JPS5855088A - Decomposing method for precursor of organic chlorine compound such as humic acid by combination use of ozone and hydrogen peroxide - Google Patents

Abstract

PURPOSE:To accelerate decomposition reaction and to use an oxidizing agent to be injected efficiently by decomposing org. materials by oxidation with ozone alone in an initial period of catalytic reaction and adding and using hydrogen peroxide in combination to and with the ozone in the 2nd reaction region where the reaction retards. CONSTITUTION:Org. materials such as humic acids in water are decomposed by oxidation with a treatment by the ozone alone in the 1st reaction region in an initial period of catalytic reaction. In the 2nd reaction region where reaction retards, hydrogen peroxide is added and used to and in combination with the ozone to accelerate the decomposition reaction. The two-stage treating method making combination use of ozone and hydrogen peroxide is effective as a method for removing humic acid as a precursor for formation of trihalomethane and prevents the formation of trihalomethane in both terms of an effet of decreasing TOC components and chemical stability of residual TOC components.

Description

[Detailed Description of the Invention] When the salt for disinfecting drinking water reacts with the salt for disinfecting drinking water, various trihalomethanes such as chloro-7-olm are produced. In order to prevent this formation, if the precursors such as the amine acids mentioned above are removed as much as possible before contact with chlorine, the amount of formation is 1.
-4, it is considered the most promising countermeasure against T, 'H, and K.Also, when decomposing these organic substances, the oxidative decomposition reaction of these substances by ozone is effective, but the There is only a momentary moment at the beginning of the reaction, and after that the reaction hardly progresses, making it practically impossible.

The present invention solves this problem and provides a practical water treatment method using ozone. Next, the aspect according to an example will be explained.

EXAMPLE When conducting an experiment using the method of the present invention, it was difficult to obtain a concentrated sample using natural water, so a reagent was used for the experiment. First, the amine acid used in the experiment was prepared by heating the amine acid reagent 51 to 7tO,I N -Na.
After stirring and dissolving for 24 hours, the insoluble substances were separated and the humic acid stock solution was adjusted to 5,000 μl/mL, ignoring the weight of the insoluble substances.

Concentration CH (number) of this humic acid solution and TOC concentration FI
CT 00 (5P-T'a/j') had a linear relationship. That is, CTOO=041 Csi+0.
11! This means that 41% of the amic acid is organic carbon, which is slightly lower than the generally accepted 50-60%. Table 1 shows the results of an oxidative decomposition experiment using dioscin and a comparison of its effects with t-TOC measurements. - The batch-type experimental equipment FIT is a small-scale experimental equipment made of glass, as shown in Figure 1. In the figure, 1 is a predetermined concentration of H2O2k
A reactor (separable beaker) filled with added sample water (2)), this reactor 1 is placed in a constant temperature water tank 2,
The water temperature in this constant temperature water tank 2 is set to 20C by the temperature controller 3.
is maintained. Further, the sample water in the reactor 1 is stirred by a magnetic stirrer 4. Further, a water supply port 5 is provided above the reactor l, and sample water and H2O2 are passed through the water supply port 5 from a sample water tank 6 and a H2O2 reservoir 7 by respective pumps 8 and 9 to a predetermined concentration during the experiment. Supplied per. In addition, air pumped by an air pump 1O is converted into ozonized air by an ozone generator 11 and then blown into the test water in the reactor 1 through a blowing pipe 12. After a part of this ozonized air reacts with the sample water, it is exhausted from the exhaust port 13 installed above the reactor 1, and the ozone concentration of the exhaust gas is measured with the ozone concentration meter 14, and the ozonized air is passed through the activated carbon tower 15. is released into the atmosphere after being adsorbed. In addition, the treated sample water is discharged into the treated water tank 18 for each experiment through a drain port 16 provided at the bottom of the reactor 1 and a multiple communication pipe 17. The change over time of the unreacted ozonized air shows a Naha turn as shown in Figure 3, and the TOC concentration history curve Ia of the humic acid solution at this time, @4
As shown in the figure, the Ctoo vs. t (time) curve t! TOC
At a removal rate of When the reaction U TOCTh is used as a reference, the reaction rate tends to be slow and becomes a zero-order reaction that is unrelated to the humic acid concentration.

When ozone treatment is carried out, the dark color of the humic acid solution is rapidly decolored, and residual ozone also appears in the transparent polyhydric water near 11 in Figures 3 and 4.

Comparing Tests 41 and 48 from Table 1 using the TOC't of the first reaction zone and the second reaction zone, the removal rate in the second zone was 7""34 compared to the first zone. It can be seen that in the second region, the reaction is extremely slow and almost no effect is obtained.

Here, in order to find the reaction equivalent of 7 minic acid and ozone, the third
The time-dependent change in ozone concentration in the reactor exhaust gas and the amount of consumed ozone (dotted line area) in the figure were determined by the gravimetric method. In this case, the amount of ozone consumed includes not only the amount of ozone consumed purely by reaction, but also the amount dissolved in water and the amount dissolved and naturally decomposed.

When organized as organic carbon versus consumed ozone amount, in ozone-only treatment, the consumed ozone amount is large in the first region discussed in the reaction rate section, and in the second region, organic carbon decomposition stops and the consumed ozone amount is large. In the first region, the curve of U TOC versus consumed ozone is Ctoc.
= KIDO3+ C"To.

A straight line is obtained, and the reaction equivalence coefficient Kl is obtained.

Figure 5 shows the reaction equivalent curve under each experimental condition. If Klt is calculated from this, K* = -0,138, which is the amount of consumed ozone that is 7.2 times the amount of TOC removed (g9). 0 Considering this point, the 0 reaction between ozone and the organic carbon content in humic acid in the first region is C+ 203 →
CO2+ 20a ('-'20a/C=96/12k
q8) is expected, and it can be seen that oxygen from the ozone generator accounts for the majority of the contribution to the decomposition of humic acid. The history curve of the ozone concentration in the exhaust gas when H2O2' is initially injected into the acid solution and ozone is injected there is shown in Figure 6. As the reaction occurs instantaneously, 03 + H2O2→OH+ HO2+ 0203 +
H2O2 → 202 + Ozone such as H2O and H2O2
The reaction of 0
In the second region, the reaction rate was improved by the addition of H2O2, making it possible to slightly decompose most of the residual TOC content of the reacted minic acid in the ozone monoi treatment. However, for the above reasons, it is not advisable to use ozone and hydrogen peroxide together in the first region. Also, in terms of reaction equivalents, the first region is disadvantageous for combined treatment with hydrogen peroxide.

Therefore, from the above state, ozone treatment alone and (03+H
2O2) Experimental results of simultaneous combined treatment: In order to utilize the oxidizing power of the OH radical reaction, the decomposition rate of the TOC component in the second region was determined. After the first region in which the hue disappears (contact time of 40 to 60 minutes under experimental conditions), a two-stage treatment method was conducted in which H2O2 was added and ozone treatment was performed. FIG. 7 shows the change in exhaust ozone concentration during two-stage treatment with Os + (034H2H2).

0 to confirm the pH dependence of the coefficient. I N -Na
Oh.

The pH of the sample water was changed by 0, IN-IC. In both the first region and the second region, in the pH circle of the experimental range, the value increases as it moves to alkali 111. This phenomenon is remarkable in the - region. This is thought to be due to the improvement in solubility due to the pH of the amic acid solution or the improvement in the self-decomposition rate of ozone on the alkali side. As shown in Table 2, when compared with
%nOpened 58-55088 (5) and improved by 25%.

However, almost complete decomposition was not possible, as was the case with secondary treated water from a certain sewage treatment plant.

Also, an interesting result is that in the batch experiment, H2O2 was 0.
T for 10 to 20 minutes immediately before and after reacting with 3 and disappearing.
A sharp drop in OC of 20-30% was observed. This is 10. 03 for TOC, as found in the results of a certain sewage treatment plant regarding the relationship between the injection amount of H2O2 and TOC-Oa.
This seems to suggest that there is an optimal injection point for H2O2 and H2O2.

The above was an experiment regarding batch processing, but this was
Further continuous processing experiments were conducted using the equipment shown in the figure.

The continuous processing experimental equipment shown in Figure 112 is a small-scale experimental equipment manufactured by Nippon Steel.
x 2000, t)), a water supply port 21 is provided above the reactor, and sample water and H2O2 are supplied from the sample water tank 22 and H2O2 storage tank 23, respectively, through the water supply 0211 by pumps 24 and 25, respectively, to a predetermined amount. Continuously supplied to achieve the desired concentration. Further, from an air supply port 26 provided below the reactor chamber, air is pumped by an air pump 27 and is blown into the ozonized air after being converted into ozonized air by an ozone generator. After some of this ozonized air reacts with the sample water in the reactor 1, it is exhausted through an exhaust port installed above the crosspiece bh reactor 1, and the ozone concentration meter J measures the exhaust ozone concentration. After adsorbing ozone in the activated carbon tower 31, it is released into the atmosphere. In addition, the treated sample water flows from the drain port 32 provided below the reactor 1 to the communication pipe 33.
The treated water is continuously discharged through the tank 34.

The method of each continuous treatment experiment will be explained below.

(1) Ozone treatment experiment The results of the batch experiment show that in the ozone treatment of amino acid, the reaction is instantaneous until the decolorization is completed (TOC removal rate is 5%, so it is removed by the ozone supply capacity of the reactor). It is thought that the effect will be different.

In continuous experiments, the humic acid concentration in raw water was approximately 20! ”22, and considering 20 l/J x 05 113q-03/ノ~4861%l-03
/i (Experimented in D range.

For TOC removal rate and reaction equivalent, the amount of ozone injected,
Regardless of changes in treatment conditions such as residence time of treated water, all experiments (test numbers 1゜2, 3, 4, 5,
6, 12, 17, 18, 19) average raw water T
The average removal rate for OC concentration No. 184 was 46%, which was in good agreement with the batch method results.

The theoretical equivalent was slightly higher than 8.

+21 Similarly, in the same simultaneous treatment experiment with ozone and hydrogen peroxide, the ozone injection amount was changed to the same as in the total ozone treatment, and the hydrogen peroxide injection amount was kept constant at 175 gf-HzO2/J. Exam number 7, 8
．． It is 9. On the contrary, test numbers 10 and 11 were conducted in which the amount of ozone injection was kept constant and the amount of hydrogen peroxide injection was varied.

Regarding the TOC removal rate and reaction equivalent, the average TOC removal rate was 2% halo, which was 16% improved compared to 46% when treated with ozone alone.

Regarding the reaction equivalents, FIGS. 8 and 9 showed good agreement.

(3) Regarding the two-stage treatment in combination with ozone and (ozone + hydrogen peroxide), as described in the batch experiment, the first region where the decolorization reaction is completed can be treated with ozone alone to remove TOC components. Therefore, a two-stage process was carried out in which the first region was treated with ozone alone, and then treated with (03+H2O2) in combination.

In terms of TOC removal rate and reaction equivalent, test number 13°14
．． 15 [These are the results when the amount of hydrogen peroxide injected was varied while the amount of ozone injected was kept constant for treated water subjected to ozone treatment alone.

There seems to be an optimal point for

Test numbers 20 and 21 for treated water residence time.

22 shows the results of changing the residence time of treated water while keeping the ozone injection amount and hydrogen peroxide injection amount as similar as possible in order to confirm the residence time of treated water during the two-stage treatment. T.O.
Looking at the C removal rate, it remains unchanged at 34% at 29 minutes and 62 minutes, but sharply decreases to 9% at 16 minutes.

Even in the case of two-stage treatment, the TOC removal reaction in the second region is slow;
A residence time of about 0 minutes or more and about 60 minutes is required O Based on the above results, a comparison of the combined treatment method and the two-stage treatment method is shown in Table 4, which shows that the amount of hydrogen peroxide injected can be significantly reduced.

Table 4 Comparison of combined treatment method and two-stage treatment method The present invention removes precursors as described above, but the trihalomethane removal effect, which is the original objective of the method of the present invention, is as follows. .

Results of trihalomethane/formation ability comparison experiment (1) Experimental method and contents Many reports have revealed that corrosive substances such as amine acids and fulvic acids are precursors of trihalomethane. We investigated changes in the trihalomethane production ability of nine samples treated by ozone treatment and two-stage treatment using ozone and hydrogen peroxide.

A humic acid solution with a TOC concentration of 184 was used as the stock solution (a solution prepared from a humic acid reagent was diluted with activated carbon-dechlorinated tap water), and the following four types of sample water were used for chlorination. Prepared OAI ozone-only treated water stock solution t? Treated with ozone for 60 minutes.

(Injected ozone concentration 241-air, amount of injected ozonized air 587-1) 2-stage ozone + (ozone 10 hydrogen peroxide) combined 2-stage treated water AI water with 124 μg of hydrogen peroxide added treated with ozone for 60 minutes.

I63 Assuming that the TOC removal rate of ozonated water diluted twice as much as the stock solution is approximately 50%,
Diluted to match TOC concentration during chlorination.

44 Sodium hypochlorite was added to each sample water for blank test as water for diluting tap water so that the chlorine concentration was 100 ■-age/no, and then 0. lN-H2SO4
The pH was adjusted to 7.0 using the following method, and the solution was sealed in a sealed glass container and left for 70 hours in a constant temperature ellipse at 20 R. After being drained, the amount of total trihalomethane produced was measured by gas chromatography using an overhead space method.

(2) Results The results of the experiment were as shown in Table 5. The effects of the ozone treatment alone or the two-stage treatment in combination with ozone (deca hydrogen peroxide) are shown in (1) TOC component reduction effect (2) Reduction in the trihalomethane conversion rate of the residual TOC component (-21 points).

Table 6 Regarding the changes in the amount of produced loroform according to each treatment method, that is, in terms of
34.2% of TOC was removed, and the amount of produced loloform was reduced by 85.3% compared to the original solution. Furthermore, by (ozonation and hydrogen peroxide) treatment, 72.8% of TOC was removed, and the amount of produced loloform was 95%. The amount of produced loroform was reduced to about 1/7 even with the ozone treatment alone, which reduced the amount by .8%.

Regarding (2), as shown in Table 7, when comparing the reduction in residual TOC and the chloroform conversion rate of TOC, it is 424 μg compared to the undiluted solution. TOC, 65 μV, 1/7 of the two-stage treated water using the method of the present invention (ozone + hydrogen peroxide)
It became Ichiga χ.

TOC remaining without being removed by the ozone treatment and the two-stage treatment (ozone + hydrogen peroxide) of the present invention
The ingredients are chemically stable, and the ability to generate trihalogen-10 methane is significantly reduced by chlorination. However, a two-stage treatment method using ozone and hydrogen peroxide in combination is effective as a method for removing 7-minic acid as a precursor for trihalomethane production, and has the effect of reducing TOC components and chemically stabilizing residual TOC components. It is extremely effective in preventing the production of trihalomethane in terms of both gender and performance.

[Brief explanation of the drawing]

Figure 1 is the layout of the batch-type experimental equipment, and Figure 2 is the layout of the continuous-type experimental equipment. Figure 3 is a graph showing the change in ozone concentration at the reactor outlet in the batch experiment, Figure 4 is a graph showing the change in TOC of the 7 minic acid solution during ozone treatment, and Figure 5 is the graph showing the change in TOC of the 7 minic acid solution during ozone treatment and 03 + (H2O2 + Oa ) Graph showing TOC concentration versus consumed ozone amount during combined two-stage treatment, No. 6
The figure is a graph showing the change in exhaust ozone concentration during simultaneous treatment of (Oa + H2O2).
Figure @8 is a graph showing the change in exhaust ozone concentration during two-stage combined treatment with (03 + H2O2), a graph showing the case where the H2O2 concentration is constant (75 products) and the amount of 03 changes in the case of simultaneous treatment with (03 + H2O2). FIG. 9 is a graph showing the change in H2O2 concentration in the case of (03+H2O3) combination sowing treatment. Patent applicant Suido Kiko Co., Ltd. Figure 3 Figure 4 +'> Key ε - Frame depth ♂

Claims (1)

[Claims] When organic substances such as amino acids mixed in water are oxidatively decomposed using ozone and hydrogen peroxide, oxidative decomposition is performed by ozone alone in the early stage of the catalytic reaction, that is, in the first reaction region, and in the first stage when the reaction stagnates. 1 reaction region, the decomposition reaction is promoted by adding all hydrogen peroxide to ozone, and the injected oxidizing agent of ozone and hydrogen peroxide is efficiently utilized. Decomposition treatment method for precursors of organic chlorine compounds such as acids O