JP3235019B2 - Construction sludge regeneration treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating construction sludge, that is, a method for regenerating construction sludge containing bentonite sludge or wastewater so that it can be used as a material for civil engineering and construction or as reclaimed soil. .

[0002]

2. Description of the Related Art Bennite sewage and high-moisture-content fine-particle sludge generated during construction are generally referred to as construction sludge. Construction sludge is excavated soil that cannot be directly used as embankment for other works as it is, so at present, most of the waste is regarded as “dirty” industrial waste unless it is partially reused. Disposal at the treatment plant.

[0003] When disposing of such construction sludge, treatment for reducing the volume of disposal or improving the handling is usually performed. Conventionally, as this type of processing method, for example, JP-A-6-134500 and JP-A-6-277698
As described in Japanese Patent Application Laid-Open Publication No. H10-209, there is known a method in which suspended particles in sludge are aggregated and solidified by adding a lime-based or cement-based solidifying agent (hereinafter, referred to as a cement-based solidifying agent) to sludge. ing.

[0004] However, since the sludge treated material solidified by the cement-based solidifying agent contains a relatively large amount of lime, the permeated water generally shows strong alkalinity. This is because when the rainwater has permeated into the sludge treated cement content of Ca ⁺² to penetrate water, OH ^- but because the ions, such as are eluted, when such alkaline osmotic water flows out to the outside, It may cause environmental pollution in the surrounding area such as groundwater pollution.

Further, since construction sludge contains various harmful substances including heavy metals, when these harmful substances are eluted from the solidified product obtained by solidifying the construction sludge, the surrounding sludge is formed in the same manner as in the above case. Cause environmental pollution.

Therefore, in order to deal with such a problem,
For example, Japanese Patent Application Laid-Open No. 6-106195 proposes that after a solidified sludge treatment product is crushed and classified, the crushed stone is subjected to a surface treatment for preventing elution of alkaline ions and the like.

[0007]

However, according to the processing technique described in the above-mentioned Japanese Patent Application Laid-Open No. 6-106195, crushed stones are added to seawater or H ₂ SO ₄ aqueous solution in order to perform a surface treatment for preventing elution of alkaline ions and the like. Must be immersed for a considerable time, or crushed stones must be blown with CO ₂ gas or the like. Therefore, apart from the equipment for solidifying the sludge, equipment, material, time, etc. for treating the surface of the crushed stone are required, and there is a problem that the treatment cost is correspondingly increased. Further, according to the conventional sludge treatment method using a solidifying agent, even if the construction sludge can be solidified, a smell peculiar to the sludge remains in the obtained solidified material, so that it cannot be used for backfill soil or the like as it is. There is a problem.

Further, crushed stones (reclaimed crushed stones) obtained by the conventional method are difficult to firmly bond together even if compacted, and cannot obtain sufficient strength. When it is used as a vehicle, the crushed stone in the lower subgrade easily escapes in the direction of the road shoulder due to the repeated load due to the vehicle weight and the like acting on the upper road surface. For this reason, there is a problem that a part of the road surface paved with asphalt or the like sinks and sinks, so that a wadachi is easily formed.

[0009] The inventor of the present application, in the above-mentioned application (Japanese Patent Application No. 8-175796), solidifies construction sludge by using a predetermined solidifying agent, crushes the obtained solidified material, and We proposed a method to recycle construction sludge effectively by using it as construction material or recycled soil. According to this method, since the soil particles in the construction sludge are strongly bonded to each other to form a hardly soluble solidified material, odorless and harmful substances are not eluted from the construction sludge to obtain civil engineering / construction materials or recycled soil. be able to. However, in this method, when the amount of the solidifying agent is reduced, the strength of the obtained solidified material is reduced. There is a problem that it is necessary to increase the blending amount of

An object of the present invention is to obtain a solidified material (sludge treated material) having a required strength and no elution of harmful substances by utilizing construction sludge which has conventionally been difficult to regenerate. It is an object of the present invention to provide a method for regenerating construction sludge which can be effectively recycled as a material for civil engineering / construction or recycled soil.

[0011]

The method for regenerating construction sludge according to the present invention is characterized in that it is constructed as follows. First, a construction sludge containing bentonite sludge or sewage, a solidifying agent, and crushed stone are mixed in a ratio of 10: 1 to 2: 1 to 1: 1.
The construction sludge is solidified by mixing and stirring at a weight ratio of 2. The reason that the mixing ratio of the solidifying agent and the crushed stone to the construction sludge is 10: 1 to 2 respectively is that if the compounding amount of the solidifying agent and the crushed stone is less than this, the required strength cannot be obtained. This is because the improvement in strength does not change.

As the solidifying agent, 65 to 70% by weight of calcium oxide (CaO), 13 to 16% by weight of silicon dioxide (SiO ₂ ), and 7 to 9% by weight of sulfur trioxide (SO
₃ ) and 4 to 6% by weight of aluminum oxide (Al
₂ O ₃ ) is used as a main component. Specifically, 67.7% by weight of CaO and 14.4% by weight of SiO
₂ , 7.8% by weight of SO ₃ and 4.8% by weight of Al ₂ O ₃
It is preferable to use a solidifying agent comprising 1.2 wt% of ignition loss and other residual components.

In using the solidifying agent, it is preferable to use 1 to 2% by weight of a high molecular weight solidifying aid (aggregating agent) based on the solidifying agent. This kind of solidification aid is added to the construction sludge at the same time as the use of the solidification agent or in the pretreatment step when pretreating the construction sludge prior to the use of the solidification agent. The reason for using such a polymer-based solidification aid together is that the effect of the solidification agent can be further exhibited. In other words, (1) the solidification rate is increased, (2) granulated treated soil is obtained, (3)
This is because the addition amount of the solidifying agent can be reduced. Examples of the polymer-based solidification aid in this case include a solidification aid obtained by adding a required amount of a natural vegetable polymer (those certified as a food additive) to polyacrylamide as a main component. Can be

In the above-mentioned pretreatment process, for example, the following processes are performed. Sand with a particle size of 70 μm or more is removed from construction sludge. Thereafter, a coagulant is added to separate the construction sludge into moisture and cake-like solids. Fine sand having a particle size of 20 μm or more is removed from the separated solid matter.

As the crushed stone, one obtained by crushing waste concrete into a predetermined size (for example, a particle diameter of 30 mm or less) is used. Instead of such crushed stone,
Any of natural stone, gravel, and residual soil having an average particle size of 5 mm or less can be used. Of course, if necessary, one or more of these may be used in combination.

Next, after the solidified sludge obtained by the solidification treatment of the construction sludge is cured for a predetermined period, it is crushed to a required size so that it can be used as civil engineering / construction material or recycled soil. The crushed material is used, for example, as a lower roadbed material or an upper roadbed material for road construction, an embankment for building residential land, a masa soil, or a backfill soil. Further, a part of the crushed sludge solidified material obtained here can be used as a crushed stone to be added to the construction sludge together with the solidifying agent in the next solidification treatment of the construction sludge.

[0017]

The solidifying agent used in the present invention is, as apparent from its chemical composition, CaO, SiO ₂ , Al ₂ O
_{3. Since} it is a cement-based solidifying agent containing SO ₃ as a main component, when it is put into construction sludge containing a large amount of water, the following hydration reaction similar to that of cement occurs as described below. _{2C 3 S + 6H 2 O →} 3CaO · 2SiO 2 · 3H
_{2 O + 3Ca (OH) 2} 2C 2 S + 4H 2 O → 3CaO · 2SiO 2 · 3H
₂ O + Ca (OH) ₂ C ₃ A + 3CaSO ₄ .2H ₂ O → C ₃ A.3C
aSO ₄ · 32H ₂ O where, C ₃ S, C ₂ S and C ₃ A may known as _{3CaO · SiO 2, 2CaO · SiO} 2 and 3CaO · Al ₂ O ₃ with compound respectively is there.

Generally, the hydration reaction of cement mainly comprises the above-mentioned reactions. However, in the solidifying agent used in the present invention, the following reactions further proceed in parallel therewith. _{3Ca (OH) 2 + Al 2} O 3 + 3CaSO 4 · 2
H ₂ O + 23H ₂ O → C ₃ A ・ 3CaSO ₄・ 32H ₂
O 2Ca (OH) ₂ + Al ₂ O ₃ + SiO ₂ + 6H _{2
O → 2CaO · Al 2 O 3} · SiO 2 · 8H 2 O

When the solidifying agent and the crushed stone are added to the construction sludge at a predetermined ratio and mixed, the above-described reaction occurs, and the CSH gel or Ca (OH) _{2 produced accordingly.}
Thus, the soil particles of the construction sludge and the crushed stone are connected to each other. The soil particles and crushed stones bonded in this manner are reinforced by needle-like crystals of ettringite generated by the reaction of or, and become precipitated and hardened as a hardly soluble hydrate. As a result, even when exposed to rainwater, C
a ^+2, OH ^- sludge solids is obtained ion such is not eluted.

The obtained sludge solid contains a predetermined amount of crushed stone added and mixed before solidification in a uniformly dispersed state. The crushed stones dispersed in the solidified material are firmly bonded to and integrated with other parts in the solidified material by the action of the solidifying agent, so that the strength of the entire solidified material is improved.

The solidified sludge thus obtained is cured for a predetermined period, crushed to a predetermined size according to the intended use, and then provided as a material or recycled soil at a civil engineering / construction site. . In this case, since the organic and harmful substances contained in the sludge before treatment are contained in the solidified material, the solidified material provided as civil engineering / construction material or recycled soil or its crushed material There is no smell peculiar to sludge and no harmful substances leak out.

The solidified sludge obtained in the present invention is dispersed in the sludge, and the strength is improved by crushed stones strongly bonded to other parts. For example, when used as a lower roadbed material, the entire lower roadbed becomes a single unitary plate-like one like a concrete plate. Therefore, even if a load such as a vehicle weight repeatedly acts on the road surface, a part of the lower roadbed material does not escape in the road shoulder direction. As a result, it is possible to avoid sinking and sinking of the road surface, which is likely to occur when the lower roadbed material is soft.

[0023]

According to the present invention, construction sludge is changed to a solidified material which does not smell sludge and does not allow harmful substances to flow out, and this solidified material (sludge treated material) is converted into, for example, backfill soil or roadbed material. Or because it can be used as embankment for building land, etc., construction sludge that has been conventionally discarded can be reused as useful civil engineering and construction materials or recycled soil in place of natural soil and natural stone, Not only can the problem of disposal of construction sludge be solved, but also the reuse of limited resources can be promoted.

[0024] From the materials for civil engineering and construction or the sludge treated materials that are recycled and reused, even if exposed to rainwater, Ca ⁺²
And OH ^- from harmful substances such as alkaline components and heavy metals will not be eluted such, there is no lead to surrounding environmental pollution. In addition, when the sludge treatment product is reused, there is no need to separately perform a treatment for preventing the elution of the alkali component after the solidification treatment as in the related art, so that the treatment cost can be reduced accordingly.

The sludge treatment product obtained by the present invention has a relatively large strength due to the reinforcing effect of the crushed stones mixed therein, and therefore does not escape in the horizontal direction even if it is subjected to repeated loads from the road surface. Therefore, if this is used for, for example, a lower roadbed of a road (particularly a road near an intersection where strength is required), it is possible to reliably avoid sinking and sinking of the road surface. Further, it is also suitable as a material for finishing a glue surface on terraced terrain such as tea plantations, or as crushed stone laid on an approach road of a construction site or a sand and sand collection site.

[0026]

EXAMPLE 1 This example relates to a case where solidified sludge obtained by solidifying construction sludge to be re-used as a backfill material such as a lower roadbed material of a road.

FIG. 1 shows a process of treating construction sludge in the method of the present invention. As shown in this figure, construction sludge
The sludge is subjected to a pretreatment described later in a pretreatment step A, and then mixed and solidified with a predetermined solidifying agent and crushed stone in a solidification step B. Thereafter, after being cured in the curing process C for a predetermined period, the material is crushed to a required size in the crushing process D so that it can be used, for example, as a lower roadbed material for road construction.

In the above-described pretreatment step A, as shown in FIG. 2, the sludge introduced into a predetermined receiving port (not shown) is first transferred to the sand master 1 to be contained in the sludge. After the sand with a particle size of 70 μm or more is removed,
It is moved to sewage pit 2. The sludge transferred to the sewage pit 2 is then temporarily stored in the tank 3 and sent to the first screw decanter 4. In the first screw decanter 4, a flocculant (solidification aid) composed of a polymer is supplied to the sent sludge, and the sludge is converted into a solid substance (cake-like sludge having a low water content) and a water content by the flocculating action. And separated. The separated solid matter is sent to the next second screw decanter 5, where fine sand having a particle size of 20 μm or more mixed in a separated state is removed.

The solid obtained in this manner can be cured as it is for a predetermined period of time, and then used as it is or crushed to a required size and used as a material for civil engineering and construction. However, since it is merely a cake-like solid due to the action of the flocculant, it does not have sufficient strength.

Therefore, in the method of the present invention, the solid matter of the sludge obtained by the above pretreatment is transferred to a solidifying machine 10 as shown in FIGS. A solidification process for obtaining a solidified product is performed. Before specifically describing the solidification process, the configuration of the illustrated solidifying machine 10 will be briefly described first.

The solidifying machine 10 used in the method of the present invention is shown in FIG.
As shown in FIG. 4 and FIG. 4, a first hopper 11 into which pretreated sludge (cake-like solid matter) sent from the second screw decanter 5 is put, and a solidification separately installed. A second hopper 12 to which a solidifying agent is supplied from a silo 50 for storing agents, and a third hopper 13 to which crushed stones supplied by an excavator 31 are supplied via a conveyor 32 or the like.
And Below these hoppers 11 to 13, a first weighing machine 14, a second weighing machine 15, and a third weighing machine 16 corresponding to each hopper are arranged. Each hopper 11-1
The lower part of 3 and each of the weighing machines 14 to 16 is provided with an outlet which is opened and closed by a gate.

Below the first to third measuring machines 14 to 16, a twin-screw mixer 17 for mixing and stirring the sludge after measurement, the solidifying agent and the crushed stone, A dust collector 18 is provided which collects dust generated and returns a part of the dust to the twin-screw mixer 17. Below the twin-screw mixer 17, the screw conveyor 2 for transferring the sludge treated material (sludge solidified material) after being mixed and stirred to the solidified material storage 20.
1 and the like, and further below, a solidified material storage 2
A water receiving pan 22 is provided for receiving water falling from the screw conveyor 21 or the like at the time of transfer to zero and returning the water to the muddy water pit. The consolidator 10 is provided with a water supply facility such as a water supply pipe 40 for supplying fresh water to the hoppers 11 to 13 and the like from the outside.

In the method of the present invention using such a solidifier 10, the above-mentioned pretreated sludge is solidified. At this time, a predetermined solidifying agent and crushed stone as shown below are added.
Solidifying agent; 67.7% by weight of CaO and 14.4% by weight of S
and iO _2, and 7.8 wt% of SO _3, 4.8 wt% of Al ₂
O ₃ , 1.2% by weight loss on ignition, and other residual components. Crushed stone: A crushed stone obtained by crushing concrete waste material (so-called waste material such as concrete waste generated when a concrete building is dismantled) into a predetermined size (for example, a particle size of 30 mm or less).

At the time of solidification, first to third hoppers 1
With the above-mentioned sludge, solidifying agent and crushed stone being supplied to the respective hoppers 1 to 13 in advance, the outlets of the respective hoppers 11 to 13 are opened, and the lower first to third weighing machines 14 corresponding thereto are opened.
The sludge, the solidifying agent and the crushed stone are respectively charged into 16, and the input amounts of the sludge, the solidifying agent and the crushed stone are respectively measured by the measuring machines 14-16. At this time, the amount of sludge, solidifying agent, and crushed stone in the first to third weighing machines 14 to 16 is adjusted by adjusting the discharge amount from each of the hoppers 11 to 13 in a weight ratio of 10: 1:
Adjust so as to be 1 to 10: 2: 2. Specifically, for example, the solidifying agent and the crushed stone are adjusted to be mixed at a ratio of 300 to 600 kg each for 3 tons of sludge.

Next, the discharge ports of the first to third measuring machines 14 to 16 are opened, and the sludge, solidifying agent and crushed stone in the measuring machines are introduced into the lower twin-screw mixer 17. Thus, the sludge, the solidifying agent, and the crushed stone weighed so as to have a weight ratio of 10: 1: 1 to 10: 2: 2 are mixed and stirred in the twin-screw mixer 17. By this mixing and stirring, a reaction in the twin-screw mixer 17, that is, a reaction in which the sludge is combined with the crushed stone and these particles by the action of the solidifying agent is promoted.
As a result, the sludge, the crushed stone and the solidifying agent form a solidified sludge solidified by the reaction or mixing of the particles with each other.

The solidified sludge obtained in the form of a block of earth is discharged from the twin-screw mixer 17 onto a screw conveyor 21 below, and is connected to an external solidification storage 2 via a conveyor connected thereto.
Transfer to 0. Thereafter, after being cured in the solidified material storage place 20 for a predetermined period, it is crushed to a predetermined size according to the use so that it can be used as a material or recycled soil at a civil engineering / construction site.

When the sludge solidified product obtained by the above-mentioned method was subjected to an elution analysis test of heavy metals and the like, the results shown in Table 1 were obtained.

[0038]

[Table 1]

As shown in Table 1, no elution of harmful heavy metals or organic substances was detected from solidified sludge obtained by regenerating construction sludge by the above-mentioned method, or even if it was detected. All were below the acceptable value. In addition, the sludge peculiar to sludge had disappeared from the obtained sludge solidified product. It is considered that this is because the organic substance serving as an odor component contained in the sludge before the treatment is enclosed in the solidified material or strongly bonded to the crushed stone particles and the like.

Next, the solidified sludge obtained above is
When the CBR value (room) was measured, the average CBR value was 47.
1%. This confirmed that the sludge solidified by the method of the present invention had sufficient strength.

In the above embodiment, as the crushed stone to be mixed with the sludge, a crushed concrete waste material is used. However, instead of such crushed stone, natural stone or gravel or an average particle size is used. Residual soil of 5 mm or less may be used. In that case, like the sludge solidified product described above,
A sludge solidified material having sufficient strength and free of harmful substances and the like and usable as a material for civil engineering and construction or a recycled soil can be obtained. Further, the obtained solidified sludge can be used alone or as a crushed stone mixed with sludge by mixing with crushed concrete, natural stone, gravel or the like.

[Brief description of the drawings]

FIG. 1 is a process chart showing an overall process in an embodiment of the present invention.

FIG. 2 is a process chart showing a pretreatment step in the embodiment.

FIG. 3 is a diagram showing a solidifying machine and peripheral equipment used in the embodiment.

FIG. 4 is an enlarged configuration diagram showing a configuration of a solidifying machine.

[Explanation of symbols]

 A pretreatment step B solidification step C curing step D crushing step 10 solidifier

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C02F 11/00 E02F 7/00 B09B 3/00

Claims (4)

(57) [Claims] 1. Construction sludge (X) comprising bentonite sludge or wastewater, 65 to 70% by weight of calcium oxide, 13 to 16% by weight of silicon dioxide, and 7 to 9% by weight of trioxide. Sulfur and 4
X: Y: Z = 10: a solidifying agent (Y) containing ６6% by weight of aluminum oxide as a main component and a crushed stone (Z) obtained by crushing concrete waste to a predetermined size. 1-2: Mixing and stirring at a weight ratio of 1 to 2 to solidify the construction sludge. After curing the obtained sludge solidified material for a predetermined period, it is used as a material for civil engineering and construction or as a reclaimed soil. A method for regenerating construction sludge that is crushed to the required size to obtain it. 2. The method for regenerating construction sludge according to claim 1, wherein prior to mixing the construction sludge, the solidifying agent and the crushed stone, the construction sludge to be used is subjected to a pretreatment step including the following steps. A step of removing sand having a particle diameter of 70 μm or more from the construction sludge; a step of adding a coagulant to separate the construction sludge into water and cake-like solids; and a fine sand having a particle diameter of 20 μm or more from the separated solids. The process of getting rid of. 3. The method for regenerating construction sludge according to claim 1, wherein natural stone or gravel or residual soil having an average particle size of 5 mm or less is used instead of said crushed stone. 4. The obtained solidified material is used as one of a lower roadbed material or an upper roadbed material for road construction, an embankment for residential land development, a masa soil substitute soil, and a backfill soil. Construction sludge regeneration method.