JP2005329378A - Anaerobic treatment apparatus and method for anaerobically treating organic waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anaerobic treatment apparatus for anaerobically treating organic waste water having high safety and high treating efficiency, and an anaerobic treatment method. <P>SOLUTION: The anaerobic treatment apparatus 1 includes an acid formation tank 12 for treating the organic waste water by acid formation bacteria, an upward flow type anaerobic treatment tank 30 for anaerobically treating treated water treated in the acid formation tank 12, a recirculation line L6 for recirculating a part of the treated water treated in the upward flow type anaerobic treatment tank 30 in the acid formation tank 12 and an ultraviolet ray irradiation device 50 for irradiating the treated water recirculated through the recirculation pipe L6 with an ultraviolet ray. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an anaerobic treatment apparatus for organic wastewater and an anaerobic treatment method.

  Organic wastewater containing organic substances is discharged from production facilities such as food, beverages, pharmaceuticals, and pulp. In recent years, anaerobic treatment methods have been widely adopted as methods for treating these organic wastewaters from the viewpoint of energy saving and the like. Organic wastewater treatment by anaerobic fermentation such as methane fermentation produces less sludge, does not require aeration power, and can recover methane gas that can be used as an energy source, compared to aerobic treatment such as activated sludge method. Has many advantages.

  Among them, UASB (Upflow Anaerobic Sludge Blanket) method and EGSB (Expanded Granular Sludge Bed) method using anaerobic granular sludge with high density and good sedimentation can treat organic wastewater at high load and high speed. It is often adopted because it is possible.

  However, in any anaerobic treatment method such as the normal anaerobic treatment method or the UASB method, when treating wastewater containing a large amount of sulfur compounds such as sulfate ions, hydrogen sulfide produced by the action of sulfate-reducing bacteria , Which inhibits methane fermentation, may not be sufficient. In addition, since hydrogen sulfide is mixed into the recovered methane gas, desulfurization treatment is required to remove hydrogen sulfide, the equipment is corroded by hydrogen sulfide, or the distribution pipe is corroded by hydrogen sulfide dissolved in the treated water. There are various problems such as generation of odors.

Therefore, in the method described in Patent Document 1, an oxygen-containing gas such as air is supplied into the methane fermenter to inactivate sulfate-reducing bacteria to suppress the generation of hydrogen sulfide.
JP 2003-136089 A

  However, in the method described in Patent Document 1 described above, since an oxygen-containing gas such as air is supplied to the methane fermenter, the activity of the methanogen that is an anaerobic bacterium is also reduced, and eventually the treatment efficiency of waste water is reduced. There was a risk of lowering. In addition, oxygen may be mixed in the recovered methane gas, causing a gas explosion.

  This invention is made | formed in view of an above-described situation, and it aims at providing the anaerobic processing apparatus and the anaerobic processing method of organic wastewater with high safety | security and high processing efficiency.

  An anaerobic treatment apparatus according to the present invention includes an acid generation tank for treating organic wastewater with acid-producing bacteria, an upward flow anaerobic treatment tank for anaerobically treating the treated water treated in the acid generation tank, A return line for returning a part of the treated water treated in the counterflow anaerobic treatment tank to the acid generation tank, and an ultraviolet irradiation device for irradiating the treated water returned through the return line with ultraviolet rays.

  The anaerobic treatment method according to the present invention includes a step of treating organic wastewater with acid producing bacteria in an acid production tank, and an anaerobic treatment of the treated water treated in the acid production tank in an upward flow type anaerobic treatment tank. The process, the step of returning a part of the treated water treated in the upward flow type anaerobic treatment tank to the acid generation tank, and the ultraviolet ray on the treated water returned from the upward flow type anaerobic treatment tank to the acid generation tank Irradiating with.

  In this anaerobic treatment apparatus and method, part of the treated water is returned from the upward flow anaerobic treatment tank to the acid generation tank through the return line. At this time, since the methanogen stays in the upward flow anaerobic treatment tank, the possibility of flowing out through the return line is low. Therefore, by irradiating the treated water to be returned with ultraviolet rays, it is possible to inhibit the metabolism of sulfate-reducing bacteria and to inactivate or decrease the activity without affecting the methanogenic bacteria. As a result, the generation of hydrogen sulfide that inhibits methane fermentation can be suppressed very efficiently, and the treatment efficiency of organic wastewater can be increased. Moreover, since the activity of the sulfate-reducing bacteria is reduced by irradiating with ultraviolet rays, there is no fear that oxygen is mixed into methane gas as in the conventional case, and safety is high.

  The anaerobic treatment method according to the present invention further comprises a step of measuring the organic acid concentration in the treated water in the acid generation tank or in the liquid feed line connecting the acid generation tank and the upward flow type anaerobic treatment tank, It is preferable to adjust the irradiation intensity of ultraviolet rays based on the measured organic acid concentration. If it does in this way, the activity of an acid production microbe can be maintained and the processing efficiency of organic wastewater can be maintained more reliably.

  ADVANTAGE OF THE INVENTION According to this invention, the anaerobic processing apparatus and the anaerobic processing method of organic wastewater with high safety | security and high processing efficiency can be provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are used for the same elements, and duplicate descriptions are omitted.

  FIG. 1 is a schematic diagram showing the configuration of the anaerobic treatment apparatus according to the present embodiment.

  The anaerobic treatment apparatus 1 includes a raw water tank 10, an acid generation tank 12, an upward flow type anaerobic treatment tank 30, and an ultraviolet irradiation device 50.

  The raw water tank 10 receives the organic wastewater that has passed through the raw water inflow pipe L1 and temporarily stores it. The raw water tank 10 is connected to the acid generation tank 12 by a raw water water pipe L2.

  The acid generation tank 12 decomposes organic substances contained in the organic wastewater received through the raw water transmission pipe L2 into lower fatty acids such as probionic acid, tangle acid, and lactic acid, and further decomposes to acetic acid. A first gas discharge line L <b> 3 for discharging the gas and odor generated in the acid generation tank 12 is connected to the upper wall of the acid generation tank 12. The acid generation tank 12 is provided with an organic acid concentration measuring device 11 for measuring the concentration of the organic acid contained in the treated water in the tank. Examples of the organic acid concentration measuring instrument 11 include a gas chromatography analyzer. The acid generation tank 12 is connected to an upward flow type anaerobic treatment tank (hereinafter also simply referred to as an anaerobic treatment tank) 30 by a water pipe L4.

  The anaerobic treatment tank 30 anaerobically treats the organic wastewater by flowing the organic wastewater upward and passing it through a sludge layer made of granular sludge (hereinafter referred to as “granule sludge”) G. . This anaerobic treatment tank 30 has a bottomed container including a cylindrical side wall. In the lower part of the anaerobic treatment tank 30, an inflow part 31 that communicates with the water supply pipe L <b> 4 and allows the organic waste water to flow into the anaerobic treatment tank 30 is provided. The inflow portion 31 is, for example, a tube in which holes are provided uniformly in the longitudinal direction. In addition, a sludge layer 32 made of granular sludge G for anaerobically treating organic wastewater is formed in the lower part of the anaerobic treatment tank 30.

  In the anaerobic treatment tank 30, the organic waste water is introduced into the inside from an inflow portion 31 provided in the lower part thereof to cause upward flow, and the organic waste water is passed through the sludge layer 32 to anaerobically treat the organic waste water. To do. Thereby, the liquid layer 33 containing the anaerobic treated water is formed above the sludge layer 32. The treated water of the liquid layer 33 includes gases such as methane gas and carbon dioxide gas generated by the anaerobic treatment.

  A cover 34 that seals the anaerobic treatment tank 30 is provided on the upper portion of the anaerobic treatment tank 30. The cover 34 is located above the liquid surface of the liquid layer 33 and below the upper end of the side wall 35 of the anaerobic treatment tank 30. A separation tank 36 for separating the gas from the treated water is provided at the center of the cover 34. The separation tank 36 is arranged so that its upper end protrudes from the cover 34 and its lower end is included in the liquid layer 33.

  An inlet for introducing the treated water into the separation tank 36 is formed at the lower end of the separation tank 36. In order to guide the treated water to the introduction port, an introduction plate 37 is provided below the separation tank 36 along the bottom of the separation tank 36. The introduction plate 37 is formed with a return port under the introduction port for returning the treated water that has not been introduced into the introduction port.

  Due to the positional relationship between the separation tank 36 and the introduction pipe 37, the treated water that has passed through the sludge layer 32 and is flowing upward is supplied to the introduction path 38 formed between the introduction plate 37 and the separation tank 36. It flows from the liquid surface side of the layer 33. At that time, since the gas contained in the treated water comes out between the cover 34 and the liquid level, the space defined by the separation tank 36, the cover 34, the side wall 35 and the liquid level is separated from the gas reservoir 39. Become. The gas collected in the gas reservoir 39 is discharged out of the anaerobic treatment tank 30 from the side wall 35 through the second gas discharge line L5, for example. A part of the treated water that has passed through the introduction path 38 flows into the separation tank 36 from the introduction port, and the other part flows downward from the return port of the introduction plate 37.

  The treated water that has flowed into the separation tank 36 overflows from the side wall of the separation tank 36 and accumulates in an area formed by the separation tank 36, the cover 34, and the side wall 35, so that the area becomes the treated water reservoir 40. . A treated water return pipe (return line) L6 for returning a part of the treated water to the acid generation tank 12 and a drain pipe L7 for draining the remaining treated water are connected to the treated water reservoir 40.

  The ultraviolet irradiation device 50 is provided on the treated water return pipe L6. The ultraviolet irradiation device 50 includes a power supply unit 51 and a light irradiation lamp 52. As the light irradiation lamp 52, a lamp that generates ultraviolet rays such as a germicidal lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a halogen lamp, a xenon lamp, or an excimer laser can be used. As an ultraviolet irradiation method, an internal irradiation type in which a light irradiation lamp 52 is placed in a water channel or a pipe through which treated water flows, or the inside of a plastic pipe made of quartz glass or Teflon (registered trademark) that transmits ultraviolet light. Either an external irradiation type in which treated water is allowed to flow through and irradiated from the outside can be used. Or the light irradiation lamp 52 can be arrange | positioned above the water channel through which treated water flows, and it can also irradiate from the exterior.

  Next, an anaerobic treatment method for organic wastewater using the anaerobic treatment apparatus 1 will be described.

  First, organic wastewater is received in the raw water tank 10 through the raw water inflow pipe L1. Next, organic waste water is caused to flow into the acid generation tank 12 through the raw water feed pipe L2. Next, in the acid generation tank 12, the organic matter contained in the organic wastewater is decomposed into an organic acid such as acetic acid by the acid-producing bacteria. At this time, since the inside of the acid generation tank 12 is acidified by the generation of the organic acid, it is preferable to add an alkali agent such as sodium hydroxide as necessary. And the treated water processed in the acid production tank 12 is introduce | transduced in the anaerobic processing tank 30 through the water pipe L4. In addition, the gas and odor produced | generated in the acid production | generation tank 12 are discharged | emitted to the process means which is not shown in figure through the 1st gas discharge line L3.

  Next, the organic waste water that has flowed in from the inflow portion 31 is caused to flow upward in the anaerobic treatment tank 30. Thereby, organic wastewater passes the sludge layer 32 and is anaerobically treated. That is, the organic acid in the organic wastewater is converted into methane, carbon dioxide gas, or the like by anaerobic bacteria such as methane-producing bacteria contained in the granular sludge G.

  The treated water that has been subjected to the anaerobic treatment flows into the introduction path 38 while releasing the gas into the gas reservoir 39. The gas accumulated in the gas reservoir 39 is discharged to a gas collection tank (not shown) or the like through the second gas discharge line L5. Then, the treated water with the reduced gas content flows into the separation tank 36 from the lower end of the separation tank 36. The treated water that has flowed into the separation tank 36 is discharged to the treated water reservoir 40. A part of the treated water collected in the treated water reservoir 40 is returned to the acid generation tank 12 through the treated water return pipe L6, and the rest is drained through the drain pipe L7. The treated water drained through the drain pipe L7 is drained out of the system after further aerobic treatment.

  Here, the ratio of the treated water drained through the drain pipe L7 and the treated water returned to the acid generation tank 12 through the treated water return pipe L6 is the organic matter concentration of the organic wastewater flowing through the raw water inlet pipe L1. It is preferable to determine based on the composition. Usually, about 20% of the treated water treated in the anaerobic treatment tank 30 is returned to the acid generation tank 12 through the treated water return pipe L6.

  Next, ultraviolet rays are irradiated by the ultraviolet irradiation device 50 to the treated water returned to the acid generation tank 12 through the treated water return pipe L6. Here, since the methanogen is granulated sludge with good sedimentation and stays in the anaerobic treatment tank 30, the methanogen is substantially contained in the treated water returned through the treated water return pipe L6. Not. Therefore, by irradiating with ultraviolet rays, the sulfate-reducing bacteria contained in the treated water returned through the treated water return pipe L6 are selectively damaged or killed without affecting the methanogenic bacteria, and inactivated or reduced in activity. Can be achieved.

  The treated water irradiated with ultraviolet rays is returned to the acid generation tank 12 through the treated water return pipe L6. Since the sulfate-reducing bacteria are inactivated or the activity is reduced, the sulfuration in the acid generation tank 12 is performed. Generation of hydrogen is suppressed. Similarly, in the anaerobic treatment tank 30, since sulfate-reducing bacteria are not supplied from the acid production tank 12, generation of hydrogen sulfide is suppressed. As a result, the methane fermentation treatment can be efficiently performed in the anaerobic treatment tank 30.

  Here, it is preferable to adjust the irradiation intensity of the ultraviolet rays by the ultraviolet irradiation device 50 based on the organic acid concentration measured by the organic acid concentration measuring instrument 11. If the irradiation of ultraviolet rays is excessive, the acid producing bacteria contained in the treated water returned to the acid producing tank 12 through the treated water return pipe L6 may be damaged or killed. Therefore, when the organic acid concentration is measured by the organic acid concentration measuring instrument 11, the treatment does not proceed well when the organic acid concentration is higher than the reference value (that is, the acid-producing bacteria may be inactivated). And the irradiation intensity is reduced or the irradiation is interrupted. Thereby, the activity of acid-producing bacteria can be maintained, and the treatment efficiency of organic wastewater can be more reliably maintained high.

  As described above in detail, in the present embodiment, the treated water returned through the treated water return pipe L6 is irradiated with ultraviolet rays, thereby inhibiting the metabolism of sulfate-reducing bacteria without affecting the methanogen. Inactivation or reduction of activity can be achieved. As a result, the generation of hydrogen sulfide that inhibits methane fermentation can be suppressed very efficiently, and the treatment efficiency of organic wastewater can be increased. Moreover, since the activity of the sulfate-reducing bacteria is reduced by irradiating with ultraviolet rays, there is no fear that oxygen is mixed into methane gas as in the conventional case, and safety is high.

  In addition, the desulphurization treatment of methane gas obtained in the anaerobic treatment tank 30 is simplified or unnecessary, and problems such as corrosion of the apparatus and odor of treated water can be solved.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, as illustrated in FIG. 2, the ultraviolet irradiation device 50 may be provided also in the raw water water pipe L <b> 2 that connects the raw water tank 10 and the acid generation tank 12. In this way, the sulfate-reducing bacteria in the organic wastewater grown during storage in the raw water tank 10 can be damaged or killed by ultraviolet rays. As a result, the generation of hydrogen sulfide in the acid generation tank 12 and the anaerobic treatment tank 30 is more effectively suppressed, and the treatment efficiency of organic wastewater can be further increased.

  Further, the organic acid concentration measuring device 11 is provided not in the acid generation tank 12 but in the water supply pipe L4, and the irradiation intensity of the ultraviolet rays by the ultraviolet irradiation device 50 is adjusted based on the organic acid concentration of the treated water passing through the liquid supply pipe L4. May be.

  In addition, the drainage pipe L7 also samples the treated water, performs component analysis, sees the concentration tendency of propionic acid, tangled acid, and acetic acid, and compares with the sampling result in the acid generation tank 12 to the liquid feeding pipe L4, Based on the result, the irradiation intensity of ultraviolet rays by the ultraviolet irradiation device 50 may be adjusted. For example, in the treated water drained from the drain pipe L7, when the treatment is good, the concentrations of propionic acid and entangling acid tend to be low, and the concentration of acetic acid tends to be high. On the other hand, when the treatment is poor, the concentrations of propionic acid and entangling acid tend to be high and the concentration of acetic acid tends to be low. This is because, when the treatment is good, the propionic acid and the entangling acid, which are macromolecules, are sufficiently decomposed and processed into a low molecular acetic acid form. Conversely, when the treatment is poor, acetic acid is not decomposed and remains in the treated water in the form of propionic acid and tangled acid.

  Hereinafter, although the Example of the anaerobic processing method which concerns on above-described embodiment is shown, this invention is not limited to this.

While supplying organic wastewater containing 600 mg / l of water-soluble COD _cr as an organic component and 1000 mg / l of SO ₄ ²⁻ as a sulfur component to the anaerobic treatment apparatus 1 shown in FIG. 1 at 0.69 m ³ / h A part of the treated water in an anaerobic treatment tank anaerobic 30 (effective volume 1 m ³ ) is stored in an ultraviolet irradiation device 50 in which a light irradiation lamp 52 (0.24 kW) for irradiating ultraviolet rays is immersed. It was passed at a speed of 1 second and returned to the acid generation tank 12 (effective volume 1 m ³ ). The acid generation tank 12 was adjusted to pH 6 to 7, the inside of the anaerobic treatment tank 30 was set to about 38 ° C., and organic waste water was supplied from the acid generation tank 12 to the anaerobic treatment tank 30 at 0.83 m ³ / h.

  As a result, methane fermentation was not inhibited by hydrogen sulfide, and good treatment with high treatment efficiency was possible.

It is the schematic which shows the structure of the anaerobic processing apparatus which concerns on this embodiment. It is the schematic which shows the modification of a structure of an anaerobic processing apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Anaerobic processing apparatus, 12 ... Acid production tank, 30 ... Upward flow type anaerobic processing tank, 50 ... Ultraviolet irradiation apparatus, L6 ... Treated water return pipe.

Claims (3)

An acid generator tank for treating organic wastewater with acid-producing bacteria;
An upflow anaerobic treatment tank for anaerobically treating the treated water treated in the acid generation tank;
A return line for returning a part of the treated water treated in the upward flow anaerobic treatment tank to the acid generation tank;
An ultraviolet irradiation device for irradiating the treated water returned through the return line with ultraviolet rays;
An anaerobic treatment apparatus comprising: A process of treating organic wastewater with acid producing bacteria in an acid producing tank;
An anaerobic treatment of the treated water treated in the acid generation tank in an upward flow anaerobic treatment tank;
Returning a part of the treated water treated in the upward flow anaerobic treatment tank to the acid generation tank;
Irradiating the treated water returned from the upward flow anaerobic treatment tank to the acid generation tank with ultraviolet rays;
An anaerobic treatment method comprising: The method further comprises the step of measuring the concentration of organic acid in the treated water in the acid generation tank or in the liquid feed line connecting the acid generation tank and the upward flow type anaerobic treatment tank,
The anaerobic treatment method according to claim 2, wherein the irradiation intensity of the ultraviolet rays is adjusted based on the measured concentration of the organic acid.

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