JPH0947792A - Treatment of waste muddy water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating waste muddy water capable of being easily applied on the waste muddy water generating site, by which sediment is easily separated from the waste muddy water, good in the handleability of the separated sediment, safety and reutilizability, with the cost of carrying it out and treatment reduced and without need to secure a reclaimed land. SOLUTION: At least one kind of waste muddy water conditioner selected from a group consisting of flocculant, dispersant, concrete retarder and pH regulator is added to the waste muddy water contg. sediment to be separated, the waste muddy water added with the conditioner is separated by a separator into sediment and muddy water, a flocculant is added to the separated muddy water to separate the contained solid, the muddy water contg. the flocculated solid is separated by a dehydrator into dehydrated cake and water, and the solid and water are separated and recovered from the waste muddy water on the waste muddy water generating site.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating waste mud, and more particularly to a method for efficiently treating waste mud generated in civil engineering / construction works, especially waste mud containing hydraulic cement.

[0002]

2. Description of the Related Art In recent years, the amount of waste mud generated in civil engineering and construction works such as underground excavation, ground improvement and dredging has been increasing. Since such waste mud water contains a large amount of water and has high fluidity, it has conventionally been carried out from the waste mud generation site using a special vehicle such as a vacuum truck, and coagulated, dehydrated, and solidified at the intermediate treatment plant. After the treatment, etc., they were landfilled at the final disposal site or dumped in the ocean. However, there is a problem that it takes a large amount of money to carry out with a special vehicle such as a vacuum vehicle, and it is becoming difficult to secure a final disposal site, and from the viewpoint of environmental protection, dumping into the sea is prohibited. Therefore, it is desired to eliminate or reduce waste as much as possible.

For this reason, various methods have been studied for carrying out the waste mud after carrying out some volume reduction processing at the site where it is generated. The volume reduction treatment is performed, for example, by separating sedimentable large-particle-size solids (hereinafter referred to as earth and sand) such as gravel and sand, and then combining operations such as agglomeration, dehydration, and solidification of fine particle solids. It is being appreciated. According to this method, since the liquidity of the waste has disappeared and the amount is small, it is possible to carry out using a cheap dump truck, and the number of wastes is small, so the carrying out cost is low. Can be reduced. In addition, the amount of waste that requires landfill processing is reduced, which is advantageous in terms of processing costs and landfill site reservation.

[0004]

However, in such a conventional waste mud treatment method for performing volume reduction treatment, depending on the characteristics of the waste mud, the operation of separating the sediment cannot be performed well, or the separated sediment may not be removed. It was often difficult to handle. In particular, waste mud water generated by the injection mixing treatment method that injects a hardening material liquid containing hydraulic cement into the ground to mix it with the soil to form a hardened body and strengthen the ground, tends to be difficult to separate the soil . As a result, the processing capacity of the waste mud decreases, and it becomes impossible to completely process the generated waste mud at the site, and when trying to secure the processing capacity, the equipment becomes large, and a large amount of equipment cost and a vast treatment site are required. There was a problem that

Further, the separated earth and sand cannot be reused as concrete aggregate because it is difficult to handle because a large amount of small particle substances such as cement, clay and silt adhere to it, and moreover, it is strongly alkaline derived from the adhered cement. Therefore, in terms of safety and health, and from the viewpoint of environmental protection, there is a problem that it cannot be reused as backfilled soil and must be disposed of as industrial waste.

The object of the present invention is to improve the above-mentioned problems in separating and recovering solids and water from waste mud containing soil, to easily implement the method at the waste mud generation site, and to separate sediment from waste mud. Provides a treatment method for waste mud water that is easy, has good handleability, safety, and reusability of separated sediment, reduces transportation and treatment costs, and reduces the need to secure landfill sites. To do.

[0007]

Means for Solving the Problems The inventors of the present invention conducted research to solve the above-mentioned problems, and after adding the waste mud conditioner specified in the present invention to the waste mud containing soil, Sediment and mud water is separated by a sediment separation device, and a coagulant is added to the separated mud water to agglomerate solid matter contained in the mud water,
Then, the muddy water containing the aggregated solids is separated into dehydrated cake and water by using a dehydrator, by performing a process consisting of a series of steps, it is easy to separate the sediment from the waste mud water and the decrease in the processing capacity is less likely to occur. The compact and inexpensive treatment equipment can efficiently reduce the amount of waste mud in a limited place on the construction site, and it is easy to carry out and reclaim the treated matter. , Clay, silt,
Since the amount of cement adhered is small, handling and safety
It was found that the reusability was good.

The present invention relates to a method of treating waste mud water for separating and recovering solids and water from waste mud water containing sediment, wherein the waste mud water before the sediment separation treatment contains a flocculant, a dispersant, and a cement hardening retarder. And a step of separating at least one waste mud adjusting agent selected from the group consisting of a pH adjusting agent, and separating the waste mud containing the waste mud adjusting agent into sediment and mud by a sediment separating device, and A step of adding a flocculant to the muddy water to cause the solid content contained in the muddy water to flocculate, and a step of separating the muddy water containing the flocculated solid content into a dehydrated cake and water by a dehydrator are performed, and a treatment consisting of the series of steps is performed. A method for treating waste mud water, which is characterized in that. "

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The waste mud water targeted by the present invention is, for example, waste mud water containing earth and sand generated in underground excavation, ground improvement, civil engineering / construction work such as dredging, and has a particle size of 74 μm.
Includes solids (soil and sand) that have a relatively large particle size and a sedimentation property such as gravel and sand that are m or more, and substances that have a relatively small particle size and that are difficult to sediment such as silt and clay that have a particle size of less than 74 μm. .

Further, in the injection mixing treatment method in which a hardening material liquid containing hydraulic cement is injected into the ground to mix with soil to form a hardened body to strengthen the ground, a strong alkaline waste mud containing cement particles is generated. Although generated, the method of the present invention is suitable for treating such waste mud water.

FIG. 1 is an explanatory diagram showing the flow of steps of the method for treating waste mud water according to the present invention. In the processing method of the present invention,
First, at least one type of waste mud conditioner selected from the group consisting of a flocculant, a dispersant, a cement hardening retarder and a pH adjuster is added to waste mud containing soil. Then, as shown in Fig. 1, the waste mud containing the waste mud conditioner is separated into sediment and mud using a sediment separator (sediment separation step).
Next, a coagulant is added to the separated muddy water to agglomerate the solid content contained in the muddy water (coagulation treatment step), and then the muddy water containing the agglomerated solid content is converted into dehydrated cake and water using a dehydrator. Separation (dehydration treatment step) is performed by a series of steps.

The treatment method of the present invention is preferably carried out at or near the site of the generation of waste mud, and the effect of the present invention becomes more remarkable. The waste mud water generated at the site of civil engineering / construction work may be stored in an appropriate facility before applying the treatment method of the present invention.

In the method of the present invention, the waste mud conditioner added to the waste mud water is a group consisting of (A) a flocculant, (B) a dispersant, (C) a cement hardening retarder, and (D) a pH modifier. It is at least one selected from.

(A) The aggregating agent is not particularly limited, and examples thereof include cationic, anionic, nonionic or amphoteric polymer-based aggregating agents, aluminum sulfate, ferrous sulfate and ferric sulfate. Inorganic flocculants such as iron, ferric chloride, sodium aluminate, and polyaluminum chloride are included, and one or more of these may be used.

The optimum amount of the flocculant to be added cannot be generally stated because the optimum range varies depending on the property of the target waste mud water and the type of the flocculant to be used, but the inorganic flocculant is added per 100 parts by weight of the solid content in the waste mud water. The amount of the agent may be 0.1 to 10 parts by weight, and the amount of the polymeric flocculant may be 0.005 to 3 parts by weight.

The coagulant used may be in the form of powder, normal phase or reverse phase emulsion.
In the case of an emulsion, it can be added as it is. In the case of powder, it is desirable to dissolve it in water in advance and add it as an aqueous solution.

It should be noted that, depending on the nature of the waste mud, relatively large agglomerates are formed when a polymer-type aggregating agent is used,
Although it tends to be discharged together with the sediment in the sediment separation process, the load in the coagulation process and the dehydration process is reduced,
The handleability of the separated sediment may be deteriorated and its use may be limited. In such a case, it is preferable to use an inorganic flocculant or a polymer flocculant having a relatively small molecular weight.

(B) The dispersant is not particularly limited, and various surfactants such as anionic surfactant, cationic surfactant, amphoteric surfactant or nonionic surfactant are used. You can

Further, when the waste mud contains hydraulic cement, it is used as a cement water reducing agent or a cement fluidity improver, and it is used as a melamine sulfonic acid formalin condensate, a naphthalene sulfonic acid formalin condensate, a lignin sulfonate, an oxy ester. Organic acid salt, alkylallyl sulfonate,
Polyoxyethylene alkyl allyl ether, polyol condensate, sulfonate of higher polyhydric alcohol, etc. are preferably used.

These dispersants may be used either individually or in combination of two or more. The addition amount of the dispersant may be appropriately set depending on the property of the target waste mud water and the concentration of solid content, but addition of a large amount is not preferable because it inhibits agglomeration in the subsequent aggregating step, Specifically, the range of 0.01 to 10 parts by weight is suitable per 100 parts by weight of the solid content in the waste mud water.

The cement retarder (C) is preferably used when the waste mud contains hydraulic cement. The cement hardening retarder is not particularly limited, and gypsum,
Inorganic compounds such as silica fluoride, phosphate, zinc oxide, zinc chloride, lead oxide, boron oxide, borax, lignin sulfonate, gluconate, polyol complex, oxycarboxylate, lactic acid, tartaric acid, citric acid Acids, 2-ketoglutaric acid, 2-ketogluconic acid, glucose, sucrose, sorbitol, pentaerythritol, and other organic compounds are included, and one or more of these can be used.

The addition amount of the cement hardening retarder may be appropriately set depending on the property of the target waste mud and the solid content concentration, but the range of 0.01 to 10 parts by weight per 100 parts by weight of the solid content in the waste mud is required. Appropriate.

(D) The pH adjusting agent is not particularly limited, and may be an acidic substance such as sulfuric acid, hydrochloric acid, acetic acid, sulfamic acid, carbon dioxide gas or an alkaline substance such as sodium carbonate, sodium hydroxide or lime. Including 1 type (s) or 2 or more types, respectively. Especially, when the waste mud contains cement, an acid is preferably used.

The addition amount of the pH adjusting agent may be appropriately set depending on the property and solid content concentration of the waste mud, and the pH of the waste mud after the addition is adjusted.
Is preferably added in a range of 5 to 9.

The above-mentioned various waste sludge conditioners may be added alone or in combination of two or more. The method for adding these waste mud water regulators to the waste mud water is not particularly limited, and it can be added and mixed by using a dedicated addition mixing tank or line mixer, and the sediment separation used in the sediment separation step. You may add and mix in an apparatus. Considering that the treatment is performed in a limited place on site, it is preferable to use a device that is as small and simple as possible.

By adding a waste mud water conditioner to the waste mud water, it becomes easier for the soil to be separated and the deterioration of the waste mud water treatment capacity is suppressed. In addition, the separated sediment reduces the amount of small-particle substances such as clay, silt, and cement that adhere, thus improving safety,
Improves handling and reusability.

In the method of the present invention, the sediment separating device used in the sediment separating step is preferably a mechanical separating system for forcibly separating the sediment, and the treatment capacity is 10 m ³ or more per hour on the basis of the amount of waste mud. Is desirable. The sedimentation device of natural sedimentation method using sand pit and sand tank
Since the separation requires a long time, the generated waste mud cannot be immediately treated on the site, and a large treatment space is required on the site to enhance the treatment capacity, which is not practical.

The sediment separating apparatus used in the method of the present invention includes, for example, a vibrating screen, a rotary classifier, a spiral classifier, a rake classifier, a cyclone classifier, a spiral swirl classifier, a circular screen and the like. It can be appropriately selected depending on the nature of the waste mud water to be treated, the size of the sediment separation, and the like.

In the sediment separating step in the method of the present invention,
It is preferable to use a device that can separate gravel and sand separately. This makes it easy to use gravel for concrete aggregates and the like, and sand for various cushioning materials, leveling materials, etc., and widens the range of reuse. As such a sediment separating device, any one of the above-mentioned devices may be used alone as long as it has a plurality of separating sizes, and a plurality of devices having different separating sizes may be used in combination.

In the aggregation treatment step in the method of the present invention,
Introduce mud water containing fine particle solids from which sediment has been separated and removed in the sediment separation step into a coagulation tank or other coagulation treatment facility and add a coagulant and stir, or mix mud water and a coagulant using a line mixer. , Agglomerate solids contained in muddy water. It is also possible to separately provide a coagulating sedimentation tank to separate clear water and reduce the load in the dehydration treatment step.

The aggregating agent used in this step is not particularly limited, and examples thereof include cationic, anionic, nonionic or amphoteric polymer aggregating agents, and
Inorganic flocculants such as aluminum sulfate, ferrous sulfate, ferric sulfate, ferric chloride, sodium aluminate, and polyaluminum chloride are included, and one or more of these may be used.
It can be appropriately selected and used depending on the property of the target waste mud, and for example, an inorganic flocculant and a polymer flocculant may be used in combination.

The optimum amount of the flocculant to be added cannot be generally stated because the optimum range varies depending on the property of the target waste mud water and the type of the flocculant used, but the inorganic coagulant is added per 100 parts by weight of the solid content in the waste mud water. The amount of the agent may be 0.1 to 10 parts by weight, and the amount of the polymeric flocculant may be 0.005 to 3 parts by weight.

The form of the aggregating agent to be used may be either powder or normal phase or reverse phase emulsion.
In the case of an emulsion, it can be added as it is. In the case of powder, it is desirable to dissolve it in water in advance and add it as an aqueous solution.

In the dehydration treatment step in the method of the present invention,
The solid content contained in the muddy water aggregated in the aggregation treatment step is dehydrated. The dehydrator used in this step is not particularly limited, and may be a filter press, a belt press,
Pressure dehydrator such as screw press, drum press, vacuum dehydrator such as oliver filter, belt filter, vacuum pressure dehydrator, centrifugal dehydrator, etc. It can be appropriately selected according to the rate.

The earth and sand separated in the earth and sand separation step may be landfilled, but depending on the size, concrete aggregate,
It can be reused as backfill soil, fill material, cushioning material, leveling material and the like.

The dehydrated cake obtained in the dehydration treatment step may be landfilled and discarded, but it can also be used for materials such as bricks, roof tiles, tiles, ceramics and ceramics. these,
A normal dump truck can be used to carry the separated sediment and dehydrated cake.

The treated water discharged from the dehydration treatment process may be subjected to treatment such as pH adjustment as necessary and discharged into the sea or river, but it is used as process water for civil works and waste mud treatment. can do. As the pH adjuster, the above-mentioned acidic substance or alkaline substance can be used.

Further, in the method of the present invention, various additives such as a dephosphorizing agent, a denitrifying agent, a cement hardening accelerator and a dehydrated cake solidifying agent are used depending on the properties of the waste mud water to be treated. You can also

An earth and sand separator used in the method of the present invention,
Considering the treatment at the waste mud water generation site, which is a preferred embodiment of the present invention, the flocculation device, the dewatering device, and other auxiliary devices are set as small and compact as possible so that they can be installed in the limited space of the treatment site. It is preferable.

[0040]

EXAMPLES Next, the present invention will be described in detail with reference to examples. The present invention is not limited to the examples below. Examples 1 to 5 and Comparative Example 1. As shown in Table 1, to the waste mud generated in the ground improvement work by the column jet grout method, various waste mud modifiers are added, and the waste mud added with the waste mud modifier is shown in the flow chart in FIG. Separation into sediment and muddy water using a vibrating screen as a sediment separation device, then an anionic polymer flocculant is added to the separated muddy water to agglomerate the solid content contained in the muddy water, and the muddy water containing the agglomerated solid content is removed. A process of separating the dehydrated cake and water was performed using a screw press as a dehydrator. For comparison, the waste mud without the addition of the waste mud conditioner was treated according to the examples.

The treated waste mud has a pH value of 12.2,
The composition per 00 parts by weight was as follows. Water content: 55 (parts by weight) Cement content: 10 Cohesive soil content: 15 Sand content: 15 Gravel content: 5 The results of evaluation of the separability of sediment and the state of adhesion of fine particles to the separated sediment are shown in Table 1. Shown in.

[0042]

[Table 1]

As shown in Table 1, when the treatments after the sediment separating step were carried out without adding the waste mud conditioner to the waste mud, the separability of the sediment was poor, and the separation The adhesion of fine particles was large (Comparative Example 1). On the other hand, when the waste mud containing the waste mud conditioner specified in the present invention is treated, the separability of earth and sand is good,
Further, the adhesion of fine particles to the separated sediment was small, and the handling of the sediment was improved (Examples 1 to 5).

[0044]

According to the treatment method of the present invention, the waste mud water,
It can be quickly separated into sediment, dewatered cake and water in a limited area of the outbreak site. Moreover, the separated solid matter, especially earth and sand, has improved safety, handleability, and reusability, which facilitates carrying out, final treatment, landfill site reservation, and the like.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a flow of steps of a method for treating waste mud water according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Doi 10-1 Daikokucho, Tsurumi-ku, Yokohama-shi, Kanagawa Nitto Chemical Industry Co., Ltd. Central Research Laboratory

Claims (3)

[Claims] 1. A method of treating waste mud water for separating and recovering solids and water from waste mud water containing sediment, wherein a coagulant, a dispersant, a cement hardening retarder and a pH adjuster are added to the waste mud water before the sediment separation treatment. At least one waste mud conditioner selected from the group consisting of agents, a step of separating the waste mud containing the waste mud conditioner into sediment and mud by a sediment separator, and aggregating the separated mud A step of aggregating the solid content contained in the mud water by adding an agent, a step of separating the mud water containing the agglomerated solid content into a dehydrated cake and water by a dehydrator, and performing a treatment consisting of the series of steps. Wastewater treatment method. 2. The method for treating waste mud water according to claim 1, wherein the waste mud water contains hydraulic cement. 3. The method for treating waste mud water according to claim 1, wherein the treatment comprising a series of steps is performed at the site where the waste mud water is generated.