JP3200314B2 - Organic wastewater treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic matter-containing acidic wastewater treatment apparatus for producing pure water or treating wastewater containing organic matter by biological treatment and deionization treatment.

[0002]

2. Description of the Related Art Ultrapure water is used as cleaning water in the manufacturing process of electronic devices such as semiconductors and liquid crystals, and the amount of ions is compared for the purpose of protecting valuable water resources, preserving the environment, and reducing manufacturing costs. Very little washing wastewater
This is collected and reused.

Generally, an ultrapure water production system includes a primary system for treating raw water by a reverse osmosis membrane device, an ion exchange device, an ultraviolet sterilizer, a vacuum deaerator, and the like, and a primary pure water obtained by the system. A secondary system for producing ultrapure water by treating the ultrapure water with an ultraviolet oxidation device, an ion exchange device, an ultrafiltration device, etc., and collecting cleaning wastewater generated by using ultrapure water for cleaning semiconductor wafers and the like. And a recovery system for reuse as ultrapure water.

[0004] The washing wastewater contains organic substances such as alcohol and surfactant used in the production process, hydrofluoric acid, sulfuric acid, and the like.
Since an acid such as phosphoric acid or acetic acid is contained, an organic matter removal treatment and a deionization treatment are required in the recovery system, and therefore, in the conventional recovery system, a biological material for performing the organic matter removal treatment is conventionally used. A processing apparatus and an ion exchange apparatus for performing deionization processing are provided.

Here, an apparatus used in a conventional recovery system will be described with reference to FIG.
H adjusting tank, 2 is a biological treatment device, 3 is a membrane separation device, and 4 is an ion exchange device. In this apparatus, collected water of ultrapure water used for cleaning a semiconductor wafer or the like, that is, cleaning wastewater is neutralized by a pH adjusting tank 1. Washing wastewater (hereinafter referred to as “treatment water”) contains an acid such as hydrofluoric acid as described above, and since the pH range is acidic, if it flows into a biological treatment apparatus in this state, the growth of microorganisms is inhibited. , Its work is lost. For this purpose, the water to be treated is neutralized by adding an alkaline solution such as caustic soda, and the pH of the water to be treated is usually adjusted to the range of 5 to 9.

[0006] The water to be treated after neutralization is sent to the biological treatment apparatus 2, where microorganisms decompose organic matter.

After the biological treatment, the water to be treated is then sent to the membrane separation device 3 to separate and remove microorganisms mixed in the water to be treated. Further, the permeated water of the membrane separation device 3 is sent to the ion exchange device 4, where the deionized treatment is performed to obtain the final treated water.

[0008] The obtained final treated water is circulated to the primary system and reused for producing ultrapure water.

[0009]

In the above-mentioned conventional apparatus, a pH adjusting tank is provided and neutralization is performed by adding an alkaline solution to the recovered water. There is a problem that the amount of cations in (recovered water) increases (for example, if a sodium hydroxide solution is used as an alkaline solution, the amount of Na ions increases).

If the amount of cations in the water to be treated increases,
In the deionization treatment performed in the latter stage of the biological treatment, the ion load on the ion exchange resin increases, and in order to cope with this, the amount of the ion exchange resin is increased or the ion exchange treatment time is shortened for regeneration. It is necessary to accelerate the cycle.

However, an increase in the amount of ion-exchange resin inevitably leads to an increase in the size of the ion-exchange apparatus, which leads to an increase in the amount of chemicals used for regeneration and the amount of waste liquid for regeneration, which leads to an increase in equipment costs and running costs. There is a defect. In addition, if the ion exchange processing time is shortened and the regeneration cycle is advanced, the problem of a rise in running cost also arises. In addition, a reverse osmosis membrane device may be used in the deionization treatment, but in this case, with an increase in the ion load, problems such as a decrease in the quality of the treated water and an increase in the concentration of the waste liquid are caused. .

The present inventors have conducted intensive studies to solve the above-mentioned conventional drawbacks. As a result, an anion exchange device filled with a weakly basic anion exchange resin was provided at the front stage of the biological treatment device.
It has been surprisingly found that if the water to be treated is subjected to ion exchange treatment by the anion exchange device, the pH of the water to be treated can be adjusted to a pH range applicable to biological treatment. This is exactly what realizes the neutralization treatment by the ion exchange treatment, and the present invention has been completed based on such knowledge.

[0013] Thus, the present invention provides a biological treatment without increasing the ion load to decompose organic substances in the water to be treated, and further perform deionization treatment to obtain an organic substance containing water with good quality. An object of the present invention is to provide an acidic wastewater treatment device.

[0014]

SUMMARY OF THE INVENTION The present invention provides (1) an apparatus for treating acidic wastewater containing organic substances, which removes anions in acid components in the water to be treated and adjusts the pH of the water to be treated.
An anion exchange device filled with a weakly basic anion exchange resin to adjust the pH range applicable to biological treatment,
A biological treatment device for performing a decomposition treatment of organic substances in the water to be treated, a solid-liquid separation device for removing microorganisms mixed in the treatment water after the biological treatment, and a treatment water after the microorganism removal treatment A deionization treatment device for deionizing water, and (2) a biological treatment device using an aerobic biofilm formed on a microorganism-adhered carrier. The organic matter-containing acidic wastewater treatment device according to the above (1), which is a gaseous biofilm treatment device,
(3) The organic matter-containing acidic wastewater treatment device according to the above (1) or (2), wherein the solid-liquid separation device is a membrane separation device provided with a separation membrane; The gist is the organic wastewater treatment apparatus according to the above (1), which is a dilute washing wastewater generated when the electronic device is washed with ultrapure water.

The present invention has an anion exchange device filled with a weakly basic anion exchange resin, a biological treatment device, and a deionization treatment device. These devices perform organic matter decomposition treatment and deionization treatment. Since microorganisms are usually mixed in the water to be treated after the treatment, a solid-liquid separation device is provided downstream of the biological treatment device to remove the microorganisms.

In order to minimize the amount of microorganisms mixed in the water to be treated after the biological treatment and to avoid an increase in the load on the downstream equipment due to excessive outflow of the microorganisms, the biological treatment device of the present invention is provided on a microorganism-attached carrier. An aerobic biofilm treatment apparatus using an aerobic biofilm is preferably used.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the apparatus of the present invention has an anion exchange apparatus 10 filled with a weakly basic anion exchange resin, and a biological treatment apparatus 12 is connected to the apparatus 10 via a connection pipe 11. Reference numeral 13 denotes a treated water supply pipe connected to the anion exchange device 10.

The anion exchange device 10 uses a weakly basic anion exchange resin. The weakly basic anion exchange resin is capable of decomposing a neutral salt such as sodium chloride to adsorb its anion, silica, heavy water, etc. without the ability to adsorb weakly anion such as _{^{carbonate, F -, sO 4 2-,}} Cl - chemically anions efficiently adsorbed in the acidic conditions such as, moreover substantially identical equivalent ion exchange capacity when reproduction It has the property of being efficiently regenerated by alkali such as sodium hydroxide.

In the present invention, the ion exchange resin to be charged into the anion exchange apparatus 10 is a weakly basic anion exchange resin because a strongly basic anion exchange resin adsorbs even anions of neutral salts in the water to be treated. For example, when the neutral salt is sodium chloride, ion exchange generates caustic soda, and the water to be treated is strongly alkaline (usually pH 9).
This is because the above cannot be applied to the biological treatment in the subsequent stage.

The biological treatment device 12 performs a process of decomposing organic substances in the water to be treated by the action of microorganisms. The biological treatment device 12 is a fluid treatment device in which microorganisms are deposited on a microorganism-adhering carrier and flow in the device. A bed type or a fixed bed type in which the set is fixed in the device, and a floating type in which the microorganisms are suspended in the device without being set on the carrier, are exemplified. An aerobic biofilm treatment apparatus using a fluidized-bed type or fixed-bed type, that is, a type in which an aerobic biofilm is formed on a microorganism-adhered carrier, is preferred to avoid an increase in load on a downstream device due to excessive outflow.

Examples of the microorganism-attached carrier used in such a biofilm treatment apparatus include fibrous activated carbon, granular activated carbon, and spherical activated carbon. Among them, fibrous activated carbon, especially a felt cloth-like molded article of fibrous activated carbon Is preferred. In the figure, reference numeral 14 denotes an air introduction pipe for supplying oxygen necessary for biological treatment.

A solid-liquid separation device 16 is connected to the biological treatment device 12 via a connection pipe 15. The solid-liquid separation device 16 is for separating and removing microorganisms mixed in the water to be treated after biological treatment, and includes a microfiltration membrane (MF),
Examples include a membrane separation device using a separation membrane such as an ultrafiltration membrane (UF) and a reverse osmosis membrane (RO), and a coagulation-sedimentation filtration device. When an aerobic biofilm treatment device is used as the biological treatment device 12, a membrane separation device is generally used as the solid-liquid separation device 16.

Further, a deionization treatment device 18 is connected to the subsequent stage of the solid-liquid separation device 16 via a connection pipe 17. The deionization apparatus 18 is for removing impurity ions in the water to be treated after biological treatment, and examples of the apparatus 18 include an ion exchange apparatus and a reverse osmosis membrane apparatus. As the ion exchange device, the same ion exchange device as that usually used for the purpose of deionization treatment in which the cation exchange resin and the anion exchange resin are packed in the same column or in separate columns is used. The deionizing device 18 is not limited to the case where one of an ion exchange device and a reverse osmosis membrane device is used, and may be a device that uses both devices in combination.

A treated water discharge pipe 19 for discharging treated water after the deionization treatment is connected to the deionization treatment device 18.

The present invention is applied to a wastewater treatment apparatus used in a recovery system for reusing recovered water after using ultrapure water as washing water or the like, that is, a recovery system in an ultrapure water production apparatus. It is particularly useful as a wastewater treatment device. However, the present invention is not limited to such applications, such as general advanced wastewater treatment,
The present invention is also applicable as a wastewater treatment device having a relatively low organic matter concentration.

The operation of the present invention will be described below with reference to FIG. 2 by taking, as an example, the case where the present invention is used as a wastewater treatment apparatus applied to a recovery system in an ultrapure water production apparatus.

Cleaning wastewater (hereinafter referred to as “treatment water”) having a relatively small amount of ions generated when cleaning an electronic device such as a semiconductor wafer with ultrapure water at a use point 20 such as a semiconductor manufacturing plant is supplied to the treatment water. It is supplied to the anion exchange device 10 in the wastewater treatment device 21 of the present invention through the pipe 13. The water to be treated contains organic substances such as alcohols and surfactants, and acids such as hydrofluoric acid, sulfuric acid, phosphoric acid, and acetic acid.

[0028] By being an ion exchange treatment in an anion exchange device 10, in the for-treatment water ^F -, SO ₄ ^2-,
Anions in acid components such as PO ₄ ³⁻ and CH ₃ COO 2 ⁻ are removed, whereby the pH of the water to be treated is adjusted to a pH range applicable to biological treatment (usually pH 6 to 9).

Next, the water to be treated is sent to the biological treatment device 12. In the device 12, biological treatment is performed by the action of microorganisms in the device in a state where air is blown into the water to be treated from the air introduction pipe 14, whereby organic matter in the water to be treated is decomposed.

The water to be treated after the biological treatment is applied to a solid-liquid separator 16.
And the microorganisms mixed into the water to be treated are separated and removed.

The treated water from which the microorganisms have been separated and removed is then supplied to a deionizer 18 where impurity ions in the treated water, such as neutral salts such as sodium chloride and weak acid components such as silica and bicarbonate, are added. , And other impurity ions are removed, and treated water having a quality similar to pure water is obtained.

The treated water thus obtained is circulated through a treated water discharge pipe 19 to a treatment device 22 comprising a reverse osmosis membrane device, an ion exchange device and the like in the primary system of the ultrapure water production device. It is fed to the reverse osmosis membrane device at 22. Here, after various treatments in the primary system are performed, the treated water is sent to the treatment device 23 in the secondary system, which includes an ultraviolet oxidizer, an ion exchanger, etc., where the various treatments are performed, and Is manufactured.

As shown in FIG. 2, when the processing system 22 including a reverse osmosis membrane device and an ion exchange device is installed in the primary system, the deionization processing device 18 is omitted,
The reverse osmosis membrane device and the ion exchange device in the primary system can be shared as the deionization treatment device 18.

When the weakly basic anion exchange resin in the anion exchange device 10 is saturated with ions, the pH of the water to be treated is changed.
Starts to fall sharply, so it is necessary to regenerate at an earlier stage. Here, in performing the regeneration treatment using the alkaline agent, the method disclosed in Japanese Patent Publication No. 5-41300 is adopted, and the alkaline agent is supplied to the upper part of the apparatus and supplied so as to sufficiently fill the inside of the apparatus. Is preferred. By doing this,
Usually, an alkaline agent can be brought into contact with a portion where bacteria can easily propagate, for example, a distributor of influent water, so that the growth of bacteria in the device can be prevented, and the flow rate due to the conventional bacterial growth can be prevented. This has the effect of preventing the adverse effects of lowering and increasing the differential pressure.

Next, a specific example in which drainage treatment is performed using the apparatus of the present invention will be described. Example Cleaning wastewater in a semiconductor manufacturing process was treated using the apparatus of the present invention shown in FIG. The water quality of the washing wastewater is as follows. pH: 2.5 TOC: 3.5 mg C / L Total cations: 10 mg CaCO ₃ / L Total anions: 110 mg CaCO ₃ / L Weakly basic anion exchange resin Amberlite IRA-68 (Rohm and Haas Co.) Was refilled with 5% w / v caustic soda solution, and the remaining caustic soda solution was extruded with extruded water and washed with washing water (pure water). 1m ³
/ Hr flow rate.

The pH of the water to be treated was adjusted in the range of 6 to 9 in the anion exchange device 10. Next, the water to be treated was supplied to the biological treatment device 12. As the biological treatment device, an aerobic biofilm treatment device was used in which a material obtained by growing microorganisms on a felt-like molded article of fibrous activated carbon was filled in the device. Air was blown from the air introduction pipe 14 at the lower part of the apparatus to perform biological treatment. The aeration air LV was 10 m / hr, and the water flow SV was 2.

The water to be treated after biological treatment is separated into a solid-liquid separator 16.
And the microorganisms were separated and removed to obtain treated water. As the solid-liquid separator 16, a microfiltration membrane device manufactured by Nippon Memtech Co., Ltd. was used. Table 1 shows the quality of the obtained treated water.

Comparative Example Using the conventional apparatus shown in FIG. 3, treatment was performed using the same washing wastewater as in the above-mentioned embodiment. First of all, washing wastewater
Was passed through the pH adjusting tank 1 at a flow rate of 1 m ³ / hr. pH
The adjusting tank 1 has a capacity of 0,0 including a stirrer and a pH meter.
Using a 5 m ³ polyethylene tank, a 0.5% w / v caustic soda solution was added to the water to be treated in the tank as an alkali agent for neutralization, and the pH of the water to be treated was adjusted.
Was adjusted to 6 to 9. After the pH was adjusted, the treatment was performed under the same conditions as in the example to obtain treated water after the solid-liquid separation treatment. Table 1 shows the quality of the obtained treated water.

[0039]

[Table 1]

As is clear from the above results, the amount of cations in the water to be treated does not increase when the apparatus of the present invention is used, but the amount of cations increases significantly when the conventional apparatus is used. I understand. Further, when the apparatus of the present invention is used, the amount of anions is reduced because the anions in the acid components in the water to be treated are removed. Thus, according to the present invention, it is found that not only the water to be treated can be neutralized without increasing the amount of cations, but also that the amount of anions can be reduced at the same time as the neutralization.

[0041]

As described above, according to the present invention, an anion exchange apparatus filled with an anion exchange resin made of a weak base is provided at the preceding stage of the biological treatment apparatus, so that water to be treated is treated by the anion exchange apparatus. Thus, the pH of the water to be treated can be adjusted to a pH range applicable to biological treatment by removing anions in the acid component in the water to be treated.

According to the present invention, since the pH is adjusted by deionization, unlike the conventional apparatus in which the pH is adjusted by adding an alkaline agent, the amount of cations in the water to be treated is increased. No defects,
Therefore, in the deionization treatment performed in the latter stage of the biological treatment, the ion load on the ion exchange resin or the like does not increase.

Further, according to the present invention, when adjusting the pH of the water to be treated, the amount of anions can be reduced simultaneously with the pH adjustment, and the ion load in the subsequent deionization can be reduced. In addition, the disadvantages of the conventional apparatus, such as an increase in the scale of the apparatus and an increase in the amount of regenerated chemicals, can be eliminated, and this has the effect of being extremely economically advantageous.

According to the present invention, treated water having good water quality can be obtained by performing biological treatment without increasing the ion load, decomposing organic substances in the water to be treated, and performing deionization treatment. There is an effect that an organic wastewater treatment device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an apparatus of the present invention.

FIG. 2 is a block diagram schematically showing a case where the apparatus of the present invention is applied to an ultrapure water production apparatus.

FIG. 3 is a block diagram schematically showing a conventional device.

[Explanation of symbols]

 Reference Signs List 10 Anion exchange device 12 Biological treatment device 16 Solid-liquid separation device 18 Deionization treatment device

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification code FI C02F 9/00 503 C02F 9/00 503B 503C 503G 1/42 1/42 B 1/44 1/44 J 1/66 510 1 / 66 510L 521 521Z 530 530G 540 540C 540J 3/06 ZAB 3/06 ZAB (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 9/00 501 C02F 9/00 502 C02F 1/42 C02F 1 / 66 C02F 3/00-3/34 101

Claims (4)

(57) [Claims] An apparatus for treating acidic wastewater containing organic matter, which removes anions in an acid component in water to be treated and adjusts the pH of the water to be treated to a pH range applicable to biological treatment. An anion exchange device filled with a weakly basic anion exchange resin, a biological treatment device for decomposing organic substances in the water to be treated, and a solid solution for removing microorganisms mixed in the water to be treated after the biological treatment. A liquid separation device;
An organic matter-containing acidic wastewater treatment device, comprising: a deionization treatment device for deionizing water to be treated after the microorganism removal treatment. 2. The organic wastewater treatment device according to claim 1, wherein the biological treatment device is an aerobic biofilm treatment device using an aerobic biofilm formed on a microorganism-adhered carrier. 3. The organic wastewater treatment apparatus according to claim 1, wherein the solid-liquid separation device is a membrane separation device provided with a separation membrane. 4. The organic wastewater treatment apparatus according to claim 1, wherein the acidic wastewater containing organic matter is a dilute washing wastewater generated when an electronic device such as a semiconductor or a liquid crystal is washed with ultrapure water.