JP2022171516A - Treatment method for high concentration organic matter-containing waste water - Google Patents

Abstract

To enable high concentration organic matter-containing waste water involving a harmful nitrogen-containing compound to be treated easily by simple equipment.SOLUTION: A treatment method includes steps of: preparing a processor; obtaining a concentrated active sludge by feeding low concentration organic matter-containing waste water and an active sludge to an aerobic biological reaction tank and aerobic-treating the low concentration organic matter-containing waste water to obtain a treated liquid, followed by solid-liquid separation by using a solid-liquid separator; obtaining anaerobic-treated liquid by feeding a high concentration organic matter-containing waste water, a concentrated active sludge and a nitrate nitrogen analog to an anaerobic biological reaction tank in a manner that the ratio of a carbon content and a nitrogen content (C/N ratio) becomes in a range of 0.5-4.6, followed by treating organic matters and harmful nitrogen-containing compounds; obtaining an aerobic-treated liquid by feeding an anaerobic treated liquid to an aerobic biological reaction tank and decomposing organic matters remaining in the anaerobic-treated liquid; and obtaining treated water while recovering the concentrated active sludge by feeding the aerobic-treated liquid to the solid-liquid separator for solid-liquid separation.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for treating waste water containing high concentrations of organic matter using activated sludge.

For example, for the purpose of efficiently treating wastewater containing high concentrations of organic substances (high TOC wastewater) derived from factory wastewater, etc., wastewater containing high concentrations of organic substances is first treated in an anaerobic biological reaction tank using activated sludge. A treatment method is known in which anaerobic treatment is performed in the presence of nitrate nitrogens, and then the anaerobic treated water and activated sludge after the anaerobic treatment are supplied to an aerobic bioreactor for further treatment ( See Patent Document 1.).

JP 2007-296436 A

However, conventionally, the standard activated sludge process, in which the reaction proceeds under aerobic conditions, has a high concentration of organic matter-containing wastewater containing nitrogen-containing compounds such as ammonia (hereinafter referred to as "toxic nitrogen-containing compounds In the treatment of high-concentration organic matter-containing wastewater, there are additional facilities for recovering the harmful nitrogen-containing compounds contained in the wastewater, and for separating the harmful nitrogen-containing compounds by biologically or chemically treating them separately. As a result, the number of steps required to complete the process has increased.

Therefore, there has been a demand for a treatment method that can easily treat wastewater containing high-concentration organic matter containing harmful nitrogen-containing compounds with simple equipment without adding additional equipment or the like.

In order to solve the above problems, the present inventors have made intensive studies and found that even high-concentration organic matter-containing wastewater containing harmful nitrogen-containing compounds can be treated under predetermined conditions to eliminate harmful nitrogen-containing compounds. The inventors have found that the treatment can be performed simply and effectively with simple equipment without adding additional equipment for the treatment, and have completed the present invention.

That is, the present invention provides the following [1] to [4].
[1] A treatment method for biologically treating wastewater containing organic substances and harmful nitrogen-containing compounds and having a TOC of 20000 mg/L or more and containing high concentrations of organic substances with activated sludge,
Step (1): An anaerobic biological reaction tank for anaerobically treating the waste water containing high-concentration organic matter, and an aeration device connected to the anaerobic biological reaction tank and capable of performing aeration treatment, an aerobic biological reactor capable of aerobically treating the anaerobic treatment liquid supplied from the anaerobic biological reactor; and an aerobic biological reactor connected to the aerobic biological reactor. a step of preparing a treatment apparatus equipped with a solid-liquid separator capable of solid-liquid separation of the aerobic treatment liquid supplied from the reaction tank;
Step (2): Feeding activated sludge and low-concentration organic matter-containing wastewater having a TOC of 0.05 times or less that of the high-concentration organic matter-containing wastewater to the aerobic bioreactor, to obtain the low-concentration organic matter-containing wastewater. A step of obtaining concentrated activated sludge by performing solid-liquid separation using the solid-liquid separator from the treated liquid obtained by aerobically treating the
Step (3): The high-concentration organic matter-containing waste water, the concentrated activated sludge, and the nitrate nitrogens are mixed so that the ratio of carbon content to nitrogen content (C/N ratio) is in the range of 0.5 to 4.6. a step of supplying to the anaerobic biological reactor and treating the organic matter and the harmful nitrogen-containing compound to obtain an anaerobic treatment solution;
Step (4): The anaerobic treatment liquid is supplied to the aerobic biological reaction tank and aerated by the aeration device to decompose the organic matter remaining in the anaerobic treatment liquid. , obtaining an aerobic treatment liquid;
Step (5): A treatment method comprising a step of supplying the aerobic treatment liquid to the solid-liquid separation device and performing solid-liquid separation to recover concentrated activated sludge while obtaining treated water.
[2] The treatment method according to [1], wherein the harmful nitrogen-containing compound is one or more selected from the group consisting of amines.
[3] The treatment method according to [2], wherein the harmful nitrogen-containing compound is ammonia.
[4] In the step (3), the high-concentration organic matter-containing wastewater, the concentrated activated sludge, and the nitrate nitrogens are mixed so that the ratio of the carbon content to the nitrogen content is in the range of 0.5 to 4.6. In addition, the treatment method according to any one of [1] to [3], which is performed by supplying to the anaerobic bioreactor.

According to the treatment method of the present invention, it is possible to easily and effectively treat wastewater containing high concentrations of organic matter containing harmful nitrogen-containing compounds with simple equipment, with a high volumetric load, without adding any additional equipment. can.

FIG. 1 is a diagram showing an outline of a processing apparatus according to this embodiment. FIG. 2 is a graph showing results in Examples.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the drawings only schematically show the shape, size and arrangement of the constituent elements to the extent that the invention can be understood. The present invention is not limited by the following description, and each component can be changed as appropriate without departing from the gist of the present invention. In the drawings used for the following description, the same components are denoted by the same reference numerals, and redundant description may be omitted. Also, the configuration according to the embodiment of the present invention is not necessarily used in the illustrated arrangement.

1. Treatment method In the treatment method of the present embodiment, wastewater containing organic substances and harmful nitrogen-containing compounds and having a TOC (total organic carbon) of 20000 mg/L or more is biologically treated with activated sludge. a method,
Step (1): An anaerobic biological reaction tank for anaerobically treating the waste water containing high-concentration organic matter, and an aeration device connected to the anaerobic biological reaction tank and capable of performing aeration treatment, an aerobic biological reactor capable of aerobically treating the anaerobic treatment liquid supplied from the anaerobic biological reactor; and an aerobic biological reactor connected to the aerobic biological reactor. a step of preparing a treatment apparatus equipped with a solid-liquid separator capable of solid-liquid separation of the aerobic treatment liquid supplied from the reaction tank;
Step (2): Feeding activated sludge and low-concentration organic matter-containing wastewater having a TOC of 0.05 times or less that of the high-concentration organic matter-containing wastewater to the aerobic bioreactor, to obtain the low-concentration organic matter-containing wastewater. a step of obtaining concentrated activated sludge from the treated liquid obtained by aerobic treatment using the solid-liquid separation device;
Step (3): The high-concentration organic matter-containing waste water, the concentrated activated sludge, and the nitrate nitrogens are mixed so that the ratio of carbon content to nitrogen content (C/N ratio) is in the range of 0.5 to 4.6. a step of supplying to the anaerobic biological reactor and treating the organic matter and the harmful nitrogen-containing compound to obtain an anaerobic treatment solution;
Step (4): The anaerobic treatment liquid is supplied to the aerobic biological reaction tank and aerated by the aeration device to decompose the organic matter remaining in the anaerobic treatment liquid. , obtaining an aerobic treatment liquid;
Step (5): A treatment method comprising a step of supplying the aerobic treatment liquid to the solid-liquid separation device and performing solid-liquid separation to recover concentrated activated sludge while obtaining treated water.

The "activated sludge" that can be suitably applied to the treatment method of the present embodiment includes any suitable conventionally known "activated sludge" that can be applied to, for example, the "standard activated sludge method".

In this embodiment, after being aerobically used (aerobically treated) in an aerobic biological reactor, the activated sludge is solid-liquid separated using any suitable solid-liquid separation device known in the art. Specifically, the activated sludge is deposited under conditions where only oxygen consumption by microorganisms occurs without supplying oxygen in the solid-liquid separation device, and concentrated and solid-liquid separated by storing under anaerobic conditions. is called "concentrated activated sludge".

Here, the activated sludge concentration (MLSS) in the concentrated activated sludge is not particularly limited, but is preferably higher than the activated sludge concentration contained in the treated liquid in a known standard activated sludge method. It is desirable that it is below the upper limit of the activated sludge concentration that can be sent.
Specifically, the MLSS of the concentrated activated sludge is preferably 3000 mg/L or more, 5000 mg/L or more, 6000 mg/L or more, more preferably 10000 mg/L or more, and 12000 mg/L or more, 15000 mg/L or more. L or more is more preferable.

The thickened activated sludge is preferably maintained at an oxygen concentration suitable for reaction in the anaerobic bioreactor. That is, as already explained, the concentrated activated sludge that has been concentrated and solid-liquid separated under anaerobic conditions in the solid-liquid separator used in steps (2) and (5) is It is preferable to supply the concentrated activated sludge to the anaerobic bioreactor while maintaining the conditions from the viewpoint of speeding up the growth of the microorganisms contained in the concentrated activated sludge and improving the efficiency of the anaerobic treatment.

For example, the oxidation-reduction potential (ORP) is known as one of the indices indicating the activity of microorganisms under anaerobic conditions. A suitable range of ORP in the concentrated activated sludge of the present embodiment is not particularly limited.

Specifically, the ORP in the anaerobic reaction tank and in the concentrated activated sludge is preferably −50 mv or less, more preferably −100 mv or less, and further preferably in the range of −150 mv to −350 mv. .

A method for maintaining the ORP of the concentrated activated sludge within the preferred range is not particularly limited. A method for maintaining the ORP of the thickened activated sludge within a preferable range includes, for example, a method of extracting the bottom part of the activated sludge deposited in the sedimentation tank as a thickened activated sludge.

(i) step (1)
The step (1) includes an anaerobic bioreactor for anaerobically treating waste water containing a high concentration of organic matter, and an aeration device connected to the anaerobic bioreactor and capable of performing an aeration treatment. an aerobic biological reactor capable of aerobically treating the anaerobic treatment liquid supplied from the biological reactor; and an aerobic biological reactor connected to the aerobic biological reactor and supplied from the aerobic biological reactor. It is a step of preparing a treatment apparatus having a solid-liquid separation device capable of solid-liquid separation of the aerobic treatment liquid.

First, with reference to FIG. 1, a configuration example of a processing apparatus (processing system) prepared in step (1) of the present embodiment will be described. FIG. 1 is a diagram showing an outline of a processing apparatus according to this embodiment.

As shown in FIG. 1, the treatment apparatus 1 of the present embodiment is connected to an anaerobic biological reaction tank 10 for anaerobically treating waste water containing high-concentration organic matter, and the anaerobic biological reaction tank 10 for aeration treatment. An aerobic biological reaction tank 20 having an aerator 22 capable of aerobically treating the anaerobic treatment liquid supplied from the anaerobic biological reaction tank 10, and an aerobic biological reaction A solid-liquid separator 30 connected to the tank 20 and capable of solid-liquid separation of the aerobic treatment liquid supplied from the aerobic biological reaction tank 20, and a liquid to be treated in the anaerobic biological reaction tank 10. The first mixing layer (first neutralization tank) 42 configured to be able to supply the liquid to be treated to the aerobic biological reaction tank 20 (second mixing layer) configured to be able to supply the liquid to be treated neutralization tank) 44.

The configuration of the anaerobic bioreactor 10 should be of a size (capacity) that can handle the desired treatment capacity and that it can handle the characteristics of wastewater containing high concentrations of organic matter (high TOC wastewater), which is the expected target liquid to be treated. It is not particularly limited. The structure of the anaerobic biological reaction tank 10 can employ any conventionally known suitable structure that is usually used for denitrification treatment of nitrate nitrogens and harmful nitrogen-containing compounds by denitrifying bacteria, for example.

In the present embodiment, high-concentration organic matter-containing wastewater (high TOC wastewater) means a liquid such as industrial wastewater containing a total organic carbon (TOC) concentration (amount) of 20000 mg / L or more. . In the present embodiment, "wastewater containing high-concentration organic matter" does not necessarily have to be "wastewater" such as factory wastewater.

In this embodiment, the concentration of total organic carbon that can be contained in the high-concentration organic matter-containing wastewater is preferably 30000 mg/L or more, more preferably 40000 mg/L or more, and usually 100000 mg/L or less.

Examples of organic carbon that can be contained in waste water containing high concentrations of organic matter include non-activation-inhibiting organic carbon such as methanol and acetic acid that do not inhibit the activity of activated sludge. Further, the high-concentration organic matter-containing waste water may contain activity-inhibiting organic carbon, such as formaldehyde (HCHO), which inhibits the activity of activated sludge.

In the high-concentration organic matter-containing waste water used in the treatment method of the present embodiment, the harmful nitrogen-containing compound is preferably one or more selected from the group consisting of amines.

Here, examples of "amines" include ammonia, N,N-diethylhydroxylamine, N-methyldiethanolamine, aminoethylethanolamine, diethanolamine, isopropanolamine, monoethanolamine, methylamine, dimethylamine, trimethylamine, ethylamine. , diethylamine, triethylamine, and hydroxylamines. The treatment method of the present embodiment is preferably applied to treatment of wastewater containing high concentrations of organic matter, which contains ammonia as a particularly harmful nitrogen-containing compound.

In the present embodiment, the concentration of harmful nitrogen-containing compounds that can be contained in wastewater containing high-concentration organic matter is preferably 0.1 mg/L or more, more preferably 10 mg/L or more, and still more preferably 100 mg/L or more. and is usually 1000 mg/L or less, more preferably 500 mg/L or less, and still more preferably 300 mg/L or less.

The anaerobic biological reaction tank 10 of the present embodiment has, for example, a capacity of about 50 m ³ , and the ability and anaerobic capacity to receive about 10 m ³ /h of "high-concentration organic matter-containing wastewater", which is the liquid to be treated. It is preferable to have a liquid transfer capability for the treatment liquid, a TOC load amount is preferably about 5000 kg / d, and a TOC volume load is preferably about 50 to 100 kg / m ³ · d. It is preferable to have a structure that can withstand treatment under conditions such as a concentration (pH) of 7 to 9.5 and a temperature of 20 to 45°C.

The anaerobic biological reaction tank 10 may be equipped with a stirrer 12 for stirring the supplied liquid to be treated, if necessary. As the stirrer 12, a conventionally known stirrer having an arbitrary and suitable configuration having sufficient functions to carry out the anaerobic treatment can be used.

The anaerobic biological reaction tank 10 is provided with a structure such as a valve that can be freely opened and closed to adjust the amount of liquid sent between the tanks. Arbitrary and suitable pumps and pipes known in the art are connected (shown as straight lines connecting a plurality of tanks in FIG. The same applies to “piping” below.)

As shown in FIG. 1 , a first mixing tank (first neutralization tank) 42 is connected to the anaerobic bioreactor 10 .

Before the first mixing tank 42 performs anaerobic treatment of waste water containing high concentrations of organic substances containing organic substances and harmful nitrogen-containing compounds supplied (liquid-fed) to the anaerobic biological reaction tank 10, for example, This tank is used for preliminary treatment, such as adjusting the concentration of hydrogen ions by adding a hydrogen ion concentration adjusting agent, adjusting the concentration of harmful nitrogen-containing compounds, and the concentration of wastewater containing high-concentration organic matter.

The first mixing tank 42 is equipped with a valve that can be freely opened and closed in addition to a conventionally known tank having an arbitrary and suitable configuration. A configuration such as a conventionally known arbitrary and suitable configuration such as a pipe and a pump is connected for supplying and supplying the agent, and for supplying and discharging the liquid to be treated from the first mixing tank 42. good too.

The treatment apparatus 1 of the present embodiment is connected to the already described anaerobic biological reaction tank 10, and is supplied from the anaerobic biological reaction tank 10 to be treated anaerobic treatment liquid, which is a liquid to be treated, and further anaerobic organisms. It has an aerobic biological reaction tank 20 capable of aerobically treating waste water containing low-concentration organic matter (low-TOC waste water) supplied without passing through the reaction tank 10 .

The configuration of the aerobic bioreactor 20 is not particularly limited, provided that it has a size (capacity) that can handle the desired treatment capacity and can handle the expected characteristics of low-concentration organic matter-containing wastewater. As the configuration of the aerobic biological reactor 20, any conventionally known and suitable configuration can be adopted. As the aerobic biological reaction tank 20, specifically, a conventionally known tank having any suitable configuration that can be applied to, for example, the "standard activated sludge process" can be used.

As shown in FIG. 1, the aerobic bioreactor 20 includes an aerator 22 capable of aerating the anaerobic treatment liquid or low-concentration organic matter-containing wastewater, which is the supplied treatment liquid to be treated. prepared inside.

As the aerator 22, for example, a conventionally known device capable of bringing sufficient gas (e.g., air) to carry out aerobic treatment by the "standard activated sludge method" into contact with low-concentration organic matter-containing waste water or anaerobic treatment liquid An aerator having any suitable configuration can be applied.

The aerobic biological reaction tank 20 is equipped with a structure such as a valve that can be freely opened and closed to adjust the amount of liquid sent between the tanks. Arbitrary and suitable conventionally known pipes and pumps for feeding and supplying the gaseous treatment liquid (and activated sludge) may be connected.

As shown in FIG. 1 , a second mixing tank (second neutralization tank) 44 is connected to the aerobic bioreactor 20 .

The second mixing tank 44 applies a hydrogen ion concentration adjusting agent to the low-concentration organic matter-containing wastewater (low-TOC wastewater) supplied (fluid-fed) to the aerobic biological reaction tank 20 before performing aerobic treatment. is added to adjust the concentration of hydrogen ions and the concentration of organic substances.

The second mixing tank 44 is equipped with a valve that can be freely opened and closed in addition to a conventionally known tank having an arbitrary and suitable configuration. A conventionally known arbitrary suitable configuration for feeding and supplying the contained wastewater, the anaerobic treatment liquid, and the hydrogen ion adjusting agent, and for feeding and discharging the liquid to be treated from the second mixing tank 44. You may have the structure, such as piping and a pump which have.

The treatment apparatus 1 of the present embodiment is connected to an aerobic biological reaction tank 20, and solid-liquid separates the aerobic treatment liquid, which is the liquid to be treated supplied from the aerobic biological reaction tank 20, A solid-liquid separator 30 is provided to separate the activated sludge produced by aerobically treating the thickened activated sludge from the treated water. A suitable example of the solid-liquid separation device 30 is a sedimentation tank (sedimentation separation tank: thickener).

As the solid-liquid separation device 30, for example, a tank having a conventionally known arbitrary suitable configuration that can be specifically applied to, for example, the "standard activated sludge process" can be used.

As shown in FIG. 1, in the solid-liquid separation device 30, the separated activated sludge is refluxed from the solid-liquid separation device 30 and supplied (liquid-fed) to the anaerobic treatment tank 10. A structure such as a conventionally known arbitrary suitable structure such as a pipe and a pump is connected to take out the treated water, which is the supernatant liquid, to the outside of the solid-liquid separator 30 .
In step (1), the processing apparatus 1 including the above configuration is prepared.

(ii) step (2)
In the step (2), low-concentration organic matter-containing wastewater having a TOC of 0.05 times or less that of high-concentration organic matter-containing wastewater and activated sludge are supplied to an aerobic bioreactor, and low-concentration organic matter-containing wastewater is preferred. In this step, concentrated activated sludge is obtained by performing solid-liquid separation using a solid-liquid separation device from the treated liquid obtained by the pneumatic treatment.

In the step (2), the activated sludge concentration (MLSS) in the system of the anaerobic biological reactor 10 in the step (3) is already reduced in order to effectively treat high-concentration organic matter-containing wastewater containing harmful nitrogen-containing compounds. It is a step that is performed because it is necessary to set it higher as explained.

The low-concentration organic matter-containing wastewater (low-TOC wastewater) in step (2) has a total organic carbon (TOC) amount of 0.05 times or less that of the high-concentration organic matter-containing wastewater having a TOC of 20000 mg/L or more. It means a liquid (waste water).

The low-concentration organic substance-containing waste water in step (2) preferably has a TOC of 0.04 times or less that of the high-concentration organic substance-containing waste water, usually 100 mg/L or more, and preferably 200 mg/L or more.

The organic carbon contained in the low-concentration organic matter-containing wastewater includes the already-described non-activation-inhibiting organic carbon, and preferably does not contain activity-inhibiting organic carbon.

Here, the "wastewater containing low-concentration organic matter" used in step (2) does not necessarily have to be "wastewater" such as factory wastewater.

The "low-concentration organic matter-containing wastewater" used in step (2) may be, for example, a liquid that is artificially adjusted so that the TOC is 0.05 times or less that of the high-concentration organic matter-containing wastewater, and is obtained in advance. It is a liquid that has been prepared so that the TOC is 0.05 times or less that of the wastewater containing high-concentration organic matter, by diluting the wastewater containing high-concentration organic matter that was previously used, or by adjusting the TOC of the wastewater containing organic matter obtained separately. There may be.

As described above, in the aerobic biological reaction tank 20, low-concentration organic matter-containing waste water or anaerobic treatment liquid is aerobically treated (aerobic treatment) using activated sludge.

Specifically, the already described aerator (aerator) 22 preferably blows air into the low-concentration organic matter-containing wastewater continuously supplied (liquid-fed) to the aerobic biological reaction tank 20 while aerobic organic carbon contained in the low-concentration organic matter-containing wastewater is decomposed by the activated sludge previously stored in the aerobic biological reaction tank 20 or supplied separately or together with the low-concentration organic matter-containing wastewater. do.

Aerobic treatment in the aerobic biological reaction tank 20 is preferably carried out in a neutral region with a hydrogen ion concentration (pH) in the range of 6 to 8 from the viewpoint of improving the activity of the activated sludge used. .

In addition, the aerobic treatment in the aerobic biological reaction tank 20 is usually performed at 25° C. or higher, preferably at 30° C. or higher, and usually at 38° C. or lower, from the viewpoint of improving the activity of the activated sludge. , preferably at a temperature of 32° C. or less.

In aerobic treatment, if the hydrogen ion concentration is outside the range, for example, by further adding a hydrogen ion concentration adjusting agent such as sulfuric acid, hydrochloric acid, sodium hydroxide, sodium carbonate, or calcium hydroxide, the hydrogen ion concentration can be carried out while adjusting to the above range.

It is preferable that the hydrogen ion concentration adjusting agent is premixed with the low-concentration organic matter-containing waste water in the already-described second mixing tank 44 and then supplied to the aerobic biological reaction tank 20 .

The amount of activated sludge used in the aerobic biological reaction tank 20 can be appropriately adjusted in consideration of the amount of TOC in wastewater containing low-concentration organic matter, the type of organic carbon, and the like.

Specifically, the amount of activated sludge used (supplied amount) is the mass ratio (TOC/MLSS) of the amount of TOC in wastewater containing low-concentration organic matter and the amount of activated sludge used in terms of suspended solids (MLSS). , usually 0.5 kg-TOC/(kg-MLSS/day) or less, and the volume of the aerobic biological reactor 20 can be made smaller, so usually 0.1 kg-TOC/(kg-MLSS・ Days) or more.

In the step (2), the activated sludge obtained by aerobic treatment of wastewater containing low-concentration organic matter in the aerobic biological reaction tank 20 is suspended in the aerobic treatment liquid after the aerobic treatment. The aerobic bioreactor 20 is withdrawn. That is, the aerobic treatment liquid containing activated sludge is usually solid-liquid separated by the solid-liquid separator 30 . Specifically, the activated sludge in the extracted aerobic treatment liquid is deposited in the solid-liquid separation device 30 under conditions where only oxygen is consumed by microorganisms without supplying oxygen, and stored under anaerobic conditions. It is possible to concentrate the activated sludge by solid-liquid separation from the aerobic treatment liquid. As a result of this solid-liquid separation, concentrated activated sludge can be obtained. The obtained concentrated activated sludge can be reused by extracting it from the solid-liquid separation device 30 and recirculating it to the anaerobic treatment tank 10 for supply (liquid transfer).

The concentrated activated sludge obtained by solid-liquid separation from the aerobic treatment liquid in the solid-liquid separator 30 after treatment in the aerobic biological reaction tank 20 may be entirely returned to the anaerobic biological reaction tank 10 and supplied. , may be supplied to the anaerobic bioreactor 10 only in part. Further, the excess thickened activated sludge after step (2) may be extracted from the solid-liquid separator 30 and discarded.

(iii) step (3)
In step (3), wastewater containing high concentration organic matter, concentrated activated sludge, and nitrate nitrogens are mixed so that the ratio of carbon content to nitrogen content (C/N ratio) is in the range of 0.5 to 4.6. Secondly, it is supplied to an anaerobic bioreactor to treat organic substances and harmful nitrogen-containing compounds to obtain an anaerobic treated liquid.

Here, the "anaerobic treatment liquid" may include activated sludge in addition to organic matter and harmful nitrogen-containing compounds that remain after anaerobic treatment.

In the present embodiment, the “ratio of carbon content to nitrogen content (C/N ratio)” specifically refers to the amount of carbon derived from organic matter in wastewater containing high-concentration organic matter, and the nitrogen-containing compounds in wastewater. It means the ratio with the amount of nitrogen derived. Examples of nitrogen-containing compounds include harmful nitrogen-containing compounds and nitrate nitrogens.

The "ratio of carbon content to nitrogen content (C/N ratio)" is preferably adjusted to be in the range of 0.5 to 4.6, and should be adjusted in the range of 0.5 to 3.5. is more preferable, and it is even more preferable to adjust it in the range of 1.0 to 3.0.

In particular, if the C/N ratio is adjusted in the range of 1.0 to 3.0, all organic carbon, nitrate nitrogens and harmful nitrogen-containing compounds derived from wastewater containing high concentrations of organic matter can be efficiently and effectively decomposed. can do.

The amount of concentrated activated sludge to be used in the anaerobic biological reaction tank 10 can be appropriately adjusted in consideration of the amount of TOC in the wastewater containing high-concentration organic matter, the amount of harmful nitrogen-containing compounds, the type of organic carbon, and the like. Specifically, from the viewpoint of promoting the growth of microorganisms and improving the treatment capacity of the microorganisms, the concentration of activated sludge in the system in the anaerobic biological reactor 10 is It is set to be, for example, about twice as high as the density. That is, the activated sludge concentration (MLSS) in the anaerobic bioreactor 10 is usually 3000 mg/L or higher, preferably 6000 mg/L or higher, and more preferably 12000 mg/L or higher.

As for the amount of concentrated activated sludge used, the mass ratio (TOC/MLSS) of the TOC amount of wastewater containing high concentration organic matter and the amount of concentrated activated sludge used in terms of MLSS is usually 0.5 kg-TOC/(kg-MLSS・Day) or less, preferably 0.3 kg-TOC/(kg-MLSS/day) or less, more preferably 0.10 kg-TOC/(kg-MLSS/day) or less. be. On the other hand, from the viewpoint of reducing the volume of the anaerobic biological treatment tank 10, it is usually 0.1 kg-TOC/(kg-MLSS/day) or more, preferably 0.2 kg-TOC/(kg-MLSS/day) or more. More preferably, it is set to 0.3 kg-TOC/(kg-MLSS/day) or more.

In step (3), the nitrate nitrogens supplied to the anaerobic bioreactor 10 may be nitrate nitrogen or nitrite nitrogen.

Nitrate nitrogen includes, for example, nitrate compounds containing nitrate ions (NO ₃ ⁻ ). Nitrite nitrogen includes, for example, nitrite compounds containing nitrite ions (NO ₂ ⁻ ).

Nitrate compounds include, for example, nitrates such as alkali metal nitrates such as sodium nitrate and potassium nitrate, and alkaline earth metal nitrates such as calcium nitrate. Nitrite compounds include, for example, nitrites such as alkali metal nitrites such as sodium nitrite and potassium nitrite, and alkaline earth metal nitrites such as calcium nitrite.

The nitric acid compounds exemplified above may be used singly or in combination of two or more.

Nitrate nitrogens are usually used as an aqueous solution of nitrate nitrogens dissolved in water. Nitrate nitrogens are preferably used as an aqueous solution obtained by dissolving the above examples of nitric acid compounds in water.

The amount of nitrate nitrogens used is adjusted so that the ratio of the amount of TOC in wastewater containing high concentrations of organic matter to the amount of nitrate nitrogens used in terms of nitrogen atoms (TOC/N) is in the range of 2 to 10. is preferable, and it is more preferable to adjust the value to be 5 or less.

Wastewater containing high-concentration organic matter, concentrated activated sludge, nitrate nitrogens, and harmful nitrogen-containing compounds are separately transferred to the anaerobic biological reaction tank 10. Alternatively, two or more of them or all of them may be mixed in advance in the already-described first mixing tank 42 and then supplied to the anaerobic bioreactor 10 .

In the anaerobic treatment by the anaerobic bioreactor 10 of the present embodiment, the oxidation-reduction potential (ORP) based on the silver chloride electrode in the system is usually −100 mV or less, preferably −200 mV or less.

The ORP of the treated liquid containing activated sludge in the anaerobic biological reactor 10 in step (3) is higher than that in the system in the aerobic biological reactor 20 in step (2), that is, the activated sludge used in the aerobic treatment. Lower is preferred, preferably higher than the ORP, which indicates absolute anaerobicity.

The anaerobic treatment in the anaerobic bioreactor 10 is preferably carried out while stirring under conventionally known arbitrary suitable conditions with the stirrer 12 already described.

The anaerobic treatment is preferably carried out in a temperature range of 30°C to 48°C from the viewpoint of improving the activity of the concentrated activated sludge.

In addition, from the viewpoint of stably performing anaerobic treatment even if the TOC of wastewater containing high-concentration organic matter fluctuates to some extent, the anaerobic treatment in the anaerobic biological reaction tank 10 is performed by adjusting the hydrogen ion concentration (pH) to 6.5 or more and 9.0 or less, preferably a neutral range of 7.0 or more and 8.5 or less.

If the hydrogen ion concentration is outside the above range, for example, by appropriately adding an acid such as sulfuric acid or hydrochloric acid or a conventionally known suitable hydrogen ion concentration adjusting agent such as sodium hydroxide, sodium carbonate, or calcium hydroxide, hydrogen It is preferable to carry out while adjusting the ion concentration.

The hydrogen ion concentration adjusting agent may be pre-mixed with the high-concentration organic matter-containing wastewater in the already-described first mixing tank 42 and then supplied to the anaerobic biological reaction tank 10, or may be passed through the first mixing tank 42. Alternatively, it may be supplied to the anaerobic bioreactor 10 separately from the high-concentration organic matter-containing waste water.

In the anaerobic biological reaction tank 10, as described above, high-concentration organic matter-containing wastewater containing harmful nitrogen-containing compounds is supplied together with concentrated activated sludge and nitrate nitrogens, and is anaerobically treated to produce high-concentration Organic matter and harmful nitrogen-containing compounds contained in organic matter-containing wastewater are decomposed. The anaerobic treatment in the anaerobic bioreactor 10 will be specifically described below.

In the anaerobic bioreactor 10, harmful nitrogen-containing compounds are reduced by being utilized for cell synthesis during the process of rapid growth of microorganisms contained in the concentrated activated sludge. Specifically, for example, ammonia, which is a harmful nitrogen-containing compound, is used for cell synthesis of microorganisms contained in concentrated activated sludge, as shown in the following formula (1).

_{C6H8O4 + NH3 + O2}
→ _C5H7NO2 + _{CO2 + 2H2O +} energy (1)

Examples of microorganisms that can be contained in the concentrated activated sludge and that can undergo the reaction (decomposition reaction) associated with the growth of microorganisms represented by the above formula (1) include the genus Zoogloea, the genus Bucillus, which are classified as BOD-oxidizing bacteria, Microorganisms (bacteria) of the genus Pseudomonas and genus Paracoccus classified as denitrifying bacteria, the genus Nitrosomonas, the genus Nitrosococcus and the genus Nitrosospira classified as nitrifying bacteria, and the genus Plantomycetes classified as anammox bacteria. From the viewpoint of efficiently advancing the reaction in the anaerobic bioreactor 10 described above, the concentrated activated sludge preferably contains at least microorganisms classified as denitrifying bacteria.

Further, in the anaerobic biological reaction tank 10, the nitrate nitrogens are hydrogen (H) generated by decomposition of the hydrogen donor by denitrifying bacteria contained in the concentrated activated sludge under anaerobic conditions and the following formula It is reduced to nitrogen gas (N ₂ ) by reactions as shown in (2) and equation (3).

NO ₃ ⁻ +2 (H)→NO ₂ ⁻ +H ₂ O (2)
2NO ₂ ⁻ +6(H)→N ₂ +2H ₂ O+2OH ⁻ (3)

As described above, in the treatment method of the present embodiment, the denitrifying bacteria contained in the concentrated activated sludge proliferate in the anaerobic biological reaction tank 10, and the organic carbon and harmful nitrogen-containing compounds contained in the high-concentration organic matter-containing wastewater are removed. It is thought that organic carbon and harmful nitrogen-containing compounds are treated simultaneously and in parallel by using them as hydrogen donors and by allowing microorganisms contained in concentrated activated sludge to take in harmful nitrogen-containing compounds and use them for cell synthesis. .

Here, when the high-concentration organic matter-containing wastewater contains, for example, acetic acid (CH ₃ COOH) as organic carbon, this acetic acid becomes a hydrogen donor, and acetic acid is decomposed as shown in the following formula (4). , hydrogen (H) is produced.

CH3COOH ₊ 2H2O→ _{2CO2 +} 8(H) (4)

In the present embodiment, in the anaerobic biological reaction tank 10, the organic carbon in the wastewater containing high-concentration organic matter is removed by the anaerobic treatment (including digestion of harmful nitrogen-containing compounds by microorganisms in the concentrated activated sludge) as described above. And the activated sludge (concentrated activated sludge) after the harmful nitrogen-containing compounds have been treated is suspended from the anaerobic biological reaction tank 10 as a suspension with the anaerobic treatment liquid obtained by the anaerobic treatment, for example, piping etc. extracted through

At this time, the anaerobic treatment liquid (and concentrated activated sludge) is supplied (liquid-fed) to the anaerobic biological reaction tank 10 so that the amount of liquid remaining in the anaerobic biological reaction tank 10 is constant. Withdrawal is performed while adjusting the amount of liquid and the amount of liquid to be withdrawn to be balanced.

More specifically, the supply of high-concentration organic matter-containing wastewater containing harmful nitrogen-containing compounds, concentrated activated sludge, and nitrate nitrogens to the anaerobic biological reaction tank 10, and after anaerobic treatment from the anaerobic biological reaction tank 10 The withdrawal of the anaerobic treatment liquid (and the concentrated activated sludge) is performed simultaneously and continuously.

The residence time (θ ₃ =V ₃ /U _H ) represented by the ratio of the liquid volume (V ₃ ) in the anaerobic bioreactor 10 to the supply rate (U _H ) of the waste water containing high-concentration organic matter is the anaerobic From the viewpoint of sufficient treatment, it is preferably 8 hours or more, and from the viewpoint of reducing the volume of the anaerobic biological reactor 10, it is preferably 6 hours or less, and more preferably 0.5 hours or more and 4 hours or less. is.

The concentrated activated sludge after anaerobic treatment extracted from the anaerobic biological reaction tank 10 is usually used to aerobically treat (aerobic treatment) wastewater containing low-concentration organic matter in the aerobic biological reaction tank 20. It has sufficient activity. Therefore, if the concentrated activated sludge after anaerobic treatment is sent (supplied) as activated sludge to the aerobic biological reaction tank 20 and refluxed, the concentrated activated sludge can be reduced to a low concentration in the aerobic biological reaction tank 20 It is preferable because it can be reused for aerobic treatment of waste water containing organic substances.

The concentrated activated sludge extracted from the anaerobic biological reaction tank 10 may be, for example, solid-liquid separated from the anaerobic treatment liquid containing the concentrated activated sludge after the anaerobic treatment and then refluxed as a solid content. The anaerobic treatment liquid in a suspended state may be refluxed without being separated from the anaerobic treatment liquid containing the concentrated activated sludge.

The solid-liquid separation of the concentrated activated sludge from the anaerobic treated liquid after the anaerobic treatment can be carried out according to a conventional method, for example, by the solid-liquid separator 30 having an arbitrary and suitable configuration as previously described.

(iv) step (4)
In the step (4), the anaerobic treatment liquid is supplied to an aerobic biological reaction tank and aerated with an aerator to decompose organic matter remaining in the anaerobic treatment liquid and perform aerobic treatment. This is the step of obtaining the liquid.

In the aerobic biological reaction tank 20, the anaerobic treated liquid anaerobically treated in step (3) is aerobically treated (aerobic treatment) in the presence of concentrated activated sludge.

The activated sludge used in step (4) may contain concentrated activated sludge that is separately extracted from the anaerobic treatment tank 10 after the anaerobic treatment in step (3) and returned through a pipe or the like.

In the anaerobic treatment liquid treated in step (4), the organic substances and harmful nitrogen-containing compounds are decomposed to the same concentration level as the low-concentration organic matter-containing wastewater described above by the implementation up to step (3). It is a liquid with reduced concentration. That is, in step (4), the organic matter (organic carbon) remaining after the treatment in step (3) is aerobically treated (aerobic treatment) to decompose to obtain an aerobic treatment liquid. It is a process.

Step (4) is carried out using an aerobic bioreactor 20 with an aerator 22 in the tank previously described.

In the step (4), the anaerobic treatment liquid continuously sent (supplied) to the aerobic biological reaction tank 20 is brought into contact with the anaerobic treatment liquid while blowing air, for example, using the aerator 22 in the tank. Then, the organic carbon contained in the anaerobic treatment liquid is decomposed by the concentrated activated sludge.

The aerobic treatment in the aerobic biological reaction tank 20 in step (4) can be carried out with a hydrogen ion concentration (pH) in the neutral range of 6 to 8 from the viewpoint of improving the activity of the concentrated activated sludge. preferable.

In the aerobic treatment of step (4), if the hydrogen ion concentration is outside the range, for example, adding a hydrogen ion concentration adjusting agent such as sulfuric acid, hydrochloric acid, sodium hydroxide, sodium carbonate, or calcium hydroxide It is preferable to carry out while adjusting the hydrogen ion concentration within the above range.

In step (4), when it is necessary to use a hydrogen ion concentration adjusting agent, the hydrogen ion concentration adjusting agent is, for example, pre-mixed with the anaerobic treatment liquid in the second mixing tank 44 already described, and then aerobic It is preferred to feed the biological reactor 20 .

From the viewpoint of improving the activity of the concentrated activated sludge, the aerobic treatment in step (4) is usually carried out at 25°C or higher, preferably at 30°C or higher, and usually at 38°C or lower and 32°C or lower. is preferably carried out at a temperature of

In step (4), the amount of concentrated activated sludge used in the aerobic biological reactor 20 is the TOC amount of the anaerobic treatment liquid treated in step (3) and supplied to the aerobic biological reactor 20, It can be appropriately adjusted in consideration of the type of organic carbon. Specifically, the mass ratio (TOC/MLSS) between the TOC amount of the anaerobic treatment liquid and the amount of concentrated activated sludge used in terms of suspended solids (MLSS) is, for example, 0.5 kg-TOC/(kg- MLSS/day) or less, and from the viewpoint of further reducing the volume of the aerobic biological reactor 20, it is preferably 0.1 kg-TOC/(kg-MLSS/day) or more.

(v) step (5)
The step (5) is a step of supplying the aerobic treated liquid to a solid-liquid separation device and performing solid-liquid separation to recover concentrated activated sludge while obtaining treated water.

In step (5), the concentrated activated sludge after aerobic treatment in the aerobic biological reaction tank 20 is suspended in the aerobic treatment liquid after the aerobic treatment and is removed from the aerobic biological reaction tank 20. It is taken out and sent to the solid-liquid separator 30 .

The aerobic treatment liquid, which is a suspension containing concentrated activated sludge sent to the solid-liquid separator 30 , is treated by the solid-liquid separator 30 . Specifically, in the solid-liquid separation device 30, oxygen is not supplied, and the concentrated activated sludge in the aerobic treatment liquid is deposited under conditions where only oxygen consumption by microorganisms occurs, and is concentrated again by storing it under anaerobic conditions. Then, solid-liquid separation is performed into treated water, which is the supernatant liquid, and concentrated activated sludge, which is the solid content.

The concentrated activated sludge that has undergone solid-liquid separation in the solid-liquid separation device 30 can be extracted from the solid-liquid separation device 30, refluxed through a pipe or the like, and supplied (liquid-fed) to the anaerobic treatment tank 10 for reuse. Moreover, the excess thickened activated sludge may be extracted from the solid-liquid separator 30 and discarded.

Treated water, which is the supernatant liquid obtained by removing the concentrated activated sludge, must be treated, provided that harmful nitrogen-containing compounds and organic carbon have been reduced or removed to at least acceptable levels. After further treatment, such as with a disinfecting chemical such as chlorine, if any, it can be released to the outside environment.

According to the treatment method of the present embodiment, even if the high-concentration organic matter-containing wastewater contains harmful nitrogen-containing compounds, it is possible to treat the high-concentration organic matter-containing wastewater with small-scale equipment without adding additional equipment. Since it is performed in the anaerobic bioreactor 10, there is no need to supply air required for aeration, and a smaller amount of activated sludge can be used for treatment. As described above, according to the treatment method of the present embodiment, it is possible to simply and effectively treat high-concentration organic matter-containing wastewater containing harmful nitrogen-containing compounds with a high volumetric load.

The present invention will be described in more detail below with reference to examples. The invention is not limited to the following examples.

<Preparation of activated sludge and aqueous solution>
Suspension containing activated sludge extracted from the bottom of the solid-liquid separator in an existing wastewater (sewage) treatment facility equipped with at least a solid-liquid separator that is a facility for solid-liquid separation and an aerobic biological reaction tank A turbid liquid (hereinafter simply referred to as "activated sludge") is prepared, and an acetic acid aqueous solution, a sodium nitrate aqueous solution and an ammonia water (hereinafter simply referred to as "solutions") are prepared, respectively, as shown in Table 1 below. Prepared by adjusting the concentration.

<Analysis method>
TOC (total organic carbon) concentration measurement is based on the combustion oxidation-infrared TOC analysis method according to JIS K 0102 22.1, and NO3-N concentration measurement is based on JIS K 0102-43.2.5. The ion chromatographic method described above was carried out using a flow analysis method based on JIS K 0102-42.6 for measuring the concentration of NH4-N.

MLSS concentration measurement of activated sludge (concentrated activated sludge) was performed in accordance with JIS K0102-14.1. pH measurement was carried out using a glass electrode method conforming to JIS K0102-12.1.

<Calculation of C/N ratio>
TOC (mg/L) at the point immediately after liquid transfer to the aerobic bioreactor (that is, the mixed liquid of the activated sludge and each solution immediately before treatment) is expressed as the amount of nitrogen converted to NO3-N (mg/ L) and the nitrogen content (mg/L) in terms of NH4-N divided by the total nitrogen content (mg/L) was calculated as the C/N ratio in each example.

[Example 1]
3 L of the activated sludge prepared as described above was put into a simulated anaerobic bioreactor (effective volume: 3 L), and while the temperature of the activated sludge was maintained at 35° C. with a heater, it was stirred with a stirrer. rice field. After that, the activated sludge prepared as above (the liquid was sent from a state where it was stirred with a stirrer and kept at a liquid temperature of 35 ° C.) was further transferred to the anaerobic biological reaction tank, and the acetic acid aqueous solution and sodium nitrate prepared as above. An aqueous solution and an aqueous ammonia solution were simultaneously fed into the anaerobic biological reaction tank as simulated high-concentration organic matter-containing wastewater (liquid to be treated), and the temperature in the anaerobic biological reaction tank was raised to 35°C. By stirring while maintaining, the decomposition reaction using activated sludge was continuously progressed for treatment. Table 1 below shows the component concentrations of the activated sludge and each solution, and the amount of liquid fed.

At this time, the retention time (θ = V/V') represented by the ratio of the internal liquid volume (V) of the anaerobic biological reactor and the total liquid volume (V') sent to the anaerobic biological reactor was 4 hours.

After 8 hours (2θ) from the start of feeding to the anaerobic biological reaction tank, the treated water obtained by overflowing from the anaerobic biological reaction tank is filtered using qualitative filter paper No. 1. The TOC concentration, NO3-N concentration and NH4-N concentration of the filtrate were measured respectively.

From the results obtained by the above measurements, the treatment rate (%) of each component, that is, the ratio (%) of the concentration decreased due to the decomposition reaction with respect to the concentration at the time when the liquid was sent to the anaerobic bioreactor was calculated. . The results are shown in Table 2 below.

[Examples 2 to 5]
The treatment properties were evaluated in the same manner as in Example 1 already described, except that the concentrations and flow rates of the activated sludge and each solution were changed as shown in Table 1 below. The results are shown in Table 2 below and FIG.

As is clear from Table 2 and FIG. 2, it was confirmed that a treatment rate close to 40% can be achieved by adjusting the C/N ratio to about 2.0 for the treatment of NH4-N. At this time, it was confirmed that a treatment rate close to 100% could be achieved for the treatment of organic carbon in terms of TOC and nitrogen in terms of NO3-N, which were simultaneously treated.

In addition, especially if the C/N ratio is adjusted in the range of 1.0 to 3.0, a high treatment rate can be obtained for all of organic carbon in terms of TOC, nitrogen in terms of NO3-N, and nitrogen in terms of NH4-N. I have confirmed that it is possible.

1 treatment device 10 anaerobic biological reaction tank 12 agitator 20 aerobic biological reaction tank 22 aerator 30 solid-liquid separation device 42 first mixing layer (first neutralization tank)
44 Second mixing tank (second neutralization tank)

<Calculation of C/N ratio>
TOC (mg / L) at the time immediately after sending the liquid to the anaerobic bioreactor (that is, the mixed liquid of the activated sludge and each solution immediately before treatment) is the amount of nitrogen converted to NO3-N (mg / L ) and the nitrogen content (mg/L) in terms of NH4-N, divided by the total nitrogen content (mg/L), was calculated as the C/N ratio in each example.

[Examples 2-3 and Comparative Examples 1-2 ]
The treatment properties were evaluated in the same manner as in Example 1 already described, except that the concentrations and flow rates of the activated sludge and each solution were changed as shown in Table 1 below. The results are shown in Table 2 below and FIG.

Claims (4)

A treatment method for biologically treating wastewater containing organic substances and harmful nitrogen-containing compounds and having a TOC of 20000 mg/L or more and containing high concentrations of organic substances with activated sludge,
Step (1): An anaerobic biological reaction tank for anaerobically treating the waste water containing high-concentration organic matter, and an aeration device connected to the anaerobic biological reaction tank and capable of performing aeration treatment, an aerobic biological reactor capable of aerobically treating the anaerobic treatment liquid supplied from the anaerobic biological reactor; and an aerobic biological reactor connected to the aerobic biological reactor. a step of preparing a treatment apparatus equipped with a solid-liquid separator capable of solid-liquid separation of the aerobic treatment liquid supplied from the reaction tank;
Step (2): Feeding activated sludge and low-concentration organic matter-containing wastewater having a TOC of 0.05 times or less that of the high-concentration organic matter-containing wastewater to the aerobic bioreactor, to obtain the low-concentration organic matter-containing wastewater. A step of obtaining concentrated activated sludge by performing solid-liquid separation using the solid-liquid separator from the treated liquid obtained by aerobically treating the
Step (3): The high-concentration organic matter-containing waste water, the concentrated activated sludge, and the nitrate nitrogens are mixed so that the ratio of carbon content to nitrogen content (C/N ratio) is in the range of 0.5 to 4.6. a step of supplying to the anaerobic biological reactor and treating the organic matter and the harmful nitrogen-containing compound to obtain an anaerobic treatment solution;
Step (4): The anaerobic treatment liquid is supplied to the aerobic biological reaction tank and aerated by the aeration device to decompose the organic matter remaining in the anaerobic treatment liquid. , obtaining an aerobic treatment liquid;
Step (5): a step of supplying the aerobic treated liquid to the solid-liquid separation device and performing solid-liquid separation to recover concentrated activated sludge while obtaining treated water. The treatment method according to claim 1, wherein the harmful nitrogen-containing compound is one or more selected from the group consisting of amines. 3. The treatment method according to claim 2, wherein said harmful nitrogen-containing compound is ammonia. In the step (3), the high-concentration organic matter-containing wastewater, the concentrated activated sludge, and the nitrate nitrogens are mixed so that the ratio of the carbon content to the nitrogen content is in the range of 0.5 to 4.6. The treatment method according to any one of claims 1 to 3, which is carried out by supplying to an anaerobic bioreactor.

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