JPH1161128A - Modifier of sludge and mud, and treatment process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject modifier that can allow sludge or mud of high water content to lose its fluidity in a shortened time and can convert the sludge or mud into treated soil that has high strength and can be readily reused by combining water glass with phosphoric acid or its salt. SOLUTION: The objective modifier is prepared by formulating (A) 0.1-30 pts.wt. of water glass per 100 pts.wt. of sludge or mud, (B) 0.1-20 pts.wt. of phosphoric acid, preferably ortho-phosphoric acid, condensed phosphoric acid (for example, pyrophosphoric acid) and/or a phosphate salt, for example, aluminum dihydrogen phosphate, per 100 pts.wt. of sludge or mud, and (C), when necessary, a water-absorbing substance and a water-soluble macromolecular compound. The component A is a high-concentration aqueous solution of sodium silicate represented by the formula: Na2 O.nSiO2 (n is 2-4) and water glass No.2 ((n) is about 2.5) and No.3 ((n) is about 3) are preferably used. The components A and B are preferably added so that the pH of the treated soil may be adjusted to 5.8-8.6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge or mud modifier and a method of treating sludge. More specifically, the present invention relates to mud, sludge, sludge, etc. generated at construction sites such as dredging work, construction work, tunnel work, etc.
Sludge generated in sewage treatment plants, etc. can be reformed into treated soil in a form that can be easily reused or disposed of in a short time.Even if sludge and mud contain harmful heavy metals, they can be safely treated. TECHNICAL FIELD The present invention relates to a sludge or mud modifier capable of reliably preventing heavy metals from being eluted from treated soil and a treating method.

[0002]

[Prior Art] Oil, gas, geothermal wells, tunnel construction, dredging works for dams, lakes, marshes, rivers, seabeds, etc., construction works, mud generated at construction sites, sludge, sludges, Sludge generated in a sewage treatment plant and the like has a high water content and a high fluidity, which makes it difficult to transport the sludge using a normal dump truck or a truck. For this reason, conventionally, these muds are treated by mixing a lime or cement-based solidifying agent, or mixed with a water-soluble polymer compound or a superabsorbent resin. For example, a treatment or a treatment for forcibly dewatering mud by a dehydration treatment machine has been performed. However, these methods have various problems, such as a long time required for treatment, limitation of reuse due to alkalinity of the treated soil, low strength of the treated soil, and special equipment. Was. Various methods of using water glass in combination with other chemicals for treating sludge and mud have been studied. For example, a method of using water glass and calcium chloride together (Joosten method) or a method of using water glass and slaked lime together (Rodio)
Construction method) has been proposed. However, according to these methods, there is a problem that the pH of the treated soil becomes alkaline, and the reuse of the treated soil is greatly restricted. Further, a method of using water glass in combination with ferric sulfate and potassium aluminum sulfate has been proposed. According to this method, the pH of the treated soil is neutral, but the gelation time is very few seconds. There is a problem that it is short and it is difficult to uniformly treat the treated soil. Furthermore, there has been proposed a method in which water glass and a strong acid such as sulfuric acid are used in combination.However, even with this method, the gelation rate of the treated soil is too high to uniformly treat the treated soil, and the solidified portion is not modified. However, there is a problem that the strength is low as a whole because of insufficient portions. Excavated mud, sludge, sludge, and the like may contain heavy metals, and the Soil Contamination Prevention Law also targets heavy metals such as cadmium, copper, and lead in the control business. Therefore, when utilizing such sludge or mud containing a heavy metal as a treated soil for landfilling, it is necessary to perform a treatment for surely preventing elution of the heavy metal in the treated soil. Conventionally, as a method for preventing the elution of heavy metals in excavated mud or sludge containing sludge, sludge, a melting method, a cement solidification method, an extraction method with an acid or other solvent, a chemical treatment method, and the like have been proposed.
Satisfactory in terms of equipment, operation management, treatment cost, pH of treated soil, etc., easily and efficiently treat mud and sludge,
A treatment technology that can reliably prevent the elution of heavy metals from treated soil has not yet been developed.

[0003]

SUMMARY OF THE INVENTION According to the present invention, sludge or mud having a high water content can be made into a treated soil having a large strength and being easily recyclable by losing its fluidity in a short time. The present invention has been made to provide a sludge or mud modifier and a method for treating sludge or mud that can be safely treated and reliably prevented from elution of heavy metals from the treated soil even when the mud contains harmful heavy metals. Things.

[0004]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above-mentioned problems, and as a result, sludge or mud has been obtained.
By adding and mixing water glass and phosphoric acid or phosphate, the gelation rate is appropriately controlled, the treated soil becomes strong in a short time, and the sludge or mud contains heavy metals. Found that heavy metals were immobilized and became difficult to elute, and based on this finding, the present invention was completed. That is, the present invention provides (1) a sludge or mud modifier characterized by combining water glass and phosphoric acid and / or phosphate, and (2) a sludge or mud containing a heavy metal. (3) a method for treating sludge or mud, which comprises adding a water glass and phosphoric acid and / or phosphate to the sludge or mud modifier according to (1); (3) The method for treating sludge or mud according to (3), wherein the sludge or mud contains a heavy metal. Furthermore, as a preferred embodiment of the present invention, (5) the water glass is water glass No. 2 or water glass No. 3, the sludge or mud modifier according to the above (1), and (6) phosphoric acid is positive. The sludge or mud modifier according to item (1), which is phosphoric acid; (7) the sludge or mud modifier according to item (1), wherein phosphoric acid is condensed phosphoric acid; (7) The sludge or mud modifier according to (7), wherein the phosphoric acid is pyrophosphoric acid, and (9) the sludge or mud modification according to (1), wherein the phosphate is aluminum dihydrogen phosphate. Plaster,
(10) The method for treating sludge or mud according to (3), wherein the amount of water glass added is 0.1 to 30 parts by weight per 100 parts by weight of sludge or mud, (11) phosphoric acid or phosphoric acid The amount of salt added is 0.1 to 100 parts by weight of sludge or mud.
The method for treating sludge or mud according to item (3), which is 20 parts by weight, (12) water glass and phosphoric acid or phosphate are added so that the pH of the treated soil is 5.8 to 8.6. The method for treating sludge or mud according to item (3), and the method for treating sludge or mud according to item (3), wherein (13) a water-absorbing substance or a water-soluble polymer compound is used in combination. .

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The sludge or mud modifier and treatment method of the present invention include oil well, gas well, geothermal well, tunnel work, foundation work, dredging work for dams, lakes, marshes, rivers, and the sea floor. It can be applied to mud generated at construction sites and other construction sites, sludge and sludge, or sludge generated at water and sewage treatment plants. The upper limit of the water content of the mud which can be treated by the modifier and the treatment method of the present invention is not particularly limited. For example, sludge or mud having a high moisture content such that the water content reaches 90% by weight can be treated. it can.
The present invention can be particularly suitably applied to sludge and mud containing heavy metals. Heavy metals that can be treated by the modifier and treatment method of the present invention include, for example, copper,
Examples include zinc, lead, cadmium, manganese, iron, nickel, cobalt, arsenic, antimony, tin, bismuth, chromium, mercury, molybdenum, tungsten, and vanadium. The sludge or mud modifier of the present invention is a combination of water glass and phosphoric acid and / or phosphate. Water glass has the general formula Na ₂ O · nSi
A concentrated aqueous solution of sodium silicate represented by O ₂ , wherein n is usually 2 to 4. The water glass used in the present invention is not particularly limited. For example, water glass No. 1 (n = about 2) and water glass No. 2 (n = about 2.
5), water glass No. 3 (n = about 3) and the like. Among these, water glass No. 2 and water glass No. 3 can be preferably used. Si in water glass used
O ₂ content is 25 to 37 wt%, it is preferable NaO ₂ content of 8-16% by weight. In the present invention, one kind of water glass can be used alone, or two or more kinds can be used in combination.
In the method of the present invention, the amount of water glass to be added is preferably 0.1 to 30 parts by weight, more preferably 0.5 to 20 parts by weight, based on 100 parts by weight of sludge or mud. When the amount of water glass added is less than 0.1 part by weight based on 100 parts by weight of sludge or mud, solidification of sludge or mud becomes insufficient, and when heavy metals are contained, heavy metals are stably It may be difficult to fix. The amount of water glass to be added is usually 30 parts by weight based on 100 parts by weight of sludge or mud, and the treated soil has sufficient strength and the heavy metals contained therein are fixed. On the other hand, addition of more than 30 parts by weight of water glass is usually unnecessary, and the amount of acid required for neutralization when the treated soil is neutralized may be excessive.

The phosphoric acid used in the modifier and treatment method of the present invention is not particularly limited. For example, orthophosphoric acid (H
₃ PO ₄ ), hypophosphorous acid (H ₃ PO ₂ ), metaphosphorous acid (H
PO ₂ ), pyrophosphorous acid (H ₄ P ₂ O ₅ ), orthophosphorous acid (H
₃ PO ₃ ), hypophosphoric acid (H ₄ P ₂ O ₆ ), metaphosphoric acid (HP
O ₃ ), pyrophosphoric acid (H ₄ P ₂ O ₇ ), triphosphoric acid (H ₅ P ₃ O)
₁₀ ) and other condensed phosphoric acids.
The phosphate used in the present invention is not particularly limited,
For example, ammonium dihydrogen phosphate, lithium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, calcium dihydrogen phosphate, barium dihydrogen phosphate,
Aluminum dihydrogen phosphate, diammonium hydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate,
In addition to salts of orthophosphoric acid such as ammonium sodium hydrogen phosphate, aluminum monohydrogen phosphate, triammonium phosphate, trisodium phosphate, and tripotassium phosphate, the above-mentioned various phosphoric acid salts and the like can be mentioned. . Among these, orthophosphoric acid and condensed phosphoric acid are preferable because the treated soil can be made neutral with a small amount of addition. Especially,
When condensed phosphoric acid such as pyrophosphoric acid is used, the reaction proceeds slowly, and uniform solidification can be performed, so that a treated soil having higher strength can be obtained. When aluminum dihydrogen phosphate (Al (H ₂ PO ₄ ) ₃ ) is used, aluminum has an effect of immobilizing heavy metals, and the elution of heavy metals can be suppressed to a lower level. In the present invention, phosphoric acid and / or phosphate may be used alone or in combination of two or more. In the method of the present invention, the amount of phosphoric acid or phosphate added is preferably 0.1 to 20 parts by weight based on 100 parts by weight of sludge or mud, and 0.2.
More preferably, the amount is from 10 to 10 parts by weight. When the addition amount of phosphoric acid or phosphate is less than 0.1 part by weight based on 100 parts by weight of sludge or mud, solidification of sludge or mud becomes insufficient, and when heavy metals are contained, There is a possibility that it may be difficult to stably fix heavy metals. If the amount of phosphoric acid or phosphate added is 20 parts by weight with respect to 100 parts by weight of sludge or mud, the treated soil will have sufficient strength and the contained heavy metals will be fixed, so that 100 parts by weight of sludge or mud The addition of more than 20 parts by weight of phosphoric acid or phosphate per part is usually unnecessary.

There is no particular limitation on the form of the sludge or mud modifier of the present invention. For example, a one-part type modifier obtained by mixing water glass and phosphoric acid or phosphate may be used. It is also possible to use a two-part modifier composed of water glass and phosphoric acid or phosphate. The one-part type modifier may be a drug obtained by adding phosphoric acid or phosphate to water glass and mixing the same, or a phosphoric acid may be added to a diluent obtained by further adding water to water glass. Alternatively, the drug may be dissolved by adding a phosphate. The two-part modifier may be a combination of a first part composed of water glass or a diluent thereof and a second part composed of phosphoric acid, phosphate or an aqueous solution thereof. Among these modifiers, the two-part type modifier can be selected arbitrarily at the time and amount of addition of each agent, and has a large sludge or mud modifying effect. It can be suitably used. In the method for treating sludge or mud of the present invention, the order of adding water glass and phosphoric acid or phosphate is not particularly limited, and water glass and phosphoric acid or phosphate can be added simultaneously. The phosphoric acid or the phosphate can be added after the addition of water, or the water glass can be added after the addition of the phosphoric acid or the phosphate. Among these addition methods, a good modifying effect can be obtained by simultaneously adding water glass and phosphoric acid or phosphate, but one of water glass and phosphoric acid or phosphate is added first. And then kneading with the other added, since each agent can be homogeneously dispersed and a higher reforming effect can be obtained, which is preferable. There is no particular limitation on the method of kneading sludge or mud to which water glass and phosphoric acid or phosphate are added, and an appropriate construction machine or the like can be selected according to the properties and amount of sludge or mud to be treated. . Examples of such a machine include a power shovel, a drag shovel, a backhoe, and a twin-screw kneader. In the method of the present invention, the ratio of the added amounts of water glass and phosphoric acid or phosphate is not particularly limited, but is added so that the pH of the treated soil obtained by the immobilization treatment becomes 5.8 to 8.6. It is preferred to select the ratio of the quantities. The ratio of the added amount of water glass and phosphoric acid or phosphate can be appropriately selected according to the type of water glass, the type of phosphoric acid or phosphate, the soil of sludge or mud, and the like. When Glass No. 3 and 75% by weight of orthophosphoric acid are used, in many cases, this condition is satisfied with the addition volume ratio of 4: 1 to 5: 1. Treated soil
By selecting the addition amount of water glass and phosphoric acid or phosphate so that the pH becomes 5.8 to 8.6, gelation proceeds at an appropriate rate, and a treated soil with high strength and easy handling is obtained. Also, the heavy metals are securely fixed.

In the method of the present invention, it is preferable to use a water-absorbing substance or a water-soluble polymer compound in combination with water glass and phosphoric acid or phosphate, because the strength of the treated soil is increased. Such water-absorbing substances include coconut dust (C
oil pits), inorganic porous substances, swellable clay minerals, and the like. Coco Pit
h) is a short fibrous or powdery substance, usually light brown or dark brown, which remains after the fiber is collected from the mesocarp of the coconut. Its properties and the like are described in Alan W.S. Me
By Erow, "TropicLine" Volume 6,
No. 2, pages 1 to 4 (1993), it is a porous material containing a large amount of lignin and cellulose and having water absorption. Coco Pit
h) has a water-absorbing effect as its characteristic, and exhibits a reinforcing effect due to the fiber structure. Excavated mud with coconut dust (Co
By adding ir pit), moisture in the excavated mud is rapidly absorbed and the treated soil is reinforced by the fiber, so that a solidified treated soil having high strength and easy to handle is obtained. Examples of the inorganic porous substance include zeolite, perlite, vermiculite, fired diatomaceous earth, fired clay mineral porous material, fired calcium silicate, and the like. Examples of the swellable clay mineral include montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, stevensite, and swellable mica. Examples of the water-soluble polymer compound include natural water-soluble polymer compounds such as starch, mannan, sodium alginate, locust bean gum, guar gum, pectin, xanthan gum, dextran, gelatin, ramzan gum, gellan gum, viscose, methyl cellulose, ethyl cellulose, Semi-synthetic water-soluble polymers such as carboxymethylcellulose, hydroxypropylcellulose, cationized cellulose, pregelatinized starch, carboxystarch, dialdehyde starch, cationized starch, dextrin, British gum, cationized guar gum, anionized guar gum, and methylglycol chitosan Compound, polyvinyl alcohol, polyvinylpyrrolidone, poly (meth) acrylamide, poly (meth) acrylate, polyethylene oxide Id, synthetic polymer compounds such as polyvinyl methyl ether, and the like.
The water-soluble polymer compound has a thickening effect, a water absorbing effect, a coagulation effect, and the like, and when included in the sludge or mud modifier of the present invention, effectively turns the sludge or mud into a treated soil having a large strength. Convert.

In the method of the present invention, when a water-absorbing substance or a water-soluble polymer compound is used in combination with water glass and phosphoric acid and / or phosphate, water glass, water glass,
Phosphoric acid or phosphate, a water-absorbing substance or a water-soluble polymer compound can be mixed and used as one agent.
Water glass, phosphoric acid or phosphate, a water-absorbing substance or a water-absorbing substance is added so that phosphoric acid or a phosphate and a water-absorbing substance are mixed and added as one agent to sludge or mud, and then water glass is separately added. Among the reactive high molecular compounds, any two types of mixtures and the remaining one type can be used as a two-part type. Furthermore, it is also possible to use water glass, phosphoric acid or phosphate, a water-absorbing substance or a water-soluble polymer compound as a three-part type in which sludge or mud is separately added. Among these addition methods, in order to uniformly mix the modifier into the sludge or mud, it is preferable to use a three-part type, and in particular, water glass and at least one of phosphoric acid and phosphate. Before adding either one, it is preferable to add a water-absorbing substance or a water-soluble polymer compound. Before adding both water glass and phosphoric acid or phosphate, the sludge or mud is not gelled, so that the water-absorbing substance and the water-soluble polymer compound can be easily and uniformly mixed. In the present invention, when the water-absorbing substance is added, the amount of addition depends on the soil quality or water content of the sludge or mud and is not particularly limited, but is usually 0.01 to 20 parts by weight per 100 parts by weight of the sludge or mud, Preferably it is 0.05 to 10 parts by weight. According to the sludge or mud modifier and treatment method of the present invention, when a heavy metal is present in the sludge or mud, the heavy metal is ion-bonded to the silicate gel and immobilized. Since it becomes a salt or a hydroxide and is adsorbed and fixed on the surface and inside of the silicate gel, the heavy metal in the sludge or mud is stabilized and can be reliably fixed to prevent elution.

[0010]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In the examples and comparative examples, the amount of copper eluted was determined by the Prime Minister's Ordinance No. 66 of 1972, “Prime Minister's Ordinance Prescribes the Method for Testing the Amount of Copper Concerning Designated Requirements for Agricultural Land Soil Contamination Countermeasures Area”. Measured by the 1M HCl extraction method. The amount of lead eluted was determined by the Environment Agency Notification No. 46, 1991, "Environmental Standards for Soil Pollution".
The measurement was carried out according to the method specified in. Example 1 Dredged soil generated at a river dredging site was treated.
This dredged soil contains 83% by weight of sand (75 μm to 2 mm), 10% by weight of silt (5 to 75 μm), and 3% by weight of clay (5 μm or less), has a water content of 36.5% by weight, and has a copper content of 36.5% by weight. The elution amount was 150 ppm. 1,500 g of the dredged soil is taken in a mortar mixer, 70 g of water glass (No. 3) is added, and the mixture is rotated at a low speed (revolution 62 rpm, rotation 140 ± 5 rpm).
After kneading for 0 second, 14 g of orthophosphoric acid (75% by weight) was added, and kneading was further performed for 30 seconds at low speed rotation. One hour after the addition of orthophosphoric acid, J was added using a cone penetrometer.
Cone index (static penetration resistance) according to IS A 1220
Was 2.3 kgf / cm ² . 0.1M
When the amount of copper eluted from the treated soil was measured by the HCl extraction method, it was 5 ppm. The pH of the treated soil was 8.1. Example 2 1,500 g of the same dredged soil as in Example 1 was placed in a mortar mixer, and 22.5 g of orthophosphoric acid (75% by weight) was added.
After kneading at low speed for 30 seconds, water glass (No. 3) 1
12 g was added, and the mixture was further kneaded at a low speed for 30 seconds.
One hour after the addition of water glass, the cone index was measured in the same manner as in Example 1 and found to be 4.5 kgf / cm ² . 0.1
When the amount of copper eluted from the treated soil was measured by the M HCl extraction method, the amount of elution was 2 ppm. The pH of the treated soil is 7.
It was 5. Example 3 The same operation as in Example 1 was repeated, except that 9.7 g of pyrophosphoric acid (95% by weight) was added instead of 14 g of orthophosphoric acid (75% by weight). One hour after the addition of pyrophosphoric acid, the corn index was measured in the same manner as in Example 1, and it was 2.7 k.
gf / cm ² . When the amount of copper eluted from the treated soil was measured by a 0.1 M HCl extraction method, the amount of elution was 4 ppm. The pH of the treated soil was 7.9. Example 4 Water glass (No. 2) 7 instead of 70 g of water glass (No. 3)
The same operation as in Example 1 was repeated except that 0 g was added and 12.6 g of pyrophosphoric acid (95% by weight) was added instead of 14 g of orthophosphoric acid (75% by weight). One hour after the addition of pyrophosphoric acid, the corn index was measured in the same manner as in Example 1 and found to be 3.0 kgf / cm ² . When the amount of copper eluted from the treated soil was measured by a 0.1 M HCl extraction method, the amount of elution was 4 ppm. The pH of the treated soil was 8.2. Comparative Example 1 Instead of 14 g of orthophosphoric acid (75% by weight), sulfuric acid (97%) was used.
The same operation as in Example 1 was repeated, except that 11.5 g was added. The cone index measured one hour after the addition of sulfuric acid was 0.7 kgf / cm ² . The copper elution amount of the treated soil measured by the 0.1M HCl extraction method was 70 ppm.
The pH of the treated soil was 6.1. Table 1 shows the results of Examples 1 to 4 and Comparative Example 1.

[0011]

[Table 1]

In Examples 1 to 4 using the modifier and the treatment method of the present invention, the cone index of the treated soil is 2.3 to 4.5 kgf / hour after one hour of adding and kneading the modifier. cm ² , which is a state having sufficient strength. In addition, the copper elution amount is a sufficiently low value of 2 to 5 ppm. On the other hand, in Comparative Example 1 using water glass and sulfuric acid, the treated soil after one hour had a cone index of 0.7 kgf / cm ² , lacking strength, and the amount of copper eluted was as large as 70 ppm. Example 5 107 g of powdered clay [Marunaka Shirato Co., Ltd., Silt F], 107 g of standard sand for cement test [from Toyoura, Yamaguchi Prefecture], and lead chloride 2
107 ml of tap water in which 0 mg was dissolved was kneaded to prepare 300 g of test mud having a water content of 50% by weight. The amount of lead eluted from the test mud was 10 ppm. 17 g of water glass (No. 3) was added to the test mud and stirred with a spatula for 30 seconds, and then 3 g of aluminum dihydrogen phosphate
And stirred with a spatula for another 30 seconds. One hour after the addition of aluminum dihydrogen phosphate, the cone index was measured using a cone penetrometer according to JIS A1220 and found to be 3.5 kgf / cm ² . When the amount of lead eluted from the treated soil was measured by the test method of the Environment Agency Notification No. 46, it was 0.01 ppm or less. The pH of the treated soil was 8.2. Example 6 To 300 g of the same test mud as in Example 5, water glass (3
No. 17 g), stirred with a spatula for 30 seconds, and crushed with a coffee mill (Coir pit).
h) Add 2 g and stir with a spatula for 30 seconds, then add another 3 g of aluminum dihydrogen phosphate and add
Stir with a spatula for 0 seconds. The cone index measured one hour after the addition of aluminum dihydrogen phosphate was 5.5 kgf / cm
^{Was 2} . The amount of lead eluted from the treated soil measured by the test method of the Environment Agency Notification No. 46 was 0.01 ppm or less.
The pH of the treated soil was 8.1. Comparative Example 2 Instead of 3 g of aluminum dihydrogen phosphate, sulfuric acid (97
The same operation as in Example 5 was repeated, except that 2.8 g (% by weight) was added. The cone index measured one hour after the addition of sulfuric acid was 1.1 kgf / cm ² . The lead elution amount of the treated soil measured by the test method of Environment Agency Notification No. 46 was 0.8 ppm. The pH of the treated soil was 3.5. Comparative Example 3 To 300 g of the same test mud as in Example 5, 15 g of coconut crushed by a coffee mill was added.
Stir for 30 seconds with a spatula. The corn index measured one hour after the addition of the coconut dust was 1.8 kgf / cm ² . The lead elution amount from the treated soil measured by the test method of the Environment Agency Notification No. 46 was 0.02 ppm. The pH of the treated soil was 7.0. Table 2 shows the results of Examples 5 to 6 and Comparative Examples 2 to 3.

[0013]

[Table 2]

In Example 5 using the modifying agent and the treatment method of the present invention, the cone index of the treated soil was 3.5 kgf / cm ² one hour after the addition and kneading of the modifying agent. It is in a state having strength. The lead elution amount is below the regulation value of 0.01 ppm, which is a sufficiently low value. In Example 6, the corn index was increased to 5.5 kgf / cm ² by using coconut dust (Coir path), which is a natural organic water-absorbing substance. On the other hand, in Comparative Example 2 using water glass and sulfuric acid, the cone index of the treated soil after 1 hour was 1.1 kgf / cm ² and the strength was insufficient, and the regulated value was 0.8 ppm for the elution amount of lead of 0.8 ppm. Of 0.01 ppm. Further, as seen in Comparative Example 3, the strength of the treated soil is not sufficiently improved even when a large amount of coconut dust is added, but a small amount of coconut dust is used when water glass and phosphate are used together. Sufficient reforming effect can be exhibited even with the addition of.

[0015]

According to the present invention, mud generated at construction sites such as tunnel works, dredging works, construction works, sludge, sludge, or sludge generated at waterworks and sewage treatment plants can be reduced in a short time. The treated soil can be easily reused or disposed. Furthermore, when the sludge or mud contains heavy metal, the heavy metal can be safely immobilized and the elution of the heavy metal from the treated soil can be reliably prevented.

Claims (4)

[Claims] 1. A sludge or mud modifier comprising a combination of water glass and phosphoric acid and / or phosphate. 2. The sludge or mud modifier according to claim 1, wherein the sludge or mud contains a heavy metal. 3. A method for treating sludge or mud, comprising adding water glass and phosphoric acid and / or phosphate. 4. The method for treating sludge or mud according to claim 3, wherein the sludge or mud contains a heavy metal.