JP2001149980A - Method for treating sewage and sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating sewage and sludge capable of storing the sludge for a long period of time while preventing the generation of putrefaction and malodors by subjecting the excess sludge to a solubilizing treatment. SOLUTION: The method for treating the sewage and the sludge which biologically treats the organic sewage by microorganisms in a biological reaction chamber 1, solubilizes the sludge generated by this biological treatment and returns the solubilized sludge to the biological reaction chamber 1 consists in solubilizing and thickening the excess sludge and returning the separated water generated by the thickening to the biological reaction chamber 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating sewage and sludge, and more particularly to a method for treating sewage and sludge by adding activated sludge to organic sewage such as sewage to perform biological treatment.

[0002]

2. Description of the Related Art Conventionally, in the treatment of organic wastewater such as sewage,
From the viewpoints of treatment stability, ease of maintenance and the like, as shown in FIG. 3, an activated sludge method in which activated sludge containing microorganisms is added to organic wastewater to carry out biological treatment is widely used.
In this activated sludge method, organic wastewater is introduced into a biological reaction tank 1 for biological treatment, and then treated water containing sludge is introduced into a solid-liquid separation tank 2 such as a sedimentation basin, so that the treated water and sludge are solidified. After liquid separation, the treated water is sterilized and then discharged into rivers, etc.
A part of the sludge is returned to the biological treatment tank 1 as returned sludge by the sludge pump 3 and reused as activated sludge, and the surplus is sent to the sludge thickening tank 4 as surplus sludge, where it is concentrated. After being sent to the concentrated sludge storage tank 6 by the transfer pump 5, it is sent to the sludge dewatering machine 8 by the sludge supply pump 7, and after being dewatered, is temporarily stored in the hopper 10 for sludge discharge via the conveying means 9 such as a belt conveyor. And discharge it out of the system.

[0003] The activated sludge method is excellent in the stability of treatment and the ease of maintenance and management. However, since a large amount of excess sludge is generated, many processes and equipment are required for the treatment of excess sludge. There is a problem that the sludge treatment cost increases and a final disposal site for the excess sludge must be secured.

[0004] Under such circumstances, there has been proposed a method for solubilizing sludge which can make the processing equipment compact and reduce the amount of excess sludge discharged outside the system. In this sludge solubilization treatment method, the solubilization treatment of sludge
Decompose sludge into solution using ozone and other oxidizing agents, various radicals, acids and alkalis, high-temperature and high-pressure treatment, mechanical destruction, ultrasonic destruction, organisms (including enzymes), etc. , This solubilized solution is returned to the biological reactor,
The sludge is biologically treated again.

[0005]

By the way, sludge is composed of an organic component and an inorganic component, and the former is composed of an easily decomposable component and a hardly decomposable component. It is difficult to decompose hardly decomposable organic components in a short time. Therefore, the hardly decomposable organic component is accumulated in the treatment system together with the inorganic component, and it is difficult to maintain a normal sludge state, and there is a problem that the quality of treated water deteriorates. Moreover, in the system incorporating the solubilization treatment of sludge, the amount of surplus sludge generated is extremely small as compared with the ordinary activated sludge method. Therefore, until a post-treatment such as discharging the surplus sludge out of the system is performed. The period of time is prolonged, and there is a possibility that a problem such as excess sludge generating a bad smell for a long time may occur.

[0006] As another problem, a system incorporating a solubilization treatment has a fatal drawback that phosphorus cannot be removed from wastewater. That is, unlike phosphorus, nitrogen, which is the same nutrient, phosphorus and heavy metals cannot be gasified and released into the atmosphere, and therefore need to be recovered as solids. Since phosphorus in water is usually immobilized in microorganisms, phosphorus was removed from the wastewater by discharging it as excess sludge to the outside of the system.However, in the method of solubilizing sludge, microorganisms are destroyed. Therefore, there is a problem that phosphorus cannot be removed at all because the immobilized phosphorus is re-eluted.

[0007] In view of the above-mentioned problems of the conventional methods for treating wastewater and sludge, the present invention performs a solubilization treatment on surplus sludge to prevent sludge and odor from being generated and store sludge for a long time. It is an object of the present invention to provide a method for treating sewage and sludge that enables phosphorus removal.

[0008]

Means for Solving the Problems To achieve the above object, a method for treating sewage and sludge of the present invention biologically treats organic sewage with microorganisms in a biological reaction tank and removes sludge generated by biological treatment. In a method for treating wastewater and sludge in which solubilized sludge is returned to a biological reaction tank, excess sludge is solubilized and concentrated, and separated water generated by the concentration is returned to the biological reaction tank. It is characterized by the following.

In this method for treating wastewater and sludge, since excess sludge is solubilized and concentrated, sludge can be stored for a long period of time while preventing rot and odor of the sludge. Since the separated water generated by the concentration of the sludge after solubilization is returned to the biological reaction tank, sound sludge can be held in the biological reaction tank and stable sludge treatment can be performed.

In this case, after solubilizing the excess sludge, a flocculant can be added to coagulate and precipitate phosphorus to concentrate the sludge together with the sludge.

[0011] This makes it possible to remove phosphorus from sewage in a solubilization treatment system for re-eluting immobilized phosphorus.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the method for treating sewage and sludge of the present invention. In the figure, 1 is a biological reaction tank,
As the biological reaction tank 1, any one of a single treatment tank used for the oxidation ditch method, a treatment tank provided with a partition wall used for the standard activated sludge method, and the like can be used. In this biological reaction tank, air (oxygen) is usually supplied while agitating and mixing the sewage and the sludge to aerobically treat the sewage.

Reference numeral 2 denotes a final sedimentation basin, which receives a mixed solution of treated water and sludge flowing out of the biological reaction tank 1 and separates the mixture into sludge and treated water by a difference in specific gravity. Then, the supernatant is subjected to a sterilization treatment and then discharged outside the system as treated water.

On the other hand, most of the sludge is returned to the biological reaction tank 1 via the sludge pump 3, and the biological treatment is continuously performed while maintaining the sludge concentration in the biological reaction tank 1 at a predetermined level. To be able to In such a normal water treatment system, a part of the sludge is introduced into the solubilization tank 11, and the solubilization tank 11 is supplied to the solubilization tank 11 from the chemical tank 13 through the chemical injection pump 12. Supply. The solubilization tank 11 is provided with a stirrer 11a for accelerating the solubilization reaction of the sludge, is stirred for a predetermined reaction time, and returns the solubilized sludge to the biological reaction tank 1 to perform biological treatment. To do.

The above configuration is the same as that of the conventional system for solubilizing sewage and sludge. However, the treatment system of this embodiment has an advantage that the amount of sludge discharged outside the system can be extremely reduced. In recent years, research has been conducted at many research institutions. In many of the research reports, it is reported that the amount of sludge discharged outside the system is zero, but it is difficult in principle to solubilize all sludge containing inorganic components and persistent organic components. In order to maintain a normal sludge state in the biological reaction tank 1, it is necessary to discharge at least a part of these sludge components out of the system as surplus sludge.

Therefore, in the present embodiment, the sludge is discharged out of the system as surplus sludge against the accumulation of the inorganic component or the hardly decomposable organic component which gradually progresses with time, thereby solving the above problem. However, the excess sludge is maintained in a preferable state by the following method so that the excess sludge can be stored for a long time until the excess sludge is discharged.

That is, in this embodiment, in the treatment of sewage and sludge incorporating the solubilization treatment system, a sludge concentration storage tank 14, a coagulant storage tank 15, and a coagulant supply pump 16 are provided as equipment. The solubilized sludge is concentrated and stored in the sludge concentration storage tank 14, and a coagulant is added to the solubilized sludge in the preceding stage of the sludge concentration storage tank 14, so that phosphorus is coagulated and precipitated to be concentrated together with the sludge. ing.

To explain this in more detail, the sludge that has been subjected to the solubilization treatment is subjected to precipitation,
The sludge that has been subjected to solubilization is separated, but the easily decomposable components of the organic components are separated from the separated water together with the separation water, so that the sludge is easily mineralized. Has changed. On the other hand, since the separated water contains solubilized sludge easily decomposable components, it is returned to the biological reaction tank 1 for biological treatment. As described above, when the sludge that has been subjected to the solubilization treatment is introduced into the sludge concentration storage tank 14, the separated water is returned to the biological reaction tank 1, and the sludge is repeatedly processed to concentrate and store the sludge in a stabilized state. To

Further, in this embodiment, the sludge concentration storage tank 1
4, a coagulant for dephosphorization together with the solubilized sludge is supplied from the coagulant storage tank 15 to the coagulant supply pump 1.
Since phosphorus is supplied through the system 6, the phosphorus is converted into a phosphate, aggregates and precipitates, is concentrated together with the sludge, and is discharged outside the system as excess sludge. Therefore, in the present embodiment, it is possible to remove phosphorus which cannot be realized by the conventional solubilization treatment.

Next, FIG. 2 shows a second embodiment of the method for treating sewage and sludge of the present invention. In the present embodiment, instead of the configuration of the first embodiment, the biological reaction tank 1 is provided with a solid-liquid separation membrane 1a for performing the membrane separation activated sludge method.

Here, the treated water is discharged out of the system via the solid-liquid separation membrane 1a, and the sludge is directly drawn out from the biological reaction tank 1 having a stable sludge concentration.
1, so that the solubilization treatment and the subsequent phosphorus coagulation treatment can be performed stably.

The other structure of the present embodiment is the same as that of the first embodiment.

The method for treating sewage and sludge of the present invention utilizes the characteristics of the solubilization treatment of decomposing, stabilizing, and disinfecting organic substances, and uses various solubilization methods to actively remove excess sludge. By decomposing and mineralizing, it is possible to prevent decay of organic components during the concentration and storage period, and to stabilize the properties of excess sludge. That is, the excess sludge that has been solubilized has a low ratio of organic matter / inorganic matter and mineralization proceeds, but the mineralized sludge has good sedimentation properties and changes its properties to the most suitable sludge for concentration and storage. At the same time, the effect of reducing the amount of stored sludge can be expected. further,
Since the solubilization treatment excluding bio-utilization has a bactericidal action,
Even when the sludge is concentrated and stored for a long time, the progress of decay can be prevented, so that the effect of suppressing the generation of offensive odor is produced. And, by the solubilization treatment, for the phosphorus eluted from the body of the microorganism, a sparingly water-soluble phosphate is formed by the action of the flocculant, and the phosphate is precipitated and pulled out together with other sludge components.
It can be processed outside the system.

The method for treating sewage and sludge of the present invention has been described based on the embodiments. However, the present invention is not limited to the configuration described in the above embodiments. The method of any of the methods that have been studied in the past is basically adopted as a means of solubilizing sludge, as long as it has the property of decomposing and stabilizing organic substances, and more preferably, having a bactericidal effect. Specifically, oxidizing agents such as ozone, various radicals, acids and alkalis, high-temperature / high-pressure treatment, mechanical destruction, ultrasonic destruction, organisms (including enzymes) and the like can be used. Can be adopted.

[0026]

According to the method for treating sewage and sludge of the present invention, the excess sludge generated is solubilized and concentrated in the pretreatment for storage, thereby preventing sludge decay and generation of offensive odor. Sludge can be stored for a long period of time, and since the separated water generated by the concentration of the sludge after solubilization is returned to the biological reaction tank, sound sludge is held in the biological reaction tank and stable. Sludge treatment can be performed.

Further, after solubilizing the excess sludge, a coagulant is added, and the phosphorus is coagulated and precipitated to be concentrated together with the sludge, so that the immobilized phosphorus is re-eluted. It becomes possible to remove phosphorus.

[Brief description of the drawings]

FIG. 1 is a processing flowchart showing a first embodiment of a method for treating sewage and sludge of the present invention.

FIG. 2 is a process flowchart showing a second embodiment of the method for treating sewage and sludge of the present invention.

FIG. 3 is a processing flowchart of a conventional method for treating wastewater and sludge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Biological reaction tank 1a Solid-liquid separation membrane 2 Final sedimentation basin 3 Sludge pump 4 Sludge concentration tank 5 Sludge transfer pump 6 Condensed sludge storage tank 7 Sludge supply pump 8 Sludge dehydrator 9 Transport means 10 Hopper for sludge discharge 11 Solubilization tank 11a Stirrer 12 Chemical injection pump 13 Chemical tank 14 Sludge concentration / storage tank 15 Coagulant storage tank 16 Coagulant supply pump

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D028 AA08 AB00 AC01 BB03 BD06 BD08 BD10 BD12 BD16 BD17 4D059 AA03 AA19 BC02 BE31 BE42 BE49 BE54 BJ01 BK12 BK13 BK22 CA22 DA43

Claims (2)

[Claims] Claims: 1. A method for treating organic wastewater with microorganisms in a biological reaction tank, solubilizing sludge generated by the biological treatment, and returning the solubilized sludge to the biological reaction tank. A method for treating sewage and sludge, comprising: solubilizing and condensing excess sludge; and returning separated water generated by the concentration to a biological reaction tank. 2. The method for treating sewage and sludge according to claim 1, wherein after solubilizing the excess sludge, a coagulant is added to coagulate and precipitate phosphorus and concentrate the sludge together with the sludge.