JP2007014864A - Anaerobic treatment method and treatment apparatus of waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anaerobic treatment method of waste water which enables a sufficient agitation inside a tank even when low concentration waste water is treated without requiring power such as a blower, and a treatment apparatus. <P>SOLUTION: In the treatment apparatus having an acid generation tank 1 and, for example, a UASB (up flow anaerobic sludge blanket process) type anaerobic reactor 2, a gas generated in the acid generation tank 1 or the anaerobic reactor 2 is stored in a gas storage tank 3 through exhaust pipes 41 to 43 and a supply pipe 44, and introduced there from an air diffusion nozzle 22a of an air diffusion pipe 22 provided on the bottom of the reactor 2, thereby agitating the granule sludge bed 20 of the reactor 2 by a gas lift effect. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wastewater treatment method and treatment apparatus, and more particularly, to a method and apparatus for treating wastewater by anaerobic treatment.

  Upflow Anaerobic Sludge Bed (UASB) and expanded granular sludge bed are methods for treating highly concentrated organic wastewater discharged in fields such as beer production, pulp and paper production, food processing and livestock processing. A method using (EGSB: Expanded Granular Sludge Bed) is known. Since both have the same principle, UASB will be described below.

  In the UASB reaction tank, a sludge bed (referred to as granule sludge) is formed by self-aggregating anaerobic microorganisms such as methane bacteria into the reaction tank to form a granular sludge bed. The treatment is performed by supplying from the bottom of the reaction tank and bringing it into contact with the granular sludge. In the granular sludge bed, microorganisms can be kept at a high concentration, and thus high concentration organic wastewater can be treated efficiently.

  In order to exert the effect of the biological sludge bed of granular sludge, it is necessary to prevent the short-circuit flow of the treated water to be supplied and increase the contact efficiency between the treated water and the granular sludge. The granule sludge bed becomes hard and thick when it is left standing, and when the contact with the water to be treated stays only on the surface or when a channel (hole) is partially formed in the granule sludge bed, This is because the water to be treated is short-circuited only from this and the contact between the water to be treated and the sludge is not sufficiently performed, and it is necessary to eliminate this.

  In the UASB type reaction tank, since the water to be treated is supplied from the bottom, the effect of expanding the sludge bed by the upward flow of the water to be treated is obtained, but it is possible to obtain a sufficient expansion and stirring effect by itself. is not. The granule sludge bed further expands due to the agitation effect of the gas lift of gas (methane gas, carbon dioxide gas, etc.) generated by the decomposition of organic matter, so that the contact between the granule and the water to be treated is performed efficiently.

Especially in high concentration wastewater whose gas generation amount exceeds 20 kg-CODcr / m ³ / day, sufficient gas lift effect is obtained, and when the concentration is higher, the flow of treated water in the reaction tank is disturbed. The gas lift effect can be obtained.

However, when low-concentration wastewater (for example, CODcr is 500 mg / l) is subjected to high-load treatment (for example, 20 kg-CODcr / m ³ / day), the amount of gas generated is small, and the agitation due to the gas lift effect is insufficient. There is a problem that processing efficiency decreases.

As described above, the technique described in Patent Document 1 is known as a technique for effectively bringing the granular sludge into the water to be treated even when the amount of generated gas is small. In this technology, the supply flow path (supply nozzle) of the water to be treated supplied to the bottom of the tank is branched into two stages, and the water to be treated is supplied into the tank from each supply nozzle to stir the tank. By doing so, it is described that the water to be treated and the granular sludge can be efficiently contacted.
JP-A-7-308686

  However, in order to sufficiently stir the inside of the tank by supplying the water to be treated, it is necessary to supply a large amount of water, and the residence time in the reaction tank of the water to be treated is shortened and the processing efficiency is lowered. There is a problem that it ends up.

  In addition, as another stirring method, a method of blowing the recovered gas into the tank using a blower or the like, which is used in the stirring of the slurry fermenter used for sewage sludge digestion, can be considered. The method requires power to drive the blower.

  It is an object of the present invention to provide an anaerobic treatment method and treatment apparatus for wastewater that can perform sufficient agitation in a tank even when treating low-concentration wastewater without requiring power such as a blower. Let it be an issue.

  In order to solve the above-mentioned problems, the anaerobic treatment method of wastewater according to the present invention decomposes water to be treated into an organic acid by acid-producing bacteria in an acid generation tank, and the water to be treated in this acid generation tank is transferred to a reaction tank. Introducing the anaerobic treatment method of wastewater that is anaerobically treated by the granular sludge bed in the reaction tank, the gas generated in at least one of the acid generation tank and the reaction tank is led from the gas phase to the gas storage tank, The pressure is adjusted from the gas storage tank to the lower part of the reaction tank, and the granular sludge bed is stirred.

  On the other hand, the anaerobic treatment apparatus for wastewater according to the present invention transfers the water to be treated by a pump from an acid generation tank having acid-producing bacteria, a reaction tank having a granular sludge bed, and from the acid generation tank to the reaction tank. Anaerobic wastewater having a transfer line and a nozzle part that is arranged in the lower layer of the reaction tank and has a nozzle part that injects water to be treated into the reaction tank by being connected to the transfer line. The gas storage tank that guides and stores the gas generated in at least one of the acid generation tank and the reaction tank from the gas phase part of the three-phase separation part of the tank, and the gas that is pressure-regulated in the gas storage tank And a gas transfer line for introducing the gas into the lower part of the reaction vessel.

  In the present invention, the gas generated in the acid generation tank or the reaction tank is stored, and the stored gas is regulated and introduced into the lower part of the reaction tank. The gas introduced into the lower part swells and stirs the granular sludge bed by stirring the inside of the reaction tank by the gas lift effect together with the newly generated gas in the reaction tank.

  Here, the gas transfer line is connected in the middle of the transfer line, and the introduced gas from the gas storage tank may be joined to the treated water being transferred from the gas storage tank to the reaction tank, or a large number of open lines may be opened. Gas and treated water are separately provided by having a second nozzle portion that has a hole, is arranged in the lower layer of the reaction tank, and is connected to a gas transfer line to inject gas into the reaction tank. You may make it introduce in.

  Here, it is preferable to arrange a valve on the gas transfer line. If this valve is an on-off valve, the gas flow rate led to the reaction vessel is adjusted by switching the opening and closing over time. Furthermore, fine adjustment can be performed with the flow rate adjusting valve.

The allowable volume load of the wastewater treatment system centering on this reaction tank is targeted for 20 kg-CODcr / m ³ / day or less. This is because in the case of high-concentration wastewater exceeding 20 kg-CODcr / m ³ / day, a sufficient gas lift effect can be obtained with only the generated gas, and it is not necessary to promote the gas lift.

  According to the present invention, by introducing gas (methane gas or carbon dioxide gas) generated in an acid generation tank or a reaction tank to the bottom of the reaction tank, circulation in the reaction tank can be efficiently performed, and microorganisms and treated water can be obtained. Contact efficiency is improved, and the treatment capacity is improved even in low-concentration wastewater. In addition, this type of processing facility requires a facility for processing the gas generated in the acid generation tank and reaction tank. Therefore, it is only necessary to install a pressure adjustment function and a transfer line. In addition, there is little increase in equipment costs when upgrading existing facilities.

  When the gas transfer line is connected to the transfer line of the water to be treated, it is particularly easy to introduce the existing facility. On the other hand, if a diffuser nozzle different from the treated water supply nozzle is provided in the reaction tank, it is possible to select nozzles having positions and shapes that are optimal for the diffused gas and treated water supply.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.

  FIG. 1 is a block configuration diagram showing a first embodiment of an anaerobic treatment apparatus for wastewater according to the present invention. This processing apparatus 100 includes an acid generation tank 1 that holds acid-producing bacteria, a reaction tank 2 that is a UASB type and has a granular sludge bed 20, a storage tank 3 that stores the generated gas, and a gas holder 4.

  The lower part of the acid generation tank 1 and the reaction tank 2 is connected by a liquid feed pipe 11 that is a transfer line of the water to be treated, and a pump that transports the water to be treated to the reaction tank 2 on the liquid feed pipe 11. P is arranged. In addition, a supply pipe 21 connected to the liquid supply pipe 11 is disposed in the reaction tank 2, and the treated water that has been sent is uniformly distributed on the supply pipe 21 to the bottom of the reaction tank 2. A water supply nozzle 21a, which is an opening for distributing and supplying, is disposed at a predetermined position. The diameter of the water supply nozzle 21a is preferably 10 mm or more in order to prevent clogging of the nozzle due to suspended substances (SS) mixed in the treated water.

  A waste water introduction pipe 10 for introducing the water to be treated is connected to the upper part of the acid generation tank 1. On the other hand, a three-phase separation unit 23 for separating the generated gas, the treatment liquid, and solids (sludge etc.) is provided at the upper part of the liquid phase of the reaction tank 2. Is connected to a discharge pipe 25 for discharging the separated processing liquid. From this discharge pipe 25, a liquid feed pipe 26 is branched and connected to the acid generation tank 1, so that a part of the processing liquid can be returned to the acid generation tank 1.

  Gas discharge pipes 41 and 42 are connected to the gas phase portions of the acid generation tank 1 and the reaction tank 2, respectively, and merge with the gas discharge pipe 43. The gas discharge pipe 43 is connected to the gas holder 4 that stores the recovered gas. On the other hand, a gas supply pipe 44 is branched from the gas discharge pipe 43 and is connected to the gas storage tank 3. A gas supply pipe 45 connected to the reaction tank 2 is connected to the gas storage tank 3.

  Valves V <b> 1 to V <b> 3 are arranged between the branch portion of the gas discharge pipe 43 to the gas supply pipe 45 and the gas holder 4 and on the gas supply pipes 44 and 45, respectively. Among these, it is preferable that V1 is an on-off valve, V2 is a check valve or on-off valve, and V3 is a flow control valve. On the gas supply pipe 45, another check valve or on-off valve, a gas flow meter, and a pressure gauge, which are not shown, may be disposed. V3 may be an on-off valve.

  A diffuser pipe 22 connected to a gas supply pipe 45 is connected to the lower part of the supply pipe 21 in the reaction tank 2. On the diffuser tube 22, an diffuser nozzle 22 a which is an opening for supplying the gas sent into the reaction tank 2 is disposed at a predetermined position. The hole diameter of the aeration nozzle 22a is preferably sufficiently smaller than the hole diameter of the water supply nozzle 21a described above so that a low-pressure gas can be continuously ejected for a long time, for example, 1 mm or less. It is preferable.

  Next, the operation of the present embodiment, that is, the anaerobic treatment method for wastewater according to the present invention will be specifically described. The organic waste water to be treated (treated water) is introduced into the acid generation tank 1 through the introduction pipe 10. The organic matter in the wastewater is decomposed into an organic acid or the like by the action of acid producing bacteria in the acid producing tank 1. A part of the organic acid is decomposed by methane bacteria sent from the reaction tank 2 to the acid generation tank 1 through the liquid feeding pipe 26, and methane and carbon dioxide gas are generated. These generated gases are discharged through the gas discharge pipe 41. In addition, it is possible to introduce | transduce into the acid production tank 1 the alkali agent for neutralization from the line 50 as needed.

  The treated water in the acid generation tank 1 is transferred to the reaction tank 2 through the liquid supply pipe 11 by the pump P. At this time, the water to be treated is sent from the water supply nozzle 21 a on the supply pipe 21 to the bottom of the reaction tank 2. On the other hand, as will be described later, a part of the gas generated in the acid generation tank 1 and the reaction tank 2 is stored in the gas storage tank 3. As will be described later, this gas is sent from the gas supply pipe 45 to the diffuser pipe 22 at an appropriate interval, and sent to the reaction tank 2 from the diffuser nozzle 22a, whereby an upward flow is formed by the gas lift effect, The granule sludge bed 20 is agitated. Thereby, the contact of to-be-processed water and granule sludge is accelerated | stimulated, and the organic acid decomposition | disassembly in organic wastewater by the methanogen etc. which form a granule is accelerated | stimulated. As a result, methane, carbon dioxide gas and the like are generated.

  In this way, the treated water, in which the organic content has been decomposed, is separated from the gas phase content such as the generated gas and the solid content such as granule sludge by the three-phase separation section 23 and discharged by the discharge pipe 25 connected to the liquid phase separation section 23a. Is done. A part of the treated water aims to maintain acid producing bacteria in the acid producing tank 1 and save the neutralizing agent to be added to the acid producing tank 1, and further reduce the concentration of organic substances in the discharged treated water. The solution is returned to the acid generation tank 1 by the liquid feeding pipe 26.

  Gases generated in the acid generation tank 1 and the reaction tank 2 are discharged through gas discharge pipes 41 and 42, respectively, and sent to the gas holder 4 through the gas discharge pipe 43. Among these, a part is sent to the gas storage tank 3 through the gas supply pipe 44. By closing the valve V1 and opening the valve V2, gas can be stored in the gas storage tank 3, and the pressure in the storage tank can be increased. On the other hand, when the valve V <b> 2 is closed and V <b> 1 is opened, the generated gas (including the circulating gas) is sent to the gas holder 4. Here, although not shown, it is preferable to provide a gas cleaning device between the valve V1 and the gas holder 4 to remove odor components and the like. The gas stored in the gas holder 4 is reused as fuel or raw material.

When the pressure of the gas storage tank 3 exceeds a predetermined pressure (a predetermined pressure higher than the water pressure in the diffuser nozzle 22a portion), the valve V2 is closed and V3 is opened so that the gas in the gas storage tank 3 is The gas is supplied to the bottom of the reaction tank 2 through the gas supply pipe 45, the air diffusion pipe 22, and the air diffusion nozzle 22a. At this time, by closing V2, it is possible to effectively prevent the stored gas from flowing back to the gas phase part of the reaction tank 2 or the acid generation tank 1 through the gas supply pipe 44 and the discharge pipes 41 to 43. it can. Of course, a check valve may be provided upstream or downstream of V2, or instead of V2. This predetermined pressure is about 0.7 to 1 kg / cm ² (about 70 to 100 kPa). In order to realize a gas pressure higher than this, a pressure-resistant container is required for the reaction tank 2 and the gas storage tank 3, which is not preferable.

  In order to prevent the granulated sludge bed 20 of the reaction tank 2 from being inadvertently disturbed by the gas supplied to the bottom of the reaction tank 2 from the diffuser nozzle 22a flowing at the start of the supply, the gas flow rate is reduced. It is preferable to adjust by the flow control valve V3. In addition, when V3 is a mere on-off valve, it is good to adjust flow volume by opening and closing V3 intermittently suitably.

By supplying the stored gas to the reaction tank 2, the pressure of the gas storage tank 3 is, for example, about the pressure (water pressure) corresponding to the water depth of the reaction tank 2 (0.5 kg / cm ² = about 50 kPa if the water depth is 5 m). When the pressure drops to V, the valves V3 and V1 are closed and V2 is opened, whereby the gas is again stored in the gas storage tank 3. By repeating this, gas supply to the bottom of the reaction vessel 2 is performed.

  The operation of these valves V1 to V3 may be performed based on a signal from a pressure gauge arranged in the gas storage tank 3 by a control device in a sequence.

  According to the present embodiment, a sufficient gas lift effect can be obtained by the gas supplied from the aeration nozzle 22a even when the amount of gas generated is low, such as when high-load treatment of low-concentration wastewater is performed. Can be sufficiently expanded, the contact efficiency between the water to be treated and the granular sludge can be increased, and the treatment efficiency can be sufficiently exhibited. On the other hand, in the case of high-load wastewater with a large amount of gas generation, a sufficient gas lift effect can be obtained with only the generated gas, and it is only necessary to stop the gas supply from the aeration nozzle 22a.

  For this reason, it is possible to treat from low load wastewater to high load wastewater by the same equipment, and it is possible to apply the UASB type anaerobic treatment apparatus to wastewater treatment equipment having a large load fluctuation.

  In addition, even when the amount of gas generated at low load is small, sufficient agitation is performed in the reaction tank 2 by aeration, so even if a large amount of suspended matter flows in along with the organic waste water, this suspension is caused by the gas lift effect. Suspended substances can be prevented from adhering to the granules and discharged together with the treated water. For this reason, accumulation of suspended substances at the bottom of the reaction tank 2 can be prevented, and the processing capacity does not decrease.

  Furthermore, since it is not necessary to provide a power source such as a pump or a blower on the gas pipe for performing air diffusion, effective stirring can be performed without power, which helps to reduce the power cost of the processing plant.

  Although the gas supply pipe 44 is branched from the gas discharge pipe 43 here, it may be branched from the gas discharge pipe 41 or 42. In these cases, only the gas discharged from either the acid generation tank 1 or the reaction tank 2 is used as the gas for aeration.

  FIG. 2 is a diagram illustrating an arrangement example of a supply pipe and an air diffusion pipe in a modification of the first embodiment. This modification is different from the first embodiment in that each of the plurality of diffuser tubes 22x to 22z is arranged at a position where the depth of the bottom of the reaction tank 2 is different.

  The gas supply pipe 45 is connected to the diffuser pipes 22x to 22z via branch pipes 45x to 45z, and valves Vx to Vz are arranged on the branch pipes 45x to 45z, respectively. Here, an example in which an air diffuser is arranged at three depths has been shown, but the arrangement may be performed at two or four or more depths. The hole diameters of the air diffuser nozzles of the air diffuser tubes 22x to 22z may be the same, or may be different according to the depth.

  In the case of this modification, according to the pressure of the gas storage tank 3 and the operating conditions of the reaction tank 2, for example, one of the valves Vx to Vz is opened and the other is closed to adjust the aeration position. It becomes possible. Here, an example in which one of the effective diffusing tubes 22x to 22z is switched and used has been described. However, for example, the middle diffusing tube 22y is always effective, and the diffusing tubes 22x and 22z are connected to each other. Any one of them may be added and validated. Alternatively, the valid / invalid combination of each of the three air diffusers may be changed. The idea is the same when two or four or more diffusers are provided.

  FIG. 3 is a block diagram showing a second embodiment of the anaerobic treatment apparatus for wastewater according to the present invention. In this embodiment, the gas supply pipe 45 extending from the gas storage tank 3 is connected to the liquid supply pipe 11 downstream of the pump P, and the dedicated diffuser pipe 22 that existed in the first embodiment shown in FIG. Does not exist.

  In this embodiment, since gas can be supplied using the water supply nozzle 21a of the existing reaction tank 2, there is an advantage that it is easy to retrofit and additionally install an existing facility. Also in this embodiment, the same effects as those of the first embodiment can be obtained, for example, the gas lift effect can be enhanced by aeration, and the granular sludge bed 20 can be effectively stirred.

  In the above description, the wastewater treatment apparatus and the wastewater treatment method using the UASB type anaerobic reaction tank have been described, but the present invention is also suitable for other upflow anaerobic treatment apparatuses such as the EGSB type. Can be applied.

It is a block block diagram which shows 1st Embodiment of the anaerobic treatment apparatus of the wastewater which concerns on this invention. It is a figure which shows the example of arrangement | positioning of the supply pipe | tube and aeration pipe | tube in the modification of 1st Embodiment. It is a block block diagram which shows 2nd Embodiment of the anaerobic processing apparatus of the wastewater which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Acid production tank, 2 ... Reaction tank, 3 ... Gas storage tank, 4 ... Gas holder, 10 ... Waste water introduction pipe, 11 ... Liquid feed pipe, 20 ... Granule sludge bed, 21 ... Supply pipe, 21a ... Water supply nozzle, 22a ... Aeration nozzle, 22, 22x to 22z ... Aeration tube, 23 ... Three-phase separation section, 23a ... Liquid phase separation section, 25 ... Discharge pipe, 26 ... Liquid feed pipe, 41-43 ... Gas discharge pipe, 44, 45 ... Gas supply pipe, 45x-45z ... Branch pipe, 50 ... Line, 100 ... Waste water treatment device, P ... Pump, V1-V3, Vx-Vz ... Valve.

Claims (10)

The water to be treated is decomposed into an organic acid by acid-producing bacteria in the acid generation tank, the water to be treated in the acid generation tank is introduced into the reaction tank, and the anaerobic treatment of the wastewater is performed by the granular sludge bed in the reaction tank. In the sex treatment method,
The gas generated in at least one of the acid generation tank and the reaction tank is led from the gas phase part of the tank to the gas storage tank, and the pressure is adjusted from the gas storage tank to the lower part of the reaction tank, An anaerobic treatment method for wastewater, characterized by stirring a granular sludge bed.   The anaerobic treatment method of wastewater according to claim 1, wherein the introduced gas from the gas storage tank is joined to the treated water being transferred from the gas storage tank to the reaction tank.   The method for anaerobic treatment of wastewater according to claim 1 or 2, wherein a gas flow rate leading to the reaction vessel is adjusted. Anaerobic treatment method of the waste water according to any one of claims 1 to 3, wherein the tolerance volume loading of the wastewater treatment system centered on the reactor is less than 20kg-CODcr ^/ m 3 / day. An acid generation tank having acid-producing bacteria, a reaction tank having a granular sludge bed, a transfer line for transferring the water to be treated from the acid generation tank to the reaction tank by a pump, and a large number of openings. In the anaerobic treatment apparatus for wastewater, which is disposed in the lower layer part of the reaction tank and has a nozzle part for injecting water to be treated into the reaction tank by being connected to the transfer line,
A gas storage tank that guides and stores the gas generated in at least one of the acid generation tank and the reaction tank from the gas phase part of the three-phase separation part of the tank;
An anaerobic treatment apparatus for wastewater, comprising a gas transfer line for introducing a gas regulated in the gas storage tank into a lower part of the reaction tank.   It has a number of apertures, and is further provided with a second nozzle part that is arranged in the lower layer part of the reaction tank and that is connected to the gas transfer line to inject gas into the reaction tank. An anaerobic treatment apparatus for wastewater according to claim 5.   The wastewater anaerobic treatment apparatus according to claim 5, wherein the gas transfer line is connected to the transfer line.   An anaerobic treatment apparatus for wastewater according to any one of claims 5 to 7, wherein a valve is disposed on the gas transfer line.   The anaerobic treatment apparatus for wastewater according to claim 8, wherein the valve disposed on the gas transfer line is a flow rate adjusting valve. Anaerobic treatment apparatus wastewater according to any one of claims 5-9 for acceptable volume load is equal to or less than 20kg-CODcr / ^{m 3} / day.

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