JP2913632B2 - Dredging mud treatment method and treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a facility for treating dredged mud for improving the water quality of the sea, lakes, or rivers.

[0002]

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

[0003] Water pollution by organic matter is largely caused by excessive inflow load from the terrestrial area, and is being gradually improved by reduction of industrial wastewater and voluntary use of organic detergents. Such organic matter is deposited on the seabed without being decomposed, and forms a sludge layer called sediment. From the sludge layer, nutrients such as nitrogen and phosphorus are eluted into water and become a factor of promoting water pollution.

Accordingly, 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 sediment.

[0005] Here, when the mud accumulated on the water bottom is dredged, a large amount of surplus water is sucked up together with the mud, and the water content becomes extremely high. Therefore, it is necessary to separate and remove such surplus water from mud by sun drying, dehydration treatment with a drain material, mechanical dehydration with a pressure dehydrator such as a filter press, or the like.

[0006]

However, even when mechanical dewatering is performed, a wide sedimentation basin is required to separate a large amount of excess water contained in the dredged mud. In view of recent land conditions, it is extremely difficult to secure such a vast land, and at the same time, there has been a problem that it is difficult to install facilities due to a bad smell scattered around.

Another problem is that it is difficult to secure a place for disposing of a large amount of dewatered cake generated in the final step of mechanical dewatering.

The present invention has been made in view of the above-mentioned circumstances, and has no need to secure a site for dewatering the dredged mud and a site for disposing of the dewatered cake, thereby treating the dredged mud. An object of the present invention is to provide a dredging mud treatment method and a treatment facility capable of preventing the progress of contamination.

[0009]

In order to achieve the above object, a method for treating dredged mud according to the present invention comprises the steps of: dredging mud deposited on the water bottom; On the other hand, a water removal treatment including a coagulation sedimentation treatment using a flocculant and a pressure dehydration treatment is performed, and then the cake generated by the water removal treatment is submerged in the water bottom.

Further, in the method for treating dredged mud according to the present invention, the water removal treatment is carried out on a floating structure floating on water.

Further, the dredging mud treatment equipment of the present invention is a dredging device for dredging mud deposited on the water bottom and a mud storage for storing the dredged mud sent from the dredging device. A tank, a coagulation sedimentation tank for coagulating and sedimenting the mud sent from the mud storage tank with a predetermined coagulant, and a pressure dehydrator for pressurizing and dewatering the coagulated and sedimented mud on a predetermined floating structure. It was installed in.

In the method and equipment for treating dredged mud according to the present invention, the dredged mud is subjected to water removal treatment including coagulation sedimentation using a coagulant and dehydration under pressure. Then, the dehydrated cake generated in the treatment is submerged on the bottom of the water, for example, the original bottom, and is finally disposed.

The dewatered cake submerged in the water bottom is prevented from dispersing in water by the effect of the coagulant and dehydration under pressure.
It will not be muddy again. Nutrients such as phosphorus and nitrogen are trapped in the dehydrated cake and do not elute into water. Therefore, if the sludge layer that promotes water pollution is treated as described above and submerged in the state of a dewatered cake to the bottom of the water, eutrophication of the water area without the need to newly secure a disposal site for the dewatered cake, Water pollution such as hypoxia is prevented from progressing.

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

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method and a facility for treating dredged mud according to the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a flowchart showing a procedure for performing a method of treating dredged mud according to the present embodiment, and FIG. 2 is a conceptual diagram showing equipment for performing a series of processes. . As can be seen from these figures, in the processing method according to the present embodiment, first, as shown in FIG.
The mud 2 deposited on the bottom of the water area 1 such as the sea, lake, river or river is dredged by the dredger 3 (step 101 in FIG. 1). For dredging, use a pump-type high-concentration dredge that can stably dredge with high concentration. 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 type mud storage tank described later without requiring a large-scale storage space such as a coagulation sedimentation tank. Therefore, a series of processes including the coagulation sedimentation process and the dehydration process, which are the subsequent processes, can be processed in the enclosed space, and it is possible to eliminate the problem of the foul odor scattering, and to control the deodorant and elution. It is easy to make the dredged mud harmless by mixing the agent.

Next, the dredged mud is transferred via a mud feeding pipe 4 to a mud storage tank 5 installed on land, and temporarily stored in the tank (step 102). The mud storage tank 5 is composed of a closed tank main body, a stirring blade disposed inside the tank body, a drive mechanism (not shown) for driving the stirring blade, and the like, and temporarily stores dredged mud without scattering odor. I can do it. The concentration in the tank 5 can be stabilized by managing the concentration in the tank 5 with a hydrometer and suspending or resuming the dredging as necessary.

In order to store mud with a reduced water content 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 storage tanks 5 may be provided. Before the dredged mud is transferred to the mud storage tank 5, it may be screened in advance to selectively remove relatively large-sized soil.

Next, the coagulant stored in the coagulant tank 6 is added to the mud sent from the mud storage tank 5, and this is agitated in a pipe by, for example, a line mixer, and then is passed through a mud feed pipe 7. The slurry is sent to a coagulation sedimentation tank 9 such as a slurry tank or a thickener by a pump 8, and the mud is coagulated and settled in the tank 9 (step 1).
03).

The coagulant is, for example, an aluminum-based coagulant such as aluminum sulfate called polysulfate band or polyaluminum chloride called PAC or a calcium-based coagulant such as slaked lime per 10 tons of dry weight per ton.
Add about 0 kg.

If necessary, a deodorant or an additive for preventing elution of harmful metal ions may be added. For example, if the cause of the odor is weakly acidic hydrogen sulfide, add cement or slaked lime to make the pH alkaline,
By adding hydrogen peroxide to oxidize sulfur, deodorization can be performed. If it is desired to suppress elution of iron, manganese and the like, the pH may be made alkaline with cement, lime or the like.

Next, the mud which has settled in the coagulation settling tank 9 is pulled out, transferred to a mechanical dewatering apparatus 10 such as a filter press, a roll press or the like, and dewatered under pressure (step 104). The supernatant water of the coagulation settling tank 9 is discharged to the original water area.

Next, as shown in FIG. 2 (b), the dewatered cake 11 generated in the dewatering step is transported to the original water area 1 using, for example, a belt conveyor 12 and a ship 13, and is submerged to the bottom of the water. It is disposed (step 105).

Here, the dewatered cake 11 submerged in the water bottom
Is prevented from dispersing in water by coagulation treatment and pressure treatment, and does not become muddy again. Then, nutrients such as phosphorus and nitrogen are trapped in the dehydrated cake and hardly elute in water.

As described above, according to the method for treating dredged mud according to the present embodiment, even in the case of a sludge layer which causes water pollution, the sludge layer is coagulated and settled by adding a flocculant as in the present embodiment. If this is dehydrated under pressure and submerged in the state of a dehydrated cake, the elution of nutrients into water can be prevented.

Therefore, it is possible to prevent the progress of water pollution such as eutrophication and hypoxia of the water area without having to secure a new disposal site for the dehydrated cake. In addition, elution of harmful metal ions and the like, not limited to nutrient salts, can be prevented.

The capacity of the dewatered cake has been greatly reduced because the original sludge has been mechanically dewatered, and there is no danger that the effective water storage capacity will be reduced by sinking the cake.

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

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

The dredging mud treatment equipment 21 includes a dredging device 22 for dredging the mud 2 deposited on the water bottom, a mud storage tank 5 for storing the dredged mud sent from the dredging device 22, and a mud storage tank 5. Sedimentation tank 9 for coagulating and sedimenting the mud sent from the plant with a predetermined coagulant, and coagulant tank 6 for storing the coagulant
Pressurized dewatering device 1 for pressurizing and dewatering the coagulated sedimented mud
0 is disposed 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 which can stably dredge with high concentration is adopted. By employing such a high concentration dredging device, the amount of surplus water contained in the dredged mud is minimized, and the dredged mud is supplied to the closed type mud storage tank without requiring a large-scale storage space such as a coagulation sedimentation tank. This can be sent and stored. Therefore, a series of processes including the coagulation sedimentation process and the dehydration process, which are the subsequent processes, can be processed in the enclosed space, and it is possible to eliminate the problem of the foul odor scattering, and to control the deodorant and elution. It is easy to make the dredged mud harmless by mixing the agent.

Next, the mud accumulated on the water bottom 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). .

It is to be noted that the dredged mud may be screened before being transferred to the mud storage tank 5 so as to selectively remove the soil having a relatively large particle diameter.

Next, the coagulant stored in the coagulant tank 6 is added to the mud sent from the mud storage tank 5, and this is stirred in a pipe by, for example, a line mixer. The slurry is sent to a coagulation sedimentation tank 9 such as a slurry tank or a thickener by a pump 8, and the mud is coagulated and settled in the tank 9 (step 1).
14).

The coagulant is substantially the same as in the above-described embodiment, and a description thereof will be omitted. Further, if necessary, a deodorant and an additive for preventing elution of harmful metal ions may be added. However, such description is omitted for the same reason.

Next, the mud which has settled in the coagulation settling tank 9 is pulled out, transferred to a mechanical dewatering apparatus 10 such as a filter press or a roll press, and dewatered under pressure (step 115). The supernatant water of the coagulation settling tank 9 is discharged to the original water area.

Next, the dewatered cake 11 generated in the dewatering step is submerged in the water bottom and is finally disposed (step 116).

The series of steps described above are performed by the floating structure 2
The process is repeated while changing the position of No. 3 little by little to treat mud on the bottom of the water in a predetermined range.

Here, the dewatered cake 11 submerged in the water bottom
Is prevented from dispersing in water by coagulation treatment and pressure treatment, and does not become muddy again. Then, nutrients such as phosphorus and nitrogen are trapped in the dehydrated cake and hardly elute in water.

As described above, according to the method and equipment for treating dredged mud according to the present embodiment, similar to the first embodiment, even in a sludge layer that promotes water pollution,
If this is added as a coagulant and coagulated and sedimented as in the present embodiment, it is possible to prevent nutrient salts from being eluted into water by dehydrating under pressure and submerging in the state of a dehydrated cake. .

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

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

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

Further, according to the present embodiment, dredging mud can be processed over a wide range if the position of the floating structure is changed by towing the floating structure in accordance with the processing of dredging mud.

In this embodiment, the construction of the sedimentation basin is omitted by the high concentration dredging. However, since the work is performed at a location away from the coast and the odor is unlikely to scatter to the city, a large floating body is required. An open sedimentation basin may be installed in the structure, and a method of treating a large amount of excess water in the sedimentation basin may be adopted.

[0046]

As described above, the method for treating dredged mud according to the present invention is to dredge mud deposited on the water bottom, and then subject the dredged mud to coagulation sedimentation treatment using a flocculant and pressurization. A water removal process including a dehydration process was performed, and then the cake generated in the water removal process was sunk to the bottom of the water. Can be prevented.

Further, the dredging mud treatment facility of the present invention comprises a dredging device for dredging mud deposited on the water bottom, a mud storage tank for storing the dredged mud sent from the dredging device, and The coagulation sedimentation tank for coagulating and sedimenting the sent mud with a predetermined coagulant, and the pressurized dewatering device for pressurizing and dewatering the coagulated and sedimented mud were installed on a predetermined floating structure, so dredged mud was removed. The dredged mud can be treated to prevent the progress of water pollution without having to secure a site for the dehydration treatment or a disposal site for the dewatered cake.

[0048]

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram showing equipment for carrying out 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 a second embodiment.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 Dredge vessel 5 Mud storage tank 6 Coagulant tank 9 Coagulation sedimentation tank 10 Pressure dehydration apparatus 11 Dehydration cake 21 Processing equipment 22 Dredging apparatus 23 Floating structure

Continuation of the front page (56) References JP-A-4-228730 (JP, A) JP-A-8-270002 (JP, A) Utility model registration 3008015 (JP, Y2) (58) Fields investigated (Int.Cl) . ^6, DB name) E02F 3/88 C02F 11/00 ZAB C02F 11/12 ZAB C02F 11/14 ZAB

Claims (3)

(57) [Claims] 1. Dredging mud deposited on the bottom of the water,
The dredged mud is subjected to a coagulation sedimentation process using a coagulant and a water removal process including a pressure dehydration process,
A method for treating dredged mud, characterized by submerging the cake generated by the water removal treatment to the bottom of the water. 2. The method for treating dredged mud according to claim 1, wherein the water removal treatment is performed on a floating structure floating on water. 3. A dredging device for dredging mud deposited on the water floor, a mud storage tank for storing the dredged mud sent from the dredging device, and a mud fed from the mud storage tank with a predetermined flocculant. A dredging mud treatment facility, wherein a coagulating sedimentation tank for coagulating and sedimenting and a pressure dewatering device for pressurizing and dewatering the coagulated sediment are installed on a predetermined floating structure.