JPH0352934B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field] The present invention relates to artificial fish reefs (solidified bodies formed and solidified with a treatment agent containing sulfuric acid-converted blast furnace slag) made from aquaculture sludge (herein also simply referred to as aquaculture sludge) generated from fish farms; The present invention relates to a manufacturing method thereof. [Prior Art] Sediment deposits on the bottom of water such as seabeds and lakebeds are dredged for purposes such as maintaining an appropriate water depth, preventing pollution, and installing underwater structures. In this case, the obtained dredged mud is transported and stored in a vast mud storage area. However, fish sludge from fish farms contains a large amount of rotten organic matter, which generates a bad odor and has a negative impact on the living environment. Therefore, the cultured sludge cannot be simply dredged and stored in a mud storage area. In fish farms, food is not digested sufficiently by fish, and it accumulates and rots on the bottom of the water, becoming aquaculture sludge, which has a negative impact on fish farms. Containing a lot of rotten organic matter leads to deterioration of water quality, and eventually,
It becomes a major cause of large-scale red tides and oxygen-deficient water masses, and causes various adverse effects associated with this. Therefore, in such fish farms, the aquaculture sludge must be removed. However, the dredged aquaculture sludge is (1) large in volume, (2) contains a large amount of water (seawater), and is difficult to dry naturally.
(3) Since the generation of bad odors caused by rotting organic matter pollutes the living environment, there is a strong desire to establish a treatment method that takes these matters into account. On the other hand, there is currently no definitive method to treat aquaculture sludge economically, and only temporary methods are being used, such as (a) interim measures;
Examples include a method of covering the surface layer of aquaculture sludge with earth and sand, and (b) a method of temporarily avoiding the problem by gradually moving the fish farm from the coast near the coastline to the offshore coast. On the other hand, the fishing area in Japan has been shrinking due to the 200 nautical mile problem, etc., and the installation of artificial reefs has recently become a focus of attention as one of the emerging measures for coastal fishing to cope with this problem. Technology development is becoming more active. However, against the above background, no practical proposal has yet been made to solve these problems all at once. [Purpose] In order to comprehensively solve the above-mentioned problems, the present invention provides an artificial fish reef made from aquaculture sludge (a solidified body formed and solidified with a treatment agent containing sulfuric acid-converted blast furnace slag).
The present invention provides a method for manufacturing the same. [Structure] In order to achieve the above object, the inventors have conducted intensive research and found that (1) aquaculture sludge can be recovered from a fish farm and an artificial fish reef can be manufactured at low cost using the sludge as a raw material. (2) Furthermore, it was found that the artificial reef obtained by the method of the present invention has excellent performance as a fish reef. That is, according to the present invention,
An artificial fish reef that can treat aquaculture sludge from a fish farm and uses the sludge as a raw material, and a method for producing the same are provided. To produce the artificial fish reef of the present invention, first, sulfuric acid modified blast furnace slag with a particle size of 300 μm or less (those with a low degree of sulfuric acid modification are used together with Sekko) is added to aquaculture sludge dredged from a fish farm. After coagulating and flocculating the colloids, water is separated, and then the obtained concentrated aquaculture sludge is mixed with Portland cement, or Portland cement and sulfuric acid modified blast furnace slag (if the sulfuric acid modified blast furnace slag has a low degree of sulfuric acid modification, The mixture is then molded into the desired shape and solidified. The shape of the molding and solidification is arbitrary, as long as it is suitable for a fish reef.
For example, a single fish reef may be a combination of a hollow regular hexahedron, a cylindrical shape with a hollow window, and a block shape such as a plate shape, a square shape, or a column shape. The molding and solidifying method may be cast molding or press molding. Press molding has the advantage that a smaller amount of processing agent is used, the strength of the molded solidified product increases quickly, and the final strength is higher than that of cast molding. On the other hand, pour molding has the advantage that it does not require special equipment like press molding and can be easily performed on-site. The aquaculture sludge handled in the present invention may contain non-suspended sediment and the like, and is pumped up from a fish farm. The pumped culture sludge contains at least 5% by weight of insoluble solids, usually about 7 to 12% by weight. In the case of the present invention, the amount of insoluble solids in aquaculture sludge is determined by measuring the water content ratio based on JIS1203-1978, and the water content is 3% by weight in seawater.
Since it contains salts such as sodium chloride, the insoluble solid content is defined as the insoluble solid content. The sulfuric acid modified blast furnace slag used in the present invention is obtained by reacting finely quenched blast furnace slag with sulfuric acid. In this case, the fine quenched blast furnace slag is obtained by quenching blast furnace slag (slag) as a by-product from a steelmaking blast furnace, and further pulverizing coarse particles to a particle size of 300 μm or less.
The main method of quenching blast furnace slag is usually a wet method in which it is granulated and rapidly cooled with water, but there are also semi-dry methods that use air and a small amount of water, and dry methods that use air cooling. The so-called blast furnace slag obtained by the wet method is sandy or granular with a particle size of about 1 to 5 mm. The composition of the quenched blast furnace slag varies slightly depending on the iron ore composition and the operating conditions of the blast furnace, but the weight ratio is approximately as follows. _SiO2 30-35%, _{Al2O3 13-18} %, CaO38-45%, _{Fe2O3 0.5-1.0} %, MgO3-6%, S0.5-1.0%, MnO0.5-1.5%, TiO ₂ 0.5 to 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. Such latent hydraulic properties can be obtained by rapidly cooling the blast furnace molten slag. The slag obtained by slowly cooling blast furnace molten slag becomes crystalline. This slowly cooled slag is a dense crystalline substance whose main constituent minerals are melilite (Gehlenite Ca ₂ Al ₂ SiO ₇ / Okermanite Ca ₂ MgSi ₂ O ₇ solid solution) and calcium orthosilicate.
No latent hydraulic properties. For this reason, even if the slow-cooled slag is atomized, 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 modified blast furnace slag of the present invention. In the present invention, in order to utilize the quenched blast furnace slag as a reaction material, it is desirable to use the quenched blast furnace slag in a state as fine as possible. Blast furnace water slag has a particle size of 1 to 5 mm.
It is unsuitable because it is coarse-grained and significantly reduces (a) metamorphosis through reaction with sulfuric acid, and (b) reaction with fine soil particles and Portland cement in sulfuric acid-converted blast furnace slag. The reason for this is that the specific surface area of coarse-grained blast furnace water slag is small. In the case of the present invention, it is important that the particle size of the quenched blast furnace slag is 300 μm or less,
Usually, finely quenched blast furnace slag with a particle size of 100 to 1 μm 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 economical and ecological standpoints, it is preferable to use waste sulfuric acid discharged from various chemical industries. 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 0.5 to 50 parts by weight (converted to 100% by weight sulfuric acid) per 100 parts by weight of blast furnace slag. The preferred degree of sulfuric acid modification differs depending on the constituent material of the treatment agent used in forming and solidifying the cultured sludge concentrate. In the present invention, (a) when using sulfuric acid modified blast furnace slag and Portland cement as the treatment agent, blast furnace slag
When using sulfuric acid modified blast furnace slag that has been modified using 5 to 50 parts by weight of sulfuric acid per 100 parts by weight, and (b) also using sulfuric acid modified blast furnace slag, setukou and portland cement as a treatment agent, the sulfuric acid modified blast furnace slag is The blast furnace slag treated with 0.5 to 5 parts by weight of sulfuric acid per 100 parts by weight is used. In other words, it is preferable to divide the composition of the treatment agent into two types, (a) and (b), with the degree of sulfuric acid modification of the blast furnace slag being 5 parts by weight per 100 parts by weight of the blast furnace slag. 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 2
It becomes water-filled. In this case, some of the alkaline components of the blast furnace slag react with sulfuric acid and dissolve, but since the solubility of calcium sulfate is lower than other sulfates, most of the sulfates eventually turn into dihydrate crystals. Remains in sulfuric acid converted blast furnace slag. Therefore, when preparing sulfuric acid modified blast furnace slag by the dipping method (b), it is preferable to repeatedly use the mother liquor from which the product is separated as a diluted solution of sulfuric acid. By using this mother liquor, it is possible to suppress consumption due to the elution of MgO and Al ₂ O ₃ from the blast furnace slag, and also prevent the dihydric slag produced during the treatment from dissolving and being lost (dihydric slag at room temperature). The dissolved amount of _CaSO4 is approximately 0.2% by weight). Further, as specific methods for implementing the method (2) above, there are two examples (a) and (b) below. (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 removed from the outside so as to maintain the PH value of the dispersion liquid in the range of 1.5 to 4. A method of adding and recovering metamorphosed blast furnace slag. In both methods (a) and (b), the above
As in case (1), the amount of sulfuric acid reacted with the blast furnace slag is adjusted within a predetermined range. Next, we will discuss Portland cement, which is one of the materials used to increase the strength of concentrated aquaculture sludge. Portland cement meets Japanese Industrial Standards
It complies with JIS R5210, and in general, one of these equivalent to ordinary Portland cement is used. However, depending on the processing conditions, Portland cement conforming to standards such as medium-early-strength Portland cement, 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. Sometimes used. In addition, when sulfuric acid modified blast furnace slag treated with 0.5 to 5 parts by weight of sulfuric acid per 100 parts by weight of blast furnace slag is used as a material for a treatment agent, slag is used as a part of the treatment agent. , dihydrate or insoluble anhydrous (type anhydrous),
(including hard shavings). However, in some cases, semi-hydrated or soluble anhydrous
A substitute for some of these setsukou may also be used. In the case of dihydric slag, the particle size is not particularly limited, and any powder or granular material may be used. In the present invention, natural sludge and various chemical sludge produced by various processes can be used. Flue gas desulfurization can be used in the form it was collected from, such as from a centrifugal separator in the final process, without having to undergo secondary processing steps such as washing with water or drying. The cultured sludge handled in the present invention (a) contains a large amount of phosphoric acid components that inhibit the hydration reaction of Portland cement, and (b) also contains hydrogen sulfide and mercaptans that cause bad odors. Therefore, it is preferable that the iron material contains iron that can chemically mask these phosphoric acid components, hydrogen sulfide, and mercaptans. Therefore, sulfuric acid waste liquids containing iron sulfate, such as waste liquids from titanium production processes,
Iron oxide-containing clay obtained by treating pickling waste acid and chemical cleaning waste liquid with sulfuric acid with lime is very effective as a clay material used in the present invention.Also, when using an insoluble anhydrous clay, In view of its dissolution rate, it is necessary to make the powder particle size 300 μm or less. In the present invention, it is possible to directly use insoluble anhydrous slag (fluoric acid sludge) which is a byproduct when producing hydrogen fluoride by thermally decomposing fluorite with concentrated sulfuric acid. That is, the particle size of fluoric acid
This is because it is produced as a dry powder of 300 μm or less. Incidentally, the weight of sludge as used in the present invention is a value as anhydrous sludge CaSO ₄ . Next, in the present invention, concentration of aquaculture sludge will be specifically explained. In the present invention, first, sulfuric acid modified blast furnace slag with a particle size of 300 μm or less (those with a low degree of sulfuric acid modification are used together with slag) is added to aquaculture sludge. This sulfuric acid modified blast furnace slag can be added by various methods. For example, (1) when pumping up aquaculture sludge, sulfuric acid modified blast furnace slag is injected in the form of slurry or powder into the transfer pipe, and (2) sulfuric acid modified blast furnace slag is poured into a coagulation/coagulation tank (sedimentation separation tank). This can be done by adding in powder form. In addition, in the present invention, when adding sulfuric acid modified blast furnace slag to aquaculture sludge, a polymer flocculant is supplementarily added,
It may also accelerate coagulation/flocculation (sedimentation of insoluble solids). Furthermore, the optimum usage amount of the sulfuric acid modified blast furnace slag in the present invention requires consideration of the following conditions including the following forming and solidifying steps. (1) How to add a treatment agent in the treatment of aquaculture sludge. For example, the addition of sulfuric acid-converted blast furnace slag involves (a) the process of concentrating the sludge by coagulation and flocculation of the aquaculture sludge (hereinafter referred to as the "concentration process"); ), add the total amount of sulfuric acid modified blast furnace slag in one step, or
(b) Or, the “concentration process” and the formation and formation of concentrated aquaculture sludge.
Should the total amount of sulfuric acid-converted blast furnace slag be added to the two stages of the solidification process (hereinafter referred to as the "forming/solidification process")? (2) What is the degree of sulfuric acid modification (ratio of sulfuric acid added to raw material blast furnace slag) of sulfuric acid modified blast furnace slag? (3) Type, quality and condition of aquaculture sludge, i.e. the ratio of organic matter to soil particles in the insoluble solids;
What about these properties, the particle size distribution of soil particles, the pH value of aquaculture sludge, and the state of impurities? (4) In the water separation in the "concentration process," whether to use a method of separating and removing surplus water by sedimentation concentration. (5) What value should be set for the target moisture content of the concentrate in the "concentration process"? (6) Which method will be used for molding and solidification: pour molding or press molding? In other words, the amount of sulfuric acid-converted blast furnace slag added to aquaculture sludge may be relatively small for the purpose of "concentration process" only, but based on the conditions (1) to (6) above, the amount of treatment agent The total amount to be used must be determined, and the amount of sulfuric acid converted blast furnace slag added that meets this requirement must be specified.
In other words, in order to produce fish reefs from aquaculture sludge, sulfuric acid-modified blast furnace slag is used as a coagulating and flocculant agent in the "concentration process," and then in the "forming and solidifying process."
It is important to specify the total amount added so that it can fully fulfill its role as a reactive material together with Portland cement. The total amount of treatment agent used varies depending on the conditions (1) to (6) above, but in general, the total amount used is 50 to 200 kg per ^1M3 of aquaculture sludge,
It is 100-400Kg per ^1M3 . As the treatment agent used in the present invention, as described above, the following two types of treatment agents [] and [] are appropriately selected and used depending on the degree of sulfuric acid modification of the sulfuric acid modified blast furnace slag. Treatment agent []: Consists of sulfuric acid modified blast furnace slag (modified using 5 to 50 parts by weight of sulfuric acid per 100 parts by weight of rapidly cooled blast furnace slag with a particle size of 300 μm or less) A and Portland cement B, and sulfuric acid modified blast furnace slag A and Weight ratio of Portland cement B A/B = 70/30
~35/65. Treatment agent []: Sulfuric acid modified blast furnace slag (modified using 0.5 to 5 parts by weight of sulfuric acid per 100 parts by weight of rapidly cooled blast furnace slag with a particle size of 300 μm or less) A ₁ , Setsukou A ₂
and Portland cement B, weight ratio of sulfuric acid modified blast furnace slag A ₁ and slag A ¹ /A ₂ =
95/5 to 60/40, and the weight ratio of the sum of sulfuric acid modified blast furnace slag A ₁ and Sekko A ₂ to Portland cement B (A ₁ +A ₂ )/B = 70/30 to 45/55. These relationships between the material amount ratios of processing agents [ ] and [ ] were determined through many experiments. The addition of the sulfuric acid-converted blast furnace slag as the treatment agent [] or the sulfuric acid-converted blast furnace slag and slag as the treatment agent [] specified in this way shall be carried out by either of the following methods (1) and (2). . (1) Add the total amount of sulfuric acid modified blast furnace slag (including slag in the case of processing agent []) in the "concentration process". (2) The total amount of sulfuric acid modified blast furnace slag (including slag in the case of treatment agent []) is added in two steps: the "concentration process" and the "forming/solidification process." The amount of sulfuric acid converted blast furnace slag added to the “concentration process” is:
In general, the method (1) is as follows. In the case of additive [], 15 to 180 kg of sulfuric acid modified blast furnace slag, preferably 20 to 140 kg, per ^1M3 of cultured sludge.
Add at the rate of In the case of additive [], 13 to 150 kg of sulfuric acid modified blast furnace slag, preferably 15 to 120 kg, per ^1M3 of cultured sludge.
(As a mixture of sulfuric acid modified blast furnace slag and slag,
20-200Kg, preferably 23-170Kg). In method (2), in which the sulfuric acid-converted blast furnace slag is added in two steps, the "concentration step" and the "forming/solidification step," a predetermined amount of the sulfuric acid-converted blast furnace slag is added in two parts as appropriate. The total amount of sulfuric acid-converted blast furnace slag added is as described above. Next, the aquaculture sludge to which sulfuric acid modified blast furnace slag (including Setsukou in the case of treatment agent []) has been added and mixed is: (a) After the colloid content in the aquaculture sludge has coagulated and flocculated, it has been dehydrated using a centrifugal dehydrator. to separate the water, or
or (b) the sludge is allowed to stand still to allow the insoluble solids to settle, and the liberated surplus water is separated and removed. In the case of the present invention, by adding sulfuric acid-modified blast furnace slag to culture sludge, coagulation and flocculation of colloids occur, and sedimentation and centrifugal dehydration of insoluble solids are significantly promoted. As a result, concentrated culture sludge with an insoluble solid content of 20 to 40% by weight can be separated. The concentrated aquaculture sludge has (a) sulfuric acid-converted blast furnace slag uniformly dispersed therein, (b) fine soil particles and organic substances exchanged with cations, and (c) hydration reaction of Portland cement. Reaction inhibitors such as organic substances and phosphates that have an adverse effect are masked. The optimum water content of concentrated aquaculture sludge differs depending on the method of forming and solidifying the insoluble solids. The optimum water content per 100 parts by weight of insoluble solids is:
100 to 400 parts by weight for pour molding, 50 to 200 parts by weight for press molding (varies depending on press pressure)
It is. As the water separation or dehydration method, conventionally known solid-liquid separation methods such as sedimentation separation method and centrifugation method are employed. When aquaculture sludge is immediately dehydrated after coagulating and coagulating, dewatering by centrifugation is very effective. Next, we will discuss the shaping and solidification of concentrated aquaculture sludge. The required strength of the molded and solidified product is uniaxial compressive strength,
It is desirable to specify at least 10 Kgf/cm ² or more. When Portland cement is added in the "forming and solidification process," the hydration reaction of Portland cement triggers various reactions between the sulfuric acid-converted blast furnace slag in the treatment agent, cement, and soil particles containing organic matter, resulting in concentration. A solidification reaction of aquaculture sludge is achieved. This solidification reaction includes ion exchange reactions of fine soil particles and organic matter, and ettringite (3CaO
_Al2O3・_3CaSO4・₂₈ ~ _32H2O ) formation reaction, tobermolite mineral-like phase (3CaO・_2SiO2・_3H2O )
Examples include pozzolanic reactions that produce , etc., and reactions that produce non-crystalline gelling substances through various reactions. In the case of the present invention. As mentioned above, the concentrated aquaculture sludge obtained in the "concentration step" has an insoluble solid content with improved reactivity. Therefore, concentrated aquaculture sludge can be mixed with Portland cement, which induces a solidification reaction.
The hydration reaction of Portland cement is carried out smoothly, and the solidification reactions are achieved very effectively.
The amounts and methods of addition of each material constituting the processing agent are as described above, but in the "molding/solidification process",
In order to shorten the setting time, (a) supplementary addition of accelerators such as calcium chloride or (b) use of ultra-early strength Portland cement or early strength Portland cement as the Portland cement. In addition, the artificial fish reef obtained by the present invention can be obtained by (a) increasing the concentration of aquaculture sludge, (b) increasing the total amount of treatment agent used, and (c) using press molding for forming and solidifying. By doing so, the strength can be increased. [Effects] According to the present invention, the problem of treating aquaculture sludge can be solved by using aquaculture sludge, which has hitherto been regarded as troublesome because it is difficult to process, as a raw material for artificial fish reefs. The molded and solidified product obtained by treating sludge has excellent performance as a fish reef and is inexpensive. [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 commercially available fine blast furnace water slag has a specific surface area of 3800 cm ² /g (i.e.,
average particle size 7 μm), composition weight ratio: SiO ₂ 34%,
Al ₂ O ₃ 15%, CaO 43%, MgO 5%, Fe ₂ O ₃ 0.7%,
It contained 0.9% S, 6% MnO, and 0.8% TiO ₂ , and was mostly glassy when observed with a polarizing microscope. 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 repeatedly used 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.
In addition, a commercially available Portland cement (specific surface area of 33000 cm ² /g as measured by the Blaine method) was used, and secondary cement was used as a by-product in the flue gas desulfurization process (exhaust desulfurization). In addition, the aquaculture sludge collected from the remains of a yellowtail farm was used. The sexual setting was as shown in Table 1.

【table】

[Table] (Coagulation and flocculation of cultured sludge) Example 1 200ml of cultured sludge was poured into a 250ml glass stoppered graduated cylinder (outer diameter
42mm, height 330mm, minimum scale 20ml), and add sulfuric acid modified blast furnace slag (fine blast furnace water slag) to the measuring cylinder.
After adding and mixing 2 g of a mixture of 1.5 g of denatured sulfuric acid (modified using 3 parts by weight of sulfuric acid per 100 parts by weight) and 0.5 g of dihydrate, the mixture was allowed to stand still. By this standing still,
The insoluble solids condensed and coagulated, forming a sedimentary 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 sedimentation layer and the overflow layer gradually descends, the volume of the sedimentation layer decreases, and the volume of the overflow layer increases. The relationship between the volume ratio of the settled layer and the standing time was as shown in Table 2. As a comparative example, in the same operation process, (a) sedimentation state of only aquaculture sludge, and (b) 1.5 g of fine blast furnace slag and 2
A test was conducted when 2 g of a mixture of 0.5 g of water sludge was added. The results are shown in Table 2. From this result, it can be understood that sulfuric acid modified blast furnace slag has a coagulation and flocculation effect, and this effect is greater than the coagulation and flocculation effect of slag.

【table】

[Table] Properties of sedimentary layer

Density (g/cm ³ ) 1.123
1.142 1.151 1.161 1.168 1.195
Weight% of insoluble solids ^* 15.0 17
.5 18.7 19.9 20.9 24.1
Seawater content weight% 85.0 82
.5 81.3 80.1 79.1 75.9

Claims (1)

[Scope of Claims] 1. An artificial reef made of cultured sludge, solidified using sulfuric acid-converted blast furnace slag obtained by reacting sulfuric acid with rapidly cooled blast furnace sludge having a particle size of 300 μm or less, and a treatment agent containing Portland cement. 2. After adding the following sulfuric acid modified blast furnace slag to the culture sludge and coagulating and coagulating the colloid content in the sludge,
Separate the water and then add to the resulting concentrated aquaculture sludge
A method for producing an artificial fish reef, which comprises adding and mixing Portland cement, or Portland cement and sulfuric acid-converted blast furnace slag, and forming and solidifying the mixture into a desired shape. Sulfuric acid modified blast furnace slag: quenched blast furnace slag with a particle size of 300 μm or less
Adding the sulfuric acid-modified blast furnace slag to cultured sludge (3) modified using 5 to 50 parts by weight of sulfuric acid per 100 parts by weight to form a sedimentation layer forming a lower layer and a spillage layer forming an upper layer, The resulting surplus water layer is separated and removed to obtain a sedimentation concentrate of aquaculture sludge, and then Portland cement, or Portland cement and sulfuric acid modified blast furnace slag is added to the sedimentation concentrate as it is or after dehydration treatment. The method according to claim 2, wherein the ingredients are added and mixed, and then molded and solidified into a desired shape. 4 Sulfuric acid modified blast furnace slag A and Portland cement B
The method according to claim 2 or 3, wherein the total weight ratio A/B used is from 70/30 to 35/65. 5 Add the following "sulfuric acid modified blast furnace slag/Setsukou" to the cultured sludge to coagulate and coagulate the colloid content in the sludge.
After coagulation, water is separated, and then Portland cement or "sulfuric acid modified blast furnace slag/Setsukou" and Portland cement are added and mixed to the obtained concentrated aquaculture sludge, and the mixture is shaped and solidified into the desired shape. A method for manufacturing an artificial fish reef. "Sulfuric acid modified blast furnace slag/Setsukou": Consists of sulfuric acid modified blast furnace slag A ₁ and Setsukou A ₂ that have been modified using 0.5 to 5 parts by weight of sulfuric acid per 100 parts by weight of rapidly cooled blast furnace slag with a particle size of 300 μm or less, and the weight ratio A ₁ /A ₂ is
Anything between 95/5 and 60/40. 6 Add the "sulfuric acid modified blast furnace slag/Setsukou" to the cultured sludge to form a sedimentation layer forming the lower layer and a spillage layer forming the upper layer, and separate the resulting spillwater layer.
to obtain a sedimentation concentrate of aquaculture sludge, and then
Claim 5, in which Portland cement or Portland cement and "sulfuric acid modified blast furnace slag/Setsukou" are added to and mixed with the sedimentation concentrate as it is or after dehydration treatment, and the mixture is formed into a desired shape and solidified. Method. 7 The total weight ratio A/B of “sulfuric acid modified blast furnace slag/Setsukou” A and Portland cement B is 70/
Claim 5 or 6 which is 30-45/55
Section method. 8. Any one of claims 5 to 7, wherein the iron oxide, which is one of the constituent materials of the treatment agent, is "iron oxide-containing iron oxide-containing iron oxide" obtained by treating iron sulfate and sulfuric acid waste liquid with lime. Method.