JPH0474080B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for treating muddy water. [Prior Art] When carrying out dredging work for ports, rivers, lakes, etc., a large amount of dredged wastewater mixed with earth and sand and sludge is obtained.
This kind of dredged mud water is put into a landfill or a sedimentation pond built on land, the surplus water is separated from the sediment, the sediment is dehydrated and solidified, and the surplus water is returned to the port or river etc. Processed by. However, in the conventional case, the processing cost was high and the results were not yet satisfactory. In other words, since the amount of dredged mud water generated during dredging work etc. is enormous,
In order to carry out the processing economically, it is strongly required that the processing efficiency is high so that the processing can be completed in a short time, and that the cost required for the processing is low. Natural sedimentation treatment of dredged mud water required an extremely long time to achieve its purpose. On the other hand, if a polymer flocculant or the like having a high flocculation effect is added to the dredged mud for the purpose of shortening the required time, the problem arises that the treatment cost of the dredged mud increases because the flocculant is expensive. Furthermore, even if the colloids in the dredged mud are coagulated and flocculated to smoothly separate the insoluble solid sediment from the surplus water, the resulting sediment still contains a large amount of water. Since natural drying is difficult, special treatments must be applied to remove moisture and increase strength of the sediment. [Purpose] As a result of extensive research into the economical treatment of dredged muddy water generated during the aforementioned dredging work, etc., and muddy water pumped up from aquaculture mud from fish farms, the inventors have found that:
The present invention has now been completed. [Configuration] That is, according to the present invention, (1) muddy water has particle size
Provided is a muddy water treatment method characterized by adding sulfuric acid modified blast furnace slag of 300 μm or less to smoothly settle insoluble solids in the mud in the presence of sodium chloride, and (2) sulfuric acid with a particle size of 300 μm or less In the presence of sodium chloride, (a) the metamorphosed blast furnace slag is treated as a slurry coagulation/flocculant, and then (b) further
The sedimentation concentrate obtained by removing and separating the surplus water used in the treatment of (a) is reacted with Portland cement in the presence of sulfuric acid modified blast furnace slag or sulfuric acid modified blast furnace slag and gypsum, and the sedimentation A method of treating muddy water is provided, which is characterized by increasing the strength of a concentrate. The muddy water referred to in the present invention contains suspended insoluble solids, and may also contain non-suspended earth and sand. Examples of such muddy water include dredged muddy water generated during dredging work for ports, rivers, lakes, etc., muddy water generated from various construction works such as tunnel construction and excavation work, and muddy water from aquaculture sludge pumped up from aquaculture farms. It will be done. The muds that are the object of the present invention contain at least 5% by weight of insoluble solids, usually from 7 to 12% by weight. In the present invention, when treating muddy water containing seawater, such as dredged muddy water generated from dredging work in a harbor, the insoluble solid content is obtained by removing salts dissolved in this muddy water. In other words, when measuring the water content ratio based on the method of JIS1203-1978, the water content is calculated and used as the water content ratio, but in the present invention, when dealing with dredged mud water obtained from port construction, the water content is converted to the seawater volume. and the rest was defined as insoluble solid content. The sulfuric acid modified blast furnace slag in the present invention is obtained by reacting fine quenched slag with sulfuric acid. In this case, fine quenched blast furnace slag is obtained by rapidly cooling blast furnace slag (slag), which is a by-product of iron-making blast furnaces, and then further increases the particle size.
It is ground to 300μm or less. Methods for rapidly cooling blast furnace slag include a wet method in which it is granulated and rapidly cooled with water, a semi-dry method that uses a small amount of water and air, and a dry method that uses air cooling. Generally, the raw material is what is called blast furnace slag produced by a wet method. This is made by rapidly cooling slag, a by-product of iron-making blast furnaces, with water, and
It is water slag crushed into sand or granules about 5 mm in size. This composition varies slightly depending on the components of the iron ore and the operating conditions of the blast furnace, but it is approximately as follows. _SiO2 30~35%, _Al2O3 13~18%, CaO38 _~ 45
%, _{Fe2O3 0.5} ~1.0%, MgO3~6%, S0.5~1.0
%, MO 0.5-1.5%, TiO ₂ 0.5-1.0% The finely quenched blast furnace slag used in the present invention has latent hydraulic properties that can exhibit hydraulic properties when stimulated by alkali or the like. This latent hydraulic property rapidly cools the blast furnace slag and avoids its crystallization.
It can be obtained by making it amorphous (glass-like) that stores crystallization energy internally. The crystalline material obtained by slowly cooling blast furnace slag is a dense crystalline material whose main constituent minerals are melilite (Gehlenite Ca ₂ Al ₂ SiO ₇ / Okermanite Ca ₂ MgSiO ₇ solid solution) and calcium orthosilicate. No latent hydraulic properties. For this reason, even if the slow-cooled slag is pulverized, it cannot function and be effective as a reactant. Therefore, it is inappropriate to use the slow-cooled slag as a raw material for the sulfuric acid-converted blast furnace slag of the present invention. Moreover, in order to utilize this rapidly cooled blast furnace slag as a reaction material, it is necessary to use it in as fine a state as possible. Coarse blast furnace water slag with a normal particle size of 1 to 5 mm is unsuitable because the reaction with sulfuric acid during sulfuric acid modification and the reactivity with fine soil particles and Portland cement of sulfuric acid modified blast furnace slag is significantly reduced.
The reason is that the specific surface area of coarse-grained blast furnace water slag is small. In the case of the present invention, the particle size of the quenched blast furnace slag is
Must be 300μm or less, usually 100μm or less
~1μm finely quenched blast furnace slag is used. Preferred industrial sulfuric acid treatment methods for fine blast furnace slag applied in the present invention are roughly divided into the following two types. (1) A method in which sulfuric acid is applied directly to finely quenched blast furnace slag. (2) In flue gas desulfurization treatment, a method in which sulfuric acid obtained by absorbing and oxidizing SOx in flue gas is applied to finely quenched blast furnace slag. The sulfuric acid used in method (1) may be commercially available sulfuric acid, but from the viewpoint of economy and ecology, it is preferable to use waste sulfuric acid discharged from various chemical factories. This sulfuric acid treatment can be carried out in various ways. For example, there are methods such as (a) spraying and adhering a dilute sulfuric acid aqueous solution to the blast furnace slag, and (b) immersing the blast furnace slag in a dilute sulfuric acid aqueous solution. In this case, the amount of sulfuric acid used in the reaction is sulfuric acid (100% by weight) per 100 parts by weight of blast furnace slag.
0.5 to 50 parts by weight (calculated as sulfuric acid) is used. The preferred degree of sulfuric acid modification differs depending on the constituent material of the treatment agent for increasing the strength of the sedimented muddy concentrate. In the present invention, (a) when using sulfuric acid modified blast furnace slag and Portland cement as the treatment agent, blast furnace slag
(b) When using sulfuric acid modified blast furnace slag modified using 3 to 50 parts by weight of sulfuric acid per 100 parts by weight, and (b) also using sulfuric acid modified blast furnace slag, gypsum and Portland cement as treatment agents, sulfuric acid modified blast furnace slag is , blast furnace slag
A product treated with 0.5 to 7 parts by weight of sulfuric acid per 100 parts by weight is used. In other words, the degree of sulfuric acid modification of blast furnace slag is 5±2 per 100 parts by weight of blast furnace slag.
Based on the weight, the composition of the treatment agent is divided into two of the above (a) and (b).
Select by type. When sulfuric acid is brought into contact with blast furnace slag, the silica and alumina components are activated, and most of the sulfuric acid eventually becomes dihydrate. In this case, a part of the alkaline component of the blast furnace slag reacts with sulfuric acid and dissolves, but since the solubility of calcium sulfate is lower than other sulfates, most of the sulfate eventually becomes dihydrate crystals. It remains in the sulfuric acid converted blast furnace slag. Therefore, when preparing sulfuric acid modified blast furnace slag using the dipping method in (b),
It is preferred to repeatedly use the mother liquor from which the product has been separated as a dilute solution of sulfuric acid. By using this mother liquor, it is possible to suppress the consumption due to the elution of MgO and Al ₂ O from the blast furnace slag, and also prevent _the dissolution and loss of dihydrate produced during processing (dihydrate at room temperature). The amount of dissolution is approximately as CaSO ₄
0.2% by weight). Further, as specific methods for carrying out the method (2) above, the following two examples (a) and (b) are given. (a) A method in which dilute sulfuric acid obtained in the flue gas desulfurization process is added to blast furnace slag and reacted. (b) Blast furnace slag is dispersed in water, and while the dispersion liquid is continuously brought into contact with SOx-containing flue gas, the blast furnace slag is added externally so as to maintain the pH of the dispersion liquid in the range of 1.5 to 4. and how to recover metamorphosed blast furnace slag. In either method (a) or (b), the amount of sulfuric acid reacted with the blast furnace slag is adjusted within a predetermined range, as in the case of (a) above. Next, we will discuss Portland cement, which is one of the materials used to increase the strength of sedimented muddy concentrate. Portland cement conforms to the Japanese Industrial Standard JIS R5210, and one of these that corresponds to ordinary Portland cement is generally used. However, depending on the processing conditions, Portland cement that conforms to standards such as medium-early-strength Portland cement, early-early-strength Portland cement, and ultra-early-strength Portland cement may be used alone, or a mixture of these and a hardening accelerator such as calcium chloride may be used. may also be used. In addition, blast furnace slag
When sulfuric acid modified blast furnace slag treated with 0.5 to 7 parts by weight of sulfuric acid per 100 parts by weight is used as one material for the treatment agent, gypsum is used as one part of the treatment agent. Suite stone or insoluble anhydrite stone (including type anhydrite stone and anhydrite stone) is used. However, in some cases, hemihydrate stone or soluble anhydrite stone may be used in place of a part of these stone stones. In the case of dihydrite, the particle size is not particularly limited, as long as it is powder or granules. In the present invention, natural stone and various chemical stones produced as by-products from various processes can be used. Flue gas desulfurization stone can be used in the form in which it was recovered, without the need for secondary treatment processes such as washing with water or drying, by recovering the stone from the final process, such as centrifugation. I can do it. In addition, when using insoluble anhydrite, the particle size should be adjusted due to its dissolution rate.
The powder must be 300μm or less. In the present invention, insoluble anhydrite (fluorite), which is produced as a by-product when hydrogen fluoride is produced by thermally decomposing fluorite with concentrated sulfuric acid, can be directly used. This is because fluorite is produced as a dry powder with a particle size of less than 300 μm. In addition,
The weight of the stone in the present invention is anhydrous stone CaSO ₄
The value is . Next, the sedimentation and concentration of insoluble solids in muddy water will be specifically explained. In the present invention, first, sulfuric acid modified blast furnace slag with a particle size of 300 μm or less is added to muddy water. There are various methods for adding this sulfuric acid modified blast furnace slag. For example, (1) when pumping muddy water from an area to a sedimentation pond and transporting it inside a pipe, sulfuric acid-converted blast furnace slag is sent in the form of a slurry into the transportation pipe; A method such as adding the slag to muddy water in the form of a slurry or powder can be carried out. Further, the optimum usage amount of the sulfuric acid-converted blast furnace slag in the present invention varies depending on the following conditions (1) to (4). (1) The purpose of processing muddy water, that is, (a) whether the purpose is only to settle and concentrate the insoluble solids in muddy water, or (b) if the strength of the settled concentrate is to be increased, the required strength setting value is How much? (2) How should the treatment agent be added in muddy water treatment? For example, when adding sulfuric acid-converted blast furnace slag, (a) should it be added in one step only during the sedimentation and concentration process of muddy water? (b)
Should it be added in two stages: the sedimentation and concentration process of the muddy water and the strength increasing process of the sedimentation concentrate? (3) What is the amount of sulfuric acid added to the raw material blast furnace slag when producing sulfuric acid-modified blast furnace slag? (4) What is the type and quality of mud water and its condition, that is, the ratio of organic matter in insoluble solids to soil particles, the quality and size distribution of soil particles, and the PH value of mud water and the state of impurities? . When the sole purpose is sedimentation and concentration of insoluble solids in muddy water, the amount of sulfuric acid modified blast furnace slag added to muddy water is generally in the range of 2 to 7 kg per 1 M ³ of muddy water. However, the optimal amount of sulfuric acid-converted blast furnace slag to be added to muddy water is
Its value depends on the degree of sulfuric acid modification during the production of sulfuric acid modified blast furnace slag. The larger the amount of sulfuric acid added during the production of sulfuric acid modified blast furnace slag, the smaller the amount of sulfuric acid modified blast furnace slag used, and conversely, the smaller the amount of sulfuric acid added, the larger the amount of sulfuric acid modified blast furnace slag added to muddy water. When the insoluble solid content of muddy water is sedimented and concentrated and the strength of the sedimented concentrate is further increased, in the present invention, the method for adding sulfuric acid-converted blast furnace slag may be carried out using either of the following methods (1) and (2). is preferred. (1) The sulfuric acid modified blast furnace slag is subjected to the "sedimentation and concentration process of muddy water"
(hereinafter referred to as the sedimentation concentration step). (2) A method in which sulfuric acid-converted blast furnace slag is added in two steps: a sedimentation concentration process and a ``strength increase process of sedimentation concentrate'' (hereinafter referred to as the strength increase process). The methods of adding (1) and (2) to this sulfuric acid-converted blast furnace slag are determined as appropriate depending on the type and quality of the slurry and its condition. For example, if the insoluble solid content contains a large amount of organic matter, method (1) above is mainly applied, whereas if the insoluble solid content is low and the insoluble solid content contains many soil particles. For those, method (2) above is mainly adopted. The muddy water to which sulfuric acid modified blast furnace slag has been added and mixed is left as it is to allow suspended insoluble solids to settle out. In the case of the present invention, by adding the sulfuric acid-modified blast furnace slag, (a) the settling of the insoluble solids is significantly accelerated due to the coagulation and flocculation effect on the colloid content in the insoluble solids, and the insoluble solids are dissolved in an extremely short time. Precipitates with a content of 13 to 25% by weight can be separated, and (b) organic substances such as humic acid and reaction inhibitors such as phosphates, which adversely affect the hydration reaction of Portland cement in the next strength increasing process, can be separated. It is possible to suppress the harmful effects of At this time, if sodium chloride (concentration in residual water is 0.01 to 4% by weight) is present, the effect of separating the sediment will be further improved, and the time required to achieve the objective in the strength increasing step can be shortened. As mentioned earlier, the amount of sulfuric acid modified blast furnace slag added to muddy water may be relatively small for the sole purpose of settling insoluble solids suspended in muddy water; In order to increase the strength of the concentrate, it is necessary to specify the total amount of sulfuric acid blast furnace slag that is sufficient to serve as a reactive material in the strength enhancement process. The sulfuric acid modified blast furnace slag acts as a coagulating and flocculant agent for suspended insoluble solids in the sedimentation concentration process, and in the strength increasing process, it contributes to the strength increasing reaction as a reaction material together with Portland cement. Therefore, in consideration of the role of the sulfuric acid modified blast furnace slag as a reaction material for increasing the strength, the amount of the sulfuric acid modified blast furnace slag to be added is determined depending on the required strength of the sedimentation concentrate. The required strength of the sediment concentrate is determined depending on its purpose, but the generally required strength is often in the range of 0.5 to 4 Kgf/m ³ in unconfined compressive strength, usually 0.5 to 2 Kgf/m ³ . The amount of treatment agent required for this strength-increasing effect varies depending on requirements such as (a) the type and PH value of the muddy water, (b) the content and quality of insoluble solids, and (c) the required strength of the sedimented concentrate. . But generally, the total usage of processing agent is 50-180Kg per ^1M3 of sedimentation concentrate,
Preferably it is 70-150Kg. As the treatment agent, in the case of the present invention, the following two additives [] and [] are appropriately selected and used depending on the degree of sulfuric acid modification of the sulfuric acid modified blast furnace slag, as described above. Treatment agent []: Sulfuric acid modified blast furnace slag (3 to 50 sulfuric acid per 100 parts by weight of blast furnace slag with a particle size of 300 μm or less)
(A) and Portland cement (B). In this case, the weight ratio of sulfuric acid modified blast furnace slag and Portland cement A/B = 70/30 to 35/65 Treatment agent []: Sulfuric acid modified blast furnace slag (sulfuric acid 0.5 to 100 parts by weight of rapidly cooled blast furnace slag with a particle size of 300 μm or less) 7
Metamorphosed using weight part A ₁ , stone smelt A ₂
and Portland cement (B). In this case, the weight ratio of Portland cement to sulfuric acid modified blast furnace slag and gypsum (A ₁ + A ₂ )/B
=70/30~45/55. The relationship between the material amount ratios of these processing agents [ ] and [ ] was determined through many experiments.
In addition, the sulfuric acid modified blast furnace slag used for each of the above treatment agents is
As described above, it is added in the first stage of the muddy settling process, or in the second stage of the muddy settling process and the settling and concentration process. Therefore, the specific method of adding the processing agent material to the sediment concentrate is (a)
There are methods of adding Portland cement, (b) Portland cement and gypsum, (c) Portland cement and sulfuric acid modified blast furnace slag, or (d) Portland cement and sulfuric acid modified blast furnace slag and gypsum. An appropriate method is selected depending on the degree of sulfuric acid modification of the blast furnace slag and whether the sulfuric acid modified blast furnace slag is added in one stage or two stages. In any case,
The sediment concentrate is strengthened by reacting with Portland cement in the presence of sulfuric acid modified blast furnace slag or sulfuric acid modified blast furnace slag and gypsum in a strength increasing step. In method (1), in which sulfuric acid-converted blast furnace slag is added in the first stage of the mud sedimentation process, approximately the following addition amounts are generally used to achieve the purpose. In the case of additive [], sulfuric acid modified blast furnace slag is added at a ratio of 8 to 65 kg, preferably 12 to 50 kg, per 1 M ³ of mud water. In the case of additive [], any method of using gypsum with sulfuric acid modified blast furnace slag (a) independently, (b) or as a mixture may be used; in case of (a), addition of sulfuric acid modified blast furnace slag The amount is about 6.5-50Kg, preferably about 10-40Kg per ^1M3 of muddy water.
Furthermore, in case (b), when treating the sulfuric acid modified blast furnace slag (A ₁ ) and gypsum (A ₂ ) as a mixture with a ratio A ₁ /A ₂ of 95/5 to 60/40, the slurry of the mixture is 1M ³
Addition amount is 11-65Kg, preferably 15-55Kg
That's about it. In method (2), in which the sulfuric acid modified blast furnace slag is added in two parts: the sedimentation concentration step and the strength increasing step, a predetermined amount of the sulfuric acid modified blast furnace slag is added in two parts as appropriate. When using the treatment agent [], gypsum can be used (a) independently, (b) or in a mixture with the sulfuric acid-converted blast furnace slag, as described above. The usual usage amount of treatment agent is, as mentioned before, 50-180 Kg, preferably 70-150 Kg per 1M ³ of sedimentation concentrate. Through the above sedimentation concentration step, the insoluble solid content settles and is separated into leftover water forming an upper layer and sediment forming a lower layer. In this case, the volume of the sediment layer decreases with the passage of time, and
The concentration of insoluble solids in the sediment increases.
In the present invention, the concentration of insoluble solids in the sediment is preferably defined to be at least 13% by weight, preferably in the range of 15 to 25% by weight. If the concentration of insoluble solids in the sediment is less than 13% by weight, the amount of residual water to be separated is small, so the amount of sediment concentrate to be subjected to strength treatment increases, which is not practical. On the other hand, if the concentration of insoluble solids in the sediment is made too high, it becomes necessary to spend a correspondingly long time on the sedimentation treatment. Therefore, the concentration of insoluble solids in the sediment is preferably set to 25% by weight or less. Next, the sediment and residual water obtained in the sedimentation and concentration step are separated from each other, and a processing agent material such as Portland cement is added and mixed with the obtained sedimentation and concentration. In this case, separation of residual water and sediment can be carried out in various ways. For example, in addition to separating and removing surplus water from a settling tank, there are also methods of separating and transferring sediment concentrate from a settling tank to another storage tank or treatment tank, and methods to transfer muddy water to be treated to a settling tank or sedimentation tank. While continuously supplying the water to the pond, it is allowed to stay there for a predetermined period of time, and the separated surplus water and sediment are separated and continuously extracted.
There are methods such as sending the sediment concentrate to another reservoir or storage tank. The addition and mixing of processing agent materials such as Portland cement to the sediment concentrate separates and separates the surplus water.
It can be carried out in a sedimentation pond after removal, or it can be carried out in a storage pond or treatment tank separate from the sedimentation basin. In the strength increasing step, the hydration reaction of Portland cement is triggered, and a reaction occurs between each material in the treatment agent and the soil particles, thereby achieving an increase in strength (solidification) of the sedimented concentrate. This strength-increasing reaction includes a cation exchange reaction of fine soil particles, ettringite (3CaO・Al ₂ O ₃・3CaSO ₄・28～
32H ₂ O) production reaction, a pozzolanic reaction that produces a travelmorite mineral-like phase (3CaO, 2SiO ₂ , 3H ₂ O), etc., and a reaction that produces an amorphous gelled substance through various reactions. In the case of the present invention, the sedimentation concentrate is such that (a) the sulfuric acid-modified blast furnace slag is uniformly dispersed therein, (b) the fine soil particles and organic substances in the sedimentation concentrate are cation-exchanged, and ( c) Organic substances such as humic acid and reaction inhibitors such as phosphates, which adversely affect the hydration reaction of Portland cement, are masked. Therefore, when Portland cement is added to the sedimentation concentrate, the hydration reaction of Portland cement is carried out smoothly, and the various strength-increasing reactions induced by this reaction are carried out extremely efficiently. can. Therefore, the present invention
The coagulation and flocculation effect of the sulfuric acid-converted blast furnace slag in the sedimentation and concentration process, together with the effect of concentrating the muddy water, can significantly increase the overall treatment efficiency. The addition method and amount of each material constituting the processing agent are as described above. [Effects] The present invention has the above-mentioned configuration, and can efficiently treat muddy water, which conventionally has been difficult to practically dehydrate and increase strength (solidification). Since the processing agent used in the present invention is inexpensive, there is an advantage that the processing cost is also low, and its industrial significance is great. [Example] Next, the present invention will be explained in more detail with reference to Examples. In the Examples described later, commercially available fine blast furnace water slag treated with sulfuric acid was used as the sulfuric acid modified blast furnace slag. The characteristics of commercially available finely quenched blast furnace slag are: specific surface area of 3800 cm ² /g (i.e., average particle size of about 7 μm) by Blaine method, composition weight ratio: SiO ₂ 34
%, _{Al2O3 15} %, CaO43%, MgO5%, _{Fe2O3 0.7}
%, S 0.9%, MnO 6%, and TiO ₂ 0.8%, and when observed with a polarizing microscope, it was mostly glassy. The sulfuric acid modified blast furnace slag was prepared by adding and mixing a predetermined amount of sulfuric acid to 1 M ³ of dilute sulfuric acid diluted with water (mother liquor) at a ratio of 1 ton of fine blast furnace water slag. The water (mother liquor) used to dilute the sulfuric acid was obtained by adding make-up water to the mother liquor obtained by filtering and collecting it during the preparation of sulfuric acid modified blast furnace slag and used repeatedly. A commercially available Portland cement (specific surface area 33000 cm ² /g measured by Blaine method) was used. In addition, when using gypsum as a material for the treatment agent, the dehydrated gypsum produced as a by-product in the flue gas desulfurization process is used as the dihydrate gypsum, and the insoluble anhydrous gypsum is used as the insoluble anhydrous gypsum.
A commercially available product of hydrofluoric acid stone, which is a by-product during the production of hydrofluoric acid, was used. The average particle size of the removed stone is 53 μm.
Moisture content: 9% by weight, weight composition: CaO31.2%,
SO ₃ is 44.1%, and the commercial product of fluorite stone is
CaO4 1.5%, _SO3 56.6%, _CaF2 1.54%, _SiO2 0.10
It is a dry product with a weight composition of 0.76% Al ₂ O ₃ and an average particle size of 10 μm. Further, as the muddy water, dredged mud obtained from dredging work on the seabed was used. Its properties were as shown in Table 1. The seawater content ratio conversion value in Table 1 is the value shown by (weight of seawater content ÷ weight of insoluble solids) x 100.

[Table] (Sedimentation and concentration of muddy water) Example 1 200ml of muddy water was mixed with 250ml of muddy water that complies with JIS R3505 and 1983 standards.
ml glass stoppered graduated cylinder (outer diameter 42mm,
330 mm in height, minimum scale 20 ml), and in the graduated cylinder, sulfuric acid modified blast furnace slag (transformed using 12 parts by weight of sulfuric acid per 100 parts by weight of fine blast furnace water slag)
2.0 g was added, mixed uniformly, and left to stand. By this standing, the insoluble solids coagulated and coagulated, forming a sediment layer containing insoluble solids (soil particles) in the lower layer and a residual water (seawater) layer in the upper layer. In this case, as time passes, the interface between the sediment layer and the spillover layer gradually descends,
The volume of the sediment layer decreases and the volume of the spillover layer increases. The relationship between the volume ratio of the sediment layer and the standing time was as shown in Table 2. In addition, as a comparative example, in the same operation process, (a) a test in which sulfuric acid modified blast furnace slag was not added, and (b) a test in which sulfuric acid modified blast furnace slag is considered to be included in 2
A test was conducted in which a mixture of 0.4 g of water stone and 1.6 g of fine blast furnace water slag was added. The results are shown in Table 2. From these results, (i) by adding sulfuric acid-converted blast furnace slag to muddy water, insoluble solids in muddy water can be sedimented and concentrated efficiently in a short time; (ii) this effect is
It can be seen that this is greater than the coagulation and flocculation effect of plaster.

[Table] * Example 2 containing added treatment agent The same slurry from the dredging work as that used in Example 1 was mixed with sulfuric acid modified blast furnace slag (using 3 parts by weight of sulfuric acid per 100 parts by weight of fine blast furnace slag). (transformed)
Add 2 g of a mixture of 1.5 g and 0.5 g of dihydrite,
The same operation as in Example 1 was performed. The result is the third
It was as shown in the table.

[Table] * Example 3 containing added treatment agent As test mud water, mud water from the same seabed dredging work as that used in Example 1 was filtered, and insoluble solids were separated and washed with water. Distilled water was added to the test sample to prepare muddy water having an insoluble solid content of 9.52% by weight and a water content of 950%. The sample separated and washed with water has an insoluble solid content (water content) of 61.4% by weight (water content 62.9%), and an organic matter content in the insoluble solid content of 11.8% by weight (JSF T6, 1968 "Particle content"). According to the ignition loss test method), other properties are
It was almost the same as shown in the table. Next, a test was conducted in the same manner as in Example 1 using the prepared muddy water and using the same sulfuric acid-converted blast furnace slag as the treatment agent. Two types of tests were conducted: one in which 10 g of sulfuric acid modified blast furnace slag (modified using 12 parts by weight of sulfuric acid per 100 parts by weight of fine blast furnace water slag) was added to each muddy water, and the other in which 8 g of sodium chloride was added to this. I did it using The result is the fourth
It was as shown in the table. In addition, additive-free sulfuric acid modified blast furnace slag does not form a surplus water layer even after being left for 15 hours.
After 24 hours, only 1.5% of the excess water layer was formed, and after 48 hours, only 3% of the excess water layer was formed.

[Table] (Increase in strength of sedimentation concentrate) Example 4 1900 ml of the same muddy water as in Example 1 was poured into a 2000 ml glass stoppered cylinder (outer diameter 87
After adding and mixing 19 g of sulfuric acid modified blast furnace slag (100 parts by weight of fine blast furnace water slag modified with 12 parts by weight of sulfuric acid),
The mixture was allowed to stand for a period of time to form a residual water layer, and 930 ml of the residual water was separated and removed to obtain a precipitated concentrate of insoluble solids. The sedimentation concentrate obtained by this operation has an insoluble solid content of 18.7% (including the added fine blast furnace water slag), a seawater content of 81.3% by weight, and a density:
It was 1.15%. Next, 19 g of the same sulfuric acid modified blast furnace slag as above and 40 g of Portland cement were added to the sedimentation concentrate.
g was added and mixed. This mixture was poured into a cylindrical mold with an inner diameter of 50 mm and a height of 100 mm.
After molding for a specified time at constant temperature and humidity with saturated humidity, the uniaxial compressive strength of the molded product was determined according to JIS A1216T, 1979.
(± uniaxial compression test method). As a result, the unconfined compressive strength (Kg
f/cm ² ) showed values of 1.04, 1.61 and 1.92. Example 5 Add sulfuric acid modified blast furnace slag (fine blast furnace slag 100
10 g of a mixture of 7.5 g (modified using 3 parts by weight of sulfuric acid per part by weight) and 2.5 g of dihydrate were added and mixed, and allowed to stand for more than a day and night to form a residual water layer and a sediment layer. A predetermined amount of residual water is removed from this residual water layer using a decantation and pipette, and then the remaining residual water and sedimentation layer are sufficiently stirred to form a uniform layer to obtain the desired test sedimentation concentrate. It was adjusted. The predetermined amount of excess water to be removed is determined theoretically by calculation. By this method, two types of test sedimentation concentrates with "insoluble solid content excluding added processing agents" of 14% and 19% by weight were prepared, and each of these was mixed with "sulfuric acid modified blast furnace slag of the same composition as above."・10g of dihydrite mixture and 20g of Portland cement
was added and mixed. The unconfined compressive strength of this mixture at 28 days old is when the above insoluble solid content is 14% by weight.
When it was 0.8Kgf/cm ² and 19% by weight, it was 1.82Kgf/cm ² . From this result, it can be understood that the higher the sedimentation concentration in muddy water, the higher the uniaxial compressive strength of the strength-enhanced product. The uniaxial compressive strength was measured in the same manner as in Example 4. Example 6 A sedimentation concentration treatment of mud using "sulfuric acid modified blast furnace slag/dihydrite slag" was carried out under the same conditions as in Example 5 to prepare a sedimentation concentrate with a desired concentration. Next, "sulfuric acid modified blast furnace slag/dihydrite" and Portland cement were added to the prepared sedimentation concentrate. At this time, the mixture of "sulfuric acid modified blast furnace slag and dihydrate slag" has a weight ratio of 3:1, and the sulfuric acid modified blast furnace slag constituting this mixture is fine blast furnace water. It is denatured with 3 parts by weight of sulfuric acid per 100 parts by weight of slag. In addition, the total amount of processing agents added in the sedimentation concentration step and the strength increasing step was 80 g per 1 sedimentation concentrate, and the weight of Portland cement added was equal to the weight of sulfuric acid modification addition.
The uniaxial compressive strength of this mixture was measured in the same manner as in Example 4. The unconfined compressive strength of the materials obtained by increasing the strength of sediment concentrates with different concentrations at 28 days old was as shown in Table 5.

[Table] Example 7 Under the conditions of Example 5, dihydrate, which is one of the materials constituting the treatment agent, was replaced with fluorite (insoluble anhydrite) (the amount added was the same as that of dihydrate). (stoichiometry), and other conditions were the same as in the examples to treat muddy water. As a result, the strength of a sedimentation concentrate adjusted to have an insoluble solid content (excluding added processing agents) of 19% by weight was found to have an unconfined compressive strength of 1.86 kgf/cm ² at 28 days of age. It was hot.

Claims (1)

[Claims] 1. A method for treating muddy water, which comprises adding sulfuric acid modified blast furnace slag with a particle size of 300 μm or less to muddy water, and causing insoluble solids to settle in the muddy water in the presence of sodium chloride. 2. In the presence of sodium chloride, sulfuric acid modified blast furnace slag with a particle size of 300 μm is used to (a) treat the muddy water by acting as a coagulating and flocculant, and (b) further, the surplus water generated from the treatment in (a) is treated. In the sedimentation concentrate obtained by removal and separation,
A method for treating muddy water, which comprises reacting Portland cement with sulfuric acid modified blast furnace slag or sulfuric acid modified blast furnace slag in the presence of gypsum to increase the strength of the sedimented concentrate. 3. The method according to claim 2, wherein the sulfuric acid modified blast furnace slag is modified using 0.5 to 50 parts by weight of sulfuric acid per 100 parts by weight of finely quenched blast furnace slag.