JPH07328687A - Anaerobic treating device - Google Patents

Abstract

PURPOSE:To provide a treating device in which a deterioration of a precipitating property of the granular sludge is prevented, the precipitating property is quickly recovered even if the precipitating property is deteriorated, and in this way, a floating and flowing out of the sludge is prevented, the sludge is proliferated stably, thus the sludge concn. in a tank can be kept high and treatment is executed in high treating efficiency. CONSTITUTION:At the time of an anaerobic treatment in which a sludge blanket 3 is formed with the granular sludge 2 in an anaerobic reaction tank 1 and a liq. to be treated which was subjected to acid fermentation in an acid forming tank 15 is allowed to flow as upward stream, the deterioration of precipitating property of the granular sludge is prevented, the floating and flowing out of the sludge is prevented, and also, the sludge is proliferated stably and a high load treatment becomes possible by grinding continuously or intermittently the granular sludge 2 forming the sludge blanket 3 with a shredder 11.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention uses organic waste liquid UASB.
The present invention relates to an anaerobic treatment device for anaerobic treatment by the (upstream sludge blanket) method.

[0002]

2. Description of the Related Art Among the methods for anaerobic treatment of organic wastewater, attention has been paid to high-load anaerobic treatment methods such as the UASB method as a method for improving the treatment efficiency of the anaerobic digestion method which has been used for a long time. There is. The anaerobic digestion method is a method of performing anaerobic digestion by directly introducing an organic waste liquid containing a solid organic matter and a soluble organic matter into a digestion tank. Since this method requires a long time in the step of solubilizing the solid organic matter, a long residence time of 20 to 40 days is required as a whole, and there is a drawback that a large-sized processing apparatus is required.

On the other hand, in the high load anaerobic treatment method, a solid organic substance having a slow digestion rate is separated and separately treated, and only a soluble organic substance having a fast digestion rate is treated at a high load and a high speed by the anaerobic treatment. Therefore, the processing can be efficiently performed using a small device. With such a processing method,
In order to carry out the treatment with a high load, a large amount of anaerobic microorganisms is retained as sludge in the tank and brought into contact with the liquid to be treated at a high flow rate for anaerobic treatment. The UASB method, which is one of such high-load anaerobic treatment methods, utilizes the self-granulating property of anaerobic bacteria to form a high-density and highly sedimentable granule sludge, which is anaerobic. It is a method of forming a sludge blanket by anaerobic treatment by filling the treatment tank with the liquid to be treated in an upward flow. Hold the sludge in the tank,
The sludge concentration in the tank can be maintained at a high level, which allows anaerobic treatment with high treatment efficiency. As described above, since the UASB method has a high sludge retention concentration, it can be treated under a high load, and has been rapidly prevalent mainly in food wastewater in recent years.

By the way, the treatment performance of the UASB method largely depends on the sedimentation property of the granulated sludge, and when the sludge sedimentation property deteriorates, the sludge retention amount may decrease and the treatment may become impossible. That is, when the particle size of the granule sludge increases, the amount of the base material that penetrates into the granule decreases, so that the bacteria inside become starved, die, and self-decompose. As a result, voids are formed inside the granules, and the gas generated there accumulates buoyancy, which deteriorates the sludge's sedimentation property, and in some cases, the sludge may float.

[0005] Such a phenomenon of deterioration of sedimentation occurs frequently especially under high load, that is, when the amount of gas generated per sludge is large, and in a remarkable case, the sludge floats and flows out, and the amount of sludge necessary for treatment can be maintained. It may disappear. Similarly, the floating phenomenon of granulated sludge is caused by the organic SS in raw water.
When is contained in a relatively high concentration, when the granule grows while including SS, the trapped SS is biodegraded for a long period of time, and voids are generated therein, and the same phenomenon as described above occurs.

[0006]

The above-mentioned floating of granule sludge is similar in phenomenon to floating of scum in the conventional anaerobic digestion method, but floating along with the gas adhering like scum. This is because the specific gravity of the granulated sludge itself becomes small, unlike the conventional scum breaker, and the sedimentation property cannot be recovered only by removing the gas adhering to the outside like a conventional scum breaker. Therefore, there is no choice but to wait for the sludge to recover its properties, and during that time, the state of low treatment efficiency will continue.

Thus, it can be said that the measures for preventing the deterioration of the settling property of the granule sludge are important items that are essential for the stable treatment of the UASB method, but at present, concrete measures have hardly been studied so far. is there. Therefore, the applicant proposed in Japanese Patent Application No. 4-337388 a method of collecting the sludge that floated in the upper part of the reaction tank, mechanically crushing it, and returning it to the reaction tank. This method is highly effective in maintaining the amount of sludge because it crushes the sludge that has floated up, but it is a coping therapy, and there is a problem that it is difficult to deal with it when a large amount of sludge floats up at one time.

An object of the present invention is to solve the above problems in the UASB method, prevent deterioration of the settling property of granule sludge, and promptly recover the settling property of sludge even when the settling property deteriorates. As a result, sludge can be prevented from floating and flowing out, and sludge can be stably propagated. Therefore, the sludge concentration in the tank can be maintained at a high level and anaerobic can be performed with high treatment efficiency. It is to provide a processing device.

[0009]

DISCLOSURE OF THE INVENTION The present invention is an anaerobic method in which a sludge blanket is formed by granule sludge containing anaerobic microorganisms, and an organic waste liquid is passed in an upward flow to anaerobically decompose organic substances. An anaerobic treatment apparatus comprising a reaction tank and a crushing device for crushing the granule sludge forming the sludge blanket.

The organic waste liquid to be treated in the present invention is a waste liquid containing a soluble organic substance, and may contain a small amount of solid organic substance. When a large amount of solid organic matter is contained, the solid organic matter removed in advance by solid-liquid separation is subjected to treatment.

The anaerobic reaction tank contains granule sludge formed by anaerobic microorganisms therein, and a sludge blanket is formed by passing the liquid to be treated in an upward flow to maintain it under anaerobic condition. , Configured to perform an anaerobic reaction. This anaerobic reaction tank may perform both the acid-producing phase and the methanogenic phase, but it is preferable that the acid-producing phase is carried out in another acid-producing tank, and this reaction tank mainly carries out the methanogenic phase.

As the crushing device for crushing the granule sludge, a homogenizer, a grinder pump or the like capable of mechanically crushing the granule sludge to expose the inner wall of the cavity is used. This crushing device may be installed in the anaerobic reaction tank to directly crush the granule sludge forming the sludge blanket, or installed outside the reaction tank to crush the granule sludge taken out from the reaction tank to the reaction tank. It may be returned to. The crushing device may be operated intermittently or continuously, but the sludge forming the sludge blanket has a particle size of 0.25 to 0.25.
It is preferable to operate so as to be 1.5 mm, preferably 0.5 to 1 mm. When operating continuously, take out the sludge little by little or crush it without taking it out.

Although the present invention is applied to a high load anaerobic treatment apparatus by the UASB method, it does not depend on the operating temperature of the UASB apparatus, and the treatable temperature is from 20 ° C to 45 ° C.
The present invention can be applied to either the intermediate temperature treatment which is between 0 ° C or the high temperature treatment which has a temperature range capable of being treated at 45 ° C or higher. The upward flow velocity of the drainage in the anaerobic reaction tank is 0.5 to
2 m / hr, preferably 1 to 1.5 m / hr, and a residence time of 4 to 48 hours, preferably 6 to 24 hours are suitable.

[0014]

In the anaerobic treatment apparatus of the present invention, the anaerobic reaction tank in which the granulated sludge has been formed is passed through the effluent containing the soluble organic matter in an upward flow to form a sludge blanket, and the anaerobic state is obtained. While maintaining, the soluble organic matter in the effluent is anaerobically decomposed by the action of anaerobic microorganisms contained in the granulated sludge, and converted into methane and carbon dioxide. At this time, the granulated sludge forming the sludge blanket is crushed by a crushing device to prevent the granulated sludge from being hollowed, so that the sedimentation property is maintained and the floating outflow due to deterioration of the sedimentation property is prevented.

Granular sludge is anaerobically treated by passing a liquid to be treated, whereby anaerobic microorganisms grow and spontaneously form due to its self-granulating property. This granule sludge grows to a large particle size by continuing the anaerobic treatment, but as the particle size becomes larger, the sedimentation property deteriorates and eventually the flotation property may occur.

As a result of examining the properties of the granulated sludge that floated in the UASB method, it was found that there is a significant difference in the particle size of the sludge and the internal structure of the sludge between the sludge that retains sedimentation and the sludge that floats. I understood. It is because the sludge that floated has a larger particle size than the sludge that has a sedimentation property.
When it is 5 mm or more, and when observing the cross section of the sludge that floated, there is a hollow part in the center, and gas is retained in the hollow part, and the apparent specific gravity has decreased. There are two points. From these observations, the cause of cavitation is that sludge granulation progresses and the particle size of sludge increases, so that the substrate cannot penetrate to the central part of the granulated sludge and the internal sludge self-extinguishes. It is presumed that this is because the methane gas and the carbon dioxide gas generated are trapped in the granule sludge.

From the above point of view, as an effective measure against the deterioration of the settling property of the granulated sludge, the present invention appropriately crushes the granulated sludge forming the sludge blanket to reduce the average particle size of the granulated sludge. At the same time, the hollow part inside is exposed to the outer surface to maintain the sedimentation property and maintain a high sludge concentration in the tank. That is, in the present invention, before the sludge floats, the particle size is controlled in advance in a range in which it is difficult to float, thereby preventing the sludge from being deteriorated in settling property or flowing out. That is, the particle size or floatability of the granulated sludge in the anaerobic reaction tank is appropriately measured, and the sludge is crushed by a crushing device so that the average particle size becomes 0.25 to 1.5 mm, preferably 0.5 to 1 mm. By mechanically crushing the sludge continuously or intermittently inside or outside the reaction tank, the sludge's sedimentation property is maintained and floating outflow is prevented.

As an index for the deterioration of the sedimentation property of the granulated sludge, it is preferable to quantify the floating property such as the floating potential described later, but the particle size is preferable from the viewpoint of the ease of measurement. Depending on the type of sludge, the particle size may not correlate accurately with the floatability, but from the perspective of long-term and stable maintenance of general sludge, the particle size of granule sludge and sludge floatability Has a strong positive correlation and it is not preferable to exceed a certain particle size range. That is, sludge with a particle size of less than 0.25 mm, and in some cases less than 0.5 mm, is likely to flow out of the reaction tank due to the rising flow rate and generated gas. On the other hand, when the particle diameter exceeds 1.5 mm, and in some cases, exceeds 1 mm, the floating tendency is not effectively reduced and many particles flow out.

By crushing the granulated sludge as described above, deterioration of the sludge settling property is prevented, floating and runoff are prevented, and fine particles generated by the crushing become new nuclei to grow the sludge. Therefore, the sludge can be stably grown, and the sludge can be densified with high density and can be treated under high load.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments of the drawings. FIG. 1 is a system diagram showing the anaerobic treatment apparatus of the embodiment.

In FIG. 1, reference numeral 1 denotes an anaerobic reaction tank according to the UASB method, in which a sludge blanket 3 is formed by granule sludge 2, a liquid to be treated inflow portion 4 is provided in the lower portion, and a gas solidified in the upper portion. A liquid separation plate 5 and a processing liquid overflow portion 6 are provided. A processed liquid supply passage 7 is connected to the processed liquid inflow portion 4, and a processing liquid discharge passage 8 is connected to the processing liquid overflow portion 6. A gas chamber 9 is formed in the upper portion of the anaerobic reaction tank 1, and a gas discharge passage 10 is connected to the top portion.

Reference numeral 11 denotes a crushing device, which is an anaerobic reaction tank 1
Sludge removal path 12 for removing granule sludge 2 from sludge blanket 3 and anaerobic reaction tank 1 for crushed sludge
The sludge return path 13 to be returned to is connected. Reference numeral 14 is a sludge property detecting device, which detects an index of floating property such as a particle size of the granulated sludge 2 and a floating potential, and the crushing device 1
1 is controlled.

Reference numeral 15 is an acid production tank, which is a drainage introducing passage 16
Is introduced to maintain an anaerobic state by introducing a waste liquid containing a soluble organic substance and perform organic acid fermentation. The acid generation tank 15 and the anaerobic reaction tank 1 are connected by a treated liquid supply passage 7 having a pump 17, and a return liquid passage 18 branched from the treated liquid discharge passage 8 communicates with the acid generation tank 15. Further, the acid generation tank 15 is provided with a circulation path 20 having a pump 19 for stirring.

In the anaerobic treatment method using the above-mentioned anaerobic treatment apparatus, the return liquid which is returned from the return liquid passage 18 by introducing the waste liquid containing the soluble organic matter from the waste liquid introduction passage 16 into the acid generation tank 15. The mixture is mixed with and maintained in an anaerobic state while being stirred by the pump 19 through the circulation path 20, and the soluble organic matter is converted into an organic acid by the action of the acid-producing bacterium. Some S in the original drainage
When the S component is contained, it is anaerobically solubilized here.

The effluent of the organic acid fermentation in the acid production tank 15 is supplied from the liquid to be treated supply line 7 to the liquid to be treated 4 by the pump 17.
Is introduced into the lower part of the anaerobic reaction tank 1 through the sludge blanket 3 in an upward flow and comes into contact with the granule sludge 2 under anaerobic condition, and thus the anaerobic microorganisms contained in the granule sludge 2 It is anaerobically decomposed by the action of methanogens and converted into methane and carbon dioxide. The reaction liquid subjected to the anaerobic treatment is separated into gas, liquid and solid in the gas solid-liquid separation plate 5, and the separated liquid overflows from the processing liquid overflow section 6 as the processing liquid. The separated solids settle as sludge on the sludge blanket 3, and the gas rises to the gas chamber 9.

The treatment liquid is discharged from the treatment liquid passage 8, and a part of the treatment liquid is returned to the acid generation tank 15 via the return liquid passage 18. As a result, the anaerobic microorganisms contained in the treatment liquid are generated in the acid production tank 15
Is supplied to the acid generation tank 15 to maintain the amount of anaerobic microorganisms in the acid generation tank 15, and the pH of the acid generation tank 15 is buffered by the alkali component contained in the treated water. The produced gas such as methane gas generated in the anaerobic reaction tank 1 is collected in the gas chamber 9 and discharged from the gas discharge passage 10.

When the granule sludge grows due to the continued anaerobic treatment and the sedimentation property deteriorates, the sludge property detecting device 14
Detects this and drives the crushing device 11, and the sludge extraction path 1
Granule sludge 2 is taken out from No. 2 and crushed by crushing device 11, and returned to anaerobic reaction tank 1 from sludge return passage 13.
Such an operation is carried out intermittently or continuously to the extent necessary and sufficient for the granule sludge forming the sludge blanket 3 to maintain a particle size exhibiting sedimentation.
The sludge property detecting device 14 may be any device that can detect the levitation index such as particle size and levitation potential.
In some cases, manual analysis may be performed.

As described above, before the granule sludge floats, the properties of the sludge are detected, and the granule sludge is crushed and returned to the anaerobic reaction tank 1 to form the sludge blanket 3. 2 is kept in a good sedimentation state, whereby floating sludge is prevented from flowing out, the amount of sludge forming a sludge blanket is appropriately maintained, and efficient treatment is performed.

The test results will be described below. FIG. 2 is a graph showing the relationship between the representative diameter of the granule sludge produced by the anaerobic treatment of brewery effluent and the floating potential. The flotation potential of FIG. 2 was obtained by adding granule sludge to an acetic acid salt of 2,000 mg / l in an Erlenmeyer flask.
In the H7 phosphate buffer, the acetic acid load on the sludge amount should be a high load of about 2 g COD / g VSS.
It is the value which was made to immerse in the condition of (degreeC), and after 24 hours, the flotation sludge and the sedimentation sludge were separated, VSS weight was measured, and it was displayed as the ratio% of the flotation sludge to the total sludge. In FIG. 2, the same symbols indicate that the granulated sludge produced from the same effluent has different particle sizes. As is clear from the results shown in Fig. 2, sludge having a large particle size has a strong tendency to float, and particularly when the particle size is 2 mm or more, the potential is 30%.
Reach This indicates that 30% of the sludge floats up and flows out when the load increases. As a result, it can be seen that sludge having a large particle size has a high floating property.

In FIG. 3, about 1 liter of granule sludge shown by (+) in FIG.
Crushing time and V when the crushing process was performed at a rotation speed of 00 rpm
It is a graph which shows the relationship of SS particle size distribution. As is clear from the results shown in FIG. 3, if the crushing time is short (for example, 2 seconds), the crushing is insufficient, and if the crushing time is long (for example, 10 seconds), the fine sludge increases and the spillage easily occurs. In the system, about 5 seconds is considered to be appropriate. “Standard” in FIG. 3 shows an example in which the value is set to an appropriate value for testing. As a result, it is understood that the degree of crushing and the crushing time are important factors for maintaining the sedimentation property of the granulated sludge.

Example 1 and Comparative Example 1 Granule sludge (average particle size of about 2.2 mm) collected from a UASB method anaerobic treatment apparatus for brewery effluent was used,
The effect of the above crushing was examined. In Example 1, this sludge 2.
0 liter (about 75 g VSS) was crushed with the household mixer for 5 seconds to give an inner diameter of 10 cm and a height of 1 as shown in FIG.
A 00 cm (volume 9 liter) experimental UASB anaerobic reactor 1 was filled. In Comparative Example 1, the same amount of granule sludge was untreated and filled in the UASB anaerobic reaction tank 1 having the same specifications. On the other hand, the acid production tank 15 has a capacity of 2.5 l
Using an iter tank, the liquid was circulated by the pump 19 to be stirred.

In the above device, glucose 2250
mg / l, ethanol 750 mg / l, yeast extract 30
mg / l, KH ₂ PO ₄ 26 mg / l, NH ₄ Cl 1
20 to 36 of 45 mg / l substrate from the drainage introducing passage 16
It was introduced into the acid production tank 15 at a rate of liter / d (1Q) to carry out acid fermentation. An anaerobic treatment (methane fermentation) was performed in an upward flow by supplying a liquid to be treated of 2Q together with the returned liquid 1Q from the returned liquid passage 18 from the acid generation tank 15 to the anaerobic reaction tank 1. At this time, the treatment temperature was controlled at 30 ° C., and the pH of the acid production tank 15 outlet, that is, the anaerobic reaction tank 1 inlet was controlled at 6.0. The CODcr load of the anaerobic reaction tank 1 is 8 to 14 kg / m ³ / d,
The sludge was not crushed by the crusher 11 and the treatment was continued for about 2 months.

As a result, in Example 1 in which the granulated sludge was crushed and filled, stable treated water was obtained continuously for about 2 months, and the CODcr removal rate was 90 to 95% by weight. On the other hand, in Comparative Example 1 in which the sludge was filled as it was without being crushed, the sludge floated upstream from the beginning of the operation, and the sludge amount gradually decreased. As a result, the CODcr removal rate after one month dropped to 80% by weight or less, and it became difficult to operate with a load higher than this. The amount of granulated sludge per CODcr for about 60 days was 2.1% by weight in Example 1, while in Comparative Example 1, the amount of granulated sludge was reduced by 38% by weight.

Table 1 shows the treated water quality after 8 weeks.

[0035]

[Table 1]

From the above results, by crushing the granulated sludge and performing the anaerobic treatment, the floating and outflow of the sludge can be prevented, the high-load treatment can be stably continued, and the sludge can also grow stably. Recognize. In addition, the sludge was crushed in the initial stage and then treated stably for 60 days without crushing it. Therefore, the sludge is crushed intermittently, or the sludge is crushed continuously or intermittently. You can see that it can be sent back.

[0037]

According to the present invention, the granule sludge forming the sludge blanket is crushed and subjected to the anaerobic treatment. Therefore, the sedimentation property of the granule sludge is prevented from being deteriorated and the sedimentation property is deteriorated. Even in this case, the sedimentation property can be promptly recovered, which prevents the sludge from floating and flowing out, and allows the sludge to grow stably. Therefore, the sludge concentration in the tank can be kept high and the treatment efficiency can be improved. Processing can be performed.

[Brief description of drawings]

FIG. 1 is a system diagram of an anaerobic treatment apparatus according to an embodiment.

FIG. 2 is a graph showing the results in Examples.

FIG. 3 is a graph showing the results of the examples.

[Explanation of symbols]

 1 Anaerobic reaction tank 2 Granule sludge 3 Sludge blanket 4 Treatment liquid inflow portion 5 Gas solid-liquid separation plate 6 Treatment liquid overflow portion 7 Treatment liquid supply passage 8 Treatment liquid discharge passage 9 Gas chamber 10 Gas discharge passage 11 Crushing Equipment 12 Sludge removal passage 13 Sludge return passage 14 Sludge property detection device 15 Acid generation tank 16 Waste liquid introduction passage 17, 19 Pump 18 Return liquid passage 20 Circulation passage

Claims (1)

[Claims] 1. An anaerobic reaction tank for forming a sludge blanket from granulated sludge containing anaerobic microorganisms, and anaerobically decomposing organic matter by passing an organic waste liquid in an upward flow, and the sludge blanket. An anaerobic treatment device comprising: a crushing device for crushing the formed granule sludge.