JP3633001B2 - Cleaning method for biological filtration device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a cleaning method for a biological filtration device in which an upward flow is passed through a filter layer filled with a floatable filter medium, and in particular, a biological filtration device provided with an air diffuser in the middle of the filter layer It is about the method.
[0002]
[Prior art]
The biofiltration device that forms a biofilm by filling a floating filter medium and passes the liquid to be treated through the filter layer for treatment, compared to the one that retains sludge such as the activated sludge method in a floating manner, Since a high concentration of organisms can be held in the tank, efficient treatment can be performed. In such a biological filtration device, when the air is diffused from the lower part of the filter layer, the organic matter can be decomposed with the whole layer as the aerobic part, but when the air diffuser is provided in the middle, the upper part is preferred. An organic substance is decomposed or nitrified as an air part, and an anaerobic process for denitrification or dephosphorization can be performed at the lower part as an anaerobic part.
[0003]
By the way, in the biofiltration device, the filter layer is blocked by the capture of SS or the growth of the biofilm, so that the filter layer needs to be washed. However, particularly when an aeration device is provided in the middle, the lower anaerobic part is severely blocked. It is difficult to clean.
Conventionally, as a cleaning method for such a biological filtration device, when the pressure loss increases due to the clogging of the filter layer, the filter layer is developed by opening the drain valve at the bottom of the device and flowing the wash water in a downward flow, and continuously There has been proposed a method in which air is intermittently or intermittently diffused from the lower part of the filter layer to loosen the filter layer and perform cleaning (for example, JP-A-5-96292).
[0004]
[Problems to be solved by the invention]
However, in the biological filtration apparatus, in order to make the distribution of the liquid to be treated uniform or to secure a development space at the time of backwashing, a considerable space is formed at the lower part of the filter layer. Thus, when the backwashing operation by the downward flow is started immediately after the water flow is stopped, the liquid to be treated filled in the space below the filter layer is discharged as it is, and the amount of the washing water increases. Also, if the filter layer is severely clogged, especially if an aeration device is provided in the middle and an anaerobic part is formed in the lower part, it is difficult to peel off the excess biofilm, and backwashing by downward flow or scattering to this will be difficult. The biofilm is peeled only gradually even if the gas is used together, and the cleaning time becomes longer and the amount of cleaning water increases. In addition, if the filter layer having an aerobic part and an anaerobic part is diffused, the filter medium in the aerobic part and the anaerobic part is vigorously mixed, and normal processing cannot be performed when liquid flow is resumed. There is.
[0005]
In order to solve the above problems, an object of the present invention is to propose a method for cleaning a biofiltration layer that can efficiently peel a biofilm and clean the filter layer in a short time with a small amount of cleaning water.
[0006]
[Means for Solving the Problems]
The present invention relates to a method for cleaning a biological filtration apparatus in which a liquid to be treated is passed in an upward flow through a filter layer formed by filling a floating particulate filter medium to form a biofilm,
Supporting the floating particulate filter medium from above, forming a filter layer,
After substantially stopping the flow with the filter layer supported from above , performing aeration from the bottom of the filter layer, and peeling the biofilm attached to the filter medium with the filter layer fixed ,
A washing method for a biological filtration device, wherein the washing water is passed in a downward flow while draining water from the lower part of the filtration layer, and the filtration layer is developed and backwashed.
[0007]
The filter medium used in the present invention is a floating granular filter medium that can form a biofilm by adhering sludge to the surface, and has a specific gravity of 0.01 to 0.9, preferably 0.03 to 0. 5 and a particle diameter of 1 to 30 mm, preferably 2 to 10 mm are desirable. The material is not limited, but plastic expanded particles such as expanded polystyrene and polyolefin are preferable.
[0008]
The biological filtration device to be cleaned in the present invention supports and floats the above floating particulate filter material from above to form a filter layer, forms a biological film on the surface of the filter material, and forms a liquid to be treated. It is the filtration apparatus comprised so that it might flow and process by an upward flow. The biofilm is spontaneously formed by introducing the liquid to be treated into the filter layer and maintaining the same conditions as in the treatment.
[0009]
As the biological filtration apparatus, any liquid to be treated can be cleaned, such as a liquid to be treated being aerobic, a liquid to be treated anaerobically, or a liquid to be treated aerobically and anaerobically. However, a biological filtration device including a case where the treatment is performed under anaerobic condition is particularly suitable as a cleaning target. In the case of processing under aerobic condition, since the aeration is usually performed, the filter bed is easily washed by backwashing by downward flow, but in the case of processing under anaerobic condition, the filter layer is severely clogged. This is because cleaning is difficult only by backwashing by downward flow, and cleaning is facilitated by using air backwashing together. Of course, even if the treatment is performed under aerobic condition, the air backwashing is performed by diffusing more intensely than usual, so that the cleaning of the present invention can be applied.
[0010]
Biological filtration devices that include anaerobic parts are also subject to cleaning, although the entire layer is an anaerobic part. An object that forms an air part and an anaerobic part in the lower part is particularly suitable as an object to be cleaned. Such an apparatus is configured to decompose or nitrify organic matter in the upper aerobic part and to perform anaerobic treatment for denitrification and / or dephosphorization in the lower anaerobic part.
In a biological filtration apparatus including such an anaerobic part, the filtration layer becomes clogged by the continuation of processing and it becomes difficult to pass the liquid, so back washing is performed, but only water back washing with downward flowing water of washing water is performed. Cleaning the clogged filter layer is difficult.
[0011]
Therefore, in the present invention, as a washing operation, first, by performing aeration from the lower part of the filter layer in a state in which the liquid flow is substantially stopped, the biological film attached to the filter medium is peeled off, and at least a part of the peeled sludge is filtered. Move to lower water layer. At this time, by substantially stopping the liquid flow, only the biofilm can be peeled while the filter layer is fixed. Such an operation can be performed on a filter layer composed of only an aerobic part, but in this case, it is necessary to ventilate a larger amount than the air diffused during the treatment.
The biofilm that peels off due to such aeration moves to the lower water layer as sludge and is dispersed or settled. Aeration is carried out at an air linear velocity of 10 m / hr or more, preferably 12 to 20 m / hr for 1 to 30 minutes, preferably 5 to 15 minutes, whereby the excess biofilm is peeled off and transferred to the lower liquid layer.
[0012]
After stopping the aeration, it is preferable to set the sludge for 0.5 to 20 minutes, preferably 1 to 15 minutes, so that the sludge is settled. This operation can be omitted.
Then, while draining water from the lower part of the filtration device, the wash water is passed in a downward flow to develop the filter layer and backwash. As a result, the exfoliated sludge previously transferred to the lower liquid layer is discharged, and the filter layer is developed and further exfoliated. The exfoliated sludge present in the filter layer is washed away by the washing water, and the filter layer is washed. Done. At this time, washing is performed in a state where the disturbance of the filter layer is small, and the filter medium in the anaerobic part and the aerobic part is not vigorously mixed. As the washing water, the water layer present at the upper part of the filter layer is used as it is, but if necessary, washing can be performed by further supplying treated water and other water. The flow rate of the washing water is 20 to 70 m / hr, preferably 40 to 60 m / hr, and the washing time is a time required for discharging sludge, but generally 0.5 to 20 minutes, preferably 0.5 to 10 minutes.
[0013]
When the water flow for the above water backwashing is stopped, the filter medium floats and forms a filter layer. If necessary, wash the water in an upward flow and wash it. Pass the fluid through to resume biofiltration. After the pressure loss increases due to the continuation of the treatment, washing is performed in the same manner, and such an operation is repeated.
In the above washing operation, the sludge discharge pattern is accelerated as compared with the case of only water back washing, so the amount of washing water and washing time are reduced, and the degree of pressure loss recovery is large. In addition, the above-mentioned aeration is particularly effective for the removal of sludge at the bottom of the filter layer, so the clogging of the upper filter layer may not be completely removed. It is possible to adopt a method such as extending the time of the aeration, repeating aeration-water backwashing, or performing aeration from an intermediate aeration device at the time of water backwashing.
[0014]
【Example】
Hereinafter, the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a biological filtration device in an embodiment.
In FIG. 1, reference numeral 1 denotes a filtration tower, in which a filter layer 2 is formed by filling a floating particulate filter medium such as expanded polystyrene or polyethylene, and is supported from above by a porous support plate 3. An air diffuser 4 for processing is disposed in the middle part of the filter layer 2 and communicates with an air supply path 5. An aerobic part 2 a is formed at the upper part of the filter layer 2, and an anaerobic part 2 b is formed at the lower part. A lower liquid layer 6 is formed below the filter layer 2 and communicates with a liquid passage 7 to be treated. A gas diffuser 8 for cleaning is provided below the fluid layer 7 and communicates with an air supply passage 9. A cleaning drainage channel 11 communicates with the bottom of the filtration tower 1. An upper liquid layer 12 is formed above the filter layer 2, the processing liquid channel 13 and the cleaning water channel 14 communicate with each other, and the circulating liquid channel 15 communicates with the lower liquid layer 6 through the liquid channel 7 to be processed. Yes.
[0015]
In the above biological filtration apparatus, when a floating particulate filter medium is introduced into the filtration tower 1, the filter medium floats and is supported by the support plate 3 to form the filter layer 2. When air is supplied from the air supply passage 5 and diffused from the air diffuser 4, the aerobic part 2a is formed in the upper part of the filter layer 2, and the anaerobic part 2b is formed in the lower part. In this state, when the liquid to be treated is introduced from the liquid path 7 to be treated and passed through the filter layer 2 in an upward flow, a biofilm for anaerobic treatment is formed in the anaerobic part 2b, and the aerobic part 2a A biofilm for aerobic treatment is formed and each treatment is performed.
[0016]
The embodiment of FIG. 1 shows an example in which nitrification denitrification is carried out. BOD remaining in the aerobic part 2a is removed and nitrification is performed on the nitrogen-containing treatment liquid, and a part of the treatment liquid is transferred from the circulation liquid path 15 to the lower part. It circulates in the liquid layer 6 and performs denitrification and BOD removal in the anaerobic part 2b. The processing liquid is discharged from the processing liquid path 13.
When dephosphorization is performed, the anaerobic part is anaerobic for dephosphorization by connecting the filter medium circulation path from the upper part of the aerobic part 2a to the lower part of the anaerobic part 2b instead of the circulating liquid path 15 and circulating the filter medium. It can be used as a process.
[0017]
When the above treatment is continued, the biofilm grows, the filter layer 2 is blocked, and the pressure loss increases. This tendency is remarkable in the anaerobic part 2b. Accordingly, the cleaning of the filter layer 2 is started, the supply of liquid from the treated liquid path 7 and the circulation liquid path 15 and the supply of air from the supply path 5 are stopped, and the flow and diffusion of the filter layer 2 are stopped. Air is supplied from the air passage 9 and is diffused from the air diffuser 8, and the biofilm attached to the filter layer 2 is peeled off and transferred to the lower liquid layer 6. At this time, aeration from the aeration device 5 may also be performed.
After aeration for a predetermined time to peel off the biological sludge, it is allowed to stand as necessary to settle the peeled sludge.
[0018]
Thereafter, the liquid is drained from the cleaning drainage path 11 and the drainage liquid containing the peeled sludge is drained from the lower liquid layer 6, and the processing liquid in the upper liquid layer 12 is passed in a downward flow to develop the filter layer 2. Let it backwash. When the processing liquid of the upper liquid layer 12 is insufficient as cleaning water, cleaning water is replenished from the cleaning water channel 14. The sludge peeled off first and the newly peeled sludge are washed away by backwashing with water in the downward direction. At this time, the aeration from the air diffuser 8 is stopped to mix the aerobic part 2a and the anaerobic part 2b. Is prevented. When the aerobic part 2a is severely blocked, aeration from the aeration device 4 can be performed during backwashing with water, and this also reduces mixing of the aerobic part 2a and the anaerobic part 2b.
[0019]
After the above water backwashing is performed for a predetermined time, when the water supply from the cleaning water channel 14 and the drainage from the cleaning drainage channel 11 are stopped, the filter medium floats to form the filter layer 2 and the air supply channel 5 again. The process is resumed by supplying air from the tank, supplying liquid from the liquid path 7 to be processed, and circulating from the circulating liquid path 15, and this operation is repeated.
[0020]
Test Example In FIG. 1, a filtration tower 1 having a cross-sectional area of 0.5 m ² is filled with a floating granular filter medium made of expanded polystyrene having a particle size of 3.5 mm and a specific gravity of 0.03 g / cm ³ , and the aerobic part 2a is 2 m. The anaerobic part 2b formed the filter layer 2 with 1 m, the lower liquid layer 6 was 1 m, and the upper liquid layer 12 was 0.6 m. The filtration tower 1 to ^{_{pH7.1, BOD 550mg / l, NH}} 4 + 105mg-N / l, NO 3 - and liquid passing 2 mg-N / l, the liquid to be treated in the SS 97 mg / l in upflow anaerobic part 2b per BOD load ^5kg / m 3 · day, aerobic part 2a per nitrification load 0.6kg ^/ m 3 · day, anaerobic section 2b per denitrification load 1.1kg ^/ m 3 · day, T as the treatment liquid target value The treatment was performed under the treatment conditions of -N 10 mg-N / l, BOD 10 mg / l, and SS 10 mg / l.
[0021]
When the pressure loss reached 2 m, when water backwashing with downward circulating water was performed at LV50 m / hr for 5 minutes at the same time as the stoppage of liquid flow (Comparative Example 1), the subsequent filtration duration was about 8 hours. . After that, if the operating conditions are not changed and the air diffuser 8 diffuses air at LV15 m / hr for 5 minutes before standing back for 5 minutes and then left to stand for 5 minutes (Example 1), the sludge discharge pattern is as shown in FIG. Since it became early, the time of water backwashing was set to 2.5 minutes. When backwashing was performed when the pressure loss reached 2 m, the filtration duration was about 10.5 hours. In this case, the amount of backwash water per day was 62% lower than that of Comparative Example 1.
[0022]
【The invention's effect】
According to the present invention, a floatable particulate filter medium is supported from above to form a filter layer, the liquid passage is substantially stopped while the filter layer is supported from above , and air is diffused from the bottom of the filter layer . After peeling off the biofilm with the filter layer fixed , the wash water was passed in a downward flow to expand the filter layer and backwash, so the biological sludge was peeled off efficiently and with a small amount of washing water. The filter layer can be washed in a short time without disturbing the filter layer, thereby increasing the filtration time.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a biological filtration device in an embodiment.
FIG. 2 is a graph showing the results of a test example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Filtration tower 2 Filter layer 2a Aerobic part 2b Anaerobic part 3 Support plate 4, 8 Air diffuser 5, 9 Air supply path 6 Lower liquid layer 7 Processed liquid path 11 Washing drain path 12 Upper liquid layer 13 Process liquid path 14 Washing water channel 15 Circulating fluid channel

Claims (1)

In the cleaning method of the biological filtration apparatus in which the liquid to be treated is passed in an upward flow through the filter layer formed by filling the floating particulate filter medium to form a biofilm,
Supporting the floating particulate filter medium from above, forming a filter layer,
After substantially stopping the flow with the filter layer supported from above , performing aeration from the bottom of the filter layer, and peeling the biofilm attached to the filter medium with the filter layer fixed ,
A washing method of a biological filtration device, wherein washing water is passed in a downward flow while draining water from a lower part of the filtration layer, and the filtration layer is developed and backwashed.

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