JP6993838B2 - Coagulation sedimentation device and coagulation sedimentation treatment method - Google Patents

Description

The present invention relates to a coagulation-sedimentation apparatus and a coagulation-sedimentation treatment method, and more particularly to an apparatus and a method for adding a coagulant to water to be treated on the upstream side of the sedimentation tank and performing coagulation and granulation in the settling tank by stirring in the settling tank.

As one of the water treatment devices, a coagulation sedimentation device is widely used for water treatment and wastewater treatment. The coagulation sedimentation device aggregates suspended solids contained in raw water and precipitates them in a settling tank, and separates the raw water into sludge and treated water. A floating dense layer (sludge blanket) of sludge is formed in the settling tank in the coagulation sedimentation device, and fine particles and suspended solids in the raw water supplied to the settling tank are captured by this sludge blanket for clear treatment. There is a technique to obtain water.

Among such coagulation and settling devices, the water to be treated (raw water) to which a coagulant is added is slowly stirred by a stirring blade in a settling tank to form coagulation flocs, and further, collisions between coagulation flocs and coagulation flocs occur. A granulation type coagulation-precipitation device is known in which the particle size of agglomerated flocs is gradually increased by repeatedly causing rolling motion to form spherical pellets. In the granulation type coagulation settling device, pellets with high density and high settling speed form a fluidized bed (pellet blanket), which enables higher speed processing and the water flow velocity in the settling tank (pellet blanket). LV) can be increased to increase the processing flow rate or reduce the size of the settling tank.

Patent Document 1 discloses a water treatment method in which a cationic polymer flocculant and an anionic polymer flocculant are used in combination. Specifically, an inorganic flocculant is added to the water to be treated to form microaggregated flocs. Next, the cationic polymer flocculant and the anionic polymer flocculant are sequentially added to the water to be treated. As a result, the aggregated flocs are coarsened, and pellets having a stronger and higher density and a high sedimentation rate can be formed, and as a result, the water flow LV of the sedimentation tank can be further increased.

Japanese Patent No. 5907273

In the coagulation-precipitation treatment, a large amount of an inorganic coagulant may be used for reducing COD (chemical oxygen demand), removing chromaticity components, and the like. However, in that case, the number of fine and light aggregate flocs derived from the inorganic flocculant and having less crosslinkability increases. As disclosed in Patent Document 1, even if a cationic polymer flocculant and an anionic polymer flocculant are used in combination, pellets having high strength and density and a high sedimentation rate may not be formed. If the amount of the inorganic flocculant added is suppressed in order to form such pellets, it becomes difficult to reduce COD and remove the chromaticity component.

The present invention provides a coagulation-sedimentation apparatus and a coagulation-precipitation treatment method capable of suppressing the addition amount of an inorganic flocculant, forming pellets having a high sedimentation rate, and efficiently reducing COD and removing chromaticity components. The purpose is to do.

The coagulation-sedimentation apparatus of the present invention has a first reaction vessel including a means for adding an inorganic coagulant to the water to be treated and a means for adding an organic coagulant to the water to be treated, and a downstream of the first reaction vessel. A means for adding a first polymer flocculant, which is an anionic polymer flocculant, to the water to be treated, which is located in the section between the first reaction tank and the front of the sedimentation tank. ,have. In one aspect, the coagulation-precipitating device is located between the first reaction vessel and the position where the first polymer coagulant is added, and the second polymer coagulant, which is a cationic polymer coagulant, is added to the water to be treated. It has a second reaction vessel provided with means for adding the agent, and in another embodiment, the first reaction vessel adds a second polymer flocculant, which is a cationic polymer flocculant, to the water to be treated. It has the means to do it. In the settling tank, the water to be treated to which the inorganic flocculant, the organic coagulant, the first polymer flocculant and the second polymer flocculant are added is stirred to form the aggregated flocs and to form the aggregated flocs. Granulation concentration is performed, and the granulated concentrated flocs are separated from the treated water. The ratio of cationic groups of the cationic polymer flocculant is 5 to 8 mol%. Here, the "section from the first reaction tank to the front of the settling tank" includes the first reaction tank, but does not include the settling tank.

In the coagulation-sedimentation treatment method of the present invention, the section between the addition of the inorganic coagulant and the organic coagulant to the water to be treated at the first addition position and the section from the first addition position to the front of the settling tank downstream thereof. At the second addition position located in , the first polymer flocculant, which is an anionic polymer flocculant, is added to the water to be treated. In one aspect, the coagulation-sedimentation treatment method is a second addition, which is a cationic polymer flocculant in the water to be treated, at a third addition position located downstream of the first addition position and upstream of the second addition position. In another aspect, the coagulation-precipitation treatment method comprises adding a polymer flocculant of the above, and at the first addition position, the second polymer flocculant, which is a cationic polymer flocculant, is added to the water to be treated. Have to add. The coagulation-sedimentation treatment method further comprises supplying water to be treated to which an inorganic coagulant, an organic coagulant, a first polymer coagulant and a second polymer coagulant are added to the settling tank, and using the settling tank. By stirring the water to be treated, the aggregated flocs are formed, the aggregated flocs are granulated and concentrated, and the aggregated flocs that have been granulated and concentrated in the settling tank are separated from the treated water. There is. The ratio of cationic groups of the cationic polymer flocculant is 5 to 8 mol%. Here, the "section from the first addition position to the front of the settling tank downstream thereof" includes the first addition position, but does not include the settling tank.

According to the present invention, an organic coagulant is added to the water to be treated together with the inorganic flocculant. As a result, the amount of the inorganic flocculant added can be suppressed, so that pellets having high strength and density and a high sedimentation rate can be formed. Therefore, it is possible to suppress the floating amount of fine and light aggregated flocs in the upper part of the settling tank, reduce COD in the water to be treated, and remove the chromaticity component. As described above, according to the present invention, a coagulation-precipitation apparatus and agglomeration capable of suppressing the addition amount of an inorganic flocculant to form pellets having a high sedimentation rate, and efficiently reducing COD and removing chromaticity components. A method for precipitating can be provided.

It is a schematic diagram which shows the whole structure of the coagulation sedimentation apparatus which concerns on 1st Embodiment. It is a schematic diagram which shows the whole structure of the coagulation sedimentation apparatus which concerns on 2nd Embodiment. It is a schematic diagram which shows the whole structure of the coagulation sedimentation apparatus which concerns on 3rd Embodiment.

Hereinafter, some embodiments of the coagulation sedimentation apparatus of the present invention will be described with reference to the drawings. The coagulation sedimentation device of the present invention is mainly used for reducing COD in wastewater and removing chromaticity components. Examples of wastewater having a high COD and wastewater containing a chromaticity component include boiler blow wastewater discharged from a factory and dyed wastewater from a dyeing factory. However, the wastewater treated by the coagulation-sedimentation apparatus of the present invention is not limited as long as the wastewater is coagulated and settled by adding an inorganic coagulant, and may be, for example, wastewater containing fluorine or phosphate ions. good. Further, the coagulation sedimentation apparatus of the present invention is a granulation type apparatus for forming granulated products (pellets) in a granulation sedimentation tank. The aggregated flocs formed by the granulation type coagulation and sedimentation device are larger than ordinary aggregated flocs, and have a high density and a high sedimentation rate. Therefore, the water to be treated can be treated at a high LV as compared with the coagulation sedimentation device which is not a granulation type, and the settling tank becomes compact.

(First Embodiment)
FIG. 1 is a schematic view of a coagulation sedimentation apparatus according to the first embodiment. The coagulation sedimentation device 1 has a raw water tank 2 for storing water to be treated (raw water), a first reaction tank 3, a second reaction tank 4, and a settling tank 5, which are pipes 11 to 13. It is connected in series with. That is, the first reaction tank 3 is connected to the raw water tank 2 by the first pipe 11, the second reaction tank 4 is connected to the first reaction tank 3 by the second pipe 12, and the settling tank 5 is the first. It is connected to the second reaction tank 4 by the pipe 13 of 3. The settling tank 5 is located downstream of the first and second reaction tanks 3 and 4, and the second reaction tank 4 is located between the first reaction tank 3 and the settling tank 5. The first pipe 11 is provided with a water supply pump 14 and a flow meter 15.

The first reaction tank 3 includes an inorganic coagulant adding means 6 for adding an inorganic coagulant to the water to be treated, an organic coagulant adding means 7 for adding an organic coagulant to the water to be treated, and a pH adjuster to the water to be treated. The pH adjuster adding means 8 is provided. That is, the first reaction tank 3 constitutes the first addition position 3 in which the inorganic flocculant, the organic coagulant, and the pH adjuster are added to the water to be treated.

The inorganic coagulant adding means 6 includes an inorganic coagulant storage tank 61, an inorganic coagulant supply pipe 62 connected to the inorganic coagulant storage tank 61, and an inorganic coagulant supply pump 63 provided on the inorganic coagulant supply pipe 62. And have. The downstream end of the inorganic flocculant supply pipe 62 is open inside the first reaction tank 3. As the inorganic flocculant, an aluminum salt such as aluminum sulfate or polyaluminum chloride (PAC), an acidic solution of ferric chloride, an acidic solution of ferric salt such as ferric polysulfate, or the like can be used.

The organic coagulant adding means 7 includes an organic coagulant storage tank 71, an organic coagulant supply pipe 72 connected to the organic coagulant storage tank 71, and an organic coagulant supply pump 73 provided on the organic coagulant supply pipe 72. And have. The downstream end of the organic coagulant supply pipe 72 is open inside the first reaction tank 3. Examples of the organic coagulant include an alkylamine / epichlorohydrin condensate, a condensate of alkylene dichloride and polyalkylene polyamine, a dicyan / diamide / formalin condensate, a dimethyldiallylammonium chloride polymer, and the like, and the molecular weight thereof is tens of thousands to several. It is about 100,000. The type of the organic coagulant is not limited to these as long as it has the effect of reducing the amount of the inorganic flocculant added to the water to be treated.

The pH adjuster adding means 8 includes a pH adjuster storage tank 81, a pH adjuster supply pipe 82 connected to the pH adjuster storage tank 81, and a pH adjuster supply pump 83 provided on the pH adjuster supply pipe 82. And have. The downstream end of the pH adjuster supply pipe 82 is open inside the first reaction vessel 3. The pH adjuster is added to adjust the pH of the water to be treated to about 6 to 8, and an alkaline agent such as NaOH or Ca (OH) ₂ can be used. The first reaction tank 3 is provided with a pH meter 16 for measuring the pH of the water to be treated. Further, the first reaction tank 3 has a stirring blade 31, and can stir the water to be treated to which the inorganic flocculant, the organic coagulant and the pH adjuster are added at high speed.

The coagulation sedimentation device 1 has a first polymer coagulant adding means 10 for adding a first polymer coagulant to the water to be treated. The first polymer flocculant addition means 10 includes a first polymer flocculant storage tank 101, a first polymer flocculant supply pipe 102 connected to the first polymer flocculant storage tank 101, and a first polymer coagulant supply pipe 102. It has a first polymer flocculant supply pump 103 provided on the polymer flocculant supply pipe 102 of 1. The downstream end of the first polymer flocculant supply pipe 102 joins the third pipe 13. The confluence point of the first polymer flocculant addition means 10 with the third pipe 13 constitutes a second addition position 17 for adding the first polymer flocculant to the water to be treated. The second addition position 17 is located between the first reaction tank 3 and the settling tank 5.

The first polymer flocculant is an anionic polymer flocculant. Examples of the anionic polymer flocculant include a polymer of acrylamide and acrylic acid. The molecular weight of the anionic polymer flocculant is, for example, preferably 10 million or more, and more preferably 15 million or more. For the anionic polymer flocculant, for example, a solution in which the amount of the flocculant added is 0.5 to 10 mg / L is dissolved in water to adjust the concentration of the flocculant to 0.05 to 0.3 w / v%. It is preferably a lysate. If the addition amount is less than 0.5 mg / L, it may take time to form a granulated product having a large particle size. Further, even if the addition amount exceeds 10 mg / L, the effect of increasing the particle size of the granulated product is small, while the amount of the anionic polymer flocculant used increases. The optimum value of the anionic group ratio of the anionic polymer flocculant differs depending on the drainage properties and the aggregated pH.

The second reaction tank 4 includes a second polymer flocculant addition means 9 for adding the second polymer flocculant to the water to be treated. The second reaction tank 4 constitutes a third addition position 4 in which the first polymer flocculant is added to the water to be treated. The third addition position 4 is located between the first addition position 3 and the settling tank 5 downstream thereof. The second polymer flocculant addition means 9 includes a second polymer flocculant storage tank 91, a second polymer flocculant supply pipe 92 connected to the second polymer flocculant storage tank 91, and a second polymer flocculant supply pipe 92. It has a second polymer flocculant supply pump 93 provided on the polymer flocculant supply pipe 92 of 2. The downstream end of the second polymer flocculant supply pipe 92 is open inside the second reaction tank 4. The second reaction tank 4 has a stirring blade 41, and can stir the water to be treated to which the second polymer flocculant has been added at high speed.

The second polymer flocculant is a cationic polymer flocculant. Examples of the cationic polymer flocculant include dimethylaminoethyl acrylate / methyl chloride quaternary salt (DAA) and dimethylaminoethyl methacrylate quaternary salt (DAM). The molecular weight of the cationic polymer flocculant is, for example, preferably 7 million or more, and more preferably 10 million or more. For the cationic polymer flocculant, for example, a solution in which the amount of the flocculant added is 0.5 to 10 mg / L is dissolved in water to adjust the concentration of the flocculant to 0.05 to 0.3 w / v%. It is preferably a lysate. If the addition amount is less than 0.5 mg / L, it is difficult to obtain the effect of the cationic polymer flocculant (the effect of using the cationic polymer flocculant and the anionic polymer flocculant together), and a large granulated product is formed. It can be difficult. Further, even if the addition amount exceeds 10 mg / L, the effect of increasing the particle size of the granulated product is small, while the amount of the cationic polymer flocculant used increases. The ratio of cationic groups of the cationic polymer flocculant is preferably 27 mol% or less. The cation group ratio is more preferably 15 mol% or less, further preferably 8 mol% or less.

The settling tank 5 has an outer container 51 and a partition plate 52 provided inside the outer container 51. The settling tank 5 is separated into a settling section 54 and a sludge concentrating section 55 by an outer container 51 and a partition plate 52. The settling portion 54 forms and aggregates aggregated flocs by slowly stirring the water to be treated to which the inorganic flocculant, the organic coagulant, the first polymer flocculant and the second polymer flocculant are added. The flocs are granulated and concentrated (pellet formation), and the granulated and concentrated aggregated flocs are separated from the treated water. The sludge concentrating unit 55 collects and concentrates sludge as a suspended solid. The top of the partition plate 52 is lower than the top of the settling section 54 so that the aggregated flocs overflow from the settling tank 5 and are collected in the sludge concentrating section 55. A sludge extraction nozzle (not shown) is provided at the lower part of the side surface of the sludge concentrating unit 55. A nozzle for taking out clear water (treated water) (not shown) is provided on the upper part of the side surface of the settling portion 54. Inside the settling portion 54, a plurality of stirring blades 58 attached to a rotating shaft 56 connected to the motor 57 are provided.

The treatment of the water to be treated by the coagulation sedimentation device 1 is performed as follows. The water to be treated is first introduced from the raw water tank 2 through the first pipe 11 to the first reaction tank 3 (first addition position 3), and the inorganic flocculant, the organic coagulant and the pH adjuster are added. , High speed stirring. As a result, aggregated flocs are formed in the water to be treated. Next, the water to be treated is introduced into the second reaction tank 4 (third addition position 4) through the second pipe 12, the second polymer flocculant is added, and the mixture is stirred at high speed. This coarsens the aggregated flocs. Next, the first polymer flocculant is added to the water to be treated at the second addition position 17 on the third pipe 13. The second polymer flocculant (cationic polymer flocculant) is in the second reaction tank 4 (third addition position 4), and the first polymer flocculant (anionic high molecular weight) is in the second addition position 17. By adding the molecular flocculant), it is possible to form pellets that are stronger and have a faster settling rate.

The water to be treated as described above is introduced into the settling tank 5. The water to be treated is supplied as an ascending flow from the water supply port 59 at the bottom of the settling section 54 to the settling section 54, and is slowly stirred by the stirring blade 58. The first polymer flocculant added at the second addition position 17 is thereby stirred and dispersed in the water to be treated. As the aggregated flocs repeatedly collide with each other and roll, the particle size of the aggregated flocs gradually increases, and spherical pellets are formed. The pellet floats inside the settling portion 54 by receiving a downward force due to gravity and an upward force due to an upward flow of the water to be treated supplied from the water to be treated water supply port 59. The aggregated flocs contained in the newly supplied water to be treated are captured by the pellets floating inside the settling portion 54 and coalesced. This further increases the pellet diameter.

The water to be treated is separated from the granulated and concentrated flocs and becomes an upflow. As a result, a layer of pellets (pellet blanket 53) is formed in the lower part of the settling portion 54, and a layer of clear water 54 separated from the pellet blanket 53 is formed in the upper part. The clear water of the layer 54 is taken out from the take-out nozzle as treated water. The top interface of the pellet blanket 53 gradually rises, and when the top interface of the pellet blanket 53 reaches the top of the partition plate 52, the pellets overflow the partition plate 52 and are collected in the sludge concentrating unit 55. After that, the water to be treated continues to overflow from the top interface of the pellet blanket 53, and the pellet blanket 53 keeps a constant height. Since the sludge concentrating part 55 does not have an ascending flow of the water to be treated, the aggregated flocs settle in the sludge concentrating part 55 by gravity and become concentrated sludge. The concentrated sludge is drawn from the drawing nozzle.

Aggregated flocs formed by inorganic flocculants such as polyaluminum chloride (PAC) and iron chloride have low crosslinkability and become fine and light aggregate flocs. Therefore, if a large amount of inorganic flocculant is used to reduce COD and remove chromaticity components, high-strength aggregate flocs can be formed even if a cationic polymer flocculant and an anionic polymer flocculant are used in combination. It may be difficult to form pellets with a granulation and precipitation device. By using the organic coagulant in the present embodiment, it is possible to reduce the amount of the inorganic coagulant added while reliably forming pellets. Further, since the amount of sludge generated can be reduced by reducing the amount of the inorganic flocculant added, a cost reduction effect can be expected. Further, even in wastewater where it is difficult to apply the pellet coagulation sedimentation treatment due to the large amount of the inorganic coagulant added, the use of the organic coagulant facilitates the formation of pellets and enables high LV treatment.

The inorganic coagulant and the organic coagulant are simultaneously added to the water to be treated in the first reaction tank 3 (first addition position 3), but the inorganic coagulant and the organic coagulant are separately added to the water to be treated. May be done. For example, a reaction tank to which the inorganic flocculant is added and a reaction tank to which the organic coagulant is added may be installed in series. In that case, the arrangement order of the two reaction tanks is not particularly limited. That is, one of the inorganic flocculant and the organic coagulant may be added to the water to be treated first, and the other may be added to the water to be treated after that. Further, when the inorganic coagulant and the organic coagulant are added to the water to be treated in the first reaction tank 3 (first addition position 3), the inorganic coagulant and the organic coagulant may be added at the same time, while the inorganic coagulant and the organic coagulant may be added at the same time. May be added first and the other may be added later.

(Second embodiment)
FIG. 2 is a schematic view of the coagulation sedimentation device 101 according to the second embodiment. The configuration and effect for which the description is omitted are the same as those in the first embodiment. In the present embodiment, the second reaction tank 4 is omitted, and the first reaction tank 3 is provided with the second polymer flocculant addition means 9. The first polymer flocculant addition means 10 is provided in the same manner as in the first embodiment, and the first polymer flocculant is an anionic polymer flocculant. That is, in the present embodiment, in the first reaction tank 3 (first addition position 3), the water to be treated contains the inorganic flocculant, the organic coagulant, the pH adjuster, and the second polymer flocculant. Is added. The second polymer flocculant is a cationic polymer flocculant. As described in Examples described later, this embodiment can also obtain the same pellet diameter and water quality of the treated water as the first embodiment. Further, since the present embodiment does not require the second reaction tank 4, it is possible to reduce the equipment cost and the required installation space.

(Third embodiment)
FIG. 3 is a schematic view of the coagulation sedimentation device 201 according to the third embodiment. The configuration and effect for which the description is omitted are the same as those in the first embodiment. In the present embodiment, the second reaction tank 4 is omitted as compared with the first embodiment, and the second polymer flocculant addition means 9 included in the second reaction tank 4 is also omitted. .. The first polymer flocculant addition means 10 is provided in the same manner as in the first embodiment, and the first polymer flocculant is an anionic polymer flocculant. However, in the present embodiment, the first polymer flocculant may be a cationic polymer flocculant or a nonionic polymer flocculant. As will be described in Examples described later, although this embodiment is slightly inferior to the first embodiment, the effect of improving the water quality of the treated water such as reduction of COD can be obtained. Further, since the present embodiment does not require the second reaction tank 4 and the second polymer flocculant addition means 9, it is possible to further reduce the equipment cost and the required installation space.

(Experimental Example 1)
Only PAC (Comparative Examples 1 and 2) or PAC and an organic coagulant (Examples 1 to 3) are added to the water to be treated (stained wastewater) of the water quality shown in Table 1, and the pH is adjusted to 7 with NaOH. , Rapid stirring was performed at 150 rpm for 5 minutes. In Examples 1 and 2 and Comparative Examples 1 and 2, 1 mg / L of a cationic polymer flocculant (cationic polymer) having a cationic group ratio of 5 mol% was subsequently added, and the mixture was rapidly stirred at 150 rpm for 1 minute. Then, 2 mg / L of an anionic polymer flocculant (anionic polymer) having an anionic group ratio of 4 mol% was added, and the mixture was rapidly stirred at 150 rpm for 1 minute. Then, slow stirring was performed at 40 rpm for 5 minutes. In Example 3, in order to aggregate with the anionic polymer, 3 mg / L of the anionic polymer was added without adding the cationic polymer, and the mixture was rapidly stirred at 150 rpm for 1 minute and then slowly stirred at 40 rpm for 5 minutes. This experimental example simulates the process of the first and third embodiments, and the slow stirring for the last 5 minutes simulates the slow stirring in the settling tank 5. After the test, the mixture was allowed to stand for 10 minutes, the diameter of the aggregated flocs was confirmed, and the water quality of the supernatant was analyzed. Table 1 shows the composition of the water to be treated, and Table 2 shows the experimental results. The target water quality of the treated water is 5 degrees or less in color, a quaternary salt of a dimethylamine / epiclohydrin condensate having a molecular weight of 30,000 as the organic coagulant A, and a dimethylamine / epiclohydrin condensate having a molecular weight of 500,000 as the organic coagulant B. A quaternary salt was used. In Table 2, COD _Mn means the chemical oxygen demand measured using potassium permanganate, and SV30 of the sludge generation amount means the amount of sludge after stagnation for 30 minutes.

As a result of the experiment, in Comparative Example 1, large pellet-like aggregated flocs were formed, but the chromaticity component could not be sufficiently removed because the amount of PAC added was insufficient. In Comparative Example 2, the chromaticity could be sufficiently reduced by adding twice the amount of PAC as in Comparative Example 1, but as the amount of PAC added increased, the aggregated floc diameter became smaller and it was difficult to form pellets. there were. In Examples 1 to 3, an organic coagulant was used in combination so that the chromaticity component could be sufficiently removed and a large and high-strength aggregate floc (pellet) could be formed. As a result, even when 600 mg / L of PAC was added, the chromaticity component could be removed to the same level as in Comparative Example 2 in which 1200 mg / L of PAC was added, and large pellet-like aggregates were formed. Further, in Examples 1 to 3, the amount of PAC added was half that of Comparative Example 2, but the amount of sludge generated could be reduced to about half by using the organic coagulant in combination.

The types of the organic coagulant were different in Examples 1 and 2, and the organic coagulant B (Example 2) was slightly better in terms of COD, TOC, turbidity, and chromaticity, but no significant difference could be confirmed. rice field. In the comparison between Example 2 and Example 3, Example 2 in which the cationic polymer flocculant and the anionic polymer flocculant are used in combination is larger than Example 3 in which only the anionic polymer flocculant is used. Pellet-like aggregates were formed.

(Experimental Example 2)
Of Examples 1 to 3 in which the target water quality of treated water (color degree 5 degrees or less) could be satisfied in Experimental Example 1, Example 2 was slightly advantageous in terms of turbidity, chromaticity, and COD reduction rate. , 3 (PAC addition amount 600 mg / L, organic coagulant B addition amount 50 mg / L) was subjected to a continuous water flow test using a small tester. Further, even under the aggregation condition of Comparative Example 2 (PAC addition amount 1200 mg / L, no organic coagulant added) in which the target water quality of treated water (chromaticity 5 degrees or less) could be satisfied in Experimental Example 1, the same continuous flow was performed. A water test was performed. Examples 1 to 4 correspond to Example 2 (first embodiment) of Experimental Example 1, but the cationic group ratios of the cationic polymer flocculants (cationic polymers) are different from each other (cationic group ratio: 5). %, 8%, 15%, 27%). Example 5 corresponds to the second embodiment, in which an inorganic flocculant, an organic coagulant, and a cationic polymer flocculant were added to the same reaction vessel. Example 6 corresponds to Example 3 (third embodiment) of Experimental Example 1, and Comparative Example 1 corresponds to Comparative Example 2 of Experimental Example 1. In each Example and Comparative Example, the anionic group ratio of the anionic polymer flocculant (anionic polymer) was set to 4% as in Experimental Example 1. The equipment specifications of the small testing machine are as follows.
<Device specifications>
Each reaction tank capacity 10L
Settlement tank capacity 2.5L (blanket height 40cm)
Settlement tank diameter 67 mm
Water flow LV Examples 1 to 6 20 m / h (71 L / h)
Comparative Example 1 15 m / h (53 L / h)
Table 3 shows the experimental results.

From the comparison of Examples 1 to 4, the largest pellet was formed when the cation group ratio was 5 to 8% (Examples 1 and 2), and the suspended solids (SS) concentration was very high, about 3 mg / L. We were able to obtain treated water with high cleanliness. Even when a cationic polymer having a cationic group ratio of 15% is used (Example 3), the pellet particle size is larger and the SS concentration is lower than when the anionic polymer alone is pelletized (Example 6). The treated water could be obtained. When the cation group ratio was increased to 27% (Example 4), the treated water quality and pellet diameter were inferior to those of Example 6, but better than those of Comparative Example 1. When the inorganic flocculant, the organic coagulant and the cationic polymer flocculant are added to the same reaction vessel as in Example 5, treated water having the same extremely high cleanliness as in Examples 1 and 2 can be obtained. Was made. On the other hand, in Comparative Example 1, it was difficult to form pellets because the amount of PAC added was large. Further, in Comparative Example 1, since many aggregated flocs having a small diameter were generated, the treated water was passed through at a water flow rate of LV15 m / h, which was lower than that of Examples 1 to 6, but the aggregated flocs still flowed out and the speed was high. It was difficult to process. From this, it was confirmed that in each example, pellet formation is possible even under continuous water flow conditions, and high-speed treatment by pellet formation is possible.

(Experimental Example 3)
A continuous water flow test was carried out using dyed wastewater from a water intake source different from that of Experimental Examples 1 and 2. The water quality of the wastewater used is shown in Table 4, and the experimental results are shown in Table 5. The target water quality was COD less than 20 mg / L. Examples 1 to 3 correspond to the first to third embodiments, respectively, and Comparative Examples 1 and 2 correspond to Comparative Examples 1 and 2 of Experimental Example 1. In Comparative Example 1, the amount of PAC added was insufficient and no organic coagulant was added, so that COD could not be reduced to less than 20 mg / L. Further, in Comparative Example 1, large pellets were formed in the lower part of the settling tank, but fine aggregate flocs with poor aggregation that were not captured by the pellet blanket tended to flow out. In Comparative Example 2, since the amount of PAC added (800 mg / L) was doubled as compared with Comparative Example 1, the COD could be reduced to less than 20 mg / L, but the aggregated flocs were very light, so that the COD could be reduced. At water LV 15 m / h, aggregated flocs flowed out into the treated water. On the other hand, in Examples 1 and 2, since the organic coagulant was used in combination, COD could be reduced to 14 to 16 mg / L even if the amount of the inorganic flocculant added was small, and large pellets could be formed. In Example 3, the SS concentration was inferior to that of Examples 1 and 2 in which the cationic polymer flocculant and the anionic polymer flocculant were used in combination, but the COD could be reduced to 16 mg / L.

1,101,201 Coagulation sedimentation device 3 First reaction tank (first addition position)
4 Second reaction tank (third addition position)
5 Sedimentation tank 6 Inorganic coagulant addition means 7 Organic coagulant addition means 9 Second polymer coagulant addition means 10 First polymer coagulant addition means 17 Second addition position

Claims (4)

A first reaction vessel comprising a means for adding an inorganic flocculant to the water to be treated and a means for adding an organic coagulant to the water to be treated.
A settling tank located downstream of the first reaction tank and
A means for adding the first polymer flocculant, which is an anionic polymer flocculant, to the water to be treated, which is located in the section between the first reaction tank and the front of the settling tank .
A means for adding a second polymer flocculant, which is a cationic polymer flocculant, to the water to be treated, which is located between the first reaction tank and the position where the first polymer flocculant is added. With a second reaction vessel ,
The settling tank is formed by stirring the water to be treated to which the inorganic flocculant, the organic coagulant, the first polymer flocculant and the second polymer flocculant are added, thereby causing the aggregated flocs. The agglomerated flocs are formed and granulated and concentrated, and the granulated and concentrated flocs are separated from the treated water.
A coagulation-precipitation device in which the ratio of cationic groups of the cationic polymer flocculant is 5 to 8 mol% . A first reaction vessel comprising a means for adding an inorganic flocculant to the water to be treated and a means for adding an organic coagulant to the water to be treated.
A settling tank located downstream of the first reaction tank and
It is located in the section between the first reaction tank and the front of the settling tank, and has a means for adding the first polymer flocculant, which is an anionic polymer flocculant, to the water to be treated. ,
The first reaction tank comprises means for adding a second polymer flocculant, which is a cationic polymer flocculant, to the water to be treated.
The settling tank is formed by stirring the water to be treated to which the inorganic flocculant, the organic coagulant, the first polymer flocculant and the second polymer flocculant are added, thereby causing the aggregated flocs. The agglomerated flocs are formed and granulated and concentrated, and the granulated and concentrated flocs are separated from the treated water.
A coagulation-precipitation device in which the ratio of cationic groups of the cationic polymer flocculant is 5 to 8 mol%. Adding an inorganic flocculant and an organic coagulant to the water to be treated at the first addition position,
At the second addition position located in the section between the first addition position and the front of the settling tank downstream thereof , the first polymer flocculant, which is an anionic polymer flocculant, is added to the water to be treated. To add and
A second polymer flocculant, which is a cationic polymer flocculant, is added to the water to be treated at a third addition position located downstream of the first addition position and upstream of the second addition position. To do and
The water to be treated to which the inorganic flocculant, the organic coagulant, the first polymer flocculant and the second polymer flocculant are added is supplied to the settling tank.
By stirring the water to be treated in the settling tank, aggregated flocs are formed, the aggregated flocs are granulated and concentrated, and the aggregated flocs are granulated and concentrated.
It has to separate the aggregated flocs that have been granulated and concentrated in the settling tank from the treated water.
A method for coagulation-precipitation treatment, wherein the cationic group ratio of the cationic polymer flocculant is 5 to 8 mol% . Adding an inorganic flocculant and an organic coagulant to the water to be treated at the first addition position,
At the second addition position located in the section between the first addition position and the front of the settling tank downstream thereof, the first polymer flocculant, which is an anionic polymer flocculant, is added to the water to be treated. To add and
At the first addition position, the second polymer flocculant, which is a cationic polymer flocculant, is added to the water to be treated.
The water to be treated to which the inorganic flocculant, the organic coagulant, the first polymer flocculant and the second polymer flocculant are added is supplied to the settling tank.
By stirring the water to be treated in the settling tank, aggregated flocs are formed, the aggregated flocs are granulated and concentrated, and the aggregated flocs are granulated and concentrated.
It has to separate the aggregated flocs that have been granulated and concentrated in the settling tank from the treated water.
A method for coagulation-precipitation treatment, wherein the cationic group ratio of the cationic polymer flocculant is 5 to 8 mol%.

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