JP2006068599A - Ammonia nitrogen-containing waste water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the suppression of the amount of trihalomethanes in treated wastewater to a very low value not more than a reference value. <P>SOLUTION: In an ammonia nitrogen-containing wastewater treatment apparatus comprising a wastewater storage tank 1, an oxidizing reaction tank 2 disposed on the downstream side of the wastewater storage tank and connected to the wastewater storage tank through piping, a reducing reaction tank 3 disposed on the downstream side of the oxidizing reaction tank and connected to the oxidizing reaction tank through piping, an oxidizing agent storage tank 4 and an alkali storage tank 5 individually connected to the oxidizing reaction tank, and a reducing agent storage tank 6 disposed on the downstream side of the reducing reaction tank and connected to the reducing reaction tank through piping, an air agitation tank 31 disposed on the downstream side of the reducing reaction tank and connected to the reducing reaction tank through piping, and an air supply mechanism for supplying air into wastewater in the air agitation tank are installed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a treatment apparatus for wastewater containing ammonia nitrogen, and more particularly to a treatment apparatus using a discontinuous point chlorine injection method.

  As treatment methods of waste water containing nitrogen, there are generally various treatment methods such as biological treatment methods, discontinuous point chlorine injection method, ammonia stripping method, wet catalytic oxidation method, ion exchange method, and electrolysis method. . In Japan, there are many cases where biological treatment methods are used for reasons such as treatment results and diversity of applied nitrogen forms. On the other hand, the biological treatment method has a drawback that the large installation space and the quality of the treated water are greatly affected by the maintenance of microorganisms.

  Therefore, if it is limited to ammonia nitrogen, a chemical treatment method such as a discontinuous point chlorine injection method may have advantages in terms of treatment stability and equipment maintenance. FIG. 2 shows an apparatus configuration example using a general discontinuous point chlorine injection method. This apparatus includes a waste water storage tank 1, an oxidation reaction tank 2, a reduction reaction tank 3, an oxidant storage tank 4, an alkaline agent storage tank 5, and a reducing agent storage tank 6.

  In the wastewater tank 1, a pipe 7 connected to a previous process (not shown) is installed, and a pump 7 a is installed in the middle of the pipe 7. The oxidation reaction tank 2 is disposed on the downstream side of the waste water storage tank 1, and both are connected by a pipe 8 provided with a pump 8a on the way. The reduction reaction tank 3 is arranged on the downstream side of the oxidation reaction tank 2, and both are connected by a pipe 9 provided with a pump 9a on the way. The reduction reaction tank 3 is connected with a pipe 10 connected to a subsequent process (not shown), and a pump 10 a is installed in the middle of the pipe 10.

  The oxidant storage tank 4 is connected to the oxidation reaction tank 2 via a pipe 11 provided with a pump 11a on the way. An electrical system 12 for controlling these pumps is electrically connected to the pumps 8a and 11a. The oxidant storage tank 4 is connected to the oxidation reaction tank 2 via a pipe 13 provided with a pump 13a on the way. An electrical system 14 for controlling the pump 13a is electrically connected to the pump 13a. A pH meter 15 for measuring the hydrogen ion concentration is disposed in the oxidation reaction tank 2, and the pH meter 15 and the electrical system 14 are electrically connected. The pump 13 a is controlled by the electrical system 14 in order to add an alkaline agent according to the hydrogen ion concentration of the pH meter 15.

  A stirrer 16 is disposed at the bottom of the oxidation reaction tank 2 for the purpose of promoting the reaction. A piping 17 connected to the reduction reaction tank 3 is installed in the reducing agent storage tank 6, and a pump 17 a is installed in the middle of the piping 17. A stirrer 18 is disposed at the bottom of the reduction reaction tank 3 for the purpose of promoting the reaction. The reduction reaction tank 3 is provided with an ORP meter 19 for measuring an oxidation potential. An electrical system 20 is electrically connected to the pump 17a and the ORP meter 19, and the pump 17a is controlled by the electrical system 20 in order to introduce a reducing agent according to the oxidation potential of the ORP meter 19.

In the apparatus having such a configuration, wastewater treatment is performed as follows.
First, the waste water discharged from the previous process (not shown) is temporarily stored in the waste water storage tank 1 by the pump 7a. Next, this waste water is sent to the oxidation reaction tank 2 by the pump 8a, and at the same time, an appropriate amount of oxidizing agent is charged by the pump 11a. On the other hand, the pump 13a is operated, and an alkali agent in an amount corresponding to the hydrogen ion concentration measured by the pH meter 15 is introduced so that the neutrality is always maintained. This is because, in this apparatus, since a chlorine-based oxidant is selected as the oxidant, use in an acidic atmosphere is dangerous because harmful chlorine gas is emitted.

  Next, the waste water treated with the oxidizing agent and the alkaline agent in this way is sent to the reduction reaction tank 3 by the pump 9a. Here, an amount of reducing agent corresponding to the oxidation potential measured by the ORP meter 19 is introduced by the pump 17a to lower the oxidation potential. The waste water thus treated is sent to a subsequent process (not shown) by the pump 10a. Here, sodium hypochlorite is generally frequently used as the oxidizing agent, but rarely calcium hypochlorite, trichloroisocyanuric acid, or the like may be used. As the reducing agent, sodium sulfite, sodium bisulfite / sodium thiosulfate and the like are generally used.

Conventionally, Patent Document 1 below is known as a technique for treating various types of wastewater such as factory wastewater, human waste treatment plant, and domestic wastewater collected in a sewage treatment plant, which effectively removes beneficial chlorine and trihalomethane contained in water The following Patent Document 2 is known as a technique.
JP 10-305273 A JP-A-4-363190

By the way, when the discontinuous point chlorine injection method is selected as the waste water treatment method, the following three drawbacks are generally considered.
First, the cost of chemicals used is relatively high. This is a calculation that requires 7.6 g of chlorine for 1 g of ammoniacal nitrogen, and a large amount of chemicals used leads to an increase in cost.

  Secondly, the residual chlorine and the oxidation potential of the waste water after chlorine injection are increased. This is due to the reaction form of nitrogen and chlorine. In general, nitrogen is only chemically changed into chloramines at the beginning of chlorine input, so that it is absolutely necessary to input excessively in order to react with nitrogen gas. However, this excessive input increases the residual chlorine and oxidation potential of the wastewater. A method for solving this problem by introducing a reducing agent shown in FIG. 2 is generally employed, and has not yet reached a major problem.

  Thirdly, there is a problem that an organic chlorine compound is by-produced in a small amount in chlorine injection. This is a by-product of chemical changes in organic matter and chlorine in the waste water. In the wastewater treatment process, chloroform is most likely to occur. For example, even if chlorine is injected into pure water, a trace amount of chloroform may be generated.

Fig. 3 is a chromatograph of trihalomethane in general waste water, Fig. 4 is a chromatograph of trihalomethane generated when sodium hypochlorite is added to general waste water, and Fig. 5 is hypochlorous in general pure water. The chromatograph of trihalomethane generated when sodium acid is added is shown.
FIG. 5 shows that even a pure water produces a trace amount of chloroform. Trihalomethane is the first hazardous chemical substance whose water quality standards have been established due to its confirmed carcinogenicity, and its value is 0.1 mg / L or less. Depending on the drainage, chlorine injection may generate 0.1 mg / L or more of trihalomethane, and the countermeasures are extremely important for water quality management.

  The present invention has been made in view of such circumstances, and provides an apparatus for treating ammonia nitrogen-containing wastewater that can suppress the amount of trihalomethane in treated wastewater to an extremely low value below a reference value. Objective.

  (1) The present invention is a wastewater storage tank, an oxidation reaction tank disposed on the downstream side of the wastewater storage tank, connected to the wastewater storage tank via a pipe, and disposed on the downstream side of the oxidation reaction tank. , A reduction reaction tank connected to the oxidation reaction layer via a pipe, an oxidant storage tank and an alkali storage tank individually connected to the oxidation reaction tank, and a downstream side of the reduction reaction tank, In the ammonia nitrogen-containing wastewater treatment apparatus comprising the reducing reaction tank and a reducing agent storage tank connected via a pipe, the apparatus is disposed downstream of the reduction reaction tank, and the reduction reaction tank and the pipe are connected to each other. An ammonia nitrogen-containing wastewater treatment apparatus comprising a connected air agitation tank and an air supply mechanism for supplying air into the wastewater of the air agitation tank.

  (2) In addition, the present invention has an ammonia nitrogen content as described in (1) above, wherein the air agitation tank has a sealed structure and an exhaust gas cleaning device for cleaning the atmosphere in the sealed structure. Wastewater treatment equipment.

  According to the present invention, the amount of trihalomethane in the wastewater after treatment can be suppressed to an extremely low value of a reference value (0.1 mg / L) or less. In the present invention, if the air stirring tank has a sealed structure, the volatile trihalomethane can be recovered.

Next, a specific embodiment of the present invention will be described with reference to FIG.
Example 1
Please refer to FIG. However, the same members as those in FIG. In addition, the inside of the dashed-two dotted line of FIG. 1 is the same structure as FIG. The description of the same members as those in FIG. 1 is omitted.

  Reference numeral 31 in the figure indicates an air stirring tank disposed on the downstream side of the reduction reaction tank 3. The reduction reaction tank 3 and the air agitation tank 31 are connected by a pipe 10 provided with a pump 10a on the way. The air agitation tank 31 is connected to a pipe 32 connected to a subsequent process (not shown), and a pump 32 a is installed in the middle of the pipe 32. A diffuser pipe 35 connected via an aeration device 33 and a pipe 34 is disposed at the bottom of the air agitation tank 31. The aeration apparatus 33, the pipe 34, and the air diffuser 35 constitute an air supply mechanism. Examples of the aeration apparatus include a blower and a compressor. Further, instead of the air diffusing tube, another air ejection member such as a porous plate may be used. By the air supply mechanism, air 37 is supplied into the waste water (treated water) 36 in the air agitation tank 31 and aeration of the treated water becomes possible.

  The treatment apparatus of ammonia nitrogen-containing wastewater according to Example 1 includes a wastewater storage tank 1, an oxidation reaction tank 2, a reduction reaction tank 3, and the oxidation reaction, which are sequentially arranged on the downstream side of the wastewater storage tank 1. An oxidant storage tank 4 and an alkali storage tank 5 individually connected to the tank 3, a reducing agent storage tank 6 connected to the reduction reaction tank 3, and air disposed downstream of the reduction reaction tank 3. The agitation tank 31 includes an air supply mechanism including an aeration device 33 that aerates the treated water in the air agitation tank 31.

In such a treatment apparatus, wastewater treatment is performed as follows.
(1) First, the waste water discharged from the previous process (not shown) is temporarily stored in the waste water storage tank 1 by the pump 7a. Next, this waste water is sent to the oxidation reaction tank 2 by the pump 8a, and at the same time, an appropriate amount of oxidizing agent is charged by the pump 11a. On the other hand, the pump 13a is operated, and an alkali agent in an amount corresponding to the hydrogen ion concentration measured by the pH meter 15 is introduced so that the neutrality is always maintained. The reason for this is as already described in the section of the prior art.

  (2) Next, the waste water treated in the oxidation-reduction reaction tank 2 is sent to the reduction reaction tank 3 by the pump 9a. Here, an amount of reducing agent corresponding to the oxidation potential measured by the ORP meter 19 is introduced by the pump 17a to lower the oxidation potential. The wastewater thus treated is sent to the air agitation tank 31 by the pump 10a. Here, specific examples of the oxidizing agent and the reducing agent are the same as those described in the section of the prior art.

  (3) The drainage sent to the air agitation tank 31 by the pump 10a is agitated by the air sent from the aeration device 33 to the air diffuser 35. By this stirring, the organic chlorine compound in the waste water is volatilized into the atmosphere, and the concentration of the organic chlorine compound in the treated water becomes substantially zero. The treated water treated in this way is sent to a subsequent process (not shown) by the pump 28a.

  The effect of the stirring is as shown in FIG. From FIG. 6, it is apparent that chloroform contained in the treated water has a relatively high concentration of 3000 ppb at the beginning, but can be removed up to 0 ppb by aeration for several minutes. Thus, by stirring, chloroform, which is one of trihalomethanes, can be reduced from the treated water.

  In the first embodiment, as shown in FIG. 1, an air agitation tank 31 is provided on the downstream side of the reduction reaction tank 3, and the treated water in the air agitation tank 31 can be aerated by the aeration apparatus 33 or the like. Therefore, it can be avoided that chloroform which is one of trihalomethanes remains in the treated water.

(Example 2)
Please refer to FIG. In the second embodiment, the trihalomethane, which is a carcinogenic substance, is volatilized in the atmosphere due to the stirring effect of the aeration apparatus in the first embodiment, and the apparatus for preventing this is proposed.
Reference numeral 41 in the figure indicates a box-shaped sealed structure that seals the air stirring tank 31. An exhaust gas cleaning device 43 is connected to the sealed structure 41 via a pipe 42.

  The treatment apparatus of Example 2 includes a waste water storage tank 1, an oxidation reaction tank 2, a reduction reaction tank 3, a oxidant storage tank 4, an alkali storage tank 5, a reducing agent storage tank 6, and an air stirring tank 31 disclosed in FIG. In addition to the structural requirements of the aeration apparatus 33 and the like, the structure further includes the sealing structure 41 and the exhaust gas cleaning device 43 that seal the air agitation tank 31. It is possible to prevent the trihalomethane from being volatilized into the atmosphere.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

Explanatory drawing of the processing apparatus of the ammoniacal nitrogen containing wastewater by Example 1 of this invention. Explanatory drawing of the processing apparatus of the conventional ammonia nitrogen containing wastewater. Chromatograph showing trihalomethane concentration in general wastewater. Chromatograph showing trihalomethane concentration when sodium hypochlorite is added to general wastewater. The chromatograph showing the trihalomethane density | concentration at the time of adding sodium hypochlorite to pure water. The characteristic view which shows the relationship between the density | concentration of chloroform at the time of using the processing apparatus by Example 1 of this invention, and elapsed time. Explanatory drawing which shows the principal part of the processing apparatus of the waste water containing ammonia nitrogen by Example 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Waste water storage tank, 2 ... Oxidation reaction tank, 3 ... Reduction reaction tank, 4 ... Oxidant storage tank, 5 ... Alkali storage tank, 6 ... Reducing agent storage tank, 7, 8, 9, 10, 11, 13, 17, 32, 34, 42 ... piping, 7a, 8a, 9a, 10a, 11a, 13a, 17a, 32a, 34a, 42a ... pump, 12, 14, 20 ... electrical system, 15 ... pH meter, 16, 18 ... Stirrer, 31 ... Air agitation tank, 33 ... Aeration device, 35 ... Aeration tube, 36 ... Drainage (treated water), 41 ... Sealed structure, 43 ... Exhaust gas cleaning device.

Claims (2)

A waste water storage tank, an oxidation reaction tank disposed downstream of the waste water storage tank, connected to the waste water storage tank via a pipe, and disposed downstream of the oxidation reaction tank, the oxidation reaction layer and a pipe A reduction reaction tank connected through the oxidation reaction tank, an oxidant storage tank and an alkali storage tank individually connected to the oxidation reaction tank, and a downstream side of the reduction reaction tank. In a treatment apparatus for wastewater containing ammonia nitrogen, comprising a reducing agent storage tank connected via
An air agitation tank disposed downstream of the reduction reaction tank and connected to the reduction reaction tank via a pipe, and an air supply mechanism for supplying air into the waste water of the air agitation tank An ammonia nitrogen-containing wastewater treatment device. 2. The ammonia nitrogen-containing wastewater treatment apparatus according to claim 1, wherein the air agitation tank has a sealed structure and an exhaust gas cleaning device for cleaning the air in the sealed structure.

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