JP7105431B2 - Method and apparatus for treating wastewater containing organic matter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technology of a treatment method and a treatment apparatus for waste water containing organic substances.

Conventionally, wastewater containing organic matter such as sewage is treated by aerobic biological treatment such as the standard activated sludge method, and then anaerobic biological treatment is performed by collecting the generated sludge and fermenting methane under anaerobic conditions. (See, for example, Patent Document 1).

Biogas such as methane gas generated by anaerobic biological treatment can be used as an energy source. Therefore, for example, in relatively large-scale sewage treatment plants, it is being considered to collect biogas generated by anaerobic treatment, convert the collected biogas into energy such as electric power, and use it.

Japanese Patent Application Laid-Open No. 2005-103486

However, in the conventional method, in the aerobic biological treatment process of the first stage, many organic substances in the wastewater are decomposed, so the amount of organic matter sent to the anaerobic biological treatment process of the latter stage decreases, and in the anaerobic biological treatment process The amount of generated biogas also decreases. As a result, the amount of energy that can be recovered as energy from biogas also decreases.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method and apparatus for treating organic matter-containing wastewater that can increase the amount of biogas generated.

In the method for treating organic matter-containing wastewater of the present invention, the wastewater is passed through a hollow fiber membrane and separated into permeated water and concentrated water containing the organic matter before biological treatment is performed on the wastewater containing organic matter. A membrane filtration step and an anaerobic biological treatment step of anaerobicly biologically treating the concentrated water containing the organic matter, the membrane filtration step is performed in multiple stages, and the concentration ratio in the second stage membrane filtration is The concentration ratio is set higher than that in the first-stage membrane filtration, and the membrane surface of the hollow fiber membrane is vibrated during the membrane filtration step.

Further, in the method for treating organic matter-containing wastewater, the concentration ratio in the membrane filtration step is preferably 50 times or more.

In the method for treating organic matter-containing waste water, the amount of organic matter in the concentrated water is preferably 75% or more of the amount of organic matter in the waste water containing organic matter.

Further, in the method for treating organic substance-containing waste water, in the membrane filtration step, it is preferable that the permeate water flow rate (m/d) of the filtration membrane is decreased toward the later stage.

Further, in the apparatus for treating organic matter-containing wastewater of the present invention, the wastewater is passed through a hollow fiber membrane before biological treatment is performed on the wastewater containing organic matter, and the permeated water and the concentrated water containing the organic matter are separated. Membrane filtration means for performing a membrane filtration step for separation, anaerobic biological treatment means for biologically treating the concentrated water containing the organic matter under anaerobic conditions, and vibrating the membrane surface of the hollow fiber membrane during the membrane filtration step and vibrating means , wherein the membrane filtration means is composed of a plurality of stages, and the concentration factor in the second stage membrane filtration is higher than the concentration factor in the first stage membrane filtration .

Advantageous Effects of Invention According to the present invention, it is possible to provide a method and apparatus for treating organic matter-containing wastewater, which can increase the amount of biogas generated.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing an example of the configuration of an apparatus for treating amine-containing wastewater according to an embodiment of the present invention; FIG. 4 is a schematic diagram showing another example of the configuration of the membrane filtration module;

An embodiment of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

FIG. 1 is a schematic diagram showing an example of the configuration of an organic matter-containing wastewater treatment apparatus according to an embodiment of the present invention. A wastewater treatment apparatus 1 shown in FIG. 1 includes a membrane filtration apparatus 10 and an anaerobic biological treatment tank 12 . The membrane filtration device 10 shown in FIG. 1 includes three membrane filtration modules (14, 16, 18). The membrane filtration modules ( 14 , 16 , 18 ) comprise, for example, hollow fiber membranes 22 arranged inside a closed filtration vessel 20 .

A waste water introduction pipe 26 is connected to the waste water inlet 24 of the first-stage membrane filtration module 14 . One end of the concentrated water pipe 30a is connected to the waste water outlet 28 of the first-stage membrane filtration module 14, and the other end of the concentrated water pipe 30a is connected to the waste water inlet 24 of the second-stage membrane filtration module 16. It is connected. One end of the concentrated water pipe 30b is connected to the waste water outlet 28 of the second-stage membrane filtration module 16, and the other end of the concentrated water pipe 30b is connected to the waste water inlet 24 of the third-stage membrane filtration module 18. It is connected. One end of the concentrated water pipe 30c is connected to the drainage outlet 28 of the third-stage membrane filtration module 18, and the concentrated water inlet (not shown) of the anaerobic biological treatment tank 12 is connected to the concentrated water pipe 30c as well as the ends are connected. Concentrated water pumps (32a, 32b, 32c) are installed in the concentrated water pipes (30a, 30b, 30c).

Inside the hollow fiber membranes 22 in the membrane filtration module 14 of the first stage, a space is formed into which the permeated water that permeates the membrane flows, and communicates with a water collection pipe 34 installed at the upper end of the hollow fiber membranes 22 . is doing. In addition, the water collection pipe 34 communicates with the permeated water pipe 38 via the treated water outlet 36 of the first-stage membrane filtration module 14 . A backwash water pipe 40 is connected to the permeated water pipe 38 . A permeated water pump 42 is installed in the permeated water pipe 38 , and a backwash pump 44 is installed in the backwash water pipe 40 . The second-stage and third-stage membrane filtration modules (16, 18) have the same piping configuration, and the description thereof is omitted.

A treated water pipe 46 is connected to a treated water outlet (not shown) of the anaerobic biological treatment tank 12 , and a biogas discharge pipe 48 is connected to an exhaust gas outlet (not shown) of the anaerobic biological treatment tank 12 .

Next, an example of the operation of the waste water treatment apparatus 1 according to this embodiment will be described.

Organic matter-containing waste water is supplied to the first-stage membrane filtration module 14 through a waste water introduction pipe 26 . Then, by operating the permeated water pump 42 to apply suction pressure (negative pressure) to the hollow fiber membranes 22, the waste water in the membrane filtration module 14 permeates the hollow fiber membranes 22 and is membrane filtered. . The permeated water that has permeated the hollow fiber membranes 22 passes through the internal space in the hollow fiber membranes 22, the water collection pipe 34, and the permeated water pipe 38, and is discharged out of the first stage membrane filtration module 14 system. In this manner, organic substance-containing waste water in the first-stage membrane filtration module 14 is concentrated. The permeate pump 42 is stopped when the organic matter-containing waste water in the first-stage membrane filtration module 14 is concentrated to a predetermined concentration ratio. Then, by operating the concentrated water pump 32a, the concentrated water containing organic substances in the first-stage membrane filtration module 14 is supplied from the concentrated water pipe 30a to the second-stage membrane filtration module 16. Similarly, in the membrane filtration modules (16, 18) in the second and subsequent stages, the concentrated water containing organic matter is subjected to membrane filtration, and the permeated water is discharged from the permeated water pipe 38 to the outside of the system, and the membrane filtration modules in the second and subsequent stages ( 16, 18) is concentrated to a predetermined concentration ratio. Here, the concentration ratio in the specification of the present application is defined by the following formula (1).

Concentration ratio = amount of permeated water / amount of concentrated water (1)
For example, when the amount of water flowing into the membrane filtration module is 100 parts by volume and 90 parts by volume of permeated water is obtained, the concentrated water is 10 parts by volume. If these are applied to the above formula (1), the concentration ratio will be 9 times.

Concentrated water containing organic matter discharged from the third-stage membrane filtration module 18 is supplied to the anaerobic biological treatment tank 12 through a concentrated water pipe 30c. In the anaerobic biological treatment tank 12, for example, organic matter in the concentrated water is anaerobicly treated with biological sludge (for example, nitrification sludge) by methane fermentation to generate biogas such as methane gas. Biogas is recovered through a biogas discharge pipe 48 . The biogas recovered from the treated water discharge pipe is converted into electric power in, for example, a biogas power generator, and used for operation of the wastewater treatment apparatus 1 (for example, operation of various pumps, etc.). Also, the treated water that has undergone anaerobic treatment is discharged from the treated water pipe 46 to the outside of the system.

In this way, before biological treatment of organic matter-containing waste water, membrane filtration treatment is performed to obtain concentrated water in which organic matter is concentrated, so that more organic matter can be supplied to the anaerobic biological treatment tank 12. Become. This makes it possible to increase the amount of biogas generated by anaerobic treatment and recover more biogas. As a result, it is also possible to increase the amount of energy that can be recovered as energy from biogas. Depending on the treatment conditions of the wastewater treatment apparatus 1, the wastewater treatment apparatus 1 may become a self-sustaining wastewater treatment apparatus 1 in which the energy used in the operation of the wastewater treatment apparatus 1 is supplemented with the energy generated from the recovered biogas.

In the conventional method, wastewater containing organic matter is treated with aerobic biological treatment using the standard activated sludge method, and then the sludge generated by the aerobic biological treatment is put into the anaerobic biological treatment tank. is, for example, 30% or less in organic matter-containing waste water. On the other hand, in the present embodiment, it is possible to put 75% or more of the organic substances in the organic substance-containing water into the anaerobic biological treatment tank. As a result, the conventional method significantly reduces the amount of biogas generated compared to the treatment method of the present embodiment. In addition, in the conventional method, the sludge fed into the anaerobic biological treatment tank contains a large amount of solid matter (SS). A certain amount of sludge retention time is required. On the other hand, in this embodiment, since the solids are captured by the filtration membrane, the amount of solids in the concentrated water that is put into the anaerobic biological treatment tank is smaller than in the conventional method, and the decomposition efficiency of organic matter by anaerobic treatment is improved. becomes possible. In addition, since the treatment method of this embodiment does not require aerobic biological treatment such as the standard activated sludge method, the energy required for aeration can also be reduced.

The treatment conditions for organic matter-containing waste water, etc. will be described below.

The wastewater to be treated in this embodiment may be wastewater derived from any source as long as it contains organic matter. and industrial wastewater generated from such processes, and process wastewater generated in association with these treatments.

The concentration ratio by membrane filtration is preferably 50 times or more, for example, 150 times or more, in that a high concentration of organic matter can be introduced into the anaerobic biological treatment tank and the amount of biogas generated can be increased. is more preferable.

Membrane filtration may be performed in one stage, but is preferably performed in multiple stages. That is, it is preferable to install a plurality of membrane filtration modules like the membrane filtration device 10 shown in FIG. For example, rather than concentrating wastewater to a predetermined concentration ratio (for example, 50 times) with a single membrane filtration module, it is better to concentrate wastewater to a predetermined concentration ratio with a multi-stage membrane filtration module. It is possible to suppress clogging. In addition, by suppressing clogging of the filtration membrane, an increase in the transmembrane pressure difference can be suppressed, so it is possible to reduce the energy required to apply a high suction pressure to the filtration membrane.

When membrane filtration is performed in multiple stages, that is, when multiple membrane filtration modules are installed, the energy consumption required for membrane filtration can be suppressed. It is preferable to make the concentration ratio higher than that in the membrane filtration module. As the concentration of organic matter increases, the energy required for membrane filtration also increases. Energy consumption required for membrane filtration can be suppressed by lowering the concentration ratio in the second-stage membrane filtration module that membrane-filters the waste water (concentrated water). For example, when concentrating wastewater up to 150 times in a two-stage membrane filtration device, the concentration ratio in the first-stage membrane filtration module is 50 times, and the concentration ratio in the second-stage membrane filtration module is 3 times. (50 times x 3 times = 150 times). In the case where three or more membrane filtration modules are installed, it is desirable that the concentration ratio in the membrane filtration modules is lower in the later stages in order to reduce energy consumption. The concentration ratio may be the same as or higher than the concentration ratio in the second-stage membrane filtration module.

In addition, when organic matter-containing wastewater contains a large amount of SS components such as solids and fibers, the concentration ratio in the second-stage membrane filtration module is set to 1 in order to stably perform membrane filtration. It is preferable to make the concentration ratio higher than that in the membrane filtration module of the stage. For example, the concentration ratio in the first-stage membrane filtration module is set to about 2 to 10 times, the SS component in the waste water is roughly removed by the filtration membrane, and the concentration ratio in the second-stage membrane filtration module is set to several tens of times. , the desired concentration ratio. In addition, in three or more stages of membrane filtration modules, when the concentration ratio in the second stage membrane filtration module is higher than the concentration ratio in the first stage membrane filtration module, the concentration in the third stage and later membrane filtration modules The magnification may be the same as or higher than the concentration magnification in the second-stage membrane filtration module. However, in terms of suppressing the energy consumption required for membrane filtration, it is preferable that the concentration ratio of at least the final-stage membrane filtration module is lower than the concentration ratio of the second-stage membrane filtration module. It is more preferable to set the concentration ratio in the filtration module lower than that in the second-stage membrane filtration module.

In addition, when membrane filtration is performed in multiple stages, that is, when membrane filtration modules are installed in multiple stages, the permeation flow rate of the filtration membrane is decreased toward the latter stage in order to reduce the energy consumption required for membrane filtration. is preferred. The permeation flow rate is the amount of permeated water per day (m ³ /d) divided by the membrane area of the filtration membrane (m ² ), and the permeation rate of wastewater per unit area of the filtration membrane per day (( m ³ /m ² /d=)m/d).

The shape of the filtration membrane used for membrane filtration is not limited to a hollow fiber membrane, and may be, for example, a tubular membrane, a flat membrane, a spiral membrane, or the like. Examples of filtration membranes include ultrafiltration membranes (UF membranes), microfiltration membranes (MF membranes), reverse osmosis membranes (RO membranes), and the like. As for the water flow system of the membrane filtration module, all water flow systems such as internal pressure type and external pressure type can be applied, and all filtration methods such as cross-flow filtration and dead-end filtration can be applied.

Materials for the filtration membrane include, for example, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyethersulfone (PES), organic membranes such as cellulose acetate (CA), inorganic membranes made of ceramics, and the like.

Moreover, when treating sewage or the like containing a large amount of solids such as sand and toilet paper, it is preferable to install a primary sedimentation tank in order to stably perform membrane filtration. In this case, the membrane filtration module may be installed in the rear stage of the primary sedimentation basin, but it is preferable to install the membrane filtration module in the primary sedimentation basin in that the installation space can be reduced. When multiple stages of membrane filtration modules are provided, it is preferable to install at least the first stage membrane filtration module in the primary sedimentation tank. When the membrane filtration module is installed in the primary sedimentation tank, the primary sedimentation tank may be used instead of the filtration vessel 20 shown in FIG.

In this embodiment, the amount of organic matter in the concentrated water obtained by membrane filtration is preferably 75% or more of the amount of organic matter in the organic matter-containing waste water (raw water). As a result, a large amount of organic matter can be introduced into the anaerobic biological treatment, and the amount of biogas generated can be increased. In addition, the amount of organic matter in the permeated water obtained by membrane filtration is 25% or less of the amount of organic matter in the organic matter-containing wastewater. can be reduced. The method for biological treatment of permeated water is not particularly limited, such as the standard activated sludge method and the trickling filter method.

In this embodiment, it is preferable to implement a backwashing process after membrane filtration. Specifically, after the permeate pump 42 is stopped, the backwash pump 44 is started. Washing water or permeated water obtained by membrane filtration is supplied to the internal space (secondary side) of the hollow fiber membranes 22 through the backwash water pipe 40, permeates the hollow fiber membranes 22, and exits the filtration vessel 20. It is discharged (backwashing process). The backwash wastewater discharged from the filtration container 20 may be supplied to the anaerobic biological treatment tank 12 or may be discharged outside the system. By carrying out such a backwashing step, deposits such as SS components adhering to the filtration membrane are removed from the membrane surface, so that stable membrane filtration treatment can be continued.

FIG. 2 is a schematic diagram showing another example of the configuration of the membrane filtration module. In the membrane filtration module 50 shown in FIG. 2, the same components as those of the membrane filtration modules (14, 16, 18) shown in FIG. The membrane filtration module 50 of FIG. 2 includes a vibration generator 52 and a vibration transmission member 54 . One end of the vibration transmitting member 54 is connected to the vibration generating portion 52, and the other end of the vibration transmitting member 54 is connected to the membrane surface of the hollow fiber membrane 22 (the membrane surface of the filtration membrane). A piezoelectric element, a giant magnetostrictive element, or the like, for example, is used for the vibration generating unit 52 . The vibration transmitting member 54 is made of, for example, metal having high rigidity.

In the membrane filtration module 50 of FIG. 2, predetermined vibrations are generated by the vibration generator 52 during or after membrane filtration. Then, the vibration generated by the vibration generating portion 52 is transmitted to the hollow fiber membranes 22 via the vibration transmission member 54, and the membrane surfaces of the hollow fiber membranes 22 are vibrated. By vibrating the membrane surface of the hollow fiber membrane 22 in this way, deposits such as the SS component adhering to the hollow fiber membrane 22 are separated from the membrane surface, so membrane filtration can be performed stably. . The method for vibrating the membrane surface of the filtration membrane is not limited to the above. For example, air scrubbing or the like in which air is introduced into the filtration container 20 to vibrate the membrane surface of the filtration membrane may be used. As another method, for example, the carrier may be put into the filtration container 20, and waste water or permeated water may be introduced into the filtration container 20 to cause the carrier to flow and come into contact with the filtration membrane.

The anaerobic biological treatment tank 12 is, for example, a methane fermentation tank or the like that anaerobicly methane-ferments organic matter to generate biogas such as methane gas. The sludge concentration in the anaerobic biological treatment tank 12 is not particularly limited, but is preferably in the range of 15,000 mg/L to 70,000 mg/L, for example. By setting it as the said range, it becomes possible to decompose an organic substance efficiently. When the sludge concentration in the anaerobic biological treatment tank 12 is less than 15,000 mg/L, for example, it is preferable to input digested sludge or granules from the outside, and when the sludge concentration exceeds 70,000 mg/L Therefore, it is preferable to discharge the sludge in the anaerobic biological treatment tank 12 to the outside. In order to maintain the microbial activity in the anaerobic biological treatment tank 12 well, for example, nutrients such as inorganic salts may be supplied to the anaerobic biological treatment tank 12 .

The pH in the anaerobic biological treatment tank 12 is, for example, preferably in the range of 5.5 to 9.0, more preferably in the range of 6.5 to 8.0, in order to efficiently decompose organic matter. . Although pH adjustment is basically unnecessary, the pH may be adjusted by supplying an acid agent such as hydrochloric acid or an alkali agent such as sodium hydroxide to the anaerobic biological treatment tank 12 .

The water temperature in the anaerobic biological treatment tank 12 is preferably, for example, 20° C. or higher, more preferably 25° C. or higher and 35° C. or lower, in order to efficiently decompose organic substances. The water temperature adjustment method includes, for example, a method of installing a heating device such as a heater in the anaerobic biological treatment tank 12 and adjusting the water temperature in the anaerobic biological treatment tank 12 with heat from the heating device. Alternatively, a method of supplying methane gas generated in the anaerobic biological treatment tank 12 to a methane gas boiler and supplying heat generated in the methane gas boiler to the anaerobic biological treatment tank 12 to adjust the water temperature may be used.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

<Example 1>
Using the three-stage membrane filtration apparatus shown in FIG. 1, actual sewage with an organic matter concentration (CODMn) of 240 mg/L was subjected to membrane filtration. The treatment conditions by the membrane filtration device are as follows.

・First-stage membrane filtration module Filtration membrane: PVDF hollow fiber membrane with a pore size of 0.1 μm Permeation flow rate: 0.144 m / d
Concentration ratio: 2.5 times Second-stage membrane filtration module Filtration membrane: PVDF hollow fiber membrane with a pore size of 0.1 μm Permeation flow rate: 0.1 m/d
Concentration ratio: 20 times Third-stage membrane filtration module Filtration membrane: PVDF hollow fiber membrane with a pore size of 0.1 μm Permeation flow rate: 0.007 to 0.015 m / d
Concentration ratio: 3 times

In the first-stage and second-stage membrane filtration modules, the vibrating device shown in FIG. 2 was used to periodically vibrate the membrane surfaces of the filtration membranes. As a result, an increase in differential pressure of the filtration membrane was suppressed, and stable treatment was possible. Separately, a treatment was also performed in which the carrier was put into the filtration container and the carrier was brought into contact with the filtration membrane. In addition, in the third-stage membrane filtration module, backwashing with washing water was periodically performed. As a result, an increase in differential pressure of the filtration membrane was suppressed, and stable treatment was possible.

A membrane filtration treatment was performed under the above treatment conditions to obtain concentrated water with a concentration ratio of 150 times. The amount of organic matter in the concentrated water was 27,000 mg/L of the amount of organic matter in actual sewage.

Next, the recoverable energy (W1) by power generation was calculated from the amount of methane gas generated when the 150-fold concentrated water was subjected to anaerobic treatment. The energy (W1) was 4,835 kWh/d as a result of assuming treatment with a treated water volume of 50,000 m ³ /d. The amount of water supplied to the anaerobic biological treatment tank was 333 m ³ /d, and the energy (W2) required for heating the anaerobic biological treatment tank was calculated to be 5,850 kWh/d. The amount of electricity recovered from 1 kg of COD in methane fermentation is 1.5 kWh. The amount of electricity that can be recovered per 1 m ³ of methane is 11 kWh, and the amount of methane generated per g-COD is 0.27 to 0.33 L.

The energy (W3) required for membrane concentration in Example 1 was 4,438 kWh/d. As a result of calculating the energy consumption (W0) in the water treatment process from these facts, it was 5,453 kWh/d. The energy consumption (W0) in the water treatment process is obtained by the following formula.
Energy consumption in the water treatment process (W0) = (Energy required for membrane concentration (W3)) + (Energy required for heating the anaerobic biological treatment tank (W2)) - (Energy recoverable by power generation (W1 ))
The energy required for membrane concentration is about 0.089 kWh/m ³ per 1 m ³ of treated water.

<Example 2>
In Example 2, the test was performed using only the first-stage membrane filtration module. Specifically, the concentration ratio of the membrane filtration module in the first stage was 50 times and the permeation flow rate was the same as in Example 1 to obtain concentrated water with a concentration ratio of 50 times. The amount of organic substances in the concentrated water was the same as in Example 1.

As in Example 1, the recoverable energy (W1) by power generation was calculated from the amount of methane gas generated when the 50-fold concentrated water was subjected to anaerobic treatment, resulting in 4,835 kWh/d.

The energy (W3) required for membrane concentration in Example 2 was 4,375 kWh/d. Further, in the same manner as in Example 1, the energy (W2) required for heating the anaerobic biological treatment tank for the 50-fold concentrated water was calculated to be 17,517 kWh/d. As a result of calculating the energy consumption (W0) in the water treatment process from these facts, it was 17,057 kWh/d.

<Comparative example>
The actual sewage was put into a biological treatment tank equipped with an aerator, and aerobic biological treatment was performed. The treated water obtained by the biological treatment was subjected to solid-liquid separation in a sedimentation tank, and the biological sludge accumulated in the sedimentation tank was collected.

As in Example 1, the amount of energy (W1) recoverable by power generation was calculated from the amount of methane gas generated when the obtained biological sludge was anaerobicly treated, and the result was 2,926 kWh/d. was lower than W1 in Examples 1 and 2. It is believed that this is because in the comparative example, the organic matter was decomposed by the aerobic biological treatment, so the amount of organic matter input to the anaerobic treatment was smaller than in Examples 1 and 2, and the amount of recovered energy was reduced. be done.

Since the membrane concentration step is not performed in the comparative example, the energy (W3) required for membrane concentration is zero. In the comparative example, the sum (W4) of the energy consumption for aerobic biological treatment and the energy consumption for sludge thickening was 10,211 kWh/d. Further, the energy consumption (W2) consumed during the anaerobic treatment of the biological sludge obtained by the aerobic biological treatment was calculated to be 5,638 kWh/d. The amount of energy consumed during the aerobic biological treatment is 0.2 kwh/m ³ per 1 m ³ of wastewater.

As a result of calculating the energy consumption (W0) in the water treatment process from these facts, it was 12,923 kWh/d. The energy consumption (W0) in the water treatment process in the comparative example is obtained by the following formula.
Energy consumption in the water treatment process (W0) = (sum of energy consumption for aerobic biological treatment and energy consumption for sludge thickening (W4)) + (required for heating the anaerobic biological treatment tank) energy (W2)) - (recoverable energy from power generation (W1))

Table 1 shows the energy consumption in the water treatment process of Examples and Comparative Examples, the energy recovered by power generation, the energy required for heating the anaerobic biological treatment tank, the energy required for membrane concentration, and the amount of aerobic biological treatment. The sum of the energy consumption for the process and the energy consumption for sludge thickening (W0, W1, W2, W3, W4) was summarized.

As can be seen from Table 1, the energy (W1) recoverable by power generation in Examples 1 and 2 was higher than that in Comparative Example. In other words, by applying membrane filtration to organic matter-containing wastewater without biological treatment, and then subjecting the resulting concentrated water to anaerobic treatment, it is possible to increase the amount of methane gas generated and increase the amount of energy recovered. It can be said that

In addition, the energy (W2) required for heating the anaerobic biological treatment tank can be suppressed in Example 1, in which the concentration ratio in the membrane filtration treatment is 150 times, compared to Example 2, in which the concentration ratio is 50 times. became. This is because by increasing the concentration ratio, the liquid volume of the concentrated water supplied to the anaerobic biological treatment tank in the latter stage was reduced, so the energy required to heat the concentrated water in the anaerobic treatment was reduced. This is due to

1 waste water treatment device, 10 membrane filtration device, 12 anaerobic biological treatment tank, 14, 16, 18, 50 membrane filtration module, 20 filtration container, 22 hollow fiber membrane, 24 waste water inlet, 26 waste water introduction pipe, 28 waste water outlet, 30a to 30c concentrated water piping, 32a to 32c concentrated water pump, 34 collecting water piping, 36 treated water outlet, 38 permeated water piping, 40 backwash water piping, 42 permeated water pump, 44 backwash pump, 46 treatment water pipe, 48 biogas discharge pipe, 52 vibration generator, 54 vibration transmission member.

Claims (5)

A membrane filtration step of passing the wastewater through a hollow fiber membrane to separate the permeated water and the concentrated water containing the organic matter before performing biological treatment on the wastewater containing organic matter;
an anaerobic biological treatment step of anaerobicly biologically treating the concentrated water containing the organic matter,
The membrane filtration step is performed in multiple stages, the concentration ratio in the second stage membrane filtration is higher than the concentration ratio in the first stage membrane filtration,
A method for treating organic matter-containing wastewater, wherein the membrane surface of the hollow fiber membrane is vibrated during the membrane filtration step. 2. The method for treating organic matter-containing wastewater according to claim 1, wherein the concentration ratio in the membrane filtration step is 50 times or more. 3. The method for treating organic matter-containing wastewater according to claim 1, wherein the amount of organic matter in said concentrated water is 75% or more of the amount of organic matter in said wastewater containing organic matter. 4. The method for treating organic matter-containing wastewater according to any one of claims 1 to 3 , wherein in the membrane filtration step, the permeated water flow rate (m/d) of the filtration membrane is decreased toward the later stages. Membrane filtration means for performing a membrane filtration step of passing the wastewater through a hollow fiber membrane to separate the permeated water and the concentrated water containing the organic matter before performing biological treatment on the wastewater containing organic matter;
Anaerobic biological treatment means for anaerobicly biologically treating the concentrated water containing the organic matter;
and vibrating means for vibrating the membrane surface of the hollow fiber membrane during the membrane filtration step.death,
The membrane filtration means is composed of a plurality of stages, and the concentration ratio in the second-stage membrane filtration is higher than the concentration ratio in the first-stage membrane filtration. An apparatus for treating organic matter-containing wastewater characterized by:

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