JP3564416B2 - Removal method of residual ozone in raw water treatment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for removing residual ozone in raw water treatment, and more particularly to a raw water treatment that can effectively and easily remove residual ozone from pre-ozone treated raw water using a simple apparatus. And a method for removing residual ozone in the above.
[0002]
[Prior art]
Conventionally, eutrophic lakes and reservoirs are susceptible to propagation of cyanobacteria such as blue-green algae, and if raw water containing these alga is used as clean water, it is necessary to remove the cyanobacteria in the raw water .
By the way, as one method of removing orchid algae, ozone (O ₃ ) is directly supplied to raw water, so-called pre-ozone treatment is performed to nullify the aggregation inhibiting component produced by blue-green algae, and then a flocculant is added. There is a method of forming and removing flocs having good sedimentation properties. As a result, it is possible to simultaneously remove a certain amount of off-flavor components, remove chromaticity, and the like.
[0003]
However, some ozone remains in the pre-ozone-treated raw water, and undesired phenomena such as corrosion of metals and volatilization of ozone into the atmosphere occur if the ozone is left to flow to the subsequent treatment process.
As a method of removing the residual ozone, (1) a method of promoting the reaction between ozone and an off-flavor component using a catalyst in which a metal or metal oxide is supported on a carbon-based carrier, and decomposing unreacted ozone (2) a method of adding a ferrous ion-containing solution to raw water containing residual ozone to reduce residual ozone (see Japanese Patent Application Laid-Open No. 02-95494), and (3) waste ozone Various methods have been proposed, such as a method of contacting with a slurry generated in a treatment step to perform an ozone treatment (see JP-A-03-229615).
[0004]
[Problems to be solved by the invention]
However, in any of the above conventional methods for removing residual ozone in raw water treatment, there is a problem that the apparatus becomes complicated, the amount of chemicals used increases, and the running cost increases.
[0005]
The present invention has been made in view of the above-described problems of the conventional method for removing residual ozone in raw water treatment, and has been intended to effectively and easily remove residual ozone from pre-ozone treated raw water using a simple device. It is an object of the present invention to provide a method for removing residual ozone in raw water treatment that enables the removal of ozone.
[0006]
[Means for Solving the Problems]
In order to achieve this object, the method for removing residual ozone in the raw water treatment according to the present invention comprises: supplying raw water supplied into the ozone treatment tower with pre-ozone treatment by blowing ozone into granular activated carbon or The hydrated manganese dioxide-coated silica sand is introduced into a deozonization tower equipped with a fluidized bed configured to flow, and residual ozone is decomposed in the fluidized bed to make it harmless. in the method of removing the ozone, the raw water flows through the fluidized bed unit, the adsorbed or decomposed chemicals ozone, the amount of the drug product, was added to control by measuring the ozone concentration in de ozone tower, de After flowing out from the ozone tower together with the treated water, the chemical component is removed in a coagulation / precipitation step .
[0007]
The method of removing residual ozone in this raw water treatment is as follows: raw water that has been pre-ozone-treated by blowing ozone into raw water supplied into the ozone treatment tower is subjected to silica sand coated with granular activated carbon or hydrated manganese dioxide from the ozone treatment tower. Is introduced into a de-ozone tower equipped with a fluidized bed configured to flow, and the residual ozone is decomposed and rendered harmless in the fluidized bed. When flowing through the fluidized bed of the ozone tower, the raw water and the silica sand coated with the granular activated carbon or hydrated manganese dioxide disposed in the fluidized bed are effectively and evenly contacted, and thereby residual ozone is reduced. Decomposed.
This makes it possible to effectively and easily remove residual ozone from pre-ozone-treated raw water using a simple device. The removal rate is improved, and continuous Thus, residual ozone can be more reliably removed, and running costs can be reduced.
In addition, because of the fluidized bed type, cells and other particle groups of the algae modified by ozone can be smoothly discharged to the next stage of agglomeration and floc formation step without being confined inside the de-ozone tower. be able to.
[0008]
Then, a chemical that adsorbs or decomposes ozone is added to the raw water that has flowed through the fluidized bed, and after flowing out from the deozone tower together with the treated water, the chemical component is removed in the coagulation / precipitation step, whereby the fluidized bed is removed. The remaining ozone contained in the raw water flowing through the section can be more reliably removed, and at this time, by adding the chemical, by controlling the ozone concentration in the deozone tower, The use amount of chemicals can be minimized.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a method for removing residual ozone in raw water treatment according to the present invention will be described with reference to the drawings.
[0010]
FIG. 1 shows an example of an apparatus used in the method for removing residual ozone in raw water treatment according to the present invention.
[0011]
This apparatus is composed of an ozone treatment tower A for ozone treatment of raw water introduced from above, and a deozone tower B for decomposing and detoxifying residual ozone contained in pre-ozone treated raw water. .
[0012]
The connection between the ozone treatment tower A and the deozone tower B is made at the lower part of the ozone treatment tower A and the deozone tower B, at the outlet 5 of the ozone treatment tower A for discharging the pre-ozonated raw water, This is performed by connecting the inflow port 10 of B with the pipe C, so that the pre-ozone-treated raw water is smoothly introduced from the ozonation tower A to the de-ozone tower B sequentially.
[0013]
The ozone treatment tower A is connected to a raw water introduction pipe 1 at an arbitrary position on the upper part, an exhaust ozone discharge pipe 2 for discharging exhaust ozone is connected to an uppermost part, and an air diffuser pipe connected to an ozone supply pipe 4 at an inner bottom part. 3, whereby ozone is supplied to the raw water introduced from the raw water introduction pipe 1 to perform a required pre-ozone treatment, and the ozone discharged from the raw water floats out of the raw water through the ozone discharge pipe 2. It is discharged to a device (not shown).
In this case, it is desirable that the outlet 5 connected to the de-ozone tower B via the pipe C is located at a position lower than the position where the air diffuser 3 is disposed in order to effectively perform the ozone treatment.
[0014]
The deozonization tower B is not particularly limited, but is installed adjacent to the ozone treatment tower A in this embodiment.
The de-ozone tower B introduces the pre-ozone-treated raw water from the inflow port 10 disposed below to the stagnation section R formed at the inner bottom portion, and thereby the residual water introduced into the de-ozone tower B is introduced. By retaining the ozone water in the retaining portion R for a certain period of time, the residual ozone is self-decomposed, and at the same time, the required ozone reaction time is extended.
A fluidized bed 6 is formed substantially at the middle of the deozonization tower B in the height direction, and a discharge pipe 7 for discharging raw water after the deozonization treatment is connected to the upper portion thereof. A drug addition nozzle 8 is desirably disposed between the discharge pipe 7 and the fluidized bed portion 6.
The drug addition nozzle 8 is connected to a drug addition pipe 81, and controls the amount of drug to be supplied in conjunction with an ozone meter 9 for measuring the residual ozone concentration in the deozone tower B.
[0015]
Although not particularly limited, the fluidized bed 6 is provided with a screen 61 at a lower portion thereof so that, for example, small-diameter granular activated carbon having a diameter of about 1 to 2 mm flows.
Accordingly, when the pre-ozone-treated raw water containing residual ozone flows through the fluidized bed section 6 through the retaining section R, most of the residual ozone is converted into oxygen (O ₂ ), carbon dioxide (CO ₂ ), and monoxide. It is converted into carbon (CO) or the like and is discharged through the drain pipe 7 in a state of being dissolved in water or as a gas.
[0016]
In this case, instead of the granular activated carbon, silica sand having a small particle diameter coated with hydrated manganese dioxide can be used.
Also in the case of using silica sand coated with this hydrated manganese dioxide, it is made to flow in the fluidized bed 6 as in the case of using granular activated carbon.
When silica sand coated with hydrated manganese dioxide is used, the residual ozone is decomposed by the catalysis due to the contact with the manganese dioxide, and the ozone concentration in the raw water passing through the fluidized bed 6 is reduced. It can be significantly reduced.
[0017]
The silica sand coated with the granular activated carbon or hydrated manganese dioxide constituting the fluidized bed section 6 comes into contact with residual ozone, so that microorganisms and the like do not adhere to and propagate on the surface. Even if the particles adhere to the surface, the particles of granular activated carbon or silica sand are in contact with each other and collide with each other, so that the adhered substances are scraped off and the residual ozone can be stably removed over a long period of time.
Even if the particles of granular activated carbon or silica sand come into contact with each other and collide with each other, and some of the particles are pulverized and flow out of the fluidized bed, these fine particles can be removed as flocs in the next coagulation / precipitation step. .
The function of the fluidized bed can be maintained by periodically replenishing the granular activated carbon or silica sand that has been pulverized and reduced in this way.
[0018]
The chemical added from the chemical addition nozzle 8 is not particularly limited as long as it is a chemical that adsorbs or decomposes ozone, but a powdered activated carbon slurry, a solution containing reducing iron ions (Fe ⁺⁺ ) , A manganese chloride solution (MnCl ₂ ), a manganese dioxide solution (MnO ₂ ) and the like can be suitably used.
[0019]
When powdered activated carbon slurry is used as a drug added from the drug addition nozzle 8, ozone is reduced and removed in the same manner as granular activated carbon in the fluidized bed, but furthermore, powder activated carbon has a unique adsorption power. Thereby, the organic substance which has not been decomposed in the pre-ozone treatment is adsorbed, and the organic substance itself flows out of the deozone tower B together with the treated water, and can be removed in the next aggregation / precipitation step.
In the coagulation / precipitation step, the activated carbon powder itself acts as a core of coagulation to promote the coagulation, so that the coagulation / precipitation step can be smoothly performed in combination with the coagulation improvement effect by the pre-ozone treatment. it can.
As described above, in a water treatment plant that uses raw water containing cyanobacteria from eutrophic lakes and reservoirs, the consumption of a small amount of powdered activated carbon can improve the difficulty of sedimentation of cyanobacteria and mitigate the sudden rise in head loss due to filtration ponds. And the quality of treated water is reflected.
In this case, it is desirable to ensure that the contact time of the powdered activated carbon is about 20 minutes.
In addition, by installing a stirrer (not shown) at a portion where the powdered activated carbon is added from the chemical addition nozzle 8 so that a severe turbulent flow condition is formed, although power is required, residual ozone and organic substances are required. Adsorption can be promoted.
[0020]
When a solution containing reducing iron ions is used as a drug added from the drug adding nozzle 8, the iron ions react with residual ozone to form iron hydroxide (Fe (OH) ₃ ) and form a flocculant. And flows out together with the treated water from the deozonation tower B, and can be removed in the next aggregation / precipitation step.
[0021]
When a manganese chloride solution is used as a chemical to be added from the chemical addition nozzle 8, the manganese chloride reduces residual ozone and turns itself into manganese dioxide (MnO ₂ ) and becomes colloidal. Together with it, and can be removed in the next aggregation / precipitation step. Also, manganese dioxide itself in the form of colloid can catalytically decompose O ₃ .
[0022]
When a manganese carbonate solution is used as the chemical added from the chemical addition nozzle 8, the manganese carbonate decomposes the residual ozone by its catalytic action, flows out from the deozone tower B together with the treated water, and is subjected to the next coagulation / precipitation step. Can be removed.
[0023]
In any case, by controlling the addition amount of the chemical supplied in conjunction with the ozone meter 9 for measuring the residual ozone concentration, it is possible to prevent the residual ozone and the chemical from flowing out to the open processing step. .
[0024]
Further, in order to remove residual ozone, a method of filling a Raschig ring made of ceramic coated with manganese dioxide in the deozone tower B can be adopted.
In this case, the residual ozone is decomposed by the catalytic action of manganese dioxide on the surface of the Raschig ring as the raw water containing the residual ozone passes through the filled portion of the Raschig ring made of ceramic coated with manganese dioxide.
The support of manganese dioxide is not limited to Raschig rings, but may be one that can coat manganese dioxide on the surface and has a shape that allows good water permeability.
[0025]
Further, a small amount of aluminum ion (Al ⁺⁺⁺⁺ ) or iron ion (Fe ⁺⁺⁺⁺ ) is added to the raw water in advance, and the raw water is subjected to pre-ozone treatment, whereby the organic compound on the particle surface is easily functionalized with ozone to form a salt with a functional group. Immediately after the reaction, aluminum ions or iron ions react with the functional groups to increase the zeta potential, and in the next flocculation / precipitation step, when a flocculant is added again for full-scale flocculation, It was confirmed by using raw water containing cyanobacteria such as blue-green algae that there was a phenomenon that cohesion was significantly improved.
In this method, it is important to adjust the addition amount of aluminum ions or iron ions to an appropriate amount. If the addition amount is large, a lump-like substance is easily generated in the ozone treatment tank A, and the subsequent steps are hindered.
The same effect can be seen when calcium ion (Ca ⁺⁺ ) or magnesium ion (Mg ⁺⁺ ) is added in addition to aluminum ion or iron ion, but the effect is weaker than aluminum ion or iron ion. Considering the amount and the like, aluminum ions and iron ions are also excellent in cost.
[0026]
As described above, the method for removing residual ozone in the raw water treatment of the present invention has been described based on the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the scope of the present invention is not deviated. The configuration can be appropriately changed.
[0027]
【The invention's effect】
According to the method for removing residual ozone in the raw water treatment of the present invention, the raw water that has been pre-ozonated by blowing ozone into the raw water supplied into the ozonation tower is converted into granular activated carbon or hydrated manganese dioxide from the ozonation tower. Is introduced into a de-ozone tower equipped with a fluidized bed configured to allow the coated silica sand to flow, and the residual ozone is decomposed and detoxified in the fluidized bed. When the raw water containing water flows through the fluidized bed section of the de-ozone tower, the raw water and the silica sand material coated with granular activated carbon or hydrated manganese dioxide disposed in the fluidized bed section come into effective and even contact, Decomposes residual ozone.
In addition, because of the fluidized bed type, cells and other particle groups of the algae modified by ozone can be smoothly discharged to the next stage of agglomeration and floc formation step without being confined inside the de-ozone tower. be able to.
Thereby, the residual ozone can be effectively and easily removed from the pre-ozone-treated raw water using a simple device, and the running cost can be suppressed.
Then, a chemical that adsorbs or decomposes ozone is added to the raw water that has flowed through the fluidized bed, and after flowing out from the deozone tower together with the treated water, the chemical component is removed in the coagulation / precipitation step, whereby the fluidized bed is removed. The remaining ozone contained in the raw water flowing through the section can be more reliably removed, and at this time, by adding the chemical, by controlling the ozone concentration in the deozone tower, The use amount of chemicals can be minimized.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of an apparatus used for a method for removing residual ozone in raw water treatment according to the present invention.
[Explanation of symbols]
Reference Signs List A Ozone treatment tower B De-ozone tower C Pipe R Retention part 1 Raw water introduction pipe 2 Waste ozone discharge pipe 3 Aeration pipe 4 Ozone supply pipe 5 Outlet 6 Fluidized bed part 61 Screen 7 Discharge pipe 8 Chemical addition nozzle 9 Ozone meter 10 Inlet

Claims (1)

The raw water supplied into the ozonation tower was blown with ozone, and the pre-ozone-treated raw water was flown from the ozonation tower to a fluidized bed configured to flow silica sand coated with granular activated carbon or hydrated manganese dioxide. In the method for removing residual ozone in raw water treatment, which is introduced into a deozone tower provided and decomposes and detoxifies residual ozone in the fluidized bed, ozone is adsorbed or decomposed on raw water flowing through the fluidized bed. The chemical to be added is added by controlling the amount of addition of the chemical by measuring the ozone concentration in the deozone tower, and is discharged together with the treated water from the deozone tower, and then the chemical component is removed in the coagulation / precipitation step. A method of removing residual ozone in raw water treatment.

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