JP2008279385A - Anaerobic treatment method and anaerobic treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably enable a high load and rate anaerobic treatment by preventing a granule sludge from collapsing under the condition of generating the collapse of the granule sludge. <P>SOLUTION: An anaerobic treatment is carried out in a reaction vessel 20 holding the granule sludge by adding a carbohydrate such as starch and the like to a wastewater having a high methanol concentration and a large bias of a substrate such as an evaporated water condensate exhausted from a pulp industry process. It is recommended that the starch is gelatinized, and added particularly in the liquid state to the reaction vessel 20 or a treatment liquid path 31 so as to be supplied to the whole granule sludge in the reaction vessel 20 as uniformly as possible. The addition of the starch allows the proliferation of microorganisms having a high capability of producing a viscous material in the granule sludge so that the strength of the granule sludge can be maintained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an anaerobic biological treatment method and anaerobic treatment apparatus for methane fermentation of organic matter-containing water, and in particular, anaerobic biological treatment by introducing organic matter-containing water into a reaction vessel holding granule sludge. The present invention relates to a biological treatment method and apparatus.

  UASB (Upflow Anaerobic Sludge Blanket) method is known as an anaerobic treatment method for waste liquids containing organic substances, which uses high-density, high-sediment granule sludge and high-load high-speed treatment. ing. In UASB, organic substance-containing water is introduced into a reaction tank holding a sludge blanket formed of granule sludge, and the mixture is brought into contact with the sludge blanket by flowing upward. In this method, in order to perform high-load and high-speed treatment, when organic material-containing water contains solid organic matter having a low digestion rate, this is separated, and soluble organic matter having a high digestion rate is anaerobically biotreated with granule sludge. . An EGSB method that develops the UASB method and allows high-load, high-speed treatment to pass through the organic substance-containing water at a higher flow rate in a high-height reaction tank and develops the sludge blanket at a high development rate. (Expanded Granule Sludge Blanket) is also known.

  In these UASB method and EGSB method, granular sludge in which anaerobic microorganisms are granulated is used, and sludge containing anaerobic microorganisms is maintained and propagated in the form of granules (grains). The biological treatment method using granular sludge can be operated at a high load because a high sludge retention concentration can be obtained as compared with a fixed bed or fluidized bed in which microorganisms are held on a carrier. In addition, granule sludge has a high microbial density and is excellent in sedimentation, so that solid-liquid separation is easy. In addition, if the granular sludge in the reaction tank that is already in operation is extracted as excess sludge and put into the newly installed reaction tank, the newly installed reaction tank can be started up in a short period of time, and stable treatment can be performed. It is recognized as an anaerobic treatment method.

  In the UASB method or the like using granular sludge, the greatest point of stably and satisfactorily treating organic substance-containing water is to maintain and propagate the granular sludge. If granule sludge cannot be maintained and propagated in the reaction tank, the treatment performance gradually decreases and may eventually become untreatable.

  Granule sludge is a kind of ecosystem in which acetic acid-assimilating microorganisms belonging to the genus Methanosaeta (formerly Methanothrix) are formed as a skeleton, and hydrogen-utilizing methane bacteria, acetic acid-producing bacteria, acid-producing bacteria, etc. coexist. Is configured. Among these microorganisms, acid-producing bacteria degrade sugars, lipids, proteins, and the like, and produce mucilage, thereby strengthening the binding force between bacteria. Therefore, the strongest granular sludge is formed by using a culture solution of a sugar substrate.

  Since organic matter-containing water such as general sewage and industrial wastewater contains carbohydrates and other high-molecular organic matter, acid-producing bacteria grow when anaerobically treated. In the process of anaerobic treatment, the above-mentioned microorganisms other than acid-producing bacteria also grow to produce organic acids, which are successively reduced in molecular weight to acetic acid, and further decomposed into methane and carbon dioxide. Under conditions in which acid-producing bacteria grow, the various microorganisms that grow by participating in the series of anaerobic treatments are bound together by mucilage to form a granular sludge with high strength. Therefore, granule sludge can be formed spontaneously by passing an ordinary organic substance-containing water in an upward flow and performing anaerobic treatment.

  However, unlike such normal organic substance-containing water, if the liquid to be treated with a low substrate concentration of acid-producing bacteria, for example, the liquid to be treated containing a lower organic substance having 4 or less carbon atoms discharged from a chemical factory or the like, granule sludge is treated. Is prone to collapse. In particular, when treating a liquid to be treated containing an organic substance having 2 or less carbon atoms such as acetic acid, ethanol, or acetaldehyde as a main component (about 70 to 90% by mass of the total organic substance), the genus Methanosarcina is a microorganism that mainly grows.

  The bacteria of the genus Methanosaeta, Methanosarcina, and Methanobacterium are less likely to form granule sludge, and the production of mucilage in sludge is reduced, so that the growth of granule sludge is not good and the strength is insufficient. For this reason, if such organic substance-containing water is used for a long period of time and the operation is continued for a long time, the granular sludge is disassembled to reduce the particle size, and the amount of sludge in the reaction tank is reduced.

  In particular, when treating a substrate having 1 carbon atom, specifically, a liquid to be treated mainly containing methanol, formic acid, formaldehyde, etc., the above Methanosaeta genus cannot assimilate these substrates. Methanobacterium methane bacteria grow and become more difficult to granulate. For example, when a UASB type treatment apparatus is operated continuously for a long time using methanol as a single substrate, the granular sludge is disassembled and refined to drastically reduce the amount of sludge. For this reason, it has been difficult to anaerobically treat the liquid to be treated mainly composed of low-molecular organic substances as described above with granular sludge.

By the way, at the time of start-up of anaerobic treatment using granular sludge such as UASB, a treatment method characterized by supplying acetic acid or a substance that generates acetic acid at the time of start-up has been proposed (for example, Patent Document 1). ). The method disclosed in Patent Document 1 gives acetic acid or a substrate for producing acetic acid when starting up an apparatus for treating organic substance-containing water which is difficult to granulate as described above, and predominates the methanogenic bacteria of the genus Methanothrix. It is a method that attempts to grow granulated sludge in a short period of time.
Japanese Patent No. 2563004

  However, since the genus Methanothrix cannot use low molecular weight compounds as substrates, after starting anaerobic treatment using granulated sludge by the method disclosed in Patent Document 1, when the acetic acid input is stopped, the genus Methanosarcina and the genus Methanobacterium gradually The disadvantage is that the methane bacteria grow and granule dismantling begins.

  On the other hand, this invention tries to maintain granule sludge by making the inside of a reaction tank into the conditions where the microorganisms which contribute to maintenance of granule sludge grow. Accordingly, it is an object of the present invention to provide an anaerobic treatment method and an anaerobic treatment apparatus capable of stably and efficiently performing an anaerobic treatment even when the treatment is performed under the condition that the granular sludge is easily disintegrated.

  The present invention provides the following.

(1) In a method of introducing an treatment liquid into a reaction tank holding granule sludge and performing anaerobic treatment by bringing it into contact with the granule sludge, the content of organic matter having 4 or less carbon atoms in the treatment liquid is all When the organic matter content is 70% by mass or more, when the liquid to be treated contains one or more agents selected from the group consisting of a chelating agent, a scale dispersant, and a bactericidal agent, or the sludge load to the reaction tank is 0. When 3 kg CODcr / kg-Vss / d exceeds or the rising flow velocity in the reaction tank exceeds 1 m / h, a saccharide is added to the reaction tank or the liquid to be treated and the liquid to be treated is brought into contact with the granular sludge. An anaerobic treatment method in which anaerobic treatment is performed.
(2) The anaerobic treatment method according to (1), wherein the liquid to be treated is evaporated condensed water discharged in a pulp manufacturing process.
(3) The anaerobic treatment method according to (1) or (2), wherein the sugar is starch.
(4) The anaerobic treatment method according to (3), wherein pregelatinized starch is added as the carbohydrate.
(5) The anaerobic treatment method according to (3) or (4), wherein the starch is added such that the added amount of the starch is 0.02 to 0.2 as the CODcr ratio with respect to the CODcr concentration of the liquid to be treated. .
(6) The anaerobic treatment method according to any one of (1) to (5), wherein an anaerobic treatment is performed while supplying a flocculant into the reaction tank.
(7) The liquid to be treated is evaporated condensed water discharged in the pulp manufacturing process, and the concentration after addition of nitric acid or nitrous acid to the reaction tank or the liquid to be treated is 1 to 1000 mg / L. The anaerobic treatment method according to any one of (3) to (6), wherein the anaerobic treatment is performed by adding to the solution.

  In the case where anaerobic treatment is performed by introducing organic substance-containing water into a reaction tank in which granule sludge is held, the present invention prevents the granule sludge from collapsing, and a certain amount or more of the granular sludge is added to the reaction tank. TECHNICAL FIELD The present invention relates to an anaerobic treatment method and apparatus for stably holding in a long term. In other words, the present invention grows granulated sludge from the granular sludge already held in the reaction vessel. The collapse of granule sludge refers to a phenomenon in which granule sludge that has already been formed collapses during anaerobic treatment.

  As described above, when a certain type of industrial wastewater, which is an anaerobic treatment method using granule sludge, is treated, the granule sludge may collapse as the treatment time elapses. Examples of such waste water include evaporative condensed water (evaporation condenser) discharged in the pulp manufacturing process. Evaporated condensed water is organic matter-containing water mainly composed of methanol, and methanol accounts for 70% by mass or more, usually about 90% by mass of the total CODcr component.

  For this reason, when evaporative condensate is treated anaerobically using granular sludge, microorganisms of the genus Methanosarcina and Methanobacterium that grow using methanol as a substrate grow rapidly, leading to the collapse of the granular sludge. In particular, water containing a small amount of protein (e.g., 10% by mass or less of the total CODcr) like evaporative condensed water tends to cause a bias in the microbial community constituting the granule sludge. The present invention can be particularly suitably applied to the case where a liquid to be treated that tends to cause a bias in the constituent microbial species of granule sludge is treated.

  In the present invention, a saccharide is added to the reaction tank or to the liquid to be treated which is introduced into the reaction tank at the time of treatment under conditions that cause the granule sludge to collapse. As the saccharide, starch is preferable, and it may be added together with the flocculant. Moreover, it is also preferable that starch is gelatinized (alpha-ized) and added as a liquid.

  According to the present invention, the granule sludge can be prevented from collapsing. Therefore, the high-load high-speed treatment using the organic substance-containing water, which has conventionally been difficult to maintain and multiply the granular sludge, can be stably continued over a long period of time.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of an anaerobic treatment apparatus (hereinafter simply referred to as “treatment apparatus”) 1 of organic substance-containing water according to a first embodiment of the present invention. The processing apparatus 1 includes nitric acid / nitrous acid addition means and a reaction tank 20. Here, the nitric acid / nitrous acid addition means is configured as equipment for adding nitrous acid, and includes a nitric acid storage tank 11 and a nitric acid addition path 12. Connected to the reaction tank 20 are a treatment liquid path 31 into which organic substance-containing water as a treatment liquid is introduced, a treatment liquid path 32 from which the treated liquid is taken out, and a gas path 33 through which the generated gas is taken out. Yes.

  The reaction tank 20 is filled with granular sludge. The liquid path 31 to be treated is connected to the lower part of the reaction tank 20. The organic substance-containing water is introduced into the reaction tank 20 by a pump P provided in the liquid passage 31 to be treated and flows through the reaction tank 20 in an upward flow. In addition, a gas-solid-liquid separator (GSS) is provided in the upper part of the reaction tank 20. The top of the GSS protrudes from the liquid level in the reaction vessel 20. The gas path 33 is connected to the upper part of the reaction tank 20. The processing liquid path 32 communicates with the inside of the GSS.

  In the reaction tank 20, the inside of the GSS is a gas-solid separation part, and the lower part thereof is a reaction part 22 where the granular sludge is developed. In the reaction part 22, the granular sludge is developed to form a sludge blanket 24. Granule sludge is sludge in which anaerobic microorganisms are self-granulated into granules having an average particle size of about 0.5 to 1.0 mm, and the density is about 1.02 to 1.1 kg / L. There is excellent sedimentation. The liquid in the reaction unit 22 is gas-solid-liquid separated inside the GSS, and the treatment liquid separated from the granular sludge is taken out from the treatment liquid path 32.

  As described above, in the processing apparatus 1, the organic sludge blanket 24 is formed by causing the organic sludge to flow through the reaction tank 20 that holds the granule sludge in an upward flow to develop the granule sludge. As a result, the contact efficiency between the organic substance-containing water and the granule sludge is increased. Therefore, in the UASB in which a sludge blanket having a height of about 3 to 5 m is developed in a reaction tank having a height of about 5 to 7 m, the sludge load is 0.1. High load high speed processing of about 0.7 kg-CODcr / kg-VSS / d and an ascending flow rate in the reaction tank of about 0.3 to 1.5 m / h is possible. In EGSB where a sludge blanket with a height of about 5 to 18 m is deployed in a reaction tank with a height of about 7 to 20 m, a sludge load of 0.1 to 1.0 kg-CODcr / kg-VSS / d, an increase in the reaction tank The flow rate can be about 3 to 10 m / h.

The organic substance-containing water introduced into the reaction tank 20 has an organic substance concentration of CODcr of 500 to 30,000 mg / L, preferably 1,000 to 20,000 mg / L. Moreover, the organic substance load with respect to the reaction tank 20 is 5-30 kg-CODcr / m < ³ > / d, Especially 8-20 kg-CODcr / m < ³ > / d is preferable. Moreover, it is preferable to set it as anaerobic conditions without supplying oxygen in the reaction tank 20, and to make temperature into 25-40 degreeC, especially 30-38 degreeC.

  Prior to performing the anaerobic treatment according to the present invention, about 20 to 50% of the granular sludge having the above properties is retained in the reaction tank 20 per reaction tank volume. Granule sludge can be formed spontaneously by anaerobic treatment of the liquid to be treated, and promotes self-granulation by adding a flocculant etc. to the reaction tank holding floating anaerobic sludge. The floating sludge can be self-granulated. However, it takes time to form naturally occurring granular sludge. Moreover, when a flocculant is added and floating sludge is granulated, the density of the formed granular sludge may become low.

  On the other hand, if the granular sludge discharged as surplus sludge from the existing UASB or EGSB type reaction tank is filled in the reaction tank and the organic substance-containing water containing the substrate for growing the granular sludge is supplied, The reaction tank can be started up in a short time (that is, a reaction tank holding a necessary amount of granular sludge can be obtained). This is because granule sludge grows in the reaction tank and is crushed by the flow of water and gas generated in the reaction tank. It is said that sludge is formed.

  In order to perform a stable treatment with UASB, granule sludge having an average particle size of 0.5 to 3.0 mm, preferably about 0.8 to 1.5 mm, and the sludge blanket 24 described above are provided in the reaction tank 20. Maintain to form. In the case of EGSB, it is necessary to stably hold granular sludge having an average particle diameter of 0.5 to 3.0 mm, preferably about 1.0 to 1.5 mm, in the reaction tank 20.

  Here, the to-be-processed liquid introduce | transduced into the reaction tank 20 should just be a liquid containing the organic substance which can be processed by making it contact with a granular sludge and performing an anaerobic process. However, depending on the properties of the liquid to be treated and the operating conditions of the reaction tank 20, the granular sludge may collapse while the treatment is continued, and the retained amount of granular sludge in the reaction tank 20 may decrease.

  The present invention is used for the treatment of the liquid to be treated, in which the granular sludge is easily broken, or for the treatment under the operating conditions. As the liquid to be treated in which granule sludge is easy to disintegrate, organic substance-containing water having a low content of organic substances (organic substances having 5 or more carbon atoms such as sugars, fats, proteins, etc.) which are substrates of acid-producing bacteria, such as acid-producing bacteria Organic substance-containing water whose content of the substrate is 30% by mass or less, particularly 20% by mass or less of the total organic substances. Specifically, a liquid to be treated mainly containing lower organic substances (for example, 70% by mass or more, particularly 80% by mass or more of the whole organic substances) can be mentioned. Here, examples of the lower organic substance include organic substances having 4 or less carbon atoms, particularly 2 or less carbon atoms, and the more sludge containing the organic substances having a smaller carbon number, the more easily the granular sludge collapses.

  For example, a waste liquid (evaporated condensed water or evaporator / condensate) discharged by distillation to reuse a cooking liquid obtained by digesting pulp into an alkaline solution has a CODcr of 2,000 to 3,000 mg. There are about / L. And most (approximately 80-90 mass%) is methanol, and the content of the organic substance having 5 or more carbon atoms that serves as a substrate for acid-producing bacteria is about 10-20 mass%. In the present invention, such a liquid to be treated is a particularly suitable treatment target.

  Even if the substrate for acid-producing bacteria is sufficiently present in the liquid to be treated, the granule sludge will disintegrate if the liquid to be treated contains a chelating agent, a scale dispersant, or a bactericidal agent. In this case, the method of the present invention is preferably applied. In particular, when a chelating agent such as EDTA (ethylenediaminetetraacetic acid) or NTA (nitrile triacetic acid) is contained in the liquid to be treated at a concentration of 3 mg / L or more, the granular sludge is likely to collapse. Moreover, dithiocarbamate especially as a disinfectant tends to disintegrate granular sludge.

  Furthermore, even if the liquid to be treated itself has no cause for causing the granular sludge to collapse, the granular sludge may be easily broken depending on the processing conditions. Examples of such a case include a case where the sludge load is high and the liquid passing speed is high.

  For example, in the case of the UASB type, the sludge load is preferably 0.2 to 0.6 kg CODcr / kg-Vss / d, and the rising flow rate is preferably 0.5 to 1.0 m / h. Is more than 0.6 kgCODcr / kg-Vss / d, or when the ascending flow rate exceeds 1 m / h, the granular sludge tends to collapse. Further, in the case of the EGSB system, the sludge load is preferably 0.2 to 0.7 kg CODcr / kg-Vss / d, the rising flow rate is preferably 2 to 5 m / h, and the sludge load is 0.7 kg CODcr / kg-Vss / d. When the ascending flow rate exceeds 5 m / h, the granular sludge tends to collapse.

  Therefore, in the case of treating the liquid to be treated having the above properties, or when the liquid to be treated is treated under the above-mentioned conditions, the present invention is applied, and a saccharide, specifically starch is added to the reaction tank 20 or in the liquid to be treated. An anaerobic treatment may be performed by adding. Hereinafter, a case where starch is pregelatinized and added to the liquid to be treated and introduced into the reaction tank 20 will be described as an example.

  However, the present invention can be carried out in other modes. For example, starch may be added to the liquid to be treated in a powder form without being pregelatinized or simply dissolved in water. Moreover, you may add starch directly to the reaction tank 20 instead of adding to a to-be-processed liquid. Furthermore, when pH adjustment is provided in the previous stage of the reaction tank 20, starch may be added to the pH adjustment tank.

  In the processing apparatus 1, the tip of the starch addition path 12 is connected to the liquid path 31 to be processed. The base end of the starch addition path 12 is connected to the starch storage tank 11 so that the pregelatinized liquid starch in the starch storage tank 11 is added to the liquid path 31 to be treated. A valve V is provided in the middle of the starch addition path 12. By opening and closing the valve V, the amount and timing of starch addition are adjusted.

  The starch solution is added to the liquid to be treated, and is brought into contact with the granular sludge in a uniformly dissolved state. The amount of starch added is preferably in a range where the ratio of CODcr to the CODcr concentration of the liquid to be treated is 0.02 to 0.2. As a method of adding the pregelatinized starch, for example, the pregelatinized starch powder may be dissolved in water and added to the liquid to be treated as a starch liquid, and the pregelatinized starch powder may be added to the liquid to be treated. It may be added directly to. Alternatively, starch that has not been pregelatinized may be used as a liquid in which starch has been pregelatinized by mixing it with water and heating or making it alkaline. Since the pregelatinized starch is excellent in solubility and easily spreads uniformly in the reaction tank, the supply of starch to the granule sludge is prevented from being partially biased and contributes to an improvement in the effect of preventing the granule sludge from collapsing.

  Further, the addition of a flocculant with starch regardless of the presence or absence of pregelatinization can further enhance the effect of preventing the granular sludge from collapsing. FIG. 2 shows an anaerobic treatment apparatus 2 of organic substance-containing water according to the second embodiment of the present invention. The processing apparatus 2 further includes a flocculant path 42 having a tip connected to the middle of the liquid path 31 to be treated and a flocculant storage tank 41 to which the base end of the flocculant path 42 is connected. Thereby, the to-be-processed liquid which contains a flocculant in addition to starch is introduce | transduced in the reaction tank 20. FIG.

  The flocculant increases the strength of the granular sludge by adhering to the surface of the granular sludge in the reaction tank 20. The kind of the flocculant to be added is not limited, and those suitable for the processing system such as nonionic, cationic, anionic and amphoteric can be used. Preferred examples of the polymer flocculant include polyacrylamide and polyethylene oxide as nonionic flocculants. Examples of the cationic system include polyaminoalkyl methacrylate, polyethyleneimine, halogenated polydiallylammonium, chitosan, and urea-formalin resin. Examples of the anionic system include sodium polyacrylate, polyacrylamide partial hydrolyzate, partially sulfomethylated polyacrylamide, poly (2-acrylamide) -2-methylpropane sulfate, and the amphoteric system includes acrylamide and aminoalkyl methacrylate. Examples include sodium acrylate copolymer. In the case of a polymer flocculant, the addition concentration of the flocculant is preferably about 0.01 to 2 mg / l, particularly about 0.01 to 1 mg / l.

  Thus, the strength of the granular sludge can be increased more reliably by the liquid in the reaction tank 20 further containing a flocculant. In the present invention, the amount of the flocculant added may be small because a viscous substance is produced by adding a microorganism using starch as a substrate to the granule sludge. The flocculant may be added continuously, but may be added intermittently. Further, the flocculant may be added before or after the starch.

  Alternatively, instead of or in addition to the flocculant, nitric acid or nitrous acid may be added to the addition reaction tank or the liquid to be treated so that the concentration after addition becomes 1 to 1,000 mg-N / L. Good. Since nitric acid or nitrous acid serves as a substrate for anaerobic denitrifying microorganisms, the denitrifying microorganisms can be grown by the presence of nitric acid or nitrous acid in the reaction tank 20. And since the denitrification microorganisms produce mucilage, the strength of the granular sludge can be maintained by the growth of the denitrification microorganisms in the reaction tank 20 by the addition of nitric acid or nitrous acid. Nitric acid or nitrous acid is not limited to a nitric acid solution or the like, and a substance that releases nitrate ions or nitrite ions when added to a liquid to be treated, such as nitrate or nitrite, may be used.

  Nitric acid or nitrous acid may be added before the reaction tank 20 or may be added directly to the reaction tank 20. The order of adding starch, nitric acid or nitrous acid, and the flocculant is not particularly limited.

  Preferred conditions for the anaerobic treatment in the reaction tank 20 are as described above. In the reaction tank 20, organic substances in the organic substance-containing water are decomposed by the action of the granular sludge, and gas containing methane is generated. Granule sludge grows using organic substance-containing water as a substrate.

  The mixed liquid containing the gas generated in the reaction tank 10 and the grown sludge is gas-solid-liquid separated inside the GSS, and the gas is taken out of the reaction tank 20 from the gas path 33 and stored in the gas holder 30. Further, the liquid component separated and clarified from the sludge is taken out of the reaction tank 20 from the treatment liquid path 32. The treatment liquid may be further treated by an aerobic biological treatment apparatus (not shown) provided at a later stage.

<Example 1>
Hereinafter, the present invention will be described in more detail based on examples. In the examples, anaerobic treatment was performed by introducing organic substance-containing water having the following properties into an experimental apparatus simulating the treatment apparatus 1 shown in FIG. As the organic substance-containing water, synthetic waste water imitating evaporative condensed water was used. Specifically, methanol is added to tap water so that the concentration as CODcr is 2,970 mg / L, and a mixed substrate in which vegetable extract and meat extract are mixed at a 1: 1 ratio includes 30 mg / L as CODcr, This is a synthetic waste water to which 30 mg-N / L of NH ₄ Cl is added as a nitrogen source and 5 mg-P / L of KH ₂ PO ₄ is added as a phosphorus source.

  The reaction tank 20 has an inner diameter of 6 cm, a height of 1.2 m, and the capacity of the reaction part 12 excluding the part where the GSS is installed is 3 L, and the capacity of the part including the GSS part is 4 L. The reaction tank 20 is filled with 1.0 L of granular sludge (density 1.03-1.1 mm, particle size 1.2-1.5 mm) taken out from the existing UASB-type reaction tank in the chemical factory. Thus, the experiment was started in a state where the start-up of the reaction vessel 20 was completed.

  In Example 1, the synthesis is performed by connecting the starch addition path 12 in the middle of the liquid path 31 to be processed so that the starch concentration of the liquid after mixing with the liquid to be processed falls within the range of 90 mg / L as CODcr. Starch was added to the wastewater. Synthetic wastewater was passed through the reaction tank 20 at a CODcr load of 10 g-CODcr / L / d and a sludge load of 0.4 to 0.7 g-CODcr / g-VSS / d. The synthetic waste water was passed through so that the ascending flow rate in the reaction tank 20 was 3 m / h, and the sludge blanket was formed by developing the granular sludge. The temperature in the reaction vessel 20 was maintained at 30 to 35 ° C., and the pH was adjusted to be pH 7.0. The pH adjustment was performed by appropriately adding a pH adjuster (acid or alkali) stored in a pH adjuster tank (not shown) to the synthetic waste water flowing in the liquid to be treated 31.

  Here, the starch was added to the liquid channel 31 to be treated as a liquid obtained by dissolving a pre-gelatinized powder in water.

  The CODcr concentration of the treatment liquid taken out from the reaction tank 20 was 40 to 80 mg / L, and the CODcr removal rate was 97% or more. In addition, no decrease in the height of the upper end (sludge interface) of the sludge blanket formed by the development of the granule sludge was observed, and during the 90-day experiment period, the amount of granule sludge exceeded the amount at the start of treatment. An amount of granular sludge could be maintained in the reactor 20. At this time, the average particle size of the granular sludge was not reduced, and the granule sludge could be prevented from collapsing.

<Example 2>
The flocculant was further added to the synthetic waste water using the processing apparatus 2 shown in FIG. As the flocculant, a cationic polymer flocculant (polyaminoalkyl acrylate) was used, and the amount added was such that the concentration after the flocculant and the liquid to be treated were mixed was 0.03 mg / L. When the experiment was conducted in the same manner as in Example 1, the CODcr concentration of the treatment liquid was 40 to 80 mg / L, and the CODcr removal rate was 97% or more. Further, the amount of granular sludge in the reaction tank 20 was not reduced, the average particle size was not reduced, and no decrease in density was observed.

<Example 3>
2 was used as Example 3, and nitric acid (sodium nitrate solution) was added instead of the flocculant. The amount of nitric acid added was such that the concentration of nitric acid after mixing the sodium nitrate solution and the liquid to be treated was 20 mg-N / L. In Example 3, the CODcr concentration of the treatment liquid was 40 to 80 mg / L, and the CODcr removal rate was 97% or more. Further, the amount of granular sludge in the reaction tank 20 was not reduced, the average particle size was not reduced, and no decrease in density was observed.

<Example 4>
In Example 4, a flocculant and nitric acid were further added to the synthetic waste water in the previous stage of the reaction tank 20. That is, in Example 4, nitric acid, a flocculant, and starch are added to the synthetic waste water. The type and amount of the flocculant and starch are the same as in Example 2 and Example 3, respectively, and other conditions are the same as in Example 1. In Example 4, the CODcr concentration of the treatment liquid was 40 to 80 mg / L, and the CODcr removal rate was 97% or more. Further, the amount of granular sludge in the reaction tank 20 was not reduced, the average particle size was not reduced, and no decrease in density was observed.

<Comparative example 1>
In Comparative Example 1, the experiment was performed under the same conditions as in Example 1 except that no starch was added. As a result, the amount of granular sludge in the reaction tank 20 decreased little by little, and its particle size also decreased.

  Examples 1-4 and Comparative Example 1 show that according to the present invention, the addition of starch can prevent the granular sludge from collapsing.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for the treatment of organic substance-containing water whose main component is methanol, such as an evaporative concentrate discharged from a paper mill or the like.

The schematic diagram of the biological treatment apparatus which concerns on 1st Embodiment of this invention. The schematic diagram of the biological treatment apparatus which concerns on 2nd Embodiment of this invention. The figure which shows the result of an Example and a comparative example. The figure which shows the result of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Anaerobic processing apparatus 11 Starch storage tank 12 Starch addition path 20 Reaction tank 22 Reaction part 24 Sludge blanket 30 Gas holder 31 Processed liquid path 32 Treatment liquid path 33 Gas path 41 Coagulant storage tank 42 Coagulant storage path 42

Claims (7)

In the method of introducing the liquid to be treated into the reaction tank holding the granule sludge and bringing it into contact with the granule sludge and performing anaerobic treatment,
When the content of the organic substance having 4 or less carbon atoms in the liquid to be treated is 70% by mass or more of the total organic substance content, the liquid to be treated is one or more selected from the group consisting of a chelating agent, a scale dispersant, and a bactericide. Or when the sludge load on the reaction tank exceeds 0.3 kg CODcr / kg-Vss / d or the rising flow rate in the reaction tank exceeds 1 m / h,
An anaerobic treatment method for performing anaerobic treatment by adding a saccharide to the reaction vessel or the liquid to be treated and bringing the liquid to be treated into contact with granular sludge.   The anaerobic treatment method according to claim 1, wherein the liquid to be treated is evaporated condensed water discharged in a pulp manufacturing process.   The anaerobic treatment method according to claim 1, wherein the carbohydrate is starch.   The anaerobic treatment method according to claim 3, wherein pregelatinized starch is added as the carbohydrate.   The anaerobic treatment method according to claim 3 or 4, wherein the starch is added so that an amount of the starch added is 0.02 to 0.2 as a CODcr ratio with respect to the CODcr concentration of the liquid to be treated.   The anaerobic treatment method according to any one of claims 1 to 5, wherein the anaerobic treatment is performed while supplying a flocculant into the reaction tank. The liquid to be treated is evaporated condensed water discharged in the pulp manufacturing process,
The anaerobic treatment according to any one of claims 3 to 6, wherein the anaerobic treatment is performed by adding nitric acid or nitrous acid to the reaction tank or the liquid to be treated so that the concentration after addition becomes 1 to 1000 mg / L. Processing method.

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