JP2013085987A - Method for amending bottom sediment and structure for amending bottom sediment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for surely and uniformly amending bottom sediment in an objective water area by using bottom sediment amendments in a closed or semi-closed water area.SOLUTION: A method for amending bottom sediment is provided which includes a step of laying a bottom sediment amendment structure A' provided with at least a support member 1 and solid amendments 2 attached to the support member 1' at predetermined intervals and containing bottom sediment amendment components. Solid amendments 2 containing bottom sediment amendment components are attached at predetermined intervals to a support member 1 in a linear, screen-like, net-like, nearly lattice-like, or like form. The formed bottom sediment amendment structure A' is laid in a closed or semi-closed water area such as a harbor, a lake, a marsh, a tideland, a canal, or a moat. The solid amendments 2 can thus be supplied into bottom mud S1 while kept definitely distant from each other, so that bottom sediment amendment can be uniformly performed. Further, because the solid amendments 2 are fixed on the support member 1, it becomes possible to adjust the amount of the solid amendments 2 supplied into the objective water area and to eliminate the risk that the solid amendments 2 are carried away by waves, a tide, or the like or that the solid amendments 2 are moved upon e.g., digging-up.

Description

  The present invention relates to bottom sediment improving means in closed / semi-closed water areas. More specifically, the present invention relates to bottom sediment improvement means for laying a bottom sediment improvement structure including a support member and a solid agent that is attached to the support member at predetermined intervals and contains a bottom sediment improvement component.

  In recent years, sediment contamination in closed and semi-enclosed waters such as harbors, lakes, tidal flats, canals and moats has become a problem.

  When industrial and domestic wastewater flows excessively into closed and semi-enclosed water areas, the concentration of nitrogen compounds and phosphorus, along with organic substances, rises and the water area becomes eutrophic. Plankton grows abnormally in eutrophied waters, and dead bodies accumulate on the bottom of the water. Plankton carcasses and other accumulated organic matter are decomposed by aerobic microorganisms, and oxygen is consumed at that time, and the vicinity of the bottom of the water becomes hypoxic. When the bottom mud is in an oxygen-deficient state, organic matter is oxidatively decomposed to produce organic acids, the bottom mud is in an acidic state or reduced state, and hydrogen sulfide is produced by anaerobic microorganisms, causing a bad odor. . Moreover, when the bottom mud is in a reduced state, phosphorus in the bottom mud elutes and promotes eutrophication.

  As a means to improve and purify the bottom sediment, a method of removing sludge with dredging, a method of covering the bottom sediment with sand, a method of supplying oxygen into the bottom mud by plowing and aeration, a method using chemicals, etc. Has been done.

  As a bottom improvement means using a chemical, for example, a method of reducing the activity of anaerobic microorganisms by suppressing the bottom mud to weak alkalinity using magnesium hydroxide to suppress the generation of hydrogen sulfide (Patent Document 1, etc.) And a method of activating aerobic microorganisms by supplying oxygen into the bottom mud using calcium peroxide or the like (see Patent Document 2, etc.).

  In addition, a method of injecting calcium nitrate or the like into bottom mud has been put into practical use as a bottom improvement means using a drug (see Patent Document 3).

  Calcium nitrate is a strong oxidizing agent, and is a compound that is easily soluble in water and highly deliquescent. When an oxidizing agent such as calcium nitrate is injected into the bottom mud, the bottom mud in a reduced state is improved to an oxidizing atmosphere, and sulfides are oxidized to prevent the generation of malodor due to hydrogen sulfide. In addition, divalent iron is oxidized to trivalent and immobilization of soluble phosphorus suppresses eutrophication of water areas due to phosphorus elution. Furthermore, activation of denitrifying bacteria promotes a reaction for decomposing organic substances into nitrogen gas and carbon dioxide gas.

  Currently, as a method of injecting calcium nitrate into the bottom mud, an aqueous solution of calcium nitrate is confined in the gel, and a pipe is installed to feed the gel from the ship to the bottom mud. In general, a method of injecting is used. However, since calcium nitrate has strong deliquescence properties, it is necessary to prepare an aqueous solution immediately before the work, and it is necessary to manage the state of the gel and have skills, and when this gel-like material is poured into the bottom mud. Large-scale equipment is required, and the injection work is relatively complicated.

On the other hand, Patent Document 4 discloses a technique for solidifying calcium nitrate or the like. As a result, it is only necessary to directly drop the solid agent on the bottom mud, so that it is not necessary to prepare calcium nitrate or the like immediately before the work, and handling is simplified. In addition, by solidifying, calcium nitrate or the like can be supplied to the bottom mud without using a large-scale injection facility and without performing complicated operations.
JP 2001-181117 A JP-A-2-218488 JP 2000-218296 A JP 2002-45888 A

  When using a solid agent containing a bottom-improving component, it is only necessary to drop the solid agent into the bottom mud from a ship or the like. It is difficult to reliably and uniformly supply a set amount of solid agent.

  Accordingly, an object of the present invention is to provide a means for reliably and uniformly improving the bottom sediment in the target water area.

  In the present invention, there is provided a bottom sediment improvement method including a step of laying a bottom sediment improvement structure having at least a support member and a solid agent attached to the support member at a predetermined interval and containing a bottom sediment improvement component. To do.

  For example, a solid agent containing a bottom sediment improving component is attached to a support member formed in a linear shape, a bowl shape, a net shape, or a substantially lattice shape at regular intervals, and the bottom sediment improving structure is attached to a harbor, Lay in closed / semi-closed waters such as lakes, tidal flats, canals and moats. Thereby, since a solid agent can be supplied in bottom mud in the state which maintained the fixed space | interval, bottom sediment improvement can be performed uniformly.

  Moreover, since the solid agent is fixed to the support member, the supply amount of the solid agent to the target water area can be adjusted. In addition, when the solid agent is supplied to the target water area, or after the supply, the solid agent is washed away by waves or tidal currents, or when the bottom mud is dug up, the solid agent moves from the supply location. There is no concern. Therefore, since the solid agent of the quantity set to the preset water area can be supplied reliably, the bottom quality improvement of a target water area can be performed reliably.

  In addition, since this bottom quality improving means can be performed without using a large-scale apparatus or the like and can be performed with a relatively inexpensive material, there is an advantage that it can be easily and inexpensively constructed.

  According to the present invention, it is possible to easily, surely and uniformly perform bottom sediment improvement in closed / semi-closed water areas.

<About the bottom sediment improvement structure according to the present invention>
The present invention includes all bottom sediment improving structures including at least a support member and a solid agent attached to the support member at predetermined intervals and containing a bottom sediment improving component.

  Hereinafter, an example of the bottom improvement structure according to the present invention will be described with reference to FIG. Note that the present invention is not limited to this embodiment.

  FIG. 1 is an external perspective partial schematic view showing an example of a sediment improvement structure according to the present invention.

  A bottom sediment improvement structure A in FIG. 1 includes a support member 1 formed in a net shape, and a solid agent 2 attached to the support member 1 at regular intervals and containing a bottom sediment improvement component.

  The support member 1 has a skeleton structure for fixing the solid agent 2. The shape of the support member 1 is not particularly limited as long as the solid agent 2 can be fixed in a state where a predetermined interval is maintained.

  For example, as shown in FIG. 1, a solid agent 2 may be attached on the support member 1 using a support member 1 formed in a net shape, or a bowl shape (see FIG. 2) or a substantially lattice shape (see FIG. 1). The support member 1 formed in 3) may be used. Moreover, you may make it the structure which made the solid agent 2 attach to the support member 1 formed in a line at a predetermined interval in a line.

  You may make it the structure which surrounds the two or four sides of the supporting member 1 with the frame 11. FIG. By adopting the configuration including the frame body 11, the structure of the bottom quality improvement structure A can be strengthened and the variation of the shape can be reduced.

  For example, when the support member 1 formed in a net shape, a cage shape, or a substantially lattice shape is used, as shown in FIG. It is formed. By making the shape having the circulation part 12, the bottom sediment improvement structure A can be reduced in weight, and by passing water and bottom mud through the circulation part 12, the bottom substance improvement structure A can be easily placed in the bottom mud. Can be installed.

  The material of the support member 1 can be widely used as well as known materials that can be formed in the above-described shape, and is not particularly limited.

  For example, natural fibers and synthetic fibers used for fishing nets, metals used for wire nets, and other synthetic resins and metals used for various other members can be widely used.

  The material of the support member 1 is not particularly limited, but iron is most suitable. For example, when the support member 1 is formed of a material containing iron, such as a wire mesh, iron is a substance that is widely present in nature, and therefore has a low environmental load even if left in water after laying. In addition, for example, in the case of using an oxidizing agent for the solid agent 2, the use of iron makes it possible to oxidize divalent iron to trivalent and immobilize soluble phosphorus. Can be suppressed.

  When the support member 1 is formed of a synthetic fiber or a synthetic resin, for example, a biodegradable plastic such as polylactic acid, polycaprolactone, polyglycolic acid, modified polyvinyl alcohol, casein, or modified starch may be used. . Thereby, the environmental load after laying can be reduced.

  The solid agent 2 is not particularly limited as long as it contains a sediment improving component as an active ingredient and is solidified.

  A well-known thing can be widely used for a bottom substance improvement component, and it is not limited narrowly. For example, it includes a wide variety of compounds that can improve the bottom sediment by modifying the bottom mud to weak alkaline, compounds that can improve the bottom sediment by supplying oxygen into the bottom mud, oxidizing agents, and the like.

  Examples of the compound capable of improving the bottom sediment by modifying the bottom mud to be weakly alkaline include magnesium compounds such as magnesium hydroxide, magnesium oxide, and magnesium nitrate. Examples of the compound that can improve the bottom sediment by supplying oxygen into the bottom mud include calcium peroxide, magnesium peroxide, and iron oxide.

  Examples of the oxidizing agent include calcium nitrate, potassium nitrate, ammonium nitrate, magnesium nitrate, manganese nitrate, and alum. These oxidants can improve the bottom mud in a reduced state to an oxidizing atmosphere, oxidize sulfides, suppress the generation of malodor due to hydrogen sulfide, etc., further oxidize divalent iron to trivalent, soluble By immobilizing phosphorus, eutrophication of the water area due to phosphorus elution is suppressed, so that it is suitable as a bottom sediment improving component according to the present invention. Of these, nitrate is more preferable because it activates denitrifying bacteria and promotes the reaction of decomposing organic matter into nitrogen gas and carbon dioxide gas.

  Of these, calcium nitrate is most preferred because it has the most powerful action as an oxidant and has a high effect of improving the bottom sediment, particularly the deodorizing effect. The calcium salt in calcium nitrate also has an action of adsorbing and fixing components such as organic acid and phosphorus dissolved in water and suppressing elution into water.

A known technique can be used for solidifying the bottom substance improving component, and is not particularly limited. For example, it can be produced by mixing the above-mentioned compound and a binder, putting them in a mold, pressurizing them (for example, 20 to 100 kg / cm ² ), and molding them into a predetermined shape. The shape of the solid agent 2 may be designed according to the purpose and application, and is not particularly limited.

  As the binder, for example, an aliphatic carboxylic acid solid at normal temperature having 11 to 31 carbon atoms (for example, stearic acid, myristic acid, behenic acid) or an ester thereof, an aromatic carboxylic acid or an ester thereof can be used. . These compounds are hydrophobic. Accordingly, for example, by appropriately adjusting the mixing ratio of these binders in the range of 1 to 40% by weight, the elution rate of the oxidizing agent in water can be appropriately adjusted according to the purpose and application.

  In addition, when the above compound and the binder are mixed, another compound may be added as appropriate according to the purpose / use and the like, followed by pressing / molding.

  Depending on the purpose and application, a part or all of the solid agent 2 may be coated with a water-insoluble or poorly water-soluble substrate. By coating the solid agent 2 with these base materials, the elution of the solid agent 2 can be delayed. Therefore, for example, both the solid agent 2 coated and not coated with the base material insoluble or hardly soluble in water, or a plurality of solid agents 2 having different coating degrees are attached to the support member 1 in order. By doing so, the effect duration can be adjusted and extended.

  Examples of water-insoluble or poorly water-soluble base materials include waxes (carnauba wax, beeswax, white beeswax, hydrogenated oil, paraffin, stearic acid and stearyl alcohol), polyoxyethylene, polyoxypropylene glycols, rosin, and hydrogenated rosin glycerin. Examples include esters, ester gums, vinyl acetate resins, agar, alginic acid, polyvinyl alcohol and the like. The coating treatment (coating treatment) of the solid agent 2 can be performed by a known means.

  As means for attaching the solid agent 2 to the support member 1, known means can be adopted and not particularly limited. For example, the solid agent 2 may be fixed to the support member 1 using a known adhesive or the like, or the solid agent 2 is fixed to the support member 1 by binding with the support member 1 or another string-like member. May be. Alternatively, the solid agent 2 may be attached to the support member 1 by pre-molding the solid agent 2 into a shape having a through-hole and inserting the support member 1 through the through-hole.

  In addition, the space | interval of each solid agent 2 can be suitably determined according to the objective and a use, the magnitude | size of the solid agent 2, the effective range of the bottom quality improvement effect, etc., and is not specifically limited.

<About the sediment improvement method according to the present invention>
The present invention provides a bottom sediment improvement method including a step of laying a bottom sediment improvement structure including at least a support member and a solid agent that is attached to the support member at predetermined intervals and contains a bottom sediment improvement component. Include.

  Hereinafter, the construction example of the sediment improvement method according to the present invention will be described with reference to FIGS. 2 and 3. In addition, this invention is not limited narrowly only to these construction examples.

  FIG. 2 is a schematic diagram showing a construction example of the bottom quality improving method according to the present invention.

  The bottom sediment improvement structure A ′ of FIG. 2 includes a support member 1 formed in a bowl shape, a solid agent 2 attached to the support member 1 at regular intervals and containing a bottom sediment improvement component, and bottom sediment improvement. And weight adjusting means 3 for sinking the structure A ′ into the bottom mud S1.

  On the ship 4, the bottom quality improving structure A 'is stored in a wound state (see reference numeral 13). By forming the bottom quality improving structure A ′ so as to be rewound, it is possible to save the space for the bottom quality improving structure A ′ and to simplify storage, transportation and installation.

  The weight adjusting means 3 is attached to the bottom sediment improving structure A ′, such as a sunk, and plays a role of sinking the bottom sediment improving structure A ′ into the water and further into the bottom mud.

  The shape and material of the weight adjusting means 3 are not particularly limited, but a material having a high specific gravity, for example, iron is preferable. In the case of using an iron-made material, as described above, there is little environmental load even if left in water after laying. When an oxidizing agent is used for the solid agent 2, divalent iron is oxidized to trivalent, soluble phosphorus In this way, there is an advantage that eutrophication of the water area due to phosphorus elution can be suppressed.

  For example, when the bottom improvement structure A ′ is laid on the water bottom S, if the bottom improvement structure A ′ does not sufficiently sink into the bottom mud S1 by its own weight alone, the weight adjustment means is provided on the bottom improvement structure A ′. By attaching 3, the bottom quality improving structure A ′ can be sunk in the bottom mud S1.

  In FIG. 2, the ship 4 is used to lay the bottom sediment improvement structure A ′ in the underwater W.

  The pile material 5 is hit against the water bottom S, and one end of the bottom quality improving structure A ′ is fixed in the bottom mud S1 in advance. Next, the bottom sediment improvement structure A 'is sequentially dropped into the water W while the ship 4 is moved forward, and the bottom sediment improvement structure A' is laid on the bottom mud S1.

  The bottom sediment improving structure A 'sinks into the bottom mud S1 by the weight of the bottom sediment improving structure A' or by the weight of the weight adjusting means 3.

  By this method, the solid agent 2 can be laid on the bottom S while maintaining a certain interval, and the solid agent 2 can be submerged in the bottom mud S1, so that the bottom quality can be improved uniformly.

  In addition, by this method, even when it is desired to improve the bottom sediment of a relatively large water area, it can be constructed with a relatively inexpensive material without using a dedicated device.

  FIG. 3 is a schematic view showing another construction example of the bottom quality improving method according to the present invention.

  3 includes a support member 1 formed in a substantially lattice shape, and a solid agent 2 attached to the support member 1 at regular intervals and containing a sediment improvement component. . Further, the bottom substance improving structure A ″ includes a frame body 11 and is formed in a panel shape.

  For example, in a water area where the bottom S is exposed at low tide, a panel-like bottom improvement structure A ″ is installed side by side on the bottom mud S1 by a diver work or work from the ship in a water area where water always exists at low tide. (See reference X1).

  The bottom sediment improving structures A ″ may be connected to each other. By adopting a configuration that allows connection, each bottom sediment improvement structure A ″ can be installed at an accurate location. A well-known method can be widely used for a connection means.

  When each bottom sediment improvement structure A ″ is laid on the bottom mud S1, if the bottom sediment improvement structure A ″ does not sink into the bottom mud S1 due to its own weight, for example, using the pressure applying means 6, After laying the bottom sediment improving structure A ″, pressure is applied from above to sink the bottom sediment improving structure A ″ into the bottom mud (see symbol X2).

  The pressure applying means 6 may be of any structure that can apply pressure from above after laying on the bottom sediment improving structure A ″.

  By this method, as described above, the solid agent 2 can be laid on the bottom S while maintaining a constant interval, and the solid agent 2 can be sunk in the bottom mud S1, thus improving the sediment quality uniformly. be able to.

  In addition, by this method, as described above, even when a relatively large water area is desired to improve the bottom sediment, it can be constructed with a relatively inexpensive material without using a dedicated device.

  That is, according to the method of the present invention, the bottom sediment can be improved simply, inexpensively and uniformly, and the bottom sediment of the target water area can be reliably improved.

  The present invention provides a solid agent in a state where a certain interval is maintained when a bottom solid is improved by using a solidifiable agent in a closed / semi-closed water area such as a harbor, a lake, a tidal flat, a canal, and a moat. Since it can be supplied into the mud, the bottom sediment can be improved uniformly, and the solid agent in the amount set in advance can be reliably supplied, so the bottom sediment improvement in the target water area can be reliably performed. Useful in terms of points. It is also useful in that it can be constructed with relatively low labor and cost, and can be applied to improve the sediment quality in a relatively wide area of water.

  As described above, the bottom sediment improvement method using calcium nitrate is a method having a bottom sediment improvement effect, particularly a high deodorizing effect. At present, a method is generally used in which an aqueous solution of calcium nitrate is confined in a gel, a tube for pumping from the ship to the bottom mud is installed, and the gel is injected into the bottom mud. .

  However, in this method, since calcium nitrate is highly deliquescent, it is necessary to prepare an aqueous calcium nitrate solution immediately before work at a construction site or the like. Moreover, in order to maintain the uniform state of the calcium nitrate aqueous solution at the construction stage, a stirring operation is required, and construction management is complicated. Furthermore, if the state management of the gel is necessary and the management is insufficient, the gel fed by pressure does not mix in the bottom mud and leaks to the bottom mud surface and dissolves in water. Therefore, there is a problem that it is difficult to inject a certain amount and uniform calcium nitrate unless a skilled worker performs it. In other words, there has been a problem that sufficient experience and a great deal of labor are required when constructing by this method.

  On the other hand, when solidified calcium nitrate is used, the labor of dropping and spraying the solid agent is greatly reduced, and handling becomes easy. However, there is a problem that it is difficult to reliably and uniformly supply a predetermined amount of the solid agent in a preset water area.

  On the other hand, the present invention comprises a support member formed in a linear shape, a saddle shape, a net shape, or a substantially lattice shape, and a solid agent attached to the support member at a predetermined interval and containing a bottom sediment improving component. By laying at least the bottom sediment improvement structure provided in the bottom mud, the bottom sediment can be improved easily, reliably and uniformly, and can be applied to solidified calcium nitrate and the like. Also, labor and cost can be greatly reduced, construction management is easy, and it can be applied to large-scale construction. Therefore, the present invention is also useful in that the bottom sediment improvement work can be performed easily, effectively and on a large scale using calcium nitrate or the like.

The external appearance partial fragmentary schematic diagram which shows the example of the sediment improvement structure which concerns on this invention. The schematic diagram which shows the construction example of the bottom quality improvement method which concerns on this invention. The schematic diagram which shows another construction example of the bottom quality improvement method which concerns on this invention.

DESCRIPTION OF SYMBOLS 1 Support member 2 Solid agent 3 Weight adjusting means 4 Ship 5 Pile material 6 Pressure applying means A Bottom sediment improvement structure S Water bottom S1 Bottom mud W Water

Claims (5)

  A bottom quality improving method comprising a step of laying a bottom quality improving structure including at least a support member and a solid agent attached to the support member at a predetermined interval and containing a bottom quality improving component.   The method for improving bottom sediment according to claim 1, wherein the supporting member is formed in a linear shape, a saddle shape, a net shape, or a substantially lattice shape.   The bottom sediment improvement structure is submerged in bottom mud by attaching weight adjusting means to the bottom sediment improvement structure or by applying pressure from above after laying on the bottom sediment improvement structure. The method for improving bottom sediment according to claim 1 or 2.   The bottom quality improvement method according to any one of claims 1 to 3, wherein the support member is formed of a material containing iron.   A bottom sediment improvement structure comprising at least a support member and a solid agent attached to the support member at predetermined intervals and containing a bottom sediment improvement component.

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