JP2002316200A - Treatment method for dredged mud - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method for dredged mud whereby dredged mud obtained from lakes and marshes, rivers, harbors, etc., is flocculated during its transport through a scour pipe, discharged into a treatment yard having a drainage mechanism installed at its bottom part, and spontaneously dehydrated in a high efficiency. SOLUTION: When dredged mud 2 having a water content of 650% or higher is being transported through a scour pipe 3 to a treatment yard 5 while the mud 2 is kept in a turbulent state as highly as possible, an anionic polymeric flocculant A of a reversed-phase emulsion type and an aqueous solution of a di- or trivalent nonmetal salt are added to the mud 2 to complete the flocculation reaction; then, the mud is discharged into a treatment yard 5 having a drainage mechanism 12' installed at its bottom part and is spontaneously dehydrated. Thus, by causing a turbulent flow and forming large flocks in a scour pipe before dredged mud obtained from lakes and marshes, rivers, harbors, etc., is discharged into a treatment yard and is spontaneously dehydrated, such results are obtained that the dehydration in the treatment yard is accelerated; the drying can be done in a short time; the repeated use of the treatment yard is made possible; and a great economical merit is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The disclosed technology is to coagulate dredged mud obtained from lakes, marshes, rivers, harbors, etc. by adding a coagulant in a sand discharge pipe for mud feeding, and thereafter providing a drainage mechanism at the bottom. Belongs to the technical field of a method of treating dredged mud which is discharged into a treated yard and naturally dewatered and dried.

[0002] In particular, the technique uses a dredging mud at a rate of 0.1 mm / sec.
It belongs to the technical field of a treatment method for treating waste sludge at a large speed of 0167 m ³ or more.

[0003]

2. Description of the Related Art As is well known, in Japan where the land is narrow, there are many mountain forests and there is a special terrain close to a long coastline, there are many rivers and lakes, There are large and small ports, so rivers,
A large amount of mud such as sludge accumulates over time in lakes and harbors, and the various functions of so-called waterfront facilities installed in rivers, lakes, harbors, etc. gradually deteriorate over time. There is a negative effect.

Conventionally, when treating such dredged mud 2 obtained from the lakes, rivers, ports, etc., as shown in FIG. 7, the mud 2 is dredged by a dredger 1 and a processing yard 5 surrounded by an embankment 4. 8, where the mud 7 is dried through the sun 8, as shown in FIG.

(A) Polyacrylamide-based flocculant 10
Add coagulation mud 7

As shown in [b], mud 7 'reduced in volume by dehydrator 11
The method has been adopted exclusively.

[0005] Such a technique is disclosed in Japanese Patent Laid-Open No. 9-1688.
The invention is disclosed in Japanese Patent Application Publication No. 00 and Japanese Patent Application Laid-Open No. 2000-426006.

[0006] In order to cope with this, the waste mud 7 sent to the treatment yard 5 by the sedimentary mud 2 is used for raising the fields and embankment in order to effectively reuse it as one resource material. The conventional mode of the treatment system for the dredged mud 7 which is designed to be used as construction soil is briefly described with reference to FIG. 3 and the following drawings. As shown in FIG. 3, the mud accumulated on the seabed by the dredger 1 is shown in FIG. 2 is dredged in a predetermined manner and is sent as a waste mud 7 to a processing yard 5 surrounded by a bank body 4 through a sand discharging pipe 3 extending from the dredger 1.
The process in which the waste mud 7 is sent through the sand discharge pipe 3 is a mud 2 having a high water content, which originally exceeds several hundred percent, so that gravity separation by sedimentation in the treatment yard 5 is performed. Drain the water through the overflow water 15 etc.
FIG. 8 shows waste mud 7 settling in the treatment yard 5 and remaining.
As shown in the above, the solar dehydration by sunshine of the sun 8 and natural self-weight consolidation perform long-term natural dehydration of about 2 to 3 years,
It is designed to condense waste mud 7 with time and use it as construction soil such as raising fields and embankments, but natural dehydration only through the long-term solar drying Because only the surface layer of the waste mud 7 dries and the middle and deep layers cannot be effectively dewatered,

As shown in (a), polyacrylamide-based flocculant 10
Is added and mixed and stirred to promote the solidification, and FIG.
of

[B] As shown in [b], a predetermined solidification treatment device 1 such as pressure dehydration
As shown in FIG. 10, high quality improved soil that can be put into practical use as a waste soil 7 ′ having increased strength by mechanically applying pressure dehydration to the waste mud 7 through the truck 12 and the like as shown in FIG. As shown in FIG. 11, the soil 13 is conveyed to a predetermined construction site, buried as an improved soil 13 'on the base soil 15, and covered with a cultivated soil 13' thereon 16 as shown in FIG. Use of a tractor, a combine, or a cultivator, and cultivation of vegetation 17 are possible.

[0007]

By the way, sludge-like substances and mud 2 are often deposited and deposited on the bottom of lakes, marshes, rivers, harbors and the like. In many cases, eutrophic substances such as nitrogen and phosphorus that are dissolved from these substances cause abnormal occurrence of phytoplankton and methane gas, resulting in significant environmental deterioration.

One of the most effective methods for purifying the polluted lakes, marshes, rivers and ports is to dredge the mud 2 of this nutrient-rich sludge-like substance with a dredger 1 and to pass through a sand discharge pipe 3. This is to send the sludge to the treatment yard 5 and remove it from the dredger 1 as described above, although the national government and many local governments have been working on this from an early stage and have achieved a certain result. Most of the sludge 2 sent through the yard 3 is stored as mud 7 in the treatment yard 5 and dried by the sun 8, and the treatment yard 5 requires a large-scale embankment construction and after the drying is over. Since it takes a long time (one year or more) before the processing yard 5 can be reused, most places have a headache in securing a disposal site.

Such drying by the sun 8 takes a long time, and even after drying, the mud 7 in the processing yard 5 does not have a pressure against the ground, and the use of the disposal site is restricted. 10 is added and solidified by a mechanical stirrer 11, which is dehydrated by the machine 11 to obtain mud 7 '. However, the mechanical stirring device and the mechanical dehydrating device 1
1 has a disadvantage that the processing capacity is small. For example, it is not suitable for mass processing such as 0.0167 m ³ or more per second.
If the operation is performed by using the mechanical dewatering device 11 or the like, the equipment cost, operation cost, maintenance cost, and required site area are enormous in terms of cost, and there is an unrealistic disadvantage.

In the treatment method for the highly water-containing dredged waste mud 7, a technique using the coagulant 10 is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 09-168800.
In the prior art, the addition of a solidifying agent such as cement to the high water content dredging waste mud 7 is frequently performed, and the high water content dredging waste mud 7 is treated using the prior art, In the process of solidifying the dredged waste mud 7,
There is a disadvantage that the pH value and COD increase due to an increase in the nitrogen-based substance due to the added cement solidifying agent 10 or the like.

Thus, as shown in FIG. 8, the hydrophobicity of the waste mud is increasing due to the drying in the treatment yard 5 through the sun 8 and the sedimentation of the waste mud through its own weight consolidation. However, there was a problem that the formation of the high quality soil 17 of the construction soil with good deterioration of the consolidation was deteriorated, and the deterioration of the consolidation deteriorated with time.

[0012]

It is an object of the invention of this application to provide a method of processing a dredger from a dredger according to the prior art described above through a long distance sand discharging pipe to a treatment yard having a sedimentation basin function. Drying and drying of the upper layer only due to self-weight consolidation by precipitation, the middle layer and the deep layer are not sufficiently dried,
In addition, even if the mechanical properties are improved by the addition of a solidifying agent such as cement, the deterioration of environmental properties due to an increase in pH or COD value is promoted on the contrary. The technical problem to be solved is to solve the problem of the improved treatment, and the treatment yard 5 through the long sand discharge pipe 3 from the dredger is used.
While premised on the conditions for sending mud to mud, the drainage is improved during mud sending through the sand drainage pipe, and dehydration is promptly accelerated. It is intended to provide an excellent method of treating dredged mud that can be used effectively at low cost and that can effectively use dredged mud as construction soil and that is beneficial to the field of civil engineering technology in the construction industry. is there.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the construction of the invention of the present application for solving the above-mentioned problems is to remove dredged mud 2 having a water content of 650% or more. In the course of sending the slurry to the treatment yard 5 by the pipe 3, first, the liquid anionic polymer flocculant A is added to firstly aggregate the dredged mud, and then the divalent or trivalent inorganic metal salt aqueous solution C is added. Then, a coagulation reaction is completed, and this is discharged to the treatment yard 5 provided with the drainage mechanism 12 at the bottom to take a technical measure for treating the dredged mud for natural dehydration.

[0014]

In the above-described configuration, the processing yard provided on the waterfront or the like through dredging of mud 2 such as sludge deposited on rivers, lakes, marshes, and harbors through a long sand discharge pipe 3 from the dredger 1. In the mud feeding process, an anionic molecular coagulant A is first added to cross-link (coarsely bond) each substance such as fine soil particles and pollutants present in the mud feeding. And then add an aqueous solution of divalent or trivalent inorganic metal salt C to complete the agglomeration reaction so that the crosslinked (coarsely bonded) coarse particles are tightened to form a strong dense floc. The free water between the flocs is easy to separate, the flocs have excellent hydrophobic properties, and the dredged mud sent on the highly permeable sand mat laid under the treatment yard to feed the mud is Free water between the above flock Since no solidifying agent such as g is added, the water is drained smoothly from the basin of the drainage pond as clear water, and the pH value and COD are controlled, and the water is discharged naturally without pollution, etc. Also, and
With the progress of the drainage of the free water, the waste mud in the treatment yard 5 to which the mud has been fed stops progressing the drainage due to natural consolidation. The exposed area of the surface layer to the sun 8 is increased through the layer 16 ', and when the solar cell is dried in the sun, natural drying is promoted, dehydration is promptly promoted, and the improved soil 62 having a large amount of soil particles is quickly solidified. As a result, the strength of the improved soil 16 'is increased, and the soil 63 can be effectively used as a construction soil 63 for raising fields or embankment.

[0015]

In the conventional coagulation treatment of dredged mud 2, a divalent or trivalent inorganic metal salt aqueous solution C is first added to the dredged mud, and the dredged mud 2 Neutralizes the negative charge of the colloidal material, then nonionic or
Means for adding the anionic polymer substance A to cause agglomeration is used, but the seed means is that the nonionic or anionic polymer substance A additive is added to the dredged mud 2 at a solid content of 0%. It is very economical, but the obtained floc is small and not suitable for natural dehydration.

As a method for solving this problem, the inventors have found that a polymer coagulant A having a molecular weight of 8 to 12 million is used, and an addition amount in terms of a pure content per solid content in the dredged mud 2. And 0.1% or more, preferably 0.2% or more. First, as in the invention of this application, a large amount of a polymer coagulant having a very high molecular weight is first added to the dredged mud in a large amount. When added (first step), the polymer flocculant wraps the suspended colloid beyond the repulsive force of the ions.

In this case, the colloidal substance is in a state of being entangled in the polymer network and forms a large floc. Next, when a divalent or trivalent inorganic salt is added (second step), it is considered that the polymer network shrinks at a stretch while containing the colloidal substance therein, resulting in a strong floc.

The anionic polymer flocculant used herein is a chain-like substance having many adsorption points with colloidal substances, for example, a copolymer of acrylamide and sodium acrylate (sodium acrylate having a ratio of 20%). However, as the divalent or trivalent inorganic metal salt used in the invention of this application, it is desirable to use an aqueous solution of polyaluminum chloride, a sulfate band, ferric chloride, etc. It is also possible to use an aqueous solution of an inorganic metal salt having a valency of 4 or more or a cationic polymer flocculant.

The addition of an anionic polymer coagulant first and then the addition of an inorganic metal polyvalent salt is described in, for example, Japanese Patent Application Laid-Open No. 3-161099, but such an anionic polymer is added. When the molecular weight of the flocculant is 8,000,000 or less, and / or when the amount added per solid content in the dredged mud is 0.1% or less, a polymer flocculant is first added to the dredged mud (first step). 1), the repulsive force of the ions hinders the polymer flocculant from wrapping the suspended colloid, so that flocculation does not occur and floc is not generated.

Aggregated flocs can be formed only by adding the inorganic metal polyvalent salt (second step). According to the study of the present inventors, the flocs thus formed have low strength,
When the flock is deposited to a certain thickness, the flock is crushed and drainage of free water becomes very poor.

On the other hand, as in the invention of this application, a polymer substance having a molecular weight of 8 to 12 million is used, and the amount of addition per solid content in the dredged mud 2 is 0.1% or more, preferably 0.1% or more. If you drastically increase it to 2% or more,
Once the viscosity rises rapidly, the suspended solids clump together as the viscosity decreases, creating large flocs.

As described above, whether or not a floc is formed in the first step is a deciding factor in whether or not a strong floc can be obtained, and no one has been able to find any technology with the technology until now.

It is preferable that the anionic polymer flocculant A is added in the form of a reversed emulsion emulsion as it is. Considering that a powder of an anionic polymer flocculant A or a reverse-phase emulsion type is dissolved in water, as is widely performed in a general flocculation process, generally, the polymer flocculant A Is a difficult operation, such as easy formation of mamako (granular undissolved matter). However, since the molecular weight of the anionic polymer flocculant A used in the invention of this application is as high as 8 to 12 million, Is particularly difficult, and the viscosity of the aqueous solution is an obstacle,
% Is the limit.

If the water content of the target dredging mud 2 is 1
200%, when the addition amount per solids and 0.2%, the addition amount of polymer coagulant solution is 0.167m ³ / Okudoro 1m
^In particular, in the case of large-scale dredging, the melting operation requires a lot of cost, labor and work site.

Therefore, the merit of adding a reversed-phase emulsion product of the anionic polymer flocculant A as it is, is very large.

The features of the invention of this application include a mechanical stirring device,
It is in the place where the dredged mud 2 is treated without using any mechanical dewatering device 11 or the like.

[0027]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the constitution of the invention of the present application, in which the above-mentioned claims are summarized, is to add a flocculant to the dredged mud 2 having a high water content. In the method for treating the dredged mud 2 stored and dewatered in the treatment yard 5, the dredged mud 2 having a water content of 650% or more is sent to the treatment yard 5 through the sand discharge pipe 3.
First, an anionic polymer coagulant A is added to the dredged mud 2, and then a divalent or trivalent inorganic metal salt aqueous solution C is added to the dredged mud 2 to complete the coagulation reaction. It is based on discharging the completed mud to a treatment yard provided with a drainage mechanism at the bottom through the above-mentioned sand drainage pipe and allowing it to naturally dehydrate. Thus, the anionic polymer flocculant A has a molecular weight of 8,000,000. To 12 million polyacrylamide-based polymer coagulant, and the anionic polymer coagulant A
The reverse phase emulsion type is added to the mud as it is, and the reverse phase emulsion type anionic polymer flocculant A has a viscosity of 0.5 Pa · S or less. The amount of the reverse phase emulsion type anionic polymer flocculant in terms of pure content is 0.1% or more, preferably 0.2%, based on the solid content in the dredged mud.
%, The length (m) of the sand drainage pipe from the time when the liquid anionic polymer flocculant A is added to the time when the divalent or trivalent inorganic metal salt aqueous solution C is added is equal to the flow rate. (M / sec) × 60-600 seconds The length (m) of the sand discharge pipe 3 from the time when the divalent or trivalent inorganic metal salt aqueous solution C is added to the time when the divalent or trivalent inorganic metal salt aqueous solution C is discharged to the processing yard 5 is determined by the flow velocity ( m / sec) x 1
8 to 300 seconds, and the Reynolds number at the time of the viscosity peak is 500 or more in the sand discharging pipe 3, and
The pipe diameter of the sand discharging pipe 3 is determined so that the average Reynolds number is 2100 or more, and the flow rate and the specific gravity of the dredging mud 2 flowing through the sand discharging pipe 3 are continuously measured, and are previously determined in a laboratory experiment. The addition rate of the flocculant was calculated from the relationship between the determined specific gravity and the addition rate of the flocculant, and the addition amount of the flocculant was automatically controlled based on the result of the flow rate × the flocculant addition rate. It takes technical measures.

[0028]

In the construction described above, dredging mud 2 such as sludge is dredged from a dredger 1 and discharged to a processing yard 5 provided in the embankment 4 by a sand discharge pipe 3 so that it is naturally dehydrated and dried by the sun 8. The polymer flocculant A in the former stage is supplied with a molecular weight of 8,000,000 to 120
100,000 polyacrylamide polymer flocculant, and a reverse phase emulsion type of anionic polymer flocculant A is added to mud 2 of sand discharging pipe 3 as it is. Further, the reverse-phase emulsion-type anionic polymer flocculant A may have a viscosity of 0.5 Pa · S or less. Is adjusted to be 0.1% or more, preferably 0.2% or more, based on the solid portion in the mud, and after adding the liquid anionic polymer flocculant A The length of the sand drainage pipe 3 before the addition of the aqueous solution C of divalent or trivalent inorganic metal salt is at a flow rate (m / sec) × 60 to 600 seconds. After adding the aqueous solution C, the treatment yard 5
The length (m) of the sand discharge pipe 3 before discharging into the pipe is set to be a flow velocity (m / sec) × 18 to 300 seconds. Number is 500 or more, and the tube diameter is determined so that the average Reynolds number is 2100 or more of the average,
Further, the mass and specific gravity of the dredged mud 2 flowing through the sand drainage pipe 3 are continuously measured, and the addition rate of the flocculant is calculated from the relationship between the specific gravity and the coagulant addition rate determined in advance in a laboratory experiment. The flow rate × the addition rate of the flocculants A and C is automatically controlled based on the result.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. 1 to 6 as embodiments of the present invention.

The same parts as those in the drawings after FIG. 7 are described using the same reference numerals.

When the dredged mud 2 is uniformly reacted with the coagulants A and C in the sand discharging pipe 3, in order to promote the reaction, the time between the time when the coagulants A and C are added and the time when the dredged mud 2 is discharged to the treatment yard 5 is increased. It is most desirable to maintain turbulence at any point.

However, the dredged mud 2 and the coagulants A and C
In this reaction, a viscous hump phenomenon, that is, a phenomenon in which the viscosity temporarily rises suddenly and then falls, is seen. Therefore, even during this peak time, the diameter of the sand discharge pipe 3 is set so that the turbulent flow state is always maintained. When trying to determine the relationship between the pressure and the amount of mud, the pressure loss generally increases, the length of the sand discharge pipe 3 becomes too long, and inconveniences often occur.

From before the addition of the polymer flocculant A to after the addition of the polymer flocculant A to before the addition of the inorganic flocculant C, and after the addition of the inorganic flocculant C to the discharge to the treatment yard 5. 3
Even if the turbulent state is always maintained by changing the diameter of the sand discharge pipe 3 in the section, it is still difficult to solve the problem that the pressure loss becomes too high.

In this regard, the present inventors have conducted many experiments, and even if laminar flow occurs at the peak, the Reynolds at the peak is 500 or more, and the average Reynolds 2
When it is 100 or more, it has been found that the coagulation reaction in the sand discharging pipe 3 is completed.

In the invention of this application, the viscosity of the dredged mud 2 itself before the addition of the flocculants A and C is too high, and / or the viscosity of the inverse emulsion type polymer flocculant itself is too high. Since the coagulant A prevents the coagulant A from spreading evenly, the water content of the dredged mud 2 is 650% or more (if the water content is low, the dredged mud 2 itself has a high viscosity and is in contact with the coagulants A and C. The viscosity of the reversed-phase emulsion-type polymer flocculant A is 0.5
It is desirable to use one having Pa · S or less.

Next, the relationship between the diameter of the sand discharge pipe 3 and the Re number (Reynolds number) will be described.

The diameter D [m] of the sand discharge pipe 3, the density ρ [kg / m ³ ] of the dredged mud 2, the viscosity μ [Pa ·
S] and the amount of mud feeding Q [m ³ / S], the number of Re = Q × ρ / (0.785 × Dμ).

Here, the density ρ of the dredged mud 2 uses the lowest value of the density of the dredged mud 2 expected.

For the viscosity μ of the dredged mud 2, an experiment is conducted in advance and the value is used.

Once the density ρ, the viscosity μ, and the amount of sludge Q are determined, the relationship between the pipe diameter and the Re number can be determined.

Next, the length (m) of the sand discharging pipe 3 from the point where the polymer flocculant A is added from the addition point 19 of the sand discharging pipe 3 to the point 20 where the inorganic metal polyvalent salt solution C is added is determined. The method will be described.

The length (m) of the sand discharging pipe 3 is determined by the flow rate (m / sec)
X Determined by the required reaction time t minutes.

It takes 60 to 600 seconds from the addition of the polymer flocculant A to the addition of the inorganic metal polyvalent salt solution C, and from the addition of the inorganic metal polyvalent salt solution C to the discharge to the treatment yard 5. As for t (time), 18 to 300 seconds is appropriate.

If the length is shorter than this, the coagulation reaction is incomplete and the natural dehydration of free water in the treatment yard 5 is hindered. If the length is longer than this, the coagulated floc formed once is destroyed. Similarly, there is a possibility that the natural dehydration of free water in the treatment yard 5 may be hindered.

Thus, the amount of the coagulant A to be used is substantially proportional to the flow rate and concentration of the dredged mud 2 flowing through the sand discharging pipe 3.

Among them, the concentration is difficult to measure continuously, so that the specific gravity of the mud 2 having a correlation with the concentration is substituted.

In the sand discharge pipe 3, the flow rate is measured by a flow meter, and the specific gravity is measured by a specific gravity meter.

The addition rate of the coagulant to be added is determined from the relationship between the specific gravity and the required amount of the coagulant, which has been determined in advance in a laboratory experiment, and the coagulant supply pump 16 is used as shown in FIG.自動 is automatically controlled.

An electromagnetic flowmeter, a Doppler flowmeter, or the like is suitable as a pipeline flow meter, and a gamma ray transmission density meter or a natural vibration type continuous density hydrometer is suitable as a pipeline hydrometer.

The optimum amount of the polymer flocculant A varies depending on the type of the flocculant A to be used. However, if the reverse emulsion type polyacrylamide flocculant A is used, the solid content in the dredged mud 2 is limited. Per net equivalent 0.1%
Above, preferably 0.2% or more is appropriate.

Below this range, the coagulant reaction is incomplete and hinders the natural dehydration of free water in the treatment yard 5.

Next, a mode in which the invention of this application is to be implemented will be described as an embodiment with reference to the drawings of FIGS. 1 to 9 (refer to FIG. 11 and subsequent figures).

The treatment yard 5 for releasing the coagulation reactant and naturally dehydrating free water is, for example, as shown in FIGS.
As shown in FIG. 3, a perforated pipe 12 'is laid on the bottom of the surrounded processing yard 5 partitioned by the embankment 4, and about 0.3 m above it.
Spread the sand 12 thick.

Then, a non-woven fabric is wound around the porous tube 12 'so that the sand 12 does not enter the tube.

The perforated pipes 12 'are connected to each other, and the filtered water that has entered the perforated pipes 12' through the layer of the sand 12 is collected in the pounds 13 'and naturally overflows outside the treatment yard 5 by the drain pump 14. Run off as water 15.

In addition, as shown in FIG. 2, a river sand 12 'is formed on the bottom of the processing yard 5 similarly partitioned into the bank 1 as shown in FIG.
And a part of the treatment yard 5 is divided by a partition wall 4 ′ to form a drainage tank 13 (drainage pound 13 ′), and the lower part of the partition wall 4 ′ and the partition wall are permeated to form a drainage tank 13.
The structure may be such that the separated water accumulated in (the drainage pond 13 ′) is discharged 15 by the drainage pump 14, or a combination of the structures of FIGS. 1 and 13.

When the coagulation reaction product is injected into the treatment yard 5 having such a structure by the mud pump 14, water is drained in 1 to 4 days, and as shown in FIG.
The coagulated sediment 62 having 6 ′ remains.

At this time, although the vertical position (level) of the surface of the coagulated sediment 62 differs depending on the concentration of the dredged mud 2, it is about 0.5 to 1 m lower than the upper end of the dam 4 'of the treatment yard 5. Usually, once or twice, the coagulation reactant 10 is once again or twice introduced into the treatment yard 5 to raise the level of the coagulated sediment surface 62 to a position near the upper end of the dam 4 ′ of the treatment yard 5. However, this is preferable in terms of effective use of the processing yard 5.

When the treatment mud 2 has been charged into the treatment yard 5 through the sand discharge pipe 3, the treatment mud 2 is left as it is, and the discharge of free water from the lower part and the drying by the sun 8 from the surface are promoted.

As the number of days passes, the strength of the coagulated sediment 62 increases, and after three months, as shown in FIG. 4, a heavy construction machine 16 such as a dozer is placed on the surface 18 and dumped as construction material 17 for the coagulated sediment 62. Truck 18 belt conveyor 16
Improved soil 1 with sufficient strength to be able to move through ´
Set to 7.

Thus, a processing yard 5 having a length of 50 m, a width of 10 m, and a depth of 2 m (volume of 1000 m ³ ) is formed at the end point (discharge point) of the sand discharging pipe 3 using the dredged mud 2 having a total length of 500 m. At the bottom of the processing yard 5, a perforated tube 1 wound with a nonwoven fabric
Four 2's were installed in one row at a distance of 10m, and river sand 12 was spread over them with a thickness of 0.3m. One end of the perforated pipe 12 'is closed, and the other side is connected and led to the vicinity of the dam 4' of the treatment yard 5 so as to enter the perforated pipe 12 ', but free water flows into the dam 4 outside the treatment yard 5. The structure was designed to allow natural drainage by gravity.

The addition point 19 of the polymer flocculant A is located 300 m upstream from the end point of the sand discharge pipe 3, and the metal-free polyvalent agent is located 50 m upstream from the end point (discharge point to the processing yard 5). An addition point 20 for salt C was provided.

The diameter of the sand drainage pipe 3 is set at 0. 1 from the start point to the end point.
The diameter of the pipe was fixed at 15 m. 0. 0 / second is applied to the sand discharge pipe 3.
0283 m ³ of a certain lake dredging mud 2 (water content is constant 1200%) is sent, and as a polymer flocculant A, a reversed-phase emulsion product of a copolymer of acrylamide and sodium acrylate (a trial product manufactured by Ternite, having a viscosity of 0.1%). 15 Pa · S) per second for 0.0000142 m ³ (equivalent to 0.0075 k in pure content)
g), as an inorganic metal polyvalent salt C, an aqueous solution of polyaluminum chloride (concentration: Al ₂ O ₃ 10%) was added at a rate of 0.0
000425 m ^{3 was} added.

The dredged mud 2 is sent by the dredger 1 through the sand discharging pipe, and up to the addition point 19 of the polymer coagulant A, and after the addition of the polymer coagulant A to the addition point of the inorganic metal polyvalent salt C. After the addition of the inorganic metal polyvalent salt C to the treatment yard 5, from the dredging when the diameter of the sand discharge pipe 3 in the three sections until the discharge is made constant to the discharge from the treatment yard 5 to the treatment yard 5. The pressure loss of the tube was calculated.

As a comparative example, the pressure loss under the same conditions as in the present embodiment was calculated by changing the diameter of the sand discharge pipe 3 in three sections.

Then, mud feeding for 9 hours (mud sending amount 918 m ³ )
Then, the treatment yard 5 became full, and the mud pumping was stopped.

Immediately after the passage of the mud, the porous tube 12 '
The discharge of free water as clear separated water into the kamaba 13 by the drain pipe 3 arranged in the basin started.

Four days later, the aggregated sediment 62 having a large number of cracks 16, 16 ′ on the surface thereof is exposed in the treatment yard 5. 'To -0.85 m from the upper end.

Agglomerated sediment 6 after standing for 50 days
Level 2 is from the top of the dam 4 'in the treatment yard 5-
It has dropped to 1.06 m.

As a result of measuring the cone index at the current location, qc =
It showed 63.7 kN / m ² .

The corn index after 90 days is qc = 2.
It showed 54 kN / m ² .

The pressure loss in each section, in which the reaction time t in this example was calculated from the Re number and the average viscosity in each section, was as shown in Table 1 below.

[Table 1] The amount of sludge is 0.0283 m ³ / sec Unit of pressure loss k
g / m ² and viscosity are the results of a simulation simulation of aggregation in a beaker. The viscosity was measured using a B-type viscometer, rotor No. It is a measured value of 3, 60 rotations. The pressure loss ΔP (turbulent flow) is ΔP = 2
It was calculated as fρV ² L / 10 ⁴ · g · D. Here, f is the friction factor in the pipe, and ρ is the specific gravity of mud (kg / m
^3), V is the flow velocity (m / sec), L is the pipe length (m), g is gravitational acceleration (m / sec ^2), D is the tube diameter (m). Here, f = 0.0059 was used.

The amount of mud feeding is 0.0283 m ³ / sec, the unit of pressure loss is kg / m ² , and the viscosity is the result of a simulation test of aggregation in a beaker.

The properties of the separated water collected from the discharge pipe 3 two days later are shown in Table 2 below.

[Table 2]

[0075]

Comparative Example 1 Before the addition of the polymer flocculant A and after the addition of the polymer flocculant A until before the addition of the inorganic metal polyvalent salt C,
The dredged mud 2 is sent to the sand discharging pipe 3 under the same conditions as in the embodiment except that the diameter of the sand discharging pipe 3 in three sections from the addition of the inorganic metal polyvalent salt C to the discharge to the treatment yard 5 is changed. The pressure loss in each section was calculated. The diameter of each sand discharge pipe 3 was set so that turbulent flow was maintained even at the maximum viscosity.

Table 3 shows the results.

[Table 3]

As shown in Table 1 of this embodiment, the dredged mud 2 having a diameter of 0.15 m and a diameter of 0.0283 m ³ / sec.
(Water content: 1200%) 2, the Reynolds number at the time of the viscosity peak in the section from the injection point 19 of the polymer flocculant A to the injection point 20 of the inorganic metal polyvalent salt C is 667, and the average Is 2106, the Reynolds number at the time of the viscosity peak in the section of the discharge port from the injection point 20 to the end point of the inorganic polyvalent salt C is 1014, and the average Reynolds number is 3167. Was satisfied.

The passage time (reaction time) was such that the reaction time with the polymer flocculant A was 156 seconds, and the reaction time with the inorganic polyvalent salt C was 30 seconds, which also satisfied the set conditions.

The total pressure loss is 10,000 kg / m ²
And was within practical range.

When the flocculated floc was visually inspected at the outlet of the sand discharging pipe 3, the floc 21 was formed in the same manner as the beaker experiment apparatus 63 shown in FIG. 6 in the laboratory. It was confirmed that spontaneous dehydration was proceeding very smoothly, for example, the surface (mud surface) was exposed.

On the other hand, as shown in Table 3, turbulence (Reynolds number 2100 or more) is maintained at any point.
From the point before the addition of the polymer coagulant A to the point 19 and after the point 19 of the addition of the polymer coagulant A to the addition point 20 of the inorganic metal polyvalent salt C, from the point 20 of the inorganic metal polyvalent salt C In the case of the comparative example in which the diameter of the sand discharge pipe 3 in three sections from the addition to the discharge to the treatment yard 5 was changed, the overall pressure loss was as high as 1850000 kg / m ² , and the retention time was also high. 18 seconds after the addition of the inorganic metal polyvalent salt from the point 20 to before the addition of the inorganic metal polyvalent salt from the point 20 to the treatment yard 5 after the addition from the point 20 of the inorganic metal polyvalent salt C. It took only 6 seconds to discharge, which proved to be impractical.

As described above, according to the invention of this application, the dredged mud 2 can be prepared without preparing a special stirring device or a mechanical dewatering device 11 if only a certain length of the sand discharge pipe 3 and the processing yard 5 are prepared.
Can be processed.

Thus, the number of days after dewatering in the processing yard 5 and transporting to the construction site by the dump 8 is only about 9 years, while the conventional drying method using the chemical-free injection sun 8 takes about one year.
Since the operation is completed in 0 days, the operation of the processing yard 5 can be repeated and the economic merit obtained is very large.

[Brief description of the drawings]

FIG. 1 is a partial side view of a first step of an embodiment of the present invention.

FIG. 2 is a schematic sectional view of the second step.

FIG. 3 is a schematic sectional view of the third step.

FIG. 4 is a schematic sectional view of a fourth step.

FIG. 5 is a schematic sectional view of the final step.

FIG. 6 is an experimental diagram of interaction between floc and free water.

FIG. 7 is a cross-sectional view of a waste mud in a dredging and processing yard according to the related art.

FIG. 8 is a sectional view of drying and dewatering in a processing yard.

9 is a cross-sectional view of the density increase of the waste mud in the processing yard, (a) is a cross-sectional view of the density increase by the coagulant, and (b) is a cross-sectional view of the density increase by the mechanical device.

FIG. 10 is a side view of the unloading of the soil with increased density.

FIG. 11 is a structural sectional view of laying of structural soil.

FIG. 12 is a structural sectional view of a processing yard based on the general technology.

FIG. 13 is a functional sectional view of a processing yard.

FIG. 14 is a plan sectional view of a processing yard.

FIG. 15 is a sectional view of a sand discharging pipe.

[Explanation of symbols]

 2 Dredging mud 5 Treatment yard 15 Dehydration 3 Sand pipe A Anionic polymer coagulant C Divalent or trivalent inorganic metal salt aqueous solution 12,12 'Drainage mechanism

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01D 21/01 111 B01D 21/01 111 C02F 11/12 C02F 11/12 A E02F 7/00 E02F 7/00 D (71) Applicant 000166627 Goyo Construction Co., Ltd. 2-2-2-8 Koraku, Bunkyo-ku, Tokyo (71) Applicant 000219406 Toa Construction Industry Co., Ltd. 5 Yonbancho, Chiyoda-ku, Tokyo (71) Applicant 000222668 Toyo Construction Co., Ltd. 4-1-1, Komyo-bashi, Chuo-ku, Osaka-shi, Osaka (71) Applicant 000155034 Honma Gumi Co., Ltd. 3300-3, Ninominato-machi, Minomachi, Niigata-shi, Niigata (71) Applicant 592251673 Rinkai Construction Co., Ltd. Tokyo 2-3-8, Shiba, Minato-ku (71) Applicant 000182030 Wakatsuki Construction Co., Ltd. 1-4-7 Hamacho, Wakamatsu-ku, Kitakyushu-shi, Fukuoka (71) Applicant 3900 26446 Tell Night Co., Ltd. 1-7-5 Hatagaya, Shibuya-ku, Tokyo (72) Inventor Masahide Tamura 1-4-6 Taito, Taito-ku, Tokyo Inside the Civil Engineering Research Center (72) Nobuaki Wada Taito-ku, Tokyo 1-6-4 Taito, Civil Engineering Research Center (72) Koji Yokoyama, Inventor Koji 1-6-4 Taito, Taito-ku, Tokyo Inside Civil Engineering Research Center (72) Inventor Toshifumi Miyake, Yamashita, Okayama City, Okayama Prefecture No. 1-113, Omotogumi Co., Ltd. (72) Inventor Hideo Hirose 3-31-5 Takada, Toshima-ku, Tokyo In-house Construction Co., Ltd. (72) Inventor Takashi Ishikura 2- Koraku, Bunkyo-ku, Tokyo 2-8 Goyo Construction Co., Ltd. (72) Inventor Hideo Suzuki 5 Yonbancho, Chiyoda-ku, Tokyo 5 Toa Construction Industry Co., Ltd. (72) Inventor Ryuichi Kawanishi 4-1-1 Komyobashi, Chuo-ku, Osaka-shi, Osaka No. 1 Toyo Construction Co., Ltd. (72) Inventor Eitaro Kawaura Nishiminatomachi, Niigata City, Niigata Prefecture 3300 Sankacho Honma Gumi Co., Ltd. (72) Inventor Tadahiko Kawada 2-8-3 Shiba, Minato-ku, Tokyo Rinkai Construction Co., Ltd. (72) Keisuke Yamada 2-chome Shimomeguro, Meguro-ku, Tokyo No. 23-18 Wakatsuki Construction Co., Ltd. (72) Inventor Katsuhisa Abe 1-7-5 Hatagaya, Shibuya-ku, Tokyo F-term (reference) 4T015 BA09 BA19 BB11 BB12 CA10 DA04 DA06 DA13 DB07 DB13 DC03 EA06 EA32 FA03 FA30 4D059 AA09 BD18 BE31 BE55 BE59 BE61 BJ16 CA03 DA16 DA17 DA24 DB24 DB28 EA01 EA02 EB11

Claims (8)

[Claims] 1. A method for treating a dredged mud in which a coagulant is added to a dredged mud having a high water content, wherein the mud is stored in a treatment yard and dewatered, wherein the dredged mud having a water content of 650% or more is passed through a sand discharging pipe. On the way to the treatment yard, first add an anionic polymer flocculant to the dredged mud, and then add an aqueous solution of divalent or trivalent inorganic metal salt to the dredged mud to complete the flocculation reaction. The mud which has completed the coagulation reaction is sent to a treatment yard provided with a drainage mechanism at the bottom through the sand pipe, discharged and spontaneously dried and dewatered, thereby treating dredged mud. Method. 2. The method according to claim 1, wherein the anionic polymer flocculant has a molecular weight of 8
The method for treating dredged mud according to claim 1, wherein the amount of the polyacrylamide-based polymer flocculant ranges from 0,000,000 to 12,000,000. 3. The method for treating dredged mud according to claim 1, wherein a reverse emulsion type of the anionic polymer flocculant is added to the mud as it is. . 4. The method for treating dredged mud according to claim 3, wherein the inverse emulsion type anionic polymer flocculant has a viscosity of 0.5 Pa · S or less. 5. The amount of the inverse emulsion type anionic polymer flocculant in terms of pure content is 0.1% or more, preferably 0.2% or more, based on the solid content in the dredged mud. The method for treating dredged mud according to claim 1, wherein: 6. The length of the sand drainage pipe from the time when the liquid anionic polymer flocculant is added to the time when the divalent or trivalent inorganic metal salt aqueous solution is added is a flow rate × 60 to 600 seconds. 2. The dredging pipe according to claim 1, wherein the length of the sand discharge pipe from the time when the divalent or trivalent inorganic metal salt aqueous solution is added to the time when the pipe is discharged to the processing yard is a flow rate × 18 to 300 seconds. Mud treatment method. 7. The pipe diameter of the sand discharging pipe is determined so that the Reynolds number at the time of peak viscosity is 500 or more and the average Reynolds number is 2100 or more in the sand discharging pipe. The method for treating dredged mud according to claim 1, wherein: 8. The flow rate and specific gravity of the dredged mud flowing through the sand discharge pipe are continuously measured, and the addition rate of the flocculant is determined from the relationship between the specific gravity and the addition rate of the flocculant determined in advance in a laboratory experiment. 2. The method for treating dredged mud according to claim 1, wherein the amount of the flocculant added is automatically controlled based on the result of calculation and the result of (flow rate x flocculant addition rate).