JP2000061497A - Treatment of organic wastewater and equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an activated sludge process for the treatment of organic wastewater without incurring any increase of the BOD load of existing activated sludge process equipment and also to drastically reduce the amount of excess activated sludge without causing any deterioration of water quality of the effluent water by using a simple process. SOLUTION: This treatment for treating organic wastewater with an activated sludge process system, involves: withdrawing at least a part of activated sludge as sludge to be treated; subjecting the constituent microbes of the sludge to be treated to sterilization treatment and solubilization treatment to obtain a treated activated sludge material; subsequently, further treating the treated activated sludge material with activated sludge contg. aerobic microbes and/or microbes capable of nitrate respiration, in an anaerobic atmosphere and in the presence of nitrate ions and/or nitrite ions; and thereafter, reintroducing the resulting treated active sludge material into the activated sludge process system, to perform the objective purification treatment of organic wastewater with activated sludge thus obtained.

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 organic wastewater in which treated water containing organic matter is treated with activated sludge, and more specifically, it does not cause deterioration of water quality of the treated liquid discharged. , A simple and economical method for treating organic wastewater, which achieves a drastic reduction in excess sludge and does not cause an increase in the BOD load of existing treatment equipment,
And an organic wastewater treatment device.

[0002]

2. Description of the Related Art Pollutants in water are decomposed and purified in nature such as rivers and lakes by being subjected to physicochemical and biological actions such as precipitation, aggregation, oxidation and reduction. In particular, contaminants containing organic substances are easily purified by microorganisms by a biological action. As a method for purifying organic wastewater using this, there is an activated sludge method of treating organic wastewater with activated sludge containing aerobic microorganisms, but the method has a high purification capacity and relatively low treatment cost. Therefore, various methods utilizing this have been proposed and are widely used in sewage treatment, industrial wastewater treatment and the like.

In the above-mentioned activated sludge method, waste water p
After performing pretreatment such as H adjustment and homogenization, the organic wastewater is led to an aeration tank (aeration tank), and in this aeration tank, organic sludge components in the wastewater indicated by BOD are decomposed by activated sludge. Purification processing is being performed (see FIG. 5). At this time, 50 to 70% of the decomposed BOD is consumed as maintenance energy for the microorganism, but the remaining 3
Since 0 to 50% is used for the growth of bacterial cells, the amount of activated sludge gradually increases with the treatment. Therefore, generally, as shown in FIG. 5, the wastewater treated in the aeration tank is guided to the settling tank, and only the amount necessary for the purification treatment of the organic wastewater is returned from the precipitated activated sludge. It is returned to the aeration tank as sludge, and excess activated sludge that is not returned is removed as excess sludge. Thus, the purification process using activated sludge has a problem that a large amount of excess sludge is generated. This excess sludge contains bio-degradable substances, etc., and has high viscosity and is difficult to handle.Therefore, when purifying organic wastewater by the activated sludge method, there is always a problem of excess sludge treatment. Let's take it.

On the other hand, currently used methods for treating excess sludge are methods such as dehydrating the excess sludge to separate water and incinerating solids or landfilling as industrial waste. Alternatively, the excess sludge is subjected to anaerobic digestion to decompose it into methane gas, carbon dioxide, hydrogen, hydrogen sulfide, etc. to reduce the amount, and then the excess sludge and other solid matter that have not been decomposed are separated by dehydration to obtain a solid content. There is a method to incinerate or dispose as industrial waste.
Furthermore, in recent years, for the purpose of reducing the excess sludge, after treating a part of the excess sludge with ozone, a method of introducing the ozone-treated sludge into the aeration tank again and performing aerobic treatment is known. (Japanese Patent Publication No. 57-19719, JP-A-7-8)
8495 gazette).

However, the above-mentioned conventional method for treating excess sludge has various problems as described below. First, when the excess sludge is concentrated by a dehydrator without performing anaerobic digestion treatment and incinerated or disposed of as industrial waste, there is a problem that the treatment cost is significantly increased due to the large amount of excess sludge. The current sludge disposal cost is 20,000 yen /
m ³ is high, and further, this disposal cost tends to rise further in the future. In addition, the effects on global environmental degradation such as the problem of securing landfill disposal sites and the problem of increased energy consumption due to sludge incineration cannot be overlooked.

The above-mentioned method for reducing excess sludge by anaerobic digestion has the advantage that energy is recovered as methane gas, but the number of days required for digestion is as long as 20 to 40 days, and excess sludge is required. The decomposition rate is low at about 60%, so a large site area is required, and undecomposed excess sludge and other solids must be separated by a dehydrator and incinerated or disposed of as industrial waste. Therefore, there is a problem that it is inefficient and the processing cost increases. Further, similarly to the above, there is an influence on the global environment.

Further, the method of treating a part of the excess sludge with ozone can considerably reduce the amount of the excess sludge, but it is necessary to provide a special ozone generator. Therefore, it is not suitable for small-scale facilities, and there is a practical problem that the facility cost is high, the operating cost is high, the treatment cost is high, and the economy is poor. Furthermore, after treating a part of the excess sludge with ozone, the treated activated sludge treatment product is re-introduced into the existing activated sludge treatment facility for treatment, resulting in an increase in the BOD load of the existing activated sludge treatment facility. However, there is a problem in that it cannot be applied to processing equipment with a high load amount.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for treating organic wastewater using the activated sludge method, which is the same as the conventional one without causing an increase in the BOD load of the existing activated sludge treatment equipment. It is possible to perform activated sludge treatment under the conditions described above, and without deteriorating the water quality of the treated water discharged at the final stage. An object of the present invention is to provide a simple and economical method for treating organic wastewater and an apparatus for treating organic wastewater capable of eliminating sludge generation.

[0009]

The above objects can be achieved by the present invention described below. That is, the present invention is a method for treating organic wastewater in which organic wastewater is purified by an activated sludge treatment system containing aerobic microorganisms, and at least a part of the activated sludge is extracted as treated sludge, and the treated sludge is treated. The constituent microorganisms are sterilized and solubilized, and subsequently the sterilized and solubilized activated sludge treated product is treated in an anaerobic atmosphere in the presence of nitrate ions and / or nitrite ions. And / or a method for treating organic wastewater, which comprises treating with activated sludge containing nitrate-respiratory microorganisms, and then reintroducing into the activated sludge treatment system for purification treatment with activated sludge, and treatment of organic wastewater It is a device.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail with reference to the preferred embodiments of the present invention. The present inventors, as a result of earnest research to solve the above-mentioned problems of the prior art, the organic wastewater, when purifying by an activated sludge method containing aerobic microorganisms, at least part of the activated sludge is extracted, After the extracted activated sludge (hereinafter, referred to as treated sludge) is sterilized and solubilized, it is immediately sterilized and solubilized without being reintroduced into the activated sludge treatment system (hereinafter, solubilized activated sludge). Are treated in the presence of nitrate ions and / or nitrite ions in an anaerobic atmosphere with an activated sludge containing aerobic microorganisms as an oxygen source, and the treated activated sludge (hereinafter, activated sludge) is treated. (Referred to as a treated product) is again introduced into the activated sludge treatment system, and subsequently treated with the activated sludge, the BOD component in the activated sludge generated by the sterilization and solubilization treatment is previously oxidatively decomposed, It is possible to efficiently treat activated sludge under the same conditions as before without causing an increase in the BOD load of the installed activated sludge treatment equipment, and to deteriorate the quality of the treated water discharged. Therefore, the present invention has been completed by finding that the generation of excess sludge can be significantly reduced without requiring a particularly large-scale device. Further, it has been found that particularly when a method of oxidative decomposition with an oxidizing agent using a metal ion as a catalyst is used as a sterilization or solubilization method, a remarkable effect can be obtained by a simple treatment. Hereinafter, the action in each treatment step of the organic wastewater treatment method of the present invention will be described in more detail.

In the biological treatment of organic wastewater with activated sludge, the organic matter in the wastewater is oxidatively decomposed by the bacteria in the activated sludge, and along with this, the bacteria themselves grow using the organic matter as a nutrient source. Further, some of these bacteria are predated by the protozoa in the activated sludge and settled into activated sludge having good cohesiveness and sedimentability, so that the amount of activated sludge gradually increases. Therefore, in the method for treating organic wastewater of the present invention, first, a part of the activated sludge that has been precipitated and separated is extracted to obtain a sludge to be treated, and bacteria (microorganisms) constituting the sludge to be treated are sterilized, or By providing a solubilization process, the bacteria themselves are converted as organic pollutants represented by BOD so as to be suitable foods for bacteria and protozoa, and then biologically treated again to produce activated sludge produced by biological treatment. Control the increase of

[0012] For example, in the process of sterilizing and solubilizing the microorganisms constituting the activated sludge, a part of the returned sludge sent from the settling tank is extracted to be treated sludge, and the treated sludge is catalyzed by metal ions. Although it is not clear that the chemical treatment by the method of oxidative decomposition with the above-mentioned oxidant produces a strong oxidant, OH (hydroxyl radical), one is that the hydroxyl radical constitutes active sludge. As a result of the decomposition or damage of the cell walls of the existing microorganisms, the microorganisms that make up the activated sludge are sterilized,
Alternatively, as a result of a part of the cells being solubilized and the polysaccharides, proteins, etc. in the cell wall being dissolved, the microorganism itself becomes the BOD component. Therefore, when the solubilized activated sludge treated in this way is placed again in the aeration tank and biologically treated, a part of the sterilized cells and the organic matter produced by the solubilization are not decomposed by normal microorganisms. It is easily oxidized and decomposed by normal microorganisms in the aeration tank. As a result, the amount of excess sludge generated can be significantly reduced.

However, as described above, the solubilized activated sludge becomes a BOD component by sterilization and solubilization treatment. Therefore, when this is put into the existing activated sludge treatment facility (aeration tank) again, it becomes a normal The BOD load of the aeration tank will be increased rather than the state. In this case, there is no problem in the treatment equipment that does not set the BOD load amount to a very high level, but depending on the type of organic wastewater, the BOD load amount of the existing activated sludge treatment facility may increase too much, and If activated sludge is treated under the same conditions as above, the treatment may be insufficient. That is, for example, in a treatment facility with a high BOD load handling organic wastewater from a food factory, the solubilized activated sludge in a state in which the sludge to be treated has been sterilized and solubilized and converted into BOD components is Once reintroduced,
There is concern that sufficient biological treatment may not be performed due to an increase in BOD load. And in this case,
The treated water discharged at the final stage may become treated water with high BOD and poor water quality.

Therefore, in the method for treating organic wastewater of the present invention, the solubilized activated sludge in which microorganisms are converted into BOD components (components that undergo microbial decomposition) by sterilization and solubilization treatment is immediately used for existing activated sludge. Instead of re-introducing into the activated sludge treatment equipment (aeration tank) that constitutes the treatment system, aerobic microorganisms and / or nitric acid are present in advance in an anaerobic atmosphere in the presence of nitrate ions and / or nitrite ions. It is constructed so that it is treated with activated sludge containing respiratory microorganisms and then introduced into the existing activated sludge treatment facility. That is,
In this way, the BOD component of the solubilized activated sludge is treated with activated sludge containing aerobic microorganisms and / or nitrate respiring microorganisms having nitrate ions and / or nitrite ions as oxygen sources, and is oxidatively decomposed. Therefore, even if it is reintroduced into the existing activated sludge treatment equipment, the BOD load amount does not increase. As a result, despite the fact that the existing activated sludge treatment facility (aeration tank) is performing the same treatment under the same conditions as the conventional one, it does not deteriorate the quality of the treated water to be discharged, and the excess sludge It is possible to significantly reduce the amount generated. Furthermore, since the treatment of the solubilized activated sludge can be performed in an anaerobic atmosphere, an aeration device is not necessary, the device does not become large, and the operating cost does not significantly increase.

As explained above, the sludge to be treated extracted from the activated sludge treatment system is sterilized at the stage of sterilization and solubilization treatment, and the microorganisms constituting the sludge to be treated are sterilized, while A part is solubilized to become a solubilized activated sludge which is converted into a part of sterilized cells and a BOD component composed of an organic substance generated by solubilization. The BOD component in this solubilized activated sludge is oxidatively decomposed in the subsequent process of activated sludge treatment in the presence of nitrate ions and / or nitrite ions, so the activated sludge treated product is reintroduced into the aeration tank. But that B
The amount of OD load is not significantly increased, and the generation of excess sludge can be significantly reduced. In the method for treating organic wastewater of the present invention in which the above-mentioned treatment is performed, the treatment capacity of activated sludge and the amount of surplus sludge generated are taken into consideration, and the above-mentioned sterilization and solubilization treatment, and subsequent nitrate ion and / or If the amount of the sludge to be treated extracted from the activated sludge system for carrying out the activated sludge treatment in the presence of nitrite ions is determined, theoretically, it becomes possible to suppress the generation of excess sludge by 100%.

In the above, the method of sterilization and solubilization treatment is exemplified by the method of oxidative decomposition with an oxidizing agent using a metal ion as a catalyst. However, the present invention is not limited to this, and the activated sludge to be treated can be treated. A state in which the cell walls of the constituent microorganisms are decomposed or damaged, the microorganisms constituting the sludge to be treated are sterilized and some of the cells are solubilized, and the solubilized activated sludge is easily predated by normal microorganisms. Any method can be used as long as it can be.

Specific embodiments of the method for treating organic wastewater of the present invention will be described in detail with reference to the drawings. In the method for treating organic wastewater of the present invention, basically, the treatment of organic wastewater is performed by a flow substantially similar to the flow of treatment by the normal activated sludge method. For example, as shown in FIG. 1, in the normal case, at least a part of the activated sludge settled in the settling tank is returned to the aeration tank as return sludge.
The characteristics of the method for treating organic wastewater of the present invention include, for example, extracting a part of the returned sludge, and guiding the extracted sludge to be treated to a sterilization and solubilization treatment step without any pretreatment. After the treatment, the microorganisms composing the sludge to be treated are converted into BOD components, and the sterilized and solubilized solubilized activated sludge is further activated in the presence of nitrate ions and / or nitrite ions. The purpose is to lead to a sludge treatment (hereinafter, also simply referred to as solubilized sludge treatment) step to oxidize and decompose the BOD component in the solubilized activated sludge, and then return the treated activated sludge treated product to the aeration tank again.

FIG. 1 explained above shows an example in which a part of the sludge returned from the settling tank to the aeration tank is taken out as the sludge to be treated, but the present invention is not limited to this and, for example, a settling tank may be used. In the case of the batch type activated sludge method, which is not provided, a part of the organic wastewater containing the activated sludge may be taken out from the aeration tank to be treated sludge. According to the above, the sterilization and solubilization treatment step and the solubilized sludge treatment step described above can be easily incorporated without adding a large change to the treatment flow of the organic wastewater by the existing activated sludge treatment having various forms. You can

The sterilization and solubilization treatment steps in the method for treating organic wastewater of the present invention will be described in detail below. First, the amount of sludge to be treated that leads to the sterilization and solubilization treatment process depends on the type of the target organic wastewater and the treatment conditions in the sterilization and solubilization treatment process, but the amount of activated sludge produced per day. It is preferably about 1 to 10 times.
As a result, when the organic wastewater is treated by the treatment method of the present invention, almost no conventional excess sludge is generated, and it is possible to dispense with excess sludge extraction and subsequent complicated excess sludge treatment. . In addition, the quality of the treated water treated according to the present invention is not inferior to the treated water treated by the generally used activated sludge method, and the quality of the treated water does not deteriorate.

In the method for treating organic wastewater of the present invention,
Oxidative decomposition by a metal ion-catalyzed oxidizing agent, which is a preferred example of a method for sterilizing and solubilizing the sludge to be treated, and more preferably, by a metal ion-catalyzed oxidizing agent in a state where the reaction solution is heated. The oxidative decomposition treatment will be described in detail.

The oxidizing agent used in the oxidation treatment is an oxidizing agent used in a conventionally known chemical oxidation method, for example, hydrogen peroxide, calcium peroxide, ammonium persulfate, alkyl hydroperoxide, peroxide ester,
Dialkyl peroxide or diacyl peroxide is used, but hydrogen peroxide is the most preferable in terms of cost and by-products.
The amount of the oxidizing agent such as hydrogen peroxide used is not particularly limited and varies depending on the content of the sludge to be treated, but the preferable amount is 0.1 to 0.0 per 1 g (dry weight) of the sludge.
The range is 01 g.

The metal ions used as the catalyst include
Iron, titanium, cerium, copper, manganese, cobalt, vanadium, chromium, lead ions and the like can be mentioned. If these metal ions are contained, the form thereof is metal, metal oxide,
Any of metal salts and complexes may be used. Especially preferred in the present invention is iron ion. For iron ions,
Although ferrous ions were used in the prior art, ferrous ions as well as ferric ions are effective in the present invention, and metallic iron such as iron scraps and iron ions are ion exchange resins, etc. Fixed iron ions fixed with can also be used. The amount of iron ions used as this catalyst is about 20 to 1000 mg per 100 mg / l of an oxidizing agent such as hydrogen peroxide.
A sufficient treatment effect can be obtained with / l.

FIG. 2 schematically shows a portion of a reaction treatment tank used for oxidative decomposition by an oxidizing agent using metal ions as a catalyst. The sludge to be treated is first introduced into the catalyst regeneration tank. In the catalyst regeneration tank, a catalyst is added, the inside of the tank is kept acidic at pH 4 or less, and heated to about 40 to 100 ° C., and the metal added as a catalyst becomes a metal ion and becomes active. Processed to have. Next, the sludge to be treated containing the metal ions in this state is introduced into a reaction tank, where an oxidizing agent such as hydrogen peroxide is added so as to have an appropriate concentration and is oxidized.

At this time, it is preferable to carry out the reaction by adjusting the pH of the reaction liquid containing the sludge to be treated to about 2 to 3.5. If nitric acid is used as the pH adjuster used at this time, it is possible to omit the addition of nitrate ions when the solubilized sludge is treated with activated sludge containing nitrate respiring microorganisms in an anaerobic atmosphere. Furthermore, the oxidation reaction is preferably performed by heating the reaction solution. The heating temperature is preferably in the range of 40 ° C to 100 ° C, more preferably 50 ° C to 80 ° C. Processing temperature is 40 ℃
If it is less than the above range, it takes time to oxidize, the oxidation efficiency is insufficient, and the utilization efficiency of an oxidizing agent such as hydrogen peroxide is insufficient. Further, even if the temperature exceeds 100 ° C., no further treatment effect can be expected, and further, the self-decomposition of the oxidizing agent such as hydrogen peroxide becomes large, the utilization efficiency is lowered, and the heating energy consumption is large. There is no special advantage. As a means for heating the reaction liquid containing the sludge to be treated, any means such as blowing steam or heat exchange with other hot water in the factory can be used, and the reaction liquid is heated to an appropriate temperature. If maintained and maintained, the heating method is not particularly limited.

The oxidation reaction time varies depending on the size of the oxidation treatment tank, the performance of the stirrer, the temperature, etc.
When the amount of sludge to be treated (solid content of about 1% by weight) obtained by extracting a part of the returned sludge is 10 m ³ and the oxidation temperature is 50 ° C. and sufficient stirring is performed, the reaction is performed for about 0.5 to 3 hours. It was confirmed that the temperature was sufficient, and that if so, most of the microorganisms constituting the sludge to be treated were killed and converted into BOD components.

Next, the reaction liquid containing the treated activated sludge is introduced into a neutralization tank, and an alkali such as sodium hydroxide is added to the reaction liquid to pH 5.0 to 7.5 for neutralization. In the present invention, as shown in FIG. 2, the neutralized reaction solution is then introduced into the bacterial tank to treat the bacteria, and then returned to a normal activated sludge treatment system to be introduced as raw water. Activated sludge treatment with organic wastewater (see Figure 1). Details of the bacterial treatment will be described later.

In addition to the above-mentioned method of oxidative decomposition with an oxidizing agent using a metal ion as a catalyst, another method of sterilizing and solubilizing sludge to be treated which can be used in the present invention is as follows. For example, ultrasonic treatment with an ultrasonic generator can be used. In this case, the treated sludge is treated with ultrasonic waves from an ultrasonic generator at a treatment output of 0.1 to 10 kW, a treatment time of 1 to 30 minutes, a treatment temperature of 20 to 100 ° C., and a treatment pH of 3 to 10. It is preferable to treat under the conditions of.

Further, in the present invention, as a method for sterilizing and solubilizing the sludge to be treated, a method by enzyme treatment can be used. As the enzyme used at this time, protease, α-amylase, lipase, glucanase, cellulase or the like is used, and the treatment temperature is 10 to 100.
It is preferable to carry out the treatment at a temperature of 0 ° C. and a treatment pH of 4 to 10.
The amount of enzyme added varies depending on the type of enzyme and the type of treated sludge, but the amount of treated sludge (solid content: about 1% by weight) is 10
In the case of m ^3, the amount of enzyme added is preferably about 0.001 to 1 kg.

Other methods for sterilizing and solubilizing the sludge to be treated include, for example, a method of treating with ozone,
Examples include addition of sodium hypochlorite, UV irradiation treatment, UV irradiation treatment performed by adding a photooxidation catalyst, and mechanical destruction. In addition, these methods may be used alone, or may be used in combination with the various treatments described above. For example, after treating with ozone, a method of oxidatively decomposing with an oxidizing agent using the above-mentioned metal ions as a catalyst, or the amount of sludge to be treated (solid content: about 1% by weight) is 1
In the case of 0 m ³ , it is also preferable to add sodium hypochlorite for ultrasonic treatment within a range of 0.05 to 1 kg, or to add enzyme for enzyme treatment and perform ultrasonic treatment.

Next, aerobic microorganisms are present in the presence of nitrate ions and / or nitrite ions under an anaerobic atmosphere, which is carried out following the above-mentioned sterilization and solubilization treatment in the method for treating organic wastewater of the present invention. And / or the solubilized sludge treatment step of treating with activated sludge containing nitrate respiratory microorganisms will be described. As the activated sludge used in the above-mentioned solubilized sludge treatment step, it is possible to use an activated sludge containing aerobic microorganisms and / or nitrate respiring microorganisms that decompose organic matter by using nitrate ions and / or nitrite ions as oxygen sources. preferable. For example, use denitrification sludge of wastewater, normal activated sludge mixed with the above-mentioned wastewater or other organic wastewater, and use the activated sludge treated by treating these wastewater in the presence of the above ions. You can Such activated sludge may be used as it is or may be supported on a carrier. When a carrier is used, any carrier conventionally used for supporting activated sludge can be used and is not particularly limited. Also, the amount of the carrier to be filled may be appropriately set according to the BOD treatment load.

As the nitrate ion and nitrite ion generating substances used in the above-mentioned solubilized sludge treatment step, water-soluble compounds which generate these ions are preferable.
Nitric acid; nitrates such as sodium nitrate, potassium nitrate, magnesium nitrate, ammonium nitrate; sodium nitrite,
Examples include nitrite salts such as potassium nitrite and ammonium nitrite. These can be used alone or in combination of two or more. Further, a nitrification solution of ammonia-containing wastewater can also be used. Further, in consideration of economy, it is preferable to use so-called waste nitric acid. Waste nitric acid is generated as wastewater from stainless steel nitric acid washing process in steel and steel manufacturing industry, wastewater from organic synthetic chemical plants such as filtration waste liquid from nitration process in organic synthesis, or nitric acid in wastewater is neutralized. Is included as nitrate. In the present invention, of these waste nitric acids, it is particularly preferable to use one that has been neutralized. Examples of products that are commercialized using waste nitric acid as a raw material include Hypox NA (manufactured by Environmental Engineering Co., Ltd.). The amount of nitrate ion and / or nitrite ion generated from these compounds varies depending on the type of surplus sludge, but is usually 0.2 to 50% with respect to the total organic substances in the solubilized activated sludge. BOD in solubilized activated sludge
The addition amount may be adjusted appropriately according to the state of the components.

The sludge treatment tank used in the solubilized sludge treatment step may be a complete mixing type, a fixed bed or a fluidized bed (upflow and downflow type). For example, as shown in FIG. Such an anaerobic tank may be used, or an upflow aerobic fluidized bed apparatus as shown in FIG. 4 may be used. The fluidized bed system has an advantage that it requires a small installation area. In addition, when using the sludge treatment tanks of either FIG. 3 or FIG. 4, even if the treatment is carried out under stirring in order to sufficiently contact the solubilized activated sludge to be treated with the activated sludge to enhance the treatment efficiency. Good. The activated sludge treatment performed in the solubilized sludge treatment step constituting the method for treating organic wastewater of the present invention using such a treatment tank is performed under an anaerobic atmosphere using nitrate ions and / or nitrite ions as oxygen sources. It does not require aeration and is different from normal aerobic treatment. That is, since the equipment and operation cost required for the aeration process are not required, economical treatment is possible.

FIG. 3 shows an anaerobic tank which is an example of a sludge treatment tank that can be used in the present invention. In the present invention, any anaerobic tank for carrying out an ordinary anaerobic decomposition treatment can be used. Since the anaerobic tank does not need to be supplemented with oxygen, it has the advantage that it can be a deep tank and does not require a large site. In the present invention, as shown in FIG. 3, solubilized sludge is introduced into such an anaerobic tank,
With nitrate and / or nitrite added,
Treat with activated sludge containing aerobic and / or nitrate respiring microorganisms.

FIG. 4 shows an upflow aerobic fluidized bed apparatus which is an example of a sludge treatment tank that can be used in the present invention. This will be described below. Solubilized activated sludge is
It is supplied to the lower part of the upward flow aerobic fluidized bed apparatus 1 from the inflow pipe 3 so as to form an upward flow by a pump or the like. The nitrate ion and / or the nitrite ion are added to the solubilized activated sludge, which is an object to be treated, by the oxygen source supply pipe 4 before being introduced. The solubilized activated sludge that has entered the apparatus is stirred at a very slow speed by a stirrer 6 together with nitrate ions and / or nitrite ions and the activated sludge 5 carried on the carrier. As a result, the BOD component in the solubilized activated sludge is brought into contact with the activated sludge 5 for biological treatment, and an upward flow of the solubilized activated sludge is formed. The treated solubilized activated sludge rises to the accumulating section 7, is discharged from the discharge pipe 8, and is sent into the aeration tank of a normal activated sludge treatment system.

The stirrer 6 in the upflow aerobic fluidized bed apparatus 1 shown in FIG. 4 can stir the contents of the apparatus at a very slow speed as much as possible, and minimize the dead space. It is preferable to use a type that can prevent channeling. Examples of such a blade include a turbine blade as a stirring blade, a slit paddle blade, and a combination thereof. The stirring speed varies depending on the size of the apparatus, but is, for example, 0.1.
It may be about 5 rpm. If a stirrer equipped with such a stirring blade is used, the BOD in the solubilized activated sludge will be
Since the contact efficiency between the components and the activated sludge can be remarkably improved, the treatment capacity per treatment tank volume is improved.
The apparatus shown in FIG. 4 is an example in which the agitator described above is installed, but an apparatus without an agitator may be used.

When the above apparatus is used, the activated sludge containing aerobic microorganisms and / or nitric acid respiring microorganisms can be used without being supported on the carrier. When an activated sludge containing aerobic microorganisms and / or nitric acid-respiring microorganisms is carried on a carrier, the flow rate of solubilized activated sludge into the device is increased and the upflow velocity in the device is increased, or
Even if a gas such as carbon dioxide gas is generated by the treatment of the BOD component in the solubilized activated sludge, the activated sludge is prevented from flowing out from the upper part of the device, so that the activated sludge concentration in the device is maintained at a high concentration, High-load processing becomes possible. Therefore, it is preferable to use activated sludge supported on a carrier.

Next, the organic wastewater treatment apparatus of the present invention will be described. In the organic wastewater treatment apparatus of the present invention, the organic wastewater treatment method of the present invention described above is applied. That is, the organic wastewater treatment apparatus of the present invention is an activated sludge treatment tank, a reaction treatment tank for sterilization and solubilization treatment, and the activated sludge treated in the reaction treatment tank is a treatment target, under an anaerobic atmosphere, nitric acid. At least an activated sludge treatment tank for treating with activated sludge containing aerobic microorganisms and / or nitrate respiring microorganisms in the presence of ions and / or nitrite ions, the reaction treatment tank being an activated sludge treatment tank and / or Alternatively, it is for treating the activated sludge at least a part of which is extracted from the settling tank connected to the activated sludge treatment tank, and is provided for sterilizing and solubilizing the microorganisms constituting the activated sludge. Furthermore, the activated sludge treatment tank further treats the solubilized activated sludge treated in the reaction treatment tank, and oxygen constituting nitrate ions and / or nitrite ions is preferable as an oxygen source. It provided for processing in sex microorganisms and / or activated sludge containing nitrate respiration microorganisms. Furthermore, in the organic wastewater treatment apparatus of the present invention,
The activated sludge treatment product, which has been treated in these two treatment tanks, is returned to the activated sludge treatment tank again.

In the apparatus for treating organic wastewater of the present invention, the activated sludge extracted from the activated sludge treatment system is sterilized and solubilized in the reaction treatment tank to sterilize the microorganisms constituting the activated sludge and the cells. BOD by solubilizing a part of
Convert to a component. Next, the treated solubilized activated sludge is introduced from the reaction treatment tank to the activated sludge treatment tank, and in the treatment tank, oxygen constituting nitrate ions and / or nitrite ions is used as an oxygen source. Treat with activated sludge containing airborne microorganisms and / or nitrate respiring microorganisms. Further, the activated sludge thus treated is introduced again into the existing activated sludge treatment tank to perform biological treatment. Therefore, the organic wastewater treatment apparatus of the present invention configured as described above does not significantly increase the BOD load amount of the existing activated sludge treatment tank, and further, it is possible to efficiently suppress the increase of activated sludge, The amount of surplus sludge can be significantly reduced compared to the conventional device.

[0039]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention. Example 1 500 liters / built according to the flow shown in FIG.
A day-scale pilot plant was used to perform activated sludge treatment of organic wastewater. The properties of the raw water used for the treatment are shown in Table 1 below, and as the raw water, organic wastewater from a food factory was used. Further, in this example, the oxidative decomposition means using an oxidizing agent with a metal ion as a catalyst was used in the sterilization or solubilization treatment step of the treatment flow shown in FIG. An iron catalyst was used as the catalyst, and Fe was added to the activated sludge treatment tank at the beginning of the test so that the iron ion content was 100 mg / l.
(OH) ₃ was added. Hydrogen peroxide was used as the oxidizing agent. The temperature of the reaction solution in the oxidative decomposition reaction tank was heated to 50 ° C. by a heater.

Table 1 Raw water condition (waste water of food factory)

First, with respect to the above raw water, pH 7.0,
The activated sludge treatment was performed under the operating conditions of a BOD load of 1.0 kg / m ³ and an HRT of 2.0 days. At that time, a part of the returned sludge was introduced into a reaction treatment tank having a structure as shown in FIG. 2 provided in the return sludge line from the settling tank to the activated sludge treatment system to perform thermal oxidation treatment. . Then, after these treatments are completed, the sterilized and solubilized solubilized activated sludge is introduced into a sludge treatment tank in an anaerobic atmosphere in the presence of nitrate ions, and aerobic microorganisms and / or nitric acid respiration It was biologically treated with activated sludge containing microorganisms. Furthermore, as shown in FIG.
The activated sludge treated product after the above treatment was returned to the normal activated sludge treatment tank (aeration tank) again, and the activated sludge treatment was continuously performed.

FIG. 2 shows a schematic view of the reaction treatment tank used in this example. In this reaction tank, the peroxide was so oxidized that the concentration of hydrogen peroxide in the reaction liquid containing sludge was 100 mg / l. Hypox NA (manufactured by Environmental Engineering Co., Ltd.) was added so that pH was kept at 3.5 by adding hydrogen. The reaction was carried out with a residence time of 60 minutes. When the viable cell count of the sludge before and after the reaction was measured, it was 10 ⁹ cells / ml before the reaction, but it was 10 ⁴ cells / ml after the reaction, and most of the microorganisms were killed and solubilized. We were able to confirm that it was proceeding.

As shown in FIG. 2, the solubilized activated sludge treated in the reaction treatment tank as described above was subsequently subjected to aerobic microorganisms and / or nitrate respiration under nitrate ion and / or nitrite ion. It is treated with activated sludge containing microorganisms.
In this example, the sludge treatment tank having a volume of 10 liters, which is the anaerobic tank shown in FIG. 3, was introduced, a part of the returned sludge was extracted and introduced as seed sludge, and aerobic microorganisms and / or nitric acid respiring microorganisms were introduced. It was treated with activated sludge containing. As for the sludge used, surplus sludge from the existing wastewater treatment facility was used as seed sludge.
The activated sludge treatment product after the solubilization sludge treatment was returned to the activated sludge treatment tank again, and the activated sludge treatment was continuously performed.

With respect to the treated water finally discharged after the above treatment, the sludge generation amount per input BOD was measured and shown in Table 3. As a result, generation of excess activated sludge was not observed at all, and it was not necessary to extract and remove excess sludge. Therefore, it was found that it is possible to omit the treatment step of excess sludge from the conventional treatment. In addition, the final treated water quality is comparable to that of Comparative Example 1 in which the treatment by the ordinary activated sludge method described later is performed, and both the BOD value and the SS value are comparable, and the water quality of the discharged water may deteriorate. There wasn't.

Example 2 Activated sludge treatment was performed in the same manner as in Example 1 except that the upflow aerobic fluidized bed apparatus shown in FIG. 4 was used as a sludge treatment tank for biological treatment of solubilized activated sludge. The test was conducted. Then, the quality of the treated water finally discharged and the sludge conversion rate were measured in the same manner as in Example 1 and shown in Table 2.

Comparative Example 1 In the same manner as in Example 1 except that the sludge return line was not provided with a heating reaction tank and a sludge treatment tank for treating the sludge to be treated extracted from the sludge return line, FIG. The activated sludge treatment test was conducted according to the conventional flow shown. Then, the quality of the treated water finally discharged and the sludge conversion rate were measured in the same manner as in Example 1 and shown in Table 2.

Comparative Example 2 An activated sludge treatment test was conducted in the same manner as in Example 1 except that a sludge treatment tank for biologically treating solubilized activated sludge was not provided. The water quality and sludge conversion rate of the obtained treated water were measured in the same manner as in Example 1, and are shown in Table 2.

Table 2 Processing results

[0049]

As described above, according to the present invention, the activated sludge treatment can be performed under the same conditions as the conventional one without causing an increase in the BOD load amount of the existing activated sludge treatment equipment. In addition, the amount of excess sludge can be greatly reduced by a simple method without deteriorating the water quality of the treated water discharged in the final stage, and it is possible to optimally eliminate the generation of excess sludge. There is provided a simple and economical method of treating organic wastewater using an activated sludge method.
Further, according to the present invention, there is provided an organic wastewater treatment apparatus which has the above-mentioned excellent effects without making a significant change to the conventional treatment apparatus and without increasing the operating cost.

[Brief description of drawings]

FIG. 1 is an example of a processing flow of a method for treating organic wastewater according to the present invention.

FIG. 2 is a schematic view of a reaction treatment tank and a sludge treatment tank used in the method for treating organic wastewater of the present invention.

FIG. 3 is a diagram showing an example of a sludge treatment tank used in the method for treating organic wastewater according to the present invention.

FIG. 4 is a diagram showing an example of a sludge treatment tank used in the method for treating organic wastewater of the present invention.

FIG. 5 is an example of a processing flow of a conventional method for treating organic wastewater.

[Explanation of symbols]

1: Upflow aerobic fluidized bed equipment 3: Solubilized sludge inflow pipe 4: Oxygen source supply pipe 5: Activated sludge supported on a carrier 6: Stirrer 7: Accumulation section 8: Discharge pipe M: Motor P: Pump

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuyoshi Suzuki             1-9-8 Higashi-Kanda, Chiyoda-ku, Tokyo Environment             Engineering Co., Ltd. F-term (reference) 4D028 AB01 BB07 BC18 BD06 BD11                       BD16 BE01 BE08                 4D059 AA03 BA03 BA11 BA22 BA34                       BA50 BA60 BC05 BF02 BF12                       BF13 BJ09 BK12 BK13 BK22                       BK24 BK30 CA01 CB30 DA22                       DA44 DA45 DA70 DB31 DB40                       EB06 EB11

Claims (4)

[Claims] 1. A method for treating organic wastewater, which comprises purifying organic wastewater with an activated sludge treatment system containing aerobic microorganisms, wherein at least a part of the activated sludge is extracted as treated sludge, and the treated sludge is constituted. Sterilizing and solubilizing the living microorganisms, followed by sterilizing and solubilizing the activated sludge treated product under an anaerobic atmosphere in the presence of nitrate ions and / or nitrite ions. Alternatively, a method for treating organic wastewater, which comprises treating with activated sludge containing nitric acid-respiring microorganisms, and then reintroducing into the activated sludge treatment system for purification treatment with activated sludge. 2. The method for treating organic wastewater according to claim 1, wherein the method of sterilization and solubilization treatment is oxidative decomposition with an oxidizing agent using a metal ion as a catalyst. 3. Oxidative decomposition, the metal ions are iron ions,
The oxidizing agent is hydrogen peroxide, and the liquid to be treated is 40 to 10
The method for treating organic wastewater according to claim 2, which is carried out under the condition of being heated to 0 ° C. 4. An organic wastewater treatment apparatus for purifying organic wastewater by an activated sludge treatment system containing aerobic microorganisms, an activated sludge treatment tank, a reaction treatment tank for sterilization and solubilization treatment, and the reaction treatment. A sludge treatment tank for treating the activated sludge treated in the tank, wherein the reaction treatment tank comprises at least a part of the activated sludge treatment tank and / or the precipitation tank connected to the activated sludge treatment tank. The extracted activated sludge is the treatment target, which is for sterilizing and solubilizing the microorganisms constituting the activated sludge, and the sludge treatment tank, the activated sludge treated in the reaction treatment tank,
For treating with activated sludge containing aerobic microorganisms and / or nitrate respiring microorganisms in the presence of nitrate ions and / or nitrite ions under an anaerobic atmosphere,
An apparatus for treating organic wastewater, which is configured to return the activated sludge treatment product that has been treated in the two treatment tanks to the activated sludge treatment tank again.