JP2011173040A - Waste water treatment method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment method and apparatus by which treated water made low in organic concentration and dissolved ion concentration is easily obtained. <P>SOLUTION: The waste water treatment method includes: an anaerobic treatment step of treating waste water containing the organic material in an anaerobic biological reaction tank 1; an osmosis membrane separation step of separating an anaerobically treated liquid in the anaerobic treatment step into a permeated liquid and a concentrated liquid by an osmosis membrane 2a; a reverse osmosis membrane separation step of introducing the permeated liquid in the osmosis treatment step into a reverse osmosis membrane separation device 5 and separating the permeated liquid into treated water and concentrated water by a reverse osmosis membrane 5a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a biological treatment method and apparatus for performing membrane separation treatment after anaerobically treating wastewater containing organic matter, and particularly suitable for wastewater treatment when the wastewater is biologically treated and used as raw water for producing pure water. The present invention relates to a method and an apparatus.

  In equipment that uses pure water and discharges its waste water, such as semiconductor manufacturing and liquid crystal manufacturing, such as electronics industry factories, organic substances such as monoethanolamine and tetramethylammonium hydroxide that are used as cleaning agents and release agents in process steps Water recovery is progressing, in which wastewater containing water is biologically treated and the treated water is used as a raw material for producing pure water. When biologically treated water is reused for producing pure water, the treated water is treated with a solid-liquid separator to separate microorganisms, and then desalted with an RO (reverse osmosis) membrane (for example, Japanese Patent Application Laid-Open No. 2007-175582). Issue gazette).

  When biological treatment is performed with aerobic treatment and solid-liquid separation is performed with an MF membrane or UF membrane, the biological metabolite produced by the aerobic treatment contaminates the MF membrane or UF membrane, and chemical cleaning must be performed frequently. . Therefore, Japanese Unexamined Patent Application Publication No. 2009-148714 proposes that biological treatment is performed by anaerobic treatment with a small amount of metabolite produced. This technology not only reduces the contamination of the MF membrane or UF membrane, but also anaerobic treatment. Therefore, compared to the aerobic treatment, there is a merit that aeration for supplying oxygen is unnecessary, power saving, and sludge generation amount is small. is there.

JP 2007-175582 A JP 2009-148714 A

  On the other hand, it is known that the anaerobic treatment requires a larger amount of inorganic salt (Na, K, Ca, Mg, Fe, Co, Ni, etc.) and sulfur than the aerobic treatment. In order to stably treat wastewater containing a small amount of these inorganic components based on pure water such as industrial wastewater, it is necessary to add a sufficient amount. Therefore, the inorganic salt concentration of anaerobic treated water is often higher than that of aerobic treatment. Furthermore, in the anaerobic treatment, most of the sulfur content added to the waste water or separately is reduced to hydrogen sulfide and remains in the treated water. When desalting the treated water containing a large amount of inorganic salts and sulfides with the RO membrane, there is a problem that the RO membranes are easily contaminated by the precipitation of inorganic salts and sulfides on the concentrated liquid side. In particular, metal sulfides such as FeS have low solubility and are likely to precipitate.

  It is an object of the present invention to stably obtain treated water having a low concentration of organic matter and dissolved ions in a method of membrane separation treatment after treating wastewater containing organic matter with anaerobic microorganisms. .

  The waste water treatment method of the present invention (Claim 1) includes an anaerobic treatment step of treating waste water containing organic substances with an anaerobic microorganism, and an anaerobic treatment solution of the anaerobic treatment step using a forward osmosis membrane and a permeate and a concentrate. And a reverse osmosis membrane separation step of separating the permeate from the forward osmosis separation step into treated water and concentrated water by a reverse osmosis membrane.

  The wastewater treatment apparatus of the present invention (Claim 2) includes an anaerobic treatment tank for treating wastewater containing organic substances with anaerobic microorganisms, and an anaerobic treatment liquid in the anaerobic treatment tank using a forward osmosis membrane and a permeate and a concentrated liquid. And a reverse osmosis membrane separation device that separates the permeate of the forward osmosis separation device into treated water and concentrated water using a reverse osmosis membrane.

  The wastewater treatment apparatus according to claim 3 is characterized in that the forward osmosis membrane separation device is arranged so that the forward osmosis membrane is in contact with the anaerobic treatment liquid in the anaerobic treatment tank.

  According to a fourth aspect of the present invention, there is provided a wastewater treatment apparatus according to the second or third aspect, further comprising means for returning the concentrated water from the reverse osmosis membrane separation device into the forward osmosis membrane separation device.

  In the present invention, wastewater containing organic matter is subjected to anaerobic treatment, and this anaerobic treatment liquid is first subjected to forward osmosis membrane separation. That is, the anaerobic treatment solution is brought into contact with a high concentration aqueous electrolyte solution (for example, a salt solution) through the semipermeable membrane, and the water in the anaerobic treatment solution is moved to the secondary side of the semipermeable membrane by the difference in osmotic pressure between the two. . Thereby, inorganic salts including dissolved sulfide are removed simultaneously with solid-liquid separation of the anaerobic treatment liquid. The forward osmosis membrane permeate treated with inorganic salts such as dissolved sulfide in this way is desalted by reverse osmosis membrane separation. Thereby, the treated water with low organic substance density | concentration and dissolved ion density | concentration can be obtained stably.

  In the wastewater treatment apparatus according to the third aspect, the forward osmosis membrane separation device is arranged in the anaerobic treatment tank, and the wastewater treatment apparatus becomes compact.

  In the wastewater treatment device according to claim 4, since the concentrated water from the reverse osmosis membrane separation device is introduced into the forward osmosis membrane separation device in this way, the salt concentration in the forward osmosis membrane separation device is It becomes a thing higher than the salt concentration in the anaerobic processing liquid in an anaerobic biological reaction tank. Due to this concentration difference, the liquid in the anaerobic biological reaction tank permeates through the forward osmosis membrane and flows into the forward osmosis membrane separation device.

It is a schematic longitudinal cross-sectional view of isolation | separation which concerns on embodiment. It is the flowchart of Example 1, and the schematic diagram of FO apparatus. 3 is a graph showing the results of Example 1 and Comparative Example 1.

  Hereinafter, a wastewater treatment method and apparatus according to an embodiment of the present invention will be described in detail with reference to FIG.

Wastewater containing organic matter is introduced into the anaerobic biological reaction tank 1 and is anaerobically decomposed by the action of anaerobic microorganisms. Organic matter having a large molecular weight in the wastewater is decomposed into higher methane and CO ₂ through higher fatty acids and acetic acid. In addition, methanol, methylamine, TMAH and the like are directly decomposed into methane and CO ₂ . At this time, the sulfur content contained in the organic matter and the sulfate ions in the wastewater are decomposed into H ₂ S. These gas components are dissolved in the liquid at a concentration that is in equilibrium with the concentration of the gas phase in the anaerobic biological reactor 1 and discharged together with the treated water, and the excess is released from the liquid into the gas phase. The The gas released into the gas phase is taken out of the anaerobic biological reaction tank 1 through the pipe 10, and a part of the gas is supplied to the diffuser pipe 13 through the blower 11 and the gas return pipe 12. . The air diffuser 13 is disposed below the forward osmosis membrane separation device (FO device) 2. When the gas diffused from the air diffuser 13 rises and hits the forward osmosis membrane (FO membrane) 2a, a membrane cleaning action is exhibited.

  The forward osmosis membrane separation device 2 includes a tank body and a forward osmosis membrane 2a provided at least at the bottom of the tank body, and the forward osmosis membrane 2a is contained in the anaerobic treatment liquid in the anaerobic biological reaction tank 1. It is piped to be immersed.

  In addition, you may comprise more parts, for example, the whole of the part which contact | connects the liquid in the anaerobic biological reaction tank 1 among the tank bodies of the forward osmosis membrane separation apparatus 2 with a forward osmosis membrane.

  An extraction pipe 3 is connected to one end of the forward osmosis membrane separation device 2, and the forward osmosis membrane liquid in the forward osmosis membrane separation device 2 passes through the pipe 3 and the pump 4 in the reverse osmosis membrane separation device (RO device) 5. To be supplied. The permeated water that has permeated through the reverse osmosis membrane (RO membrane) 5a of the reverse osmosis membrane separation device 5 is taken out of the system from the pipe 7 as treated water. The concentrated water that has not permeated through the reverse osmosis membrane 5 a is returned to the other end side in the forward osmosis membrane separation device 2 through the pipe 6.

  Thus, since the concentrated liquid from the reverse osmosis membrane separation device 5 is introduced into the forward osmosis membrane separation device 2, the salt concentration in the forward osmosis membrane separation device 2 is anaerobic in the anaerobic biological reaction tank 1. It is higher than the salt concentration in the chemical treatment solution. Due to this concentration difference, the liquid in the anaerobic biological reaction tank 1 permeates through the forward osmosis membrane 2 a and flows into the forward osmosis membrane separation device 2.

  Inorganic salts such as dissolved sulfide in the anaerobic treatment liquid in the anaerobic biological reaction tank 1 cannot permeate the forward osmosis membrane 2a and remain in the anaerobic biological reaction tank 1. Since the liquid from which inorganic salts such as dissolved sulfides are removed is introduced from the forward osmosis membrane separation device 2 to the reverse osmosis membrane separation device 5, the reverse osmosis membrane 5a is contaminated by the precipitation of sulfides and other inorganic salts. And reverse osmosis membrane separation treated water (permeated water) can be obtained stably.

  The forward osmosis membrane 2a is not particularly limited as long as it is a semi-permeable membrane. If it is a reverse osmosis membrane, it can generally be used as a forward osmosis membrane.

  In the present invention, the organic matter-containing wastewater to be treated is not particularly limited as long as it is an organic matter-containing wastewater that is normally biologically treated. Examples thereof include electronic industrial wastewater, chemical factory wastewater, and food factory wastewater. Can be mentioned. For example, in the electronic component manufacturing process, a large amount of various organic wastewater is generated from the development process, peeling process, etching process, cleaning process, etc., and the wastewater can be collected and purified to a pure water level for reuse. As desired, these wastewaters are suitable as the wastewater to be treated of the present invention.

  Examples of such organic wastewater include organic wastewater containing isopropyl alcohol, methanol, diethylene glycol monobutyl ether, organic nitrogen such as monoethanolamine (MEA) and tetramethylammonium hydroxide (TMAH), and ammonia nitrogen. And organic wastewater containing organic sulfur compounds such as dimethyl sulfoxide (DMSO).

  Any anaerobic biological treatment means for anaerobically biologically treating the wastewater may be used as long as it is excellent in the decomposition efficiency of organic matter, and various anaerobic biological treatment type biological reaction tanks can be used.

  The anaerobic biological reaction tank may be of any method such as a floating method (stirring method) or a sludge bed method (sludge blanket method), or may be a carrier addition type or a granulated sludge type.

  In the above embodiment, the forward osmosis membrane separation device 2 is disposed in the anaerobic biological reaction tank 1, but the anaerobic biological reaction tank and the forward osmosis membrane separation device are separately provided as in Example 1 described later. The biological treatment liquid from the anaerobic biological reaction tank may be supplied to the primary side of the forward osmosis membrane separation device by a pump. However, when the forward osmosis membrane separation device 2 is immersed in the anaerobic biological reaction tank 1 as shown in FIG. 1, such a pump is unnecessary.

Hereinafter, examples and comparative examples will be described.
[Example 1]
As shown in FIG. 2 (a), the following waste water was treated in the anaerobic biological reaction tank 18 and then treated in the FO device 20 and the RO device 30. That is, the biological treatment liquid from the anaerobic biological reaction tank 18 was supplied to the primary chamber 21 of the FO apparatus 20, and the permeated liquid of the FO membrane 23 was supplied from the secondary chamber 22 to the RO apparatus 30. The liquid that did not pass through the FO film 23 was returned to the anaerobic biological reaction tank 18. The concentrated water of the RO device 30 was returned to the secondary chamber 22 of the FO device 20, and the permeated water of the RO membrane 31 was taken out as treated water. The waste water, the anaerobic biological reaction tank, the FO device, and the RO device used in the examples are as follows.

<Drainage>
What added P, Na, K, Ca, Mg, Fe, and another metal suitably as a nutrient with respect to the waste_water | drain of a liquid crystal factory was used as waste water. The characteristics of this drainage are as follows.

Monoethanolamine: 300 mg / L
Tetramethylammonium hydroxide: 300 mg / L
Dimethyl sulfoxide: 300 mg / L
TOC: 360 mg / L
ThOD: 1,280 mg / L
TN: 110 mg / L
TS: 120 mg / L

<Anaerobic biological reaction tank>
The waste water was averaged and introduced into a 500 L reactor equipped with a stirrer 19 at 85 L / Hr. The waste water was stirred at 120 rpm and the temperature was maintained at 35 ° C.

<FO equipment>
As the FO apparatus, the apparatus shown in FIG. 2 (b) was produced and used. The FO device 20 is configured such that a primary chamber 21 and a secondary chamber 22 are separated by an FO film 23. Note that both the primary chamber 21 and the secondary chamber 22 are open on the surface facing the FO film 23. The volume of the primary chamber 21 is ◯ L, the volume of the secondary chamber 22 is 2.5 L, and the area of the FO membrane is 5,000 cm ² . As the FO film 23, an RO flat film (manufactured by Nitto Denko Corporation: ES-20) was used. The biological treatment liquid was introduced into the primary chamber 21 from the anaerobic biological reaction tank by a pump at a flow rate of 4.5 m ³ / hr so that the membrane surface flow rate was 0.5 m / sec. The secondary chamber 22 was filled with a 2% NaCl aqueous solution at the beginning of operation, and concentrated water from the RO device 30 was introduced after the operation started. The effluent water from the secondary chamber 22 was supplied to the RO device 30.

<RO equipment>
As the RO device 30, a 2-inch RO module (manufactured by Nitto Denko Corporation: ES-20 spiral type) was used. To this RO apparatus, the permeate from the FO apparatus was supplied by a pump so that the supply pressure was 1.5 MPa. A 10% hydrochloric acid aqueous solution was added to the inflowing water to the RO device 30 so that the pH was 5.5, and the recovery rate was 50%.

<Driving>
Sewage digested sludge (TS 2%, VS / TS ratio 0.65) is used as seed sludge, and after acclimatization for 3 months, the ThOD load of the anaerobic bioreactor is set to 5 kg / m ³ · d (HRT 6 hr). The operation was performed for 2 months, and the biological treatment liquid was passed through the FO device 20 and the RO device 30 in this order as shown in FIG. The relationship between the RO flux and the elapsed days is shown in FIG.

[Comparative example]
In Example 1, the biological treatment liquid from the anaerobic biological reaction tank 18 was used by using an outside-type UF module (manufactured by Norit Japan Ltd .: 33PE) in place of the FO apparatus, with a membrane surface flow rate of 0.5 m / sec. Was filtered with this outside UF module, and this UF permeated water was supplied to the RO device, and the operation was performed under the same flow and conditions as in Example 1. The results are shown in FIG.

[result]
The TOC removal rate of the inflow water to the RO device for two months is 98% or more in both Example 1 and Comparative Example 1, and the average value of the TOC of the RO device inflow water is 1.1 mg in Example 1. / L, Comparative Example 1 was 4.2 mg / L. Moreover, the TOC average value of RO permeated water was 0.8 mg / L in Example 1 and 0.9 mg / L in Comparative Example 1, and there was almost no difference between the two. However, in Example 1, the value of the RO flux decreased only about 15% in two months, whereas in Comparative Example 1, the value rapidly decreased immediately after the start of water flow, and one week later. 1/2 of the value immediately after the start, 1/3 in 2 weeks, and 1/10 in 2 months. After the test, black deposits were adhered to the surface of the RO membrane of Comparative Example 1. This was analyzed by SEM-EDX and found to be iron sulfide. From Example 1 and Comparative Example 1, according to the present invention, wastewater containing organic matter is treated with anaerobic microorganisms, and then treated with FO membrane and RO membrane separation to obtain treated water with low organic matter concentration and dissolved ion concentration. It was found that it can be obtained stably.

1,18 Anaerobic biological reaction tank 2,20 Forward osmosis membrane separation device (FO device)
2a, 23 Forward osmosis membrane 5,30 Reverse osmosis membrane separation device (RO device)
5a, 31 Reverse osmosis membrane 13 Air diffuser

Claims (4)

An anaerobic treatment process in which wastewater containing organic matter is treated with anaerobic microorganisms;
A forward osmosis membrane separation step of separating the anaerobic treatment liquid of the anaerobic treatment step into a permeate and a concentrated liquid with a forward osmosis membrane;
A wastewater treatment method comprising a reverse osmosis membrane separation step of separating the permeate in the forward osmosis separation step into treated water and concentrated water using a reverse osmosis membrane. An anaerobic treatment tank for treating wastewater containing organic matter with anaerobic microorganisms;
A forward osmosis membrane separation device for separating the anaerobic treatment liquid of the anaerobic treatment tank into a permeate and a concentrated liquid with a forward osmosis membrane;
A wastewater treatment device comprising a reverse osmosis membrane separation device that separates the permeate of the forward osmosis separation device into treated water and concentrated water using a reverse osmosis membrane.   3. The wastewater treatment apparatus according to claim 2, wherein the forward osmosis membrane separation device is disposed so that the forward osmosis membrane is in contact with the anaerobic treatment liquid in the anaerobic treatment tank.   4. The wastewater treatment apparatus according to claim 2, further comprising means for returning the concentrated water from the reverse osmosis membrane separation device into the forward osmosis membrane separation device.

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