JP2003080289A - Treating method for ammonia solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ammonia solution treating method adopting an activated sludge process which makes a high-load treatment possible, facilitates an operation management, maintenance and inspection of an activated sludge facility and uses high-concentration oxygen-containing gas. SOLUTION: The method of introducing the ammonia solution 10 generated from a coke furnace into an aerator 1 and subjecting the ammonia solution to an activated sludge treatment, comprises steps of extracting a portion of the activated sludge in the aerator 1, injecting the high-concentration oxygen- containing gas 11 therein to form the enriched oxygen activated sludge, then jetting and circulating the activated sludge in the aerator 1, measuring the concentration of dissolved oxygen in the vessel, regulating the concentration of the dissolved oxygen so as to attain a prescribed value, expelling the carbon dioxide formed by decomposition of the organic matter contained in the ammonia solution by diffusion of air or nitrogen and performing the activated sludge treatment at a prescribed pH.

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 low water, and in particular, injecting a high-concentration oxygen-containing gas into an aeration tank,
The present invention relates to a method for efficiently treating ammonium hydroxide by adjusting the dissolved oxygen concentration within an appropriate range.

[0002]

2. Description of the Related Art Anhydrous water generated in a coke oven for carbonization of coal contains harmful substances such as phenol, ammonia compounds, cyan compounds, and sulfides, and is usually distilled to remove ammonia. It is processed by the activated sludge method.

[0006] However, in the conventional treatment of activated carbon by the activated sludge method, due to the characteristics of biological treatment, fluctuations in the amount of inflow of activated water, components to be treated, such as chemical oxygen demand (CO).
There is a problem that it is difficult to control the dissolved oxygen concentration in the aeration tank due to fluctuations in D) and the like, mixing of hardly decomposable substances, etc., and stable treatment cannot be continued. For example, when air is excessively aerated in order to follow changes in COD, ammonia in the water to be treated is nitrified to produce nitric acid, which causes a problem that the activity of the thiocyan-degrading bacteria is inhibited.
On the other hand, as a wastewater treatment method using activated sludge capable of handling high-load treatment, for example, an oxygen activated sludge method using pure oxygen instead of air is known.

FIG. 5 is an explanatory view of a conventional apparatus adopting an oxygen activated sludge method using pure oxygen as an oxygen source. In FIG. 5, this apparatus comprises an aeration tank 31 having a closed structure, a plurality of aeration zones 33 partitioned by partition walls 32 in the aeration tank 31, and a surface aerator 34 provided in each aeration zone 33. An oxygen supply device 35 for supplying oxygen to the upper space of the aeration tank 31 and an exhaust gas line 36 for discharging exhaust gas are mainly included. 37 and 3
Reference numerals 8 are a pressure gauge and an oximeter, which are provided in the upper space of the aeration tank 31, respectively.

The water to be treated 39 introduced into the aeration tank 31 is
In the first aeration zone 33, the surface is agitated by the surface aerator 34, comes into contact with oxygen introduced from the oxygen supply device 35 by the surface aeration method, and a part of the pollutants in the waste water is treated by the activated sludge. The water 39 to be treated, which has been partially treated with pollutants, overflows the partition wall 32 and sequentially flows into the adjacent aeration zone 33, and after the pollutants have been similarly treated, it is treated water 40 from the aeration tank 31. leak.

However, the above conventional technique has the following problems. That is, since the closed / multi-stage aeration tank is adopted, the device is complicated, the equipment cost is increased, and the operation management and maintenance / inspection are difficult. Also,
Since it is a closed type aeration tank, there is a problem that carbon dioxide gas generated by the decomposition of organic substances stays in the upper space and the partial pressure increases, resulting in a decrease in the pH of the activated sludge. Further, since the surface aeration method using pure oxygen is adopted, there is a risk that when hydrocarbons are mixed in the water to be treated, it reacts with oxygen as a combustion supporting agent and explodes. In addition,
Such a pure oxygen activated sludge method has been conventionally used for various reasons.
It was not applied to the treatment of cheap water discharged from the coke oven.

[0007]

The object of the present invention is to solve the above-mentioned problems of the prior art, to easily manage the dissolved oxygen concentration in the aeration tank, and to carry out high-load treatment. An object of the present invention is to provide a method for treating cheap water that employs an activated sludge method using.

[0008]

In order to solve the above problems, the invention claimed in the present application is as follows. (1) In a method of introducing activated water generated from a coke oven into an aeration tank to treat activated sludge, a high-concentration oxygen-containing gas is injected into the aeration tank, the dissolved oxygen concentration in the tank is measured, and the dissolved oxygen is dissolved. A method for treating cheap water, which comprises treating activated sludge by adjusting the oxygen concentration to a predetermined value. (2) In the method of introducing activated water generated from a coke oven into an aeration tank to treat activated sludge, a part of the activated sludge in the aeration tank is extracted and a high-concentration oxygen-containing gas is injected to activate the oxygen-rich activated sludge. After that, while ejecting and circulating in the aeration tank, the dissolved oxygen concentration in the tank is measured, and the activated water is treated so that the dissolved oxygen concentration is adjusted to a predetermined value. Processing method.

(3) The carbon dioxide gas produced by the decomposition of organic substances contained in the ammonium hydroxide is expelled by air or nitrogen diffusion to adjust the pH in the aeration tank. The method according to (2). (4) The pH in the aeration tank is adjusted by neutralizing a carbonic acid component generated by the decomposition of organic matter contained in the ammonium hydroxide with a neutralizing agent, according to the above (1) or (2). Method.

In the present invention, an activated sludge method using a high concentration oxygen-containing gas is adopted. This makes it easier to adjust the dissolved oxygen concentration in the aeration tank and maintains the dissolved oxygen concentration at a higher value compared to the activated sludge method using air, which improves the responsiveness to load fluctuations and increases the Even low-concentration low-water concentration can be treated stably.

In the present invention, the high-concentration oxygen-containing gas means a mixed gas having a high oxygen concentration, and the oxygen concentration in the high-concentration oxygen-containing gas is 30 to 100%, preferably 60 to 100%. It is preferably 90 to 100%. The higher the oxygen concentration in the mixed gas, the better the controllability of the dissolved oxygen concentration in the aeration tank, and the easier the management.

In the present invention, carbon dioxide gas generated by the decomposition of organic matter contained in the ammonium hydroxide causes a decrease in pH in the aeration tank. Therefore, it is preferable to disperse air or nitrogen for expulsion. Air or nitrogen aeration may be continuous or intermittent. Instead of expelling carbon dioxide gas by air diffusion, the pH in the tank may be controlled by injecting a neutralizing agent such as caustic soda to neutralize the carbonic acid component.

In the present invention, the dissolved oxygen concentration (DO) in the aeration tank is 0.5 to 7.0 mg / L, preferably 1.
0-5 mg / L, more preferably 2.0-3.0 mg / L
Adjusted to L. If the dissolved oxygen concentration is too low, the pollutants in the ammonium hydroxide cannot be sufficiently treated, while if it is too high, the oxygen consumption increases and the treatment efficiency decreases. The pH in the aeration tank is 5.5 to 7.5, preferably 6.0 to 7.0,
It is more preferably adjusted to 6.0 to 6.5. If the pH is too low or too high, the functions of the microorganisms are deteriorated and sufficient treatment cannot be performed.

In the present invention, the MLSS in the aeration tank is
5,000 to 15,000 mg / L, preferably 7,0
00 to 12,000 mg / L, more preferably 8.0
It is 00-10,000 mg / L. If the MLSS concentration is too low, the pollutants cannot be sufficiently treated, and if it is too high, the oxygen consumption increases and it is uneconomical.

In the present invention, the dissolved oxygen concentration adjusting means in the aeration tank is, for example, a circulation line of activated sludge provided in the aeration tank and a venturi as a means for injecting a high concentration oxygen-containing gas provided in the circulation line. , And an injection nozzle as a means for injecting the oxygen-rich activated sludge after oxygen injection into the aeration tank. Further, a high concentration oxygen-containing gas of fine bubbles can be diffused and supplied directly to the aeration tank using an ultrafine bubble diffuser instead of the activated sludge circulation and oxygen injection means.

In the present invention, the dissolved oxygen concentration adjusting means can be directly applied to the existing activated sludge treatment equipment. In this case, it is possible to effectively use the existing equipment without requiring a large-scale modification. it can.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view of an activated sludge device using a high concentration oxygen-containing gas applied to the present invention. In FIG. 1, this apparatus comprises an upper open aeration tank 1, a circulation line 2 for circulating a part of activated sludge in the aeration tank 1, a circulation pump 3 and a venturi 4 provided in the circulation line 2. And a jet nozzle 5, a dissolved oxygen detector (DO meter) 6 for detecting dissolved oxygen in the aeration tank 1, and a flow rate control valve for adjusting the amount of oxygen supplied to the venturi 3 based on the detection value of the DO meter 6. 7 and an air or nitrogen diffuser 8 provided at the bottom of the aeration tank 1.

In such a structure, a part of the activated sludge in the aeration tank 1 is extracted by the circulation pump 3 and is injected into the venturi 4 provided in the sludge circulation line 2 via the flow rate control valve 7. The oxygen-containing gas 11 is mixed and melted under pressure to form oxygen-rich activated sludge accompanied by fine bubbles of oxygen, which is jetted from the jet nozzle 5 into the aeration tank 1 as a high-speed flow to the entire aeration tank 1. Oxygen is supplied to adjust and maintain the dissolved oxygen concentration in the tank to 2.3 mg / L, for example. At this time, the temperature in the bath is maintained at 30 ° C., for example. CO2 contained in the ammonium hydroxide 10, which is the water to be treated, is introduced into the aeration tank 1 in which the dissolved oxygen concentration is adjusted.
Phenol, thiocyan, NH _3, etc. are purified and treated by the action of microorganisms supplied with oxygen. At this time, carbon dioxide gas (CO ₂ ) generated by the decomposition of organic matter is expelled from the aeration tank 1 by the air or nitrogen 12 supplied from the air diffuser 8, and the tank pH is, for example, pH = 6.
It is maintained at 0. The treated water 13 overflows from the aeration tank 1 and flows into, for example, a final settling tank (not shown).

According to this embodiment, a part of the activated sludge in the aeration tank 1 is extracted and the venturi 4 mixes and dissolves the high-concentration oxygen-containing gas 11 into the oxygen-rich activated sludge. By circulating in the tank through
The injected oxygen is subjected to shearing force to form fine bubbles and is jetted at high speed into the tank together with the activated sludge, so that the oxygen becomes finer bubbles and is efficiently dissolved in the aeration tank 1. Therefore, the followability in the dissolved oxygen concentration control is improved compared to the conventional air aeration type activated sludge method, and it is possible to maintain an appropriate dissolved oxygen concentration with the minimum necessary amount of oxygen and efficiently process the ammonium hydroxide. . Further, since it becomes easy to adjust the dissolved oxygen concentration in the aeration tank 1, the MLSS concentration is set to, for example, 5,0.
It can be operated in a wide range of 00 to 15,000 mg / L. Therefore, it is possible to carry out high load treatment which is 2 to 3 times as high as that of the conventional technique, and, for example, fluctuations in the amount of introduced untreated water, C
Stable processing is possible without being greatly affected by load fluctuations such as OD. Further, in the case of the same load as in the conventional air aeration system, the equipment can be downsized and the equipment cost and the operation management cost can be reduced.

According to this embodiment, since the air diffuser 8 for diffusing air or nitrogen 12 is provided, the carbon dioxide gas generated by the decomposition of the organic matter contained in the ammonium hydroxide 10 can be quickly expelled from the aeration tank 1. Therefore, it is possible to avoid an abnormal decrease in pH in the aeration tank 1 and to continue stable treatment for a long time with an appropriate pH.

Further, according to the present embodiment, since the open type aeration tank can be adopted as the aeration tank 1, the equipment cost is reduced as compared with the conventional technique adopting the closed type aeration tank, and the operation management is performed. , Maintenance and inspection becomes easy. Also, since the aeration power is consumed only for carbon dioxide degassing, power consumption is reduced compared to the conventional air aeration type activated sludge method,
The running cost can be reduced. In the present embodiment, the introduction of the ammonium hydroxide 10 into the aeration tank 1 may be performed at the same time as or before the start of adjusting the dissolved oxygen concentration.

Embodiment 2 FIG. 2 is an apparatus system diagram showing another embodiment of the present invention.
In FIG. 2, this device is different from the device in FIG. 1 in that an ultrafine bubble diffuser 14 is provided instead of the sludge circulation line 2 as an oxygen supply means. In such a configuration, the high-concentration oxygen-containing gas 11 is supplied into the aeration tank 1 through the ultrafine bubble diffusing device 14, and is evenly supplied into the aeration tank 1 to achieve the same safety as in the above embodiment. Water 10 is treated.

According to this embodiment, the ultrafine bubble diffuser 1
By providing No. 4, the control followability of the dissolved oxygen concentration is improved and the proper dissolved oxygen concentration in the tank is maintained even if the properties of the ammonium hydroxide are changed, so that the minimum required oxygen can be obtained. It can be processed efficiently. Also, similar to the above embodiment,
The carbon dioxide gas generated by the decomposition of the organic matter can be quickly expelled from the aeration tank 1 by the air or nitrogen 12 introduced from the air diffuser 8, so that a significant decrease in pH in the aeration tank can be avoided and the stability can be kept stable for a long period of time. Water treatment can be continued.

Next, specific examples of the present invention will be described. Example 1 Using the apparatus of FIG. 1 with the aeration tank capacity of 970 L, raw water charge: 0.17 to 0.52 L / min, dilution water charge: 0.26 to 0.78 L / min, sludge Circulation flow rate:
8.0 L / min, DO in the aeration tank: 0.5 to 2.5 mg
/ L, MLSS: 8,000-10,000 mg / L,
Aeration air amount for carbon dioxide purging: 30 to 50 NL / mi
n, the temperature in the aeration tank was set to 30 ° C., and when the low water discharged from the coke oven was treated, the pH in the aeration tank was 6.0.
Stable at 7.0, COD: 115 mg / L, total cyan:
Treated water of 4.6 mg / L, thiocyanate: 5.6 mg / L, phenol: trace was obtained.

The results are shown in Table 1. In Table 1, it can be seen that 90% or more of COD and thiocyanate were removed, and almost 100% of phenol was removed. It should be noted that NH ₃ is hardly treated because the high concentration oxygen-containing gas is used to remove the D 3 in the aeration tank.
Since O could be easily and stably maintained, it is considered that nitric acid was not produced by digestion of ammonia in the water to be treated.

Example 2 Under the conditions of Example 1, when the COD load in the raw water was gradually increased and continuous treatment was carried out for about 2 months, COD
Even if the load is increased to 3.5 kg / m ³ · D, p in the aeration tank
H was stable at 6.0 to 7.0, and good treatment could be continued for a long time.

Example 3 A COD load of 1.0 kg / m ³ · D was obtained when the same continuous treatment was carried out as in Example 2 except that air or nitrogen was not diffused to expel carbon dioxide. The pH in the aeration tank began to drop from around the point where it was exceeded.

The results of Example 2 and Example 3 are shown in FIGS. 3 and 4, respectively. From FIG. 3 and FIG. 4, it is possible to expel the carbon dioxide gas generated by the decomposition of the organic matter from the aeration tank by aerating the air or nitrogen. Therefore, it is possible to avoid a decrease in pH and perform a stable treatment for a long period of time. It turns out that can be continued.

[0029]

According to the invention described in claim 1 of the present application,
Since the followability of DO adjustment in the tank is improved and the applicable range of MLSS is expanded, it is possible to efficiently treat the ammonium hydroxide with an appropriate dissolved oxygen concentration. According to the invention described in claim 2 of the present application, the same effect as the above invention can be obtained.

According to the invention described in claim 3 of the present application, in addition to the effects of the above-mentioned invention, even if the concentration of the ammonium hydroxide is high, the pH in the aeration tank is not lowered, and it is stable for a long period of time. Can be processed. According to the invention of claim 4 of the present application, similar to the above-mentioned invention, it is possible to continuously and stably treat the ammonium hydroxide for a long period of time without lowering the pH in the aeration tank.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus system applied to the present invention.

FIG. 2 is a diagram showing another device system applied to the present invention.

FIG. 3 is a diagram showing a result of one example of the present invention.

FIG. 4 is a diagram showing the results of another example of the present invention.

FIG. 5 is an explanatory diagram showing a conventional technique.

[Explanation of symbols]

1 ... Aeration tank, 2 ... Sludge circulation line, 3 ... Circulation pump, 4
... Venturi, 5 ... Injection nozzle, 6 ... DO meter, 7 ...
Flow rate control valve, 8 ... Air diffuser, 10 ... Ansui, 11 ... High concentration oxygen-containing gas, 12 ... Air or nitrogen, 13 ... Treated water,
14 ... Ultrafine air bubble diffuser, 31 ... Aeration tank, 32 ... Partition wall, 33 ... Aeration zone, 34 ... Surface aeration machine, 35 ... Oxygen supply device, 36 ... Exhaust gas line, 37 ... Pressure gauge, 38
... Oxygen meter, 39 ... Treated water, 40 ... Treated water.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshikazu Nemoto             9-3 Kitankita 4-chome, Chiyoda-ku, Tokyo             Dochemco Ltd. (72) Inventor Kazuya Ikeda             3-1, Okawa-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             Ryoka Koki Co., Ltd. F-term (reference) 4D011 AA15 AD03                 4D028 AB05 BC26 BD00 BD07 BD10                       CA04 CA09 CB02 CC07 CD01                 4D029 AA01 AB03 CC01                 4D037 AA11 AB11 BA03 BB01 BB05                       CA07

Claims (4)

[Claims] 1. A method of introducing activated water generated from a coke oven into an aeration tank to treat activated sludge, injecting a high-concentration oxygen-containing gas into the aeration tank, and measuring the dissolved oxygen concentration in the tank, A method for treating ammonium hydroxide, which comprises treating the activated sludge by adjusting the dissolved oxygen concentration to a predetermined value. 2. A method for treating activated sludge by introducing an ammonium hydroxide generated from a coke oven into an aeration tank, extracting a part of the activated sludge in the aeration tank, and injecting a high-concentration oxygen-containing gas into the oxygen-rich oxygen. After activated sludge is ejected and circulated in the aeration tank, the dissolved oxygen concentration in the tank is measured, and the activated oxygen is adjusted so that the dissolved oxygen concentration becomes a predetermined value. Water treatment method. 3. The pH in the aeration tank is adjusted by diffusing air or nitrogen to expel carbon dioxide gas generated by the decomposition of organic matter contained in the ammonium hydroxide, thereby adjusting the pH in the aeration tank. The method described. 4. The pH in the aeration tank is obtained by neutralizing a carbonic acid component produced by decomposition of organic matter contained in the ammonium hydroxide with a neutralizing agent.
The method according to claim 1 or 2, characterized in that