JP6197016B2 - Water purification method and water purification device - Google Patents

Description

  The present invention relates to a suitable water purification treatment method and apparatus using a polymer flocculant, and more specifically, can prevent filtration clogging that occurs when a polymer flocculant is used. The present invention relates to a method and an apparatus capable of obtaining an excellent coagulation treatment effect in the coagulation sedimentation step used.

  Conventionally, in water purification treatment, an inorganic flocculant such as a sulfate band or polyaluminum chloride (PAC) is injected into water to be treated containing suspended solids (hereinafter also referred to as “raw water”), and suspended solids are taken in. Suspended substances were removed by forming agglomerated floc and allowing the agglomerated floc to settle and separate.

  However, in recent years, eutrophication of lakes and rivers has progressed, and algae have grown. These algae have poor cohesiveness and have an adverse effect on sand filtration. A large amount of an inorganic flocculant is required to agglutinate the grown algae, and the treated water becomes acidic by injecting a large amount of the inorganic flocculant, which makes it unsuitable as drinking water. In addition, the amount of sludge generated from the inorganic flocculant is increased, and there is a problem that the cost for processing this sludge increases.

  The use of an anionic polymer flocculant in combination with an anionic polymer flocculant in order to improve the sedimentation property of the flocs by an inorganic flocculant in water purification treatment has been pointed out. In other words, the polymer flocculant injected in the water purification treatment is solid-liquid separated together with the generated floc and is mostly removed, but a part remains on the treated water side along with the fine floc. The remaining polymer flocculant may be adsorbed on the filter medium in the sand filtration tower in the subsequent step and cause clogging of the filter.

  As means for preventing clogging by the polymer flocculant, a method of injecting the flocculant sequestering agent, measuring the flow current in the floc forming tank, and determining the surplus or deficiency of the flocculant based on the measured flow current And a method of controlling the injection amount of the flocculant.

JP2003-340208 JP2007-61718

  However, the above method also has the following problems. The method of injecting the coagulant sequestering agent may increase the processing cost. In the method of measuring the flow current in the floc forming tank and controlling the injection amount of the flocculant based on the measured flow current, the suspended substance and the flocculant react without excess and deficiency and become electrically neutral. However, in water purification treatment, the neutralization point does not always give a good treatment result, and Patent Document 1 discloses treatment water turbidity. There is no suggestion about the effect on temperature or filtration.

  In view of the above-mentioned problems, the present inventors have studied various polymer flocculants. As a result, when a specific polymer flocculant is used, an excellent turbidity removal effect can be obtained even at low turbidity. And the problem of the filtration blockage | capacitance which may arise when using a polymer flocculant was solved, it discovered that the stable water purification process was possible, and came to complete this invention.

  In order to solve the above problems, the water purification method of the present invention can be configured as follows.

(1) The water purification treatment method of the present invention is a method of injecting a polymer flocculant after injecting an inorganic flocculant into water to be treated, and the polymer flocculant has a 0.1% salt viscosity of 2 to 2. A poly (meth) acrylate having a colloid equivalent value of −9.0 or less is 5 mPa · s. The unit of this colloid equivalent value is meq / g.

  The poly (meth) acrylate is a concept including one or both of a polyacrylate and a polymethacrylate.

  (2) Preferably, the injection amount of the inorganic flocculant is 10 to 200 mg (10 mg / L to 200 mg / L) per liter of water to be treated. Moreover, the injection amount of poly (meth) acrylate is preferably 0.05 to 20 mg (0.05 mg / L to 20 mg / L) per liter of the water to be treated after the inorganic flocculant is injected.

  (3) The timing for starting the injection of poly (meth) acrylate is not particularly limited, but preferably after the injection of the inorganic flocculant, the time when the diameter of the aggregated floc in the treated water becomes 0.1 mm or more is injected. The start timing is determined, and injection of poly (meth) acrylate is started at that time or after that time.

  (4) When a polymer flocculant such as poly (meth) acrylate is injected, the floc floc grows and becomes large. It is also effective to return the enlarged floc to the water to be treated before injecting the polymer flocculant.

  Moreover, the water purification apparatus of this invention can be set as the following structures.

(5) an agglomeration mixing tank for introducing treated water from a supply source, a supply means for injecting an inorganic flocculant into the agglomeration mixing tank, a flock forming tank for introducing treated water after injecting the inorganic flocculant, The water purification apparatus is provided with a supply means for injecting a polymer flocculant into the floc-forming tank, and the supply means has a 0.1% salt viscosity of 2 to 5 mPa · s as the polymer flocculant, and A poly (meth) acrylate having a colloid equivalent value of −9.0 or less is injected.

  (6) These supply means can control the injection amount as required. For example, the supply means for inorganic flocculant injects 10 to 200 mg of inorganic flocculant per liter of water to be treated, and polymer agglomeration The supply means for the agent injects 0.05 to 20 mg of the polymer flocculant per liter of water to be treated.

  (7) It is preferable to provide a return means in the water purification apparatus. This returning means returns either one or both of the water to be treated after the polymer flocculant is injected and the precipitate of the water to be treated. It is connected to the above devices. That is, any one or more of the coagulation mixing tank and the coagulation mixing tank and the supply source are used as the return place, and either one or both of the water to be treated and the precipitate are returned.

  ADVANTAGE OF THE INVENTION According to this invention, the continuous operation possible time of a water purification apparatus becomes long, and also purified water with low turbidity is obtained. Since the polymer flocculant does not contain acrylamide as a polymerization component, it has little influence on the human body.

It is a schematic diagram which shows an example of the water purification apparatus of this invention.

  Hereinafter, the present invention will be specifically described, but the present invention is not limited to a specific example.

  The present invention includes means and a process for injecting a specific polymer flocculant to grow into an aggregated floc after injecting an inorganic flocculant into the water to be treated to form an aggregated floc. Specific examples of the inorganic flocculant and polymer flocculant used in the present invention will be described below.

[Inorganic flocculant]
The inorganic flocculant used for this invention is not specifically limited, The inorganic flocculant normally used for a water purification process can be used. Specifically, one or both of an iron-based flocculant and an aluminum-based flocculant can be used, and more specifically, a sulfuric acid band, polyaluminum chloride (PAC), aluminum chloride, polyferric sulfate. Any one or more selected from the group consisting of (polyiron), ferric chloride, and mixtures thereof can be used.

[Polymer flocculant]
The polymer flocculant is not particularly limited as long as it contains a poly (meth) acrylate having a 0.1% salt viscosity of 2 to 5 mPa · s and a colloid equivalent value of −9.0 or less. content of the (meth) acrylic acid salt is at least 50 wt% or more, preferably 80 mass% or more, particularly preferably not less than 99 mass%, consisting essentially of the poly (meth) acrylic acid salt .

  Here, the poly (meth) acrylate is not particularly limited. For example, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, polymethacrylic acid, polysodium methacrylate, polypotassium methacrylate. Any one or more selected from the group consisting of polyammonium methacrylate can be used, and preferably sodium polyacrylate.

  The poly (meth) acrylate may be either a homopolymer or a copolymer, and preferably contains (meth) acrylic acid or a salt thereof, maleic acid or a salt thereof, vinylsulfonic acid or a salt thereof as a polymerized unit. Copolymer or homopolymer. In the case of a copolymer, acrylamide can be used as a copolymerization component, but it is more preferable not to use acrylamide.

  Poly (meth) acrylates can be used alone or as a mixture. When using a mixture of poly (meth) acrylates, the 0.1% salt viscosity of the entire mixture is preferably 2 to 5 mPa · s.

  In addition, the salt viscosity measured the sample which melt | dissolved the poly (meth) acrylate in the sodium chloride aqueous solution of 1N so that the density | concentration might be 0.1 mass% on 25 degreeC conditions with a B-type viscosity meter. It is a value and the unit is mPa · s.

  If the 0.1% salt viscosity is less than 2 mPa · s, the flocs flocs are not so large and improvement in sedimentation cannot be expected. On the other hand, if the 0.1% salt viscosity exceeds 5 mPa · s, the floc forming tank after injection In this case, it is necessary to increase the stirring speed in the floc forming tank, and there is a risk of breaking the floc.

The colloid equivalent value can be obtained by the following measurement method, and the unit is meq / g. Prepare a 0.1% aqueous solution of poly (meth) acrylate, add 5 ml of methyl glycol chitosan solution (N / 200), add 2 to 3 drops of toidin blue indicator after stirring, and add polyvinyl potassium sulfate solution (PVSK, Titrate with N / 400), and change the color and hold for 10 seconds or longer as the end point. A blank test is performed without adding a sample by the same operation, and a colloid equivalent value Cv is calculated by the following formula.

Colloid equivalent value (Av) [meq / g] =
(Blank titration ml-Sample titration ml) x 1/2 x PVSK titer

When using a mixture of poly (meth) acrylic acid, the colloid equivalent value of the mixture may be measured directly, but the colloid equivalent value (Av) [meq / g] of each poly (meth) acrylate is known. In this case, the value obtained by multiplying the colloid equivalent value (Av) of the individual poly (meth) acrylate by the mass ratio (individual mass / total mass) occupied by the poly (meth) acrylate in the entire mixture is added. And the colloid equivalent value of the entire mixture.

The colloid equivalent value is preferably −9.0 or less, and more preferably the colloid equivalent value is −11.0 to −9.0. If the colloid equivalent value exceeds this range, the aggregated flocs do not grow greatly and the turbidity of the treated water tends to increase, and if it falls below this range, the filtration resistance of the treated water tends to increase.

In general, a polymer flocculant having a colloid equivalent (meq / g) of -7 or less is highly anionic, and a polymer flocculant having a colloid equivalent of -2.8 or less and exceeding -7.0 is medium anionic. , colloid equivalent of polymer flocculant in excess of -2.8 -0.7 or less is low anionic. The poly (meth) acrylate used in the present invention has a colloid equivalent value of −9.0 or less, that is, has a higher anionic property among the highly anionic flocculants.

  Next, the processing apparatus and processing method of the present invention using the above-mentioned inorganic flocculant and polymer flocculant will be described.

[Water purification equipment]
Water purification equipment (water purification equipment) to which the present invention can be applied is not particularly limited, and it is possible to adopt all normal equipment in practical use. For example, water purification equipment having a cross-flow type precipitation equipment, high-speed coagulation sedimentation Water purification facilities with facilities are listed. Either a slurry circulation type or a sludge / blanket type can be applied as the high-speed coagulating sedimentation equipment.

  A schematic diagram of a water purification apparatus 10 having a cross-flow type precipitation facility is shown in FIG. The water purification apparatus 10 includes a flocculation / mixing tank 31, a flock formation tank 41 connected to the flocculation / mixing tank 31, and a filtration connected to the flock formation tank 41 directly or via another device (such as a precipitation basin 51). Means 55.

  One aggregation mixing tank 31 and one flock formation tank 41 may be installed, or a plurality of either one or both may be installed. When installing a plurality of these tanks 31, 41, the same kind of tanks 31, 41 are connected in series or in parallel, more preferably in series, and the water to be treated passes through the plurality of tanks, and the next treatment step. Design to be sent to.

  The water to be treated that passes through the agglomeration and mixing tank 31 and the flock formation tank 41 is directly or indirectly injected with the above-described inorganic flocculant and polymer flocculant from the supply means 35 and 45 or manually.

  For example, the inorganic coagulant supply means 35 is one of one or a plurality of coagulation / mixing tanks 31 and an apparatus upstream from the coagulation / mixing tank 31 (supply source 1, piping 21, landing well, etc.). It is connected to one or more units, and the inorganic flocculant is directly injected into the coagulation mixing tank 31 separately from the water to be treated, or indirectly from the upstream apparatus together with the water to be treated to the coagulation mixing tank 31. Injected.

  The agglomeration mixing tank 31 is provided with stirring means such as a stirring blade and a stirring pump. The stirring means is set with a stirring speed (number of rotations) for applying predetermined stirring energy, and rapidly stirs the water to be treated into which the inorganic flocculant has been injected. The index of agitation energy is not particularly limited, but an example thereof is G value (square root of value obtained by dividing viscosity coefficient μ of water to be treated from work amount P per unit time unit volume, Japan Water Works Association Water Facility Design Guidelines 2000, P188. More).

  As a result of rapid stirring, turbidity in the water to be treated aggregates and grows as fine flocs (micro flocs), and the water to be treated containing fine flocs is supplied to the floc forming tank 41.

  In addition to observing the floc aggregation state visually, a measuring means 37 may be provided in the water purification apparatus 10. In either case, the observed (measured) floc growth degree can be used to determine the timing of injecting the polymer flocculant.

  The polymer flocculant supply means 45 is one or more of one or a plurality of flock formation tanks 41 and devices upstream of the flock formation tank 41 (aggregation mixing tank 31, pipe 22 and the like). The polymer flocculant described above is directly injected into the floc forming tank 41 separately from the water to be treated, or indirectly from the upstream apparatus to the floc forming tank 41 together with the water to be treated. Injected.

As with the agglomeration mixing tank 31, the flock formation tank 41 is provided with stirring means such as stirring blades and a stirring pump. The stirring means is set to have a stirring speed so as to give a lower stirring energy (for example, G value of 10 to 80 seconds ⁻¹ ) than the stirring means of the agglomeration mixing tank 31, and the processing target in which the polymer flocculant is injected Stir the water slowly to enlarge the fine flocs.

  In order to separate the huge floc, preferably, a sedimentation means (sedimentation basin 51) is installed between the floc formation tank 41 and the filtration means 55, and the water to be treated containing the huge floc is transferred from the floc formation tank 41 to the sedimentation basin 51. send.

  The structure of the sedimentation basin 51 is not particularly limited. Generally, an inclined plate or an inclined tube is provided in the inside of the sedimentation basin 51. The treated water from the flock formation tank 41 is mainly composed of a huge floc in the sedimentation basin 51. Is separated into a precipitate (sludge) contained in the liquid phase and a liquid phase from which the giant floc is separated.

  It is also possible to return some or all of the giant floc to the upstream device after or before this separation. Specifically, the return means 59 is connected to one or more of the flock formation tank 41, the sedimentation basin 51, and the pipe 23 between them, and the cover containing either or both of the separated sediment and the giant floc is included. The treated water is returned to any one or more return places among the agglomeration mixing tank 31 and the upstream devices (pipe 21, landing well, etc.). The return means 59 is not particularly limited, but generally has a return pipe 29 for returning flocs and, if necessary, other members such as a water pump, a switching valve, and a storage tank.

  On the other hand, the liquid phase after separation of the giant floc is sent from the sedimentation basin 51 to the filtering means 55, and residual contaminants such as excess polymer flocculant and residual floc are removed, resulting in purified water 6. The filtration means 55 is not particularly limited, and a filtration tower, a filtration membrane (filter), or the like can be used. Particularly preferred is a filtration tower filled with a filter medium. The filter medium is not particularly limited, and one or both of a particulate filter medium and a fibrous filter medium can be used, and a particulate filter medium is particularly preferable.

  Examples of the particulate filter medium include filtration sand (silica sand) (effective diameter 0.35 to 1.0 mm, uniformity coefficient 1.7 or less, specific gravity 2.57 to 2.67), anthracite (effective diameter 0.7 to 4). 0.0 mm, uniformity coefficient 1.4 or less, specific gravity 1.4 to 1.6), garnet (effective diameter about 0.3 mm, uniformity coefficient 1.5 or less, specific gravity 3.8 to 4.1), manganese sand (effective Diameter 0.35 to 0.60 mm, uniformity coefficient 1.5 or less, specific gravity 2.58 to 2.65), ceramic (effective diameter 0.3 to 2.0 mm, specific gravity 1.0 to 1.2), One or more types can be used, but in the case of water supply applications, those containing either one or both of silica sand and anthracite are most preferable, and other filter media can be further combined with these filter media. . The filter medium may be a single layer or a multilayer structure, and the filter medium and the filter may be combined.

  In the prior art, the filter medium as described above has a problem such as clogging, but the water purification apparatus 10 and the water purification method of the present invention dramatically improved this problem.

  Next, the water purification method of the present invention using the water purification device 10 will be specifically described.

[Water purification treatment method]
Particularly suitable as water to be treated in the present invention is river water, lake water, reservoir water, rain water, underground water, ground water, and well water. These to-be-treated water (raw water) is supplied to the flocculation / mixing tank 31 directly from the water source or via a pretreatment part (a landing well or the like).

  If necessary, the quality of the water to be treated is checked in advance by a jar test or the like, the injection amount of the inorganic flocculant is set in advance according to the water quality, and the water to be treated is supplied from the supply means 35 or manually by the operator. The inorganic flocculant is injected in the range of 5 to 200 mg, preferably 10 to 100 mg per liter. The water to be treated into which the inorganic flocculant has been injected is rapidly stirred to flocculate turbid components in the water to be treated.

  In order to determine the point (timing) at which the polymer flocculant is injected, the degree of growth of the fine floc is measured periodically or continuously. The floc growth degree can be measured mechanically by the measuring means 37 or visually by the operator (with the naked eye, a microscope). As the floc growth degree, various indices such as floc diameter and water turbidity to be treated can be used. Although it is possible to employ, preferably the floc diameter is measured.

  Generally, it is said that the floc diameter (diameter) that can be recognized by the operator with the naked eye is 0.1 mm or more, and the floc diameter (preferably the average particle diameter) is 0.1 mm or more, preferably in the range of 1 mm to 2 mm. The time point is determined as the timing at which injection is possible, and the injection of the polymer flocculant is started from the supply means 45 or manually by the operator.

  The amount of the polymer flocculant, that is, the above-mentioned poly (meth) acrylate, can be appropriately changed depending on the quality of the raw water, but is preferably set within a range of 0.05 to 20 mg per liter of water to be treated. To do.

  Unlike an anionic polymer flocculant such as polyacrylamide, poly (meth) acrylate does not contain acrylamide as a copolymerization component, so that no acrylamide monomer is mixed in purified water. Therefore, even if this poly (meth) acrylate is used in a large amount exceeding 1 mg / liter, there is no health problem for the human body. However, for treated water for clean water, the injection amount is 20 mg. Since the viscosity of the excess polymer may cause problems such as clogging of the filtration pond when the amount exceeds / liter, the upper limit of the injection amount is preferably 20 mg / liter.

  The water to be treated into which the polymer flocculant has been injected is slowly stirred to grow flocs, and part or all of the flocs are solid-liquid separated in the sedimentation basin 51, while the separated liquid phase passes through the filtration means 55. In addition, residual pollutants such as turbidity not captured by floc and free floc not solid-liquid separated are removed from the treated water.

  A polymer flocculant is adhered to the surface of this free floc, and when a known acrylamide polymer flocculant is used, filtration clogging may occur.

When water to be treated is treated with an inorganic flocculant and then treated with poly (meth) acrylate having a 0.1% salt viscosity of 2 to 5 mPa · s and a colloid equivalent value of −9.0 or less In this case, the filtration blockage is unlikely to occur, and even if the filtration blockage occurs, it is easily recovered by a normal backwash process.

  The filtration blockage can occur not only due to the type of polymer flocculant but also due to other factors. For example, when the turbidity of raw water is low and the amount of turbidity that is the core of flocs is too small, the flocs are not grown sufficiently, and the residual polymer flocculant that cannot contribute to floc growth increases. In such a case, even if the polymer flocculant is used in combination with the inorganic flocculant, the effect of reducing turbidity is not observed, and filtration clogging easily occurs due to an increase in the residual polymer flocculant and free floc.

  Therefore, in another embodiment of the present invention, in addition to the use of the polymer flocculant, the return means 59 is used to return the floc from either one or both of the flock formation tank 41 and the sedimentation tank 51 to the upstream side. To do.

  Specifically, any one or more of raw water turbidity, floc growth after injection of inorganic flocculant, and floc growth after injection of polymer flocculant is measured, and the measured value reaches a preset value. If not, return the floc in an amount corresponding to the measured value to the upstream side and mix with the water to be treated before injecting the polymer flocculant.

  The floc return place is not particularly limited as long as it is an agglomeration mixing tank 31 or an upstream apparatus (pipe 21 or the like), and can be returned to one or more of these return places. However, the return place can be switched according to the measured value. Specifically, when the raw water turbidity is low, the water is returned to the water to be treated (raw water) upstream from the agglomeration mixing tank 31.

  Since the polymer flocculant adheres to the surface of the floc that has been returned and itself has an aggregating ability, the flocs collide with each other to form a larger floc than when the floc is not returned. As a result, solid-liquid separation is promoted by enlarging the floc, preventing clogging of the filtration means 55 by the flocs, and the amount of the polymer flocculant injected can be reduced.

  The floc to be returned is not particularly limited. However, when the floc is returned from the sedimentation basin 51, it is preferable to avoid returning the sedimentation floc completely precipitated and concentrated in the sedimentation basin 51. Precipitation flocs that have been completely precipitated and concentrated are difficult to adjust to the target turbidity concentration upon return, and the required amount of inorganic flocculant and polymer flocculant may increase. Moreover, the adsorption | suction site | part (active group) of the polymer flocculent exposed to the precipitation floc surface reduces by concentration, and floc formation capability will fall extremely.

  When returning flocs, one or more additives, for example, clayey inorganic fine particles such as kaolin or fine sand, may be returned together, and these additives will make the flocs stronger and have a higher weight. Therefore, the turbidity effect is more exhibited.

  The place where these additives are mixed with the return flock is not particularly limited. For example, the flock return pipe 29 is preferable in the course of returning the flock, and more preferably, immediately before mixing the flock with the water to be treated (introduction of raw water) For example, immediately before reaching the piping 21 and the agglomeration mixing tank 31). Further, instead of the return pipe 29, a means for injecting clay inorganic fine particles and fine sand can be separately provided at the point of return to the raw water introduction pipe 21 and the coagulation mixing tank 31.

  The return of floc and the addition of the polymer flocculant use the measurement result of the floc growth degree for determining the start of the process in any process, but the measurement method is not particularly limited.

  For example, when the operator observes the floc with the naked eye and determines the start of the injection of the polymer flocculant, the floc can be visually confirmed (that is, the floc diameter is 0.1 mm or more), and the maximum floc diameter that can be confirmed is 2 mm. The following case is set as the timing for starting the injection of the polymer flocculant. When the turbidity is measured visually by an operator, a colorimetric tube or the like can be used (visual turbidity).

  When the floc growth degree is mechanically measured by the measuring means 37, a commonly used measuring apparatus can be widely used. For example, the measuring means 37 has an optical sensor, acquires optical data such as the transmittance, absorbance, and scattered light of the water to be treated, and measures the floc diameter and turbidity from the optical data. The turbidity measured by the measuring means 37 is, for example, scattered light turbidity, integrating sphere turbidity, or translucent turbidity, and the floc diameter is, for example, an average particle diameter by an absorbance fluctuation analysis method.

  In addition, the processing apparatus 10 and the processing method of the present invention can be modified in any way other than those described above. For example, additives used in normal water purification treatment such as pH adjusters, coagulant aids, and bactericides, and other The polymer flocculant can be added to the water to be treated, and the addition timing and addition means are not particularly limited.

  Hereinafter, the present invention will be described more specifically with reference to examples.

  A water purification test was conducted under the following experimental conditions using the water purification apparatus 10 of FIG.

-Raw water: flow rate 100m ³ / day, river water, turbidity 15-25 degrees, pH 7.0-7.4
-Inorganic flocculant: polyaluminum chloride (PAC)
-Polymer flocculant: sodium polyacrylate,
0.1% salt viscosity 3.5mPa · s, colloid equivalent value -9.4meq / g
-Coagulation mixing tank: Effective volume 200 liters x 2 tanks (peripheral speed 1.5 m / s)
-Flock formation tank: effective volume 1200 liter x 2 tank sedimentation basin (peripheral speed 0.5 m / s)
-Filtration speed 100m / day,
-Filter media: 2 layers (Anthracite layer height 400mm, Silica sand layer height 400mm)

<Example 1>
In the apparatus 10 of FIG. 1, 20 mg / liter of PAC was injected into the coagulation mixing tank 31 and rapidly stirred to form micro flocs. Collect the water to be treated in the coagulation mixing tank 31 in a measuring cylinder, and after confirming that the floc diameter has become 1 to 2 mm with the naked eye, in the water to be treated just before flowing into the floc forming tank 41 (pipe 22), The polymer flocculant was injected at a rate of 1.0 mg / liter and stirred gently, and the aggregate floc diameter after the polymer flocculant was injected was measured with the naked eye. This treated water is further treated in the sedimentation basin 51 and the filtering means 55, and the liquid phase (aggregated sedimentation treated water) after separation in the sedimentation basin 51 and the purified water 6 (filtered water) after passing through the filtration means 55 are Turbidity was measured using a turbidimeter “WA 6000” manufactured by Denshoku Industries Co., Ltd.

  Furthermore, the water purification process by the processing apparatus 10 was performed continuously, and the time which can be normally filtered without obstruction | occlusion was also measured.

<Examples 2 and 3>
A water purification test was conducted in the same manner as in Example 1 except that the polymer flocculant injection amount was 1.5 mg / liter and 0.3 mg / liter.

<Example 4>
A water purification test was carried out in the same manner as in Example 1 except that the place where the polymer flocculant was injected was the second tank of the floc forming tank 41.

<Example 5>
The test was performed under the same conditions as in Example 3 except that the polymer flocculant was changed to sodium polyacrylate (0.1% salt viscosity: 4.4 mPa · s, colloid equivalent value: −9.8 meq / g).

<Example 6>
The test was performed under the same conditions as in Example 1 except that the polymer flocculant was changed to sodium polyacrylate (0.1% salt viscosity was 2.7 mPa · s, colloid equivalent value was −9.5 meq / g).

<Comparative Example 1>
A water purification test was conducted under the same conditions as in Example 1 except that the polymer flocculant was not used and the PAC was used alone.

<Comparative Examples 2 and 3>
As the polymer flocculant, a commercially available polymer flocculant (medium anionic acrylamide / sodium acrylate copolymer) was injected at 0.5 mg / liter (Comparative Example 2) and 1.0 mg / liter (Comparative Example 3). A water purification test was conducted in the same manner as in Example 1.

  The test results of the above Examples and Comparative Examples are shown in Table 1 below together with the flocculant injection rate.

  As apparent from Table 1 above, Examples 1 to 6 in which the injection amount of sodium polyacrylate was injected at 0.3 mg / liter 1.0 mg / liter and 1.5 mg / liter had a filtration duration of 40 hours or more. There was little difference compared with Comparative Example 1 in which no polymer flocculant was used, and the state of the filtering means 55 was stable.

  On the other hand, in Comparative Examples 2 and 3 in which acrylamide / sodium acrylate copolymer was injected at 0.5 mg / liter and 1.0 mg / liter, the filtration duration was shortened to 22 hours and 16 hours. In Comparative Example 3 in which 1.0 mg / liter was injected, the treated water turbidity was also high.

DESCRIPTION OF SYMBOLS 1 Supply source 10 Water purification apparatus 31 Coagulation mixing tank 35 Inorganic flocculant supply means 37 Measuring means 41 Flock formation tank 45 Polymer flocculant supply means 55 Filtration means 59 Return means

Claims (9)

After injecting the inorganic flocculant into the treated water,
A water purification method characterized by injecting a poly (meth) acrylate having a 0.1% salt viscosity of 2 to 5 mPa · s and a colloid equivalent value of −9.0 or less. Injecting 10 to 200 mg of the inorganic flocculant per liter of the water to be treated,
The water purification method according to claim 1, wherein 0.05 to 20 mg of the poly (meth) acrylate is injected per liter of the water to be treated.   3. The injection of the poly (meth) acrylate is started after the diameter of the floc aggregated by the injection of the inorganic flocculant becomes 0.1 mm or more. 4. Water purification method.   The purified water according to any one of claims 1 to 3, wherein flocs grown by the injection of the poly (meth) acrylate are returned to the water to be treated before the poly (meth) acrylate is injected. Processing method. The water purification method according to any one of claims 1 to 4, wherein the water to be treated is selected from the group consisting of river water, lake water, reservoir water, rain water, underground water, ground water, and well water. An agglomeration mixing tank into which treated water is introduced from a supply source;
Inorganic flocculant supply means for injecting the inorganic flocculant into the flocculent mixing tank,
A floc-forming tank into which water to be treated after injecting the inorganic flocculant is introduced;
Polymer flocculant supply means for injecting poly (meth) acrylate having a 0.1% salt viscosity of 2 to 5 mPa · s and a colloid equivalent value of −9.0 or less into the floc forming tank And a water purification apparatus characterized by comprising: The inorganic flocculant supply means injects 10 to 200 mg of the inorganic flocculant per liter of water to be treated,
The water purifier according to claim 6 , wherein the polymer flocculant supply means injects 0.05 to 20 mg of the poly (meth) acrylate per liter of water to be treated. The water to be treated after injecting the poly (meth) acrylate, and a return means for returning either or both of the precipitates of the water to be treated,
Said return means, to any one or more positions of the return location between said source and said mixing flocculation tank, said to claim 6 or 7 returns either or both of the precipitate with water to be treated The water purification apparatus as described. The purified water according to any one of claims 6 to 8, which is used for the purification of the treated water selected from the group consisting of river water, lake water, reservoir water, rain water, underground water, ground water, and well water. Processing equipment.

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