JPH06170127A - Method for filtering treatment of original water and its apparatus - Google Patents

Abstract

PURPOSE:To make clogging of a filter material hardly occur and to apply directly filtering treatment without performing pretreatment even when the concn. of suspending substances in an original water is high by making the amt. of the floating substances caught by the filter material decrease remarkably. CONSTITUTION:A filtering container 2 wherein sands 3 and 4 are placed in the lower part and a space 6 is formed in the upper part is used and an original water W1 contg. suspending substance SS and a power water W4 wherein a large amt. of air is dissolved under pressure are fed in the space so as to mix both waters and majority of the suspending substance SS in the original water W1 is caught with a number of air bubbles A coming out from the power water W1. Then, the suspending substance SS with the air bubbles A is floated and separated on the uppermost part of the filtering container 2 and the original water wherein the amt. of susbending substance SS is decreased by floating and suspending is passed though the sands 3 and 4 to make the remaining suspending substance SS is the original water W1 caught by the sands 3 and 4 and the original water W1 is turned thereby into a clean treated water W2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing suspended solids contained in raw water by filtration to obtain clear treated water, and an apparatus therefor. The present invention relates to a filtration treatment method and apparatus applicable even when the concentration of a substance is high.

[0002]

2. Description of the Related Art A conventional general filtering method is carried out by using a filtering apparatus 50 as shown in FIG. In other words, inside the filtration container 51 having a cylindrical closed structure,
As a filter medium, in order from the top, a small sand 52 with a particle size of 0.5 to 1.0 mm and a thickness of about 600 mm, a particle size of 2 to 3 mm and a thickness of 3
A medium-sized sand 53 of about 00 mm and a large-sized sand 54 having a particle size of 3 to 10 mm and a thickness of about 300 mm are laminated, and a small stone 70 is laid at the bottom. Further, an air vent valve 71 is provided above the filtration container 51.

Raw water W1 containing suspended solids SS supplied to a raw water tank 55 is pumped up by a raw water pump 56 and sent to a raw water injection pipe 57, a raw water injection valve 58 and an injection port member 59.
It is injected into the upper part of the filtration container 51 via. In addition, the coagulant F in the coagulant tank 60 is fed through the metering pump 6 during the water supply.
1. Add to raw water W1.

In the filter container 51, while the raw water W1 flows downward and passes through the sands 52, 53, 54, the suspended matter SS
Is first trapped on the upper surface of the small sand 52, and each sand 5
It is trapped between 2,53,54 particles. The clear treated water W2 obtained in this way passes through the treated water discharge valve 62 and the treated water discharge pipe 63 from the lower part of the filtration container 51, and is treated water tank 6
4 and is discharged from the treated water tank 64.

[0005]

However, along with the progress of the above-mentioned filtration treatment, the suspended solids S due to the sand 52, 53, 54
When the amount of captured S increases, the sand 52, 53, 54 is clogged, the flow of raw water W1 deteriorates, and the filtration container 5
The pressure in 1 rises. Therefore, it is necessary to frequently interrupt the filtration process and repeat the backwash process described below at short intervals to separate the suspended solids SS from the sands 52 to 54 and take them out of the filtration container 51.

That is, the indication of the pressure gauge 65 provided on the upper part of the filtration container 51 indicates a predetermined set value (for example, 1.0 kg / cm).
² ), the raw water injection valve 58 and the treated water discharge valve 62 are automatically closed to inject the raw water W1 and the treated water W.
Discharge of 2 stops. Subsequently, the backwash water pump 66 in the treated water tank 64 is operated, and a part of the treated water W2 is injected as backwash water W3 into the lower portion of the filtration container 51 through the backwash water valve 67 and flows backward upward. Therefore, the suspended solids SS are separated from the sands 52, 53, 54 and become concentrated sludge, which is taken out from the upper part of the filtration container 51 via the floating substance take-out valve 68 and the floating substance take-out pipe 69. Conventionally, this backwashing treatment required a treatment time of about 3 to 5 minutes and a large amount of backwashing water. After this backwashing process, the filtering process is restarted, and thereafter,
The filtering process and the backwashing process are frequently repeated.

In order to compensate for the decrease in the filtration processing speed due to the above clogging during the filtration processing, the pressure in the filtration container 51 is appropriately set within the range of 0.5 to 1.5 kg / cm ² , and the filtration is performed under high pressure. Since the treatment was performed, it was necessary to pay attention to the pressure resistance of the filtration container 51. Moreover, since it was owed only to the filtration with the sands 52, 53, 54, it was necessary to use a large amount of the sands 52, 53, 54 for reliable clarification.

Conventionally, such a filtration treatment method has been used in raw water W.
It has been considered that this method cannot be directly applied when the concentration of suspended solids SS in 1 is high. This is because when the concentration of the suspended solids SS is high, the backwashing process becomes necessary because the sand 52, 53, 54 is clogged only by performing the filtration process for only a few minutes to a dozen minutes. This is because it takes much time and is inefficient. In addition, the clogging of the sand 52, 53, 54 does not recover even if the backwashing process is performed while the filtration process and the backwashing process are repeated only a few times or a dozen times. It is very uneconomical because it needs to be replaced.

For this reason, the conventional filtration treatment method uses the raw water W
When the concentration of suspended solids in 1 is low (eg 10 mg
/ L) only was applied directly. To apply when the concentration of suspended solids is high, a purification treatment by another purification device (for example, a gravity separation device) is performed as a pre-treatment of the filtration treatment to reduce the concentration of suspended solids in advance, and then Since it was necessary to carry out a filtration process, there was a problem that the equipment became large, complicated, and expensive, and could not be easily introduced.

The object of the present invention is to solve the above problems and to significantly reduce the amount of suspended solids trapped in the filter medium to prevent clogging of the filter medium, thereby improving the filtration processing speed and reducing the amount of the filter medium used. It is possible to prolong the service life of filter media, extend the interval of backwashing, shorten the time of backwashing, reduce the amount of backwashing water used, and even when the concentration of suspended solids in the raw water is high. Revolutionary filtration that can be applied directly without any pre-treatment, and can treat this high-concentration raw water with one filtration container, which can achieve downsizing, simplification and cost reduction of equipment. It is to provide a processing method and an apparatus thereof. However, the present invention does not deny / exclude performing the pre-stage process, and may add the pre-stage process of the specific function.

[0011]

In order to achieve the above object, in the method for filtering raw water of the present invention, a filtration container having a filter medium in the lower part and a space in the upper part is used, and a suspended substance is contained. The raw water and the pressurized water in which a large amount of gas is dissolved under pressure are injected into the space of the filtration container so that both water are mixed, and most of the suspended substances in the raw water are innumerable bubbles released from the pressurized water. And float the floating material together with air bubbles to the uppermost part of the filter container, pass the raw water in which the floating material is reduced by the floating separation through the filter medium, and trap the remaining floating material in the raw water on the filter medium. As a result, the means for converting the raw water into clear treated water was adopted.

The apparatus for filtering raw water of the present invention comprises a filtration container having a filter medium in the lower portion and a space formed in the upper portion, a pressurized water producing apparatus for producing pressurized water in which a large amount of gas is dissolved under pressure, and a floating vessel. A raw water injection pipe for injecting raw water containing a substance into the space of the filtration container, and a pressurized water injection pipe for injecting the pressurized water produced by the pressurized water producing device into the space by mixing with the raw water. did.

In the present invention, "filter material" includes sand and
Granules such as activated carbon, anthracite, garnet, metal
Examples include a mesh-like body made of synthetic resin or the like, cloth, or a combination thereof. Examples of the "gas" to be dissolved in the pressurized water include air, nitrogen, carbon dioxide, or a mixture thereof, and, for example, ozone may be mixed with these to obtain a sterilizing action or a deodorizing action.

In order to mix the raw water and the pressurized water into the space of the filtration container, the following method can be exemplified. A pressurized water injection pipe is connected to a portion near the connection end of the raw water injection pipe to the filtration container, and the raw water and the pressurized water are mixed at a region near the connection end of the raw water injection pipe and then injected into the space of the filtration container. The raw water injection pipe and the pressurized water injection pipe are respectively connected to the filtration container in a predetermined positional relationship so that the raw water and the pressurized water are collisionally mixed or swirl mixed in the filtration container for the first time.

[0015]

According to the method and apparatus for filtering raw water of the present invention, when the raw water and the pressurized water are mixed and injected into the space of the filtration container, the pressure applied to the pressurized water is released. As a result, a large amount of air dissolved in the pressurized water becomes supersaturated, and is released all at once to become innumerable bubbles. Therefore, most of the suspended matter in the raw water adheres to and is trapped by the innumerable bubbles, and floats and separates at the top of the filtration container together with the bubbles, so that the suspended matter is gradually concentrated and becomes sludge-like. . The suspended matter that has become this concentrated sludge can be easily taken out from the uppermost part of the filtration container.

The raw water and the pressurized water, in which the suspended solids have been reduced by the floating separation, flow downward and pass through the filter medium. At this time, the remaining suspended solids in the raw water are captured by the filter medium, so the raw water that has passed through the filter medium becomes clear treated water. In this embodiment, most of the suspended matter can be removed by the floating separation, so that the filter medium is less likely to be clogged.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a raw water filtering method and apparatus embodying the present invention will be described below with reference to FIG.

First, the filtration apparatus 1 of the present embodiment will be described. Reference numeral 2 denotes a filtration container having a closed structure, which has a cylindrical shape in which both upper and lower ends are conically closed, and its diameter is 60.
The length is 0 mm and the length is 1000 mm. In the lower part of the filter container 2, as a filter medium, the particle size is 0.5 to 1.0 m in order from the top.
m / thickness about 200 mm, small sand 3, particle size 2-3 mm
Medium-grained sand 4 with a thickness of about 100 mm and wire mesh 5 of the 2 mm
Are stacked. As described above, in this embodiment, the use amount of the small-grain sand 3 and the medium-grain sand 4 is reduced as compared with the conventional example, and the thin wire net 5 is used instead of the large-grain sand, so that the upper surface position of the small-grain sand 3 is changed. The height is made low so that the largest space 6 is formed in the upper portion of the filtration container 2. Further, an air vent valve 7 and a pressure gauge 8 are provided above the filtration container 2.

The following raw water injection device and treated water discharge device are connected to the filtration container 2. 10 is a raw water tank for temporarily storing raw water W1 containing suspended matter SS,
The raw water W1 is pumped up by a raw water pump 11 in the tank, and is sent through a water supply pipe 12 and a water supply valve 13.
In the middle of the water pipe 12, the coagulant F supplied from the coagulant tank 14 by the metering pump 15 in a constant amount is fed into the raw water W.
Flocculant tube 16 for addition to 1 is connected to flocculant F
Therefore, the suspended solids SS in the raw water W1 are aggregated and coarsened to facilitate the capture. Examples of the coagulant F include polyaluminum chloride (PAC), other polymer coagulants, caustic soda, and the like.

The tip of the water supply pipe 12 is connected to the inlet of a cyclone-type wire netting filter 17, and when the raw water W1 which rotates and flows therein passes through the tubular wire netting 18 from the outside to the inside, a particularly large dust or floating The substance SS can be captured, and thereafter, this dust or the like can be discarded through the discard valve 19. A raw water injection pipe 20 and a raw water injection valve 21 are connected to the outlet of the wire mesh filter 17, and the tip of the raw water injection pipe 20 is an injection port formed of a multi-hole pipe horizontally arranged in the space 6 of the filtration container 2. The raw water W1 is connected to the member 22 and the space 6
It can be diffused and injected into. This inlet member 2
The shape of 2 can be changed appropriately. Further, a treated water discharge pipe 23 and a treated water discharge valve 24 for discharging the filtered treated clear treated water W2 are connected to the lower portion of the filtration container 2,
A treated water tank 25 is provided at the tip of the treated water discharge pipe 23.

Next, the following pressurized water producing device is connected to the raw water injection pipe 20 through the pressurized water injection pipe. Reference numeral 30 is a pressurized water pump, and at its inlet, a water supply pipe 31 and a water supply valve 32 for supplying a part of the treated water W2 in the treated water tank 25, and an air supply pipe 33 for supplying air.
And are connected. The pressurized water pump 30 pressurizes the supplied treated water W2 and air to dissolve a large amount of air in the treated water W2 to produce the pressurized water W4. Reference numeral 34 is a flow rate adjusting valve connected in parallel with the pressurizing pump. Reference numeral 35 is a pressurized water tank connected to the output of the pressure pump 30, and the pressure of the pressurized water W4 inside is appropriately set within the range of ^{3 to} 6 kg / cm ² . Three
Reference numerals 6 and 37 are a pressure adjusting pipe and a pressure adjusting valve for returning a part of the pressurized water W4 to the treated water tank 25 for the pressure adjustment. A pressurized water injection pipe 38 and a pressurized water injection valve 39 are connected to the outlet of the pressurized tank 35, and the tip of the pressurized water injection pipe 38 is connected to a portion of the raw water injection pipe 20 near the connection end to the injection port member 22.

Next, the following backwashing device is connected to the filtration container 2. Reference numeral 40 denotes a backwash water pump put in the treated water tank 25 so that a part of the treated water W2 can be injected as the backwash water W3 into the lower portion of the filtration container 2 through the backwash water pipe 41 and the backwash water valve 42. It has become. Reference numeral 43 denotes a backwash air pump, which is an air diffuser horizontally arranged at the boundary between the small-grain sand 3 and the medium-grain sand 4 via the backwash air pipe 44 for the backwash air B taken from the outside. It can be sent to 45 and jetted into the filtration container 2. 46 is small sand 3
Is a rotary stirring member disposed inside of the above, and is rotated at a low speed of 2 to 3 times / minute via a rotation shaft 48 thereof by a motor 47 attached to the upper portion of the filtration container 2.

Next, the following floating material extraction device is connected to the filtration container 2. Reference numeral 26 is a floating substance extraction pipe connected to the uppermost part of the filtration container 2, and the floating substance SS which has been floated and separated into concentrated sludge can be taken out to the floating substance tank 9 via the floating substance extraction valve 27 as described later. It is like this. Reference numeral 28 is a residual suspended solids extraction pipe connected to the middle of the filtration container 2, and the residual suspended solids S that are about to fall on the upper surface of the small-sized sand 3 at the end of the backwashing process as described later.
S can be taken out to the floating substance tank 9 through the residual floating substance taking-out valve 29.

The filtration treatment method of this embodiment, which is carried out by using the filtration treatment apparatus 1 having the above-mentioned structure, is as follows. (1) Filtration Treatment Step The raw water pump 11 and the metering pump 15 are operated to add the coagulant F to the pumped raw water W1 and guide the raw water W1 to the wire mesh filter 17. The raw water W1 from which dust and the like have been removed by the wire mesh filter 17 is guided to the raw water injection pipe 20.

On the other hand, the pressurized water pump 30 is operated,
As described above, pressurized water W4 in which a large amount of air is dissolved under pressure
Is manufactured and stored in the pressurized water tank 35. This pressurized water W
4 is guided to the pressurized water injection pipe 38.

The raw water W 1 and the pressurized water W 4 collide and mix in the raw water injection pipe 20 through the raw water injection valve 21 and the pressurized water injection valve 39. At this time, the pressure applied to the pressurized water W4 until then is released, so the pressurized water W4
A large amount of air dissolved in the air becomes supersaturated, and is released all at once to become innumerable bubbles. In this way, the raw water W1 and the pressurized water W4 containing innumerable bubbles are collected in the raw water injection pipe 2
It is diffused and injected into the space 6 in the filtration container 2 through the injection port member 0 and the injection port member 22.

In the raw water W 1 and the pressurized water W 4 injected into the space 6, most of the suspended matter SS aggregated and coarsened by the aggregating agent F adheres to and is captured by the innumerable bubbles A, and together with the bubbles A Since it floats and separates to the uppermost part of the filtration container 2, this suspended solid SS is gradually concentrated and becomes sludge-like.

Suspended matter SS that became this concentrated sludge
Is taken out to the floating substance tank 9 through the floating substance taking-out pipe 26 by opening the floating substance taking-out valve 27 at regular intervals.

The raw water W 1 and the pressurized water W 4 whose suspended solids SS are significantly reduced by the floating separation flow downward and pass through the small-grain sand 3 and the medium-grain sand 4. At this time, the remaining small amount of suspended solids SS in the raw water W1 is first captured on the upper surface of the small sand 3 and further between the particles of the sands 3 and 4, so that the raw water W1 which has passed through the medium sand 4 is finished. Is clear treated water W2
Becomes In this embodiment, the floating substance S is obtained by the floating separation.
Since most of S can be removed, sufficiently clear treated water W2 can be obtained even if the amounts of sands 3 and 4 used are small as described above. Also, the sands 3 and 4 are hardly clogged.

The treated water W2 is discharged to the treated water tank 25 through the treated water discharge pipe, and the treated water W2 that overflows the treated water tank 25 is discharged.

As described above, in this embodiment, the sands 3 and 4 are less likely to be clogged during the filtration process, so the filtration process speed is high and the pressure in the filtration container 2 is about 0 to 0.3 kg / cm ² . It is enough to set (of course, it can be higher). Therefore, the design of the filter container 2 is easy.

(2) Backwashing Process In the present embodiment, the backwashing process can be performed only when necessary, at regular intervals, or based on the pressure rise in the filtration container 2. , Here, the last method is explained. When the indication of the pressure gauge 8 of the filtration container 2 reaches a predetermined set value (for example, 0.3 kg / cm ² ), the raw water injection valve 21 and the like are automatically closed and the filtration process is stopped.

Then, the backwash water pump 40 in the treated water tank 25 is operated, and a part of the treated water W2 is transferred to the lower portion of the filtration container 2 as the backwash water W3 through the backwash water pipe 41 and the backwash water valve 42. Injected and flows upwards. At the same time, the backwash air pump 43 is operated, and the backwash air B taken from the outside is jetted into the filtration container 2 through the backwash air pipe 44 and the air diffusing member 45. In addition, the motor 47 operates and the rotary stirring member 46 rotates at a low speed of 2 to 3 times / minute. Due to the backflow of the backwash water W3, the vibration of the backwash air B, and the rotation of the rotary stirring member 46, the sands 3 and 4 are vigorously stirred in all directions, so that the suspended solids SS are separated from the sands 3 and 4 and become sludge. Then, it is taken out to the floating substance tank 9 through the floating substance taking-out pipe 26.

At the end of this backwashing process, the operation of the backwashing water pump 40 and the like is stopped, and the residual suspended solids extraction valve 29
Is opened, the backwash water W3 in the filter container 2 and the residual suspended matter SS suspended therein are taken out to the suspended matter tank 9 through the residual suspended matter take-out pipe 28. Since the inner end of the residual suspended solids extraction pipe 28 is opened near the upper surface of the small sand 3 which calms down after stirring, even the residual suspended solids SS that are about to fall onto the upper surface of the small sand 3 can be extracted. Yes, ideal backwashing is possible.

After the backwashing process, the filtering process is restarted, and thereafter, the filtering process and the backwashing process are repeated. As described above, in the present embodiment, since the sands 3 and 4 which are originally difficult to be clogged are backwashed, the backwashing interval is extended, the backwashing time is shortened, and the amount of backwashing water used is reduced. be able to. Further, even if the filtering process and the backwashing process are repeated many times, the slight clogging of the sands 3 and 4 can be easily recovered, so that the life of the filter medium can be extended.

Next, a comparative test operation between the present embodiment and the conventional example performed to confirm the effect of the present invention will be described. [Test operation conditions of this example] Filtration treatment device: As shown in Fig. 1 and the above description Raw water: Kani City, Gifu Prefecture Kani Industrial Park Pond water of terminal monitoring and regulating pond Concentration of suspended solids: 50 mg / l Composition of suspended solids: solid Material and phytoplankton Filtration processing speed: 2.0 m ³ / hr Apparent flow velocity in the filtration container 8 m / hr Pressure of pressurized water: 4.0 kg / cm ² Amount of air dissolved in pressurized water: 0.5 l / min [Conventional example] Test Conditions of Filtration Device: As shown in FIG. 2 and the above description Other: Same as the above test conditions except that pressurized water is not used

In the test operation of the present example, the suspended matter extraction valve 27 was opened once an hour, and about 30 l of suspended matter SS that became concentrated sludge was taken out. When operated in this manner, the pressure in the filtration container 2 does not rise even if filtration treatment is continuously performed for 24 hours (no backwash treatment),
Clarified treated water W2 could be continuously obtained. This 2
After 4 hours, the test operation was stopped, the water was removed from the filtration container 2 and the inspection was performed. As a result, it was found that the suspended matter SS was slightly attached to the upper surface of the small sand 3, and the small sand 3 was also the medium sand 4. Was as soft and holeless as at the beginning of the test. Therefore, the filtration process could be continued.

On the other hand, in the test run of the conventional example, the pressure in the filtration container 51 began to rise immediately after the start of the filtration process, so the backwash process was repeated once every 20 minutes. Backwash water W
The amount of 3 used was 500 liters at a time. When this filtration treatment and backwashing treatment were repeated for 6 hours, filtration leakage occurred and the suspended solid SS began to be mixed into the treated water W2. Therefore, at this time point, the backwashing process was performed, but it did not recover and the filtration process became impossible. Stop the test run and filter 51
When water was drained from the container and inspected, holes were formed in the small-grain sand 52 and the medium-grain sand 53, and the suspended material SS had entered the inside of the small-grain sand 52 and the medium-grain sand 53 and became hard. Therefore, each sand was replaced.

The present invention is not limited to the configuration of the above-described embodiment, and can be embodied by appropriately changing it without departing from the spirit of the invention.

[0040]

Since the method for filtering raw water and the apparatus therefor according to the present invention are configured as described above, the suspended matter trapped in the filter medium is drastically reduced to prevent clogging of the filter medium, thereby facilitating filtration. Improvement of processing speed, reduction of filter material usage, prolongation of filter material life, extension of backwash processing interval,
The backwashing time can be shortened, the amount of backwashing water used can be reduced, and even when the concentration of suspended solids in the raw water is high, it can be directly applied without pretreatment. It is possible to treat high-concentration raw water with a single filtration container, and it is possible to reduce the size of equipment, simplify the equipment, and reduce the cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an apparatus for filtering according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a conventional filtration processing apparatus.

[Explanation of Codes] 1 Filtering device 2 Filter container 3 Small-grain sand 4 Medium-grain sand 5 Wire mesh 6 Space 20 Raw water injection pipe 30 Pressurized water pump 31 Water supply pipe 32 Water supply valve 33 Air supply pipe 34 Flow rate control valve 35 Pressurized water tank 36 Pressure adjusting pipe 37 Pressure adjusting valve 38 Pressurized water injection pipe 39 Pressurized water injection valve W1 Raw water W2 Treated water W3 Backwash water W4 Pressurized water SS Suspended matter A Bubbles

Claims (2)

[Claims] 1. A filter container having a filter material in the lower part and a space formed in the upper part is used so that both water mixes raw water containing suspended substances and pressurized water in which a large amount of gas is dissolved under pressure. It is injected into the space of the filtration container, most of the suspended matter in the raw water is trapped in the innumerable bubbles released from the pressurized water, and the suspended matter is floated and separated along with the bubbles on the top of the filter vessel, and the floating A method for filtering raw water in which raw water reduced in suspended matter due to separation is passed through the filter medium, and the remaining suspended matter in the raw water is captured by the filter medium to make the raw water clear treated water. 2. A filtration container in which a filter medium is placed in the lower part to form a space in the upper part, a pressurized water production device for producing pressurized water in which a large amount of gas is dissolved under pressure, and raw water containing suspended matter is stored in the filtration container. An apparatus for filtering raw water, comprising: a raw water injection pipe for injecting into the space; and a pressurized water injection pipe for injecting into the space the pressurized water produced by the pressurized water producing device so as to mix with the raw water.