JP2015085219A - Flocculation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means of water treatment or water purification by sedimentation, having high flocculation effect with reduced cost.SOLUTION: The flocculation method includes a procedure of separately adding an iron salt and polysaccharide containing components derived from blue-green algae and water-soluble neutral polysaccharide. In Figure 2, a test section 8 shows the results of adding 50% of the components derived from blue-green algae and 50% of tapioca starch as polysaccharide, and a test section 9 shows the results of adding 50% of the components derived from blue-green algae and 50% of glucomannan as polysaccharide, respectively. It is shown that the addition of components derived from blue-green algae and a water-soluble neutral polysaccharide with a reduced amount of the components derived from blue-green algae added achieves high flocculation effect approximately equal to the case of addition of the components derived from blue-green algae alone as polysaccharide (test section 1). Various kinds of water-soluble neutral polysaccharide can be mass-produced at relatively low cost in general. Consequently, the flocculation cost can be reduced corresponding to the reduction in the amount of components derived from blue-green algae added.

Description

  The present invention relates to water treatment / water purification technology by agglomeration treatment of waste water, muddy water, muddy water, and other various types of suspended water. More specifically, the present invention relates to an aggregation treatment method including a procedure of individually adding an iron salt and two or more kinds of polysaccharides.

  In order to supply water suitable for drinking at a water purification plant or the like, it is necessary to purify the water by removing organic substances, inorganic substances and harmful substances from the viewpoint of safety. Industrial wastewater, domestic wastewater, livestock wastewater, etc. must be discharged after removing pollutants and harmful substances as much as possible from the viewpoint of reducing environmental impact.

  When performing civil engineering work in water areas such as rivers, canals, harbors, inner bays, and lakes, it is necessary to take measures to suppress the generation of muddy water and muddy water. In closed and semi-enclosed waters such as harbors, lakes, tidal flats, canals, and moats, there are cases where large amounts of sea lions and microalgae (phytoplankton) are generated, and it is necessary to effectively remove them.

  A sedimentation separation method is known as a method for treating waste water, muddy water, muddy water, and other various types of suspended water. A flocculant is added to the suspension of mud, pollutants, etc. to agglomerate and settle, and these substances are separated from the water and removed.

  As the flocculant, inorganic flocculants such as polyaluminum chloride are widely used. However, it is difficult to form a sufficiently large floc even when these flocculants are used. Moreover, since polyaluminum chloride has poor biodegradability, there is a concern about the influence on the natural environment when used in large quantities in water.

  A method using a polysaccharide as a flocculant has also been proposed. For example, Patent Document 1 discloses a water treatment flocculant in which guar gum, which is a neutral plant-produced water-soluble polysaccharide, is dissolved in an acidic ferric aqueous solution, and Patent Document 2 includes an iron salt added in advance. Each method for generating floc is described in which a polysaccharide (xanthan gum or sodium alginate) is added after adjusting the pH.

Suizenjinori (scientific name "Aphanothece sacrum") is a photosynthetic microorganism of freshwater cyanobacterium that grows naturally in the Kyushu region of Japan. The present inventors have recently reported, for example, that a high aggregating effect can be obtained by individually adding an iron salt and a cyanobacterium-derived component such as suizendinori (Patent Document 3).
Japanese Patent Laid-Open No. 2001-219005 Japanese Patent Laid-Open No. 10-216737 JP 2012-217972 A

  Natural suizenginori inhabits only in the springs of specific areas and is rare. Field farming is also carried out, but the production volume is decreasing year by year. In addition, indoor mass production culture techniques have been tried, but they are still under development and have not yet been mass-produced. On the other hand, polysaccharides derived from suizendinori have been studied for use as food materials, cosmetic materials, rare earth recovery materials, water retention materials, etc., and there is a possibility that demand will increase in the future.

  Therefore, for example, when using a cyanobacterium-derived component such as a scorpion dinosaur as a flocculant, there is a problem that a high flocculation effect can be obtained while the cost is increased. Therefore, an object of the present invention is to provide means for reducing costs while maintaining a high coagulation effect in water treatment and water purification by sedimentation separation.

  In the case of performing water treatment / water purification by agglomeration treatment by sedimentation separation, the present inventors, when adding iron salt and polysaccharide separately, as a polysaccharide, in addition to the cyanobacterium-derived component, It has been newly found that by adding a plurality of water-soluble neutral polysaccharides, it is possible to maintain a high aggregation effect while reducing the amount of cyanobacterium-derived components added.

  Therefore, in the present invention, an aggregating treatment method including a procedure for individually adding an iron salt and a polysaccharide, wherein the aggregating treatment method is performed by adding a cyanobacteria-derived component and a water-soluble neutral polysaccharide as the polysaccharide. provide.

  In this method, the amount of the cyanobacterium-derived component added can be reduced by adding the cyanobacterium-derived component and the water-soluble neutral polysaccharide together. Since many water-soluble neutral polysaccharides can be mass-produced and are generally relatively inexpensive, the cost for the coagulation treatment can be reduced by reducing the amount of the cyanobacterium-derived component added.

  On the other hand, in this method, even if the addition amount of the cyanobacterium-derived component is reduced, a large floc can be formed almost the same as the case where the iron salt and the cyanobacterium-derived component are individually added. The same high agglomeration effect can be maintained. In addition, a wide variety of suspensions such as mud, pollutants and harmful substances can be aggregated.

  Therefore, the present invention can be applied to, for example, removal of organic substances / inorganic substances / hazardous substances in water treatment plants, removal of pollutants / hazardous substances in wastewater treatment plants, and recovery / removal of harmful substances contained in water, etc. Of mud and muddy water in civil engineering works and removal of pollutants and mud, collection and removal of harmful substances rolled up from the bottom of the water during civil engineering work in the water area, blue seaweed and microalgae (phytoplankton) in the water area It is effective for the removal of organic suspensions.

  In addition, all the substances used in this method are components derived from nature, and even if they are added in a relatively large amount to a water area, the environmental load is small. In addition, since this coagulation treatment method has a high coagulation effect, there is almost no residual coagulant in the supernatant after coagulation / sedimentation. Therefore, even if these flocculants are added to water or the like, there is an advantage that the influence on the environment is small.

  According to the present invention, costs can be reduced while maintaining a high coagulation effect in water treatment and water purification by sedimentation separation.

  The present invention is an aggregating treatment method including a procedure of individually adding an iron salt and a polysaccharide, and includes all aggregating treatment methods of adding a cyanobacteria-derived component and a water-soluble neutral polysaccharide as the polysaccharide. To do.

  For example, after collecting suspended water, either iron salt or polysaccharide is added and stirred and mixed. Next, after adding the other, stirring and mixing, the suspended water is allowed to stand and the suspension is allowed to settle. Then, when the transparency of the supernatant liquid reaches the reference value, the suspension is settled and separated, and when it does not reach the reference value, the same water treatment is repeated. Thereby, various suspensions can be effectively aggregated, settled, separated and removed.

  The iron salt and polysaccharide may be added individually to the suspension water, and the order of addition is not particularly limited. When either iron salt or polysaccharide is added first, almost the same agglomeration effect can be obtained.

  Although the iron salt used by this method is not specifically limited, For example, ferric salts, such as ferric chloride, ferric sulfate, and polyferric sulfate, can be used conveniently. These substances may be added to the suspension water in the form of, for example, a solid agent containing at least a ferric salt or an aqueous solution.

  For example, in the case of ferric chloride, the addition amount of the ferric salt is preferably 0.5 to 1,000 mg, more preferably 1 to 500 mg, and most preferably 5 to 100 mg per liter of suspended water.

  In this method, cyanobacteria-derived components and water-soluble neutral polysaccharides are added as polysaccharides. Addition of cyanobacteria-derived components while maintaining the same high agglomeration effect as when iron salt and cyanobacteria-derived components are added separately by adding the cyanobacteria-derived component and water-soluble neutral polysaccharide together The amount can be reduced. Therefore, costs can be reduced while maintaining a high coagulation effect in water treatment and water purification by sedimentation separation.

  The amount of polysaccharide added is preferably 0.5 to 2,000 mg, more preferably 1 to 1,000 mg per liter of suspended water, including the cyanobacterium-derived component and one or more water-soluble neutral polysaccharides. From 3 to 500 mg is most preferred.

  Considering the coagulation effect and the cost of the coagulant, the ratio of the amount of the cyanobacterium-derived component and the water-soluble neutral polysaccharide is preferably 15:85 to 90:10, and 18:82 to 75:25 It is more preferable that the ratio is 20:80 to 60:40.

  The cyanobacterium-derived component employed in the present invention is not particularly limited as long as it contains a polysaccharide as an active ingredient. As a cyanobacteria-derived component containing a polysaccharide as an active ingredient, for example, a paste prepared from algae bodies of cyanobacteria may be used, or a component such as a polysaccharide extracted from cyanobacteria may be directly or prepared. May be used.

  Cyanobacteria (scientific name "Chroococcaceae") microorganisms, for example, Chroococcus limneticus (scientific name), Chroococcus disperses (scientific name), Merismopedia elegans (scientific name), suizenjinori (scientific name " Aphanothece sacrum "), Aphanothece clathrata (scientific name), and the like are more preferable, and a swallowtail (scientific name" Aphanothece sacrum ") or its related species is most preferable. For example, these cyanobacteria may be hydroponically cultivated or field-cultivated and used as a raw material for cyanobacteria-derived components.

  As a method of preparing the algal body of cyanobacteria in a paste form, a known method can be adopted and is not particularly limited. For example, algal bodies of cyanobacteria are placed in a low-concentration sodium hydroxide aqueous solution, mixed and pulverized with a mixer or the like until a paste is formed, the paste-like material-containing solution is boiled for several hours, and then allowed to cool. A cyanobacteria-derived paste can be prepared by the above procedure.

  As a method for extracting a component such as a polysaccharide from cyanobacteria, a known method can be adopted, and the method is not particularly limited. For example, cyanobacterium is directly or after preparing a dry pulverized product, it is immersed in a solvent for a certain period of time to remove water-soluble and fat-soluble pigments. As the solvent, for example, an organic solvent such as ethanol can be used. Next, it transfers to aqueous solution, such as sodium hydroxide and sodium carbonate, and hydrolyzes by heat-processing for a fixed time. By the above procedures, active ingredients such as polysaccharides can be extracted from cyanobacteria.

  Moreover, the component extracted from the cyanobacterium may be neutralized, and the solution may be used as an aqueous solution of the cyanobacterium-derived component. In addition, for example, what was dried at low temperature after dehydration and pulverized, what the powder was solidified, and what the powder was dissolved in a solution may be used as the cyanobacteria-derived component.

  The cyanobacteria-derived component is preferably a polysaccharide having a weight average molecular weight of 5 million to 40 million, more preferably a polysaccharide having a weight average molecular weight of 8 million to 30 million, and more preferably a weight. A polysaccharide having an average molecular weight of 10 to 20 million is contained as an active ingredient. The weight average molecular weight can be measured by a known method, for example, by gel filtration chromatography.

  The polysaccharide contained in the cyanobacteria-derived component preferably includes 5 to 30 types, more preferably 8 to 30 types, and even more preferably 11 to 30 types of constituent monosaccharides. This polysaccharide includes various sugar chain molecules having slightly different structures in the molecular structure, and also contains many sulfate groups, carboxylic acid groups, amino groups, and the like, and is an ampholyte. Therefore, it has a wide range of expression of ion exchange capacity, and has stability of material properties against changes in pH and the like. Therefore, the coagulation treatment method according to the present invention has the advantage that the procedure for performing pretreatment such as pH adjustment can be omitted or simplified, and the suspension can be coagulated and settled more easily and effectively.

  Examples of the constituent monosaccharides of polysaccharides contained in cyanobacteria-derived components include neutral sugars such as glucose, galactose, mannose, rhamnose, fucose, xylose, and arabinose, which are acidic sugars such as uronic acids (glucuronic acid and galacturonic acid) , Sulfated muramic acid and the like, as well as galactosamine which is an amino sugar.

  The polysaccharide contained in the cyanobacteria-derived component preferably contains at least uronic acids as constituent monosaccharides. The ratio of uronic acids in all the constituent monosaccharides in the polysaccharide contained in the cyanobacteria-derived component is not particularly limited, but for example, 2 to 20% is preferable, 4 to 15% is more preferable, and 5 to 12 % Is most preferred.

  In addition, the qualitative / quantitative analysis of the constituent monosaccharide can be performed by a known method, for example, by high performance liquid chromatography, analysis by a mass spectrometer, or the like.

  The polysaccharide contained in the cyanobacteria-derived component preferably has 1 to 20%, more preferably 3 to 15%, and even more preferably 5 to 10% of a constituent monosaccharide containing a sulfate group.

  In addition, the quantitative analysis of a sulfate group can be performed by a well-known method, for example by analysis by a mass spectrometer. The sulfur content in the polysaccharide can be determined by a known method such as ICP emission spectroscopy.

  The water-soluble neutral polysaccharide employed in the present invention broadly includes water-soluble neutral polysaccharides, that is, water-soluble neutral polysaccharides that contain almost no uronic acid, ester sulfate, etc. in the constituent monosaccharides. .

  In addition, the water-soluble neutral polysaccharide used in the present invention is, for example, α-formated as long as it has water-solubility or is acquired, and the constituent monosaccharide does not substantially contain uronic acid or ester sulfate. , Acetylation and the like are also widely included.

  As water-soluble neutral polysaccharides, for example, starch, glucomannan, galactomannan, guar gum, dextran, pullulan, etc., polysaccharides having aldohexose as a constituent monosaccharide, especially glucose, mannose, or galactose It is preferable to use a polysaccharide as a monosaccharide, and it is most preferable that the water-soluble neutral polysaccharide is tapioca starch and / or glucomannan.

  The molecular weight of the water-soluble neutral polysaccharide is preferably about 10,000 to 4 million, more preferably 20,000 to 3 million, and most preferably 25,000 to 2.5 million.

  In the present invention, both the case where one type of water-soluble neutral polysaccharide is used and the case where two or more types of water-soluble neutral polysaccharide are used are widely included.

  As described above, the present invention can be applied to a wide range of suspended water coagulation treatments. For example, removal of organic and inorganic substances in water treatment plants, removal of pollutants in wastewater treatment plants, suppression of mud and muddy water generation in civil engineering works and removal of pollutants and mud, aquatic and microalgae in water areas ( It is effective for removing organic suspensions such as phytoplankton).

  In addition, the present invention, for example, was removed from the bottom of the water at the time of removal of harmful substances in water purification plants, wastewater treatment plants, etc., recovery / removal of harmful substances contained in water, and civil engineering work in water areas. It has the advantage of being effective for collecting and removing harmful substances.

  Hazardous substances that can be removed include, for example, heavy metals such as lead, copper, chromium, cadmium, mercury, zinc, arsenic, manganese, cobalt, nickel, molybdenum, tungsten, tin, bismuth, uranium, plutonium, cesium, strontium, zinc, Examples include radioactive isotopes such as manganese.

  In addition, the present invention is effective for any suspension water of fresh water, brackish water, and seawater.

  In Example 1, it was examined whether polysaccharides other than cyanobacteria-derived components could be substituted for the aggregation treatment using polysaccharides.

  The polysaccharides to be tested include polysaccharide-containing cyanobacteria-derived components, Dieutan gum (trade name “KELCO-CRETE DG / DG-F”, the same applies hereinafter), xanthan gum (trade name “KELTROL F”, the same applies hereinafter), α Acetylated acetylated tapioca starch (trade name “Alpha Tapioca Starch AC”, hereinafter the same) and glucomannan (trade name “Propol A”, hereinafter the same) were prepared.

  The polysaccharide-containing cyanobacterium-derived component was prepared by the following procedure. A field-cultivated suizendinori was soaked in ethanol for a certain period of time to remove water-soluble pigments and fat-soluble pigments. Next, it moved to the sodium hydroxide aqueous solution, heat-processed, and extracted the component which mainly has the polysaccharide of the weight average molecular weight 2 million-20 million from cyanobacteria. Hydrochloric acid was added dropwise to this extract to neutralize it to around pH 7. A part of the sample was collected and quantified using high performance liquid chromatography (the same applies to the following examples).

Dieutan gum is a natural water-soluble acidic polysaccharide composed of 2 glucose, 1 glucuronic acid, and 3 rhamnose, and has a molecular weight of 100,000 to 10 ¹³ . Xanthan gum is a water-soluble acidic polysaccharide having two glucose and one glucuronic acid as structural units, and has a molecular weight of 1 million.

  The tested α-acetylated tapioca starch is a processed cassava-derived starch, is a water-soluble neutral polysaccharide having glucose as a structural unit, and has a molecular weight of 40,000 to 340,000. Glucomannan is a water-soluble neutral polysaccharide derived from cornflower that is polymerized by β-1,4 bonds in a molar ratio of D-glucose and D-mannose of about 1: 1.6, and has a molecular weight of 2 million or more.

  To the tap water was added kaolin (post soil made by Wako Pure Chemical Industries, Ltd.) to prepare muddy water with a turbidity of about 200 NTU.

Add 200 mL of turbid water to each of test groups 1 to 5, add 800 μL of polyferric sulfate aqueous solution (final concentration 7.1 mg / L), stir for 6 minutes, and then add the polysaccharides shown in Table 1 to the final concentration in each test group The mixture was added to 6 mg / L, stirred for 4 minutes, stopped stirring, and allowed to stand for 5 minutes.

  10 mL of the agglomerated particles that settled after stirring and resting were collected, placed in a 20 mL glass bottle, shake-treated left and right at 150 rpm for 2 minutes, and then dropped into a cylinder with a depth of 30 cm to measure the sedimentation rate.

  The results are shown in Figure 1. FIG. 1 is a graph showing the particle sedimentation rate when each polysaccharide is used as a flocculant. In the graph, the horizontal axis represents the results of each test group, and the vertical axis represents the particle sedimentation rate (unit: mm / min).

  As shown in FIG. 1, when polysaccharides other than cyanobacteria-derived components are added (test groups 2 to 5), the particle sedimentation rate is in the range of 400 to 800 mm / min for any polysaccharide, and floc particles are formed. Aggregation / sedimentation was observed, but when the cyanobacteria-derived component was added as a polysaccharide (test area 1), the particle sedimentation rate (1,000 mm / min or more) was lower and the aggregation was equivalent to that of the cyanobacteria-derived component. The effect was not obtained.

  In Example 2, in the aggregating treatment using the polysaccharide, a cyanobacteria-derived component and other polysaccharides were added, and the aggregating effect was examined.

As in Example 1, 200 mL of turbid water was added to each of test sections 6 to 9, 800 μL of aqueous ferric sulfate solution (final concentration 7.1 mg / L) was added, and the mixture was stirred for 6 minutes. The two polysaccharides shown were combined and added to a final concentration of 6 mg / L, stirred for 4 minutes, stopped and left for 5 minutes. Then, 10 mL of the agglomerated particles that settled after stirring and resting were collected, placed in a 20 mL glass bottle, shaken for 2 minutes at 150 rpm, and dropped into a cylinder with a depth of 30 cm to measure the sedimentation rate.

  The result is shown in figure 2. FIG. 2 is a graph showing the particle sedimentation rate when two kinds of polysaccharides are added as a flocculant. In the graph, the horizontal axis represents the results of each test group, and the vertical axis represents the particle sedimentation rate (unit: mm / min). In the graph, test group 1 represents the results in Example 1.

  As shown in FIG. 2, the particle sedimentation rate (test sections 6 and 7) when adding a cyanobacteria-derived component and diutan gum or xanthan gum as a polysaccharide is the same as when the cyanobacteria-derived component was added alone (test group). It was lower than 1). In addition, the particle sedimentation rate is only slightly increased compared to the case where diuthanum gum or xanthan gum is added alone as a polysaccharide (in Fig. 1, Test Zone 2 and Test Zone 3), or almost the same range. It was in.

  On the other hand, the particle sedimentation rate when the cyanobacterium-derived component and α-acetylated tapioca starch or glucomannan are added as polysaccharides (test sections 8, 9) is the case where the cyanobacterium-derived component is added alone (test It was almost the same as ward 1). In addition, the particle sedimentation rate was remarkably increased as compared with the case where α-acetylated tapioca starch or glucomannan was added alone as the polysaccharide (in FIG. 1, test group 4 and test group 5).

  As described above, diyutan gum and xanthan gum are water-soluble acidic polysaccharides that contain glucuronic acid as a constituent monosaccharide, and pregelatinized tapioca starch and glucomannan are water-soluble neutral polysaccharides that contain aldohexose as a constituent monosaccharide. It is. Therefore, this experimental result shows that in the agglomeration treatment in which the iron salt and the polysaccharide are added separately, the cyanobacteria-derived component is added alone by adding the cyanobacteria-derived component and the water-soluble neutral polysaccharide as the polysaccharide. It shows that the addition amount of the cyanobacteria-derived component can be reduced while maintaining the coagulation effect almost the same as that of the case.

  The molecular weight of polysaccharides contained in cyanobacteria-derived components is about 16 million, whereas the molecular weight of water-soluble neutral polysaccharides added together is higher than the molecular weight of polysaccharides contained in cyanobacteria-derived components. We presume that a smaller one is preferable. Considering the molecular weight of the polysaccharide used in this experiment, it is estimated that the molecular weight of the water-soluble neutral polysaccharide is preferably about 10,000 to 4,000,000.

  In Example 3, the ratio of addition of the cyanobacterium-derived component was examined in the aggregation treatment using the cyanobacterium-derived component and the water-soluble neutral polysaccharide.

As in Example 1 and the like, 200 mL of turbid water was added to each of test sections 10 to 14, 800 μL of polyferric sulfate aqueous solution was added (final concentration 7.1 mg / L), and the mixture was stirred for 6 minutes. Two or more kinds of polysaccharides shown in (2) above were combined and added to a final concentration of 6 mg / L, stirred for 4 minutes, stopped stirring, and allowed to stand for 5 minutes. Then, 10 mL of the agglomerated particles that settled after stirring and resting were collected, placed in a 20 mL glass bottle, shaken for 2 minutes at 150 rpm, and dropped into a cylinder with a depth of 30 cm to measure the sedimentation rate.

  The results are shown in Figure 3. FIG. 3 is a graph showing the particle sedimentation rate when adding two or more kinds of polysaccharides as a flocculant and changing the ratio of addition of cyanobacteria-derived components and other polysaccharides. In the graph, the horizontal axis represents the results of each test group, and the vertical axis represents the particle sedimentation rate (unit: mm / min). In the graph, test group 1 represents the results in Example 1.

  As shown in FIG. 3, in the agglomeration treatment using the cyanobacterium-derived component and the water-soluble neutral polysaccharide, the particle sedimentation rate when the cyanobacterium-derived component addition ratio of the added polysaccharide is 25% ( The test groups 10 to 12) were almost equivalent to the case where the cyanobacteria-derived component was added alone (test group 1). On the other hand, the particle sedimentation rate (test zone 13, test zone 14) when the rate of addition of cyanobacteria-derived components in the polysaccharide to be added is 10% is when the cyanobacteria-derived component is added alone (test The value was lower than in District 1).

  The result of this experiment is that, in the agglomeration treatment in which the iron salt and the polysaccharide are added individually, when the cyanobacterium-derived component and the water-soluble neutral polysaccharide are added as the polysaccharide, the cyanobacterium-derived component of the polysaccharide to be added It is shown that when the ratio of the addition of is at least 15% or more, an agglomeration effect substantially equivalent to the case of adding the cyanobacteria-derived component alone is obtained.

In Example 1, the graph which shows the particle sedimentation rate at the time of using each polysaccharide as a flocculant. In Example 2, the graph which shows the particle sedimentation rate at the time of adding two types of polysaccharides as a flocculant. In Example 3, the graph which shows the particle sedimentation speed | velocity | rate at the time of changing the ratio of the addition of a cyanobacterium origin component and another polysaccharide.

Claims (4)

A coagulation treatment method including a procedure of individually adding an iron salt and a polysaccharide,
A coagulation treatment method in which a cyanobacteria-derived component and a water-soluble neutral polysaccharide are added as the polysaccharide.   The aggregation treatment method according to claim 1, wherein the ratio of the amount of the cyanobacterium-derived component and the water-soluble neutral polysaccharide is 15:85 to 90:10.   The aggregation treatment method according to claim 1 or 2, wherein a polysaccharide having aldohexose as a constituent monosaccharide is used as the water-soluble neutral polysaccharide. The aggregation treatment method according to any one of claims 1 to 3, wherein the water-soluble neutral polysaccharide is tapioca starch and / or glucomannan.

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