JPH0971966A - Method and facility for treating dredged mud - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dredge mud on the bottom of water without requiring the security of a site for treating dehydrated cake by dredging mud on the bottom of water, conducting coagulating treatment and dehydration treatment such as pressure dehydration and sedimenting generated cake onto the bottom of water. SOLUTION: Mud 2 deposited on the bottom of water in a water area 1 is dredged by a dredger 22, and mud is transferred into a mud storage tank 5. A coagulant is added to mud being forwarded from the mud storage tank 5 from a coagulant tank 6, and mud is sent into a coagulating tank 9 by a pump 8 in a mud feed pipe 7 while being inline-agitated by a line mixer. Mud sedimented and separated in the coagulating tank 9 is drawn out, and dehydrated by pressure by a filter press, a roll press, etc., 10. Dehydrated cake 11 is sunk on the bottom of water and finally disposed. Accordingly, nutrient salts are confined in dehydrated cake, eutrophication and poor oxygen condition are prevented, and the progress of water pollution is obviated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method and a facility for treating dredged mud for the purpose of improving the water quality of the sea, lakes and rivers.

[0002]

2. Description of the Related Art The sea, lakes and marshes and rivers are attracting attention as spaces for multipurpose use, including living and leisure, but on the other hand, eutrophication and hypoxia due to organic matter in closed water areas There is an urgent need to take measures against such water pollution.

Water pollution due to organic substances is largely caused by an excessive inflow load from land areas, and is gradually being improved by reduction of industrial wastewater and self-restraint of the use of organic detergents. Such organic substances are not decomposed and are deposited on the seabed to form a sludge layer called bottom sediment, from which nutrient salts such as nitrogen and phosphorus are eluted into water and become a factor to promote water pollution.

Therefore, by taking measures such as removing mud having a high organic matter content by dredging,
It is important to reduce the elution of nutrients from the sediment.

Here, when dredging the mud deposited on the bottom of the water, a large amount of excess water is sucked up together with the mud, and the water content ratio becomes extremely high. Therefore, it is necessary to separate and remove the surplus water from the mud soil by sun drying, dehydration treatment with a drain material, mechanical dehydration with a pressure dehydration device such as a filter press.

[0006]

However, even if mechanical dewatering is performed, a wide settling tank is required to separate a large amount of excess water contained in the dredged mud. Considering the land situation in recent years, it is extremely difficult to secure such a vast land, and the bad odor scattered around has become a bottleneck, making it difficult to install the facility.

Further, there has been a problem that it is difficult to secure a place for disposing a large amount of dehydrated cake produced in the final step of mechanical dehydration.

The present invention has been made in consideration of the above-mentioned circumstances, and it is possible to treat the dredged mud by treating the dredged mud without the need to secure a site for dewatering the dredged mud and a site for disposing of the dehydrated cake. It is an object of the present invention to provide a method and a treatment facility for dredged mud that can prevent the progress of pollution.

[0009]

In order to achieve the above object, the method for treating dredged mud according to the present invention comprises, as set forth in claim 1, dredging the mud deposited on the bottom of the water, and then dredging the mud. On the other hand, a water removal process including a coagulation sedimentation process using a coagulant and a pressure dehydration process is performed, and then the cake generated by the water removal process is submerged on the water bottom.

In addition, the method for treating dredged mud of the present invention is one in which the water removal treatment is performed on a floating structure floating on water.

Further, as described in claim 3, the treatment facility for dredged mud according to the present invention has a dredging device for dredging the mud accumulated on the bottom of the water and a storage mud for storing the dredged mud sent from the dredging device. A tank, a flocculation settling tank for flocculating the mud sent from the mud tank with a predetermined flocculant, and a pressure dehydrator for dewatering the flocculated mud under pressure on a predetermined floating structure. It was installed in.

In the method and treatment equipment for the dredged mud of the present invention, the dredged mud is subjected to water removal treatment including coagulation sedimentation using a flocculant and pressure dehydration. Then, the dehydrated cake generated by the treatment is submerged in the water bottom, for example, the original water bottom, for final disposal.

The dehydrated cake submerged in the bottom of the water is prevented from being dispersed in water by the effect of the coagulant and pressure dehydration,
It will not be mud again. Then, nutrient salts such as phosphorus and nitrogen are trapped in the dehydrated cake and do not elute in water. Therefore, if the sludge layer that promotes water pollution is treated as described above and submerged in the original state of the dehydrated cake at the bottom of the water, it is not necessary to newly secure a disposal site for the dehydrated cake, and eutrophication of the water area, The progress of water pollution such as deoxidation is prevented.

Here, when the water removal treatment is performed on the floating structure floating on the water, the problem of securing land on land is also solved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method for treating dredged mud and a treatment facility according to the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a flow chart showing a procedure for performing a method for treating dredged mud according to the present embodiment, and FIG. 2 is a conceptual diagram showing equipment for performing a series of treatments. . As can be seen from these figures, in the processing method according to this embodiment, first, as shown in FIG.
The mud 2 deposited on the bottom of the water 1 such as the sea, lakes and rivers is dredged by the dredger 3 (FIG. 1, step 101). For dredging, use a pump-type high-concentration dredger that is capable of high-concentration and stable dredging. By adopting such a high-concentration dredger, the amount of surplus water contained in the dredged mud is minimized,
The dredged mud can be fed to and stored in a closed mud storage tank described later without requiring a large-scale storage space such as a coagulation sedimentation basin. Therefore, a series of processes including a coagulation sedimentation process and a dehydration process, which are post-processes, can be processed in a closed space, and it is possible to solve the problem of odor scattering, and to eliminate deodorant and elution control. It becomes easier to make the dredged mud soil harmless by mixing agents.

Next, the dredged mud is transferred to the mud storage tank 5 installed on land through the mud sending pipe 4 and temporarily stored in the tank (step 102). The mud storage tank 5 is composed of a sealed tank body, a stirring blade arranged inside the tank body, a drive mechanism (not shown) for driving the stirring blade, and the like, and temporarily stores the dredged mud without scattering a bad odor. You can do it. Further, if the concentration in the tank 5 is controlled by a densitometer and the dredging is temporarily stopped or restarted, the concentration in the tank can be stabilized.

Since the mud with a low water content ratio is stored by using a high-concentration dredger, the tank capacity of the mud storage tank 5 is relatively small, but the processing capacity of the dredger 3 is large. In this case, a plurality of mud storage tanks 5 may be installed. Further, before the dredged mud is transferred to the mud storage tank 5, it may be screened in advance so as to selectively remove the earth and sand having a relatively large particle size.

Next, the coagulant stored in the coagulant tank 6 is added to the mud sent from the mud storage tank 5, and the coagulant is stirred in the pipe with, for example, a line mixer, and then through the mud pipe 7. The pump 8 sends the slurry to a coagulation / sedimentation tank 9 such as thickener, in which the mud is coagulated and settled (Step 1
03).

As the coagulant, for example, an aluminum-based coagulant such as aluminum sulfate called a sulfuric acid band or polyaluminum chloride called PAC or a calcium-based coagulant such as slaked lime is used in an amount of 10 to 15 per ton of dry weight.
Add about 0 kg.

If desired, deodorants and additives for preventing the elution of harmful metal ions may be added. For example, when the cause of odor is weakly acidic hydrogen sulfide, cement or slaked lime is added to make the pH alkaline,
Deodorization can be achieved by adding hydrogen peroxide to oxidize the sulfur content. Further, if it is desired to suppress the elution of iron, manganese, etc., the pH may be made alkaline with cement, lime, etc.

Next, the mud that has settled in the flocculation settling tank 9 is drawn out and transferred to a mechanical dewatering apparatus 10 such as a filter press or roll press for pressure dewatering (step 104). The supernatant water of the coagulating sedimentation tank 9 is discharged to the original water area.

Next, as shown in FIG. 2 (b), the dehydrated cake 11 produced in the dehydration step is conveyed to the original water body 1 by using, for example, the belt conveyor 12 and the ship 13, and it is submerged in the bottom of the water to finally finish. It is discarded (step 105).

Here, the dehydrated cake 11 sunk on the bottom of the water
The coagulation treatment and the pressure treatment suppress the dispersion in water, and do not make mud again. Then, nutrient salts such as phosphorus and nitrogen are trapped in the dehydrated cake and are less likely to be eluted in water.

As described above, according to the method for treating dredged mud according to the present embodiment, even in the sludge layer which promotes water pollution, the coagulant is added to the sludge layer as in the present embodiment. Then, if this is dehydrated under pressure and submerged as it is in the dehydrated cake, it is possible to prevent the nutrient salt from being eluted into water.

Therefore, it is possible to prevent the progress of water pollution such as eutrophication and hypoxia in the water area without having to newly secure a disposal site for the dehydrated cake. In addition, not only nutrient salts but also harmful metal ions can be prevented from being eluted.

The capacity of the dehydrated cake is greatly reduced because the original sludge is mechanically dehydrated, and there is no fear that the effective water storage amount will be decreased by sinking the cake.

(Second Embodiment) Next, a method and equipment for treating dredged mud soil according to a second embodiment will be described. It should be noted that substantially the same devices and the like as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 3 is a flow chart showing the procedure for performing the method for treating dredged mud according to this embodiment, and FIG. 4 is a conceptual diagram showing the equipment for performing these treatments. As can be seen from these figures, in the treatment method according to the present embodiment, first, the treatment facility 21 for dredged mud shown in FIG. 4 is floated on the water surface and towed to a predetermined water area 1 (FIG. 3,
Step 111).

The treatment facility 21 for the dredged mud comprises a dredging device 22 for dredging the mud 2 deposited on the bottom of the water, a mud tank 5 for storing the dredged mud sent from the dredging device 22, and the mud tank 5. A coagulant settling tank 9 for coagulating and sedimenting the mud sent from the coagulant with a predetermined coagulant, and a coagulant tank 6 storing the coagulant
And a pressure dewatering device 1 for dewatering the coagulated and sedimented mud under pressure
0 is installed on the floating structure 23. The floating structure 23 can be manufactured by appropriately connecting concrete blocks or hollow steel pipes, for example.

As the dredging device 22, a device capable of dredging with high concentration and stability is adopted. By adopting such a high-concentration dredging device, the amount of surplus water contained in the dredged mud can be minimized, and the dredged mud can be supplied to a closed-type storage tank without requiring a large-scale storage space such as a coagulation sedimentation basin. It can be sent and stored. Therefore, a series of processes including a coagulation sedimentation process and a dehydration process, which are post-processes, can be processed in a closed space, and it is possible to solve the problem of odor scattering, and to eliminate deodorant and elution control. It becomes easier to make the dredged mud soil harmless by mixing agents.

Next, the mud accumulated on the bottom of the water is dredged by the dredging device 22 (step 112), and subsequently, the dredged mud is transferred to the mud storage tank 5 and temporarily stored in the tank (step 113). .

Before the dredged mud is transferred to the mud storage tank 5, it may be screened in advance to select and remove earth and sand having a relatively large particle size.

Next, the coagulant stored in the coagulant tank 6 is added to the mud sent from the mud storage tank 5, and the coagulant is stirred in the pipe with, for example, a line mixer, and then, through the mud pipe 7. The pump 8 sends the slurry to a coagulation / sedimentation tank 9 such as thickener, in which the mud is coagulated and settled (Step 1
14).

The aggregating agent is almost the same as that in the above-mentioned embodiment, and therefore its explanation is omitted. If necessary, a deodorant or an additive that prevents the elution of harmful metal ions may be added, but the description thereof will be omitted for the same reason.

Next, the mud that has settled in the flocculation settling tank 9 is drawn out and transferred to a mechanical dewatering apparatus 10 such as a filter press or roll press for pressure dewatering (step 115). The supernatant water of the coagulating sedimentation tank 9 is discharged to the original water area.

Next, the dehydrated cake 11 produced in the dehydration process is submerged at the bottom of the water for final disposal (step 116).

The series of steps described above are applied to the floating structure 2
Repeatingly changing the position of 3 little by little, the mud on the bottom of the water in a predetermined range is treated.

Here, the dehydrated cake 11 sunk on the bottom of the water
The coagulation treatment and the pressure treatment suppress the dispersion in water, and do not make mud again. Then, nutrient salts such as phosphorus and nitrogen are trapped in the dehydrated cake and are less likely to be eluted in water.

As described above, according to the treatment method and treatment equipment for dredged mud according to the present embodiment, even in the sludge layer which promotes water pollution, as in the first embodiment,
If a coagulant is added to this as in the present embodiment to cause coagulation and sedimentation, and this is dehydrated under pressure to be submerged in the original state of the dehydrated cake, it is possible to prevent the nutrient salt from being eluted into water. .

Therefore, it is possible to prevent the progress of water pollution such as eutrophication and hypoxia in the water area without having to newly secure a disposal site for the dehydrated cake. In addition, not only nutrient salts but also harmful metal ions can be prevented from being eluted.

The capacity of the dehydrated cake is greatly reduced because the original sludge is mechanically dehydrated, and there is no fear that the effective water storage amount will be reduced by sinking the cake.

Further, according to this embodiment, since the water removal treatment such as coagulation sedimentation and pressure dehydration is performed on the floating structure floating on the water surface, it is not necessary to secure a land on the land.

Further, according to the present embodiment, if the floating structure is towed and its position is changed in accordance with the treatment of the dredged mud, the dredged mud can be treated over a wide area.

In the present embodiment, the construction of the sedimentation basin is omitted due to the high concentration dredging. However, since it is a work at a place away from the coast and the bad odor is unlikely to be scattered to the urban area, a large floating body is required. An open type sedimentation tank may be installed in the structure and a large amount of excess water may be treated in the sedimentation tank.

[0046]

As described above, the method for treating dredged mud of the present invention comprises: dredging the mud deposited on the bottom of the water, and then subjecting the dredged mud to a coagulation sedimentation treatment using a coagulant and pressurization. The water removal process including the dehydration process was performed, and then the cake generated by the water removal process was sunk to the bottom of the water. Therefore, it is not necessary to secure a new disposal site for the dehydrated cake. Can be stopped.

Further, the treatment facility for dredged mud of the present invention comprises a dredging device for dredging mud deposited on the bottom of the water, a storage tank for storing the dredged mud sent from the dredging device, and the mud tank. Since the coagulation sedimentation tank that coagulates and sediments the sent mud with a prescribed coagulant and the pressure dewatering device that pressurizes and dehydrates the coagulated and sedimented mud are installed on the prescribed floating structure, the dredged mud It is possible to prevent the progress of water pollution by treating the dredged mud without having to secure a site for the dehydration treatment or a disposal place for the dehydrated cake.

[0048]

[Brief description of drawings]

FIG. 1 is a flowchart showing a method for treating dredged mud according to the first embodiment.

FIG. 2 is a conceptual diagram showing equipment for implementing the method for treating dredged mud according to the first embodiment.

FIG. 3 is a flowchart showing a method for treating dredged mud according to the second embodiment.

FIG. 4 is a conceptual diagram showing equipment for implementing the method for treating dredged mud according to the second embodiment.

[Explanation of Codes] 3 Dredger 5 Mud Tank 6 Coagulant Tank 9 Coagulation Sedimentation Tank 10 Pressurized Dewatering Device 11 Dewatering Cake 21 Processing Facility 22 Dredging Device 23 Floating Structure

Claims (3)

[Claims] 1. Muddy soil deposited on the bottom of the water is dredged and then
Performing moisture removal treatment including coagulation sedimentation treatment using a flocculant and pressure dehydration treatment on the dredged mud, then,
A method for treating dredged mud, characterized in that the cake produced by the water removal treatment is submerged at the bottom of the water. 2. The method for treating dredged mud according to claim 1, wherein the moisture removal treatment is performed on a floating structure floating on water. 3. A dredging device for dredging the mud deposited on the bottom of the water, a mud tank for storing the dredged mud sent from the dredging device, and a predetermined flocculant for the mud sent from the mud tank. A treatment facility for dredged mud, characterized in that a flocculation settling tank for flocculating and settling in step 2 and a pressure dehydrator for dewatering the coagulated and settled mud under pressure are installed on a predetermined floating structure.