JPH10272496A - Sulfiding treatment of heavy metal-containing bottom mud - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfiding treatment method for heavy metal-contg. bottom mud capable of subjecting the bottom mud contg. harmful heavy metals, such as lead, cadmium, mercury, copper, zinc and hexad chromium, to sulfiding and insolubilizing treatments. SOLUTION: Fillings 10 are prepd. by laminating bottom mud layers 11, 11' contg. the hazardous heavy metals, sand layers 12, 12' and gravel layers 13. The respective sand layers 12, 12' are supplied and impregnated with prescribed chemical solns. from perforated pipes 14. The chemical solns. are forced to flow down and penetrate in the form of perpendicularly downward penetration flow into the lower bottom mud layers 11, 11', by which the harmful heavy metals are sulfided and insolubilized. The leaching water from the gravel layers 13 is released by impervious sheets 17 and channels 2. Rain guard sheets 18 are put on the fillings 10. The front surfaces of the respective bottom mud layers 11, 11' are provided with pack drains 16 where the chemical solns. easily penetrate to accelerate the infiltration of the chemical solns. into the respective bottom mud layers 11, 11'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sulfidizing heavy metal-containing bottom mud, and more particularly, to lead, cadmium,
The present invention relates to a method for purifying sediment of rivers and lakes mainly containing harmful heavy metals such as mercury, copper, zinc and hexavalent chromium by insolubilizing the heavy metals in the form of sulfides.

[0002]

2. Description of the Related Art Conventionally, as a sulfidation treatment of sediment containing harmful heavy metals, a chemical solution containing sodium sulfide is added to the sediment and mixed with a heavy machine such as a backhoe to sulfurize the harmful heavy metals. -The method of insolubilization is generally adopted.

[0003]

However, it is difficult to make the chemical solution and the harmful heavy metal react uniformly and sufficiently by mixing with a heavy machine, and unreacted harmful heavy metal or excess sodium sulfide is added to the treated mud. There still remains a problem that, for example, it hinders the reuse of treated soil.

[0004] It is an object of the present invention to provide a method of sulfurizing heavy metal-containing sediment, which can surely sulfurate (insolubilize) sediment containing harmful heavy metals.

[0005]

According to the present invention, there is provided a method of sulfurizing heavy metal-containing bottom mud according to the present invention, comprising a bottom mud layer comprising heavy metal containing bottom metal which is sulfurized and insolubilized by a predetermined chemical solution, and sand or gravel soil. A sand layer or a gravel layer is laminated so that at least the uppermost layer becomes a sand layer or a gravel layer, and the chemicals are supplied to and penetrate into the adjacent sand layer or the gravel layer adjacent to each other to flow down and permeate into the lower bottom mud layer. And characterized by discharging leachate from the bottom layer.

That is, in the present method, a predetermined chemical solution is supplied and permeated into a sand layer or a gravel layer having a higher water permeability than the bottom mud layer, so that the chemical solution is formed into a vertically downward permeation flow to the lower bottom mud layer. This is to repeat sampling over a medium to long term until the harmful heavy metals are completely sulfurized and insolubilized, and the leachate from the bottom layer is appropriately purified. Release. The bottom mud also contains clay and the like, and is dehydrated before lamination to a water content of about 50 to 100%.

The lamination of the bottom mud layer and the sand layer and / or the gravel layer is preferably embankment-like, and the lowermost layer is preferably a gravel layer, and the uppermost layer and the intermediate layer are preferably sand layers.

[0008] As the predetermined chemical, lead, cadmium,
Using an aqueous solution of reducing sulfur compounds such as hydrogen sulfide, sodium hydrogen sulfide, mercaptoethanol, mercaptopropionic acid and trimercaptotriazine to insolubilize harmful heavy metals such as mercury, copper, zinc and hexavalent chromium in the form of sulfides, Soluble calcium carbonate is added to adjust the pH of the drug solution.

In the present invention, means for preventing the infiltration of rainwater into the bottom mud layer, the sand layer and / or the gravel layer can be provided, and specific examples of such means include a water-blocking sheet. . That is, rainwater dilutes chemicals,
In order to complicate the treatment of leachate from the bottom layer, a rain barrier sheet is used to avoid rain. In addition, since the impermeable sheet generally has gas impermeability, it also prevents oxidation of the chemical solution due to permeation of oxygen in the air into the bottom mud layer or the like.

In the present invention, means for assisting the penetration of the chemical solution into the bottom mud layer can be provided. As a specific example of such means, a bag made of synthetic fibers having water permeability is filled with sand. Pack drain (sand-filled bag). That is, since the chemical liquid may flow out from the upper surface of the bottom mud layer without flowing down and permeating the bottom mud layer, the pack drain into which the chemical liquid easily penetrates may be appropriately buried from the upper surface of the bottom mud layer. Through the packed drain into the bottom mud layer.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows bottom mud layers 11 and 11 ′ made of bottom mud containing harmful heavy metals and dehydrated so as to have a water content of about 70% or less, sand layers 12 and 12 ′ made of sand, and sand and gravel. FIG. 2 is an explanatory diagram showing a cross section of an embankment layer 10 formed by laminating a gravel layer 13 made of soil on the ground 1 (hereinafter referred to as “embankment”). A sand layer 12 and a gravel layer 13 are formed on the uppermost and lowermost layers of the embankment 10, and a two-layered bottom mud layer 1 is formed on the intermediate layer as an example.
1, 11 'are provided respectively. In addition, each layer 11, 1
The thickness of 1 ', 12, 12', and 13 was set to 30 to 100 cm, and the total height of the embankment 10 was set to 1.5 to 2 m.

A perforated pipe 14 communicating with a chemical solution adjusting tank 15 serving as a chemical solution supply source for supplying a chemical solution to the entire area of the sand layers 12 and 12 'is provided on the upper surface or inside of each of the sand layers 12 and 12'.
Is arranged. The chemical liquid adjustment tank 15 is aerated with nitrogen gas in order to prevent oxidation of the reducing sulfur agent in the chemical liquid by oxygen in the air. In addition, each bottom mud layer 11, 11 '
Pack drains 16 formed by filling a bag made of synthetic fibers having water permeability with sand are buried at appropriate intervals from the upper surface to the inside as a chemical liquid permeation assisting means.

A groove 2 for discharging leachate is provided around the embankment 10 of the ground 1, and a water-blocking sheet 17 is laid at each bottom of the gravel layer 13 and the groove 2. Further, a simple water-impervious sheet 18 is put on the upper surface and each slope of the embankment 10 as rainwater intrusion prevention means. The water-blocking sheet 18 also prevents oxygen in the air from penetrating into the embankment 10 and prevents oxidation of the chemical solution in the embankment 10.

For the embankment 10, a chemical solution adjusting tank 15
Supplies a chemical solution to each of the sand layers 12, 12 'through each perforated pipe 14. Each of the sand layers 12, 12 'is saturated with the penetrating chemical solution, while the chemical solution flows down and permeates into the bottom mud layers 11, 11' as a vertically downward penetrating flow. At this time, a part of the chemical liquid directly permeates from the upper surfaces of the bottom mud layers 11 and 11 ′, and another part of the chemical liquid penetrates into the pack drain 15 and is saturated, and then permeates into the bottom mud layers 11 and 11 ′. The leachate from the gravel layer 13 is discharged after flowing into the groove 2 from above the impermeable sheet 17, but when the leachate contains a low concentration of harmful heavy metals, a purification treatment is performed before the release.

The above-mentioned chemical solution supply is repeated at appropriate intervals, for example, for one week, until the harmful heavy metal is completely sulfurized and insolubilized while sampling a part of the bottom mud layers 11, 11 'while sampling. Can be reliably purified.

[0017]

As described above, in the method for sulfurating heavy metal-containing bottom mud according to the present invention, a predetermined chemical solution is supplied and permeated to a sand layer or a gravel layer having a higher water permeability than the bottom mud layer. In addition, the chemical solution can flow down and permeate into the lower bottom mud layer as a vertically downward permeation flow, and by repeating this as appropriate, a large amount of bottom mud can be surely subjected to collective sulfurization and insolubilization treatment.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a cross section of an embankment formed by laminating a bottom mud layer, a sand layer, and a gravel layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ground 2 Groove 10 Embankment 11, 11 'Bottom mud layer 12, 12' Sand layer 13 Gravel layer 14 Effective pipe 15 Chemical liquid adjustment tank 16 Pack drain 17, 18 Waterproof sheet

Claims (3)

[Claims] 1. A bottom mud layer made of a bottom mud containing a heavy metal which is sulfurized and insolubilized by a predetermined chemical solution, and a sand layer or a gravel layer made of sand or gravel so that at least the uppermost layer becomes a sand layer or a gravel layer. A heavy metal-containing bottom, characterized in that the chemical liquids are stacked and supplied and permeated into an upper sand layer or a gravel layer adjacent to each other, and allowed to flow down and permeate into a lower bottom mud layer, thereby discharging leachate from the lowest layer. Sulfur treatment method for mud. 2. The method according to claim 1, further comprising a step of preventing rainwater from entering the bottom mud layer, the sand layer and / or the gravel layer. 3. The method for sulfurating heavy metal-containing bottom mud according to claim 1, further comprising means for assisting penetration of the chemical solution into the bottom mud layer.