JPH04312696A - Sludge treatment method and device therefor - Google Patents

Abstract

PURPOSE:To increase treatment capability through continuous sludge treatment and, at the same time, to reduce treatment equipments and equipment costs, to make unnecessary for neutralization treatment and to utilize finally obtained solidification treated bodies as construction materials. CONSTITUTION:Solid contents haying mainly larger than 74mum of particle size are classified and removed from sludge withdrawn from a construction site by means of screens 2 and 4 and primary cyclones 6 and 6, and sludge containing solid contents having mainly less than 74mum of particle size after the classification are stored in an adjustment tank 8. The sludge in the adjustment tank 8 is circulated to a shield facing again. Dehydration and concentration treatment of the sludge in the adjustment tank 8 is made by secondary cyclones 12 and 12. Overflowed sludge having low concentration is circulated into the adjustment tank 8 and, at the same time, underflowed sludge having high concentration is stored in an extra sludge tank 13. The sludge having high constration stored in the extra sludge tank 13 is sent to a sludge solidification device 15, a solidified material is mixed from a solidified material silo 16 and, at the same time, it is mixed in the device 15, and is dehydrated and solidified to withdraw.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention is applicable to, for example, a muddy shield construction method in which a face is stabilized by applying a predetermined pressure to muddy water and circulating it, and excavation is carried out while draining the excavated soil along with the muddy water, and an underground continuous wall. This invention relates to a mud water treatment method and device for separating and adjusting mud water in construction methods, etc.

0002

[Prior art] Mud water treatment equipment such as the muddy shield method that has been used in the past separates the mud discharged from the shield machine body according to particle size, adjusts the mud content, and sends the mud again to the face. At the same time, excess mud is generally dehydrated using a press to form a cake. The filtrate generated during the dewatering process is used as dilution water to adjust the specific gravity of the muddy water, and is also subjected to turbidity and pH treatment to meet compliance standards depending on the situation, and then discharged.

[0003] An example of a muddy water treatment device for the muddy water shield construction method that has been used in the past will be described in detail below based on the treatment process flowcharts shown in FIGS. 4 and 5. The treatment of muddy water discharged from the shield face consists of a primary treatment that removes grit and sand with a diameter of approximately 74 μm or more, a secondary treatment that classifies and dehydrates silt and clay with a diameter of approximately 74 μm or less, and discharge. It is divided into tertiary treatment, which involves clarifying turbid water and adjusting pH (hydrogen ion concentration). First, the earth and sand excavated by the shield machine is pumped together with muddy water sent from the muddy water treatment device F for the purpose of stabilizing the ground and transporting the earth and sand, and is sent again to the primary treatment device F. Since the excavated earth and sand contains large particles such as cobblestones, lumpy clay, and shells, a vibrating system with two types of screens, screen 2 for processing sand and screen 4 for processing sand, is used. A dehydration sieve 1 is provided. Wet cyclones 6, 6 are provided above the vibrating dehydration sieve 1, and the muddy water sent from the shield face first passes through the raking screen 2, and then is stored in the under tank 3 of the vibrating dehydration sieve 1. , the sand is sent to wet cyclones 6, 6 by a pump 5, where sand particles mainly having particles of 74 μm or more are classified, dehydrated by a sand screen 4, and then transported out. A layer of sand and sand to be collected is formed on the sand screen 2 or the sand screen 4, and some silt and viscosity are recovered as muddy water adhering to the sand and sand. In addition, in the material balance calculation, 10
%, and 40% of the weight of sand is recovered from muddy water.
As a result, in the primary treatment device F, the sand particles with a water content of about 25% are classified. The over muddy water from the wet cyclones 6, 6, containing mainly particles of 74 μm or less, is sent to the adjustment tank 8, from where it is sent to the shield face again by the pump 9.

[0004] The above-mentioned primary treatment device F cannot remove water contained in the excavated rock and mainly particles of 74 μm or less, so as shield excavation progresses, the absolute amount, specific gravity, viscosity, etc. of mud water gradually increase. Therefore, the surplus muddy water is
The slurry is sent from the adjustment tank 8 to the surplus slurry tank 23 by the pump 22, and further, in order to shorten the dewatering time, an inorganic flocculant such as aluminum sulfate or polyaluminum chloride is mixed in from the flocculant tank 26, and the slurry is sent to the slurry tank 23. Sent to 25. Then, this surplus muddy water is stirred and mixed in the slurry tank 25 and agglomerated. This agglomerated slurry is sent to a filter press 28 by a pump 27, where it is pressed and stored in a storage hopper 34 as a dewatered cake. On the other hand, the filtrate generated by this pressing process is temporarily stored in the filtrate tank 30, and most of it is circulated by the pump 31 to the adjustment tank 8 as dilution water and used for adjusting the specific gravity of the muddy water. Some of the surplus filtrate is removed by the tertiary treatment equipment H by the pump 32.
The water is sent to the neutralization treatment device 33, where the SS value (suspended solids amount) is treated with a thickener, and the pH is adjusted with carbon dioxide gas etc.
By adjusting the value, the water is adjusted to below the discharge standard and discharged. In addition, the water content ratio is 250 by the filter press 28.
It is possible to dewater muddy soil up to a moisture content of about 60 to 70%.

[0005]

[Problems to be Solved by the Invention] However, the aforementioned muddy water treatment apparatus has the following problems. Since the processing by the filter press 28 is batch processing,
The processing capacity is small compared to the scale of the machine required, and if the soil quality changes and the appropriate amount of flocculant is no longer added in the pretreatment of the filter press 28, the dewatering time will be significantly longer and the processing capacity will be further reduced. decreases. Furthermore, in the case of dewatering using a press, useful muddy material is also discarded at the same time, which is uneconomical, and since the dehydrated cake is mechanically dehydrated, when it comes into contact with rainwater, it becomes highly water-containing and turns into muddy soil. There are problems such as there being no way to reuse the waste water, and since excess filtrate is discharged, neutralization equipment, thickeners, etc. are required to bring it below the discharge standard. In addition, since there is a considerable amount of water contained in the dehydrated cake, depending on the soil conditions, the overall material balance may be disrupted, and it may be necessary to add makeup water from outside the circulation system.

In addition, the storage hopper 34, filtered water tank 30, and slurry tank 25 are enlarged to supplement the processing capacity of the filter press 28, and as a result, the overall size of the muddy water treatment apparatus becomes large, resulting in high equipment costs. Further, since the filtrate in the filtrate tank 30 is circulated as dilution water to the adjustment tank 8, there are problems such as complicated management of mud water adjustment.

[0007] Therefore, the main problem of the invention is to make it possible to continuously treat muddy water, improve processing capacity, reduce the size of mechanical equipment and reduce equipment costs, and eliminate the need for make-up water without generating surplus water. The purpose of the present invention is to provide a method and device for treating muddy water, in which the residual soil finally obtained can be used as a construction material.

[0008]

[Means for solving the problem] The above problem is to classify and remove solids with a relatively large particle size from wastewater from a construction site, and send the remaining muddy water containing solids with a small particle size to a regulating tank. There is a primary treatment process in which the muddy water in the adjustment tank is stored and circulated again to the shield face, and the muddy water in the adjustment tank is sent to a cyclone, where it is dehydrated and concentrated, and the overflowing low-concentration muddy water is removed. At the same time, the highly concentrated muddy water that underflows from the cyclone is stored in the surplus muddy tank, and the highly concentrated muddy water stored in the surplus muddy tank is sequentially and continuously pumped. This can be solved by including a secondary treatment process in which the solidifying material is mixed, dehydrated and solidified, and then discharged.

[0009]

[Operation] In the present invention, first, in the primary treatment process, solids with a relatively large particle size, specifically solids with a particle size of about 74 μm or more, are classified and removed from the waste water from the shield face. At the same time, a circulation system is constructed in which muddy water containing solids having a particle diameter of about 74 μm or less after classification is stored in a regulating tank and circulated from this regulating tank to the shield face again. With shield drilling, the absolute amount of muddy water,
Since the specific gravity, viscosity, etc. gradually increase, the slurry in the adjustment tank is sent to a secondary cyclone, where it is dehydrated and concentrated. The overflowing low-concentration muddy water is circulated to the adjustment tank to adjust the muddy water, and the underflowing high-concentration muddy water is stored in the surplus muddy water tank. Regarding the amount of muddy water in the adjustment tank, the amount that is more than necessary for circulation to the shield face again can be sent directly to the surplus muddy water tank to adjust the amount of muddy water. In this way, the specific gravity and amount of mud in the adjustment tank are controlled. Further, the highly concentrated muddy water stored in the surplus muddy water tank is mixed with addition of a solidification material in the muddy water solidification treatment means, dehydrated and solidified, and then discharged.

As described above, in the present invention, first, the final treatment of muddy water is carried out by chemical dehydration and solidification treatment that can be continuously processed, so that the slurry tank 25, filter press 28, filtration tank 30 and Since the storage hopper 34 is not required, the installation area and volume of the entire processing apparatus can be reduced, and the equipment cost can also be reduced. In addition, in order to chemically solidify all of the high water content mud,
No filtrate is generated and neutralization treatment is not required. Furthermore, the solid particles of the muddy water to be dehydrated and solidified are dehydrated and concentrated by passing through the primary and secondary cyclones, and the water content is approximately 100% or less. It becomes mud with properties that can be easily improved with lime-based soil conditioners (solidifying agents), and can be used as fill soil, roadbed material, etc. In addition, when using a conventional filter press, for safety management reasons, the filter press 1
Previously, one operator was required for each machine, but in the case of the present invention, automatic operation is possible and labor savings can be achieved.

As described above, the gist of the present invention is to perform mechanical and physical dehydration/concentration treatment, and then chemical dehydration/solidification treatment of the highly concentrated muddy water. This produces various effects.

0012

Embodiments The present invention will be explained in detail below based on embodiments shown in FIGS. 1 to 3. FIG. 1 shows an overall schematic diagram of the muddy water treatment process, and FIG. 2 shows its flow diagram. In FIG. 1, muddy water sent by a pump from a shield face passes through a screening screen 2 of a vibrating dehydration sieve 1, where waste particles with a particle size of 2 mm or more are classified.

The muddy water containing solids with a particle size of less than 2 mm is stored in the under tank 3 of the vibrating dehydration sieve 1, and then sent to the primary cyclones 6, 6 by the pump 5. The primary cyclones 6, 6 classify sand with a particle size of 74 μm or more in the muddy water, and feed this into the sand screen 4 as an underflow. Through the above filtration process, the vibrating dehydration sieve 1 mainly classifies grains and sand with a particle size of 74 μm or more. The muddy water that overflows from the primary cyclones 6, 6 and mainly contains solid matter with a particle size of 74 μm or less is stored in a regulating tank 8, and is sent to the shield face again by a pump 9. Note that the device group that performs the above processing is the primary processing device F.

As described above, muddy water circulates between the shield face and the adjustment tank 8, but as shield excavation progresses, the amount, specific gravity, and concentration of muddy water stored in the adjustment tank 8 gradually decrease. To increase. Therefore, in this embodiment, muddy water mainly containing solids with a particle size of 74 μm or less, which is stored in the adjustment tank 8 by the pump 11, is sent to the secondary cyclones 12, 12 by the feeding path 20, where it is dehydrated and concentrated. do. The low-concentration muddy water that overflows in the secondary cyclones 12, 12 is circulated through the circulation path 19 to the adjustment tank 8, while the high-concentration muddy water that underflows is stored in the excess muddy water tank 13. In addition,
The classification and concentration performance of the secondary cyclones 12, 12 can be appropriately determined depending on soil conditions, solidification conditions, etc.

Between the adjustment tank 8 and the surplus mud water tank 13, in addition to the feed path 20 and its circulation path 19 from the adjustment tank 8 to the secondary cyclones 12, 12, there is also a feed amount and a circulation path. Separately independent feed passages 21 are formed to maintain the material balance with the quantity, and based on the flowmeters 18 disposed in each of the passages, the feed passages 20 and their circulation passages 19 are
The feed amount of the feed path 21 is determined according to the difference in the feed amount.

In addition to the above-mentioned flowmeter 18, as a means for detecting the feed amount of the feed path 21, for example, a device shown in FIG.
As shown in FIG.
1) and the amount of muddy water (H1) can be determined using the following equation to determine the amount of feed to the secondary cyclones 12, 12 and the amount of feed through the feed path 21. ΔP1=PH1−PL1 −−−−−−−−(1) ρ
1=ΔP1/h1------(2)H1=PH1
/ρ1 ------- (3) Although the muddy water stored in the surplus muddy water tank 13 varies depending on the soil conditions caused by the cyclone 12, it is generally composed of silt and water with a water content of 100% or less and a particle size of 74 μm or less. It can be surplus muddy water containing viscosity. By the way, in the above-mentioned specific example, in addition to the feeding path 20 and its circulation path 19, there is a separate independent feeding path 2.
1 is formed, for example, the secondary cyclone 12 is
, 12 and its feed amount, and determine the performance of the feed path 2.
You can also eliminate 1.

The muddy water stored in the surplus muddy water tank 13 is
The slurry is sent to a muddy water solidifying device 15 by a squeeze pump 14 or the like. In the muddy water solidification device 15, the flow rate of muddy water is measured by the flowmeter 1.
8, and in accordance with this, an appropriate amount of solidifying material such as cement or lime is added from the solidifying material silo 16 and is chemically dehydrated and solidified by mixing in the device 15. It is carried out by a truck 17. Note that the group of devices that perform processing up to the muddy water solidification device 15 is the secondary treatment device G.

[0018] The amount of the solidifying agent added is, for example, 10 to 60 kg/m3, preferably 50 kg/m3 in the case of a lime-based solidifying agent.
~60kg/m3. In the case of a cement-based solidifying material, the amount is about 5 to 100 kg/m3, preferably about 30 to 70 kg/m3.

[0019] In the reaction caused by adding a lime-based solidifying agent, an ion exchange reaction occurs between the soil and calcium ions generated by the dissolution of lime, and the calcium ions are adsorbed to the surface of the soil particles, causing the fine particles in the soil to aggregate. The soil particles that have adsorbed calcium ions then react with lime in an alkaline atmosphere, causing a pozzolanic reaction that produces stable crystalline minerals, which solidify. On the other hand, the remaining lime that did not take part in the pozzolanic reaction reacts with carbonic acid or carbon dioxide gas in the soil, causing a carbonation reaction in which it solidifies. In the case of quicklime, the quicklime absorbs water in the soil and generates heat due to its own hydration reaction, and about 32% of the amount of water in the quicklime is solidified. Through such reactions, clayey soil with a high moisture content is improved in terms of soil quality, such as a decrease in moisture content, improvement in soil particle size, decrease in soil plasticity index, and improvement in trafficability. It also has an unconfined compressive strength of 0.5 kg/cm2 or more, making it possible to use it as earth fill and roadbed material.

Next, various comparisons were made under the assumption that the muddy water treatment apparatus of the present invention is applied to excavation using a concrete muddy shield method. The excavation conditions for the muddy shield method were as shown in Table 1.

[0021]

[Table 1]

[0022] Perform material balance calculations under the above conditions, first determine the capacity, scale, number, etc. of the required equipment under conventional processing conditions, and also determine the necessary two Determine the capacity of the next cyclone, the number of installed units, the capacity of surplus mud water, the capacity and scale of the solidification equipment,
For each case, we compared the load capacity, required equipment installation area, installation volume, equipment cost, maintenance cost required for treatment, etc. The results are shown in Table 2.

[0023]

[Table 2]

As is clear from Table 2 above, in the case of the present invention, it has been found that all of the listed items can be significantly reduced compared to the conventional system.

[0025]

As described above in detail, according to the present invention, continuous muddy water treatment is possible, the treatment capacity can be improved, and the mechanical treatment equipment can be downsized and the equipment cost can be reduced.

Furthermore, since muddy water is chemically solidified as it is, no surplus water is generated and neutralization treatment is not necessary, and the solidified body finally obtained can be used as a construction material.

[Brief explanation of drawings]

FIG. 1 is an overall treatment process diagram in a muddy water treatment apparatus according to the present invention.

FIG. 2 is a processing flow diagram by the muddy water treatment apparatus according to the present invention.

FIG. 3 is a diagram showing a method for detecting the specific gravity of muddy water and the amount of muddy water in a regulating tank.

FIG. 4 is an overall treatment process diagram in a conventional muddy water treatment device.

FIG. 5 is a process flow diagram using a conventional muddy water treatment device.

[Explanation of symbols]

1... Vibrating dehydration sieve, 2... Screen for reki, 3... Under tank, 4... Screen for sand, 6... Primary cyclone, 8
...Adjustment tank, 12...Secondary cyclone, 13...Excess mud tank,
15...Mud water solidification device, 16...Solidification material silo, 18...Flow meter, 35...Pressure gauge

Claims (2)

[Claims] Claim 1: Classifying and removing solids with a relatively large particle size from wastewater from a construction site, storing the remaining muddy water containing solids with a small particle size in a regulating tank; The muddy water in the above-mentioned adjustment tank is sent to a cyclone, where it is dehydrated and concentrated, and the overflowing low-concentration muddy water is circulated to the above-mentioned adjustment tank, and the muddy water is recirculated to the shield face. At the same time, the highly concentrated muddy water that underflows from the cyclone is stored in a surplus muddy tank, and the highly concentrated muddy water stored in this surplus muddy tank is successively mixed with a solidifying agent and dewatered. - A muddy water treatment method characterized by comprising a secondary treatment step of solidifying and discharging the water. Claim 2: A screen and a primary cyclone for classifying and removing relatively large-sized solids from wastewater from a construction site, and adjustment for storing muddy water containing small-sized solids remaining after classification. a primary treatment device that circulates the muddy water in the adjustment tank to the shield face again; and a secondary cyclone that dehydrates and thickens the muddy water in the adjustment tank, and a muddy water regulating means for circulating low-concentration muddy water into the regulating tank; a surplus muddy tank for storing high-concentration muddy water that underflows from the secondary cyclone; 1. A muddy water treatment device comprising: a secondary treatment device comprising dehydration and solidification means for mixing muddy water with a solidifying agent, and dewatering and solidifying the muddy water.