WO2016020957A1

WO2016020957A1 - Filtration method and filtration device

Info

Publication number: WO2016020957A1
Application number: PCT/JP2014/004147
Authority: WO
Inventors: 和典小石
Original assignee: 和典小石
Priority date: 2014-08-08
Filing date: 2014-08-08
Publication date: 2016-02-11
Also published as: JPWO2016020957A1; JP5698881B1

Abstract

[Problem] To provide a filtration method and filtration device with which it is possible to remove fine suspended matter at low cost even from high-turbidity water to be treated and in which clogging due to filtration is less apt to occur. [Solution] When suspended-matter-containing water to be treated is filtered, a coagulant is introduced in a given concentration into the water. The water is filtered through a filter medium including a particle layer having a particle diameter of 1-100 μm, without any treatment for suspended-matter coagulation and sedimentation due to stagnation. The coagulant contains Al cations and is introduced into the water so as to result in an Al mass concentration of 0.04 mg/l or higher. The filtration device (1), which is suitable for practicing such filtration method, is configured of a coagulant injector (3) and a pressure vessel (4) in which a filter medium (5) has been placed. The filter medium (5) comprises a plurality of layers (15, 16, 17, 18, 20, 21, and 22) differing in particle diameter, among which the layer having a minimum particle diameter, that is, particle layer (18), is composed of particles having a diameter of 1-100 μm.

Description

Filtration method and filtration device

The present invention relates to a filtration method and a filtration device for filtering water to be treated containing turbidity, and although not limited thereto, raw water taken from rivers, lakes and the like is treated water and filtered. Thus, the present invention relates to a filtration method suitable as a method for obtaining purified water, and a filtration apparatus for carrying out such a filtration method.

Purified water used for domestic water, drinking water, etc. is obtained by purifying treated water such as raw water taken from rivers, lakes, dams, etc., or groundwater pumped from the ground. The water to be treated contains suspended substances in which microorganisms and dust are suspended in a colloidal state, so-called turbidity, which must be removed by filtration through a filter basin or a filtration device. The filter basin or the filtration device is provided with a filter medium for filtering the water to be treated. As the filter medium, a granular filter medium made of particles such as filter sand is well known. For example, filtration is performed with a layer of filter sand having an average particle size of 0.45 to 0.7 mm in a rapid filtration basin, and with a layer of filter sand having an average particle size of 0.3 to 0.45 mm in a slow filtration pond. It has become. In addition, Patent Document 1 filed by the present applicant describes a filtering device including a filtering material including a particle layer having a particle diameter of 1 to 50 μm. In this filtration device, when water to be treated is supplied at a predetermined water pressure, the water to be treated is filtered at a sufficient filtration speed, but fine turbidity can be removed by the particle layer.

By the way, the above-mentioned slow filtration pond and the filtration device described in Patent Document 1 are suitable for filtering the water to be treated with relatively little turbidity. However, many raw waters may contain a relatively large amount of turbidity. When such raw water is filtered through a slow filtration basin or directly filtered by the filtration device described in Patent Document 1, the filter medium is clogged at an early stage, and the filter medium needs to be washed frequently, which is practical. Not. Therefore, a rapid filtration method is adopted in many water purification plants that filter the water to be treated with relatively high turbidity. In the rapid filtration method, a flocculant such as polyaluminum chloride is poured into the water to be treated, stirred in a stirring pond, and then retained in a settling basin for a predetermined time. Then, the colloidal turbidity aggregates to form flocs, and the flocs settle in the sedimentation basin. Then, only the supernatant water of the sedimentation basin is filtered through the rapid filtration basin. In this way, most of the turbidity is removed in the sedimentation basin, so the filter medium is not easily clogged.

There are other methods of filtration using a coagulant, for example, a so-called micro floc filtration method or a so-called chemical injection filtration method is well known. The former method is a method in which a flocculant is injected into the water to be treated and stirred, and this is sent directly to the filtration basin for filtration. A sedimentation basin for retaining the water to be treated is not required. In this method, since the water to be treated is not retained after the injection of the flocculant, a large floc is not formed, and only a minute floc, that is, a micro floc is formed. Since such micro floc enters from the surface of the filter medium and reaches a predetermined depth and is filtered, the filter medium is used as a whole and clogging is less likely to occur. The latter method, the chemical injection filtration method, is a method in which a flocculant is poured into the water to be treated and stirred, and then quickly filtered in a filtration basin. However, in the chemical injection filtration method, the injection rate of the flocculant is made smaller than in the micro floc filtration method. As a result, flocs that can be recognized by the naked eye are not formed, and the turbidity hardly aggregates. Since it does not aggregate, the turbidity is in a fine state and is smaller than the gap between the filter sands constituting the filter medium. If you look at it in terms of size, you shouldn't be able to strain it with filter media. However, the flocculant to be injected has a positive charge, and can electrically neutralize filter sand and turbidity which are charged with a negative charge and electrically repelled. As a result, the fine turbidity adheres to the filter sand and is picked and collected. In both the micro floc filtration method and the chemical injection filtration method, the particles used as the filter medium of the filter basin have a particle size of 0.6 to 1.1 mm, which is slightly larger than the filter sand of the rapid filter basin. This is considered to be because clogging is less likely to occur because all the suspended matter is removed with a filter medium without being removed by sedimentation with floc.

JP 2014-18741 A JP 2009-90227 A JP 2003-170185 A

Patent Document 2 also describes a filtration method similar to the micro floc filtration method or the chemical injection filtration method. In the filtration method described in Patent Document 2, a filtration device is used in which the filter medium includes a first layer made of anthracite and a second layer made of silica sand. In this method, the water to be treated is sent to the filtration device by a predetermined pump. However, the flocculant and sodium hypochlorite are injected into the water to be treated and mixed and then supplied to the filtration device for filtration. Yes. As the flocculant, polyaluminum chloride, aluminum sulfate, or ferric chloride is used, and an organic polymer type flocculant is also used in combination as appropriate. The anthracite and silica sand used as filter media have a particle size of 0.9 mm and 0.5 mm, respectively, and are equal to or larger than the filter sand of the rapid filtration basin.

Patent Document 3 describes a membrane filtration method using a membrane as a filter medium. As is well known, a membrane used as a filter medium has a large number of minute holes, and when treated water containing turbidity is sent under a predetermined pressure, the turbidity is trapped in the membrane. Yes. The membrane filtration method has a drawback in that the turbidity is trapped in a minute hole so that the membrane is easily clogged at an early stage and the membrane must be backwashed frequently. In the method described in Patent Document 3, when the water to be treated is supplied to the filtration device having a membrane, a flocculant is injected and supplied. As a result, the turbidity aggregates, and the film is less likely to be clogged.

When filtering the water to be treated, as an example of filtering without injecting a flocculant, the slow filtration pond and the filtration device described in Patent Document 1 were described. As described above, there is a problem that when the water to be treated having a lot of turbidity is filtered, the filter medium is clogged at an early stage. Moreover, in the filtration apparatus of patent document 1, although it can filter at a high filtration rate and can remove fine turbidity, there also exists a problem that turbidity smaller than the clearance gap between particle layers cannot be removed. Therefore, the filtration device described in Patent Document 1 is not suitable for filtering water to be treated having a very high turbidity. Highly turbid water to be treated contains a large amount of turbidity, so a large amount of turbidity that is smaller than the gap between the particle layers slips through the filter medium, resulting in sufficiently low turbidity of the filtered water. Because it will not be. If the turbidity is not small enough, there is a problem when using filtered water as purified water. Next, about the method of inject | pouring a flocculant and filtering after that, there exist a rapid filtration method, a micro floc filtration method, a chemical injection filtration method, and the filtration method of patent document 2, as mentioned above. Each of these is excellent. In addition, the filtration method described in Patent Document 3 in which a flocculant is injected into the water to be treated and then filtered with a filtration device equipped with a membrane is excellent because it can suppress clogging of the membrane. However, there are also problems to be solved for each of these. First, regarding the rapid filtration method, a sedimentation basin for retaining the water to be treated is indispensable, and there is a problem that a large site is necessary and the cost of equipment increases. Next, in the micro floc filtration method, the chemical injection filtration method, or the filtration method described in Patent Document 2, there is a problem when the turbidity of the water to be treated is high and the turbidity is high. When the water to be treated has high turbidity, flocculation does not proceed rapidly even if a flocculant is injected. In other words, most of the turbidity is dispersed and floated in a colloidal form at the timing of filtration with the filter medium. The filter medium used in these methods is equivalent to or larger in diameter than the filter sand of the rapid filtration basin, so the suspended matter in a colloidal floating state is a filter medium consisting of relatively coarse particles. Will slip through. Alternatively, turbidity with high turbidity is not easily neutralized electrically and hardly adheres to filter sand. If it does so, a part of muddy substance will mix in filtered water. That is, in the micro floc filtration method, the chemical injection filtration method, or the filtration method described in Patent Document 2, high turbidity turbidity cannot be sufficiently filtered, and there is no guarantee that safe purified water can be obtained. Next, regarding the filtration method described in Patent Document 3, it can be said that the problem is that the membrane of the filter medium is expensive. If the membrane is used for a long period of time, it needs to be replaced, resulting in high costs for obtaining purified water.

The present invention aims to provide a filtration method and a filtration device made in view of the above-mentioned problems. Specifically, even though it is a low-cost filtration method, even with water to be treated containing high-turbidity turbidity, it is possible to reliably remove fine turbidity and to prevent filtration clogging, and its It aims at providing the filtration apparatus which enforces such a filtration method.

In order to achieve the above object, the first aspect of the present invention is to obtain a filtered water by filtering the treated water containing turbidity, injecting a flocculant into the treated water, The filtration method is characterized by filtering through a filter medium having a particle layer having a particle size of 1 to 100 μm without undergoing agglomeration / sedimentation.
According to a second aspect of the present invention, in the filtration method according to the first aspect, the flocculant contains an Al cation so that the mass concentration of Al is 0.04 mg / l or more with respect to the water to be treated. It is comprised as a filtration method characterized by inject | pouring into.
A third aspect of the present invention is the filtration method according to the second aspect, wherein the flocculant is an extract obtained by immersing granite powdered in dilute sulfuric acid for a predetermined time. Configured as a method.

Invention of Claim 4 is a filtration apparatus which filters the to-be-processed water containing turbidity, Comprising: The said filtration apparatus consists of a coagulant | flocculant injection apparatus and the pressure vessel in which the filter material was put, The said, The filter medium includes a particle layer having a particle size of at least 1 to 100 μm, and the water to be treated is supplied to the pressure vessel after the coagulant is injected in the coagulant injection device, and is filtered by the filter medium. It is comprised as a filtration device characterized by becoming.
According to a fifth aspect of the present invention, in the filtration device according to the fourth aspect, the filter medium is laminated so that the particle diameter is gradually reduced from the lower side to the upper side, and the uppermost part is the particle layer. And a particle outflow prevention unit laminated on the particle layer so that the particle size sequentially increases from the bottom to the top, and is filled so as to reach the ceiling of the pressure vessel. In addition, the water to be treated is configured as a filtering device that is filtered through the filter medium upward.
According to a sixth aspect of the present invention, in the filtration device according to the fourth aspect, the filter medium is laminated so that the particle size is gradually reduced from the lower side to the upper side, and the uppermost part is the particle layer. And a particle outflow prevention unit laminated on the particle layer so that the particle size sequentially increases from below to above, and the upper part of the particle outflow prevention unit is predetermined. The water to be treated is filtered downward by passing through the filter medium upward and is filtered.

As described above, in the present invention, when the water to be treated containing turbidity is filtered to obtain filtered water, a flocculant is injected into the water to be treated, and the turbid matter is not subjected to flocculation / sedimentation due to retention. In addition, it is configured to filter with a filter medium having a particle layer having a particle diameter of 1 to 100 μm. Since the filter medium to be used is a filter medium having a particle layer, the cost is small. In the present invention, the flocculant is injected into the water to be treated, but this is immediately filtered. Then, the suspended matter in the water to be treated slightly starts to aggregate and flocs are formed, but flocs having a size that can be visually recognized by the naked eye are not formed and are filtered. However, since the particle layer of the filter medium is composed of particles having a particle diameter of 1 to 100 μm, even a fine floc can be sufficiently strained with a particle layer. By the way, most of the turbidity aggregates and becomes a floc larger than the gap between the particle layers and is captured by the particle layer, but the suspended turbidity is not aggregated but is dispersed in the water to be filtered. There is also. However, since these turbid substances are also electrically neutralized by the flocculant, they adhere to flocs already captured by the particle layer when passing through the particle layer. As a result, the fine turbidity can be removed substantially completely. In the present invention, the turbidity is crushed in the form of fine flocs in this way, so that a gap is secured between the flocs. This gap makes it difficult for the filter medium to be clogged, and it can be filtered for a long time. According to another invention, the flocculant is composed of an extract obtained by adding dilute sulfuric acid to powdered granite. Such an extract contains not only Al cations and iron cations that exert an aggregating effect, but also other trace elements, that is, minerals. If it does so, a mineral will be added to filtered water and drinking water with high added value can be obtained.

It is side surface sectional drawing which shows typically the filtration apparatus which concerns on embodiment of this invention. It is side surface sectional drawing which shows typically the filtration apparatus which concerns on the 2nd Embodiment of this invention.

DETAILED DESCRIPTION A filtration device 1 according to an embodiment of the present invention will be described. The filtration device according to the present embodiment includes an upward filtration device 2 and a flocculant injection device 3. As will be described later, the filtration method according to the present embodiment is configured to inject the flocculant at a predetermined injection rate into the water to be treated containing turbidity, and then quickly filter with a predetermined filter medium. Has been. The flocculant injection device 3 is a device that injects the flocculant into the water to be treated, and the upward filtration device 2 is a device that filters the water to be treated into which the flocculant has been injected.

First, the upward filtration device 2 will be described. The upward filtration device 2 includes a hollow pressure vessel 4, a filter medium 5 provided in the pressure vessel 4, and the like. The pressure vessel 4 is made of a steel plate having a predetermined thickness, and has a cylindrical barrel portion 7 and a head portion 8 having a dome shape that is liquid-tightly attached to the upper portion of the barrel portion 7. 7 and a dome-shaped bottom portion 9 that is liquid-tightly attached to the lower portion of the base plate 7. Since it is formed in such a shape, the pressure vessel 4 has high resistance to the internal pressure. Moreover, since the pressure vessel 4 can be easily disassembled, the filter medium 5 can be maintained or replaced.

The filter medium 5 is composed of gravel, filter sand, particles, and the like, and includes a plurality of layers laminated according to different particle sizes. The filtering device 1 according to the present embodiment is characterized in that the water to be treated into which the flocculant has been injected is filtered. However, the filtering device 1 having a very fine particle layer is used for filtering. There is also a feature. In order to provide such a layer of fine particles, the method of laminating the filter media 5 has a feature, and the filter media 5 composed of a plurality of layers is roughly divided into two layers. That is, it is composed of a filtration unit 11 as a lower layer and a particle outflow prevention unit 12 as an upper layer. The layer of the filtration unit 11 has an effect of removing turbidity from the water to be treated, and the particle outflow prevention unit 12 is configured to prevent the particles constituting the filtration unit 11 from flowing out. The filtration part 11 is laminated | stacked on the some layer from the particle | grains from which a particle size differs, and is a layer with a small particle size in an order from the lowest layer. Specifically, the lowermost layer 15 is made of particles having a relatively large particle size such as gravel, the middle layer 16 is made of filter sand, and the upper layer 17 is made of filter sand having a small particle size. The minimum particle layer corresponding to the uppermost layer of the filtration unit 11, that is, the particle layer 18 is composed of particles having a particle diameter of 1 to 100 μm. The particle size of the particle layer 18 should be smaller as the particle size is smaller. However, in the present invention, since the flocculant is injected into the water to be treated and filtered, the fine turbidity can be obtained. Are aggregated together and trapped in the filter medium. As will be clarified later in the examples, if the filtration method of the present invention is carried out, a sufficiently fine turbidity can be trapped even if the particle diameter is not so fine. Accordingly, the particle size of the particle layer 18 is preferably 20 μm or more in order to prevent early clogging due to turbidity. Further, the larger the particle size of the particle layer 18 is, the more advantageous it is because the filtration resistance becomes smaller and the filtration can be efficiently performed. However, if the particle size is large, the turbidity may not be removed when the filtration rate is increased. . Accordingly, the particle size is preferably 80 μm or less. That is, the particle diameter of the particle layer 18 is 1 to 100 μm, preferably 20 to 80 μm. By the way, as for the upward filtration apparatus 2 which concerns on this Embodiment, to-be-processed water flows through the inside of the filter medium 5, and is filtered. If it does so, the filtration part 11 will be laminated | stacked so that a particle size may become small sequentially in the direction through which to-be-processed water flows. As a result, the large turbidity is collected in the lower layer and the small turbidity is collected in the upper layer, and the filtration unit 11 as a whole exerts a filtering action.

The particle outflow prevention unit 12 is different from the filtration unit 11 in the lamination method. The particle outflow prevention unit 12 is laminated so that the particle diameter increases sequentially from the lower layer to the upper layer. That is, the lowermost layer 20 in contact with the particle layer 18 is made of filter sand having a small particle size, the middle layer 21 is made of filter sand, and the uppermost layer 22 is made of particles having a relatively large particle size such as gravel. Since they are stacked in this way, the particles of the particle layer 18 of the filtration unit 11 are prevented from flowing upward and flowing out. In the filtration device 1 according to the present embodiment, the pressure vessel 4 of the upward filtration device 2 is filled until the filter medium 5 reaches the ceiling. Therefore, even if pressure is applied and the water to be treated is supplied from below the pressure vessel 4, the filter medium 5 does not rise. As a result, the filter medium 5 can continue to be filtered while the laminated state is maintained.

A supply pipe 24 for supplying the water to be treated is connected to the bottom portion 9 of the pressure vessel 4 so that the water to be treated is sent from the flocculant injecting device 3 described below. A first valve 25 is interposed in the supply pipe 24. Also connected to the bottom portion 9 is a drain pipe 26 for discharging cleaning waste water when backwashed, and a second valve 27 is interposed in the drain pipe 26. A water supply pipe 28 for supplying the filtered water is connected to the head portion 8 of the pressure vessel 4.

The flocculant injection device 3 will be described. In the present embodiment, the flocculant injection device 3 includes a mixing tank 30 and an injector 31 that injects the flocculant at a treatment injection rate. In the mixing tank 30, the water to be treated supplied from the water to be treated supply pipe 32 is filled with a certain amount, but since the capacity is relatively small, there is almost no residence time. In the present embodiment, the injector 31 injects a flocculant obtained from a predetermined rock. The aggregating agent contains an aluminum cation and an iron cation, and has an action of aggregating turbidity charged to a negative charge, such as polyaluminum chloride (PAC) which is a conventionally known aggregating agent. The flocculant is injected into the water to be treated at a predetermined injection rate. In the present embodiment, preferably, the mass concentration of aluminum with respect to 1 l of the water to be treated is 0.04 mg / l or more. Injection is performed so that the concentration is 0.08 mg / l or more, and more preferably 0.2 mg / l or more. When the mass concentration of these aluminums is converted by the PAC injection rate, they correspond to 0.6 ppm, 1.2 ppm, and 3.0 ppm, respectively. A pump 35 is provided in the mixing tank 30 of the flocculant injection device 3, and the water to be treated is supplied to the supply pipe 24 at a water pressure of 0.05 MPa or more.

The filtration method according to this embodiment will be described. First, in the filtration device 1 according to the present embodiment, the first valve 25 is opened, and the second valve 27 is closed. Raw water taken from a river or the like is treated water, which is supplied from the treated water supply pipe 32 to the mixing tank 30 of the flocculant injection device 3. The flocculant is injected from the injector 31 and the pump 35 is driven. Although the flocculant is injected into the water to be treated, the residence in the mixing tank 30 is slight, so that the water to be treated is not necessarily mixed sufficiently in the mixing tank 30. However, when the water to be treated into which the flocculant is injected by the pump 35 is sent to the supply pipe 24, the mixing is promoted and the flocculant is sufficiently diffused in the water to be treated. Then, the turbid matter charged with a negative charge in the treated water and dispersed in a colloidal form is electrically neutralized by the flocculant. However, the water to be treated does not stay sufficiently, so that the suspended matter is slightly aggregated and a floc having a size that can be visually observed is not formed. Thus, the water to be treated which has just started to aggregate turbidity is supplied to the lower part of the pressure vessel 4 of the upward filtration device 2 via the first valve 25, and the water to be treated flows upward through the filter medium 5. The turbidity of the water to be treated is agglomerated even if it is slight, so when it flows through the filter medium 5, it is crushed by a predetermined layer of the filtration unit 11. The suspended turbidity is in an agglomerated state, that is, in a lump or granular form. In other words, it is not distributed. Therefore, the filter medium 5 is not easily clogged even if the turbidity is removed. Some turbidity is not aggregated in the water to be treated. Such turbidity can flow through the filter medium 5, but adheres to massive or granular turbidity that has already been picked up by the filter medium 5. This is because the turbidity easily adheres to other trapped turbidity because the flocculant is added and electrically neutralized. That is, as a result, fine turbidity that has not been agglomerated is also collected. After the fine turbidity is collected in the particle layer 18 which is the smallest particle layer, the water to be treated flows upward through the particle outflow prevention unit 12 and exits from the upper part of the pressure vessel 4. That is, purified water is obtained. The purified water is sent to the outside through a water pipe 28.

If filtration of the water to be treated is continued, turbidity accumulates in the filter medium 5 and the filtration efficiency decreases. Therefore, after filtration for a predetermined time, backwashing is performed to remove turbidity from the filter medium 5. Specifically, the pump 35 is stopped, the first valve 25 is closed, and the second valve 27 is opened. The purified water is pumped in the opposite direction from the water pipe 28. Then, the purified water flows down the filter medium 5 of the upward filtration device 2. The turbidity trapped in the filtration unit 11 is pushed out by purified water and flows downward. By the way, the turbidity is separated from the filter sand, particles, and the like constituting the filter medium 5 because it is formed into a fine lump by the flocculant. That is, the filter medium 5 can be easily washed. The purified water containing turbidity is discharged from the drain pipe 26 to the outside. When backwashing is performed for a predetermined time, the supply of purified water from the water pipe 28 is stopped, the second valve 27 is closed, and the first valve 25 is opened. As already explained, the pump 35 is operated to restart the filtration of the water to be treated.

Production of flocculant according to the present embodiment In conducting the experiment of the filtration method according to the present embodiment, the flocculant according to the present embodiment used in the experiment was produced as follows.
Raw material: Granite (1) The raw granite was crushed into a powder and immersed in dilute sulfuric acid for a predetermined time.
(2) It filtered with the back paper, and made the filtrate into the coagulant | flocculant which concerns on this Embodiment.
The components of the flocculant according to the present embodiment were analyzed, and data in the following table was obtained. It was confirmed that many trivalent aluminum cations having an aggregating effect were contained, and that iron cations were also contained.

Experiment 1 of filtration method according to the present embodiment
An experiment to confirm that purified water can be obtained by removing the turbidity from the water to be treated containing turbidity by performing the filtration method according to the present embodiment using the flocculant according to the present embodiment. went.
Experimental conditions: Using the filtration device 1 according to the present embodiment shown in FIG. 1, the water to be treated containing turbidity is filtered at a filtration rate of 500 m / day, and the turbidity of the filtered water by a turbidimeter. Was measured. To-be-treated water was prepared by adding kaolin, which is artificial turbidity, to tap water and adjusted so that the turbidity was 5 degrees.
In Experiment 1, the particle layer 18 had a particle diameter of 80 μm and a layer thickness of 10 cm.
Experiment 1-1: First, an experiment was conducted in which the water to be treated was filtered in the filtration device 1 without adding a flocculant. The turbidity of filtered water after 3 minutes from the start of filtration was 0.9 degree, and the turbidity of filtered water after 5 minutes was also 0.9 degree.
Experiment 1-2: Next, the flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 100 ppm, and filtered in the filtration device 1. As shown in Table 1, the flocculant according to this embodiment contains 7.65 g of aluminum in 1 liter. Therefore, when the injection rate of 100 ppm is expressed by the mass concentration of aluminum, it is 0.765 mg / l. Become. In this experiment, the turbidity of filtered water 3 minutes after the start of filtration was 0.06 degrees, and the turbidity of filtered water 5 minutes later was 0.01 degrees.
Experiment 1-3: Next, filtration was performed using polyaluminum chloride instead of the flocculant according to the present embodiment. Polyaluminum chloride was injected into the water to be treated so that the mass concentration of aluminum was the same as in Experiment 1-2, that is, 0.765 mg / l. Since polyaluminum chloride contains 65.52 g of aluminum in one liter, 0.765 / 65.52 × 1000 = 12 ppm with respect to the water to be treated so that the aluminum mass concentration is 0.765 mg / l. Injected. The turbidity of filtered water 3 minutes after the start of filtration was 0.5 degrees, and the turbidity of filtered water 5 minutes later was 0.2 degrees.
Consideration: When filtration is performed without injecting the flocculant into the water to be treated from Experiment 1-1, part of the turbidity is mixed into the filtered water, and the turbidity does not decrease below a certain value, that is, below 0.9 degrees. I understood. On the other hand, when the flocculant was injected into the water to be treated and filtered, it was confirmed that most of the turbidity was crushed with a filter medium and the turbidity of the filtered water was lowered. Even when polyaluminum chloride, which is a conventional flocculant, was injected into the water to be treated and filtered, it was confirmed that turbidity was sufficiently crushed with a filter medium, but the flocculant according to the present embodiment was injected. In this case, it was confirmed that the effect of removing the turbidity was further enhanced. Since the flocculant according to the present embodiment contains not only aluminum cations but also iron cations, it is considered that the aggregating effect was high.

Experiment 2 of the filtration method according to the present embodiment
Using the flocculant according to the present embodiment, the filtration method according to the present embodiment was performed while changing the injection rate of the flocculant, and an experiment was performed to confirm the effect.
Experimental conditions: Using the filtration device 1 according to the present embodiment shown in FIG. 1, the water to be treated containing turbidity is filtered at a filtration rate of 500 m / day, and the turbidity of the filtered water by a turbidimeter. Was measured. Water to be treated was prepared by adding kaolin, which is artificial turbidity, to tap water and adjusted so that the turbidity was 10 degrees.
In Experiment 2, the particle layer 18 had a particle diameter of 80 μm and a layer thickness of 10 cm.
Experiment 2-1: The flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 5 ppm, and filtered through the filtration device 1. That is, the flocculant was injected into the water to be treated so as to be 0.038 mg / l in terms of the mass concentration of aluminum. In this experiment, the turbidity of filtered water 5 minutes after the start of filtration was 0.45 degrees, and the turbidity of filtered water 10 minutes later was 0.4 degrees.
Experiment 2-2: The flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 10 ppm, and filtered in the filtration device 1. That is, the flocculant was injected into the water to be treated so as to be 0.076 mg / l in terms of the mass concentration of aluminum. In this experiment, the turbidity of filtered water 5 minutes after the start of filtration was 0.24 degrees, and the turbidity of filtered water 10 minutes later was 0.1 degrees.
Experiment 2-3: The flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 25 ppm, and filtered in the filtration device 1. That is, the flocculant was injected into the water to be treated so as to be 0.19 mg / l in terms of the mass concentration of aluminum. In this experiment, the turbidity of filtered water 5 minutes after the start of filtration was 0.2 degrees, and the turbidity of filtered water 10 minutes later was 0.15 degrees.
Consideration: If the flocculant was poured into the water to be treated so that the mass concentration of aluminum was 0.038 mg / l, it was confirmed that turbidity could be removed to some extent during subsequent filtration. As compared with Experiment 1-1 in which the flocculant was not injected into the water to be treated, it was confirmed that the turbidity removal effect by the injection of the flocculant was sufficient. However, it can be confirmed that the turbidity can be further removed by injecting to 0.076 mg / l, and the turbidity can be more efficiently removed by injecting the aluminum mass concentration to 0.19 mg / l. It was confirmed that Therefore, it was found that the aluminum mass concentration should be poured into the water to be treated so that the aluminum mass concentration is 0.04 mg / l or more, preferably 0.08 mg / l or more, more preferably 0.2 mg / l or more. .

Experiment 3 of filtration method according to this embodiment
An experiment was conducted to confirm the effect of the filtration method according to the present embodiment by changing the particle size of the particles of the particle layer 18.
Experimental conditions: Using the filtration device 1 according to the present embodiment shown in FIG. 1, the water to be treated containing turbidity is filtered at a filtration rate of 500 m / day, and the turbidity of the filtered water by a turbidimeter. Was measured. Water to be treated was prepared by adding kaolin, which is artificial turbidity, to tap water and adjusted so that the turbidity was 10 degrees.
Experiment 3-1: The particle diameter of the particle layer 18 was 5 μm, and the layer thickness was 10 cm. The flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 25 ppm, and filtered in the filtration device 1. That is, the flocculant was injected into the water to be treated so as to be 0.19 mg / l in terms of the mass concentration of aluminum. In this experiment, the turbidity of filtered water 5 minutes after the start of filtration was 0.00 degrees, and the turbidity of filtered water 10 minutes later was also 0.00 degrees.
Experiment 3-2: The particle diameter of the particle layer 18 was 20 μm, and the layer thickness was 10 cm. The flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 25 ppm, and filtered in the filtration device 1. That is, the flocculant was injected into the water to be treated so as to be 0.19 mg / l in terms of the mass concentration of aluminum. In this experiment, the turbidity of the filtered water 5 minutes after the start of filtration was 0.02 degrees, and the turbidity of the filtered water 10 minutes later was 0.00 degrees.
Experiment 3-3: The particle diameter of the particle layer 18 was 100 μm, and the layer thickness was 10 cm. The flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 25 ppm, and filtered in the filtration device 1. That is, the flocculant was injected into the water to be treated so as to be 0.19 mg / l in terms of the mass concentration of aluminum. In this experiment, the turbidity of filtered water 5 minutes after the start of filtration was 0.4 degrees, and the turbidity of filtered water 10 minutes later was 0.2 degrees.
Experiment 3-4: The particle diameter of the particle layer 18 was 200 μm, that is, 0.2 mm, and the layer thickness was 10 cm. The flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 25 ppm, and filtered in the filtration device 1. That is, the flocculant was injected into the water to be treated so as to be 0.19 mg / l in terms of the mass concentration of aluminum. In this experiment, the turbidity of filtered water 5 minutes after the start of filtration was 1.5 degrees, and the turbidity of filtered water 10 minutes later was 1.4 degrees.
Discussion: It was confirmed from Experiments 3-1 and 3-2 that when the particle size of the particle layer 18 was 20 μm or less, the turbidity was substantially completely removed. If the particle diameter of the particle layer 18 becomes smaller, the resistance at the time of filtration becomes that much. Considering the efficiency of filtration, the particle size is preferably 20 μm or more. Experiment 3-3 confirmed that turbidity could be sufficiently removed even when the particle size of the particle layer 18 was 100 μm. On the other hand, Experiment 3-4 confirmed that the turbidity could not be sufficiently removed when the particle diameter of the particle layer 18 was 200 μm.

Experiment 4 of filtration method according to this embodiment
A high turbidity water to be treated was filtered by the filtration method according to the present embodiment, and an experiment was conducted to confirm the effect.
Experimental conditions: Using the filtration device 1 according to the present embodiment shown in FIG. 1, the water to be treated containing turbidity is filtered at a filtration rate of 500 m / day, and the turbidity of the filtered water by a turbidimeter. Was measured. The treated water used was tap water with added artificial turbid kaolin. The particle diameter of the particle layer 18 was 80 μm, and the layer thickness was 10 cm.
Experiment 4-1: The turbidity of the water to be treated was set to 300 degrees, and filtration was performed in the filtration apparatus 1 without injecting the flocculant. In this experiment, the turbidity of filtered water 5 minutes after the start of filtration was 41.9 degrees, and the turbidity of filtered water 15 minutes later was 60.5 degrees.
Experiment 4-2: The turbidity of the water to be treated was set to 300 degrees, and the flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 25 ppm. That is, the flocculant was injected into the water to be treated so as to be 0.19 mg / l in terms of mass concentration of aluminum. In this experiment, the turbidity of filtered water 5 minutes after the start of filtration was 1.03 degrees, and the turbidity of filtered water 15 minutes later was 0.09 degrees.
Experiment 4-3: The turbidity of the water to be treated was set to 100 degrees, and filtration was performed in the filtration apparatus 1 without injecting the flocculant. In this experiment, the turbidity of the filtered water 5 minutes after the start of filtration was 12.3 degrees, and the turbidity of the filtered water 15 minutes later was 20.7 degrees.
Experiment 4-4: The turbidity of the water to be treated was set to 100 degrees, and the flocculant according to the present embodiment was poured into the water to be treated so as to have a concentration of 25 ppm. That is, the flocculant was injected into the water to be treated so as to be 0.19 mg / l in terms of mass concentration of aluminum. In this experiment, the turbidity of the filtered water 5 minutes after the start of filtration was 0.00 degrees, and the turbidity of the filtered water 15 minutes later was also 0.00 degrees.
Discussion: From Experiments 4-1 and 4-3, it was confirmed that considerable turbidity would be mixed into the filtered water when filtered without injecting the flocculant into the treated water. In contrast, Experiment 4-2 and Experiment 4-4 confirmed that most of the turbidity was removed when the flocculant was injected into the water to be treated. As apparent from comparison with Experiment 2-3, especially when the turbidity of the treated water is 100 degrees, the turbidity of the filtered water is smaller and more efficient than when the turbidity of the treated water is 10 degrees. It was confirmed that it could be removed. When the turbidity of the water to be treated is high to some extent, it is expected that the turbidity aggregates with each other to form a lump and is easily captured by the filter medium 5.

The filtration method or the filtration device 1 according to the present embodiment can be variously modified. FIG. 2 shows a filtration device 1 ′ according to the second embodiment. The same members as those in the filtration device 1 according to the previous embodiment are denoted by the same reference numerals, and the description thereof is omitted. The filtering device 1 ′ according to the second embodiment has various features, but first, the filter medium 5 is not filled so as to reach the ceiling of the pressure vessel 4. In this embodiment, the upper part of the filter medium 5 is pressed by a predetermined pressing member 41, and the pressing member 41 is biased downward by

spring bodies

40, 40. This prevents the filter medium 5 from floating. In addition, the filtration device 1 ′ according to the second embodiment is characterized in that the flocculant injection device 3 ′ is composed of only the injection machine 31. The injector 31 is connected to the treated water supply pipe 32 so that the flocculant is directly injected into the treated water. The treated water supply pipe 32 is connected to the supply pipe 24 so that the flocculant is mixed while the treated water flows through a short pipeline. The water supply pipe 24 is directly placed in the pressure vessel 4 and has

small holes

38, 38,. The water to be treated is supplied to the filter medium 5 through the

holes

38, 38,. Note that in the filtration device 1 ′ according to the second embodiment, the water to be treated is supplied at a predetermined water pressure, and therefore no pump is provided.

The filtration device can be further modified, and the treated water may be filtered downward. The water to be treated may be filtered in any direction in the filter medium as long as the filter medium has a particle layer with a particle diameter of 1 to 80 μm. The flocculant can also be modified, and aluminum sulfate or other flocculants can be used.

DESCRIPTION OF SYMBOLS 1 Filtration apparatus 2 Upward filtration apparatus 3 Flocculant injection apparatus 4 Pressure vessel 5 Filter material 11 Filtration part 12 Particle outflow prevention part 24 Supply pipe 26 Drain pipe 28 Water supply pipe 30 Mixing tank 31 Injection machine 32 Water to be treated supply pipe 35 Pump

Claims

When filtering the water to be treated containing turbidity to obtain filtered water, a flocculant is injected into the water to be treated, and particles having a particle size of 1 to 100 μm are not subjected to turbid aggregation or sedimentation due to retention. A filtration method comprising filtering through a filter medium having a layer.
2. The filtration method according to claim 1, wherein the flocculant contains an Al cation and is injected into the water to be treated so that the mass concentration of Al is 0.04 mg / l or more. Method.
3. The filtration method according to claim 2, wherein the flocculant is an extract obtained by immersing granite powdered in dilute sulfuric acid for a predetermined time.
A filtration device for filtering water to be treated containing turbidity, the filtration device comprising a flocculant injection device and a pressure vessel in which a filter material is placed,
The filter medium comprises a particle layer having a particle size of at least 1 to 100 μm,
The water to be treated is supplied to the pressure vessel after the flocculant is injected in the flocculant injection device, and is filtered by the filter medium.
5. The filtration device according to claim 4, wherein the filter medium is laminated so that the particle size is gradually reduced from the bottom toward the top, and the top portion is the particle layer, and the particles The particle outflow prevention unit is laminated so that the particle size is gradually increased from the bottom to the top on the layer, and is filled so as to reach the ceiling of the pressure vessel. A filtration device characterized by being filtered through a filter medium upward.
5. The filtration device according to claim 4, wherein the filter medium is laminated so that the particle size is gradually reduced from the bottom toward the top, and the top portion is the particle layer, and the particles A particle spill prevention part that is laminated on the layer so that the particle size increases sequentially from the bottom to the top, and the particle spill prevention part has its upper part pressed downward by a predetermined pressing member. And the water to be treated is filtered by passing the filter medium upward.