JPH09168800A - Treatment method of high water content dredging sludge - Google Patents

Abstract

(57) [Abstract] [Problem] To provide a method for quickly and economically treating a large amount of high-water-content sludge accumulated in the bottom of lakes, rivers, harbors, etc., and landfill without land subsidence. It is to provide a processing method which is not limited in the use of the ground. SOLUTION: In a treatment method of adding flocculant to a high water content dredging sludge to make flocs, and then removing water by natural dehydration or mechanical dehydration, first, a solidifying material is added, and then a coagulant is added. A method comprising forming flocs containing solidifying material particles, or, first, adding a nonionic or anionic polymer flocculant, then adding a solidifying agent to replace the inorganic flocculant, and further adding as necessary. By a method comprising supplementing an inorganic flocculant or a cationic flocculant to form flocs containing the solidifying material particles.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the rapid dredging of a large amount of highly water-containing sludge accumulated on the bottom of lakes, rivers, shores, etc.
Regarding how to handle.

[0002]

2. Description of the Related Art Conventionally, when dredging and treating high water-containing sludge accumulated in the bottom of lakes, rivers, harbors, etc., if it is in a small amount, it is left as no chemical injection or coagulated by adding a coagulant. After that, a method of obtaining a treated product having a low water content by using a dehydrator has been used. Further, when treating a large amount of water so that a dehydrator cannot be used, a method in which dredged sludge is sent to a bank surrounded by a dike and dried in the sun has been mainly used.

[0003]

The high-water content sludge accumulated in the bottom of lakes, rivers, harbors, etc. is often a sludge-like substance rich in nutrient salts, and the rich nutrients such as nitrogen and phosphorus that are dissolved from it. It causes phytoplankton abnormalities and methane gas generation, resulting in significant environmental degradation. One of the effective methods for cleaning sludges, rivers and shores where sludge has advanced is to remove this nutrient-rich sludge-like substance by dredging, and the government and many local governments have been working on this early on. Has paid a certain amount of results. However, in most of the methods, the sludge sent from the dredger is stored in the treatment yard and dried in the sun, so large-scale embankment work is required in the treatment yard. Also, it will take a long time (1
Since it takes more than a year), there are many places that have a hard time securing the disposal site.

[0004] The sun drying takes time, and since the ground pressure does not occur in the disposal site even after the drying, the use of the disposal site is limited. Therefore, a method of mechanical dehydration as it is without chemical injection or by adding a flocculant is also partially adopted. However, mechanical dewatering has a small processing capacity and is not suitable for large-scale processing.

Further, a method is conceivable in which a flocculant is added to a high water content sludge to form a floc, and the floc is sent to a treatment yard made in consideration of drainage to naturally dehydrate the sludge. This method is a powerful treatment method in which the speed of dehydration is much faster than that in the sun drying if strong flocs can be produced. However, the strength cannot be obtained by just coagulating dehydration, and since the dehydration continues little by little even after the initial rapid dehydration, the ground subsides for a long time. It is difficult to use the disposal site for purposes such as building things.

There is also a method of mixing sun-dried or naturally dried sludge after coagulation treatment with a solidifying material by using a construction machine to give strength to treated soil to prevent ground subsidence. However, not only is the work difficult, it is difficult to prevent uneven mixing, and there is a high possibility of unequal settlement. If the high water content sludge is solidified with the solidifying material as it is without dehydration, a huge amount of the solidifying material must be used because of the high water content. Therefore, a wide disposal site must be secured because it does not fit economically and the amount is not reduced. In the dredging of harbors, work is often done to solidify the dredged sludge with cement and then dump it into the sea to create a landfill. In this case, if the dredging sludge and cement are mixed and dumped into the sea before solidification, even if the device such as a tremie pipe is used to gently throw it in, considerable marine pollution is unavoidable. In order to avoid this, the dredging sludge and cement are mixed and temporarily set on the quay for several days to 10 days until it hardens, and then dumped into the sea, but in this case, it is a large temporary yard. In addition to the above, a large amount of labor and mechanical force are required for the work of cutting the deposited material again, and the cost is enormous.

An object of the present invention is to provide a method for overcoming the above drawbacks and for treating a large amount of high water content sludge accumulated at the bottom of lakes, rivers, shores, etc. quickly and economically. The purpose of the present invention is to provide a treatment method that does not limit the use of landfills by creating a land that has high water permeability and is free from land subsidence.

[0008]

In the method for treating high water content sludge according to the present invention, first, a high water content sludge is mixed with an organic or inorganic coagulant and a solidifying material using a continuous mixer. The mixing order is to add the solidifying agent first, and then add one or several kinds of organic or inorganic coagulant, first add the nonionic or anionic organic polymer (polymeric coagulant), and then add the solidifying agent. In addition, if necessary,
There are two methods of adding an inorganic coagulant or a cationic coagulant, or both. As the continuous mixer, a paddle mixer or a continuous stirring tank is generally used, but the type is not limited as long as the sludge and the chemical can be continuously mixed. When the water content of the sludge is very high or when the solidifying material is added in the form of a slurry, a line-incorporated mixer such as a line mixer or a static mixer can also be used.
In the process, the sludge replaces the sludge containing hydrophobic flocs containing the solidifying material particles. At this time, it is a sturdy floc that does not collapse even if it piles up several meters or more of sludge in the sedimentation site and can be naturally dehydrated by gravity, or it does not atomize even if force is applied by mechanical dehydration. Is generated.

Next, the agglomerated sludge is sent to a sedimentation site for natural dewatering by gravity or forced dewatering by a machine, and the resulting dewatered cake is transported to a landfill and deposited. The sedimentation site may be a landfill as it is, or the sedimentation site may be in the sea. Even if it is put into seawater, its hydrophobicity makes it possible to substantially prevent pollution of seawater. When using a pump to transfer sludge, a type of pump that does not break the flocs is suitable, such as a hose pump or a mono pump. In the case of natural dehydration on land, devise a drainage facility to drain water. For example, open a required number of drainage wells in the sedimentation site and pump up the water accumulated in the wells to reduce the water level, or use a deep well method of 5 mm to 30 mm for gravel of 10 cm to 50 mm.
It is spread under a thickness of cm, and a culvert pipe is laid inside it to create a sedimentation site, and coagulated sludge is sent onto it, and water dehydrated by gravity is collected through the culvert pipe and pumped by a pump pump. And so on. On the other hand, in the case of mechanical dewatering, a belt press, a roll press, a screw press, a filter press, a centrifuge or the like can be used, but its processing capacity is limited, which is a drawback. If you can stably build a durable flock,
A conveyor using a mesh belt may be used as a simple dehydrator for mass processing. The collected water is neutralized and subjected to other necessary water treatment before being discharged. FIG. 1 shows a flow sheet summarizing the above steps.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The sludge treatment method according to the present invention comprises:
It is characterized by the order of addition of the solidifying material, and consists of two methods as described above. The first method is high water content sludge (water content ratio 50
% Or more), a solidifying material is added first, and then a flocculant is added to form flocs containing solidifying material particles. The second method is to add a nonionic or anionic polymer coagulant to a high water content sludge (water content ratio of 50% or more), and then add a solidifying material to replace the inorganic coagulant, and further Is a method of supplementing with an inorganic coagulant or a cationic coagulant to form flocs containing solidifying material particles. In both cases, the solidification reaction by the solidifying material slowly proceeds over several days to several tens of days, and completely over several hundred days. Therefore, between several hours and several tens of hours when the dehydration is completed, only a negligible solidification reaction occurs, and during that time, the floc state is hydrophobic. The flocs are formed to the size of adzuki beans on average.

The sludge to which the present invention is applied will be described. Generally, the properties of sludge can be broadly classified into three types: one with a large amount of sand and a low liquidity limit, one with a large amount of clay and a high liquidity limit, and one in the middle. Sludge treatment methods such as mechanical dehydration or natural dehydration depend on these properties. It has a high sand content and a low liquidity limit and a water content ratio of 50.
% Sludge, sludge with a large amount of clay and high liquidity limit and a water content ratio of less than 120%, and sludge having an intermediate property between them and a water content ratio of less than 80%, does not show a liquid state from the beginning, There is no processing advantage. Therefore, the sludge targeted by the present invention has a water content ratio of at least 50% or more when the properties are not taken into consideration. The water content ratio (%) as used herein means a value obtained by multiplying the ratio of the weight of water to the weight of dried sludge by 100. The water content ratio was measured according to JIS A-1203 "Soil water content test method".

The solidifying material used in the present invention is most preferably a special cement commercially available for sludge, high water content, and high organic matter. For example, Geolite series (made by Chichibu Onoda Co., Ltd.), Asano Clean Set series (made by Nippon Cement Co., Ltd.), and UKC series (made by Ube Cement Co., Ltd.) can be mentioned. In addition to ordinary cement (eg Portland cement), blast furnace cement,
It can be used as long as it elutes a metal ion having a divalent or higher charge and the solidification reaction proceeds slowly, such as a mixture of various cements and slaked lime or gypsum. The addition amount of the cement-based solidifying material depends on the type of the target sludge, the dehydration method of mechanical dehydration or natural dehydration, the required strength of the treated soil (landfill), that is, the purpose of reuse. Therefore, although it is difficult to specify the range, it is 1% by weight to 20% by weight based on the dry treatment weight of sludge.

The aggregating agent used in the present invention is a combination of an anionic or nonionic aggregating agent and a cationic aggregating agent, a combination of an anionic or nonionic aggregating agent and inorganic salts, an anionic or nonionic aggregating agent. It is preferable to use any one of a combination of an agent, a cationic flocculant, and an inorganic salt. As the nonionic or anionic flocculant, as a natural type, guar gum, roasted guar gum, seed polysaccharides such as locust bin gum, arabinogalactan gum, resin polysaccharides such as arabic gum, alginic acid, seaweed polysaccharides such as agar, Fruit polysaccharides such as pectin and silium gum, rhizome polysaccharides such as starch and konjac, fiber polysaccharides such as cellulose,
Animal-based gelatin, such as microbial Zansangum, Zancoat, Zanflow, curdlan, and succinoglucan.
Examples include casein, albumin and shrack. Also,
Oxidation, methylation, carboxymethylation of starch, guar gum, roasted guar gum, cellulose, alginic acid, etc.
There are starch derivatives, guar gum derivatives, roasted guar gum derivatives, cellulose derivatives, alginic acid derivatives and the like obtained by treatments such as hydroxyethylation, phosphorylation and cationization. Examples of the cellulose derivative include methyl cellulose, carboxymethyl cellulose, carboxymethyl hydroxyethyl cellulose, hydroxypropyl cellulose and the like. Examples of the alginic acid derivative include alginates and propylene glycol alginate. The anionic or nonionic flocculant, as a synthetic system, polyacrylamide, polyvinyl alcohol, maleic anhydride polymer, polyacrylic acid ester, acrylamide and acrylate polymer, polystyrene sulfonic acid, polyacrylic acid, There are polymers such as polyvinyl sulfonic acid and polymaleic acid. As a cationic flocculant,
Chitosan is a natural product. Examples of the cationic coagulant include synthetic ones such as polyacrylic acid ester-based, polymethacrylic acid ester-based, polyamine-based, dicyandiamide-based, polyacrylamide-based, and vinylformaldehyde-based polymers. The molecular weight of synthetic anions and nonionic flocculants is 10,000,000 to
25 million, preferably 12 to 18 million, and the molecular weight of the synthetic cationic flocculant is 10,000 to 90.
It is in the range of 0,000. The polymer flocculant may be added as an undiluted liquid of an inverse emulsion type as it is, or may be added as a powder or a liquid dissolved in water.

The inorganic salts used in the present invention include polyvalent aluminum chloride, ferric chloride, sulfuric acid band, ferrous sulfate, calcium chloride, sodium aluminate, sodium borate, sodium silicate, and other metals having a valence of 2 or more. These water-soluble salts can be used alone or in admixture of several kinds.

According to the first method of the present invention, as shown in the schematic diagram 1 (FIG. 2), a solidifying material is first added to a high water content sludge, and then two kinds of coagulants are added to solidify. This is a method of forming flocs containing material particles. After adding the solidifying material, the coagulant A is first added.
Is a nonionic or anionic polymeric flocculant, which is a long fibrous polymer, so that it is entangled with the dredged soil particles and the solidifying material particles. Next, the coagulant B is added. The coagulant B is an inorganic coagulant or a cationic coagulant, and is an inorganic or organic cation. Therefore, when the coagulant B encounters with the coagulant B, the long fibrous polymer rapidly contracts (coagulates) as if the limbs are rolled. It has the property of making round flock. At this time, the dredged soil particles and the solidifying material particles are included in the flocs. The strength of flocs is determined by the molecular weight of the polymer, ionicity, the charge amount of cations, solid particles, the polymer, the absolute amount of cations and the ratio of the three, and is complicated. Based on my experience, I added some anionic or nonionic flocculant to some excess first,
It is effective to add either the cationic flocculant or the inorganic salt, or a mixture of both, in order to obtain a strong floc. The anionic or nonionic flocculant is added in a slight excess, because when these polymers encounter subsequent cationic flocculants or inorganic salts, they coagulate themselves into hydrophobic particles to enhance the filterability. This is for the purpose of In the conventional method of adding the solidifying material after the addition of the cationic flocculant such as a sulfuric acid band, even if flocs are formed by the flocculating agent, the floc is broken into small particles by the addition of the solidifying material thereafter, and the natural dehydration cannot be performed. I had no choice but to rely on inefficient mechanical dehydration. However, in the first method according to the present invention, the flocculating agent was included in the floc, and the hydrophobicity of the floc made the natural dehydration very effective. Further, since this floc retains sufficient strength, it is not atomized even when a load is applied by mechanical dehydration, and the efficiency of mechanical dehydration is significantly improved.

In the second method according to the present invention, as shown in the schematic diagram 2 (FIG. 3), an anionic or nonionic organic polymer (polymer flocculant) A is first added, and then a solidifying material is added. The method further comprises adding an inorganic coagulant or a cationic coagulant B, or both, as required. In this case, the polyvalent metal ions eluted from the solidifying material act as the flocculant B of the first method, and contribute to the formation of flocs. When the shrinkage (aggregation) of the polymer is insufficient and the floc strength is weak only by the action of the polyvalent metal ions eluted from the solidifying material, an inorganic or organic cation (aggregating agent B in the schematic diagram 2) is added at the end. In the case of the first method according to the present invention, that is, the method of adding the solidifying material first, and then adding one or several kinds of organic and inorganic coagulants, there is a large amount of polyvalent metal ions eluted from the solidifying material. Due to the addition of anionic or nonionic flocculants to the polymer, hydration of the polymer is suppressed and a considerable excess of polymer is required. On the other hand, the second method according to the present invention, that is, the method of using the solidifying material as the secondary flocculant, is characterized in that the addition amount of the polymer may be small. For example, when 5% by weight of the solidifying material is used with respect to the dry sludge, the addition amount of the anionic or nonionic flocculant is
It is 0.8% by weight, and it is halved to 0.4% by weight in the second method. Also in the second method according to the present invention,
The floc contained a solidifying material, and due to the hydrophobic nature of this floc, natural dehydration became very effective. Further, regardless of the order of addition of the solidifying material, as in the first method according to the present invention, since this floc retains sufficient strength, it is not atomized even when a load is applied by mechanical dehydration, and the efficiency due to mechanical dehydration is also improved. It was markedly improved.

The sludge containing hydrophobic flocs obtained by the above-mentioned two methods is then subjected to natural dehydration or mechanical dehydration in the case of land treatment. In case of natural dehydration,
At the same time as sedimentation, natural dehydration due to the action of gravity begins, and the water content drops sharply. Dehydration is almost completed within a few hours, at least a dozen hours, and the water content at that time is 900 water.
300% to 450% even if starting from more than 50% sludge
To decline. In the case of mechanical dehydration, dehydration will be completed in a few minutes,
At that time, the water content falls to 100% to 300%.
Whichever dehydration method is used, the full-scale solidification reaction begins after dehydration and the strength of the landfill continues to increase. In both cases, the solidification reaction proceeds slowly over a period of days to tens of days, or even hundreds of days. Therefore, only a negligible solidification reaction takes place within a few minutes to a few tens of hours when the dehydration is completed. That is, in the method according to the present invention, no matter how high the water content of sludge is, the target of solidification by the solidifying material is 300% to 450% in the case of natural dehydration and 100% in the case of mechanical dehydration.
It is a sludge with a water content of 100% to 300% and solidifies at almost the same water content. This means that the water content after dewatering is almost constant, and that water content is roughly determined in advance, and it is possible to obtain the same strength with a smaller amount of solidifying material than when solidifying high water content sludge as it is. It means that you can do it. On the other hand, the final strength can be adjusted by the addition amount of the solidifying material. Therefore, the required final strength is obtained from the purpose of reusing the landfill, and the type of solidifying material and the addition amount are determined accordingly. Taking special cement as an example, the standard addition amount thereof is 1 to 20 parts by weight, preferably 3 to 10 parts by weight, based on 100 parts by volume of dredged sludge. In the case of treatment of harbor dredged soil, if the treatment method of the present invention is applied, even if the treated matter is immediately put into the sea, the treated matter is formed of hydrophobic and strong flocs, which may cause marine pollution. Absent. The processed material is deposited on the seabed, and is subjected to the denseness due to its own weight (the amount of buoyancy works, which is smaller than on land) and dehydrated. Since the solidification reaction of cement proceeds even in water, the strength of the sediment gradually increases. Since the dredging, treatment, and dumping in the sea can be performed continuously without interruption, the merit of saving work cost is remarkably large.

[0018]

EXAMPLES Examples 1 to 3 and Comparative Examples 1 and 2 of the present invention will be described. In this embodiment, the water content ratio is 600%, 65
Sludge adjusted to 0% and 900% was used. These measures the water content of sludge pumped up from the bottom of a lake according to JIS A-12.
Measured according to No. 03 (520% in this example) and was obtained by adding the required amount of water. As the cement-based solidifying material, Geolite 25 (manufactured by Chichibu Onoda Co., Ltd.), Asano Clean Set 10 (manufactured by Nippon Cement Co., Ltd.), and as an anionic flocculant, polyacrylamide reverse phase emulsion type Super Flock (manufactured by Mitsui Cytec) ( A molecular weight of about 12 million) was used. The uniaxial compressive strength was measured according to JIS A-1216.

Example 1 Moisture content of 600% and 900
% Of the sludge at the bottom of the lake and marsh was added to a mortar mixer having a capacity of 5 liters, and Geolite 25 as the cement-based solidifying material was added to the former and Asano Clean Set 10 was added to the latter and mixed well. Next, an anionic flocculant polyacrylamide reverse-phase emulsion type was added, and after confirming that the viscosity rapidly increased, an 8 wt% aqueous solution of a sulfuric acid band was further added to cause flocculation. Subsequently, the agglomerates were made of wire mesh with a bottom of 30 mesh, diameter 5 cm, height 15 cm
It was transferred to a cylindrical container of and dehydrated naturally. Amount of drug added,
Dehydration amount after 1 day, uniaxial compressive strength after 3 days, immediately after and 3
Table 1 shows the water permeation rates of the aggregates after the day. The water permeability of the aggregate was measured according to JIS A-1218.

(Example 2) Moisture content of 600% and 900
2 liters of the sludge at the bottom of the lake adjusted to 5% was placed in a mortar mixer having a volume of 5 liters, and the anionic flocculant acrylamide reverse phase emulsion type was added thereto and mixed well. Next, Asano Clean Set 10 was added as a cement-based solidifying agent to cause coagulation, and an 8 wt% sulfuric acid band solution was further added to strengthen the floc. Then the aggregates,
Diameter 5 cm, height 15 cm made of 30 mesh wire mesh
It was transferred to a container and dried naturally. Table 1 shows the amounts of the chemicals added and the treatment results.

(Example 3) Sludge at the bottom of a lake adjusted to a water content ratio of 650% was sent to a continuous battle mixer at a rate of 3 kiloliters per hour, and first, an anionic flocculant polyacrylamide reverse phase emulsion type was used for 1 minute. 20
Add at a rate of 0 ml and mix well. Next, the cementitious solidifying material was added at a rate of 2.5 kg for 1 minute to coagulate, and further an 8 wt% sulfuric acid band solution was added at a rate of 300 ml for 1 minute to strengthen the flocs. Subsequently, the aggregate was fully deposited in a pit having a length of 1.1 m, a width of 2.2 m, and a depth of 2 m. A perforation tube having a length of 2.5 m and a diameter of 20 cm was inserted to the bottom at two places in the center of the deposit, and the water accumulated at the bottom was pumped up and drained. In the perforated tube, ten slits each having a length of 1.5 m and a width of 3 cm were cut in the longitudinal direction, and a wire mesh of 30 mesh was attached around the slit. The natural dehydration was completed 8 hours after the start of drainage, and the total amount of drainage during that period was 1240 liters. 7 days later
When the pseudo-Cone index of the sediment was measured, the average was 1.
It was 9 kg / cm ² . The height of the deposit after 7 days is
At 1.3 m, the volume reduction rate was 35%.

Comparative Example 1 Moisture content of 600% and 900
% Of sludge on the bottom of lake and marsh was taken into a mortar mixer with a capacity of 5 liters, and Asano Clean 10 was added as a cement-based solidifying material to the mixture, and the mixture was mixed with a diameter of 5 cm.
The contents were transferred to a vinyl chloride cylindrical container having a height of 15 cm and allowed to cure indoors. At this time, the relationship between the addition amount of the cement-based solidifying material and the strength after solidification and the water permeation rate were examined. Table 1 shows the results. This comparative example is a case of solidifying as it is without any aggregation dehydration. Therefore, since the water content of sludge is high, more solidifying material was needed to solidify. In addition, the water permeation rate was remarkably low because the coagulation operation was not included.

(Comparative Example 2) 2 liters of sludge at the bottom of a lake adjusted to a water content of 900% was placed in a mortar mixer with a volume of 5 liters, and first, a nonionic flocculant polyacrylamide reverse phase emulsion type 7 with a molecular weight of about 12 million.
After adding 20 ml of 8 wt% sulfuric acid band solution and aggregating, 100 g of Asano Clean Set 10 as a cement-based solidifying material was added and mixed well. A part of this reaction product was transferred to a cylindrical container having a bottom of 30 mesh and having a diameter of 5 cm and a height of 15 cm and naturally dehydrated. The water content ratio obtained from the amount of dehydration and the water permeation rate immediately after dehydration were as shown in Table 1.

[0024]

[Table 1]

As is clear from the results shown in Comparative Example 1, if the sludge having a high water content is solidified as it is, the required amount of the solidifying material is increased as compared with the methods of Examples 1 and 2. This tendency increases as the water content increases. In contrast,
As shown in Examples 1 and 2, the coagulant according to the present invention and the treatment method in which natural dehydration and solidification are used together determine the water content ratio after dehydration, so that regardless of the original water content ratio, The amount of the solidifying material is almost constant, and the same strength can be expected with a much smaller amount of the solidifying material than the solidified material. Unlike mixing with the solidifying material after dehydration, no large-scale machine is required, uneven mixing does not occur, and ground subsidence does not occur. Further, in Comparative Example 1, the water permeation rate is remarkably small, and it is difficult to use the site formed by the deposit treated by this method. Even if a soil of about 1 m is applied, the soil will be washed away or become muddy if it is exposed to heavy rain. To prevent this, drainage work must be carried out at an enormous cost. On the other hand, the treated products of the present invention described in Examples 1 and 2 have a high hydraulic conductivity even after the land is filled and the strength gradually increases after landfilling. There are unknown advantages. Next, Comparative Example 2
As shown in, even if you try to dehydrate naturally after adding a solidifying material to the floc after aggregation, the floc will be broken,
Almost no natural dehydration. On the other hand, as shown in Examples 1 and 2, the method of adding the solidifying material first or as a secondary flocculant instead of the inorganic salt has a water permeability of 0. 014 cm / sec to 0.032c
It shows a high value of m / sec and gravel level, indicating that a strong floc with high water permeability can be formed. Example 3 shows that the deep well method is extremely effective for natural dehydration.

[0026]

The sun drying method, which has been widely adopted in the past, requires a long period of time until the completion of drying, the cost of embankment work is high, it is necessary to make every effort to prevent a fall accident, and the strength of the landfill is strong. It has many problems such as its weakness and limited use. On the other hand, the method of the present invention is
It has many features such as short-term treatment, completion of landfill, large processing capacity, unlimited use of landfill, economical, etc. The economic effect of rapidly treating high water content sludge is immeasurable.

[Brief description of the drawings]

FIG. 1A is a flow sheet 1 showing a method of first adding a solidifying material to a high-water content dredging sludge, and then adding a flocculant, and then dehydrating the same. (B) shows as flow sheet 2 a method of adding a polymer flocculant to a high-water content dredging sludge, then adding a solidifying agent, and further adding another flocculant if necessary, followed by dehydration.

FIG. 2 shows a schematic diagram 1.

FIG. 3 shows a schematic diagram 2.

4 shows the appearance (A) of the sample obtained in Example 1 and the appearance (B) of the sample obtained in Comparative Example 1. FIG.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Seiichi Sato 21-7 Nishinodai, Taniwahara Village, Tsukuba-gun, Ibaraki Prefecture (72) Inventor Katsuhisa Abe 1-9-12 Midorigaoka, Sakata City, Yamagata Prefecture

Claims (3)

[Claims] 1. A treatment method in which floc is formed by adding a flocculant to a high water content dredging sludge, and then water is removed by natural dehydration or mechanical dehydration, firstly a solidifying material is added, and then a flocculant is added. The method for treating high water content sludge is characterized in that flocs containing solidifying material particles are formed. 2. A process of adding floc by adding a nonionic or anionic polymer flocculant and an inorganic flocculant or a cationic flocculant to a high water content dredging sludge to remove water by natural dehydration or mechanical dehydration. In the method, first, a nonionic or anionic polymer flocculant is added, then a solidifying agent that replaces the inorganic flocculant is added, and further an inorganic flocculant or a cationic flocculant is added, if necessary, and the solidifying agent particles are added. A method for treating high water content sludge, which comprises forming flocs containing 3. The dredged sludge is replaced with a permeable ground by removing water by natural dehydration or mechanical dehydration after forming a floc containing the solidifying material. 2. The method for treating high water content dredging sludge according to 2.