JP6716664B2 - Batch type carrier water treatment method - Google Patents

Description

The present invention relates to a batch type carrier water treatment method capable of effective denitrification.

Patent Document 1 uses a carrier that can be settled in a reaction tank, aerates and stirs the carrier, and when the carrier is settled after the aeration is stopped, the activated sludge adheres to the carrier, so that the activated sludge is provided before the activated sludge alone. A treatment method is described in which the activated sludge is allowed to settle, and the activated sludge settles on the upper part of the carrier with a slight delay from the carrier.

JP, 9-70594, A JP, 2005-73911, A

In the method of Patent Document 1, since there is a risk of preventing the carrier from flowing out from the reaction tank, a carrier outflow preventing means is provided, and a mesh net is used as the carrier outflow preventing means, and there is a gap below the reaction tank. It is provided with a space.
In this method, a carrier to which sludge is attached is accumulated on a mesh wire mesh, and further, sludge is clogged in the upper part of the carrier or between the carriers. The treated water is obtained by pumping out from below the wire net, but sludge falls from the wire net, and clarification has a drawback that it is difficult to obtain the treated water.

Patent Document 2 performs batch-type activated sludge treatment using a microorganism-immobilized carrier. However, in order to facilitate solid-liquid separation of activated sludge and treated water, a carrier with high microbial habitability is used, In the precipitation step, the sedimentation of the carrier carrying the microorganisms is accelerated to facilitate the separation of the treated water and the microorganisms.

However, in Patent Document 2, since the carrier in the treatment tank is settled together with the sludge, there is a problem that the treatment cannot be performed until the settling ends up.

Therefore, it is an object of the present invention to provide a batch-type carrier water treatment method capable of advancing the treatment even during sedimentation in a state in which the carrier in the batch tank is suspended and shortening the treatment time.

Other problems of the present invention will be clarified by the following description.

The above problems can be solved by the following inventions.

(Claim 1)
After aeration of sludge in the batch tank is stopped, mechanical stirring is stopped, the sludge in the batch tank is allowed to settle, and solid sludge is separated into sedimented sludge and supernatant water, and at least nitrification or nitrite conversion is possible. An anaerobic second step in which a carrier carrying aerobic bacteria and denitrifying bacteria is floated near the liquid surface, while introducing waste water containing ammonia nitrogen, and treating water is taken out of the batch tank,
An aeration device provided in the batch tank while contacting the wastewater introduced in the anaerobic second step with the aerobic bacteria floating in the batch tank or the aerobic bacteria carried on the carrier. An aerobic nitrification step of supplying air from a nitrification reaction including a nitrite reaction and a nitrification reaction,
In the aerobic nitrification step, the supply of air is stopped, and while the liquid in the batch tank is being stirred in an anaerobic state, there is a anaerobic first step in which nitrogen gas is generated by a denitrification reaction by denitrifying bacteria. A batch-type carrier water treatment method comprising:
(Claim 2)
The batch type carrier water treatment method according to claim 1, wherein the treatment cycle of the anaerobic second step, the aerobic nitrification step, and the anaerobic first step is sequentially repeated in the batch tank.
(Claim 3)
The batch type carrier water treatment method according to claim 1 or 2, wherein the carrier floating near the liquid surface filters suspended suspended matter (ss) contained in the supernatant water.
(Claim 4)
The batch type carrier water treatment method according to claim 1, wherein the carrier is a carrier having a plurality of cells.
(Claim 5)
The batch type carrier water treatment method according to claim 4, wherein the carrier has a size of 2 to 50 [mm square] and a true specific gravity of 0.03 to 0.05 [g/cm ³ ].

According to the present invention, it is possible to provide a batch-type carrier water treatment method in which a carrier in a batch tank is suspended and the treatment can proceed even during sedimentation, and the treatment time can be shortened.

Block diagram showing an example of a batch-type carrier water treatment method of the present invention The figure explaining an example of the batch type carrier water treatment apparatus which implements the batch type carrier water treatment method of this invention. The figure explaining the function of this invention. A graph showing changes over time in batch operation and the concentrations of NH ₄ -N and NO _x -N. Graph showing the relationship between the elapsed time and the floatation rate of the carrier due to the difference in the methanol addition rate Diagram showing the state of the carrier in the tank Graph showing the relationship between the NO x _-N removal amount and carrier flying rate

Hereinafter, modes for carrying out the present invention will be described.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of a batch type carrier water treatment method of the present invention, and FIG. 2 is a concept of an example of a batch type carrier water treatment apparatus for carrying out the batch type carrier water treatment method of the present invention. FIG.

The wastewater (also referred to as raw water) to be treated by the present invention is not particularly limited as long as it contains ammonia nitrogen (NH ₄ —N). In the present invention, a wastewater containing an organic substance together with ammonia nitrogen is preferable, and for example, digestive liquid or human waste after methane fermentation of organic waste such as kitchen garbage, septic tank sludge and the like can be preferably mentioned. It is particularly preferable to use a filtrate obtained by subjecting the digested juice, human waste, and septic tank sludge to a dehydration treatment in advance.

The batch type carrier water treatment method of the present invention has a form shown in FIG. 1 as a preferred embodiment, and has an anaerobic second step 100, an aerobic nitrification step 101, and an anaerobic first step 102.
An example of an apparatus that carries out each of the above steps is shown in FIG.
The batch type carrier water treatment device shown in FIG. 2 includes a raw water tank 1 for storing raw water containing ammonia nitrogen, a batch tank 2 for biologically nitrifying and denitrifying raw water introduced from the raw water tank 1. A discharge tank 3 that stores the treated water that has flowed out from the batch tank 2 is provided.

The raw water tank 1 and the batch tank 2 are connected by a raw water supply pipe 4. The raw water supply pipe 4 is provided with a raw water supply pump 5 for supplying the raw water in the raw water tank 1 to the batch tank 2 via the raw water supply pipe 4.

Further, the batch tank 2 is provided with a raw water inflow section 6 connected to the raw water supply pipe 4 and a treated water outflow section 7 for outflowing the treated water after the treatment in the batch tank 2.

The treated water outflow unit 7 is composed of at least a treated water drawing pump 71, a screen 72, and a treated water pipe 73.
In the treated water outflow unit 7, the treated water drawn out by driving the treated water withdrawal pump 71 is introduced into the discharge tank 3 through the treated water pipe 73. The screen 72 is provided to prevent the carrier 20 from flowing out.
Alternatively, the treated water withdrawal pump 71 may not be provided, and the amount of the waste water introduced into the batch tank 2 may be overflowed so that the treated water treated in the batch tank 2 is pushed out and introduced into the discharge tank 3.

An agitator 21 for agitating the sludge is provided in the batch tank 2, and the agitator 21 has an agitation blade 210 arranged in the sludge in the batch tank 2 and a motor 211 for driving the agitation blade. It is composed by.

Further, the batch tank 2 is provided with an aeration device 22 for aeration of the sludge in the batch tank 2. The aeration device 22 is composed of an air diffuser 23 arranged in the lower part of the batch tank 2 and a blower 24 connected to the air diffuser 23. Reference numeral 25 is a membrane member capable of adjusting the size of air bubbles diffused.

The aeration device 22 is used when performing nitrification treatment or organic substance decomposition treatment of waste water in the batch tank 2. By supplying oxygen to the sludge in the batch tank 2, aerobic nitrifying bacteria and aerobic nitrites can be activated.

The batch tank 2 is preferably provided with a nitrogen sensor 26 for measuring the nitrogen concentration. Thereby, the processing time can be adjusted by the nitrogen concentration.

The apparatus of this embodiment is provided with a methanol storage tank 27 that supplies methanol as a BOD source. Methanol is supplied from the methanol storage tank 27 to the batch tank 2 via the methanol supply pipe 28. The methanol supply pipe 28 is provided with a methanol supply pump 29.

The batch tank 2 is filled with a carrier 20 for supporting nitrifying bacteria and nitrites for nitrification or for supporting denitrifying bacteria for denitrification.

As the carrier 20 used in the batch tank 2, a carrier having a plurality of cells is preferably used, and has a size of 2 to 50 [mm square], a true specific gravity of 0.03 to 0.05 [g/cm ³ ], and a cell. A carrier having a number of 25 to 55 [pieces/25 mm], an air permeability of 1.1 to 1.4 [dm ³ /sec], and a specific surface area of 4500 to 5500 [m ² /m ³ ] is preferably used.

The batch type carrier water treatment method of the present invention is carried out in the batch tank 2 at least once in the treatment cycle including the anaerobic second step 100, the aerobic nitrification step 101 and the anaerobic first step 102. It is preferable that the treatment cycles are sequentially repeated.

Each processing step will be described below.
<Anaerobic second step 100>
This step is a step of introducing waste water and a step of extracting treated water.
In the previous step (anaerobic first step 102 described later) of this step, aeration of the sludge in the batch tank 2 is stopped and mechanical agitation is performed to perform denitrification treatment, but the process proceeds to the anaerobic second step 100. At this time, mechanical stirring is also stopped.
When the mechanical agitation is stopped, the sludge in the batch tank 2 is settled and solid-liquid separated into the settled sludge and the supernatant water.

On the other hand, the wastewater containing ammonia nitrogen is introduced with the carrier 20 carrying at least aerobic bacteria capable of nitrifying or nitrite and denitrifying bacteria for denitrification being floated near the liquid surface.

By introducing this waste water, the treated water can be taken out of the batch tank. At this time, the retention time of the waste water (raw water) in the batch tank 2 is sufficiently secured, and the waste water is not discharged untreated from the treated water pipe 73 due to a short pass. If necessary, a shielding plate (not shown) may be provided to prevent a short path.

When introducing the waste water (raw water) into the batch tank 2, the raw water supply pump 5 is driven to introduce the waste water from the raw water tank 1 into the batch tank 2.

Examples of the bacterial cells carried on the carrier 20 include aerobic bacteria such as nitrite bacteria capable of nitrite nitrating ammonia nitrogen and nitric acid bacteria capable of nitrite nitrite in order to function the next nitrification step. To be Further, the denitrifying bacteria may be carried on the carrier 20 at this stage. Therefore, in the present invention, the carrier 20 may carry nitric acid bacteria, nitrite bacteria, and denitrifying bacteria. Nitrifying treatment activates nitric acid bacteria and nitrite bacteria, and denitrifying treatment activates denitrifying bacteria. Turn into.

In the present invention, in the aerobic nitrification step 101, while the wastewater introduced in the anaerobic second step 100 is contacted with aerobic bacteria floating in the batch tank 2 and aerobic bacteria carried on the carrier 20, the batch Air is supplied from the aeration device 22 provided in the tank 2 to perform nitrification reaction including nitrite reaction and nitrification reaction. That is, in the aerobic nitrification step 101, the aerobic bacteria carried on the carrier 20 is brought into contact with the ammonia nitrogen contained in the wastewater, and the nitrite reaction and the nitrification reaction are carried out by the air supplied from the air diffuser 23. Perform nitrification reaction including.

Specifically, the waste water introduced into the batch tank 2 and the bacterial cells floating in the batch tank 2 or the bacterial cells carried on the carrier 20 are brought into contact with each other by the air supplied from the air diffuser 23 to Carry out a nitrification reaction.

[Nitrification]
(Nitrite type) NH ₄ ⁺ +1.5O ₂ →NO ₂ ⁻ +H ₂ O+2H ⁺
(Nitric acid type) NH ₄ ⁺ +2O ₂ →NO ₃ ⁻ +H ₂ O+2H ⁺

When nitrite type nitrification is performed, it is possible to suppress the oxidation of ammoniacal nitrogen to nitric acid (NO ₃ ⁻ ) and to stop the oxidation to nitric acid (NO ₂ ⁻ ).

In the anaerobic first step 102 shown below, the following denitrification reaction is performed on the nitrified nitrite nitrogen and nitrate nitrogen by denitrifying bacteria.
[Denitrification]
(Nitrite type) 6NO ₂ ⁻ +3CH ₃ OH+3CO ₂ →3N ₂ +6HCO ₃ ⁻ +3H ₂
(Nitrate ^{_{type) 6NO 3 - + 5CH 3 OH}} + CO 2 → 3N 2 + 6HCO 3 - + 7H 2

A method of executing the anaerobic first step 102 and the anaerobic second step 100 will be described with reference to FIG.
In order to carry out the anaerobic first step 102, after the aeration in the batch tank 2 in the state of FIG. 3(A) is stopped, as shown in FIG. Stir the liquid in anaerobically. The stirring is performed by driving the stirrer 21. The processing time in this step is preferably 30 to 50 minutes.

When performing the denitrification treatment, it is preferable to drive the methanol supply pump 29 to supply methanol to the sludge. If the raw water contains a sufficient amount of organic matter, the supply of methanol can be appropriately omitted.

In this step, nitrogen gas is generated by the denitrification reaction by the denitrifying bacteria.
When the treatment time has passed a predetermined time and the denitrification reaction ends, the process of the anaerobic first step 102 ends.

In order to execute the above-described anaerobic second step 100, driving of the stirrer 21 is stopped and stirring is stopped. When the stirring is stopped and the liquid in the batch tank is allowed to stand still, as shown in FIG. 3(C), the sludge in the batch tank 2 is settled and solid-liquid separated into the settled sludge and the supernatant water.

In the anaerobic second step 100, the nitrogen gas generated by the denitrification reaction is taken into the carrier 20. Since the carrier 20 preferably has a plurality of cells, nitrogen gas is taken into the cells. Since the carrier 20 carries microorganisms, the plurality of cells have a structure in which nitrogen gas is easily taken in due to the presence of microorganisms.

In the present invention, the carrier 20 is preferable because it has a cell because a room in which nitrogen gas can be taken in well can be secured.

In the present invention, as shown in FIG. 3(C), the carrier 20 is floated near the liquid surface. That is, as the denitrification treatment by the carrier 20 progresses, the carrier 20 entrained with the nitrogen gas generated by the denitrification reaction floats above the tank.
Then, the carrier 20 containing the nitrogen gas forms the carrier floating layer 30 above the liquid surface in the batch tank 2.

Then, the carrier 20 allows the carrier floating layer 30 to be formed, and the denitrification treatment can be promoted by the carrier 20 even while the sludge is settled.
Then, the wastewater is introduced in the anaerobic second step 100, and accordingly, in the treated water outflow section 7, the supernatant water is drawn out from the batch tank 2 as treated water and transferred to the discharge tank 3. At this time, the floating suspended substance (ss) contained in the supernatant water can be filtered by the carrier 20 floating near the liquid surface in the upper part of the tank.

It is related to the physical properties of the carrier that the carrier 20 is floated near the liquid surface, and preferably the carrier floating layer 30 is formed. In the present invention, the carrier 20 has a size of 2 to 50 [mm square] and a true specific gravity. 0.03 to 0.05 [g/cm ³ ], the number of cells is 25 to 55 [cells/25 mm], the air permeability is 1.1 to 1.4 [dm ³ /sec], and the specific surface area is 4500 to 5500 [. it is preferably ^{m 2} / m ^3].

In the present invention, it is preferable that the batch tank 2 is used to execute each of the anaerobic second step 100, the aerobic nitrification step 101, and the anaerobic first step 102. In the present invention, it is preferable to repeat one cycle including these steps in sequence for a plurality of cycles.

In the illustrated example, it is preferable that the total time of one cycle is set to 240 minutes. It is possible to operate a plurality of cycles per day. Switching of each process (duration of each process) may be performed by timer control or may be controlled by nitrogen concentration by the above-mentioned nitrogen sensor.

By performing the operation in the above cycle, the treated water discharged from the batch tank 2 is stored in the discharge tank 3. When the treated water drawing pump 71 is used, the treated water in the discharge tank 3 preferably satisfies the river discharge standard. In addition, when introducing into the discharge tank 3 by overflow, without using the treated water extraction pump 71, it is preferable to satisfy the sewer discharge standard suitably. In addition, when introducing into the discharge tank 3 by overflow, it is also preferable to provide a finishing treatment tank (not shown) in the subsequent stage of the discharge tank 3. In this case, the treatment in the finishing treatment tank can satisfy the river discharge standard.

In the aerobic nitrification step 101, since a sufficient stirring action can be obtained by aeration, the stirrer 21 may be stopped appropriately.
The duration of the aerobic nitrification step is preferably set within the range of 1.5 to 3 times the duration of the anaerobic step.

The batch type carrier water treatment apparatus is exemplarily shown in FIG. 2, but the present invention is not limited to this, and aerobic nitrification is treated by using an apparatus different from the apparatus of the present invention, and the nitrification is performed. The treatment liquid may be introduced into the batch tank 2 of the present invention so that only the above-mentioned denitrification step is performed.

Examples of the present invention will be described below, but the present invention is not limited to the examples.

(Example 1)
<Processing performance confirmation test>
Using the batch type carrier water treatment device shown in FIG. 2, a test was conducted to confirm that nitrification denitrification was completed.
Anaerobic 2nd process (precipitation, wastewater inflow, treated water outflow) ⇒ Aerobic nitrification process (ammonia to nitric acid/nitrite oxidation) ⇒ Anaerobic 1st process (denitrification) as 1 cycle, 2 cycle test went. This is to ensure that the processing status of each process is understood.

The test conditions were as shown in Table 1 below. As the carrier used in the test, a carrier having the properties shown in Table 2 below was used.

FIG. 4 is a graph showing changes over time in batch operation and changes in the concentrations of NH ₄ —N and NO _x —N under the above test conditions.

<Evaluation>
As can be seen from FIG. 4, NH ₄ —N decreases in the aerobic nitrification step (marked as “aerobic” in the figure) and NO _x − in the anaerobic first step (marked as “anaerobic 1” in the figure). N decreased and denitrification was progressing.
In the anaerobic second step (labeled as "anaerobic 2" in the figure), raw water-derived NH ₄ -N derived from raw water is increasing. The amount of NO _x -N continued to decrease, and denitrification proceeded in this step as well.

(Example 2)
<Carrier levitation characteristics confirmation test>
The same carrier was used except that the size of the carrier in Example 1 was changed to 5 [mm square], and the confirmation test of the carrier floating characteristics was performed after nitrification (NH ₄ -N→NO _X -N). Tested with liquid and carrier.

The test conditions were as shown in Table 3 below.

The methanol addition rate was 4.2 (Condition 1), 2.8 (Condition 2), 2.1 (Condition 3), 1.4 (Condition 4), 0 (Condition 5) [kg-CH ₃ OH/kg- N] to change the floatation rate of the carrier. The test results are shown in Table 4. Further, FIG. 5 shows a graph showing the relationship between the elapsed time and the floating rate of the carrier due to the difference in the methanol addition rate.

(Evaluation)
As can be seen from FIG. 5, as the methanol addition rate increases, the floating rate of the carrier also rises. A diagram showing the state of the carrier in the tank is shown in FIG. In FIG. 6, it was visually confirmed that the floatation rate of the carrier increased with the increase of the methanol addition rate.

Further, as can be seen from Table 4 and FIG. 5, FIG. 7 is a graph showing the relationship between the NO _x —N removal amount by the methanol addition rate and the floating rate of the carrier under the condition 1. As can be seen from FIG. 7, it was found that there is a proportional relationship in which the floating rate of the carrier increases with the amount of NO _x —N removed.

100: Anaerobic second step 101: Aerobic nitrification step 102: Anaerobic first step 1: Raw water tank 2: Batch tank 21: Stirrer 210: Stirring blade 211: Motor 22: Aeration device 23: Air diffuser 24: Blower 25: Membrane member 26: Nitrogen sensor 27: Methanol storage tank 28: Methanol supply pipe 29: Methanol supply pump 3: Discharge tank 4: Raw water supply pipe 5: Raw water supply pump 6: Raw water inflow part 7: Treated water outflow part 71: Treated water Drawout pump 72: Screen 73: Treated water pipe 20: Carrier 30: Carrier floating layer

Claims (4)

A batch type carrier water treatment method in which a treatment cycle of an anaerobic second step, an aerobic nitrification step, and an anaerobic first step is sequentially repeated in one batch tank,
The anaerobic second step is a step of introducing waste water containing ammoniacal nitrogen and a step of taking out denitrified treated water, and from the anaerobic first step in which aeration of sludge in the batch tank is stopped. When proceeding to the anaerobic second step, mechanical stirring is also stopped , the sludge in the batch tank is allowed to settle and solid-liquid separation is performed into the settled sludge and the treated water, and the nitrogen produced in the anaerobic first step is also used. With the carrier entrained with gas floating in the vicinity of the liquid surface of the batch tank , the treated water is taken out of the batch tank to advance denitrification treatment,
The aerobic nitrification step, the wastewater introduced in the anaerobic second step, while contacting the aerobic bacteria floating in the batch tank, and the aerobic bacteria carried on the carrier, the batch tank Air is supplied from the aeration device provided inside to perform nitrification reaction including nitrite reaction and nitrification reaction,
The anaerobic first step is characterized in that the supply of air in the aerobic nitrification step is stopped, the liquid in the batch tank is stirred in an anaerobic state, and nitrogen gas is generated by a denitrification reaction by denitrifying bacteria. Batch type carrier water treatment method. Claim 1 batch carriers water treatment method, wherein the carrier has emerged in the vicinity of the liquid level, to filter the suspended suspended solids (ss) contained in the treated water. The batch carrier water treatment method according to claim 1 or 2 , wherein the carrier is a carrier having a plurality of cells. The batch type carrier according to claim 1, 2 or 3 , wherein the carrier has a size of 2 to 50 [mm square] and a true specific gravity of 0.03 to 0.05 [g/cm ³ ]. Water treatment method.