JP2017051912A - Anaerobic treatment method and anaerobic treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological treatment system which uses two-stage anaerobic treatment, thereby can materialize a high treatment efficiency and reduction in an installation space.SOLUTION: An anaerobic treatment method is provided in which organic waste water is caused to sequentially pass through for treatment a first-stage anaerobic treatment tank 2 and a second-stage anaerobic treatment tank 3 that are arranged in series. The first-stage anaerobic treatment tank 2 is a strongly mixing type fluidized bed anaerobic treatment tank filled with a carrier, while the second-stage anaerobic treatment tank 3 is a plug-flow-type fluidized bed or fixed bed anaerobic treatment tank filled with a carrier. The first-stage anaerobic treatment tank 2 subjects the organic waste water of a CODof 2,500 mg/L or more to anaerobic treatment to obtain treated water of a CODof 500 mg/L or less.SELECTED DRAWING: Figure 1

Description

  The present invention provides an anaerobic treatment method that achieves a high tank load and a high organic matter removal rate by a two-stage anaerobic treatment of a positive mixing type fluidized bed type anaerobic treatment tank and a plug flow type fluidized bed or a fixed bed type anaerobic treatment tank. And an anaerobic treatment apparatus.

  An anaerobic treatment method using a high tank load type reactor represented by the UASB (upward flow sludge blanket) method is to self-granulate anaerobic bacteria and maintain a high concentration in the tank. Can be achieved.

  In general, anaerobic microorganisms have lower substrate affinity for organic matter than aerobic microorganisms, so that the lower the substrate concentration in the tank, the lower the removal rate. In particular, propionic acid-degrading bacteria that decompose propionic acid into hydrogen and acetic acid, and methane bacteria that produce methane using hydrogen and acetic acid as substrates are compared with microorganisms that hydrolyze and acid-ferment proteins and carbohydrates, respectively. It is known that the speed is particularly low.

  The methane fermentation tank of an anaerobic treatment apparatus that is currently practically used is generally composed of one tank. In such an apparatus, when an organic substance contained in the treated water, that is, a substrate is to be removed to a lower concentration, the decomposition rate is reduced as the removal rate is improved.

  On the other hand, in high load treatment, it is known to perform treatment in an anaerobic treatment tank provided in series in two or more stages in order to cope with sludge overflow from the anaerobic treatment tank by the generated gas (Japanese Patent Laid-Open No. 2000-237786). ). In addition, it is known to employ a two-stage anaerobic treatment for the decomposition of a hardly decomposable organic substance (Japanese Patent Laid-Open No. 2012-239929). Furthermore, a technique of performing anaerobic treatment using a fluid non-biological carrier after oil / water separation of oil / fat-containing water and oil / fat separation sludge after methane fermentation is also known (Japanese Patent Laid-Open No. 2012-210585).

  Further, it has been proposed that an anaerobic treatment tank is added to a fluidized bed carrier so that anaerobic treatment is performed while stably retaining methane bacteria in the tank even when the substrate concentration is low (Japanese Patent Laid-Open No. 2012-110820). Gazette, international publication WO2012 / 070493)

JP 2000-237786 A JP 2012-239929 A JP 2012-210585A JP 2012-110820 A International Publication WO2012 / 070493

  In the conventional anaerobic treatment, even if the bacterial cell concentration in the anaerobic treatment tank is increased, the organic matter removal rate per bacterial cell cannot be increased. Moreover, there was a limit to the improvement of the bacterial cell concentration in the tank.

Therefore, in order to improve the quality of treated water, it is common to provide an aerobic treatment tank after the anaerobic treatment tank, increasing the space of the entire biological treatment system including the anaerobic treatment tank and the aerobic treatment tank, The amount of sludge generated and the running cost for them increased.
And in the conventional method, even if the two-stage anaerobic treatment was performed, such a problem could not be solved.

  In view of the above problems, an object of the present invention is to provide a biological treatment system that can obtain high treatment efficiency by two-stage anaerobic treatment and can reduce installation space.

  As a result of intensive studies to solve the above problems, the present inventors have conducted a positive mixing type fluidized bed type anaerobic treatment tank filled with a carrier, a plug flow type fluidized bed or a fixed bed type anaerobic tank filled with a carrier. It has been found that a high tank load and a high organic matter removal rate can be achieved in the entire biological treatment system by providing a treatment tank in series and processing under predetermined operating conditions.

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

[1] An anaerobic treatment method in which organic waste water is sequentially passed through a first-stage anaerobic treatment tank and a second-stage anaerobic treatment tank arranged in series, and the first-stage anaerobic treatment tank includes: A positively mixed fluidized bed type anaerobic treatment tank filled with a carrier, and the second stage anaerobic treatment tank is a plug flow type fluidized bed or a fixed bed type anaerobic treatment tank filled with a carrier; In the anaerobic tank of the stage, the organic wastewater of COD _Cr 2500 mg / L or more is anaerobically treated to obtain treated water of COD _Cr 500 mg / L or less (hereinafter referred to as “first anaerobic treated water”). An anaerobic treatment method characterized by.

[2] In [1], the active mixing in the first-stage anaerobic treatment tank is performed by stirring and mixing by rotating a rotating blade provided in the tank at a G value of 2.9 sec ⁻¹ or more. The air lift pipe communicated in the tank is provided inside or outside the tank, and air lift mixing by circulating the liquid in the tank at a circulation flow rate of 5 m / hr or more, or a part of the first anaerobic treated water is circulated by the treated water circulation pump. An anaerobic treatment method, which is performed by any one of return mixing by circulating to the front stage of the first stage anaerobic treatment tank so as to be 0.5Q or more.

[3] The anaerobic treatment method according to [1] or [2], wherein the second-stage anaerobic treatment tank is upward circulation water.

[4] In any one of [1] to [3], the tank load of the second stage anaerobic treatment tank is the tank load of the first stage anaerobic treatment tank and the tank of the second stage anaerobic treatment tank. An anaerobic treatment method characterized by being 25% or less of the total load.

[5] In any one of [1] to [4], an acid generation tank is provided in front of the first stage anaerobic treatment tank, and treated water in the acid generation tank is passed through the first stage anaerobic treatment tank. An anaerobic treatment method characterized by returning the treated water of the second stage anaerobic treatment tank to the acid generation tank or its upstream side.

[6] The first-stage anaerobic treatment tank and the second-stage anaerobic treatment tank installed in series, and the organic waste water sequentially passed through the first-stage anaerobic treatment tank and the second-stage anaerobic treatment tank. The first stage anaerobic treatment tank is a positively mixed fluidized bed type anaerobic treatment tank filled with a carrier, and the second stage anaerobic treatment tank is filled with a carrier. Plug flow type fluidized bed or fixed bed type anaerobic treatment tank, wherein the organic waste water of 2500 mg / L or more of COD _Cr is anaerobically treated in the first stage anaerobic treatment tank to obtain COD _{Cr of} 500 mg / L or less An anaerobic treatment apparatus characterized in that the treated water (hereinafter referred to as “first anaerobic treated water”) is obtained.

[7] In [6], the active mixing in the first-stage anaerobic treatment tank is performed by stirring and mixing by rotating a rotating blade provided in the tank at a G value of 2.9 sec ⁻¹ or more, Part of the first anaerobic treated water by air lift mixing by circulating the liquid in the tank at a circulation flow rate of 5 m / hr or more by an air lift pipe communicating with a circulation path provided inside or outside the tank, or by a treated water circulation pump An anaerobic treatment apparatus characterized in that it is performed by any one of the return mixing by circulating the product to the front stage of the first stage anaerobic treatment tank so that the circulation ratio is 0.5Q or more.

[8] The anaerobic treatment device according to [6] or [7], wherein the second-stage anaerobic treatment tank is upward circulation water.

[9] In any one of [6] to [8], the tank load of the second stage anaerobic treatment tank is the sum of the tank load of the anaerobic treatment tank and the tank load of the second stage anaerobic treatment tank. An anaerobic treatment apparatus characterized by being 25% or less.

[10] In any one of [6] to [9], an acid generation tank provided in a preceding stage of the first stage anaerobic treatment tank, and treated water in the acid generation tank are used in the first stage anaerobic treatment tank. An anaerobic treatment apparatus comprising: means for passing water; and means for returning the treated water of the second stage anaerobic treatment tank to the acid generation tank or the upstream side thereof.

According to the present invention, a high tank load and a high organic matter removal rate can be achieved in the entire biological treatment system.
In other words, the first-stage anaerobic treatment tank that needs to perform high-load treatment is a positively mixed fluidized bed type anaerobic treatment tank filled with a carrier, so that the carrier and sludge flow out even if actively mixed. Can prevent high load processing.
The second-stage anaerobic treatment tank has a lower load treatment than the first-stage anaerobic treatment tank, so that stable treatment is difficult. However, this second-stage anaerobic treatment tank is a plug flow type flow filled with a carrier. By using a floor or fixed-bed anaerobic treatment tank, stable treatment is possible even at low loads. In particular, by using the second stage anaerobic treatment tank as upward circulation water, an increase in the differential pressure can be prevented, so that advanced treatment is possible.

  For this reason, in the present invention, since the load on the entire biological treatment system that performs anaerobic treatment can be increased, the tank area can be reduced, and the quality of the anaerobic treated water is improved. Even when a treatment tank is provided, the tank area can be reduced.

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

Embodiments of the present invention will be described below in detail with reference to the drawings.
In the present invention, “Q” indicating the circulation ratio indicates the amount of water to be treated (excluding the circulated anaerobic treated water) flowing into the anaerobic treatment tank that circulates the anaerobic treated water. “0.5Q” means that anaerobic treated water having a water amount 0.5 times the amount of treated water other than the circulating anaerobic treated water flowing into the anaerobic treated tank is circulated. This means that a total of 1.5Q of water flows in. Similarly, “circulation ratio 2Q” means to circulate anaerobic treated water whose amount is twice the amount of treated water other than the circulating anaerobic treated water flowing into the anaerobic treated tank. Means that a total of 3Q of water flows in.

  1 and 2 are system diagrams showing an example of an embodiment of the anaerobic treatment apparatus of the present invention. In the anaerobic treatment apparatus of FIG. 1, the raw water (organic waste water) is pH-adjusted in the pH adjustment tank 1. Thereafter, anaerobic treatment is performed in the first stage anaerobic treatment tank (hereinafter referred to as “first anaerobic treatment tank”) 2 in which the fluidized bed 2A of the carrier is formed in the tank, and the anaerobic treatment from the first anaerobic treatment tank 2 is performed. Part of the water (hereinafter referred to as “first anaerobic treated water”) is circulated to the pH adjustment tank 1 and the remainder is the second stage anaerobic treatment in which the fluidized bed or fixed bed 3A of the carrier is formed in the tank. Water is passed through a tank (hereinafter referred to as “second anaerobic treatment tank”) 3 for anaerobic treatment. Part of the anaerobic treated water (hereinafter referred to as “second anaerobic treated water”) from the second anaerobic treatment tank 3 is circulated to the pH adjustment tank 1, and the remainder is aerobically treated in the aerobic treatment tank 4. Treated water is discharged outside the system. In FIG. 1, the circulation pipes of the first and second biologically treated water are joined on the way. In addition, although not shown in figure, the gas discharge piping which discharges | releases methane gas is provided in the upper part of each anaerobic processing tank 2,3. The anaerobic treatment apparatus of FIG. 2 has an acid generation tank 5 in the previous stage of the pH adjustment tank 1, and the anaerobic treatment of FIG. 1 is that the first anaerobic treated water and the second anaerobic treated water are circulated to the acid production tank 5. Unlike the device, the rest of the configuration is the same.

<Action mechanism>
According to the present invention, the first stage anaerobic treatment tank is a positively mixed fluidized bed type anaerobic treatment tank filled with a carrier to prevent the carrier and sludge from flowing out even if actively mixed. High load processing can be performed.
The second-stage anaerobic treatment tank has a lower load treatment than the first-stage anaerobic treatment tank, so that stable treatment is difficult. However, this second-stage anaerobic treatment tank is a plug flow type flow filled with a carrier. By using a floor or fixed-bed anaerobic treatment tank, stable treatment is possible even at low loads. In particular, by using the second stage anaerobic treatment tank as upward circulation water, an increase in the differential pressure can be prevented, so that advanced treatment is possible.

For example, the half-saturation constant Ks at which the conversion rate of acetic acid, which is the main substrate of methane bacteria, to half of its maximum value is 164 mg / L at a water temperature of 35 ° C. (Lawrence and McCarty, 1969). Here, when the treated water acetic acid concentration is about 500 mg / L, which is the maximum metabolic rate for the substrate, the utilization rate is about twice that when the treated water acetic acid concentration is about 160 mg / L.
Therefore, when two anaerobic treatment tanks are connected in series, and the acetic acid concentration of the anaerobic treatment water in the first stage anaerobic treatment tank is about 500 mg / L, the acetic acid concentration of the anaerobic treatment water in the first stage anaerobic treatment tank The acetic acid can be processed at a rate twice as high as about 160 mg / L, and the tank load of the first stage anaerobic tank can be increased four times.

In addition, when the tank volume of the second stage anaerobic treatment tank is made larger than the tank volume of the first stage anaerobic treatment tank, or when the amount of carrier to be added is increased, the acetic acid concentration in the treated water is reduced to a lower concentration. (For example, up to 100 mg / L or less). As described above, an aerobic treatment facility is generally attached to the subsequent stage of the anaerobic treatment facility. In this case, the volume of the aerobic treatment tank and the amount of sludge generated can be reduced.
Moreover, since the treated water pH is increased by reducing the concentration of acetic acid in the treated water, the amount of alkali for pH adjustment used in the anaerobic treatment tank can be greatly reduced by returning the treated water. .

<Organic drainage>
Examples of the organic wastewater to be treated in the present invention include manufacturing wastewater such as food factories, organic wastewater such as chemical factories, and general sewage, but are not limited thereto. In the present invention, among these organic wastewaters, particularly for the treatment of high-concentration organic wastewater whose COD _Cr flowing into the first anaerobic treatment tank 2 is 2500 mg / L or more, for example, 2500 to 10,000 mg / L. It is valid.

  The substrate that flows into the first anaerobic treatment tank 2 is a low-molecular organic compound such as a single-chain volatile fatty acid and desirably does not contain protein or carbohydrate. For this reason, when these substances are contained in the organic waste water, an acid generation tank is provided in front of the first anaerobic treatment tank 2 as shown in FIG. 2, or a raw water tank with an HRT of 4 hours or more is provided. It is preferable to decompose them.

<First anaerobic treatment tank>
In the present invention, as the first anaerobic treatment tank 2, a positive mixed fluidized bed anaerobic treatment tank filled with a carrier is used. Here, “aggressive mixing” means that the liquid that has flowed into the tank is actively mixed so that immediately after the liquid flows in, the liquid can be uniformly dispersed and diffused throughout the tank. On the other hand, the “plug flow” of the second anaerobic treatment tank 3 to be described later refers to a state in which the liquid flowing into the tank flows in a substantially parallel flow in one direction.

Although there is no restriction | limiting in particular in the system which mixes this 1st anaerobic processing tank 2 positively, Any of the following (1)-(3) is employable. These may be used in combination of two or more.
(1) Stir mixing by rotating a rotating blade provided in the first anaerobic treatment tank 2 at a G value of 2.9 sec ⁻¹ or more, for example, 2.9 to 5 sec ⁻¹ (2) An air lift pipe communicated with a circulation path Is provided in the first anaerobic treatment tank 2 or outside the tank, and air lift mixing is performed by circulating the liquid in the tank so that the average linear velocity of the upward flow in the tank is 5 m / hr or more, for example, 5 to 25 m / hr. (3) The first stage of the first anaerobic treatment tank 2 (for example, an acid generation tank or a raw water tank) so that a part of the first anaerobic treated water is 0.5Q or more, for example, 0.5Q to 5Q, by the treated water circulation pump. , Recirculation mixing by circulating from the raw water tank to the acid generation tank)

  In the 1st anaerobic processing tank 2, in order to reduce the usage-amount of a pH adjuster (alkali), when a part of the 1st anaerobic treated water is provided in the pH adjusting tank 1 (the acid generation tank 5 as shown in FIG. 2). Is preferably circulated to the acid generation tank 5), and therefore, it is also preferable to perform active mixing by the method (3). In this case, as shown in FIG. 1, it is preferable to provide a treated water inlet to the first anaerobic treatment tank 2 at the bottom of the tank and mix the inside of the tank with the upward flow of the treated water and the generated gas. That is, since the first anaerobic treatment tank 2 is operated at a high tank load, a large amount of gas is generated. Thus, by using upward circulation water at a high circulation ratio, the inside of the tank is actively mixed. can do.

  The carrier filled in the first anaerobic treatment tank 2 is preferably a fluid non-biological carrier having a size of 1.0 to 5.0 mm and a sedimentation speed of 200 to 500 m / h.

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

The size of the carrier is usually referred to as “particle size”. For example, in the case of a rectangular parallelepiped carrier, the length of its long side is referred to, and in the case of a cubic carrier, the length of one side thereof is defined. In the case of a cylindrical carrier, it represents the larger one of the diameter and the height of the cylinder. The particle diameter of the irregularly shaped carrier other than these shapes is the interval between the plates where the interval between the plates becomes the largest when the carrier is sandwiched between two parallel plates.
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.

  On the other hand, if the sedimentation rate of the carrier is too small, the carrier tends to float due to water flow or generated gas, and accumulates in a scum shape near the water surface. That is, in the case of a method using a non-biological carrier, a biofilm is formed on the surface and a reaction in which gas is generated proceeds inside the biofilm, so that the apparent specific gravity of the carrier becomes lighter as the biofilm is formed. In consideration of the influence of this biofilm, it is necessary to determine the specific gravity and sedimentation rate of the carrier itself. Conversely, if the sedimentation rate of the carrier is too high, the contact efficiency with the water to be treated will be poor, and sufficient treatment efficiency will not be obtained, or solid matter will accumulate in the deposited layer of the carrier and the channel will be blocked. coming out. A more preferable sedimentation rate of the carrier used in the present invention is 200 to 500 m / hr.

  The sedimentation speed of the carrier is the amount of sedimentation by submerging the carrier in water (fresh water such as tap water), taking it into a graduated cylinder in water (fresh water such as tap water) This is a value obtained by measuring the distance. In the present invention, measurement is carried out on 10 or more, preferably 10-20, carriers, and the average value is taken as the sedimentation rate.

There are no particular restrictions on the constituent material of the carrier, but those made of the following foams (I) and / or (II) are preferred. It is also preferable in terms of easy adjustment.
(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 ( 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, the surface of which is Foam having melt fracture state

  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.

  The treatment conditions in the first anaerobic treatment tank 2 are not particularly limited as long as desired treatment efficiency can be obtained. For example, the following conditions can be set.

Carrier filling rate: 20-60%
HRT: 2-12 hr
Ascending flow velocity (LV): 5 to 25 m / hr
Tank load: 10-40 kg-COD _Cr / m ³ / day
Sludge load: 1.3 to 5 kg-COD _Cr / kg-VSS / day
pH: 6.3-7.5
Temperature: 25-35 ° C

In addition, the tank load of the 1st anaerobic treatment tank 2 is the sum of the tank load of the 2nd anaerobic treatment tank 3 and the tank load of the 1st anaerobic treatment tank 2, as will be described later. The tank load is 25% or less, that is, the tank load of the first anaerobic treatment tank 2 is more than three times the tank load of the second anaerobic treatment tank 3, and the organic load is high. It is preferable for achieving the removal rate.
In the first anaerobic treatment tank 2, the organic waste water of COD _Cr 2500 mg / L or more is anaerobically treated to obtain a first anaerobic treated water of COD _Cr 500 mg / L or less, preferably COD _Cr 300 to 500 mg / L. By setting the conditions, processing with a high tank load becomes possible.

<Second anaerobic treatment tank>
In the present invention, a plug flow type fluidized bed or a fixed bed type anaerobic treatment tank filled with a carrier is used as the second anaerobic treatment tank 3. The second anaerobic treatment tank 3 is particularly preferably upward circulation water from the viewpoint of preventing an increase in differential pressure.

  As the carrier filled in the fluidized bed type second anaerobic treatment tank 3, the same carrier as that filled in the first anaerobic treatment tank 2 described above can be used. As the carrier filled in the fixed bed type second anaerobic treatment tank 3, activated carbon, resin, fiber, or the like can be used.

  In addition, the processing conditions in the second anaerobic processing tank 3 are not particularly limited as long as desired processing efficiency can be obtained. For example, the following conditions can be set.

Carrier filling rate: 20-60%
HRT: 4-24 hr
Ascending flow velocity (LV): 0.5-5 m / hr
Tank load: 5 to 20 kg-COD _Cr / m ³ / day
Sludge load: 0.8 to 2.2 kg-COD _Cr / kg-VSS / day
pH: 6.3-7.5
Temperature: 25-35 ° C

  Set the operating conditions so that the tank load of the second anaerobic treatment tank 3 is 25% or less with respect to the total of the tank load of the first anaerobic treatment tank 2 and the tank load of the second anaerobic treatment tank 3. Is preferred. Thus, by setting the second anaerobic treatment tank 3 to be small with respect to the entire tank load, the first anaerobic tank is composed of an active mixed fluidized bed type anaerobic treatment tank filled with a carrier and capable of high load treatment. The treatment tank 2 comprises a plug flow type fluidized bed or a fixed bed type anaerobic treatment tank filled with a carrier after being subjected to a high load treatment, and is excellent in the ability to decompose and remove organic matter even at a low load. 2 The load of the anaerobic treatment tank 3 can be effectively utilized to perform high load and high efficiency treatment. However, if the tank load of the second anaerobic treatment tank 3 is too small with respect to the entire tank load, the first anaerobic treatment tank 2 is overloaded, and the processing performance in the second anaerobic treatment tank 3 tends to decrease. Therefore, the tank load of the second anaerobic treatment tank 3 is preferably 10% or more, and particularly preferably 10 to 20% with respect to the entire tank load.

  A part of the second anaerobic treated water is circulated to the pH adjusting tank 1 and the remaining part is introduced into the aerobic treating tank 4 to further reduce the amount of the pH adjuster (alkali) used. Alternatively, treated water may be obtained. Here, the circulation ratio of the second anaerobic treated water circulating in the pH adjusting tank 1 is preferably about 0Q (not circulated) to 0.5Q from the viewpoint of reducing the power of the pump.

Although the two-stage anaerobic treatment has been described as an example in FIG. 1, when organic wastewater is treated at a higher load, or when organic effluent contains substances that inhibit methane fermentation, low temperature and low pH Or, when processing under conditions where methane fermentation is susceptible to inhibition, such as high pH, or when you want to reduce the organic matter concentration of the treated water to a higher level, an anaerobic treatment tank is further provided to perform multi-stage anaerobic treatment of 3 or more stages. May be.
In addition, as described above, the substrate flowing into the first anaerobic treatment tank 2 is a low-molecular organic compound such as a single-chain volatile fatty acid and preferably contains no protein or carbohydrate. As shown in FIG. 2, an acid generation tank 5 may be provided in the previous stage (the previous stage of the pH adjustment tank 1) as necessary. In this case, you may circulate the 1st, 2nd anaerobic treated water to the acid production tank 5 or its front | former stage. When the raw water contains an organic acid, the acid generation tank 5 is not necessarily required.

Hereinafter, the present invention will be described more specifically with reference to examples.
In all of the following examples and comparative examples, treatment was performed at a flow rate of 48 L / day using simulated wastewater of food factory wastewater of 2500 mg / L of COD _Cr as raw water. All the anaerobic treatments were performed at a temperature of 35 ° C.

[Example 1]
The raw water is adjusted to pH 6.3 in the pH adjustment tank 1 by the apparatus shown in FIG. 1 and then sequentially passed through the positive mixing type fluidized bed type anaerobic treatment tank 2 and the upward flow plug flow type fluidized bed type anaerobic treatment tank 3. Water and anaerobic treatment.
The first anaerobic treatment tank 2 was a positively mixed anaerobic treatment tank by return mixing in which a part of the first anaerobic treated water was circulated to the pH adjustment tank 1 at a circulation ratio of 2Q. A part of the second anaerobic treated water from the second anaerobic treatment tank 3 was circulated to the pH adjustment tank 1 at a circulation ratio of 0.5Q.

  The specifications and operating conditions of each anaerobic treatment tank are as follows.

<First anaerobic treatment tank>
Capacity: Approximately 4L (diameter 5cm, height 100cm)
Carrier: cylindrical polyolefin resin carrier with a diameter of 2 mm, a height of 3 mm, and a sedimentation speed = 300 m / hr Carrier filling rate: 60%
HRT: 2 hr
Ascending flow velocity (LV): 5 m / hr
Tank load: 40 kg-COD _Cr / m ³ / day
Sludge load: 5 kg-COD _Cr / kg-VSS / day

<Second anaerobic treatment tank>
Capacity: Approximately 8L (diameter 5cm, height 200cm)
Carrier: cylindrical polyolefin resin carrier with a diameter of 2 mm, a height of 3 mm, and a sedimentation speed = 300 m / hr Carrier filling rate: 60%
Ascending flow velocity (LV): 1 m / hr
HRT: 4 hours
Tank load: 10 kg-COD _Cr / m ³ / day
Sludge load: 1.2 kg-COD _Cr / kg-VSS / day

Table 1 shows the operating conditions (tank load and circulation ratio) and treatment results of each anaerobic treatment tank.
As shown in Table 1, high treatment performance was achieved with a high tank load.

[Comparative Example 1]
In Example 1, the positive mixing type fluidized bed type anaerobic treatment tank which is the first anaerobic treatment tank is omitted, and the upward flow plug flow type fluidized bed type anaerobic treatment tank (the tank volume) which is the second anaerobic treatment tank. 1-stage anaerobic treatment was performed using only 8 L, carrier filling rate 60%).
Table 1 shows operating conditions (tank load and circulation ratio) and processing results.
As shown in Table 1, a high tank load could not be taken in order to exhibit sufficient processing performance.

[Comparative Example 2]
Using only one UASB type anaerobic treatment tank (vessel volume 12 L), raw water adjusted to pH 6.3 was subjected to one-stage anaerobic treatment.
Table 1 shows operating conditions (tank load and circulation ratio) and processing results.
As shown in Table 1, a high tank load could not be taken in order to exhibit sufficient processing performance.

[Comparative Example 3]
A two-stage UASB type anaerobic treatment tank (tank volume 6 L) was provided in series, and the raw water adjusted to pH 6.3 was subjected to two-stage anaerobic treatment.
Table 1 shows operating conditions (tank load and circulation ratio) and processing results.
As shown in Table 1, a high tank load could not be taken in order to exhibit sufficient processing performance.

1 pH adjustment tank 2 First anaerobic treatment tank 3 Second anaerobic treatment tank 4 Aerobic treatment tank 5 Acid generation tank

Claims (10)

In the anaerobic treatment method in which organic waste water is sequentially passed through the first-stage anaerobic treatment tank and the second-stage anaerobic treatment tank arranged in series,
The first stage anaerobic treatment tank is a positively mixed fluidized bed type anaerobic treatment tank filled with a carrier,
The second-stage anaerobic treatment tank is a plug flow type fluidized bed or fixed bed type anaerobic treatment tank filled with a carrier,
In the first-stage anaerobic treatment tank, the organic waste water of COD _Cr 2500 mg / L or more is anaerobically treated, and treated water of COD _Cr 500 mg / L or less (hereinafter referred to as “first anaerobic treated water”). An anaerobic treatment method characterized by obtaining. The active mixing in the first stage anaerobic treatment tank according to claim ¹ is communicated by agitation mixing and a circulation path by rotating a rotary blade provided in the tank at a G value of 2.9 sec ^-1 or more. An air lift pipe is provided inside or outside the tank, and a part of the first anaerobic treated water is circulated by 0.5Q by circulating the liquid in the tank at a circulation flow rate of 5 m / hr or more, or by a treated water circulation pump. An anaerobic treatment method, which is performed by any one of return mixing by circulating to the front stage of the first stage anaerobic treatment tank as described above.   The anaerobic treatment method according to claim 1, wherein the second-stage anaerobic treatment tank is upward circulation water.   In any 1 item | term of Claim 1 thru | or 3, the tank load of the said 2nd stage anaerobic treatment tank is the sum total of the tank load of the said 1st stage anaerobic treatment tank, and the tank load of this 2nd stage anaerobic treatment tank An anaerobic treatment method characterized by being 25% or less.   In any 1 item | term of Claim 1 thru | or 4, While providing an acid production tank in the front | former stage of the said 1st stage anaerobic treatment tank, and passing the process water of this acid production tank to this 1st stage anaerobic treatment tank, An anaerobic treatment method characterized by returning treated water from the second stage anaerobic treatment tank to the acid generation tank or the upstream side thereof. A first-stage anaerobic treatment tank and a second-stage anaerobic treatment tank installed in series; and means for sequentially passing organic wastewater through the first-stage anaerobic treatment tank and the second-stage anaerobic treatment tank; In an anaerobic treatment apparatus having
The first stage anaerobic treatment tank is a positively mixed fluidized bed type anaerobic treatment tank filled with a carrier,
The second-stage anaerobic treatment tank is a plug flow type fluidized bed or fixed bed type anaerobic treatment tank filled with a carrier,
In the first-stage anaerobic treatment tank, the organic waste water of COD _Cr 2500 mg / L or more is anaerobically treated, and treated water of COD _Cr 500 mg / L or less (hereinafter referred to as “first anaerobic treated water”). An anaerobic treatment apparatus characterized by being obtained. The active mixing in the first-stage anaerobic treatment tank according to claim 6, wherein the mixing is performed by rotating a rotating blade provided in the tank at a G value of 2.9 sec ^-1 or more, in the tank or in the tank. A part of the first anaerobic treated water is circulated by air lift mixing by circulating the liquid in the tank at a circulation flow rate of 5 m / hr or more by an air lift pipe communicating with a circulation path provided outside, or by a treated water circulation pump. An anaerobic treatment apparatus characterized in that the anaerobic treatment device is performed by any one of return mixing by circulating to the front stage of the first stage anaerobic treatment tank so as to be 0.5Q or more.   The anaerobic treatment apparatus according to claim 6, wherein the second-stage anaerobic treatment tank is upward circulation water.   9. The tank load of the second stage anaerobic treatment tank according to claim 6, wherein the tank load of the second stage anaerobic treatment tank and the tank load of the second stage anaerobic treatment tank are 25% or less. An anaerobic treatment apparatus characterized by being.   In any 1 item | term of the Claims 6 thru | or 9, the acid production tank provided in the front | former stage of the said 1st stage anaerobic treatment tank, and the treated water of this acid production tank are water-flowed to this 1st stage anaerobic treatment tank And an anaerobic treatment apparatus characterized by comprising means for returning the treated water of the second stage anaerobic treatment tank to the acid generation tank or its upstream side.

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