JP3391498B2 - Gravity filtration device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gravity filter for filtering and purifying clean water, sewage, industrial water, and other liquids. 2. Description of the Related Art Generally, in a gravity filtration apparatus, a filter medium layer having an increased filtration resistance due to accumulation of turbid matter trapped during filtration is backwashed. Air washing is performed in which air is injected from the lower part of the bed to flow and stir the filter medium bed. [0003] Prior to washing the filter medium layer with air, unless the water level in the tank is sufficiently lowered beforehand from the upper end of the backwash drainage gutter, the water surface expands due to the air injected from the lower part and becomes a fluid state. The filter media overflows into the backwash drain gutter, causing loss of the filter media. For that purpose, a mechanical and electrical control device was attached to the filtration device, and a special operation for lowering the water level in the tank was performed. Further, in order to make such a control device and operation as simple as possible, as shown in Japanese Utility Model Publication No. 60-22964, a drain valve is provided on a side wall between a backwash drainage gutter and a filter medium layer. One that opens an intermediate drain pipe has also been proposed. [0005] However, in order to lower the water level in the tank sufficiently below the backwash drain gutter, for example, when anthracite or activated carbon is used for the filter medium, it is about 200 mm or less from the surface of the filter medium layer. When an intermediate drain pipe is opened on the side wall of the tank, horizontal flow (lateral flow) occurs due to outflow of water in the tank.
Due to this horizontal flow, the filter medium located on the surface of the filter medium layer begins to fluidize, and the filter medium flows out of the intermediate drain pipe. Will be leaked. In order to prevent such outflow of the filter medium, Japanese Utility Model Laid-Open No. Sho 61-155509 and Japanese Utility Model Laid-Open No. Sho 60-112312 have been proposed.
No., a drainage channel with an inclined surface
No.5009) or inclined drain pipe (Jpn.
No. 2312). However, those described in the above-mentioned publications are merely designed to prevent the outflow of the filter medium at the inclined portion (slope or pipe) and to return the filter medium to the filter medium layer. Therefore, there is a problem that the filter medium flows out depending on the flow rate. This tendency is particularly noticeable in light filter media. The present invention has been made in view of the above-mentioned circumstances, and it is possible to sufficiently lower the water level without draining out a filter medium when draining water in a tank by an intermediate drain pipe prior to the air cleaning. It is an object to provide a gravity filtration device. [0008] In order to achieve the above-mentioned object, the present invention relates to a gravity type filtration device having an intermediate drainage pipe opened between a backwash drainage gutter in a tank and a filter medium layer. an opening having a wider opening area than the opening of the intermediate discharge pipe consecutively provided to the intermediate discharge pipe, only <br/> setting a plurality of inclined plates or inclined tube into the opening, the plurality of inclined plate or inclined Inclination of pipe from horizontal plane
The angle is set in the range of 40 ° to 80 ° . According to the present invention having the above-mentioned structure, prior to air cleaning, when water in the tank is discharged from the intermediate drain pipe to the outside of the tank in order to lower the water level in the tank from the backwash drain gutter, the opening of the intermediate drain pipe is opened. Since the inclined plate or inclined pipe is installed in the continuous opening, the lateral flow phenomenon near the surface layer of the filter medium layer is extremely reduced, and the filter medium in the drainage flowing from the opening is It is separated by the deceleration of the apparent average flow velocity, falls along the inclined surface, and finally returns to the filter medium layer. The wastewater from which the filter media has been separated in this way flows out of the system through the intermediate drainage pipe,
The prevention of the outflow of the filter medium is effectively performed. Further, in addition to the inclined plate or the inclined pipe, the drainage of the opening having an opening area larger than the opening of the intermediate drainage pipe can reduce the drainage of the filter medium more effectively. As described above, by setting the opening of the intermediate drain pipe, in the filter medium layer of anthracite or activated carbon, even if the opening surface is reduced to a distance of about 50 mm from the surface of the filter medium layer, the effect of preventing the filter medium from flowing out is obtained. is there. An embodiment of a gravity filter according to the present invention will be described below with reference to the drawings. FIG. 1 is a view showing the overall configuration of a filtration device. In FIG. 1, the inside of a tank 1 is partitioned by a vertical partition wall 2 into a filtration chamber 3 and a drainage channel 4, and filtered water is collected at the bottom of the filtration chamber 3. A collecting water chamber 5 is formed. And anthracite, sand,
A filter medium layer 6 filled with activated carbon or another filter medium is supported, and a backwash drainage gutter 7 is provided above the filter medium layer 6, and one end thereof is connected to the drainage ditch 4. A filtered water outflow pipe and a backwash water pipe 8 are connected to the water collecting chamber 5 of the filtration chamber 3.
Is provided with a filtered water outflow valve 9 and a backwash valve 10, and further connected to the water collecting chamber 5 is an air inflow pipe 12 provided with an air valve 11 for air cleaning. Further, a backwash drain pipe 14 having a backwash drain valve 13 is connected to the culvert 4. An intermediate drainage pipe 15 composed of a siphon pipe is disposed across the vertical partition wall 2. One end of the intermediate drainage pipe 15 is provided between the backwash drainage gutter 7 in the filtration chamber 3 and the filter medium layer 6. And the other end is opened and drained in the culvert 4. As shown in detail in FIG. 2, an opening 16 having an opening area larger than the opening 15 a is provided continuously with the opening 15 a of the intermediate water distribution pipe 15. Flat inclined plates 17 are arranged. The inclination angle (θ) of the inclined plate 17 from the horizontal plane is set in the range of 40 ° to 80 °, and is preferably set to 60 °. Further, the intermediate drain pipe 15
Is connected to a vacuum pump 20 via a siphon vacuum valve 19, and a siphon vacuum tube 18 is connected to the top of the siphon vacuum tube 18.
Is provided with a siphon break valve 21. Reference numeral 22 denotes a water level electrode. Next, the operation of the gravity-type filtration device configured as described above will be described. During filtration, the raw water introduced into the tank 1 passes downward through the filter medium layer 6 due to gravity, and during this time, turbidity in the raw water is captured. It flows out through the water pipe 8. As the filtration is continued, the filtration resistance of the filter medium layer 6 increases due to the accumulation of the trapped turbidity. When the resistance reaches a predetermined resistance value, the filter medium layer 6 is backwashed. In backwashing, the introduction of raw water is stopped,
First, in order to lower the water level in the tank sufficiently below the backwash drain gutter 7,
The water in the tank is discharged to the outside from the backwash drainage pipe 14 via the intermediate drainage pipe 15 by the siphon action. When the tank water flows into the opening 16 connected to the intermediate drain pipe 15, the filter medium particles P contained in the drain water advance toward the inclined plate 17 as shown in FIG. That is, assuming that the flow velocity of the intermediate wastewater in the opening 16 is Vt and the sedimentation velocity of the filter medium particles P is Vs, the filter medium particles P are inclined at a traveling speed Vo obtained by combining Vt and Vs.
Proceed towards 7. And the filter medium particles P are inclined plate 1
After abutment with the filter 7, it sinks down along the inclined plate 17 and finally returns to the filter medium tank 6. That is, the inclined plate 17 installed in the opening 16
By this, the apparent average flow velocity of the intermediate wastewater is reduced, so that the outflow of the filter medium out of the tank is prevented. In addition, since the opening 16 has an opening area larger than the opening 15a of the intermediate drain pipe 15,
The flow rate of the intermediate drainage flowing through the opening 16 is slower than that in the intermediate drainage pipe 15. Therefore, the above-mentioned average flow velocity Vt of the intermediate drainage is smaller than the average flow velocity in the intermediate drainage pipe 15, and from this point, the outflow of the filter medium out of the tank is also prevented. As described above, according to the present invention, the filter medium outflow preventing action by decelerating the apparent average outflow of the intermediate drainage by the inclined plate 17 and the opening 16 having an opening area larger than the opening 15 a of the intermediate drainage pipe 15. Therefore, a synergistic effect of the filter medium outflow preventing action by reducing the average flow velocity can be expected, and outflow can be prevented even with a light filter medium. After the drainage from the intermediate drain pipe 15 is completed as described above, the siphon is broken, air is injected into the water collecting chamber 5 from the air inlet pipe 12, and the filter medium layer 6 is flow-stirred and captured. Exfoliate suspended matter. During this time, the flowing filter medium does not overflow into the backwash drainage gutter 7 because the water level in the tank is sufficiently lowered. Next, while continuing press-in of the air from the air inlet pipe 12, washing water is introduced from the backwash valve 10 into the collecting chamber 5 through the filtered water outlet pipe and the backwash water pipe 8, and the air and water are simultaneously injected. After the cleaning, the press-in of the air from the air inflow pipe 12 is stopped to perform water cleaning to wash the filter medium layer 6, and the backwash drainage together with the separated turbidity is sent to the backwash drainage gutter 7. It overflows and is discharged to the outside from the backwash drainage pipe 14 through the drainage channel 4. After the filter medium layer 6 is backwashed for a predetermined time in this way, the filtration operation is restarted. FIG. 4 shows another embodiment of the present invention, in which the opening connected to the intermediate drain pipe 15 is a substantially frustoconical opening, and a concentric inclined plate is installed in this opening. Things. FIG. 4A is a sectional view of the opening, and FIG. 4B is a bottom view. As shown in FIG. 4, a substantially frustum-shaped opening 26 is continuously provided at the opening 15 a of the intermediate drain pipe 15, and a plurality of inclined plates 27 are arranged in a circular shape at the opening 26. . The inclination angle (θ) of the inclined plate 27 is set similarly to the inclined plate 17 of FIG. The center 26 of the opening 26
a is a dead zone. The operation and effect of this embodiment are the same as those of the first embodiment shown in FIG. FIG. 5 shows still another embodiment of the present invention, and FIGS. 5 (a) and 5 (b) are views of the opening viewed from the bottom. Is installed. In the embodiment shown in FIG. 5A, a large number of inclined tubes 37 having a square cross section are provided in the opening 36 in a lattice shape. In the embodiment shown in FIG.
A large number of inclined tubes 47 having a hexagonal cross section are installed in the opening 46 in a honeycomb shape. The inclination angles (θ) of the inclined tubes 37 and 47 are set in the same manner as the inclined plate 17 of FIG. By arranging the inclined pipes 37 or 47 in the openings 36 or 46 in this manner, the same operation and effects as those of the inclined plates 17 and 27 shown in FIGS. Can be expected. As described above, according to the present invention, the water level in the tank can be sufficiently lowered from the upper end of the backwash drainage gutter prior to the air cleaning of the filter medium layer, and the outflow of the filter medium can be achieved. Can be effectively prevented, and air cleaning can be performed without any trouble.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing one embodiment of a gravity filtration device according to the present invention. FIG. 2 is a sectional view showing an opening connected to an intermediate drain pipe in the gravity filtration device according to the present invention. FIG. 3 is an explanatory view showing the operation of the gravity filtration device according to the present invention. FIG. 4 is a view showing another embodiment of the gravity filtration device of the present invention, wherein FIG. 4 (a) is a sectional view and FIG. 4 (b) is a bottom view. FIG. 5 is a bottom view showing still another embodiment of the present invention;
FIG. 5A shows an example in which inclined tubes are arranged in a grid pattern, and FIG.
Is an example in which inclined tubes are arranged in a honeycomb shape. [Description of Signs] 1 tank 2 vertical partition wall 3 filtration room 4 drainage ditch 5 water collection room 6 filter medium layer 7 backwash drainage gutter 8 filtered water outflow pipe and backwash water pipe 9 filtered water outflow valve 10 backwash valve 11 air valve 12 Air inflow pipe 13 Backwash drain valve 14 Backwash drain pipe 15 Intermediate drain pipe 16, 26, 36, 46 Opening 17, 27 Inclined plate 18 Siphon vacuum pipe 19 Siphon vacuum valve 20 Vacuum pump 37, 47 Incline pipe

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 24/46 B01D 24/02 B01D 29/62

Claims (1)

(57) [Claim 1] In a gravity filtration device having an intermediate drainage pipe opened between a backwash drainage gutter and a filter medium layer in a tank, an opening of the intermediate drainage pipe is provided in the intermediate drainage pipe. consecutively provided an opening having a wider opening area than, <br/> set only a plurality of inclined plates or inclined tube into the opening, the inclination of the horizontal plane of the plurality of inclined plate or inclined tube
A gravity filtration device, wherein the angle is set within a range of 40 ° to 80 ° .