JP2010069482A - Biological treatment method for organic waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain further an improvement in treatment efficiency and the reduction of excessive sludge production amount while keeping the stable quality of treated water in a multistage activated sludge method utilizing the predation of microorganisms. <P>SOLUTION: This biological treatment method for organic waste water includes a first biological treatment process of transforming BOD (biological oxygen demand) in organic waste water to dispersed fungus bodies through high load treatment and a second biological treatment process of flocculating the transformed dispersed fungus bodies and allowing the microorganisms to coexist. The second biological treatment process is performed under conditions of pH 5 to 6. Otherwise, such an excessive sludge treatment process that sludge of the second biological treatment process and/or at least a part of the sludge obtained by solid-liquid separation of the sludge of the second biological treatment process is decomposed under aerobic conditions and the treated sludge is returned to the first biological treatment process and/or the second biological treatment process is performed under conditions of pH 5 to 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biological treatment method for organic wastewater that can be used for treatment of organic wastewater in a wide concentration range including domestic wastewater, sewage, food factories and pulp factories. The present invention relates to a biological treatment method for organic wastewater that can improve the treatment efficiency and reduce the amount of excess sludge generation without deteriorating.

The activated sludge method used when biologically treating organic wastewater is widely used for sewage treatment, industrial wastewater treatment, and the like because of its advantages such as good treated water quality and easy maintenance. However, since the BOD volumetric load in the activated sludge method is about 0.5 to 0.8 kg / m ³ / d, a large site area is required. Moreover, since 20% of the decomposed BOD is converted into microbial cells, that is, sludge, a large amount of excess sludge treatment also becomes a problem.

For high load treatment of organic waste water, a fluidized bed method with a carrier added is known. When this method is used, it is possible to operate with a BOD volume load of ³ kg / m ³ / d or more. However, this method has a disadvantage that the amount of generated sludge is about 30% of the decomposed BOD, which is higher than the normal activated sludge method.

  In Japanese Examined Patent Publication No. 56-48235, organic wastewater is first treated with bacteria in a first treatment tank, and organic matter contained in the wastewater is oxidatively decomposed and converted into non-aggregating bacterial cells, followed by second treatment. It is said that the amount of excess sludge can be reduced by precipitating and removing the sticking protozoa in the tank. Japanese Patent Publication No. 62-54073 also describes a similar two-stage biological treatment. In these methods, high-load operation is possible and the activated sludge treatment efficiency is improved.

  In Japanese Patent No. 3360076, in such a two-stage biological treatment method, activated sludge containing protozoa is extracted from the biological treatment tank, sterilized and solubilized in the reaction treatment tank, and returned to the biological treatment layer. A method for further reducing the amount of excess sludge generation is described.

  Japanese Patent No. 3410699 discloses a method of further reducing the amount of surplus sludge generated by using a carrier fluidized bed as the first biological treatment and a multistage activated sludge treatment as the second biological treatment. In this method, the activated sludge treatment at the latter stage is operated at a low load of BOD sludge load 0.1 kg-BOD / kg-MLSS / d, so that the sludge is self-oxidized and the amount of sludge extraction can be greatly reduced.

Japanese Patent Publication No. 56-48235 Japanese Examined Patent Publication No. 62-54073 Japanese Patent No. 3360076 Japanese Patent No. 3410699

  The multi-stage activated sludge method using the predation action of micro-organisms as described above has already been put to practical use in organic wastewater treatment. Depending on the target wastewater, it is possible to improve treatment efficiency and reduce the amount of generated sludge. is there.

  However, although the sludge reduction effect varies depending on the treatment conditions and the water quality of the wastewater, it is about a half of the amount of sludge generated by the single tank activated sludge method. This is due to the fact that most of the sludge remains without being predated and the microbes involved in the predation cannot be maintained at a high concentration in the subsequent microbiological tank for preying the bacteria-based sludge.

  Therefore, the present invention is a multi-stage activated sludge process that uses the predation action of micro-organisms, and maintains organic wastewater quality and further improves the treatment efficiency and reduces the amount of excess sludge generated. An object is to provide a processing method.

Organic biological treatment how waste water of the present invention includes a first biological treatment step of converting the BOD in the organic waste water by high-load processing in a distributed cells, the converted dispersed bacteria as well as flocculation In the organic wastewater biological treatment method having a second biological treatment step in which micro-organisms coexist, the sludge of the second biological treatment step and / or the sludge of the second biological treatment step is separated into solid and liquid. A surplus sludge treatment step of decomposing at least a part of the obtained sludge under aerobic conditions, and returning the treated sludge of the surplus sludge treatment step to the first biological treatment step and / or the second biological treatment step The organic wastewater biological treatment method is characterized in that the excess sludge treatment step is performed under conditions of pH 5-6.

When aerobic treatment of organic wastewater is carried out in an acidic region of pH 6 or less by the conventional single tank activated sludge method, a large amount of fungi are generated, which causes bulking. However, as in the method of the present invention performs a first biological treatment step of converting the BOD to dispersed bacteria in the neutral region of pH 6-8, the surplus sludge treatment process for sludge reduction in pH5~6 By performing in the acidic region, it is possible to greatly reduce the amount of generated sludge. This allows the surplus sludge treatment process micro organisms that coexist With pH 5-6, enables efficient predatory unaggregated sludge from the first biological treatment step of performing BOD treatment, while the for growth of most micro-organisms involved in predation unaffected by pH be in the range of pH 5-8, in surplus sludge treatment process, the ratio of the minute organisms occupying the VSS to the high concentration of 20% or more By being able to increase.

Thus, according to the present invention, by adapting the environmental conditions in accordance with the respective functions in the surplus sludge treatment process for the first biological treatment process and sludge reduction for BOD treatment, both Thus, the processing efficiency can be improved and the amount of excess sludge generated can be reduced .

In the present invention , the surplus sludge treatment step may be a sludge return-type biological treatment step in which solid-liquid separation means is provided at the subsequent stage of the biological treatment tank and the sludge separated from the solid and liquid is returned to the biological treatment tank. It may be a fluidized bed biological treatment process in which a carrier is added to the treatment tank.

In addition , the second biological treatment step includes a solid-liquid separation means at the subsequent stage of the biological treatment tank, and a sludge return-type biological treatment step for returning the solid-liquid separated sludge to the biological treatment tank, a carrier in the biological treatment tank. Either a fluidized bed biological treatment process or a membrane separation biological treatment process to which is added, and the first biological treatment process is a fluidized bed biological treatment in which a carrier is added to a biological treatment tank, or You may carry out by the multistage process of 2 steps or more.

  According to the organic wastewater biological treatment method of the present invention, in the multi-stage activated sludge method utilizing the predation action of micro-organisms, the treatment efficiency can be further improved and the amount of excess sludge generated while maintaining stable treated water quality. Reduction can be achieved.

It is a systematic diagram which shows embodiment of the biological treatment method of the organic waste_water | drain which concerns on a reference example . Another embodiment of the biological treatment process of organic waste water of the present invention is a system diagram showing. It is a systematic diagram which shows other embodiment of a surplus sludge process. 4A is a system diagram showing the experimental apparatus used in Reference Example 1, and FIG. 4B is a system diagram showing the experimental apparatus used in Example 1. FIG. Reference Example 1 is a graph showing the relationship between the charged BOD volume and excess sludge generation amount in Example 1及 beauty Comparative Examples 1 and 2.

  Embodiments of a biological treatment method for organic wastewater according to the present invention will be described below in detail with reference to the drawings.

Figure 1 is a system diagram showing an embodiment of the biological treatment process of organic waste water according to a reference example, FIG. 2 is a system diagram showing an embodiment of the biological treatment process of organic waste water of the present invention.

In the method of FIG. 1, raw water (organic wastewater) is first introduced into a first biological treatment tank (dispersed bacteria tank) 1 and is 70% or more, preferably 80% of BOD (organic component) due to non-aggregating bacteria. More preferably, 90% or more is oxidatively decomposed. The pH of the first biological treatment tank 1 is 6 or more, preferably pH 6-8. Moreover, the BOD volumetric load to the 1st biological treatment tank 1 shall be 1 kg / m < ³ > / d or more, for example, 1-20 kg / m < ³ > / d, HRT (raw water residence time) shall be 24 h or less, for example, 0.5-24 h. Thus, it is possible to obtain treated water in which non-aggregating bacteria predominate, and by shortening the HRT, wastewater having a low BOD concentration can be treated with a high load, which is preferable. Further, by adding a carrier, it becomes possible to reduce a high load and a residence time.

  The treated water in the first biological treatment tank 1 is introduced into a second biological treatment tank (micro biological tank) 2 controlled to a pH of 5 to 6, preferably pH 5 to 5.5, and remains there. The sludge is reduced by oxidative degradation of organic components, self-degradation of non-aggregating bacteria, and predation by micro-organisms.

  In the method of FIG. 1, the second biological treatment tank 2 is multistaged, and two or more biological treatment tanks are provided in series, and the treatment is performed at a pH of 5 to 6, preferably pH 5 to 5.5, in the preceding biological treatment tank. In this case, the treatment may be performed at a pH of 6 or more, preferably at a pH of 6 to 8 in the biological treatment tank on the rear stage side. By such multistage treatment, predation of sludge is effectively performed in the biological treatment tank on the front stage side. It is possible to improve the solid-liquid separation property of sludge and the quality of treated water in the biological treatment tank on the rear stage side.

  The treated water in the second biological treatment tank 2 is solid-liquid separated in the precipitation tank 3, and the separated water is discharged out of the system as treated water. A part of the separated sludge is discharged out of the system as surplus sludge, and the remaining part is returned to the first biological treatment tank 1 and the second biological treatment tank 2. In addition, this sludge return is performed in order to maintain the amount of sludge in each biological treatment tank. For example, the first biological treatment tank 1 and / or the second biological treatment tank 2 is loaded with a carrier as described below. In the case of an added fluidized bed type, sludge return may not be necessary. Moreover, when the BOD volumetric load of the 1st biological treatment tank 1 is low, sludge return is good also as the 2nd biological treatment tank 2 only.

  In the method of FIG. 2, raw water (organic waste water) is sequentially introduced into the first biological treatment tank 1 and the second biological treatment tank 2 which are both controlled to pH 6 or less, preferably pH 6 to 8, and the method of FIG. Similarly, 70% or more, desirably 80% or more, more desirably 90% or more of the organic components are oxidatively decomposed by non-aggregating bacteria in the first biological treatment tank 1 and then remain in the second biological treatment tank 2. The sludge is reduced by oxidative degradation of organic components, self-degradation of non-aggregating bacteria and predation by micro-organisms. The treated water in the second biological treatment tank 2 is solid-liquid separated in the precipitation tank 3, and the separated water is discharged out of the system as treated water. At least a part of the generated sludge generated from the second biological treatment tank 2 (in FIG. 2, a part of the separated sludge of the sedimentation tank 3 into which treated water of the second biological treatment tank 2 is introduced) has a pH of 5-6. Preferably, it is fed to an excess sludge treatment tank 4 controlled in the range of pH 5 to 5.5, where it is decomposed by aerobic digestion. The treated sludge in the excess sludge treatment tank 4 is returned to the first biological treatment tank 1 and / or the second biological treatment tank 2. In FIG. 2, a part of the remaining sludge in the sedimentation tank 3 is discharged out of the system as surplus sludge, and the remaining part is returned to the second biological treatment tank 2.

  Of the separated sludge in the sedimentation tank 3, the ratio of the sludge amount to be fed to the surplus sludge treatment tank 4 and the sludge quantity to be returned to the second biological treatment tank 2 can maintain a suitable surplus sludge treatment tank residence time described later. Thus, it sets suitably according to the amount of generated sludge. The ratio of the amount of sludge to be returned to the first and second biological treatment tanks 1 and 2 among the treated sludge in the surplus sludge treatment tank 4 or which biological treatment tank to return depends on the sludge retention of each biological treatment tank It is set as appropriate so that the amount can be maintained.

  The surplus sludge treatment tank 4 may be charged with half of the total amount of generated sludge when the apparatus is started up or when the amount of generated sludge is high. This excess sludge treatment tank 4 has not only a sludge reduction effect but also an effect of supplying micro-organisms to the second biological treatment tank 2. The sludge retention time of the excess sludge treatment tank 4 is 6 hours or longer, preferably 12 hours or longer, for example, 12 to 240 hours. For example, as shown in FIG. By using an aerobic treatment method, a fluidized bed to which a carrier is added, or a membrane separation type aerobic treatment method, the sludge residence time can be further increased. As the carrier for the excess sludge treatment tank 4, those described later as the carrier for the first biological treatment tank can be used.

1 and 2, when a large amount of organic matter remains in the treated water of the first biological treatment tank 1 introduced into the second biological treatment tank 2, the oxidative decomposition is performed in the second biological treatment tank 1. 2 will be done. It is known that when oxidative degradation of organic matter by bacteria occurs in the second biological treatment tank 2 in which a large amount of micro organisms are present, it proliferates in a form that is difficult to prey, as a countermeasure to escape from predation of micro organisms. The bacterial group thus grown is not preyed on by the micro-organisms, and their decomposition depends only on self-digestion, and the effect of reducing the amount of sludge generated decreases. In the method of the present invention, which sets the surplus sludge treatment tank 4 to the acidic range, if the organic material has a large amount of residual becomes also cause bulking such ends up proliferate fungi utilizing the organics . Therefore, as described above, in the first biological treatment tank 1, most of the organic matter, that is, 70% or more of the raw water BOD, desirably 80% or more, more desirably 90% or more, is decomposed into cells. It needs to be converted. Therefore, when expressed by the sludge load due to the soluble BOD in the second biological treatment tank 2, it is operated at 0.5 kg-BOD / kg-MLSS / d or less, for example, 0.01 to 0.1 kg-BOD / kg-MLSS / d. It is preferable to do.

The method of FIG. 2 shows an example of an embodiment of the present invention, and the present invention is not limited to the illustrated method unless it exceeds the gist.

For example, the first biological treatment tank is a fluidized bed system with a carrier added in addition to returning a part of the separated sludge from the subsequent sedimentation tank for high load treatment, or two or more biological treatment tanks in series. It is also possible to perform multi-stage processing by providing them. In particular, the addition of a carrier is preferable because a high load treatment with a BOD volume load of 5 kg / m ³ / d or more is possible. In this case, the shape of the carrier to be added is arbitrary such as a spherical shape, a pellet shape, a hollow cylindrical shape, and a thread shape, and the size may be about 0.1 to 10 mm. The material of the carrier is arbitrary such as a natural material, an inorganic material, or a polymer material, and a gel material may be used. Further, in the second biological treatment tank 2, in order to utilize the action of micro-organisms whose growth rate is slower than that of bacteria and the self-degradation of bacteria, operating conditions and processing devices are adopted so that the micro-organisms and bacteria stay in the system. For this reason, as shown in FIG. 2 , the second biological treatment tank is separated into the tank as shown in FIG. 2 in addition to performing sludge return biological treatment for returning sludge. It is also desirable to perform membrane separation activated sludge treatment by immersing the membrane. More desirably, the amount of micro-organisms retained in the tank can be increased by adding a carrier to the aeration tank. As the carrier in this case, the same carrier as described above as the carrier added to the first biological treatment tank can be used.

The present invention will be described more specifically with reference to the following reference examples, examples and comparative examples.

Reference example 1
As shown in FIG. 4 (a), an activated sludge tank with a capacity of 3.6L (no sludge return) is used as the first biological treatment tank 11, and an immersion membrane activated sludge tank with a capacity of 15L is used as the second biological treatment tank 12. The organic waste water (BOD630mg / L) treatment by this invention was performed using the connected experimental apparatus. The pH of the first biological treatment tank 11 was adjusted to 6.8, and the pH of the second biological treatment tank 12 was adjusted to 5.0. Table 1 shows the results 4 months after the start of the experiment. Moreover, the excess sludge generation amount (sludge conversion rate) with respect to the input BOD is shown in FIG.

In this reference example, the soluble BOD volumetric load on the first biological treatment tank 11 is 3.5 kg-BOD / m ³ / d, HRT is 4 h, and the soluble BOD sludge load on the second biological treatment tank 12 is 0.022 kg- BOD / kg-MLSS / d, HRT was 17h, BOD volumetric load was 0.75kg-BOD / m ³ / d, HRT was operated under the conditions of 21h. Sludge conversion rate was 0.1kg-MLSS / kg Although it became -BOD, the treated water BOD was below the detection limit.

Example 1
As shown in FIG. 4 (b), an activated sludge tank with a capacity of 3.6L (no sludge return) as the first biological treatment tank 11, and a submerged membrane activated sludge tank with a capacity of 15L as the second biological treatment tank 12. The organic waste water (BOD 630 mg / L) according to the present invention was treated using an experimental apparatus in which an excess sludge treatment tank 13 having a capacity of 1 L was connected. The pH of both the first biological treatment tank 11 and the second biological treatment tank 12 was adjusted to 6.8, and the pH of the excess sludge treatment tank 13 was adjusted to 5.0. The sludge in the tank is drawn out from the second biological treatment tank 12 at a rate of 0.5 L / d and introduced into the surplus sludge treatment tank 13, and the sludge in the tank is drawn out from the surplus sludge treatment tank 13 at 0.5 L / d. This was returned to the second biological treatment tank 12. The residence time of the excess sludge treatment tank 13 was SRT = HRT = 1 day. Table 1 shows the results 4 months after the start of the experiment. Moreover, the excess sludge generation amount (sludge conversion rate) with respect to the input BOD is shown in FIG.

In this example, the soluble BOD volumetric load on the first biological treatment tank 11 is 3.85 kg-BOD / m ³ / d, HRT is 4 h, and the soluble BOD sludge load on the second biological treatment tank 12 is 0.022 kg- BOD / kg-MLSS / d, HRT was 17h, BOD volumetric load was 0.75kg-BOD / m ³ / d, HRT was operated under the conditions of 21h. Sludge conversion rate was 0.11kg-MLSS / kg −BOD, and the treated water BOD was below the detection limit.

Comparative Example 1
In Reference Example 1, the first biological treatment tank was omitted, and the organic wastewater (BOD 630 mg / L) was treated using an experimental apparatus consisting only of a submerged membrane activated sludge tank with a capacity of 15 L of the second biological treatment tank. . Table 1 shows the results 4 months after the start of the experiment. Moreover, the excess sludge generation amount (sludge conversion rate) with respect to the input BOD is shown in FIG.

In this comparative example, when the soluble BOD volumetric load was 0.76 kg-BOD / m ³ / d and the HRT was operated under the conditions of 20 h, the treated water quality was good as shown in Table 1, but the sludge conversion rate Was 0.40 kg-MLSS / kg-BOD.

Comparative Example 2
In Reference Example 1, treatment of organic waste water (BOD 630 mg / L) was performed in the same manner except that both the first biological treatment tank and the second biological treatment tank were adjusted to pH 6.8. Table 1 shows the results 4 months after the start of the experiment. Moreover, the excess sludge generation amount (sludge conversion rate) with respect to the input BOD is shown in FIG.

In this comparative example, the soluble BOD volumetric load 3.85 kg-BOD / m ³ / d for the first biological treatment tank 11, the HRT is 4 h, the soluble BOD sludge load of the second biological treatment tank 12 is 0.022 kg-BOD / kg-MLSS / d, HRT was 17h, overall BOD volumetric load was 0.75kg-BOD / m ³ / d, and HRT was operated for 21h. As shown in Table 1, the quality of the treated water was good. However, the sludge conversion rate was 0.2 kg-MLSS / kg-BOD.

Reference Example 1, the following can be seen from the results of Example 1及 beauty Comparative Examples 1 and 2.

  Comparative Example 1 is a conventional activated sludge method, and Comparative Example 2 is a multi-stage biological treatment method that does not include a biological treatment step in an acidic region. In the conventional activated sludge method (Comparative Example 1), the sludge conversion rate was 0.40 kg-MLSS / kg-BOD, but by introducing multistage biological treatment as in Comparative Example 2, the sludge conversion rate was 0. It became 20 kg-MLSS / kg-BOD, and the sludge generation amount could be reduced to ½. This sludge reduction effect is similar to the multistage biological treatment methods reported so far.

On the other hand, in Example 1 were introduced biological treatment process in an acidic region as in the present invention, the sludge conversion rate 0. It was 11 kg-MLSS / kg-BOD, and the amount of generated sludge was reduced to ¼ compared to the conventional method, and to ½ compared to the conventional multistage biological treatment method.

  The biological treatment method for organic wastewater of the present invention can be used for treatment of organic wastewater in a wide concentration range including domestic wastewater, sewage, food factories and pulp factories.

1,11 First biological treatment tank 2,12 Second biological treatment tank 3 Precipitation tank 4,13 Excess sludge treatment tank

Claims (6)

A first biological treatment process for converting BOD in organic wastewater into a dispersed cell by high-load treatment;
In a biological treatment method for organic wastewater, which has a second biological treatment step for flocking the converted dispersed cells and coexisting with micro-organisms,
A method for biological treatment of organic wastewater, characterized in that the second biological treatment step is carried out under conditions of pH 5-6.   The organic treatment according to claim 1, wherein the second biological treatment step is a multistage treatment of two or more stages, and in the second biological treatment step, the biological treatment of pH 6 or more is performed after the biological treatment of pH 5-6. Biological treatment method for effluent. A first biological treatment process for converting BOD in organic wastewater into a dispersed cell by high-load treatment;
In a biological treatment method for organic wastewater, which has a second biological treatment step for flocking the converted dispersed cells and coexisting with micro-organisms,
A surplus sludge treatment step of decomposing at least a part of the sludge obtained by solid-liquid separation of the sludge of the second biological treatment step and / or the sludge of the second biological treatment step under aerobic conditions; A biological treatment method for organic wastewater that returns the treated sludge of the excess sludge treatment step to the first biological treatment step and / or the second biological treatment step,
A biological treatment method for organic waste water, wherein the excess sludge treatment step is performed under conditions of pH 5-6.   In Claim 3, the surplus sludge treatment process is a sludge return-type biological treatment process in which solid-liquid separation means is provided at the subsequent stage of the biological treatment tank and the sludge separated into solid and liquid is returned to the biological treatment tank, or biological treatment A biological treatment method for organic wastewater, which is a fluidized bed biological treatment process in which a carrier is added to a tank.   5. The sludge return according to claim 1, wherein the second biological treatment step is provided with solid-liquid separation means at a subsequent stage of the biological treatment tank, and the sludge separated by solid-liquid is returned to the biological treatment tank. A biological treatment method for organic waste water, which is a biological treatment process, a fluidized bed biological treatment process in which a carrier is added to a biological treatment tank, or a membrane separation biological treatment process.   The first biological treatment step according to any one of claims 1 to 5, wherein the first biological treatment step is performed by a fluidized bed biological treatment in which a carrier is added to a biological treatment tank or a multistage treatment of two or more stages. Biological treatment method for organic wastewater.

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