JP2000326000A - Dehydrating treatment of muddy water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently dehydrate highly concentrated and highly viscous muddy water discharged at a time of civil engineering/building construction. SOLUTION: Muddy water with a specific gravity of 1.2 or more is supplied to a paddle type flocculation reaction tank 1 constituted so that a pair of paddle shafts 4a, 4b having a large number of stirring feed blades 3, 3... attached to the outer peripheries thereof are mutually rotated in opposite directions while meshing the stirring feed blades 3, 3... and a dehydrating agent consisting of a cationic polymeric flocculant, an anionic polymeric flocculant and a water soluble salt is also added to the reaction tank 1 and muddy water and the dehydrating agent are stirred and mixed by the paddle shafts 4a, 4b to form flocs by the flocculation of a mud component and these flocs are dehydrated to form a dehydrated cake low in water content.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently dewatering high-concentration, high-viscosity mud among mud discharged during civil engineering and construction works and mud generated by various industrial wastewater treatments. And a method for dehydrating muddy water.

[0002]

2. Description of the Related Art Since muddy water of various properties is discharged in civil engineering work and construction work such as tunnel excavation, boring, and pile driving, dewatering is reduced and carried out at a site where muddy water is generated in a short time. The work environment has been maintained and the cost of unloading has been reduced to the extent possible.

[0003] In such a general method of treating mud, a flocculant is added to the mud to aggregate into flocs of an appropriate size, which are then dewatered and separated into solids and liquids. (Sludge solids) and separated water are subjected to post-treatment if necessary depending on the type and amount of muddy water, and finally to a dehydrated cake with a certain strength, which is used for backfilling, subgrade materials, embankments and residential land development, etc. Used as soil or fertilizer, the separated water is discharged to rivers and other places.

[0004] The coagulant used for dehydrating this mud (hereinafter, referred to as
Examples of the “dehydrating agent” include various types of dehydrating agents such as a single use of a cationic polymer flocculant and a combination of a cationic polymer flocculant and an anionic polymer flocculant. Various methods have been proposed as methods.

[0005]

The dehydration treatment using these high-molecular coagulants generally has insufficient cohesive force.
In the subsequent dewatering process, sufficient dewatering is not possible, which is not economical, and high-concentration, high-viscosity mud with low water content among mud discharged from building construction sites, etc. After treatment with an agent and hardening, or after absorbing water in muddy water and diluting it, it is subjected to coagulation treatment with an anionic polymer.

[0006] However, the means for treating with a solidifying agent is as follows:
It has the drawback that the cost increases because it is necessary to use a large amount of a solidifying agent to solidify the muddy water, and the diluting means requires water for diluting the muddy water, so it is applicable in a place where water supply is inconvenient. However, there are many problems to be solved, such as requiring a new facility for dilution and weakening the cohesive force, resulting in a small volume reduction rate and not being economical.

The present invention has been made in view of the above situation and as a result of intensive research, it has been found that a cationic organic polymer flocculant, an anionic organic polymer flocculant and a dehydrating agent comprising a water-soluble salt can be converted into high-concentration, high-viscosity muddy water. It has been completed by the fact that it has been found that mixing and aggregation can be performed quickly and efficiently by stirring and mixing with a twin-screw stirrer.

[0008]

That is, the muddy water dewatering method of the present invention comprises a pair of left and right paddle shafts having a large number of stirring and feeding blades on the outer periphery thereof, which are rotated in opposite directions while engaging the blades with each other. Paddle-type coagulation reaction tank,
While supplying muddy water having a specific gravity of 1.2 or more, a dehydrating agent composed of a cationic polymer flocculant, an anionic polymer flocculant and a water-soluble salt is added, and the muddy water and the dehydrating agent are stirred and mixed by a paddle shaft. And dewatering by forming flocs.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Muddy water discharged in civil engineering work or construction work, that is, muddy water or tunnel discharged in underground continuous wall construction in which soil and a cement suspension are mixed to form a wall in the ground Drilling mud discharged through a propulsion pipe installed during excavation work has a very high concentration and viscosity, and its specific gravity is generally 1.2 to 1.7, making dehydration extremely difficult with conventional methods. It is.

In the present invention, the dehydrating agent used for dehydrating the mud having a specific gravity of 1.2 or more, which is extremely difficult to dehydrate, is a cationic polymer flocculant, an anionic polymer flocculant and a water-soluble salt, particularly 5 The pH of the aqueous solution of 4.5% by weight is 4.5 to 9.
0 is a water-soluble salt.

Specific examples of the cationic polymer flocculant used in the present invention include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, and a quaternary or tertiary compound thereof. Copolymers and copolymers of these with acrylamide or methacrylamide, Mannich-modified polyacrylamide or polymethacrylamide or quaternized products thereof, Hoffman decomposition products of polyacrylamide or polymethacrylamide, homopolymers of diallyldimethylammonium or Known ones such as chitosan acetate can be mentioned.

Among these, in particular, cationic polymer aggregation such as a homopolymer of quaternary methyl chloride of dimethylaminoethyl (meth) acrylate or an acrylamide copolymer containing at least 80 mol% of the quaternary compound. Agents are preferred and have a colloid equivalent value of 3.0 to 5.2 me.
Those having a range of q / g are preferably used.

Specific examples of the anionic polymer coagulant include sodium polyacrylate, a copolymer of (meth) acrylamide and sodium (meth) acrylate, a partial hydrolyzate of poly (meth) acrylamide, Copolymer of acrylamide and sodium 2-acrylamide-2-methylpropanesulfonate (hereinafter referred to as AMPS), terpolymer of acrylamide with sodium acrylate and sodium methacrylate, (meth) acrylamide and (meth) Sodium sodium acrylate and said AM
And a terpolymer with PS and sodium alginate.

Of these, anionic polymeric flocculants having a weak anion to a strong anion are preferred, and those having a colloid equivalent value in the range of -0.7 to -5.5 meq / g are preferred. Among them, -0.7 to -3.
A copolymer of acrylamide and sodium acrylate, a terpolymer of acrylamide and sodium acrylate, and the above-mentioned AMPS, which is an anionic polymer flocculant having a weak anion to a medium anion of 0 meq / g, is preferable.

The water-soluble salt used together with the cationic polymer flocculant and the anionic polymer flocculant includes:
It is preferable that the pH of the 5% by weight aqueous solution be 4.5 to 9.0, specifically, ammonium sulfate, ammonium chloride, ammonium nitrate, magnesium sulfate, magnesium chloride, calcium chloride, sodium chloride, potassium chloride, sodium nitrate, Potassium nitrate and the like, of which calcium chloride and ammonium chloride are particularly preferred.

The preferred proportions of the cationic polymer flocculant and the anionic polymer flocculant in the dehydrating agent are 20 to 95% by weight of the cationic polymer flocculant and 80 to 95% by weight of the anionic polymer flocculant. 5% by weight, more preferably 30 to 90% by weight of the cationic polymer coagulant, and 70 to 10% by weight of the anionic polymer coagulant.

The preferred amount of the water-soluble salt to be added to the cationic and anionic polymer flocculants is at least 1 time (by weight), more preferably 5 to 5 times the total amount of both polymer flocculants. If the amount is 10 times or more, and if it is less than 1 time, the viscosity of the muddy water does not decrease, and the dewatering property may be deteriorated.

The addition of the dehydrating agent to the mud depends on the properties of the mud to be treated, but about 1 to 5% by weight of the polymer of each polymer flocculant with respect to the solid content of the mud is used.

The mixing of the muddy water and the dehydrating agent is performed in a paddle-type coagulation reaction tank 1 comprising a main body 2 for receiving muddy water and a lid 9 for closing an upper opening of the main body 2 as shown in FIG. It is implemented. The device body 2 is provided with a pair of paddle shafts 4a, 4b having a large number of stirring and feeding blades 3, 3,.
Are arranged so as to rotate in opposite directions while meshing with each other, the variable speed motor 5 is connected to one of the paddle shafts 4a, and the other paddle shaft 4b is rotated by the gear 6 in synchronization with the paddle shaft 4a. It is configured as follows.

The other lid 10 is connected to a supply pipe 10 for supplying muddy water into the apparatus main body 2 and a supply pipe 11 for supplying and adding a dehydrating agent.
., Muddy water supplied into the apparatus main body 2 through the supply pipe 11 is stirred and mixed with the dehydrating agent supplied through the supply pipe 11 by a number of stirring feed blades 3, 3,. The flocculated mud formed by coagulation and solidification by the dehydrating agent and the separated sewage are both dewatered by a known dehydrator (not shown) such as a belt press through the overflow section 8 to reduce the water content. It should be a cake-like thing.

The paddle-type coagulation reaction tank 1 of this structure has a high concentration and a high viscosity by rotating a pair of paddle shafts 4a and 4b having a large number of stirring and feeding blades 3, 3. The muddy water and the dehydrating agent can be efficiently agitated, and at the same time, the muddy water can be coagulated to form flocs, so that the muddy water can be coagulated with high efficiency. In addition, 7 is a drainage pipe.

[0022]

The method for dehydrating mud of the present invention comprises a cationic polymer flocculant, an anionic polymer flocculant and a water-soluble salt,
Particularly, when a high-concentration, high-viscosity muddy water having a specific gravity of 1.2 or more is coagulated and solidified using a dehydrating agent composed of a water-soluble salt having a pH of 4.5 to 9.0 in a 5% by weight aqueous solution, a large number of By performing the stirring and feeding in a paddle type coagulation reaction tank having a pair of paddle shafts protruding from the outer periphery, the stirring and mixing of the muddy water and the dehydrating agent can be performed very efficiently, and dewatering can be performed.

At this time, the dehydrating agent used is excellent in water solubility and water dispersibility, and does not cause hydrolysis of the cationic group. The generated floc has excellent dewatering properties and does not corrode equipment.

[0024]

EXAMPLES The method for dehydrating high-concentration, high-viscosity mud according to the present invention will be described in more detail with reference to examples. <Example 1> As a cationic polymer coagulant, 90 g of a 2-methacryloyloxymethyltrimethylammonium chloride-acrylamide copolymer having a colloid equivalent value of 3.0 meq / g, and as an anionic polymer coagulant,
10 g of a sodium acrylate-acrylamide copolymer having a colloid equivalent value of -2.7 meq / g and 1 kg of sodium chloride as a water-soluble salt were dissolved in 20 liters of distilled water. Using this solution as a dehydrating agent, high-concentration mud water 1 with a specific gravity of 1.5 generated from soil containing mainly silt and small amounts of sand and clay, respectively, by the propulsion method.
Then, the mixture was stirred and aggregated in a paddle-type aggregation reaction tank 1 shown in FIG.

The aggregate removed from the paddle-type aggregation reaction tank 1 was dehydrated by a belt press dehydrator.
A dehydrated cake having a water content of 31% was obtained. The obtained dewatered cake can be sufficiently used as backfill material, subgrade material, embankment and building land development, etc., so that the filtered water will not cause any problem even if it is discharged to rivers and other places. It was clear.

[0026]

According to the method for dehydrating muddy water of the present invention, the pH of a cationic polymer flocculant, an anionic polymer flocculant and a water-soluble salt, particularly, a 5% by weight aqueous solution is adjusted to 4.5 to 9.5. 0
Using a dehydrating agent consisting of a water-soluble salt of high concentration and high viscosity with a specific gravity of 1.2 or more, a pair of left and right paddle shafts having a large number of stirring and feeding blades on the outer periphery are engaged in opposite directions while engaging the blades with each other. It is possible to obtain a dewatered cake having a low water content by aggregating the mud while stirring and mixing in a paddle type coagulation reaction tank provided so as to rotate, and dewatering the obtained agglomerated mud. It is excellent in that a dehydration cake can be formed by performing dehydration treatment extremely efficiently by a combination of the above-mentioned specific dehydrating agent and a device having a specific structure.

The dewatered cake dewatered by the muddy water dewatering method of the present invention can be sufficiently used as a material for backfilling materials, roadbed materials, embankments and residential land development, etc. The water is so clean that it does not cause any problems if discharged into rivers and other places.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a paddle-type coagulation reaction tank used for stirring and coagulating mud in the mud dewatering treatment method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 2 Paddle type coagulation reaction tank 2 Device main body 3 Stirring sending blade 4a, 4b Paddle shaft 5 Motor 6 Gear 7 Drainage pipe 8 Overflow part 9 Lid body 10, 11 Supply pipe

Continued on front page F-term (reference) 4D015 BA11 BA28 BB08 BB17 CA10 DB03 DB05 DB07 DB10 DB12 DB32 DB33 DC07 DC08 EA02 EA06 EA39 4D059 AA03 AA09 BE08 BE16 BE57 BE59 BE60 BJ03 CC10 DA01 DA07 DA09 DA35 DA46 DB18 DB24 DB25 DB28

Claims (1)

[Claims] 1. A muddy water having a specific gravity of 1.2 or more is supplied to a paddle-type coagulation reaction tank provided with a pair of left and right paddle shafts having a large number of stirring and feeding blades on the outer periphery so as to rotate in opposite directions while meshing the blades with each other. Supplying and adding a dehydrating agent consisting of a cationic polymer flocculant, an anionic polymer flocculant and a water-soluble salt, stirring and mixing the muddy water and the dehydrating agent with a paddle shaft to form a floc and dewater. A method for dehydrating muddy water.