JPH10328700A - Treatment of waste sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent method for treating sludge in which execution is easily performed in the generation site of waste sludge and both dewatering and solidification of waste sludge are easy and liquid spill from solid matter is prevented and transport is easy and utilization is enabled and therefore the carrying treatment expense is reduced and necessity for securing a landfill site is made little. SOLUTION: The method for treating waste sludge consists of a flocculation separation and dewatering process, in which a flocculant containing both sides of at least an inorganic flocculant and a polymer flocculant is added to waste sludge and fine granular solid matter in sludge is flocculated and thereafter the flocculated solid matter is dehydrated, and of a solidification process in which a solidifying agent is added to dehydrated cake obtained in the flocculation separation and dewatering process and the mixture is kneaded and solidified. Thereby, a large quantity of waste sludge generating in the civil engineering and construction works is easily treated in the site of generation. Treated material is recovered as sand, ballast, solid matter and water in whole and everyone is reutilized. Also, handing properties and utilization are enhanced and carrying-away is easy and trouble for securing a landfill site is solved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater, and more particularly to a method for treating wastewater generated in civil engineering and construction works.

[0002]

2. Description of the Related Art In recent years, a large amount of muddy water has been generated in civil engineering and construction works such as underground excavation, ground improvement, and dredging, but the amount of this muddy water tends to further increase. This wastewater usually contains a large amount of water and has a high fluidity, so it is difficult to handle.Conventionally, the wastewater is transported out of the wastewater generation site using a special vehicle such as a vacuum truck, and then discharged to an intermediate treatment plant. After treatments such as coagulation and dehydration, they were landfilled in final disposal sites or dumped in the ocean. However, unloading by special vehicles such as vacuum vehicles requires a large amount of money, it has become difficult to secure final disposal sites, and ocean dumping has been banned in principle from the viewpoint of environmental protection. There are many problems and it is desired to eliminate or minimize waste.

[0003] For this reason, various methods for carrying out the wastewater after performing some volume reduction treatment at the generation site thereof have been studied. As the volume reduction treatment, for example, sedimentable large-particle-size solids such as sand and gravel are separated, followed by coagulation and sedimentation of fine solid particles and dehydration. According to this method, the waste has a reduced fluidity and a reduced volume, so that the waste can be carried out using a cheap dump truck, and the number of the waste can be reduced, thereby reducing the cost of carrying out the waste. It is possible to do. In addition, since the amount of waste that needs to be landfilled is reduced, it is also advantageous in terms of processing costs and securing land for landfill.

[0004]

However, in the conventional method of treating waste water that performs volume reduction treatment, it is difficult to coagulate or sufficiently dewater the waste water depending on the properties of the waste water, or the dewatered material may vibrate during transportation. In many cases, the fluidization or stickiness caused the poor handling. In particular, muddy water generated by the injection mixing method of injecting a hardening material liquid containing hydraulic cement into the ground and mixing it with the soil to form a hardened body and strengthening the ground usually contains a large amount of cement and has a pH , Solids concentration,
There are many problems, such as high viscosity, poor separability of sand / gravel and muddy water, and difficulty in dewatering the separated muddy water efficiently, and furthermore, the dewatered cake is easily fluidized during transportation and difficult to handle.

[0005] For this reason, compared with the case of treating ordinary soil, the treatment capacity in treating such wastewater is reduced, and it becomes impossible to treat the wastewater on site.
Alternatively, there is a problem in that the apparatus becomes large in size in order to secure the processing capacity, and a large facility cost and a large processing site are required. In addition, the water content of the dewatered cake is high, it is fluidized as it is, and it is difficult to handle, it is difficult to further dewater or solidify it, and it is transported with care to prevent environmental pollution due to dripping etc. and industrial waste There was also a problem that it had to be disposed of as waste.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems when separating and recovering solids and water from wastewater, which can be easily carried out at a wastewater generation site. Separation of sand and gravel from muddy water is easy, and the separated sand and gravel are easy to handle, safe and reusable.
Easy separation, dewatering and solidification of solids contained in muddy water that does not originally contain sand and gravel and muddy water from which sand and gravel have been separated, with little dripping from these solids, easy transport, and reusable Accordingly, an object of the present invention is to provide an excellent method for treating wastewater, which can reduce the cost of carrying out the wastewater and reduce the necessity of securing a landfill site.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, added a flocculant to the muddy water to carry out coagulation separation and dehydration for dewatering the fine solid particles in the muddy water. Thereafter, a solidifying agent is added to the obtained dewatered cake, and the solidified material is kneaded and solidified.If the solidified material is preferably shaped into granules or a lump, solidification / dehydration of solids in muddy water, shaping is easy, and The present inventors have found that the obtained excipient has less dripping, is easy to transport, can be dehydrated and solidified from muddy water, and can be reused as a construction material, and has reached the present invention.

[0008] That is, the gist of the present invention is to provide a coagulation separation / dehydration step of adding a coagulant containing at least both an inorganic coagulant and a polymer coagulant to wastewater to dewater solid fine particles in the muddy water. There is provided a method for treating wastewater comprising a solidification step of adding a solidifying material to the dewatered cake obtained in the separation / dewatering step, kneading and solidifying.

The wastewater targeted by the present invention is mainly generated in civil engineering and construction works such as underground excavation, ground improvement, and dredging. In many cases, silt / clay having a particle size of less than 74 μm is used. Etc., which contain substances having relatively small particle size and poor sedimentation. In addition, it often contains solids having a relatively large particle size and good sedimentation, such as sand and gravel having a particle size of 74 μm or more.

In particular, in the injection mixing method in which a hardening material liquid containing hydraulic cement is injected into the ground and mixed with the soil to form a hardened body and strengthen the ground, a large amount of strongly alkaline wastewater containing cement is produced. This wastewater is difficult to agglomerate and dewater silt and clay in the muddy water by conventional treatment methods, whereas the method of the present invention facilitates coagulation, dewatering and shaping. It is suitable for treating wastewater.

[0011] In the method of the present invention, when the wastewater contains gravel having a particle size of 2 mm or more, preferably sand or gravel having a particle size of 1 mm or more, it is necessary to first separate the sand and gravel from the wastewater. This is preferable because the possibility of damaging the dehydrating device, the solidifying device, and the shaping device in the dehydrating step is reduced, and the reusability of the solidified product is improved.

The separation device used in this step includes:
Practically, a compact one having a large processing capacity is preferable.For example, a vibrating sieve, an in-plane moving sieve, a rotating sieve, a liquid cyclone, or the like can be suitably used. Can be appropriately selected depending on the separation size, amount and the like.

In the step of separating sand and gravels, it is preferable to use an apparatus capable of separating gravels and sand separately. This allows
Gravel is easy to use for concrete aggregates and sand, and sand is easy to use for concrete aggregates, cushioning materials, leveling materials and the like, and the range of reuse is widened. As such a sand / gravel separation device, the above device can be used alone as long as it has a plurality of separation sizes, and a plurality of devices having different separation sizes may be used.

When a sieve is used, there is no particular limitation on the type of the sieve surface, and any of a woven mesh, a bar screen, and a punched mesh (perforated plate) can be used, but the mechanical strength is high and clogging is difficult. What is preferred is a bar screen (wedge wire screen) and a punching net. The mesh may be square, rectangular, circular, oval, etc.
It can be appropriately selected according to the properties of the target wastewater. Regarding the aperture, about 2 mm to 30 mm for separation of gravel,
Preferably 3 mm to 20 mm is used, and about 74 μm to 2 mm, preferably 0.15 to 1 mm for separation of sand.
mm.

When the solid content of the wastewater to be treated in the sand / gravel separation step is high in concentration, high in viscosity, or contains a large amount of cement, the efficiency of sand / gravel separation is reduced. In addition, fine particles such as silt, clay, cement, etc. may adhere to the separated sand and gravel, reducing their handling and recyclability. To the muddy water before separation, a fluidizing agent, a dispersant, a flocculant, a pH adjuster and at least one type of muddy water adjuster selected from the group consisting of a cement setting retarder,
Dilution of muddy water, washing of water when separating sand and gravel, etc. may be performed according to the situation.

Examples of the fluidizing agent used herein include alkali (earth) metal salts of acids such as lignin sulfonic acid, naphthalene sulfonic acid, melamine sulfonic acid, polycarboxylic acid, oxycarboxylic acid, and alkyl allyl sulfonic acid. Of formalin condensate, etc., as the dispersing agent, silicic acid, metasilicic acid, phosphoric acid, polyphosphoric acid, alkali metal salts of acids such as hexametaphosphoric acid and sodium hydroxide,
Sodium carbonate and the like can be mentioned, as the coagulant, aluminum sulfate, aluminum chloride, polyaluminum chloride, ferrous sulfate, ferric sulfate, ferric polysulfate, inorganic coagulant such as ferric chloride and Examples of the pH adjusting agent include acids and acid salts such as sulfuric acid, hydrochloric acid and carbon dioxide, and alkalis such as sodium hydroxide, slaked lime and sodium carbonate.

When the wastewater contains cement, any of the above dispersants other than silicic acid and metasilicic acid can be used as the dispersant.
Gypsum, silicofluoride, phosphate, zinc chloride, zinc oxide, boric acid, borax, boron oxide, citric acid, sodium citrate,
Examples thereof include lactic acid, tartaric acid, gluconic acid, and salts thereof, and sugars such as glucose, sucrose, sorbitol, and pentaerythritol. One or more of these can be used as necessary. The amounts of these various additives used may be appropriately selected depending on the properties and solids concentration of the target muddy water.
It is preferably 0.01 to 10 parts by weight.

In the present invention, a coagulant is added to mud which originally contains no fine particles such as silt or clay, or contains no fine particles such as silt or clay. To aggregate the solids contained in the muddy water and dewater it. In this step, first, in coagulation of the solid content in the muddy water, a coagulation tank may be provided and the coagulant may be added to the muddy water and stirred and mixed. Mixing is preferred because the purified floc is less likely to break and the device becomes compact.

As the coagulant used here, it is necessary to use a coagulant containing at least both an inorganic coagulant and a polymer coagulant. As the polymer coagulant, it is preferable to use an anionic polymer coagulant. Further, it is more preferable to use a combination of an anionic polymer flocculant and a cationic polymer flocculant. By using such a flocculant combination, a large and strong floc can be obtained, the water content of the dehydrated cake is low, and the filtrate is free from turbidity due to the suspension, and efficient and good dehydration can be performed.

The inorganic coagulant used here includes ferric chloride, ferrous sulfate, ferric sulfate, ferric polysulfate,
Iron salts such as polyferric chloride, aluminum salts such as aluminum sulfate, aluminum chloride, potassium aluminum sulfate, ammonium ammonium sulfate, sodium aluminate, polyaluminum chloride, and polyaluminum sulfate;
Examples include iron / aluminum salts such as iron-containing aluminum sulfate and aluminum-containing polyiron sulfate, zinc salts such as zinc chloride and zinc sulfate, and the like. Ferric chloride, ferric sulfate, ferric polysulfate, polyaluminum chloride, poly Preferred examples thereof include aluminum sulfate, iron-containing aluminum sulfate, and aluminum-containing polyiron sulfate. One or more of these can be used as the inorganic flocculant, depending on the target wastewater.

Examples of the anionic polymer flocculant used here include acrylamide and a copolymer of (meth) acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid or salts thereof, and polyacrylamide. A partial hydrolyzate can be exemplified, and its molecular weight is 5
It is preferably at least 100,000, more preferably at least 10,000,000.

Examples of the cationic polymer flocculant include copolymerization of acrylamide with a cationic monomer such as dialkylaminoalkyl (meth) acrylate, dialkylaminoalkyl (meth) acrylamide or a salt or quaternary compound thereof. Or a homopolymer or copolymer of these cationic monomers, preferably having a molecular weight of 2,000,000 or more, more preferably 3,000,000 or more. These polymer coagulants may be used in combination of two or more if necessary, or may be obtained by adding a small amount of another water-soluble monomer copolymerizable with the above monomer. Can also be used.

When the muddy water contains cement,
The pH of the mud is 10 or more, and when the cement concentration is high such as mud generated by the injection mixing method, the pH often becomes 12 or more. However, it is impractical to neutralize this muddy water because a large amount of acid is required. Therefore, a coagulant is usually added to such high-pH muddy water for coagulation and dehydration. Therefore, in the case of a cement-containing mud, an iron salt-based inorganic coagulant that can be used even in a strongly alkaline region and has a high floc density is preferably used as the inorganic coagulant to be used.

The anionic polymer flocculant has a degree of anion (ion equivalent, pH 10, colloid titration) of 0.1.
A weak anionic polymer flocculant having a concentration of 5 to 1.5 meq / g is preferred, and a weak anionic polymer having a degree of anion of 0.5 to 1.0 meq / g is more preferred. As cationic polymer flocculant, degree of cation (ion equivalent, pH 4, colloid titration)
And a weak cationic polymer flocculant having a cation degree of 1.0 to 2.0 meq / g is preferably used.
Those having 0 meq / g are more preferred.

The amount of the coagulant to be added cannot be unconditionally determined because the optimum range varies depending on the properties of the target mud water, the solid concentration, and the type of the coagulant. 0.1 to 10 parts by weight of the agent, 0.005 to 3 parts by weight of the polymer coagulant, and 0.2 to
Preferably, 5 parts by weight and 0.01 to 0.5 parts by weight of the polymer coagulant are used. When anionic and cationic are used together as a polymer flocculant, the weight ratio of the respective amounts added is preferably from 1: 0.5 to 5, more preferably from 1 to 1 to 3.

The form of the flocculant to be used may be a powder, an aqueous solution or an emulsion. In the case of an emulsion, it may be a normal phase emulsion or a reverse phase emulsion, but is preferably an aqueous solution or an emulsion.

The dehydrating apparatus used in the present invention includes a pressure dehydrator such as a filter press, a screw press, a belt press and a drum press, a vacuum dehydrator such as an Oliver filter and a belt filter, a vacuum pressure dehydrator, a screw decanter and the like. Although it is possible to use a centrifugal dewatering machine, considering that it is most effective to treat the wastewater at the site of generation, it is preferable to use a screw that is as small as possible, has a high treatment capacity, and is easy to maintain. A press or a screw decanter is preferably used, and among these, a screw decanter is more preferable. The centrifugal force of the screw decanter is 200 to 120 in consideration of maintainability.
0G is preferable, and 300-800G is more preferable.

When a screen decanter is used, it is particularly preferable to carry out washing for discharging solidified substances remaining inside the screw decanter after the dehydration operation from the viewpoint of maintenance. As this washing, in addition to the operation of supplying and washing water after the end of the supply of wastewater that is normally performed,
It is preferable to perform one or more of the following two cleaning operations, and it is more preferable to use these two together.

1) This is a washing operation of the same portion for effectively removing solid matter adhering to the clearance between the bowl of the screw decanter and the screw conveyor, and specifically, by the completion of the dewatering operation. After stopping the screw decanter, 1G or more again, preferably 3 to 100G
After rotating to a rotational speed that gives a centrifugal force of a certain degree, a washing operation of turning off the power for rotation and passing water until the rotation is stopped can be exemplified, and this operation is performed one or more times, preferably 2 to 7 times.
It is good to repeat about once. 2) An operation for washing the inside of the casing for effectively removing solid matter adhering to the inside of the casing of the screw decanter. For example, a water injection nozzle is provided on the inner surface of the casing, and after completion of the dehydration operation, water is applied at an appropriate pressure and fountain amount. Washing operation of injecting this operation.
Preferably, it is performed about 2 to 7 times. For example, the pressure can be about 0.5 to ⁷ kg / cm ² , and the fountain amount can be 1 to 5 m ³ , depending on the size of the screw decanter. When these two operations are used in combination, they may be performed separately, but if they are performed simultaneously, the cleaning time is reduced.
It is preferable that the above operations are systematized so that the operations are performed automatically. In addition, when the emphasis is placed on lowering the water content of the dehydrated cake, a filter press may be preferable depending on the situation.

The water discharged in the dewatering step can be used on site as washing water for the apparatus, cutting water, kneading water for cement and the like. If necessary, treatment such as pH adjustment and the like can be carried out. As the pH adjuster, the above-mentioned acidic substances and alkaline substances can be used.

In the present invention, a solidifying agent is added to a dewatered cake obtained by dewatering muddy water in the dewatering process, and the solidified product is kneaded and solidified. The solidified material obtained simultaneously with or in the solidifying process is granulated. Or, it has a shaping step of shaping into a lump. As a solidifying agent, when the wastewater does not contain cement, a hydrophilic acrylic polymer, sodium silicate and its hardener, and sodium silicate and cement can be used, but when the wastewater contains cement, it contains sodium silicate A solidifying agent or a combination of a solidifying agent and a hydrophilic acrylic polymer is preferably used.

The solidifying agent containing sodium silicate means an aqueous solution of sodium silicate (hereinafter referred to as water glass), powdered water glass, crystalline sodium silicate or a mixture of these and other substances, regardless of their form. Water glass is preferred from the viewpoint of handleability and miscibility with waste mud.

Examples of the hydrophilic acrylic polymer include a polymer derived from an acrylic nonionic monomer or an acrylic ionic monomer, or a copolymer of both. And a copolymer with a crosslinkable monomer. Such acrylic nonionic monomers include acrylamide, isopropylacrylamide,
Diacetone acrylamide, dimethyl acrylamide,
Diethylacrylamide and the like can be exemplified, and as the acrylic ionic monomer, an anionic monomer, (meth)
Acrylic acid, 2-acrylamido-2-alkylpropanesulfonic acid, vinylsulfonic acid or salts thereof,
Dialkylaminoalkyl, a cationic monomer
(Meth) acrylate, dialkylaminoalkyl (meth)
Acrylamide or a salt or quaternary compound thereof can be exemplified. Examples of the water-soluble crosslinkable monomer include methylene bis (meth) acrylamide, 1,2-dihydroxyethylenebisacrylamide, and ethylene glycol di (meth) acrylate. The hydrophilic acrylic polymer may be copolymerized with a small amount of another water-soluble monomer copolymerizable with the above monomer, if necessary, unless the physical properties are significantly changed.

The hydrophilic acrylic polymer may be water-soluble or water-insoluble, and may be a powder or a liquid. However, a partially crosslinked but polymerizable acrylic polymer having spinnability is also preferably used by adding a water-soluble polymer or a water-soluble monomer and adding a crosslinkable monomer of about 3 to 100 ppm together with the water-soluble monomer. Can be When the polymer is a chain polymer (water-soluble polymer), the molecular weight of the hydrophilic acrylic polymer is preferably 1,000,000 or more from the viewpoint of aggregation performance. Further, the hydrophilic acrylic polymer is a particle having a particle size of 100 μm or less because of the ease of addition and mixing.
Those which are in a state of being dispersed in an oil or an aqueous salt solution which does not dissolve them are preferably used. In this case, the concentration of the acrylic polymer in the dispersion is preferably 10% by weight or more in order to reduce the amount of liquid added to the dewatered cake and to reduce the adverse effect on the prevention of the flow of the dewatered cake. From the viewpoint of properties, the viscosity of this dispersion is preferably 3000 mPa · s or less.

When sodium silicate or an acrylic polymer is used in combination therewith as a solidifying agent for a dehydrated cake, the use of a hardening agent for an aqueous solution of sodium silicate or a hardening aid as a solidifying aid further shortens the time. Curing can be performed in a short time, and the solidified material can have high strength. Such solidifying aids include quicklime, slaked lime, gypsum, cement, slag,
Calcium compounds such as calcium chloride, and sodium, potassium chlorides, sulfates, hydrogen sulfates, and hydroxides such as sodium chloride, potassium chloride, sodium sulfate, sodium hydrogen sulfate, sodium hydroxide, sodium carbonate, and sodium hydrogen carbonate , Carbonates, bicarbonates, etc., magnesium chloride, aluminum chloride, aluminum sulfate,
Sodium aluminate, magnesium sulfate, magnesium such as magnesium oxide, aluminum compounds, sulfuric acid,
Hydrochloric acid, phosphoric acid, acids such as acetic acid, and glyoxal, ethylene glycol diacetate, ethylene carbonate,
Organic compounds such as γ-butyl lactone and triacetin can be exemplified, and one kind or two or more kinds may be added. The amount of addition of these solidification aids depends on the amount of sodium silicate added,
It depends on the type of the solidification aid, the composition of the muddy water and the like, and cannot be unconditionally determined, but is preferably 1 to 15 kg per 100 kg of the dewatered cake.

When the muddy water contains cement, 1 to 30 kg of sodium silicate is used per 100 kg of the dehydrated cake when a solidifying agent containing sodium silicate is used, and when pure water is used, 0.01 to 30 kg is used when a hydrophilic acrylic polymer is used. It is preferable that the weight is 2 kg.
It is preferable that the weight is 5 kg and the latter is 0.01 to 1.0 kg in pure content. In any case, when the added amount of the solidifying agent is within the above range, the solidification is excellent, and the strength of the solidified product is excellent, but even if the amount exceeds the upper limit of the above range, a remarkable effect cannot be obtained. Economic efficiency is reduced.

When the dehydrated cake to be solidified contains cement, the solidified as described above has a relatively short solidification time, a high strength, and has little dripping from the solidified product. Reusable as an aggregate or a cement additive is also possible and preferable. Therefore, in the case of wastewater containing no cement or wastewater having a low cement content, the cement content of the dewatered cake is 3% by weight or more, preferably 6% or more. Weight% or more,
More preferably, 10% by weight or more of cement may be added or added.

To add and knead the solidifying agent and the solidification aid to the dewatered cake, any material can be used as long as sufficient kneading can be achieved, but it is small, has a high kneading effect, and has a large processing capacity. A continuous type is preferable, and a continuous kneader, a pug mixer, and a screw feeder are preferably used. Further, as the kneading machine, a blade having a shape that gives an appropriate kneading effect to the extent that the dewatered cake that has been solidified or solidified is not destroyed and that provides an appropriate extrusion speed to increase the processing amount, for example, a pug-shaped blade More preferably, it is a continuous kneader having paddle-shaped blades.

The solidified material thus obtained is a roadbed material,
It can be reused as a material for roadbed materials, surface covering materials, bricks, tiles, porcelain, etc., as a raw material for cement, etc., and even when discarded, it is crushed or dripped by transportation with a dump truck etc. It can be transported without any special consideration. This solid is reused as described above,
Uniaxial compressive strength of 50 kPa from the viewpoint of ease of transportation and disposal
It is preferable that it is above.

In the present invention, it is preferable that the dewatered cake solidified by adding and mixing the solidifying agent or the solidification aid is formed into granules or blocks. It is preferable that the excipient be a granular or lump having a minor axis of 2 to 200 mm.

The treatment method of the present invention is preferably carried out at or near a site where muddy water is generated, whereby the effects of the present invention become more remarkable. An example of the relationship between the approximate installation area and the treatment capacity when the apparatus based on the treatment method of the present invention is provided at a muddy water generation site is shown, for example, in an installation area of 120 to 160 m ² , the sludge treatment capacity is 15 to ³⁰ m ^3.
/ h, so that a large-capacity device can be obtained in a relatively small space. This wastewater may be stored in an appropriate facility before the treatment method of the present invention is performed.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the examples, four types of mud water having the following composition generated at the ground improvement construction site by the column jet grout method were used. Note that the muddy water 2 is muddy water that does not contain cement and is generated by the preceding water drilling. Wastewater composition (% by weight) Water Cement Silt / Clay Sand Gravel pH Wastewater 1 (S1) 48 10 20 17 5 12.5 Wastewater 2 (S2) 55 0 25 15 5 9.0 Wastewater 3 (S3) 60 16 26 10 13.1 Wastewater 4 (S4) 4509 10 30 7 12.2

Reference Examples Production examples of two types of hydrophilic acrylic polymers used as solidifying agents are shown below. Polymer A: 426.0 parts of a 50% aqueous solution of acrylamide, 72.0 parts of acrylic acid, and 88.9 parts of 45% sodium hydroxide were added to 67.3 parts of water to prepare an aqueous phase. The IP-solvent 2028 3 manufactured by Idemitsu Petrochemical Co., Ltd. was added to the aqueous phase.
06.9 parts and Leodol MS-60 manufactured by Kao Corporation 10.
An oil phase containing 2 parts and 20.4 parts of REODOL SP-010 was added and stirred in a Waring blender for 1 minute to obtain a water-in-oil emulsion.

This emulsion was charged into a 1500 ml separable flask equipped with a stirrer, a nitrogen gas blowing tube, a thermometer and a gas outlet tube, and benzoin ethyl ether (0.05 part in 1 ml of methanol) was added. After blowing nitrogen gas into this emulsion to remove dissolved oxygen,
The polymerization temperature was maintained at 40 ° C. on a water bath, and the mixture was irradiated with light from an ultraviolet lamp until the residual monomer became 1% or less. To the water-in-oil emulsion thus obtained, 20.4 parts of Kao's Emulgen 910 and Emulgen 90
6 10.2 parts were added to obtain a water-in-oil polymer oil emulsion which can be converted into an oil-in-water emulsion when dropped into water. The obtained hydrophilic acrylic polymer (hereinafter, referred to as polymer A) was water-soluble, had a pure polymer content of about 30%, a molecular weight of the polymer of about 10,000,000, and a viscosity of 400 to 600 mPa · s.

Polymer B: A water-in-oil emulsion of an acrylamide / acrylic acid copolymer was obtained in the same manner as in Polymer A except that 0.0029 parts of methylenebisacrylamide was further added in the preparation of the aqueous phase. . Hereinafter, it is referred to as polymer B. This emulsion has a pure polymer content of about 30% and a viscosity of 400 to 600 mPa · S. Since this polymer has a partially crosslinked structure, this polymer is dispersed in water to give a polymer content of 0.1%. Aqueous solution with a pore size of 1
The filter filtration rate when filtered with a μm filter is 5% or less. In addition, this polymer content 0.1
After holding a glass rod having a diameter of 6.6 mm with a rounded tip 10 mm from the liquid surface in an aqueous solution having a
It shows a spinnability of 10 mm in a spinnability test that measures the distance until the yarn composed of the aqueous liquid attached to the glass rod is cut off by pulling up at a speed of 0 mm / min.

Incidentally, the water-soluble polymer A has a filter transmittance of 98% or more, the spinnability is 0 mm, and the polymer B and the polymer A have different properties.

Examples 1 to 10 and Comparative Examples 1 to 5 Table 1 shows the muddy water regulating agent shown in Table 1 as it is or the muddy water generated at the ground improvement construction site by the column jet grouting method shown in Table 1 as it is. , And continuous treatment was performed at a treatment amount of 1 m ³ / h. That is, the gravel is separated from the muddy water by a rotary sieve consisting of a punching net having a hole of 5 × 15 mm, and then the sand is separated from the muddy water from which the gravel has been removed by a vibrating sieve consisting of a wedge wire screen having an aperture of 0.5 mm. Then, the inorganic coagulant and the polymer coagulant shown in Table 1 were mixed with the muddy water from which the sand was separated by the amount line shown in Table 1 to coagulate the solid content in the muddy water. The mixture was centrifugally dehydrated at 600 G to separate into a dewatered cake and water, and then the solidifying agent and the solidification aid shown in Table 1 were added to the dewatered cake using a continuous kneader as a solidifying device, and kneaded. It was solidified and shaped into a size of 2 to 200 mm, and the performance of the wastewater treatment method was evaluated. Table 1 shows the results.
Shown in For maintenance of the dewatering device, after the screw decanter is stopped at the end of the dewatering process, the operation is again performed so that the screw decanter is rotated to have a centrifugal force of 30 G to inject water and brake the rotation of the screw decanter to stop. The operation of injecting water from the nozzle to a location where solids easily accumulate was repeated 5 times to wash the screw decanter.

[0048]

[Table 1]

In Table 1, AS in the column of the muddy water conditioner indicates aluminum sulfate, and NSF indicates a salt of formalin condensate of naphthalenesulfonic acid. In the column of inorganic coagulant, FC is ferric chloride, PSF is ferric polysulfate, FS is ferric sulfate, P
AC indicates polyaluminum chloride. Each of the anionic polymer flocculants is composed of an acrylamide polymer having a molecular weight of about 15 million, and weak 1 in the same column indicates an anion degree of 0.7 me.
q / g weak anionic polymer flocculant, weak 2 is a weak anionic polymer flocculant with anion degree of 1.4 meq / g, medium is 2.0 meq / g medium anionic polymer flocculant, strong Represents a strong anionic polymer flocculant having an anion degree of 3.0 meq / g.

The cationic polymer flocculant is an acrylamide polymer having a molecular weight of about 6,000,000, weak 1 in the same column is a weak cationic polymer flocculant having a cation of 1.2 meq / g, and weak 2 is A weak cationic polymer flocculant having a cation degree of 1.9 meq / g, a medium cationic polymer flocculant having a cation degree of 2.5 meq / g, and a strong cation degree of 4.5 meq / g.
1 shows a q / g strong cationic polymer flocculant.

Nos. 2 and 3 in the water glass column are JIS K, respectively.
The No. 2 water glass and No. 3 water glass described in 1408 are shown, and A and B in the polymer solidifying agent column indicate the polymer A and the polymer B prepared in the above Reference Example, respectively. PC in the column of solidification aid, etc. is ordinary Portland cement, CC is calcium chloride, PHS
Shows potassium hydrogen sulfate. The numerical values in the muddy water conditioner column and the flocculant column indicate the added parts by weight per 100 parts by weight of the solid content in the muddy water (however, PSF and PAC are parts by weight of the liquid). The values in the solidification column and the solidification aid column are the values of the dehydrated cake 10
Kg for 0 kg, but water glass and polymer solidifying agent indicate kg of the liquid.

In Table 1, the column of sand / gravel indicates the result of visual evaluation of the state of attachment of the fine particles to the separated sand / gravel. Δ indicates that the adhesion was slight, and X indicates that the adhesion was large. The moisture content of the dehydrated cake indicates the water content (%) in the dehydrated cake obtained in the dehydration step, and the cake fluidity is the degree of liquefaction when the same operation as the following breathing is performed on the dehydrated cake. Was evaluated. ○ in the same column indicates that liquefaction is slight, △ indicates that there is liquefaction,
X shows that liquefaction is large. In the turbidity column of the dehydrated filtrate, ○ indicates no or very slight turbidity.
Indicates that there is slight turbidity, and x indicates that there is considerable turbidity.

In the solidified physical property column in Table 1, the granularity in the shape column is 2 to 20 mm in a short diameter, and the lump exceeds 20 mm in a lump.
Less than 00 mm, large lump indicates more than 200 mm. The strength is an index when the uniaxial strength of the solidified product 30 minutes after the addition of the solidifying agent is measured. ◎ is 100 kPa or more, ○ is 50 kPa or more and less than 100 kPa, and × is 50 kPa.
It shows that it is less than Pa. It should be noted that, when the vehicle cannot be stacked in a pile, when it cannot be walked on it, and when it is fluidized during transportation, the standard is 50 uniaxial compressive strength.
It is less than kPa.

Breathing was carried out by the solidification treatment.
A lump of the solidified matter having a weight of about 60 g was picked up and subjected to reciprocating vibration 30 times in 15 seconds, and the amount of water that had oozed out was visually evaluated. ○ indicates no or very little breathing, △ indicates that there is breathing, and x indicates that there is breathing. The stickiness was measured by taking the solidified product obtained by the solidification treatment on a SUS304 plate, pressing it lightly, and then peeling the solidified product from the plate to evaluate the stickiness and stringiness of the solidified product. ○ indicates that there is neither stickiness nor stringiness, △ indicates that there is some stickiness and stringiness, and x indicates that there is stickiness and stringiness. The transportability was determined as to whether or not the truck could be transported without any problem. ○ indicates that there was no problem in transporting, △ indicates that there was some problem with breathing, adhesion, etc., × indicates breathing, dripping, This indicates that transport on a dump truck is difficult due to adhesion or the like.

[0055]

According to the present invention, a large amount of muddy water generated by civil engineering construction can be easily treated at the site where the wastewater is generated, and the treated matter is all recovered as sand / gravel, solidified matter and water. Both can be reused. That is, sand is used as concrete aggregate or cushion material, gravel is used as concrete aggregate, etc., and solidified material is used as roadbed material, subgrade material, surface covering material or brick,
It can be used for materials such as tiles and ceramics, as a raw material for cement, etc., and all are useful. Moreover, the handling and reusability are improved, the cargo can be easily carried out, and the problem of securing a landfill site is solved.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Go Nakagawa 10-1 Ogurocho, Tsurumi-ku, Yokohama-shi, Kanagawa Nitto Chemical Industry Co., Ltd.

Claims (11)

[Claims] 1. A dewatering step of adding a coagulant containing at least both an inorganic coagulant and a polymer coagulant to wastewater to dewater coagulated solids in the muddy water, and solidifying the dewatered cake obtained in the dewatering step. A method for treating wastewater comprising a solidification step of adding, kneading and solidifying an agent. 2. The method for treating wastewater according to claim 1, wherein the wastewater contains cement. 3. The method for treating wastewater according to claim 1, wherein the solidified material obtained in the solidifying step is shaped simultaneously with the solidifying step or in the form of granules or a lump. 4. The method according to claim 1, wherein the polymer flocculant is an anionic polymer flocculant or a combination thereof with a cationic polymer flocculant. . 5. An inorganic coagulant is used in an amount of 0.1 to 10 parts by weight and a polymer coagulant is used in an amount of 0.00 to 10 parts by weight per 100 parts by weight of solids in muddy water.
5 to 3 parts by weight, the polymer flocculant is an anionic polymer flocculant, or the weight ratio of the anionic polymer flocculant to the cationic polymer flocculant is 1: 0. .
The method for treating wastewater according to claim 4, wherein the number is 5 to 5. 6. The inorganic coagulant is an iron-based inorganic coagulant,
The anionic polymer flocculant satisfies at least one of a weak anionic polymer flocculant and a cationic polymer flocculant being a weak cationic polymer flocculant. The method for treating wastewater according to claim 4 or 5. 7. The method for treating wastewater according to claim 1, wherein the solidifying agent contains a solidifying agent containing sodium silicate or further contains a hydrophilic acrylic polymer. 8. The treatment of waste water according to claim 7, wherein the hydrophilic acrylic polymer is a water-soluble acrylic polymer or a partially crosslinked but spinnable hydrophilic acrylic polymer. Method. 9. The method for treating wastewater according to claim 1, wherein the wastewater is mud after separation of sand and gravel in the original wastewater. 10. A dewatering device used in the dewatering step is a screw decanter. After the dewatering step is completed, at least a clearance portion between the bowl and the screw conveyor in the screw decanter and / or a solid substance remaining on the inner surface of the casing is washed and removed. The method for treating muddy water according to any one of claims 1 to 9, wherein an operation is performed. 11. The wastewater treatment according to claim 1, wherein the solidification device used in the solidification step is a continuous kneader having a blade shape of a pug type or a paddle type. Method.