JPH08294695A - Water treatment apparatus - Google Patents

Abstract

PURPOSE: To improve the quality of treated water by holding bacteria to a highly active state by arranging a catalyst bed of which the height is made less than that of the activated carbon bed of a biological activated carbon tank on the downstream side of an ozone contact tank and passing treated water through a catalyst bed to decompose dissolved ozone before introducing the same into the biological activated carbon tank. CONSTITUTION: An ozone stagnation tank 9 is arranged on the downstream side of an ozone contact tank 8 and a biological activated carbon tank 18 is further arranged on the downstream side thereof. A catalyst 23 for decomposing dissolved ozone is arranged to the inner peripheral surface of the ozone stagnation tank 9. As the catalyst 23, activated carbon is pref. used and the height h0 of the catalyst bed 24 of the tank 9 is set less than the height (h) of the activated carbon bed 20 of the biological activated carbon tank 18. Water w0 to be treated is treated with ozone introduced from an air pipe 11 in the ozone contact tank 8. The water TW in which ozone is dissolved is passed through the catalyst 23 to decompose dissolved ozone. Next, the treated water is introduced into the biological activated carbon tank 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment device for treating water to be treated with ozone and further treating it with biological activated carbon in a water purification plant or a sewage treatment plant.

[0002]

2. Description of the Related Art With the deterioration of water quality of water sources such as river water and lake water, for example, in a water treatment plant, instead of the current rapid filtration method, the precipitated water after coagulating sedimentation or the filtered water after sand filtration is subjected to ozone treatment. In addition, so-called biological activated carbon treatment,
There is a tendency to adopt advanced water treatment methods. This type of advanced water purification method is disclosed in JP-A-2-149397, JP-A-6-63571 and JP-A-4-281893.

In this method, raw water from a river or the like that has been taken in is subjected to coagulation-sedimentation treatment, and then precipitation water (or sand filtration water) to be treated is introduced into an ozone contact tank, where organic matter in the water, etc. Decolorize, deodorize, oxidize or modify. After that, the treated water that has been subjected to ozone treatment is introduced into a biological activated carbon tank, and by the action of microorganisms propagated on the surface or inside of activated carbon, ammonia nitrogen that cannot be removed by ozone treatment is nitrified and removed, and dissolved organic substances are metabolically removed.

[0004]

In this type of advanced water purification method, when ozone is injected into the water to be treated, not all ozone is dissolved, but part is discharged as ozone in the gas phase and dissolved. Ozone is the difference between the amount of injected ozone and the amount of discharged ozone. On the other hand, dissolved ozone is consumed by organic substances in the water to be treated, and residual ozone, that is, dissolved ozone, is the difference between the dissolved ozone amount and the ozone consumption amount in the liquid phase.

Here, if the amount of ozone consumed by organic substances or the like exceeds the amount of dissolved ozone, the dissolved ozone concentration becomes undetected, and the amount of organic substances not treated by ozone treatment increases and the quality of treated water deteriorates. Therefore, ozone is injected into the water to be treated so as to exceed the amount of ozone consumed by organic substances and the like. However, since not all of the dissolved ozone is consumed, there is dissolved ozone in the treated water after the ozone injection, and the treated water containing this dissolved ozone flows through the ozone retention tank located downstream of the ozone contact tank. After that, it will be introduced into the biological activated carbon tank.

The biological activated carbon tank is filled with activated carbon as a carrier, and acclimated and propagated microorganisms are present on the surface or inside of the activated carbon. This microorganism grows with the passage of time, but as the microorganism grows, the clogging in the activated carbon layer proceeds, and the pressure loss between the inlet and outlet of the activated carbon layer increases. As a result, the amount of treated water from the biological activated carbon tank decreases, so that when a predetermined pressure loss is reached, backwash water is introduced from the outlet side of the activated carbon layer to backwash the activated carbon layer.

In this case, since the activated carbon layer is fluidized and mixed by the backwashing, the activated carbons located in the surface layer portion of the activated carbon before and after the backwashing are different, and the activated carbon located in the inside or the like is a new activated carbon surface layer portion. And changes every time it is backwashed.

By the way, the treated water containing dissolved ozone is introduced into the biological activated carbon tank as described above, but the microorganisms such as the activated carbon surface located on the new surface layer by backwashing are affected by the dissolved ozone in the treated water. Receive necrosis or damage. In particular, since it is more strongly affected by dissolved ozone than microorganisms located inside, necrotic or damaged microorganisms cause biological leakage from the biological activated carbon tank, and there is a risk that microorganisms will mix into the treated water from the biological activated carbon tank. is there. This biological leakage is likely to occur at the beginning when the treated water is passed after the backwashing is completed, and occurs every time the backwashing is completed.

On the other hand, in the ozone treatment to be treated, it is required that the treated water quality after the ozone injection treatment is stable, as well as the high removal of organic substances. Furthermore, the ozone generation efficiency of the ozonizer is low, and the power consumption rate is about 20 kWh /
Since it is as high as kg · O ₃ , it is required to efficiently treat the water to be treated with the minimum required ozone injection amount. Generally, when the treated water is subjected to ozone treatment using raw water whose water quality fluctuation is relatively small as a water source, water amount proportional control is performed in which ozone is injected at a constant injection rate proportional to the water amount.
However, if the water quality of the water to be treated fluctuates greatly, ozone is injected excessively or insufficiently in the above-described water amount proportional control method, and the water quality after ozone injection treatment is not stable. If the amount of injected ozone is too small, the amount of treated organic matter and the like in the water to be treated decreases, resulting in deterioration of water quality. On the other hand, if ozone is excessively injected, the electricity consumption rate of ozone is high, and thus the running cost required for ozone injection processing becomes high. As means for solving the various inconveniences described above, for example, in ozone treatment at a water purification plant, the concentration of exhaust ozone discharged from the ozone contact tank to the gas phase after injection of ozone, or the dissolved ozone concentration in the liquid phase is detected, and this ozone concentration is detected. A method is adopted in which the ozone injection amount is controlled so that is a constant value.

However, the solubility of ozone in water, the self-decomposition of ozone in a liquid, etc. change under the influence of the water temperature, pH and contact time of the water to be treated. Therefore, even if the concentration of organic matter in the water to be treated and its composition are constant, the water temperature, p
When H or the like changes, the concentration of exhausted ozone or the concentration of dissolved ozone changes, and the change is perceived as a change in the concentration of organic matter.
For example, when the dissolved ozone concentration decreases, the ozone consumption increases as the organic matter concentration increases, and as a result, the dissolved ozone concentration decreases and more ozone than necessary is injected. As a result, it is difficult to control ozone injection with a high control system that corresponds to the quality of treated water and its changes, and in general, excessive ozone is injected in consideration of operational safety. Therefore, it is difficult to reduce the running cost required for ozone treatment.

The present invention has been made in order to eliminate the above-mentioned inconvenience in a water treatment apparatus in the case of performing ozone injection treatment and then biological activated carbon treatment. The purpose is to damage microorganisms by dissolved ozone. The present invention aims to provide a simplified water treatment device capable of suppressing microorganisms and maintaining microorganisms in a highly active state, improving the quality of treated water, and reducing the amount of injected ozone.

[0012]

In order to achieve the above-mentioned object, the present inventors investigated the dissolved ozone concentration in the treated water flowing into the bioactive carbon layer and the distribution of the dissolved ozone concentration at each height of the bioactive carbon layer. . The relationship between the inflowing dissolved ozone concentration and the dissolved ozone concentration at each layer height was obtained under the following conditions.

Activated carbon packed bed height: 50 cm, water passage time: 60
Minute (for each concentration), LV: 6.5 m / h, water flow method:
Continuous water flow from low dissolved ozone concentration to high dissolved ozone concentration. Dissolved ozone concentration measurement point: Surface layer, 10, 20, 30 from surface layer
And 50 cm.

As a result, as shown in FIG. 4, which shows the state of dissolved ozone concentration with respect to the height of the activated carbon layer, it is 10 cm from the surface layer of the activated carbon.
The dissolved ozone concentration becomes undetectable at the measurement point of, and the dissolved ozone at the same position becomes undetectable without being affected by the dissolved ozone concentration flowing into the activated carbon layer. From these results, it was clarified that the dissolved ozone in the treated water flowing into the activated carbon layer was decomposed by the catalytic action of the activated carbon, and the dissolved ozone was decomposed mainly in the surface layer portion 10 cm or less from the surface layer of the activated carbon layer.

Therefore, after backwashing as described above, in order to protect the microorganisms of the bioactive carbon, which is a new surface layer, from the influence of dissolved ozone, the treated water is provided downstream of the ozone contact tank separately from the bioactive carbon layer. The catalyst layer for decomposing the dissolved ozone may be arranged. Since the dissolved ozone is decomposed in the surface layer portion as described above, the height of the catalyst layer arranged independently of the biological activated carbon layer should be at least filled in the biological activated carbon tank. It was found that the bed height can be set lower than that of activated carbon.

From the above point, the feature of the present invention is that it comprises an ozone contact tank into which water to be treated is introduced and ozone is injected, and a biological activated carbon tank into which treated water after the ozone injection is introduced. In the water treatment apparatus, a catalyst layer having a bed height lower than the bed height of the activated carbon filled in the biological activated carbon tank is arranged on the downstream side of the ozone contact tank, and dissolved ozone in the treated water is This is because the treated water that has passed through the catalyst layer and decomposed and passed through the catalyst layer is introduced into the activated carbon tank in the biological activated carbon tank.

Next, when the catalyst layer is arranged on the downstream side of the ozone contact tank as described above, the kind of the catalyst was examined. The catalyst is prepared by impregnating a solution containing an active ingredient in a carrier, then drying and calcining, but when used for a long time in treated water containing dissolved ozone, it depends on the kind of the supported active ingredient, On the contrary, the quality of the treated water may be deteriorated due to dissolution of the active ingredient or inclusion of carrier fragments accompanying carrier brittleness.

With respect to the above points, the activated carbon is as described above.
Since the activated carbon itself as a carrier has a catalytic action and does not have a supported active component, the active component is not dissolved in the treated water and the quality of the treated water is not deteriorated, which is preferable.

Therefore, a preferred embodiment of the present invention is characterized in that the catalyst disposed downstream of the ozone contact tank is activated carbon.

As described above, by disposing the catalyst layer for decomposing dissolved ozone in the treated water on the downstream side of the ozone contact tank, the microorganisms in the biological activated carbon tank can be protected from the influence of dissolved ozone. On the other hand, in addition to the protection of microorganisms, it is necessary to improve the quality of treated water by ozone injection treatment.

Here, the dissolved ozone in the treated water is decomposed by the catalyst, and hydroperoxy radicals (HO _2. ) And hydroxyl radicals (OH.) Are generated in the process of decomposition. These generated OH and HO ₂ radicals do not have selectivity with respect to an organic substance or the like as an oxidizable substance, and have high oxidation reactivity. On the other hand, the oxidation reaction of an organic substance or the like by only ozone molecules has selectivity with respect to the molecular structure of the substance to be oxidized, and the reaction is relatively slow. Therefore, the dissolved ozone in the treated water is decomposed by the catalyst, and the radicals generated in association with the decomposition can accelerate the oxidation of the organic matter in the water to be treated, so that the quality of the treated water can be improved by the ozone injection treatment.

In this case, in order to efficiently treat the organic matter in the water to be treated by the radicals generated by the decomposition of the dissolved ozone and to improve the quality of the treated water, the catalyst layer is arranged at an appropriate position. It is important to secure a sufficient retention time for the treated water after passing through the catalyst layer to flow into the biological activated carbon layer, and to accelerate the reaction by the retention time. Here, in the process of ozone injecting the water to be treated, considering the above-mentioned conditions, the water to be treated is subjected to the ozone injecting treatment in the ozone contact tank, and thereafter the treated water containing dissolved ozone is treated in the ozone contact tank. It is introduced into the ozone retention tank arranged on the downstream side. In this case, in this ozone retention tank, a sufficient retention time is secured in order to promote the reaction between ozone and organic substances, and to promote the self-decomposition of dissolved ozone in the treated water to reduce the dissolved ozone. .

Therefore, by disposing the catalyst layer in this ozone retention tank, it is possible to secure a sufficient retention time until the treated water after passing through the catalyst layer flows into the biological activated carbon layer.
The residence time can accelerate the reaction of radicals and organic substances generated by the decomposition of dissolved ozone by the catalyst. That is, it is a preferred embodiment that a catalyst that decomposes dissolved ozone in the treated water is arranged in the ozone retention tank.

From the above-mentioned point, another feature of the present invention is that an ozone contact tank into which water to be treated is introduced and ozone is injected, and the ozone contact tank is provided downstream of the ozone contact tank. An ozone retention tank into which treated water from the tank is introduced, and a biological activated carbon tank located downstream of the ozone retention tank and into which treated water from the ozone retention tank is introduced,
A catalyst layer having a bed height lower than that of the activated carbon filled in the biological activated carbon tank is disposed in the ozone retention tank, and dissolved ozone in the treated water is decomposed by passing through the catalyst tank. The treated water that has passed through the catalyst layer is introduced into the activated carbon layer in the biological activated carbon tank.

When the catalyst layer is arranged in the ozone retention tank as described above, activated carbon is a preferred embodiment as the catalyst species as described earlier in this specification.

[0026]

As described above, the catalyst layer for decomposing dissolved ozone in the treated water is arranged on the downstream side of the ozone contact tank, and the treated water after passing through the catalyst layer is introduced into the biological activated carbon layer, Moreover, since the layer height of this catalyst layer is set lower than the layer height of the activated carbon filled in the biological activated carbon tank, it is possible to suppress the necrosis or damage of microorganisms due to the influence of dissolved ozone with a small catalyst filling amount. it can.

That is, with the backwashing of the biological activated carbon tank, new microorganisms are present in the surface layer of the activated carbon layer in place of the activated carbon located inside. In this case, since the treated water after the dissolved ozone is decomposed by the catalyst layer arranged on the upstream side of the activated carbon layer is introduced into the activated carbon layer, the microorganisms located on the surface side of the activated carbon layer are not affected by the dissolved ozone. Not be necrosed or damaged. As a result, it is possible to suppress the leakage of microorganisms from the biological activated carbon tank due to the influence of dissolved ozone. However, as explained earlier in this specification, the dissolved ozone in the treated water is decomposed in the surface layer of the activated carbon layer having a catalytic action and does not reach the inside of the activated carbon layer. Therefore, as a catalyst for decomposing the dissolved ozone in the treated water, its bed height can be set lower than that of the biological activated carbon layer, and the dissolved ozone in the treated water can be decomposed effectively with a small catalyst filling amount. You can

On the other hand, although the microorganisms in the biological activated carbon tank grow over time, if the microorganisms grow too much, the oxygen uptake accompanying the growth of the microorganisms also increases. For this reason, the dissolved oxygen concentration in the biological activated carbon tank decreases and anaerobic progresses, while the activity of microorganisms decreases and the quality of treated water from the biological activated carbon tank may decrease. However, when the dissolved ozone in the treated water is decomposed by a catalyst, the dissolved ozone becomes oxygen, which becomes dissolved oxygen.Therefore, the dissolved oxygen in the treated water flowing through the catalyst layer into the biological activated carbon layer is in a high concentration state. Maintained at. Therefore, even if the oxygen uptake increases with the growth of microorganisms, the treated water containing a high concentration of dissolved oxygen flows into the biological activated carbon tank, so that anaerobicization in the tank can be suppressed.

Furthermore, when the dissolved ozone in the treated water is decomposed by the catalyst, OH and HO ₂ radicals are generated in the process of decomposition, and these radicals have a selectivity with respect to an organic substance which is an oxidizable component. It has high oxidation reactivity.
Oxidation reaction of organic substances or the like by only ozone molecules has selectivity with respect to the molecular structure of the substance to be oxidized, and the reaction is relatively slow. Therefore, not only the dissolved ozone in the treated water is decomposed, but also the amount of radicals produced by the catalyst is accelerated, thereby predominantly effecting the oxidation reaction between the radicals having a high oxidation reactivity and the organic substances, thereby improving the treatment efficiency of the organic substances. Can be increased. As a result, unless the production amount of radicals is accelerated, the treated water quality cannot be improved unless the ozone injection amount is increased, and it is difficult to reduce the injected ozone amount. On the other hand, if dissolved ozone is decomposed by a catalyst and the amount of generated radicals is increased, it is possible to treat organic substances and the like with radicals having high oxidation reactivity without increasing the amount of injected ozone, and the amount of injected ozone is reduced. Is possible.

Therefore, a catalyst layer whose bed height is set lower than the bed height of the activated carbon filled in the biological activated carbon tank is arranged on the downstream side of the ozone contact tank to allow dissolved ozone in the treated water to pass through the catalyst layer. If the treated water that has been decomposed and passed through the catalyst layer is introduced into the biological activated carbon tank, the microorganisms can be maintained in a highly active state and the treated water quality can be improved, and the amount of injected ozone can be reduced. A water treatment device can be provided.

Next, when the catalyst layer is arranged on the downstream side of the ozone contact tank as described above, when activated carbon is arranged as a catalyst species, even if no active component is supported, the activated carbon itself is liable to catalyze. Since it decomposes dissolved ozone,
Since the active ingredient is not dissolved in the treated water, it is possible to prevent deterioration of the treated water quality due to the dissolution of the active ingredient.

Further, when the catalyst layer is arranged in the ozone retention tank located on the downstream side of the ozone contact tank, the treated water passes through the catalyst layer in this seed water treatment process. It is possible to secure a long residence time from the start to the flow into the biological activated carbon tank. As a result,
The reaction between the highly reactive radicals generated by the decomposition of dissolved ozone by the catalyst and the organic matter in the water to be treated can be promoted over a long residence time, and the quality of the treated water can be improved.

From the above, when arranging the catalyst layer in the ozone retention tank, activated carbon, which does not dissolve the active ingredient in the treated water, is the preferred embodiment as the catalyst species, and the treatment accompanying the dissolution of the active ingredient of the catalyst The deterioration of water quality can be suppressed.

[0034]

An embodiment of the present invention will be described below with reference to the drawings. In the system flow of a water treatment plant as an example in which the water to be treated shown in FIG. 1 is subjected to ozone injection treatment and then to biological activated carbon treatment, raw water RW taken from a river or the like passes through a water conduit (not shown) to a sand basin ( (Not shown), where sand or the like having a large particle size is removed, and then the water is guided to the landing well 1. The raw water RW is then led to the chemical mixing pond 2 where the sulfuric acid band or PAC (polyaluminum chloride) is used.
The coagulant 3 or the like or an alkaline agent serving as a coagulation aid is injected and rapidly mixed. After that, it is sent to the flock formation pond 5.

In the floc formation pond 5, fine particles in the raw water are aggregated to promote the growth of microflocs. Reference numeral 6 denotes a flocculator that agitates micro flocs. After that, the flocculated water containing flocs having a large particle size is guided to the settling tank 7, where the flocs are separated by sedimentation.

The settling water SW from which flocs are settled and separated through the above-described process is then introduced into the ozone contact tank 8 as the water to be treated Wo to be subjected to the ozone injection treatment. In addition, in one Example of this invention, although the ozone contact tank 8 is comprised from the front | former stage tank 8A and the back | latter stage tank 8B, the number of tanks is not specifically limited. Further, in the embodiment of the present invention, the ozone injection treatment is performed by using the settling water SW from the settling tank 7 as the water to be treated Wo. In this case, if a sand filter (not shown) is provided on the downstream side of the sedimentation tank 7, it is needless to say that the filtered water from the sand filter may be subjected to ozone injection treatment as treated water Wo. However, the target of the ozone injection process is not limited to the precipitation water SW.

Reference numeral 9 denotes an ozone retention tank, which is disposed downstream of the ozone contact tank 8. Ozone gas OG is injected into the ozone contact tank 8 from an ozonizer 10 through a ventilation pipe 11. More specifically, the source gas RG (air or oxygen) is supplied to the ozonizer 10, where the oxygen becomes ozone due to the silent discharge, and this ozone is disposed in the ozone contact tank 8 and has a large number of small holes (see FIG. It is injected through the air diffuser 11A (not shown). Here, the water Wo to be treated flows countercurrently to the ozone gas OG injected into the ozone contact tank 8 and flows down to the front tank 8A.
The treated water Wo into which the ozone gas has been injected flows into the rear tank 8A, and ozone gas OG is injected in the same manner as in the former tank.

When the ozone gas OG is injected into the ozone contact tank 8, the amount of ozone injected into the water to be treated Wo is arbitrarily set according to the flow rate of the water to be treated Wo and the concentration of organic substances in the water to be treated Wo. And set by an operator or the like.

Reference numeral 12 is a mist separator for removing the water in the exhaust ozone gas EG discharged from the ozone contact tank 8 to the gas phase, and an ozone decomposition treatment tank 13 serving as ozone decomposition treatment means is disposed downstream of this mist separator. It is set up.
Reference numeral 14 denotes an ozone decomposition catalyst filled in the ozone decomposition treatment tank 13, which is generally filled with a granular or honeycomb MnO ₂ catalyst. In addition, activated carbon and at least one element such as Ni and Fe, a catalyst such as an oxide or a composite oxide are filled, but the type and shape of the catalyst used are not particularly limited. Further, in one embodiment of the present invention, the exhaust ozone gas EG is decomposed using a catalyst. However, for example, a method of thermally decomposing ozone at about 350 ° C. or a method of decomposing it by irradiating ultraviolet rays may be used. The decomposing means is not particularly limited.

When a catalyst is used as the ozone decomposition treatment means, the reaction temperature of the catalyst 14 filled in the ozone decomposition treatment tank 13 is adjusted to an appropriate temperature by the heating means 15 provided on the inlet side of the treatment tank 13 or inside the tank. Maintained at. As a catalyst
When the MnO ₂ catalyst is used, the catalytic reaction temperature is maintained at about 40 ° C to 50 ° C.

A blower 17 sucks the exhaust ozone gas EG from the ozone contact tank 8. This blower is arranged on the outlet side of the ozone decomposition treatment tank 13.

Reference numeral 18 denotes a biological activated carbon tank into which treated water TW after ozone gas OG is injected into treated water Wo is introduced.
This biological activated carbon tank is arranged on the downstream side of the ozone retention tank 9. The treated water TW flowing into the biological activated carbon tank 18 is the tank 1
8 Run down from the top. The biological activated carbon tank 18 is filled with activated carbon 19 serving as a carrier of microorganisms, and this forms an activated carbon layer 20. Initially, when activated water 19 is filled and water flow is started, few microorganisms are present on the surface or inside of this activated carbon 19, but with the passage of time, microorganisms acclimatized and propagated are present on the surface or inside of activated carbon 19.
Pseudomonas and the like are mentioned as the dominant species of microorganisms.

In the treated water TW after the ozone injection treatment, the ammoniacal nitrogen, which is difficult to remove by the ozone treatment, is nitrified and removed by the action of the above-mentioned microorganisms, and at the same time, the ozone treatment reduces the molecular weight to easily decompose organic compounds and the like. Metabolism is removed. The treated water AW from the biological activated carbon tank 18 thus treated is then sent to a distribution reservoir (not shown) or the like.

Reference numeral 21 denotes a backwash water pipe into which the backwash water BW is introduced into the tank 18 when backwashing the biological activated carbon tank 18 as necessary. The backwash water BW flows from the lower part of the biological activated carbon tank 18 toward the upper part, and the wastewater that has washed the activated carbon layer 20 is discharged to the outside of the tank 18 via the drain pipe 22 arranged at the upper part of the biological activated carbon tank 18. It

Reference numeral 23 is a catalyst for decomposing dissolved ozone in the treated water TW after the ozone has been injected into the treated water Wo, and this catalyst is arranged on the downstream side of the ozone contact tank 8. In the embodiment of the present invention, it is arranged in the ozone retention tank 9 located downstream of the ozone contact tank 8. As the 23 kinds of catalysts, treated water TW is used.
Activated carbon in which supported active components are not dissolved in is preferable, and the bed height ho of the catalyst layer 24 made of activated carbon is set lower than the bed height h of the activated carbon layer 20 filled in the biological activated carbon tank 18. That is, as described earlier in this specification, the dissolved ozone in the treated water TW is decomposed in the surface layer portion 10 cm or less from the surface layer of the activated carbon layer 20. Therefore, the catalyst layer 24 that protects the activated carbon layer 20 from the influence of dissolved ozone has at least a layer height corresponding to the surface layer portion, and the relationship between the layer heights is h> ho.

In the case of the above-mentioned structure, the water Wo to be treated is introduced into the ozone contact tank 8 where the ozone OG is injected from the ozonizer 10 side, in order to explain the operation of the following structure. In this case, the ozone injected into the water Wo to be treated is not completely dissolved in the liquid phase, and a part thereof is discharged to the gas phase, and the exhaust ozone gas EG is converted (decomposed) into oxygen by the ozone decomposition catalyst 14, It is discharged outside the system.

On the other hand, ozone dissolved in the liquid phase is treated water W.
The residual ozone that is consumed by the ozone consuming components such as organic matter in o and is not consumed by the organic matter exists in the treated water TW as dissolved ozone.

In this case, the treated water TW after the ozone has been injected into the water to be treated Wo flows down the ozone retention tank 9 containing the dissolved ozone, and is then introduced into the biological activated carbon tank 18. Here, when the biological activated carbon tank 18 is backwashed and the surface layer of the biological activated carbon layer is newly replaced, the microorganisms located in the surface layer may be necrotic or damaged due to the influence of dissolved ozone in the treated water TW. There is. When the microorganism is necrosed or damaged, the microorganism separates from the activated carbon of the carrier and flows down, and is mixed into the treated water AW from the biological activated carbon tank 9 to cause deterioration of the treated water quality.

However, the dissolved ozone in the treated water TW is decomposed by the catalyst layer 24 arranged on the downstream side of the ozone contact tank 8 before the inflow of the biological activated carbon tank 18. Then, since the treated water TW in which the dissolved ozone is decomposed flows into the activated carbon layer 20 of the biological activated carbon tank 18, the activated carbon layer 20, particularly the microorganisms located in the surface layer portion of the activated carbon layer, are affected by the dissolved ozone. It can be prevented from receiving necrosis or damage.

On the other hand, when the dissolved ozone in the treated water TW is decomposed by the catalyst as described above, since the dissolved ozone is decomposed in the surface layer portion of the catalyst layer 24, the bed height ho of this catalyst layer is at least the activated carbon layer. The layer height h of 20 can be made lower, and dissolved ozone can be decomposed efficiently with a small amount of catalyst. As a result, the means for protecting the microorganisms of the bioactive carbon layer from the influence of dissolved ozone is simplified.

Further, the dissolved ozone becomes oxygen after being decomposed by the catalyst, and this oxygen becomes dissolved oxygen. Therefore, the dissolved oxygen in the treated water TW flowing through the catalyst layer 24 into the biological activated carbon tank 18 is Maintained at high concentration. Therefore, even if the oxygen uptake increases with the growth of the microorganisms, the treated water TW containing a high concentration of dissolved oxygen flows into the biological activated carbon tank 18, so that the microorganisms can be maintained in a highly active state.

Further, when the dissolved ozone is decomposed by the catalyst arranged on the downstream side of the ozone contact tank 8, the treated water W is generated by the highly reactive radicals generated by the decomposition.
Oxidation reaction of organic substances and the like in o is promoted and the quality of treated water can be improved over the quality of treated water when a catalyst is not arranged. In particular, when the catalyst layer 24 is arranged in an ozone retention tank having a long retention time as in one embodiment of the present invention, the radicals (OH, etc.) generated along with the decomposition of dissolved ozone by the catalyst and the water W to be treated.
It is possible to accelerate the reaction with the organic substances in o over a long residence time, and it is possible to improve the quality of the treated water and reduce the amount of ozone injected into the water to be treated Wo by promoting the reaction. The running cost required for can be reduced.

[0053]

According to the present invention, it is possible to provide a simplified water treatment apparatus capable of suppressing the damage of microorganisms due to dissolved ozone to maintain the microorganisms in a highly active state and improving the quality of treated water.

[Brief description of drawings]

FIG. 1 is a system flow diagram of a water treatment device showing an embodiment of the present invention.

FIG. 2 is a partially enlarged detailed view of the system flow diagram shown in FIG.

FIG. 3 is a decomposition characteristic diagram of dissolved ozone according to the present invention.

[Explanation of symbols]

1 ... landing well, 2 ... chemical mixing pond, 5 ... floc formation pond, 7
... sedimentation tank, 8 ... ozone contact tank, 9 ... ozone retention tank, 10
... Ozonizer, 11 ... Vent pipe, 12 ... Mist separator, 13 ... Ozone decomposition treatment tank, 14 ... Ozone decomposition catalyst,
17 ... Blower, 18 ... Biological activated carbon tank, 19 ... Activated carbon,
20 ... Activated carbon layer, 21 ... Backwash water pipe, 23 ... Catalyst, 24 ...
Catalyst layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C02F 9/00 503 C02F 9/00 503A 504 504A 504E (72) Inventor Koji Ojiyama Omikami, Hitachi City, Ibaraki Prefecture 7-1-1, Machi, Hitachi Co., Ltd. Hitachi Research Laboratory

Claims (4)

[Claims] 1. A water treatment apparatus comprising an ozone contact tank for introducing treated water into contact with ozone and a biological activated carbon tank for introducing treated water treated in the ozone contact tank to perform biological activated carbon treatment. , A catalyst layer having a bed height lower than that of the activated carbon filled in the biological activated carbon tank is installed on the downstream side of the ozone contact tank, and dissolved ozone contained in water treated in the ozone contact tank Is passed through the catalyst layer for decomposition and then introduced into the biological activated carbon tank. 2. The water treatment device according to claim 1, wherein the catalyst filled in the catalyst layer is made of activated carbon. 3. An ozone contact tank for introducing water to be treated into contact with ozone, and an ozone retention tank disposed downstream of the ozone contact tank for introducing ozone-treated water from the ozone contact tank. A biological activated carbon tank disposed downstream of the ozone retention tank and into which treated water from the ozone retention tank is introduced, and the bed height is set lower than the bed height of the activated carbon filled in the biological activated carbon tank. The treated catalyst layer is disposed in the ozone retention tank, and dissolved ozone in the treated water in the ozone retention tank is passed through the catalyst layer to be decomposed. 4. The water treatment apparatus according to claim 3, wherein the catalyst filled in the catalyst layer arranged in the ozone retention tank is made of activated carbon.