JPH02131195A - Soil water treatment device - Google Patents

Abstract

PURPOSE:To treat continuously for a long time with high water applying speed by forming waterproof fiber into non-woven fabric and filling a fiber medium with void at the time of applying water not to be varied substantially in a filter layer for microbe contacting. CONSTITUTION:Raw water from a raw water inflow pipe 4 flows into a treat ment tank 1, and air (O2) from an air diffusion pipe 7 on a bottom section is fed to microbes, and treated water passing through a filter layer 2 is dis charged through an extrusion pipe 5 and a discharge pipe 6. Plastic fibers 13, a number of bending processed waterproof fibers, are coated with bonding agent into non-woven three-dimensional mesh in said filter layer 2 filled with fiber filter mediums 12 having non-varying void content substantially at the time of applying water. Thus, pressure loss of the filter layer is small, and continuous treatment at high rate of water filtration without damaging removal efficiency of BOD and SS can be carried out for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sewage treatment device for treating organic wastewater such as urban sewage and industrial wastewater, or secondary treated sewage water by a biofilm filtration method.

[Prior art] A sewage treatment device using the biofilm filtration method is equipped with a biofilm filter layer made of granular filter media such as gravel, crushed stone, and Raschig ring in the treatment tank, and is provided with an aeration means for blowing air from the bottom of the filter layer. This is a device that oxidizes and decomposes BOD components in raw water by the action of aerobic microorganisms that grow on the surface of the filter medium or in the pores of the filter layer. This device has high oxygen dissolution efficiency due to good gas-liquid contact within the filter layer, and also has the function of removing suspended solids (hereinafter referred to as SS) at the same time as removing organic matter. , In recent years, development research has been conducted on its application.

For example, research results have been published on advanced treatment of treated water using the activated sludge method using a biological filtration membrane method in which the filter layer is filled with granular filter media (Proceedings of the 25th Sewerage Research Conference). , pp. 294-296, 1988). FIG. 6 is an explanatory diagram of this device. In FIG. 6, this apparatus has a processing tank 2o filled with 1 m of 4 to 7 granular filter media to form a filter layer 21. A raw water inflow pipe 22 is installed in the upper part of the treatment tank 20, and a treated water discharge pipe 23 is installed in the lower part of the treatment tank 20. Also, below the filter layer 21, air is provided to supply oxygen to the microorganisms attached to the filter medium. A supply pipe 24 is installed. In the figure, 25 is a backwash water supply pipe that is connected to the treated water discharge pipe 23 and allows cleaning water to flow into the treatment tank 20, and 26
indicates a backwash drain pipe, and the air supply pipe 24 also serves as an air supply pipe for blowing air during backwashing.

In the apparatus configured as described above, BOD and SS are removed from the raw water supplied from the raw water inflow pipe 22 while passing through the filter layer 21, and the treated water is discharged from the treated water discharge pipe 23. During this purification process, the pressure loss of the filter layer 21 increases due to the capture of SS and the growth of microorganisms, so the filter layer 21 is backwashed when the pressure loss reaches a certain limit.

The results show that both BOD and SS are removed well, but the pressure drop after 24 hours of water flow tends to be high as shown in Figure 7. The required frequency of backwashing based on this pressure drop result is a filtration rate of 6 m/hour (144 m/day).
It is stated that this happens about once every two days.

[Problem to be solved by the invention] Although the above-mentioned conventional technology is a useful technology, the pressure loss is high and
Backwashing must be performed in a relatively short period of time, and there is still room for improvement.

An object of the present invention is to solve the above-mentioned problems and provide a wastewater treatment device using a biofilm filtration method that can continue treatment for a long time without impairing the removal efficiency of BOD and SS.

[Means for Solving the Problems] In order to achieve the above object, in the sewage treatment apparatus of the present invention, the filter layer for contacting microorganisms in the treatment tank is formed with water-resistant fibers in a non-woven manner. It is filled with a fiber filter medium whose porosity does not substantially change when wet. Plastic fibers or metal fibers are used as the water-resistant fibers forming this fibrous filter medium.

Further, the filter layer is divided into at least two parts, and the filter layer at the initial stage of treatment through which the raw water first passes (hereinafter referred to as the initial filter layer) includes the fiber filter material having a porosity of 99.5% to 95%. The filter layer at the end of the treatment (hereinafter referred to as
The processing efficiency can be further increased by filling the fibrous filter medium having a porosity of 5% to 70% into the final filter layer.

Furthermore, the treatment tank is equipped with at least one filter layer of different filter media, the initial filter layer is filled with the above-mentioned fibrous filter media, and the final filter layer is filled with granular filter media, thereby utilizing the characteristics of the granular filter media. At the same time, it is possible to suppress an increase in pressure loss throughout the filter layer.

In the sewage treatment device having at least two filter layers with different filter media in the treatment tank, the initial filter layer is divided into at least two, and the first divided filter layer has nine filter layers,
Filling the fiber filter medium with a porosity of 5% to 95%,
The efficiency of the initial filter layer can be further increased by filling the last partitioned filter layer with the fiber filter medium having a porosity of 95% to 70%.

[Function] The fiber filter medium to be filled in the filter layer of the device of the present invention was discovered as a result of various filter medium selection experiments, and is made by bending water-resistant fibers such as curling them into a small elastic body. This bent fiber is formed into a non-woven material. Therefore, the porosity is much larger than that of granular filter media, and therefore the pressure loss of a filter layer filled with this fibrous filter media is extremely small. Moreover, as mentioned below, BOI). It has the property of not impairing SS removal efficiency.

The fibrous filter medium used has a porosity of 70% to 99.5%. This porosity was determined on the premise that the pressure drop would not increase in a short period of time during water flow and that the SS removal rate would be good. If the porosity is less than 70%, the pressure drop will increase rapidly with water passing for a short time, so the purpose of the present invention cannot be achieved, and if the porosity exceeds 99.5%, the SS removal rate will be insufficient. Its function as a filter medium is insufficient.

In addition, fiber filter media can be manufactured with an appropriate porosity over a wide range of porosity, so the porosity can be adjusted appropriately depending on the quality of the raw water, especially the particle size of the SS contained. You can choose what you want. A filter medium with a small porosity has a good SS removal rate, but the pressure drop increases at a high rate due to SS capture.

In addition, filter media with large porosity have a small pressure drop increase rate, but S
The removal rate of S is low. For this reason, mainly S with large particle size
For treating raw water containing S, use one with a high porosity.
In addition, when treating raw water that mainly contains SS with a small particle size, by using a material with a small porosity, it is possible to suppress the increase in pressure drop due to the capture of SS, and also to ensure the targeted SS removal rate. Filter media can be selected.

When treating raw water containing a mixture of SS with large particle size and SS with small particle size, the filter layer is divided into at least two parts,
It is preferable to fill each filter layer with fiber filter media having different porosity. In the device configured in this way, the initial filter layer is filled with a fiber filter medium with a high porosity for the purpose of removing SS with a large particle size, and the final filter layer is filled with a fiber filter medium with a smaller porosity than that filled in the initial filter layer. A fiber filter medium is filled to capture SS that could not be removed by the initial filter layer. If the filter layer is formed by filling the fiber filter media in this order, the load on the final filter layer filled with the fiber filter media with a small porosity will be reduced, and it can be used for a long time without causing a sudden increase in pressure drop. The process can be continued and the SS removal rate can be increased. Note that, if necessary, a required number of intermediate filter layers may be provided between the initial filter layer and the final filter layer. The porosity of the fiber filter medium filled in the intermediate filter layer is
It is smaller than the fiber filter medium filled in the initial filter layer and larger than the fiber filter medium filled in the final filter layer.

Furthermore, in a device in which the initial filter layer is filled with a fibrous filter medium and the final filter layer is filled with a granular filter medium, large SS is mainly removed in the initial filter layer filled with a fibrous filter medium, and in the final filter layer filled with a granular filter medium. Even minute SS is removed. Furthermore, S is brought into the final filter layer by the action of the initial filter layer.
Since the amount of S is significantly reduced, processing can be continued for a long time even in an apparatus filled with granular filter media.

In a device equipped with the above-mentioned initial filter layer filled with fiber filter media and final filter layer filled with granular filter media, the initial filter layer filled with fiber filter media is divided into at least two parts, and raw water is added to the divided filter layer parts. If filter media with small porosity are filled sequentially according to the water flow direction, even if raw water containing SS with a wide particle size distribution is treated, the rate of increase in pressure drop in the initial filter layer will not increase, and the final filter will be It is possible to reduce the load on the layers and continue processing for a long time.

[Example] Examples of the present invention will be described below.

FIG. 2 is an explanatory diagram schematically showing a fiber filter medium to be filled in the apparatus of the present invention. The fiber filter medium 12 is made of a non-woven material in which a large number of bent plastic fibers 13, which are water-resistant fibers, are coated and bonded with a binder to form a three-dimensional mesh-like structure. The fibers 13 constituting the fiber filter medium 12
The diameter is 100 denier (approximately 0.091 ml+
) to 10000101 tenier (approximately 0-91 mm). The porosity of the fiber filter medium 12 is 70% to 99.5% as described above.
Select within the range.

The diameter of the fibers 13 constituting the fiber filter medium 12 was determined as follows based on the results of a filter medium selection experiment. If the filled fiber filter medium 12 is compressed and reduced in volume during water flow, the porosity will decrease and the processing performance will change, which is not preferable. For this reason, the fibers 13 need to have enough strength to prevent the fiber filter medium 12 from being substantially compressed during water passage, and the diameter of the fibers 13 that meets this condition needs to be about 100 deniers or more. However, if the fibers 13 become too thick, the effective surface area of the filter medium per unit volume of the filter medium decreases,
Processing efficiency deteriorates. Thus, in consideration of the relationship with processing efficiency, it is desirable that the diameter of the fibers 13 be 10,000 deniers or less.

FIG. 1 is a sectional view schematically showing a first embodiment of the present invention. A vertical treatment tank 1 is provided with a filter layer 2 filled with a fiber filter medium as shown in FIG. The lower and upper ends of the filter layer 2 are provided with a filter layer holding material 3 in the form of a perforated plate, a grid, etc., which has virtually no water flow resistance, and is used to support the filter layer 2 or to prevent the filter material from lifting up. It is fixed. Various types of piping are connected to the treatment tank 1. A raw water inflow pipe 4 is connected to the upper part of the tank 1, a treated water withdrawal pipe 5 is connected to the bottom of the treatment tank 1, and a treated water discharge pipe 6 is connected to the treated water withdrawal pipe 5. They are connected to form a flow path for raw water and treated water. Further, an aeration tube 7 is provided at the bottom of the filter layer 2 to supply oxygen to microorganisms that have grown on the filter layer 2, and an air supply tube 8 is connected to the aeration tube 7. As a means for backwashing the filter layer 2, a backwash water supply pipe 9 is provided connected to the treated water withdrawal pipe 6, and the outer periphery of the treatment tank 1 located above the filter layer 2 is provided with a backwash water supply pipe 9. One or more backwash water discharge pipes 10 connected to the water collecting pipe 11 are installed respectively. Further, the air diffuser pipe 7 and the air supply pipe 8 are also used as air blowing means during backwashing.

The operation of this device will be explained. Raw water is introduced from the raw water inlet pipe 4, and when the raw water reaches the upper end of the filter layer 2,
The inflow of raw water is interrupted, air is blown into the treatment tank 1 from the aeration pipe 7, and the treated water is discharged from the treated water discharge pipe 6. While the raw water passes through the filter layer 2, BOD is decomposed and most of the SS is captured and removed, resulting in a low BOD concentration.
The treated water has a low SS concentration.

The treatment continues in this manner, but as the treatment continues for a long time, the pressure loss in the filter layer 2 gradually increases, so when the pressure loss reaches a certain limit, the filter layer 2 is backwashed. When backwashing is performed, the supply of raw water and the extraction of treated water are stopped, the process is temporarily interrupted, and air is blown through the air blowing pipe 8.

At this time, the SS adhering to the filter layer 2 is peeled off and suspended in the remaining raw water. After blowing air for a specified time,
Backwash water is introduced from the backwash water supply pipe 9, and backwash water containing a large amount of SS is discharged from the backwash water collection pipe 11 via the backwash water discharge pipe 10.

FIG. 3 is a sectional view schematically showing a second embodiment of the present invention. In FIG. 3, the same components of the structure 13 as in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted. Furthermore, since the operation of this apparatus is basically the same as that of the apparatus shown in FIG. 1, the explanation thereof will be omitted. The filter layer 2 is filled with the fiber filter medium shown in FIG. 2, and the filter layer 2 is divided into three sections from the top: an initial filter layer 2a, an intermediate filter layer 2b, and a final filter layer 2c. The fibrous filter media filled in the filter layers 2a, 2b, and 2c have different porosity, and the initial filter layer 2
A is filled with a fiber filter medium having a large porosity with a porosity of about 99.5% to 95%, and the final filter layer 2c has a porosity of 95% to 95%.
It is filled with a fiber filter medium that has a small porosity of about 70%. The filter medium filled in the intermediate filter layer 2b is the initial filter layer 2a.
The porosity is determined by the porosity of the fibrous filter medium filled in the filter layer 2c and the fibrous filter medium filled in the final filter layer 2c, and one with a porosity between the two is used. The porosity of the fiber filter medium actually used is determined by the quality of the raw water to be treated (particularly the SS concentration, SS particle size, etc.).

In this example, the filter layer was divided into three sections, but the number of filter layers requires at least two layers, an initial filter layer 14 and a final filter layer, and the arrangement of three or more filter layers is not possible. is determined appropriately depending on the properties of the raw water to be treated.

FIG. 4 is a cross-sectional view schematically showing a third embodiment of the present invention.6 In FIG. 4, the same components as in FIG. Furthermore, since the operation of this apparatus is basically the same as that of the apparatus shown in FIG. 1, the explanation thereof will be omitted. The treatment tank 1 is equipped with two filter layers 2 filled with different filter media, the initial filter layer 2a is filled with the fibrous filter material shown in FIG. 2, and the final filter waste 2c is filled with granular filter media. has been done.

The fiber filter medium to be filled in the initial filter layer 2a is determined by the quality of the raw water to be treated (particularly the SS concentration, SS particle size distribution, etc.), the target water quality of the treated water, etc.
0% is selected as appropriate. As the granular filter medium to be filled in the final filter layer 2C, anthracite, gravel, sand, chamotte (expanded shale), granular activated carbon, plastic particles, ceramic particles, etc. are used. The particle size of this granular filter medium is determined by the quality of the raw water to be treated (particularly the particle size distribution of SS) and the target quality of the treated water, but is usually in the range of about 0.3 mm to 20 liters.

FIG. 5 is a sectional view schematically showing a fourth embodiment of the present invention. In FIG. 5, the same components as in FIG. 1 are denoted by the same reference numerals, and explanations thereof will be omitted. Furthermore, since the operation of this apparatus is basically the same as that of the apparatus shown in FIG. 1, the explanation thereof will be omitted. In this embodiment, two filter layers 2 filled with different filter media are provided in the processing tank 1, and an initial filter layer 2a
is filled with the fiber filter medium shown in FIG. 2, and the final filter layer 2c
is filled with granular filter media. This configuration is similar to the embodiment shown in FIG. 4, but in this embodiment, the initial filter layer 2a is further divided into a first filter layer section 2a' and a final filter layer section 2a.
The first filter layer section 2a' is filled with a fiber filter medium with a porosity of 99.5% to 95%, and the last filter layer section 2a'' is filled with a fiber filter medium with a porosity of 99.5% to 95%. 95%
Filled with ~70% fibrous filter media.

As mentioned above, this example uses SS with a large particle size distribution width.
The aim is to efficiently remove SS from raw water containing SS. The fiber filter media to be filled in each filter layer portion 2a' and 2a'' is determined in the same manner as in the embodiment shown in FIG.

As the granular filter medium filled in the final filter layer 2c, the same one as in the embodiment shown in FIG. 4 is used.

In this embodiment, the initial filter layer 2a is divided into two sections and the porosity of the fiber filter medium is set to two levels, but depending on the case, the number of sections may be three or more.

Although each embodiment has been described above, the embodiments of the present invention are not limited to the above embodiments. For example, the material of the fibers constituting the filter medium is not limited to polyvinylidene chloride, but may also be made of polyethylene, polypropylene, etc. It may be made of plastic or metal such as stainless steel. Further, the flow of raw water passing through the filter layer may be either a downward flow or an upward flow. Furthermore, the filter layer filled with fiber filter media is not only formed by laying out cubes or rectangular parallelepipeds as shown in Figure 2, but also filter media filled with moderately sized cubes or spheres or It may be filled with an irregularly shaped filter medium. Alternatively, the filter medium may be packed in a basket-like container and a plurality of these packs may be filled to form a filter layer, or one filter layer may be formed integrally.

Next, the results of experiments conducted using the sewage treatment apparatus having the above configuration will be explained.

(Example 1) An apparatus having the same configuration as the apparatus shown in Fig. 1, in which a filter layer was formed by filling a fiber filter medium in an acrylic resin treatment tank with an inner diameter of 5c2I1 and a height of 2.5m, was used to treat sewage water. Next, we conducted a treatment experiment using the biofilm filtration method for the treated water.

The fiber filter material filled in the filter layer was made of polyvinylidene chloride fibers, and the filling height was 100 cm. As a comparative example using a granular filter medium, an experiment in which 100 cm of anthracite with a particle size of 3 to 7 mm was filled was also conducted at the same time. These experimental conditions and results are shown in Table 1.

Table 1 ('MM Example 1) (Example 2) The filter layer filled with fiber filter media was divided into three sections, and the initial filter layer,
Using an apparatus having three layers, an intermediate filtration layer and a final filtration layer, and having the same configuration as the apparatus shown in FIG. 3, a treatment experiment was conducted using the biofilm filtration method for secondary sewage treatment water. The filling height of each filter layer was 30σ. The conditions of the comparative example were the same as those of Example 1. These experimental conditions and results are shown in Table 2.

In Table 1, the final pressure drop indicates the pressure drop at the end of the treatment experiment (treatment duration). As is clear from this table, BOD
, SS removal, there is almost no difference between the example and the comparative example. However, regarding the final pressure drop, in the example, the pressure drop after 240 hours (10 days) at a water flow rate of 120 m/day was only 2 to 3 cmH20, whereas in the comparative example, the pressure drop reached 110 cmH20, which was significant. There is a difference. Similar results were obtained when the water flow rate was increased to 240 m/day.

In Table 2, the final pressure drop of the comparative example increases rapidly, and there is a very large difference between the example and the comparative example, as in the case of example 1. In this experiment, since the filter layer was divided and filled with a filter medium having a small porosity, better results were obtained in terms of SS removal than in Example 1.

(Example 3) A biofilm filtration method for secondary treated sewage water was carried out using a device having the same configuration as the device shown in Fig. 4, including an initial filter layer filled with a fiber filter medium and a final filter layer filled with anthracite. A processing experiment was conducted using Anthusite with a particle size of 3 to 4 was used. The filling height is the initial filter layer 50 filled with fiber filter media.
Ω, the final filter layer filled with anthracite was 20 cm. The conditions of the comparative example were the same as those of Example 1. These experimental conditions and results are shown in Table 3.

Table 3 (Example 3) In Table 3, the final pressure drop of the comparative example increases rapidly, and there is an extremely large difference between the example and the comparative example, similar to examples 1 and 2. . In this experiment, since the example was equipped with a fibrous filter layer before the anthracite filter layer, the removal of BOD and ss was better than in the comparative example.

221 (Example 4) Using the apparatus of Examples 1 to 3 (configured similarly to the apparatuses of Figures 1, 3, and 4), primary treated sewage water with high BOD and high SS concentrations was subjected to biological treatment. An experiment was conducted using membrane filtration. These experimental conditions and results are shown in Table 4.

In Table 4, the pressure drop after 48 hours for each example is approximately 20
~35ΩH20, whereas in the comparative example it rose rapidly to 110cmH20 even after 24 hours.
Processing could not continue for a long time. As is clear from these results, it was confirmed that the apparatus of the present invention can be applied to primary treated sewage water with a high SS concentration.

[Effects of the Invention] The sewage treatment equipment of the present invention has a filter layer for contacting microorganisms in the treatment tank formed with non-woven water-resistant fibers such as plastic fibers or metal fibers, and has a substantial porosity during water flow. Filled with a fiber filter that does not change in temperature, this filter layer has a very small pressure drop and does not impair the removal efficiency of BOD and SS, so it can be continuously processed for an extremely long time at a high water flow rate. can.

Further, in the sewage treatment apparatus of the present invention, in which the filter layer filled with the fiber filter medium is divided into at least two parts, the initial filter layer is filled with a fiber filter medium with a high porosity, and the final filter layer is filled with fibers with a low porosity. Since the filter medium is filled, SS is efficiently removed by particle size, and even when raw water containing SS with a wide particle size distribution is passed through, the entire filter layer captures SS, so it can be used for a long time. can be processed.

Furthermore, in the sewage treatment apparatus of the present invention having at least two filter layers with different filter media, the initial filter layer is filled with the above-mentioned fibrous filter media, and the final filter layer is filled with the granular filter media. The load on the final stage filter layer filled with SS is significantly reduced, fine SS can be removed, and processing can be carried out for a long time.

In the sewage treatment apparatus of the present invention in which the initial filter layer is divided into at least two parts, the first divided filter layer is filled with a fiber filter medium having a large porosity, and the last divided filter layer is filled with a fiber filter medium having a large porosity. is filled with a fiber filter medium with a high porosity, so
SS in the initial filter layer is efficiently removed according to particle size, and the final filter layer filled with granular filter media is not clogged, allowing long-term treatment.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing a first embodiment of the present invention;
FIG. 2 is an explanatory diagram schematically showing a fiber filter medium to be filled in the apparatus of the present invention, FIG. 3 is a sectional view schematically showing a second embodiment of the present invention, and FIG. FIG. 5 is a cross-sectional view schematically showing the fourth embodiment of the present invention, FIG. 6 is an explanatory diagram of a sewage treatment device using a conventional biofilm filtration method, FIG. 7 is a diagram showing the measurement results of pressure drop in the sewage treatment apparatus using the conventional biofilm filtration method shown in FIG. 1... Processing tank, 2... Filter layer, 2a... Initial filter layer,
2c... Final filter layer, 2a... Initial filter layer part, 2a
...Last filter layer section, 4...Raw water inflow pipe, 5...
Treated water extraction pipe, 6... Treated water discharge pipe, 7... Aeration pipe, 8... Air supply pipe, 12... Fiber filter medium, 13
...Plastic fiber.

Claims (6)

[Claims] (1) In a sewage treatment equipment equipped with a filter layer for contact with microorganisms in the treatment tank, the filter layer includes a fibrous filter material made of non-woven water-resistant fibers and whose porosity does not substantially change during water flow. A sewage treatment device characterized by being filled. (2) The sewage treatment device according to claim 1, wherein the water-resistant fibers forming the fiber filter medium are plastic fibers. (3) The sewage treatment device according to claim 1, wherein the water-resistant fibers forming the fiber filter medium are metal fibers. (4) The filter layer is divided into at least two parts, and the filter layer at the initial stage of treatment through which the raw water passes first is filled with a fiber filter medium having a porosity of 99.5% to 95%, through which the raw water passes last. 4. The sewage treatment apparatus according to claim 1, wherein the filter layer at the final stage of treatment is filled with a fiber filter medium having a porosity of 95% to 70%. (5) In a sewage treatment equipment equipped with a filter layer for contact with microorganisms in the treatment tank, the treatment tank has at least two filter layers with different filter media, and the filter layer in the initial stage of treatment through which raw water first passes is water-resistant. The method is characterized in that it is filled with a fibrous filter medium in which non-woven fibers are formed and whose porosity does not substantially change during water flow, and the filter layer at the end of the treatment through which raw water passes is filled with a granular filter medium. sewage treatment equipment. (6) In the sewage treatment apparatus according to claim 5, the filter layer at the initial stage of treatment through which the raw water first passes is divided into at least two parts, and the first divided filter layer has a water content of 99.5% to 95%. A sewage treatment device characterized in that a fiber filter medium having a porosity is filled, and the last divided filter layer section is filled with a fiber filter medium having a porosity of 95% to 70%.