JPS60212297A - Treatment of mud on bottom of water - Google Patents

Abstract

PURPOSE:To modify the bottom of the water on which soft mud is piled up, by such a simple means that a hydraulic bonding material is added to and mixed with soft mud such as sludge collected in a high sludge content state to solidify the same in a block form and the solidified mud is again discarded to the bottom of the water. CONSTITUTION:A hydraulic bonding material such as various cementicious bonding materials or other various org. bonding materials is added to and mixed with soft mud such as sludge collected from the bottom of the water of rivers, lakes and marshes or coastal areas in a high sludge content state by dredging to be solidified in a block form and the solidified mud is again discarded to the bottom of the water. As an apparatus for collecting soft sludge in a high sludge content state by dredging, an apparatus, wherein a pump for pumping up soft mud is arranged to the center of the under surface of a plane main body frame formed by welding square pipes and a pair of Archimedes' screw rotors are arranged to both sides thereof while a suction port and a sensor for detecting the direction of the main body are arranged to the rear surface thereof and a pressure resistance receiving operation valves on the forward central line to the front surface thereof, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves dredging and collecting soft mud such as sludge deposited on the bottom of rivers, lakes, coastal waters, etc. with a high sludge content, and adding water such as a cement-based binder to this soft mud. This patent relates to a method for treating underwater mud, which is characterized by adding and mixing a hard binder and solidifying it into a block shape, and then dumping it back to the bottom of the water as soon as possible. Already special Nt
THL applied dredging machine (Japanese Patent Application No. 57-112504, Patent Application No. 57-112505, Patent Application No. 57-188989)
No. 58-59181).

Industrial fields to which the present invention can be directly applied include pollution prevention, dredging for water bottom reform, and the environmental civil engineering industry, but the present invention can also be applied to the development of the fisheries industry, such as seafood aquaculture and coastal fishing. It is something that contributes.

Many technologies have already been disclosed for treating soft mud such as sludge deposited on rivers, lakebeds, seabeds, etc., but no definitive treatment method has yet been established.
At present, there are still difficulties in disposing of soft mud due to issues such as the location of the dumping site.

In other words, conventional treatment methods include: ■ dumping in the ocean, ■ converting into a compost and using it as a fertilizer or soil conditioner, ■ spreading clay, etc. on the bottom soil to cover the sludge surface, and ■ removing the bottom sludge. Methods such as cultivating the soil to make it harmless have been proposed, but none of these methods is the deciding factor in the treatment of underwater mud where soft mud such as sludge has accumulated. This is a major obstacle in countermeasures against sludge.

The present invention has been made as a result of intensive research to solve the above-mentioned problems, and its purpose is to provide a simple method for improving the water bottom of rivers, lakes, seabeds, etc. where soft mud such as sludge has accumulated. This method not only contributes to environmental improvement and pollution prevention, but also contributes to the development of the fisheries industry, such as fish and shellfish aquaculture and coastal fishing. That is, along with recent economic growth, urbanization and industrialization have progressed, and as a result, coastal areas such as oceans, lakes, marshes, and rivers have become increasingly polluted. In particular, red tide is reported to occur every year in areas where there is insufficient exchange of seawater with the open ocean, such as in inner bays. In recent years, fish and shellfish farming has become more and more popular in the hydrops industry, and fish farms are mainly located in areas like this.
It is said that the yield of sea cucumber aquaculture is decreasing year by year due to contamination of the bottom sediment. Many factors have been pointed out to cause marine pollution, not just the influx of urban sewage and industrial wastewater, but it is also said to be caused by harmful layers such as sludge that is accumulating on the ocean floor. It is of great significance to eliminate such factors that hinder the development of the aquaculture industry, and the present invention is designed to remove harmful sludge and other soft mud collected through dredging into a harmless form. By changing the shape and returning it to the bottom of the water, they also tried to solve the problem of a lack of dumping sites.

That is, in the present invention, a hydraulic binder is added to soft mud such as sludge collected by dredging at a high mud content from the bottom of rivers, lakes, coastal waters, etc., mixed to solidify it into a block shape, and then returned to the bottom of the water. This is a method for treating underwater mud, which is characterized by dumping it.

Dredging and collecting soft mud such as sludge deposited on rivers, lakebeds, seabeds, etc. in as thick a state as possible, that is, in a state with a high mud content, is possible by reducing the amount of hydraulic binders such as cement binders. This is desirable from the perspective of reducing costs, but as a device for dredging and collecting in such a high mud content state,
For example, a pump for lifting soft mud is placed in the center of the bottom of the flat body frame made of welded square tubes, a pair of Archimedean screw rotors are placed on both sides, a suction port is placed in the rear, and the top is located on the front center line. A dredger with a pressure-resistant container that houses the operating valves at the back, a sensor to detect the orientation of the main body at the rear, and floating bodies on both sides to adjust the underwater weight so that the main body lands on the bottom floating on soft mud. Use mud pumping equipment. In this dredging mud device, the Archimedean screw rotor rotates, and when the main body moves forward, the soft mud collected between the rotors is sucked into the suction port by the pump. At this time, by matching the forward speed and the suction capacity of the pump, it is possible to pump soft mud with a high mud content.

Table 1 shows the analytical value of the gold mud ratio when soft mud deposited on the seabed is dredged using this dredging mud lifting device, and the mud content ratio analysis basket based on the principle at that time.

Table 1 Example of gold mud ratio analysis value of dredged mud and principle As shown above,
This dredging and sludge lifting device is capable of dredging and lifting soft mud such as sludge deposited on rivers, lakebeds, seabeds, etc. in as thick a state as possible, that is, in a high mud content state.

Various cement-based binders and various other organic binders are used as the hydraulic bond I to solidify the dredged sludge and other soft mud with high mud content into blocks. However, the amount of binder added,
It is preferable to use a cement-based binder from the viewpoints of availability and other pollution concerns. Furthermore, since soft mud such as sludge deposited on rivers, lakebeds, seabeds, etc. is usually organic mud that prevents cement-based binders from hardening, it is desirable that the binder be a fast-hardening binder.

In other words, as a cementitious binder, ■ Ordinary normal, early-strength, ultra-early-strength Portland cement, or these with a hardening accelerator such as calcium chloride added ■ Commercially available jet cement (manufactured by Sumitomo Cement, Onoda Cement, quick-hardening cement) Quick-hardening cement such as cement product name or commercially available alumina cement■11CaO"7At2
03”Cax2 (X is a halogen atom or 12CaO
-7At203 and 4CaO-3At203 (803),
3CaO-8iO2, 2CaO8i02, CaSO4
A dredging Φ pack consisting of the following components can be used: 1 ■A harmless assimilation treatment agent, such as Masking (product name manufactured by Sumitomo Cement) ■A well-known ground improvement material with a hardening accelerator added. can. Table 2 shows an experimental example in which the dredged mud (31) listed in Table 1 was assimilated using some of these cement thread binders.

As can be seen from Table 2, when a Portland cement-based binder is used, the addition rate is approximately 20 to 25%, and when jet cement is used, the addition rate is 15% or more.
When a binder for dredging is used, it is possible to solidify soft mud such as sludge that has been pumped up in a short time of about one day by adding the addition rate of 1O- or more, and it is possible to solidify the sludge and other soft mud in a short period of time, such as one day. It is possible to dispose of it in In particular, it is well known that the binder for dredging can be solidified in a short time by adding a small amount, and the assimilation reaction continues even in water. It is also effective in solidifying harmful organic and inorganic substances contained in soft mud such as sludge. To outline the reaction process when the above-mentioned binding material for dredging is used, one of the constituent components, 1I
CaO-7At203 "CaX2 dissolves at the same time as water is poured, and due to the dissolution of the other constituent calcium silicate phase,
Reacts with the generated calcium hydroxide to quickly form At(O
H) 2X or CaO・At203・10 H2O,
2CaO-At203・8H20, 3CaO'At20
8-6H20.

Calcium aluminate hydrates such as 4Ca()A4% and 19H20 begin to be produced. These hydrates react with calcium sulfate eluted from other components to quickly generate calcium aluminate-sulfate hydrate, which changes to ettringite in response to changes in ion concentration in the liquid phase. It is said that it will continue.

11CaO"7At203-CaX2 +, 5.a(O
H)2+6CaSO4+68i(20-+6(3Ca
O-At203-CaS04'12H20n12AtC
OH)2X3CaO-At203-CaS04-12H
20+ 2CaS04+ 20H20-+ 3CaO-
At203-3CaS04-32H20, 11Ca
O-7At2U3” 12CaO・instead of CaX2
Even when using 7At203, ettringite, 3CaO.
t203” 3 Ca504-32 H2Ok is generated.

In addition, 4Ca0.3At203 (S03) forms a calcium aluminate-sulfate hydrate at an early stage, similar to the above-mentioned fast-hardening component.

4 CaO”'A%0iSOa) + 5 Ca(OH
)2+3CaS04+29H2043(3CaO"At
203・Ca5tJ4-12 H2O) 15O33C
aO-At203- Ca5O, -12H2O+ 2
CaSO4+ 201-120+ 3CaO-At20
3-3CaSO, -32H20 Ettringite produced from the above reaction is a special hydrate that exhibits needle-shaped crystals, has the ability to fix a large amount of excess water in mud, and has the property of not being inhibited by organic matter from hardening. Since this is generated early and in large quantities, it is particularly effective for muddy soils with high water content and organic matter.

Also, is it harmful in muddy soil? As aluminum atoms solidify, the aluminum atoms of ettringite are easily replaced with titanium, chromium, manganese atoms, etc., which have a similar ionic radius.

When solidifying soft mud such as dredged sludge using these fast-hardening binders, a commonly used cement-based molding device can be used as is as a molding means. As the method, an extrusion molding method, a briquette molding method in which the material is pressed into a mold, or a general pellet molding method may be used.

A simple method for forming blocks is to pour the kneaded material obtained as described above into a suitably shaped container whose inner surface is coated with a release agent, wait for it to solidify, and then take it out. You can also do this.

It may also be used as a container for solidifying by pouring it into a container such as a straw basket and leaving it in the container to solidify.

The present invention involves adding and mixing a hydraulic binder to sludge-like soft mud collected by dredging from the bottom of rivers, lakes, coastal waters, etc. with high mud content, solidifying it into blocks, and dumping it back into the water. Therefore, it is possible to reform the sludge-like water bottom by returning the soft mud, which has conventionally been difficult to dispose of, to its original location without causing water pollution.

Recently, the number of sea areas where the growth of seaweed has been inhibited due to a phenomenon known as ``Isoyake'' has increased, and as a countermeasure, large amounts of crushed stone are thrown into the sea as part of rock-throwing projects, and the underwater bottom is being reformed. Administrative guidance is given to ensure quality.

This stone throwing project has been carried out because it has been recognized that by promoting the growth of seaweed, it becomes food for shrimp and shellfish, and is also useful as a breeding ground for small fish. The cost of collecting, crushing, and transporting a large amount of stone to a designated sea area for disposal is not small.

According to the present invention, by dredging and removing harmful sludge-like soft mud from the water bottom, solidifying this soft mud that is difficult to dispose of, and returning it to the water, the effects of the stone-throwing project described above can be achieved. It can be said that it is a win-win.

Claims (1)

[Claims] A hydraulic binder is added and mixed to soft mud such as sludge collected by dredging from the water bottom of rivers, lakes, coastal waters, etc. in a high mud content state, solidified into a block shape, and then dumped to the water bottom again. A method for treating underwater mud that is highly effective.