JP2000262818A - Solid-liquid separation method and solid-liquid separation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-liquid separation method and a solid-liquid separation apparatus with which solid matter separation can economically be carried out at improved precision while prolonging the life of the filter medium in a rotary drum type filtration apparatus in which the filter medium is mounted. SOLUTION: This solid-liquid separation method includes processes of carrying out solid-liquid separation of a raw liquid by passing the raw liquid from the outside to the inside while rotating the filtration drum 9 equipped with a filter medium 11, back-washing the filter medium 11 by jetting washing water from the rear side, and front-washing the filter medium 11 from the front side. In the method, at least the washing from the front side is carried out and stopped corresponding to the water level in the drum. This apparatus is provided with a rotation filtration drum 9 equipped with the filter medium 11, a back- washing means for jetting washing water from the rear side of the filter medium 11, a front-washing means for jetting washing water from the front side of the filter medium 11, and a switching control means for operating or stopping at least the front-washing means corresponding to the water level in the filtration drum 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-liquid separation method and a solid-liquid separation apparatus for undiluted liquids such as sewage, drainage, and factory water pools while rotating a filtration drum equipped with a filter medium. The present invention relates to a solid-liquid separation method and a solid-liquid separation device for washing a filter medium mounted on a rotary drum type continuous filtration device.

[0002]

2. Description of the Related Art A rotary drum type continuous filtration method and a filtration apparatus for mounting a filter medium, performing continuous filtration while washing and recovering the mounted filter medium, and improving the removal rate of solids are disclosed in 8-155220, JP-A-9-155220
No. 164305 is known. The technologies typified by these methods include intermittently washing the filter medium, appropriately forming a clogged state on the surface of the filter medium itself by the solid matter captured on the filter medium, and improving the removal rate of the solid matter in the raw water. It is intended for that purpose.

[0003] However, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Publication No. 05-2005, in a system in which the filter medium is intermittently washed for a certain period of time by one or both of a surface washing means and a backwash means, the raw water state (raw water concentration, raw water viscosity, etc.) If it changes to a high level, the filter media will not be able to catch up with the clogging, and it will not be possible to obtain a stable amount of filtered water.In addition, the water level in the rotating drum will reach the set water level, and it will be necessary and sufficient to continuously clean both cleaning means. It has been found that the setting of the washing time cannot be simply determined because the setting of the washing time varies greatly depending on the operation elapsed time of the apparatus itself, the concentration of the adhering components such as slime, scale, etc., which promote the clogging of the filter medium, and the time change. did.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of performing intermittent washing in a rotary drum type continuous filtration apparatus equipped with a filter medium, whereby a stable amount of filtered water can be obtained, and the service life of the filter medium can be improved and economical. Another object of the present invention is to provide a solid-liquid separation method and a solid-liquid separation device capable of improving the solid matter separation accuracy.

[0005]

In order to achieve the above-mentioned object, a solid-liquid separation method of the present invention performs a solid-liquid separation by filtering a stock solution from the inside to the outside while rotating a filtration drum equipped with a filter medium. Inject washing water and backwash from the back of the filter media,
A solid-liquid separation method for washing a surface from the surface of a filter medium is characterized in that at least the surface washing is started and stopped according to the water level in a drum.

Further, the solid-liquid separation device of the present invention comprises a rotary filter drum equipped with a filter medium, a backwashing means for spraying washing water from the back surface of the filter medium, and a face washing means for spraying washing water from the surface of the filter medium. And a switching control means for activating and stopping at least the surface washing means in accordance with the water level in the filtration drum.

Further, in the above-mentioned solid-liquid separation device, it is preferable that at least the surface of the filter medium is provided with a napped filter layer of ultrafine fibers having a thickness in the range of 0.1 to 20 μm.

[0008] Further, it is preferable that the above-mentioned surface washing means is such that the injection nozzle is arranged at an angle such that the nap of the filter medium is opposite to the rotation direction of the filtration drum.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on one embodiment. FIG. 1 is a longitudinal sectional view showing a flowchart of one embodiment of the solid-liquid separation device of the present invention,
FIG. 2 is a cross-sectional view of FIG.

In FIG. 1 and FIG. 2, the rotary drum type filtration device 1 is partitioned by a partition wall 3 and an overflow weir 5, and a raw water tank 2, a filtration water tank 4, and a discharge tank 6 are formed. In the filtration water tank 4, a filtration drum 9 around which a filter medium 11 is mounted is rotatable by a bearing around a central pipe serving as a washing water discharge pipe 28 and a central pipe also serving as an outer pipe for passing a washing water supply pipe. Supported. The filtration drum 9 is provided with a gear 12 on one end outer periphery, and a gear 13 of a drum drive motor (not shown) is meshed with the gear 12. A sealing material 10 is provided in the filtration water tank 4 and at one end of the filtration drum 9. The sealing material 10 is in contact with the surface of the partition wall 3, so that the liquid in the raw water tank 2 and the liquid in the filtration water tank 4 are separated. And is divided. In addition, the surface of one end of the filtration drum 9 where the sealing material 10 is provided has an open structure, and the liquid in the raw water tank 2 can freely flow into the inside of the filtration drum 9. Therefore, the water level in the filtration drum 9 becomes the same level as the water level 22 of the raw water tank 2. On the other hand, the surface on the other end side of the filtration drum 9, that is, the surface on the overflow weir 5 side has a closed structure.

A backwash pipe 14 having a plurality of backwash nozzles 15 arranged in the axial direction of the drum is disposed on the upper side of the outer side of the filter drum 9. Is provided with a washing drainage receiving hopper 27. The backwash pipe 14 is connected to a backwash pipe 16 having a backwash pump 17 which opens below the liquid level of the filtered water tank 4.

On the other hand, on the upper inside of the filtration drum 9, a number of washing nozzles 19 arranged in the axial direction of the drum are provided downstream of the backwash pipe 14 in the direction of rotation of the filtration drum (the direction of the arrow in FIG. 2). A face washing pipe 18 is provided. This front washing pipe 18 is the same as the backwash pipe 14, and
Is connected to a surface cleaning pipe 20 having a surface cleaning pump 21 which opens below the liquid level. Backwash pipe 16 and front wash pipe 2
0 indicates the pressure gauges 25a and 25b and the pressure adjustment valve 26, respectively.
a and 26b are provided.

A water level detecting device 23 having a plurality of electrode rods is provided inside the raw water tank 2, and is connected to a front washing pump 21 and a back washing pump 17 via a control panel 29 by electric wiring 24. Note that the water level detecting device 23 having the plurality of electrode rods may be another device.

In order to explain the operation of the above-described embodiment of the present invention, in FIG. 1, raw water 7 'supplied from a raw water inlet 7 provided at a lower part of a raw water tank 2 of a rotary drum type filtration device 1 is shown. Is introduced into the filtration drum 9 from one end surface of the filtration drum 9 having a release structure. The introduced raw water is regulated by the partition wall 3, the sealing member 10, and the other end surface of the filtration drum 9 having a closed structure.
Accumulate inside.

On the other hand, the filtration drum 9 is rotated at a constant speed in the direction of the arrow (FIG. 2) via gears 13 and 12 by a motor (not shown), and the raw water introduced into the filtration drum 9 The liquid level passes through the filter medium 11 due to the liquid level difference h (FIG. 2) in the filtration water tank 4 defined by the partition wall 3 and the overflow weir 5, and only the liquid component flows out into the filtration water tank 4, and furthermore, the overflow weir 5, a discharge water outlet 8 of a discharge tank 6
It is discharged as effluent water 8 '. On the other hand, the solid components in the raw water captured inside the filter medium 11 eventually reach the position of the backwash pipe 14 with the rotation of the filtration drum 9, and from the backwash nozzle 15 via the pipe 16 equipped with the pump 17, The filtered water in the filtered water tank 4 is separated from the filter medium by being sprayed from the outside of the filter medium 11. Usually, the pressure used for backwashing is set to ³ to 5 kg / cm ² . At this time filter material 11
Wash effluent 28 ′ separated with the wash water that has passed through
Are discharged out of the system through the washing drain receiving hopper 27 and the washing drain outlet pipe 28.

After that, with the rotation of the filtration drum 9, it reaches the vicinity of the washing pipe 18 and traces a small amount of solid components still remaining on the surface side of the filter medium to the washing pipe 20 having the washing pump 21.
Then, it is washed by the filtered water in the filtered water tank 4 which is jetted from the washing nozzle 19 and then subjected to the next solid-liquid separation again.
Usually, the pressure used for the surface washing is set to 1-2 kg / cm ² . The reason for setting the surface washing pressure lower than the backwash pressure in this way is to prevent the surface washing spray water from passing through the filter medium 11.
This is because the filtered water quality deteriorates due to solids passing through the filter and accompanying solids.

In the present invention, in order to solve the conventional problems, the backwash and the front wash of the filter medium 11 are started and stopped according to the water level in the filtration drum 9. That is, in FIG. 1, when the water level 22 in the filtration drum reaches the predetermined low water level L, the front washing pump 21 and the backwash pump 17 are stopped. If the filtration is continued as it is, the filter medium 11 is clogged with the captured solid components, and the water level 22 in the filtration drum rises as the filtration resistance increases. When the water level reaches a predetermined high water level H, the flushing pump 21
And the backwash pump 17 is operated. Subsequently, the filtration is continued, and the clogging of the filter medium 11 can be eliminated by washing. When the water level 22 in the filtration drum reaches a predetermined low water level L, the front washing pump 21 and the back washing pump 17 are stopped as described above. By repeating such an operation, solid-liquid separation in raw water is continuously advanced.

The above operation is an example in which both the back washing and the front washing are started and stopped in accordance with the water level in the filtration drum 9. In the case of raw water having a high solids concentration, for example,
The backwashing pump 17 may be operated continuously, and the front washing pump 21 may be operated and stopped according to the water level in the filtration drum 9.

In the above-described embodiment, the filter medium 11 is preferably a fiber filter medium such as a woven fabric, a knitted fabric, or a nonwoven fabric. It is more preferable that at least the surface side (raw water supply side) of the filter medium be raised to provide a raised layer. Further, the nap is made of ultrafine fibers, and more preferably one having a single fiber diameter of 0.1 to 20 μm. By using such an ultrafine fiber, the gap between the fibers forming the nap becomes narrower, and a denser nap layer can be formed, so that the solid material separation accuracy is improved. As the material of the ultrafine fibers, synthetic fibers such as polyethylene terephthalate, polyamide, polypropylene, and polyvinylidene chloride are preferably used. The nap can be performed using a needle cloth, sand paper, sand net, steel brush, sand roll, or the like.

Next, in the case of using a fiber filter medium provided with a densely raised hair layer, the direction of the raised hair on the surface side (raw water supply side) of the filter cloth greatly affects the separation accuracy of solids in the raw water. A more preferred embodiment will be described with reference to FIG.

In a preferred method, the direction of the nap is aligned with the direction of rotation of the filtration drum 9 in the opposite direction. For this purpose, as shown in FIG. 3, the intersection of the center line of the washing nozzle 19a provided on the washing spray pipe 18a and the filter medium 11 (the point of collision 3 between the washing spray and the filter medium).
0) and a line connecting the center axis of the drum, the angle 31a (front washing nozzle angle) is set to 30 ° to 60 °, preferably 45 ° to 60 °. By doing so, the direction of the nap 11a of the filter medium is aligned in the opposite direction to the rotation direction of the filtration drum 9, which helps to improve the accuracy of separating solids.

FIG. 4 shows an example in which the washing nozzle is directed in the direction in which the nap layer is disturbed. The nap is in the same direction as the rotation direction of the filtration drum 9 as indicated by 11b, and the nap is irregular and disturbed. This is an example in which this part is undesired because it is submerged in raw water with the rotation of the drum, and the accuracy of separating solids is reduced at the stage where the filtering action is performed.

[0023]

Next, the effects of the present invention will be specifically described based on examples of the present invention. [Example 1, Comparative Example 1] First, as a filtration device for advanced sewage treatment, the first embodiment using the apparatus of the present invention, targeting the secondary treated sewage water, and the conventional high water level in the drum Table 1 shows a comparison with Comparative Example 1 in which the filter medium washing operation was performed for a certain period of time (30 minutes) after the detection, and the filter medium cleaning operation was performed.

In Example 1, the filtration apparatus of the present invention having the structure shown in FIG. 1 was used. The device used in Comparative Example 1 detects only the high water level (symbol H) of the water level detection device in FIG.
21 was used.

[0025]

[Table 1]

Target raw water: Secondary effluent from sewage Average raw water SS (suspended solids) concentration: 3.3 mg / L Target model: Trelome RDK-10A4 (Rotary drum type filtration device manufactured by Toray Industries, Inc.) fiber napped filter material throughput: as indicated in 780m ³ / d table 1, compared with Comparative example 1 (conventional apparatus), example 1 (apparatus of the present invention) in the filter medium life is increased to 1.3 times, 24% reduction in power consumption per year due to shortening of the operation time of the washing pump, and the required amount of filter medium washing water is 22
%, And the effect of the device of the present invention is clearly shown. [Examples 2 to 4] Next, comparison was made with the following apparatus for swimming pool water for swimming. Fig. 1
, The backwash pump 1 is omitted.
In the case where the type of the installed filter medium is changed by using a device in which the discharge pipe of No. 7 is branched and connected to the face washing pipe to perform face washing and back washing with one pump, and FIG. ,
Table 2 shows the results of a comparative study on the case where the spray direction of the face-wash spray was changed as shown in FIG.

[0027]

[Table 2]

Target Raw Water: Swimming Pool Water for Swimming Average Raw Water SS (Floating Solids) Concentration: 1.2 mg / L Target Model: Tolerome RD-750A3 (Rotary Drum Type Filtration Device manufactured by Toray Industries, Inc.) Fitting Filter Material: Polyester Napped filter medium using fibers Processing amount: 1500 m ³ / d From Table 2, Example 2 using a filter medium having a thickness of the napped fibers of the present invention and using a device having a structure of a face-wash spray direction of the present invention, In Example 2 and Example 3 in which a filter medium having a conventional thickness was used only for the thickness of the nap fiber, the difference in the voids formed in the filter medium appears as a difference in the SS removal rate. This shows that Example 2 was able to improve the SS removal rate by 29% compared to Example 3.

On the other hand, in comparison between Example 2 and Example 4 in which only the direction of the spray nozzle was reversed (shown in FIG. 4), Example 2 had the same SS removal rate as Example 4 but had the same SS removal rate. 23% has been improved.

As described above, the extremely fine nap fibers (5.2 thickness)
μm), the effect of improving the SS rejection by a device equipped with a filter medium, and the direction of the face-washing spray nozzle "to align the napped portion in the direction opposite to the rotation direction of the filtration drum"
Thus, the effect of improving the rejection rate is clear.

[0031]

According to the present invention, the following advantages can be obtained by adopting the above-mentioned structure.

Since the washing of the filter medium of the rotary drum type filtration device equipped with the filter medium is started and stopped according to the water level of the filtration drum corresponding to the clogging of the filter medium, it is possible to substantially clean the filter medium required. It became. That is, conventionally, regarding the recovery of clogging due to intermittent cleaning of the filter media, when the back material after the stop of the cleaning device gradually clogs and the water level in the filtration drum reaches a high water level, regardless of the strength of the clogging of the filter media. The cleaning operation was performed for a certain period of time, and extra cleaning was performed far beyond the time required for clogging recovery.In the present invention, however, the cleaning device is operated from a predetermined high water level in the filtration drum to a predetermined low water level. By operating only during the water level period, necessary and sufficient operation of the cleaning device became possible.

In other words, the present invention makes it possible to eliminate the conventional excessive washing time of the filter medium. The first effect is that the life of the filter medium is improved by applying only the minimum necessary impact force for cleaning the filter medium. Second, the excess power consumption of the cleaning pump has been reduced. Third, cleaning water used for cleaning can be saved. Furthermore, with this, the amount of washing wastewater after washing the filter media can be reduced, and at the same time the concentration of washing wastewater can be maintained at a high concentration. When the washing wastewater is concentrated in the next process and collected as a dewatered cake, the treatment process is greatly shortened. That is, each effect such as being able to be exhibited.

Further, in the case where the filtering treatment is continued for a long period of several months for ponds and lakes and marshes where the seasonal fluctuations are intense, when the clogging component is difficult to peel off from the filter material in seasons, When slime is generated on the surface of the filter medium, etc., clogging of the filter medium could not be recovered only by operating the washing time for a certain time as in the conventional method, but in the present invention, the water level in the filtration drum is set to the lower limit. By continuously operating up to the value, clogging could be recovered for the first time, and a stable amount of treated water could be secured.

As described above, according to the present invention, the washing of the filter medium can be arbitrarily changed according to the magnitude of the solid matter concentration of the raw water and the difficulty of detachability of the solid matter attached to the filter medium from the filter medium. This makes it possible to greatly facilitate the operation and maintenance of the rotary drum type filtration device equipped with the filter medium.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a filtration method and a filtration device of the present invention.

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is a view showing a relative state between a direction of spray water for front washing and a direction of napped filter cloth, which is a preferred example of the present invention.

FIG. 4 is a view showing a case where the direction of the spray water for washing the face is reversed in FIG. 3;

[Explanation of symbols]

 1: Rotary drum type filtration device 2: Raw water tank 3: Partition wall 4: Filtration water tank 5: Overflow weir 6: Discharge tank 7: Raw water inlet 7 ': Raw water 8: Discharge water outlet 8': Discharge water 9: Filtration drum 10: Seal material 11: Filter media 11a, 11b: Napped filter media 12: Gear (filtration drum side) 13: Gear (motor side) 14: Backwash pipe 15: Backwash nozzle 16: Backwash pipe 17: Backwash pump 18 , 18a, 18b: washing pipe 19, 19a, 19b: washing nozzle 20: washing pipe 21: washing pump 22: water level in filtration drum (same as water level in raw water tank) 23: water level detector 24: electric wiring 25a, 25b: Pressure gauges 26a, 26b: Adjustment valve 27: Cleaning drainage receiving hopper 28: Cleaning drainage outflow pipe 28 ': Cleaning drainage water 29: Control panel 30: Filter medium collision point of front cleaning spray 31a, 31b: Front wash nozzle angle

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroyasu Kato 1-1-1, Sonoyama, Otsu-shi, Shiga F-term in the Shiga Plant of Toray Industries (reference) 4D026 BA01 BB01 BC24 BC26 BC30 BD09 BF06 BF09 BF18

Claims (5)

[Claims] 1. A stock solution is filtered from the inside to the outside while rotating a filtration drum on which a filter medium is mounted, solid-liquid separation is performed, washing water is sprayed to backwash the back side of the filter medium, and the front side of the filter medium is washed. A solid-liquid separation method, wherein at least the surface washing is started and stopped according to the water level in the drum. 2. A rotary filtration drum equipped with a filter medium, a backwashing means for injecting washing water from the back surface of the filter medium, a face washing means for injecting washing water from the front side of the filter medium, and at least the surface washing means in the filtration drum. A solid-liquid separation device comprising switching control means for operating and stopping according to the water level. 3. A filter medium having a thickness of at least 0.1 to at least a surface.
The solid-liquid separation device according to claim 2, wherein a nap filter layer of ultrafine fibers in a range of 20 µm is formed. 4. The surface washing means according to claim 2, wherein the spray nozzle is disposed at an angle such that the nap of the filter medium is opposite to the rotation direction of the filtration drum. Solid-liquid separator. 5. A method for producing fresh water, comprising using the solid-liquid separation method according to claim 1 or the solid-liquid separation apparatus according to any one of claims 2 to 4.