JP4648872B2 - Wastewater treatment method for wastewater containing high concentration organic matter - Google Patents

Description

The present invention may be referred to as high-concentration organic substance-containing wastewater [hereinafter referred to as high-TOC wastewater. In detail, the present invention relates to a method of biologically treating high TOC wastewater having a TOC (total organic carbon) of 20000 mg / L or more with activated sludge.

As a method of treating wastewater (A) containing organic carbon with activated sludge (B), a wastewater treatment facility (1 ′) equipped with an aerobic treatment tank (2) as shown in FIG. In general, a method in which wastewater (A) is brought into contact with activated sludge (B) in an aerobic atmosphere in which the air is sufficiently brought into contact with air inside the aerobic treatment tank (2) [Non-patent document 1: “Water pollution prevention technology” And Biological Hydraulic Processing Technology and Apparatus ", edited by Chemical Engineering Association, Baifukan Co., Ltd., published on October 20, 1978, pages 114-116]. According to such a method, the organic carbon in the waste water (A) can be decomposed with the activated sludge (B) and treated with waste water.

However, this conventional wastewater treatment method has a low volumetric load indicating the amount of organic carbon that can be decomposed per unit time per unit volume of the aerobic treatment tank (2), and the TOC is 20000 mg as wastewater (A). In order to treat high TOC waste water (AH) of / L or more, it was necessary to use a large volume aerobic treatment tank (2) or to take a long time for waste water treatment.

"Water pollution prevention technology and equipment 4. Biological hydraulic treatment technology and equipment" edited by Japan Society for Chemical Engineering, Baifukan Co., Ltd., published on October 20, 1978, pages 114-116

Therefore, as a result of intensive studies to develop a method capable of treating wastewater from high TOC wastewater (AH) with high volume load, the present inventor has low concentration organic matter-containing wastewater that exhibits low TOC (hereinafter referred to as low TOC wastewater). There is. The activated sludge (B) after the aerobic treatment of (AL) in the aerobic treatment tank (2) is a high volume load in the presence of nitrate nitrogen (C) in an anaerobic atmosphere. The inventors have found that it can be decomposed and have arrived at the present invention.

That is, the present invention is a method of biologically treating high TOC wastewater (AH) having a TOC of 20000 mg / L or more and 100000 mg / L or less with activated sludge,
As activated sludge, after TOC is aerobic treatment in a low TOC drainage (AL) aerobic treatment tank (2) of 0.05 times or less of the high TOC water discharge 100 mg / L or more (AH), after aerobic treatment Using activated sludge (B) separated from aerobic treated water (AL ') ,
Anaerobic treatment tank (3) with high TOC wastewater (AH) and activated sludge (B) and nitrate nitrogen (C)
Continuously fed into the anaerobic treatment tank (3) by the activated sludge (B) and the nitrate nitrogen (C)
While anaerobically treating the high TOC wastewater (AH) in the presence of
Anaerobic treated water (AH ') and activated sludge (B') after anaerobic treatment are continuously extracted,
The extracted activated sludge (B ') is recirculated to the aerobic treatment tank (2) ,
An aerobic treated water (AL ') after separating the activated sludge (B) after the aerobic treatment is led out of the system. The high TOC wastewater (AH) wastewater treatment method is provided. Is.

FIG. 1 and FIG. 2 schematically show an example of a wastewater treatment facility (1) for wastewater treatment of high TOC wastewater (AH) by the wastewater treatment method of the present invention. This wastewater treatment facility (1) comprises an aerobic treatment tank (2) for aerobically treating low TOC wastewater (AL) in the presence of activated sludge (B),
An anaerobic treatment tank (3) for anaerobically treating high TOC wastewater (AH) with activated sludge (B) in the presence of nitrate nitrogen (C). The wastewater treatment facility (1) is an aerobic treatment tank (2) which is subjected to aerobic treatment of low TOC wastewater (AL) and then separated from aerobic treated water (AL ') after aerobic treatment. Sludge (B) is continuously supplied to the anaerobic treatment tank (3) together with high TOC wastewater (AH) and nitrate nitrogen (C).
From the anaerobic treatment tank (3), anaerobic treated water (AH ') and activated sludge (B') after anaerobic treatment are continuously withdrawn,
Activated sludge (B ') extracted from the anaerobic treatment tank (3) is recirculated to the aerobic treatment tank (2) ,
The aerobic treated water (AL ') after separating the activated sludge (B) after the aerobic treatment is configured to lead out of the system .

According to the waste water treatment method of the present invention, high TOC waste water (AH) having a TOC of 20000 mg / L or more can be treated with high volume load.

Hereinafter, the waste water treatment method of the present invention will be described with reference to FIGS. 1 and 2.
High TOC wastewater applied to waste water treatment method of the present invention (AH) is, TOC is 20000 mg / L or more, preferably 30000 mg / L or more, preferably 40000mg / L or more, less drainage 1 00000mg / L. Examples of organic carbon contained in such high TOC wastewater (AH) include non-inhibitory organic carbon that does not inhibit the activity of activated sludge (B), such as methanol and acetic acid. Further, it may contain an activity-inhibiting organic carbon that inhibits the activity of the activated sludge (B) such as formaldehyde [HCHO].

Activated sludge used in the method (B) of the present invention, TOC is more than 0.05 times the height TOC drainage (AH), preferably 0.04 times or less, 1 200 mg / L or more, preferably more lower 200mg The TOC waste water (AL) is subjected to an aerobic treatment in an aerobic treatment tank (2). Examples of the organic carbon contained in the low TOC waste water (Al) include non-inhibitory organic carbons similar to those described above, and preferably do not include the same active-inhibitory organic carbons as described above.

In the aerobic treatment tank (2), low TOC wastewater (AL) is aerobically treated in the presence of activated sludge. As an aerobic treatment tank (2), for example, as shown in FIG. 1 and FIG. 2, an aerator (21) is provided inside, and air (D) is blown by the aerator (21). A normal aerobic treatment tank that continuously supplies low TOC wastewater (AL) and decomposes organic carbon contained in the low TOC wastewater (AL) with activated sludge (B) can be used.

The aerobic treatment is usually performed in the neutral region of hydrogen ion concentration pH 6 to pH 8 in terms of the activity of the activated sludge (B). When the hydrogen ion concentration is outside the above range, for example, an acid such as sulfuric acid or hydrochloric acid, A hydrogen ion concentration adjusting agent (E) such as an alkali such as sodium hydroxide, sodium carbonate or calcium hydroxide is added to adjust the hydrogen ion concentration within the above range. The hydrogen ion concentration adjusting agent (E) is usually mixed with the low TOC waste water (AL) in a mixing tank (neutralization tank) (22) before being supplied to the aerobic treatment tank (2).

The aerobic treatment is performed at a temperature of usually 25 ° C. or higher, preferably 30 ° C. or higher, usually 38 ° C. or lower, preferably 32 ° C. or lower in terms of the activated sludge activity.

The amount of activated sludge (B) used in the aerobic treatment tank (2) varies depending on the TOC amount of low TOC wastewater (AL), the type of organic carbon, etc. The mass ratio (TOC / MLSS) of the activated sludge (B) converted to suspended suspended solids [MLSS] is usually less than 0.5 kg-TOC / (kg-MLSS · day), aerobic treatment In order to reduce the volume of the tank (2), it is usually about 0.1 kg-TOC / (kg-MLSS · day) or more.

Activated sludge (B) after aerobic treatment of low TOC wastewater (AL) in such aerobic treatment tank (2) is usually suspended in aerobic treated water (AL ') after aerobic treatment. Extracted from the aerobic treatment tank (2). Withdrawn activated sludge (B) is Ru is supplied after being separated from the sedimentation separation tank [thickener] (23) in aerobic treatment water (AL ') in the anaerobic treatment tank (3).

The amount of activated sludge (B) used in the anaerobic treatment tank (3) varies depending on the TOC amount of high TOC wastewater (AH) and the type of organic carbon, but the TOC amount of high TOC wastewater (AH) and MLSS The mass ratio (TOC / MLSS) with the amount of activated sludge converted (B) is usually less than 0.5 kg-TOC / (kg-MLSS · day), and the volume of the anaerobic treatment tank (3) Is usually about 0.15 kg-TOC / (kg-MLSS · day). The activated sludge (B) extracted from the aerobic treatment tank (2) may be entirely supplied to the anaerobic treatment tank (3), or a part thereof is supplied to the anaerobic treatment tank (3). May be.

The nitrate nitrogen (C) may be nitrate nitrogen or nitrite nitrogen. Examples of nitrate nitrogen include nitrate compounds containing nitrate ions (NO ₃ ⁻ ), and examples of nitrite nitrogen include nitrite compounds containing nitrite ions (NO ₂ ⁻ ). Examples of nitrate compounds include nitrates such as alkali metal nitrates such as sodium nitrate and potassium nitrate, alkaline earth metal nitrates such as calcium nitrate, and nitrite compounds such as sodium nitrite and potassium nitrite. Examples thereof include nitrites such as alkali metal nitrites and alkaline earth metal nitrites such as calcium nitrite, and these may be used alone or in combination of two or more. May be.

Nitrate nitrogen (C) is usually used as an aqueous solution of nitrate nitrogen dissolved in water. For example, a solution obtained by dissolving nitrate nitrogen (C) described above in water is used.

The amount of nitrate nitrogen (C) used is the ratio (TOC / N) of the TOC amount of high TOC wastewater (AH) and the amount of nitrate nitrogen (C) converted to nitrogen atom (TOC / N), usually 2 10, preferably 5 or less.

High TOC wastewater (AH), activated sludge (B) and nitrate nitrogen (C) are, for example, high TOC wastewater (AH), activated sludge (B) and nitrate nitrogen as shown in FIGS. (C) may be independently supplied to the anaerobic treatment tank (3), or two or all of them may be mixed in advance and supplied to the anaerobic treatment tank (3).

As the anaerobic treatment tank (3), for example, the same one as that usually used for denitrification of nitrate nitrogen (C) by denitrifying bacteria can be used. The redox potential (ORP) based on the silver chloride electrode in the system in the anaerobic treatment is usually −100 mV or less, preferably −200 mV or less.

The anaerobic treatment is usually performed while stirring with a stirrer (31) or the like, and is usually performed in a temperature range of 30 ° C. to 48 ° C. in terms of the activity of the activated sludge (B). In addition, it can be stably anaerobically treated even if the TOC of the high TOC wastewater (AH) fluctuates, so that the hydrogen ion concentration is generally pH 6.5 or more and pH 9.0 or less, preferably pH 7.0 or more and pH 8.5 or less. When the hydrogen ion concentration is outside this range, for example, by adding an acid such as sulfuric acid or hydrochloric acid or a hydrogen ion concentration adjusting agent (E) such as sodium hydroxide, sodium carbonate or calcium hydroxide. It is performed while adjusting the hydrogen ion concentration. The hydrogen ion concentration regulator (E) may be supplied to the anaerobic treatment tank (3) after being mixed with the high TOC waste water (AH) in the mixing tank (neutralization tank) (32) in advance. You may supply to an anaerobic processing tank (3) independently of waste_water | drain (AH).

By supplying high TOC waste water (AH) to the anaerobic treatment tank (3) together with activated sludge (B) and nitrate nitrogen (C), the presence of nitrate nitrogen (C) is caused by activated sludge (B). Below the high TOC wastewater (AH) is anaerobically treated.

および式（２）

に従って反応させて窒素〔Ｎ₂〕に還元する脱窒細菌が含まれており、本発明の排水処理方法では、高ＴＯＣ排水(AH)に含まれる有機態炭素が、この水素供与体として働くことにより分解されるものと考えられる。例えば高ＴＯＣ排水(AH)が有機態炭素として酢酸〔ＣＨ₃ＣＯＯＨ〕を含む場合には、この酢酸が水素供与体となり、式（３）

に従い分解して、水素〔(Ｈ)〕を生成する。 The activated sludge (B) contains nitrate nitrogen (C) in an anaerobic atmosphere, hydrogen ((H)) generated by decomposition of the hydrogen donor and formula (1).

And formula (2)

Includes a denitrifying bacteria reduced to nitrogen [N _2] is reacted accordingly in the wastewater treatment method of the present invention, organic carbon is contained in the high TOC drainage (AH), to act as the hydrogen donor It is thought that it is decomposed by. For example, when high TOC wastewater (AH) contains acetic acid [CH ₃ COOH] as organic carbon, this acetic acid becomes a hydrogen donor, and the formula (3)

To produce hydrogen [(H)].

Activated sludge (B ') after decomposing organic carbon in high TOC wastewater (AH) by anaerobic treatment was usually suspended together with anaerobic treated water (AH') after anaerobic treatment. In the state, it is extracted from the anaerobic treatment tank (3). At this time, the anaerobic treated water (AH ′) and the activated sludge (B ′) are extracted so that the amount of high TOC wastewater (A) staying inside the anaerobic treatment tank (3) is constant.

Supply of high TOC wastewater (AH), activated sludge (B) and nitrate nitrogen (C) to the anaerobic treatment tank (3), and anaerobic treatment after anaerobic treatment from the anaerobic treatment tank (3) Extraction of water (AH ') and activated sludge (B') is carried out continuously, respectively, and the liquid volume (V ₃ ) in the anaerobic treatment tank ( ₃ ) and the supply rate (U) of high TOC waste water (A) _The residence time (θ ₃ = V ₃ / U _H ) indicated by the ratio to _H ) is usually 0.5 hours or more in terms of sufficient anaerobic treatment, and the volume of the anaerobic treatment tank (3) Is usually 5 hours or less in that it can be made smaller.

The activated sludge (B ') extracted from the anaerobic treatment tank (3) often exhibits sufficient activity for aerobic treatment of low TOC wastewater (AL). By recirculating to the treatment tank (2), this activated sludge (B) can be reused for aerobic treatment of low TOC wastewater (AL) in the aerobic treatment tank (2). . The activated sludge (B ′) extracted from the anaerobic treatment tank (3) may be separated from the anaerobic treated water (AH ′) after the anaerobic treatment, for example, as shown in FIG. However, as shown in FIG. 2, the mixture may be refluxed in a mixed state without being separated from the anaerobic treated water (AH ′). Separation of the activated sludge (B ′) and the anaerobic treated water (AH ′) can be performed by a normal sedimentation tank (thickener) (33) as shown in FIG. Part or all of the activated sludge (B ′) after being separated in the settling separation tank (33) is circulated to the aerobic treatment tank (2).

According to the wastewater treatment method of the present invention, high TOC wastewater (AH) can be treated with activated sludge (B) at a high volume load, so the time required for wastewater treatment of high TOC wastewater (AH) can be shortened, and the equipment Can be made relatively small. Moreover, since the high TOC wastewater (AH) wastewater treatment is performed in the anaerobic treatment tank (3), it is not necessary to supply air required for aeration, and wastewater treatment can be performed with a small amount of activated sludge (B).

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this Example.

Example 1
A wastewater treatment facility (1) provided with an aerobic treatment tank (2) and an anaerobic treatment tank (3) as shown in FIG. 2 was prepared.

In the aerobic treatment tank (2) of the wastewater treatment facility (1), low TOC wastewater (TOC 500 mg / L, temperature of about 20 ° C.) (AL) containing mainly acetic acid [CH ₃ COOH] as organic carbon is 50 to 50 Continuously supplied at 200 volume parts / h, continuously supplied with air (D) from the aerator (21) at the bottom and aerated to perform aerobic treatment at a temperature of 32 ° C to 38 ° C. Aerobic treated water (AL ′) and activated sludge (B) after aerobic treatment were continuously withdrawn so that the amount of low TOC wastewater (2) inside the aerobic treatment tank (2) was constant.

At this time, aerobic treatment tank (2) the amount of liquid in the (V ₂₎ and the feed rate of the low TOC drainage (AL) (U _L) and residence time indicated by the ratio of _{(θ 2 = V 2 / U} L) Was 15 hours. The mass ratio (TOC / MLSS) between the amount of low TOC wastewater (AL) converted to TOC and the amount of activated sludge (B) converted to MLSS supplied to the aerobic treatment tank (2) is 0.25 kg-TOC / (kg- MLSS / day).

The extracted aerobic treated water (AL ′) and the suspension of activated sludge (B) (AL ′ + B) are sent to the sedimentation tank (23), where the activated sludge (B) is allowed to settle, It was extracted from the bottom of the sedimentation separation tank (22) and isolated. The isolated activated sludge (B) contained water, and its MLSS was 25000 mg / L. Moreover, when TOC was measured, it was about 150 mg / L.

In the anaerobic treatment tank (3), the activity obtained by isolating high TOC waste water mainly containing methanol as organic carbon (TOC 45000 mg / L, temperature 25 ° C.) (AH) at 1 volume part / h as described above. Part of sludge [temperature 38 ° C.] (B) at 10 parts by volume / h and NaNO ₃ aqueous solution [nitrogen equivalent concentration 66000 mg / L, about 20 ° C.] (D) at 0.2 parts by volume / h, respectively. The anaerobic treatment water (AH ') and the activated sludge (B') after the anaerobic treatment are continuously withdrawn. It was.

Anaerobic treatment tank (3) the amount of liquid in the (V ₃₎ and feed rate (U _H) and residence time indicated by the ratio of the high TOC drainage _{(AH) (θ 3 = V} 3 / U H) is about It was 3 hours. During the anaerobic treatment, acid and alkali (E) were not added, but the hydrogen ion concentration inside the anaerobic treatment tank (3) was kept in the range of pH 7.0 to 8.0. The mass ratio (TOC / MLSS) between the amount of high TOC wastewater (AH) converted to TOC and the amount of activated sludge (B) converted to MLSS supplied to the anaerobic treatment tank (3 ) is 0.2 kg-TOC / (kg -MLSS · day). The anaerobic treated water (AH ′) and activated sludge ( B ′ ) extracted as a suspension (AH ′ + B ′ ) were directly refluxed to the aerobic treatment tank (2). A part of the suspension (AH ′ + B ′ ) extracted from the anaerobic treatment tank (3) was taken out, filtered through filter paper, and the amount of TOC was measured to be about 250 mg / L.

It is a figure which shows typically an example of the waste water treatment facility (1) for carrying out the waste water treatment of the high TOC waste water (AH) by the waste water treatment method of the present invention. It is a figure which shows typically another example of the waste water treatment facility (1) for carrying out the waste water treatment of the high TOC waste water (AH) by the waste water treatment method of the present invention. It is a figure which shows the conventional waste water treatment facility (1 ') typically.

Explanation of symbols

A: Wastewater A ': Treated water
AH: Wastewater containing high concentration organic matter [High TOC wastewater] AH ': Anaerobic treated water
AL: Wastewater containing low concentration organic matter [Low TOC wastewater] AL ': Aerobic treated water B, B': Activated sludge C: Nitrate nitrogen D: Air E: Hydrogen ion concentration regulator 1: Wastewater treatment equipment 1 ': Conventional wastewater treatment equipment 2: Aerobic treatment tank 21: Aerobic machine 22: Mixing tank 23: Sedimentation separation tank 3: Anaerobic treatment tank 31: Stirrer 32: Mixing tank 33: Sedimentation separation tank

Claims (2)

It is a method of biologically treating wastewater containing high concentration organic substances (AH) having a TOC of 20000 mg / L or more and 100000 mg / L or less with activated sludge,
As activated sludge, after TOC is aerobic treatment in the aerobic treatment tank 0.05 times or less of low density organic-containing wastewater (AL) of the high-concentration organic waste water containing 100 mg / L or more (AH) (2), good Using activated sludge (B) separated from aerobic treated water (AL ') after aerobic treatment ,
The high-concentration organic matter-containing waste water (AH) is continuously supplied to the anaerobic treatment tank (3) together with the activated sludge (B) and nitrate nitrogen (C), and the anaerobic treatment tank (3) While the activated sludge (B) continuously anaerobically treats the wastewater containing high concentration organic matter (AH) in the presence of the nitrate nitrogen (C),
Anaerobic treated water (AH ') and activated sludge (B') after anaerobic treatment are continuously extracted,
The extracted activated sludge (B ') is recirculated to the aerobic treatment tank (2) ,
An aerobic treated water (AL ') after separating the activated sludge (B) after the aerobic treatment is led out of the system . A wastewater treatment facility (1) for treating wastewater (AH) containing high-concentration organic matter by the wastewater treatment method according to claim 1,
An aerobic treatment tank (2) for aerobically treating the wastewater containing low-concentration organic matter (AL) in the presence of activated sludge (B);
Anaerobic treatment tank (3) for anaerobically treating the wastewater containing high concentration organic matter (AH) with activated sludge (B) in the presence of nitrate nitrogen (C),
After the aerobic treatment tank (2) aerobically treated the low-concentration organic substance-containing wastewater (AL), the activated sludge (B) separated from the aerobic treated water (AL ') after aerobic treatment , Supply continuously to the anaerobic treatment tank (3) together with wastewater containing high concentration organic matter (AH) and nitrate nitrogen (C),
From the anaerobic treatment tank (3), anaerobic treated water (AH ′) and activated sludge (B ′) after anaerobic treatment are continuously extracted,
Activated sludge (B ') extracted from the anaerobic treatment tank (3) is refluxed to the aerobic treatment tank (2) ,
A wastewater treatment facility (1) characterized in that aerobic treated water (AL ') after separating activated sludge (B) after aerobic treatment is led out of the system .

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