JP2012179571A - Anaerobic organism processing method and device for organic waste liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anaerobic organism processing method and a device for organic waste liquid, by which recovery water with high water quality can be effectively obtained while preventing the clogging of a reverse osmosis membrane by effectively removing hydrogen sulfide in organism processing liquid by a simple device and operation for obtaining the recovery water with the high water quality by subjecting the organic waste liquid to anaerobic organism processing, filtering the filtrate through the membrane, and subjecting the filtrate to the reverse osmotic membrane processing.SOLUTION: The organic waste liquid is subjected to the anaerobic organism processing in the anaerobic processing device 1, the anaerobically processed liquid is subjected to solid/liquid separation by membrane filtering in the membrane filtering device 2 in an aerobic condition, the membrane filtered liquid is stored in an aeration device 3 while the membrane filtered liquid is kept in the anaerobic condition, the membrane filtered liquid is aerated with the gas not containing oxygen and hydrogen sulfide desulfurized in a desulfurizing device 6 to remove the hydrogen sulfide, the aerated liquid is subjected to the reverse osmosis membrane processing by supplying the same to a reverse osmosis membrane processing device 4, and the permeated liquid is recovered.

Description

  TECHNICAL FIELD The present invention relates to an anaerobic biological treatment method and apparatus for organic wastewater, which is obtained by treating an organic wastewater with an anaerobic biological treatment and treating the treated liquid with a reverse osmosis membrane to obtain high-quality recovered water. The present invention relates to an anaerobic biological treatment method and apparatus for organic effluent that efficiently collects recovered water by preventing clogging of a reverse osmosis membrane when the membrane filtrate is subjected to a reverse osmosis membrane treatment.

  The method of treating an organic matter-containing effluent with an anaerobic organism is often applied to a highly concentrated or hardly degradable organic matter-containing effluent that is not suitable for treatment with an aerobic organism such as an activated sludge process. For this reason, the treatment liquid still contains a relatively high concentration of organic matter. In order to obtain high-purity recovered water from such anaerobic treatment liquid with high organic matter concentration, the organic matter concentration is reduced by aerobic biological treatment or the like, and then reverse osmosis membrane treatment is performed to obtain high-quality recovered water. Things have been done.

  As such a method, Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-175582) discloses a membrane in order to prevent an organic substance from accumulating on the membrane surface, causing a significant increase in filtration resistance and making it difficult to pass water. It has been proposed to install an aerobic biological treatment device in front of the separation device to reduce the concentration of organic substances in the effluent prior to membrane separation treatment. However, such a method has a problem that the apparatus and the operation are increased in size and complexity, and the processing cost is increased.

  On the other hand, in patent document 2 (Unexamined-Japanese-Patent No. 2009-148714), an organic substance containing liquid is introduce | transduced into an anaerobic biological treatment tank, an anaerobic biological treatment is carried out by the methanogen group in an anaerobic biological treatment tank, and anaerobic biological treatment is carried out. The biological treatment method for organic matter-containing liquids is obtained by subjecting the treatment liquid obtained by the above to a membrane filtration while exposing the generated gas in an anaerobic state without being subjected to an aerobic biological treatment, and treating the membrane filtrate with a reverse osmosis membrane in an anaerobic state. Has been proposed.

  The sulfur content in the effluent is decomposed into hydrogen sulfide by anaerobic treatment. The hydrogen sulfide produced in the liquid is partly discharged out of the system together with the generated gas while maintaining the gas phase, that is, the gas generated by the anaerobic treatment and the dissolution equilibrium (hydrogen sulfide in the gas is dry desulfurization) Or can be removed from the gas relatively easily by wet (biological) desulfurization), but the remainder is discharged in a dissolved form in the treatment liquid. Dissolved hydrogen sulfide is easily oxidized with oxygen in the air to produce fine sulfur particles. Therefore, when the anaerobic biological treatment liquid is exposed to air and then desalted with a reverse osmosis membrane, there is a problem that the generated sulfur fine particles clog the membrane. In addition, even those dissolved in the form of hydrogen sulfide have a problem in that when they are concentrated by a reverse osmosis membrane, they are deposited on the membrane surface as sulfides such as FeS having low solubility and clog the membrane.

  In Patent Document 3 (Japanese Patent Laid-Open No. 2000-94000), a desulfurized gas obtained by desulfurizing a generated gas when a solid solution is separated by subjecting an anaerobic treatment liquid obtained by anaerobic biological treatment to membrane filtration with a microfiltration membrane. It has been shown that injection onto the membrane surface of the microfiltration membrane prevents clogging of the membrane surface of the microfiltration membrane. However, this method is for preventing the turbidity contained in the anaerobic treatment liquid from adhering to the filtration membrane. Even if this method is applied to the membrane filtration of Patent Document 2, it prevents the adhesion of sulfur. Is useless. In other words, since the sulfur content is deposited and adhered on the film surface, the deposit cannot be peeled off even if the desulfurization gas is injected after reaching the film surface and depositing. Moreover, when such a method is applied to a reverse osmosis membrane, a high pressure is applied to the reverse osmosis membrane, so that the gas dissolves and a peeling action cannot be expected.

JP2007-175582 JP2009-148714 JP2000-94000

  An object of the present invention is to perform anaerobic biological treatment of organic effluent, membrane-treat the treatment liquid, and reverse-osmosis membrane treatment of the membrane filtrate to obtain high-quality recovered water by simple equipment and operation. Organic drainage anaerobic biological treatment method and apparatus capable of effectively removing hydrogen sulfide in biological treatment liquid, thereby preventing clogging of reverse osmosis membrane and efficiently obtaining high-quality recovered water Is to get.

The present invention is the following organic anaerobic anaerobic biological treatment method and apparatus.
(1) an anaerobic treatment process for treating an organic drainage with an anaerobic organism;
A membrane filtration step for solid-liquid separation by membrane filtration while the anaerobic treatment liquid remains in an anaerobic state,
An exposure step of storing the membrane filtrate while maintaining anaerobic conditions and exposing the membrane filtrate to a gas not containing oxygen and hydrogen sulfide to remove hydrogen sulfide,
And a reverse osmosis membrane treatment step of subjecting the air exposure liquid to a reverse osmosis membrane treatment under pressure and recovering the permeate.
(2) The method according to (1) above, wherein the membrane filtrate is exposed to air at pH 2-7.
(3) The method according to (1) or (2) above, wherein a gas obtained by desulfurizing a gas generated by anaerobic biological treatment is used as the gas not containing oxygen and hydrogen sulfide.
(4) an anaerobic treatment apparatus for treating an organic drainage with an anaerobic organism;
A membrane filtration device for solid-liquid separation by membrane filtration while the anaerobic treatment liquid remains in an anaerobic state;
An air exposure device that stores the membrane filtrate in an anaerobic condition and exposes it with a gas not containing oxygen and hydrogen sulfide to remove hydrogen sulfide;
A biological treatment apparatus for organic drainage, comprising: a reverse osmosis membrane treatment apparatus for treating an air exposure liquid with a reverse osmosis membrane under pressure and collecting a permeate.
(5) The device according to (4) above, comprising a pH adjusting device for adjusting the membrane filtrate to be exposed to pH 2-7.
(6) The apparatus according to (4) or (5), further including a gas supply device that desulfurizes a gas generated by anaerobic biological treatment as a gas that does not contain oxygen and hydrogen sulfide and supplies the gas to an air exposure device.

  In the present invention, the organic drainage to be treated is a drainage containing an organic substance and contains a sulfur content, but may further contain a nitrogen content and other components, particularly an inorganic substance. The organic matter contained may be of any composition, properties and characteristics, from low to high molecular weight, or from soluble to solid. The sulfur content and nitrogen content may include components discharged from factories such as ammonia, tetramethylammonium hydroxide, alcohol and the like from natural sources such as proteins. As such organic drainage, the organic matter content is 200-50000 mg-CODcr / L, especially 1000-20000 mg-CODcr / L, the sulfur content is 10-1000 mg-S / L, especially 10-200 mg-S / L. Are suitable for the processing of the present invention.

In the present invention, an anaerobic biological treatment method (apparatus) for treating these organic effluents with anaerobic biological treatment can employ the anaerobic treatment method and apparatus conventionally employed in water treatment. For organic effluent containing solid organic matter, floating anaerobic treatment such as anaerobic digestion and methane fermentation in which the organic effluent is mixed with anaerobic microorganisms and retained for 10 to 30 days is preferable. For organic waste liquids that do not contain solid organic matter but contain soluble organic matter, high-load anaerobic treatment using a sludge blanket such as granular sludge and carrier-carrying sludge, a fluidized bed, or the like is preferable. These treatment methods are selected according to the composition and properties of the organic drainage, the treatment target water quality, the treatment cost, and the like.

  The anaerobic treatment liquid generated in the anaerobic treatment is a solid content of 3000 to 120,000 mg / L in the case of floating anaerobic treatment, a solid content in the case of a high load anaerobic treatment of about 2000 to 100,000 mg / L. Although the substance content is about 50 to 3000 mg / L and the organic substance content is about 30 to 2500 mg / L, in any case, in the membrane filtration step (apparatus), solid-liquid separation is performed by membrane filtration. Membrane filtration is performed through filtration membranes such as microfiltration (MF) and ultrafiltration (UF) to mainly remove solids, colloids, polymer substances and the like. The particle size of the solids to be removed here is about 1 to 500 μm. In the membrane filtration, the anaerobic treatment liquid is passed through the filtration membrane while the anaerobic treatment solution is kept in an anaerobic state to separate solids and the like. At this time, the gas generated in the anaerobic treatment step can be supplied to the filtration membrane surface to prevent clogging of the membrane surface. The gas supplied to the membrane surface may be desulfurized.

  In the air exposure step (apparatus), the membrane filtrate is stored while being kept under anaerobic conditions, and is exposed to a gas not containing oxygen and hydrogen sulfide to remove hydrogen sulfide. The air exposure device can also serve as a storage tank. As the gas not containing oxygen and hydrogen sulfide, a gas obtained by desulfurizing a gas generated by an anaerobic biological treatment is preferably used, but other gases such as nitrogen gas may be used. Membrane filtrate flows out in a state containing hydrogen sulfide, but if it is supplied directly to the reverse osmosis membrane, clogging due to precipitation of sulfur occurs even if gas is injected, so hydrogen sulfide is used in the exposure step (apparatus). By removing, the clogging of the reverse osmosis membrane can be effectively prevented, and the reverse osmosis membrane treatment can be performed efficiently. The amount of gas for aeration of the membrane filtrate is 0.2 to 3 L / L · min, preferably about 0.5 to 2 L / L · min. The hydrogen sulfide content in the gas supplied to the reverse osmosis membrane is 200 ppm. Hereinafter, it is preferably 50 ppm or less.

  In the reverse osmosis membrane treatment step (apparatus), the air exposure liquid is supplied to the reverse osmosis membrane under pressure to perform the reverse osmosis membrane treatment, and the permeate is recovered as a recovery liquid. A reverse osmosis membrane is a semipermeable membrane that permeates water as a solvent by osmotic pressure and blocks ions, salts, organic substances, colloids, and the like as solutes. Commercially available products can be used. The reverse osmosis membrane treatment is an operation of permeating water as a solvent against the osmotic pressure by supplying an air exposure liquid to the reverse osmosis membrane under pressure. The pressure when supplying the air exposure liquid to the reverse osmosis membrane is a pressure exceeding the osmosis, and varies depending on the reverse osmosis membrane to be used, but is generally 0.3 to 2 MPa, preferably 0.5 to 1.5 MPa. Is done. Since the recovered water has high purity, it can be used as pure water or used as ultrapure water or other raw materials.

  In reverse osmosis membrane treatment, if the liquid to be treated is supplied to the reverse osmosis membrane under conditions where oxygen is dissolved, hydrogen sulfide is oxidized and the precipitated sulfur adheres to the membrane surface, resulting in clogging. By maintaining the anaerobic state, oxidation of hydrogen sulfide and clogging due to precipitated sulfur can be prevented. However, when the liquid is concentrated in the reverse osmosis membrane treatment, when hydrogen sulfide is contained, iron sulfide is deposited on the membrane surface due to the concentration of iron, and clogging occurs. For this reason, it is possible to prevent precipitation of iron sulfide by removing hydrogen sulfide from the liquid to be treated. However, even if gas is blown to the membrane surface of the reverse osmosis membrane, iron sulfide is deposited from the hydrogen sulfide that has already reached the membrane surface. I can't prevent you from doing it.

  In the present invention, in the air exposure step (apparatus), the membrane filtrate is exposed to a gas containing no oxygen and hydrogen sulfide to remove the hydrogen sulfide, so that the hydrogen sulfide can be effectively removed. Here, the concentration of hydrogen sulfide in the aeration liquid after removal is a concentration at which iron sulfide is not precipitated in a state where the iron content is concentrated, and is set to 1 mg / L or less. Since the concentration of iron does not occur in the membrane filtration step, hydrogen sulfide may be included.

In the air exposure process, the membrane filtrate is stored while maintaining anaerobic conditions and exposed to a gas that does not contain oxygen and hydrogen sulfide, so that the hydrogen sulfide in the membrane filtrate is transferred to the gas phase without being oxidized. It can be removed from the water, but at this time, the membrane filtrate is exposed to air at pH 2 to 7, whereby the removal rate of hydrogen sulfide can be increased. In this case, the pH can be adjusted by injecting a pH adjusting agent such as hydrochloric acid or sulfuric acid into the membrane filtrate being transferred by the pH adjusting device or the air exposure liquid in the air exposure device.

  When a gas obtained by desulfurizing a gas generated by anaerobic biological treatment is used as a gas that does not contain oxygen and hydrogen sulfide, the gas generated by the anaerobic biological treatment is desulfurized by a desulfurizer and supplied to the air exposure device. Thus, the gas supply device is configured. By using the generated gas in this way, the generated gas can be purified and circulated, and the generated gas can be prevented from being diluted and effectively used. As the desulfurization apparatus, a dry desulfurization apparatus containing a hydrogen sulfide adsorbent is used. In this case, if the desulfurization device is configured so that the gas supplied to the air exposure device is desulfurized and the gas supplied to the membrane filtration process is not desulfurized, the amount of gas passing through the desulfurization device is reduced and the desulfurization is efficiently performed. It can be carried out.

  According to the present invention, the organic effluent is subjected to anaerobic biological treatment, the anaerobic treatment liquid is subjected to solid-liquid separation by membrane filtration in an anaerobic state, the membrane filtrate is stored while being maintained under anaerobic conditions, oxygen and Since hydrogen sulfide was removed by gas exposure without containing hydrogen sulfide, and the reverse exposure osmosis membrane treatment was performed on the air exposure solution under pressure, the permeate was collected. Hydrogen sulfide is effectively removed, thereby preventing clogging of the reverse osmosis membrane, and recovered water with high water quality can be obtained efficiently.

It is a flowchart which shows the biological treatment method of the organic drainage of embodiment. It is a graph which shows the relationship between the water flow time in an Example, and the flux of a reverse osmosis membrane.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a biological treatment method and apparatus for organic drainage according to an embodiment, wherein 1 is an anaerobic treatment apparatus, 2 is a membrane filtration apparatus, 3 is an air exposure apparatus, 4 is a reverse osmosis membrane treatment apparatus, and 5 is pH. A regulator tank, 6 is a desulfurizer, and 7 is a gas tank. The anaerobic treatment apparatus 1 is composed of a floating anaerobic treatment apparatus that retains anaerobic biological sludge in the tank and mixes it with the organic drainage liquid that enters the liquid passage L1 to be treated for anaerobic biological treatment. The liquid passage L2 communicates with the membrane filtration device 2, and the generated gas passage L3 communicates with the desulfurization device 6.

  The membrane filtration device 2 includes a filtration membrane module 11 made of an ultrafiltration membrane, and is configured to supply the anaerobic treatment liquid sent from the anaerobic treatment liquid path L2 to the filtration membrane module 11 for membrane filtration. Yes. From the membrane filtration device 2, the membrane filtrate channel L 4 communicates with the aeration device 3, the concentrated solution channel L 5 communicates with the anaerobic treatment device 1 from the module 11, and the gas supply channel L 6 extends from the generated gas channel L 3 to the lower part of the module 11. To contact.

  The aeration apparatus 3 is configured such that a desulfurization gas path L7 communicates with the aeration apparatus 12 provided in the lower portion from the desulfurization apparatus 6 to perform aeration, and the aeration gas is sent so as to send the aeration gas to the desulfurization apparatus 6 from above. Gas path L8 is in communication. The air exposure device 3 is provided with a pH meter 13, and a pH adjuster passage L <b> 9 communicates from the pH adjuster tank 5. Further, an air exposure liquid path L11 from the air exposure apparatus 3 communicates with the concentrated liquid chamber 14 of the reverse osmosis membrane treatment apparatus 4, and a concentrated liquid path L12 communicates with the air exposure apparatus 3 from the concentrated liquid chamber 14. A gas extraction passage L10 communicates with the gas tank 7 from the desulfurization gas passage L7.

The reverse osmosis membrane treatment device 4 is divided into a concentrated liquid chamber 14 and a permeated liquid chamber 16 by a reverse osmosis membrane module 15. It is comprised so that a film | membrane process may be carried out. A brine discharge path L13 branches from a concentrated liquid path L12 that circulates from the concentrated liquid chamber 14 to the aeration apparatus 3. A permeate passage L14 communicates from the permeate chamber 16 outside the system.

  The biological treatment method of organic effluent in the above apparatus is performed as follows. The organic waste liquid is introduced into the anaerobic treatment apparatus 1 from the liquid path L1 to be treated, and is mixed with the anaerobic biological sludge retained therein to perform the anaerobic biological treatment. At this time, the reaction can be promoted by heating as necessary. Although the anaerobic processing apparatus 1 shows an example of a floating type anaerobic processing apparatus, a high-load anaerobic processing apparatus using a sludge blanket, a fluidized bed, or the like can also be used. The anaerobic treatment liquid is taken out from the anaerobic treatment apparatus 1 continuously or intermittently and sent to the membrane filtration apparatus 2 from the anaerobic treatment liquid path L2. When taking out an anaerobic processing liquid intermittently, the storage tank of an anaerobic processing liquid can be provided. The generated gas is sent from the generated gas passage L3 to the desulfurization device 6 and dry desulfurized, and the desulfurized gas is sent from the gas outlet passage L10 to the gas tank 7. The gas in the gas tank 4 is taken out from the gas discharge path L16.

  In the membrane filtration device 2, the anaerobic treatment liquid is supplied from the anaerobic treatment liquid path L2 to the filtration membrane module 11 by the pump P1, and the membrane is filtered in an anaerobic state. At this time, the amount of membrane filtrate can be adjusted by suction with the pump P2. Further, the generated gas in the generated gas path L3 is blown from the gas supply path L6 to the lower part of the module 11 by the blower B1, and membrane filtration is performed while preventing solid matter from adhering to the film surface and clogging. The concentrated liquid exiting the filtration membrane module 11 circulates from the concentrated liquid path L5 to the anaerobic treatment apparatus 1, but is discharged out of the system from a sludge discharge path L15 that branches a part thereof. The membrane filtrate is sent to the air exposure device 3 from the membrane filtrate channel L4. Although the example which has the filtration membrane module 11 which consists of an ultrafiltration membrane is shown, the membrane filtration apparatus 2 has a filtration membrane module which consists of a microfiltration membrane (MF) membrane by the composition and property of an anaerobic processing liquid May be used.

  In the air exposure device 3, the membrane filtrate is stored while maintaining anaerobic conditions. Then, the membrane filtrate is exposed to air by supplying the desulfurization gas from the desulfurization device 6 through the desulfurization gas passage L7 through the blower B2 to the aeration device 12 provided in the lower portion. Thereby, hydrogen sulfide and other gas components in the membrane filtrate are released. The aeration gas is sent from the upper part of the aeration apparatus 3 to the desulfurization apparatus 6 through the aeration gas path L8, where it is desulfurized and circulated, or sent to the gas tank 7. The pH of the liquid in the tank of the air exposure device 3 is measured by the pH meter 13. Then, the pH adjusting agent is injected from the pH adjusting agent tank 5 through the pH adjusting agent passage L9 by the pump P3 so that the pH becomes 2-7. The air exposure liquid in the air exposure apparatus 3 is sent from the air exposure liquid path L11 to the concentration chamber 14 of the reverse osmosis membrane treatment apparatus 4, and the concentrate is circulated from the concentrate liquid path L12 to perform air exposure.

  In the reverse osmosis membrane treatment apparatus 4, the air exposure liquid sent from the air exposure liquid path L11 is pressurized by the pump P4 and supplied to the concentrated liquid chamber 14, and the reverse osmosis membrane module 15 performs the reverse osmosis membrane treatment. The permeate that has permeated through 15 is collected from the permeate chamber 16 through the permeate passage L14 as a collect liquid. The concentrated liquid in the concentrated liquid chamber 14 circulates from the concentrated liquid path L12 to the aeration apparatus 3, and a part of the concentrated liquid is discharged from the brine discharge path L13 along the way.

  When the reverse osmosis membrane treatment apparatus 4 performs the reverse osmosis membrane treatment, if the liquid to be treated is supplied to the reverse osmosis membrane under conditions where oxygen is dissolved, hydrogen sulfide is oxidized and the precipitated sulfur adheres to the membrane surface and becomes clogged. However, in the present invention, the anaerobic treatment liquid is subjected to membrane filtration in an anaerobic state, and the membrane filtrate is exposed to air while maintaining the anaerobic state. It is possible to prevent clogging. The membrane filtrate is exposed to a gas that does not contain oxygen and hydrogen sulfide, so that hydrogen sulfide is removed from the aerated solution without dissolving oxygen. Therefore, even if iron is concentrated in the reverse osmosis membrane treatment, Iron sulfide is not deposited on the film surface, and clogging with iron sulfide can be prevented.

  Even if the method of Patent Document 3 is applied to the reverse osmosis membrane treatment apparatus 4 and gas is jetted onto the membrane surface of the reverse osmosis membrane, the gas dissolves and the jetting effect is reduced, and the hydrogen sulfide removal rate is reduced. It is impossible to prevent iron sulfide from precipitating from hydrogen sulfide that has already reached the film surface. On the other hand, in the air exposure apparatus 3 as in the present invention, after removing hydrogen sulfide by exposure with a gas not containing oxygen and hydrogen sulfide, the effect of preventing clogging by iron sulfide is obtained by treating with a reverse osmosis membrane. Get higher.

  Further, as in Patent Document 3, if desulfurization gas is used to prevent clogging in the membrane filtration device 2, the hydrogen sulfide concentration of the gas processed in the desulfurization device 6 is lowered and the amount of gas to be treated is increased. However, by restricting the supply of the desulfurization gas only to the air exposure device 3, the desulfurization efficiency of the desulfurization device 6 can be increased and an efficient process can be performed.

  Examples of the present invention and comparative examples will be described below. The organic effluent treated in Examples and Comparative Examples has an organic composition of isopropyl alcohol 500 mg / L, dimethyl sulfoxide 100 mg / L, tetramethylammonium hydroxide 100 mg / L, TOC 380 mg / L, TN 15 mg / L. , T-S 41 mg / L synthetic waste water.

The anaerobic treatment apparatus 1 has a tank capacity of 1 m ³ , a hydraulic residence time of 0.5 d, an SS concentration of 12,000 mg / L (VSS / SS ratio of 0.90), and is acclimated for 3 months using sewage digested sludge as seed sludge. Anaerobic biological sludge is retained, and anaerobic biological treatment is performed at a temperature of 35 ° C.

The membrane filtration device 2 is equipped with an outer tank type tubular UF module (pore diameter 30 nm), and performs membrane filtration with a sludge circulation flow rate: 4 m ³ / hr (in-membrane flow velocity 0.5 m / sec) and a flux 0.6 m / d. The generated gas generated from the anaerobic biological treatment tank is vented from the lower part of the film at 4 Nm ³ / hr (in-film flow rate 0.5 m / sec) to prevent clogging.

  The reverse osmosis membrane treatment apparatus 4 includes a spiral type reverse osmosis membrane module having a wholly aromatic polyamide ultra-low pressure membrane, and performs reverse osmosis membrane treatment at a water supply pressure of 750 kPa and a water supply amount of 80 L / hr. .

[Comparative Example 1]
The separated water of the membrane filtration device 2 was temporarily stored in an open tank (capacity 200 L, residence time 2.4 hr), and supplied to the reverse osmosis membrane treatment device 4 without air exposure.

[Comparative Example 2]
The separation water of the membrane filtration device 2 is temporarily stored in a closed tank (liquid capacity 200 L, residence time 2.4 hr) communicated with the gas phase portion of the anaerobic treatment device 1, and the separation water is not exposed to air (oxygen). After doing so, it was supplied to the reverse osmosis membrane treatment apparatus 4 without performing air exposure.

[Example 1]:
The separated water of the membrane filtration device 2 was temporarily stored in a tank (capacity 200 L, residence time 2.4 hr) aerated with nitrogen and supplied to the reverse osmosis membrane treatment device 4.

[Example 2]:
The separation water of the membrane filtration device 2 is temporarily stored in a tank (capacity 200 L, residence time 2.4 hr) aerated with a gas obtained by dry desulfurization of the gas generated from the anaerobic treatment device 1, and then supplied to the reverse osmosis membrane treatment device 4. Supplied.

[Example 3]:
The separation water of the membrane filtration device 2 is adjusted to pH 4 with sulfuric acid, and temporarily stored in a tank (capacity 200 L, residence time 2.4 hr) aerated with the gas generated from the anaerobic treatment device 1 by dry desulfurization, It supplied to the reverse osmosis membrane processing apparatus 4.

  FIG. 2 shows the transition of water passage time (hr) and reverse osmosis membrane flux (permeated water amount) (m / d) in Comparative Examples 1 and 2 and Examples 1 to 3. In FIG. 2, the flux rapidly decreases immediately after the start of water flow in Comparative Examples 1 and 2, and after about 1 day, it has decreased to 1/3 of the initial value in Comparative Example 1 and 1/2 of the initial value in Comparative Example 2. It was. On the surface of the reverse osmosis membrane after the test, yellowish white sulfur was mainly precipitated in Comparative Example 1, and black iron sulfide was mainly precipitated in Comparative Example 2, which were considered to clog the membrane.

  On the other hand, in Examples 1 and 2, the decrease in flux was as small as about 20% even after one day, and the flux was stable at around 70% of the initial value even when water flowed for 150 hours. Furthermore, in Example 3, the flux was very small at about 20% even when water was passed for 150 hours. On the reverse osmosis membrane surface after the test, slight precipitation of iron sulfide was observed in Examples 1 and 2, but almost no precipitation was observed in Example 3.

  The present invention relates to an organic anaerobic biological treatment method and apparatus, particularly anaerobic biological treatment liquid, which is obtained by treating an organic waste liquid with an anaerobic biological treatment and treating the treatment liquid with a reverse osmosis membrane to obtain high-quality recovered water. When membrane filtration is performed and the membrane filtrate is subjected to a reverse osmosis membrane treatment, the reverse osmosis membrane is prevented from being clogged, and can be used for an organic anaerobic biological treatment method and apparatus for efficiently obtaining recovered water.

1: Anaerobic treatment device, 2: Membrane filtration device, 3: Exposure device, 4: Reverse osmosis membrane treatment device, 5: pH adjuster tank, 6: Desulfurization device, 7: Gas tank, 11: Filtration membrane module, 12 A diffuser, 13 a pH meter, 14 a concentrate chamber, 15 a reverse osmosis membrane module, 16 a permeate chamber,
L1: Liquid to be treated, L2: Anaerobic treatment liquid path, L3: Gas generation path, L4: Membrane filtrate liquid path, L5: Concentrated liquid path, L6: Gas supply path, L7: Desulfurization gas path, L8: Air exposure Gas path, L9: pH adjusting agent path, L10: Gas extraction path, L11: Air exposure path, L12: Concentrated liquid path, L13: Brine discharge path, L14: Permeate liquid path, L15: Sludge discharge path, L16: Gas Discharge channel,
B1, B2: Blower, P1-P4: Pump.

Claims (6)

An anaerobic treatment process for treating organic drainage with anaerobic organisms;
A membrane filtration step for solid-liquid separation by membrane filtration while the anaerobic treatment liquid remains in an anaerobic state,
An exposure step of storing the membrane filtrate while maintaining anaerobic conditions and exposing the membrane filtrate to a gas not containing oxygen and hydrogen sulfide to remove hydrogen sulfide,
And a reverse osmosis membrane treatment step of subjecting the air exposure liquid to a reverse osmosis membrane treatment under pressure and recovering the permeate.   The method according to claim 1, wherein the membrane filtrate is exposed to air at pH 2-7.   The method according to claim 1 or 2, wherein a gas obtained by desulfurizing a gas generated by an anaerobic biological treatment is used as the gas not containing oxygen and hydrogen sulfide. An anaerobic treatment device for anaerobic biological treatment of organic drainage;
A membrane filtration device for solid-liquid separation by membrane filtration while the anaerobic treatment liquid remains in an anaerobic state;
An air exposure device that stores the membrane filtrate in an anaerobic condition and exposes it with a gas not containing oxygen and hydrogen sulfide to remove hydrogen sulfide;
A biological treatment apparatus for organic drainage, comprising: a reverse osmosis membrane treatment apparatus for treating an air exposure liquid with a reverse osmosis membrane under pressure and collecting a permeate.   5. The apparatus according to claim 4, further comprising a pH adjusting device for adjusting the membrane filtrate to be exposed to pH 2-7.   6. The apparatus according to claim 4 or 5, further comprising a gas supply device that desulfurizes a gas generated by anaerobic biological treatment as a gas not containing oxygen and hydrogen sulfide and supplies the gas to an air exposure device.

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