JP6841721B2 - Water treatment system - Google Patents

Description

The present invention relates to a water treatment system and a water treatment method, and more particularly to a water treatment system and a water treatment method that can be suitably used in a water purification plant or the like.

Conventionally, as a water treatment process used in water purification plants and the like, advanced water treatment in which the water to be treated is coagulated with a coagulant and then the water to be treated is further oxidized with ozone. The process is known (see, for example, Patent Document 1). In such an advanced water treatment process, organic substances can be removed by coagulation treatment using a coagulant, so that it is possible to suppress the generation of trihalomethane when the obtained treated water is chlorinated. .. Further, since the odorous substance can be oxidatively decomposed by the oxidative treatment using ozone, the treated water with the reduced odorous substance can be obtained.

Then, in Patent Document 1, after the aggregation treatment is performed at pH 4 to 6, the oxidation rate of the odorous substance in the oxidation treatment is improved by performing the oxidation treatment using ozone while maintaining the pH at 4 to 6. ing.

Japanese Unexamined Patent Publication No. 2000-237772

However, there is room for improvement in the above-mentioned conventional advanced water treatment process in that odorous substances in the water to be treated are removed more efficiently.

Therefore, the present invention is to be treated in a water treatment system and a water treatment method in which the water to be treated is coagulated with a coagulant and then the water to be treated is subjected to an oxidation treatment using ozone. The purpose is to make it possible to efficiently remove odorous substances in water.

An object of the present invention is to solve the above problems advantageously, and the water treatment system of the present invention is a coagulation treatment apparatus that coagulates water to be treated with a coagulant to obtain coagulation-treated water. A water treatment system including an ozone oxidation treatment device for oxidizing an odorous substance in the coagulation-treated water using ozone, and water flowing into the ozone oxidation treatment device and water flowing in the ozone oxidation treatment device. It is further provided with an alkali adding device for adding alkali to at least one of them. In this way, if an alkali adding device for adding alkali to the water flowing into the ozone oxidation treatment device and / or the water flowing in the ozone oxidation treatment device is provided, the pH is raised by adding alkali as compared with the case of coagulation treatment. Oxidation treatment using ozone can be performed in this state to efficiently remove odorous substances.

Here, in the water treatment system of the present invention, the ozone oxidation treatment device includes a plurality of ozone contact portions connected in series, and the alkali addition device is the nth from the upstream side in the water flow direction (provided that the water treatment device is nth from the upstream side. , N is an integer of 2 or more), and it is preferable to add alkali to the water flowing in the ozone contact portion. If the ozone contact portion to which the alkali is added is the second or later from the upstream side, the efficiency of removing odorous substances can be improved while suppressing the generation of bromate ions when the oxidation treatment using ozone is performed. Because it can be done.

In the water treatment system of the present invention, the ozone oxidation treatment device is connected to a plurality of ozone contact portions connected in series and is nth from the upstream side in the water flow direction (however, n is an integer of 2 or more). It is equipped with an oxidant addition mechanism that adds hydrogen peroxide to the water flowing in the ozone contact portion of the above, and the alkali addition device is used for the water flowing in the ozone contact portion after the ozone contact portion to which the hydrogen peroxide is added. On the other hand, it is preferable to add alkali. This is because if an oxidizing agent addition mechanism for adding hydrogen peroxide to the water flowing in the ozone contact portion is provided, odorous substances can be removed more efficiently by the advanced oxidation process (AOP). .. Further, when the normal oxidation treatment in which hydrogen peroxide is not added and the oxidation treatment in which hydrogen peroxide is added (AOP) are carried out in combination, the ozone contact portion to which the alkali is added is the ozone contact portion to which AOP is carried out. This is because the efficiency of removing odorous substances can be improved while suppressing the production of bromate ions by the reduction reaction derived from hydrogen peroxide.

Further, the present invention aims to advantageously solve the above problems, and the water treatment method of the present invention uses a flocculant to coagulate the water to be treated at the first pH to coagulate. A second step in which the ozone oxidation treatment step is higher than the first pH, including a coagulation treatment step for obtaining treated water and an ozone oxidation treatment step for oxidizing an odorous substance in the coagulation treatment water using ozone. It is characterized by including a step of performing an oxidation treatment using ozone at pH. As described above, if the ozone oxidation treatment step including the step of performing the oxidation treatment using ozone at the second pH higher than the first pH at the time of the aggregation treatment is carried out, the pH is raised as compared with the time of the aggregation treatment. Oxidation treatment using ozone can be performed in this state to efficiently remove odorous substances.

Here, in the water treatment method of the present invention, the ozone oxidation treatment step includes a first step of performing an oxidation treatment using ozone at a pH lower than the second pH, and a second step after the first step. It is preferable to include a second step of performing an oxidation treatment using ozone at the pH of. If the second step of performing the oxidation treatment at a second pH is carried out after the first step of performing the oxidation treatment at a pH lower than the second pH, the generation of bromate ions during the ozone oxidation treatment step is suppressed. This is because the efficiency of removing odorous substances can be improved.

Further, in the water treatment method of the present invention, it is preferable that the second step is an accelerated oxidation step in which an oxidation treatment using ozone is performed in the presence of hydrogen peroxide. This is because if the second step is an accelerated oxidation step, odorous substances can be removed more efficiently by an advanced oxidation process (AOP). Further, when the first step of performing the oxidation treatment at a pH lower than the second pH and the second step of performing the oxidation treatment at the second pH are carried out in combination, the second step is referred to as the accelerated oxidation step. For example, it is possible to improve the efficiency of removing odorous substances while suppressing the production of bromine ions by the reduction reaction derived from hydrogen peroxide.

Further, in the water treatment method of the present invention, the first pH is preferably 6.8 or less. When the first pH is 6.8 or less, the efficiency of removing organic substances in the coagulation treatment step can be improved, and the amount of inorganic carbon (IC) in the coagulation treatment water can be reduced to reduce the amount of inorganic carbon (IC) in the coagulation treatment step. This is because the oxidation treatment efficiency can be improved and the removal efficiency of odorous substances can be further improved.

In the water treatment method of the present invention, the second pH is preferably 7.0 or more and 7.5 or less. This is because when the second pH is 7.0 or more, the efficiency of removing odorous substances can be further improved. Further, when the second pH is 7.5 or less, it is possible to sufficiently suppress the generation of bromate ions during the ozone oxidation treatment step.

According to the water treatment system and the water treatment method of the present invention, odorous substances in the water to be treated can be efficiently removed.

It is explanatory drawing which shows the schematic structure of an example of the water treatment system according to this invention. It is explanatory drawing which shows the schematic structure of another example of the water treatment system according to this invention. It is explanatory drawing which shows the modification of the ozone oxidation treatment apparatus which can be used in the water treatment system according to this invention. It is a graph which shows the relationship between the oxidation treatment time and the odor substance concentration in water at the time of treating river water in an Example and a comparative example. It is a graph which shows the relationship between the oxidation treatment time and the bromate ion concentration in water at the time of treating river water in an Example and a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, those having the same reference numerals indicate the same components.

(Water treatment system)
The water treatment system of the present invention is not particularly limited, and can be suitably used when performing advanced treatment of water, for example, in a water purification plant or the like.

Here, FIG. 1 shows a schematic configuration of an example of the water treatment system of the present invention. The water treatment system 100 shown in FIG. 1 is provided after the coagulation treatment device 10 into which the water to be treated flows, the sand filtration device 20 arbitrarily provided after the coagulation treatment device 10, and the sand filtration device 20. The ozone oxidation treatment device 30 and an alkali addition device 40 for adding alkali to the water flowing in the ozone oxidation treatment device 30 are provided.

Then, in the water treatment system 100, without particular limitation, for example, river water, dam lake water, lake water or groundwater, or pretreatment of them (for example, sand filtration for removing impurities, organic substances, etc. Pre-treated water (such as biooxidation treatment to remove ammoniacal nitrogen) is treated as water to be treated. Further, the treated water obtained by the water treatment system 100 can be arbitrarily post-treated (for example, activated carbon treatment, high-speed sand filtration, chlorination, etc.) and then supplied to, for example, a water supply.

Here, the coagulation treatment device 10 of the water treatment system 100 shown in FIG. 1 is a device that coagulates the water to be treated with a coagulant to obtain the coagulation-treated water, and mixes the water to be treated and the coagulant. A stirring tank 11 and a settling tank 12 for precipitating the produced aggregates (flocks) are provided. Further, the stirring tank 11 includes a stirrer 13 and a coagulant addition mechanism 14 for adding a coagulant such as polyaluminum chloride (PAC), and arbitrarily adjusts the pH of the water to be treated to be coagulated. A pH adjuster addition mechanism 15 for adding a pH adjuster (for example, sulfuric acid, sodium hydroxide, etc.) for adjusting is further provided.
The stirring tank 11 of the coagulation treatment device 10 may be composed of a rapid stirring tank and a slow speed stirring tank.

Further, the sand filtration device 20 is a device that removes flocs and the like remaining in the coagulation-treated water flowing out from the coagulation treatment device 10 by sand filtration to obtain coagulation-treated water from which the flocs and the like have been removed.

The ozone oxidation treatment device 30 is a device that uses ozone to oxidize an odorous substance contained in coagulation-treated water. In the ozone oxidation treatment apparatus 30, organic substances other than odorous substances contained in the coagulation-treated water can also be oxidized. Further, the ozone oxidation treatment apparatus 30 can kill protozoans and the like contained in the coagulation-treated water.

Here, a plurality of ozone oxidation treatment devices 30 are installed in the water tank 38 through which the coagulation-treated water flowing out from the sand filtration device 20 flows, and from the upstream side (the side in which the coagulation-treated water flows in) in the water tank 38. It is provided with a partition wall 31 as an extruded flow that bypasses the flow of water flowing to the downstream side (the side from which the treated water flows out) up and down. Further, the ozone oxidation treatment device 30 is provided between the inner wall of the water tank 38 (the inner wall on the left side in the illustrated example) and the partition wall 31 located above the water tank 38 (the partition wall 31 that does not extend to the bottom surface of the water tank 38) and in the water tank. Ozone aeration devices 35, 36, 37 that aerate ozone are provided at the bottoms of a plurality of (three in the illustrated example) ozone contact portions 32, 33, 34 formed between the partition walls 31 located on the upper side of the 38. ing. That is, the ozone oxidation treatment device 30 has a plurality of (three in the illustrated example) ozone contact portions 32, 33, 34 connected in series in the water tank 38.

The alkali adding device 40 is a device that adds an alkali (for example, sodium hydroxide or the like) to the water flowing in the ozone oxidation treatment device 30. Specifically, in the water treatment system 100 shown in FIG. 1, the alkali addition device 40 is the nth ozone contact portion (where n is an integer of 2 or more) from the upstream side when viewed in the water flow direction (illustrated example). Then, alkali is added to the water flowing in the ozone contact portion 33) second from the upstream side.

Then, in the water treatment system 100 shown in FIG. 1, the water to be treated can be coagulated in the coagulation treatment apparatus 10, and a part of the organic substance and the suspended substance contained in the water to be treated can be removed. It is possible to obtain treated water in which the concentration of suspended substances and the ability to produce trihalomethanes are reduced.

Further, in the water treatment system 100, since the odorous substance in the coagulation-treated water can be oxidized by using ozone in the ozone oxidation treatment device 30, it is possible to obtain the treated water in which the odorous substance is reduced. Further, in the water treatment system 100, organic substances other than odorous substances, protozoans and the like can be reduced by the oxidation treatment using ozone. Then, in the water treatment system 100, in particular, the alkali addition device 40 adds alkali to the water flowing in the ozone oxidation treatment device, and the oxidation treatment using ozone is performed in a state where the pH of the water to be oxidized is raised. Since it can be carried out, the oxidative decomposition of the odorous substance can be promoted, and the odorous substance can be efficiently removed.

Furthermore, when water containing bromide ions is oxidized with ozone, bromate ions are likely to be generated particularly under high pH conditions. However, in the water treatment system 100, since the ozone contact portion to which the alkali is added is the second or later ozone contact portion from the upstream side (in the illustrated example, the ozone contact portion 33 is the second from the upstream side), the aggregation flowing into the ozone oxidation treatment apparatus 30 It is possible to suppress the generation of bromate ions as compared with the case where an alkali is added to the treated water or the water flowing in the first ozone contact portion and the oxidation treatment is performed for a long time under high pH conditions. Therefore, according to the water treatment system 100, it is possible to improve the efficiency of removing odorous substances as compared with the case where no alkali is added, while suppressing the generation of bromate ions.

Next, FIG. 2 shows a schematic configuration of another example of the water treatment system of the present invention. The water treatment system 100A shown in FIG. 2 is provided with an oxidizing agent addition mechanism 50 that adds _{hydrogen peroxide (H 2} O ₂ ) to the water flowing in the ozone contact portion of the ozone oxidation treatment device 30. The alkali adding device 40 has the same configuration as the water treatment system 100 shown in FIG. 1 except that the alkali adding device 40 adds alkali to the water flowing in the ozone contact portion after the ozone contact portion to which hydrogen peroxide is added. There is.
In the following, description of the same configuration as the water treatment system 100 shown in FIG. 1 will be omitted.

Here, the oxidizing agent addition mechanism 50 adds hydrogen peroxide to the water flowing in the ozone contact portion, and promotes oxidation in the ozone contact portion to which the hydrogen peroxide is added and the ozone contact portion located downstream of the hydrogen peroxide contact portion. It is a device for performing processing (AOP). Then, in the water treatment system 100A shown in FIG. 2, the oxidizing agent addition mechanism 50 is the nth ozone contact portion (where n is an integer of 2 or more) from the upstream side when viewed in the water flow direction (upstream in the illustrated example). Hydrogen peroxide is added to the water flowing in the ozone contact portion 34) third from the side.

Further, the alkali adding device 40 adds alkali to the water flowing in the ozone contact portion 34 to which hydrogen peroxide is added by the oxidizing agent adding mechanism 50.

Then, in the water treatment system 100A, as in the water treatment system 100, it is possible to obtain treated water having a reduced suspension substance concentration and trihalomethane production ability.

Further, in the water treatment system 100A, the ozone oxidation treatment apparatus 30 can perform accelerated oxidation treatment (AOP) on the odorous substance in the coagulation-treated water, so that the oxidative decomposition of the odorous substance can be further promoted and the odorous substance can be made more efficient. Can be removed. In the ozone oxidation treatment apparatus 30 of the water treatment system 100A, organic substances other than odorous substances and protozoans contained in the coagulation-treated water can also be subjected to accelerated oxidation treatment.

Further, in the water treatment system 100A, since the alkali is added to the ozone contact portion where AOP is carried out by the alkali adding device 40, the effect of improving the efficiency of removing odorous substances by performing the oxidation treatment in a state where the pH is raised is obtained. At the same time, the production of bromate ions can be suppressed by the reduction reaction derived from hydrogen peroxide.

Although the water treatment system of the present invention has been described above with reference to one example and other examples, the water treatment system of the present invention is not limited to the above-mentioned one example and other examples.

Specifically, in the water treatment systems of the above-mentioned example and other examples, the alkali addition device adds alkali to the water flowing in the ozone oxidation treatment device, but in the water treatment system of the present invention, it flows into the ozone oxidation treatment device. Alkali may be added to the water to be treated (coagulation-treated water), or alkali may be added to both the water flowing into the ozone oxidation treatment device and the water flowing in the ozone oxidation treatment device. Further, the alkali adding device may add alkali to a plurality of places in a plurality of stages.

Further, in the water treatment systems of the above-mentioned example and the other examples, an ozone oxidation treatment device having a plurality of ozone contact portions formed by partition walls was used, but the ozone oxidation treatment device of the water treatment system of the present invention is used. It may have only one ozone contact portion, or as shown in FIG. 3, a plurality of ozone aeration devices 35, 36, 37 are watered in one water tank 38 in which the coagulated treated water flows in an extruded flow. The ozone oxidation treatment device 30B may have a plurality of ozone contact portions 32, 33, 34 formed by arranging the ozone contact portions 32, 33, 34 apart from each other in the flow direction of the ozone. Further, the ozone oxidation treatment apparatus may be formed by connecting a plurality of ozone contact portions made of a water tank provided with an ozone aeration apparatus in series.

Further, in the water treatment system of the other example described above, the oxidant addition mechanism 50 adds hydrogen peroxide only to the water flowing in the ozone contact portion 34, but in the water treatment system of the present invention, the oxidant addition mechanism May add hydrogen peroxide to a plurality of locations. When hydrogen peroxide is added to a plurality of locations, the alkali adding device is used for the water flowing in the ozone contact portion after the ozone contact portion located on the most upstream side of the ozone contact portions to which hydrogen peroxide is added. It is preferable to add alkali.

(Water treatment method)
The water treatment method of the present invention is not particularly limited, and can be suitably used when performing advanced treatment of water, for example, in a water purification plant or the like. The water treatment method of the present invention is not particularly limited, and can be suitably used, for example, when continuously treating the water to be treated by using the water treatment system of the present invention described above.
The water treatment method of the present invention may be used when treating water to be treated by using a batch type water treatment apparatus.

Here, in the water treatment method of the present invention, a coagulant is used, and ozone is used after the coagulation treatment step of coagulating the water to be treated at the first pH to obtain the coagulation-treated water and the coagulation treatment step. Coagulation treatment Includes an ozone oxidation treatment step of oxidizing odorous substances in water. Further, an example of the water treatment method of the present invention requires that the ozone oxidation treatment step includes a step of performing an oxidation treatment using ozone at a second pH higher than the first pH.

Examples of the water to be treated by the water treatment method of the present invention include those similar to those exemplified as the water to be treated in the water treatment system described above. In addition, the treated water obtained by the water treatment method of the present invention can be arbitrarily post-treated (for example, activated carbon treatment, high-speed sand filtration, chlorination, etc.) and then supplied to, for example, a water supply.

Then, in the coagulation treatment step, the water to be treated and the coagulant (for example, PAC) are mixed at the first pH while adding a pH adjuster (for example, sulfuric acid, sodium hydroxide, etc.) as necessary. Aggregates suspended substances and the like contained in the water to be treated. The produced aggregates (flocks) can be separated by using a known method such as precipitation or filtration.

In this way, if the water to be treated is coagulated in the coagulation treatment step, a part of the organic substances and the suspended substances contained in the water to be treated can be removed, so that the suspended substance concentration and the trihalomethane production ability can be removed. Can be obtained with reduced treatment water.

The lower limit of the first pH is preferably 5.0 or more, more preferably 5.5 or more, further preferably 6.0 or more, and the upper limit is 6. It is preferably 8 or less, more preferably 6.5 or less, and even more preferably 6.3 or less. When the first pH is at least the above lower limit value, the labor and cost required for neutralizing the treated water obtained by using the water treatment method of the present invention can be reduced. Further, when the first pH is not more than the above upper limit value, the charge neutralizing power of the coagulant can be increased, the removal efficiency of organic substances can be improved, and the amount of inorganic carbon (IC) in the coagulation-treated water can be improved. It is possible to improve the oxidation treatment efficiency in the ozone oxidation treatment step and further improve the removal efficiency of odorous substances.

Further, in the ozone oxidation treatment step of oxidizing the odorous substance in the coagulation-treated water using ozone, the coagulation-treated water and ozone are brought into contact with each other by using a known method such as aeration, and the odorous substance in the coagulation-treated water is oxidized. To do. In the ozone oxidation treatment step, organic substances and the like contained in the coagulation-treated water can also be oxidized. Further, in the ozone oxidation treatment step, protozoans and the like contained in the coagulation-treated water can be killed.

Then, in the ozone oxidation treatment step, it is necessary to carry out the step of performing the oxidation treatment using ozone at a second pH higher than the first pH, and ozone is used at a pH lower than the second pH. It is preferable to carry out the first step of performing the oxidation treatment and the second step of performing the oxidation treatment using ozone at the second pH after the first step.

In this way, if the step of performing the oxidation treatment using ozone at the second pH higher than the first pH is carried out, the organic substance is efficiently removed at the relatively low first pH in the coagulation treatment step. On the other hand, in the ozone oxidation treatment step, the odorous substance can be efficiently removed by promoting the oxidative decomposition of the odorous substance in a state where the pH is raised by, for example, addition of an alkali.

Further, when water containing bromide ions is oxidized with ozone, bromate ions are likely to be generated particularly under high pH conditions. However, if the second step of performing the oxidation treatment using ozone at the second pH is carried out after the first step of performing the oxidation treatment using ozone at a pH lower than the second pH, the ozone oxidation treatment step It is possible to suppress the formation of bromate ions as compared with the case where the oxidation treatment is performed at the second pH from the beginning. Therefore, the efficiency of removing odorous substances is improved as compared with the case where the pH is not raised to the second pH, which is higher than the pH (first pH) of the coagulation treatment step, while suppressing the production of bromate ions. Can be done.

The method for adjusting the pH of the water to be oxidized during the ozone oxidation treatment step is not particularly limited, and examples thereof include the following methods. That is, in a continuous water treatment system such as the water treatment system shown in FIGS. 1 and 2, an alkali or the like is used at a predetermined position in the water flow direction with respect to the oxidation-treated water flowing in the water treatment system. A method of adding a pH adjuster can be mentioned. Further, in a batch type water treatment system in which the ozone oxidation treatment step is performed in a single water tank, a method of adding a pH adjuster such as alkali to the water tank at a predetermined timing after the start of the ozone oxidation treatment step can be mentioned. ..

In the water treatment method of the present invention, the lower limit of the second pH is preferably 6.5 or more, more preferably 7.0 or more, and the upper limit is 8.0 or less. It is preferably present, and more preferably 7.5 or less. When the second pH is at least the above lower limit value, the oxidative decomposition of the odorous substance can be sufficiently promoted, and the efficiency of removing the odorous substance can be further improved. Further, when the second pH is not more than the above upper limit value, it is possible to sufficiently suppress the generation of bromate ions during the ozone oxidation treatment step.
When the first step and the second step are carried out in the ozone oxidation treatment step, the pH of the first step is not particularly limited, but is usually equal to or higher than the first pH, and is subject to the aggregation treatment step. It is preferable that the pH of the treated water is the same as that obtained by coagulating the treated water and separating the produced agglomerates using a known method such as precipitation or filtration.

Further, in the water treatment method of the present invention, when the first step and the second step are carried out in the ozone oxidation treatment step, the second step is an accelerated oxidation step in which the oxidation treatment using ozone is carried out in the presence of hydrogen peroxide. You can also do it. If the second step is an accelerated oxidation step, the reduction reaction derived from hydrogen peroxide is carried out while obtaining the effect of improving the removal efficiency of odorous substances by performing the oxidation treatment in a state where the pH is raised to the second pH. The production of bromate ions can be suppressed. In addition, the accelerated oxidation treatment (AOP) can further promote the oxidative decomposition of the odorous substance, and the odorous substance can be removed more efficiently.

Although the water treatment method of the present invention has been described above, the water treatment method of the present invention is not limited to the above-mentioned contents.
Specifically, in the ozone oxidation treatment step of the water treatment method of the present invention, in addition to the first step and the second step, one or more oxidation treatments are performed at a pH other than the pH of the first step and the second pH. It may further include steps. Further, the ozone oxidation treatment step of the water treatment method of the present invention may further include a step of performing accelerated oxidation treatment at a pH other than the second pH after the second step.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
<Coagulation treatment process>
Sulfuric acid as a pH adjuster was added to river water (TOC: 3.2 mg / L, bromide ion concentration: 0.2 mg / L) as the water to be treated that was put into the batch type reaction tank, and the pH was adjusted to 6. The pH was adjusted to 0.0 (first pH). Then, under the condition of a temperature of 25 ° C., PAC as a coagulant was added so that the injection rate was 50 mg / L, and the mixture was rapidly stirred at 150 rpm for 2 minutes and then slowly stirred at 50 rpm for 10 minutes to coagulate river water. Processing was performed. Then, the produced agglomerates were removed by precipitation to obtain agglomeration-treated water.
<Ozonolysis process>
13 L of the obtained coagulation-treated water was put into a reaction vessel, and ozone was aerated in the reaction vessel for 12 minutes under the condition of a temperature of 25 ° C. During aeration, sodium hydroxide as an alkali was added into the reaction vessel to adjust the pH to 6.5 (second pH).
Then, with respect to the water in the reaction vessel, the time-dependent change in the odorous substance concentration was measured by gas chromatography, and the time-dependent change in the bromate ion concentration was measured by ion chromatography. The measurement results are shown in FIGS. 4 and 5, respectively.

(Example 2)
The coagulation treatment step and the ozone oxidation treatment step were carried out in the same manner as in Example 1 except that the pH was adjusted to 7.0 in the ozone oxidation treatment step, and the river water was treated. Moreover, the time-dependent change of the odorant substance concentration and the time-dependent change of the bromate ion concentration were measured in the same manner as in Example 1. The measurement results are shown in FIGS. 4 and 5, respectively.

(Example 3)
The coagulation treatment step and the ozone oxidation treatment step were carried out in the same manner as in Example 1 except that the pH was adjusted to 8.0 in the ozone oxidation treatment step, and the river water was treated. Moreover, the time-dependent change of the odorant substance concentration and the time-dependent change of the bromate ion concentration were measured in the same manner as in Example 1. The measurement results are shown in FIGS. 4 and 5, respectively.

(Example 4)
In the ozone oxidation treatment step, sodium hydroxide is not added for the first 6 minutes, ozone is aerated at pH 6.0 (first step), and sodium hydroxide as an alkali is placed in the reaction vessel 6 minutes after the start of aeration. The river water was treated by performing a coagulation treatment step and an ozone oxidation treatment step in the same manner as in Example 1 except that the mixture was added and ozone was aerated for another 6 minutes at pH 7.0 (second step). Moreover, the time-dependent change of the odorant substance concentration and the time-dependent change of the bromate ion concentration were measured in the same manner as in Example 1. The measurement results are shown in FIGS. 4 and 5, respectively.

(Example 5)
In the ozone oxidation treatment step, sodium hydroxide was not added for the first 6 minutes, ozone was aerated at pH 6.0 (first step), and 6 minutes after the start of aeration, sodium hydroxide as an alkali and as an oxidizing agent were used. Hydrogen peroxide was added into the reaction vessel, and ozone was exposed to ozone for another 6 minutes at pH 7.0 (second step; accelerated oxidation step), and the coagulation treatment step and ozone oxidation treatment step were carried out in the same manner as in Example 1. , Treated river water. Moreover, the time-dependent change of the odorant substance concentration and the time-dependent change of the bromate ion concentration were measured in the same manner as in Example 1. The measurement results are shown in FIGS. 4 and 5, respectively.

(Comparison example)
In the ozone oxidation treatment step, the coagulation treatment step and the ozone oxidation treatment were carried out in the same manner as in Example 1 except that sodium hydroxide was not added and ozone was aerated for 12 minutes at the same pH of 6.0 as the first pH of the coagulation treatment step. The process was carried out and the river water was treated. Moreover, the time-dependent change of the odorant substance concentration and the time-dependent change of the bromate ion concentration were measured in the same manner as in Example 1. The measurement results are shown in FIGS. 4 and 5, respectively.

From FIG. 4, it can be seen that in Examples 1 to 5, the odorous substances in the river water could be efficiently removed as compared with Comparative Example 1.
Further, from FIGS. 4 and 5, it can be seen that in Examples 4 and 5, the odorous substances in the river water could be efficiently removed while suppressing the production of bromate ions.

According to the water treatment system and the water treatment method of the present invention, odorous substances in the water to be treated can be efficiently removed.

10 Coagulation treatment device 11 Stirring tank 12 Sedimentation tank 13 Stirrer 14 Coagulant addition mechanism 15 pH adjuster addition mechanism 20 Sand filtration device 30, 30B Ozone oxidation treatment device 31 Partition wall 32, 33, 34 Ozone contact parts 35, 36, 37 Ozone aeration device 38 Water tank 40 Alkaline addition device 50 Oxidizing agent addition mechanism 100, 100A Water treatment system

Claims (2)

A coagulation treatment device that coagulates the water to be treated with a coagulant to obtain coagulation-treated water,
A water treatment system including an ozone oxidation treatment device that oxidizes an odorous substance in the coagulation-treated water using ozone.
Further comprising an alkali addition device for adding an alkali for the water flowing through the ozone oxidation processing apparatus,
The ozone oxidation treatment apparatus includes a plurality of ozone contact portions connected in series.
The alkali addition device, n-th from the upstream side as viewed in the flow direction of the water (where, n is an integer of 2 or more) you adding alkali to water flowing through the ozone contact portion of the water treatment system. A coagulation treatment device that coagulates the water to be treated with a coagulant to obtain coagulation-treated water,
A water treatment system including an ozone oxidation treatment device that oxidizes an odorous substance in the coagulation-treated water using ozone.
An alkali addition device for adding alkali to the water flowing in the ozone oxidation treatment device is further provided.
The ozone oxidation treatment device is used for a plurality of ozone contact portions connected in series and water flowing in the nth ozone contact portion (where n is an integer of 2 or more) from the upstream side in the water flow direction. Equipped with an oxidizing agent addition mechanism that adds hydrogen peroxide
A water treatment system in which the alkali adding device adds alkali to water flowing in the ozone contact portion after the ozone contact portion to which the hydrogen peroxide is added.

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