JPS59162997A - Organic filthy water disposal - Google Patents

Abstract

PURPOSE:To perform efficient anaerobic treatment, in the anaerobic treatment of organic filthy water, by adjusting a pH to a specified value to inhibit the formation of hydrogen sulfide gas. CONSTITUTION:Organic filthy water is supplied through an inflow pipe 3 to an acid-forming reaction tank 2. A bed 4 packed with a granular body prepd. by conditioning limestone into a granular state having a diameter of about 2-50mm. is laminated on a supporting floor 4' in the acid-forming reaction tank 2, and a pipe 5 for withdrawing an acid-forming liquid is provided at the upper part of said tank. The filthy water flows upwards through the packed bed 4. During said circulation, organic substance in the filthy water is efficiently converted into an organic acid such as acetic acid by acid-forming bacteria adherently grown up on the surfaces of the filler particles. At the same time, a calcium part is exuded from the filler, and the reaction is continued at a pH of 7.5-9.0 without the formation of hydrogen sulfide gas. Hereon, the pH adjustment is performed in a circulation line 5' in which a circulator pump P is incorporated. The reaction liquid from the acid-forming reaction tank 2 is sent to a methane-forming reaction tank 6 to perform methane-forming reaction therein and then sent to a nitrogen removing part 1' to perform denitrification.

Description

[Detailed Description of the Invention] This invention deals with organic sewage, such as human waste, sewage, other industrial wastewater, or sludge and other organic waste generated from human waste treatment plants (hereinafter simply referred to as "sewage"). It relates to a biological treatment method, particularly an anaerobic treatment method.

The present applicants previously conducted anaerobic treatment of wastewater, a.

:-Desulfovibrio
), we proposed an effective anaerobic treatment method by efficiently converting propionic acid and butyric acid to acetic acid using bacteria. Hydrogen sulfide generated by anaerobic treatment of wastewater when containing
We also proposed a denitrification treatment method that uses hydrogen as a hydrogen donor for autotrophic denitrifying bacteria such as s dent trif jeans. The method for utilizing hydrogen sulfide here is to install equipment to collect hydrogen sulfide gas from the anaerobic tank and guide it back to the anaerobic tank or to the denitrification tank, but hydrogen sulfide has a bad odor and is a toxic substance. Therefore, there was an operational inconvenience in that dangerous substances had to be handled.

The present invention is intended to eliminate such drawbacks, and when treating organic wastewater anaerobically, the pH is adjusted to 7.5 to 9.0 to prevent the generation of hydrogen sulfide gas due to the anaerobic treatment. It is characterized by performing anaerobic treatment.

The sulfate-reducing bacteria described above are obligate anaerobic bacteria and oxidize and decompose organic matter using the bound oxygen of sulfate as a hydrogen acceptor. However, this reaction is generally incomplete and tends to accumulate in the form of acetic acid. Therefore, propionic acid and the like, which are rate-limiting for the reaction of anaerobic treatment, are decomposed into acetic acid, so the methane production reaction proceeds quickly and anaerobic treatment can be carried out efficiently.

Furthermore, denitrification treatment using autotrophic bacteria uses (j) sulfur compounds such as hydrogen sulfide (H2S), sodium sulfide (NazS), and sulfur (So) as hydrogen donors, Denitrification is performed by reducing nitrogen to nitrogen gas.

Now, the anaerobic treatment in the present invention is carried out by adjusting the pH to 7.5 to 9.0, preferably around 8.5, so that what was conventionally generated as hydrogen sulfide gas is converted into soluble hydrogen sulfide and sulfur such as calcium sulfide. Form a compound and keep it in the liquid. When the pH is less than 7.0, hydrogen sulfide is not fixed in the liquid, but the activity of acid-producing bacteria or methanogens is inhibited, so the pH range mentioned above is appropriate.

A neutralizing agent such as caustic soda or quicklime can be used for this pH adjustment. When using such a neutralizing agent, equipment such as a chemical dosing device is required, but as described later, when using a packed bed consisting of calcium-containing granules, the pH
Particularly preferred (4) is because it has the role of regulation and the role of immobilizing microorganisms. For anaerobic treatment, either a two-phase system consisting of an acid-generating phase and a methane-generating phase, or a mixed-phase system can be adopted. As one method for adjusting the pH of this anaerobic treatment of the present invention, calcium-containing granules, such as limestone (stone),
This can be carried out by filling a column with rocks containing CaCO3 as a main component, such as marble and coral, adjusted to a particle size of about 5 to 50 grains, and allowing the wastewater to pass through the column. In addition,
The granules are not limited to natural ones, but may be the same as artificially manufactured calcium carbonate to the above particle size.A support bed of gravel and gravel is formed in the column, and a layer of the above granules is placed on top of this. It can be easily made by laminating layers.

The direction of water flow may be either downward flow or upward flow, but it should be possible to perform backwashing when clogging occurs. In addition, the amount of granules packed is determined by the pH of the anaerobically treated water being 7.5 to 9.0.
1 It is determined from the contact time of waste water and particulate matter so that it is preferably around 8.5.

Therefore, the filling height is determined by determining the column diameter and water flow linear velocity. Of course, the column diameter etc. may be determined after first determining the packing height.

Note that the contact time between wastewater and particulate matter is largely influenced by the diameter of the particulate matter. That is, the smaller the particle size is, the larger the contact area becomes, and the predetermined pH is reached in a shorter time. However, if the particle size is too small, water head loss due to clogging will occur quickly and backwashing must be performed frequently, so the particle size is about 2 to 50 - which makes backwashing easy and prevents clogging from occurring. is good.

Note that the waste water may be circulated through the packed bed until a predetermined pH is reached or a predetermined contact time is obtained. In this case, continuous treatment can be made possible by supplying raw water into the circulation path and extracting a portion of the water from the circulation path as treated water.

As described above, since the anaerobic treatment in the present invention is carried out while passing through an immersed bed consisting of a packed bed of calcium-containing granules, a biofilm layer is generated on the surface of the granules, and the anaerobic treatment is more effective at retaining microorganisms than in the sludge blanket format. Since the amount can be maintained high, processing efficiency is excellent. Then, organic acids such as acetic acid produced by anaerobic treatment of organic matter dissolve calcium salts. In other words, calcium hydroxide eluted from the granules progresses neutralization and brings the wastewater to a predetermined pH level.
It can be raised up to H. If the pH is maintained around 8.5 and anaerobic treatment is performed, the acid production reaction will not be maintained well, and the sulfur component will not be generated as hydrogen sulfide gas, but soluble hydrogen sulfide ions (H2N or calcium sulfide (Ca)
S) can be retained in wastewater in the form of sulfur compounds. Furthermore, since methanogens can be active in the vicinity of p, F (8,5), the methane production reaction can be carried out efficiently.In addition, the sulfur compounds in the liquid are 200mg/
It has been confirmed that if it is less than #, there is no practical problem, and in particular, if it is 1004α, it will not have an adverse effect on the methane production reaction. Therefore, sewage with a concentration within this range (7) can be said to be suitable raw water for the present invention.

Note that in the anaerobic treatment process, hydrogen sulfide is generated during the reaction up to the production of organic acid, so if the anaerobic treatment process is a two-phase system, it is only necessary to adjust the pH of the acid generation phase.

Therefore, only the silicic acid production phase is required, which is treated using the above-mentioned packed bed, and a known reaction tank such as a sludge blanket type or a fluidized bed type can be used for the next methane generation phase.

When performing this anaerobic treatment using sulfate-reducing bacteria, it is performed by adding an ionic compound, but the sulfur compound to be added can be sulfate obtained by oxidizing Has generated during anaerobic treatment. . In other words, since hydrogen sulfide is present in the gas generated by anaerobic treatment, it is possible to obtain cisulfuric acid by oxidizing the generated gas, such as ozone catalytic combustion or biological sulfur oxidation method, and use it. can.

When wastewater, especially sewage or industrial wastewater, contains nitrogen components, the treatment cannot be considered complete unless these substances are also removed (8). Therefore, in order to anaerobically treat these wastewaters, it is necessary to further denitrify the anaerobically treated water. For example, there is a method in which wastewater is first treated in an anaerobic denitrification tank, then sequentially passed through an aerobic nitrification tank, and a considerable amount of the nitrified liquid from the nitrification tank is circulated to the denitrification tank.

In the case of this nitrification and denitrification method, the anaerobic treatment in the first stage is performed at a pH of 7.
5 to 9.0, sulfur compounds are present in the treated water, that is, in the raw water for denitrification. The denitrification reaction is effectively promoted by nitrifying bacteria.

In addition, since BOD components are present in anaerobically treated water, Pseudomonas denitrificans (Pseudomonas denitrificans) is grown using this as a hydrogen donor.
The denitrification reaction by heterotrophic denitrifying bacteria such as ns) is also promoted, and the denitrification process is carried out satisfactorily.

In this denitrification reaction, since the pH of the raw water is high, the pH is maintained near neutral where denitrifying bacteria are likely to be active, so that the denitrification reaction can proceed favorably.

A suitable treatment flow for carrying out the present invention in the case of wastewater containing nitrogen components is illustrated below.

In this processing flow, 1 is an anaerobic treatment section, and 1' is a nitrogen removal section. First, wastewater is introduced into the lower part of the acid production reaction tank 2 of the anaerobic treatment section 1 via the wastewater inlet pipe 3. In the acid production reaction tank 2, a packed bed 4 of granular material prepared by adjusting limestone into particles with a diameter of about 2 to 50 m+ is stacked on a support bed 4', and an acid production liquid extraction pipe 5 is provided at the top of the tank. There is. Therefore, the wastewater flows upward through the packed bed 4, and during this time, organic substances in the wastewater are efficiently exchanged into organic acids such as acetic acid.

At the same time, the calcium content is eluted from the packed material, and the above-mentioned reaction proceeds at around p) (8.0 to 8.5.
H adjustment is performed by the filling height and the circulation amount, which will be described later.

A circulation path 5' with a circulation pump P interposed therebetween is provided from the pipe 5 to the sewage inlet pipe 3 in order to adjust the effective contact time for carrying out a certain acid production reaction.

Since the packed bed becomes clogged after long-term use, a backwash cleaning operation is performed in the same way as the backwash cleaning of a filtration device used for the purpose of removing ordinary SS. Piping equipment, etc. are omitted.

The reaction liquid from the acid production reaction tank 2 is sent through a pipe 5 to a methane production reaction tank 6 of either a sludge blanket type or a sessile organism type. In the methane production reaction tank 6, the raw water received has a pH of around 8.0 to 8.5, so the methane production reaction proceeds efficiently. In addition, sulfur compounds are present in the raw water of 2 because the hydrogen sulfide produced in step 2 does not become a gas in the acid production reaction. However, this is 2 if the S concentration is 1.
If it is less than 00 m976, it will not affect the methane production reaction.

Note that the methane generation reaction tank 6 is provided with a methane gas collection mechanism and equipment for energy recovery is omitted from the illustration.

Next, the anaerobic treatment liquid from the anaerobic treatment section 1 is transferred to the nitrogen removal section 1.
’. That is, the anaerobic treatment liquid is first introduced into the de-Is via the pipe 7. Nitrification liquid from a nitrification tank 10 (described later) is sent to the denitrogen tank via v13, and sludge returned from the settling tank 12 is sent to the tank via pipe 14. The denitrification tank is stirred by an anaerobic mixing and stirring means (not shown). Therefore, denitrification tank 8
In this case, anaerobic treated water containing sulfur compounds and BOD components is mixed with nitrate or nitrite nitrogen, and the denitrification reaction is promoted by autotrophic denitrifying bacteria and oligotrophic denitrifying bacteria. . Note that this reaction occurs because the anaerobic treated water, which is the raw water, is maintained at a high pH, so the pH is low enough for denitrifying bacteria to become active.
The denitrified water from the denitrification tank 8 is received through the pipe 9 into the nitrification tank 10, where the nitrogen components are oxidized to nitric acid or nitrite nitrogen by air aeration means (not shown). Ru.

Most of the nitrification liquid from the nitrification tank 10 is transferred to the pipe 1 as described above.
3, it is returned and circulated to the denitrification tank 8, and the remainder is sent to the precipitation tank 12 via the pipe 11 (12), where it is subjected to solid-liquid separation treatment. The supernatant water of the settling tank 12 is drained from the pipe 15 as treated water. On the other hand, a portion of the solid content is returned to decrystallization as return sludge through the pipe 14 as described above.

In the above-described flow, the methane generation tank 6 may be omitted. Further, the denitrification tank 8 and the nitrification tank 10 can be formed using a rotating disk method or a fluidized bed method, which is used as a fixed biological type treatment. When this fluidized bed type is used, there is an advantage that the settling tank 12 can be omitted.

Example 1 Glucose was added to synthetic wastewater containing 200119713.
Nitrogen to organic carbon (TOC) in wastewater
01-) to about 1.5 tymg)/13 (TOC vs. t
5O4-) and treated with a two-phase anaerobic treatment.

First, sewage is mixed with limestone particles (3 to 5 mm in diameter).
00III+ columns are stacked to a height of 2000 m to form a packed bed to form an acid generation tank (effective volume 11.8 [)]. The generation process was performed. At this time, the temperature of the acid-generated treated water is room temperature (18-20C) and pH is about 8.
It remained constant at 5. Next, the acid production treated water was put into a sludge blanket type methane production tank (effective volume 75β), and a methane production reaction was carried out at room temperature with a residence time of 1 hour.

In the above treatment, no hydrogen sulfide gas was observed to be generated from the acid generation tank.

Example 2 Among the conditions of Example 1, the acid generation tank was a sludge blanket type tank (effective volume 15B), and 0.1N1 of N
The treatment was carried out under the same conditions as in Example 1, except that an OH solution was added as a neutralizing agent to adjust the pH to about 8.5 and the residence time was 15 minutes.

In the above treatment, no hydrogen sulfide gas was observed to be generated from the acid generation tank.

Comparative Example In Example 2, when a neutralizing agent was added to adjust the pH to 7.0, a hydrogen sulfide odor was observed from the acid generation tank.

(15) Although no hydrogen sulfide gas was generated from the acid generation tank, the anaerobic treatment time (total residence time of two phases) required to obtain approximately 1 mole of methane gas generation per mole of glucose. Approximately 10 times more was required than at pH 8.5. This indicates that the activities of acid-producing bacteria and methanogenic bacteria were inhibited at this pH.

Example 3 Sewage (BOD 120m9/p) total nitrogen CT as wastewater
-N) 32189/13) was processed according to the illustrated flow.

In the acid production reaction tank 2, coal stone particles (particle size approximately 5 + m) are stacked in a column with a diameter of 11001I1 to a height of 2000 m + a to form a packed bed, and the sewage is poured into the LV2? n/h
This is the effluent from the acid production reaction tank at this time, which was passed through in an upward flow. The pH of the acid production reaction solution was constant at about 8.5. Note that the temperature inside the acid production reaction tank was 18C. At this time, the generation of hydrogen sulfide gas from the acid production reaction tank is stopped, and the liquid from the acid production reaction tank is charged into the methane production reaction tank 6 (effective (16) volume 50K), and the residence time is 0. The methane production reaction was carried out for 3 days. The pH of the anaerobically treated liquid, which was the effluent from this methane production reaction tank, was about 8.7.

Returned liquid from the nitrification tank and 0.3 times the amount of returned sludge from the settling tank were introduced into the denitrification tank 8 and mixed and stirred anaerobically with respect to the above anaerobically treated liquid l.

The residence time in this denitrification tank is 3 hours, and the pH is approximately 7.
,2.

The mixed liquid from the denitrification tank was aerobically treated in the next nitrification tank 10 to a nitrification rate of 97 cm, and as described above, a portion was discharged into the denitrification tank and the remainder was discharged through the sedimentation tank 12.

The quality of the treated water at this time was BOD 12/8 and T-N 5 da/.

As described above, according to the present invention, high-quality treated water can be obtained without generating hydrogen sulfide gas during anaerobic treatment and without requiring addition of methanol or the like during denitrification treatment.

[Brief explanation of the drawing]

The drawing shows a process flow suitable for carrying out the present invention, in which 1 is an anaerobic treatment section, 2 is an acid production reaction tank, 6 is a methane production reaction tank, 8 is a denitrification tank, 10 is a nitrification tank and 12
indicates a precipitated layer. Patent applicant Mibe Matsui Kurita Industries Co., Ltd.

Claims (1)

[Claims] 1) When organic wastewater is treated anaerobically, the pH is adjusted to 7.5.
2) A method for treating organic sewage characterized by adjusting the pH to 9.0 and performing anaerobic treatment while preventing the generation of hydrogen sulfide gas. 3) The method for treating organic sewage according to claim 1, which is carried out by passing organic sewage through the process. 3) The second claim, wherein the calcium-containing granules are limestone particles. 4) The method for treating organic wastewater according to any one of claims 1 to 3, wherein the anaerobic treatment is carried out by adding sulfate. Treatment method 5) The method for treating organic wastewater according to claim 4, wherein the sulfate is obtained by oxidizing H2S generated by anaerobic treatment. 6) Organic wastewater contains nitrogen components, and when performing nitrogen removal treatment on the wastewater following anaerobic treatment, the anaerobic treatment is adjusted to pH 7.5 to 9.0 to prevent the generation of hydrogen sulfide gas. 7) A method for treating organic wastewater, characterized in that the nitrogen removal treatment is carried out while preventing the nitrogen from being removed, and the nitrogen removal treatment is performed using autotrophic denitrifying bacteria that utilizes sulfur compounds generated from anaerobic treatment. 7) pH adjustment 8) A method for treating organic sewage according to claim 6, which is carried out by passing the organic sewage through a packed bed consisting of calcium-containing granules. 8) The calcium-containing granules are limestone particles. 9) A method for treating organic wastewater as claimed in a patent, characterized in that the nitrogen removal treatment consists of two treatment steps: nitrification and denitrification.