JP2006000715A - Equipment and method for flocculation precipitation treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide compact equipment and a method for flocculation precipitation treatment which require a lower rate of injection of a coagulant than that of conventional equipment, permit high-speed treatment and have excellent concentrating and dehydrating properties of produced sludge. <P>SOLUTION: The equipment carries out flocculation precipitation treatment comprising adding a coagulant to raw water containing suspended matter to separate into coagulated floc and clear water through flocculation precipitation. It has a flocculation vessel 10 stirring the raw water added with the coagulant to form coagulated floc and a precipitation vessel 12 which allows the flocculated water from the vessel 10 to flow in from its lower part, causes clear water to flow out from its upper part and separates coagulated flock through adsorption with the floc blanket layer formed within the vessel 12. In the vessel 12, stirring is carried out with a GT value, a product of the stirring intensity G, sec-1, and the residence time T, sec, of ≥200,000. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coagulation-precipitation treatment apparatus and a coagulation-precipitation treatment method in which a flocculant is added to raw water containing a suspended substance and separated into coagulated floc and clear water by coagulation precipitation.

  Conventionally, in water purification treatments that purify raw water such as river water, ground water, lake water, etc., rapid agitation / slow agitation (floc formation) / precipitation is a turbidity treatment method that removes organic and inorganic suspended substances in the raw water. There is known a method using a conventional type coagulation sedimentation processing apparatus constituted by three unit processes of separation. In this method, (1) the flocculant is injected rapidly and the flocculant is brought into contact with the suspended substances in the raw water to form fine flocs. (2) The fine flocs are collided and assembled by slow stirring. Growing into large flocs, and (3) precipitating water that is a supernatant is obtained by precipitating flocs and separating them to obtain a supernatant. Then, the sedimentation water is subjected to sand filtration and the like, and then sterilized and drained.

  However, in the conventional type coagulation sedimentation processing method, if the flocculant floc is not sufficiently large, the fine aggregation floc flows out from the sedimentation tank, and the filter medium is clogged in the subsequent filtration process. For this reason, there has been a problem that a large amount of a flocculant has to be injected in order to improve the removal rate of suspended substances in the coagulation sedimentation treatment. In addition, there is a problem that a large amount of the flocculant causes an increase in the amount of sludge generated.

In order to solve this problem, Japanese Patent Laid-Open No. 2002-192163 (Patent Document 1) proposes that the stirring intensity G value be 300 sec ⁻¹ or more in the rapid stirring step. Thereby, it is said that the amount of sludge generation can be reduced by reducing excess flocculant, which reduces suspended matter derived from the flocculant and suppresses clogging of the filter medium.

  On the other hand, the high-speed coagulation precipitation device that combines the three processes of rapid stirring / slow stirring (floc formation) / precipitation separation or the latter two processes in one apparatus is faster than conventional type coagulation precipitation treatment methods. A number of coagulation-precipitation methods that can be processed have been adopted. In this high-speed coagulation sedimentation apparatus, as the high-speed coagulation sedimentation, a floc blanket type high-speed coagulation sedimentation basin that performs flocculation treatment by water flow stirring, a slurry circulation type high-speed coagulation sedimentation basin that performs slow stirring by mechanical stirring, or a composite type of these A high-speed coagulation sedimentation basin is used.

JP 2002-192163 A

  However, the conventional type coagulation sedimentation treatment apparatus as in Patent Document 1 has a problem that a large installation area is required.

  Moreover, according to the high-speed coagulation sedimentation apparatus, although stable treatment is performed over a wide range from raw water with low turbidity to raw water with high turbidity, it requires a lot of site area because the processing speed is slow. It has been pointed out as a problem that the sludge treatment facility becomes large due to poor concentration and dehydration. Another problem is that the amount of generated sludge is increased by adding a large amount of flocculant so as not to leave fine floc in the treated water.

  The present invention is a compact coagulation sedimentation treatment apparatus and coagulation sedimentation treatment method that has a lower coagulant injection rate than conventional devices, enables high-speed treatment, and is excellent in the concentration and dewatering properties of generated sludge.

The present invention relates to a flocculation / precipitation treatment apparatus in which a flocculant is added to raw water containing a suspended substance and separated into agglomerated floc and clarified water by agglomeration precipitation, and the raw water to which the flocculant is added is stirred to agglomerate floc A flocculation tank that forms a coagulation treatment water from the lower flocculation tank, and a clarification water that flows out from the upper part and a flocculation blanket layer that is formed in the tank, In the agglomeration tank, stirring is performed when the GT value, which is the product of the stirring strength G value (sec ⁻¹ ) and the residence time T (sec), is 200,000 or more.

  In the coagulation sedimentation treatment apparatus, the coagulant is an aluminum-based inorganic coagulant, and the coagulation treatment is performed by injecting coagulant having an AlT ratio of 0.1 or less, which is the amount of aluminum added to the turbidity component of the raw water. It is preferable to be performed at a rate.

  In the coagulation sedimentation processing apparatus, the coagulant is an iron-based inorganic coagulant, and the coagulant is injected with an coagulant having an FeT ratio of 0.2 or less, which is an amount of iron added to the turbidity component of the raw water. It is preferable to be performed at a rate.

  Moreover, in the said coagulation sedimentation processing apparatus, it is preferable that the water flow rate in the said coagulation process is 5 m / hr or more.

  Further, in the coagulation sedimentation treatment apparatus, further, above the interface between the flock blanket layer and the clarified water, it is inclined to prevent the mother flock from the flock blanket layer from flowing out to the supernatant water layer. It is preferable to arrange a tilting device in which plate members are arranged at intervals.

  Moreover, in the said coagulation sedimentation processing apparatus, it is preferable to arrange | position the said inclination apparatus in multistage in the depth direction.

The present invention also relates to a flocculation / precipitation treatment method in which a flocculant is added to raw water containing suspended substances and separated into flocculated floc and clarified water by flocculation / precipitation, wherein the flocculant is added to the raw water; Agglomeration treatment step of stirring the added water to which the flocculant is added to form an agglomeration floc; and the agglomeration treatment water that has undergone the agglomeration treatment is allowed to flow from the lower part, and the clarified water is allowed to flow from the upper part and is formed in the tank. A step of absorbing and separating agglomerated flocs by a floc blanket layer, and in the agglomeration treatment, a GT value that is a product of a stirring intensity G value (sec ⁻¹ ) and a residence time T (sec) is 200000 Stirring is performed as described above.

  In the coagulation sedimentation treatment method, the coagulant is an aluminum-based inorganic coagulant, and the coagulation treatment is performed by injecting the coagulant with an AlT ratio of 0.1 or less, which is the amount of aluminum added to the turbidity component of the raw water. It is preferable to be performed at a rate.

  In the coagulation sedimentation treatment method, the coagulant is an iron-based inorganic coagulant, and the coagulation treatment is performed by injecting the coagulant with an FeT ratio of 0.2 or less, which is the amount of iron added to the turbidity component of the raw water. It is preferable to be performed at a rate.

  Moreover, in the said coagulation sedimentation processing method, it is preferable in the said coagulation process that a water flow rate is 5 m / hr or more.

  In the coagulation sedimentation treatment method, a tilting device in which tilted plate members are arranged at an interval above the interface between the flock blanket layer and the clarified water is disposed, and the mother from the flock blanket layer is disposed. It is preferable to prevent the floc from flowing into the supernatant water layer.

  Moreover, in the said coagulation sedimentation processing method, it is preferable to arrange | position the said inclination apparatus in multiple steps in the depth direction.

  According to the present invention, in a coagulation sedimentation processing apparatus in which a coagulant is added to raw water containing suspended solids and separated into coagulated floc and clarified water by coagulation sedimentation, a rapid stirring apparatus capable of giving high agitation strength is provided. Therefore, a compact coagulation sedimentation treatment device and a coagulation sedimentation treatment method that have a lower coagulant injection rate than conventional coagulation sedimentation treatment devices, are capable of high-speed treatment, and are excellent in the concentration and dewatering properties of the generated sludge. Can do.

  Hereinafter, embodiments of the present invention will be described.

First, presupposed matters of the present invention will be described. The coagulation sedimentation processing apparatus according to the present embodiment is a coagulation precipitation treatment apparatus that adds a coagulant to raw water containing a suspended substance and separates it into coagulation floc and clarified water by coagulation precipitation, and the raw water to which the coagulant is added Agglomeration tank that forms agglomeration floc by agitation, and agglomerated water from the agglomeration tank is allowed to flow in from the lower part, and clear water is allowed to flow out from the upper part, and the floc blanket layer formed in the tank absorbs the agglomerated flocs In the coagulation tank, stirring is performed when the GT value, which is the product of the stirring strength G value (sec ⁻¹ ) and the residence time T (sec), is 200,000 or more.

  In the agglomeration treatment with conventional high-speed agglomeration sedimentation equipment, the high-speed agglomeration sedimentation basin includes a floc blanket type high-speed agglomeration sedimentation basin that performs agglomeration treatment by water flow agitation and a slurry circulation type high-speed agglomeration sedimentation basin that performs slow agitation by mechanical agitation Alternatively, a composite high-speed coagulation sedimentation basin or the like is used.

  In the floc blanket type high-speed coagulation sedimentation basin, the raw water mixed with the flocculant passes from below the slurry layer (floc blanket layer) of the ready-made floc that is in a floating state due to the rising water flow. Contact and become one. The flocs that have grown and have a sedimentation velocity greater than the ascending water flow are separated from the ascending water flow and join the existing flocs. The clarified water from which the floc has been separated flows out from the outlet located near the water surface, and excess slurry is eliminated. Stirring is performed by water flow stirring.

  In the slurry circulation type high-speed coagulation sedimentation basin, the raw water mixed with the coagulant is brought into contact with the circulating slurry of the existing flocs by the slow stirring by mechanical stirring, and is flocked. Then, it flows into the separation section together with the circulating flow, where it is separated into an ascending water flow of clarified water and a circulating downward slurry flow. The clarified water from which the floc has been separated flows out from the outlet located near the water surface, and excess slurry is eliminated. Stirring is performed as slow stirring by mechanical stirring using a stirring blade or the like.

In the conventional conventional coagulation sedimentation processing method, the stirring intensity G value of rapid stirring is as low as about 150 sec ⁻¹ . Here, the G value (sec ⁻¹ ) is a value indicating the agitation intensity, and the energy consumption rate ε ₀ (erg / cm ³ · sec) of the agitation blade is expressed as water as shown in the equation (1). It is represented by the square root of the value divided by the viscosity coefficient μ.
G = (ε ₀ / μ) ^1/2 (1)

  Also, in the agglomeration treatment by the conventional high-speed agglomeration precipitation apparatus, mechanical stirring or water flow stirring is employed, but in any case, a low G value is employed.

  The inventors of the present application have studied the poor concentration and dewatering properties of the generated sludge in a conventional high-speed coagulation sedimentation apparatus. In the agglomeration process in which the flocculant is added to the raw water containing the suspended solids and stirred to agglomerate as flocs, when the treatment is performed at a low flocculant injection rate in order to suppress sludge generation, Precipitation separation, as well as the mother floc forming the flock blanket layer, contains fine floc that flows into the treated water without being absorbed, and this increases the turbidity of the treated water. However, in order to reduce the fine flocs and obtain a treated water quality equivalent to the conventional type coagulation sedimentation treatment method, conventionally, only means for increasing the coagulant injection amount has been performed.

  Also, when the stirring intensity is weak and the stirring time is shortened, the unaggregated turbidity tends to increase, and this unaggregated turbidity determines the treated water turbidity, but in order to suppress the generation of sludge, the flocculant injection rate is reduced. The tendency becomes stronger as the stirring intensity is decreased.

  The inventors of the present application examined a new coagulation turbidity treatment method capable of improving the concentration and dewatering properties of the generated sludge. Although it can be achieved, the turbidity of the treated water is high, and the number of remaining fine particles of 7 μm or less, particularly 1 μm or less, cannot be reduced. However, the GT value, which is the product of the rapid stirring strength G and the residence time T, is appropriately controlled to perform the agglomeration treatment, and then the contact / suction with the mother flock such as a flock blanket layer to perform water flow. The present inventors have found that the water quality can be improved compared with the treated water of the conventional coagulation sedimentation treatment apparatus despite the high speed.

That is, after performing the flocculation treatment under the high GT value condition, the flocculation water was allowed to flow into the high-speed flocculation settling device.
(1) Regarding improvement of the treatment property of generated sludge, it is known that the coagulant injection rate may be reduced from cases such as the coagulation filtration method. However, in the existing high-speed coagulation sedimentation basin, since the G value is low even in the water flow stirring or the occasional stirring, the coagulant injection rate is increased as the standard of the purified water turbidity becomes stricter. This is a study that, as described in Reference 1 (Shogo Tsunoda, Industrial Water, No. 132, pages 29-38 (1969)), in the existing high-speed coagulation sedimentation basin, if the stirring strength is increased, the quality of the treated water is rather deteriorated. It is thought that the result is reflected. Therefore, the existing high-speed coagulation sedimentation basin cannot improve the treatment efficiency of the generated sludge.
(2) In addition to lowering the AlT ratio, when the stirring strength is increased, the floc formed becomes finer and has a small diameter that cannot be easily separated by precipitation. In the floc blanket layer turbidity treatment having a mother floc and high impact absorptive efficiency, it is possible to separate such a small floc with a small diameter, but in this embodiment, in a coagulation tank (rapid stirring tank) By setting the rapid stirring condition such that the product GT value of the stirring strength G (sec ⁻¹ ) and the stirring time T (sec) is 200,000 or more, the existing agglomeration can be achieved even if the flocculant injection rate is lower than the conventional one. It is confirmed that it is equivalent to the treated water quality of the precipitation device. The fine flocs formed under such agitation conditions are small although they are small in diameter, and the mother flocs that have become large by sucking such fine flocs are also small in diameter but dense and have a large sedimentation property. High-speed processing becomes possible. Moreover, since the number of the mother flocs per unit volume of the floc blanket, although having a small diameter, is remarkably increased, the suction efficiency of the fine flocs is increased and the quality of the treated water can be improved.
(3) In this embodiment, although the aggregated floc is dense and has a high sedimentation property, the floc diameter is small. Therefore, the higher the speed, the larger the amount of outflow of the mother floc constituting the flock blanket layer. Therefore, it is preferable to dispose a tilting device for preventing the mother flock outflow above the interface between the flock blanket layer and the supernatant water. By disposing the tilting device, the quality of the treated water can be improved while maintaining the flock blanket layer. In addition, although a single stage has a corresponding effect, the treatment effect can be improved by installing multiple stages, at least two stages, in the depth direction.
I found out.

  FIG. 1 is a block diagram showing a configuration of an example of a coagulation sedimentation processing apparatus according to the present embodiment. The coagulation sedimentation processing apparatus 1 according to this embodiment includes a coagulation tank (rapid agitation tank) 10, a sedimentation tank 12, a sludge concentration storage tank 14, a stirring blade 16, a motor 18, a turbidity measuring device 20, a control unit 22, and a pump 24. The tilting device 26 is included.

Raw water such as river water, ground water, lake water, etc. flows into the agglomeration tank 10 first. The flocculant is added to the inflowing raw water in the coagulation tank 10 and rapid stirring is performed. The rapid stirring is performed at a stirring strength G of 300 sec ⁻¹ or more, and the suspended matter in the raw water is finely flocked.

  As the flocculant, inorganic flocculants such as aluminum salts and iron salts can be used. Specific examples include a polyaluminum chloride flocculant (PAC) and an iron-silica inorganic polymer flocculant (PSI) in which iron and polymerized silicic acid (silica) which is an inorganic anionic polymer are combined.

  The flocculant is added using the pump 24. The flocculant injection rate at this time is preferably controlled according to the turbidity of the raw water. At this time, the flocculant injection rate is preferably controlled by the control unit 22 based on the turbidity of the raw water measured by the turbidity measuring device 20. The control unit 22 includes a control element such as a CPU and a storage unit such as a semiconductor memory.

  When the flocculant is an aluminum-based inorganic flocculant, the flocculant treatment is preferably performed at a flocculant injection rate with an AlT ratio of 0.1 or less. If the AlT ratio exceeds 0.1, the amount of sludge generated solids may increase as much as the amount of flocculant increases. However, the volume of generated sludge increases due to deterioration of the concentration of the generated sludge. There is a case.

  Further, when the aggregating agent is an iron-based inorganic aggregating agent, the aggregating treatment is preferably performed at an aggregating agent injection rate of FeT ratio of 0.2 or less. When the FeT ratio exceeds 0.2, the amount of the flocculant increases and the amount of sludge generated may increase. Here, the FeT ratio is the amount of iron added to the turbidity component of raw water.

Agitation in the agglomeration tank 10 is performed by a stirring blade 16 driven by a motor 18 or the like. The stirring strength G in the coagulation tank 10 is 300 sec ⁻¹ or more. In the present embodiment, the stirring strength G refers to the stirring strength in the rapid stirring step in the aggregation tank (rapid stirring tank) 10. Agitation intensity G is preferably further in the range of ^{450sec -1 ~800sec -1,} and more preferably in the range of 600sec ^-1 ~800sec -1. Stirring strength G is less than 300 sec ^-1, may 1μm following number of particles unaggregated turbidity component increases, when it exceeds 800 sec ^-1, or because once formed flocs are broken 800 sec ^The treated water turbidity may be slightly higher than ^-1 or less.

The GT value (= G × T), which is the product of the stirring intensity G value (sec ⁻¹ ) and the residence time T (sec), in the coagulation tank 10 is 200,000 or more, but is in the range of 300,000 to 500,000. It is preferable. In the present embodiment, the residence time T refers to the residence time in the rapid stirring process in the aggregation tank (rapid stirring tank) 10. When the GT value is less than 200000, the turbidity and the number of particles of 1 μm or less may be high, and when it exceeds 500,000, the improvement effect such as turbidity may be reduced with respect to the applied power.

  In the flocculation treatment in the flocculation tank 10, the water flow rate is preferably 5 m / hr or more, and more preferably in the range of 7.5 m / hr to 15 m / hr. If the water flow rate is less than 5 m / hr, the apparatus may become large, and if it exceeds 15 m / hr, the quality of the treated water may deteriorate. This is thought to be because the porosity of the floc blanket increases at high speed flow, that is, the distance between the particles of the mother floc increases, so that the impact absorption efficiency of the fine flocs decreases, resulting in deterioration of the quality of the treated water. .

  A plurality of tanks may be installed as the aggregation tank 10. Moreover, the aggregation tank 10 may be divided | segmented into the some tank. In these cases, the residence time is the total residence time of each tank.

  In the agglomeration tank 10, the agglomerated water containing the fine flocs subjected to the agglomeration process flows out from the lower part of the agglomeration tank 10. The flocculated water that has flowed out flows from the lower part of the settling tank 12. In the settling tank 12, the agglomerated water passes from below the slurry layer 28 (floc blanket layer) of the ready-made flocs that are in a floating state due to the rising water flow, so that the suspended solids come into contact with a large number of the ready-made flocs and become integral. . The flocs that have grown and have a sedimentation velocity greater than the ascending water flow are separated from the ascending water flow and join the existing flocs. The clarified water from which the floc has been separated flows out from the clarified water outlet 30 disposed at a position near the water surface.

  Excess slurry is discharged from a sludge outlet 32 disposed near the upper surface of the flock blanket layer 28. The discharged surplus slurry is disposed as sludge 34. The sludge 34 is dehydrated by a filtration process such as a filter press.

  Further, as described above, it is preferable to dispose the tilting device 26 above the interface between the flock blanket layer 28 and the clear water. In addition, the inclination apparatus 26 arrange | positions the inclined board | plate material at intervals. Although the aggregate flocs are dense and have a high sedimentation property, the floc diameter is small. Therefore, the higher the speed, the larger the amount of outflow of the mother flocs constituting the flock blanket layer 28 tends to increase. Can be prevented. By disposing the tilting device 26, it is possible to improve the quality of the treated water while maintaining the flock blanket layer 28. In addition, the tilting device 26 has a corresponding effect even in a single stage, but it is more preferable to install multiple stages and at least two stages in the depth direction because the treatment effect can be improved. FIG. 1 shows an example in which the tilting device 26 is installed in two stages. When installing in two stages, it is preferable to install one (26a) near the water surface and the other (26b) near the upper part of the interface between the flock blanket layer 28 and the clarified water. As the tilting device 26, for example, a tilting plate 36 as shown in FIG. 2 can be used.

  Since the existing high-speed coagulation sedimentation basin does not have a stirrer that can give a high G value for a predetermined time as in this embodiment, the method of reducing the coagulant injection rate for improving sludge treatment is Inevitable, a method for reducing the amount of the non-aggregated floc by increasing the flocculant injection rate has been taken. When the flocculant injection rate is increased, the floc diameter is increased, the distance between flocs in the floc blanket layer is increased, and the probability of collision with fine flocs is decreased.

  In this embodiment, in addition to increasing the rapid stirring strength, the rapid stirring time is lengthened to perform the agglomeration treatment, and then the processing by contact / sucking with the mother flock such as a flock blanket layer is performed, whereby the water flow rate is increased. However, the water quality can be improved as compared with the treated water of the conventional coagulation sedimentation treatment apparatus.

  This is because the fine flocs formed by rapid stirring become smaller and denser when the flocculant injection rate is lowered, and the diameter of the mother floc that grows becomes smaller as the flocculant injection rate is lower. The solids concentration in the blanket increases. That is, contrary to the above example, although the mother floc diameter is small, the number of flocs increases, and therefore the distance between the flocs is much narrower than in the above example, so the collision probability with the inflowing fine flocs As a result, it is presumed that, as a result, the turbidity of the treated water is improved despite the high flow rate treatment.

  Regarding this phenomenon, Document 2 (Tanho Norihito et al., Water Supply Association Magazine, No. 417, pages 7 to 17 (June 1969)), Reference 3 (Tanbo Norihito, Water Supply Association Magazine, No. 386, pages 38 to 46) (January 1966)) According to the research results described in (1966), if the water is passed directly through the blanket layer as micro flocs after rapid stirring (low strength), the treated water turbidity rapidly at a flow rate of 3 m / hr or higher. Reported that the degree deteriorated. However, in the present embodiment, 10 m / hr is about 3.3 times that of the experimental examples of References 2 and 3 while maintaining the same point that microfloc is allowed to flow directly into the blanket layer by giving only rapid stirring. Despite treatment, it was confirmed that the treated water turbidity remained at a much lower value.

  Regarding the high-speed coagulation sedimentation basin, references 2 and 3 and the water supply facility design guidelines describe the problems at the time of high turbidity, which are thought to result from the relationship with the sedimentation and concentration of the generated sludge. In the present application in which the concentration can be greatly improved, these problems can be greatly reduced.

  In addition, as described in References 1 and 4 (Sho Tsunoda, Industrial Water, No. 133, pages 39 to 47 (1969)), after the rapid flocculation sedimentation basin was developed, It is common knowledge that the turbidity of the treated water deteriorates when the agitation is strengthened, and the speeding up of the water treatment in the high-speed coagulation sedimentation basin is achieved by suppressing the agitation strength and creating a large floc. It was thought.

According to this embodiment, it breaks through and appropriately manages the GT value which is the product of the stirring intensity G value (sec ⁻¹ ) and the residence time T (sec), thereby reducing the majority of the year. In the treatment of the raw turbidity water, the treatment water turbidity lower than the treatment water quality of the existing high-speed coagulation sedimentation basin can be secured by the treatment at a high speed despite the low AlT treatment.

  Furthermore, as shown in FIG. 7, the result that the quality of the treated water is improved is also obtained for the treatment of high turbidity raw water accompanying sudden rainfall.

  At present, the coagulant injection rate in the coagulation sedimentation process is determined by performing a jar test and selecting an injection rate with the best supernatant water turbidity, large flocs and good sedimentation. As a result, as described above, the flocculant is excessively injected, which leads to a marked deterioration in the treatment property of the generated sludge.

  When processing at a low coagulant injection rate as in the present embodiment, the conventional jar test method has a small floc diameter and does not clarify the supernatant water. However, by performing the treatment under the above conditions, a treated water quality equivalent to or better than that of the conventional method can be secured. However, as a control method therefor, the raw water turbidity is about 100 degrees, for example, with an AlT ratio of 0.03. By controlling the turbidity proportionally, that is, by controlling the turbidity by further reducing the AlT ratio from 0.02 to 0.01 when the degree of turbidity is 100 degrees or more, the flocculant injection control over the entire turbidity range can be performed.

Thus, in the coagulation sedimentation processing apparatus and the coagulation sedimentation processing method according to the present embodiment,
(1) Preliminary agglomeration tank (rapid agitation tank) capable of giving high agitation strength, GT value which is the product of agitation intensity G value (sec ⁻¹ ) and residence time T (sec) in the agglomeration tank By properly managing
More preferably,
(2) Treatment with low coagulant injection rate (3) High flow rate treatment (4) By installing a tilting device for preventing mother floc outflow and a tilting device for improving the quality of treated water, compared to conventional coagulation sedimentation treatment equipment In addition, the coagulant injection rate is low, high-speed treatment is possible, and a compact coagulation sedimentation treatment apparatus and coagulation sedimentation treatment method excellent in the concentration and dewatering properties of the generated sludge can be obtained.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail more specifically, this invention is not limited to a following example, unless the summary is exceeded.

Example 1
Using the coagulation sedimentation processing apparatus shown in FIG. 1, raw water was treated under the following conditions while changing the residence time T in the coagulation tank (rapid stirring tank) and the stirring strength G value. FIG. 3 shows the relationship between the product GT value of the stirring intensity G (sec ⁻¹ ) and the residence time T (sec) and the turbidity (mg / L) of the treated water. FIG. 4 shows the relationship between the product GT value of the stirring intensity G (sec ⁻¹ ) and the residence time T (sec) and the number of residual fine particles (pieces / mL).

[Processing conditions]
Raw water turbidity: 20mg / L
Water flow speed: 10m / hr
Flock blanket layer height: 1600mm
Flocculant: PAC
Coagulant injection rate: AlT ratio = 0.05

As can be seen from FIG. 3, the turbidity of the treated water (clear water) is improved by setting the product GT value of the stirring intensity G (sec ⁻¹ ) and the residence time T (sec) to 200,000 or more. At that time, as can be seen from FIG. 4, by setting the product GT value of the stirring intensity G (sec ⁻¹ ) and the residence time T (sec) to 200,000 or more, the number of residual fine particles (number / mL / mL) of the treated water ) Decreases.

(Example 2)
Using the coagulation sedimentation treatment apparatus shown in FIG. 1, raw water was treated under the following conditions while changing the coagulant injection rate AlT ratio, the stirring strength G value, and the residence time T. The relationship between the AlT ratio and the turbidity (mg / L) of treated water is shown in FIG.

[Processing conditions]
Raw water turbidity: 20mg / L
Water flow speed: 10m / hr
Flock blanket layer height: 730mm
Flocculant: PAC
Coagulant injection rate: AlT ratio = 0.02, 0.03, 0.04, 0.05, 0.10
GT value: 150 sec ⁻¹ × (4.83 × 60) sec, 650 sec ⁻¹ × (12.64 × 60) sec

As can be seen from FIG. 5, the treated water turbidity is improved by setting the product GT value of the stirring intensity G (sec ⁻¹ ) and the residence time T (sec) to 200,000 or more.

Example 3
Using the coagulation sedimentation treatment apparatus shown in FIG. 1, raw water was treated under the following conditions while changing the coagulant injection rate AlT ratio. The relationship between the AlT ratio and the turbidity (mg / L) of treated water is shown in FIG.

[Processing conditions]
Raw water turbidity: 20mg / L
Water flow speed: 10m / hr
Flock blanket layer height: 1600mm
Flocculant: PAC
Coagulant injection rate: AlT ratio = 0.02, 0.03, 0.04, 0.05, 0.10
GT value: 650 sec ⁻¹ × (12.64 × 60) sec

  As can be seen from FIG. 6, the turbidity of the treated water (clear water) is good even when the AlT ratio is 0.1 or less.

Example 4
Using the coagulation sedimentation processing apparatus shown in FIG. 1, the raw water was treated under the following conditions while changing the turbidity of the raw water. FIG. 7 shows the relationship between the treatment time, raw water, and turbidity (mg / L) of the treated water.

[Processing conditions]
Raw water turbidity: 100, 400, 800 mg / L
Water flow speed: 10m / hr
Flock blanket layer height: 1330mm
Flocculant: PAC
Coagulant injection rate: AlT ratio = 0.01 (when raw water turbidity is 100 mg / L), 0.05 (when raw water turbidity is 400,800 mg / L)
GT value: 650 sec ⁻¹ × (12.64 × 60) sec

  As can be seen from FIG. 7, the turbidity of the treated water (clear water) is good even for the treatment of high turbidity raw water.

(Example 5)
The sludge obtained using the coagulation sedimentation processing apparatus shown in FIG. 1 was dehydrated by a filter press. The raw water was treated and dehydrated under the following conditions by changing the flocculant injection rate AlT ratio. FIG. 8 shows the relationship between the AlT ratio and the pressure dehydration filtration rate (kg-days / m ² · hr) per unit area. FIG. 9 shows the relationship between the AlT ratio and the moisture content (%) of the dehydrated cake.

[Processing conditions]
Raw water turbidity: 20mg / L
Water flow speed: 10m / hr
Flock blanket layer height: 1600mm
Flocculant: PAC
Coagulant injection rate: AlT ratio = 0.01, 0.02, 0.03, 0.04, 0.1, 0.2
GT value: 650 sec ⁻¹ × (12.64 × 60) sec

  As can be seen from FIG. 8, when the AlT ratio is lowered, the filtration rate is increased, and the processing amount per unit time is increased. Further, as can be seen from FIG. 9, when the AlT ratio is lowered, the moisture content of the dehydrated cake is reduced.

It is a figure which shows the structure of an example of the coagulation sedimentation processing apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the inclination board in the coagulation sedimentation processing apparatus which concerns on embodiment of this invention. It is a figure which shows the relationship between the product GT value of the stirring intensity | strength G and the residence time T, and the turbidity of treated water in Example 1 of this invention. It is a figure which shows the relationship between the product GT value of the stirring intensity | strength G and the residence time T, and the number of residual fine particles in Example 1 of this invention. It is a figure which shows the relationship between AlT ratio and the turbidity of a treated water in Example 2 of this invention. It is a figure which shows the relationship between AlT ratio and the turbidity of a treated water in Example 3 of this invention. It is a figure which shows the relationship between AlT ratio in Example 4 of this invention, and the turbidity of a treated water. It is a figure which shows the relationship between AlT ratio and the dehydration filtration speed | velocity in Example 5 of this invention. It is a figure which shows the relationship between AlT ratio in Example 5 of this invention, and a dehydrated cake moisture content.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Coagulation sedimentation processing apparatus, 10 Coagulation tank, 12 Precipitation tank, 14 Sludge concentration storage tank, 16 Agitation blade, 18 Motor, 20 Turbidity measurement apparatus, 22 Control part, 24 Pump, 26 Inclination apparatus, 28 Flock blanket layer, 30 Kiyosumi water outlet, 32 sludge outlet, 34 sludge, 36 inclined plate.

Claims (12)

A flocculation / precipitation treatment apparatus for adding a flocculant to raw water containing suspended substances and separating the flocculated floc and clear water by flocculation / precipitation,
A flocculation tank for stirring the raw water to which the flocculant is added to form a flocculation floc;
A settling tank in which the agglomerated treated water from the agglomeration tank is allowed to flow from the lower part and the clarified water is allowed to flow out from the upper part, and the aggregated flocs are absorbed and separated by the flock blanket layer formed in the tank,
Have
In the coagulation tank, the coagulation sedimentation processing apparatus is characterized in that stirring is performed when the GT value, which is the product of the stirring intensity G value (sec ⁻¹ ) and the residence time T (sec), is 200,000 or more. The coagulation sedimentation processing apparatus according to claim 1,
The flocculant is an aluminum-based inorganic flocculant,
The coagulation treatment apparatus is characterized in that the coagulation treatment is performed at a coagulant injection rate with an AlT ratio of 0.1 or less, which is the amount of aluminum added to the turbidity component of the raw water. The coagulation sedimentation processing apparatus according to claim 1,
The flocculant is an iron-based inorganic flocculant,
The coagulation treatment apparatus is characterized in that the coagulation treatment is performed at a coagulant injection rate with an FeT ratio of 0.2 or less, which is the amount of iron added to the turbidity component of the raw water. The coagulation sedimentation processing apparatus according to any one of claims 1 to 3,
In the flocculation process, the water flow rate is 5 m / hr or more, and the flocculation process apparatus. It is a coagulation sedimentation processing apparatus as described in any one of Claims 1-4,
Furthermore, in order to prevent the mother floc from the flock blanket layer from flowing out into the supernatant water layer above the interface between the flock blanket layer and the clarified water, the inclined plate members are arranged at intervals. An apparatus for coagulating sedimentation, comprising an apparatus. The coagulation sedimentation processing apparatus according to claim 5,
A coagulating sedimentation processing apparatus, wherein the tilting apparatus is arranged in multiple stages in the depth direction. A coagulation-precipitation treatment method in which a flocculant is added to raw water containing suspended solids and separated into coagulation floc and clear water by coagulation precipitation,
Adding the flocculant to the raw water;
Agglomeration treatment step of stirring the raw water to which the flocculant is added to form an agglomeration floc;
A step of causing the agglomerated water to flow from the lower part and causing the clarified water to flow out from the upper part, and sucking and separating the agglomerated flocs by a flock blanket layer formed in the tank;
Including
In the agglomeration treatment, the agglomeration precipitation treatment method is characterized in that agitation is performed when the GT value, which is the product of the agitation strength G value (sec ⁻¹ ) and the residence time T (sec), is 200,000 or more. The coagulation sedimentation processing method according to claim 7,
The flocculant is an aluminum-based inorganic flocculant,
The coagulation treatment method is characterized in that the coagulation treatment is performed at a coagulant injection rate with an AlT ratio of 0.1 or less, which is the amount of aluminum added to the turbidity component of the raw water. The coagulation sedimentation processing method according to claim 7,
The flocculant is an iron-based inorganic flocculant,
The coagulation treatment method is characterized in that the coagulation treatment is performed at a coagulant injection rate with an FeT ratio of 0.2 or less, which is the amount of iron added to the turbidity component of the raw water. It is the coagulation sedimentation processing method according to any one of claims 7 to 9,
In the coagulation treatment, the water flow rate is 5 m / hr or more, and the coagulation sedimentation treatment method. It is a coagulation sedimentation processing method according to any one of claims 7 to 10,
Further, an inclination device in which inclined plate members are arranged at an interval is disposed above the interface between the flock blanket layer and the clarified water so that the mother flock from the flock blanket layer flows out to the supernatant water layer. A method for coagulating and precipitating, characterized in that It is the coagulation sedimentation processing method according to claim 11,
A method for coagulating sedimentation, wherein the tilting device is arranged in multiple stages in the depth direction.

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