JP2015006643A - Method and device for treating organic material-containing water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for treating organic material-containing water, which performs biological treatment, membrane separation, RO treatment, and ion exchange treatment, with a reduced load on ion exchanger.SOLUTION: The method and device for treating organic material-containing water includes: biologically treating organic material-containing water in an MBR tank 1; membrane separating the treated solution obtained in the biological treatment with a solid-liquid separating membrane 3; treating the separated water obtained by the membrane separation with a reverse osmosis membrane device 5; and ion exchanging the water passing through the reverse osmosis membrane. The pH of the MBR tank 1 is adjusted to lower than 6.

Description

  The present invention relates to a method and apparatus for treating organic substance-containing water, and in particular, an organic substance-containing water treatment method and apparatus for treating organic substance-containing water by treating it with biological treatment, membrane separation treatment, reverse osmosis membrane treatment and ion exchange treatment. About.

  In recent years, water recovery has been progressing in which wastewater containing organic matter is biologically treated in facilities that use pure water such as liquid crystal and semiconductor manufacturing plants to discharge the wastewater, and that treated water is used as a raw material for the production of pure water. . Patent Documents 1 and 2 describe methods of treating organic-containing water that perform such water recovery by treating organic-containing water by biological treatment, membrane separation treatment, reverse osmosis membrane (RO) treatment, and ion exchange treatment. ing.

  Patent Document 3 describes that a flat panel display manufacturing wastewater is subjected to calcium phosphate production treatment with a calcium compound, then biologically treated, filtered, and then subjected to ion exchange treatment. In paragraph 0045 of Patent Document 3, it is described that biological treatment may be performed in a submerged membrane reactor.

JP 2009-148714 A JP 2008-246386 A JP 2010-89051 A

  The preferable pH of the biological treatment tank for biologically treating organic substance-containing water is 6 to 9 in Patent Document 1 (paragraph 0018) and 6.5 to 8.5 in Patent Document 3 (paragraph 0041). When biological treatment is performed under this pH condition, the nitrification reaction proceeds and nitrate ions are generated. Since the nitrate ions easily pass through the RO membrane, the load on the ion exchange device increases.

  An object of the present invention is to reduce the load on an ion exchange device in a treatment method and apparatus for organic matter-containing water that performs biological treatment, membrane separation, RO treatment, and ion exchange treatment.

  In the method for treating organic substance-containing water of the present invention, the organic substance-containing water is biologically treated in a biological treatment tank, the treatment liquid obtained by the biological treatment is subjected to membrane separation, and the membrane separation water obtained by this membrane separation is reversed. In the method for treating organic substance-containing water, which is treated with an osmosis membrane and ion exchange-treats the permeated water of the reverse osmosis membrane, the biological treatment tank has a pH of less than 6.

  In this invention, it is preferable that pH of the said biological treatment tank shall be 4.5-5.5.

The TOC load of the biological treatment tank is preferably 0.2 to 1.0 kg-TOC / m ³ / day. Moreover, it is preferable that DO of the said biological treatment tank shall be 0.5-5.0 mg / L.

  In this invention, it is preferable that the pH of the said membrane separation water introduce | transduced into the said reverse osmosis membrane is 5.0-8.0.

  The organic substance-containing water treatment apparatus of the present invention includes a biological treatment tank for biologically treating organic substance-containing water, a membrane separation apparatus for membrane-separating a treatment liquid from the biological treatment tank, and reverse osmosis of the separation water of the membrane separation apparatus PH control which controls pH of the said biological treatment tank to less than 6 in the processing apparatus of the organic substance containing water which has the reverse osmosis membrane apparatus which performs membrane treatment, and the ion exchange apparatus which ion-exchange-processes the permeated water of this reverse osmosis membrane apparatus Means are provided.

  According to the method and apparatus for treating organic substance-containing water of the present invention, by setting the pH of the biological treatment tank to less than 6, the growth of nitrifying bacteria in the biological treatment tank is suppressed, and the production of nitric acid is suppressed. Thereby, the load of the latter ion exchange apparatus is reduced. Furthermore, by lowering the pH of the biological treatment, protein in the biological metabolite is denatured, so that an increase in the membrane differential pressure and membrane leakage during membrane separation are suppressed. Flux reduction can be suppressed.

It is a flowchart which shows the processing method and apparatus of the organic substance containing water which concern on embodiment. It is a flowchart which shows the processing method and apparatus of the organic substance containing water which concern on another embodiment. It is a flowchart which shows the processing method and apparatus of the organic substance containing water which concern on another embodiment.

  Hereinafter, the present invention will be described in more detail with reference to FIGS.

  In the method and apparatus for treating organic substance-containing water shown in FIG. 1, raw water (organic substance-containing water) is introduced into a biological treatment tank (hereinafter sometimes referred to as an MBR tank) 1 provided with a submerged solid-liquid separation membrane 3. After the raw water is biologically treated by the organisms in the tank, it passes through the solid-liquid separation membrane 3 and is supplied to the RO device 5, and the RO concentrated water is taken out of the system from the line 6. The RO permeated water is subjected to ion exchange treatment by the ion exchange device 7, and deionized water is taken out as treated water. The MBR tank 1 is provided with a pH meter (not shown) and an acid addition means 10 as pH control means. In addition, although the said biological treatment is based on a floating method, you may form a fluid bed or a fixed bed in a tank using a support | carrier.

  The concentrated water of the RO device 5 is preferably discharged from the line 6 to the outside of the system, but a part thereof may be returned to the MBR tank 1. The same applies to the flows shown in FIGS. Excess sludge in the MBR tank 1 is discharged through a sludge line 4.

  In the flow of FIG. 1, the solid-liquid separation membrane is immersed in the biological treatment tank, but in the flow of FIG. 2, the biological treatment tank 1 </ b> A and the membrane separation tank 1 </ b> B having the solid-liquid separation membrane 3 are separately provided. It is installed. In the flow of FIG. 2, raw water is introduced into the biological treatment tank 1A and biologically treated. This biologically treated water is introduced into the membrane separation tank 1B, subjected to membrane separation treatment by the solid-liquid separation membrane 3 made of MF membrane, UF membrane, NF membrane or the like, and the membrane permeated water is supplied to the RO device 5 and the RO membrane permeated water. Is passed through the ion exchanger 7 and deionized water is taken out as treated water.

  The flow of FIG. 3 is the one in which the outside tank type membrane separation device 8 is installed instead of the membrane separation tank 1B in the flow of FIG. Biologically treated water from the biological treatment tank 1A is circulated to the outside membrane separation device 8 and subjected to membrane separation treatment by a solid-liquid separation membrane. The membrane permeated water is supplied to the RO device 5, and the RO membrane permeated water is ion exchanged. Water is passed through the apparatus 7 and deionized water is taken out as treated water.

  The membrane separation device 8 is a device in which a solid-liquid separation membrane module is installed in a vessel. The concentrated water of the membrane separation device 8 is returned to the biological treatment tank 1A.

  1 to 3, the MBR tank 1 and the biological treatment tank 1 </ b> A are provided with a pH meter (not shown) and an acid addition means 10. The acid addition means 10 includes an acid solution tank and a chemical injection pump. The acid is added from the adding means 10 so that the pH detected by the pH meter is less than 6, preferably 4.5 or more and less than 6, particularly preferably 4.5 to 5.5. By setting the pH of the MBR tank 1 and the biological treatment tank 1A to less than 6, nitrification during biological treatment is suppressed, generation of nitric acid is suppressed, and the nitrogen component is present in the form of ammonia. Although the removal rate of nitric acid on the RO membrane is about 95%, the removal rate of ammonia is 99% or more, and nitrate ions and ammonia hardly flow into the ion exchange device 7, and the load of the ion exchange resin is reduced. It will be extremely small. Thereby, in the case of a regenerative ion exchange apparatus, the regeneration frequency is significantly reduced.

  As the solid-liquid separation membrane of the solid-liquid separation membrane 3 and the membrane separation device 8, an MF membrane, a UF membrane or an NF membrane is suitable. The membrane shape is preferably a flat membrane, tubular membrane, hollow fiber membrane or the like, and the membrane material is preferably PVDF, PE, PP, polysulfone, cellulose or the like, but is not limited thereto. An MF membrane is preferred, and for example, a PVDF membrane having a pore diameter of 0.01 to 1 μm can be suitably used from the viewpoint of strength.

  As the ion exchange resin of the ion exchange device 7, various types such as a gel type and a porous type can be used. The ion exchange device may be a mixed bed of a cation exchange resin and an anion exchange resin, or may be one in which a cation exchange resin bed and an anion exchange resin bed are separately provided. In the latter case, it is preferable to pass RO permeated water in the order of cation exchange resin → anion exchange resin.

In the flows of FIGS. 1 to 3, the raw water is an electronic industrial wastewater discharged from the manufacturing process of liquid crystals, semiconductors and the like, and usually contains 5 to 100 mg / L of ammoniacal nitrogen (ammonia nitrogen), and has a TOC concentration of 100 mg / L. It is a dilute electronic industrial wastewater of L or less, for example, about 10 to 100 mg / L, particularly about 20 to 80 mg / L. In the MBR tank 1 and the biological treatment tank 1A, the raw water is set so that the TOC load is 0.2 to 1.0 kg-TOC / m ³ / day, more preferably 0.4 to 0.8 kg-TOC / m ³ / day. Is preferably introduced.

  The MBR tank 1 and the biological treatment tank 1A are preferably aerated by installing a diffuser tube so that the DO concentration is 0.5 to 5.0 mg / L, more preferably 0.5 to 3.0 mg / L. When nitrification occurs in the MBR tank 1 and the biological treatment tank 1A, it is preferable to increase the amount of aeration.

In the present invention, biological treatment is usually carried out by a floating method, but microorganisms may be attached to a carrier.
Examples of the material of the carrier include inorganic carriers such as ceramics, foam glass, and foam concrete, and plastic carriers such as polyurethane, polyester, vinyl chloride, polyethylene, polypropylene, and polystyrene, but are not limited thereto. Moreover, it can be set as a fluidized bed or a fixed bed, and when it is set as a fixed bed, although the shape is illustrated by a honeycomb tube, a corrugated sheet, a string-like contact material, etc., it is not limited to these. The filling rate of the carrier in the tank is preferably 10 to 80%, particularly 30 to 70%.

  The sludge concentration in the membrane separation means, that is, the sludge concentration in the MBR tank 1 and the membrane separation tank 1B in FIGS. 1 and 2 and the sludge concentration in the biological treatment liquid introduced into the membrane separation apparatus 8 in FIG. 3 are 3000 to 50000 mg / L, particularly 5000. About 15000 mg / L is suitable.

  The RO membrane of the RO device 5 may be any of a polyether amide composite membrane, a polyvinyl alcohol composite membrane, an aromatic polyamide membrane, etc., and the RO membrane shape may be any of spiral type, hollow fiber type, tubular type, etc. Good. The pH of the RO water supply is preferably 5.0 or more and 8.0 or less. When the pH of the RO water supply is higher than 8, the ammonia removal rate by the RO membrane is lowered. On the other hand, when the pH of the RO water supply is lower than 5, the desalination rate by the RO membrane decreases.

  In any of the flows of FIGS. 1 to 3, as described above, the load of the ion exchange device 7 is low, and treated water with good water quality can be stably obtained over a long period of time.

Hereinafter, examples and comparative examples will be described. In the following Examples and Comparative Examples, electronic industrial wastewater having TOC concentrations of 100 mg / L, NH ₄ —N 100 mg / L, PO ₄ —P ₂ mg / L, and pH = 10 containing methanol, ethanol and isopropyl alcohol was used as raw water.

[Example 1]
Electronic industrial wastewater was treated at 1500 L / day using the flow apparatus shown in FIG. The main conditions are as follows.
MBR tank 1 volume: 300L
PH of MBR tank 1 is adjusted by acid addition so as to be 5.0 TOC load: 0.9 kg-TOC / m ³ / day
DO in MBR tank: 2.0 mg / L
Sludge extraction: Sludge extraction at 7.5 L / day for SRT 40 days Solid-liquid separation membrane 3: Submerged hollow fiber MF membrane (pore size 0.4 μm, manufactured by Mitsubishi Rayon Co., Ltd.), membrane area 3 m ² , filtration for 7 minutes RO membrane: aromatic polyamide type spiral yarn membrane (manufactured by Nitto Denko Corporation), membrane area 2 m ²
RO water supply pH = 6.0
Add 5ppm slime control agent (Kurita Kogyo Co., Ltd. Krivata EC503) to RO water supply Ion exchange resin: Strongly acidic cation exchange resin 100mL and 200mL strongly basic anion exchange resin manufactured by Mitsubishi Chemical Corporation are separately provided in this order. = 50 [1 / hr].

[Examples 2 and 3, Comparative Examples 1 and 2]
In Example 1, it is the same except that MBR tank pH was set to 5.5 (Example 2), 4.5 (Example 3), 7.0 (Comparative Example 1), and 6.5 (Comparative Example 2). The raw water was treated. The results (3-month average value) are shown in Table 1.

  As shown in Table 1, according to the present invention, the concentration of nitrate ions in the biologically treated water is low, and the frequency of regeneration of the ion exchange resin is low.

DESCRIPTION OF SYMBOLS 1 MBR tank 1A Biological treatment tank 1B Membrane separation tank 3 Solid-liquid separation membrane 5 RO apparatus 7 Ion exchange apparatus 8 Outside-type membrane separation apparatus 10 Acid addition means

Claims (6)

Biologically treating organic substance-containing water in a biological treatment tank,
Membrane separation of the treatment liquid obtained by the biological treatment,
The membrane separation water obtained by this membrane separation is treated with a reverse osmosis membrane,
In the method for treating organic substance-containing water in which the permeated water of this reverse osmosis membrane is subjected to ion exchange treatment,
A method for treating organic substance-containing water, wherein the pH of the biological treatment tank is less than 6.   In Claim 1, pH of the said biological treatment tank shall be 4.5-5.5, The processing method of organic substance containing water characterized by the above-mentioned. In Claim 1 or 2, the TOC load of the said biological treatment tank is 0.2-1.0kg-TOC / m < ³ > / day, The processing method of organic substance containing water characterized by the above-mentioned.   In any 1 item | term of Claim 1 thru | or 3, DO of the said biological treatment tank shall be 0.5-5.0 mg / L, The processing method of organic substance containing water characterized by the above-mentioned.   The method for treating organic substance-containing water according to any one of claims 1 to 4, wherein the pH of the membrane separation water introduced into the reverse osmosis membrane is 5.0 to 8.0. A biological treatment tank for biological treatment of organic-containing water;
A membrane separation device for membrane-separating the treatment liquid from the biological treatment tank;
A reverse osmosis membrane device for treating the separated water of the membrane separation device with a reverse osmosis membrane;
In the treatment apparatus for organic matter-containing water having an ion exchange apparatus for performing ion exchange treatment on the permeated water of the reverse osmosis membrane apparatus,
An apparatus for treating organic substance-containing water, comprising pH control means for controlling the pH of the biological treatment tank to less than 6.

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