WO2014136550A1

WO2014136550A1 - Particulate water treatment agent for environment and method for treating water polluted by harmful substances using same.

Info

Publication number: WO2014136550A1
Application number: PCT/JP2014/053502
Authority: WO
Inventors: 吉川　英一郎; 飯島　勝之; 智之古田; 宏介森; 後藤　義己
Original assignee: 株式会社神戸製鋼所
Priority date: 2013-03-07
Filing date: 2014-02-14
Publication date: 2014-09-12
Also published as: JP5981863B2; CN105008285A; CN105008285B; JP2014171953A

Abstract

The present invention pertains: to a particulate water treatment agent for the environment, for eliminating a harmful substance, and characterized by resulting in a granulated form by adding pure water to a composition configured from iron powder, magnesia, and an acidic inorganic sulfate salt; and a method that is for treating water polluted by harmful substances and that is characterized by bringing into contact polluted water containing harmful substances and the particulate water treatment agent for the environment.

Description

Granular environmental water treatment agent and method for treating water contaminated with harmful substances using the same

The present invention relates to a granular environmental water treatment agent for removing harmful substances from groundwater, river water, lake water, various industrial effluents, etc. contaminated with harmful substances that are harmful to human bodies and cause health problems, The present invention relates to a method for treating water contaminated with harmful substances.

Hazardous substances that are harmful to the human body and cause health problems (for example, heavy metals such as cadmium, hexavalent chromium, selenium, lead, arsenic) are harmful to the human body if ingested above a certain amount. is there. Water quality standards such as environmental standards and drainage standards have been established so that health hazards will not be caused by ingesting water contaminated with harmful substances or animals and plants grown in a contaminated environment. ing. Therefore, when harmful substances contained in water such as rivers, lakes, groundwater, and various industrial wastewaters exceed the water quality standards, it is necessary to remove these harmful substances from the water.

Various water treatment agents and water treatment methods have been devised as means for removing (purifying) harmful substances from water contaminated with harmful substances (hereinafter referred to as “polluted water”). As a general water treatment agent and water treatment method, a method using an inorganic flocculant such as an iron salt or an aluminum salt (hereinafter referred to as a precipitation treatment method) is performed. This precipitation method is a method in which after adding an inorganic flocculant to contaminated water and adjusting the pH to precipitate the flocs of metal hydroxide, the flocs take in harmful substances and co-precipitate them for separation. It is. Further, a polymer flocculant may be used in combination with the flocculant.

However, in order to sufficiently reduce the concentration of harmful substances in the contaminated water by such a precipitation treatment method, a large amount of water treatment agent is required. In addition, the aggregated floc incorporating toxic substances is an aggregate of amorphous fine particles, and requires a large amount of equipment and a long time to settle. Furthermore, there is a problem in that a large amount of precipitate (sludge) treatment is complicated and requires many steps.

As a water treatment method that solves the problem of such a precipitation treatment method, an adsorbent such as activated carbon, activated alumina, zeolite, titanate, zirconium hydrate, etc. is brought into contact with contaminated water containing harmful substances, and harmful substances are brought into contact. A method for adsorbing and removing (hereinafter referred to as an adsorption method) has been proposed. The adsorption method can achieve a high adsorption / removal efficiency by selecting an adsorbent having an excellent adsorption / removal capability. However, since such an adsorbent is usually expensive, an increase in processing cost is inevitable.

Therefore, attention has been paid to iron powder, which is cheaper and more versatile than the adsorbent described above, and an adsorption method using this as an adsorbent has been proposed. However, ordinary iron powder has insufficient adsorption and removal capability, and a satisfactory removal effect cannot be obtained. Therefore, development of iron powder with enhanced adsorption and removal capability of harmful substances has been promoted.

For example, in Patent Document 1, iron powder containing an appropriate amount of at least one selected from phosphorus, sulfur, and boron as iron powder for removing harmful substances, and further, a specific amount of carbon and inevitable impurities (for example, Si) Water atomized iron powder containing Mn) has been proposed. In this technology, by adding specific elements in specific amounts in iron powder, the elution rate of iron into contaminated water can be increased, and harmful substances such as phosphorus compounds, heavy metals, and organic chlorine compounds in contaminated water can be increased. It is disclosed that it can be removed efficiently. However, as can be seen from the examples of Patent Document 1, this technology mainly removes phosphorus compounds in contaminated water, and the adsorption removal ability of heavy metals such as cadmium, hexavalent chromium, selenium, lead, arsenic, etc. Not considered. In addition, when the present inventors confirmed the adsorption removal ability of heavy metals etc. about the said iron powder, it could not be said that the adsorption removal ability of heavy metals etc. was enough.

Patent Document 2 proposes a method for producing reducible sponge iron containing a predetermined amount of sulfur and its use as an environmental purification agent for treating contaminated water that has a reducing ability for organic halogen compounds, heavy metals, etc. and has excellent sustainability. Has been. In this technique, a technique is disclosed in which an organic halogen compound is reduced and dehalogenated or heavy metal or the like is reduced and insolubilized with sponge iron (also referred to as sponge iron) having an excellent reducing ability. Sponge iron is considered to be an industrially effective method because it has a higher surface area than ordinary iron powder and thus has high removal performance and efficiency, and is cheaper than other adsorbents. However, since sponge iron is more expensive than ordinary iron powder obtained by the water atomization method, there is still room for further improvement from the viewpoint of versatility on an industrial scale.

Moreover, as a big problem which iron powder like patent document 1 and patent document 2 has, when iron powder is impregnated with water in order to treat contaminated water, iron powder is influenced by water molecules or dissolved oxygen. Since the surface of the iron is covered with iron oxide, iron hydroxide, iron oxyhydroxide, etc., and the generation of iron ions is hindered, the adsorption and removal ability derived from the action of iron ions cannot be maintained for a long time. It is done.

In addition to this, the development of an insolubilization / purification technology that combines the ability of adsorption and removal of heavy metals, etc., possessed by iron powder and the insolubilization capability of heavy metals, etc., possessed by other materials is also underway. For example, in Patent Document 3, a contaminated soil insolubilizing solidifying agent characterized by containing MgO and iron powder, and a sulfate, hydrochloride, sulfamic acid, phosphoric acid, and a phosphorus compound whose aqueous solution has a pH of 7 or less. Contaminated soil insolubilizing solidifying agent containing one or two or more auxiliary agents selected from the group consisting of, and one or two selected from the group consisting of water-soluble gums, water-soluble fibrin derivatives and clays. A contaminated soil insolubilizing solidifying agent containing a viscosity imparting agent of more than seeds has been proposed.

In this technology, MgO and iron powder reduce and insolubilize harmful substances in the soil (in the example of Patent Document 3, lead, arsenic and trichlorethylene are targeted), and MgO solidifies the soil by solidifying soil. It can contain harmful substances insolubilized in it, and when an auxiliary agent is added, insolubilization of harmful substances in the soil is promoted, and the gel strength of the solidified soil can be improved. It is disclosed that the settling of iron powder in the insolubilized solidifying agent can be prevented.

However, as described in the specification and Examples of Patent Document 3, since 1 to 50 parts by mass of iron powder is usually added to 100 parts by mass of MgO, heavy metals and the like in this technique are used. The insolubilization ability is largely due to the insolubilization ability and soil solidification ability of MgO. Therefore, after the reaction between the MgO component and the soil proceeds and the MgO component is consumed, the insolubilizing ability may not be exhibited. Furthermore, as disclosed in Patent Document 3, the purpose of use of the technology is specified to insolubilize and solidify harmful substances in contaminated soil, and its application to water treatment agents has not been studied at all, and the description is also suggested. I have not done it.

In addition to this, technologies relating to water treatment purifiers using insolubilization / purification technology that combines the ability to adsorb and remove heavy metals, etc., in iron powder and the insolubilization capabilities, such as heavy metals, in other materials are disclosed in, for example, Patent Literature 4 and Patent Document 5.
In Patent Document 4, it is a purification material that is mixed with soil and installed at a thickness of 5 cm or more below or on the side or both of contaminated soil or waste, and is capable of adsorbing heavy metals by contact with water, Iron hydroxide, iron oxide or hydrate thereof, magnesium hydroxide, magnesium oxide or hydrate thereof, cerium carbonate fluoride, cerium hydroxide, cerium oxide or hydrate thereof, or powder containing one or more thereof There has been proposed a purification material characterized by comprising a material mixed with a fibrous material having an average diameter of 1 to less than 1000 μm and a ratio of fibrous material / powder material = 0.33 to 3.
In this technology, by arranging the aforementioned purification material below or on the side or both of the contaminated soil or waste, while obtaining a smooth flow of water containing heavy metals leached from the contaminated soil or waste, It is disclosed that purification can be advanced promptly. However, this technique has not been devised and studied for maintaining a proper combination and blending ratio of various powder materials, or adsorption / removing ability for a long period of time, and there is room for further improvement.

In patent document 5, it is a purification material formed by granulating metal iron powder and / or iron oxide powder, magnesium hydroxide and / or magnesium oxide, and a pH adjuster with a binder, and the pH adjuster is treated. A purification material characterized in that the pH value of the contaminated water to be controlled is adjusted to 4 to 10, a purification material obtained by granulating the purification material containing cerium oxide and / or cerium hydroxide, and the pH adjusting agent. The purification agent is 10 to 100 parts by weight with respect to 100 parts by weight of magnesium hydroxide and / or magnesium oxide, and the pH adjuster is selected from aluminum sulfate, iron sulfate, iron chloride, acid clay, and citric acid One or more types of purification materials have been proposed.
This technology is intended to mitigate the effects of increased pH values caused by metal iron powder, magnesium oxide, and magnesium hydroxide produced by hydration of magnesium oxide on contaminated soil that is complexly contaminated with heavy metals. It has been disclosed that a purifying material granulated including a pH adjusting agent can uniformly maintain various materials and can always maintain an optimum pH value at which the purifying action of metallic iron powder can be exhibited.

However, in this technique, a binder is essential for granulating, and since an aqueous binder is used as described in the specification of Patent Document 5, the binder dissolves and flows out in water. There is concern that eutrophication will adversely affect the surrounding environment. In addition, although there is no mention of the hardness of the granulated purification material, there is a possibility that the hardness may be remarkably lowered due to the outflow of the aqueous binder, or there is a possibility that the granulated state will collapse. It is suggested that time cannot be maintained. Furthermore, in the claim and specification of Patent Document 5, the specific blending ratio of metal iron powder and / or iron oxide powder and magnesium hydroxide and / or magnesium oxide is not shown. It is only shown that the blending ratio of magnesium and magnesium is 1: 1 (mass ratio), and is optimal as a water treatment agent, such as metal iron powder and / or iron oxide powder, and magnesium hydroxide and / or magnesium oxide. The blending ratio of is not disclosed.

Japanese Unexamined Patent Publication No. 2000-80401 JP 2004-331996 A JP 2005007256 A Japanese Patent No. 4187223 JP 2011-110476 A

From the above, it is a granular type environmental water treatment agent for treating contaminated water containing heavy metals (eg, cadmium, hexavalent chromium, selenium, lead, arsenic), etc., and has sufficient hardness, such as heavy metals Thus, there has been a demand for a water treatment agent and a method using the same that can maintain the adsorption / removal ability for a long time without causing environmental pollution. In addition, in the case of using in a packed state in a contaminated water treatment column or the like, there has been a demand for a granular environmental water treatment agent having a low water flow resistance and easy handling, and a method using the same.

That is, the present invention has sufficient hardness and can maintain the adsorption and removal ability of heavy metals for a long time, does not cause environmental pollution, has high versatility, and is resistant to water flow even when used in a column or the like. It is an object of the present invention to provide a granular environmental water treatment agent that is easy to handle, and a method for treating water contaminated with harmful substances using them.

As a result of intensive studies by the inventors, the above-mentioned problem is that granulated by adding fresh water to a composition in which magnesia and acidic inorganic sulfate are mixed at a specific ratio with respect to iron powder. As a result, the present invention has been completed.

That is, the first of the present invention for solving the above-mentioned problems is a water treatment agent for removing harmful substances, which comprises adding fresh water to a composition containing iron powder, magnesia, and acidic inorganic sulfate. A granular environmental water treatment agent characterized by being in a granulated form.

According to a second aspect of the present invention, the particulate environmental water treatment agent according to the first aspect is further characterized by any one or more of the following (a) to (d).
(A) The composition contains 10 to 50 parts by mass of magnesia and 5 to 50 parts by mass of acidic inorganic sulfate with respect to 100 parts by mass of iron powder.
(B) The fresh water is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the composition;
(C) The magnesia is obtained by pulverizing light-burned magnesia containing 60% by mass or more of magnesium oxide, and is in a powder form having a maximum particle size of 2.0 mm or less.
(D) The acidic inorganic sulfate is at least one selected from iron (II) salt, iron (III) salt, and aluminum salt, and has a maximum particle size of 2.0 mm or less.

According to a third aspect of the present invention, in the granular environmental water treatment agent according to the first or second aspect, the hardness of the granular material is 80% or more when measured according to JIS K 1474-2007. .

A fourth aspect of the present invention is the particulate environmental water treatment agent according to the first or second aspect, wherein the composition is granulated by adding fresh water, and then the particle size is adjusted in the range of 0.1 to 2.0 mm. It is characterized by being in the form of a granular material.

5th of this invention is the processing method of the water contaminated with the harmful | toxic substance characterized by making the contaminated water containing a hazardous | toxic substance and the granular-type environmental water treatment agent as described in 1st or 2 contact. .

6th of this invention is the processing method of the water contaminated with the harmful substance of 5th invention, The said contaminated water is from the soil containing a hazardous substance, sludge, coal ash, incineration ash, dust, and industrial waste. It is contained in the kind chosen.

A seventh aspect of the present invention is the method for treating water polluted with harmful substances according to the fifth aspect, wherein polluted water containing harmful substances is passed through the packed bed filled with the particulate environmental water treatment agent. It is made to contact.

According to the first aspect of the present invention, the harmful substance can be adsorbed and removed from the contaminated water containing the harmful substance only by using a readily available material, and the granular material has high hardness. Since harmful substances can be adsorbed and removed over a period of time and does not contain an organic compound binder or the like, the influence on the environment can be reduced.

According to the second (a) of the present invention, the amount of magnesia used can be reduced as compared with the conventional one, and at the same time, the hardness of the granular environmental water treatment agent can be made sufficient.

According to the second (b) of the present invention, no water-based binder is used, environmental pollution is not caused, and hydraulic action of magnesia and acidic inorganic sulfate can be expressed. A processing agent can be made into moderate hardness.

According to the second (c) of the present invention, since it is distributed as an industrial product, it can be easily obtained, and powdery light-burned magnesia that is generally used in a wide variety can be used. It can be highly versatile and economical.

According to the second (d) of the present invention, not only is it possible to use acidic inorganic sulfates which are distributed as industrial products and are easily available and generally used in a wide variety of fields. These acidic inorganic sulfates are highly soluble in water, can adjust the pH quickly, and can exhibit more excellent adsorption and removal ability due to the aggregation and precipitation action and reduction action of these acidic inorganic sulfates.

According to the third aspect of the present invention, since it is a granule that is granulated by adding only fresh water without using an aqueous binder, it is impregnated with water or subjected to external force. Therefore, the shape of the granular material can be maintained for a long time because it does not easily collapse.

According to the fourth aspect of the present invention, when used in a contaminated water treatment column or the like, while making the granulated product into a specific particle size range, the water flow resistance is reduced and clogging is suppressed. It is possible to pack densely, sufficiently ensure the contact area and contact time between the water treatment agent and the contaminated water, and increase the efficiency of adsorbing and removing harmful substances from the contaminated water.

According to the fifth aspect of the present invention, by bringing contaminated water containing a harmful substance into contact with a water treatment agent, the harmful substance can be adsorbed and removed from the contaminated water, and the concentration of the harmful substance can be reduced as compared with that before the treatment. .

According to the sixth aspect of the present invention, the harmful substances can be adsorbed and removed from the contaminated water and the concentration of the harmful substances can be reduced more than before the treatment, so that the diffusion of the harmful substances to the environment can be prevented.

According to the seventh aspect of the present invention, a contact time between the water treatment agent and the contaminated water is provided by providing a packed bed filled with the water treatment agent and allowing the contaminated water containing harmful substances to pass through and contact the packed bed. Therefore, the efficiency of adsorbing and removing harmful substances from contaminated water can be increased.

FIG. 1 is a schematic view showing an example of a method for treating water contaminated with harmful substances when the granular environmental water treatment agent of the present invention is used in a column.

-Granular environmental water treatment agent The present invention is described in detail below.
The particulate environmental water treatment agent of the present invention is intended for contaminated water contaminated with harmful substances that are harmful to the human body and cause health problems. In the present invention, the particulate environmental water treatment agent refers to a water treatment agent that is granular and does not cause environmental pollution and can adsorb and remove harmful substances.

The water treatment agent of the present invention is made into a granulated form by adding fresh water to a composition containing iron powder, magnesia, and acidic inorganic sulfate. The composition may contain other components as necessary.
The amount of the iron powder is, for example, 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more, and further preferably 65% by mass with respect to the entire composition from the viewpoint of adsorbing and removing harmful substances. For example, it is 97% by mass or less, preferably 90% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less.
From the viewpoint of adsorbing and removing harmful substances, the amount of magnesia is, for example, 2% by mass or more, preferably 4% by mass or more, more preferably 6% by mass or more, and further preferably 8% by mass or more based on the entire composition. For example, it is 36% by mass or less, preferably 34% by mass or less, more preferably 32% by mass or less, and further preferably 30% by mass or less.
The amount of the acidic inorganic sulfate is, for example, 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, further preferably from the viewpoint of a hydraulic reaction with magnesia. For example, it is 14% by mass or less, preferably 13% by mass or less, more preferably 12% by mass or less, and further preferably 11% by mass or less. The balance may be inevitable impurities.
This granulated product can be further granulated as necessary to form a granular environmental water treatment agent. The ability to adsorb and remove harmful substances from contaminated water can be achieved by the ability to adsorb and remove the harmful substances derived from the material of the water treatment agent.
In addition, the water treatment agent of the present invention preferably does not contain a binder, and water is used instead of the conventional binder, and a hydraulic reaction is caused by a chemical reaction such as magnesia and water, magnesia and acidic inorganic sulfate and water. It can be expressed to increase the hardness of the granulated product, and can remove adsorbed harmful substances from contaminated water over a long period of time. Furthermore, since no conventional binder is used, there is no environmental pollution.

1-1. Composition A. The role of iron powder, which is a constituent of iron powder, is as follows: (1) Iron ions (Fe ²⁺ ) eluted in the vicinity of the iron powder surface are anions (selenate ion (SeO ₄ ^2- ), arsenate in contaminated water) (2) Cation (lead ion (Pb ²⁺ ), cadmium ion (Cd), effect of adsorbing and immobilizing poorly soluble iron compounds produced by reaction with ions (AsO ₄ ^3- )) on the surface of iron powder ²⁺ )) in which the harmful substances dissolved in water are reduced to metals by the iron anodic reaction (Fe → Fe ²⁺ + 2e ⁻ ), and deposited on the surface of the iron powder to be immobilized, or ( 3) The poorly soluble chromium hydroxide produced by the reaction of hydroxide ions generated by the supply of electrons to water by the iron anode reaction and chromium ions (Cr ³⁺ , Cr ⁶⁺ ) on the iron powder surface The effect of adsorbing and immobilizing can be mentioned. Adsorb and remove harmful substances.

The iron powder used in the present invention is distributed as an industrial product, is easily available, is generally used in a wide variety of ways, is highly versatile, and economical, and is an atomizing method. Is preferable. Furthermore, the atomized iron powder produced by the water atomization method can be mass-produced, is economical, has the same components and particle size, and has a stable adsorption removal capability with little variation in performance. To more preferable.
In the present invention, sponge iron powder, cast iron powder, iron-base alloy powder (pre-alloy alloy powder) and the like can be used in addition to the atomized iron powder as long as the effects of the present invention are achieved.

The smaller the particle size (average particle size) of the iron powder used in the present invention, the greater the surface area (specific surface area) and the higher the rate of adsorption and removal of harmful substances. It becomes difficult to pass through, has an adverse effect on adsorption removal efficiency, tends to generate heat during storage and transportation, deteriorates storage stability, accelerates the oxidation reaction of iron powder, and the surface of iron powder becomes oxide Problems such as being easily covered with a film arise. On the other hand, the larger the particle size of the iron powder, the higher the yield and the better the handleability, but the harmful substance removal rate decreases.
Moreover, the preferable average particle diameter of the raw iron powder that improves the hardness of the granulated body by the action of the iron powder as an aggregate in the granulation step is 1000 μm or less, more preferably 100 μm or less, and still more preferably 80 μm or less. It is. Further, the lower limit of the average particle size of the iron powder is preferably 50 μm or more, more preferably 55 μm or more, and further preferably 60 μm or more.
In the present invention, the “average particle size” means a particle size distribution obtained by a dry sieving test using a sieve (sieving) specified in JIS Z 8801, wherein the percentage above the cumulative sieve or the percentage below the cumulative sieve is 50 mass. % Particle size.

B. The role of magnesia, which is a component of magnesia, is as follows: (1) The effect of adsorbing harmful substances (lead, arsenic, etc.) on magnesium hydroxide (Mg (OH) ₂ ) produced by hydration of magnesia (MgO), (2) Due to the formation of magnesium hydroxide, the pH in the vicinity increases to about 10 to 11, and harmful substances (lead, cadmium, etc.) that form poorly soluble hydroxides in this range of pH are precipitated and insolubilized. Or (3) the effect of adsorbing harmful substances when magnesium hydroxide reacts with carbon dioxide to produce basic magnesium carbonate (mMgCO ₃ · Mg (OH) ₂ ) · nH ₂ O) These adsorb and remove harmful substances from contaminated water.

The magnesia used in the present invention is distributed as an industrial product, is easily available, and is generally widely used. For example, magnesium hydroxide purified from seawater is calcined. The magnesia obtained by baking the natural ore magnesite obtained in this way, etc. can be used. In the present invention, magnesia that rapidly hydrates and contains a large amount of magnesium oxide (MgO) is preferable in order to improve the ability to adsorb and remove harmful substances. It is preferable that it is obtained by pulverizing magnesia as necessary. Magnesium oxide is more preferably 70% by mass or more, more preferably 75% by mass or more, preferably 99% by mass or less, more preferably 98% by mass or less, and still more preferably 95% by mass or less in light-burned magnesia. is there.

The firing temperature when producing light-burned magnesia varies depending on the raw material, but in general, when magnesium hydroxide purified from seawater is used as the raw material, it is about 350 ° C or higher. When natural ore magnesite is used as the raw material, Baking at about 540 ° C. or higher is preferred. On the other hand, when the firing temperature is higher than 1,000 ° C., the hydration reactivity of magnesia is impaired. Therefore, in order to obtain light calcined magnesia having a high hydration reactivity, firing at a temperature lower than this is required. preferable.

In order to efficiently obtain the adsorption removal ability of harmful substances derived from magnesia, the magnesia used in the present invention should be a powder obtained by pulverization so that the maximum particle size is 2.0 mm or less. preferable. In the present invention, “the maximum particle size is 2.0 mm or less” of magnesia is, for example, a cumulative sieving percentage of the particle size distribution obtained by a wet sieving test using a sieve (sieve) specified in JIS Z 8801 is 100. It means that the particle size is mass%. When the maximum particle size is larger than 2.0 mm, the contact area between magnesia and water becomes small due to the presence of coarse particles, and the hydraulic reaction in the granulation process due to the insufficient amount of magnesium hydroxide produced by the hydration reaction. There is a risk of reducing the contribution to. A preferable range of the maximum particle size is 0.60 mm or less, more preferably 0.15 mm or less, and further preferably 0.045 mm or less. The lower limit of the maximum particle size is not particularly limited as long as it exists as particles, but for example, the size of primary particles observed with a scanning electron microscope is usually 0.001 μm or more (particularly 0.01 μm or more). The preferable average particle diameter of magnesia is 100 μm or less, more preferably 50 μm or less, further preferably 20 μm or less, preferably 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 1 μm or more. . The average particle size is a particle size corresponding to a cumulative 50% of the volume reference particle size measured by a laser diffraction / scattering particle size distribution measuring apparatus (the dispersion medium uses an organic solvent such as isopropanol).

C. The role of the acidic inorganic sulfate, which is a constituent of the acidic inorganic sulfate, mainly includes an effect of promoting a hydraulic reaction with magnesia to form a curable substance. The acidic inorganic sulfate used in the present invention is distributed as an industrial product, is easily available, and is generally used in a wide variety, and those exhibiting pH acidity are preferable, and iron (II) One or more selected from a salt, an iron (III) salt, and an aluminum salt can be used. Preferred acidic inorganic sulfates include ferrous sulfate such as ferrous sulfate and ferric sulfate, aluminum sulfate and the like. Among these, ferrous sulfate (FeSO ₄ ) or a hydrate thereof (for example, monohydrate, tetrahydrate, pentahydrate, heptahydrate) is particularly preferable.

In addition, in order to improve hydraulic reactivity, these salts are preferably in the form of a powder having a maximum particle size of 2.0 mm or less. When the maximum particle size is larger than 2.0 mm, the contact area between magnesia, acidic inorganic sulfate and water becomes small, and due to insufficient magnesium oxysulfate production, it contributes to the hydraulic reaction in the granulation process. May lead to suppression. A preferable range of the maximum particle size is 1.0 mm or less, more preferably 0.6 mm or less, and is usually 0.05 μm or more (particularly 0.1 μm or more). The average particle size of the acidic inorganic sulfate is preferably 600 μm or less, more preferably 300 μm or less, still more preferably 106 μm or less, preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. In addition, “the maximum particle size is 2.0 mm or less” of the acidic inorganic sulfate is, for example, a cumulative percentage of the particle size distribution obtained by a dry sieving test using a sieve defined in JIS Z8801 is 100. It means that the particle size is mass%. The “average particle diameter” of the acidic inorganic sulfate has the same meaning as in the case of the iron powder.

For example, iron sulfate is preferably 70% by mass or more, more preferably 75% by mass or more, still more preferably 80% by mass or more, preferably 99% by mass or less, more preferably 98% by mass in the acidic inorganic sulfate. Hereinafter, it is more preferably 95% by mass or less.

The composition preferably contains 10 to 50 parts by mass of magnesia and 5 to 50 parts by mass of acidic inorganic sulfate with respect to 100 parts by mass of iron powder, and more preferably 100 parts by mass of iron powder. 12 to 48 parts by mass of magnesia, 6 to 30 parts by mass of acidic inorganic sulfate, more preferably 15 to 45 parts by mass of magnesia and 7 to 20 parts by mass of acidic inorganic sulfate with respect to 100 parts by mass of iron powder To do. When mixed in such a ratio, the water treatment agent granulated and granulated as follows can have sufficient hardness.

When the composition is used by being packed in a contaminated water treatment column or the like, the water resistance is reduced and the clogging factor is avoided by making the composition into a granular form having excellent handleability. Granulation is easily achieved by adding an appropriate amount of fresh water to the degree of granulation by the granulation step and granulating. The reason why it can be granulated is that the magnesium hydroxide contained in the water treatment agent binds the constituent particles together, and the magnesium hydroxide produced by magnesia hydration gives an appropriate viscosity. This is considered to be due to the effect of maintaining the granular form in the grain process. In the present invention, since magnesia is mixed in a ratio sufficient to granulate the water treatment agent, it is an organic compound binder for obtaining thickening and binding properties that are essential in the granulation process. Granulation can be carried out without using.

<Hardening of magnesia by hydration reaction>
When magnesium hydroxide is produced by the hydration reaction of magnesia, it exhibits hydraulic properties. The fine magnesium hydroxide produced promotes densification of the hydrated cured product by filling the gaps between the coarse particles.
MgO + H ₂ O → Mg (OH) ₂

In addition, the hardness of the granulated product is increased by carbonation of magnesium hydroxide (generation of magnesium carbonate or basic magnesium carbonate).
Mg (OH) ₂ + CO ₂ + 2H ₂ O → MgCO ₃ .3H ₂ O
[m + 1] Mg (OH) ₂ + mCO ₂ + xH ₂ O → mMgCO ₃ .Mg (OH) ₂ .nH ₂ O
(m = 3-5, n = 3-7, x = 0-2)

On the other hand, granulation is also expected to be promoted in the formation of a curable substance by a hydraulic reaction between acidic inorganic sulfate and magnesia. For example, in the case of iron sulfate mentioned as a preferable acidic inorganic sulfate, it is expected that a curable substance called magnesium oxysulfate is formed by the hydraulic reaction with magnesia and promotes granulation.

<Hardening with reaction product of magnesia and ferrous sulfate>
When lightly burned magnesia and ferrous sulfate react in the presence of water, the following compounds (magnesia and magnesium sulfate double salt (magnesium oxysulfate) and iron (II) hydroxide) are generated, Of these, magnesium oxysulfate increases the hardness of the granulated product.
[m + 1] MgO + FeSO ₄ · H ₂ O + nH ₂ O → mMgO · MgSO ₄ · nH ₂ O + Fe (OH) ₂

Finally, due to the hydraulic reaction of magnesia and the hydraulic reaction of magnesia and acidic inorganic sulfate, iron powder has a role as an aggregate (skeleton), and hydraulic reactivity generated by the reaction of other materials It is considered that the compound fills the gaps between the material particles and advances the densification, and as a result, the strength of the cured body (granulated product) is increased.

The granulation method in the granulation step required for granulating the water treatment agent of the present invention is performed when granulating iron powder, magnesia and acidic inorganic sulfate mixed at a specific blending ratio. There is no particular limitation as long as it can be granulated by adding an appropriate amount of fresh water to the extent that it is granulated. The fresh water is not particularly limited as long as the composition can be granulated. For example, industrial water, tap water, pure water, ion-exchanged water, or the like may be used.

Examples of granulation methods include mixed granulation (rolling granulation (rotary dish type, rotary cylindrical type, rotary conical type), fluidized bed granulation (fluidized bed type, fluidized spouted bed type, spouted bed type), composite Fluidized bed (centrifugal rolling type, rolling flow type, spiral flow type), stirring granulation (Pagmill type, Henschel type, Eirich type)), forced granulation (compression molding (compression roll type, briquetting roll type) , Tableting type), extrusion granulation (screw type, rotary porous die type, rotary blade type), crushing granulation (rotary knife (horizontal) type, rotary knife (ナイフ) type, rotary bar type)) and the like. . In particular, when a granulation method such as rolling granulation, forced granulation or extrusion granulation is used, iron powder particles are used as the core, and when iron powder particles are bound together by magnesia or magnesium hydroxide, rolling is performed. When subjected to dynamic motion, compressive force, or pushing force, the granular material mainly composed of iron powder having a large specific gravity is easily consolidated, and as a result, a heavy granular material with sufficient hardness is easily obtained. Therefore, it is preferable.

D. Fresh water The amount of fresh water in the granulation step varies depending on the combination of materials, the blending ratio of the materials, the particle size of the material, and the granulation method employed, and may be adjusted to an optimum amount according to the conditions. The fresh water is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 3 parts by mass or more and 45 parts by mass or less, and further preferably 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the composition. Even more preferably, it is 10 parts by mass or more and 35 parts by mass or less. Alternatively, the amount of water added to each of iron powder, magnesia, and acidic inorganic sulfate is as follows. For example, the amount of water added for granulation is (1) 5 to 15 parts by weight with respect to 100 parts by weight of iron powder. (2) 30 to 150 parts by mass with respect to 100 parts by mass of magnesia, and (3) 10 parts by mass or less with respect to 100 parts by mass of acidic inorganic sulfate. However, if the amount of fresh water is too large, the solid content per granular material becomes small and heavy granular materials cannot be obtained, so there is a risk that the hardness of the granular materials will be insufficient. If the amount is too small, it is necessary to be careful because granulation may not be achieved or sufficient hardness may not be obtained due to insufficient hydraulic properties of magnesia and insufficient amount of magnesium hydroxide.

What is necessary is just to select the hydration method of fresh water according to the granulation method. In the case of mixed granulation, it is added while spraying fresh water during granulation. At this time, if fresh water of about 15 to 40% by mass of an appropriate amount of water is added and mixed in advance before the granulation step, the efficiency of granulation can be increased. In the case of forced granulation, it is advisable to add and mix an appropriate amount of fresh water before the granulation step. In addition, if it is allowed to stand for a long time after adding fresh water, the material hardens and solidifies due to the hydraulic properties of magnesia, and granulation becomes difficult. It is preferable.

Even if the obtained particulate matter is used immediately after granulation, it does not affect the ability to adsorb and remove harmful substances, but it improves handling when it is used in a column for treating contaminated water. Therefore, it is preferable that a certain degree of hardness is obtained. In this case, if it is cured for about 2 to 3 hours after granulation, it is possible to obtain a hardness that does not easily disintegrate, and further hardness can be obtained by curing for 1 day or more after granulation. The longer the curing time, the better the hardness. There is no particular problem with the curing of granular materials at normal indoor and outdoor temperatures and humidity. However, it is necessary to increase the temperature to obtain hardness in a short time, and to increase the humidity to improve hardness. preferable. However, care should be taken when aging at high temperatures and high humidity for a long time because it may promote the iron oxidation reaction and reduce the ability to adsorb and remove harmful substances.

The particle size of the granular material can be used without any problem in the state obtained in the granulation step. However, by adjusting the particle size according to the purpose of use, harmful substances can be efficiently adsorbed and removed. Examples of the method for adjusting the particle size of the granular material include classification by sieving and adjustment by pulverization. In addition, when packed in a column for treatment of contaminated water, etc., it is possible to secure a sufficient contact area and contact time between the water treatment agent and the contaminated water by densely packing the particulate matter, and from the contaminated water to harmful substances The efficiency of adsorbing and removing can be increased. In order to densely fill the granular material, it is preferable to adjust the particle size of the granular material to a range of 0.1 to 2.0 mm, more preferably 0.2 to 1.8 mm, and still more preferably 0.00. Adjust to the range of 25-1.4mm. Furthermore, by adjusting the average particle size of the granular material to a range of 0.5 to 1.0 mm, not only can the granular material be densely packed, but also an appropriate gap (water passage) between the filled granular materials. Can reduce water flow resistance and lead to no clogging. As a result, not only the contact area and contact time between the water treatment agent and the contaminated water can be sufficiently secured, but also the granular material filled with the contaminated water can pass through all the parts. It can be used efficiently.

In order to further improve the handleability of the granular environmental water treatment agent of the present invention when used in a contaminated water treatment column or the like, it is impregnated with water or by receiving external force. It is preferable to maintain the shape of the granular material for a long time without easily disintegrating. For that purpose, the hardness of the granular material is preferably 85% or more, more preferably 90% or more, still more preferably 95% or more, as measured by JIS K 1474-2007 (activated carbon test method, hardness). It is. Further, when packed in a contaminated water treatment column or the like and used in a large amount of contaminated water for a long period, the hardness is preferably 95% or more.

The granular environmental water treatment agent of the present invention is suitably used for the treatment of contaminated water containing hazardous substances (for example, heavy metals such as lead, chromium, arsenic, selenium, cadmium).

-Method for treating water contaminated with harmful substances The method for treating water contaminated with harmful substances of the present invention is characterized in that contaminated water containing harmful substances is brought into contact with the water treatment agent of the present invention. As a result, the harmful substances can be adsorbed and removed from the contaminated water, and the concentration of the harmful substances can be reduced more than before the treatment. The method for bringing the contaminated water into contact with the water treatment agent is not particularly limited. For example, the water treatment agent is filled in a suitable container and the contaminated water is allowed to pass through the container, and the water treatment agent is contaminated. After adding to water, the method of adsorbing harmful substances by stirring and dispersing can be used.

The concentration of harmful substances contained in contaminated water is not particularly limited, but the lower the concentration of harmful substances, the easier it is to adsorb and remove harmful substances to an environmental standard value or lower. When the concentration of the harmful substance is high, it is possible to adsorb and remove the harmful substance to the environmental standard value or less by repeatedly performing the treatment with the water treatment agent of the present invention many times. In addition, the type or total amount of harmful substances contained in the contaminated water affects the adsorption / removal capacity and adsorption / removal efficiency. Select the composition of the water treatment agent and the contact method with the contaminated water. Thus, the efficiency of adsorption removal can be improved.

Contaminated water is not particularly limited as long as it contains harmful substances, and examples thereof include groundwater, river water, lake water, and various industrial wastewater.

Also, the contaminated water may be contained in at least one selected from soil containing toxic substances, sludge, coal ash, incinerated ash, dust, and industrial waste. For example, if it is contained in at least one selected from soil, sludge, coal ash, incinerated ash, dust, and industrial waste that originally contained hazardous substances, it will be converted into hazardous substances at the stage of leaching or passing through them. By contacting the contaminated water with the water treatment agent of the present invention, harmful substances can be adsorbed and removed from the contaminated water, and the concentration of harmful substances can be reduced compared to before treatment. It is possible to prevent diffusion.

Examples of harmful substances include arsenic, selenium, lead, cadmium and chromium.
In the method of the present invention, in the contact method between the contaminated water and the water treatment agent, a packed bed filled with the water treatment agent of the present invention may be provided, and the contaminated water containing harmful substances may be passed through the packed bed and contacted. Good. Such a method is preferable because the contact time between the water treatment agent and the contaminated water can be sufficiently secured, and the efficiency of adsorbing and removing harmful substances from the contaminated water is increased. The water treatment agent packed layer is not particularly limited as long as the granular material can be densely packed and the contact area and contact time between the water treatment agent and the contaminated water can be sufficiently ensured. Examples include a column in which a contaminated water treatment column is filled with a water treatment agent, or a water treatment agent spread and leveled and stacked to give a sufficient thickness. The column for the contaminated water treatment is selected to have an appropriate size according to the target treatment amount of the contaminated water and the treatment time. Further, for the packed bed spread with a water treatment agent, the layer thickness is adjusted according to the amount of contaminated water passing through the packed bed, the concentration and type of harmful substances.

In the method of the present invention, one or a plurality of packed beds may be used. When a plurality of packed beds are used, the particle size of the water treatment agent may be changed according to the degree of contamination of the contaminated water. The contaminated water may be adsorbed and removed by supplying the packed bed or the treatment apparatus including the packed bed twice or more.

Water that has been leached from or passed through one or more selected from soil, sludge, coal ash, incineration ash, dust, and industrial waste containing harmful substances, after collecting the contaminated water In addition, toxic substances can be adsorbed and removed by contact with a water treatment agent, but when these are disposed of in landfills, contaminated water is continuously generated each time rainwater passes through. The packed bed of the water treatment agent of the present invention may be disposed in the downward direction or the lateral direction of the landfill site so that it can be continuously treated.

An example of a method for treating contaminated water containing harmful substances of the present invention is shown in FIG. In the loss head measuring device 1 of FIG. 1, it is preferable that the contaminated water containing harmful substances is supplied to the tank 2 and stored. Next, the contaminated water containing harmful substances is preferably sent from the tank 2 to the packed tower 5 containing the water treatment agent 4 via the metering pump 3. At this time, it is preferable to monitor the pressure of the water before sending the contaminated water to the packed tower and the pressure of the water after the harmful substances are adsorbed and removed from the packed tower by the differential pressure gauge 6. For example, it is possible to monitor whether or not the water flow resistance of the water treatment agent in the packed tower is increased by a differential pressure gauge. When the pressure difference of the differential pressure gauge is high, the contaminated water may be further diluted or the water treatment agent may be replaced.

This application claims the benefit of priority based on Japanese Patent Application No. 2013-045960 filed on March 7, 2013. The entire contents of Japanese Patent Application No. 2013-045960 filed on March 7, 2013 are incorporated herein by reference.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and appropriate modifications are made within a range that can meet the above and the following purposes. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

<Raw material for granular type environmental water treatment agent>
・ Iron powder: average particle size 65μm
Maximum particle size measurement method: Dry sieving test using a sieve (sieving) specified in JIS Z 8801. Light burned magnesia: obtained by calcining seawater-derived magnesium hydroxide at about 500 ° C and adjusting the particle size Lightly burned magnesia powder: MgO content 89.0% by mass
Maximum particle size of magnesia: 0.045mm
Measuring method of maximum particle size: Wet sieving test using sieve (screen) specified in JIS Z 8801 Average particle size of magnesia: 3.4 μm
Average particle size measurement method: Particle size equivalent to 50% cumulative volume reference particle size measured by a laser diffraction / scattering particle size distribution analyzer LA-920 manufactured by HORIBA, Ltd. (using isopropanol as a dispersion medium)
・ Ferrous sulfate monohydrate: FeSO ₄ content 92.9% by mass
Maximum particle size of ferrous sulfate monohydrate: 1.00mm
Measuring method of maximum particle size: Dry sieving test using sieve (sieving) specified in JIS Z 8801 Average particle size of ferrous sulfate monohydrate: 26 μm
Measurement method of average particle size: Dry sieving test using sieve (screen) specified in JIS Z 8801 ・ Granular activated carbon: Kuraray Co., Ltd. Kuraray Coal KW10X32 (applied as a comparative reference material for hardness and water resistance test) )

<Preparation Method of Granular Environmental Water Treatment Agent>
The raw material species shown in Table 1 and the blending amount of each raw material species were weighed, and a predetermined amount of fresh water was added while spraying while mixing and stirring with a small soil mixer (rotation speed 140 rpm).
The obtained mixture was extruded using an extrusion granulator having a discharge port having a diameter of 1.5 mm, and left in the atmosphere for 24 hours. The rod-shaped solid material obtained by this operation was pulverized, and particles larger than 1.4 mm and particles smaller than 0.25 mm were removed by sieving, classified and adjusted in particle size to obtain a granular type environmental treatment water treatment agent.

About the obtained water treatment agent, intensity | strength (hardness) was measured with the following method.
<Measurement of strength (hardness) of water treatment agent>
The strength of the water treatment agent was measured according to JIS K 1474-2007. First, 100 mL of the sieved sample (water treatment agent) was collected. Along with 15 steel balls each having a diameter of 12.7 mm and 9.5 mm, the sample collected was placed in a hardness test dish, attached to a sieve shaker, and shaken for 30 minutes. Next, all the samples excluding the steel balls were put on a sieve whose mesh size was two steps lower than the lower limit particle size at the time of sieving. Each sample was weighed by shaking for 3 minutes on a sieve shaker. The mass ratio (mass% with respect to the whole) of the sample remaining on the sieve was measured and used as an index of strength (hardness) (the larger the value, the higher the strength). The obtained results are shown in Table 2.

About the obtained water treatment agent, the water flow resistance was measured by the following method.
<Measurement of water resistance with a loss head measuring device>
A column made of quartz glass having a length of φ25 mm × 1200 mm was filled with a water treatment agent at a height of 1000 mm, and the upper part of the column and each tube were connected to each other while injecting water into the column so as not to chew air. Using a liquid feed pump, water was passed through the downward flow at a predetermined LV (linear velocity), and the differential pressure was measured when the differential pressure became stable (the differential pressure gauge made by Kiso Keiki Seisakusho was used with a maximum of 20 kPa). . The differential pressure was measured after the water flow rate was LV = 30 m / hr and the differential pressure was stabilized. The obtained results are shown in Table 2, and an outline of the loss head measuring device is shown in FIG.

In Comparative Example 1, only three kinds of raw material powders were mixed and stirred with a small soil mixer (rotation speed: 140 rpm).

The results of Examples 1 and 2 satisfying the hardness values were obtained, and good values were obtained even when compared with the granular activated carbon used as the reference material. On the other hand, also in the water flow resistance, two of the examples resulted in the same value as the granular activated carbon. In Comparative Example 1 in which granulation is not performed, it can be seen that the water flow resistance exceeds the limit of the differential pressure gauge (20 kPa), and there is a high possibility of causing a failure in water flow.

<Hazardous substance removal performance test of granulated products>
In order to judge the adsorption removal performance of harmful substances, tests using adsorption performance using heavy metal species of arsenic, selenium, lead, cadmium and chromium were conducted. Potassium arsenate (KH ₂ AsO ₄ ) as a model solution for arsenic-containing wastewater, sodium selenate (Na ₂ SeO ₄ ) as a model solution for selenium-containing wastewater, and lead (II) nitrate (Pb) as a model solution for lead-containing wastewater (NO ₃ ) ₂ ), cadmium chloride hemihydrate (CdCl ₂ · 2.5H ₂ O) as a cadmium-containing wastewater model solution, and potassium dichromate (K ₂ Cr) as a chrome-containing wastewater model solution A solution in which ₂ O ₇ ) was dissolved in water was used. As raw water concentrations of the five heavy metal species, water to be treated was prepared that was 10 times the environmental standard value (that is, 0.1 mg / L for arsenic, selenium, lead, and cadmium; 0.5 mg / L for chromium). 250 ml of each water to be treated is put in a 500 ml plastic container, and each water treatment agent prepared in the example is added to 2.5 g (solid / liquid ratio 1: 100), and shaken at room temperature for 24 hours. It was. Next, shaking was stopped, and the water treatment agent and the supernatant were separated by filtration through a membrane filter having an opening of 0.45 μm, and the residual heavy metal concentration in the supernatant was measured as follows.
Arsenic is JIS K0102 61.3, selenium is hydride generation ICP emission spectrometry according to JIS K0102 67.3, lead is ICP mass spectrometry according to JIS K0102 54.4, cadmium is according to JIS K0102 55.4. ICP mass spectrometry, chromium was measured by ICP mass spectrometry according to JIS K0102 65.1.5. The results are shown in Table 3.

Examples 1 and 2 all showed good heavy metal removal performance. Specifically, in the water treatment agent of Example 1, the concentrations of arsenic, selenium, lead, cadmium, and chromium are about 1/100 times or more, about 1/8 times, about 1/20 times, and about 1/20 times, respectively. It shows that the concentration can be reduced to 4 times or about 1/5 times. In the water treatment agent of Example 2, the concentrations of arsenic, selenium, lead, cadmium, and chromium were about 1/100 times or more, about 1/4 times, about 1/3 times, about 1/4 times, and about 1 respectively. This indicates that the concentration can be reduced to /2.5 times. From the above, with respect to selenium, lead, and chromium, it can be seen that the water treatment agent of Example 1 has higher removal ability than that of Example 2.

The granular type environmental water treatment agent of the present invention is a low-priced industrial product that contains magnesia and acidic inorganic sulfate at a predetermined ratio in iron powder that can be manufactured by the atomizing method, and is added with fresh water to the composition. Granulates by granulation. Such a water treatment agent can easily adsorb and remove harmful substances from water contaminated with harmful substances that are harmful to human body and cause health problems, and can maintain the adsorption removal ability for a long time. In addition, since no organic compound binder is used, there is no concern about environmental pollution due to the organic compound, and it can be manufactured at low cost. On the other hand, in removing heavy metals in the cartridge type water purification method, the water resistance required to increase the purification efficiency can be reduced, and the industrial utility value is high.

1: Loss head measuring device 2: Tank 3: Metering pump 4: Water treatment agent 5: Packing tower 6: Differential pressure gauge

Claims

A water treatment agent for removing toxic substances, characterized by adding granulated form by adding fresh water to a composition containing iron powder, magnesia, and acidic inorganic sulfate Water treatment agent.
The granular environmental water treatment agent according to claim 1, further comprising one or more of the following (a) to (d):
(A) The composition contains 10 to 50 parts by mass of magnesia and 5 to 50 parts by mass of acidic inorganic sulfate with respect to 100 parts by mass of iron powder.
(B) The fresh water is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the composition;
(C) The magnesia is obtained by pulverizing light-burned magnesia containing 60% by mass or more of magnesium oxide, and is in a powder form having a maximum particle size of 2.0 mm or less.
(D) The acidic inorganic sulfate is at least one selected from iron (II) salt, iron (III) salt, and aluminum salt, and has a maximum particle size of 2.0 mm or less.
The hardness of a granular product obtained by adding fresh water to the composition and granulating it is 80% or more as measured by JIS K 1474-2007. The granular type environmental water treatment agent according to 1.
3. The composition according to claim 1 or 2, wherein the composition is granulated by adding fresh water and then adjusted to a particle size in a range of 0.1 to 2.0 mm to form a granular material. The particulate environmental water treatment agent as described.
A method for treating water contaminated with harmful substances, comprising contacting contaminated water containing harmful substances with the particulate environmental water treatment agent according to claim 1 or 2.
The harmful substance according to claim 5, wherein the contaminated water is contained in at least one selected from soil containing harmful substances, sludge, coal ash, incinerated ash, dust, and industrial waste. How to treat contaminated water.
The method for treating water contaminated with harmful substances according to claim 5, wherein contaminated water containing harmful substances is passed through and contacted with the packed bed filled with the particulate environmental water treatment agent.