JPS63166499A - Apparatus for biological denitrification/ dephosphorization treatment of sewage - Google Patents

Abstract

PURPOSE:To effectively remove nitrogen and phosphorus, by providing an aeration stirrer having both stirring and aeration functions in one tank and by mounting reaction tanks communicating with each other to be capable of being changed over to either one of aerobic and anaerobic treatments. CONSTITUTION:Inflow sewage and return sludge are introduced into one anaerobic tank 5 to be stirred under an anaerobic condition. Two reaction tanks 1, 2 are connected to the outflow part of the anaerobic tank 5 through a change- over introducing means 4 such as an inflow change-over valve and a liquid mixture is intermittently supplied to be reaction tank 1 through an inflow passage or to the reaction tank 2 through an inflow passage by changing over the change-over valve 4. The reaction tanks 1, 2 are interconnected through a communication passage 7 so as to be capable of communicating with each other at a proper time. The outflow passages from the reaction tanks 1, 2 go toward a solid-liquid separation means 3 such as a sedimentation tank through a change-over introducing means 6 and treatment process water is treated to be clarified. By this method, nitrogen/phosphorus removing efficiency can be enhanced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an apparatus for biologically simultaneously removing nitrogen and phosphorus from wastewater such as sewage and wastewater, and more specifically, an apparatus for biologically simultaneously removing nitrogen and phosphorus from wastewater such as sewage and wastewater. The present invention relates to an anaerobic/aerobic dual-type treatment device that removes with high efficiency.

[Conventional technology]

Conventionally, biological nitrogen and phosphorus removal methods for wastewater include (11) a method of providing an anaerobic tank at the front stage of the modified activated sludge circulation method, (2) a method of step-dispensing the circulation method itself, and (3) a method of dispensing the circulation method itself in the first stage. In the modified circulation method with an anaerobic tank, there is a method of adding lime to returned sludge or surplus sludge to recover phosphorus components, but both methods are efficient in recovering both nitrogen and phosphorus and have low installation and operating costs. There were difficulties in implementing the treatment method.

Also, as shown in Japanese Patent Application Laid-open No. 55-73398,
A denitrification/dephosphorization method has been proposed in which an anaerobic process, a nitrification process, and a denitrification process are connected in series in multiple stages, and concentrated activated sludge is returned to the raw water for injection and/or to the anaerobic process.

[Problem that the invention seeks to solve]

However, the method described in JP-A-55-73398 requires a large number of treatment tanks, agitators, aerators, piping, land, etc., resulting in high costs and inflexibility in terms of performance. have.

The present invention was developed in view of the above points, and is a device that performs biological nitrification and denitrification by using two reaction tanks and switching the inside of each tank alternately between anaerobic and aerobic conditions. The object of the present invention is to provide a device that exhibits excellent nitrogen and phosphorus removal performance by adding an anaerobic tank.

Means and operation for solving problem C] The biological denitrification/dephosphorization treatment apparatus of the present invention will be described with reference to the drawings. an anaerobic tank 5 equipped with an anaerobic tank, and a switching introduction means 4 for introducing the outflow water from the anaerobic tank into either of the reaction tanks 1.2.
and a separate agitator and aerator, or an aerobic agitator that functions as both agitation and aeration in one tank, and communicated with each other for either aerobic or anaerobic treatment. Two reaction tanks 1.2 that can be switched, and the reaction tank 1
．． 2, a switching introduction means 6 for introducing the mixed liquid flowing out from either of the reaction vessels 1.2 into the solid-liquid separation means, a solid-liquid separation means 3 for solid-liquid separation of the mixed liquid flowing out from the reaction tank 1.2, and the solid-liquid separation means. The system is characterized by comprising a sludge return line 8 for returning a part of the sludge separated in the anaerobic tank 5 to the anaerobic tank 5.

Inflow sewage and return sludge are introduced into an anaerobic tank (dephosphorization tank) 5, where they are anaerobically stirred. Next, the mixed liquid is supplied to the reaction tank 1 or the reaction tank 2 by the switching introduction means 4.

The treatment process water from any of the reaction tanks enters the solid-liquid separation means 3 via the switching introduction means 6, and the treated water clarified here is discharged, and most of the settled sludge flows through the sludge return system 8. After that, it is returned to the anaerobic tank 5.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 shows a flow diagram of the device according to the invention. - The inflowing sewage and return sludge are led to the anaerobic tank 5, where they are anaerobically stirred. The two reaction tanks 1.2 are connected to the outflow section of the anaerobic tank 5 via switching introduction means 4 (hereinafter referred to as switching valve 4) such as an inflow switching valve, and by switching the switching valve 4, the mixed liquid flows into the inflow. into reaction tank 1 via a channel, or into reaction tank 2 via an inlet channel.
Each outlet passage from the zero reaction tanks 1 and 2, which are interconnected via the communication path 7, is equipped with a switching system such as an outflow switching valve so that the zero reaction tanks 1 and 2, which are continuously supplied to the zero reaction tanks 1 and 2, can communicate with each other in a timely manner. The means 6 (hereinafter referred to as the switching valve 6) is directed to the solid-liquid separation means 3 (hereinafter referred to as the settling tank 3) such as a settling tank, and by switching the switching valve 6, the treatment process from either reaction tank is transferred. Water enters the settling tank 3, and the treated water clarified here is discharged from the settling tank 3.

Most of the settled sludge in the settling tank 3 passes through the sludge return line 8,
The sludge is returned to the anaerobic tank 5, which is a dephosphorization tank, and a portion is discharged outside the system as surplus sludge.

The present invention will be explained in more detail based on FIG. Second
The figure shows one embodiment of the apparatus of the invention, 1-7 indicating the same equipment of FIG. 9 is a stirrer provided in the anaerobic tank 5. 0 Reaction tanks 1.2 each have internal stirring means 10.11 and air blowing means 12.13 or oxygen blowing means as independent or integrated mechanisms. The raw water capacity 14.15 of the provided 0 reaction tank 1.2 is switchably connected to the raw water supply pipe 16 via the three-way switching valve 4. In addition, the reaction treated water outlet 17.18 of the reaction tank 1.2
are switchably connected to the settling tank 3 via switching valves 6a, 6b. Furthermore, both reaction vessels 1.2 are connected to a communication pipe 7.
are interconnected by. 20 is an aeration blower, 121 is a raw water supply pump, 22 is a return sludge pump, 2
3 is a surplus sludge pump.

In the anaerobic tank 5, the mixed liquid is agitated anaerobically using a stirrer, a submersible pump, etc., and while it is being provided as an anaerobic atmosphere in the reaction tank 1 or 2, it is anaerobically stirred so that suspended sludge can be stirred. While creating an aerobic atmosphere, air is supplied by an aeration device or the like. The anaerobic stirring devices used in the anaerobic tank 5 and reaction tank 1.2 include various types of stirrers such as Kai type, gate type, turbine type, and propeller type, as well as in-tank types such as submersible pumps, submersible stirrers, ejectors, and injectors. There are devices that circulate inert gas such as combustion waste gas and N in the tank. Devices that make the reaction tank an aerobic atmosphere include air diffusers, air diffusers, paddle rotors, submersible aeration stirrers,
There are submersible injectors (ejectors), clusters, etc., and in addition to the above-mentioned agitators, there are submersible aeration agitators that operate with only air supplied or perform small amounts of air lacing. You can also.

Regarding the shape of the anaerobic tank, in addition to the economic efficiency of the equipment, it is desirable to avoid as much air as possible from the outside during the mixing of inflow sewage and returned sludge and the anaerobic stirring action, and it is desirable to minimize the area of water in contact with outside air in the tank. For this purpose, it is desirable that the shape near the liquid surface be shaped like the mouth of a glass bottle, with a liquid level constriction type.

An example for carrying out operation with the device of the present invention is as follows:
In the apparatus shown in FIG. 2, raw water and returned sludge are first led to an anaerobic tank 5, and the effluent from the anaerobic tank 5 is first supplied to one reaction tank 1 as a mixed liquid through a three-way switching valve 4. , this reaction tank 1 is brought into an anaerobic state, and the other reaction tank 2 is
is set in an aerobic state, and the reaction treated water is introduced from the reaction tank 2 into the settling tank 3. Next, one reaction tank 1 is set in an aerobic state and the other reaction tank 2 is set in an aerobic state, and the reaction treated water is introduced from the reaction tank 2. is introduced into the settling tank 3, or the mixed liquid inflow is led to the reaction tank 2, the reaction tank 2 is brought into an anaerobic state, the reaction tank 1 is brought into an aerobic state, and the reaction treated water is introduced from the reaction tank 2 into the settling tank 3. Then, the inflow of the mixed liquid is connected to the reaction tank 1, reaction tank 1 is set to an anaerobic state, and reaction tank 2 is set to an aerobic state, and the reaction treated water is introduced from the reaction tank 2 to the settling tank 3, and then mixed. Connect the liquid inflow path to reaction tank 2, set reaction tank 2 in an anaerobic state and reaction tank 1 in an aerobic state, and introduce the reaction treated water from reaction tank 1 into settling tank 3, and then set reaction tank 1 in an aerobic state. The reaction tank 2 is in an aerobic state, the reaction treatment liquid is introduced from the reaction tank 1 into the settling tank 3, and the No. 1 raw water inlet is switched to supply the mixed liquid to the reaction tank 1. The reaction treated water is transferred from the reaction tank 1 to the sedimentation tank 3 while the reaction tank 2 is in the anaerobic state and the reaction tank 2 is in the aerobic state.
Then, the mixed liquid is allowed to flow into the reaction tank 2, and the reaction treated water is introduced from the reaction tank 2 into the precipitation tank 3, with the reaction tank 2 in an anaerobic state and the reaction tank 1 in an aerobic state.

The flow system for both reaction tanks for nitrification and denitrification mentioned above is as follows:
For example, they are operated in the sequence shown schematically from A1 to A in FIG. 3 or from B1 to B in FIG. 4.

Steps A1 to A- of the A sequence will be described, in which hatched reaction vessels in the figure indicate an anaerobic state, and non-hatched reaction vessels indicate an aerobic state. In step A, raw sewage is supplied to reaction tank 1, which is connected to reaction tank 2, and from reaction tank 2 to settling tank 3.An anaerobic atmosphere is provided in reaction tank 1, and nitric acid A denitrification reaction of nitrogen is performed, and in the reaction tank 2, oxidation of BOD components and nitrification of ammonia nitrogen are performed in an aerobic atmosphere. Subsequently, in step ^yo, both reaction vessels 1 and 2 are brought into an aerobic state, and mainly oxidation of Boil components and nitrification of ammonia nitrogen are performed. Next, in step A3, similarly to A1, denitrification reaction is performed in the reaction tank 1 in an anaerobic atmosphere, and nitrification of ammonia components is performed in the reaction tank 2 in an aerobic atmosphere. In step A, the raw water mixture is connected to reaction tank 2 instead of reaction tank 1, and an anaerobic atmosphere is provided in reaction tank 2 so that reaction tank 1 is connected to precipitation tank 3. An aerobic atmosphere is provided inside the reaction tank 1. This state is the same as the state in which the positions of the reaction vessels were swapped with each other in step A1. Thereafter, the procedure proceeds to step ^1 and A in the same manner, and after A, the flow path is switched to the state of A again, and the series of operations from steps A to A- are repeated sequentially.

Regarding the operating conditions of the apparatus of the present invention, the residence time in the anaerobic tank is preferably 1 to 5 hours. If the time is less than 1 hour, the amount of phosphorus released from the returned sludge will be insufficient, impairing the phosphorus removal performance, and if it exceeds 5 hours, the volume of the anaerobic tank will become too large, increasing equipment costs, resulting in an inappropriate 0 reaction. The total residence time of the two tanks is preferably 6 to 20 hours. If the residence time is less than 6 hours, the nitrification and denitrification of nitrogen will not be sufficiently achieved, and if it exceeds 20 hours, the equipment cost will increase, making it unsuitable. It is.

The repeated operation unit time (one cycle of the sequence) of this process is preferably 2 to 6 hours. If it is less than 2 hours, it will not be possible to sufficiently follow each setting atmosphere even with switching operations, so appropriate processing will be achieved. Yes, if it takes more than 6 hours,
This is unsuitable because the frequency of nitrification and denitrification is reduced. Here, the unit time for switching the reaction tank is preferably 0.2 to 2 hours.

If it is less than 0.2 hours, an aerobic/anaerobic atmosphere cannot be maintained properly, and if it exceeds 2 hours, proper nitrification and denitrification cannot be carried out, which is inappropriate. In order to obtain suitable denitrification/dephosphorization ability, FILss of the mixed liquid in the anaerobic tank and reaction tank must be
It is preferable that the concentration is 2,000 to 5,000 fflr/It. Also, the BOD/SS load is 0.05 to 0.
, 2k+rBOD/pupil SS·day. At 0.05kgBOD/kgss/Himizo, the capacity of the type is excessive, whereas 0.2kgBOD
If the temperature exceeds /krss·day, the nitrification reaction cannot occur and it is inappropriate.

The sludge agitation capacity in the anaerobic tank 5 is set at the lowest level of agitation that prevents the sludge from settling and achieves uniform mixing in the tank, in order to prevent the introduction of dissolved oxygen due to the mixing of air in the atmosphere. The method is preferred. The stirring speed is 10 for sludge.
The range of am/5ecy 100as/sec is desirable.* If it is less than 10cm7sec, sludge will settle and proper mixing will not be achieved, which will hinder the release of phosphorus from the sludge, and if it exceeds 100as/sec, the anaerobic tank will The sludge becomes turbulent, air gets mixed into the liquid in the tank, the tank is not sufficiently anaerobic, and the sludge breaks down and becomes finer, making it unsuitable. Also, the ORP value (oxidation-reduction potential) in the anaerobic tank is -40
It is desirable to maintain the voltage between 0mV and +10011V.
If it is less than 400 s+V, the residence time in the anaerobic tank will be extremely excessive, making it difficult to realize it, and if it exceeds +100 mV, sufficient sludge will not be discharged, which is inappropriate. By the way, in the anaerobic tank 5, the anaerobic atmosphere is damaged when the water surface of the mixed liquid comes into contact with the atmosphere, so in order to minimize the area of the water surface, a narrow-mouthed water tank is used, or the water surface is replaced with an inert gas such as h. By doing so, a sufficient anaerobic atmosphere can be established.

The wastewater targeted by the treatment method using the device of the present invention includes:
It can be applied to a variety of wastewater containing nitrogen and phosphorus, such as sewage, human waste, community drainage, various industrial wastewater, garbage landfill leachate, and dredging overflow.

According to the present invention, nitrogen and phosphorus removal performance of sewage wastewater can easily achieve a nitrogen removal rate of 80% or more and a phosphorus removal rate of 90% or more. At the same time, BOD is 95
% or more can be removed. In addition, 5VI (sludge settling index) is also ML.
S54000w/1 can maintain a low value of 100 to 200 even though it is a highly concentrated mixed liquid.

〔Example〕

Examples and comparative examples of the present invention will be described below.

Example 1, Comparative Example 1 According to the flow shown in FIG. 1, denitrification and dephosphorization treatment of sewage was carried out under the following conditions. The operating system was as shown in Figure 3 or Figure 4. The results are shown in Table 1.

Inflow sewage treatment flow rate: 247/day Reaction tank retention time: 11 hours (2 tanks) Sedimentation tank retention time: 0 to 3 hours Return sludge ratio: 1 Dissolved oxygen concentration: 0 to 5 ■/i Water temperature: 20℃ 1st Note that sequences F-62 and F-61 represent the operating methods shown in FIGS. 4 and 3, respectively.

As can be seen from Table 1, according to this example, a removal rate of 86% or more was achieved as a phosphorus removal performance, and a removal rate of 80% or more was achieved as a nitrogen removal performance.

Example 2, Comparative Example 2 Under the same conditions as Example 1, the capacity of the anaerobic tank was made the same using the operation method F-61, and the shape near the water surface was changed as shown in FIGS. 5 to 7. The anaerobic tank 5a in FIG. 5 is a wide-mouthed or normal type, the anaerobic tank 5b in FIG. 6 is a narrow-mouthed type, and the anaerobic tank 5C in FIG. 7 is a narrow-mouthed type. I tried to cut off air contact with the area. 25 is an N2 gas cylinder. The results were as shown in Table 2.

(The following is a blank space) Table 2 As is clear from Table 2, good phosphorus removal performance could be obtained by employing the anaerobic tanks shown in FIGS. 6 and 7.

〔Effect of the invention〕

Since the present invention is configured as described above, it has the effect of being able to efficiently remove nitrogen and phosphorus from wastewater at the same time. Because they are not arranged in series, they are compact and have the advantage of simplifying piping, circulation pumps, and other equipment.

[Brief explanation of the drawing]

Figure 1 is a flow sheet showing an example of the biological denitrification/dephosphorization treatment equipment for wastewater of the present invention, Figure 2 is a flow sheet depicting the equipment shown in Figure 1 in more detail, Figures 3 and 3 are 4
The figure is an explanatory diagram showing a sequence in an example, and the shaded area shows a reaction tank in an anaerobic state. Figure 5 shows comparative example 2.
FIG. 6 and FIG. 7 are explanatory diagrams of the anaerobic tank in Example 2. 1.2... Reaction tank, 3... Solid-liquid separation means, 4...
Switching introduction means, 5.5a, 5b, 5c...anaerobic tank, 6
...Switching introduction means, 6a, 6b...Switching valve, 7...
・Communication path, 8...Sludge return system path, 9...Agitator, 1
0.11... Stirring means, 12.13... Air blowing means, 14.15... Raw water inlet, 16... Raw water supply pipe, 17.18... Reaction treated water outlet, 20...・Aeration blower 121...Raw water supply pump, 22...Return sludge pump, 23...Excess sludge pump, 24...Narrow mouth, 25...N2 gas cylinder Applicant: Kawasaki Heavy Industries, Ltd. No. Figure C + Az A)1
(Use now fh'l) 0. the law of nature
0.5 Pi diagram

Claims (1)

[Claims] 1 An anaerobic tank (5) equipped with a stirrer that receives sewage and returned sludge and processes it anaerobically, and a switch to introduce the effluent from the anaerobic tank into either the reaction tank (1) or (2). The introduction means (4), a stirrer and an aerator may be installed separately, or an aeration stirrer that functions as both stirring and aeration may be installed in one tank, and communicated with each other to provide an aerobic or anaerobic system. Two reaction tanks (1) that can be switched to either treatment
, (2), and a switching introduction means (
6), solid-liquid separation means (3) for solid-liquid separation of the mixed liquid flowing out from the reaction tanks (1) and (2), and a part of the sludge separated by the solid-liquid separation means to be transferred to the anaerobic tank ( 5) A biological denitrification/dephosphorization treatment device for sewage, comprising a sludge return line (8) for returning the sludge to the sludge.