JP2022042384A - Method for treating organic wastewater and apparatus for treating organic wastewater - Google Patents

Abstract

To provide a method for treating organic wastewater by biologically treating organic wastewater using a carrier, in which the amount of excess sludge generated is suppressed and the significant decrease in BOD removal rate is suppressed.SOLUTION: The present disclosure is a method for treating organic wastewater by biologically treating organic wastewater under aerobic condition using a reaction vessel 12 provided with a carrier 44, in which the biological treatment is performed while maintaining the concentration of soluble phosphorus in the reaction vessel 12 at 0.5 mg/L or less and maintaining the concentration of soluble nitrogen in the reaction vessel 12 at 3 mg/L or more.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a method for treating organic wastewater and an apparatus for treating organic wastewater.

The activated sludge method is generally used for the treatment of organic wastewater, but since the BOD volume load is about 0.5 to 1.0 kg / m ³ / day, a large site area is required. On the other hand, the biological treatment method using a carrier can increase the load by BOD volume load of 1.5 kg / m ³ / day or more, and can reduce the site area.

For example, Patent Document 1 describes the source in a biological treatment method using a carrier for treating organic wastewater in which the amount of nitrogen and phosphorus with respect to BOD is less than 100: 5: 1 in the weight ratio of BOD: nitrogen: phosphorus. Bacteria to the volume load of the carrier while adding the deficient nitrogen and / or phosphorus to the raw water so that the amount of nitrogen and phosphorus in the water is BOD: nitrogen: phosphorus 100: 5: 1 or more by weight. After the number of cells is measured and the number of cells of the carrier becomes almost constant, the amount of nitrogen and / or phosphorus added to the raw water is 100: 2.5: 0 in the weight ratio of BOD: nitrogen: phosphorus. A treatment method for reducing the amount to 5.5 or less is disclosed.

Japanese Unexamined Patent Publication No. 2001-149974

By the way, in the biological treatment method using a carrier, there is a problem that a large amount of excess sludge is generated. Another problem is that the BOD removal rate is significantly reduced when trying to suppress the amount of excess sludge generated.

Therefore, an object of the present disclosure is to suppress the amount of excess sludge generated and to suppress a significant decrease in the BOD removal rate in an organic wastewater treatment method and a treatment apparatus for biologically treating organic wastewater using a carrier. With the goal.

The present disclosure is a method for treating organic wastewater by biologically treating organic wastewater under aerobic conditions using a reaction vessel provided with a carrier, in which the concentration of soluble phosphorus in the reaction vessel is maintained at 0.5 mg / L or less. Moreover, the biological treatment is carried out while maintaining the concentration of soluble nitrogen in the reaction vessel at 3 mg / L or more.

Further, in the method for treating organic wastewater, the reaction vessel is composed of a reaction vessel having two or more stages in series, and the soluble phosphorus concentration is set to 0 in at least one of the reaction tanks having two or more stages in series. It is preferable to carry out the biological treatment while maintaining the concentration at 1.5 mg / L or less and the soluble nitrogen concentration at 3 mg / L or more.

Further, in the method for treating organic wastewater, it is preferable that the reaction tank is a fluidized bed type reaction tank, and the BOD volume load of the reaction tank is 1.5 kg / m ³ / day or more.

Further, the present disclosure is a device for treating organic wastewater by biologically treating organic wastewater under aerobic conditions using a reaction tank provided with a carrier, and the concentration of soluble phosphorus in the reaction tank is 0.5 mg / L or less. It is characterized in that the biological treatment is carried out while maintaining the concentration at 3 mg / L or more in the reaction vessel.

Further, in the organic wastewater treatment apparatus, the reaction tank is composed of reaction tanks having two or more stages in series, and the soluble phosphorus concentration is set to 0 in at least one reaction tank among the reaction tanks having two or more stages in series. It is preferable to carry out the biological treatment while maintaining the concentration at 1.5 mg / L or less and the soluble nitrogen concentration at 3 mg / L or more.

Further, in the organic wastewater treatment apparatus, the reaction tank is preferably a fluidized bed type reaction tank, and the BOD volume load of the reaction tank is preferably 1.5 kg / m ³ / day or more.

According to the present disclosure, in an organic wastewater treatment method and a treatment apparatus for biologically treating organic wastewater using a carrier, it is possible to suppress the amount of excess sludge generated and to suppress a significant decrease in the BOD removal rate. ..

It is a schematic diagram which shows an example of the structure of the organic wastewater treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows another example of the structure of the organic wastewater treatment apparatus which concerns on this embodiment.

Embodiments of the present disclosure will be described below. The present embodiment is an example of carrying out the present disclosure, and the present disclosure is not limited to the present embodiment.

FIG. 1 is a schematic diagram showing an example of the configuration of the organic wastewater treatment apparatus according to the present embodiment. The treatment device 1 shown in FIG. 1 includes a raw water tank 10, a reaction tank 12, a treated water tank 14, a control device 16, a raw water pump 18, detectors 20a and 20b, an inflow line 22, and a treated water line 24. Further, the processing device 1 shown in FIG. 1 is a nitrogen source supply device that supplies a nitrogen source to the reaction tank 12, a phosphorus source supply device that supplies a phosphorus source to the reaction tank 12, and a flocculant that supplies a flocculant to the raw water tank 10. Equipped with a supply device. The nitrogen source supply device shown in FIG. 1 includes a nitrogen source tank 26 for accommodating a nitrogen source such as ammonium chloride, a nitrogen source addition line 28, and a nitrogen source addition pump 30 installed in the nitrogen source addition line 28. The phosphorus source supply device shown in FIG. 1 includes a phosphorus source tank 32 for accommodating a phosphorus source such as phosphoric acid, a phosphorus source addition line 34, and a phosphorus source addition pump 36 installed in the phosphorus source addition line 34. The coagulant supply device shown in FIG. 1 includes a coagulant tank 38 for accommodating a coagulant such as PAC and iron chloride, a coagulant addition line 40, and a coagulant addition pump 42 installed in the coagulant addition line 40.

One end of the coagulant addition line 40 is connected to the raw water tank 10, and the other end of the coagulant addition line 40 is connected to the coagulant tank 38. One end of the inflow line 22 is connected to the raw water outlet of the raw water tank 10, and the other end of the inflow line 22 is connected to the inlet of the reaction tank 12. A raw water pump 18 is installed in the inflow line 22. Further, one end of the nitrogen source addition line 28 is connected to the inflow line 22, and the other end of the nitrogen source addition line 28 is connected to the nitrogen source tank 26. Further, one end of the phosphorus source addition line 34 is connected to the inflow line 22, and the other end of the phosphorus source addition line 34 is connected to the phosphorus source tank 32. One end of the treated water line 24 is connected to the outlet of the reaction tank 12, and the other end of the treated water line 24 is connected to the inlet of the treated water tank 14. The control device 16 and each pump and each detector are, for example, electrically connected to each other.

The reaction tank 12 is filled with a carrier 44 containing microorganisms. The carrier 44 is not particularly limited, and examples thereof include a plastic carrier, a sponge-like carrier, and a gel-like carrier.

An aeration device 46 is installed at the bottom of the reaction vessel 12. For example, a blower (not shown) is connected to the aeration device 46, and the air supplied from the blower is supplied from the aeration device 46 into the reaction tank 12.

Detectors 20a and 20b are installed in the reaction tank 12. The detector 20a is a device for detecting the concentration of soluble nitrogen in the reaction vessel 12. Further, the detector 20b is a device for detecting the concentration of soluble phosphorus in the reaction vessel 12. The detectors 20a and 20b may be installed in the treated water tank 14 or the treated water line 24. Then, the soluble nitrogen concentration and the soluble phosphorus concentration of the treated water measured by the detectors 20a and 20b may be used as the soluble nitrogen concentration and the soluble phosphorus concentration in the reaction vessel 12. The soluble nitrogen is, for example, nitrogen derived from a nitrogen source supplied from a nitrogen source supply device, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, etc. contained in the wastewater from the beginning. Further, the soluble phosphorus is, for example, phosphorus derived from a phosphorus source supplied from a phosphorus source supply device, a phosphorus compound contained in wastewater from the beginning, and the like.

The control device 16 is composed of, for example, a CPU for calculating a program, a microcomputer composed of a ROM and a RAM for storing the program and the calculation result, an electronic circuit, and the like, and reads out a predetermined program stored in the ROM or the like. The program is executed to control the operation of the processing device 1. For example, the control device 16 controls the operation / stop of the raw water pump 18. Further, for example, the operation / stop of the nitrogen source addition pump 30 is controlled based on the soluble nitrogen concentration or the like detected by the detector 20a. Further, for example, the control device 16 controls the operation / stop of the phosphorus source addition pump 36 and the flocculant addition pump 42 based on the soluble phosphorus concentration or the like detected by the detector 20b.

Next, the operation of the processing device 1 shown in FIG. 1 will be described.

When the raw water pump 18 is operated by the control device 16, the organic wastewater in the raw water tank 10 passes through the inflow line 22 and is supplied to the reaction tank 12. Then, air is supplied to the reaction tank 12 from the aeration device 46, and the organic matter in the organic waste water in the reaction tank 12 is biologically treated by microorganisms and the like attached to the carrier 44 under aerobic conditions (biological treatment step). .. The treated water treated in the reaction tank 12 is supplied to the treated water tank 14 through the treated water line 24.

By the way, phosphorus and nitrogen in the organic waste water are taken into the cells of the microorganism as a nutrient source for the microorganism in the reaction tank 12. Therefore, it is preferable to add a phosphorus source or a nitrogen source to the organic wastewater from the viewpoint of promoting the growth of microorganisms in the reaction vessel 12 and the decomposition of organic substances. However, as a result of diligent studies by the present inventors, it has been found that when the concentration of soluble phosphorus in the reaction vessel 12 is high, the amount of excess sludge generated due to the decomposition of organic matter increases. Therefore, as a result of further studies, the concentration of soluble phosphorus in the reaction vessel 12 should be maintained in a depleted state, specifically, 0.5 mg / L or less, preferably 0.1 mg / L or less. Therefore, it was found that the amount of excess sludge generated can be suppressed. On the other hand, if the concentration of soluble nitrogen in the reaction vessel 12 is depleted, the BOD removal rate will be significantly reduced. Therefore, the concentration of soluble nitrogen in the reaction vessel 12 is maintained in a residual state, specifically, 3 mg / L or more, preferably 5 mg / L or more, thereby suppressing a significant decrease in the BOD removal rate. can.

Therefore, in the processing device 1 shown in FIG. 1, the nitrogen source addition pump 30 and the phosphorus source addition pump 36 may be operated by the control device 16 to introduce the nitrogen source and the phosphorus source into the reaction tank 12. The control device 16 has a soluble phosphorus concentration of 0.5 mg / L or less and a soluble nitrogen concentration of 3 mg in the reaction vessel 12 based on the soluble phosphorus concentration and the soluble nitrogen concentration measured by the detectors 20a and 20b. Control the supply of nitrogen and phosphorus sources so that they are maintained above / L.

Further, when the phosphorus concentration in the organic wastewater introduced into the raw water tank 10 is high and the soluble phosphorus concentration measured by the detector 20b exceeds 0.5 mg / L, the control device 16 aggregates. By operating the agent addition pump 42 and adding the coagulant to the raw water tank 10 to reduce the soluble phosphorus concentration in the organic wastewater, the soluble phosphorus concentration in the reaction tank 12 is reduced to 0.5 mg / L or less. maintain. Further, the phosphorus concentration in the organic wastewater introduced into the raw water tank 10 is low, and the soluble phosphorus concentration measured by the detector 20b is 0.5 mg / L or less even if the phosphorus source is not supplied to the organic wastewater. Even in this case, the phosphorus source may be supplied to the organic wastewater as long as the concentration of soluble phosphorus in the reaction vessel 12 does not exceed 0.5 mg / L.

Further, the nitrogen concentration in the organic wastewater introduced into the raw water tank 10 is high, and the soluble nitrogen concentration measured by the detector 20a is 3 mg / L or more even if the nitrogen source is not supplied to the organic wastewater. Even in some cases, a nitrogen source of organic wastewater may be supplied. However, considering the discharge standard and the like, the upper limit of the soluble nitrogen concentration in the reaction vessel 12 is preferably maintained at 20 mg / L or less, and more preferably maintained at 10 mg / L or less.

The concentration of soluble phosphorus and the concentration of soluble nitrogen in the reaction vessel 12 are preferably analyzed online by a detector, but if a detector is not installed, manual analysis by an operator may be used.

Further, for example, the detectors 20a and 20b are installed in the raw water tank 10, and the soluble phosphorus concentration and the soluble nitrogen concentration in the reaction tank 12 are estimated from the soluble phosphorus concentration and the soluble nitrogen concentration of the organic wastewater. May be good. In this case, for example, a map (or formula, table, etc.) showing the correlation between the soluble phosphorus concentration in the organic wastewater and the soluble phosphorus concentration in the reaction vessel 12 and the soluble nitrogen concentration in the organic wastewater are obtained by experiments or the like in advance. A map (or formula, table, etc.) showing the correlation of the soluble nitrogen concentration in the reaction vessel 12 is created and stored in the control device 16. Then, the control device 16 applies the soluble phosphorus concentration and the soluble nitrogen concentration of the organic wastewater measured by the detectors 20a and 20b to the above map and the like, and applies the soluble phosphorus concentration and the soluble nitrogen in the reaction tank 12 to the above map and the like. Estimate the concentration. When the estimated soluble phosphorus concentration in the reaction tank 12 exceeds 0.5 mg / L, the control device 16 operates the flocculant addition pump 42, adds the flocculant to the raw water tank 10, and 0.5 mg. In the case of / L or less, the phosphorus source addition pump 36 is operated so that the phosphorus source is not added or the phosphorus source is added within the range where the soluble phosphorus concentration in the reaction vessel 12 does not exceed 0.5 mg / L. Let me. When the estimated soluble nitrogen concentration in the reaction vessel 12 is less than 3 mg / L, the control device 16 operates the nitrogen source addition pump 30 to supply the nitrogen source into the reaction vessel 12 at 3 mg / L. If it exceeds L, the nitrogen source addition pump 30 is operated so that no nitrogen source is added or a predetermined amount of nitrogen source is added.

As a method for reducing the soluble phosphorus concentration of the organic wastewater, it is desirable to add a flocculant to the organic wastewater. For example, the treated water in the treated water tank 14 is supplied to the raw water tank 10 to dilute the organic wastewater. It may be a method of doing.

FIG. 2 is a schematic diagram showing another example of the configuration of the organic wastewater treatment apparatus according to the present embodiment. In the processing device 2 of FIG. 2, the same components as those of the processing device 1 of FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. The processing apparatus 2 of FIG. 2 includes a reaction tank group having a first reaction tank 12a and a second reaction tank 12b. The reaction tank group has a configuration in which the first reaction tank 12a and the second reaction tank 12b are arranged in series with the first reaction tank 12a as the first stage and the second reaction tank 12b as the second stage. The reaction tank group may be configured such that the reaction tanks are arranged in series in three or more stages.

One end of the inflow line 22a is connected to the raw water outlet of the raw water tank 10, and the other end of the inflow line 22a is connected to the inlet of the first reaction tank 12a. One end of the inflow line 22b is connected to the outlet of the first reaction tank 12a, and the other end of the inflow line 22b is connected to the inlet of the second reaction tank 12b. One end of the treated water line 24 is connected to the outlet of the second reaction tank 12b, and the other end of the treated water line 24 is connected to the inlet of the treated water tank 14. Further, one end of the nitrogen source addition line 28a is connected to the inflow line 22a, and the other end of the nitrogen source addition line 28a is connected to the nitrogen source tank 26a. Further, one end of the phosphorus source addition line 34a is connected to the inflow line 22a, and the other end of the phosphorus source addition line 34a is connected to the phosphorus source tank 32a. Further, one end of the nitrogen source addition line 28b is connected to the inflow line 22b, and the other end of the nitrogen source addition line 28b is connected to the nitrogen source tank 26b. Further, one end of the phosphorus source addition line 34b is connected to the inflow line 22b, and the other end of the phosphorus source addition line 34b is connected to the phosphorus source tank 32b.

Next, the operation of the processing device 2 shown in FIG. 2 will be described.

The control device 16 operates the raw water pump 18, and the organic wastewater in the raw water tank 10 passes through the inflow line 22a and is supplied to the first reaction tank 12a. Then, air is supplied from the aeration device 46 to the first reaction tank 12a, and the organic matter in the organic wastewater in the first reaction tank 12a is biologically treated by microorganisms and the like attached to the carrier 44 under aerobic conditions (the organic matter in the first reaction tank 12a). First biological treatment step). The first treated water treated in the first reaction tank 12a passes through the inflow line 22b and is supplied to the second reaction tank 12b. Then, air is supplied from the aeration device 46 to the second reaction tank 12b, and the organic matter in the first treatment water is biologically treated in the second reaction tank 12b by microorganisms and the like attached to the carrier 44 under aerobic conditions ( Second biological treatment step). The treated water treated in the second reaction tank 12b is supplied to the treated water tank 14 through the treated water line 24.

Here, when the reaction tank is composed of two or more stages, the soluble phosphorus concentration should be maintained in a depleted state, specifically, 0.5 mg / L or less in at least one of the reaction tanks. It may be preferably maintained at 0.1 mg / L or less, and the soluble nitrogen concentration may be maintained in a residual state, specifically, 3 mg / L or more, preferably 5 mg / L or more. As a result, the amount of excess sludge generated can be suppressed, and a significant decrease in the BOD removal rate can be suppressed. In the processing device 2 shown in FIG. 2, for example, the control device 16 makes a first reaction based on the soluble phosphorus concentration and the soluble nitrogen concentration measured by the detectors 20a and 20b installed in the first reaction tank 12a. The nitrogen source addition pump 30a and the phosphorus source addition pump 36a (or the flocculant addition pump 42) are maintained so that the soluble phosphorus concentration in the tank 12a is maintained at 0.5 mg / L or less and the soluble nitrogen concentration is maintained at 3 mg / L or more. ) Is controlled. Similarly, the second reaction tank 12b also has the soluble phosphorus in the second reaction tank 12b based on the soluble phosphorus concentration and the soluble nitrogen concentration measured by the detectors 20a and 20b installed in the second reaction tank 12b. Even if the operation of the nitrogen source addition pump 30b and the phosphorus source addition pump 36b (aggregator addition pump 42) is controlled so that the concentration is maintained at 0.5 mg / L or less and the soluble nitrogen concentration is maintained at 3 mg / L or more. good. When the reaction tank is composed of two or more stages, it is preferable to deplete the soluble phosphorus and leave the soluble nitrogen in the residual state in the first stage reaction tank. In this case, most of the organic matter is removed in the first-stage reaction tank, and less organic matter is removed in the second-stage reaction tank. Therefore, the phosphorus residual state is not controlled in the second-stage and subsequent reaction tanks. However, the amount of excess sludge in the entire system can be suppressed.

Hereinafter, the operating conditions and the like of the processing apparatus of this embodiment will be described.

The pH in the reaction vessel is preferably adjusted to, for example, weakly acidic to weakly alkaline, and more preferably adjusted to the range of pH 6 to 8 from the viewpoint of growing microorganisms.

The dissolved oxygen concentration in the reaction vessel is, for example, preferably 0.5 mg / L or more, and more preferably 1 mg / L or more.

A solid-liquid separation device may be installed in the subsequent stage of the reaction vessel. In particular, when the treated water is discharged into a river, it is preferable to install a solid-liquid separation device at the subsequent stage of the reaction tank. The solid-liquid separation device is a conventionally known device or the like, and examples thereof include a settling pond, a pressurized flotation device, a turbid film device, and an MBR.

The reaction vessel may be either a fixed bed type in which the carrier does not flow or a fluidized bed type in which the carrier flows. The fluidized bed type has merits such as the fact that a short pass of raw water is difficult to occur, the maintenance is excellent, and the introduction cost is low.

Further, the BOD volume load of the reaction tank (in the case of the reaction tank group, the BOD volume load of all the reaction tanks) is preferably 1.5 kg / m ³ / day or more, and more preferably 2.0 kg / m ³ / day or more.

The nitrogen source is not particularly limited as long as it is a nitrogen compound, and examples thereof include ammonium chloride, ammonium sulfate, diammonium hydrogen phosphate, and urea. Excess ammonium sulfate generated in the factory can also be applied.

The phosphorus source is not particularly limited as long as it is phosphoric acid or a phosphorus compound, and examples thereof include dipotassium phosphate, disodium phosphate, monopotassium phosphate, monosodium phosphate, and ammonium phosphate.

Nutrients and trace elements other than nitrogen sources and phosphorus sources may be added to the raw water, and examples thereof include calcium, magnesium, iron, copper, zinc, and manganese.

Examples of the carrier include a plastic carrier, a sponge-like carrier, a gel-like carrier, and the like, and among these, a sponge-like carrier is preferable in terms of cost and durability.

The number of cells (number of pores) of the carrier is preferably 30 cells / 25 mm or more, more preferably 30 cells / 25 mm or more, and 100 cells / 25 mm or less in terms of improving the processing speed of biological treatment. More preferably, it is 40 pieces / 25 mm or more and 100 pieces / 25 mm or less, and particularly preferably 46 pieces / 25 mm or more and 100 pieces / 25 mm or less. The number of cells of the carrier is determined based on, for example, JIS K 6540-1 (Annex 1).

The surface area of the carrier is preferably 3000 m ² / m ³ or more, more preferably 3500 m ² / m ³ or more, and further preferably 4000 m ² / m ³ or more in terms of improving the treatment speed of biological treatment. Particularly preferably, it is 4500 m ² / m ³ or more. The upper limit of the surface area of the carrier may be determined in consideration of the number of cells, the size of the carrier, and the like, and is not particularly limited.

The biofouling amount of the carrier is preferably 500 mg / L or more, and more preferably 1000 mg / L or more, in terms of improving the treatment speed of the biological treatment. The larger the amount of biofouling of the carrier, the better, and there is no particular upper limit, but the upper limit is, for example, 5000 mg / L.

The shape of the carrier is not particularly limited, and examples thereof include a square shape such as a cube, a granular shape, a spherical shape, a pellet shape, a cylindrical shape, a fibrous shape, and a film shape.

The size of the carrier is not particularly limited and may be appropriately set according to the size of the reaction vessel, the shape of the carrier, etc. For example, in the case of a cube, the length of one side is in the range of 3 to 20 mm. If it is spherical, the diameter is preferably in the range of about 0.5 to 20 mm. The size of the carrier can be measured using a caliper, a microscope, or the like.

The specific gravity of the carrier is preferably at least 1.0 and more, preferably 1.1 or more as a true specific gravity, or 1.01 or more as an apparent specific gravity in order to form a fluid state inside the reaction vessel.

The amount of the carrier charged into the reaction vessel is preferably in the range of 10 to 70% with respect to the volume of the reaction vessel. If the amount of carrier charged is less than 10% of the volume of the reaction tank, the reaction rate may decrease, and if it exceeds 70%, the carrier will not flow easily, and the raw water will be short-circuited due to clogging due to sludge during long-term operation. It may pass and the treated water quality may deteriorate.

Hereinafter, the present disclosure will be described in more detail with reference to Examples and Comparative Examples, but the present disclosure is not limited to the following Examples.

Under the test conditions shown below, isopropyl alcohol-containing wastewater was passed through a single reaction vessel for biological treatment.

<Test conditions>
Reaction tank volume: 2L
Carrier: Sponge-like carrier made of hydrophobic polyurethane Carrier filling rate: 20% as bulk volume Dwelling time: 6 hours Isopropyl alcohol-containing wastewater: BOD is about 800 mg / L, N is 2 mg / L or less, P is 0.1 mg / L or less BOD volumetric load: Approximately 3.2 kg / m ³ / day
Water temperature: Approximately 20 ° C
In-tank DO: 2 mg / L or more In-tank pH: 6.5-8.0

<Comparative Example 1>
Ammonium chloride and phosphoric acid were added to the isopropyl alcohol-containing wastewater, and the N concentration was 54 mg / L and the P concentration was 9.6 mg / L. Was 19 mg / L, and the soluble phosphorus concentration was 4.4 mg / L. As a result, the sludge generation rate per removed BOD was 31%, and the BOD removal rate was 2.8 kg / m ³ / day.

<Example 1>
Ammonium chloride was added to the isopropyl alcohol-containing wastewater, and the N concentration was 36 mg / L and the P concentration was 0.012 mg / L. At L, nitrogen remained, and at a soluble phosphorus concentration of 0.005 mg / L, phosphorus was depleted. As a result, the sludge generation rate per removed BOD was 16%, and the BOD removal rate was 2.0 kg / m ³ / day.

<Example 2>
Ammonium chloride and phosphoric acid were added to the isopropyl alcohol-containing wastewater, and the N concentration was 37 mg / L and the P concentration was 2.6 mg / L. At 23 mg / L, nitrogen remained, and at a soluble phosphorus concentration of 0.062 mg / L, phosphorus was depleted. As a result, the sludge generation rate per removed BOD was 20%, and the BOD removal rate was 2.5 kg / m ³ / day.

<Example 3>
Ammonium chloride and phosphoric acid were added to the isopropyl alcohol-containing wastewater, and the N concentration was 14 mg / L and the P concentration was 1.3 mg / L. At 3.5 mg / L, nitrogen remained, and at a soluble phosphorus concentration of 0.056 mg / L, phosphorus was depleted. As a result, the sludge generation rate per removed BOD was 20%, and the BOD removal rate was 2.0 kg / m ³ / day.

<Comparative Example 2>
Phosphorus was added to the isopropyl alcohol-containing wastewater, and the N concentration was 1.4 mg / L and the P concentration was 6.7 mg / L. At 1.6 mg / L, nitrogen was depleted, and at a soluble phosphorus concentration of 6.5 mg / L, phosphorus remained. As a result, the sludge generation rate per removed BOD was 29%, and the BOD removal rate was 1.3 kg / m ³ / day.

From the results of Examples and Comparative Examples, by depleting the soluble phosphorus concentration in the reaction vessel and leaving the soluble nitrogen concentration in the reaction vessel in the residual state, the amount of excess sludge generated can be suppressed and the BOD removal rate can be increased. It can be said that a significant decrease can be suppressed.

1,2 Treatment equipment, 10 Raw water tank, 12 Reaction tank, 12a 1st reaction tank, 12b 2nd reaction tank, 14 Treatment water tank, 16 Control device, 18 Raw water pump, 20a, 20b detector, 22, 22a, 22b Inflow Line, 24 treated water line, 26,26a, 26b nitrogen source tank, 28,28a, 28b nitrogen source addition line, 30,30a, 30b nitrogen source addition pump, 32,32a, 32b phosphorus source tank, 34,34a, 34b Phosphorus source addition line, 36, 36a, 36b Phosphorus source addition pump, 38 coagulant tank, 40 coagulant addition line, 42 coagulant addition pump, 44 carrier, 46 aeration device.

Claims (6)

A method for treating organic wastewater by biologically treating organic wastewater under aerobic conditions using a reaction tank equipped with a carrier.
The biological treatment is characterized by maintaining the concentration of soluble phosphorus in the reaction vessel at 0.5 mg / L or less and maintaining the concentration of soluble nitrogen in the reaction vessel at 3 mg / L or more. How to treat organic wastewater. The reaction vessel is composed of a reaction vessel having two or more stages in series, and the soluble phosphorus concentration is maintained at 0.5 mg / L or less and dissolved in at least one of the reaction tanks having two or more stages in series. The method for treating organic wastewater according to claim 1, wherein the biological treatment is carried out while maintaining the sex nitrogen concentration at 3 mg / L or more. The method for treating organic wastewater according to claim 1 or 2, wherein the reaction tank is a fluidized bed type reaction tank, and the BOD volume load of the reaction tank is 1.5 kg / m ³ / day or more. .. An organic wastewater treatment device that biologically treats organic wastewater under aerobic conditions using a reaction tank equipped with a carrier.
The biological treatment is characterized by maintaining the concentration of soluble phosphorus in the reaction vessel at 0.5 mg / L or less and maintaining the concentration of soluble nitrogen in the reaction vessel at 3 mg / L or more. Organic waste treatment equipment. The reaction vessel is composed of a reaction vessel having two or more stages in series, and the soluble phosphorus concentration is maintained at 0.5 mg / L or less and dissolved in at least one of the reaction tanks having two or more stages in series. The organic waste treatment apparatus according to claim 4, wherein the biological treatment is carried out while maintaining the sex nitrogen concentration at 3 mg / L or more. The organic wastewater treatment apparatus according to claim 4 or 5, wherein the reaction tank is a fluidized bed type reaction tank, and the BOD volume load of the reaction tank is 1.5 kg / m ³ / day or more. ..

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