JP2012110820A - Method and apparatus for anaerobic treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a stable high-load treatment by preventing surfacing of a non-biological carrier having fluidity in a reaction tank and blocking due to adhesion of bubbles, and by recovering the sedimentation properties of the carrier floating due to the adhesion of bubbles effectively by a simple method, when an anaerobic treatment is carried out by filling the reaction tank with the non-biological carrier so that a biofilm is formed on the surface of the non-biological carrier and by passing water to be treated therethrough under anaerobic conditions.SOLUTION: The non-biological carrier having a size of 1.0-5.0 mm and a settling rate of 200-500 m/hr is used as a fluid non-biological carrier to be filled into a reaction tank. The bubbles adhering to the carrier surfaced and flowed out of the reaction tank are separated and removed by passing the carrier through a pipe with a drop of 50 cm or more downwardly, and the resulting carrier is returned to the reaction tank.

Description

  The present invention relates to an anaerobic treatment method in which a non-biological carrier having fluidity is filled in a reaction tank, a biological film is formed on the surface of the non-biological carrier, and the treated water is passed under anaerobic conditions for treatment. Relates to the device.

  As an anaerobic treatment method for organic wastewater, a sludge blanket is formed by forming granular sludge with high density and high sedimentation in the reaction tank, and upwardly circulating organic wastewater containing soluble BOD. The UASB (Upflow Anaerobic Sludge Blanket) method, which performs high-load and high-speed processing by contacting with a slab, is employed. In this method, solid organic substances with a low digestion rate are separated and treated separately, and only soluble organic substances with a high digestion rate are processed at high speed with high load by anaerobic treatment using granular sludge with high anaerobic microorganism density. It is. In addition, as a development of this UASB method, EGSB is used to conduct anaerobic treatment at a higher load by passing water at a higher flow rate using a high-height reaction vessel, deploying a sludge blanket at a higher deployment rate. (Expanded Granule Sludge Blanket) method is also performed.

  Anaerobic treatment using granular sludge, such as UASB method and EGSB method, is a method in which sludge containing anaerobic microorganisms is maintained and grown in a granular state for treatment. This method can achieve a high sludge retention concentration compared to the treatment with a fixed bed or fluidized bed that holds sludge on the carrier, so that it can be operated at a high load, and surplus sludge from an already operating treatment system. Can be started up in a short period of time, and is generally recognized as the most efficient anaerobic treatment method.

However, these methods using granular sludge are very efficient when the COD concentration of the wastewater is high (COD _Cr concentration is approximately 2000 mg / L or more), but when the COD concentration is low (COD _Cr concentration is approximately 2000 mg). / L or less), it is necessary to flow a large amount of water into the reaction tank, and there is a tendency that the risk of granule outflow increases and stable performance cannot be exhibited.

  It is also known that depending on the type of drainage, there is drainage in which granule is difficult to form, and the initially charged granule gradually dismantles, making it impossible to operate.

  On the other hand, in the method using a fluid non-biological carrier, it is possible to prevent the carrier from flowing out of the reaction tank by a mechanical method such as a screen, and the carrier surface can always be secured as a place for growing microorganisms. There is an advantage that it can be applied to low-concentration COD wastewater and wastewater in which granules are dismantled.

  In addition, the non-biological carrier has a high degree of freedom in designing the specific gravity and size, and the sedimentation rate can be set very large as compared with granules. If a carrier with a high sedimentation rate is used, the mechanism for solid-liquid separation (GSS) required in the granule method is not required, and the effective volume of the reaction vessel can be increased and the construction cost can be significantly reduced. There are also advantages.

  However, in the method using a fluid non-biological carrier, microorganisms adhere to the carrier, a biofilm is formed on the surface of the carrier, a reaction that generates gas inside the biofilm proceeds, and the generated gas adheres to the carrier. As a result, there is a problem that the apparent specific gravity of the carrier becomes small, and the carrier floats in the reaction tank and flows out together with the treated water. Such problems can be alleviated by using a carrier having a large specific gravity and a large sedimentation speed. However, in the case of a carrier having an excessively large specific gravity and an excessively large sedimentation speed, the contact efficiency with the water to be treated. However, there is a problem that sufficient processing efficiency cannot be obtained and solid matter accumulates in the sedimentation layer of the settled carrier and the flow path is blocked. On the other hand, when a carrier that does not have such a problem is used It is difficult to avoid the floating and outflow of the carrier due to the generated gas.

  Conventionally, in order to prevent the carrier from floating, a method has been proposed in which the inside of the reaction vessel is stirred with a stirring blade, and bubbles adhering to the carrier are separated and removed by a swirling flow by stirring to recover the sedimentation property of the carrier. In this method, there is a problem of breakage of the carrier due to collision between the stirring blade and the carrier.

  On the other hand, Patent Documents 1 and 2 propose an apparatus in which the floated carrier is extracted from the reaction tank, and the extracted carrier is returned to the reaction tank again by a circulation pipe routed outside the reaction tank.

JP-A-8-117777 JP-A-2-138960

  It is possible to separate and remove bubbles adhering to the carrier in the process of circulating through the circulation pipe by extracting the floated carrier from the reaction tank and circulating it to the reaction tank through the circulation pipe. Thus, in the past, since the sedimentation property of the carrier has not been considered, it has been found that simply circulating the carrier cannot solve the problem of the floating and sticking of the carrier in the reaction tank. In addition, since the relationship between the sedimentation property of the carrier and the circulation means is not taken into account, there is a problem that a complicated mechanism is required for circulation, and the equipment configuration is complicated, so that the burden of maintenance management is large. there were. For example, in Patent Document 1, a complicated recovery, reflux pipe and liquid jet mechanism are provided for circulating the carrier, but such a mechanism cannot be easily attached to an existing reaction tank. It is easy to break down, and maintenance management becomes complicated. Also in Patent Document 2, an ejector mechanism is provided in the circulation pipe of the carrier, but there is a similar problem with such a mechanism.

  The present invention solves the above-mentioned conventional problems, fills a reaction vessel with a non-biological carrier having fluidity, forms a biofilm on the surface of the non-biological carrier, and allows water to be treated to flow under anaerobic conditions. In anaerobic treatment, the carrier in the reaction vessel is prevented from floating and clogging due to sticking, and the sedimentation of the carrier that has floated due to the adhesion of bubbles is effectively recovered by simple means for stable high-load treatment. It is an object of the present invention to provide an anaerobic treatment method and apparatus that can be realized.

  As a result of repeated studies to solve the above-mentioned problems, the present inventors have used a fluid non-biological carrier that satisfies a specific size and settling velocity to prevent the carrier from floating and blocking due to fixation, Moreover, it discovered that the sedimentation property of the support | carrier which floated by bubble adhesion can be easily recovered by a simple means.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] In an anaerobic treatment method in which water to be treated is passed through a reaction tank filled with a fluid non-biological carrier under anaerobic conditions to form a biofilm on the surface of the non-biological carrier to treat the water to be treated. , A non-biological carrier having a size of 1.0 to 5.0 mm and a sedimentation speed of 200 to 500 m / hr is filled in the reaction vessel, and bubbles attached to the carrier contained in the treated water flowing out of the reaction vessel An anaerobic treatment method characterized by returning the carrier to the reaction vessel after separating and removing.

[2] In [1], the treated water containing the carrier that has flowed out of the reaction vessel is circulated in a downward flow through a pipe having a drop of 50 cm or more to separate and remove bubbles attached to the carrier. An anaerobic treatment method.

[3] The anaerobic treatment method according to [1] or [2], wherein the carrier from which the bubbles have been separated and the treated water are separated by a screen or a sedimentation tank and then returned to the reaction tank by a pump. .

[4] In an anaerobic treatment apparatus for treating treated water by passing treated water through a reaction tank filled with a fluid non-biological carrier under anaerobic conditions to form a biofilm on the surface of the non-biological carrier. The size of the carrier filled in the reaction tank is 1.0 to 5.0 mm, the sedimentation speed is 200 to 500 m / hr, and the bubbles attached to the carrier contained in the treated water flowing out from the reaction tank An anaerobic treatment apparatus comprising: means for separating and removing the carrier; and means for returning the carrier from which the bubbles are separated and removed to the reaction tank.

[5] In [4], the means for separating and removing bubbles adhering to the carrier is a pipe having a drop of 50 cm or more through which the treated water containing the carrier that has flowed out of the reaction tank flows in a downward flow. An anaerobic treatment device characterized.

[6] In [4] or [5], the means for returning the carrier from which the bubbles have been separated and removed to the reaction vessel is a screen or precipitate for separating the carrier from which the bubbles have been separated and removed from the treated water. An anaerobic treatment apparatus comprising a tank and a pump for returning the carrier that has passed through the screen or the precipitation tank to the reaction tank.

  According to the present invention, a non-biological carrier having fluidity is filled in a reaction tank, a biofilm is formed on the surface of the non-biological carrier, and the water to be treated is passed under anaerobic conditions for anaerobic treatment. In addition, it is possible to prevent clogging due to floating and sticking of the carrier in the reaction tank, and to effectively recover the sedimentation property of the carrier that has floated due to the adhesion of bubbles by simple means, thereby performing stable high-load processing.

It is a systematic diagram which shows embodiment of the anaerobic processing apparatus of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  The present invention, when water to be treated is passed under anaerobic conditions into a reaction tank filled with a fluid non-biological carrier, a biofilm is formed on the surface of the non-biological carrier, and the water to be treated is anaerobically treated. Using a carrier having a size of 1.0 to 5.0 mm and a sedimentation speed of 200 to 500 m / hr, separating and removing bubbles adhering to the carrier that floated in the reaction tank and flowed out together with the treated water, It returns to this reaction tank, It is characterized by the above-mentioned.

  First, the fluid non-biological carrier used in the present invention will be described.

  The fluid non-biological carrier used in the present invention has a size of 1.0 to 5.0 mm and a sedimentation speed of 200 to 500 m / hr. Here, the size of the carrier and the sedimentation rate refer to the size and the sedimentation rate of the carrier that is filled in the reaction tank and to which no microorganisms or bubbles are attached.

  If the size of the carrier is too large, the surface area per volume of the reaction vessel will be small, and if it is too small, the sedimentation rate will be slow and separation from the treated water will be difficult. The preferred size of the carrier used in the present invention is 2.5 to 4.0 mm.

Here, the size of the carrier is usually referred to as “particle size”. For example, in the case of a rectangular parallelepiped carrier, it indicates the length of the long side, and in the case of a cubic carrier, This refers to the length of one side, and in the case of a cylindrical carrier, the larger one of the diameter and the height of the cylinder. Further, in the case of a carrier having an irregular shape other than these shapes, when the carrier is sandwiched between two parallel plates, the interval between the plates where the interval between the plates becomes the largest is given.
In the present invention, the average size of the carrier may be in the range of 1.0 to 5.0 mm, preferably 2.5 to 4.0 mm. Also good.

  In addition, if the sedimentation rate of the carrier is too small, it is likely to float due to water flow or generated gas. Conversely, if the sedimentation rate of the carrier is too large, the contact efficiency with the water to be treated is deteriorated and sufficient treatment efficiency cannot be obtained. Alternatively, there is a problem that solids accumulate in the deposited layer of the carrier and the flow path is blocked. The preferred sedimentation rate of the carrier used in the present invention is 200 to 500 m / hr.

  Here, the settling speed of the carrier is taken out by immersing the carrier in water (fresh water such as tap water) and taking it out and putting it into a graduated cylinder in water (fresh water such as tap water). It is a value obtained by measuring the sedimentation distance per unit time. In the present invention, 10 to 20 carriers were measured, and the average value was taken as the sedimentation speed.

The carrier used in the present invention is not particularly limited as long as its size and sedimentation rate satisfy the above ranges, and the constituent material of the carrier is not particularly limited. For example, the foaming of the following (I) and / or (II) If it consists of such a resin foam, it is preferable also in the point that adjustment of specific gravity and a particle size is easy.
(I) A foam containing 30 to 95% by weight of a resin component mainly composed of a polyolefin-based resin and 5 to 70% by weight of a hydrophilizing agent for cellulose powder, the surface of which has a melt fracture state ( Hereinafter, it may be referred to as “foam (I)”.
(II) A foam comprising 30 to 95% by weight of a resin component mainly composed of a polyolefin resin, 4 to 69% by weight of a hydrophilizing agent for cellulose powder, and 1 to 30% by weight of an inorganic powder, Has a melt fractured state (hereinafter sometimes referred to as “foam (II)”)

  Here, the melt fracture is generally known as a phenomenon in which irregularities are formed on the surface of a molded product during plastic molding (a state in which there is no smooth surface). For example, in the extrusion molding of plastic material, when the internal pressure of the extruder becomes extremely high, the extrusion speed becomes extremely large, or the temperature of the plastic material becomes too low, irregular irregularities on the surface of the molded product This refers to a phenomenon in which surface gloss or surface gloss is lost.

A preferable melt fracture state of the carrier according to the present invention satisfies the specific surface area ratio represented by the following formula (1).
B / A = 1.5 to 4.0 (1)

Here, A indicates the apparent specific surface area of the foam, and B indicates the actual specific surface area of the foam.
The apparent specific surface area A of the foam indicates a specific surface area in a state where the surface of the foam is smooth, that is, a state where no melt fracture occurs, and the actual specific surface area B indicates a state where the melt fracture occurs. The actual specific surface area at is shown. That is, the value of B / A represented by the above formula (1) indicates the rate of increase in specific surface area due to the occurrence of melt fracture, and those having a B / A of 1 depend on the melt fracture on the surface. It means that there is no unevenness.

  When the value of B / A is less than 1.5, the contact area between the water to be treated and the carrier is small, and thus the treatment capacity is undesirably small. When the value of B / A is larger than 4.0, the melt fracture on the surface is easily scraped by contact between the carriers at the time of use, which is not preferable. As the apparent specific surface area A and the actual specific surface area B, values measured by an automatic specific surface area / pore distribution measuring device (Tristar 3000, manufactured by Shimadzu Corporation) can be used.

  The resin component constituting the foam preferably has a melt flow index of 5 to 25 g / 10 min. If the melt flow index is less than 5 g / 10 min, the fluidity of the resin component is insufficient, so that it is unsuitable for foam molding, and if it exceeds 25 g / 10 min, a phenomenon of crushing during foam molding may occur.

  Here, the melt flow index (hereinafter, sometimes simply abbreviated as “MFI”) is one of the measures for the fluidity of a resin in a molten state, and is defined under a certain pressure and a certain temperature. It is generally known as an index expressed by weight per 10 minutes (unit: g / 10 min) by measuring the amount of resin flowing out from a nozzle (orifice) having dimensions. In the present invention, the value at 230 ° C. and 21.6 N load (DIN 53735) is adopted.

  Preferred resin components constituting the foams (I) and (II) are polyethylene (hereinafter sometimes simply abbreviated as “PE”), polypropylene (hereinafter simply abbreviated as “PP”). ), An ethylene-vinyl acetate copolymer (hereinafter sometimes simply referred to as “EVA”), and the like. These resins may be used alone or as a mixture appropriately combined. Further, the resin component constituting the foams (I) and (II) may be one obtained by adding another thermoplastic resin component to a polyolefin resin. As other thermoplastic resin components, polystyrene (hereinafter sometimes abbreviated as “PS”), polyethylene terephthalate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyurethane, polyamide, polyacetal, polylactic acid, polymethyl methacrylate , ABS resin and the like.

  Polyethylene is particularly preferable as the resin component constituting the foams (I) and (II). However, within the above MFI range, a mixture of PE and other polyolefin resins, for example, PE and PP It may be a mixture, a mixture of PE and EVA, a mixture of PE, PP and EVA, a mixture of PE, PP and PS, a mixture of PE, PP, EVA and PS, or a mixture obtained by further mixing other thermoplastic resins. Specifically, the composition ratio (weight ratio) of other thermoplastic resins including PE, PP, EVA, PS is 100, and other thermoplastic resins including PE: PP: EVA: PS = 100. It is preferable that it becomes -60: 40-0: 20-0: 15-0. In order to improve the wear resistance of the carrier, it is preferable to contain 10% by weight or more of EVA in the resin component. These resin components may be recycled resins.

  On the other hand, examples of the cellulose-based powder as the hydrophilizing agent include wood powder, cellulose powder, hemp cellulose powder, and the like, such as sawdust, avicel, arbocel, paper powder, cellulose beads, microcrystalline cellulose, and microfibrillated cellulose. However, it is particularly preferable to use wood flour. Any of these may be used alone, or two or more of them may be mixed and used in an arbitrary ratio.

  The hydrophilizing agent has a spherical shape, an elliptical shape, a wedge shape, a whisker shape, a fiber shape, and the like, but may have other shapes. The particle size of the hydrophilizing agent is 200 mesh pass product, preferably 100 mesh pass product, more preferably 40 mesh pass product.

  In the present invention, the hydrophilizing agent has a role of imparting a water permeation function to the foam having closed cells. For this purpose, the hydrophilizing agent is desirably exposed or protruded from the surface of the foam. . Here, exposure means that part of the surface of the hydrophilizing agent appears on the foam surface, and protrusion means that part of the hydrophilizing agent protrudes from the foam surface. . That is, being exposed or protruding means that the whole or part of the hydrophilizing agent is buried in the foam and a part of the surface of the hydrophilizing agent appears on the foam surface, or It means a state in which a part of the hydrophilizing agent protrudes from the foam surface.

  Examples of the inorganic powder used for the foam (II) include barium sulfate, calcium carbonate, zeolite, talc, titanium oxide, potassium titanate, and aluminum hydroxide, and barium sulfate is particularly preferable. Any of these inorganic powders may be used alone, or two or more kinds of inorganic powders may be used.

  In the foams (I) and (II), if the ratio of the resin component is larger than the above range and the ratio of the hydrophilizing agent is small, the effect of imparting the water penetration function by using the hydrophilizing agent is not sufficient, It takes a long time to settle in the resin, and conversely, if the proportion of the resin component is less than the upper range and the proportion of the hydrophilizing agent is large, the strength of the carrier is lowered.

  In addition, in the foam (II), the inorganic powder is blended for the purpose of adjusting the core material and the specific gravity during foaming, but further reducing the amount of resin components and hydrophilizing agents to reduce production costs. Is. If the proportion of the inorganic powder is less than the above range, such a blending effect of the inorganic powder cannot be sufficiently obtained, and if it is large, the specific gravity becomes too high.

  As will be described later, the foams (I) and (II) are foamed using a foaming agent. The foaming ratio is 2 to 10 times, and the specific gravity determined from the apparent volume is 0.10 to 0.00. It is preferably 80 g / ml.

  If the expansion ratio of the foams (I) and (II) is smaller than the above lower limit, the specific gravity becomes too large, and a large force is required when flowing in water. On the other hand, if the expansion ratio is larger than the above upper limit, the specific gravity is small, and it tends to float on the water surface, which is not preferable.

  Moreover, even if the specific gravity calculated | required from an apparent volume is smaller or larger than the said minimum, it may become unable to satisfy the sedimentation speed prescribed | regulated by the above-mentioned this invention. Here, the specific gravity determined from the apparent volume of the foam is a value (unit: g / ml) obtained by measuring 30 ml of the foam in an apparent volume in a 50 ml graduated cylinder and calculating from the weight. It shall indicate a substantial specific gravity. This is because the foams (I) and (II) have a melt-lacquered state on the surface, and it is very difficult to measure the true volume. Hereinafter, the specific gravity obtained from the apparent volume of the foam is simply referred to as “specific gravity”.

  Foams (I) and (II) are prepared by melting and kneading the above-mentioned polyolefin resin, hydrophilizing agent, and further inorganic powder, and further foaming a mixture obtained by melting and kneading the foaming agent. It can be manufactured by cutting into a size.

Examples of the foaming agent include sodium bicarbonate (bicarbonate) and azodicarbonamide. A foaming agent is not restricted to these, A chemical foaming agent, a physical foaming agent, etc. are mentioned.
Examples of the chemical foaming agent include azo compounds such as barium azodicarboxylate, nitroso compounds such as N, N-dinitrosopentamethylenetetramine, hydrazine derivatives such as 4,4′-oxybis (benzenesulfonylhydrazide), and semicarbazide. Compounds, azide compounds, triazole compounds, isocyanate compounds, bicarbonates such as sodium bicarbonate, carbonates, nitrites, hydrides, mixtures of sodium bicarbonate and acids (eg sodium bicarbonate and citric acid, etc.), peroxidation Examples thereof include a mixture of hydrogen and an enzyme, a mixture of zinc powder and an acid, and the like. Examples of the physical foaming agent include aliphatic hydrocarbons (eg, butane, pentane, hexane, etc.), chlorinated hydrocarbons (eg, dichloroethane, dichloromethane, etc.), fluorinated chlorohydrocarbons (eg, trichloromono). Fluoromethane, dichlorodifluoromethane, dichloromonofluoromethane, dichlorotetrafluoroethane, etc.), alternative chlorofluorocarbons, air, carbon dioxide, nitrogen gas, water and the like. Among these, it is particularly preferable to use sodium bicarbonate (sodium bicarbonate) from the viewpoint of low decomposition temperature and low cost.

  Furthermore, as the foaming agent, a so-called self-supporting foaming agent (also referred to as an independent foaming agent, microsphere, or thermally expandable microcapsule) can be used. Since this self-supporting foaming agent becomes hollow spherical particles having an outer wall surface by foaming, the resin composition may be extruded in the gas phase (for example, in the air) instead of being extruded and foamed in water. The hollow portion of the foam is maintained without being crushed, and a foam having a desired expansion ratio is obtained. As the self-supporting foaming agent, for example, vinylidene chloride-acrylonitrile copolymer or acrylonitrile-methacrylonitrile copolymer is used as the polymer for the outer wall, and isobutane, isopentane, etc. are used as the volatile liquid contained therein. Is mentioned. Specific examples include EXPANSEL (Nippon Philite Co., Ltd.) and EPD-03 (Eiwa Chemical Industry Co., Ltd.). In addition, in this invention, since water permeate | transmits also to the foam by a self-supporting foaming agent by presence of the hydrophilizing agent of a cellulose powder, the obtained foam becomes the thing excellent in water permeability.

  These foaming agents may be used alone or in combination of two or more. In order to obtain the above-mentioned preferable expansion ratio, the foaming agent is 100 parts by weight of the polyolefin resin and the hydrophilizing agent in the foam (I), and the polyolefin resin and the hydrophilic in the foam (II). It is preferably used in a ratio of 0.5 to 8 parts by weight with respect to a total of 100 parts by weight of the agent and the inorganic powder.

  When anaerobic treatment is performed by filling a reaction vessel with a non-biological carrier having a size of 1.0 to 5.0 mm and a sedimentation speed of 200 to 500 m / hr as described above, the carrier usually floats in large quantities. However, when there is a large load fluctuation, fine bubbles adhere to the surface of the carrier, and the apparent specific gravity is reduced, so that the carrier floats up and flows out of the reaction tank together with the treated water. May end up.

  In the present invention, air bubbles floating on the reaction tank and flowing out of the reaction tank together with the treated water are separated and removed, and after the sedimentation property of the support has been recovered, it is returned to the reaction tank.

Although there is no restriction | limiting in particular as this bubble separation / removal method, For example, the following methods are employable.
(1) By flowing the treated water containing the carrier in a downward flow through a pipe having a drop of 50 cm or more (hereinafter sometimes referred to as “bubble separation pipe”), bubbles are generated using the drop of the water flow. Remove.
(2) The treated water containing the carrier is introduced into the water tank provided with the screen, and the bubbles are removed by the effect of the water flow, bubbles for cleaning the screen, and the like. That is, since an aeration device for cleaning is provided at the lower part of the screen, bubbles can be removed by this aeration airflow.

  Among these, since the bubbles can be efficiently separated and removed with a simple configuration, it is preferable to employ the method using the bubble separation pipe (1).

  In the method of (1) above, the bubble separation pipe is a pipe having a height difference of 50 cm or more in the vertical direction, and has a horizontal portion in the middle or has a slight inclination with respect to the vertical direction. However, from the viewpoint of the efficiency of separating and removing bubbles, the inclination of the bubble separation pipe with respect to the vertical direction is preferably 30 ° or less, and is preferably a straight tube without a horizontal portion or the like.

  In addition, if the drop of the bubble separation pipe is excessively small, the bubbles cannot be sufficiently separated and removed. If the drop is excessively large, the circumference of the pipe is excessively large, and is about 50 to 500 cm, particularly about 100 to 200 cm. Is preferred.

  Also, if the cross-sectional area of the bubble separation pipe is too small, it is difficult to circulate the treated water containing the carrier smoothly, but if the cross-sectional area is too large, the downward flow having a high effect of separating and removing bubbles in the pipe The cross-sectional area of this pipe varies depending on the amount of treated water to be circulated, but it is preferable to have a nominal diameter of about 150A to 500A. In particular, it is preferable that the size of the treated water containing the carrier flows down at a flow rate of 0.5 to 3 m / sec.

  The carrier having a specific size and settling velocity used in the present invention recovers the settling property by falling off the bubbles while flowing down such a bubble separation pipe, and flows down and settles at a higher rate, An even higher bubble separation and removal effect can be obtained.

  The carrier from which bubbles have been separated and removed in this manner is returned to the reaction tank. At that time, it is preferable in terms of water treatment efficiency to separate the treated water and return the water having a high carrier concentration to the reaction tank. .

  Therefore, the treated water containing the carrier from which bubbles have been separated and removed is preferably subjected to solid-liquid separation with a screen or a precipitation tank (such as a tank provided with an inclined surface), and the treated water having an increased carrier concentration is returned to the reaction tank. The carrier used in the present invention itself has a relatively high sedimentation speed. Therefore, the carrier from which bubbles are removed can immediately settle and can be easily concentrated by a solid-liquid separation means having a simple structure.

  The return of the carrier to the reaction vessel can be smoothly performed by pumping. Although there is no restriction | limiting in particular in the kind of pump used for transfer of a support | carrier, Since the support | carrier to be transferred is harder than sludge, it can be returned using the pump which can transfer the water containing a granular solid.

  When processing such as separation and removal of bubbles, solid-liquid separation, and pump transfer is performed on granule, which is granulated sludge, there is a problem of granule disintegration and dispersion. Without causing such problems, separation and removal of bubbles, solid-liquid separation, and pump transfer can be performed.

  In addition, in order to smoothly pump the treated water containing the carrier while suppressing the amount of treated water returned to the reaction tank, the carrier concentration in the water returned to the reaction tank is about 1 to 30% as a volume%. It is preferable.

  In the present invention, the water to be treated may be any liquid containing an organic substance that can be treated by anaerobic treatment by contacting with anaerobic microorganisms, and the composition and concentration are not particularly limited.

The COD concentration of the water to be treated is not particularly limited, but as described above, the anaerobic treatment using a carrier is a low-concentration wastewater that is difficult to apply to treatment using granules such as the UASB method and the EGSB method. Since particularly excellent effects are exhibited in the treatment, the water to be treated in the present invention is effective for the treatment of low-concentration wastewater having a COD _Cr concentration of 2000 mg / L or less, for example, 500 to 2000 mg / L.
Such wastewater includes, but is not limited to, manufacturing wastewater from food factories, organic wastewater from chemical factories, general sewage, and the like.

  When polymer components such as sugar and protein are contained in the water to be treated, as a pretreatment means for a reaction tank filled with a fluid non-biological carrier, as in the anaerobic treatment apparatus shown in FIG. You may provide the acid generation tank which decomposes | disassembles a molecule | numerator into low molecular organic acids, such as an acetic acid and propionic acid.

In this case, the treatment conditions of the acid generation tank vary depending on the conditions such as biodegradability of the water to be treated, but the pH is 5 to 8, preferably 5.5 to 7.0, and the temperature is 20 to 40 ° C., preferably 25 to 25 ° C. A temperature of 35 ° C. and HRT of 2 to 24 hours, preferably 2 to 8 hours is suitable.
When the molecular weight reduction is sufficiently advanced by such an acid generation tank, the treatment in the reaction tank filled with the fluid nonbiological carrier in the subsequent stage proceeds well.

  In the case of wastewater containing only compounds that can be directly used by methanogenic bacteria such as methanol and acetic acid, there is no need for an acid generator tank, and the treated water is directly passed through a reaction tank filled with a fluid non-biological carrier. Can do.

In the present invention, the reaction tank filled with the above-described fluid non-biological carrier and into which the water to be treated is passed is a fully mixed reaction tank using a stirrer or the like, an upward mixing in the tank with water flow and generated gas. Although a flow-type reaction tank or the like can be used, it is preferable to use an upward flow-type reaction tank because the height and shape of the reaction tank can be freely set and a large amount of carrier can be charged. As described above, in the method using a carrier, a gas-solid-liquid separation mechanism (GSS) such as a granule method is not required. For example, even in an upward flow type reaction tank with a water depth of about 5 m, the tank load is 15 to 20 kg-COD. _Cr / m ³ / day or higher load processing can be performed.

  The processing conditions in the complete mixing type reaction tank and the upward flow type reaction tank are not particularly limited as long as desired processing efficiency can be obtained. For example, the following conditions can be set.

<Completely mixed reaction tank>
Carrier filling rate: 10-30%
HRT: 1.0-24 hr
Tank load: 4.0 to 12.0 kg-COD _Cr / m ³ / day
Sludge _{load: 0.8~3.0kg-COD Cr / kg-} VSS / day
pH: 6.5-7.5
Temperature: 25-38 ° C
<Upward flow reactor>
Carrier filling rate: 10-80%
HRT: 1.0-24 hr
Ascending flow velocity (LV): 1.0 to 20 m / h
Tank load: 4.0 to 32 kg-COD _Cr / m ³ / day
Sludge _{load: 0.8~3.0kg-COD Cr / kg-} VSS / day
pH: 6.5-7.5
Temperature: 25-38 ° C

  Hereinafter, an example of the anaerobic treatment apparatus of the present invention will be described with reference to FIG. 1, but the anaerobic treatment apparatus of the present invention is not limited to that shown in FIG.

This anaerobic treatment apparatus treats water to be treated (raw water) in the acid generation tank 1, then feeds it to the pH adjustment tank 2 to adjust the pH, and the pH-adjusted water is supplied to the fluid abiotic carrier 4 by the pump P _1. The water is treated by passing water upward in the reaction tank 3 filled with the above. On the upper side wall of the reaction tank 3, there is provided an outflow pipe 5A for extracting the treated water in the reaction tank 3 together with the carrier that has floated, and a bubble separation pipe 5 having a drop of 50 cm or more is vertically connected to the outflow pipe 5A. Has been.
The outlet side of the bubble separation pipe 5 opens into the treated water tank 6 whose bottom surface is inclined. 6A is a screen. The treated water containing the floating carrier flowing out from the reaction tank 3 flows down the bubble separation pipe 5 through the outflow pipe 5A, and is then fed to the treated water tank 6 having the screen 6A. The carrier in the treated water that has flowed out of the reaction tank 3 recovers its sedimentation by separating and removing bubbles while flowing down the bubble separation pipe 5, and quickly settles in the treated water tank 6. A part of the permeated water of the screen 6 </ b> A of the treated water tank 6 is discharged out of the system as treated water, and the remainder is circulated to the acid generation tank 1. Meanwhile, the carrier of sediment in the process water tank 6 is returned to the reaction vessel 4 with the treated water by a pump P _2. 1A and 2A are pH meters. In FIG. 1, the screen 6A is provided inside the treated water tank 6. However, a screen box (not shown) is provided in the middle of the outflow pipe 5A to separate the carrier and return it to the reaction tank 3. The water tank can be omitted.

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

[Example 1, Comparative Examples 1 and 2]
Using the anaerobic treatment apparatus shown in FIG. 1, a water flow test was conducted using synthetic wastewater (COD _Cr concentration: 2000 mg / L, pH 7.0) mainly composed of sugar and protein as raw water.
The anaerobic treatment apparatus, after processing the raw water with acid production tank 1, and pH adjusted fed to pH adjustment tank (volume 0.5 L) 2, flowable non-biological carrier pH adjusted water by a pump P ₁ 4 is passed through the reaction tank 3 filled with 4 in an upward flow. The effluent water from the reaction tank 3 flows down the bubble separation pipe 5 and then is fed to the treated water tank 6 having a screen 6A. From the reaction tank 3, the carrier floating in the reaction tank 3 flows out together with the treated water, but the carrier in the effluent water is recovered by settling by removing the bubbles while flowing down the bubble separation pipe 5. Then, it settles quickly in the treated water tank 6. A part of the permeated water of the screen 6 </ b> A of the treated water tank 6 is discharged out of the system as treated water, and the remainder is circulated to the acid generation tank 1. Meanwhile, the carrier of sediment in the process water tank 6 is returned to the reaction vessel 4 with the treated water by a pump P _2.

The processing conditions of the acid generation tank 1 and the reaction tank 3 were as follows.
<Acid production tank>
Capacity: 200L
HRT: 2.0 hr
pH: 6.5
Temperature: 30 ° C

<Reaction tank>
Capacity: Approximately 400L
HRT: 6.0 hr
Ascending flow velocity (LV): 10 m / hr
pH: 7.0
Carrier filling rate: 40%

The specifications and conditions of the bubble separation pipe 5 are as follows.
<Bubble separation piping>
Head (vertical length): 50cm
Diameter: 15cm
Cross-sectional area: 177 cm ²
Bubble separation pipe flow velocity (LV): 1.0 m / hr

  Further, the carrier concentration in the treated water returned from the treated water tank 6 to the reaction tank 4 was 1.0 to 10.0%.

As the carrier to be filled in the reaction tank, a polyolefin resin carrier having the size shown in Table 1 (the height of the cylinder) and the sedimentation speed is used, and dispersed anaerobic sludge is used as seed sludge at the start of the treatment. The reaction vessel 3 was charged. Moreover, the COD _Cr density | concentration of the obtained treated water was measured from the start of water flow of raw | natural water, and the process which raises a load gradually was performed on the conditions used as the treated water COD _Cr density | concentration of 200 mg / L or less.

  The results of each treatment are shown in Table 1.

  From the above results, according to the present invention, in the anaerobic treatment using a non-biological carrier, even when a phenomenon occurs in which the carrier floats and flows out due to the attachment of fine bubbles, the specific size and sedimentation occur. A non-biological carrier with a high speed is used to settle by removing bubbles adhering to the surface of the carrier that has flowed out of the reaction tank, separated from the treated water, and then returned to the reaction tank using a pump. It can be seen that stable processing can be performed.

DESCRIPTION OF SYMBOLS 1 Acid production tank 2 pH adjustment tank 3 Reaction tank 4 Fluid non-biological carrier 5 Bubble separation piping 6 Treated water tank

Claims (6)

In an anaerobic treatment method of treating water to be treated by passing water to be treated into a reaction tank filled with a fluid non-biological carrier under anaerobic conditions, forming a biofilm on the surface of the non-biological carrier,
A non-biological carrier having a size of 1.0 to 5.0 mm and a sedimentation speed of 200 to 500 m / hr is charged into the reaction vessel,
An anaerobic treatment method comprising separating and removing bubbles attached to the carrier contained in the treated water flowing out of the reaction tank, and then returning the carrier to the reaction tank.   The anaerobic material according to claim 1, wherein the treated water containing the carrier that has flowed out of the reaction tank is circulated in a downward flow through a pipe having a drop of 50 cm or more to separate and remove bubbles attached to the carrier. Sex processing method.   3. The anaerobic treatment method according to claim 1, wherein the carrier from which the bubbles have been separated and the treated water are separated by a screen or a sedimentation tank, and then returned to the reaction tank by a pump. In an anaerobic treatment apparatus for treating water to be treated by passing water to be treated into a reaction tank filled with a fluid non-biological carrier under anaerobic conditions and forming a biofilm on the surface of the non-biological carrier.
The size of the carrier filled in the reaction tank is 1.0 to 5.0 mm, the sedimentation speed is 200 to 500 m / hr,
Anaerobic, characterized by having means for separating and removing bubbles attached to the carrier contained in the treated water flowing out of the reaction tank, and means for returning the carrier from which the bubbles have been separated and removed to the reaction tank Processing equipment.   5. The means for separating and removing bubbles adhering to the carrier according to claim 4, wherein the treated water containing the carrier that has flowed out of the reaction tank is a pipe having a drop of 50 cm or more that flows in a downward flow. Anaerobic treatment device.   The means for returning the carrier from which the bubbles have been separated and removed to the reaction tank according to claim 4 or 5, a screen or a precipitation tank for separating the carrier from which the bubbles have been separated and removed from the treated water, and the screen Or an anaerobic treatment apparatus comprising a pump for returning the carrier that has passed through the precipitation tank to the reaction tank.

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