 g / l.
It was liter. The entire amount of the non-permeated liquid was supplied to the drainage tank 48 through the concentrated liquid return line 49 and mixed with the drainage.

Example 5 Wet oxidation treatment was performed in the same manner as in Example 1 except for the following conditions. The inside of the reaction column 1 was not filled with a catalyst and was an empty column. Sewage sludge containing various organic substances was used as wastewater. The COD (Cr) of the waste water was 9.7 g / liter and the pH was 2.8.

(Oxidation treatment step) The waste water and a non-permeated liquid which will be described later are mixed in the waste water tank 18, and the waste water supply pump 5 pressurizes and feeds it at a flow rate of 1.6 liters / hour, and then the heater 3 heats it to 230 ° C. And was fed from the bottom of the reaction tower 1. An aqueous solution of sodium hydroxide was supplied from the alkali supply line 8 to the waste water using the alkali supply pump 7 so that the pH of the treatment liquid after the wet oxidation treatment was about 6.5.
Air was supplied in the same manner as in Example 1 so that the ratio of O _{2 /} COD (Cr) was 1.5. In the reaction tower 1, oxidation / decomposition treatment was performed while keeping the wastewater at 230 ° C. using the electric heater 2. The obtained treatment liquid was cooled to 30 ° C. in the cooler 4 via the treatment liquid line 12, and then sent to the gas-liquid separator 13 to perform gas-liquid separation. At this time, the pressure is 4.
It was controlled so as to maintain 9 MPa (Gauge). The COD (Cr) of the obtained treatment liquid was 3.3 g / liter, and 89% of all TOC components was acetic acid. The ammonia concentration was 0.14 g / liter.

(Reverse Osmosis Membrane Treatment Step) After the obtained treatment liquid was filtered using a filter having a filtration accuracy of 1 μm, it was supplied to the reverse osmosis membrane treatment device 20 so as to maintain a pressure of 2.9 MPa (Gauge). The amount of non-permeate liquid was controlled to be about 1/3 of the amount of treatment liquid applied to the reverse osmosis membrane. As a reverse osmosis membrane, a polyamide-based composite membrane (desalination rate (exclusion rate) 99.5) was used.
%)It was used. The resulting permeate has a COD (Cr) of less than 0.1 g / liter and an ammonia concentration of 0.01 g
/ Liter was less than. In addition, the COD (C
r) is 9.8 g / liter, and the ammonia concentration is 0.39.
It was g / liter. And 70% of this non-permeate
Was supplied to the drainage tank 18 through the concentrate return line 19 and mixed with the drainage.

Example 6 The same wet oxidation treatment as in Example 4 was performed except for the following conditions.
As a solid catalyst, 1.3 liters of a catalyst containing activated carbon, ruthenium and palladium as main components, a ruthenium content of 0.4 mass% and a palladium content of 0.1 mass% were filled in the reaction tower 31. did. As the wastewater, wastewater containing a long-chain alcohol and a solvent and having a COD (Cr) of 76 g / liter and a pH of 8.5 was used.

(Oxidation treatment step) The waste water, the total amount of the non-permeated liquid described later, and a part of the wet oxidation treatment liquid are collected in the drain tank 4.
Mixing was carried out at 8, and the COD (Cr) of the waste water was controlled to be 35 g / liter. The drainage supply pump 35
Was used for pressure-feeding at a flow rate of 0.65 liter / h, then heated to 140 ° C. by the heater 33, supplied from the upper part of the reaction tower 31, and controlled so that the processing pressure was 0.9 MPa (Gauge). . Further, air is supplied from the oxygen-containing gas supply line 40 and the pressure is increased by the compressor 39.
The flow rate was controlled by the oxygen gas flow rate control valve 41 so that the ratio was O ₂ /COD(Cr)=0.82, and the wastewater was supplied to the wastewater before the heater 33. In the reaction tower 31, the treatment was carried out in a gas-liquid downward cocurrent flow. In the reaction tower 31, the temperature of the waste water was kept at 140 ° C. by using the electric heater 32, and the oxidation / decomposition treatment was performed. The obtained treatment liquid had a COD (Cr) of 6.5 g / liter and a pH of 2.8, and contained 80% of all TOC components.
The above are organic acids such as succinic acid, acetic acid, and propionic acid. Further, 50% of this organic acid was acetic acid.

(Reverse Osmosis Membrane Treatment Step) 25% of the obtained treatment liquid after the wet oxidation treatment is returned to the drainage tank 48 from the concentrated liquid return line 49, and the rest is subjected to the reverse osmosis membrane treatment process at 1.5%.
The pressure was supplied so as to maintain the pressure of MPa (Gauge), and the treatment was performed so that the amount of the non-permeated liquid became about 1/2 of the supplied amount. At this time, the treatment liquid after the wet oxidation treatment was subjected to air bubbling treatment in advance to release carbon dioxide in the liquid, and an aqueous ammonia solution was further added to control the treatment liquid to have a pH of about 6. As the reverse osmosis membrane, a polyamide composite membrane (desalination rate (exclusion rate) 99.5%) was used. COD (Cr) of the obtained permeate is less than 0.1 g / liter,
The ammonia concentration was less than 0.1 g / liter, and the COD (Cr) of the non-permeate was 13 g / liter. Then, the total amount of this non-permeated liquid is returned to the concentrated liquid return line 49.
Returned to the drainage tank 48.

Example 7 (Oxidation treatment step) Wet oxidation treatment was carried out using the same wastewater as in Example 1. The wet oxidation treatment was performed in the same manner as in Example 1 except that the non-permeated liquid was not supplied to the drain tank 18. The obtained treatment liquid had a COD (Cr) of 2.9 g / liter and a pH of 3.0, and 90% of all TOC components was acetic acid.

(Reverse osmosis membrane treatment step (first time)) The obtained treatment solution was mixed with the non-permeate obtained in the second reverse osmosis membrane treatment step described later, and the same reverse osmosis membrane treatment as in Example 1 was performed. The process was added. The treatment liquid was supplied so as to maintain a pressure of 4.9 MPa (Gauge), and the same reverse osmosis membrane as in Example 1 was used, and the amount of non-permeation liquid was about 1 of the treatment liquid amount applied to the reverse osmosis membrane.
It was controlled to be / 5. This reverse osmosis membrane treatment step (1
The COD (Cr) of the permeated liquid obtained by
It was 2 g / liter, and COD (Cr) of the non-permeate was 9.6 g / liter.

(Reverse osmosis membrane treatment step (second time)) The same reverse osmosis membrane treatment step as in the first time is supplied with the permeate obtained in the first reverse osmosis membrane treatment step, and the treatment is performed with the reverse osmosis membrane. did. At this time, the obtained non-permeated liquid amount (second time) was controlled to be about 1/3 of the supplied liquid amount. Then, the second non-permeate liquid was supplied to the treatment liquid obtained through the wet oxidation treatment. COD (Cr) of the second reverse osmosis membrane non-permeate
Is 2.9 g / liter, and COD (C
r) was 0.5 g / liter.

(Acetic acid recovery step) The first non-permeated liquid was subjected to the acetic acid recovery step. The solvent extraction method and the distillation method were used in the acetic acid recovery step. In the solvent extraction method, a separating funnel having a volume of 1 liter was used, and extraction was performed three times using ethyl acetate as a solvent. Acetic acid was recovered by mixing the extractant phases obtained three times and performing a distillation treatment with a distillation apparatus. It was possible to recover 85% of acetic acid in the treatment liquid subjected to the recovery step.

Comparative Example 3 (Acetic Acid Recovery Step) The treatment liquid obtained in Example 7 was subjected to the same acetic acid recovery step as in Example 7 without the reverse osmosis membrane treatment step. 7 of acetic acid in the treatment liquid that was subjected to acetic acid recovery process
8% was recovered.

Example 8 (Oxidation treatment step) The same wet oxidation treatment as in Example 7 was performed except that the aqueous sodium hydroxide solution was supplied through the alkali supply line 8. The supply amount of the sodium hydroxide aqueous solution was controlled so that the liquid pH after the wet oxidation treatment was about 6. COD (Cr) of the obtained treatment liquid is 3.3 g.
/ Liter and 92% of all TOC components were acetic acid. In addition, sodium ion was contained in an amount of about 1.5 mole times that of acetic acid.

(Reverse osmosis membrane treatment step) The obtained treatment solution was subjected to the same reverse osmosis membrane treatment step as in Example 1. Incidentally, 4.9
The pressure was supplied so as to maintain the pressure of MPa (Gauge), and the amount of the non-permeated liquid was controlled to be about 1/5 of the amount of the supplied liquid.
The resulting permeate has a COD (Cr) of less than 0.1 g / liter and the non-permeate has a COD (Cr) of 16.5 g / l.
It was liter.

(Acetic acid recovery step) This non-permeated liquid was used in Example 7.
Acetic acid was recovered by subjecting it to the same acetic acid recovery step. It was possible to recover 97% of acetic acid in the treatment liquid that was subjected to the acetic acid recovery step.

Comparative Example 4 (Acetic Acid Recovery Step) The treatment liquid obtained by the wet oxidation treatment of Example 8 was subjected to an acetic acid recovery step to directly extract acetic acid with a solvent.
It was possible to recover 81% of the acetic acid in the treatment liquid that was subjected to the acetic acid recovery step.

Example 9 (Oxidation treatment step) Wet oxidation treatment was carried out under the same conditions using the same equipment and drainage as in Example 3 except that the non-permeate was not supplied to the drainage tank 18. The obtained treatment liquid had an ammonia concentration of 0.59 g / liter and a pH of 7.2.

(Reverse osmosis membrane treatment step) As a result of being subjected to the same reverse osmosis membrane treatment step as in Example 3, the permeated liquid obtained had an ammonia concentration of less than 0.01 g / liter, and the non-permeated liquid had an ammonia concentration. Was 1.8 g / liter.

(Ammonia recovery step) The resulting non-permeated liquid was subjected to an ammonia recovery step using a distillation method to recover ammonia. It was possible to recover 95% of ammonia in the treatment liquid that was subjected to the ammonia recovery step.

Comparative Example 5 (Ammonia recovery step) The treatment liquid obtained by the wet oxidation treatment of Example 9 was subjected to the same ammonia recovery step as in Example 9 to recover ammonia. It was possible to recover 83% of ammonia in the treatment liquid that was subjected to the ammonia recovery step.

[0098]

EFFECTS OF THE INVENTION Waste water is subjected to an oxidation treatment step, and an organic acid (acetic acid etc.) or an oxidant such as ammonia contained in the obtained treatment liquid is treated with a reverse osmosis membrane having a high desalination rate. By processing, it can be concentrated and included in the non-permeate,
Also, highly purified treated water containing almost no oxides could be obtained as the permeate. Moreover, when the pH of the treatment liquid when treated with the reverse osmosis membrane was set to 4 or more, the separation performance of the reverse osmosis membrane could be remarkably improved.

[Brief description of drawings]

FIG. 1 is one of embodiments of a treatment apparatus for wet oxidation treatment according to the present invention.

FIG. 2 is one of the outlines of the method for treating wastewater according to the present invention.

FIG. 3 is one of the embodiments of the treatment apparatus for the wet oxidation treatment according to the present invention.

FIG. 4 is one of the outlines of the wastewater treatment method according to the present invention.

FIG. 5 is a diagram showing a change in COD (Cr) concentration of the permeated liquid obtained in Example 1.

[Explanation of symbols]

1,31 reaction tower 2,32 electric heater 3,33 heater 4,34 cooler 5,35 Drainage supply pump 6,36 Drainage supply line 7,37 Alkali supply pump 8,38 Alkali supply line 9,39 Compressor 10,40 Oxygen-containing gas supply line 11,41 Oxygen-containing gas flow rate control valve 12,42 Processing liquid line 13,43 gas-liquid separator 14,44 Pressure control valve 15 Liquid level control valve 16,46 gas discharge line 17,47 Processing liquid discharge line 18,48 drainage tank 19,49 Concentrated liquid return line 20,50 Reverse osmosis membrane treatment equipment LC liquid level controller PC pressure controller

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-59-95989 (JP, A) JP-A-49-97457 (JP, A) JP-A-58-118538 (JP, A) JP-A-50- 77310 (JP, A) International publication 99/42407 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 1/44 B01D 61 / 02,71 / 56

Claims (7)

(57) [Claims] 1. A number of 2 or more organic compounds carbon and / or nitrogen compounds containing waste water, in a method of treating waste water is subjected to a wet oxidation process using a solid catalyst, the wet acid <br/> treatment The treatment liquid obtained through the process has a high desalination rate.
A method for treating wastewater, which comprises separating a non-permeate and a permeate using a polyamide composite membrane ( reverse osmosis membrane ) . 2. The method according to claim 1, wherein all or part of the impermeable liquid is subjected to an oxidation treatment step together with the drainage. 3. The method according to claim 1, wherein all or part of the non-permeate is subjected to a step of recovering an organic acid and / or ammonia. 4. The pH of a treatment liquid treated with the reverse osmosis membrane
The method according to claim 1, wherein the value is 4 or more. 5. The method according to any one of the oxidation treatment process is heated, according to claim 1-4 is a wet oxidation treatment performed under pressure. 6. The method according to any one of the claims 1 to 5 non-permeate is an organic acid and / or ammonia-containing solution. 7. A part of the treatment liquid obtained through the oxidation treatment step and / or a part or all of the permeate,
The method according to any one of claims 1 to 6 subjected to the oxidation treatment process together with the waste water.