JP2001038397A - Method for decreasing volume of excess sludge and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to decrease the volume of excess sludge by allowing at least either of an alkali agent or a bacteriolytic agent as a solubilizing agent to be in contact with the excess sludge generated by the aerobic biological treatment, at the same time, intermittently applying ultrasonic wave to the excess sludge, solubilizing the same and treating the solubilized sludge with the aerobic micro-organisms. SOLUTION: The sludge generated in large amount at the time of subjecting organic waste water to the decomposition and digestion treatment in a biological treatment vessel utilizing the aerobic micro-organisms is properly pulled out of a sludge storing vessel 1 and is fed into a solubilizing agent contact vessel 2. Subsequently, alkali (for example, sodium hydroxide) which is a solubilizing agent for chemically decomposing the sludge is added to the solubilizing agent contact vessel 2 and the initial pH is set to be the order of 10-12. Further, the sludge mixed with the chemical treating agent is circulated between an ultrasonic wave treatment vessel 3 and the solubilizing agent contact vessel 2, thereby, is brought into contact with the chemical treating agent and is subjected to the action of ultrasonic wave. Subsequently, the solubilized sludge which is solubilized thereby is fed into the biological treatment vessel by the aerobic micro-organisms and is subjected to the biological decomposition and digestion treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for reducing excess sludge generated when biologically treating wastewater such as sewage and a biological treatment apparatus using the method. The "excess sludge" refers to a part of the sludge after solid-liquid separation from the treated water. In the present specification, the sludge after solubilizing the microorganisms in the excess sludge (sludge solubilized product) It may be collectively referred to as sludge.

[0002]

2. Description of the Related Art In biological treatment methods such as an activated sludge treatment method known as a treatment method for organic wastewater treatment, specifically, a treatment method in which organic matter is decomposed and digested by the life cycle of aerobic microorganisms, microorganisms are active. It is well known that a large amount of surplus (active) sludge is generated due to multiplication, and various treatment modes have conventionally been considered and implemented depending on the properties of the water to be treated.

[0003] A biological treatment method using an aerobic microorganism such as an activated sludge treatment method is an excellent method for treating organic wastewater. However, as described above, a large amount of excess sludge generated is generated. Disposal is a problem. As a method of disposing of this excess sludge, some of it is used as a soil conditioner or as a compost material, but it has not reached a fundamental solution, and in most cases, the excess sludge is dewatered. At present, it is treated as industrial waste by incineration or landfill.

However, recently, in the above-mentioned incineration, there is a concern that harmful substances such as so-called environmental hormones such as dioxin may be generated due to the incineration. There is a growing tendency to be concerned about the problem, and as a more fundamental solution,
Technology is required to reduce the volume of excess sludge to be disposed of itself.
Many proposals for this have been made.

There are various methods for reducing the volume of excess sludge that have been conventionally proposed, but they are generally classified into the following methods. That is: Anaerobic digestion method by living organism (anaerobic digestion method): A method in which sludge is pretreated physically, chemically or biologically and then treated with microorganisms.

[0006] Among the above methods, anaerobic microorganisms such as methanogens decompose organic components in sludge to generate methane and carbon dioxide, so that sludge can be reduced and energy resources can be recovered at the same time. There are advantages. However, sludge retention time is long and the facility becomes large, which makes it difficult to implement it industrially. "

On the other hand, the above-mentioned method is basically based on microbial treatment. However, as a pretreatment, sludge is brought into a state suitable for microbial treatment (that is, microbes that are mostly surplus sludge). (Disruption of cell membrane)), and several methods have been proposed for each of the different physical, chemical or biological pretreatment methods as follows.

For example, as a method of performing a physical pretreatment, Japanese Patent Application Laid-Open No. 58-76200 discloses an efficient method for treating sludge microbiologically with anaerobic microorganisms such as methane-producing bacteria. For this reason, a method of removing extraneous matter on the surface of surplus sludge (microorganism) by ultrasonic waves has been proposed. Japanese Patent Application Laid-Open No. 7-323300 proposes that sludge subjected to ultrasonic treatment or the like prior to anaerobic digestion is mixed with untreated sludge at a predetermined ratio.

However, the ultrasonic pretreatment methods in these methods are extremely inefficient in the effects obtained by the ultrasonic action as described in Japanese Patent Publication No. 4-38478, so that actual industrial It has not been implemented even in strategic situations.

[0010] Also, Japanese Patent Publication No. 4-38478 describes that
It proposes a method to promote the destruction of sludge (microorganisms) by adding inorganic particles that move randomly by ultrasonic waves, but the possibility of collision between microorganisms and fine particles is governed by the amount of inorganic particles added. In addition, since a part or most of the inorganic particles are included in the final disposal (treated water, excess sludge treatment, etc.), this is not necessarily an efficient treatment method.

In contrast to the above method, Japanese Patent Publication No. 57-1971
The method proposed in Japanese Patent Publication No. 9 is a method of crushing microorganisms using an ultrasonic wave, a homogenizer, a mixer ozone gas or the like to provide a nutrient source for aerobic microorganisms. It does not indicate knowledge. The method disclosed in Japanese Patent No. 2806495 also discloses a method for increasing the efficiency of anaerobic digestion by mechanically crushing excess sludge, which is disclosed in Japanese Patent Publication No. 57-19719. There is no substantial difference from the way it is. Japanese Patent Application Laid-Open No. 7-116885 discloses a pretreatment method for thermally decomposing excess sludge, but has a problem in that the running cost expended on thermal energy increases.

Japanese Patent Application Laid-Open Nos. 51-57955 and 5-61994 disclose a method for decomposing sludge by acid.
Japanese Unexamined Patent Publication (Kokai) No. Hei 7-116865 describes that sludge is solubilized in order to improve the sedimentation and dewatering properties of sludge. Physical methods such as heat decomposition, oxidative decomposition with ozone, In addition to a method of performing a chemical pretreatment such as dissolution and alkali dissolution, a method of combining a physical method and a chemical method is also described formally. However, it does not describe sonication, nor does it specifically describe the combination of the above physical method and chemical method, and does not suggest any additive effect of the combination. Not.

Apart from the above prior art, a method of ozone treatment (Japanese Patent Publication No. 57-19719 and Japanese Patent Application Laid-Open No. 11-904) is used as a chemical treatment method for reducing the volume of excess sludge.
No. 96), a method of reacting hydrogen peroxide (Japanese Unexamined Patent Publication No.
No. 0-12898), a method of solubilizing excess sludge under hot alkaline conditions (Japanese Patent Application Laid-Open No. 5-345200, Japanese Patent Publication No. 48-11813), utilizing microorganisms which maintain the pH at alkaline. A method for decomposing sludge (JP-A-11-77099) and a method for reducing sludge using bacteria that produce sludge-solubilizing enzymes (JP-A-8-2)
43595, and JP-A-9-253699) have also been proposed.

[0014]

As described above, in a treatment apparatus for biologically treating organic wastewater using microorganisms, it has been conventionally desired to reduce the volume of excess sludge generated. Various proposals for this have been made as described above, but all of them have difficulties such as difficult operation management and high running costs in proportion to the effects. Has not yet been found.

That is, the physical cell crushing method requires high equipment and running costs to achieve a sufficient effect, leading to an increase in cost, and also has a problem that operation management is difficult, and sludge solubilizing enzymes such as thermophilic bacteria are used. The method using the produced bacteria has a problem that it is difficult to select the bacteria and control the operation, and the method of adding an oxidizing agent such as ozone also has a problem that the capital investment is high.

The high-temperature heat treatment method has an advantage that the operation management is relatively easy, but has a problem that the energy cost is high due to the heating.

Furthermore, the method of adding an alkali, an acid, an enzyme, a lysing agent, or the like is difficult to employ as industrial equipment because the consumption of the drug increases to achieve a practical effect and the running cost increases. Furthermore, the method of adjusting the pH has a problem that a post-treatment step is required because the generated treatment liquid cannot be drained as it is.

In view of such circumstances, the present invention provides a method of reducing the volume of surplus sludge which is inexpensive and easy to operate and manage, and a biological system of organic wastewater which is an efficient system using this method. The purpose of the present invention is to provide an objective processing device.

[0019]

According to the above object, the present inventor crushes and solubilizes microbial cells to make them soluble (easy to dissolve).
Physical, chemical and biological methods were studied in general, with the aim of realizing operation management and low running costs. As a result, we came to the basic direction, specific goals, and the means to achieve them. In other words, as a basic direction, in order to facilitate operation management and to enable upsizing for performing on an industrial scale, as a powerful method for efficiently decomposing bacterial cells, It is suitable to use cheap chemical agents. However, in the above-described conventional method of performing a solubilization reaction at a high pH, a large amount of an alkali agent is used, and a large amount of a neutralizing agent is used after the solubilization reaction, which increases the cost and increases the industrial cost. There is a problem that it is difficult to practically use the apparatus on a large scale.

From these facts, in the method using a chemical agent (solubilizing agent), it is desired to develop a method that requires a small amount of a chemical agent or the like. One of such methods is sludge. However, since a large amount of heat energy is required to raise the temperature, the problem of increasing running costs is not sufficiently solved even though the use of chemical agents can be reduced. In other words, in the method using a chemical agent, a method that can accelerate the solubilization reaction at room temperature or at a relatively low heating temperature and with a small amount of the chemical agent is desired. As described above, it is not easy.

On the other hand, as a means for physically destroying (solubilizing) cells, a method of heating sludge to a high temperature, a method of grinding, and a method of irradiating ultrasonic waves are considered as proposed in the related art. Can be However, the ultrasonic irradiation method is a sufficiently effective method on a laboratory scale,
An industrial scale device must treat a considerable amount of sludge, and it is necessary to irradiate ultrasonic waves of high sound intensity for a long time to destroy cells. Practical application of solubilization of sludge is actually difficult and has not actually been industrialized. In addition, it is difficult to carry out high-temperature heating and grinding methods on an industrial scale.

The present inventor made further studies on the premise of the results of various studies on the prior art as described above. As will be described later, the present inventor analyzed the reaction process of sludge solubilization. According to the reaction, after the chemical agent solubilized the sludge in the same reaction, the concentration in the vicinity region where the concentration decreased due to the consumption of the chemical agent in the vicinity of the microbial cells (cells), which is the main component of the sludge, in the reaction was reduced. Increasing it was considered to be a powerful measure to promote the reaction. And from such a viewpoint, as a result of conducting a test using an ultrasonic action in combination with a chemical method using an alkali, an acid or a lytic agent,
It has been confirmed that the use of these methods alone can promote extremely excellent solubilization of sludge, which could not be predicted, and the present invention provides a synergistic effect by the mechanism. It is.

That is, the object of the present invention is achieved by the invention described in each claim of the above-mentioned claims.

According to the invention of the method for reducing the volume of excess sludge according to claim 1 of the present invention, ultrasonic waves are applied while contacting excess sludge generated by aerobic microorganism treatment with at least one of an alkali agent and a lytic agent as a solubilizing agent. It is characterized in that it is solubilized by intermittent action, and the solubilized (solubilized) sludge solubilized biologically is treated with an aerobic microorganism.

According to a second aspect of the present invention, in the above-mentioned invention, the ultrasonic waves are continuously applied instead of intermittently acting.

As a premise for making such an invention, the present inventor examined in detail a preliminary test in which the chemical treatment method was used alone, and found that a certain period of time after starting the reaction (about 20 hours in this preliminary test). Minutes), the progress of the reaction reached a plateau. Even at the same pH, the longer the elapsed time, the lower the solubilizing effect.
It is considered that the mass transfer became rate-limiting, and from the viewpoint of kinetics, the process of solubilizing the microbial cells was analyzed as follows.

(1) An attachment process in which a drug moves to the vicinity of a microbial cell.

(2) A reaction process in which microbial cells react with and dissolve with a drug.

(3) A diffusion process in which the lysed cell portion (lysate) diffuses into the liquid body.

(4) Repeat the above process.

To summarize these processes, since (1) and (3) are mass transfer processes, the dissolution process can be divided into mass transfer processes (1) and (3) and reaction process (2). Become.

Based on the above analysis, the action of each step and the dissolution rate of the entire solubilization were further analyzed. That is, in order to increase the dissolution rate of the entire solubilization, the above-described (1) to (1)
This is because the slow process of the three processes (3) must be promoted.

Considering the dissolution process (2) from this point of view, in this process, the chemicals are consumed by reacting with the microorganisms, and microscopically, the concentration of the chemicals in contact with the microbial cells is low. And the speed of the reaction is reduced. Also, when the microbial cells that have reacted with the chemical are solubilized, the viscosity of the surrounding liquid increases, and the rate at which the substance adheres to the microbial cells or the substance produced by the solubilization of the microbes diffuses into the liquid decreases. As a result, the above (1),
The mass transfer process (3) is a rate-determining process. In other words, it is understood that promotion of mass transfer is an important factor for the dissolution effect and speedup.

Therefore, it is conceivable to promote this mass transfer, for example, to agitate the sludge. However, since the excess sludge is generally a viscous liquid having a high concentration of microorganisms and a viscous liquid, the usual agitation using a stirring blade or the like is used. It is difficult to obtain an appropriate stirring effect by the method.

The present inventor has generally used the above-described substance while not using it for the purpose of stirring, but focusing on ultrasonic waves that cause a change in density in the medium and considering the combination with a chemical treatment method. When an attempt was made to promote the migration, as shown in the examples described below, it was confirmed that the effect of promoting the solubilization of microorganisms, which was extremely excellent and could not be predicted from the conventional method, was confirmed. It was reached.

Although it is not always clear whether mass transfer can be obtained as described above by the action of ultrasonic waves in the above invention, it is not ultrasonic waves strong enough to destroy bacterial cells, It can be obtained by using ultrasonic waves of weak sound intensity that cannot destroy bacterial cells by itself when used alone. It was therefore surprising that the use of weak ultrasonic waves, which had been considered to have little effect with the conventional method, became possible, and that the practice resulted in extremely excellent effects. From these facts, it is considered that the rate of mass transfer was reduced by the action of the ultrasonic wave to increase the solubilization rate.

The frequency of the ultrasonic wave used in the present invention is generally 10 to 3000 KHz, preferably 3
~ 1500KHz, more preferably 10 ~ 200KH
z, optimally a frequency of about 10 to 50 KHz is appropriate, and the sound wave strength is 0.05 to 5.0 W / cm ² ,
Preferably 0.05-3.0 W / cm ² , more preferably 0.1-1.5 W / cm ² , optimally 0.2-1.2.
It is preferably about W / cm ² .

The operation of the ultrasonic wave can be performed continuously as in the invention of the second aspect, but it can also be applied intermittently. It is often preferable to carry out the method at the time when the time at which the rate of solubilization by the solubilizing agent decreases with time elapses. The time required for the solubilization rate to decrease is not necessarily uniform depending on the type of microorganism, the concentration of sludge, the type of solubilizing agent to be used, and the like, and is often, for example, about 5 minutes to 45 minutes. The operation time of the intermittently applied ultrasonic wave is not particularly limited, but can be selected based on the capability of the device to be used, the power consumption, and the like. In general, the irradiation time is preferably about 5 to 600 seconds.

The alkaline agent used as a solubilizer in the above invention includes, for example, NaOH, KOH, Mg
(OH) ₂ , Ca (OH) ₂ , CaO, Na ₂ O _{3 and the} like can be exemplified. Examples of the lysing agent used for the solubilizing agent include H ₂ O ₂ , O ₃ , and other lysing agents capable of dissolving bacterial cells. These may be used alone or in combination.

The method for reducing the volume of excess sludge of the present invention typically uses a biological treatment tank (activated sludge) while treating wastewater containing organic matter as raw water and adjusting the flow rate per unit time with a flow rate adjustment tank. Treatment method, biofilm treatment method, etc.), generally, flowing into an aeration tank to decompose and digest the BOD component with aerobic microorganisms, and settle the sludge containing microorganisms as the main solid component in the treatment water in a precipitation tank. The excess sludge of the biological treatment method of separating and discharging clear treated water, returning a part of the sludge to the biological treatment tank as return sludge, and discharging the remaining sludge outside the system as excess sludge Applied to the processing of

According to the present invention, as compared with the case where only an alkali agent or a lysing agent is used alone, or the case where ultrasonic waves are acted alone, it can be expected in a short time and with the conventional method. The sludge can be solubilized up to this point, and the excess sludge can be reduced very efficiently.

According to a third aspect of the present invention, the excess sludge generated by the aerobic microorganism treatment is solubilized by continuously or intermittently applying ultrasonic waves while contacting an alkali agent as a solubilizing agent. It is characterized by biologically treating a substance with an aerobic microorganism without neutralizing the substance.

According to the present invention, the solubilized sludge becomes alkaline by adding an alkaline agent.
Since the organic acid generated by the activity of microorganisms in the aerobic microorganism treatment tank and the pH tend to decrease due to carbonic acid,
Even if the sludge liquid remaining alkali is not neutralized, the pH naturally becomes a neutral range, so that the neutralization operation can be omitted. That is, the excess alkali content of excluding the amount consumed in the solubilization of the sludge is neutralized by organic acids and CO ₂ generated and carbon dioxide in the air aerated aerobic biological treatment apparatus, in biodegradation of BOD Because it is done.

According to the present invention, the surplus alkali is neutralized by the dissolution of carbon dioxide in the air by aeration in the aerobic biological treatment apparatus or the organic acid generated by BOD biodegradation, and the biological activity by the aerobic microorganism. Can be used to treat solubilized sludge as it is,
Since the operation of the neutralization treatment and the equipment for this are not required, it is advantageous in terms of equipment.

The invention of claim 4 of the present application differs from the above-mentioned inventions in that ultrasonic waves are continuously or intermittently acted on while contacting an excess sludge generated by aerobic microorganism treatment with an acid as a solubilizing agent. And solubilized to neutralize the sludge solubilized product, and then biologically treated with an aerobic microorganism. In this case, if possible, a lytic agent may be used together with the acid.

Examples of the acid used in the present invention include mineral acids (H ₂ SO ₄ , HCl, etc.).

According to the invention of claim 5 of the present application, the solubilization treatment of excess sludge is a batch treatment, and the intermittent action of the ultrasonic wave is as follows:
After adding the solubilizing agent to the excess sludge, the process is performed every time when the time at which the solubilization rate decreases over time elapses.

According to the present invention, as described above, it is possible to suppress the power consumption of the ultrasonic wave when reducing the rate of mass transfer by the action of the ultrasonic wave.

[0049] The invention of claim 6 of the present application is characterized in that the solubilization of excess sludge is carried out at a normal temperature to 70 ° C.

The solubilization of the sludge according to each of the above-mentioned inventions can be carried out efficiently even at room temperature, but can be carried out in a heated state in order to promote a general reaction. 70 ° C
This is merely an example, and the present invention is not limited to this value. In the case of the method of the present invention, since the solubilization of sludge proceeds rapidly, the degree of heating takes into account thermal energy costs and the like. And decide.

The invention of claim 7 of the present application is directed to a biological treatment tank for treating raw water containing organic wastewater with aerobic microorganisms, and then to a separation tank for solid-liquid separation of sludge from treated water in this order. A part of the separated sludge is regarded as surplus sludge, and the solubilized sludge solubilized product is introduced into the biological treatment tank for the biological treatment by aerobic microorganisms after solubilization of the surplus sludge. The present invention according to claim 8 is characterized in that the sludge solubilized material is returned to the flow control tank and the initial sedimentation tank (first sedimentation tank) provided before the biological treatment tank.
It is characterized by having.

According to these inventions, the treatment of the solubilized sludge with the aerobic microorganisms can be performed in the biological treatment tank provided for decomposing the raw water with the aerobic microorganisms. Is advantageous because there is no need to provide a new (separate) tank.

In particular, when the raw water is returned to the aerobic microorganism treatment tank via the raw water flow control tank or the primary sedimentation tank, the following effects can be obtained.

That is, a flow control tank or an initial sedimentation tank is generally provided at the inflow end of the organic wastewater (raw water) of the biological treatment apparatus. When nutrients are high, for example, the sludge of the present invention after solubilization is used. When the sludge solubilized product is returned to these tanks, it is difficult to become aerobic even after aeration, but rather becomes anaerobic, and the decay such as organic acid fermentation progresses to lower the pH, and organic acids and hydrogen sulfide And other odors are generated in large quantities.

However, the sludge solubilized material treated with the alkali agent as described above is not directly sent to the aeration tank of the aerobic treatment part, but the above-mentioned tank (flow rate adjusting tank) which tends to be anaerobic at the inflow end of raw water. Etc.), the pH in the tank deviates from the optimum pH (near neutral) for the growth of putrefactive bacteria and becomes alkaline, so that rot and odor generation in the tank can be prevented. Therefore, by controlling appropriate operating conditions, the addition or reduction of the neutralizing agent can be reduced, and the effect of two birds per stone can be obtained. In addition, the method of returning to the biological treatment tank with aerobic microorganisms of the original biological treatment system system (hereinafter referred to as “main system system”) without using neutralization after using an alkaline agent also requires a neutralizing agent. This is extremely effective in suppressing running costs.

The ninth aspect of the present invention is characterized in that the ultrasonic action on the excess sludge is performed while the sludge is stirred.

The method of stirring the sludge is not particularly limited, such as a method using a mechanical stirring device using a swirling blade or the like, and a method of air aeration. However, it is appropriate to use a mechanical stirring device. Often.

As a method for accelerating the solubilization, as mentioned above, even if the sludge to which the solubilizing agent is added is stirred by a stirring blade or the like, an appropriate effect cannot be obtained. We have experimentally found that when agitation is performed, a very remarkable effect is obtained in that solubilization is remarkably promoted as compared with the case where ultrasonic waves are simply applied, and this fact has been confirmed. It is surprising that approaches that have little effect on their own or do not find significant industrial advantages have very significant effects as a result of their combination in certain relationships.

[0059] The invention of the biological treatment apparatus according to claim 11 of the present application comprises a biological treatment tank for treating raw water containing organic wastewater with aerobic microorganisms, and a sludge grown in the biological treatment tank for treating the wastewater. Tank, a part of the separated sludge taken out as surplus sludge, and a solubilizer contact tank for contacting any of an alkali agent, an acid, or a bactericide, and applying ultrasonic waves to the surplus sludge containing the solubilizer. And a biological treatment tank for contacting the solubilizer with the solubilizing agent and treating the solubilized sludge solubilized by the ultrasonic action with an aerobic microorganism.

In the above description, the biological treatment tank for treating the solubilized sludge solubilized product by the aerobic microorganisms may be different from the biological treatment tank constituting the main system. Alternatively, the tank of the main system may be used. When the tank of the main system is used for the decomposition treatment of the solubilized sludge, a pipe for returning the solubilized sludge to the main line may be provided.

The apparatus for reducing the volume of excess sludge of the present invention may be one that performs sludge treatment in a batch system or one that performs continuous sludge treatment.

The solubilizer contact tank for promoting the dissolution of sludge by a solubilizer such as an alkali is, for example, a solubilizer reaction tank (solubilizer contact tank) as described in claim 12.
In addition to a single shared tank configured by combining an ultrasonic oscillator with the above, another tank as in the invention of claim 13 can be used.

In order to reduce the size and power consumption of the ultrasonic device, it is preferable to employ the ultrasonic wave intermittently only at the stage where the mass transfer is rate-determining. The following can be exemplified as suitable combinations of the reaction tank and the ultrasonic device. One is a system in which a reaction tank and an ultrasonic device are separately configured, and sludge is circulated between them, whereby the sludge is intermittently irradiated with ultrasonic waves. In addition, in the tank, the area where the reaction by the chemical agent such as alkali without the action of the ultrasonic wave proceeds, and the area where the action of the ultrasonic wave is further divided into areas along the path through which the sludge flows. In a reaction tank having a flow path in which the residence time of the sludge is almost the same as that of the extruded flow (not completely mixed), the sludge is placed in the middle of the path between the inflow end and the outflow end of the sludge. A configuration in which a sound wave irradiation device is installed can be exemplified, but the configuration is not limited thereto.

According to a thirteenth aspect of the present invention, in the above device invention, the solubilizer contact tank and the ultrasonic action tank are separate tanks.
A sludge circulation path for circulating sludge between these tanks is provided.

According to the present invention, the ultrasonic action is applied intermittently to the sludge. That is, even when the ultrasonic generator is continuously operated, the circulating sludge is subjected to the ultrasonic action only when passing through the ultrasonic action tank, so that it is intermittently affected. In this way, the ultrasonic working tank can be made small in capacity, so that a small ultrasonic oscillator can be used, and therefore, there is an advantage that an industrial scale apparatus can be operated at low cost and with simple operation. can get.

The invention of claim 14 is characterized in that, in the above-mentioned apparatus invention, the biological treatment tank for treating the solubilized sludge is a biofilm treatment tank.

The present invention is particularly effective in the following cases. That is, when the method for reducing the volume of excess sludge of the present invention is applied to an existing biological treatment apparatus, only the amount of the solubilized sludge that is solubilized and brought into the biological treatment tank of the main system system, The nutrients flowing into the biological treatment tank increase and the load increases. For example, there is a possibility that the treatment capacity becomes insufficient according to the design standards of the existing facility. In such a case, if a biofilm treatment tank capable of supporting a large amount of bacterial cells is added to the previous stage of the biological treatment tank of the existing apparatus, the above-described method is used if the increased nutrient load is treated. In addition, since the biofilm treatment tank can be configured to be relatively small, it can be dealt with without greatly increasing the number of facilities.

A fifteenth aspect of the present invention is directed to the biochemical apparatus according to the above invention, wherein the sludge solubilized in the solubilizing agent contact tank and the ultrasonic action tank is treated with aerobic microorganisms in raw water containing organic wastewater. A path for returning to the raw water inflow end of the chemical treatment tank is provided.

According to the present invention, there is no need to provide a separate tank for decomposing and digesting the solubilized sludge, which is advantageous in terms of equipment costs.

The invention of claim 16 is to provide a raw water flow control tank and / or an initial sedimentation tank before the raw water inflow end of a biological treatment tank for treating raw water containing organic waste water with aerobic microorganisms, so as to dissolve sludge. The path for returning the material to the raw water inflow end of the biological treatment tank is connected to the raw water flow control tank and / or the initial sedimentation tank.

According to the present invention, especially when alkali is used as a solubilizing agent, when sludge is returned to the flow control tank or the primary sedimentation tank without neutralization, the growth of putrefactive bacteria in the tank is improved. Can be prevented.

A seventeenth aspect of the present invention is characterized in that, in each of the above-described apparatus inventions, sludge stirring means is provided in the ultrasonic action tank.

The stirring device can be used without any particular limitation as long as it is effective for stirring the sludge.

According to the present invention, there is obtained an advantage that the decomposition action of the solubilizing agent into sludge by the ultrasonic action is further promoted.

[0075]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below based on embodiments shown in the drawings.

Embodiment 1 FIG. 1 shows sludge dissolution (solubilization) for reducing excess sludge.
Fig. 1 shows an outline of the system configuration.
In the sludge storage tank 1 corresponding to a sedimentation tank (separation tank) for sedimenting and separating a large amount of sludge generated when an organic wastewater is decomposed and digested in a biological treatment tank utilizing aerobic microorganisms, from the treated water. It is appropriately extracted and supplied to the solubilizing agent contact tank 2, and an alkali (eg, sodium hydroxide) as a solubilizing agent for chemically decomposing sludge is added to the solubilizing agent contact tank 2 to adjust the initial pH. It should be about 10-12. Then, the sludge to which the chemical treating agent has been added is circulated to and from the ultrasonic treatment tank 3 so as to provide an ultrasonic action while being in contact with the chemical treating agent.

The solubilized sludge solubilized by the above operation is supplied to a biological treatment tank (not shown) for aerobic microorganisms, and is biologically decomposed and digested.

The solubilizing agent contacting tank 2 in the above is a tank for changing the pH by adding an alkali, and is hereinafter referred to as a pH adjusting tank 2. Also,
When an acid (for example, hydrochloric acid) is added to the pH adjusting tank 2 instead of the alkali, the initial pH is set to about 2 to 5. Further, when returning the sludge solubilized by adding an alkali to a flow control tank or the like in front of the biological treatment tank of the main system, the initial pH may be about 10 to 13.

The supply (or return) of the sludge solubilized product to the biological treatment tank (or raw water flow control tank or primary sedimentation tank) should be performed after neutralizing the alkali or acid remaining in the sludge. However, as for alkali, by supplying the remaining alkali agent without neutralization, waste of consuming the neutralizing agent is eliminated. In the case where there is a problem that the bacteria grow, it is preferable because the pH can be prevented from becoming alkaline by the alkali contained in the returned sludge solubilized matter, and the generation of putrefaction odor can be prevented.

FIG. 1 (b) shows an example in which a lysing agent is added to the pH adjusting tank 2 together with the alkaline agent, and the other configuration is the same as that of FIG. 1 (a).

Also in this case, the same effect as in the case of FIG.

Embodiment 2 The present embodiment shown in FIG. 2 shows an example in which the sludge dissolving system described in FIG. 1 is incorporated in a system for returning excess sludge.

In this figure, reference numeral 11 denotes a raw water flow control tank (or a primary sedimentation tank) in a main line of a biological treatment apparatus using organic waste water as raw water, in which organic substances are decomposed and digested by aerobic microorganisms at the next stage. The aeration tank 12 serves as a buffer tank that functions to supply and treat raw water at a constant flow rate.

Reference numeral 12 denotes an aeration tank, which decomposes and digests organic substances contained in raw water by the biological activity of aerobic microorganisms, and the microorganisms proliferate. In addition, this aeration tank may be any of a so-called activated sludge method in which microorganisms are used in a suspended state, and a biofilm method in which microorganisms are fixed on an appropriate carrier surface and multiplied.

Reference numeral 13 denotes a sedimentation tank (final sedimentation tank), which sediments microorganisms contained in the treated water flowing out of the aeration tank 12 and pulls out sludge from the bottom of the treated water, and separates the microorganisms. The treated water is provided so as to be discharged out of the system by an overflow method, for example.

The raw water flow control tank 11, the aeration tank 12 and the sedimentation tank 13 constitute the main system of the biological treatment apparatus of this embodiment.

The sludge extracted from the sedimentation tank 13 is
Part of the sludge is returned as sludge via the return pipe 14 to the aeration tank 1.
Returned to 2. The remaining sludge is concentrated as excess sludge in the present embodiment in a sludge concentration device 15 including a second-stage settling tank or a centrifugal separator.
After being solubilized by the sludge dissolution system 16 having the configuration shown in FIG.

According to such a facility, in the treatment of biological organic wastewater, a large amount of excess sludge is solubilized by the sludge dissolution system and supplied to the aeration tank 12 for decomposing organic substances. Since it is returned and decomposed and digested, there is an advantage that the generation of excess waste sludge from the equipment can be significantly reduced or substantially eliminated. Moreover, the sludge dissolving system shown in FIG. 1 is capable of solubilizing sludge very quickly, and has a low running cost.

Further, when a method of adding an alkali agent for solubilizing sludge is employed, even if an excess alkali agent remains after the solubilization treatment, the surplus alkali agent is returned to the main system to be autonomous. Therefore, there is an advantage that there is no need to perform a neutralization treatment.

Further, in this embodiment in which the alkali is returned to the raw water flow control tank 11 without being neutralized, the pH in the raw water flow control tank 11 assumes an alkaline state and is not suitable for the growth of spoilage bacteria and the like. Since the pH state is high, there is an advantage that the problem that putrefactive bacteria multiply in the same tank 11 to generate putrefactive odor can be prevented.

Embodiment 3 In this example, in an existing activated sludge method biological treatment facility, excess sludge is solubilized and then returned to the main system to be decomposed and digested. Considering that the amount of BOD in the organic wastewater increases due to the solubilization of
This is an example in which a biofilm type biological treatment apparatus in which a microbial carrier is filled in a tank is incorporated in a stage preceding the aeration tank.

That is, the raw water of the organic wastewater is supplied to the biofilm type aerobic microorganism treatment device 22 having a high concentration of the bacterial cells after flowing into the raw water flow control tank 21 at a constant flow rate per unit time. You. The treated water that has passed through the biofilm type aerobic microorganism treatment device 22 is further treated with microorganisms in an aeration tank 23, and the treated water and sludge are separated in a precipitation tank 24, and the treated water is drained out of the system.

On the other hand, the sludge separated by settling is supplied to a pH adjusting tank 25 of the sludge dissolving system, and the pH is adjusted by, for example, addition of an alkaline agent. Circulated through the pipe 27,
The sludge solubilized material after the solubilization treatment is returned to the raw water flow rate adjusting tank 21 through the pipe 28.

[0094] According to the biological treatment apparatus having such a configuration, it is possible to increase the processing capacity of the existing equipment without requiring a large area, and therefore, even when the excess sludge is solubilized and decomposed and digested. , There is an advantage that can fully cope.

[0095]

The present invention will be described in more detail with reference to the following examples. Test Example 1 A solubilization test of sludge obtained when an organic wastewater was treated with an aerobic microorganism under the following conditions. The apparatus shown in FIG. 1 was used as an apparatus for solubilizing sludge, and an ultrasonic oscillator was also provided in the pH adjusting tank 2 for performing continuous ultrasonic irradiation. In addition, the ultrasonic oscillator in the present example includes an ultrasonic oscillator UT-35Z2 and an ultrasonic oscillator UE-200Z26S.
6 / 2-53A (all manufactured by Ultrasonic Industry Co., Ltd.) was used.

Sludge concentration: 12020 mg / liter, pH 6.3 Sludge amount in pH adjusting tank: 1 liter Alkaline agent added to pH adjusting tank: NaOH pH in pH adjusting tank: initial pH 12, final pH (described in the figure) Residence time in the pH adjustment tank: 90 minutes Irradiation ultrasonic frequency: 27 KHz, output 200 W Ultrasonic intermittent irradiation time: described in the figure Ultrasonic power supply voltage: 100 V Reaction temperature: 28 ° C. In test 1 of this example, The case where the sound wave was continuously irradiated and the case where the sound wave was simply irradiated under the above conditions were performed. For comparison, the other conditions were the same, and the tests were conducted for the case where only the ultrasonic wave was irradiated without adding the alkali to the sludge and the case where the ultrasonic wave was not irradiated with the alkali added to the sludge. did. The results are shown in FIG.

The index of solubilization was measured by centrifuging the sludge by centrifugation (4000 rpm, 10 minutes), and measuring the recovered liquid using the oxygen consumption (COD _M n) of potassium permanganate at 100 ° C. Judgment was made based on the increase in the COD concentration in the sludge.

As is apparent from the results shown in FIG. 4, when only ultrasonic waves were irradiated, almost no solubilization of sludge was obtained. When only an alkali agent was added, high solubilization was obtained in the initial stage of the reaction, but reached a plateau after about 20 minutes, and finally a high solubilizing effect was obtained. Did not. Also, the pH was significantly lower than the initial value.

As a result of experiments using various initial pH value systems, there was a remarkable difference in the dissolution rate depending on the time of the start of action even at the same pH value. That is, the reaction rate was high in the early stage of the reaction, but the reaction speed was considerably reduced after about 20 minutes of the reaction. Further, even when the ultrasonic wave wp was intermittently irradiated, an effect almost similar to continuous irradiation was obtained. This phenomenon is comprehensively analyzed from kinetics as described above. In other words, in the alkaline method, the alkali acting on the microbial cell wall is consumed and the concentration decreases as the reaction proceeds, but the dissolved cell wall is not peeled off due to the increase in the solution viscosity and alkali ions do not penetrate from the liquid body, and the reaction rate decreases. It is thought that it will reach a plateau at last. This is the so-called mass transfer process rate-limiting.

On the other hand, when ultrasonic irradiation is applied to the alkali reaction, the degree of solubilization is remarkable as compared with the case where only the alkali is added and only the ultrasonic irradiation is performed. In both cases of continuous irradiation and intermittent irradiation, a large difference in the degree of solubilization gradually appeared compared to the case of only alkali addition, and it was revealed that there was a synergistic effect of alkali addition and ultrasonic irradiation. . In particular, the fact that an effect close to continuous irradiation can be obtained even when the ultrasonic irradiation is intermittently performed at an output intensity of a level for ordinary cleaning is extremely useful in terms of the configuration of an apparatus used for implementation on an industrial scale.

For reference, when stirring and alkali addition were performed instead of ultrasonic irradiation using a swirling blade type stirring device, no remarkable difference was observed from the case where only alkali was added.

Test Example 2 In order to further confirm the effect of the ultrasonic irradiation, a test was conducted while changing the conditions for intermittent ultrasonic irradiation. The conditions other than the ultrasonic irradiation were the same as in Test Example 1. Fig. 5 shows the results.
It was shown to.

As can be seen from these results, ultrasonic irradiation is effective even if it is intermittent, but if the intermittent time is made longer and the irradiation time is made shorter, the effect of solubilization tends to decrease. However, a remarkable effect was recognized as compared with the case of using only alkali and only using ultrasonic waves.

Test Example 3 Using the system shown in FIG. 3, a biological treatment was carried out without adjusting the pH of the solution whose dissolution was accelerated by ultrasonic waves at normal temperature and alkaline conditions (initial pH 12) without adjusting the pH. The effect was confirmed. The results are shown in Table 1 below.

The other test conditions are as follows.

Raw water flow rate and water quality: 50 liters / day, B
OD: 1000 mg / L Raw water flow control tank: 50 L Aeration tank: 70 L Return sludge amount: 40 L / day Sludge amount supplied to the sludge dissolution system: 1.5 L / day Solubilizer: NaOH Ultrasonic irradiation conditions: Intermittent time 15 minutes, irradiation time 1 minute

[0107]

[Table 1]

As can be seen from the results in this table, in the system in which the excess sludge dissolution system was introduced, the amount of SS multiplied was substantially reduced at the same time when the treated water quality was almost the same as in the conventional system without the excess sludge dissolution system. did. That is, it was confirmed that the excess sludge dissolving system can minimize the amount of excess sludge generated.

Test Example 4 Using the apparatus of Test Example 1, the excess sludge was solubilized using a lysing agent. The test was carried out under the following conditions for alkaline agent + lysing agent + ultrasonic irradiation, and lysing agent + ultrasonic irradiation, and for comparison, only lysing agent (no ultrasonic irradiation) and alkali agent + lysing agent ( (Without ultrasonic irradiation). The results are shown in FIG. Sludge concentration using H ₂ O ₂ as a lysing agent: 12000 mg / liter Sludge amount in pH adjusting tank: 1 liter Lysing agent: H ₂ O ₂ (30% solution), addition amount 2.5 m
1 / l (sludge) Alkaline agent added to pH adjustment tank: NaOH pH of pH adjustment tank: Initial pH 11.0, final pH (described in the figure) Residence time in pH adjustment tank: 100 minutes Irradiation ultrasonic frequency: 27 KHz, output 200 W Ultrasonic power supply voltage: 100 V Reaction temperature: 28 ° C. As can be seen from the results in FIG.
Compared to the case where only the alkali agent was added to the sludge, it was recognized that the solubilization was clearly promoted when this was further irradiated with ultrasonic waves.

Test Example 5 In order to improve the processing capacity of the existing equipment, a system equipped with a biofilm reactor having the configuration shown in FIG.
The test was performed under the conditions of the intermittent ultrasonic irradiation of Test Example 1. For comparison, a test was performed under the same conditions without using a biofilm reactor.

As a result, in the equipment where the biofilm reactor was not attached to the existing equipment, the outflow of undecomposed organic matter was found in the treated water. However, in the equipment where the biofilm reactor was attached to the existing equipment, No outflow of undecomposed organic matter was observed, and the biofilm reactor significantly improved the processing capacity of the existing equipment, confirming that it was effective in reducing the volume of excess sludge in the existing biological treatment equipment Was done.

Test Example 6 A stirrer was attached to the pH adjusting tank 2 of the apparatus of FIG. 1 used in Test Example 1, and ultrasonic irradiation and stirring were performed simultaneously.

Stirrer: Wing type stirrer (TYPE 600)
G (manufactured by Shinto Kagaku)) Stirring speed of swirl blade: 360 rpm Sludge pH: pH 12 Reaction temperature: room temperature (29 ° C.) Ultrasonic irradiation: continuous irradiation for 10 minutes For comparison, stirring was not performed using a stirrer. A comparison test in which only ultrasonic irradiation was performed was performed. The results are shown in Table 2 below.

[0114]

[Table 2]

As can be seen from these results, the COD concentration in the supernatant water increases remarkably when agitation is performed as compared with the case where only the ultrasonic irradiation is performed. It turns out that it is very effective for solubilization.

[0116]

According to the present invention, the following effects can be obtained by an ultrasonic combination that enhances the effect of chemical treatment on biological sludge generated from organic wastewater treatment and an efficient biological treatment system configuration related thereto. .

(1) By promoting mass transfer in the process of solubilizing biological sludge by an alkali reaction, the output ultrasonic waves used in a general ultrasonic cleaning apparatus are intermittent or continuous. Irradiation can effectively promote the solubilization of sludge, and particularly in the case of intermittent ultrasonic irradiation, the benefits such as miniaturization of the apparatus are extremely large.

(2) Apart from the above alkali, a lysing agent,
The solubilization of sludge can be effectively promoted by continuous ultrasonic irradiation or intermittent ultrasonic irradiation by using an acid or by using a combination thereof.

(3) The sludge solution dissolved by the alkali reaction is sent to an anaerobic part (for example, a raw water flow rate adjusting tank) at the raw water inflow end of the activated sludge method, so that the neutralization step can be omitted, and the cost can be reduced. The purpose of suppressing odor generation can be achieved.

(4) By incorporating a bioreactor using an aerobic bioimmobilized membrane in the first stage, it is possible to reduce the volume of surplus sludge without a large increase in existing facilities that do not have much processing capacity. It becomes possible.

(5) In addition to the addition of a solubilizing agent such as an alkali and the application of ultrasonic waves, a mechanical stirring action by a stirrer or the like is provided to further promote the solubilization of sludge.
The volume reduction of excess sludge which is desired to be realized on an industrial scale is effectively performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a sludge dissolution system for solubilizing sludge according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an outline of the configuration of a biological treatment apparatus incorporating the sludge dissolution system of Embodiment 2;

FIG. 3 is a diagram showing an outline of the configuration of a biological treatment apparatus incorporating the sludge dissolution system of Embodiment 3.

FIG. 4 shows the results of Test Example 1.

FIG. 5 shows the results of Test Example 2.

FIG. 6 shows the results of Test Example 4.

[Explanation of symbols]

 1: Sludge storage tank 2: pH adjustment tank (solubilizing agent contact tank) 3: Ultrasonic treatment tank

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor ▲ Zhang ▼ ▲ Book ▼ Courthouse 1-21-14 Hakusan, Bunkyo-ku, Tokyo 302 Ito 302 F term (reference) 4D059 AA05 BF14 BJ01 BK12 BK22 CA28 DA01 DA32 DA33 DA44 EB06 EB20

Claims (17)

[Claims] 1. An excess of sludge generated by aerobic microbial treatment is solubilized by intermittently applying ultrasonic waves while contacting at least one of an alkali agent and a lysing agent as a solubilizing agent. A method for reducing the volume of excess sludge, which comprises biologically treating the sludge with an aerobic microorganism. 2. An excess sludge generated by aerobic microbial treatment is solubilized by continuously operating ultrasonic waves while contacting at least one of an alkali agent and a lytic agent as a solubilizing agent. A method for reducing the volume of excess sludge, which comprises biologically treating the sludge with an aerobic microorganism. 3. An ultrasonic agent is continuously or intermittently solubilized while contacting an alkaline agent as a solubilizing agent with excess sludge generated by aerobic microorganism treatment to neutralize the sludge solubilized product. A method for reducing the volume of excess sludge, wherein the sludge is biologically treated with an aerobic microorganism. 4. A method for solubilizing excess sludge generated by aerobic microorganism treatment by continuously or intermittently applying ultrasonic waves while contacting an acid as a solubilizing agent, and neutralizing the sludge solubilized product. A method for reducing the volume of excess sludge, wherein the sludge is biologically treated with an aerobic microorganism. 5. The solubilization treatment of the excess sludge is a batch treatment, and the intermittent action of the ultrasonic wave is such that the time during which the solubilization rate decreases with time after the addition of a solubilizer to the excess sludge elapses. 4. The method according to claim 1, wherein the step is carried out every time the point is set.
Or the method for reducing the volume of surplus sludge described in any of 4 or 4. 6. The method for reducing the volume of excess sludge according to claim 1, wherein the solubilization of the excess sludge is carried out at a temperature of room temperature to 70 ° C. 7. The excess sludge passes through a biological treatment tank for treating raw water containing organic wastewater with aerobic microorganisms, and then a separation tank for solid-liquid separation of the sludge from the treated water. The sludge solute is returned to the raw water inflow end of the biological treatment tank for the biological treatment by the aerobic microorganism after solubilization of the excess sludge. The method for reducing the volume of surplus sludge according to any one of claims 1 to 6. 8. The step of returning the sludge solubilized product to the raw water inflow end of the biological treatment tank, wherein the step of returning the sludge solute to the raw water inflow end of the biological treatment tank is at least one of a raw water flow control tank and / or an initial sedimentation tank provided upstream of the biological treatment tank. The method for reducing the volume of excess sludge according to claim 7, wherein the method is carried out through a process. 9. The method according to claim 1, wherein the ultrasonic action on the excess sludge is performed while the sludge is stirred.
The method for reducing the volume of excess sludge according to any one of the above. 10. The ultrasonic wave has a frequency of 3 to 3000K.
The method for reducing the volume of excess sludge according to any one of claims 1 to 9, wherein the frequency of the sludge is 0.05 to 5.0 W / cm ² . 11. A biological treatment tank for treating raw water containing organic wastewater with aerobic microorganisms, a separation tank for separating sludge grown in the biological treatment tank from treated water, and a separated sludge. Part is taken out as excess sludge,
A solubilizer contacting tank for contacting either an acid or a lysing agent, an ultrasonic acting tank for applying ultrasonic waves to excess sludge containing the solubilizing agent, A biological treatment apparatus for treating excess sludge, comprising: a biological treatment tank for treating a solubilized sludge solubilized product by an aerobic microorganism. 12. The solubilizing agent contact tank and the ultrasonic action tank are a single dual-purpose tank, and are provided so as to intermittently or continuously apply ultrasonic waves to the sludge in this tank. The biological treatment device for surplus sludge according to claim 11, characterized in that: 13. The method according to claim 11, wherein the solubilizer contact tank and the ultrasonic action tank are separate tanks, and a sludge circulation path for circulating sludge is provided between these tanks. Surplus sludge biological treatment equipment. 14. The biology of surplus sludge according to claim 11, wherein the biological treatment tank for treating the solubilized sludge solubilized material is a biofilm treatment tank. Processing equipment. 15. A sludge solubilized in the solubilizing agent contact tank and the ultrasonic action tank is returned to a raw water inflow end of a biological treatment tank for treating raw water containing organic wastewater with aerobic microorganisms. The biological sludge treatment apparatus according to any one of claims 11 to 14, wherein a path is provided. 16. A raw water flow regulating tank and / or an initial sedimentation tank is provided in front of a raw water inflow end of a biological treatment tank for treating raw water containing organic waste water with aerobic microorganisms, and sludge solubilized biologically. 16. The biological treatment apparatus for surplus sludge according to claim 15, wherein the path returning to the raw water inflow end of the processing tank is connected to the raw water flow control tank and / or the initial sedimentation tank. 17. The biological treatment device for surplus sludge according to claim 11, wherein sludge stirring means is provided in said ultrasonic action tank.