JPH09187785A - Recovery and purification device for drain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lowering of removing effect for bacteria adhered to a separating membrane surface of a membrane separation device and lower ing of flux from occurring by feeding pressurized water in which oxygen is pressure dissolved into a fluidized biological treatment device. SOLUTION: A fluidized biological treatment device 2 is constituted of a biological reaction tank 6 and a pressurized water preparation device 10 for pressure dissolving the oxygen. Optional type pressurized water preparation devices 10 can be used as far as the pressurized water is brought into contact with oxygen containing gas or air in the devices. For instance, compressed air from an air compressor 11 is mixed with treated water from a tank 3 in an ejector 12 to prepare oxygen containing pressurized water, which is stored in a pressure tank 14. The oxygen containing pressurized water is fed into the bottom section of a biological reaction tank 6 by a feed pipe 16. A large amount of oxygen is replenished into the biological reaction tank 6 by the arrangement. Biological degradation, therefore, can be carried out sufficiently even when the organic matter concentration is high, and nitrification can be carried out perfectly, and even when NH4 <+> concentration is high, adhered bacteria can be removed completely and the lowering of flux can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for recovering and purifying cleaning waste water flowing out from a cleaning process using ultrapure water in a semiconductor, liquid crystal, etc. manufacturing plant and using it as raw water for manufacturing ultrapure water. Related to wastewater collection and purification equipment.

[0002]

2. Description of the Related Art In recent years, due to regulation of water intake and drainage,
The cleaning wastewater flowing out from the cleaning process using ultrapure water is recovered, the pH is neutralized in the pH adjusting tank 1 as shown in FIG. 1 (A), and then the water is supplied to the fluid biological treatment apparatus 2 by the pump. Isopropyl alcohol, methanol,
Organic substances (TOC) such as acetic acid and acetone, and NH ₄ + are decomposed and removed, and Cl is used as a bactericide from the treated water tank 3.
₂ is continuously supplied to the sterilization tank 4, and the sterilization tank pressurizes the membrane separation device 5 such as an ultrafiltration membrane or a microfiltration membrane with a pump to supply the bacteria from the fluid biological treatment apparatus. The body is separated, and the permeated water that has permeated the membrane is used as raw water for ultrapure water production and is sent to the ultrapure water production system. The continuous addition of Cl _{2 in} the sterilization tank is for preventing the bacterial cells from adhering to the membrane surface of the membrane separation device at the subsequent stage and lowering the flux due to continuous operation.

A conventional fluid-type biological treatment apparatus 2 used in the past is a biological reaction tank 6 and an oxygen dissolution tank 8 as shown in FIG.
The biological reaction tank 6 has a packed bed 7 of activated carbon in the form of granules or pellets carrying microorganisms, and the wastewater to be treated is passed through the packed bed in an upward flow to make the packed bed uniform. expand. Further, an air diffuser 9 is provided in the oxygen dissolving tank 8, the air diffuser aerates air into the water and dissolves it in water, and the circulation pump P1 transfers water containing dissolved oxygen in the oxygen dissolving tank to the biological reaction tank. Oxygen is supplied to the microorganisms adhering to the activated carbon in the bioreactor, which is supplied to the bottom of No. 6.

[0004]

When the amount of collected wastewater increases due to regulation of the amount of water intake and the amount of wastewater, the TOC concentration in the wastewater is 2 to 10 ppm and the concentration of NH ₄ ⁺ is 10 to 30 ppm.
To increase. These TOC and NH ₄ ⁺ have the following (1)
According to the equations and equations (2) and (3), TOC becomes CO ₂ ,
NH ₄ ⁺ is decomposed into NO ₃ ⁻ . _{CH 3 COOH + 2O 2 → 2CO} 2 + 2H 2 O ········ (1) NH 4 + + 2O 2 → NO 2 - + 2H 2 O ·············· (2) ^{_{NO 2 - + (1/2) O}} 2 → NO 3 - ················ (3) in other words, TOC of 1ppm (= 2.5ppmasCH ₃
Dissolved oxygen is 2.7ppm, N to decompose COOH)
Dissolved oxygen is 4.4 ppm to nitrify 1 ppm of H ₄ ⁺
Will be needed. Therefore, in the case of the above-mentioned wastewater containing a high concentration of TOC and NH ₄ ⁺ , since dissolved oxygen was supplied to the biological reaction tank in the conventional oxygen dissolution tank, TOC can be sufficiently biodegraded, but NH ₄ ⁺ is nitrified. The amount of dissolved oxygen is insufficient, NH ₄ ⁺ cannot be nitrified completely, and the treated water in which NH ₄ ⁺ remains flows into the sterilization tank 4. Then, NH ₄ ⁺ and Cl ₂ are combined in the sterilization tank to form chloramine, which has a weak bactericidal power, so that the effect of removing the bacterial cells adhering to the membrane surface of the separation membrane of the membrane separation device becomes low and the flux is lowered. The problem arises.

[0005]

In order to solve the above-mentioned problems, the present invention was developed by paying attention to the fact that the amount of air dissolved in water is proportional to the pressure of water. Wastewater flowing out from a washing process using ultrapure water, which is equipped with a flow-type biological treatment device having a carrier and a membrane separation device for adding a chlorine-based bactericide to the outflow water from the biological treatment device to perform membrane filtration. In the collecting and purifying apparatus, the pressurized biological water treatment apparatus is supplied with pressurized water in which oxygen is dissolved under pressure.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Fluidized biological treatment apparatus 2 of the present invention
As shown in FIG. 1B, the biological reaction tank 6 similar to that shown in FIG.
And a pressurized water producing apparatus 10 for supplying pressurized water in which oxygen is dissolved under pressure to the biological reaction tank. This pressurized water producing apparatus can employ any means as long as it brings water into contact with oxygen-containing gas or air in a pressurized state, but in the illustrated embodiment, as shown in FIG. 1 (B). The compressed air from the air compressor 11 and the treated water from the tank 3 by the pump P are supplied to the ejector 12 arranged vertically from below, and the gas-liquid mixed in the ejector is connected to the upper end of the ejector. In the process of flowing in the gas dissolving pipe 13 that meanders in the direction, air is dissolved in the liquid and jetted into the pressure tank 14. The air not dissolved in the liquid is returned to the return pipe 15 connected to the top of the pressure tank.
Then, it is returned to the negative pressure portion of the ejector 12, and mixed again with the liquid to be dissolved.

Therefore, by supplying the pressurized water obtained in the pressurized tank 14 to the bottom of the biological reaction tank 6 through the supply pipe 16, a large amount of oxygen dissolved in the pressurized water can be supplied to the biological reaction tank.

The amount of air supplied from the air compressor 11 to the ejector 12 and the amount of air dissolved in the pressurized water supplied to the biological reaction tank 6 through the supply pipe 16 are controlled to be always constant and equal. However, since such control is difficult in practice, the amount of air supplied to the ejector by the air compressor is set to be slightly larger than the amount of air dissolved in the pressurized water. As a result, the area occupied by the air not dissolved in the liquid for returning to the ejector in the return pipe 15 gradually increases in the pressurized tank. And
Since the pressurized water in the pressurized tank is supplied to the biological reaction tank through the supply pipe 16, the liquid level is lowered, and it is impossible to supply the pressurized water having a fixed pressure in which a fixed amount of air is dissolved at a constant flow rate to the biological reaction tank. .

In order to prevent this, the pressure tank is provided with a liquid level detector 17 for exchanging predetermined upper and lower limits of the liquid level,
The signal is transmitted to an electromagnetic on-off valve 19 provided in a compressed air supply pipe 18 of an air compressor of an air compressor via an appropriate amplifier circuit (illustration) to control the electromagnetic on-off valve 19. That is, when the liquid level in the pressurized tank falls below the lower limit, the liquid level detector 17 detects this and closes the electromagnetic opening / closing valve 19 to stop the compressed air from the air compressor to the ejector. As a result, the ejector sucks the air in the pressurized tank through the return pipe 15, mixes it with the liquid from the treated water tank, and dissolves it. In this way, the area occupied by the air in the pressurized tank is reduced, the liquid level of the pressurized water rises, and when the upper limit is reached, the liquid level detector detects this and the solenoid opening / closing valve 19
The air compressor supplies compressed air to the ejector to mix and dissolve it in the liquid. By repeating this operation, the level of the pressurized water in the pressurized tank is maintained between the upper limit and the lower limit, the amount of dissolved air (oxygen) is constant, and the pressurized water pressurized to a constant pressure has a constant flow rate. It can be fed to the reaction vessel.

Thus, according to the present invention, the cleaning waste water flowing out from the cleaning process using the ultrapure water is recovered, and the pH adjusting tank 1 is collected.
To neutralize the pH with a pump, and then feed the biological reaction tank 6 with a pump to pass through the packed bed 7 of the activated carbon in the form of granules or pellets in an upward flow. _At the time of decomposing with ₄ ⁺ , since the pressurized water in which oxygen is sufficiently dissolved from the pressurized water producing device 10 is supplied to the bioreaction tank, the biodegradation can be sufficiently performed even if the concentration of TOC is high, and the NH ₄ ⁺ It can be completely nitrified even if the concentration is high. Since the treated water supplied to the sterilization tank 4 does not contain NH ₄ ⁺ , chloramine combined with Cl ₂ is not generated. Therefore, C added in the sterilization tank
Since l ₂ sufficiently removes the bacterial cells adhering to the membrane surface of the membrane separator, the flux of the membrane separator does not decrease, and the treated water that has permeated the membrane can be supplied to the ultrapure water production system.

The ultrapure water production system can use a usual treatment method. For example, it is constituted by a pretreatment step including coagulation, precipitation, filtration, adsorption and the like, ion exchange, reverse osmosis membrane desalination, deaeration and the like. It is formed from a primary pure water production process including a secondary pure water production process including ultraviolet oxidation, sterilization, ion exchange, and membrane filtration. The recovered water treated according to the present invention may be supplied to the pretreatment step of the ultrapure water production system together with raw water such as industrial water, city water, and groundwater, and the treated recovered water may be supplied to the ultrapure water production system. It may be supplied to the primary pure water production process. Further, an ion exchange and reverse osmosis membrane desalting step may be provided subsequent to the treatment step of the recovered water of the present invention to improve the water quality of the recovered water and supply it to the secondary pure water producing step.

The comparison test results of the purifying apparatus of FIGS. 1A and 1B according to the present invention and the conventional purifying apparatus of FIGS. 1A and 2 are shown below. The collected wastewater used is the semiconductor A's semiconductor washed wastewater, TOC ≈ 10 ppm, NH ₄ ⁺ ≈
It was 10 ppm. All bioreactors have a diameter of 1
m, height 4 m, the packed bed was composed of 2.5 m ³ of 10/32 mesh granular activated carbon. Waste water was supplied to each device at a flow rate of 10 m ³ / hour. In the purification device of the present invention, dissolved oxygen is 5
Pressurized water of 0ppm from pressurized water production equipment 3m ³ / hour × 6
The bioreactor was fed at kg / cm ² . Also, in the conventional purifier, the dissolved oxygen is 8.5 p from the oxygen dissolution tank with the circulation pump.
Water containing pm was fed to the bioreactor at 13.5 m ³ / h.

As a result, the dissolved oxygen content of the treated water that has permeated the membrane of the membrane separator of the conventional purifier is <1 ppm, NH ₄ ⁺
Is 5 to 6 ppm and TOC is 0.3 ppm, whereas the amount of dissolved oxygen in the treated water that has permeated the membrane of the membrane separation device of the purification device of the present invention is _{4 to 5} ppm, and NH ₄ ⁺ is <1 pp.
m and TOC were 0.2 ppm, NH ₄ ^{+ in the} treated water could be reduced to 1 ppm or less by supplying pressurized water to the biological reaction tank, and the membrane flux was also stabilized.

[0014]

EFFECTS OF THE INVENTION As is clear from the above, in the present invention, pressurized water in which oxygen is dissolved under pressure is supplied to the fluid-type biological treatment apparatus. Therefore, when decomposing TOC and NH ₄ ⁺ in wastewater in the biological reaction tank, Since there is sufficient dissolved oxygen in the water, biodegradation can be sufficiently performed even if the concentration of TOC is high, and even if the concentration of NH ₄ ⁺ is high, this can be completely nitrified. Since the treated water supplied to the sterilization tank 4 does not contain NH ₄ ⁺ , chloramine combined with Cl ₂ is not generated. Therefore, since Cl ₂ added in the sterilization tank sufficiently removes the bacterial cells attached to the membrane surface of the membrane separation device, the flux of the membrane separation device does not decrease, and the treated water that has permeated the membrane is processed into ultrapure water. Can be supplied to the system.

[Brief description of the drawings]

FIG. 1A is a flow sheet of a wastewater recovery and purification device, B
Is a flow-type biological treatment apparatus according to the present invention.

FIG. 2 is a flow type biological treatment device used in a conventional waste water recovery and purification device.

[Explanation of symbols]

 1 pH adjusting tank 2 Fluid type biological treatment apparatus 3 Treated water tank 4 Sterilization tank 5 Membrane separation apparatus 6 Bioreactor tank of fluid type biological treatment apparatus 7 Packing layer of biological reaction tank 10 Pressurized water production apparatus 11 Air compressor 12 Ejector 13 Gas Melting pipe 14 Pressurized tank 15 Return pipe 16 Supply pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C02F 1/50 540 C02F 1/50 540A 550 550H 560 560E 560H 1/76 ZAB 1/76 ZABA

Claims (1)

[Claims] 1. Ultrapure water comprising a fluid-type biological treatment apparatus having a carrier having organisms attached thereto, and a membrane separator for adding a chlorine-based bactericide to the outflow water from the biological treatment apparatus to perform membrane filtration. In a device for collecting and purifying wastewater flowing out from a washing process using the above, a device for collecting and purifying wastewater, characterized in that pressurized water in which oxygen is dissolved under pressure is supplied to the fluid biological treatment device.