JPH06114388A - Biological filtering method - Google Patents

Abstract

PURPOSE:To always keep a denitrifying ratio high and to obtain stable treated water quality by connecting two biological filter tanks in series or in parallel and removing a suspended substance in the front stage biological filter tank and performing denitrifying treatment in the post stage biological filter tank and performing the alteration of a passage accompanied by washing operation at every predetermined time. CONSTITUTION:Two biological filter tanks 1, 2 are arranged to front and post stages and, after the post stage biological filter tank 2 is washed, the passage from an upstream part is connected to the post and front stage biological filter tanks 2, 1 to perform water treatment operation. Immediately after denitrification is performed in the front stage biological filter tank 1, the suspended substance in inflow raw water can be caught in the post stage biological filter tank 2. Therefore, the advance of breakthrough can be suppressed and the denitrifying ratio of the front stage biological filter tank 1 can be kept. After the front stage biological filter tank 1 is washed, the passage from the upstream part is connected to the front and post stage biological filter tanks 1, 2 to perform water treatment operation. By this constitution, the suspended substance in raw water can be removed in the front stage biological filter tank 1 and denitrification can be performed in the post stage biological filter tank 2. Therefore, the treated water is kept in good quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for purifying organic wastewater such as sewage and industrial wastewater, or secondary treated water of organic wastewater, and more particularly to a biological filtration method for denitrifying using a biofilm. Regarding

[0002]

2. Description of the Related Art Biological denitrification methods include (1) anaerobic and aerobic circulation method, (2) C source (carbon source) addition non-circulation method, and (3)
C source-free non-circulation method (endogenous denitrification method) and the like are known.

FIG. 4 is a schematic configuration diagram of a biological filtration device by the above-mentioned conventional endogenous denitrification method. In the figure, the water nitrified in the preceding nitrification tank, that is, the nitrification liquid, is stored in the open / close valve 91.
It is supplied to the biological filtration tank 93 via a pipe 92 having a.
The supplied water passes through the filter medium 94 and is discharged as treated water through the pipe 95. A biofilm adheres to the filter medium 94 by this water treatment operation. This biofilm is separated by supplying air with pressurized air from the air source to the biofiltration tank 93 through the pipe 97 by closing the open / close valve 91 and opening the open / close valve 96, and by air washing. The separated biofilm is discharged from the pipe 99 by opening the opening / closing valve 98.

[0004]

However, the above-mentioned conventional biological filtration device has the following problems. As shown in FIG. 5, the TN (Total Nitrogen: total nitrogen) removal rate, that is, the denitrification rate, increases to about 70% within about 3 to 4 days after the water treatment operation is started, but it is low until then, especially for cleaning. Immediately after T
The N removal rate was 0%. In other words, there was a problem that denitrification was not stable.

This is because the endogenous denitrification method occurs with an appropriate amount of biofilm, and most of the biofilm is peeled off immediately after washing,
It will not be denitrified. The conditions for denitrification in the endogenous denitrification method are
The DO (dissolved oxygen concentration) must be low and the amount of biofilm must be high until the carbon source in the biofilm elutes. However, if the amount of biofilm is increased until denitrification occurs, the filter medium 9
4 is closed, breaks through and water does not flow, and the water treatment operation cannot be continued unless it is washed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a biological filtration method capable of always maintaining a high denitrification rate and always obtaining a stable treated water quality. .

[0007]

In order to achieve the above object, the present invention purifies the water to be treated by decomposing and adsorbing the organic matter of the biofilm formed on the surface of the filter medium filled in the biological filtration tank. In addition, in the biological filtration method having the function of cleaning the biological filtration tank, at least two biological filtration tanks are connected in series or in parallel, and an opening / closing valve and a pipe are provided so that the flow path of the treated water can be changed. Place and
When water to be treated is passed, the suspended matter is removed in the biological filtration tank in the previous stage, denitrification is performed in the biological filtration tank in the next stage, and the biological filtration tank in the next stage is washed, and then the flow path of the treated water is washed. It is characterized in that the biological filtration tank thus prepared is changed to a former stage, and thereafter, the same flow path change is carried out at every predetermined time with the washing operation.

[0008]

According to the biological filtration method of the present invention, at least 2
Since the biological filtration tank of the tank is arranged at the front stage and the rear stage, after cleaning the biological filtration tank of the latter stage, the water treatment operation is performed by setting the flow path from the upstream to the biological filtration tank of the latter stage and the biological filtration tank of the former stage. ,
Immediately after denitrification in the front biological filtration tank, the suspended matter of the inflowing raw water can be captured in the rear biological filtration tank, so that the progress of breakthrough can be suppressed and the denitrification rate of the front biological filtration tank can be maintained.
Furthermore, after washing the front biological filtration tank, the water treatment operation is performed by setting the flow path from the upstream to the front biological filtration tank and the rear biological filtration tank. Can be removed and denitrification can be performed in the biological filtration tank in the latter stage. Therefore, good treated water is maintained.

[0009]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a biological filtration device according to an embodiment of the present invention. As shown in the figure, the biological filtration device according to the present embodiment includes a first biological filtration tank 1 and a second biological filtration tank 2. The upper part of the first biological filtration tank 1 has an upper overflow end 3 and a lower overflow end 4, and the upper part of the second biological filtration tank 2 has an upper overflow end 5 and a lower overflow end 6. There is. Further, an air diffusing pipe 7 is arranged below the first biological filtration tank 1 and the second biological filtration tank 2 is provided.
An air diffuser 8 is arranged in the lower part of the.

A pipe 10 is arranged below the first biological filtration tank 1, and the pipe 10 has a connecting portion 11 and an opening / closing valve 12.
3, and the pipe 15 is connected through the connecting portion 14 in sequence. The connecting portion 14 includes a pipe 17 having an opening / closing valve 16, a connecting portion 18, and a pipe 1.
It is connected to the lower part of the second biological filtration tank 2 via 9 sequentially.
The connecting portion 11 is connected to the upper overflow end 5 of the second biological filtration tank 2 via a pipe 21 having an opening / closing valve 20. The connecting portion 18 is connected to a pipe 23 having an opening / closing valve 22 and is connected to the upper overflow end 3 of the first biological filtration tank 1. The lower overflow end 4 is connected to a pipe 25 having an opening / closing valve 24, and the lower overflow end 6 is connected to a pipe 27 having an opening / closing valve 26. Further, a pipe 31 having an opening / closing valve 30 is arranged at the bottom of the first biological filtration tank 1, and a pipe 33 having an opening / closing valve 32 is arranged at the bottom of the second biological filtration tank 2.

An air diffuser 7 provided at the bottom of the first biological filtration tank 1.
Is connected to an air source 44 through a pipe 41 having an opening / closing valve 40, a connecting portion 42, and a pipe 43 in this order. Further, the air diffusing pipe 8 provided in the lower portion of the second biological filtration tank 2 is connected to the connecting portion 42 via a pipe 46 having an opening / closing valve 45.

On the other hand, inside the first biological filtration tank 1, plastic is provided between the upper support plate 50 and the lower support plate 51.
A filter medium 52 such as cement balls and anthracite is filled. Similarly, inside the second biological filtration tank 2, the same filter medium 55 as the filter medium 52 is filled between the upper support plate 53 and the lower support plate 54. Although not shown in the figure, a timer controller for ON / OFF controlling all the on-off valves is provided.

Next, the operation of the biological filtration method of this embodiment will be described. FIG. 2 shows the operating process, the cleaning process, and the TN (total nitrogen) removal rate of the biological filtration apparatus according to the present embodiment in time series, which will be described below with reference to this drawing.

<At startup (t = 0 to 7 days)> The flow path of the water treatment operation is from the first biological filtration tank 1 (abbreviated as the first tank in the figure) to the second biological filtration tank 2 (in the figure). It is the direction (D) in the second tank). That is, the on-off valves 16, 20, 24, 3
0, 32, 40, 45 are closed, and open / close valves 12, 22, 26
Open. In this state, the liquid obtained by nitrifying the sewage, that is, the nitrification liquid 60, is connected to the pipe 15, the connecting portion 14, the pipe 13, and the connecting portion 1.
1, and is sequentially supplied to the first biological filtration tank 1 through the pipe 10. In the process of the supplied nitrification liquid passing through the filter medium 52, suspended matter SS in the nitrification liquid is attached to the filter medium 52 and removed. Since the denitrifying bacteria are mixed in the nitrification solution, the TN removal rate gradually increases as the adherence of the suspended matter SS progresses, and reaches about 70% at t = about 5 days ( A)
And (B).

The water from which the TN has been removed passes through the upper overflow end 3, the opening / closing valve 22, the pipe 23, the connecting portion 18, and the pipe 19 in this order to the second
It is supplied to the biological filtration tank 2. The supplied water passes through the filter medium 55 and is sequentially discharged through the lower overflow end 6, the on-off valve 26, and the pipe 27 as treated water 61 to a river or the like.

<Cleaning Step of Second Biological Filtration Tank 2 and Water Treatment Operation at Cleaning (t = 7 to 7.1 days)> When t = 7 days, the first biological filtration tank 1 to the second biological filtration tank 2 From the operation (D) to the operation (D), the flow path for supplying the nitrification liquid 60 is switched to the operation (H) of only the first biological filtration tank 1. In other words, by closing the on-off valve 22 and the on-off valve 26 and opening the on-off valve 24, the water that has passed through the filter medium 52 causes the water to pass through the lower overflow end 4, the on-off valve 24, and the pipe 25.
Is sequentially discharged as treated water 62.

Subsequently, the on-off valve 45 is opened to supply air from the air source 44 through the pipe 43, the connecting portion 42, the on-off valve 45, the pipe 46, and the diffuser pipe 8 in the furnace material 55 of the second biological filtration tank 2. To the air and start the operation of washing with air (G). At this time, the biofilm excessively attached to the surface of the filter medium 55 is forcibly peeled off by the cutting force of the air. Next, the on-off valve 45 is closed and the on-off valve 32 is opened, and the excessively separated biofilm is discharged through the pipe 33. The time required for this step is 0.1 day (about 2 hours).

<Water treatment operation after cleaning the second biological filtration tank 2 (t = 7.1 to 14 days)> After completion of the cleaning process, the on-off valve 32,
By closing 12 and opening the on-off valves 16, 20, 24, the flow path of the water supplying the nitrification liquid 60 is changed from the operation of only the first biological filtration tank 1 to the second biological filtration tank 2 Switch to operation to tank 1 (E).

At this time, in the first biological filtration tank 1, the TN
The removal rate is about 70%, and since the suspended matter SS in the nitrification liquid is removed by the second biological filtration tank 2, the first biological filtration tank 1
Stable TN removal is performed without breakthrough of the filter medium 52. That is, the nitrification liquid 60 is supplied to the second biological filtration tank 2 through the pipe 15, the connecting portion 14, the pipe 17, the opening / closing valve 16, the connecting portion 18, and the pipe 19 in this order, and the nitrification liquid 60 is supplied by the filter medium 55.
Suspended matter SS inside is removed and the water is removed from the upper overflow end 5,
It is supplied to the first biological filtration tank 1 through the on-off valve 20, the pipe 21, the connecting portion 11, and the pipe 10 in this order. This first biological filtration tank 1
The nitrate nitrogen in the nitrification solution is denitrified by the denitrifying bacteria attached to the filter medium 52 therein. The denitrified water is discharged as treated water 62 through the lower overflow end 4, the on-off valve 24, and the pipe 25 in this order.

<Washing Step of First Biological Filtration Tank 1 and Water Treatment Operation at Washing (t = 14 to 14.1 Days)> When t = 14 days, from the second biological filtration tank 2 to the first biological filtration tank 1. From the operation (E) to (2), the flow path for supplying the nitrification liquid 60 is switched to the operation of only the second biological filtration tank 2 (I). That is, the on-off valve 2
By closing 0 and 24 and opening the opening / closing valve 26, the nitrification liquid 60 is supplied to the second biological filtration tank 2 through the pipe 15, the connecting point 14, the opening / closing valve 16, the connecting point 18 and the pipe 19 in order, It is denitrified by the denitrifying bacteria attached to the filter medium 55. The denitrified water is discharged as treated water 61 through the lower overflow end 6, the on-off valve 26, and the pipe 27 in this order.

Subsequently, the on-off valve 40 is opened and air is supplied from the air source 44 to the first biological filtration tank 1 through the pipe 43, the connecting point 42, the on-off valve 40, the pipe 41 and the disperser pipe 7 in this order. The supplied air forcibly separates the biofilm by the uniform force of the air that has risen to the filter medium 52. Next, the opening / closing valve 40 is closed and the opening / closing valve 30 is opened, and the separated biofilm is discharged through the pipe 31. After the mud is discharged, the open / close valve 30 is opened. The time required for this cleaning step and the water treatment operation during cleaning is 0.1 day (about 2 hours).

Then, after washing the first biological filtration tank 1 (t =
(14.1 days), switch to the water treatment operation from the first biological filtration tank 1 to the second biological filtration tank 2. The operation at this time is t =
Do as in 0-7 days. Hereinafter, the first biological filtration tank 1
And the operation of alternately switching the flow paths of the second biological filtration tank 2 is continued.

As described above, according to this embodiment,
The following effects can be obtained. (1) Switching operation between the first biological filtration tank 1 and the second biological filtration tank 2 can be turned ON / OFF simply by opening / closing the opening / closing valve by the timer controller, which facilitates maintenance. (2) Since the upper overflow end and the lower overflow end are arranged and water flows according to the head difference between them, the energy for water flow is not required and the running cost is very small. (3) Since air cleaning was used to clean the biological filtration tank, the pump, adjustment tank, water tank, etc. required for cleaning water and chemicals are not required,
The installation area is small and the running cost is small.

(Other Embodiments) The representative embodiments of the present invention have been described above. However, the present invention is not limited to this, and is applicable to the following embodiments, for example. (1) In the embodiment of FIG. 1, two biological filtration tanks, a first biological filtration tank and a second biological filtration tank, were used, but the number of biological filtration tanks need not be limited to this. It is also possible to arrange three tanks, four tanks, ... In series, or to arrange them in parallel.

For example, as shown in FIG. 3, three first biological filtration tanks 70, a second biological filtration tank 71, and a third biological filtration tank 72 can be sequentially arranged in series. In addition, 56, 57, 5
8 is a filter medium, and 63, 64 and 65 are treated water. In this case, the water treatment operation and the cleaning timing are as shown in Table 1. In this table, the first biological filtration tank is abbreviated as the first tank, and similarly, the second tank and the third tank. That is, after cleaning the second biological filtration tank from the upstream side, the flow path of the water treatment operation before cleaning is switched to the flow path of the third tank → first tank → second tank. In this case as well, as in the case of FIG. 1, denitrification can always be favorably maintained, the suspended matter SS flowing out in the third tank can be captured, and clear treated water can be obtained.

[0026]

[Table 1]

(2) In the embodiment of FIG. 1, air cleaning is used for cleaning the filter material of the biological filtration tank, but it is also possible to use water cleaning and a combination of air cleaning and water cleaning. There is no need to limit it.

(3) In the embodiment shown in FIG. 1, the flow of water is changed by changing the overflow position at the upper part of the biological / biological filtration tank. However, as a water supply method, a pump, an air lift or the like should be used. Is also possible.

(4) The shape of the biological filtration tank, the flow direction of water, and the type of filter medium need not be limited to those in the above embodiments.

[0030]

As described above, according to the present invention,
It is possible to provide a biological filtration method that can always maintain a high denitrification rate and can always obtain stable treated water quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a biological filtration device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the operation and cleaning steps in time series for explaining the operation of FIG.

FIG. 3 is a schematic configuration diagram of a biological filtration device according to another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional biological filtration device.

FIG. 5 is a diagram for explaining an operation and a washing process for explaining the operation of the wastewater treatment device of FIG.

[Explanation of symbols]

1 ... 1st biological filtration tank, 2 ... 2nd biological filtration tank, 3, 5 ... upper overflow end, 4, 6 ... lower overflow end, 44 ... air source, 52,
55, 56, 57, 58 ... Filter medium, 60 ... Nitrification liquid, 61,
62, 63, 64, 65 ... Treated water.

Claims (1)

[Claims] 1. A biological filtration method having a function of purifying treated water by an organic substance decomposing action and an adsorbing action of a biological film formed on the surface of a filter medium filled in the biological filtration tank, and having a function of washing the biological filtration tank. In, at least two biological filtration tanks are connected in series or in parallel, and on-off valves and pipes are arranged so that the flow path of the treated water can be changed. After removing suspended solids in the tank, denitrifying in the next-stage biological filtration tank, and cleaning the next-stage biological filtration tank, the flow path of the water to be treated was changed to the previous biological filtration tank. Then, the biological filtration method is characterized in that the same flow path change is carried out with a washing operation every predetermined time.