JP2011212585A - Method and apparatus for treating organic matter-containing wastewater - Google Patents

Abstract

An organic matter-containing wastewater treatment method capable of efficiently treating organic matter-containing wastewater by anaerobic biological treatment and reverse osmosis membrane treatment is provided.
SOLUTION: An organic matter-containing wastewater is treated with an anaerobic organism, a treatment liquid obtained by the anaerobic biological treatment is separated into a membrane with a first membrane separation solution, and the permeated water from the first membrane separation is reverse osmosis. In the method for treating organic matter-containing wastewater treated with a membrane, the permeated water from the first membrane separation means is decarboxylated, preferably with ammonia stripping, and then treated with the reverse osmosis membrane.
[Selection] Figure 1

Description

  The present invention relates to a method and apparatus for treating organic matter-containing wastewater.

  In electronic industry factories such as semiconductor manufacturing and liquid crystal manufacturing, alcohols such as isopropyl alcohol and methanol, nitrogen-containing organic substances such as monoethanolamine and tetramethylammonium hydroxide, and sulfur-containing organic substances such as dimethyl sulfoxide are used in the process steps. It is used as a cleaning agent and a release agent. In recent years, in these electronic industrial factories, water recovery is progressing by biologically treating wastewater containing organic matter and using the treated water as a raw material for producing pure water.

  When biologically treated water is reused for producing pure water, the treated water may be treated with a solid-liquid separation device to separate microbial bodies, and then desalted with a reverse osmosis membrane separation device (for example, Japanese Patent Laid-Open No. 2007-2007). -175582). Japanese Patent Application Laid-Open No. 2009-148714 describes a method of treating wastewater containing organic matter with an anaerobic MBR (membrane bioreactor) and supplying the treated water directly to a RO (reverse osmosis membrane) device to recover the wastewater. Yes. Japanese Patent Application Laid-Open No. 2002-336886 describes that an organic matter-containing wastewater is treated with biological activated carbon and then treated with a reverse osmosis membrane.

JP 2007-175582 A JP 2009-148714 A JP 2002-336886 A

  Since anaerobic MBR can separate sludge into solid and liquid with a simple structure, treated water can be supplied directly to RO as in JP 2009-148714. However, anaerobic MBR treated water contains high amounts of carbonic acid, ammonium ions, and sulfide ions. Since it is often contained in the concentration and the salt load of RO increases, the RO flux decreases. In addition, these ammonia, carbonic acid, and hydrogen sulfide often exist in a non-dissociated state at 7 to 8, which is the normal pH of treated water, and because of their low molecular weight, they pass through the RO membrane and remain in the recovered water. There was a problem that.

  An object of this invention is to provide the processing method and apparatus of organic matter containing waste water which can process organic matter containing waste water efficiently by anaerobic biological treatment and reverse osmosis membrane treatment.

  The organic matter-containing wastewater treatment method according to claim 1 is characterized in that the organic matter-containing wastewater is subjected to anaerobic biological treatment, and the treated water obtained by the anaerobic biological treatment is subjected to membrane separation by a first membrane separation means. In the method for treating drainage containing organic matter, wherein the permeated water from the separation means is treated with a reverse osmosis membrane, the permeated water from the first membrane separation means is decarboxylated and then treated with the reverse osmosis membrane. To do.

  The method for treating organic matter-containing wastewater according to claim 2 is characterized in that, in claim 1, decarboxylation treatment is performed by subjecting the permeated water from the first membrane separation means to aeration or reduced pressure treatment at a pH of 9.5 or less. To do.

  The method for treating wastewater containing organic matter according to claim 3 is characterized in that, in claim 1 or 2, alkali is added to decarboxylated water so as to have a pH of 9.5 or higher and the reverse osmosis membrane is used. .

  The method for treating organic matter-containing wastewater according to claim 4 is the method according to claim 3, wherein alkali is added to the decarboxylated water so as to have a pH of 9.5 or more, and then aeration is performed to remove ammonia, and then the reverse osmosis membrane It is characterized by processing.

  The apparatus for treating organic matter-containing wastewater according to claim 5 comprises an anaerobic biological treatment means for anaerobically treating organic matter-containing wastewater, and a first membrane separation means for membrane-separating treated water from the anaerobic biological treatment means, In a processing apparatus for organic matter-containing wastewater having a reverse osmosis membrane apparatus for processing the permeated water from the first membrane separation means, after the treated water from the first membrane separation means is decarboxylated by the decarboxylation means The treatment is performed by the reverse osmosis membrane device.

  The organic matter-containing wastewater treatment apparatus according to claim 6 is characterized in that, in claim 5, an alkali addition means for adding alkali so as to have a pH of 9.5 or higher with respect to decarbonated water from the decarboxylation means is characterized. To do.

  The organic matter-containing wastewater treatment apparatus according to claim 7 is the ammonia according to claim 6, wherein the alkali is added to the decarbonated water from the decarboxylation means so as to have a pH of 9.5 or more, and then aerated to remove ammonia. A removing means is provided.

  Decarboxylation of anaerobic biological treatment water or further deammonification treatment reduces carbonate ions, sulfide ions, ammonium ions, which are the main ions dissolved in anaerobic biological treatment water, and salts to RO The load is greatly reduced, and the RO flux (permeation flux) can be increased.

  By adding alkali to decarboxylated decarbonated water and subjecting it to RO treatment at pH 9.5 or higher, the growth of slime on the RO membrane can be suppressed without adding a bactericidal agent, etc., and a surfactant. Contamination due to adsorption of organic matter such as can be reduced. In addition, since carbonic acid and sulfide that have not been removed in the previous stage exist as ions under high pH conditions, they are removed at a high removal rate by RO and do not remain in the recovered water. At this time, since it has been decarboxylated in advance, the pH buffering ability of the anaerobic biological treated water is lowered, and the pH is 9.5 or more with a smaller addition amount than adding alkali directly to the anaerobic biological treated water. can do. Since there is little alkali addition amount, the salt load to RO by the added alkali is also reduced.

It is a flowchart which shows an example of this invention. It is a graph which shows the result of an Example and a comparative example.

  Hereinafter, embodiments of the method and apparatus for treating wastewater containing organic matter of the present invention will be described in detail. FIG. 1 is a flowchart showing an example of the method and apparatus of the present invention.

[Organic wastewater]
In the present invention, the organic matter-containing wastewater to be treated is not particularly limited, and examples thereof include electronic industrial wastewater and chemical factory wastewater. In the manufacturing process of electronic parts such as semiconductors and liquid crystals, a large amount of various organic wastewater is generated from the development process, peeling process, etching process, cleaning process, etc., and the wastewater is collected and purified to the pure water level for reuse. Therefore, these wastewaters are suitable as the wastewater to be treated of the present invention.

  Organic substances in such organic wastewater include organic nitrogen such as isopropyl alcohol (IPA) and ethyl alcohol, organic ethanol such as monoethanolamine (MEA) and tetramethylammonium hydroxide (TMAH), and ammonia nitrogen. Examples include organic wastewater containing water, and organic sulfur compounds such as dimethyl sulfoxide (DMSO), but are not limited thereto.

[Anaerobic biological treatment]
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 treatment means may be a single tank type in which the acid generation reaction and the methane generation reaction are performed in the same tank, or a two tank type in which each reaction is performed in separate tanks. Each reaction vessel 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.

  The anaerobic biological treatment means is not particularly limited, but a UASB (upward flow type anaerobic sludge blanket) or MBR (membrane bioreactor) type, particularly an MBR type reaction tank is preferable because it can be operated at a high load. .

The COD _Cr load in the anaerobic tank is preferably 1 to ³⁰ kg / m ³ · d, particularly 2 to 10 kg / m ³ · d. The temperature of the anaerobic tank is preferably 25 to 40 ° C. or 45 to 60 ° C., and the HRT is preferably about 6 to 72 hr, particularly preferably 12 to 48 hr.

  Membrane separation is suitable as a means for performing solid-liquid separation of anaerobic biologically treated water. This film is preferably an MF, UF, or NF (nanofilter) film. The membrane shape may be any of a flat membrane, a tubular membrane, a hollow fiber membrane and the like. The arrangement of the film may be either an immersion type or an outside tank type.

[Decarboxylation]
In the present invention, the anaerobic biologically treated water subjected to the anaerobic biological treatment and then solid-liquid separation is decarboxylated. In order to perform decarboxylation, a chelating agent is added to the anaerobic biologically treated water as necessary, and then aeration or vacuum suction is preferably performed at a pH of 9.5 or less, particularly preferably 8.0 or less. Thereby, the dissolved carbon dioxide gas and hydrogen sulfide are removed. In the case of aeration, the gas to be used may be any gas that does not contain carbon dioxide and hydrogen sulfide, such as air, nitrogen, oxygen, etc. A gas that does not contain oxygen is preferable. The pH of the anaerobic MBR treated water that is operating well is 7-8. Normally, pH adjustment in the decarboxylation process is unnecessary, but an inorganic acid such as hydrochloric acid or sulfuric acid is added to lower the pH. May be decarboxylated.

  As the anaerobic biological treated water is decarboxylated, the pH of this treated water rises to around 9 (depending on the original type of drainage). If the pH exceeds 9.5, it is preferable to adjust the pH to 9.5 or less by adding an acid.

  Note that the lower the pH of the water to be decarboxylated, the easier it is to remove carbon dioxide and hydrogen sulfide by decarboxylation, but a large amount of alkali is required to adjust the pH to 9.5 or higher later, which is uneconomical. In addition, the salt concentration rises and becomes a load on the subsequent RO, which is not desirable.

[Ammonia stripping]
In the present invention, prior to RO treatment of decarboxylated anaerobic biologically treated water, an alkali such as NaOH or KOH is added and the pH is adjusted to 9.5 or higher, preferably 10 to 11, and then aerated. It is preferable to remove the dissolved ammonia.

  By performing ammonia stripping in this way, the salt load in the subsequent RO treatment is reduced, and the RO flux is increased. In addition, by treating high-pH water with a pH of 9.5 or higher with RO, the growth of slime in the RO device can be suppressed without adding a bactericidal agent, and contamination due to adsorption of organic substances such as surfactants can be prevented. Can be reduced. In addition, since carbonic acid and sulfides that have not been removed in the previous stage are mostly present as ions under high pH conditions, a high removal rate is obtained with RO, and they do not remain in the recovered water. Since the decarboxylation treatment has been performed in advance, the pH buffering ability of the treated water is low, and the amount of alkali added can be smaller than adding alkali directly to the anaerobic biological treated water. Since there is little added alkali, the salt load to RO is also reduced.

[Prefilter]
The ammonia stripping treated water is preferably supplied to the RO device after being filtered by a prefilter. An MF membrane or the like can be used as the prefilter, but is not limited to this.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Example 1]
Raw water was treated according to the flow shown in FIG. 1 (however, the prefilter was omitted). The main conditions are as follows.
<Raw water>
TOC 600 mg / L, ThOD 2,400 mg / L, TN 150 mg / L, TP 3.0 mg / L
Composition of organic substance Tetramethylammonium hydroxide 1,000mg / L
Dimethyl sulfoxide 250mg / L
<Anaerobic MBR>
Temperature 37 ° C
Real capacity 10L
HRT 9.5 hr (ThOD load 6 kg / m ³ · d)
The sewage purification sludge is used as seed sludge for 6 months, and the operation is continued by extracting the sludge so that MLSS in the tank is maintained at 12,000 mg / L.
Membrane: Tubular UF with internal pressure type tank (pore size 0.03 μm, manufactured by Norit Japan)
<Decarbonation tank>
HRT 30min
Scale dispersant (Kurita Kogyo Welclean A801) added to 30 ppm No pH adjustment (changes from 8.8 to 9.0)
Aeration: After the gas generated from the anaerobic tank is washed with water, the gas treated with an iron-based desulfurizing agent is used. CO ₂ 3%, H ₂ S 10 ppm
Aeration amount 0.5 Nm ³ / m ³ / hr
Temperature: 30-33 ° C
<Ammonia stripping tank>
HRT 30min
Adjust pH to 10.5 with 2N NaOH. Aeration: Use gas generated in anaerobic tank after passing through water and then vented through column filled with iron-based desulfurization agent. CO ₂ 3%, H ₂ S 10ppm
Aeration amount 0.5 Nm ³ / m ³ / hr
Temperature: 30-33 ° C
<RO equipment>
Flat membrane cell type RO device (The membrane uses Nitto Denko Corporation ES-20)
Adjust to pH 10.5 with 2N NaOH Pressure 1.5 MPa
Temperature 25 ° C

  Table 1 shows the quality of anaerobic MBR treated water, decarboxylated treated water, ammonia stripping treated water and RO treated water. In Table 1, IC represents inorganic carbon. FIG. 2 shows the change with time in the permeation flux (flux) of the RO device.

[Comparative Example 1]
In Example 1, the UF permeate of anaerobic MBR-treated water was supplied as it was (that is, without decarboxylation and ammonia stripping) to the RO apparatus. Otherwise, the treatment was performed under the same conditions as in Example 1. The water quality and RO flux of the RO water supply and RO permeated water at this time are shown in Table 1 and FIG.

  As shown in Table 1, in Example 1, the conductivity of RO water supply decreased to about 3/4 by reducing carbonic acid, ammonia, and sulfide in the anaerobic MBR-treated water. As a result, as shown in FIG. 2, the RO flux after 100 hours of water passage was 0.70 m / d in Example 1 compared to 0.46 m / d in Comparative Example 1, which was improved 1.5 times. . In addition, the amount of NaOH used in the process was 14.3 mmol / L in Example 1 with respect to 23.4 mmol / L-treated water of Comparative Example, which was reduced to about 60%.

Claims (7)

Wastewater containing organic matter is treated with anaerobic organism, treated water obtained by the anaerobic biological treatment is separated by a first membrane separation means, and permeate from the first membrane separation means is treated with a reverse osmosis membrane. In the processing method of wastewater containing organic matter,
A method for treating organic matter-containing wastewater, wherein the permeated water from the first membrane separation means is decarboxylated and then treated with the reverse osmosis membrane.   2. The method for treating organic matter-containing wastewater according to claim 1, wherein a decarboxylation treatment is performed by subjecting the permeated water from the first membrane separation means to aeration or reduced pressure treatment at a pH of 9.5 or less.   3. The method for treating organic matter-containing wastewater according to claim 1, wherein an alkali is added to decarboxylated water so that the pH is 9.5 or higher and the reverse osmosis membrane is used.   4. The organic matter-containing wastewater according to claim 3, wherein alkali is added to the decarboxylated water so as to have a pH of 9.5 or higher, then aeration is performed to remove ammonia, and then the treatment is performed with the reverse osmosis membrane. Processing method. Anaerobic biological treatment means for anaerobic biological treatment of organic matter-containing waste water; first membrane separation means for membrane separation of treated water from the anaerobic biological treatment means;
In a treatment apparatus for organic matter-containing wastewater having a reverse osmosis membrane apparatus for treating permeated water from the first membrane separation means,
An organic matter-containing wastewater treatment apparatus, wherein treated water from the first membrane separation means is decarboxylated by a decarboxylation means and then treated by the reverse osmosis membrane apparatus.   6. The apparatus for treating organic matter-containing wastewater according to claim 5, further comprising alkali adding means for adding alkali so as to have a pH of 9.5 or higher with respect to decarbonated water from the decarbonation means.   7. An organic substance-containing composition according to claim 6, further comprising an ammonia removing means for removing ammonia by aeration after adding alkali so that the pH of the decarbonated water from the decarboxylation means is 9.5 or higher. Wastewater treatment equipment.

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