JP3800426B2 - How to treat dredged mud - Google Patents

Description

  The present invention relates to a method for treating mud soil dredged from the bottom of a sea, lake, or river.

  When water pollution of the sea, lakes, or rivers is progressing, it is extremely important from the viewpoint of maintaining the ecosystem to prevent such water pollution from progressing and restore a good environment.

  The cause of water pollution is the inflow of organic substances from the outside and the elution of nutrients from the bottom mud. Therefore, it is effective to remove and remove the bottom mud to improve the water quality of the lake. Is.

  However, dredged mud has a high water content and a huge amount, and as it is, it is difficult to secure a disposal site and reuse it. Therefore, it is essential to reduce the volume and increase the strength of the dredged mud.

  Conventionally, a coagulant is added to dredged mud to pre-agglomerate the soil particles, and then the volume is reduced by dehydrating with a filter press or the like. I was trying to improve.

JP-A-6-319916 JP-A-6-31206

  However, in order to reduce the volume of dredged mud soil with a high water content to a certain ratio and improve its strength, a large amount of aggregating agent and solidifying material are required, resulting in high material costs, filter presses, etc. When the dehydrating apparatus is used, the overall equipment cost increases, and a problem arises that a large installation space must be secured.

  The present invention has been made in view of the above-described circumstances, and provides a method for treating dredged mud that can reduce the scale of dewatering equipment and save the amount of aggregating agent and solidifying material used. With the goal.

  In order to achieve the above object, the dredged mud treatment method according to the present invention dredged the bottom mud of the sea, rivers, lakes, etc., and then classifies the dredged mud by centrifugation. And then agglomerating the portion overflowed in the classification with a predetermined flocculant, and then dewatering the agglomerated component by centrifugation, wherein all of the centrifugation is screwed This is done in a decanter.

  In the method for treating dredged mud according to the present invention, the flocculant is not directly added to the dredged mud with high water content and dehydrated, but the dredged mud is classified in advance by centrifugation, and the fraction overflowed by the classification treatment. A flocculant is added to the water to perform dehydration.

  In this way, about half of the solid content in the dredged mud will be separated in advance by centrifugation, so that the amount of flocculant used can be saved, and the processing equipment required for dehydration treatment Can also be reduced.

  Here, in the case of dehydrating the agglomerated portion by centrifugation, the equipment scale can be made more compact than a pressure dewatering method such as a filter press.

  Also, instead of adding a solidifying material directly to dredged soil with a high water content as in the past, use a solidifying material when adding a solidifying material to cake discharged by classification or dehydration and solidifying it. The amount can be saved.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a dredged mud disposal method according to the present invention will be described with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.

  FIG. 1 is a flowchart showing the flow of the dredged clay treatment method according to the present embodiment, and FIGS. 2 and 3 are also explanatory diagrams. As can be seen from these drawings, in the dredged mud processing method according to the present embodiment, first, the bottom mud 1 such as the sea, a river, or a lake is dredged by the dredger 2 (FIG. 1, step 101). The dredged bottom mud 1 is stored in a water storage tank 4 after removing foreign matter such as scum with a screen 3.

  Next, the mud stored in the water storage tank 4 is classified by a centrifugal separator 5 called a screw decanter (step 102), and the under portion generated by the classification is discharged as a cake.

  Next, after the amount overflowed by the classification treatment is once stored in the water storage tank 6, the inorganic flocculant contained in the inorganic flocculant tank 7 is added and stirred in the slurry tank 8 to perform the flocculant treatment. The polymer flocculant taken out from the molecular dissolution tank 9 and the polymer storage tank 10 is further added to promote aggregation and precipitation (step 103).

  Here, as an inorganic flocculant, polyaluminum chloride called a sulfate band or PAC is used, and as a polymer flocculant, it can be appropriately selected from commercially available products manufactured from water-soluble polyacrylamide.

  Next, the agglomerated part is dehydrated by another screw decanter 11 (step 104), and the under part generated by the dehydration process is discharged as a cake.

  Next, after the portion overflowed by the dehydration treatment is once stored in the separation water tank 12, the inorganic flocculant accommodated in the inorganic flocculant tank 13 and the polymer flocculant stored in the polymer dissolution storage tank 14 are added. While coagulating and sedimenting with the square thickener 15, the supernatant is neutralized and discharged in the pH adjusting tank 16, and the aggregated sediment is returned to the slurry tank 8 through the sludge storage tank 17 (step 105).

  On the other hand, the cake discharged by the screw decanters 5 and 11 is kneaded and solidified by the kneader 19 together with the solidifying material such as cement stored in the solidifying material silo 18 and pumped by the pump 20 as shown in FIG. And reused as landfill (step 106).

  As described above, according to the method for treating dredged mud according to this embodiment, the flocculent is not directly added to the dredged mud with high water content and dehydrated, but the dredged mud is centrifuged in advance with a screw decanter. Then, the flocculant was added to the portion overflowed by the classification treatment to perform the dehydration treatment, so that about half of the solid content in the dredged mud was separated in advance by centrifugation, Thus, the amount of the flocculant used can be saved, and the scale of processing equipment necessary for the dehydration process can be reduced.

  Further, since the screw decanter is used not only for the classification process but also for the dehydration process, the scale of equipment required for dehydration can be made more compact when compared with a pressure dehydration system such as a filter press. In addition, as a result of comparing the treatment method according to this embodiment with a method of adding a flocculant to dredged mud and performing a coagulation treatment and then dehydrating and solidifying with a filter press, the equipment cost according to this embodiment is It was found that the cost of equipment can be reduced to about 60% when using.

  In addition, by performing the classification process before the dehydration process, the water removal is performed in two steps, and the volume reduction rate of the dredged mud soil can be increased.

  Also, instead of adding solidification material directly to dredged mud with a high water content as in the past, solidification material was added to the cake discharged by classification treatment or dehydration treatment to solidify it. The amount of material used can be saved.

  In this embodiment, the solidified material is added to the cake discharged by the screw decanter and reused. However, when the strength is not required, the cake may be disposed as it is without adding the solidified material. .

The flowchart which showed the procedure of the processing method of dredged mud according to this embodiment. Explanatory drawing which showed the flow of the processing method of dredged mud according to this embodiment. Explanatory drawing which similarly showed the flow of the processing method of dredged mud according to this embodiment.

Explanation of symbols

1 Bottom mud 5, 11 Screw decanter 7, 13 Coagulant tank

Claims (1)

The bottom mud of the sea, rivers, lakes, and the like is dredged, and then the dredged mud is classified by centrifugation, and then the portion overflowed by the classification treatment is agglomerated with a predetermined flocculant, and then the agglomeration A method for treating dredged mud soil, wherein the treated portion is dehydrated by centrifugation, wherein the centrifugal separation is all performed with a screw decanter.

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