JPS6312398A - Biological treatment - Google Patents

Abstract

PURPOSE:To stabilize a biological treatment by transferring granular media together with part of treated water from the lower part to the upper part of a granular medium packed bed and stripping the excess sludge stuck to the granular media during the transfer and discharging the separated excess sludge to the outside of the system. CONSTITUTION:The packed bed 4 of the granular media 3 to be stuck with microorganisms is formed in a tank 2 and the liquid 1 to be treated is passed in downward countercurrent. The aerobic biological treatment and filtration treatment are simultaneously executed in the packed bed 4. The granular media 3 are transferred together with part of the treated water from the lower part to the upper part of the packed bed 4 and the rate of the transfer is changed so as to meet the amt. of the microorganism sticking to the granular media 3. The excess sludge sticking to the granular media during the transfer is stripped therefrom. After the granular media and the excess sludge are separated, the separated granular media are returned to the upper part of the packed bed 4. The separated excess sludge 12 is discharged to the outside of the system. As a result, the clogging inevitably arising heretofore is prevented and the biological treatment is stably and effectively executed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to relatively polluted river water, lake water, sewage, human waste, industrial wastewater, etc., in which organic matter or nitrogen is added from a low concentration to a high concentration. This invention relates to biological treatment technology that uses microorganisms to purify contained liquids.

[Conventional technology]

Many biological treatment techniques have existed since ancient times and are still widely used today. Among these, those using microbial adhesion media have made numerous technological advances in recent years.
In particular, a method using granular materials as a medium is extremely useful as it allows for high-load operation.

[Problem that the invention seeks to solve]

However, when granular materials are used as a medium for microbial adhesion, they tend to become clogged due to their low porosity (and cleaning is essential).

For example, in the case of the gravel-to-gravel contact method, when cleaning, a large amount of excess sludge gets mixed into the treated water, and when cleaning is too aggressive, the amount of microorganisms decreases significantly, causing deterioration of the treatment.

Of course, if the cleaning is insufficient, it will quickly become clogged, making it difficult to adjust the degree of cleaning.

Furthermore, as another method to prevent clogging, a method of backwashing using treated water or air has emerged, but since a large amount of treated water or air is used at once, the backwashing equipment becomes enormous. Many problems remained, including the need to separately consider the treatment of cleaning wastewater.

The present invention provides a drastic solution to clogging, which is a fundamental problem that inevitably occurs and cannot be avoided when granular materials are used as a microbial adhesion medium, and also stabilizes biological treatment. The aim is to provide a method that can be used effectively.

[Means for solving problems]

In the present invention, as a means for solving the above problems,
A biological treatment method in which a packed bed of granular media for adhesion of microorganisms is formed in a tank, and the liquid to be treated is passed in a downward flow to simultaneously perform aerobic biological treatment and T-filtration treatment in the packed bed. , the granular medium is continuously or intermittently transferred from below the packed bed upward together with a portion of the treated water, and the amount of the transferred medium is varied in accordance with the amount of microorganisms attached to the granular medium, and After peeling off the excess sludge that adhered to the granular media during transfer and further separating the granular media from the excess sludge, the separated granular media is returned to the upper part of the packed bed, and the separated excess sludge is removed from the system. The present invention provides a biological treatment method characterized by discharging to

[For production]

The present invention will be described in detail below with reference to FIG. 1 showing one embodiment B.

The liquid to be treated 1 flows into the treatment tank 2 from the upper part and flows downward in the filled layer 4 formed of the granular medium 3 .

As the granular medium 3, any suitable particle size may be used as long as it is granular and can be transported in large quantities underwater, such as sand, gravel, hunthrasite, activated carbon, lightweight aggregate, plastic furnace material, and artificial stone. Judging from the state of movement of
Among them, those with a relatively small particle size of about 1 to 4 grains are preferable.

Further, in the packed bed 4, an oxygen-containing gas such as air 5 is introduced by an aeration device 6 disposed below to maintain an aerobic state, and the liquid to be treated 1 is transferred to the packed bed 40 and granules 3. Due to the biofilm attached to the surface of the water, aerobic biological treatment and filtration are performed at the same time, and the water is gradually purified as it moves downward through the packed bed 4, and flows out as treated water 8 from the treated water outflow pipe 7.

Incidentally, during the purification process, an excessive biofilm is generated and adhered to the granular medium 3 due to suspended matter in the liquid to be treated 1 and grown microorganisms. Continue the above process in this state.
a'Irrt, the voids present in the filling l114 will be occupied by excess biofilm, and -FG
It becomes what is called a "clogged condition" and water cannot flow through it.

Therefore, the granular medium 3' with excessive biofilm adhering to it is guided from below the filling N4 to the transfer pipe 9 together with a part of the treated water 8, and is transferred by the medium transfer device 10 to the separation device located above the packed bed 4. Transferred to 11. As the medium transfer device 10, a non-obstructive pump or an air lift is desirable, and an ejector or the like may also be used.

The granular medium 3' is transferred continuously in small amounts or intermittently, and the amount of granular medium 3' transferred is changed depending on the amount of biofilm attached to the granular medium 3'. That is, the amount of biofilm attached to the granular media 3 varies depending on the water quality and amount of the liquid to be treated l, and when the amount of biofilm is large, the amount of granular media 3' transferred is increased, and the biological IP! ! When t is small, the driving force of the medium transfer device 10 is increased or decreased (when an air lift is used as the medium transfer device 10, the air supply amount is changed) so as to reduce the transfer amount of the granular medium 3', By adjusting the opening degree of the valve provided in the transfer pipe 9, etc., the transfer amount of the granular medium 3 is changed, and an appropriate biofilm is always maintained to stabilize the treatment.

Furthermore, the transport of the granular medium 3' will be described.

fit When the granular medium 3' is continuously transferred When the water quality and water amount of the liquid to be treated 1 are relatively unchanged, the medium transfer device IO is continuously operated to continuously transfer the granular medium 3'. However, when the amount of biofilm generated is small, continuous transfer may cause the biofilm to be excessively peeled off and the processing capacity may be reduced, so the amount of granular medium 3' transferred is reduced. In this way, the amount of granular media 3' transferred is changed depending on the degree of biofilm formation, but in the case of continuous transfer of granular media 3', as a result of various experiments, the amount of granular media 3' transferred per day is A suitable range is 1.5 to 3 times the amount of the entire granular medium 3 forming the layer 4, which allows proper maintenance of the biofilm and enables stable treatment.

(2) When the granular medium 3' is transferred intermittently, the liquid to be treated 1
If the water quality or amount of water varies greatly, it becomes necessary to change the amount of granular medium 3' transferred more than in the case of continuous transfer. In such a case, the medium transfer device 10 may be operated intermittently by using a timer or by detecting an increase in water flow resistance. Particularly in this case, the timer can of course be set freely, and the medium transfer device 10 can be operated at its highest efficiency point, resulting in energy savings.

Furthermore, it is desirable that the amount of granular media 3' to be transported is in the range of 1/4 fit to 8 times the amount of the total granular media 3 per day.6 Originally, the amount of granular media 3' to be transported depends on the degree of contamination,
In other words, it is a property that should be changed depending on the properties of the liquid to be processed 1 and processing conditions, but there are upper and lower limits for the following reason. That is, in the case of comparatively quiet and smooth test water with a BoD of about 10II 1g/e, the water flow resistance of the packed bed 4 increases by several degrees per hour, and judging from the viewpoint of SS capture in the packed bed 4, The amount of granular media 3' to be transported is approximately 1/10i of the total granular media 3 per day. However, when experiments were continued for a long period of time, the biofilm attached to the granular media 3 was highly adhesive, so the granular media often bonded together and formed large clumps, making transportation difficult. As a result of repeated experiments under various conditions, the amount of granular media 3' transferred per day was 1/41 ft of the total granular media 3.
It has been found that the above-mentioned problem does not occur.

On the other hand, in order to prevent the granular media from bonding with each other, the amount of granular media 3' transferred was extremely large (as a result, it became difficult for organisms to adhere to the surface of the granular media 3, resulting in a decrease in processing capacity). Therefore, we determined the upper limit of the transfer amount through trial and error, and found that if it was within 8 times the total amount of granular media per day, no reduction in the amount of biofouling that would cause deterioration of treatment would be observed. .

Furthermore, an example of a performance curve when an air lift is used as the medium transfer device IO is shown in FIG.
1 x Height 2600 x 2600cm, taking as an example an airlift pipe with an immersion ratio of 1.0, when the air flow rate is very small, the granular media 3'
cannot be transferred at all, but as the air supply amount is gradually increased, the transfer it (lift amount) of the granular medium 3' also begins to increase.

However, even if the amount of air supplied is further increased, the scene remains the same.

In other words, this curve is convex upward. Therefore, the highest energy efficiency is achieved by operating the air lift at a point of contact in a straight line passing through the origin.

In addition, in the transfer pipe 9 or the medium transfer device 10, the granular medium 3' is subjected to strong agitation, so the granular medium 3'
Excessive biofilm adhering to ′ will be peeled off. In particular, since the granular medium 3' is slurried with a portion of the treated water 8, the cleaning effect is higher than when raw water (liquid to be treated 1) is used.

In the separation M device 11, washed granular media 3 and excess biofilm (excess sludge) 12 are separated, and the granular media 3 is filled with W
Returns to the upper part of J4, and excess sludge 12 is discharged outside the tank.
The separation device 11 may be any device as long as it effectively separates the granular media 3 and excess sludge 12, such as a combination of a hydrocyclone or a panful plate, but it may be used depending on the sedimentation rate of the granular media 3 and excess sludge 12. A method that utilizes the difference is preferable.

The separation device 11 may be installed outside the tank or inside the tank, but it is effective to install it below the water surface in the tank as shown in FIG. 1.

When the separator 11 is installed below the water surface in the tank, the sinking speed of the granular media 3 is generally as fast as about 5 to 20 m/win, so the granular media 3 is separated from the excess sludge 12 by gravity and is directly transferred to the packed bed. 4, easily return to 212 minutes
It is possible to omit pipes that are likely to cause blockages from the tank to the inside of the tank, and if the separation device 11 is combined with a baffle plate or the like to guide the water inside the tank, excess sludge 12 can be removed from the tank. This facilitates the discharge of

In the first illustrated example, the transfer piping 9 is provided outside the tank, but it can also be provided inside the tank.

〔Example〕

Next, we will show a comparative example between the present invention and the conventional method.
The method described in No. 1889 was used.

In both of these comparative examples, sewage-subprocessed water is used as raw water, the amount of treated water is 100 r/day, and the BODa load is 3-w/rd day. shows a comparison of the processing results.

(The following is a margin) Comparison of "kL" *Anthracite with a specific gravity of 1.5 and a particle size of 3 to 51 was used as a filler.

As is clear from these Tables 1 and 2, according to the present invention, incidental equipment such as a treatment water tank, a wastewater storage tank, a backwash pump, a backwash blower, etc. Although the treated water quality was almost the same for each method, there was a large difference in the amount of excess sludge discharged. Compared to the conventional method, the amount of excess sludge discharged was significantly reduced by approximately 60% in continuous transfer in which the air flow rate of the filler transfer blower was switched to two stages, and by approximately 40% in intermittent transfer using a timer.

In addition, when we conducted an experiment in which the amount of air blown by the filler transfer blower was not changed and the amount of filler transferred was always constant, we found that the amount of excess sludge discharged was the same as with the conventional method, or even increased. . Furthermore, when the plant was operated for a long period of time, the quality of the treated water tended to deteriorate, probably due to a decrease in biomass.

〔Effect of the invention〕

As described above, according to the present invention, in biological treatment using granular materials as a bioadhesion medium, the granular media can be used as a slurry! While being transferred little by little under J-a'E, a strong stirring force is applied to ensure that excess sludge is removed. In addition, the dispersion medium of this slurry is the same as the treated water, so it has a higher cleaning effect compared to those using raw water as a dispersion medium, and there is no need to use special water for cleaning, so granular media It is easy to separate the excess sludge from the sludge, which prevents clogging that conventionally inevitably occurs, and at the same time significantly reduces the amount of excess sludge discharged.

Furthermore, since the amount of granular media transferred for removing excess sludge can be changed and the microorganisms required for biological treatment can be maintained appropriately at all times, stable and effective biological treatment is possible.

In addition, there is no need to perform one round of backwashing as in the conventional method.9
, the amount of incidental equipment required for backwashing can be greatly reduced, and extremely rational processing can be performed.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, and the second
The figure is a diagram showing an example of an airlift performance curve. DESCRIPTION OF SYMBOLS 1... Liquid to be treated, 2... Processing tank, 3, 3'... Granular medium, 4... Filled bed, 5... Air, 6... Air diffuser, 7... Treated water outflow pipe, 8... Treated water, 9...
- Transfer piping, 10...Medium transfer device, 11...Separation device, 12...Excess sludge.

Claims (3)

[Claims] (1) Biological treatment in which a packed bed of granular media for adhesion of microorganisms is formed in the tank, and the liquid to be treated is passed in a downward flow to perform aerobic biological treatment and filtration treatment at the same time in the packed bed. In the method, the granular medium is continuously or intermittently transferred from below the packed bed upward together with a portion of the treated water, and the amount of the transferred medium is varied in accordance with the amount of microorganisms attached to the granular medium. After peeling off excess sludge adhering to the granular medium during transfer and further separating the granular medium from the excess sludge, returning the separated granular medium to the upper part of the packed bed,
A biological treatment method characterized by discharging separated excess sludge to the outside of the system. (2) the granular medium is continuously transported;
2. The biological treatment method according to claim 1, wherein the amount transferred is varied within a range of 1.5 to 3 times the total amount of granular media per day. (3) The granular medium is intermittently transferred, and the amount of the granular medium transferred is varied within a range of 1/4 to 8 times the total amount of granular media per day. processing method.