JP2000237786A - Anaerobic treatment device for organic waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of water quality of treated water and lowering of treating efficiency due to the flowing-out of sludge particles, since an organic load of organic waste water to be treated is high and a generation quantity of anaerobic gas is high and the anaerobic sludge particles for decomposing organic matters to anaerobic gas are discharged into the treated water. SOLUTION: Plural upward counterflow type anaerobic treating tanks having a gas, solid, and liquid separator 11, a sedimentation and treated water-takeout part 12 partitioned with the separator 11 and an anaerobic reaction part 13 provided at the lower part of the separator 11, are installed in series, and a raw water feed means 3 for feeding at least a portion of raw water to be treated to the anaerobic reaction part of the treating tank in a pre-stage, a treated water feed means 9 for feeding the treated water discharged from the sedimentation and treated water-takeout part of the treating tank in the pre- stage part to the anaerobic reaction part of the treating tank in the post stage, and a sludge returning means 16 for returning sludge-containing liquid in the anaerobic reaction part of the treating tank in the post stage to the anaerobic reaction part of the treating tank in the pre-stage, are provided on the device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for converting organic matter in organic wastewater into granules composed of anaerobic microorganisms constituting sedimentation and self-granulating sludge (granules having a small particle size). Finally, it is decomposed into anaerobic gas mainly composed of methane and carbon dioxide to remove organic matter, and the treated water after the decomposition of organic matter is separated from the generated anaerobic gas and sludge. The present invention relates to an anaerobic treatment device of a UASB type (upflow sludge blanket type) and an EGSB type (expanded granular sludge blanket type) which are separated and taken out.

[0002]

2. Description of the Related Art The applicant of the present invention has disclosed Japanese Patent Application Laid-Open No. 10-1659.
According to Japanese Patent Publication No. 80, an organic substance in an organic wastewater is decomposed into anaerobic gas by the action of granular sludge (anaerobic sludge), and a gas-solid liquid separating the anaerobic gas, sludge and treated water. We have proposed a UASB anaerobic treatment device in which a separation device is provided in a treatment tank.

[0003]

With the above anaerobic treatment apparatus, the organic wastewater (raw water) has a high CODcr load, and even if a large amount of anaerobic gas is generated, the organic matter in the raw water is biologically treated to discharge the treated water. However, it is difficult to completely prevent the outflow of sludge particles accompanying the treated water by a gas-solid-liquid separator provided in the tank. Particularly during high-load operation, the amount of anaerobic gas generated increases, and the increase in the gas amount increases the upward flow velocity of the liquid in the treatment tank, and the sludge particles settle from the settling and treated water removal section to the anaerobic reaction section. Roll up,
This has an adverse effect on the flow of liquid in the settling and treated water removal section, and makes solid-liquid separation insufficient. The outflow of sludge into the treated water causes deterioration of treated water quality and a decrease in treatment effect due to a decrease in sludge concentration in the anaerobic reaction section.

It is also known to carry out treatment by installing two upward-flow anaerobic treatment tanks, but this is accomplished by supplying raw water in parallel to individual treatment tanks and treating the sedimentation and treatment water in each tank. Since the treated water is obtained from the take-out part and the two treated tanks are not connected in series, sludge particles are mixed with the treated water discharged from each of the treated tanks, and the same problem occurs.

[0005]

SUMMARY OF THE INVENTION The present invention has been developed in order to solve the above-mentioned problems, and comprises a gas-solid liquid separation device, a settling / treatment water take-out section partitioned by the separation device, and
A plurality of upward-flow anaerobic treatment tanks having an anaerobic reaction section provided below the separation device are installed in series, and at least a part of the raw water to be treated is subjected to anaerobic treatment in the treatment tank in the preceding stage. Means for supplying raw water to be supplied to the reaction section, and means for supplying treated water for supplying treated water discharged from the settling and treated water take-out section of the preceding treatment tank to the anaerobic reaction section of the subsequent treatment tank And sludge return means for returning the sludge-containing liquid in the anaerobic reaction section of the processing tank of the subsequent stage to the anaerobic reaction section of the processing tank of the preceding stage.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A plurality of U installed in series in the present invention
Each of the anaerobic treatment tanks of the ASB type or the EGSB type is provided below the separation device 11, a gas-solid liquid separation device 11, a sedimentation / treatment water removal section 12 partitioned by the separation device 11, and the separation device 11. As long as the anaerobic reaction section 13 is provided, for example, the preceding apparatus described in the above-mentioned prior art (paragraph 0002) may be used. However, in FIG. 2, the upper end protrudes above the water surface and above the water surface. Opposing sides 1, 1 and a bottom 2, extending diagonally downward from the lower end of each side toward the opposing side opposite to each other, and maintaining a gap in the vertical direction.
2 shows an upflow anaerobic treatment tank 10 equipped with a gas-solid separation apparatus 11 comprising the above-mentioned 2 and capable of implementing the present invention. The gas-solid separation device may be of any shape and structure as long as it can separate generated anaerobic gas, sludge particles and water. Further, each gas-solid-liquid separation device provided in each anaerobic treatment tank may have the same shape and structure, or may have different shapes, and may have a simpler shape and structure as the later anaerobic treatment tank. .

[0007] The treatment tank 10 is provided with a sludge layer 14 of anaerobic microorganisms on the bottom of the tank and raw water containing organic matter is provided through a raw water supply pipe 3 provided below the sludge layer. An anaerobic reaction section 13 is provided, which is composed of a sprinkler pipe 15 for flowing water upward in a sludge layer, and organic matter in raw water is biologically treated with anaerobic microorganisms in the sludge layer, and contains methane and carbon dioxide as main components. Decomposed into anaerobic gas and removed. The sludge layer in the anaerobic reaction section is developed by the raw water flowing upward from the water sprinkling pipe 15 into a fluid state up to the middle of the height of the treatment tank, or is developed until it becomes a mixed state as a whole. And the anaerobic gas generated by the biological treatment, as shown by the arrow a,
The sides 1, 1 of the gas-solid separation device are inclined by the lower surfaces of the bottoms 2, 2.
And rises between the respective side portions and the inner wall of the processing tank, floats on the liquid surface, and is discharged from the exhaust pipe 5 of the top wall 4 that closes the processing tank.

The liquid flowing upward in the anaerobic reaction section 13 is accompanied by a part of the sludge particles in the reaction section 13 and the up and down direction of the staggered bottom portions 2 and 2 as shown by the arrow b. Flows into the settling and treated water take-out section 12 between the side portions 1 and 1 from below through the gap 6, and the sludge particles entrained during the stagnation there are settled. The water overflows into the overflow troughs 7 at the upper part of the inner surface, and is taken out of the tank from the drain pipe 8 as treated water. Incidentally, the sludge settled in the settling and treated water take-out section 12 descends to the anaerobic reaction section 13 through the gap 6 as shown by an arrow c.

However, as described above, during high-load operation, the amount of anaerobic gas generated increases, whereby the upward flow velocity of the liquid in the processing tank increases, and the sludge flows into the processing water. Deterioration of water quality, sludge falling back to the anaerobic reaction section is reduced, and treatment efficiency is reduced due to insufficient sludge concentration in the anaerobic reaction section.

In order to prevent this, in the present invention, FIG.
As shown in (A), two upward flow anaerobic treatment tanks 10 are provided.
-1, 10-2, or three or more upflow anaerobic treatment tanks 10-1,..., 10 as shown in FIG.
-(N-1), 10-n are installed in series.

The raw water to be treated is shown in FIG.
In either embodiment of (B), the pump P ₁By raw water supply
The anaerobic reaction section 13 of the first stage treatment tank 10-1 is connected to the water pipe 3
And organic matter in the raw water for biological treatment as described above.
Decomposed into more anaerobic gas and removed, and the resulting treated water is
In the case of the embodiment of FIG. 1 (A), a two-stage treatment water supply pipe 9 is used.
It is supplied to the anaerobic reaction section of the processing tank 10-2 at the last stage of the eye,
In this case as well, it remains in the treated water from the first stage
Organic matter is decomposed into anaerobic gas by biological treatment and removed,
The treated water is drained from the sedimentation / treated water take-out part by the drain pipe 8,
Discharge or perform advanced treatment such as aerobic treatment.

The amount of organic substances contained in the treated water supplied to the anaerobic reaction section of the final treatment tank through the treated water supply pipe 9 from the settling and treated water take-out section of the first treatment tank is the first Very small amounts are decomposed by biological treatment in the first treatment tank.
Therefore, even if the biological treatment is performed in the final treatment tank, the amount of anaerobic gas floating in the liquid in the tank is small, and the sludge mixed in the treatment water supplied from the first treatment tank is small. The particles are not disturbed by the flow of the liquid by the generated anaerobic gas, settle in the anaerobic reaction section, and almost no sludge particles exist in the treated water discharged out of the tank by the drain pipe 8.

In the embodiment shown in FIG. 1B, the treated water discharged from the first-stage treatment tank is supplied to the second treatment tank 9 by the treated water supply pipe 9.
The treated water supplied to the anaerobic reaction section of the first-stage treatment tank and discharged from the second-stage treatment tank is transferred to the next-stage treatment tank by the treated water supply pipe, and thus the final-stage treatment tank 10-n. The treated water in the treatment tank 10- (n-1) before this is supplied to the anaerobic reaction section by the treated water supply pipe 9, and the final treatment is performed from the sedimentation / treated water take-out section of the final treatment tank. Water is drained through drain 8.

Since the processing tanks in each stage from the first stage to the final stage perform anaerobic biological treatment of the organic matter in the liquid, the amount of organic matter in the water is smaller as the treated water supplied to the later stage. As a result, the amount of generated anaerobic gas decreases. Therefore, if the sludge particles are mixed in the treatment water supplied from the treatment tank of the previous stage, the sludge particles can be settled in the anaerobic reaction section without being hindered by the anaerobic gas, and Treated water containing no sludge particles is discharged from the treatment tank.

When the operation is continued in this manner, the sludge particles in the anaerobic reaction section of the first-stage treatment tank, in the case of the embodiment shown in FIG. 1B, the sludge particles in the anaerobic reaction section of the first-stage treatment tank are removed from the anaerobic reaction section of the second-stage treatment tank. The sludge particles in the anaerobic reaction section of the second processing tank are transferred to the anaerobic reaction section of the next processing tank, and finally the final processing tank 10-.
In the anaerobic reaction section of n, the processing tank 10- (n-
The sludge particles in the anaerobic reaction section of 1) are each taken out to a small amount.

The amount of sludge present in the anaerobic reaction section of each treatment tank is determined to be an amount required to decompose organic substances in the liquid supplied to the treatment tank into anaerobic gas. Therefore, as described above, when a small amount of sludge particles in the anaerobic reaction section of the previous processing tank is taken out to the anaerobic reaction section of the next processing tank, the anaerobic reaction of the previous processing tank is performed. The amount of sludge in the section is insufficient for the organic matter to be decomposed into anaerobic gas in the treatment tank, and the sludge concentration in the anaerobic reaction section gradually decreases as the treatment tank in the previous stage hinders anaerobic treatment. Will come.

[0017] Therefore, the final stage anaerobic reactor section a first stage of the treatment tank sludge-containing liquid pump P ₂ of the processing tank 10-2 (second stage) in the embodiment of FIG. 1 (A) A sludge return pipe 16 for returning to the anaerobic reaction section 10-1 is provided, and FIG. 1 (B)
In the embodiment, the processing tank 10-n in the final stage (second stage)
The sludge return pipe 1 for returning the anaerobic reactor unit sludge containing liquid in the anaerobic reaction of the first stage of the treatment tank 10-1 by the pump P ₂
6 to maintain the sludge concentration in the anaerobic reaction section of the preceding treatment tank at a predetermined level.

The return of the sludge by the pump P ₂ and the sludge return pipe 16 may be intermittent or continuous. For example, a sludge level meter that detects the sludge interface is installed in the anaerobic reaction section of the processing tank in the later stage, and when the amount of sludge reaches that level or higher, or the sludge interface is installed in the anaerobic reaction section of the processing tank in the previous stage. sludge level meter that detects provided, if the amount of the sludge is below that level, respectively, a pump P ₂ is controlled by a timer or the like of the processing tank of the stage after driving predetermined time sludge prior stage It may be returned to the processing tank. In the case of the embodiment shown in FIG. 1B, the sludge is taken out most in the first treatment tank and the sludge is stored in the second treatment tank. May be provided only between the second stage and the anaerobic reaction section of the first stage treatment tank. Of course, sludge may be returned to the preceding stage from any stage.

When the raw water to be treated is waste water having a large amount of solid content, as shown in FIG. 1, a pre-sedimentation tank 21 is provided to separate the solid content and then supplied to an acid generation tank 22. In the acid production tank, the organic matter in the raw water is converted into organic acids such as acetic acid, propionic acid and lactic acid by acid fermentation by mixing with acid producing bacteria under anaerobic conditions. The pH is usually 4 to 6. Since the pH of the raw water suitable for the methanogen in the upward flow anaerobic treatment tank to decompose the organic matter in the raw water is about 6 to 8, the raw water treated in the acid generation tank is then replaced with a pH adjustment tank. 23,
Add an alkali adjuster, such as NaOH, to add p
H is adjusted to 6-8 suitable for the activity of methanogens,
Was adjusted raw water by the pump P ₁ is supplied to the anaerobic reactor 13 of the first stage of the treatment tank 10-1 water supply pipe 3, the organic acid in the raw water is decomposed into anaerobic gas is removed by biological treatment ,
The generated treated water is supplied to the anaerobic reaction section of the next-stage treatment tank through the treated water supply pipe 9, and is treated as described above.

The raw water is not entirely supplied to the first stage treatment tank,
The water may be partially supplied to the first-stage processing tank and the subsequent processing tanks. In this case, the distribution amount of the raw water to each processing tank adversely affects the gas-solid-liquid separation device of the final-stage processing tank. It is optional if the amount of anaerobic gas generated is suppressed to such an extent that, for example, in the case of the two tanks shown in FIG. : 0, preferably 7: 3
-10: 1.

As shown in FIG. 1, the treated water discharged from the final treatment tank is stored in the treated water tank 24, and a part of the treated water is discharged from the treated water tank to the pump P ₃ and the circulation pipe as necessary. 2
It may be returned to the acid generating tank in 5 and used for dilution of raw water, pH adjustment, breeding of acid generating bacteria, etc., and the remaining part may be discharged or subjected to advanced treatment such as aerobic treatment.

[0022]

As is clear from the above, according to the present invention, the sedimentation / treatment water extraction section of the upstream treatment tank of the plurality of upward flow anaerobic treatment tanks and the anaerobic reaction section of the subsequent treatment tank are provided. Connected in series with a treated water supply pipe to supply the treated water of the preceding treatment tank to the anaerobic reaction section of the subsequent treatment tank, to maximize the organic matter load in the first stage, and to reduce the organic matter load in the later stage; In the final stage, the generation amount of the anaerobic gas is minimized so as not to adversely affect the solid-liquid separation of the gas-solid liquid separation device, thereby preventing the sludge particles from flowing into the treated water. As a result, even if sludge particles are mixed in the treated water discharged from the first stage or in the middle of the treatment tank, the sludge particles are separated from the treated water in the sedimentation / treated water take-out part in the final stage treatment tank. And settle in the anaerobic reaction zone. As a result, the sludge particles in the preceding treatment tank are released into the treatment water and sequentially move to the anaerobic reaction section of the later treatment tank, and the sludge concentration in the later treatment tank gradually increases. The sludge concentration of the sludge-containing liquid in the anaerobic reaction section of the subsequent treatment tank is reduced by the sludge concentration of the sludge in the preceding treatment tank. A sludge return means for returning to the anaerobic reaction section is provided, which can be prevented by maintaining the sludge concentration in the preceding anaerobic reaction section at a predetermined level, and good water quality with almost no sludge particles mixed in from the final treatment tank. It is possible to obtain a treated water.

[Brief description of the drawings]

FIG. 1 (A) is a flow sheet according to an embodiment of the present invention,
(B) is a flow sheet of another embodiment of the present invention.

FIG. 2 is a sectional view of an upward anaerobic treatment tank that can be used in the present invention.

[Explanation of symbols]

 Reference Signs List 3 Raw water supply pipe (raw water supply means) 8 Treated water discharge pipe 9 Treated water supply pipe (treated water supply means) 10 Treatment tank 11 Gas-solid liquid separator 12 Precipitation and treated water take-out part 13 Anaerobic reaction part 14 Anaerobic Sludge layer in anaerobic reaction section 15 Sprinkler pipe in anaerobic reaction section 16 Sludge return pipe (sludge return means)

Claims (1)

[Claims] 1. A plurality of upward anaerobic anaerobic devices having a gas-solid liquid separating device, a settling / treated water removal portion partitioned by the separating device, and an anaerobic reaction portion provided below the separating device. Raw water supply means for installing at least part of the raw water to be treated to the anaerobic reaction section of the preceding treatment tank, and installing and removing the treated water from the preceding treatment tank Means for supplying the treated water discharged from the anaerobic reaction section of the subsequent treatment tank to the treated water discharged from the section, and treating the sludge-containing liquid in the anaerobic reaction section of the subsequent treatment tank to the preceding step An anaerobic treatment apparatus for organic waste water, comprising: a sludge return means for returning the sludge to an anaerobic reaction section of the tank.