JP6288049B2 - Sludge reforming method and sludge reforming material - Google Patents
Sludge reforming method and sludge reforming material Download PDFInfo
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- JP6288049B2 JP6288049B2 JP2015228377A JP2015228377A JP6288049B2 JP 6288049 B2 JP6288049 B2 JP 6288049B2 JP 2015228377 A JP2015228377 A JP 2015228377A JP 2015228377 A JP2015228377 A JP 2015228377A JP 6288049 B2 JP6288049 B2 JP 6288049B2
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- 239000000463 material Substances 0.000 title claims description 126
- 239000010802 sludge Substances 0.000 title claims description 91
- 238000002407 reforming Methods 0.000 title claims description 79
- 238000000034 method Methods 0.000 title claims description 55
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- 238000009628 steelmaking Methods 0.000 claims description 67
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 65
- 239000002245 particle Substances 0.000 claims description 44
- 229910052742 iron Inorganic materials 0.000 claims description 32
- 239000011148 porous material Substances 0.000 claims description 30
- 238000009825 accumulation Methods 0.000 claims description 12
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- 239000011575 calcium Substances 0.000 claims description 10
- 229910052791 calcium Inorganic materials 0.000 claims description 10
- 230000032683 aging Effects 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 8
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- 238000004062 sedimentation Methods 0.000 claims description 7
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 19
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 19
- 238000010828 elution Methods 0.000 description 17
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 13
- 239000000126 substance Substances 0.000 description 9
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- IBIRZFNPWYRWOG-UHFFFAOYSA-N phosphane;phosphoric acid Chemical compound P.OP(O)(O)=O IBIRZFNPWYRWOG-UHFFFAOYSA-N 0.000 description 6
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- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 235000011941 Tilia x europaea Nutrition 0.000 description 2
- FPWJLQXCGHQXLL-UHFFFAOYSA-N [P].OP(O)(O)=O Chemical compound [P].OP(O)(O)=O FPWJLQXCGHQXLL-UHFFFAOYSA-N 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 229910001424 calcium ion Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000005261 decarburization Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
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- 239000004571 lime Substances 0.000 description 2
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- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
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- 238000005507 spraying Methods 0.000 description 2
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- 241000894006 Bacteria Species 0.000 description 1
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 239000003905 agrochemical Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000001506 calcium phosphate Substances 0.000 description 1
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- 150000004677 hydrates Chemical class 0.000 description 1
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- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- -1 iron ions Chemical class 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
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- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
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- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
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- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 1
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Description
本発明は、水底に懸濁物質が沈降・堆積することにより生じる浮泥を改質し、浮泥からの硫化水素の発生抑制、栄養塩の溶出抑制、浮泥の巻き上げによる再懸濁の防止などを図るための浮泥の改質方法及び浮泥改質材に関するものである。 The present invention modifies the floating mud generated by sedimentation and accumulation of suspended substances on the bottom of the water, suppresses the generation of hydrogen sulfide from the floating mud, suppresses the elution of nutrients, and prevents resuspension by lifting the floating mud. The present invention relates to a sludge reforming method and a sludge reforming material.
環境保全のため、排水や土壌に関しての環境基準が設けられているが、水底の底質に関しての環境基準は現状では設けられていない。しかしながら、近年の環境問題に対する関心は、湖沼や海域などの環境水の浄化や、海域などの環境における底質の改質に向けられている。このため、従来から、様々な環境水の浄化方法や底質の改質方法が検討されてきた。しかし、環境水の浄化に関しては、一定の浄化方法が開発され、実用化がなされてはいるものの、底質の改質については、未だ種々の問題が残されている。 Environmental standards for drainage and soil have been established for environmental conservation, but no environmental standards have been established for bottom sediment. However, in recent years, interest in environmental problems has been directed toward the purification of environmental water in lakes and marshes and the improvement of bottom sediments in environments such as marine areas. For this reason, various environmental water purification methods and bottom quality reforming methods have been studied. However, with respect to the purification of environmental water, although a certain purification method has been developed and put into practical use, various problems still remain with respect to the reforming of the bottom sediment.
底質には、生活排水や農薬などの流入により、硫化物などの硫黄分が含まれる場合が多いことが報告されているが、場合によっては、有毒でかつ悪臭を放つ硫化水素が発生する懸念がある。上述した底質の改質方法としては、例えば、石灰を散布したり、覆砂を施すなどの方法が挙げられる。しかしながら、石灰を散布した場合、その散布の直後には、一定の底質の改質効果は得られるものの、長期間の持続性に問題がある。 It has been reported that the sediment often contains sulfur such as sulfides due to the inflow of domestic wastewater and agricultural chemicals, but in some cases there is a concern that hydrogen sulfide that is toxic and has a bad odor may be generated. There is. Examples of the above-described method for modifying the bottom sediment include a method of spraying lime or covering sand. However, when lime is sprayed, immediately after the spraying, a certain bottom sediment reforming effect is obtained, but there is a problem in long-term sustainability.
また、底質上に沈降する浮泥についても、底質と同様に生活排水の流入やプランクトンの死骸に由来するものなどにより構成されており、硫化物や有機物、栄養塩などが含まれている。これらは底質を覆って底質を還元的にすることにより、底質からの硫化水素発生を助長するほか、浮泥自体からも硫化水素が発生し、水底環境を悪化させる。このように、底質とともに浮泥の改質も海域環境の改善に重要な因子となるが、浮泥改質に関する既往の検討は少ない。 In addition, the floating mud that settles on the sediment is composed of inflows of domestic wastewater and dead bodies of plankton, similar to the sediment, and contains sulfides, organic matter, nutrient salts, etc. . By covering the bottom and making the bottom reductive, these promote the generation of hydrogen sulfide from the bottom, and also generate hydrogen sulfide from the floating mud itself, deteriorating the bottom environment. As described above, reforming of floating mud as well as bottom sediment is an important factor for improving the marine environment, but there are few previous studies on mud reforming.
特許文献１には、海底底質からのリンの溶出を抑制するため、製鋼スラグを海域のヘドロ状底泥に覆砂する方法が開示されている。また、特許文献２には、汚泥からの硫化水素の発生や硫化物の溶出を抑制するため、所定の間隙率を有する製鋼スラグを含む底質改質材を、底質改質材が埋没しない量だけ底質に投入する方法が開示されている。
また、特許文献３には、浮泥を回収して浄化する技術として、海底に設けた凹部に浮泥を集め、この凹部近傍に表層水を循環流に乗せる形で送り込むことにより、栄養塩類の溶出や硫化水素等の有害物質の生成を防止するとともに、凹部近傍を好気性環境に変える技術が開示されている。
Patent Document 1 discloses a method of covering steelmaking slag with sludge bottom mud in the sea area in order to suppress phosphorus elution from the seabed sediment. Further, in Patent Document 2, in order to suppress the generation of hydrogen sulfide from sludge and the elution of sulfide, the bottom quality modifier does not bury the bottom quality modifier including steelmaking slag having a predetermined porosity. A method is disclosed in which an amount is added to the bottom sediment.
Further, in Patent Document 3, as a technique for collecting and purifying the floating mud, the floating mud is collected in a concave portion provided on the seabed, and the surface water is put in the form of circulating water in the vicinity of the concave portion, thereby A technique for preventing elution and generation of harmful substances such as hydrogen sulfide and changing the vicinity of the recess to an aerobic environment is disclosed.
しかしながら、特許文献１、２の方法は、製鋼スラグで対象となる底質を覆うだけなので、特に硫化物を含有する底質においては、効果を維持するためには、対象となる底質上の海域のｐＨ値を適宜監視する必要がある。また、特許文献１、２には、製鋼スラグ敷設後に堆積する浮泥への対策はなんら開示されていない。
また、特許文献３の技術は、浮泥を集める凹部を構築し、さらに表層水を海底部に送り込む比較的大規模な装置の構築が必要であり、さらには、装置を動かす電力の供給も必要であり、このため、適用できる海域が限られるうえ、多大なコスト（設備コスト、運転コスト）がかかる。
However, since the methods of Patent Documents 1 and 2 only cover the target sediment with steelmaking slag, especially in the sediment containing sulfide, in order to maintain the effect, the method on the target sediment. It is necessary to appropriately monitor the pH value of the sea area. Patent Documents 1 and 2 do not disclose any countermeasures against floating mud accumulated after laying steelmaking slag.
In addition, the technology of Patent Document 3 requires the construction of a recess that collects floating mud, the construction of a relatively large-scale device that feeds surface water to the seabed, and the supply of electric power to move the device. For this reason, the applicable sea area is limited and enormous costs (equipment cost, operation cost) are required.
したがって本発明の目的は、以上のような従来技術の課題を解決し、水底に懸濁物質が沈降・堆積することにより生じる浮泥を改質し、浮泥からの硫化水素の発生や栄養塩（リン酸態リンなど）の溶出を抑制できるとともに、浮泥の巻き上げによる再懸濁を防止することができる浮泥の改質方法及び浮泥改質材を提供することにある。 Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, to reform the floating mud generated by sedimentation and deposition of suspended substances on the bottom of the water, and to generate hydrogen sulfide from the mud and nutrient salts An object of the present invention is to provide a method for reforming floating mud and a floating mud reforming material that can prevent elution of (phosphoric acid phosphorus or the like) and prevent resuspension due to hoisting of the floating mud.
本発明者らは、上記課題を解決できる方法を見出すべく検討を重ねた結果、所定の全鉄含有量の製鋼スラグを主体とするとともに、空隙率を最適化した浮泥改質材を水底の底質上に敷設し、この敷設された浮泥改質材から、その上に堆積する浮泥に鉄成分およびカルシウム成分を供給することにより、この堆積する浮泥を、同浮泥からの溶存硫化物や栄養塩（リン酸態リンなど）の溶出が抑制されるとともに、硫化水素の発生が抑制され、巻き上げられた場合も再堆積しやすい性状に改質できることを見出した。また、浮泥の改質効果をより高めるには、浮泥改質材とこれを構成する製鋼スラグの粒度を最適化すること、敷設された浮泥改質材の上面に適当な高低差の起伏を設けること、浮泥改質材を敷設する前の水底での浮泥堆積厚さに応じて浮泥改質材の敷設厚さを最適化すること、浮泥改質材の下層に底質改質材を敷設すること、などが有効であることが判った。 As a result of repeated studies to find a method that can solve the above-mentioned problems, the present inventors have mainly made a steelmaking slag having a predetermined total iron content, and have added a sludge modifying material having an optimized porosity to the bottom of the water. By laying on the bottom sediment and supplying iron and calcium components to the buoyant mud deposited on the buoyant mud modifier, the deposited buoyant mud is dissolved from the buoyant mud. It has been found that elution of sulfides and nutrient salts (such as phosphoric phosphate) is suppressed, generation of hydrogen sulfide is suppressed, and even when rolled up, it can be reformed into a property that is easy to redeposit. In addition, in order to further improve the sludge reforming effect, it is necessary to optimize the particle size of the sludge reforming material and the steelmaking slag that composes the sludge reforming material. Providing undulations, optimizing the laying thickness of the buoyant mud modifier according to the accumulated mud thickness at the bottom of the water before laying the buoyant mud modifier, It has been found that laying quality modifying materials is effective.
本発明は、このような知見に基づきなされたもので、以下を要旨とするものである。
［1］水底に懸濁物質が沈降・堆積することにより生じる浮泥の改質方法であって、
全鉄含有量が１０質量％以上の製鋼スラグを６０質量％以上含み、空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）が２０体積％以上である浮泥改質材を水底の底質上に敷設し、この敷設された浮泥改質材から、その上に堆積する浮泥に鉄成分およびカルシウム成分を供給することを特徴とする浮泥の改質方法。
［2］上記［1］の改質方法において、浮泥改質材の空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）が４０体積％以上であることを特徴とする浮泥の改質方法。
The present invention has been made on the basis of such knowledge and has the following gist.
[1] A method for reforming floating mud generated by sedimentation and accumulation of suspended matter on the bottom of the water,
60% by mass or more of steelmaking slag having a total iron content of 10% by mass or more, and the porosity (however, the ratio of gaps between particles of the float mud modifier relative to the entire volume of the float mud modifier) is 20% by volume. The floating mud modifier is laid on the bottom sediment of the water bottom, and the iron component and calcium component are supplied from the laid floating mud modifier to the floating mud deposited thereon. A method for improving mud sludge.
[2] In the reforming method of [1] above, the porosity of the sludge reforming material (however, the ratio of the gap between the particles of the sludge reforming material to the total volume of the sludge reforming material) is 40% by volume. A method for reforming floating mud characterized by the above.
［3］上記［1］又は［2］の改質方法において、事前に、敷設された浮泥改質材の上に堆積する浮泥の厚さと浮泥間隙水の水質との関係を調査し、浮泥間隙水の水質が悪化すると判断される限界浮泥厚さｘを求めておき、浮泥改質材が敷設された水底において、浮泥改質材の上に堆積する浮泥の厚さを計測し、該浮泥の厚さが限界浮泥厚さｘを超える前または限界浮泥厚さｘを超えた時点で浮泥改質材を追加的に敷設することを特徴とする浮泥の改質方法。
［4］上記［1］〜［3］のいずれかの改質方法において、浮泥改質材は粒径１０ｍｍ以上の割合が７０質量％以上であり、製鋼スラグは粒径１ｍｍ以下の割合が５〜３０質量％であることを特徴とする浮泥の改質方法。
[3] In the reforming method of [1] or [2] above, the relationship between the thickness of the floating mud deposited on the laid floating mud modifier and the water quality of the floating mud pore water is investigated in advance. The critical mud thickness x, which is judged to deteriorate the water quality of the floating mud pore water, is obtained, and the thickness of the floating mud deposited on the floating mud modifier at the bottom where the float mud modifier is laid. The float is further laid before the thickness of the float mud exceeds the limit float mud thickness x or when the thickness exceeds the limit float mud thickness x. Mud reforming method.
[4] In the reforming method according to any one of [1] to [3], the ratio of the particle size of 10 mm or more is 70% by mass or more, and the ratio of the steelmaking slag is 1 mm or less. A method for reforming floating mud characterized by being 5 to 30% by mass.
［5］上記［1］〜［3］のいずれかの改質方法において、浮泥改質材は粒径２０ｍｍ以上の割合が７０質量％以上であり、製鋼スラグは粒径１ｍｍ以下の割合が５〜３０質量％であることを特徴とする浮泥の改質方法。
［6］上記［1］〜［5］のいずれかの改質方法において、敷設された浮泥改質材の上面は、高低差が５〜５０ｃｍの起伏を有することを特徴とする浮泥の改質方法。
［7］上記［1］〜［6］のいずれかの改質方法において、製鋼スラグが３ヶ月以上大気エージングしたものであることを特徴とする浮泥の改質方法。
［8］上記［1］〜［7］のいずれかの改質方法において、製鋼スラグが溶銑予備処理スラグであることを特徴とする浮泥の改質方法。
[5] In the reforming method according to any one of [1] to [3] above, the float mud modifier has a ratio of particle size of 20 mm or more is 70% by mass or more, and the steelmaking slag has a ratio of particle size of 1 mm or less. A method for reforming floating mud characterized by being 5 to 30% by mass.
[6] In the reforming method according to any one of the above [1] to [5], the upper surface of the laid floating mud modifier has an undulation with a height difference of 5 to 50 cm. Modification method.
[7] A method for reforming floating mud according to any one of the above [1] to [6], wherein the steelmaking slag has been air-aged for 3 months or more.
[8] A method for reforming floating mud according to any one of the above [1] to [7], wherein the steelmaking slag is hot metal pretreatment slag.
［9］上記［1］〜［8］のいずれかの改質方法において、浮泥改質材を敷設する前の水底での浮泥堆積厚さｔ１（ｃｍ）に応じて、下記（1）、（2）式を満足する敷設厚さｔ２（ｃｍ）で浮泥改質材を敷設することを特徴とする浮泥の改質方法。
・浮泥堆積厚さｔ１が１５ｃｍ未満の場合
浮泥改質材の敷設厚さｔ２≧底質と混ざり合う浮泥改質材の厚さｔ３＋５ …（1）
・浮泥堆積厚さｔ１が１５ｃｍ以上の場合
浮泥改質材の敷設厚さｔ２≧底質と混ざり合う浮泥改質材の厚さｔ３＋５＋｛（浮泥堆積厚さｔ１−１５）／（浮泥改質材の空隙率／１００）｝ …（2）
但し 底質と混ざり合う浮泥改質材の厚さｔ３：敷設厚さｔ２で敷設された浮泥改質材のうち、水底を構成する既存の底質と混ざり合った浮泥改質材の厚さ（ｃｍ）
［10］上記［1］〜［8］のいずれかの改質方法において、水底の底質上に底質改質材を敷設した後、該底質改質材の上に浮泥改質材を敷設することを特徴とする浮泥の改質方法。
[9] In the reforming method according to any one of the above [1] to [8], the following (1) depending on the sludge accumulation thickness t 1 (cm) at the bottom of the water before laying the sludge reforming material ) And a mud reforming method characterized by laying the mud sludge modifying material at a laying thickness t 2 (cm) satisfying the expression (2).
・ When the sludge accumulation thickness t 1 is less than 15 cm: The laying thickness t 2 of the sludge modifying material ≧ The thickness t 3 +5 of the sludge modifying material mixed with the bottom sediment (1)
-When the mud deposit thickness t 1 is 15 cm or more The laying thickness t 2 of the mud modifier is equal to or greater than the thickness t 3 +5 + {(the mud deposit thickness t 1 mixed with the bottom sediment) -15) / (porosity of floating mud modifier / 100)} (2)
However, the thickness t 3 of the floating mud modifying material mixed with the bottom sediment: Among the floating mud modifying materials laid at the laying thickness t 2 , the floating mud reforming mixed with the existing bottom sediment constituting the water bottom. Material thickness (cm)
[10] In the reforming method according to any one of [1] to [8] above, after a bottom modifier is laid on the bottom sediment of the water bottom, the floating mud modifier on the bottom modifier A method for reforming floating mud characterized in that
［11］水底に懸濁物質が沈降・堆積することにより生じる浮泥を改質するために水底に投入される浮泥改質材であって、
全鉄含有量が１０質量％以上の製鋼スラグを６０質量％以上含み、空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）が２０体積％以上であることを特徴とする浮泥改質材。
［12］上記［11］の浮泥改質材において、空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）が４０体積％以上であることを特徴とする浮泥改質材。
[11] A float mud modifier that is introduced into the bottom of the water to modify the suspended mud generated by sedimentation and accumulation of suspended matter on the bottom of the water,
60% by mass or more of steelmaking slag having a total iron content of 10% by mass or more, and the porosity (however, the ratio of gaps between particles of the float mud modifier relative to the entire volume of the float mud modifier) is 20% by volume. A sludge modifying material characterized by the above.
[12] In the float mud modifier of [11] above, the porosity (however, the ratio of the gap between the particles of the float mud modifier to the total volume of the float mud modifier) is 40% by volume or more. A floating mud modifier.
［13］上記［11］又は［12］の浮泥改質材において、粒径１０ｍｍ以上の割合が７０質量％以上であり、製鋼スラグは粒径１ｍｍ以下の割合が５〜３０質量％であることを特徴とする浮泥改質材。
［14］上記［11］又は［12］の浮泥改質材において、粒径２０ｍｍ以上の割合が７０質量％以上であり、製鋼スラグは粒径１ｍｍ以下の割合が５〜３０質量％であることを特徴とする浮泥改質材。
［15］上記［11］〜［14］のいずれかの浮泥改質材において、製鋼スラグが３ヶ月以上大気エージングしたものであることを特徴とする浮泥改質材。
［16］上記［11］〜［15］のいずれかの浮泥改質材において、製鋼スラグが溶銑予備処理スラグであることを特徴とする浮泥改質材。
[13] In the float mud modifier according to the above [11] or [12], the ratio of the particle size of 10 mm or more is 70% by mass or more, and the steelmaking slag has the ratio of the particle size of 1 mm or less of 5 to 30% by mass. Flotation mud modifier characterized by that.
[14] In the float mud modifier of [11] or [12] above, the ratio of the particle size of 20 mm or more is 70% by mass or more, and the steelmaking slag has the ratio of the particle size of 1 mm or less of 5 to 30% by mass. Flotation mud modifier characterized by that.
[15] The float mud modifier according to any one of [11] to [14] above, wherein the steelmaking slag has been aged for 3 months or more.
[16] The float mud modifier according to any one of [11] to [15] above, wherein the steelmaking slag is hot metal pretreatment slag.
本発明によれば、敷設された浮泥改質材から、その上に堆積する浮泥に鉄成分およびカルシウム成分を供給することにより、浮泥を溶存硫化物や栄養塩（リン酸態リンなど）の溶出が抑制されるとともに、硫化水素の発生が抑制され、巻き上げられた場合も再堆積しやすい性状に改質することができる。このため、堆積した浮泥からの硫化水素の発生や栄養塩の溶出を抑制できるとともに、浮泥の巻き上げによる再懸濁を防止することができる。
また、浮泥改質材として使用する材料についても、特別な処理を加えたものではなく、通常の工程で得られる製鋼スラグを用いることができ、また、砕石などの投入と同様の方法で施工することができ、施工後のメンテナンスも不要または簡便であるため、特許文献３に開示された技術などに比べて格段に低いコストで実施できる利点がある。
According to the present invention, an iron component and a calcium component are supplied from a laid floating mud modifier to the floating mud deposited thereon, so that the floating mud is dissolved in sulfides and nutrient salts (such as phosphate phosphorus). ) Is suppressed, generation of hydrogen sulfide is suppressed, and even when rolled up, it can be reformed into a property that is easy to redeposit. For this reason, generation | occurrence | production of the hydrogen sulfide from the accumulated floating mud and elution of a nutrient can be suppressed, and the resuspension by winding up of a floating mud can be prevented.
In addition, the material used as the sludge modifier is not specially treated, and steelmaking slag obtained in a normal process can be used. Since maintenance after construction is unnecessary or simple, there is an advantage that it can be implemented at a significantly lower cost than the technique disclosed in Patent Document 3.
本発明の浮泥改質方法は、水底に懸濁物質が沈降・堆積することより生じる浮泥の改質方法であり、全鉄含有量が１０質量％以上の製鋼スラグを６０質量％以上含み、空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）が２０体積％以上である浮泥改質材を水底の底質上に敷設し（すなわち、底質上に浮泥改質材層を形成する）、この敷設された浮泥改質材から、その上に堆積する浮泥に鉄成分およびカルシウム成分を供給するものである。なお、「敷設された浮泥改質材の上に堆積する浮泥」には、浮泥改質材の粒子間の間隙に入り込む浮泥も含まれる。また、浮泥改質材を敷設する前の水底に既に堆積していた浮泥であって、浮泥改質材を敷設した結果、当該浮泥改質材上や浮泥改質材の粒子間の間隙に堆積することとなった浮泥も含まれる。
ここで、底質とは、一般に海域や河川・湖沼などの水域における水底を構成する物質のことであり、主に、河川の上流側から川の流れによって運ばれてきた砂泥、生物（プランクトンなど）の遺骸などの有機物、不溶性塩などの沈降物などが堆積して形成されたものである。
The floating mud reforming method of the present invention is a method for reforming floating mud caused by sedimentation and accumulation of suspended substances on the bottom of the water, and includes 60% by mass or more of steelmaking slag having a total iron content of 10% by mass or more. Laying a floating mud modifier with a porosity (however, the ratio of the gap between the particles of the floating mud modifier relative to the entire volume of the mud modifier) on the bottom sediment of the water bottom (20% by volume or more) That is, a floating mud reforming material layer is formed on the bottom sediment), and an iron component and a calcium component are supplied from the laid floating mud modifying material to the floating mud deposited thereon. The “floating mud that accumulates on the laid sludge modifying material” includes floating mud that enters the gaps between the particles of the sludge modifying material. In addition, the floating mud already deposited on the bottom of the water before laying the buoyant mud modifier, and as a result of laying the buoyant mud modifier, particles on the buoyant mud reformer It also includes floating mud that has accumulated in the gaps between them.
Here, the bottom sediment is a substance that generally constitutes the bottom of the water in sea areas, rivers, and lakes, and mainly sand mud and organisms (plankton) carried by the river flow from the upstream side of the river. Etc.) such as remains and sediments such as insoluble salts.
製鋼スラグとは、溶鉄を精錬する過程で副生する酸化精錬スラグであり、工程により成分の異なったスラグが発生する。具体的には、溶銑予備処理スラグ、転炉脱炭スラグ、電気炉酸化スラグなどがある。また、溶銑予備処理スラグとしては、脱珪スラグ、脱リンスラグ等がある。これらを単独で使用しても、また２種以上を適宜混合して使用してもよい。ただし、溶銑予備処理スラグは転炉脱炭スラグと比べて塩基度が小さく、ｐＨ上昇抑制および鉄分溶出に有利であるので、特に溶銑予備処理スラグが好ましい。 Steelmaking slag is oxidation refining slag produced as a by-product in the process of refining molten iron, and slag having different components is generated depending on the process. Specific examples include hot metal pretreatment slag, converter decarburization slag, and electric furnace oxidation slag. Examples of the hot metal pretreatment slag include desiliconization slag and dephosphorization slag. These may be used alone, or two or more kinds may be appropriately mixed and used. However, the hot metal pretreatment slag has a lower basicity than the converter decarburization slag, and is advantageous for pH increase suppression and iron elution, so the hot metal pretreatment slag is particularly preferable.
本発明において浮泥改質材として使用する製鋼スラグは、全鉄（トータルＦｅ）の含有量を１０質量％以上、好ましくは１５質量％以上とする。製鋼スラグの全鉄含有量が１０質量％未満では、鉄分の溶出が不足し、浮泥の改質が不十分となる。全鉄含有量の上限は特にないが、製鋼スラグの資源化の観点からは、全鉄含有量が高すぎると不経済であるため、３０質量％程度を上限とするのが合理的である。 In the present invention, the steelmaking slag used as the sludge modifying material has a total iron (total Fe) content of 10 mass% or more, preferably 15 mass% or more. If the total iron content of the steelmaking slag is less than 10% by mass, the elution of iron is insufficient and the reforming of the floating mud becomes insufficient. Although there is no particular upper limit on the total iron content, from the viewpoint of steelmaking slag resource recycling, it is uneconomical if the total iron content is too high, so it is reasonable to set the upper limit to about 30% by mass.
また、浮泥改質材中での製鋼スラグの含有量（割合）は、浮泥の改質効率の面から６０質量％以上とする。浮泥改質材中での製鋼スラグの含有量の上限はなく、全量が製鋼スラグであってもよい。
浮泥改質材が製鋼スラグ以外の材料を含む場合、その材料としては、有害物質の溶出がないものであれば任意のものを用いることができ、例えば、他の鉄鋼スラグなどのスラグ類、天然砂、天然砕石、浚渫砂などの天然材、建設残土、廃コンクリートなどの１種以上を用いることができる。
The steelmaking slag content (ratio) in the sludge reforming material is set to 60% by mass or more from the viewpoint of the sludge reforming efficiency. There is no upper limit of the content of steelmaking slag in the sludge reforming material, and the entire amount may be steelmaking slag.
When the sludge modifying material contains a material other than steelmaking slag, any material can be used as long as it does not elute harmful substances, for example, other slag such as steel slag, One or more kinds of natural materials such as natural sand, natural crushed stone and dredged sand, construction residual soil, and waste concrete can be used.
浮泥改質材の空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）は２０体積％以上、好ましくは４０体積％以上とする。ここで、本発明における浮泥改質材の空隙率とは、ＪＩＳ Ａ１１０４に準拠して実積率を求め、この実積率から求めた空隙率とする。
浮泥改質材の空隙率が小さいと、製鋼スラグから溶出した成分（鉄成分、カルシウム成分）が浮泥に到達するまでの通り道が確保できず、溶出成分が浮泥に到達しにくくなる。浮泥改質材の空隙率を２０体積％以上、好ましくは４０体積％以上とすることにより、製鋼スラグからの溶出成分が浮泥に到達するまでの通り道が十分確保できる。ここで、浮泥改質材の空隙率は、浮泥改質材の粒度分布や粒子形状などを変えることで調整することができ、例えば、浮泥改質材の粒度分布を狭くすること、或いは浮泥改質材の粒子を異形状（非球状）とすることにより、浮泥改質材の空隙率を大きくすることができる。
The porosity of the sludge reforming material (however, the ratio of the gap between particles of the sludge reforming material to the total volume of the sludge reforming material) is 20% by volume or more, preferably 40% by volume or more. Here, the porosity of the sludge improving material in the present invention is determined based on JIS A1104, and the porosity determined from the actual volume ratio.
If the porosity of the sludge modifying material is small, it is difficult to secure a path for the components (iron component, calcium component) eluted from the steelmaking slag to reach the sludge, and the eluted components are difficult to reach the sludge. By setting the porosity of the sludge reforming material to 20% by volume or more, preferably 40% by volume or more, a sufficient path can be secured until the elution component from the steelmaking slag reaches the sludge. Here, the porosity of the sludge modifying material can be adjusted by changing the particle size distribution or particle shape of the sludge modifying material, for example, narrowing the particle size distribution of the sludge modifying material, Alternatively, the porosity of the sludge modifying material can be increased by making the particles of the sludge modifying material have an irregular shape (non-spherical shape).
浮泥改質材として使用する製鋼スラグの塩基度［質量％ＣａＯ／質量％ＳｉＯ２］は、３以下が好ましく、２以下がより好ましい。製鋼スラグの塩基度が３を超えると、スラグ直上水およびスラグ間隙水のｐＨが高くなりすぎるおそれがある。スラグ間隙水のｐＨが高くなりすぎると、酸化還元電位が低下して硫酸還元菌の活性を高めてしまうおそれがある。また、塩基度が２以下であれば、エージング期間中にスラグ中に含有される金属鉄の酸化量が増大し、さらに好ましい状況となる。溶鉄の酸化精錬で発生する塩基度が３以下の製鋼スラグは、遊離ＣａＯの含有量が非常に低いため、エージング前後での粒径変化は顕著ではない。したがって、エージング処理を実施しないでも、水中に敷設後に、ＣａＯの水和反応による膨張でスラグ粒子が崩壊したり、粉化したりする問題はなく、上述したエージング処理は、水酸化鉄の生成促進を目的に実施することになる。 The basicity [mass% CaO / mass% SiO 2 ] of the steelmaking slag used as the sludge modifier is preferably 3 or less, and more preferably 2 or less. If the basicity of the steelmaking slag exceeds 3, the pH of the slag direct water and slag pore water may be too high. If the pH of the slag interstitial water becomes too high, the redox potential may be lowered and the activity of sulfate-reducing bacteria may be increased. Moreover, if basicity is 2 or less, the oxidation amount of metallic iron contained in slag will increase during an aging period, and it will become a more preferable situation. Steelmaking slag having a basicity of 3 or less generated by oxidative refining of molten iron has a very low free CaO content, so the particle size change before and after aging is not significant. Therefore, even if the aging treatment is not performed, there is no problem that the slag particles are collapsed or pulverized due to the expansion due to the hydration reaction of CaO after being laid in water, and the aging treatment described above promotes the generation of iron hydroxide. It will be implemented for the purpose.
塩基度の下限は特にないが、製鋼スラグでは、一般的に０．５以上であり、溶出水が弱アルカリ性〜アルカリ性になるのが一般的である。ただし、塩基度が高いスラグは、エージング期間を長くすることでアルカリ溶出を低減することができ、例えば、塩基度が３を超えるスラグでは、１２ヶ月以上自然エージング処理することが望ましく、２４ヶ月以上自然エージング処理することがさらに望ましい。これは、エージングにより表面が炭酸化し、安定化するためである。
また、水底（底質）上での浮泥改質材の敷設厚さは特に制限はないが、１００ｍｍ以上が好ましく、２００ｍｍ以上がより好ましい。
Although there is no lower limit of basicity, in steelmaking slag, it is generally 0.5 or more, and the elution water is generally weakly alkaline to alkaline. However, slag with high basicity can reduce alkali elution by lengthening the aging period. For example, slag with basicity exceeding 3 is desirably subjected to natural aging treatment for 12 months or more, and more than 24 months. It is further desirable to perform natural aging treatment. This is because the surface is carbonated and stabilized by aging.
Moreover, the laying thickness of the sludge modifying material on the water bottom (bottom) is not particularly limited, but is preferably 100 mm or more, and more preferably 200 mm or more.
本発明によれば、敷設された浮泥改質材から浮泥に鉄成分およびカルシウム成分が供給されることで、浮泥を溶存硫化物や栄養塩（リン酸態リンなど）の溶出が抑制されるとともに、硫化水素の発生が抑制され、巻き上げられた場合も再堆積しやすい性状に改質することができる。鉄成分により浮泥（間隙水）中の硫化物の溶出が抑制されるのは、スラグ中から溶出する鉄成分が二価または三価の鉄イオンまたはその錯体イオンの形態で溶出し、海水交換や拡散により浮泥（間隙水）に供給され、下記（1）〜（3）に示すように硫化物と反応して、無害な硫化鉄（ＦｅＳ、ＦｅＳ２）や単体硫黄（Ｓ）を生成させるためである。
ＨＳ−＋Ｆｅ２＋→ＦｅＳ＋Ｈ＋ …（1）
ＨＳ−＋２Ｆｅ３＋→Ｓ０＋２Ｆｅ２＋＋Ｈ＋ …（2）
ＦｅＳ＋Ｓ０→ＦｅＳ２ …（3）
According to the present invention, the elution of dissolved sulfides and nutrient salts (such as phosphate phosphorus) is suppressed by supplying iron and calcium components to the mud from the suspended mud modifier. At the same time, the generation of hydrogen sulfide is suppressed, and even when it is wound up, it can be modified to a property that is easy to redeposit. The iron component suppresses the elution of sulfides in the floating mud (pore water) because the iron component eluted from the slag elutes in the form of divalent or trivalent iron ions or their complex ions, and exchanges seawater. And supplied to floating mud (pore water) by diffusion and reacts with sulfides as shown in (1) to (3) below to produce harmless iron sulfide (FeS, FeS 2 ) and elemental sulfur (S) This is to make it happen.
HS − + Fe 2+ → FeS + H + (1)
HS − + 2Fe 3+ → S 0 + 2Fe 2+ + H + (2)
FeS + S 0 → FeS 2 (3)
また、カルシウム成分により浮泥（間隙水）中のリン酸態リンの溶出が抑制されるのは、カルシウム成分はカルシウムイオンの形態で溶出し、海水交換や拡散により浮泥（間隙水）に供給され、リン酸カルシウムを生成するためである。
浮泥の巻き上げを抑制するメカニズムは、下記のように推定される。浮泥中のシリカ（ＳｉＯ２）成分がカルシウムイオンと反応し、水和物をつくる。このときに浮泥はカルシウムが凝集・粗大化する。このため、浮泥巻き上げによる再懸濁が抑制される。
Moreover, the elution of phosphate phosphorus in the floating mud (pore water) is suppressed by the calcium component. The calcium component is eluted in the form of calcium ions and supplied to the floating mud (pore water) by seawater exchange and diffusion. Is to produce calcium phosphate.
The mechanism that suppresses the lifting of the floating mud is estimated as follows. Silica (SiO 2 ) components in the mud react with calcium ions to form hydrates. At this time, calcium floats and aggregates in the floating mud. For this reason, resuspension due to floating mud is suppressed.
本発明において、浮泥の改質効果をより高めるには、さらに以下のような条件を満たすことが望ましい。
浮泥改質材の粒度は、粒径１０ｍｍ以上の割合が７０質量％以上であることが好ましく、さらに、粒径２０ｍｍ以上の割合が７０質量％以上であることがより好ましい。浮泥改質材がこのような粒度を有することにより、製鋼スラグから溶出した鉄成分を浮泥に供給することが容易になる。すなわち、浮泥改質材の粒子間の空間を大きくすることで、海水交換や拡散による鉄成分の浮泥への供給が起こりやすくなる（溶出した鉄成分が浮泥に移動しやすくなる）ためである。同じ空隙率の場合、大きい粒径のほうが拡散や海水交換が起こりやすくなる。
In the present invention, it is desirable that the following conditions be further satisfied in order to further improve the effect of improving mud sludge.
As for the particle size of the sludge modifying material, the ratio of the particle size of 10 mm or more is preferably 70% by mass or more, and the ratio of the particle size of 20 mm or more is more preferably 70% by mass or more. When the floating mud modifier has such a particle size, it becomes easy to supply the iron component eluted from the steelmaking slag to the floating mud. In other words, by increasing the space between the particles of the floating mud modifier, it becomes easier for iron components to be supplied to the floating mud by seawater exchange and diffusion (the eluted iron components are more likely to move to the floating mud). It is. In the case of the same porosity, diffusion and seawater exchange are likely to occur with a larger particle size.
また、浮泥改質材を構成する製鋼スラグの粒度は、成分の溶出性と空隙率の両方を確保する観点から、粒径１ｍｍ以下の割合が５〜３０質量％であることが好ましい。したがって、浮泥改質材が製鋼スラグのみからなる場合には、製鋼スラグの粒度は、この粒度条件に加えて、粒径１０ｍｍ以上の割合が７０質量％以上であることが好ましく、さらに、粒径２０ｍｍ以上の割合が７０質量％以上であることがより好ましい。 Moreover, as for the particle size of the steelmaking slag which comprises a floating mud modifier, it is preferable that the ratio of a particle size of 1 mm or less is 5-30 mass% from a viewpoint of ensuring both the elution property of a component and a porosity. Therefore, in the case where the sludge modifying material is made only of steelmaking slag, the particle size of the steelmaking slag is preferably 70% by mass or more in addition to the particle size condition, and the ratio of the particle size of 10 mm or more is more preferable. The ratio of the diameter of 20 mm or more is more preferably 70% by mass or more.
浮泥改質材として使用する製鋼スラグは相当量の遊離ＣａＯを含有しており、この遊離ＣａＯによる施工時のアルカリ上昇を防止するため、製鋼スラグは３ヶ月以上大気エージングしたものであることが好ましい。
水底に敷設された浮泥改質材（浮泥改質材層）の上面は、スラグが露出しやすい場所をつくるために、すなわち、厚い浮泥が堆積しても施工域全面でスラグの効果がなくなるほど埋もれてしまわないようにするために、図２に示すように適当な高低差がある起伏を有することが好ましい。また、起伏があると底層流による海水交換が起きやすくなるため好ましい。起伏の高低差は、小さすぎると効果が乏しく、一方、大きすぎると浮泥と接触する機会が少ない部位が多くなるため、５〜１００ｃｍ程度が好ましい。また、起伏は単位面積当たり（例えば５〜１０ｍ四方）の高低差が５〜１００ｃｍとなるようにするのが好ましい。
Steelmaking slag used as a sludge modifying material contains a considerable amount of free CaO, and in order to prevent alkali rise during construction due to this free CaO, the steelmaking slag must have been aged for 3 months or more. preferable.
The upper surface of the floating mud reformer (floating mud reformer layer) laid on the bottom of the water is used to create a place where slag is easily exposed. In order not to be buried so as to disappear, it is preferable to have a relief with an appropriate height difference as shown in FIG. Further, it is preferable that there is an undulation because seawater exchange by the bottom layer flow is likely to occur. If the height difference of the undulation is too small, the effect is poor. On the other hand, if it is too large, there are many sites where there is little chance of contact with the floating mud. Moreover, it is preferable that the undulations have a height difference of 5 to 100 cm per unit area (for example, 5 to 10 m square).
本発明では、底質上に直に浮泥改質材を敷設してもよいが、浮泥改質材の下層に底質改質材を敷設すること、すなわち、水底の底質上に底質改質材を敷設した後、この底質改質材の上に浮泥改質材を敷設する（底質改質材と浮泥改質材を相前後して敷設する）ようにしてもよい。これにより、浮泥の改質とともに、既存の底質の改質を同時に行うことができる。
底質改質材としては、浮泥改質材と同様、全鉄含有量が１０質量％以上の製鋼スラグを６０質量％以上含み、空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）が２０体積％以上のものが好ましい。その理由は、浮泥改質材と同様である。また、底質改質材とこれに含まれる製鋼スラグの好ましい条件も、さきに述べた浮泥改質材と同様である。
In the present invention, the sludge modifying material may be laid directly on the bottom sediment, but the bottom sediment modifying material is laid on the bottom layer of the sludge modifying material, that is, the bottom on the bottom sediment of the water bottom. After laying the quality modifying material, the floating mud modifying material is laid on the bottom modifying material (laying the bottom modifying material and the floating mud modifying material before and after). Good. Thereby, the modification of the existing sediment can be performed simultaneously with the modification of the floating mud.
As with the sludge modifier, the bottom sediment modifier contains 60% by mass or more of steelmaking slag having a total iron content of 10% by mass or more, and the porosity (however, The ratio of the gaps between the mud modifier particles is preferably 20% by volume or more. The reason is the same as that of the sludge modifier. Moreover, the preferable conditions of the bottom quality modifier and the steelmaking slag contained therein are the same as those of the float mud modifier described above.
底質改質材は、底質と混ざり合うことにより効果を発揮し、硫化物の溶出や硫化水素の発生を抑える。
なお、本発明において、底質改質材として浮泥改質材の条件を満足する材料を用いる場合、底質と混ざり合った部分が底質改質材（底質改質材層）であり、その上の底質と混ざりあっていない部分が浮泥改質材（浮泥改質材層）である。したがって、１回の投入で敷設された場合でも、底質中に埋入して混ざり合った部分が底質改質材（底質改質材層）、その上の底質と混ざりあっていない部分が浮泥改質材（浮泥改質材層）ということになる。
Sediment modifiers are effective when mixed with sediments and suppress the elution of sulfides and the generation of hydrogen sulfide.
In the present invention, when a material satisfying the conditions of the sludge modifier is used as the bottom modifier, the portion mixed with the bottom is a bottom modifier (bottom modifier layer). The part that is not mixed with the bottom sediment is the floating mud reforming material (floating mud reforming material layer). Therefore, even when laid with a single charge, the portion embedded in and mixed with the bottom sediment does not mix with the bottom sediment modifier (bottom sediment modifier layer) and the bottom sediment above it. The part is called a mud reforming material (floating mud reforming material layer).
本発明を海域に適用する場合、浮泥改質材を敷設する前の水底（底質）上に既に浮泥が堆積していることが多いが、その浮泥堆積厚さが１５ｃｍ未満の場合、敷設された浮泥改質材が底質（水底を構成する既存の底質）と混ざり合わない層が５ｃｍ以上あれば、浮泥の改質を効果的に行うことができること、一方、浮泥堆積厚さが１５ｃｍ以上の場合は、１５ｃｍを超える分を浮泥改質材の空隙内に取り込む必要があり、その分の層厚を加えることで、浮泥の改質を効果的に行うことができることが判った。 In the case where the present invention is applied to the sea area, in many cases, floating mud has already accumulated on the bottom of the water (bottom sediment) before laying the floating mud modifier, but the thickness of the mud deposit is less than 15 cm. If there is a layer of 5 cm or more in which the laid sludge modifying material does not mix with the bottom sediment (existing bottom sediment that constitutes the bottom of the water), the sludge reforming can be carried out effectively. When the mud deposit thickness is 15 cm or more, it is necessary to take the portion exceeding 15 cm into the void of the floating mud reforming material, and the layer thickness is added to effectively improve the mud mud. It turns out that you can.
このため本発明の好ましい一実施形態では、浮泥改質材を敷設する前の水底での浮泥堆積厚さｔ１（ｃｍ）に応じて、下記（1）、（2）式を満足する敷設厚さｔ２（ｃｍ）で浮泥改質材を敷設する。
・浮泥堆積厚さｔ１が１５ｃｍ未満の場合
浮泥改質材の敷設厚さｔ２≧底質と混ざり合う浮泥改質材の厚さｔ３＋５ …（1）
・浮泥堆積厚さｔ１が１５ｃｍ以上の場合
浮泥改質材の敷設厚さｔ２≧底質と混ざり合う浮泥改質材の厚さｔ３＋５＋｛（浮泥堆積厚さｔ１−１５）／（浮泥改質材の空隙率／１００）｝ …（2）
但し 底質と混ざり合う浮泥改質材の厚さｔ３：敷設厚さｔ２で敷設された浮泥改質材のうち、水底を構成する既存の底質と混ざり合った浮泥改質材の厚さ（ｃｍ）
Therefore, in a preferred embodiment of the present invention, the following formulas (1) and (2) are satisfied according to the floating mud accumulation thickness t 1 (cm) at the bottom of the water before laying the floating mud modifier. The floating mud modifier is laid at a laying thickness t 2 (cm).
・ When the sludge accumulation thickness t 1 is less than 15 cm: The laying thickness t 2 of the sludge modifying material ≧ The thickness t 3 +5 of the sludge modifying material mixed with the bottom sediment (1)
-When the mud deposit thickness t 1 is 15 cm or more The laying thickness t 2 of the mud modifier is equal to or greater than the thickness t 3 +5 + {(the mud deposit thickness t 1 mixed with the bottom sediment) -15) / (porosity of floating mud modifier / 100)} (2)
However, the thickness t 3 of the floating mud modifying material mixed with the bottom sediment: Among the floating mud modifying materials laid at the laying thickness t 2 , the floating mud reforming mixed with the existing bottom sediment constituting the water bottom. Material thickness (cm)
浮泥改質材を水底に敷設（施工）した際、その敷設層の下部が水底を構成する底質（既存の底質）にめり込み、浮泥改質材粒子間の空隙が底質で埋められ、浮泥改質材と底質が混ざり合った層となる。上述したように、この底質と混ざり合った敷設材料は底質改質材として機能する。「底質と混ざり合う浮泥改質材の厚さｔ３」とは、そのような層の厚さ、すなわち、敷設厚さｔ２で敷設された浮泥改質材のうち、水底を構成する既存の底質と混ざり合った浮泥改質材の厚さを指す。 When laying mud modifying material on the bottom of the water (construction), the lower part of the laying layer sinks into the bottom sediment that constitutes the bottom of the water (existing bottom sediment), and the gap between the sludge modifying material particles is filled with the bottom sediment. As a result, it becomes a layer in which the floating mud modifier and the sediment are mixed. As described above, the laying material mixed with the bottom material functions as a bottom material modifier. “Thickness t 3 of the floating mud modifier mixed with the bottom sediment” means the thickness of such a layer, that is, the floating mud reformer laid at the laying thickness t 2 This refers to the thickness of the sludge modifier mixed with the existing sediment.
この底質と混ざり合う浮泥改質材の厚さｔ３は、対象海域（水底）において、使用する浮泥改質材であらかじめ測定しておく必要がある。この測定方法としては、対象海域（水底）において、内径１５ｃｍ以上のパイプ（アクリルパイプなど）を用いて底質のコアサンプル（厚さ２０ｃｍ以上）を採取する。この底質を採取したパイプを立てて置き、パイプ内の底質上に海水を５０ｃｍ高さ以上充填して静置した後、パイプ内に層厚３０ｃｍ程度となるように浮泥改質材を装入して静置する。装入時に巻き上がった底質がほとんど沈降したのち、パイプ外周の４箇所以上において浮泥改質材と底質の混合部の厚さを計測し、その平均値を「底質と混ざり合う浮泥改質材の厚さｔ３」とする。 The thickness t 3 of浮泥modifier mix with the sediment in a subject waters (sea bed), it is necessary to previously measured by浮泥modifier used. As this measuring method, a core sample (thickness of 20 cm or more) of a sediment is collected using a pipe (such as an acrylic pipe) having an inner diameter of 15 cm or more in a target sea area (water bottom). Place the pipe from which this sediment was collected upright, fill the bottom sediment in the pipe with seawater at a height of 50 cm or more and let it stand, and then add the floating mud modifier to the layer thickness of about 30 cm in the pipe. Insert and leave still. After the bottom sediment rolled up at the time of charging almost settles, the thickness of the mixed part of the sludge reforming material and bottom sediment is measured at four or more locations on the outer periphery of the pipe. The thickness of the mud modifying material is t 3 ”.
この実施形態は、例えば、以下のようにして実施する。本発明を適用する海域において、後述する方法（「海上保安庁 水路測量業務準則施行細則 第８節 底質調査」に記載の方法）で「浮泥堆積厚さｔ１」を測定するとともに、上記の方法で「底質と混ざり合う浮泥改質材の厚さｔ３」を測定する。
そして、例えば、浮泥改質材の空隙率５０％、底質と混ざり合う浮泥改質材の厚さｔ３が３ｃｍの場合であって、浮泥堆積厚さｔ１が１２ｃｍの場合には、上記（1）式に従い３＋５＝８ｃｍ以上の敷設厚さｔ２で浮泥改質材を敷設する。一方、浮泥堆積厚さｔ１が１８ｃｍの場合には、上記（2）式に従い３＋５＋｛（１８−１５）／（５０／１００）｝＝１４ｃｍ以上の敷設厚さｔ２で浮泥改質材を敷設する。
This embodiment is implemented as follows, for example. In the sea area to which the present invention is applied, the “floating mud deposition thickness t 1 ” is measured by the method described later (the method described in the “Detailed Regulations for Enforcement of the Japan Coast Guard Water Survey Survey Regulations Section 8 Sediment Survey”), and The “thickness t 3 of the sludge modifying material mixed with the bottom sediment” is measured by the method described above.
Then, for example, porosity of 50%浮泥modifier, even when the thickness t 3 of浮泥modifier mix with sediment of 3 cm, in the case浮泥deposition thickness t 1 is 12cm Lay the floating mud modifier with a laying thickness t 2 of 3 + 5 = 8 cm or more according to the above equation (1). On the other hand, when the sludge accumulation thickness t 1 is 18 cm, the sludge reforming is performed with a laying thickness t 2 of 3 + 5 + {(18−15) / (50/100)} = 14 cm or more according to the above equation (2). Lay the material.
また、浮泥改質材の敷設後、その上に堆積する浮泥の厚さが厚くなると浮泥改質の効果が低下してくるので、浮泥改質の効果を持続させるために、浮泥改質材の上に堆積する浮泥の厚さに応じて、浮泥改質材を追加的に敷設することが好ましい。
具体的な方法としては、事前に、敷設された浮泥改質材の上に堆積する浮泥の厚さと浮泥間隙水の水質との関係を調査し、浮泥間隙水の水質が悪化すると判断される限界浮泥厚さｘを求めておき、浮泥改質材が敷設された水底において、浮泥改質材の上に堆積する浮泥の厚さを計測し、この浮泥の厚さが限界浮泥厚さｘを超える前または限界浮泥厚さｘを超えた時点で浮泥改質材を追加的に敷設することが好ましい。浮泥改質材を追加的に敷設するタイミングは、計測された浮泥の厚さが「限界浮泥厚さｘを超える前」または「限界浮泥厚さｘを超えた時点」のいずれでもよいが、前者の方がより好ましい。
In addition, after laying the sludge reforming material, if the thickness of the sludge deposited on it increases, the sludge reforming effect decreases. It is preferable to additionally lay the floating mud modifying material according to the thickness of the floating mud deposited on the mud modifying material.
As a specific method, the relationship between the thickness of the floating mud deposited on the laid sludge reforming material and the water quality of the floating mud pore water is investigated in advance. The critical mud thickness x to be judged is obtained, and the thickness of the mud deposited on the mud modifier is measured at the bottom where the mud modifier is laid. It is preferable to additionally lay the sludge improving material before the thickness exceeds the limit float mud thickness x or when the limit float mud thickness x is exceeded. The timing for additionally laying the sludge modifying material is either when the measured sludge thickness is "before the limit float mud thickness x" or "when the limit float mud thickness x is exceeded". Although the former is better, the former is more preferable.
ここで、浮泥の厚さの計測は、「海上保安庁 水路測量業務準則施行細則 第８節 底質調査」に記載の方法で測定することができる。この方法は、図３に示すように、浮泥の上面位置を音響測深機によって測定するとともに、浮泥と底質の境界位置を円錐型錘により測定し、両測定値から浮泥の厚さを求めるものである。
また、限界浮泥厚さｘを決めるための浮泥間隙水の水質の評価基準としては、例えば、浮泥改質材の施工前に測定した浮泥間隙水中の硫化物濃度（例えば２０ｍｇ／Ｌ）の例えば１／２（１０ｍｇ／Ｌ）となる浮泥厚みに達した場合に、「浮泥間隙水の水質悪化」と評価する。
Here, the thickness of the mud can be measured by the method described in “Section 8 Survey on sediment quality” of the Japan Coast Guard Watercourse Surveying Rules. In this method, as shown in FIG. 3, the position of the upper surface of the mud is measured with an acoustic sounding instrument, and the boundary position between the mud and the sediment is measured with a conical weight. Is what you want.
Moreover, as an evaluation standard of the floating mud pore water quality for determining the critical floating mud thickness x, for example, the sulfide concentration (for example, 20 mg / L) in the floating mud pore water measured before construction of the floating mud modifier ), For example, is evaluated as “deterioration of water quality of floating mud pore water”.
本発明の浮泥改質材は、以上述べた浮泥の改質方法に用いられる材料、すなわち水底に懸濁物質が沈降・堆積することにより生じる浮泥を改質するために水底に投入される材料であり、全鉄含有量が１０質量％以上の製鋼スラグを６０質量％以上含み、空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）が２０体積％以上である浮泥改質材である。この浮泥改質材の好ましい条件（浮泥改質材を構成する製鋼スラグの好ましい条件を含む）は、上述した通りである。 The sludge modifying material of the present invention is supplied to the bottom of the water in order to modify the material used in the above described sludge reforming method, that is, the sludge generated by sedimentation and deposition of suspended substances on the bottom of the water. 60% by mass or more of steelmaking slag having a total iron content of 10% by mass or more, and porosity (however, the ratio of gaps between particles of the floating mud reforming material to the entire volume of the floating mud reforming material ) Is a mud modifier whose volume is 20% by volume or more. The preferable conditions for the sludge reforming material (including the preferable conditions for the steelmaking slag constituting the sludge reforming material) are as described above.
［実施例１］
図１に示すような試験装置を用い、以下のような試験を行った。大型水槽内に設置された水槽（内径１４ｃｍ）内に、実海域から採取したヘドロ状底質（高さ１０ｃｍ）を入れ、その上に敷設材料として全鉄含有量が異なる種々の製鋼スラグを投入し、ヘドロ状底質の上部と製鋼スラグが高さ３ｃｍ程度で入り混じるような状態をつくった。その上に、敷設材料として製鋼スラグを５ｃｍ厚になるように上置きし、さらに、その上に実海域から採取した浮泥を種々の厚みで投入した。その後、静かに海水を入れ、蓋をして気密性を保持した。製鋼スラグとしては、溶銑予備処理スラグである脱リンスラグ（塩基度［質量％ＣａＯ／質量％ＳｉＯ２］：１．３、粒径１０ｍｍ以上の割合：７０質量％、粒径２０ｍｍ以上の割合：３０質量％、粒径１ｍｍ以下の割合：１０質量％、空隙率：５０体積％）を用いた。また、比較のために、製鋼スラグに代えて天然砂をヘドロ状底質上に上置きしたもの、製鋼スラグや天然砂などの敷設材料を上置きしないでヘドロ状底質と人工海水のみを入れたものを作製し、対照試料とした。
[Example 1]
The following tests were conducted using a test apparatus as shown in FIG. Sludge bottom sediment (height 10cm) collected from the actual sea area is placed in a large tank (inner diameter 14cm), and various steelmaking slags with different total iron contents are placed on it The upper part of the sludge bottom sediment and the steelmaking slag were mixed at a height of about 3 cm. On top of that, steelmaking slag was placed as a laying material so as to have a thickness of 5 cm, and the floating mud collected from the actual sea area was put thereon in various thicknesses. After that, seawater was gently put in and covered with a lid to maintain airtightness. As steelmaking slag, dephosphorization slag (basicity [mass% CaO / mass% SiO 2 ]: 1.3, ratio of particle diameter of 10 mm or more: 70 mass%, ratio of particle diameter of 20 mm or more: 30 as hot metal pretreatment slag Mass%, ratio of particle size of 1 mm or less: 10 mass%, porosity: 50 volume%). For comparison purposes, instead of steelmaking slag, natural sand is placed on sludge bottom sediment, and only sludge bottom sediment and artificial seawater are placed without placing steellaying slag or natural sand. A control sample was prepared.
試験開始後２０日目に、敷設材料の上に堆積した浮泥の中央部から間隙水（浮泥間隙水）を採取し、その水質を測定した。測定した水質は、浮泥間隙水のｐＨ、溶存硫化物濃度、リン酸態リン濃度、アンモニア態窒素濃度、溶存酸素濃度、硫化水素ガス濃度（気相中の硫化水素濃度）である。その結果を、敷設材料の種類および全鉄含有量、浮泥の厚みとともに表１に示す。 On the 20th day after the start of the test, pore water (floating pore water) was collected from the center of the floating mud deposited on the laying material, and the water quality was measured. The measured water quality is pH of the floating mud water, dissolved sulfide concentration, phosphate phosphorus concentration, ammonia nitrogen concentration, dissolved oxygen concentration, hydrogen sulfide gas concentration (hydrogen sulfide concentration in the gas phase). The results are shown in Table 1 together with the type of laying material, the total iron content, and the thickness of the floating mud.
表１によれば、敷設する製鋼スラグの全鉄含有量が高いほど、浮泥間隙水の溶存硫化物濃度、リン酸態リン濃度、アンモニア態窒素濃度および硫化水素ガス濃度は低くなり、溶存酸素濃度は高くなる。特に、本発明例（ただし、浮泥厚みが１５ｃｍのNo.１０を除く）では、溶存硫化物濃度≦０．２ｍｇ／Ｌ、リン酸態リン濃度≦３．４ｍｇ／Ｌ、アンモニア態窒素濃度≦２２ｍｇ／Ｌ、硫化水素ガス濃度＜０．１ppm溶存酸素濃度≧０．４ｍｇ／Ｌであり、浮泥の改質が適切になされることが判る。 According to Table 1, the higher the total iron content of the steelmaking slag to be laid, the lower the dissolved sulfide concentration, phosphoric acid phosphorus concentration, ammonia nitrogen concentration, and hydrogen sulfide gas concentration of floating mud pore water, and dissolved oxygen The concentration becomes higher. In particular, in the present invention example (except for No. 10 having a flotation thickness of 15 cm), dissolved sulfide concentration ≦ 0.2 mg / L, phosphate phosphorus concentration ≦ 3.4 mg / L, ammonia nitrogen concentration ≦ It can be seen that 22 mg / L, hydrogen sulfide gas concentration <0.1 ppm dissolved oxygen concentration ≧ 0.4 mg / L, and the mud reforming is appropriately performed.
［実施例２］
敷設材料として、製鋼スラグ（実施例１のNo.４と同じ製鋼スラグ）とその他の材料で構成される混合材料を用いた。その他の材料として、天然石とコンクリート殻を用い、製鋼スラグ：その他の材料の質量比率を８０：２０、６０：４０、４０：６０とした。製鋼スラグの空隙率は５０体積％であるが、混合材料の空隙率も５０体積％になるように調整した。
試験方法は実施例１と同様であり、試験開始後２０日目に、敷設材料の上に堆積した浮泥の中央部から間隙水（浮泥間隙水）を採取し、その水質を測定した。その結果を、敷設材料の種類および浮泥の厚みとともに表２に示す。
表２によれば、本発明例ではいずれも良好な結果が得られているが、製鋼スラグの割合が６０質量％未満の敷設材料を用いた比較例では、浮泥間隙水の溶存硫化物濃度、アンモニア態窒素濃度、硫化水素ガス濃度が特に高くなっている。
[Example 2]
As the laying material, a steelmaking slag (the same steelmaking slag as No. 4 in Example 1) and a mixed material composed of other materials were used. As other materials, natural stone and concrete shells were used, and the mass ratio of steelmaking slag: other materials was 80:20, 60:40, and 40:60. The porosity of the steelmaking slag was 50% by volume, but the porosity of the mixed material was also adjusted to be 50% by volume.
The test method was the same as in Example 1. On the 20th day after the start of the test, pore water (flood pore water) was collected from the center of the floating mud deposited on the laying material, and the water quality was measured. The results are shown in Table 2 together with the type of laying material and the thickness of the mud.
According to Table 2, good results were obtained in all the examples of the present invention, but in the comparative example using the laying material in which the ratio of the steelmaking slag was less than 60% by mass, the dissolved sulfide concentration of the floating mud pore water The ammonia nitrogen concentration and the hydrogen sulfide gas concentration are particularly high.
［実施例３］
敷設材料として、実施例１のNo.４と同じ化学成分の製鋼スラグであって、空隙率と粒度が異なるものを用いた。
試験方法は実施例１と同様であり、試験開始後２０日目に、敷設材料の上に堆積した浮泥の中央部から間隙水（浮泥間隙水）を採取し、その水質を測定した。その結果を、敷設材料の構成および浮泥の厚みとともに表３に示す。
表３によれば、本発明例ではいずれも良好な結果が得られているが、空隙率が２０体積％未満の敷設材料（製鋼スラグ）を用いた比較例では、浮泥間隙水の溶存硫化物濃度、リン酸態リン濃度、アンモニア態窒素濃度、硫化水素ガス濃度が特に高くなっている。
[Example 3]
As the laying material, steelmaking slag having the same chemical composition as No. 4 in Example 1 and having different porosity and particle size was used.
The test method was the same as in Example 1. On the 20th day after the start of the test, pore water (flood pore water) was collected from the center of the floating mud deposited on the laying material, and the water quality was measured. The results are shown in Table 3 together with the construction of the laying material and the thickness of the floating mud.
According to Table 3, good results were obtained in all of the examples of the present invention, but in the comparative example using the laying material (steel slag) having a porosity of less than 20% by volume, the dissolved sulfide of floating mud pore water The substance concentration, phosphate phosphorus concentration, ammonia nitrogen concentration, and hydrogen sulfide gas concentration are particularly high.
［実施例４］
敷設材料として、実施例１のNo.４と同じ製鋼スラグを用い、敷設された敷設材料の上面に起伏を設けた。
試験方法は実施例１と同様であり、試験開始後２０日目に、敷設材料の上に堆積した浮泥の中央部から間隙水（浮泥間隙水）を採取し、その水質を測定した。その結果を、起伏の有無と高低差、浮泥の厚みとともに表４に示す。
表４によれば、敷設された敷設材料の上面に起伏を設けることにより、浮泥間隙水のリン酸態リン濃度、アンモニア態窒素濃度が低下し、溶存酸素濃度が高くなっている。
[Example 4]
As the laying material, the same steelmaking slag as in No. 4 of Example 1 was used, and undulations were provided on the upper surface of the laid material.
The test method was the same as in Example 1. On the 20th day after the start of the test, pore water (flood pore water) was collected from the center of the floating mud deposited on the laying material, and the water quality was measured. The results are shown in Table 4 together with the presence or absence of undulations, the height difference, and the thickness of the floating mud.
According to Table 4, by providing undulations on the upper surface of the laid material, the phosphorous phosphorus concentration and the ammonia nitrogen concentration in the floating mud pore water are lowered, and the dissolved oxygen concentration is increased.
［実施例５］
事前に、浮泥改質材の上に堆積する浮泥の厚さと浮泥間隙水の水質との関係を調査したところ、ある海域の浮泥の元の浮泥間隙水の硫化物濃度は２０ｍｇ／Ｌであった。
実施例１と同様に、水槽内に、実海域から採取したヘドロ状底質（高さ１０ｃｍ）を入れ、その上に製鋼スラグ（実施例１のNo.４と同じ製鋼スラグ）を投入し、ヘドロ状底質の上部と製鋼スラグが高さ３ｃｍ程度で入り混じるような状態をつくった。その上に製鋼スラグ（実施例１のNo.４と同じ製鋼スラグ）を５ｃｍ厚になるように上置きした。さらに、その上に実海域から採取した浮泥を種々の厚みで投入した。浮泥間隙水の溶存硫化物濃度が１０ｍｇ／Ｌ（＝元の浮泥の溶存硫化物濃度の１／２）となる限界浮泥厚さｘを求めたところ、ｘ＝２０ｃｍであった。この状態で新たに製鋼スラグを５ｃｍ厚敷設したところ、浮泥間隙水の溶存硫化物濃度は０．５ｍｇ／Ｌに減少した。
[Example 5]
When the relationship between the thickness of the floating mud deposited on the floating mud modifier and the water quality of the floating mud pore water was investigated in advance, the sulfide concentration of the original floating mud pore water of the floating mud in a certain sea area was 20 mg. / L.
Like Example 1, the sludge bottom sediment (height 10cm) collected from the actual sea area is put in the water tank, and steelmaking slag (the same steelmaking slag as No. 4 of Example 1) is put on it, The upper part of the sludge bottom sediment and the steelmaking slag were mixed at a height of about 3 cm. A steelmaking slag (the same steelmaking slag as No. 4 in Example 1) was placed thereon so as to have a thickness of 5 cm. In addition, floating mud collected from the actual sea area was added in various thicknesses. The critical float mud thickness x at which the dissolved sulfide concentration of the floating mud water was 10 mg / L (= 1/2 of the dissolved sulfide concentration of the original float) was found to be x = 20 cm. When 5 cm thick steelmaking slag was newly laid in this state, the dissolved sulfide concentration of floating mud pore water was reduced to 0.5 mg / L.
［実施例６］
敷設材料として、実施例１のNo.４で用いたものと同じ製鋼スラグを用いた。
試験方法は実施例１と同様であり、ヘドロ状底質の上に製鋼スラグを投入し、ヘドロ状底質の上部と製鋼スラグが高さ３ｃｍで混ざり合う層を作り、その上に製鋼スラグを厚さ変えて上置きしてスラグ層（浮泥改質材層）を形成した後、その上に浮泥を種々の厚みで投入した。試験開始後２０日目に、敷設材料の上に堆積した浮泥の中央部から間隙水（浮泥間隙水）を採取し、その水質を測定した。その結果を、敷設材料の敷設厚さ、浮泥の厚み、（1）式又は（2）式を満足する敷設材料（浮泥改質材）の最小敷設厚さ等とともに表５に示す。
表５によれば、敷設材料（浮泥改質材）を（1）式又は（2）式を満足する厚さで敷設することにより、特に浮泥間隙水の溶存硫化物濃度と硫化水素ガス濃度が低減している。
[Example 6]
As the laying material, the same steelmaking slag as that used in No. 4 of Example 1 was used.
The test method is the same as in Example 1. Steelmaking slag is put on the sludge bottom sediment, and a layer in which the top of the sludge bottom sediment and the steelmaking slag are mixed at a height of 3 cm is formed. After the slag layer (floating mud reforming material layer) was formed by changing the thickness and placing it on top, the floating mud was charged in various thicknesses. On the 20th day after the start of the test, pore water (floating pore water) was collected from the center of the floating mud deposited on the laying material, and the water quality was measured. The results are shown in Table 5 together with the laying thickness of the laying material, the thickness of the floating mud, the minimum laying thickness of the laying material (floating mud reforming material) that satisfies the formula (1) or (2), and the like.
According to Table 5, by laying the laying material (floating mud reforming material) with a thickness that satisfies formula (1) or (2), the dissolved sulfide concentration and hydrogen sulfide gas, The concentration is decreasing.
Claims (6)
全鉄含有量が１０質量％以上で且つ粒径１ｍｍ以下の割合が５〜３０質量％の製鋼スラグを６０質量％以上含み、粒径１０ｍｍ以上の割合が７０質量％以上で且つ空隙率（但し、浮泥改質材全体の体積に対する浮泥改質材の粒子間の隙間の割合）が４０体積％以上である浮泥改質材を水底の底質上に敷設し、この敷設された浮泥改質材の上面は、高低差が５〜１００ｃｍの起伏を有し、この敷設された浮泥改質材から、その上に堆積する浮泥に鉄成分およびカルシウム成分を供給する浮泥の改質方法であり、
事前に、敷設された浮泥改質材の上に堆積する浮泥の厚さと浮泥間隙水の水質との関係を調査し、浮泥間隙水の水質が悪化すると判断される限界浮泥厚さｘを求めておき、浮泥改質材が敷設された水底において、浮泥改質材の上に堆積する浮泥の厚さを計測し、該浮泥の厚さが限界浮泥厚さｘを超える前または限界浮泥厚さｘを超えた時点で浮泥改質材を追加的に敷設することを特徴とする浮泥の改質方法。 A method for reforming floating mud produced by sedimentation and accumulation of suspended matter on the bottom of the water,
60% by mass or more of steelmaking slag having a total iron content of 10% by mass or more and a particle size of 1 mm or less in the range of 5 to 30% by mass, a particle size of 10 mm or more in the proportion of 70% by mass or more and porosity (however, The ratio of the gap between the particles of the sludge reforming material to the total volume of the sludge reforming material) is laid on the bottom sediment of the bottom of the water. The upper surface of the mud modifying material has undulations with a height difference of 5 to 100 cm. From the laid floating mud modifying material, the floating mud supplying iron components and calcium components to the floating mud deposited thereon A reforming method,
Investigating the relationship between the thickness of floating mud deposited on the laid mud modifier and the quality of the floating mud pore water in advance, the limit floating mud thickness that is judged to deteriorate the quality of the floating mud pore water The thickness x is determined, and the thickness of the suspended mud deposited on the suspended mud modifier is measured at the bottom of the water where the suspended mud modifier is laid. A method for reforming floating mud characterized by additionally laying a floating mud reforming material before exceeding x or when the limit floating mud thickness x is exceeded.
・浮泥堆積厚さｔ１が１５ｃｍ未満の場合
浮泥改質材の敷設厚さｔ２≧底質と混ざり合う浮泥改質材の厚さｔ３＋５ …（1）
・浮泥堆積厚さｔ１が１５ｃｍ以上の場合
浮泥改質材の敷設厚さｔ２≧底質と混ざり合う浮泥改質材の厚さｔ３＋５＋｛（浮泥堆積厚さｔ１−１５）／（浮泥改質材の空隙率（％）／１００）｝ …（2）
但し 底質と混ざり合う浮泥改質材の厚さｔ３：敷設厚さｔ２で敷設された浮泥改質材のうち、水底を構成する既存の底質と混ざり合った浮泥改質材の厚さ（ｃｍ） Float mud with laying thickness t 2 (cm) satisfying the following formulas (1) and (2) according to the floating mud accumulation thickness t 1 (cm) at the bottom of the water before laying the mud modifier The reforming method for floating mud according to any one of claims 1 to 4, wherein a modifying material is laid.
・ When the sludge accumulation thickness t 1 is less than 15 cm: The laying thickness t 2 of the sludge modifying material ≧ The thickness t 3 +5 of the sludge modifying material mixed with the bottom sediment (1)
-When the mud deposit thickness t 1 is 15 cm or more The laying thickness t 2 of the mud modifier is equal to or greater than the thickness t 3 +5 + {(the mud deposit thickness t 1 mixed with the bottom sediment) -15) / (Porosity ratio of floating mud modifier (%) / 100)} (2)
However, the thickness t 3 of the floating mud modifying material mixed with the bottom sediment: Among the floating mud modifying materials laid at the laying thickness t 2 , the floating mud reforming mixed with the existing bottom sediment constituting the water bottom. Material thickness (cm)
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