JPH11207366A - Chlorine treatment and chlorine treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a remaining chlorine concentration in treated water at an adequate value. SOLUTION: In a chlorine mixing reaction tank 18, excessive chlorine is fed by a primary chlorine myection pump 22, and here ammoniacal nitrogen is decomposed and removed. An active carbon slurry is fed to a rapid agitation tank 24, and is brought into contact with the treated water from the chlorine mixing reaction tank 18 to remove the remaining chlorine. Chlorine is poured into the treated water from which the remaining chlorine is once removed by a secondary chlorine pouring pump 40, then a specified remaining chlorine concentration of treated water is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chlorination method and a chlorination apparatus for water in which ammonia nitrogen is dissolved, and more particularly to a method for properly adjusting the residual chlorine concentration of treated water even when the ammonia nitrogen concentration fluctuates greatly. Related to what can be held.

[0002]

2. Description of the Related Art Conventionally, a sanitizing treatment (chlorination treatment) for injecting a chlorinating agent has been performed in waterworks, pool water and the like. In this chlorination, if ammonia nitrogen is present in the raw water, the ammonia nitrogen and chlorine react. Normally, as chlorine is added, chloramine is first generated, and residual chlorine increases. As the amount of added chlorine further increases, the reaction of chloramine and chlorine causes a nitrogen removal reaction, and the residual chlorine decreases. Then, chlorine added after the removal of nitrogen is completed is dissolved in water as free residual chlorine.

[0003] Therefore, if the amount of chlorine injected is insufficient, chloramine is generated and odor is generated. Also, depending on the amount of chlorine injected, the residual chlorine becomes almost zero. Furthermore, if the chlorine injection amount is too large, unnecessary residual chlorine will remain in the water.

In waterworks and swimming pools, the minimum concentration of residual chlorine is legally regulated, and the residual chlorine concentration must be controlled. Therefore, in a normal case, chlorine is injected in a much larger amount than the concentration of ammoniacal nitrogen to prevent shortage of residual chlorine in the treated water.

However, the concentration of ammonia nitrogen often changes every moment. In this case, it is difficult to control the amount of chlorine to be injected appropriately. Therefore, the ammonia nitrogen concentration is measured, and the chlorine injection amount is controlled so that the chlorine amount is injected according to the measured ammonia nitrogen concentration.

[0006] However, chlorine is a strong oxidizing agent and reacts with other substances such as organic substances contained in raw water. For this reason, it is often not possible to maintain an appropriate amount of chlorine injection simply by measuring the concentration of ammoniacal nitrogen. Therefore, raw water is sampled, and a preliminary test of chlorine injection is performed on the raw water to determine the chlorine injection amount. According to this method, an appropriate chlorine injection amount can be determined, but there is a problem that a time delay becomes large and it is impossible to follow a change in raw water.

[0007] Therefore, conventionally, the chlorine injection amount is set relatively large so that the chlorine injection amount does not become insufficient.

[0008]

However, the conventional method as described above has a problem that the concentration of residual chlorine at normal time becomes considerably high, and it is difficult to control the concentration to a predetermined concentration. In many cases, there is no problem even if the residual chlorine concentration is high to some extent, but there is also a demand for controlling the concentration to an appropriate concentration.

The present invention has been made in view of the above problems, and provides a chlorination apparatus and a chlorination method capable of controlling the residual chlorine concentration of treated water to an appropriate level with respect to water in which ammonia nitrogen is dissolved. The purpose is to provide.

[0010]

According to the chlorination method of the present invention, an excessive amount of chlorinating agent is added to water in which ammoniacal nitrogen is dissolved, in excess of an amount necessary for a decomposition reaction of ammoniacal nitrogen. Thereafter, the excess chlorine agent is injected, and the remaining chlorine is removed by contacting the activated carbon with water from which ammonia nitrogen has been removed, and thereafter, a further necessary amount of chlorine agent is injected.

Further, the chlorination apparatus according to the present invention is characterized in that a first chlorine injection section for injecting excess chlorine agent in an amount of water necessary for a decomposition reaction of ammonia nitrogen into water containing ammonia nitrogen. An activated carbon treatment unit that removes residual chlorine by contacting the activated carbon with water obtained by injecting excess chlorine agent and removing ammoniacal nitrogen, and a necessary amount of chlorine agent in water treated with activated carbon. And a second chlorine injecting section for injecting.

As described above, according to the present invention, in the first chlorine injection, chlorine is injected in a necessary amount or more. By this, ammonia nitrogen in water is decomposed and removed,
The amount of residual chlorine in the treated water varies greatly. But,
Activated carbon is brought into contact with the treated water, decomposed by the catalytic action of the activated carbon, and once all residual chlorine is removed. Then, as a second chlorine injection, necessary chlorine is injected. In this case, since the ammonia nitrogen in the water has been removed, the amount of residual chlorine can be controlled appropriately. Furthermore, activated carbon can remove organic substances and the like that react with chlorine, so that the residual duration of chlorine is lengthened and the required chlorine concentration can be reliably maintained for a long time.

The residual chlorine concentration in the treated water is controlled to a predetermined value by measuring the residual chlorine concentration of the treated water after the second chlorine injection and controlling the second chlorine injection amount according to the measurement result. It is also preferred to do so.

Further, as a pretreatment for ammonia decomposition by chlorination, adsorption and removal of ammonia nitrogen using zeolite may be performed. By performing such an adsorption treatment with zeolite, the amount of chlorine to be injected into water containing a large amount of ammoniacal nitrogen can be reduced to perform an effective treatment.

[0015]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

First Embodiment FIG. 1 shows the overall configuration of a water treatment system including a chlorination device according to a first embodiment. Raw water is introduced into the zeolite mixing tank 10. This zeolite mixing tank 10 includes a zeolite slurry tank 12.
A zeolite slurry in which zeolite powder is suspended in water is supplied by a zeolite injection pump 14. Therefore, raw water and zeolite slurry are mixed in the zeolite mixing tank 10. Since zeolite selectively adsorbs (selective ion exchange) ammonia nitrogen, much of the ammonia nitrogen contained in the raw water is removed in the zeolite mixing tank 10. In addition,
The removal of ammonia nitrogen by the zeolite is not essential and may be omitted. In particular, when the concentration of ammonia nitrogen is low, it is preferable to omit this. In the present embodiment, the bypass pipe 16 is provided so that the raw water can be supplied to the next step by bypassing the zeolite mixing tank 10. In particular, when the time when a large amount of ammonia nitrogen is contained is limited, the treatment with zeolite may be performed only at that time.

The treated water from the zeolite mixing tank 10 is introduced into a chlorine mixing reaction tank 18. This chlorine mixing reactor 1
8, sodium hypochlorite is supplied as a chlorine agent from a chlorine storage tank 20 via a primary chlorine injection pump 22. Then, in this chlorine mixing reaction tank 18, the ammonia nitrogen is decomposed and removed by chlorine. In particular, the chlorine mixing reaction tank 18 is supplied with an excess chlorine agent in excess of a necessary amount of chlorine in consideration of decomposition of ammonia nitrogen and other substances consuming chlorine. Thereby, in the chlorine mixing reaction tank 18, almost all of the ammonia nitrogen in the water is removed, and a considerable amount of chlorine remains. That is, in order to remove ammonia nitrogen, chlorine 5 is necessary for ammonia nitrogen 1 as a reaction equivalent ratio. Therefore, even a small change in the concentration of ammonia nitrogen causes a large change in the residual chlorine amount. Therefore, the concentration of residual chlorine contained in the treated water discharged from the chlorine mixing reaction tank 18 varies greatly. In addition, in order to inject sufficient chlorine to remove ammoniacal nitrogen, the treated water from the chlorine mixing reaction tank 18 basically contains free chlorine.

In the present embodiment, sodium hypochlorite is used as a chlorine agent, but chlorine gas may be directly injected or calcium hypochlorite may be added. Further, the residence time of the chlorine mixing reaction tank 18 is preferably about 30 to 60 minutes, and it is preferable that the reaction is sufficient.
Minutes are required.

The treated water in which the residual chlorine amount (free chlorine) from the chlorine mixing reaction tank 18 fluctuates greatly is introduced into the rapid stirring tank 24. A flocculant from a flocculant storage tank 26 is supplied to the rapid stirring tank 24 by a flocculant injection pump 28. Further, the activated carbon from the activated carbon slurry tank 30 is supplied to the rapid stirring tank 24 by an activated carbon slurry pump 32. Therefore, in the rapid stirring tank 24, the agitation and mixing of the treated water containing excess chlorine, the coagulant and the activated carbon are performed. PAC (polyaluminum chloride) or the like is used as the coagulant. The activated carbon slurry is obtained by suspending powdered activated carbon in water.

By this rapid stirring tank 24, fine solids contained in the water are collected by the flocculant. Further, since activated carbon is mixed, residual chlorine is decomposed and removed by the catalytic function of the activated carbon surface. In addition, trace amounts of dissolved organic substances are also adsorbed and removed by the activated carbon. Furthermore, even if a by-product is generated by the reaction between the organic matter and chlorine, the by-product is adsorbed and removed by the activated carbon.

In the rapid stirring tank 24, the treated water in which the flocculant and the activated carbon are mixed is introduced into the slow stirring tank 34,
Here, the mixture is slowly stirred to promote the formation of flocculated flocs. In addition, reactions such as decomposition and removal of chlorine by activated carbon are continued. A settling tank 36 is connected to the slow stirring tank 34, where solids such as flocculated flocs are precipitated and separated. The powdered zeolite added to the zeolite mixing tank 10 and the powdered activated carbon added to the rapid stirring tank 24 are also flocculated and separated by precipitation. The sludge settled and separated is discharged and treated separately.

The supernatant water of the sedimentation tank 36 is supplied to a filtration tank 38, where it is subjected to gravity filtration. The filtration tank 38 may be a pressure type rapid filtration. Note that by adding granular activated carbon to the uppermost part of the filter medium to be filled in the filtration tank 38, it is possible to replace the addition of the activated carbon slurry.
Further, the activated carbon slurry can be added to the middle stage of the slow stirring tank 34 or the like.

As described above, the residual chlorine is completely removed from the supernatant of the precipitation tank 36 or the filtered water in the filtration tank 38. The chlorine agent in the chlorine storage tank 20 is injected into the filtered water via the secondary chlorine injection pump 40. The treated water after the injection of the chlorine agent is introduced into a mixer (in-line mixer) 42, where a mixed contact treatment of chlorine and treated water is performed. In this case, there is almost no ammoniacal nitrogen or residual organic matter in the treated water, and a residual chlorine amount (free chlorine) corresponding to the injection amount can be obtained. And
Since the residual chlorine may be left in the water as it is, it is not necessary to provide a reaction mixing tank and perform sufficient reaction as in the first chlorine injection. Therefore, a mixer 42 for mixing in a pipe is used.
Is enough. A chlorine concentration meter 44 is disposed in a pipe of the treated water discharged from the mixer 42, and the chlorine concentration meter 44 measures the residual chlorine concentration in the treated water.

The detection output of the chlorine concentration meter 44 is
Is supplied to the secondary chlorine injection pump 40 as an input for adjustment. And the secondary chlorine injection pump 40
Feedback control is performed by the output from the converter 46. As described above, since the chlorine injection amount and the residual chlorine amount have a good correlation, the feedback control can be performed with high accuracy, and the chlorine concentration in the treated water can be accurately controlled. When sterilizing the filtration tank 38, the second chlorine injection may be performed on the water flowing into the filtration tank 38, as shown by the broken line in the figure.

As described above, according to the present embodiment, in the first chlorine injection, chlorine is injected in an amount equal to or more than that necessary for decomposing ammoniacal nitrogen. As a result, the ammoniacal nitrogen in the water is decomposed and removed, but the amount of residual chlorine in the treated water fluctuates greatly. However, this treated water is brought into contact with activated carbon to remove all residual chlorine once. Then, thereafter, a necessary amount of chlorine is injected as a second chlorine injection. In this case, since the ammonia nitrogen in the water has been removed, it is extremely easy to control the amount of residual chlorine to an appropriate level. Furthermore, activated carbon can remove organic substances and the like that react with chlorine, so that the residual duration of chlorine is lengthened and the required chlorine concentration can be reliably maintained for a long time.

Further, according to the present embodiment, since ammonia nitrogen removal using zeolite is performed as a pre-treatment of chlorination, the amount of chlorine injected into water containing a large amount of ammonia nitrogen is reduced. Effective processing can be performed with a reduction.

Although the zeolite and the activated carbon are supplied as a slurry, the powder may be added as it is.

The configuration of the first embodiment as described above is based on a water treatment facility, and the present invention can be suitably used particularly as a water treatment facility.

[Second Embodiment] FIG. 2 shows the configuration of the second embodiment. In the second embodiment, the zeolite packed tower 5
0, an intermediate pump 52, and an activated carbon packed tower 54. Raw water is supplied to a zeolite packed tower 50 in which granular zeolite is filled. Then, as the raw water passes through the zeolite packed bed, the ammonia nitrogen in the raw water is adsorbed and removed. The zeolite packed tower 50 can be bypassed by the bypass pipe 16.

Then, the treated water in the zeolite packed tower 50 is supplied to the chlorine mixing reaction tank 18. As in the first embodiment, the chlorine mixing reaction tank 18 is supplied with a chlorine agent from a chlorine storage tank 20 by a primary chlorine injection pump. Here, excessive chlorine is injected to remove ammoniacal nitrogen and the like. An oxidation treatment with chlorine is performed. Then, the treated water containing residual chlorine from the chlorine mixing reaction tank 18 is supplied to the activated carbon packed tower 54 by the intermediate pump 52. The activated carbon packed tower 54 is filled with granular activated carbon, and the residual chlorine in the water is decomposed and removed by allowing water containing residual chlorine to pass therethrough. Also,
The removal of organic substances by activated carbon is also performed.

Then, the chlorine agent from the chlorine storage tank 20 is added to the treated water from the activated carbon packed tower 54 from which residual chlorine has been removed by the secondary chlorine injection pump 40. The water that has undergone the chlorine injection is mixed in the mixer 42. The residual chlorine concentration of the treated water from the mixer 42 is measured by the chlorine concentration meter 44, and the measurement result is fed back to the secondary chlorine injecting pump 40 via the converter 46, so that the residual chlorine concentration of the treated water becomes a predetermined value. The amount of chlorine injected by the secondary chlorine injection pump 40 is controlled such that

As described above, in the second embodiment, instead of adding the zeolite slurry and the activated carbon slurry,
These packed towers are provided. In addition, the coagulation sedimentation process
Not provided.

The configuration of the second embodiment is particularly suitable for chlorination of pool water. However, it is also preferable to carry out the water treatment by combining the configuration of the second embodiment with a coagulation sedimentation treatment, a filtration treatment and the like.

Furthermore, the present invention can be applied to chlorination of water containing ammoniacal nitrogen without being limited to the above-mentioned water treatment and pool water treatment.

[0035]

EXAMPLE The processing was performed by the apparatus according to the second embodiment shown in FIG. Ammonia nitrogen concentration is 0.12-0.4
For raw water that changes in the range of 0 mg / L, chlorine (Cl
₂ ) was injected so as to have an injection rate of 10 mg / L,
The reaction was performed for 30 minutes in the reaction tank 18 to decompose ammoniacal nitrogen. As a result, the concentration of residual chlorine in the treated water changed in the range of 0.2 to 1.3 mg / L, and the concentration of ammoniacal nitrogen became almost zero.

This treated water is passed through an activated carbon packed tower 54,
Chlorine was injected into the treated water so as to have an injection rate of 0.5 mg / L. As a result, the residual chlorine concentration after the chlorine injection was approximately constant at about 0.5 mg / L.

As is clear from the above results, simply injecting an excessive amount of chlorine from the theoretical amount with respect to the ammonia nitrogen concentration in the raw water can decompose the ammonia nitrogen, but the residual chlorine in the treated water can be decomposed. The concentration is 0.2-1.3m
g / L. However, by treating the treated water after decomposing ammoniacal nitrogen with activated carbon and then injecting chlorine again, treated water having a substantially constant residual chlorine concentration can be obtained. This shows that the management of the residual chlorine concentration becomes very easy.

[0038]

As described above, according to the present invention,
By making the addition of the chlorine agent in excess of the amount necessary for the decomposition of the ammonia nitrogen in the removal of the ammonia nitrogen, it is easy to control the addition amount, and thereby the ammonia nitrogen can be reliably removed. In addition, since chlorine is once again removed by activated carbon and chlorine is injected again, the amount of residual chlorine in the treated water can be accurately controlled. Furthermore, the activated carbon can remove organic substances that react with chlorine, so that the residual duration of chlorine becomes longer,
The required chlorine concentration can be reliably maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment.

FIG. 2 is a diagram illustrating a configuration of a second embodiment.

[Explanation of symbols]

10 zeolite mixing tank, 12 zeolite slurry tank, 14 zeolite injection pump, 16 bypass pipe,
18 chlorine mixing reaction tank, 20 chlorine storage tank, 22 primary chlorine injection pump, 24 rapid stirring tank, 26 flocculant storage tank, 2
8 Coagulant injection pump, 30 activated carbon slurry tank, 32
Activated carbon slurry pump, 34 Slow stirring tank, 36 Precipitation tank, 38 Filtration tank, 40 Secondary chlorine injection pump, 42
Mixer, 44 chlorine concentration meter, 46 converter, 50 zeolite packed tower, 52 intermediate pump, 54 activated carbon packed tower.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/50 520 C02F 1/50 520L 531 531M 550 550C 550H 560 560B 1/58 1/58 P

Claims (2)

[Claims] 1. An excess chlorine agent is injected into the water in which ammonia nitrogen is dissolved, in excess of an amount required for the decomposition reaction of ammonia nitrogen, and then the excess chlorine agent is injected to remove ammonia nitrogen. A chlorination method comprising removing remaining chlorine by contacting the removed water with activated carbon, and thereafter injecting a necessary amount of a chlorinating agent. 2. A first chlorine injecting section for injecting an excess amount of chlorine agent in an amount of water necessary for a decomposition reaction of ammonia nitrogen into water containing ammonia nitrogen, and an obtained excess chlorine agent. Activated carbon treatment unit that removes chlorine remaining due to contact between water and activated carbon from which ammonia nitrogen has been removed, a second chlorine injection unit that injects a required amount of chlorinating agent into water treated with activated carbon, A chlorination apparatus comprising: