JP2005334730A - Composition for sludge solidification and sludge solidification method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a composition for sludge solidification and to provide a sludge solidification method which have high safety, have no fear of environmental pollution due to the elution of heavy metals, such as hexavalent chromium, and alkaline components, and solidify water-containing sludge to form a solidified material which is not swollen and broken by rain water, sea water, and the like. <P>SOLUTION: The composition for sludge solidification comprises paper sludge, bagasse or their incinerated ash, ferrous sulfate, and at least one functional agent selected from a pH adjustor, a coagulant, a surface-active agent, a water absorption-reinforcing agent, and a dispersing agent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sludge solidifying composition and a sludge solidifying method for solidifying hydrous sludge to swell and disintegrate with rainwater or seawater, or to form a solidified material from which heavy metals such as hexavalent chromium are not eluted.

  In recent years, in rivers, lakes, and harbors, organic substances associated with inflow loads from the terrestrial area (living systems, livestock systems, natural systems: including fields), organic materials such as feeding by pearl farming and fish farming, and excretion have been long Over the bottom sediment layer. When the accumulated organic sludge is decomposed, a large amount of dissolved oxygen is consumed, which causes problems such as depletion of the sediment layer and deterioration of the fishing ground.

  For example, sediment containing organic matter existing on the bottom of the lake or the seabed, or hydrous sludge discharged from activated sludge treatment facilities, etc., may reduce the moisture content by temporarily dewatering or coagulating sludge sludge. It is processed by a method used for landfilling, a method of further incineration, a method of processing into a molded body such as a brick or a block using a cement-based or lime-based solidifying agent.

On the other hand, a method has also been proposed in which dredged sludge (soil) is returned to the seabed as an important unused resource and reused as a bottom layer suitable for growing seaweed, seaweed algae and seafood. .
For example, (1) solidifying agent in which minerals, calcium, silica and other inorganic compounds and surfactants are blended with incinerated ash of cement and fly ash and paper sludge, and (2) ferrous sulfate in hydraulic materials such as cement A hydraulic composition containing an anhydrous salt and / or a monohydrate, and (3) a cement slurry containing an appropriate amount of a substance that reduces hexavalent chromium has been proposed (see, for example, Patent Documents 1 to 3). .

  However, when cement or lime-based solidifying agent is added to and mixed with dredged soil to solidify sludge, there is a problem that alkali components and heavy metals are eluted from the solidified product. In particular, when the clay is solidified using a cement-based solidifying agent, there is a concern that elution of hexavalent chromium may occur even though the amount is very small (for example, “Handbook of Concrete Admixtures” edited by the Japan Society of Materials Science) First Edition, NTS Corporation, April 23, 2004, p. 417 (5.4 Other Sections: see Non-Patent Document 1).

Japanese Patent No. 3274376 JP 2001-151554 A JP 2001-335780 A The Japan Society of Materials Science, "Handbook of concrete admixtures", first edition, NTS Corporation, April 23, 2004, p. 417 pages (5.4 Other sections)

With the above solidifying agent substantially containing cement, when the solidified product is placed in water for a long period of time, elution of hexavalent chromium is feared even though it is a trace amount.
Therefore, the present invention is highly safe, and there is no concern about environmental pollution due to elution of heavy metals such as hexavalent chromium and alkaline components, and the water-containing sludge is solidified and a solidified product that does not swell and collapse due to rainwater, seawater, etc. An object is to provide a composition for solidifying sludge and a method for solidifying sludge.

  The inventors of the present invention have found the fact that sludge with a high water content is solidified in a granular form by blending ferrous sulfate with a specific solidifying agent containing paper sludge, bagasse or incinerated ash thereof, Furthermore, even when the solidified product was returned to the seabed or the like, it was confirmed that the solidified product did not swell and disintegrate, and no harmful substances such as alkali metals and heavy metals such as hexavalent chromium were eluted.

  Thus, according to the present invention, at least one selected from paper sludge, bagasse or incinerated ash thereof, ferrous sulfate, a pH adjuster, a flocculant, a surfactant, a water absorption enhancer, and a dispersant. The composition for sludge solidification characterized by including these functional agents is provided.

Moreover, according to this invention, the solidification method of the sludge characterized by adding and mixing said sludge solidification composition to sludge with a water content ratio of 200-900 weight%, and solidifying sludge is provided.
Furthermore, according to this invention, the solidified product solidified in the form of aggregate by the above-described sludge solidifying method is provided.

According to the present invention, a sludge solidifying composition for solidifying a sludge having a high water content into a granular shape with a small amount of addition, and forming a solidified product that does not swell and collapse due to rainwater, seawater, etc. And a method for solidifying sludge using the product.
The solidified product solidified by the solidification method of the present invention is returned to the seabed and reused as a bottom layer suitable for growth of useful resources such as seaweed, seaweed algae and seafood. be able to.

  The composition for solidifying sludge according to the present invention is at least selected from paper sludge, bagasse or incinerated ash thereof, ferrous sulfate, a pH regulator, a flocculant, a surfactant, a water absorption enhancer, and a dispersant. And one kind of functional agent.

Papermaking sludge is sludge discharged in the papermaking industry. In the present invention, dried and pulverized ones and further incinerated ones are used, and incinerated ash is particularly preferable in terms of water absorption effect. Incinerated ash is particularly preferable because it is porous and has the property of adhering and absorbing organic substances, heavy metals, odors and the like in sludge in a short time.
When the incineration ash is added to the sludge, the incineration ash absorbs the water in the sludge, the hydrated mineral in the incineration ash causes a hydration reaction, and ethrin guide (entry gite) is quickly generated. This hydration reaction proceeds while reducing the water content of the sludge. The generated ethrin guide is a needle-like crystal, and it is considered that this crystal quickly solidifies while surrounding the incinerated ash and the soil particles in the sludge, and the sludge aggregates.

Bagasse is a sugarcane squeeze discharged in the sugar industry, and in this invention, crushed and incinerated products are used.
Bagasse consists of components similar to paper sludge, and its effect is similar to paper sludge or its incinerated ash.

  Next, each functional agent will be described. As the functional agent, compounds having the same function can be used alone or in combination of two or more.

Examples of the pH regulator include alkaline inorganic compounds such as alkali metal, alkaline earth metal or aluminum hydroxide, specifically sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, aluminum hydroxide and the like. Can be mentioned.
The amount added is about 0.01 to 0.07 parts by weight with respect to 100 parts by weight of the main raw material (paper sludge, bagasse or incinerated ash thereof).

As the flocculant, inorganic flocculants such as aluminum sulfate (sulfuric acid band), ferric chloride, polyaluminum chloride or water-soluble aniline resin hydrochloride, polyethyleneimine, polyamine, polydiallyldimethylammonium chloride, chitosan and hexamethylenediamine -Polymers with moderate polymerization degree (molecular weight: thousands to tens of thousands) such as epichlorohydrin polycondensate, polyvinyl imidazoline, polyalkylamino acrylate, polyalkylamino methacrylate, polymethacrylate (including copolymers) And cationic polymer flocculants such as polyacrylamide and their Mannich modified products and partial hydrolysates. Among the polymer flocculants, polyacrylamide, polyacrylamide partial hydrolyzate, and poly (meth) acrylate copolymer are preferable, and poly (meth) acrylate copolymer is particularly preferable.
The addition amount is about 0.3 to 15 parts by weight with respect to 100 parts by weight of the main raw material.

Surfactants include anionic surfactants such as alkylbenzene sulfonate, lignin sulfonate, stearate, polyoxyethylene alkylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyalkylene block copolymer, allyl group Nonionic surfactants such as polyoxyethylene alkylphenyl ether having a polymerizable unsaturated bond such as anionic surfactants such as alkylbenzene sulfonate, lignin sulfonate and stearate are particularly preferable.
The addition amount is about 0.1 to 1 part by weight with respect to 100 parts by weight of the main raw material.

Examples of the water absorption enhancer include anhydrous gypsum and hemihydrate gypsum, and anhydrous gypsum is particularly preferable.
The addition amount is about 0.7 to 30 parts by weight with respect to 100 parts by weight of the main raw material.

Examples of the dispersant include tripolyphosphate and hexametaphosphate, and tripolyphosphate is particularly preferable.
The amount added is about 0.04 to 0.3 parts by weight with respect to 100 parts by weight of the main raw material.

Ferrous sulfate is generally known as a reducing agent, and is used, for example, for the reduction of heavy metals. Also in this invention, what is functioning as a reducing agent is considered.
Ferrous sulfate is preferably contained in 0.75 to 10 parts by weight, particularly preferably 1 to 5 parts by weight, in 100 parts by weight of the sludge solidifying composition. When the addition amount of ferrous sulfate is less than 0.75 parts by weight, the desired effect is not sufficiently exerted, and therefore it is not preferable. Moreover, when the addition amount of ferrous sulfate exceeds 10 weight part, since sludge becomes difficult to solidify, it is unpreferable.

The sludge solidifying composition of the present invention preferably further contains a polyvinyl alcohol resin (PVA resin). By combined use with this PVA resin, the strength of the sludge solidified product obtained by adding and mixing to sludge having a high water content ratio is enhanced, and a further excellent anti-swelling action is exhibited in water.
The PVA resin can be obtained by saponifying aliphatic polyvinyl esters obtained by polymerizing aliphatic vinyl esters. The polymerization degree and the saponification degree of the PVA resin are not particularly limited, but the average polymerization degree is 200 or more, preferably 500 or more in terms of preventing swelling collapse and redispersion when the solidified product is added to water. The saponification degree is 80 mol% or more, preferably 97 mol% or more. Moreover, you may use a crosslinking agent for superposition | polymerization.

Examples of the aliphatic vinyl esters used in the production of the PVA resin include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, vinyl stearate, etc., but vinyl acetate is preferred industrially. Moreover, you may use the copolymer of the unsaturated monomer and aliphatic vinyl ester which can be copolymerized with aliphatic vinyl ester in the range which does not impair the effect of this invention.
PVA-type resin can also be used individually or in combination of 2 or more types, respectively.

  The blending ratio of the composition for solidifying sludge of this invention and the PVA resin is preferably in the range of 100: 1 to 1:10 as a weight ratio. In addition, it has the effect of solidifying sludge with a high water content with addition of a small amount of water, the effect of preventing swelling and disintegration of the solidified product when it is returned to water such as the seabed, and the effect of preventing re-elution of harmful substances. Therefore, the blending ratio is preferably 20: 1 to 1: 1, and more preferably 10: 1 to 2: 1.

In order to increase the amount of organic matter absorbed in the sludge, the sludge solidifying composition of the present invention may contain wood waste such as sawdust, aquatic plants, seaweed, etc., or diatomaceous earth to make the solidified material more porous. Bentonite, activated carbon or silica may be added. Moreover, in order to accelerate | stimulate the microbial decomposition | disassembly in sludge, you may add an enzyme, a fungus | fungi body, and a required nutrient.
When the solidified material is used as cultivated soil, sand, humus soil, kanuma soil, red ball soil, vermiculite or the like may be added in order to change water retention or air permeability.

  Furthermore, the composition for solidifying sludge of the present invention includes binders other than PVA resin, for example, cellulose derivatives such as methylcellulose and carboxymethylcellulose; raw starch, oxidized starch, phosphorylated within the range not impairing the effects of the present invention. Starch derivatives such as starch; emulsion polymers such as vinyl acetate emulsion, EVA emulsion and acrylic emulsion; seaweeds such as agar, carrageenan and sodium alginate; animal proteins such as glue, casein and gelatin; fermentation viscosity such as pullulan and dextran Quality; synthetic polymers such as polyacrylamide, polyethyleneimine, polyvinylpyrrolidone, polyethylene glycol; polylactic acid emulsions and the like may be added. Moreover, you may add a well-known antifoamer, a pH adjuster, antioxidant, etc. to the sludge solidification composition of this invention as needed.

In the present invention, the target water-containing sludge is a dredged soil (sea bottom sediment sludge) containing organic matter existing in river bottom, lake bottom, sea bottom, etc., having a water content of 200 to 900% by weight, so-called sludge and activity. Examples include sedimentation sludge from sludge treatment facilities. Among such water-containing sludges, seabed sludge having a water content ratio of 250 to 600% by weight is particularly preferable.
When sludge having a water content ratio exceeding 900% by weight is used, for example, known polymer water absorption such as crosslinked polyacrylate resin, polyaminomethylacrylamide, aluminum sulfate, calcium hydroxide, bentonite, silica gel, zeolite, etc. The present invention is applied after adding or mixing an agent, a polymer flocculant, an inorganic flocculant, etc., or adjusting the water content by the mechanical pressing method such as a filter press or a screw press. preferable.

The sludge solidification method of the present invention is characterized in that the above-mentioned sludge solidification composition is added to and mixed with sludge having a water content of 200 to 900% by weight to solidify the sludge.
The amount of the sludge solidifying composition added in the sludge solidification method of the present invention is 10 to 100% by weight, preferably 10 to 50% by weight based on 100 parts by weight of the dried sludge.

  The method for adding the sludge solidifying composition of the present invention to the target sludge is not particularly limited. For example, (1) a method of adding to the sludge an aqueous solution in which the sludge solidifying composition is dissolved or dispersed in water or seawater, 2) A method in which the sludge solidifying composition is added to sludge as a fine powder having a particle size of 200 μm or less and dissolved and dispersed while kneading. In addition, when using PVA-type resin together, you may add PVA-type resin to sludge as aqueous solution or fine powder separately from another component.

  Addition and mixing can be performed using a known apparatus such as a twin-screw kneader, a twin-screw kneading extruder, and a tank mixer, and the operation may be either a batch type or a continuous type.

It is preferable in terms of cost and operation that the sludge to which the sludge solidifying composition is added and mixed as described above is formed into a desired shape and solidified by drying at sun or room temperature.
The aggregated solid product obtained in this way can be reused as a bottom layer suitable for the growth of seaweed, seaweed algae and seafood.

(Example)
The present invention will be described in more detail with reference to the following test examples, but the present invention is not limited to these test examples.

The compounds used in the test are shown below. Commercially available reagents were used for the compounds as other functional agents.
Papermaking sludge: Incineration ash A and B shown in Table 1
Ferrous sulfate: Commercially available reagent PVA: Degree of polymerization 1750, degree of saponification 99 mol%

(Test Example 1)
The amount of hexavalent chromium eluted from the composition for solidifying sludge was measured in accordance with the dissolution test of Sho 48 Ring 13 and the analysis method of JIS K0102-65.2.
First, solidifying agent a and solidifying agent b were prepared with the compounds shown in Table 2 and the blending amounts thereof.
Next, ferrous sulfate was added to the obtained solidifying agent a and solidifying agent b in the amounts shown in Table 3 to obtain the sludge solidifying compositions of Examples 1 and 2. The solidifying agent a and the solidifying agent b not containing ferrous sulfate were used as the sludge solidifying compositions of Comparative Examples 1 and 2, respectively.
50 ml of the sludge solidifying composition of Examples 1 and 2 and 50 g of the sludge solidifying composition of Comparative Examples 1 and 2 were each adjusted to pH 5.8 to 6.3 by adding hydrochloric acid to pure water. The mixture was mixed at a ratio by weight / volume ratio of 10% and continuously shaken at normal temperature and pressure for 6 hours at a shaking frequency of 200 times / minute and a shaking width of 4 to 5 cm.
The obtained solution was allowed to stand for about 10 to 30 minutes, and centrifuged at a rotational speed of about 3,000 rpm for 20 minutes to obtain a supernatant. This supernatant was designated as No.1. Filtration was performed using 6 filter paper (manufactured by Toyo Roshi Kaisha, Ltd.), and the obtained filtrate was collected, and the elution amount (mg / l) of hexavalent chromium in the filtrate was measured by the above test method.
The obtained results are shown in Table 3 together with the constituent components and the blending amount of the sludge solidifying composition.

  From the results of Table 3, in the composition for solidifying sludge of the present invention (Examples 1 and 2), hexavalent chromium was not eluted from the composition itself (detection limit: 0.04 mg / l), and the environmental standard of soil: It can be seen that 0.05 mg / l is satisfied. On the other hand, in the sludge solidifying compositions of Comparative Examples 1 and 2, it can be seen that hexavalent chromium is slightly eluted.

(Test Example 2)
To the solidifying agent a and solidifying agent b shown in Table 2, ferrous sulfate and polyvinyl alcohol were added in the blending amounts shown in Table 4, and sludge solidifying compositions of Examples 3 to 5 were obtained.
To 100 g of sludge collected at a certain place in Mie Prefecture (sea bottom sludge: water content ratio 567 wt%), the sludge solidifying composition of Examples 3 to 5 and solidified product a as Comparative Example 3 are each 3 wt%. And mixed for 2 minutes to solidify the sludge. The obtained solidified product was filtered, and the elution amount (mg / l) and pH of hexavalent chromium in the filtrate were measured in the same manner as in Test Example 1. After the obtained solid was dried at room temperature for 3 days , 10 g of the obtained solid was taken in a 500 ml beaker, 500 ml of filtered seawater was added, and the mixture was stirred at a rotation speed of 70 rpm for 24 hours. The mixed solution is allowed to stand to collect the supernatant seawater, and the turbidity of the supernatant seawater is measured using a compact fine particle counter / high sensitivity turbidimeter NP500T manufactured by Nippon Denshoku Industries Co., Ltd. The degree of collapse was confirmed.
The obtained results are shown in Table 4 together with the constituent components and the blending amount of the sludge solidifying composition.

From the results of Table 4, the sludge solidifying composition of the present invention (Examples 3 to 5) solidifies sludge having a high water content into a lumpy shape by addition of a small amount, and solidifies even when the solidified product is returned to the seabed. It can be seen that the material swells and disintegrates and the harmful substances are difficult to elute again.
The sludge filtrate (treatment liquid) treated with the sludge solidifying composition of the present invention (Examples 3 to 5) satisfies the water quality standard of pH 5.8 to 8.6, which can be discharged into the sea or river. It can be seen that the pH of the sludge filtrate treated with the sludge solidifying composition of Comparative Example 3 is weakly alkaline (outside the above range), and the sludge filtrate cannot be discharged as it is.

Claims (9)

  Containing papermaking sludge, bagasse or incinerated ash thereof, ferrous sulfate, and at least one functional agent selected from a pH regulator, a flocculant, a surfactant, a water-absorbing enhancer, and a dispersant. A composition for solidifying sludge.   The composition for solidifying sludge according to claim 1, wherein ferrous sulfate is contained in an amount of 0.75 to 10 parts by weight in 100 parts by weight of the composition for solidifying sludge.   The pH regulator is an alkali metal, alkaline earth metal or aluminum hydroxide, and the flocculant is aluminum sulfate, ferric chloride, polyaluminum chloride or poly (meth) acrylic acid ester copolymer, and the interface The sludge according to claim 1 or 2, wherein the activator is an alkylbenzene sulfonate, lignin sulfonate, or stearate, the water absorption enhancer is anhydrous gypsum or hemihydrate gypsum, and the dispersant is tripolyphosphate. Solidifying composition.   The composition for solidifying sludge according to any one of claims 1 to 3, wherein the sludge is seabed sludge.   The composition for solidifying sludge according to any one of claims 1 to 4, further comprising a polyvinyl alcohol-based resin.   A method for solidifying sludge, comprising adding and mixing the composition for solidifying sludge according to any one of claims 1 to 5 to sludge having a water content of 200 to 900% by weight to solidify the sludge.   The method for solidifying sludge according to claim 6, wherein the amount of the sludge solidifying composition added is 10 to 100 parts by weight with respect to 100 parts by weight of the dried sludge.   The method for solidifying sludge according to claim 6 or 7, wherein the sludge is seabed sludge.   A solidified product solidified in a granular form by the sludge solidifying method according to any one of claims 6 to 8.