JPS62279807A - Concentrator of liquid - Google Patents

Abstract

PURPOSE:To reduce the pollution of a membrane surface and to effectively wash the polluted membrane surface by providing a plurality of membrane modules containing many discoid membranes to a hollow rotary shaft and independently changing over both a flowing process of liquid to be treated and a washing process of the discoid membranes. CONSTITUTION:The following a plurality of membrane separation means 20 are parallel provided in which a membrane module 36 parallel fitted with a plurality of discoid membranes 40 to a hollow rotary shaft 38 is housed in a cylindrical case 32. Liquid to be treated such as organic waste water subjected to activated sludge treatment in an aeration tank 10 is distributed and fed to the membrane separation means 20 and also the rotary shafts 38 are rotated by rotary driving sources 44. The permeation liquid permeated through the rotating discoid membranes 40 is collected in the hollow parts of the rotary shafts 38 and discharged through ducts 52. Concentrates high in the concn. of sludge are returned to the aeration tank 10 through branched pipes 26 for outflow and a conduit 22. Solid material stuck on the membrane surfaces is made easily peelable by the rotation of the membranes 40 and the pollution of the membrane surfaces is reduced. Further even when the membranes are polluted, the polluted membrane separation means 20 can be independently washed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a liquid concentrating device using membrane separation means,
In particular, the present invention relates to a liquid concentrator suitable for treating organic wastewater with activated sludge.

The organic substances in the wastewater were aerobically oxidized and decomposed by the action of activated sludge. The treated wastewater is sent to the next settling tank along with the floating activated sludge, and the supernatant water from the settling tank is discharged as treated water. A portion of the precipitated activated sludge was returned to the aeration tank to maintain a constant sludge concentration in the aeration tank, and the rest was disposed of as surplus sludge. The higher the concentration of activated sludge in the aeration tank, the higher the BOD load can be, and the efficiency of wastewater treatment is improved.

However, in the next stage settling tank, if the sludge concentration of the inflowing wastewater (which is almost the same as the sludge concentration in the aeration tank) is high, the sludge will not settle sufficiently within the specified retention time, and the supernatant water that should be discharged will A large amount of sludge will be mixed in. For this reason, it is necessary to significantly increase the capacity of the sedimentation tank or to filter the supernatant water using a separate filtration means, but in both cases it has been generally accepted that the amount of water in the apparatus should be maintained at around 5000 mg/ml.

However, in recent years, there has been a growing trend to reconsider activated sludge treatment, and in particular, effective ways to omit settling tanks, which require a huge amount of land, are being sought. If the sedimentation treatment is omitted, the sludge concentration in the aeration tank can be greatly increased as described above, and the wastewater treatment efficiency can be significantly improved. As one such attempt, it has been proposed to directly filter or membrane-separate the wastewater treated in the aeration tank in which activated sludge is suspended in the aeration tank, and to discharge only the permeate to the outside of the aeration tank. ing. In addition, as another attempt, it has been proposed to condense similar wastewater outside the aeration tank by filtration or membrane separation without passing through a settling tank, return the concentrated water to the aeration tank, and discharge the permeate. . However, in all of these methods, sludge adheres and accumulates on the membrane surface, resulting in a rapid decrease in the amount of permeate (a problem that the invention seeks to solve). The technical issues in processing are common to liquid concentrators using membrane 5+ separation means, and are to eliminate contamination of the membrane surface as much as possible, and to remove the contaminated membrane surface quickly and without interfering with other operations. The reality is that no effective means of cleaning has been found.

The purpose of the present invention is to solve the above-mentioned problems of the prior art, and to reduce the amount of contamination of the membrane surface in the membrane separation means. Our goal is to provide the following.

[Means for solving problems]

This invention includes a storage tank equipped with an inlet for the liquid to be treated, a liquid to be treated extracted from the storage tank, which is distributed to a plurality of membrane separation means, and a liquid to be treated concentrated by the membrane separation means is returned to the storage tank for circulation. The structure is such that a mock module is housed in the concentration circulation system, and the permeated liquid from the disk membrane is discharged to the outside of the apparatus via the hollow part of the hollow rotating shaft, and each of the membrane separation means to be treated is It is characterized in that the liquid passing process and the disc membrane cleaning process can be switched independently.

[For production]

The membrane separation means according to the present invention rotates a hollow rotating shaft in which a large number of disc membranes are arranged in parallel in a cylindrical case filled with a liquid to be treated, and the permeate from the disc membranes is passed through the hollow shaft. It is discharged outside the device via the hollow part of the rotating shaft. The solid content in the liquid to be treated that adheres to the surface of the disc membrane is easily peeled off by the rotation of the disc membrane. Therefore, the membrane surface is less likely to be contaminated by adhesion and accumulation of solid matter. Furthermore, since the concentration polarization of the solute at the membrane surface can be suppressed, the membrane separation means can be individually cleaned even if the disc membrane becomes contaminated because it is permeated. Therefore, the concentration operation can be performed continuously without stopping the apparatus.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is an apparatus system diagram of an embodiment in which the present invention is applied to activated sludge treatment of organic wastewater. The storage tank 10 is equipped with an organic wastewater inflow pipe 12 and an aeration means 14, and functions as an aeration tank. The storage tank 10 has a pipeline 1 for circulating the liquid to be treated.
6 is provided, and a pump 1 is provided in the middle of this pipe line 16.
8, the liquid to be treated is distributed to a plurality of membrane separation means 20.

The liquids to be treated that have passed through each membrane separation means 20 are returned to the storage tank 10 through the conduit 22 after joining together. Each membrane separation means 20
The branch pipe 24 for inflow of the liquid to be treated and the membrane separation means 20 are connected to the second
As shown in the figure, both ends of the cylindrical case 320 are connected to the flanges 3
4, and a membrane module 36 is housed inside.

The membrane module 36 has a plurality of disk membranes 40 on a hollow rotating shaft 38.
One end is connected to an external rotational drive source 44 via a shaft seal 42 from the flange 34. In addition, in the figure, 46 means a bearing, and 48 means a shaft coupling. Also, the other end of the hollow rotating @38 is connected to an external rotary pipe joint 50 via the shaft seal 42 from the flange 34.
This pipe joint 50 is connected to a pipe line 5 equipped with a gate valve 54.
Connect to 2.

Returning to FIG. 1, reference numeral 56 is a storage tank for cleaning liquid for cleaning the membrane surface, and the cleaning liquid in the cleaning liquid storage tank 56 is supplied to each of the membrane separation means 20 by a pump 60 in the middle of the pipe line 58. The cleaning liquid that has passed through the membrane separation means 20 is sent to the pipe 6.
2 is returned to the cleaning liquid storage tank 56 so that it can be circulated. A switching valve 68 is provided in each membrane and outflow branch pipe 66.
and 70 are the specifications.

In the above configuration, first, organic wastewater is injected into the storage tank 10 from the inflow pipe 12, seed sludge is introduced, and the wastewater in the storage tank 10 is aerated by the aeration means 14. The input seed sludge oxidizes and decomposes the organic substances in the wastewater under aerobic conditions through aeration, thereby purifying the wastewater, and the sludge multiplies using the organic substances as a nutrient source. If the injection of wastewater continues, it is necessary to discharge purified wastewater out of the storage tank in proportion to the amount of injection.

For this purpose, the pump 18 is operated to distribute and supply the liquid to be treated to each membrane separation means 20. The liquid to be treated that is supplied to each membrane separation means 20 through the inflow branch pipe 24 and the switching valve 28 passes through the rotating disc membrane 40 while passing through the case 32.
As a result, the permeate is separated and discharged from the membrane separation means in a concentrated state with a high sludge concentration. It is collected in the hollow part of and is discharged from the apparatus through the pipe line 52. This permeated liquid is obtained by separating the wastewater purified in the storage tank 10 using a membrane, and is therefore sufficiently clear and can be discharged as is or reused as water for use. By repeating the above-described circulation of the liquid to be treated to the membrane separation means 20, the sludge concentration of the liquid to be treated in the storage tank 10 gradually increases. Therefore, the oxidative decomposition of organic substances in the wastewater, which is the liquid to be treated, becomes active. In other words, the efficiency of wastewater treatment is significantly improved. In the membrane separation means 20, the sludge concentration is 10
000 to 30,000 η/l is to be membrane-separated, and it is a shame that the sludge will adhere to the membrane surface of the disc membrane 40, but since the disc membrane 40 is rotating, , a shearing force acts between the disk membrane surface and the liquid to be treated,
The attached sludge is easily peeled off from the membrane surface. Furthermore, concentration polarization of solutes on the membrane surface can be suppressed. Therefore, the disk membranes of the plurality of membrane separation means 20 are individually cleaned. In this cleaning step, first, in any one of the plurality of membrane separation means 20, the switching valve 28, 30 and the gate valve 54 are closed, and then the drain valve 72 of the membrane separation means 20 shown in FIG. The pent valve 74 is opened, and the liquid to be treated in the case 32 is discharged from the drain valve 72. Thereafter, after closing the drain valve 72 and pent valve 74, the switching valves 68 and 70 connected to the cleaning liquid storage tank 56 are opened.
The cleaning liquid is circulated within the case 32 by operating the pump 60. Through this circulation of the cleaning liquid, the membrane surface of the disc membrane 40 is cleaned, and the desired amount of permeated liquid is restored. Then,
After the cleaning liquid in the case 32 is discharged by operating each switching valve in the reverse order to that described above, the process moves to the process of passing the liquid to be treated.

By performing the switching operation between the liquid passing step and the washing step independently for each membrane separation means, most of the membrane separation means can be operated as the liquid passing step for the liquid to be treated. Activated sludge grows more than necessary using the sludge as a nutrient source.

Therefore, when the sludge concentration exceeds a certain value, the gate valve 76 is opened and excess sludge is drawn out from the pipe line 78.

Since the membrane separation means requires driving pressure for membrane separation, the lift of the pump 18 is selected to be sufficiently high, and the branch pipe 26 for outflowing the liquid to be treated is provided with a throttle valve or By making the switching valve 30 a valve with a throttling function, the liquid to be treated in the case 32 is maintained within a desired pressure range.

In addition, in the membrane separation means shown in FIG. 2, the liquid to be treated that flows in from the inflow branch pipe 24 does not come into sufficient contact with the disc membrane 40, and instead contacts the inner surface of the case 32 and the outer peripheral edge of the disc membrane 40. There is a disadvantage that it passes through the case 32 by bypassing the gap between the two. In order to eliminate this drawback, for example, as shown in FIG.
Install as a slope. In addition, the disk membrane 40 serving as the inlet 80 for the liquid to be treated stirs the liquid to be treated in the case 32, and the liquid to be treated that has flowed into the case easily flows along the membrane surface of the disk membrane 40. Therefore, there is sufficient contact between the liquid to be treated and the disc membrane.

As shown in FIG. 4, another configuration for solving the above-mentioned drawbacks is to provide a flow path forming member 84 for the liquid to be treated, which is inscribed in the case 32. This member 84 has an elastic body 88 attached to the outside of the cylindrical body 86 all around or partially, and
Inside the disk membrane 40, disks 90 having a center hole are arranged in parallel with the same pinch as the parallel pitch of the disk membranes 40. This member 84
After the disks 90 and the disk membranes 40 are assembled with the membrane module 36 so as to be positioned alternately, they are inserted into the case 32 from one open end of the case 32 (the right side in FIG. 4). During insertion, the elastic body 88 attached to the outside of the cylindrical body 86 is compressed, brought into close contact with the inner surface of the case 32, and pushed to the stopper 92 position. When the liquid to be treated is supplied from the inflow branch pipe 24 to the member 84 and the membrane module membrane separation means 20, the liquid to be treated meander through the gap between the disc membrane 40 and the disc 90 and advance through the case 32. become,
The contact between the liquid to be treated and the disc membrane 40 becomes sufficient.

FIG. 5 shows a modification of the membrane separation means 20. In this example, the cross section of the case 32 is made into a 1' circular shape, and this case 3
2, two membrane modules 36 are attached to each disk membrane 4.
Store them so that the 0's interlock with each other alternately. By rotating each membrane module in the same direction, collapse of the liquid to be treated is promoted in the region 9.1 where the disc membranes 40 intersect, and the disc membranes 4
0 and the liquid to be treated come into good contact.

Further, since the solid f+ attached to the membrane surface of the disc membrane 40 is easily peeled off in this region 94, the membrane surface can be kept clean at all times. To avoid this, the frequency of the cleaning process can be reduced.

The membrane separation module 36 according to the present invention is removed from the case 20 and repaired or replaced when the membrane separation function is significantly degraded due to damage to a part of the disk membrane 40 due to case operation.

The cleaning process according to the present invention is not limited to the method explained based on the broom 1 diagram. For example, as shown in FIG.
6 may be connected, and in the cleaning process, the switching valve 98 provided in this pipe line 96 may be opened to allow the cleaning liquid to flow into the membrane module 36.

The cleaning liquid is supplied to the inside of the disk membrane 40 from the pipe line 96 through the pipe line 52 and the hollow rotating shaft 38, and permeates through the membrane surface while backwashing the membrane surface of the disk membrane 40 from the inside to the outside. . The cleaning liquid that has passed through the membrane surface and reached the inside of the case 32 is extracted from a pipe (not shown) and is circulated and used as necessary. According to this embodiment, since the cleaning liquid acts to backwash the membrane surface,
The cleaning effect is further improved. The cleaning process is performed by combining the cleaning described in FIG. 1 and the backwashing described above.
The figure shows the configuration of a disc membrane 40 suitable for backwashing.

As shown in FIG. 7(A), the disc membrane 40 is made by pasting a membrane material 1.02 such as a UF membrane or a reverse osmosis membrane on a porous substrate 100, and has a small hole in the hollow rotating shaft 38. hole 10
Spacer 106 so that the center of substrate lOO coincides with 4.
Positioned by The disc membrane 40 and the spacer 106 are tightened together via the O-ring 108 by a pressing mechanism (not shown) to form a liquid seal. The permeated liquid that has passed through the membrane material 102 passes through the porous portion of the substrate 100, reaches the small hole 104 of the hollow rotating shaft 38, reaches the hollow part of the hollow rotating shaft 38, and is discharged outside the apparatus as described above.

The film material 102 is attached to the substrate 100 using adhesive only in the necessary parts.
Paste it on. Therefore, when reverse pressure is applied, that is, during backwashing, it expands, separates from the substrate 100, and is likely to burst. For this reason, as shown in FIG.
By using 0, the expansion of the membrane material 102 can be minimized and it will not burst. Instead of stretching the threads 112, the surface of the membrane material 102 may be covered with a wire mesh.

FIG. 8 shows another embodiment of the present invention. In this embodiment, six membranes 5+separating means 2o are installed, and three of these six units are divided into blocks to form a two-block membrane separation system. Collection pipe 114 for permeate of each block
are each provided with a flow meter 116 and a concentration meter 118 for the permeate, and when at least one membrane separation means in each block is in the process of passing the liquid to be treated, the flow rate of the permeate is measured. and concentration are detected constantly or intermittently. If the Rt of the permeated liquid is below a predetermined reference value depending on the number of membrane separation means 20 in operation, it indicates that the amount of permeated liquid in at least one membrane separation means has decreased. It can be determined that a failure has occurred in the membrane separation function due to damage to the membrane surface, etc., if each membrane separation means is individually cleaned by using an appropriate method and connected to a cleaning system (not shown). Therefore, the membrane separation means is fixed by an appropriate method and its operation is stopped.

Next, the membrane module is inspected and repaired. According to this embodiment, a plurality of membrane separation means 20 in a block are equipped with a sensor that detects the flow rate and concentration of a common permeate, and the operational performance of the membrane separation means for each block can be monitored based on the signal from this sensor. Therefore, it is possible to monitor a large number of membrane separation means, switch operating processes, inspect, and repair relatively easily with a minimum number of sensors.

In the above embodiments, artificial sampling may be performed instead of the sensor.

The present invention is applicable not only to activated sludge treatment of organic wastewater but also to general liquid concentrators. Further, the membrane separation means need not be arranged horizontally, but may be arranged inclined or vertically.

〔Effect of the invention〕 [Brief explanation of the drawing]

Fig. 1 is a device system showing an embodiment of the present invention, Fig. 2 is a side sectional view showing an embodiment of the membrane separation means according to the invention, and Figs. 3 to 5 are modified examples of the membrane separation means. An explanatory diagram showing
FIG. 6 is an explanatory diagram when backwashing the membrane separation means, and FIG. 7 is a diagram showing the structure of the disc membrane maintained in the present invention, (a) is a side sectional view, middle) is a front view, FIG. 8 is an apparatus system diagram showing another embodiment of the present invention. IO...Storage tank, 12...Inflow pipe 16
...Circulation pipe line, 18...Pump 20...Membrane separation means, 22...(Concentrate return) pipe line 28
．． 30...Switching valve, 32...Case 36...
38... Hollow rotating shaft 40... Disc membrane, 44... Rotating drive source 56... Cleaning liquid storage tank, 60... Pump Fig. 1 Fig. 2 Fig. 4 Fig. 5

Claims (2)

[Claims] (1) A storage tank equipped with an inlet for the liquid to be treated, and the liquid to be treated extracted from this storage tank is distributed to a plurality of membrane separation means, and the liquid to be treated concentrated by the membrane separation means is returned and circulated to the storage tank. In a liquid concentrating device comprising a concentrating circulation system, the membrane separation means has a plurality of disk membranes mounted in parallel on a hollow rotating shaft within a cylindrical case equipped with an inlet and an outlet for the liquid to be treated. The structure is such that the membrane module is housed and the permeated liquid from the disc membrane is discharged to the outside of the apparatus through the hollow part of the hollow rotating shaft, and a plurality of membrane separation means are respectively used in the process of passing the liquid to be treated and A liquid concentrating device characterized by being able to independently switch the cleaning process of a disc membrane. (2) The liquid to be treated is organic wastewater, and the storage tank is equipped with an aeration means, and the organic substances in the liquid to be treated are oxidized and decomposed by activated sludge grown in the storage tank. Claim No. (1) characterized in that
A device for concentrating liquids as described in Section.