JPH079084Y2 - Residual chlorine measuring device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention further relates to a residual chlorine measuring device for measuring the residual chlorine concentration in sample water using a polarographic I ₂ substitution type residual chlorine meter. Then, it relates to an apparatus particularly preferably used for measuring residual chlorine in sewage and seawater discharged water.

[Conventional technology]

The sewage discharge water is usually discharged after chlorine sterilization, but in recent years, from the viewpoint of environmental protection, it has been required to control the residual chlorine concentration in the sewage discharge water to an extremely low concentration.

In this case, for the residual chlorine concentration in the sewage discharge water, a polarographic residual chlorine meter using potassium iodide as a reagent in an electrode system consisting of a platinum detection electrode and a platinum counter electrode is currently used. The measurement principle of this residual chlorine meter is as follows. That is, the addition potassium iodide (KI) to sample water containing free chlorine and combined chlorine, KI is potassium ion (K ⁺⁾ and iodide ion in aqueous solution (I ^-) ionized in the following (1)
As shown in the formula (4), the same amount of iodine ion (I ₂ ) as both chlorine is released.

Free chlorine ^{_{Cl 2 + 2I - → I 2}} + 2Cl - ... (1) combined chlorine ^{_{(chloramines) NH 2 Cl + 2I - +}} 2H + → I 2 + NH 4 Cl ... (2) NHCl 2 + 4I - + 3H + → 2I 2 + NH 4 Cl + Cl - ... (3) NCl ₃ ＋ 6I ⁻ ＋ 4H ⁺ → 3I ₂ ＋ NH ₄ Cl ＋ 2Cl… (4) Rotate the minute platinum electrode in the sample water after the above reaction, and use it as the detection electrode, and use platinum with a relatively large area as the stationary counter electrode. When a direct voltage is applied between both electrodes from the outside, a voltage-current curve similar to that of the dropping mercury electrode (polarographic)
Is obtained.

[Problems to be solved by the device]

The residual chlorine meter described above replaces the residual chlorine in the sample water with iodine, reduces the iodine at the detection electrode, produces iodine at the counter electrode, and indirectly determines the residual chlorine concentration from the flowing current. Is an iodine electrode.

However, in principle, this I ₂ substitution type residual chlorine meter needs to be present for measurement, and if it is exposed to sample water in which residual chlorine is almost absent for a long time, the iodine on the surface of the counter electrode is washed away and the counter electrode is removed. There is a problem that it does not work as an iodine electrode and the unipolar potential shifts. That is, when measuring the sample water containing residual chlorine, usually following formula _{^{(5) 2I - → I 2}} +2 - ... and place the reaction at the counter electrode shown in (5), thus the counter electrode may act as I ₂ electrode However, the reaction of the above formula (5) does not proceed unless I ₂ is present to some extent in the sample water, and therefore residual chlorine that is replaced with I ₂ in the discharged water of the sewage which is the sample water. If a state where is almost absent continues for a long time, the counter electrode I ₂ flows out and becomes unstable and does not work. When such a counter electrode does not function as an I ₂ electrode, a voltage-current curve shift as shown in Fig. 2 occurs, and a zero point is generated in the low concentration region near the zero point, which is important for the management of sewage discharge water. Drift will occur and low concentration of residual chlorine cannot be measured accurately. That is, in FIG. 2, a is 5 mg / lC
Characteristics of l _2, b is 2.5 mg / LCL ₂ properties, c is 5 mg / LCL ₂ Characteristics of 0mg / LCL ₂ after measuring, d is 0mg / LCL ₂ to 0mg after measuring long / LCL ₂ As can be seen from this figure, if the applied voltage is set to −0.4V, Cl _{2 will change} from the flowing current.
Although the density can be obtained, the error at the zero point becomes large in the state of d.

In addition, when residual chlorine in sewage discharge water is measured with a residual chlorine meter, filamentous fungi, algae, plankton, etc. contained in the discharge water adhere to the electrode system, sample water line, pump, etc. There is also a problem that the number of maintenance works increases.

The present invention has been made in view of the above circumstances, and it is possible to accurately measure residual chlorine in sample water, particularly low-concentration residual chlorine even after performing measurement of sample water in which residual chlorine is almost absent. An object of the present invention is to provide a residual chlorine measuring apparatus capable of favorably preventing the fungi and algae in the sample water from adhering to and proliferating on the electrode system.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention adds potassium iodide as a reagent to sample water, and at this time, iodine released by the reaction between residual chlorine and iodine ions in the sample water is released as a detection electrode and a counter electrode to which a constant voltage is applied. The residual chlorine meter that continuously measures the residual chlorine concentration in the sample water by using the residual chlorine meter and the sample water to which potassium iodide near the detection electrode and counter electrode of this residual chlorine meter is added An ozone supply mechanism for supplying the residual chlorine is provided.

[Action]

In the device of the present invention, the residual chlorine concentration in the sample water is measured by the residual chlorine meter (see the above formulas (1) to (4)), and ozone is periodically added to the sample water near the electrode of the residual chlorine meter. Supply.

In this case, ozone is potassium iodide (KI) as is Cl _2.
Reacts with iodine ions (I ⁻ ) in the added sample water to release iodine (I ² ) (see the above formula (5)). Therefore,
In the present invention, even when the counter electrode is exposed to the sample water containing almost no residual chlorine for a long period of time, the counter electrode is periodically replenished with iodine, and the counter electrode always stably acts as the iodine electrode.

In addition, since ozone is regularly supplied to the detection electrode and the counter electrode, fungi and algae are killed by the sterilizing action of ozone,
These fungi and algae are prevented from adhering to the electrode and propagating.

In addition, the supply of iodine to the counter electrode and the sterilization of fungi and algae can also be performed by supplying sodium hypochlorite.
However, ozone can be easily supplied because air is the supply source, but hypochlorous acid must be supplied as a reagent (solution), which complicates the mechanism of the device and promptly decomposes ozone. Therefore, the safety is high, but sodium hypochlorite is difficult to decompose, and thus there is a safety problem. Moreover, since the residual chlorine meter is originally a device for checking the emission of chlorine from an environmental point of view, means for causing chlorine to flow out is not preferable. Therefore, ozone is used in the present invention.

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.

〔Example〕

FIG. 1 shows a residual chlorine measuring apparatus according to an embodiment of the present invention, in which 1 is a sample water introduction pipe, 2 is a valve, 3 is an overflow tank, 4 is an overflow pipe, 5 is a sample water flow pipe. , 6 is a liquid feed pump, 7 to 17 are components of a residual chlorine meter, 7 is an electrode cell, 8 is a rotation detection electrode made of platinum,
9 is a detection pole rotation motor, 10 is a counter electrode made of platinum, 11 is a voltage application circuit, 12 is an ammeter, 13 is a drain pipe, 14 is a reagent tank, 15 is a reagent (potassium iodide), 16 is a reagent introduction pipe, 17 is a liquid feed pump, 18 is an ozone generator, 19 is an ozone introduction pipe, 20 is an electromagnetic valve, 21 is a wash water introduction pipe, 22 is an electromagnetic valve, and 23 is a first
The washing water flow pipe and 24 are the second washing water flow pipes, respectively.

When measuring the residual chlorine concentration in the sample water with this device, the pump 6 is operated to pass through the sample water flow pipe 5.
While flowing sample water into the electrode cell 7 at a flow rate of about ml / min,
By operating the pump 17, 2 ml of the reagent 15 in the sample water of the embodiment
It is introduced at a flow rate of about min, and the residual chlorine concentration in the sample water is measured by the detection electrode 8 and the counter electrode 10 according to the measurement principles of the formulas (1) to (4).

In addition, in this device, the ozone generator 18
Ozone is generated in the sample water, and this ozone is introduced into the sample water flowing in the sample water flow pipe 5 by operating the valve 20. As a result, fungi, algae, etc. attached to the inner wall of the sample water flow pipe 5, the inside of the pump 6, the inner wall of the electrode cell 7, the surfaces of the detection electrode 8 and the counter electrode 10, and the like are killed by the sterilizing action of ozone, and ozone is removed. water sample iodine ions (I ^-) reaction of iodine (I ²⁾ is released by the, the I ² is supplied to the counter electrode 10. The ozone supply cycle to the sample water varies depending on the degree of contamination of the sample water, but is preferably every 4 to 12 hours.

Furthermore, in this apparatus, the apparatus is washed with washing water after the introduction of ozone. That is, the pump 6 and the valve
By the operation of 22, the cleaning water is introduced into the cleaning water introducing pipe 21 at a flow rate of about 3 l / min. Then, this wash water is divided into the first wash water flow pipe 23 and the second wash water flow pipe 24, and the wash water that has passed through the first wash water flow pipe 23 becomes a water jet state. Of the sample water flow pipe 5
Since the inner diameter of the water is about 3 mm, when a large flow of washing water is introduced into this flow pipe 5, it becomes a water jet state and splits in both directions.) The washing water in this water jet state causes the sample water introducing pipe 1 and the overflow tank. 3, the sample water flow pipe 5, the pump 6, the cell 7, the detection electrode 8, the counter electrode 10, etc. are washed with a water jet, and the fungi and algae killed by the action of ozone are also washed out and discharged. On the other hand, the wash water that has passed through the second wash water flow pipe 24 is also jetted into the cell 7 in a water jet state, and the inner wall of the cell 7 and the surfaces of the detection electrode 8 and the counter electrode 10 are directly jet-washed with this wash water. The stains attached to these places are surely removed. In addition, the excess of I ² generated by the introduction of ozone is discharged by the cleaning with the cleaning water.

After the introduction of ozone and the cleaning with cleaning water are completed, the residual chlorine concentration in the sample water is measured in the same manner as described above.

Therefore, according to this device, since I ² is regularly supplied to the counter electrode 10, the counter electrode 10 stably acts as an iodine electrode even when the counter electrode 10 is exposed to the sample water in which residual chlorine does not exist for a long time. Since the zero point drift as shown in FIG. 2D does not occur, the residual chlorine concentration in the sample water, especially the low concentration residual chlorine near the zero point, can always be accurately measured. In addition, the bactericidal action of ozone kills the fungi and algae adhering to the pipe system and electrode system, and the fungi killed by the action of ozone by washing with wash water, the surplus of I ² generated by the action of ozone, etc. Since the water is washed out and discharged, the device can be kept in a stable state at all times. Therefore, according to the device of this example, the residual chlorine concentration is extremely low, and the residual chlorine concentration in the discharged water of the sewage containing a lot of fungi and algae is responsive and stable over a long period of time, and almost no maintenance is required. It can be automatically measured without requiring.

The piping system of the device of the present invention is not limited to the above-mentioned embodiment, and other suitable flow paths can be formed. Also, the ozone supply means and other configurations may be variously modified without departing from the scope of the present invention.

[Effect of device]

As described above, in the residual chlorine measuring apparatus of the present invention, I ² is regularly supplied to the counter electrode, so that the zero-point drift occurs even when the state in which the residual chlorine is almost absent in the sample continues for a long time. In this way, the electrode performance is stably maintained, and therefore residual chlorine in the sample water, especially low concentration residual chlorine, can always be accurately measured. Further, even when fungi or algae are contained in the sample water, it is possible to favorably prevent the fungi or algae from adhering to the electrode system and proliferating, and it is possible to keep the apparatus in a stable state at all times. Therefore,
The device of the present invention has a residual chlorine concentration that is inherently low like sewage or seawater discharge water, and is particularly suitably used for continuously measuring the residual chlorine concentration in sample water containing fungi and algae. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a residual chlorine measuring apparatus according to an embodiment of the present invention, and FIG. 2 is a graph showing a zero point drift. 5 ... Sample water flow pipe, 8 ... Detection electrode 10 ... Counter electrode, 15 ... Reagent 18 ... Ozone generator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsumi Kimura 1-2-10 Kamiochiai, Shinjuku-ku, Tokyo Ochiai Public Building 204 (72) Yukio Motoyama 3-2-5 Shinkawagishi, Itabashi-ku, Tokyo Shin-Kagishi Public Building B-202

Claims (1)

[Scope of utility model registration request] 1. A method of adding potassium iodide as a reagent to sample water and detecting iodine liberated by the reaction between residual chlorine and iodine ions in the sample water at this time using a detection electrode and a counter electrode to which a constant voltage is applied. A residual chlorine meter that continuously measures the residual chlorine concentration in the sample water with an ozone meter, and an ozone supply mechanism that periodically supplies ozone to the sample water containing potassium iodide near the detection and counter electrodes of the residual chlorine meter. An apparatus for measuring residual chlorine, comprising: