JP2018196844A - Water treatment system, and water treatment method - Google Patents

Abstract

To provide a water treatment system capable of efficiently removing an odorant in water to be treated.SOLUTION: The water treatment system comprising a flocculation treatment apparatus that carries out a flocculation treatment of water to be treated using a flocculant to obtain water subjected to a flocculation treatment, and an ozone oxidation treatment apparatus that oxidizes an odorant in the water subjected to a flocculation treatment using ozone, further comprises an alkali addition apparatus of adding an alkali to at least one of water flowing into the ozone oxidation treatment apparatus and water flowing through the ozone oxidation treatment apparatus.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment system and a water treatment method, and 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, etc., advanced water treatment in which water to be treated is agglomerated using a flocculant, and then the water to be treated subjected to agglomeration is further subjected to oxidation treatment using ozone. A process is known (see, for example, Patent Document 1). In such an advanced water treatment process, organic substances can be removed by coagulation using a coagulant, so that generation of trihalomethane can be suppressed when the obtained treated water is sterilized with chlorine. . Moreover, since the odorous substance can be oxidatively decomposed by the oxidation treatment using ozone, treated water with reduced odorous substance can be obtained.

  And in patent document 1, after performing an aggregation process by pH 4-6, the oxidation rate of the odor substance in an oxidation process is improved by performing the oxidation process using ozone in the state which maintained pH 4-6. ing.

JP 2000-237772 A

  However, the conventional advanced water treatment process has room for improvement in terms of more efficiently removing odorous substances in the water to be treated.

  Therefore, the present invention provides a water treatment system and a water treatment method in which water to be treated is agglomerated using a flocculant and then subjected to an oxidation treatment using ozone to the water to be treated which has been subjected to the agglomeration treatment. The object is to enable efficient removal of odorous substances in water.

  An object of the present invention is to advantageously solve the above-mentioned problems, and a water treatment system according to the present invention includes a flocculation treatment apparatus that flocculates water to be treated using a flocculant to obtain flocculated water. A water treatment system comprising an ozone oxidation treatment device that oxidizes odorous substances in the agglomerated treatment water using ozone, wherein water flows into the ozone oxidation treatment device and water flowing in the ozone oxidation treatment device It further comprises an alkali adding device for adding an alkali to at least one of them. In this way, if an alkali addition device for adding alkali to the water flowing into the ozone oxidation treatment device and / or the water flowing through the ozone oxidation treatment device is provided, the pH is raised more than that during the coagulation treatment by adding the alkali. In this state, it is possible to efficiently remove odorous substances by performing an oxidation treatment using ozone.

  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 nth from the upstream side in the flow direction of water (however, , N is an integer of 2 or more) It is preferable to add an alkali to the water flowing in the ozone contact portion. If the ozone contact part to which alkali is added is the second or later from the upstream side, it is possible to improve the removal efficiency of odorous substances while suppressing the formation of bromate ions when oxidation treatment using ozone is performed. Because you can.

  In the water treatment system of the present invention, the ozone oxidation treatment apparatus includes a plurality of ozone contact portions connected in series and the nth from the upstream side in the flow direction of water (where n is an integer of 2 or more). And an oxidant addition mechanism for adding hydrogen peroxide to water flowing in the ozone contact portion of the ozone contact portion, wherein the alkali addition device supplies 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 an alkali. This is because if an oxidant addition mechanism for adding hydrogen peroxide to water flowing in the ozone contact portion is provided, odorous substances can be more efficiently removed by an advanced oxidation process (AOP). . Further, when the normal oxidation treatment without adding hydrogen peroxide and the oxidation treatment (AOP) with addition of hydrogen peroxide are carried out in combination, the ozone contact portion to which alkali is added is replaced with the ozone contact portion for carrying out AOP. This is because the removal efficiency of 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-mentioned problems, and the water treatment method of the present invention uses a flocculant and agglomerates the treated water at a first pH. 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, wherein the ozone oxidation treatment step is higher than the first pH. It includes a step of performing an oxidation treatment using ozone at a pH. As described above, if the ozone oxidation treatment process 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 performed, the pH is increased as compared with the time of the aggregation treatment. In this state, it is possible to efficiently remove odorous substances by performing an oxidation treatment using ozone.

  Here, in the water treatment method of the present invention, the ozone oxidation treatment step includes an oxidation treatment using ozone at a pH lower than the second pH, and the second step after the first step. It is preferable to include a second step of performing an oxidation treatment using ozone at the pH. If the second step of oxidizing at the second pH is performed after the first step of oxidizing at a pH lower than the second pH, the formation of bromate ions is suppressed during the ozone oxidation process. This is because the odor substance removal efficiency can be improved.

  In the water treatment method of the present invention, the second step is preferably 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 more efficiently removed 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 carrying out the oxidation treatment at the second pH are performed in combination, the second step is referred to as an accelerated oxidation step. For example, it is possible to improve the removal efficiency of odorous substances while suppressing the production of bromate ions by the reduction reaction derived from hydrogen peroxide.

  Furthermore, in the water treatment method of the present invention, the first pH is preferably 6.8 or less. If the first pH is 6.8 or less, the organic substance removal efficiency 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 ozone oxidation treatment step. This is because the oxidation treatment efficiency can be improved and the odor substance removal efficiency 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 if the second pH is 7.0 or more, the removal efficiency of odorous substances can be further improved. Moreover, if the second pH is 7.5 or less, it is possible to sufficiently suppress the formation 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 schematic structure of an example of the water treatment system according to this invention. It is explanatory drawing which shows schematic structure of the other 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 for the water treatment system according to this invention. It is a graph which shows the relationship between the oxidation process time and the odor substance density | concentration in water at the time of processing river water in an Example and a comparative example. It is a graph which shows the relationship between the oxidation time at the time of processing river water in an Example and a comparative example, and the bromate ion concentration in water.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, what attached | subjected the same code | symbol shall show the same component.

(Water treatment system)
The water treatment system of the present invention is not particularly limited, and can be suitably used, for example, when performing advanced water treatment at 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. A water treatment system 100 shown in FIG. 1 is provided in a flocculation treatment device 10 into which water to be treated flows, a sand filtration device 20 arbitrarily provided in the subsequent stage of the flocculation treatment device 10, and a subsequent stage of the sand filtration device 20. An ozone oxidation treatment device 30 and an alkali addition device 40 for adding alkali to water flowing in the ozone oxidation treatment device 30 are provided.

  The water treatment system 100 is not particularly limited. For example, river water, dam lake water, lake water or ground water, or pretreatment thereof (for example, sand filtration for removing contaminants, organic substances, Pretreated water or the like formed by biological oxidation treatment for removing ammonia nitrogen is treated as water to be treated. In addition, the treated water obtained by the water treatment system 100 can be supplied to, for example, a water supply after being optionally subjected to post-treatment (for example, activated carbon treatment, high-speed sand filtration, chlorine disinfection, etc.).

Here, the coagulation treatment apparatus 10 of the water treatment system 100 shown in FIG. 1 is an apparatus for coagulating treated water using a coagulant to obtain coagulated treated water, and the treated water and the coagulant are mixed. A stirring tank 11 and a precipitation tank 12 for precipitating the produced aggregates (floc) are provided. The stirring tank 11 includes a stirrer 13 and a flocculant addition mechanism 14 for adding a flocculant such as polyaluminum chloride (PAC), for example. A pH adjuster addition mechanism 15 for adding a pH adjuster (for example, sulfuric acid, sodium hydroxide, etc.) for adjustment is further provided.
In addition, the stirring tank 11 of the aggregation treatment apparatus 10 may be configured by a rapid stirring tank and a slow stirring tank.

  The sand filtration device 20 is a device for obtaining flocculent treated water from which flocs and the like have been removed by removing flocs and the like remaining in the agglomerated water flowing out from the flocculating device 10 by sand filtration.

  The ozone oxidation treatment apparatus 30 is an apparatus that oxidizes odorous substances contained in the agglomerated treated water using ozone. In the ozone oxidation treatment apparatus 30, organic substances other than odorous substances contained in the agglomerated treated water can be oxidized. Moreover, in the ozone oxidation treatment apparatus 30, protozoa and the like contained in the agglomerated treated water can be killed.

  Here, the ozone oxidation treatment device 30 includes a water tank 38 through which the agglomerated treated water flowing out from the sand filtration device 20 flows, and a plurality of water tanks 38 installed in the water tank 38 from the upstream side (the side into which the agglomerated treated water flows). A partition wall 31 is provided as an extruding flow that bypasses the flow of water flowing to the downstream side (side from which treated water flows out) up and down. In addition, the ozone oxidation treatment apparatus 30 is provided between the inner wall of the water tank 38 (the left inner wall 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 the water tank. Ozone aeration devices 35, 36, and 37 for aeration of ozone are provided at the bottoms of a plurality (three in the illustrated example) of ozone contact portions 32, 33, and 34 formed between the partition walls 31 positioned above 38. ing. That is, the ozone oxidation treatment apparatus 30 has a plurality (three in the illustrated example) of ozone contact portions 32, 33, and 34 connected in series in the water tank 38.

  The alkali addition device 40 is a device that adds alkali (for example, sodium hydroxide) to 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 has an n-th ozone contact portion (where n is an integer of 2 or more) from the upstream side in the water flow direction (illustrated example). Then, alkali is added to the water flowing in the second ozone contact portion 33) from the upstream side.

  And in the water treatment system 100 shown in FIG. 1, since the to-be-treated water is agglomerated in the agglomeration treatment apparatus 10, a part of organic substances and suspended substances contained in the to-be-treated water can be removed. Treated water with reduced suspended matter concentration and trihalomethane formation ability can be obtained.

  Moreover, in the water treatment system 100, the ozone oxidation treatment apparatus 30 can oxidize the odorous substance in the coagulated treated water using ozone, so that treated water with reduced odorous substance can be obtained. In the water treatment system 100, organic substances other than odorous substances, protozoa, and the like can be reduced by oxidation treatment using ozone. And especially in the water treatment system 100, the alkali addition apparatus 40 adds an alkali with respect to the water which flows in an ozone oxidation treatment apparatus, and the oxidation process using ozone in the state which raised the pH of the water to be oxidized is carried out. Therefore, 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 conditions of high pH. However, in the water treatment system 100, the ozone contact portion to which alkali is added is the second or later from the upstream side (the second ozone contact portion 33 from the upstream side in the illustrated example), and therefore the agglomeration that flows into the ozone oxidation treatment apparatus 30. Compared with the case where alkali is added to the treated water and the water flowing in the first ozone contact portion and the oxidation treatment is performed for a long time under a high pH condition, generation of bromate ions can be suppressed. Therefore, according to the water treatment system 100, it is possible to improve the removal efficiency of odorous substances as compared with the case where no alkali is added while suppressing the production 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 includes an oxidant addition mechanism 50 that adds hydrogen peroxide (H ₂ O ₂ ) to water flowing in the ozone contact portion of the ozone oxidation treatment apparatus 30, and The alkali addition apparatus 40 has the same configuration as the water treatment system 100 shown in FIG. 1 except that alkali is added to the water flowing in the ozone contact portion after the ozone contact portion to which hydrogen peroxide is added. Yes.
In addition, below, description is abbreviate | omitted about the structure similar to the water treatment system 100 shown in FIG.

  Here, the oxidant 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 hydrogen peroxide has been added and the ozone contact portion located downstream thereof. It is an apparatus for performing processing (AOP). In the water treatment system 100A shown in FIG. 2, the oxidant addition mechanism 50 is the nth (where n is an integer equal to or greater than 2) ozone contact portion (where n is an integer of 2 or more) as viewed in the water flow direction. Hydrogen peroxide is added to the water flowing in the third ozone contact section 34) from the side.

  Moreover, the alkali addition apparatus 40 adds an alkali with respect to the water which flows through the ozone contact part 34 to which hydrogen peroxide is added by the oxidizing agent addition mechanism 50.

  And in the water treatment system 100A, similarly to the water treatment system 100, treated water with reduced suspended matter concentration and trihalomethane production ability can be obtained.

  Further, in the water treatment system 100A, since the odorous substance in the agglomerated treated water can be accelerated and oxidized (AOP) in the ozone oxidation treatment apparatus 30, the oxidative decomposition of the odorous substance is further promoted, and the odorous substance is more efficiently produced. Can be removed. In addition, in the ozone oxidation treatment apparatus 30 of the water treatment system 100A, organic substances, protozoa, and the like other than odorous substances contained in the agglomerated treated water can be subjected to accelerated oxidation treatment.

  Furthermore, in the water treatment system 100A, since alkali is added to the ozone contact portion that performs AOP by the alkali addition device 40, an effect of improving the removal efficiency of odorous substances by performing oxidation treatment in a state where the pH is raised is obtained. However, the production of bromate ions can be suppressed by the reduction reaction derived from hydrogen peroxide.

  As mentioned above, although the water treatment system of this invention was demonstrated using an example and another example, the water treatment system of this invention is not limited to the example mentioned above and another example.

  Specifically, in the water treatment system of the above-described 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, the alkali addition device flows into the ozone oxidation treatment device. Alkali may be added to the water (aggregated treated water), or alkali may be added to both the water flowing into the ozone oxidation treatment apparatus and the water flowing through the ozone oxidation treatment apparatus. Moreover, the alkali addition apparatus may add the alkali to a plurality of locations in multiple stages.

  Moreover, in the water treatment system of the above-described example and another example, an ozone oxidation treatment apparatus having a plurality of ozone contact portions partitioned by a partition wall was used, but the ozone oxidation treatment apparatus of the water treatment system of the present invention is One ozone contact portion may be provided, or a plurality of ozone aeration devices 35, 36, and 37 may be placed in a single water tank 38 in which the agglomerated treated water flows as shown in FIG. The ozone oxidation treatment apparatus 30 </ b> B in which a plurality of ozone contact portions 32, 33, and 34 are formed by being spaced apart from each other in the flow direction may be used. Moreover, the ozone oxidation treatment apparatus may be formed by connecting a plurality of ozone contact portions formed 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. In addition, when hydrogen peroxide is added to a plurality of locations, the alkali addition device is used for the water flowing in the ozone contact portion after the ozone contact portion located on the most upstream side among the ozone contact portions to which hydrogen peroxide is added. It is preferable to add an alkali.

(Water treatment method)
The water treatment method of the present invention is not particularly limited, and can be suitably used when performing advanced water treatment at, for example, a water purification plant. And the water treatment method of this invention is not specifically limited, For example, when using the water treatment system of this invention mentioned above and to-be-processed water continuously, it can use suitably.
In addition, you may use the water treatment method of this invention, when processing to-be-processed water using a batch type water treatment apparatus.

  Here, the water treatment method of the present invention uses an aggregating agent, and coagulates the water to be treated at a first pH to obtain an agglomerated water, and uses ozone after the agglomeration treatment step. And an ozone oxidation treatment step for oxidizing the odorous substance in the coagulated water. Moreover, 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.

  In addition, as the to-be-processed water processed with the water treatment method of this invention, the thing similar to what was illustrated as the to-be-processed water of the water treatment system mentioned above is mentioned. Moreover, the treated water obtained by the water treatment method of the present invention can be supplied to, for example, waterworks after optionally performing a post-treatment (for example, activated carbon treatment, high-speed sand filtration, chlorine disinfection, etc.).

  In the coagulation treatment step, the water to be treated and the coagulant (for example, PAC, etc.) are mixed at the first pH while adding a pH adjuster (for example, sulfuric acid, sodium hydroxide, etc.) as necessary. Aggregates suspended substances contained in the water to be treated. In addition, the produced | generated aggregate (floc) can be isolate | separated using known methods, such as precipitation and filtration.

  In this way, if the water to be treated is agglomerated in the agglomeration process, part of the organic substances and suspended substances contained in the water to be treated can be removed. Can be obtained.

  The lower limit of the first pH is preferably 5.0 or more, more preferably 5.5 or more, still more preferably 6.0 or more, and the upper limit is 6. It is preferably 8 or less, more preferably 6.5 or less, and still more preferably 6.3 or less. If 1st pH is more than the said lower limit, the effort and cost which are required for the neutralization etc. of the treated water obtained using the water treatment method of this invention can be reduced. If the first pH is not more than the above upper limit, the charge neutralization power of the flocculant can be increased, the organic substance removal efficiency can be improved, and the amount of inorganic carbon (IC) in the flocculated water Thus, the oxidation treatment efficiency in the ozone oxidation treatment step can be improved, and the removal efficiency of odorous substances can be further improved.

  In addition, in the ozone oxidation treatment process that uses ozone to oxidize odorous substances in the agglomerated treated water, the agglomerated treated water and ozone are brought into contact with each other using a known method such as aeration to oxidize the odorous substances in the agglomerated treated water. To do. In the ozone oxidation treatment step, an organic substance or the like contained in the agglomerated treated water can be oxidized. In the ozone oxidation treatment step, protozoa and the like contained in the agglomerated treated water can be killed.

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

  As described above, if the step of performing the oxidation treatment using ozone at the second pH higher than the first pH is performed, the organic substance is efficiently removed at the relatively low first pH in the aggregation treatment process. On the other hand, in the ozone oxidation treatment step, for example, the oxidative decomposition of the odorous substance can be promoted in a state where the pH is raised by adding an alkali or the like, and the odorous substance can be efficiently removed.

  Further, when water containing bromide ions is oxidized with ozone, bromate ions are likely to be generated particularly under conditions of high pH. However, if the second step of performing the oxidation treatment using ozone at the second pH is performed after the first step of performing the oxidation treatment using ozone at a pH lower than the second pH, the ozone oxidation treatment process Compared with the case where the oxidation treatment is performed at the second pH from the beginning, the formation of bromate ions can be suppressed. Therefore, it is possible to improve the removal efficiency of odorous substances as compared with the case where the pH is not raised to a second pH higher than the pH of the aggregation treatment step (first pH) while suppressing the formation of bromate ions. Can do.

  In addition, it does not specifically limit as a method of adjusting pH of the water oxidized during implementation of an ozone oxidation treatment process, For example, the following method is mentioned. That is, in a continuous water treatment system such as the water treatment system shown in FIGS. 1 and 2, alkali or the like is present at a predetermined position in the water flow direction with respect to the water to be oxidized that is flowing in the water treatment system. The method of adding a pH adjuster is mentioned. Moreover, in the batch-type water treatment system which performs an ozone oxidation treatment process in a single water tank, a method of adding a pH adjusting agent such as an alkali into the water tank at a predetermined timing after the start of the ozone oxidation treatment process can be mentioned. .

In the water treatment method of the present invention, the second pH has a lower limit value of preferably 6.5 or more, more preferably 7.0 or more, and an upper limit value of 8.0 or less. It is preferable that it is 7.5 or less. If 2nd pH is more than the said lower limit, the oxidative decomposition | disassembly of an odor substance can fully be accelerated | stimulated and the removal efficiency of an odor substance can further be improved. Moreover, if 2nd pH is below the said upper limit, it can fully suppress that a bromate ion produces | generates during an ozone oxidation treatment process.
In the case where the first step and the second step are performed in the ozone oxidation treatment process, the pH of the first step is not particularly limited, but is usually equal to or higher than the first pH, and the pH in the aggregation treatment process is not limited. It is preferable that the pH is the same as the pH of the agglomerated treated water obtained by aggregating the treated water and separating the produced agglomerates using a known method such as precipitation or filtration.

  In the water treatment method of the present invention, when the first step and the second step are performed in the ozone oxidation treatment step, the second step is an accelerated oxidation step in which an oxidation treatment using ozone is performed in the presence of hydrogen peroxide. You can also If the second step is an accelerating oxidation step, 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 is obtained by a reduction reaction derived from hydrogen peroxide. Generation of bromate ions can be suppressed. Further, the oxidative decomposition of the odorous substance can be further promoted by accelerated oxidation treatment (AOP), and the odorous substance can be removed more efficiently.

As mentioned above, although the water treatment method of this invention was demonstrated, the water treatment method of this invention is not limited to the content mentioned above.
Specifically, the ozone oxidation treatment step of the water treatment method of the present invention includes one or more oxidation treatments at a pH other than the first step and the second pH in addition to the first step and the second step. A step may be further included. Moreover, the ozone oxidation treatment process of the water treatment method of the present invention may further include a step of performing an accelerated oxidation treatment at a pH other than the second pH after the second step.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples.

Example 1
<Aggregation treatment process>
Sulfuric acid as a pH adjusting agent is added to river water (TOC: 3.2 mg / L, bromide ion concentration: 0.2 mg / L) as water to be treated, which was put into a batch reaction tank, and the pH was adjusted to 6 Adjusted to 0.0 (first pH). Then, under the condition of a temperature of 25 ° C., PAC as a flocculant is added so that the injection rate is 50 mg / L, and after rapidly stirring at 150 rpm for 2 minutes, it is gently stirred at 50 rpm for 10 minutes to aggregate river water. Processed. And the produced | generated aggregate was removed by precipitation and the aggregation process water was obtained.
<Ozone oxidation treatment process>
13 L of the obtained flocculated water was put into the reaction tank, and ozone was aerated into the reaction tank for 12 minutes under the condition of a temperature of 25 ° C. During aeration, sodium hydroxide as an alkali was added to the reaction vessel to adjust the pH to 6.5 (second pH).
And about the water in a reaction tank, the time-dependent change of the odor substance density | concentration was measured by the gas chromatography, and the time-dependent change of bromate ion concentration was measured by the ion chromatography. The measurement results are shown in FIGS. 4 and 5, respectively.

(Example 2)
Except that the pH was adjusted to 7.0 in the ozone oxidation treatment step, the agglomeration treatment step and the ozone oxidation treatment step were performed in the same manner as in Example 1 to treat the river water. Further, in the same manner as in Example 1, the change over time in the odorous substance concentration and the change over time in the bromate ion concentration were measured. The measurement results are shown in FIGS. 4 and 5, respectively.

Example 3
Except that the pH was adjusted to 8.0 in the ozone oxidation treatment step, the coagulation treatment step and the ozone oxidation treatment step were performed in the same manner as in Example 1 to treat the river water. Further, in the same manner as in Example 1, the change over time in the odorous substance concentration and the change over time in the bromate ion concentration were measured. The measurement results are shown in FIGS. 4 and 5, respectively.

(Example 4)
In the ozone oxidation treatment process, sodium hydroxide is not added for the first 6 minutes, ozone is aerated at pH 6.0 (first step), and 6 minutes after the start of aeration, sodium hydroxide as an alkali is put into the reaction vessel. The river water was treated by carrying out the coagulation treatment step and the ozone oxidation treatment step in the same manner as in Example 1 except that it was added and ozone was aerated for 6 minutes at pH 7.0 (second step). Further, in the same manner as in Example 1, the change over time in the odorous substance concentration and the change over time in the bromate ion concentration were measured. The measurement results are shown in FIGS. 4 and 5, respectively.

(Example 5)
In the ozone oxidation treatment process, sodium hydroxide is not added for the first 6 minutes, ozone is aerated at pH 6.0 (first step), and after 6 minutes from the start of aeration, sodium hydroxide as an alkali and an oxidizing agent are used. The coagulation treatment step and the ozone oxidation treatment step were performed in the same manner as in Example 1 except that hydrogen peroxide was added to the reaction vessel and ozone was aerated at pH 7.0 for another 6 minutes (second step; accelerated oxidation step). , Treated river water. Further, in the same manner as in Example 1, the change over time in the odorous substance concentration and the change over time in the bromate ion concentration were measured. The measurement results are shown in FIGS. 4 and 5, respectively.

(Comparative example)
In the ozone oxidation treatment step, the aggregation 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 6.0 as the first pH of the aggregation treatment step. A process was performed to treat the river water. Further, in the same manner as in Example 1, the change over time in the odorous substance concentration and the change over time in the bromate ion concentration were measured. The measurement results are shown in FIGS. 4 and 5, respectively.

From FIG. 4, it can be seen that in Examples 1 to 5, odorous substances in river water were efficiently removed as compared with Comparative Example 1.
4 and 5, it can be seen that in Examples 4 and 5, odorous substances in the river water could be removed efficiently while suppressing the formation 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.

DESCRIPTION OF SYMBOLS 10 Aggregation processing apparatus 11 Agitation tank 12 Precipitation tank 13 Agitation machine 14 Coagulant addition mechanism 15 pH adjuster addition mechanism 20 Sand filtration apparatus 30, 30B Ozone oxidation treatment apparatus 31 Partition walls 32, 33, 34 Ozone contact parts 35, 36, 37 Ozone aeration device 38 Water tank 40 Alkali addition device 50 Oxidant addition mechanism 100, 100A Water treatment system

Claims (8)

An aggregating treatment device for aggregating treated water using an aggregating agent to obtain agglomerated treated water;
An ozone oxidation treatment apparatus that oxidizes odorous substances in the coagulation treated water using ozone;
A water treatment system comprising:
The water treatment system further provided with the alkali addition apparatus which adds an alkali with respect to at least one of the water which flows into the said ozone oxidation processing apparatus, and the water which flows through the inside of the said ozone oxidation processing apparatus. The ozone oxidation treatment apparatus includes a plurality of ozone contact portions connected in series,
2. The water according to claim 1, wherein the alkali adding device adds alkali to the water flowing in the nth (where n is an integer of 2 or more) ozone contact portion from the upstream side in the water flow direction. Processing system. The ozone oxidation treatment device is connected to a plurality of ozone contact portions connected in series and water flowing in the nth (n is an integer of 2 or more) ozone contact portion from the upstream side in the water flow direction. With an oxidizing agent addition mechanism for adding hydrogen peroxide,
The water treatment system according to claim 1 or 2, wherein the alkali addition device adds an alkali to water flowing in an ozone contact portion after the ozone contact portion to which the hydrogen peroxide is added. A coagulation treatment step using a coagulant to obtain coagulation treated water by coagulating the water to be treated at a first pH;
An ozone oxidation treatment step of oxidizing the odorous substance in the coagulation treated water using ozone;
Including
The water treatment method, wherein the ozone oxidation treatment step includes an oxidation treatment using ozone at a second pH higher than the first pH.   The ozone oxidation treatment step performs an oxidation treatment using ozone at a pH lower than the second pH, and an oxidation treatment using ozone at the second pH after the first step. The water treatment method of Claim 4 including a 2nd step.   The water treatment method according to claim 5, wherein the second step is an accelerated oxidation step of performing an oxidation treatment using ozone in the presence of hydrogen peroxide.   The water treatment method according to any one of claims 4 to 6, wherein the first pH is 6.8 or less.   The water treatment method according to any one of claims 4 to 7, wherein the second pH is 7.0 or more and 7.5 or less.

Images