JP7276769B2 - Flocculant for turbid water treatment - Google Patents

Description

The present invention is a turbid water treatment used to easily treat turbid water generated from civil engineering work, construction work, etc., and turbid water generated when washing high water content mud accumulated at the bottom of lakes, rivers, port shores, etc. for flocculants.

Conventionally, as a treatment method for high water content mud generated from dredging work, after solid-liquid separation with an organic synthetic polymer flocculant, water is removed and cement or the like is added to the slurry to solidify it. Two-stage treatment such as using a cationic organic synthetic polymer for the turbid water generated, or adding an aqueous solution of an inorganic flocculant such as PAC (polyaluminum chloride), aluminum sulfate, and polyferric chloride, and an organic synthetic polymer flocculant. Processing methods for volume reduction have been adopted.

Against this background, facilities have become more sophisticated, complex, and huge, and in construction work in mountains and marshes where yards cannot be secured, processing often takes a long time and transporting sludge becomes difficult.

In addition, as a countermeasure to this, for example, as disclosed in Patent Document 1, flocs are made with a polymer flocculating agent, cement or the like is added instead of an inorganic flocculating agent, and flocs containing solidifying material particles are added. However, a cement-based solidification agent is recommended, and this is nothing but a restriction on the conversion of construction soil by alkalinizing the treated soil.

Further, as disclosed in Patent Document 2, a soluble aluminum compound, an iron salt compound, a reducing agent, an organic synthetic polymer flocculant, a natural polymer flocculant, an alkali metal carbonate and/or cement granules, a high A flocculant composition composed of silicate-alumina-based soil mineral granules containing silicon oxide and alumina as main components has been proposed for zeta potential activity, but specific stirring methods and dehydration methods are also mentioned. do not have.

JP-A-9-168800 Japanese Patent Application No. 9-287555

The present invention addresses the problems associated with the technology for treating turbid water generated during conventional civil engineering and construction work, as well as turbid water that accumulates on the bottom of lakes, rivers, port shores, and the like. In view of this, it is possible to eliminate the agitating equipment for agitating turbid water and chemicals even in a narrow yard and simplify the method of treating the sludge that accumulates at the bottom. It is an object of the present invention to provide a coagulant for treating turbid water, which promotes dehydration from flocs while maintaining pH neutrality of flocs and contributes to development of strength of sludge.

In order to achieve the above object, the flocculant for treating turbid water of the present invention contains two or more anionic synthetic polymer flocculants, one or more natural polymer flocculants, and alkaline earth metals. Two or more kinds of calcium-based compounds are blended, two or more kinds of aluminum compounds are blended, one or more kinds of alkaline earth metals, magnesium oxides or carbonates are blended as pH adjusters, and powder of porous material is blended. It is characterized by

More specifically, the flocculant for treating turbid water of the present invention contains 55w% to 65w% anhydrous calcium sulfate, 7w% to 12w% sodium carbonate, 5w% to 10w% calcined diatomaceous earth, and 0.5w calcium carbonate. % to 5w%, 10w% to 20w% of aluminum sulfate, 0.5w% to 5w% of polyaluminum chloride, 2w% to 4w% of low molecular weight anionic polymer, 0.5w% to 5w% of high molecular weight anionic polymer, It is characterized by containing 1w% to 4w% of alginate.

In this case, the anionic synthetic polymer flocculant is a high molecular weight anionic polymer having an anion degree of 13 million to 15 million and an anion degree of 30 mol % to 50 mol % (the aggregation reaction is slow, but large flocs are generated ), and as a low-molecular-weight anionic polymer, a polymer flocculant having an anion degree of 10 mol% to 30 mol% and an anion degree of 6 million to 12 million (specifically, a polymer flocculant composed of fine powder of 200 mesh (75 μm or less) agent.) (does not produce large flocs, but the aggregation reaction is fast) can be used.

Moreover, as a natural flocculant, one or more of alginates (targeted for finer particles than low-molecular-weight anionic polymers and having a fast flocculation reaction), chitin, chitosan, and the like can be contained. Further, it is more desirable to use a fine powder (0.2 μm to 60 μm) produced by spray drying or the like.

In addition, as the calcium-based compound, calcium carbonate and calcium sulfate, which do not greatly affect the pH, are used. In order to obtain the caking strength of the sludge, the calcium sulfate is desirably semi-water calcium sulfate or anhydrous. is particularly preferred as a soluble natural anhydrous.

Further, it is preferable to use a mixture of powders of polyaluminum chloride and aluminum sulfate as the aluminum-based compound, and it is particularly preferable that the ratio of aluminum sulfate is high in mud sludge and the like. This is because the combination of calcium sulfate and aluminum sulfate has a high flocculating action, and the combination of polyaluminum chloride and natural anhydrous calcium sulfate or calcium dihydrate and aluminum sulfate is particularly desirable.

In addition, it is desirable to use a carbonate or magnesium oxide in order to return the pH of the acidic side to neutral with an aluminum-based compound, and more preferably, magnesium oxide that releases Mg ²⁺ with a strong coagulation effect is blended, Most desirably, magnesium oxide produced by the seawater method is preferred.

The powder of the porous substance is for adsorbing fine particles, pigments, and radioactive elements contained in the turbid water, and fine powders of zeolite, activated carbon, and diatomaceous earth can be used. , For the purpose of forming sludge with a high hydraulic conductivity, calcined diatomaceous earth (pH is in the neutral range (about pH 7.7 ± 0.5), median diameter (D50) 8 ~ 12 μm, specific surface area 1 ~ 5 m ² /g) is most preferred.

According to the coagulant for turbid water treatment of the present invention, the coagulant for turbid water treatment is added to the high water content mud sucked up by vacuum, and the coagulant for turbid water treatment is not required to be stirred by a submersible pump or a stirrer, and the suspended particles can be separated only by stirring with running water. It is capable of flocculation reaction, has immediacy of flocculation reaction, produces sludge with high dehydration property while pH remains neutral, and can obtain flocs with high strength in the process of dehydration. The floc that is formed is characterized by its extra-large size, and even in mountainous areas where it is difficult to install a filter press or when only a narrow work space can be secured, after forming flocculated flocs, the residue that has been dehydrated with a dewatering filter cloth or the like can be removed. It does not easily adhere to the filter cloth, is easy to peel off, and has good dewatering properties. By doing so, it is possible to solve problems such as securing work space.

Hereinafter, embodiments of the flocculant for treating turbid water of the present invention will be described based on specific embodiments.

The flocculant for turbid water treatment of the present invention does not require large equipment such as a submersible pump or stirrer for agitating the agent and high water content mud or turbid water. Using two different types of synthetic polymer flocculants, one natural polymer flocculant to effectively flocculate fine particles, calcium carbonate to give weight to the floc, and calcium sulfate to give strength after dehydration. By blending two or more types of aluminum compounds with different basicities, such as polyaluminum chloride and aluminum sulfate, it is possible to neutralize a wide range of zeta potentials, and adjustment to counteract pH fluctuations due to the use of aluminum compounds. By using sodium bicarbonate and magnesium oxide as agents, it is possible to prevent high reactivity and aluminum saturation, and by using calcined diatomaceous earth, it is possible to create highly water-permeable sludge and give it strength after dehydration, making it possible to secure work space. It is designed to eliminate

The table below shows the results of turbid water treatment tests in which the formulations under the following conditions and the materials used were changed, in which the changes were particularly large during repeated examinations.
In the test method, two beakers were used, and the change was measured by a turbidity meter when the transfer operation was performed eight times.

[Test object 1]
・Fukushima prefecture irrigation pond dredging: specific gravity 1.01-1.02
・Muddy water pH: 6.56
・ Turbidity: 500 degrees or more (turbidity meter: TD-M500 / Optex Co., Ltd.)
[Test object 2]
・ Tochigi quarry mud: specific gravity 1.22 (adjusted to specific gravity 1.01 by diluting with tap water)
・Muddy water pH: 5.86
・ Turbidity: 500 degrees or more (turbidity meter: TD-M500 / Optex Co., Ltd.)

From the results of Tables 3 to 5, it was determined that the preferred formulation exhibits a wide selective flocculation effect near Experimental Example 5. 5w% to 10w% of calcium carbonate, 0.5w% to 5w% of calcium carbonate, 10w% to 20w% of aluminum sulfate, 0.5w% to 5w% of polyaluminum chloride, 2w% to 4w% of a low-molecular anionic polymer, It was determined that it was desirable to incorporate 0.5w% to 5w% macromolecular anionic polymer and 1w% to 4w% alginate.

From the results in Tables 6 and 7, the diatomaceous earth used in the present invention is desirably calcined diatomaceous earth that is a calcined product. (D50) of 8 to 12 μm and a specific surface area of 1 to 5 m ² /g were judged to be more desirable.

As described above, the flocculant for treating turbid water of the present invention has been described based on the embodiments, but the present invention is not limited to the description of the above embodiments, and the configuration can be changed as appropriate without departing from the spirit of the present invention. It is something that can be done.

The coagulant for turbid water treatment of the present invention has the characteristics of saving labor in turbid water treatment work, promoting dehydration from flocs while maintaining the pH of treated water and flocs generated, and contributing to the development of sludge strength. Therefore, it can be suitably used for treating turbid water generated from civil engineering and construction work, and turbid water generated when washing high water content mud accumulated at the bottom of lakes, marshes, rivers, port shores, etc. can.

Claims (2)

As a synthetic polymer flocculant, a polymer flocculant with an anion degree of 30 to 50 mol% of 13 to 15 million and an anion degree of 0.5 to 5 w% and a polymer flocculant of 6 to 12 million and an anion degree of 10 to 30 mol%. Formulated with 2w% to 4w% ,
Alginate 1w% to 4w% is blended as a natural polymer flocculant,
55w% to 65w% of anhydrous or hemihydrate calcium sulfate and 0.5w% to 5w% of calcium carbonate are blended from alkaline earth metals,
10w% to 20w% of aluminum sulfate and 0.5w% to 5w% of polyaluminum chloride are blended as an aluminum compound,
Contains 7w% to 12w% sodium carbonate as a pH adjuster,
A coagulant for treating turbid water, characterized in that 5w% to 10w% of calcined diatomaceous earth powder is blended as a porous material. The flocculant for turbid water treatment according to claim 1 , wherein the calcined diatomaceous earth has a median diameter of 8 to 12 µm and a specific surface area of 1 to 5 m ² /g.