JPH07199B2 - Organic wastewater treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating sewage containing organic matters such as sewage, night soil, waste water and river water by an aerobic filter bed method which effectively utilizes exhaust ozone gas generated by ozone treatment. The exhausted ozone gas referred to in the present specification refers to a mixed gas exhausted from the ozone treatment step, and does not refer only to the ozone component in the gas.

[0002]

2. Description of the Related Art In the aerobic filter bed method, water to be treated is usually passed from the upper part of the filter bed and an oxygen-containing gas is introduced from the lower part of the filter bed, so that not only the physical filtering action but also the filter material is highly effective. Oxidative decomposition of BOD and decomposition of ammoniacal nitrogen are performed by the action of microorganisms attached to the density. For this reason, it is excellent in compactness and is widely used as a method for treating wastewater containing organic substances. However, chromaticity, odor, and persistent COD components are difficult to remove by the aerobic filter method, so ozone treatment is often used together. Came to be.

For example, in the ozone treatment for decomposing the chromaticity component, sterilization and inactivation, reducing substances such as nitrite nitrogen and ozone consuming substances such as SS are previously removed by the aerobic filter method. Ozone treatment combined with aerobic filter method, which performs post-ozone treatment, is performed. Further, since the persistent COD component present in the wastewater is converted into the easily degradable component and the BOD component by the ozone treatment, the persistent COD component which is subjected to the ozone treatment in advance and then treated by the aerobic filter bed method is used.
There is also a biological treatment method for wastewater containing D component.

As described above, the use of ozone treatment in combination with the aerobic filter method or the combined use of the aerobic filter method with the ozone treatment for the purification treatment of the organic sewage complements the drawbacks of each single method. It is a very good treatment method. However, when ozone treatment is used, waste ozone treatment equipment is indispensable as described below. For example, FIG. 2 shows a conventional process in which a reducing substance such as nitrite nitrogen and SS are removed in advance by an aerobic filter bed method, and then an ozone treatment for decomposing the chromaticity component and sterilizing / inactivating is performed. Show. In FIG. 2, sewage secondary treated water is introduced into the aerobic filter bed 1, air is blown from the aeration blower 6 into the aerobic filter bed 1, and the water to be treated and the nitrification treated water treated by countercurrent flow into the ozone reaction tank 2. It is a process of sending water and performing processing such as decomposition and sterilization of chromaticity components by ozone gas from the ozone generator 4 and sending the treated water to the treated water tank 3, but the exhaust ozone gas generated from the ozone reaction tank 2 is The gas was sent to the exhaust gas processing tank 5 through the exhaust ozone conducting pipe 7 for processing. For this reason, in the aerobic filter method where compact treatment is an advantage, the advantage of compactness is lost and the treatment becomes expensive, and the combined use of the aerobic filter method and ozone treatment has become widespread. I didn't.

The ozone treatment is carried out by using ozone generated by an ozone generator using air or oxygen as a raw material. Therefore, ozone is contacted with sewage in an ozone treatment tank and decomposed, but even after the decomposition, about 2 mg-O ₃ / N liter of ozone remains in the exhaust gas (exhausted ozone gas). Since ozone is a gas harmful to humans and living organisms, the exhaust gas of ozone treatment needs to be treated with activated carbon or the like, and incidental equipment for detoxification is required.

When ozone is decomposed, it becomes oxygen. Therefore, oxygen is contained in the components in the exhaust gas generated from the exhaust ozone gas treatment facility. In particular, when ozone produced from a gas containing a high concentration of oxygen is used for the treatment, it is almost oxygen, and a large amount of oxygen is released to the atmosphere without being used. On the other hand, an aerobic filter bed is aerated with oxygen-containing gas in order to maintain microbial activity, but conventionally air or the like is blown from the outside. Also,
Since the aerobic filter bed retains microorganisms, the microorganisms that grow with use may form slime at the bottom, which may worsen the aeration state or partially anaerobically.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a rational and efficient aerobic method which removes exhausted ozone gas without providing a special facility and utilizes unused oxygen for aerobic condition formation. It provides a sewage treatment method using a filter bed.

[0008]

The above object can be achieved by the method for treating organic wastewater according to the present invention. That is, 1) In a method of treating wastewater, which comprises passing an organic wastewater through an aerobic filter bed filled with a biofouling carrier under aeration of an oxygen-containing gas, introducing the wastewater into an ozone reaction tank and contacting it with an ozone-containing gas,
A method for treating organic sewage, wherein exhausted ozone gas discharged from the ozone reaction tank is guided to the aerobic filter bed.
Alternatively,

2) In the method of treating wastewater, in which the organic wastewater is introduced into the ozone reaction tank and brought into contact with the ozone-containing gas, and then the water is passed through the aerobic filter bed filled with the biofouling carrier under aeration of the oxygen-containing gas, A method for treating organic sewage, wherein exhausted ozone gas discharged from the ozone reaction tank is guided to the aerobic filter.

Any aerobic filter and ozone reactor can be applied to the present invention. For example, the aerobic filter bed has a filter bed to which microorganisms are attached in the apparatus, for example, one or more packed beds filled with a carrier, and an oxygen-containing gas is supplied to at least a part of the filter bed. It may be configured using any one. The sewage supply system may be an upward flow or a downward flow, a continuous system or a batch system, and the filter bed may be a fixed bed or a partially fluidized bed. Further, a gravel, block, or other supporting material may be provided in the lower stage of the filling layer, a space may be provided through a lattice material, a porous material, or other water-passing member, or the bottom of the device may be filled. It may be a layer. As for the ventilation method, air can be diffused from the diffuser tube, the diffuser, the gas permeable membrane, or any other means from the inside of the above-mentioned packed bed, the inside of the support layer, the space and their boundary, or any other place. The air diffuser may be single or plural.

Also, the ozone reaction tank may be of any type as long as the ozone-containing gas and the sewage contact and react with each other. For example, it is possible to use a method of allowing sewage to stay for a certain period of time while diffusing ozone-containing gas by any diffusing means, or to diffuse it with a membrane, and to spray / spray water in a tank filled with ozone-containing gas, or any other method. But good. In addition, as the ozone gas, any of the air, oxygen-enriched gas, and high-purity oxygen can be supplied as a raw material by an arbitrary ozone generator. Further, ozone produced elsewhere may be transferred and supplied by an arbitrary method, and the supply form of ozone is not limited to the gas state. As a method of supplying the exhaust ozone gas to the aerobic filter, the exhaust ozone gas and the diffused gas can be supplied separately or in a mixture. If the exhaust ozone gas has sufficient oxygen, this may be sufficient.

In the above-mentioned step of performing ozone treatment for decomposing and sterilizing / inactivating chromaticity components after removing reducing substances such as nitrite nitrogen and SS by the aerobic filter method in advance. An example of applying the treatment method of the present invention in which exhaust ozone gas generated in an ozone reaction tank is sent to an aerobic filter bed is shown in FIG.
Shown in. FIG. 1 shows that the sewage secondary treated water is introduced into the aerobic filter bed 1, and the exhaust ozone gas generated in the ozone reaction tank 2 in the next step is sent to the aerobic filter bed 1 through the exhaust ozone conducting pipe 7. The treated nitric acid treated water is treated in countercurrent with the water to be treated, and the resulting nitrification treated water is sent to the ozone reaction tank 2, where the ozone gas generated by the ozone generator 4 decomposes and sterilizes chromaticity components. It is a process flow diagram which performs and sends treated water to the treated water tank 3.

Further, in the step of performing ozone treatment in advance in the case of sewage containing persistent COD components and the like, and treating by the aerobic filter method, the exhaust ozone gas generated in the ozone reaction tank is converted into the aerobic filter bed. An example to which the processing method of the present invention for supplying air is applied is shown in FIG. FIG. 3 shows that the sewage secondary treated water is first introduced into the ozone reaction tank 2, where the ozone gas generated by the ozone generator 4 is used to decompose or sterilize the chromaticity components and to perform ozone treatment. Water is sent to the aerobic filter bed 1, and the exhaust ozone gas generated in the ozone reaction tank 2 is sent to the aerobic filter bed 1 via the exhaust ozone conducting pipe 7 and treated in countercurrent with the water to be treated, thereby treating the treated water. It is a process flow diagram of sending water to the treated water tank 3.

(Operation) As described above, the exhaust ozone gas generated in the ozone treatment step is decomposed into oxygen. Especially when a high concentration oxygen-containing gas is used as a raw material, most of the exhaust ozone gas is oxygen. On the other hand, in the aerobic filter method, air is supplied from the lower part of the reaction filter bed to make the inside of the reaction filter aerobic and perform biological treatment. Oxygen in the air supplied at this time is used for biological reactions such as nitrification and BOD decomposition. That is, the biological reaction is limited by the oxygen supply amount. Therefore, if oxygen is used instead of air, the efficiency of the biological reaction naturally increases. For example, LV (filtration speed) of 200 m / day is used to treat sewage with an aerobic filter bed, the treated water is allowed to flow into an ozone reaction tank, and ozone gas with an ozone concentration of 50 mg-O ₃ / N liter is injected at a rate of 10 mg-O ₃ / When liters are supplied to the ozone reaction tank and treated, the amount of exhausted ozone gas generated is 0.03 Nm ³ / (m ² · min) with respect to the aerobic filter bed.

When the oxygen concentration in the exhaust ozone gas is 90%, the oxygen concentration is 4.5 times that of air, and the amount of oxygen in the exhaust ozone gas is equivalent to 0.135 Nm ³ / (m ² · min) in the air. Will be done. Therefore, if the amount of air supplied to the aerobic filter bed is 0.1 Nm ³ / (m ² · min), oxygen exceeding this amount of air can be covered only by the exhaust ozone gas.

In order to uniformly disperse the aeration gas of the aerobic filter bed in the filter medium layer, the aeration amount is 0.03 Nm ³ / (m ² ·
Min) or more is preferable. Therefore, the amount of exhausted ozone gas generated by the ozone treatment is 0.03 with respect to the aerobic filter bed.
If it is Nm ³ / (m ² · min) or more, it is possible to directly ventilate the aerobic filter bed. When the amount of exhaust ozone gas is less than that, exhaust ozone gas and air may be separately ventilated, or may be mixed with air in advance and ventilated. For mixing with air, for example, as shown in FIG. 4, the exhaust ozone conducting pipe 7 may be connected to the air suction pipe 9 of the ventilation blower 6. In this case, if the suction amount of the ventilation blower 6 becomes excessively large compared to the generated amount of exhaust ozone gas, the ozone reaction tank 2 becomes negative pressure, and if the suction amount of air is large and the suction amount of exhaust ozone gas is too small, ozone reaction occurs. There is a possibility that exhausted ozone gas may leak due to the pressure applied to the tank 2. In order to prevent the ozone reaction tank 2 from having a negative pressure when the amount of suction of the exhaust ozone gas becomes excessive, the exhaust ozone conducting pipe 7 is provided with an air suction pipe 1 with an intake valve.
It is sufficient to set 0. Further, in order to prevent the suction amount of the exhaust ozone gas from becoming too small, the orifice 8 or the like may be provided in the air suction pipe to suppress the suction amount of the mixed air.

More specifically, as shown in FIG. 5, for example, the exhaust ozone discharge pipe 7 is connected to the intake side of the ventilation blower 6 of the air suction pipe 9, and the mixing device 12 is installed at the connecting portion. Ozone / outside air mixing can be realized by the mixing device 12. In FIG. 5, the ejector 12 is actuated by the air intake amount of the ventilation blower 6, and the exhaust ozone gas is sucked by the ejector 12. The air intake amount of the ventilation blower 6 can be adjusted by providing an adjusting damper 8 if necessary. The air from the aeration blower 6 and the exhaust ozone gas from the ejector 12 are mixed by passing through the mixing section 14 of the device 12 filled with glass wool, and are mixed and sent to the aerobic filter bed.

The structure and operation of the exhaust ozone mixing device 12 shown in FIG. 5 will be described below. The exhaust ozone mixing device 12 communicates with at least the ozone reaction tank 2 for introducing the exhaust ozone gas, the exhaust ozone flow rate adjusting pipe 15 having the metering valve 13 and the ejector 12, and the flow rate adjusting as necessary for introducing the outside air. Intake flow control pipe 16 with damper 8
And the exhaust ozone flow rate control tube 15 from the intake flow rate control tube 16
The ejector 12 has a control unit 18 including a bypass pipe 17 for introducing air of a pressure insufficient to the ejector 12, and a mixing unit 14 for mixing external air and exhaust ozone gas as necessary. It is preferable that the mixing section 14 is filled with glass wool or the like to collect mist and dust in the gas, and the collected matter is appropriately discharged from a drain provided in the lower part of the mixing section 14.

Each element of the adjusting section 18 operates as follows. The exhaust ozone flow rate control pipe 15 is provided with a metering valve 13 for equalizing the flow rate of the exhaust ozone gas to prevent an overpressure, and in order to solve the negative pressure, the ejector 12 is provided with an intake flow control pipe. It has a bypass pipe 17 for introducing outside air from 16 and a bypass valve. Here, the ejector 12 acts so as not to cause a backflow of outside air or the like. The intake flow rate adjusting pipe 16 may be configured such that one end thereof is simply released to the outside air, but an adjusting damper 8 may be provided to prevent excessive suction, blockage, and other accidents. These valves and dampers can be configured to be controlled in conjunction with the flowmeter and the like. Of course, the embodiment of the present invention does not necessarily require the exhaust ozone mixing device disclosed for the purpose of description here, and the exhaust ozone mixing device is not limited to the structure shown in FIG.

An exhaust ozone mixing apparatus 1 as illustrated in FIG.
2, for example, as shown in FIG. 6, an exhaust ozone conducting pipe 7 from the ozone reaction tank 2 to the biofilm filtration tank (aerobic filter bed 1).
And on the upstream side of the ventilation blower 6. Here, it is preferable that a flow meter 19 and a flow rate adjusting valve 20 are provided on the discharge side of the aeration blower 6 so that the biofilm filtration tank 1 can be adjusted so that an appropriate amount of ventilation is provided.

Mixing the exhaust ozone gas with air not only increases the aeration amount of the aerobic filter bed and evenly disperses the ventilation gas in the filter medium layer, but also dilutes the ozone gas when the ozone concentration in the exhaust ozone gas is high. This has the effects of preventing the processing performance of the aerobic filter bed from being reduced by the exhaust ozone gas and facilitating the processing of the exhaust ozone gas in the aerobic filter bed. Even in the case of such mixing, the amount of aeration gas can be smaller than that in the case of using only air. Further, by ventilating the exhaust ozone gas through the aerobic filter bed, harmful ozone is decomposed. In addition, slime generation due to excessive growth of microorganisms in the aerobic filter bed can be suppressed by the bactericidal action of residual ozone in the exhaust ozone gas.

When the persistent COD component is contained in the organic wastewater, it is easier to remove the persistent COD component by ozone treatment than by directly passing water through the aerobic filter bed for biological treatment. It is preferable that the ozone-treated water is passed through an aerobic filter bed for biological treatment after conversion to degradable components or BOD components. Also in this case, the exhaust ozone gas from the ozone treatment tank can be supplied to the aerobic filter bed for the post-treatment to decompose harmful residual ozone in the exhaust ozone gas.

As described above, the present invention is a method for rendering harmful exhaust ozone gas harmless and effectively utilizing it when the exhaust ozone gas contains a high concentration of oxygen. Specifically, in the treatment of sewage using the aerobic filter method and ozone treatment in combination, residual ozone can be removed only by aeration of the exhaust ozone gas generated in the sewage ozone treatment through the aerobic filter bed.
No special facility required. When the pressure of the exhaust ozone gas is low and cannot be directly sent to the aerobic filter bed, the exhaust ozone gas may be sent to the aerobic filter bed by pressurizing with a booster blower. By supplying exhaust ozone gas to the aerobic filter bed, ozone is decomposed in the aerobic filter bed, and when the exhaust ozone gas contains a high concentration of oxygen,
Oxygen required for biological treatment of aerobic filter bed can be covered with a smaller amount of gas than when air is used, so an exhaust ozone treatment device is not required, and exhaust ozone gas can be effectively used and aeration blower of aerobic filter bed can be used. Power costs can be reduced. Further, by suppressing the generation of slime at the bottom of the aerobic filter bed, it is not necessary to increase the discharge pressure of the blower for cleaning the filter bed, and the frequency of backwashing is also reduced.

[0024]

EXAMPLES Examples of the present invention will be shown below. However, the present invention is not limited to the following specific embodiments.

(Example 1) FIG. 1 shows an example in which the present invention is applied to the case where the secondary treated water of the sewage is used as raw water, which is treated by the aerobic filter method in the first stage and the ozone treatment is performed in the second stage. The amount of raw water passed through the aerobic filter bed 1 was LV 200 m / day. The ozone treatment tank 2 has an ozone concentration of 50 mg-O.
Injection rate of ₃ / N liter of ozone gas is 15 mg-O ₃ /
It was supplied by N liters for treatment, and the exhaust gas from the ozone treatment tank 2 was supplied to the aerobic filter bed 1. Here, the injection rate is the amount of ozone (mg) required for ozone treatment of 1 liter of water (which is equal to the amount of raw water passing through the aerobic filter bed 1) flowing into the ozone treatment tank 2. The converted amount (volume) of ozone gas having an ozone concentration of 50 mg-O ₃ / N liter used in the present invention is 0.3 liter / liter (that is, 0.3 m ³ / m ³ ).

When the cross-sectional area of the aerobic filter bed is Am ² , L
The amount of raw water passed at V200m / day is Q = 200 ×
Since Am ³ /day=0.139×Am ³ / min and the injection rate is 0.3 m ³ / m ^3, it is used in the present invention required to treat raw water passing through the aerobic filter bed 1. The ozone gas amount R is R = (0.139 × Am ³ /min)×0.3 m ³ / m
³ = 0.042 × Am ³ / min About 0.04 Nm ³ per unit area of aerobic filter bed
/ M ² · min.

When such treatment is carried out, the aerobic filter bed 1
Table 1 shows the results of measurement of ozone concentration, ozone odor and treated water quality in the gas discharged from the plant.

[0028]

[Table 1]

Even when exhausted ozone gas having an ozone concentration of 4 mg-O ₃ / N liter was supplied to the aerobic filter bed 1, no ozone was detected in the gas discharged from the aerobic filter bed 1.

(Comparative Example 1) FIG. 2 shows an example of a conventional treatment method in which the secondary treated water of sewage is used as raw water and treated by the aerobic filter method in the first stage and ozone treatment in the second stage. Air was supplied to the aerobic filter bed at 0.1 Nm ³ / (m ² · min), and the treated water quality obtained under the same treatment conditions as in Example 1 was the same as in Example 1. Table 2 shows the results of measurement of water quality items.

[0031]

[Table 2]

As shown in Tables 1 and 2, Example 1
Then, the amount of gas supplied to the aerobic filter bed 1 is 0.04 Nm ³ /
(M ² · min) and 0.1 Nm ³ / (m ^{2 in} the case of Comparative Example 1
Although the amount of ammonia nitrogen was decreased, the odor intensity and chromaticity of the aerobic filter-treated water were lower than those of Comparative Example 1. The other water quality was the same as in Comparative Example 1, and the exhaust ozone gas could be made harmless without impairing the treatment performance of the aerobic filter, and the exhaust ozone gas could be effectively used. Further, in Example 1, the power cost of the ventilation blower of Comparative Example 1 could be reduced.

(Example 2) FIG. 3 shows an example in which the present invention is applied to a case where the secondary treatment water of sewage is used as raw water, the ozone treatment is performed in the first stage, and the treatment by the aerobic filter method is performed in the second stage. The treatment conditions of the aerobic filter bed 1 and the treatment conditions of the ozone treatment tower were the same as in Example 1, and the same analysis as in Example 1 was performed.
The results are shown in Table 3.

[0034]

[Table 3]

As in Example 1, no ozone was detected in the gas discharged from the aerobic filter, and the quality of treated water was good.

[0036]

According to the present invention, in the treatment of sewage using the aerobic filter method and the ozone treatment in combination, the exhaust ozone gas generated by the ozone treatment of the sewage is supplied to the aerobic filter bed to remove the exhaust ozone gas. No need for an exhaust ozone device to detoxify, oxygen in exhaust ozone gas can be used for biological treatment of aerobic filter beds, and the action of residual ozone can suppress the generation of microbial slime at the bottom of filter beds. ,
The quality of treated water will also be improved.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of an organic sewage treatment method for supplying exhaust ozone gas of the present invention to an aerobic filter bed.

FIG. 2 is a flow chart showing a typical example of a conventional organic sewage treatment method combined with ozone treatment.

FIG. 3 is a flow chart showing an example of an organic wastewater treatment method that precedes the ozone treatment of the present invention and supplies waste ozone gas to an aerobic filter bed.

FIG. 4 is a flow chart showing an example of an organic wastewater treatment method of the present invention, in which air is mixed with exhaust ozone gas and supplied to an aerobic filter bed.

FIG. 5 is a structural explanatory view of a mixing device for mixing exhaust ozone and outside air according to the present invention.

FIG. 6 is a diagram showing an example of a flow from the ozone reaction tank of the present invention to the aerobic filter bed through a mixing device.

[Explanation of symbols]

 1 Aerobic filter bed 2 Ozone reaction tank 3 Treated water tank 4 Ozone generator 5 Exhaust gas treatment tank 6 Aeration blower 7 Exhaust ozone conduction pipe 8 Adjustment damper 9 Air suction pipe 10 Air suction pipe 11 Intake valve 12 Ejector 13 Constant flow valve 14 Mixed Part 15 Exhaust ozone flow rate control pipe 16 Intake flow rate control pipe 17 Bypass pipe 18 Control part 19 Flow meter 20 Flow rate control valve

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Ken Sasaki 2-8-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Tokyo Metropolitan Sewer Bureau (72) Inventor Hiroshi Sakuma 1-6-27, Konan, Minato-ku, Tokyo Ebara Inn Filco Co., Ltd. (72) Inventor Toshihiro Tanaka 1-6-27 Konan, Minato-ku, Tokyo Ebara Inn Filco Co., Ltd. (72) Inventor Kazuo Fujita 1-6-27 Konan, Minato-ku, Tokyo Ebara-in Filco Stock In-company (72) Inventor Manabu Ikeguchi 1-6-27 Konan Minato-ku, Tokyo Ebara Infilco Co., Ltd. (56) Reference JP-A-49-4354 (JP, A)

Claims (2)

[Claims] 1. A method for treating sewage, which comprises passing an organic sewage through an aerobic filter bed filled with a biofouling carrier under aeration of an oxygen-containing gas, and then introducing the sewage into an ozone reaction tank to contact with an ozone-containing gas. A method for treating organic sewage, which comprises introducing waste ozone gas discharged from an ozone reaction tank to the aerobic filter bed. 2. A method for treating sewage, which comprises introducing an organic sewage into an ozone reaction tank and bringing it into contact with an ozone-containing gas, and then passing it through an aerobic filter bed filled with a biofouling carrier under aeration of an oxygen-containing gas, A method for treating organic sewage, wherein exhausted ozone gas discharged from the ozone reaction tank is guided to the aerobic filter bed.