JPH1133586A - Treatment method for wastewater containing ethanolamine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating wastewater containing ethanolamine simply and efficiently. SOLUTION: A treatment method for wastewater containing ethanolamine comprises the first anaerobic decomposition process 1 in which wastewater containing ethanolamine is mixed with the treated water of the first aerobic decomposition process 2 to be subjected to the action of microorganisms under anaerobic conditions, the first aerobic decomposition process 2 in which the treated water of the first anaerobic decomposition process 1 is subjected to the action of microorganisms under aerobic conditions, the second anaerobic decomposition process 3 in which the treated water of the first aerobic decomposition process 2 is subjected to the action of microorganisms under anaerobic conditions, and the second aerobic decomposition process in which the treated water of the second anaerobic decomposition process is subjected to the action of microorganisms under aerobic conditions. Wastewater is treated by these processes in sequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating ethanolamine-containing wastewater discharged from a heat exchanger used in a nuclear power plant or a thermal power plant.

[0002]

2. Description of the Related Art Conventionally, hydrazine (N ₂ H) has been used as a rust preventive for a heat exchanger coolant used in a nuclear power plant or the like.
₄ ) and ammonium ion (NH ₄ ⁺ ) were added together. However, in recent years, ethanolamine has attracted attention as a substance having a greater rust preventive effect, and the use of ethanolamine instead of ammonium ions has been studied. Therefore, it is expected that hydrazine and ethanol will be used in combination in such applications in the future.

[0003] When a rust inhibitor containing ethanolamine is added to a coolant passing through a heat exchanger, blow water discharged from the heat exchanger constantly or unsteadily contains ethanolamine. It is. However, ethanolamine increases the concentration of COD (Chemical Oxygen Demand), an environmentally regulated substance, and must be treated in some way before emission. As a method for treating ethanolamine, a wet catalytic oxidation method, a submerged combustion method, and the like have already been proposed, but have not yet reached practical use at present. In addition, there has been no report on a treatment method using microorganisms without any success.

[0004] In order to overcome these unresolved problems, the present applicant (Mitsubishi Heavy Industries) has previously reported Pseudomonas sp. As a microorganism that decomposes ethanolamine in wastewater. Found that it has the ability, and it was found that Pseudomonas sp.
A method for treating wastewater that decomposes and removes ethanolamine by aerobically acting (Japanese Patent Application No. 8-108).
No. 214445). Furthermore, when hydrazine coexists in the ethanolamine-containing wastewater, hydrazine is a reducing agent, so that when its concentration is increased, the activity of microorganisms, especially aerobic microorganisms, is inhibited. Therefore, when treating wastewater with microorganisms, it is necessary to reduce the hydrazine concentration to a predetermined value or less before the step of decomposing ethanolamine by microorganisms. For these reasons, a method of treating wastewater in which hydrazine is decomposed and removed in advance by pretreatment has also been proposed (also described in Japanese Patent Application No. 8-214445).

Hereinafter, the processing method proposed by the present applicant will be described with reference to FIG. FIG. 3 schematically shows what is described in the specification of the application, and the reference numerals and names are not the same as those described therein. The ethanolamine-containing wastewater a in which hydrazine coexists is introduced into the neutralization tank 11, and a copper compound k, for example, copper sulfate is added so that the concentration becomes about 0.1 mg / L, and a neutralizing agent such as sodium hydroxide is added. pH 8 ~ depending on b
After the adjustment to 9, an oxidizing agent j such as hydrogen peroxide is further added.
By adding and reacting so that hydrogen peroxide / hydrazine (molar ratio) = 2.4, hydrazine in the waste water is decomposed into nitrogen gas (N ₂ ) and water (H ₂ O).

[0006] The treated water from which hydrazine has been decomposed and removed is led to the mixing tank 12, where the nutrient c, for example, phosphoric acid, is removed from the wastewater.
D: Phosphoric acid (weight ratio) = 100: 2, and the pH is adjusted to about 7 with a neutralizing agent b 'such as sodium hydroxide.
p. Is led to the aeration tank 13 where the inhabitants live. The neutralizing agent b ',
The nutrient c may be added to wastewater in a pipe on the way from the mixing tank 12 to the aeration tank 13.

The mixed solution 1 flowing into the aeration tank 13 is appropriately diluted with water and aerated with air f to convert ethanolamine in the mixed solution 1 into carbon dioxide (CO ₂ ), water (H
₂ O) and ammonia (NH ₃ ), which is finally decomposed by nitrifying bacteria into nitrate ions (NO
₃ ^-) and a. The biologically treated water that has undergone these decomposition treatments is sent to the sedimentation tank 14 where it is settled and separated, the separated treated water m is discharged, and a part of the generated sludge is returned sludge n ′.
To the aeration tank 13 and the remaining part is discharged out of the system as excess sludge n. Table 1 shows that Pseudomonas sp. Is the experimental result when ethanolamine was decomposed by using Experiment No. 1. Experiment No. 1 shows the case where hydrazine is present in the wastewater, and Experiment No. 2 shows the case where hydrazine is not present in the wastewater.

[0008] However, according to this treatment method, most of the hydrazine can be removed in the pretreatment step. Here, ethanolamine and a part of the hydrazine react under aerobic conditions, and biodegradation occurs. Can not do,
Biorefractory substances, including 1H-imidazole, piperazine, dimethylpiperazine, nitro-1H pyrazole and other unidentified substances, are by-produced, and all of these substances appear as COD. As a result, as shown in Table 1, although ethanolamine is almost decomposed in the subsequent biological treatment step, it remains as COD in the biologically treated water, so that it appears as if ethanolamine had not been treated. It was found that the quality of the treated water was good.

Further, it has been found that ammonium ions generated by the decomposition of ethanolamine become nitrate ions, but total nitrogen (TN) hardly decreases. Here, total nitrogen and ammonium nitrogen (NH ₄ -N), nitrite nitrogen (NO ₂ -N), nitrate nitrogen (NO ₃ -N)
Is the total amount of That is, ethanolamine in the wastewater is only decomposed into nitrate ions, but does not decrease as total nitrogen. If the concentration of ethanolamine in the wastewater becomes high, a large amount of this nitrate ion remains as total nitrogen, and it is difficult to conform to the value specified in the N (nitrogen) regulation of the discharge water. Removal of nitrogen is required.

[Table 1] (Note) ETA = ethanolamine COD _Mn : Indicates that potassium permanganate was used as an oxidizing agent used for COD measurement.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and has as its object to provide a simple and efficient wastewater treatment method.

[0011]

As described above, when a wastewater in which ethanolamine and hydrazine coexist is treated under aerobic conditions, a biodegradable substance serving as a COD source is generated. Chemicals (nitrite and / or nitrate, or returned nitrite and / or nitrate ions) without contact with a gas containing nitrogen, and biological difficulties before treating this mixture under aerobic conditions. When degradable substances are not yet generated and biodegradable, it is preferable to degrade ethanolamine in advance under microorganisms under anaerobic conditions and then to degrade hydrazine, thereby obtaining reliable processing performance. Was confirmed as a result of experiments by the present inventors.

[0012] In addition, as microorganisms used for nitrifying and denitrifying organic substances containing nitrogen, denitrifying bacteria (denitrifying bacteria) belonging to facultative anaerobic bacteria and nitrites belonging to aerobic bacteria are used. And nitric acid bacteria. These microorganisms tend to gain resistance and increase resistance levels to substances that inhibit their activity, generally by means of habituation. Among these microorganisms, aerobic microorganisms are considered to be less resistant than anaerobic microorganisms from the original habitat, even to hydrazine, which has the effect of depriving oxygen as a reducing agent.
As a result of the experiment, these aerobic microorganisms are acclimated similarly to the anaerobic microorganisms, or as the wastewater in which these hydrazines coexist is treated for a long time, the resistance gradually increases and the resistance concentration is increased, and ethanolamine becomes a practical problem. It turned out to be decomposed without.

Further, using these microorganisms, first, most of the ethanolamine is decomposed in the first-stage anaerobic treatment, and most of hydrazine is decomposed in the second-stage aerobic treatment. What is treated is CO in the treated water
It is most effective for reducing D, and in this case, nitrite ions and nitrate ions necessary for the first-stage anaerobic treatment can be supplied by returning the treatment liquid generated in the second-stage aerobic treatment. It was found that there was no need to add new chemicals, and as a result, the nitrogen load of the wastewater could be reduced.

The present invention has been made based on these findings.
That is, in order to achieve the above object, the invention according to claim 1 is a method of treating wastewater containing ethanolamine, wherein the wastewater is mixed with treated water of a first aerobic decomposition step described later. A first anaerobic decomposition step in which microorganisms act under anaerobic conditions; and a first anaerobic decomposition step in which the microorganisms act on the treated water in the first anaerobic decomposition step under aerobic conditions.
An aerobic decomposition step, a second anaerobic decomposition step in which microorganisms act on the treated water of the first aerobic decomposition step under anaerobic conditions, and an aerobic condition for the treated water of the second anaerobic decomposition step. And a second aerobic decomposition step in which microorganisms are actuated below, and the wastewater is sequentially treated according to these steps.

According to a second aspect of the present invention, in the method for treating wastewater according to the first aspect, the wastewater is supplied to the first anaerobic decomposition step without being brought into contact with a gas containing oxygen. It is characterized by the following. According to a third aspect of the present invention, in the method for treating wastewater according to the first or second aspect, the treatment liquid in the first aerobic decomposition step is returned to the first anaerobic decomposition step. Features. The invention described in claim 4 is the method for treating wastewater according to claim 1, 2, or 3, wherein the second anaerobic decomposition step comprises:
An organic compound that does not bind nitrogen is added. The invention described in claim 5 is the first invention.
In the method for treating wastewater according to any one of claims 4 to 4,
The wastewater is a wastewater containing hydrazine.

According to a sixth aspect of the present invention, in the method for treating wastewater according to the fifth aspect, the wastewater is subjected to a first anaerobic decomposition step, a first aerobic decomposition step, a second anaerobic decomposition step, It is characterized in that the method further comprises a step of removing hydrazine after sequentially treating through a second aerobic decomposition step. The invention described in claim 7 is used in the method for treating wastewater according to claim 5 or 6, when the wastewater is treated in a first anaerobic decomposition step and then in a first aerobic decomposition step. The microorganism is characterized by being acclimated in the presence of hydrazine and acquiring hydrazine resistance.
According to an eighth aspect of the present invention, in the wastewater treatment method according to any one of the fifth to seventh aspects, the step of removing the hydrazine includes a step of adding a copper compound and performing aeration treatment with a gas containing oxygen. It is characterized by being. Claim 9
In the method for treating wastewater according to any one of claims 5 to 8, the step of removing hydrazine comprises decomposing hydrazine by adding hydrogen peroxide or sodium hypochlorite. Characterized in that:

[0017]

Next, each step of the method for treating wastewater according to the present invention will be described in more detail in the order of steps. (1) First anaerobic decomposition step Ethanolamine-containing wastewater in which hydrazine coexists is added to a nutrient such as phosphoric acid for growing microorganisms under anaerobic conditions, and water is added in the presence of nitrite ions and nitrate ions. By adjusting the pH to 8.0 to 9.5 with a neutralizing agent such as sodium oxide, ethanolamine is consumed as an energy source by the action of denitrifying bacteria, and most of it is decomposed.
Nitrite and nitrate ions are reduced and decomposed to nitrogen gas. As the ethanol-degrading denitrifying bacterium, one that has acquired hydrazine resistance by previously acclimating to wastewater in which hydrazine coexists is used, and thereby it is possible to decompose organic substances such as ethanolamine without lowering the activity of microorganisms.

As the phosphoric acid source, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate,
Dipotassium hydrogen phosphate can be mentioned. As the neutralizing agent, sodium hydroxide, potassium hydroxide,
An alkaline agent such as calcium hydroxide can be used. However, considering the economic efficiency, the amount of generated sludge, etc., sodium hydroxide is most advantageous. The same applies to other neutralizing agents using sodium hydroxide described below. The nitrite ion and / or nitrate ion necessary for this step may be supplied by adding a chemical such as nitrite such as sodium nitrite and potassium nitrite and / or nitrate such as sodium nitrate and potassium nitrate. Although it is possible to use those contained in the circulating liquid returned from the first aerobic decomposition step described below, it is not necessary to add such a chemical again.

In addition, since ethanolamine is first decomposed under anaerobic conditions, a biodegradable substance such as that produced by the reaction under aerobic conditions is not produced. In this case, the load on the BOD oxidizing bacteria can be reduced. The reaction in this step is mainly as follows. NH ₂ CH ₂ CH ₂ OH + 2NO ₃ ⁻ → N ₂ + 2OH ⁻ + H ₂ O + 2CO ₂ + NH ₃ 3NH ₂ CH ₂ CH ₂ OH + 10NO ₂ ⁻ → 5N ₂ + 10OH ⁻ + H ₂ O + 6CO ₂ + 2NH ₃

(2) First Aerobic Decomposition Step The treatment liquid in the first anaerobic decomposition step is adjusted to pH 7.0 to 8.5 with a neutralizing agent such as sodium hydroxide and the like, and aerated by supplying air. Thus, as shown in the following equation, ethanolamine remaining in the liquid under aerobic conditions and most of the hydrazine contained in the wastewater are biochemically decomposed, and the produced ammonium ion is further decomposed. It is oxidized to nitrite or nitrate by the action of nitrite or nitrate that has acquired hydrazine resistance. As described above, by returning a part of the treatment liquid as the circulating liquid to the first anaerobic decomposition step, the nitrite ions and nitrate ions contained therein can be used in the anaerobic treatment. The reaction in this step is mainly as follows. NH ₂ CH ₂ CH ₂ OH + 5 / 2O ₂ → 2CO ₂ + 2H ₂ O + NH ₃ (NH ₃ + H ₂ O → NH ₄ ⁺ + OH ⁻ ) NH ₄ ⁺ + 3 / 2O ₂ → NO ₂ ⁻ + 2H ⁺ + H ₂ O NO _{2 ^{- + 1 / 2O 2 → NO}} 3 - N 2 H 4 + O 2 → N 2 + 2H 2 O in this case, only processes only ethanolamine remaining in undegraded, while reducing the load of the BOD-oxidizing bacteria Since the nitrification treatment is performed, the size of the apparatus and the like can be reduced.

(3) Second Anaerobic Decomposition Step To the treatment liquid of the first anaerobic decomposition step, an organic compound having no nitrogen bonded, such as methanol, is added as an energy source for metabolizing microorganisms. With neutralizing agent
By adjusting the pH to 8.0 to 9.5, an anaerobic reaction by denitrifying bacteria similar to that described in the first anaerobic decomposition step occurs under anaerobic conditions, and ethanolamine remaining in the liquid is decomposed. At the same time, nitrite ions and nitrate ions are reduced to nitrogen gas.

(4) Second Aerobic Decomposition Step The treatment liquid in the second anaerobic decomposition step is adjusted to pH 6.5 to 8.0 with a neutralizing agent such as sodium hydroxide and supplied with air to be aerated. As a result, the organic compound such as methanol added in the second anaerobic decomposition step, and hydrazine when a part thereof remains, are biologically oxidized by the action of BOD oxidizing bacteria and decomposed into carbon dioxide gas, nitrogen gas, and the like. The treated water from which the COD has been removed is settled and separated as necessary to remove solids, and then discharged or reused.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 of the present invention will be described below with reference to the drawings. Example 1 In a secondary system of a PWR plant, in order to prevent impurities from flowing into and accumulating in a heat exchanger and reduce heat exchange performance, a coolant is periodically purified by an ion exchange resin. Ethanolamine-containing wastewater coexisting with NaOH-based and HCl-based hydrazine is discharged as a regeneration waste liquid when regenerating the ion-exchange resin having deteriorated performance. FIG. 1 is a process chart showing an example of a treatment method in the first embodiment of the present invention for the secondary blow water of the PWR nuclear power plant. That is, the wastewater a is introduced into the first anaerobic decomposition tank 1 where the facultative anaerobic microorganisms inhabit as the dominant species so as not to come into contact with the air as much as possible. Here, the nutrient c such as phosphoric acid or phosphate is added and mixed, and the pH is adjusted to 8.0 with a neutralizing agent b such as sodium hydroxide in the presence of nitrite ions and nitrate ions. It is adjusted to 9.5, preferably 8.5 to 9.0, and held. Nutrient c is added as BOD in wastewater as phosphorus
About 2 parts by weight is appropriate for 100 parts by weight.

As the nitrite ion and nitrate ion required for this step, those contained in the circulating liquid d returned from the first aerobic decomposition step 2 described later can be used. In this case, the chemical is added again. It is not necessary and is very economical. The circulating liquid d is a part of the processing liquid in the first aerobic decomposition tank 2 and also includes some undecomposed organic substances such as ethanolamine. Thus, the first anaerobic decomposition tank 1
In anaerobic conditions, most organic substances such as ethanolamine contained in wastewater a are biochemically decomposed by the action of denitrifying bacteria, which are facultatively anaerobic microorganisms, while nitrite ions and nitrate ions are biochemically decomposed. It is decomposed into nitrogen gas, carbon dioxide gas, etc., and released as a decomposition gas g. In this reaction, hydrazine was initially 80 mg / L.
Although the activity of the microorganism was inhibited by the presence of the microorganism to a certain extent, the decomposition of ethanolamine was not sufficient. However, as a result of acclimation of the microorganism for about one month, hydrazine resistance was obtained and even when hydrazine was present at about 200 mg / L, ethanol was removed. It was confirmed that the decomposition of the amine was promoted.

Next, the treated water from the first anaerobic decomposition tank 1 is led to the first aerobic decomposition tank 2 in which aerobic microorganisms such as nitrites, nitrates and BOD oxidizing bacteria inhabit as dominant species. PH with a neutralizing agent b 'such as sodium hydroxide
By aerating with air f while adjusting and maintaining the pH at 8.5, preferably 7.5 to 8.0, a part of the liquid remains in the liquid by the action of nitrite and nitrate under aerobic conditions. Ammonium ions generated by decomposing organic substances such as ethanolamine are partially assimilated and mostly oxidized to nitrite ions and nitrate ions. A part of the processing liquid in the first aerobic decomposition tank 2 is returned to the first anaerobic decomposition tank 1 described above. Most of the hydrazine contained in the solution is biodegraded by microorganisms to form ammonium ions. In this reaction, an aerobic microorganism consisting of nitrite and nitrate was acclimated for about one month. As a result, it was confirmed that these microorganisms were treated without any problem without being inhibited by hydrazine, and that they had acquired hydrazine resistance.

The remainder of the processing liquid in the first aerobic decomposition tank 2 is led to the second anaerobic decomposition tank 3 and the pH is adjusted to 8.0 to 9.5, preferably to 8.0 with a neutralizing agent b such as sodium hydroxide. By adding and mixing an organic substance such as methanol e as an energy source for microbial metabolism while maintaining the pH adjusted to 5 to 9.0, similar to the case of the first anaerobic decomposition tank 1, the anaerobic condition is maintained. As a result, organic substances such as ethanolamine remaining in a part of the liquid are decomposed by the action of denitrifying bacteria, and nitrite ions and nitrate ions are converted into nitrogen gas. Second anaerobic decomposition tank 3
Is introduced into the second aerobic decomposition tank 4, and the pH is adjusted to 6.5 to 8.0, preferably 7.0 to 7.5, and maintained with a neutralizing agent b 'such as sodium hydroxide. While aerating with air f, the methanol added in the second anaerobic decomposition tank 3 contained in the liquid by the action of the BOD oxidizing bacteria under aerobic conditions, and ethanolamine that only partially remains in the liquid, etc. Organic matter and hydrazine are decomposed.

The biologically treated water discharged from the second aerobic decomposition tank 4 is settled in a sedimentation tank 5 if necessary to separate sludge, and a part of the separated sludge is returned to the first anaerobic decomposition i 'as sludge. It is returned to the tank 1 so that the concentration of microorganisms in the tank is kept almost constant, and the remainder is discharged out of the system as excess sludge i. The supernatant water is discharged or reused as treated water h. Through the above steps, almost all of the ethanolamine and hydrazine in the waste water are decomposed and removed as shown in the experimental results described below, and COD and total nitrogen (T-
N) is equal to or less than the discharge reference value.

However, when the growth conditions of the microorganism are not sufficiently adjusted, hydrazine sometimes rarely remains in the treated water. Normally, a treatment for this is not necessary, but in order to ensure completeness, a copper compound k, for example, copper sulfate is added to the treated water h so that its concentration becomes about 0.1 mg / L, and sodium hydroxide or the like is added. After adjusting the pH to 8 to 9 with a neutralizing agent, an oxidizing agent, for example, hydrogen peroxide is added and reacted so that hydrogen peroxide / hydrazine (molar ratio) = 2.4, and hydrazine in the waste water is removed. It may be decomposed into nitrogen gas water.

Embodiment 2 FIG. 2 is a process diagram showing a treatment method according to a second embodiment of the present invention, which is directed to secondary blow water of a PWR nuclear power plant, as described in the first embodiment. In the figure, the first anaerobic decomposition tank 1 ', the first aerobic decomposition tank 2', the second anaerobic decomposition tank 3 ', and the second aerobic decomposition tank 4' each employ a submerged filter system. Is different from the first embodiment. The submerged filter tower is filled with a plastic filter medium, and anaerobic microorganisms such as denitrifying bacteria, or aerobic microorganisms such as BOD oxidizing bacteria, nitrites, and nitrates are attached and inhabited therein. Organic substances and nitrogen compounds are decomposed, and their functions and reaction conditions are almost the same as those in the first embodiment. When these biodegradation tanks are of the submerged filter type, the settling tank 5 at the final stage becomes unnecessary.

That is, as in the case of the first embodiment, the waste water a containing ethanolamine and hydrazine is supplied to the first anaerobic decomposition tank 1 ', the second aerobic decomposition tank 2' and the second anaerobic decomposition tank 3 '. It is sequentially treated to decompose most of ethanolamine and hydrazine, and to decompose and remove nitrite ions and nitrate ions, which are decomposition products thereof, and then introduce them into the second aerobic decomposition 4 '. Here, pH 6.0 to 9.2, preferably 6.8, with a neutralizing agent b such as sodium hydroxide.
By adjusting to に 8.0, the excess methanol that is added in the second anaerobic decomposition tank 3 is decomposed and removed. Sludge separated from the filter medium generated by this treatment is discharged out of the system, and the treated water h is discharged or reused.

Through the above steps, almost all of the ethanolamine and hydrazine in the waste water are decomposed and removed, as shown in the experimental results described below, and the COD and total nitrogen in the treated water become equal to or lower than the discharge standard value. As described in the first embodiment, if hydrazine remains in the treated water, the treatment for this is not usually required, but the treated water h may be continuously oxidized if desired. .

Experimental Results The wastewater containing ethanolamine and hydrazine was subjected to
Table 2 summarizes the experimental results when treated by the methods of Examples 1 and 2. As a result, in any of the treatment methods, ethanolamine is completely biochemically decomposed without being affected by hydrazine, and C is contained in the treated water in the final stage.
It was found that no OD component remained.

[Table 2] (Note) 1. ETA = ethanolamine

[0033]

As is apparent from the above description, according to the present invention, a method for simply and efficiently treating wastewater containing ethanolamine is provided, and the following effects are expected by the above-described structure. be able to. (1) Ethanolamine contained in wastewater can be largely decomposed by denitrifying bacteria under anaerobic conditions, and the treatment efficiency is extremely high as compared with the conventional method in which only treatment under aerobic conditions is performed. . (2) In addition, ammonium ions generated by the decomposition of ethanolamine in wastewater are converted into nitrate ions by the action of nitrite or nitrate under aerobic conditions, and the treated solution containing these ions is converted under anaerobic conditions. By treating with denitrifying bacteria, almost all of nitrite and nitrate ions can be decomposed into nitrogen gas. Therefore, even when ethanolamine is contained in the wastewater at a high concentration, the value specified in the N (nitrogen) regulation of the discharge water can be satisfied without remaining as total nitrogen in the treated water. No equipment is required. (3) Ethanolamine and hydrazine are used in order to decompose most of the ethanolamine under anaerobic conditions without intervening oxygen-containing liquid such as air in the wastewater before the wastewater treatment. It is extremely effective in reducing COD in treated water without producing biodegradable substances despite coexistence.

(4) By treating with a microorganism having a hydrazine-resistant ethanolamine-decomposing function,
Ethanolamine remaining in the solution without being inhibited by hydrazine can be efficiently decomposed and removed. In particular, in the first anaerobic decomposition treatment, the presence of hydrazine acting as a reducing agent in the wastewater results in the deprivation of oxygen dissolved in the liquid to enhance anaerobic conditions, and rather activates anaerobic microorganisms. There is a preferred advantage of improving the processing efficiency. (5) Following the first anaerobic treatment, the remaining aerobic treatment decomposes only the remaining ethanolamine,
The load on the BOD oxidizing bacteria can be greatly reduced, and the nitrification reaction proceeds much more easily than when the treatment is performed only under aerobic conditions, thereby reducing the size of peripheral devices such as a blower. Therefore, the power cost for the operation is small and the cost is very high. (6) Part of the processing liquid generated in the aerobic processing is returned to the above-described anaerobic processing step, and the nitrite ions and nitrate ions contained in the processing liquid are used for the anaerobic decomposition processing of ethanolamine. Therefore, the cost of chemicals can be reduced without the necessity of adding a new nitrogen compound from the outside, and the nitrogen load in the wastewater treatment is reduced, so that it is possible to comply with the nitrogen regulation of the wastewater. be able to. (7) By performing such multi-stage treatment combining anaerobic treatment and aerobic treatment, the habitat environment of microorganisms is optimally maintained and activated, and a reliable and economical treatment corresponding to the contained components such as ethanolamine and hydrazine is performed. A processing process may be established.

[Brief description of the drawings]

FIG. 1 is a process explanatory view according to a first embodiment of the present invention.

FIG. 2 is a process explanatory diagram according to a second embodiment of the present invention.

FIG. 3 is a process explanatory view according to a conventional processing method.

[Explanation of symbols]

 1,1 'first anaerobic decomposition tank 2,2' first aerobic decomposition tank 3,3 'second anaerobic decomposition tank 4,4' second aerobic decomposition tank 5 sedimentation tank 11 neutralization tank 12 mixing tank 13 Aeration tank 14 Sedimentation tank a Ethanolamine-containing wastewater b, b 'Neutralizer c Nutrient d Circulating fluid e Methanol f Air g, g' Decomposed gas h Treated water i Excess sludge i 'Returned sludge j Oxidizer k Copper compound l Mixed liquid m Treated water n Surplus sludge n 'Return sludge

Continued on the front page. (72) Inventor Hideki Kamiyoshi 5-1-1-16 Komatsu-dori, Hyogo-ku, Kobe-shi, Hyogo Prefecture Inside Shinryo High-Tech Co., Ltd. (72) Kazuo Fukunaga 5-1-1 Komatsu-dori, Hyogo-ku, Kobe-shi, Hyogo No. 16 Inside Shinryo High-Tech Co., Ltd.

Claims (9)

[Claims] 1. A method for treating a wastewater containing ethanolamine, wherein the wastewater is mixed with treated water in a first aerobic decomposition step described below, and a first anaerobic decomposition in which microorganisms act under anaerobic conditions. A first aerobic decomposition step in which microorganisms act on the treated water of the first anaerobic decomposition step under aerobic conditions; and a microorganism under anaerobic conditions in the treated water of the first aerobic decomposition step. A second anaerobic decomposition step in which the microorganisms act on the treated water in the second anaerobic decomposition step under aerobic conditions, and the wastewater is sequentially treated according to these steps. A method for treating wastewater containing ethanolamine, comprising: 2. The method for treating wastewater according to claim 1, wherein the wastewater is supplied to a first anaerobic decomposition step without being brought into contact with a gas containing oxygen. 3. The method for treating wastewater according to claim 1, wherein the treatment liquid in the first aerobic decomposition step is returned to the first anaerobic decomposition step. 4. The method according to claim 1, wherein an organic compound that does not bind nitrogen is added in the second anaerobic decomposition step. 5. The method for treating wastewater according to claim 1, wherein said wastewater is wastewater containing hydrazine. 6. The wastewater is subjected to a first anaerobic decomposition step,
The method for treating wastewater according to claim 5, further comprising a step of sequentially removing the hydrazine after sequentially performing the aerobic decomposition step, the second anaerobic decomposition step, and the second aerobic decomposition step. 7. The method according to claim 1, wherein the wastewater is treated in the first anaerobic decomposition step, and then the microorganism used in the treatment in the first aerobic decomposition step is one that has acclimated in the presence of hydrazine and has acquired hydrazine resistance. The method for treating wastewater according to claim 5 or 6, wherein: 8. The method for treating wastewater according to claim 5, wherein the step of removing hydrazine is a step of adding a copper compound and performing aeration treatment with a gas containing oxygen. . 9. The method according to claim 5, wherein the step of removing hydrazine comprises decomposing hydrazine by adding hydrogen peroxide or sodium hypochlorite. Wastewater treatment method.