JPH0729114B2 - Method and apparatus for biological treatment of organic wastewater - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel treatment device for highly purifying organic wastewater such as sewage, various industrial wastewater, septic tank sludge, and human waste.

[Conventional technology]

A conventional aerobic biological filter device is a tank as shown in FIG.
Below the water surface of 21, a packed bed of various granular solids such as sand, anthracite, granular activated carbon and chamotte (called a biological filter bed 22) was provided, and an air diffuser 23 was arranged in the lower part of the biological filter bed 22. It is a thing. A single type of filter medium is used for the filling layer, and a plurality of types of filter medium are not used.

This aerobic filter media unit has a settling tank 24 and a treated water storage tank 2
8. A washing drainage storage tank 30 is attached.

In the organic sewage (raw water), after SS which easily settles in the settling tank 24 is settled and separated, the settling overflow water flows into the upper part of the treatment tank 21 from the pipe 25 and flows downward in the biological filter bed 22. In contact with microorganisms on the surface of the granular filter medium and air bubbles supplied from the blower 26, BOD is biologically removed and fine SS is removed by filtration, resulting in clarified treated water and treated water through the outflow pipe 27. It flows into the storage tank 28.

As such operation continues, the trapped SS in the biological filter bed 22
Due to the increase in the amount, the filtration resistance increases and the quality of the treated water also begins to deteriorate.
Is supplied to the lower part of the filter and the biological filter bed 22 is backwashed.

The washing drainage of the biological filter bed 22 overflows from the upper part of the tank 21 and flows into the washing drainage tank 30, and then is supplied to the sedimentation basin 24 by the pump 31 to separate the SS content by sedimentation and to separate the raw water and the washing drainage flow rate. The total amount is again fed to the submerged filter bed 22.

[Problems to be Solved by the Invention]

However, the conventional device shown in FIG. 2 has the following major drawbacks, and it is the actual situation that a further excellent device and system are desired.

When the raw water SS is large, as shown in Fig. 2, a sedimentation basin must be installed in front of the aerobic biological filter bed to remove the SS and reduce the concentration to an acceptable level for the biological filter bed.

Otherwise, the filter bed of the aerobic biological filter bed will be rapidly clogged (blocked), and it will be impossible to continue the operation of the biological filter bed. The frequency of cleaning the filter bed also increases dramatically. Moreover, since the sedimentation separation speed of the sedimentation tank can be set to only about 30 m / day,
The installation space of the sedimentation basin and the construction cost are large.

SS carryover from the settling tank inevitably occurs when the flow rate fluctuates and flows into the aerobic biological filter bed,
Speed up the clogging of the filter bed.

Scum is generated in the sedimentation tank, and bad odors such as hydrogen sulfide are also emitted from the surface of the sedimentation tank, resulting in poor appearance and working environment.

Even if a sedimentation tank is installed before the aerobic biological filter bed, the SS removal rate in the sedimentation tank is not high, so clogging of the aerobic biological filter bed progresses quickly and washing of the filter bed once a day is required. It must be made. Therefore, the production efficiency of the treated water deteriorates.

The object of the present invention is to completely solve the above-mentioned drawbacks of conventional devices,
An object of the present invention is to provide a biological treatment method and apparatus for organic sewage, which can purify organic sewage such as sewage extremely effectively and rationally.

[Means for Solving the Problems]

The present invention is described in the following (1) and (2),
This can solve the above problem.

(1) After circulating organic wastewater together with oxygen-containing bubbles in an upward flow from the lower part of the first aerobic immersion filter bed, the outflow water from the first immersion filter bed is subjected to a second aerobic immersion filter. A method for biological treatment of organic wastewater, characterized in that it is circulated in an upward flow together with oxygen-containing bubbles from the lower part of the bed, and the outflow water from the second filter bed is filtered by a filter device. The particle size of the granular filter medium of the aerobic immersion filter bed of _{No. 1} is d ₁ , and the specific gravity of the filter medium is s
g ₁ , the particle size of the granular filter medium of the second aerobic immersion filter bed is d ₂ , the specific gravity of the filter medium is sg ₂ , the particle size of the granular filter medium when the filter is a filter bed is d ₃ , the specific gravity of the filter medium Let sg ₃ be d ₁ ＞ d ₂ ≧ d ₃ and sg ₁
A biological treatment method for organic sewage, which satisfies the relationship of <sg ₂ ≤ sg ₃ .

(2) A first aerobic immersion filter bed for treating by treating organic sewage together with oxygen-containing bubbles in an upward flow, and effluent water from the first filter bed together with oxygen-containing bubbles in an upward flow. A biological treatment apparatus for organic wastewater, comprising: a second aerobic immersion filter bed to be treated by the above-mentioned treatment; and a filter device for filtering outflow water from the second filter bed. The particle size of the granular filter material in the aerobic immersion filter bed is d ₁ , and the specific gravity of the filter material is
sg ₁ , the particle size of the granular filter medium of the second aerobic immersion filter bed is d ₂ , the specific gravity of the filter medium is sg ₂ , the particle size of the granular filter medium when the filter is a filter bed is d ₃ , the specific gravity of the filter medium Let sg ₃ be d ₁ ＞ d ₂ ≧ d ₃ and s
A biological treatment apparatus for organic wastewater, which satisfies the relationship of g ₁ <sg ₂ ≤ sg ₃ .

The present invention has two towers of aerobic immersion filter beds, namely, a first aerobic immersion filter bed (hereinafter referred to as the first filter bed) and a second aerobic immersion filter bed (hereinafter referred to as the second filter bed). And a filtration device (hereinafter,
Particularly, when the filter device is a filter bed, it is referred to as a third filter bed. ) Are combined in series.

Then, the first filter bed and the second filter bed are used as an upflow treatment device, and the treated water obtained by treating the organic sewage introduced into the first filter bed, that is, the outflow water is introduced into the lower part of the second filter bed. The treatment is carried out in countercurrent, and the treated water (effluent) is highly treated by an optional third filtration device.

That is, in the present invention, most of the BOD component contained in the organic wastewater by microorganisms is subjected to biooxidation treatment by the granular filter medium having the biofilm in the first filter bed and the second filter bed, and non-living matter such as SS. Most of the oxidizing components are removed by physical filtration through a granular filter medium, leaving traces of traces remaining in the treated water from the second filter bed.
Highly treated water is obtained by highly physically filtering SS and the like with a third filtration device.

Hereinafter, a case where the third filter bed is used as the filter device will be described.

In the present invention, the packing density of the granular filter material of the first filter bed is smaller than that of the granular filter material of the second filter bed, and the packing density of the third filter bed is equal to or larger than that of the second filter bed. , First
The particle size of the granular filter medium (hereinafter referred to as the first filter medium) of the filter bed is
d ₁ , the particle size of the granular filter medium of the second filter bed (hereinafter referred to as the second filter medium) is d ₂ , and the particle size of the granular filter medium of the third filter bed (hereinafter referred to as the third filter medium) is d _3. If d ₁ > d ₂ ≧ d ₃ , and the specific gravity of the first filter medium is sg ₁ , the specific gravity of the second filter medium is sg ₂ and the specific gravity of the third filter medium is sg ₃ , then sg ₁ <sg ₂ ≦ sg _It can be set by setting it to ₃ .

That is, since the space between the filter media of the first filter bed can be made larger than that of the second filter bed and the third filter bed, SS of wastewater can be sufficiently captured and retained as compared with the second filter bed and the third filter bed. . In addition, the second filter bed has a smaller space between the filter media and a higher packing density than the first filter bed, so SS and the like not removed by the first filter bed are filtered and removed, and residual BOD and the like are removed. be able to. In addition, the third filter bed has the same or smaller space between the filter media as compared to the second filter bed, and the packing density can be made higher, so that minute SS etc. not removed by the second filter bed can be highly reliably filtered. Can be removed. Also, SS capture is the first
Since the functional separation is performed by the three columns of the 3rd filter bed and the absolute trapping amount increases, the cleaning frequency can be reduced and BOD etc.
Since it is removed in an upward flow in two stages of the filter bed and the second filter bed, the waste water component does not stay on the surface of the first filter bed, the second filter bed, and then the third filter bed, so that the waste water component is removed from the system. It is possible to prevent the offensive odor from being released.

In this case, the treatment method of the second filter bed in the third filter bed, that is, the treatment method of the outflow water is not particularly limited as long as it is a filtration treatment.
Upflow or downflow, biological treatment or abiotic treatment may be used.

Further, as the third filtration device, a filter cloth, an ultrafiltration membrane or the like may be used alone or in combination with the filter bed.

Specific removal rates of BOD, SS, etc. of organic wastewater in the first filter bed, the second filter bed, and the third filter device in the present invention are 50 to 70% in the first filter bed in terms of BOD, 80-90% in the second filter bed, 90-99% in the third filter device, regarding SS,
The first filter bed may be set to 60 to 70%, the second filter bed to 80 to 95%, and the third filter device to 95 to 99%.

The average particle size of the first filter medium of the present invention is in the range of 4 to 20 mm, preferably 5 to 10 mm, and the average particle size of the second filter medium is 2 mm.
-4 mm, preferably 2.5-3.5 mm, and the third filter medium has an average particle size of 1-4 mm, preferably 2-3 mm. The specific gravity of the first filter medium is 2.6 or less, the specific gravity of the second filter medium is 1.5 to 2.6, and the specific gravity of the third filter medium is 1.5 to 2.6.
A range of 2.6 is preferred.

The material for the first to third filter media is not particularly limited as long as it is capable of forming a biofilm and has appropriate strength and corrosion resistance, and known inorganic materials such as ceramics, coal and rocks. And the like, and organic materials such as various resins such as plastics can be used.

Preferable examples of the first filter medium include a porous body having a large specific surface area, and chamotte, lightweight aggregate, that is, neolite (trade name; fired anti-fire stone) and the like,
Preferable examples of the second filter medium and the third filter medium include sand, granular activated carbon and anthracite.

The biofilm-forming microorganism used in the present invention is not particularly limited, but examples include BOD-oxidizing bacteria, nitrifying bacteria,
Examples thereof include denitrifying bacteria and yeast.

The apparatus of the present invention can use known means for maintaining the first filter bed and the second filter bed, or optionally the third filter bed under aerobic conditions. For example, an oxygen-containing gas is provided under each filter bed. It is possible to provide an air diffuser for supplying Alternatively, a means such as dissolving oxygen in the water to be treated before introducing the water to be treated into the apparatus can be used.

In addition, in the present invention, any treatment space having other functions can be provided in addition to the three filter beds of the first to third filter beds. For example, a space for precipitating and retaining the settling SS of wastewater can be provided under the first filter bed integrally with the first filter bed.
In this case, the coagulant may be added before introducing the waste water into the space.

In the present invention, the organic sewage is introduced from the inlet at the lower part of the first filter bed, but the introduction means is not particularly limited, and even if it is directly introduced, it is first stored in the sewage storage tank before being introduced. You may.

The method for washing the three filter beds in the present invention comprises:
Any method can be used without particular limitation.

For example, air may be supplied from the air diffuser to each filter bed, and treated water or raw water may be passed to send the wash water from the upper part of each filter bed to the waste water storage tank.

The volume ratio of the first filter bed, the second filter bed and the third filter bed in the present invention depends on the water quality of the treated raw water, but SS is 100 to 300 mg / l, and BO
When D is in the range of 100 to 200 mg / l, the first filter bed: the second filter bed: the third filter bed = 1: 0.5 to 1: 0.5 to 1, more preferably 1: 1: 0.5
It is recommended to set it in the range.

In the case of the above water quality, BOD is 10 mg / l or less and SS is 10 mg / l.
The filtration speed for obtaining treated water of 1 or less can be set to 200 to 300 m / day, and the first filtration bed or the second filtration bed of the present invention can be used.
A filtration rate of 10 to 15 times can be achieved as compared with a conventional upflow treatment apparatus comprising a filter bed corresponding to only one of the filter beds.

In this case, the continuous filtration time required for washing in the device of the present invention is about 48 hours for the first filter bed and about 60 hours for the second filter bed and the third filter bed, but in the conventional device, 12
Time, and the present invention can achieve continuous filtration time of about 4 to 5 times that of the conventional device.

A specific embodiment of the present invention will be described in detail with reference to FIG.

Each part of FIG. 1 will be described.

1 is a 1st filter bed, 2 is a 2nd filter bed, These are aerobic biological filter beds which are the fixed bed immersed in water. Three
Is a third filter bed that employs a filter bed as a filter device. Reference numeral 4 is an inflow portion of the organic wastewater, and 5 is a sedimentation portion of the settling SS, and a conventional sedimentation tank can be removed before the inflow portion. Reference numeral 6 is a sludge pipe, and 7 is an air supply pipe.

Reference numeral 8 is a primary treated water outlet, 9 is an air supply pipe, and 10 is a secondary treated water outlet. Reference numeral 11 is an air supply pipe, which is operated when the third filter bed is used as an aerobic biological filter bed, but is stopped when only the normal filtration treatment is performed. Further, 12 is a third treated water outlet, and 13 is a treated water storage tank, which is used for washing the first filter bed 1, the second filter bed 2, and the third filter bed 3.

Reference numeral 15 is a washing water supply pump, and the washing water 14 is supplied to the lower portion of each filter bed when washing the filter beds 1 to 3. Also 16, 1
7 and 18 are drainage pipes for washing wastewater.

Next, the principle of operation of the present invention will be described.

Organic wastewater such as sewage flows from the inflow section 4 through the pipe line to the first filter bed 1
Flows into the lower part of the sewage, and the sedimentary SS in the wastewater is separated by sedimentation, and then enters the first filter bed 1 in an upward flow. At the same time, air bubbles (which may be oxygen-containing gas bubbles) form an ascending flow and enter the first filter bed 1.

A biofilm adheres to the surface of the granular filter material of the first filter bed 1, and BOD in wastewater is biologically decomposed and removed. At the same time, fine SS and colloid in the wastewater are removed by filtration. In the present invention, the first filter medium is made to be quite large (about 4 to 20 mm is suitable), and only a part of SS and BOD in the wastewater is intentionally removed, and the remaining SS and BOD are the subsequent second filter bed. It is important to supply upflow to.

Next, the treated water treated in the first filter bed (hereinafter referred to as the primary treated water) flows from the primary treated water outflow section 8 to the second filter bed 2 through a pipe line.
Flows into the upper stream together with air bubbles from the air supply pipe 9,
Most of SS and BOD (about 90%) remaining in the secondary treated water is removed by biological action and filtration action.

The important points in the second filter bed 2 are to select a second filter medium having a particle size smaller than the average particle size of the first filter medium and to pass water in an upward flow instead of a downward flow.

According to the experimental study by the present inventor, the average particle size of the second filter medium is preferably 2 to 4 mm.

As a result, it becomes possible to effectively remove BOD and SS remaining in the primary treated water and to significantly increase the filter bed trapping capacity of SS. If the first filter bed and the second filter bed are operated in a downward flow and the particle size of the first filter medium is smaller than the particle size of the second filter medium, the continuous filtration time becomes significantly shorter than that of the present invention ( It was confirmed as a result of the experiment.

The treated water flowing out from the second filter bed (hereinafter referred to as the secondary treated water) is reduced to 20 to 30 mg / l for both BOD and SS.

The secondary treated water is supplied from the outflow section 10 to the third filter bed 3 in an upward flow (in the case of the drawing) or a downward flow, and is subjected to a finishing treatment (polishing). The particle size of the third filter medium is equal to or less than the particle size of the second filter medium.

When performing filtration treatment while supplying air from the lower part of the third filter bed using the air supply pipe, it is important to set the air supply amount to be smaller than the air supply amount to the second filter bed. Therefore, the amount of leakage of SS from the third filter bed can be extremely reduced.

The filtration treatment of the secondary treated water by the granular filter material of the third filtration bed
Instead of the filter bed, the secondary treated water may be filtered with a filter cloth or a membrane, or the treatment with a granular filter material and the treatment with a filter cloth or a membrane may be used in combination.

Then, the tertiary treated water obtained by treating the secondary treated water with the third filter bed becomes SS and BOD of several mg / l and is not discharged to the public water area or reused as water.

In the present invention, if the filling tank thickness of the first filter bed to the third filter bed is too small, the effect cannot be sufficiently exerted, but there is no particular limitation in the direction of increasing the layer thickness, and the raw water type and the treatment speed are not limited. Accordingly, it may be appropriately determined experimentally.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

Example A continuous treatment experiment was conducted on the group groundwater of BOD 150 mg / l and SS 170 mg / l by the method of the present invention shown in FIG. Raw water treatment amount is 5m ³ /
Is the day.

The experimental conditions are shown in Table-1.

As a result, SS and BOD of the tertiary treated water flowing out from the 3rd filter bed
The average value of SS = 1.8 mg / l, BOD = 5.5 mg / l, which is extremely good, and the continuous filtration time is 60, respectively for the first filter bed, the second filter bed and the third filter bed. It was possible to continue filtration for a very long time of 60 and 60 hours.

Comparative Example 1 In Table 1, the flow direction was all changed to downward flow, and the other conditions were the same. When the experiment was conducted under the same conditions, the treated water from the third filter bed was used.
The SS and BOD were the same as those in the above-mentioned examples, but the filtration continuable time was remarkably shortened, and the first filter bed, the second filter bed,
The third filter bed was reduced to 12 hr, 10 hr, and 20 hr, respectively, which was not practical.

Comparative Example 2 The sectional area of each filter bed of the present invention shown in Table 1 is 5 m ^{3 of} treated raw water.
/ Day, both the first filter bed and the second filter bed are 0.025m ² ,
The first filter bed 0.01 m ^2, a total of 0.06 m ^2. Therefore, the cross-sectional area of the first filter bed was 0.06 m ² , the water flow rate was 83.3 m / day, and the second filter bed and the third filter bed were omitted for operation.

Regarding the air supply amount, a total amount of 4.5 m ³ / day shown in Table 1 was supplied to the first filter bed.

As a result, SS of treated water from the first filter bed was 38 mg / l and BOD was 3
It was 5 mg / l, which was significantly worse than that of the examples of the present invention. Also,
The filtration duration was 36 hr.

That is, in Comparative Example 2, although the apparatus installation area was the same as that of the present invention, the treatment result was remarkably inferior.

〔The invention's effect〕

As described above, according to the present invention, the following important effects can be obtained, and all the drawbacks of the conventional aerobic biological filter can be solved.

For raw water with a high concentration of SS, it is not necessary to provide a separate settling tank in front of the aerobic filter bed, and SS carry-over, scum generation, and malodor emission from the settling tank are completely eliminated. The installation area can be greatly reduced to 1/5 to 1/8 that of conventional equipment.

Since clear treated water flows out from the upper part of the aerobic biological filter bed, it is aesthetically excellent, and the malodorous components in the raw water are also biologically deodorized so that no odor is emitted.

Since the filtration continuation time can be set to be 2 to 3 times longer than that of the conventional apparatus, the frequency of cleaning the filter medium is low and the amount of cleaning waste water generated is reduced. Maintenance is also easy. The production efficiency of treated water is high.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of a concrete embodiment of the present invention, and FIG. 2 is a flowchart showing a conventional method. Explanation of code 1: 1st filter bed, 2: 2nd filter bed 3: 3rd filter bed, 4: Inflow part of organic wastewater 5: Sedimentation part, 6: Sludge pipe 7: Air supply pipe, 8: 1 Secondary treated water outlet 9: Air supply pipe, 10: Secondary treated water outlet 11: Air supply pipe, 12: Tertiary treated water outlet 13: Treated water storage tank, 14: Wash water 15: Wash water supply pump 16, 17, 18: Discharge pipe for cleaning wastewater

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C02F 9/00 502 D 7446-4D 503 C 7446-4D 504 A 7446-4D D 7446-4D

Claims (2)

[Claims] 1. An organic sewage is allowed to flow together with oxygen-containing bubbles in an upward flow from the lower part of a first aerobic submerged filter bed, and then the water discharged from the first submerged filter bed is subjected to a second aerobic filter. A biological treatment method for organic sewage, characterized in that it is circulated in an upward flow together with oxygen-containing bubbles from the lower part of the immersion filter bed, and the outflow water from the second filter bed is filtered by a filter device. , First
, The particle size of the granular filter medium of the aerobic immersion filter bed is d ₁ , the specific gravity of the filter medium is sg ₁ , the particle size of the granular filter medium of the second aerobic immersion filter bed is d ₂ ,
If the specific gravity of the filter medium is sg ₂ , the particle size of the granular filter medium when the filter is a filter bed is d ₃ , and the specific gravity of the filter medium is sg ₃ , then d ₁ > d ₂ ≧ d ₃ and sg ₁ <sg ₂ ≦ sg A biological treatment method for organic sewage characterized by satisfying the relationship of ₃ . 2. A first aerobic submerged filter bed for treating organic sewage together with oxygen-containing bubbles in an upward flow for treatment.
A second aerobic immersion filter bed for treating the effluent water from the filter bed by circulating it in an upward flow together with oxygen-containing bubbles, and a filtration device for filtering the effluent water from the second filter bed. A biological treatment apparatus for organic wastewater, characterized by:
The particle size of the granular filter medium of the first aerobic immersion filter bed is d ₁ , the specific gravity of the filter medium is sg ₁ , and the particle size of the granular filter medium of the second aerobic immersion filter bed is d 1.
_{2. If} the specific gravity of the filter medium is sg ₂ , the particle size of the granular filter medium when the filter is a filter bed is d ₃ , and the specific gravity of the filter medium is sg ₃ , then d ₁ > d ₂ ≧ d ₃
And a biological treatment apparatus for organic wastewater, which satisfies the relationship of sg ₁ <sg ₂ ≤ sg ₃ .