JPH0681363A - Dredging method - Google Patents

Abstract

PURPOSE:To prevent the pollution of the water quality by draining the water in a box frame on the deposition ground until the floating mud starts to be mixed, recovering the fine particles in the drain, putting and mixing a solidifying agent into the box frame, then dredging the solidified ground. CONSTITUTION:The water in the first box frame 24a is drained with a sand pump 31 until the floating mud starts to be mixed, then the water in the box frame 24a is fed to a processed water tank to store the upper layer A1 of the deposition ground A. A coagulant is put into the water tank, bubbles are fed to the bottom section of the water tank with a bubble generator, and floating objects on the water surface are dehydrated and recovered. A solidifying agent is put into the box frame 24a and mixed with a stirring machine, then the box frame 24a is lifted. The second box frame 24b is buried in the ground A, the same work is repeated, then the box frame 24b is lifted. The lower layer A2 of the solidified ground A is dredged with a power shovel 50, the dredged mud is dehydrated, a dehydrated cake is fed by pressure onto the ground, and a processed liquid is fed to the water tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dredging, dehydrating and pumping sludge accumulated in lakes, reservoirs, urban rivers, etc., and particularly to the diffusion of muddy water during dredging and the quality of water produced by dehydration treatment liquid. It relates to a construction method that can be applied when regulations such as pollution are strict.

[0002]

2. Description of the Related Art Generally, slurry-like sludge deposited on the bottom of a bay has various adverse effects on the surrounding environment such as offensive odor caused by gas generation, killing of cultured fish, and pollution of seawater. It is strongly desired to dispose of it. Therefore, conventionally, the sludge accumulated in a bucket or the like has been scooped up and carried to the land.

[0003]

However, fine particles having a low specific gravity in the accumulated sludge diffuse into water when scooped up in a bucket, and cannot be recovered well, and conversely spread pollution.

In the disposal process, it is necessary to dry the collected sludge to some extent and then transport it by truck, or prepare a special container for storing the sludge. It is preferable to reduce the water content by reducing the content as much as possible.

The present invention has been made paying attention to such a point, and the purpose thereof is to pump up the upper layer portion of the accumulated sludge and separate and collect fine particles from it. On the other hand, the lower layer part is solidified with a solidifying agent, then scooped up and dehydrated to reduce the water content and to be recovered.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the dredging method according to claim 1 is to install a box frame on the sedimentary ground and then drain the water in the box frame until the floating mud soil begins to mix. After that, the water in the box frame is sent to the treated water tank, and then fine particles are separated from the water in the treated water tank to be collected, and after the solidifying agent is put into the box frame and mixed, the box frame is pulled up, Then, the solidified ground is dredged, and then the dredged mud is dehydrated.

According to a second aspect of the dredging method of the present invention, in the step of separating the fine particles from the water in the treated water tank by collecting the fine particles from the water in the treated water tank, first, a coagulant is introduced, and then bubbles are generated, and then the water surface is formed. This is a configuration including a step of collecting the fine particles that have floated on the surface and performing a dehydration treatment.

The dredging method according to claim 3 is the dredging method according to claim 1, in which two box frames are provided side by side, each box frame is used alternately, and a plurality of independently operable boxes are provided around each box frame. The suspension means are connected.

According to a fourth aspect of the dredging method, in the dredging method of the first aspect, the dehydration treatment liquid produced in the step of dehydrating the dredged mud is sent to a treated water tank, and then fine particles are separated from the water in the treated water tank. It is configured to include a step of dehydrating the sediment that has settled in the treated water tank.

[0010]

According to the first aspect of the invention, the upper layer portion of the accumulated sludge is accumulated in the treated water tank, and the fine particles are separated and recovered from the accumulated water tank. The fine particles contain substances such as nitrogen and phosphorus. In that case, since the drainage work is carried out in the box frame, fine particles do not diffuse into the water.

Further, since the lower layer portion of the accumulated sludge is solidified and then scooped up, the sludge does not diffuse into water.
Moreover, since the solidified sludge is dehydrated, the water content at the time of recovery becomes low.

According to the second aspect of the present invention, when the coagulant is added, the organic substances in the water are hydrolyzed and coagulate with each other to form flocs. When air bubbles are generated there, the flocs that have agglomerated rise to the surface of the water one after another. In that case, since a film of bubbles is formed under the flocs, the flocs do not settle, and therefore, when scraped by a scrubber or the like, organic substances and the like are collected. Then, if dehydration treatment is performed, the water content becomes low.

According to the invention of claim 3, two box frames are provided side by side.
Since each box frame is used alternately, it is possible to install the other box frame on the piled ground while treating the drainage and the like in one box frame.

Further, by independently operating each suspending means, the box frame can be installed in an inclined state according to the inclination of the piled ground.

According to the fourth aspect of the invention, the fine particles are recovered from the dehydration treatment liquid produced in the step of dehydrating the dredged soil and the remaining water is purified. Moreover, the sediment content in the treated water tank can also be collected by reducing the water content.

[0016]

EXAMPLES Examples of the present invention will be described below. 1 to 3 show a dredging vessel 10 for carrying out the dredging method of the embodiment. The dredging vessel 10 is composed of a work vessel located on the front side (left side in FIG. 1) and a propulsion vessel located on the rear side (right side in FIG. 1). Among them, the propulsion ship is provided with a device for changing the position of the ship. That is, 11 is a fixed pile that is erected so that it can slide up and down at the four corners of the propulsion ship. Reference numeral 12 denotes two movable piles, which are attached to a pair of slide devices 13 extending in the front-rear direction of the propulsion ship, respectively, and are also attached to the slide devices 13 so that they can slide up and down. ing. Therefore, with the fixed piles 11 lifted, the movable piles 12 are lowered and thrust into the underwater ground, and then the slide device 13
By sliding the moving pile 12 back and forth by the above, the dredger 10 is relatively moved to a desired position.

The work boat is provided with a ground partitioning device 20. That is, 21 is a hoist, and a pair of carriers that are movable in the front-rear direction are installed on this hoist. Each carrier is attached with four sets of suspending means 22 which can be operated independently. The suspending means 22 includes four winding mechanisms for winding the wire,
Each wire is provided with a wire that descends from each winding mechanism, a vibrator that is connected to a lower end of each wire, and a hook that is attached to each vibrator. Reference numerals 24a and 24b are first and second rectangular tubular box frames that are used alternately, and four hooks of one carrier are connected to the four corners of the first box frame 24a, and the second box frame 24b. 4 of the other carrier in the 4 corners
Two hooks are connected.

A particulate collection device 30 is provided on the ship. That is, 31 is a sand pump installed on the previous ship, and is a box frame 24a installed on the sedimentary ground,
The water in 24b is sucked in. A treated water tank 32 as shown in FIG. 4 is installed in the propulsion ship, and water is supplied from the sand pump 31. A charging device (not shown) for charging a coagulant is provided above the treated water tank 32.
A bubble generator 33 is installed on the side of the treated water tank 32 to supply extremely fine bubbles to the bottom of the treated water tank. A scraper (not shown) for scraping up floating objects on the water surface is provided above the treated water tank 32.

The work boat has a screw type agitator 40.
(Not shown) is provided. The stirrer 40 descends into the box frames 24a and 24b installed on the piled ground to stir the vicinity of the piled ground. Also on the workboat,
A device (not shown) for introducing the solidifying agent into the box frames 24a and 24b is provided. This solidifying agent is a silicic acid-based binder, and mainly contains an active silicic acid sol that emits an active silanol group. The activated silanol group causes a silanol dehydration condensation reaction to form a siloxane bond. Therefore, when this solidifying agent is added to sludge or the like, the sludge condenses while containing water and becomes a gel. The pH value of this condensate is 6 to 8 neutral, there is no risk of secondary pollution, and it is irreversible and does not cloud or diffuse in water.
If pressurized and dehydrated, it becomes a dehydrated cake, which can be used as soil for vegetation, for example.

On the other hand, a power shovel 50 equipped with a closed bucket is rotatably installed on the propulsion ship. Further, 60 is a press-type dehydrator provided on the propulsion ship,
A hopper 61 to which the dredged mud is supplied, and a main body 62 for compressing the dredged mud received from the hopper 61 to squeeze water.
It has and. The water discharged from the main body 62, that is, the dehydration treatment liquid is sent to the treatment water tank 32. Further, the propulsion ship is provided with a dehydrator (not shown) for dehydrating the sediment deposited in the treated water tank 32.

A delivery device 70 is provided with a belt conveyor 71 extending from the lower side of the dehydrator 60 to the upper rear side.
A hopper 72 that receives a delivery from this belt conveyor 71
And a vane type rotary pump 73 for pressurizing the delivered product from the hopper 72, and the rotary pump 7
A delivery pipe 74 connected to the discharge port 3 and extending to the land
And an air ejector 75 for supplying compressed air to the delivery pipe 74, and the dehydrated cake discharged from the dehydrator 60 is pressure-fed to the land. In addition, 91 is a power generation unit,
Reference numeral 92 is a hydraulic unit, and 93 is a compressor.

Next, the dredging method carried out by the dredger 10 will be described with reference to FIGS. 5 to 10. Dredge 1
0 sequentially moves from the right to the left in each figure, during which the sedimentation ground A is solidified, and thereafter the solidified sedimentation ground A is solidified.
Dredging. First, in the state shown in FIG. 5, the fixed pile 11 and the movable pile 12 are pushed against the ground A to fix the dredging tip 10. And the first one in place
The box frame 24a is moved forward by the hoist 21 (FIG. 6) and is lowered onto the piled ground A before the solidification treatment by the four sets of suspending means 22 and is vibrated by the four vibrators (FIG. 7). At this time, the box frame 24a passes through the upper layer A1 made of fine particles having a low specific gravity among the accumulated sludge,
It digs into the lower layer A2 below and is buried. At that time, 4
Since the pair of suspension means 22 can be operated independently,
The box frame 24a can be installed in an inclined state according to the inclination of the piled ground A, and can be used on the bottom of a bay in any terrain.

Next, as shown in FIG. 7, the sand pump 3
1, the water in the box frame 24a is drained until the floating mud begins to mix, and then the water in the box frame is sent to the treated water tank 32. As a result, the upper layer A1 of the sediment ground A becomes the treated water tank 32.
It will be stored in. Then, the fine particles are separated and collected from the water in the treated water tank 32. That is, a coagulant is charged from the charging device into the treated water tank 32 (for example, 50 to 100 ppm), extremely fine bubbles (for example, 3 microns) are supplied to the bottom of the treated water tank by the bubble generator 33, and the surface of the water is floated by the scraper. Objects are scraped.
The floating material is dehydrated and collected, while the treated water is discharged outside the ship.

On the other hand, as shown in FIG. 8, the first box frame 2
After adding the solidifying agent into 4a and mixing with the stirrer 40,
The first box frame 24a is filled with water and the box frame 24a is pulled up (FIG. 9). The solidified sedimentary ground A is solidified in a short time, for example, 10 to 15 minutes. In the meantime, as shown in FIG. 8, the second box frame 24b in the fixed position is lowered by the hoist 21 and the suspending means 22 onto the sedimentation ground A for solidification treatment, and is buried therein. Then, similarly to the first box frame 24a, the water in the box frame is drained, the fine particles are separated and collected from the remaining water in the treated water tank 32, and the solidifying agent is charged and mixed in the box frame ( (Figure 9). That is, each box frame 24
In this configuration, a and 24b are used alternately. When the above work is completed, the fixed pile 11 is lifted, the movable pile 12 is slid, and the dredging boat 10 is advanced to a desired position. And
The second box frame 24b is pulled up.

Next, the lower layer A2 of the solidified sedimentary ground A is dredged, and then the dredged mud is dehydrated. That is,
The lower layer A2 solidified by the power shovel 50 is dredged. The dredged mud is supplied to a press-type dehydrator 60 and separated into a dehydration cake and a dehydration treatment liquid, and the dehydration cake is pressure-fed to the land by a delivery device 70, while the dehydration treatment liquid is again supplied to the treatment water tank 32. Sent to. Also treated water tank 3
The sediment settled in 2 is sent to the dehydrator 60, and is separated into a dehydration cake and a dehydration treatment liquid in the same manner as above.

Therefore, in the above embodiment, the upper layer A1
Regarding the recovery of the soil, the floating material collected by the scraper is dehydrated to remove the upper layer A1 of the sediment ground A.
Fine particles containing substances such as nitrogen and phosphorus can be efficiently separated and recovered from the above, and these can be effectively reused. At this time, since the drainage work is performed while being surrounded by the box frames 24a and 24b, the fine particles do not diffuse into the water.

In this case, since a film of bubbles is formed under the flocs, the flocs do not settle, and therefore organic substances can be easily collected by scraping with a scrubber or the like. The water content can be lowered by dehydration treatment.

Regarding the lower layer A2, since it is solidified and then scooped up, sludge does not diffuse into water. Moreover, since the solidified sludge is dehydrated by the dehydrator 60, the water content at the time of recovery becomes low.

Further, since the respective box frames 24a, 24b are used alternately, it is necessary to install the other box frame on the piled ground while treating the drainage in one of the box frames. As a result, dredging work can be performed with good setup, and work efficiency is improved.

Further, by means of the respective suspension means 22, the box frame 2
4a and 24b can be installed in an inclined state according to the inclination of the sedimentary ground A.

Further, fine particles can be recovered from the dehydration treatment liquid produced in the step of dehydrating the dredged soil and the remaining water can be purified. Further, the sediment that has settled in the treated water tank 32 can also be collected by reducing the water content.

In the above embodiment, the step of separating and recovering the fine particles from the water in the treated water tank is carried out by first introducing a coagulant,
Next, the process was performed with the procedure of generating bubbles and then collecting the fine particles floating on the water surface and performing a dehydration treatment, but the fine particles may be separated and collected by another method such as filtration. Further, in the embodiment, two box frames are provided side by side, and each box frame is used alternately, and around each box frame,
I connected several hanging means that can work independently,
A single box frame may be lifted and lowered by a single suspending means. Further, in the example, the dehydration treatment liquid produced in the step of dehydrating the dredged sludge is sent to the treated water tank, and then fine particles are separated and collected from the water in the treated water tank, and the sediment deposited in the treated water tank is dehydrated. Although the processing step is provided, it is not always necessary to provide such a step.

[0033]

As described above, according to the dredging method of claim 1, the box frame is installed on the piled ground, and then the water in the box frame is drained until the mud soil begins to mix, and then the box frame. The water inside is sent to the treated water tank, and then the fine particles are separated from the water in the treated water tank and collected, and after the solidifying agent is put into the box frame and mixed, the box frame is pulled up and then the solidified ground Since the dredged soil is dehydrated, and then the dredged mud is dehydrated, fine particles containing substances such as nitrogen and phosphorus can be well recovered from the upper layer of the accumulated sludge without diffusing into the water, and the lower layer of the accumulated sludge can be collected. Since the water content can be collected without diffusing the part into water and the water content can be reduced, it is the most suitable as a construction method that can be applied especially when there are strict regulations on diffusion of turbid water during dredging and water pollution by dehydration treatment liquid.

Further, in the dredging method of claim 2, the step of separating and recovering the fine particles from the water in the treated water tank is performed by first introducing a flocculant, then generating bubbles, and then removing the fine particles floating on the water surface. Since the process is provided with a procedure of collecting and dehydrating, organic matter in water can be easily collected with a low water content.

Further, in the dredging construction method of claim 3, two box frames are provided side by side, the box frames are alternately used, and a plurality of suspending means which can be independently operated are provided around each box frame. Since it is connected, the dredging work can be done in good setup using two box frames, the work efficiency is improved, and the box frames can be installed in an inclined state according to the inclination of the piled ground, so that it can be installed on the bottom of any terrain. Can be used.

Further, in the dredging method of claim 4, the dehydration treatment liquid produced in the step of dehydrating the dredged mud is sent to the treated water tank, and then fine particles are separated from the water in the treated water tank to be recovered, Since it has a process to dehydrate the sediment that has settled in the treated water tank, it is possible to collect fine particles from the dehydrated liquid produced in the process of dehydrating the dredged mud, and to purify the remaining water and contribute to pollution prevention. Also, the sediment that has settled in the treated water tank can be collected by reducing the water content.

[Brief description of drawings]

FIG. 1 is a plan view of the dredger of the embodiment,

FIG. 2 is a vertical side view of the same.

FIG. 3 is a vertical sectional side view of the same main part,

FIG. 4 is a schematic explanatory view of a treated water tank of an example,

5 is a first explanatory view of the dredging method of the embodiment, FIG.

FIG. 6 is a second explanatory view of the dredging method of the embodiment,

FIG. 7 is a third explanatory view of the dredging method of the embodiment,

FIG. 8 is a fourth explanatory view of the dredging method of the embodiment,

FIG. 9 is a fifth explanatory view of the dredging method of the embodiment,

FIG. 10 is a sixth explanatory view of the dredging method of the example.

[Explanation of symbols]

 A sedimentary ground A1 upper layer A2 lower layer 10 dredger 20 ground partitioning device 22 suspending means 24a box frame 24b box frame 30 particle recovery device 32 treatment water tank 33 bubble generator 40 stirrer 60 dehydrator 70 transfer device

Claims (4)

[Claims] 1. A box frame is installed on the piled ground, and then the water in the box frame is drained until the floating mud begins to mix, and then the water in the box frame is sent to a treated water tank, and then the treated water tank. In addition to separating and collecting fine particles from the water of the above, after mixing the solidification agent by putting it in the box frame, the box frame is lifted up, then the solidified ground is dredged, and then the dredged mud is dehydrated. Dredging method. 2. The step of separating and collecting fine particles from the water in the treated water tank is provided with a step of first introducing a coagulant, then generating bubbles, and then collecting the fine particles floating on the water surface, followed by dehydration treatment. The dredging method according to claim 1, which is a different process. 3. The dredging method according to claim 1, wherein two box frames are provided side by side, each box frame is alternately used, and a plurality of independently operable suspending means are connected around each box frame. . 4. The dehydration treatment liquid produced in the step of dehydrating the dredged mud is sent to a treated water tank, and then fine particles are separated and collected from the water in the treated water tank, and the sediment deposited in the treated water tank is dehydrated. The dredging method according to claim 1, further comprising a treatment step.