JPS6151958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for solid-liquid separation of dredging slurry or landfill slurry.

When dredging sea areas, lakes, marshes, rivers, etc., the bottom sediment is extracted in the form of slurry, but in order to transport it to another location for dumping or use it for landfill, it is necessary to remove the solid content by solid-liquid separation. It needs to be concentrated. A precipitation separation method is adopted as a solid-liquid separation method for such slurry, and sedimentation treatment is carried out using earth transport vessels, landfill areas, etc. as precipitation areas. This method allows relatively heavy sediment to settle easily, but fine turbidity is difficult to settle, and there is a problem that turbid water that does not settle in the settling area flows out as surplus water and pollutes external water bodies. Ta. This is true not only for sedimentation separation of dredged slurry or reclamation using this, but also for reclamation using mountain soil, dam/tunnel excavation mud, gravel wastewater, etc. In other words, not only when mountain soil, etc. is transferred as a slurry and settles in a landfill area, but also when mountain soil, etc. is directly thrown into a landfill area, slurry is generated from the input, and surplus water containing turbidity flows out from the landfill area. The surplus water generated from these locations is usually
Contains SS500~20000ppm.

Conventionally, the method of treating such surplus water and separating solid-liquid is to treat SS to around 60 ppm by multi-stage coagulation sedimentation treatment, and then use sand filter equipment to reduce SS to around 60 ppm.
Previously, the water was discharged after reducing the concentration to 20 ppm, but this method required large treatment equipment, which was complicated to operate, difficult to move, and required a large amount of chemicals, which was unfavorable from an environmental standpoint. . Although filtration is generally used as a means for solid-liquid separation, ordinary filtration machines are not suitable for treating such surplus water and have not been adopted. This is because the method of sedimentation treatment of dredging slurry or reclamation slurry in the sedimentation area causes a large change in the quality of the surplus water.
This is because ordinary machinery cannot handle this problem. In this method, the sediment is concentrated and accumulated in the sedimentation zone,
As the sedimentation process progresses, the area, water depth, and volume of the sedimentation section used for the sedimentation process decrease, so the residence time of the surplus water in the sedimentation area becomes shorter and the flow velocity increases, and the turbidity concentration of the surplus water decreases. It increases as the precipitation process progresses. In addition, in the sedimentation zone, sludge and other accumulated stagnation causes the elution of putrefactive substances and the generation of plankton, etc., which worsens the overgrowth. In general, filtration machines are suitable for treating low-concentration turbid water, but cannot be used for high-concentration turbid water because they require frequent backwashing and become clogged with plankton.

In order to treat such qualitatively changing surplus water, the present inventor proposed the use of a long blanket (see Japanese Patent Application No. 52-136031 = Japanese Patent Application Laid-open No. 54-69873). It is possible to continuously treat surplus water with SS2000ppm or less using a long blanket. Therefore
For surplus water with high turbidity exceeding SS2000ppm,
It is necessary to reduce the SS to 2000 ppm or less through pretreatment, and for this reason, the present inventors previously proposed coagulation and precipitation as a pretreatment. However, coagulation-sedimentation had the drawback of increasing the size of the apparatus. Since the pre-treatment for filtration with a long blanket can be lowered to about SS2000, there is no need for large equipment that performs advanced treatment like conventional coagulation sedimentation equipment, and although the processing rate is low, it is small and easy to operate. Preferably.

In the present invention, the purpose of pre-treatment is achieved by using the inclined plate type sedimentation device, and by treating the treated water as it is with a long blanket, it is possible to highly treat surplus water that is accompanied by qualitative changes. In addition, the inclined plate type sedimentation apparatus has conventionally been used to purify water containing relatively low concentrations of SS (100 ppm or less), but the present inventors have found that the inclined plate type sedimentation apparatus can purify water with a relatively low concentration of SS (100 ppm or less). It has been found that it is suitable for rough treatment, and in particular can treat leftover water whose concentration and quality change to produce treated water with a concentration of approximately 2000 ppm or less, which can be treated by filtering through a long blanket. Furthermore, since the inclined plate type sedimentation device has such properties, the suspension separation device that follows it may be of other types, such as a circular or cross-flow type sedimentation tank, a sand filter, etc., in addition to a long blanket filtration device.

The present invention provides a method for solid-liquid separation of dredging slurry or landfill slurry, in which the slurry is introduced into a sedimentation zone, the solid content is concentrated and accumulated in the sedimentation zone through sedimentation treatment, and the separated surplus water is divided into (a) a plurality of Water is passed through an inclined plate sedimentation device in which inclined plates with fin plates arranged in an inclined direction are lined up at intervals for treatment, and then (b) water is sequentially passed through several other suspended matter separation devices for treatment. ,(c)
The suspended matter separated and concentrated in the inclined plate sedimentation device and the other plurality of suspension separators is precipitated and separated in a thickener, the supernatant water is returned to the inclined plate sedimentation device along with the remaining water, and the solid content is returned to the settling area. This is a solid-liquid separation method for dredging and landfill slurry.

The present invention will be explained below with reference to the drawings. The drawings show an embodiment, and FIG. 1 is a system diagram, FIG. 2 is a perspective view of an inclined plate sedimentation device, and FIG. 3 is a sectional view of a long-hair filter.

In FIG. 1, reference numeral 1 indicates a sedimentation area, and the reclaimed area constituted by a closed water area surrounded by an enclosure 2 made of sheet piles or the like is used as it is as the sedimentation area. 3 is a dredging area where a dredger 4 is used to pump up and dredge the bottom earth and sand as slurry. Here, the dredged slurry is pumped up from the pumping pipe 5, and fed into one end of the sedimentation area 1 from the pipe 7 as a slurry for reclamation by the pump 6 to perform sedimentation treatment. The slurry introduced into the precipitation zone 1 is separated into solid and liquid, and solids such as heavy earth and sand are precipitated and concentrated and accumulated. The separated turbid water flows through the settling area toward the overflow port 8 at the other end, during which the solid content is separated by sedimentation separation, and flows out from the overflow port 8 to the pipe 9 as surplus water containing some turbidity. . 10 is a flocculant injection means, which communicates with the pipe 7 or the settling zone. Although it is preferable to inject a flocculant to speed up the settling of solids in the slurry, it may be omitted.

Reference numeral 11 indicates an inclined plate type sedimentation device, 12 indicates a thick long-hair filter, and 13 indicates a thin long-hair filter.
4 and 15 are connected in series. 16 is a treated water pipe. Sludge removal pipes 17 of the inclined plate settling device 11, the thick long-hair filter 12, and the thin long-hair filter 13,
18 and 19 each contacted Chickner 20,
The treated water pipe 21 of the thickener 20 is connected to the pipe 9,
A sludge drain pipe 22 of the thickener 20 communicates with the settling zone 1.

As shown in Fig. 2, the inclined plate sedimentation device has a structure in which inclined plates 24, each having a plurality of fin plates 23 arranged in an inclined direction, are lined up at intervals in a tank 25, and the raw water flows in the direction indicated by the arrow. As shown at 27, the water flows approximately horizontally. The fin plates have an appropriate height, are lined up in parallel at appropriate intervals, and are placed on the inclined plate 2.
4 is protruded from the top surface. A large number of inclined plates 24 are arranged in parallel so that the fin plates 23 are positioned in the direction of inclination of the upper surface. A space is maintained between the tip of the fin plate 23 and the back surface of the opposing inclined plate 24 to form a water flow path, and a rectangular parallelepiped-shaped chamber with an open top is provided between the fin plates. It is configured.
The bottom of the tank 25 is a mud collection chamber 26, and a mud collection pipe 17 is connected thereto.

The height of the fin plate 23 is 2 to 12 cm (preferably 5 to 12 cm)
8 cm), the interval is 2 to 8 cm, the distance between the tip of the fin plate 23 and the opposing inclined plate 24 is 1 to 5 cm, the number of steps of the inclined plate is 5 to 20, the angle of inclination is 30 to 60 degrees, the ridgeline part of the fin plate The flow velocity between the upper and upper inclined plates shall be 70 to 350 cm/min.

Pour raw water into this type of inclined plate sedimentation device in the direction of arrow 27.
When water flows in the direction (approximately perpendicular to the fin plate), the ridge line of the fin plate becomes a separation point and separation of the boundary layer occurs, which collides with the next fin plate and creates a rotational flow, resulting in a flow between the fin plates. A stable vortex is generated in the rectangular parallelepiped chamber. The suspended particles in the raw water are separated and captured in the vortex, and fall in a spiral motion due to the action of gravity. This rotation and falling motion causes particles to collide,
They combine to form flocs, increasing their apparent specific gravity and increasing their falling speed. Since such a phenomenon occurs at each fin plate, the separation effect becomes extremely large. Suspended water may be passed through as raw water, but when a flocculant is injected, flocculation occurs due to the vortex flow, producing heavy flocs, which increases the separation effect. In this case, an inorganic flocculant (such as PAC) or a polymer flocculant (such as polyacrylamide or its hydrolyzate) can be used alone, but it is possible to obtain even better quality flocs by using both together. can.

As described above, the inclined plate sedimentation device has good suspended matter separation efficiency and can be widely applied to raw water whose concentration changes, and can produce treated water with an almost constant concentration of SS of about 2000 ppm or less.

Thick long hair filter 12 and thin long hair filter 13
The structure of is shown in FIG. In FIG. 3, reference numeral 28 denotes an overbody, which consists of a long blanket 32 wound in a drum shape on a support frame 31 suspended between the peripheries of two circular end plates 30 rotatably provided in an overtube 29. has been done. The long blanket 32 is a cloth in which long hairs of synthetic fibers such as acrylic fibers are flocked at an angle and woven into a fur-like shape.
Due to the rotation of the fibers and the passage of water from the outside, the long fibers planted in the base fabric are layered three-dimensionally in the circumferential direction, making the overlapping surface denser and increasing the thickness of the fabric, forming a thick overlayer. do. In the case of long blankets made of acrylic fibers, thin long blankets have 2 to 5 deniers, thick long blankets have 5 to 10 deniers, the pile length is 50 to 70 mm, and the fabric weight is 700 to 2500.
Use the one.

An overwater outlet 3 is provided at the center of the end plate 30 of the overbody 28.
3 is provided, and an overwater pipe 34 which also serves as a rotating shaft is connected thereto, and the other end of the overwater pipe 34 is connected to an overwater tank 35. A mud collecting hopper 37 is provided below the overbody 28 and is pressed against the long blanket by rollers 36, and the mud collecting hopper 37 is connected to the mud draining pipe 38 (sludging pipes 18 and 1 in FIG. 1).
9). A raw water pipe 39 (corresponding to pipes 14 and 15 in FIG. 1) is provided at the top of the supertank 29 to introduce raw water into the supertank 29 while maintaining a constant water level. Treated water pipe 40 (pipe 15 and treated water pipe 16 in Figure 1)
) is provided to drain excess water while keeping the water level of the excess water tank 35 constant. A drain pipe 41 is connected to the bottom of the tank and is provided for periodically draining water or solid matter from the tank. As mentioned above, this filter machine attaches long hair fibers to a cylindrical rotating body and passes them from the outside to the inside.
It is configured to wash the slag with excess water.
The water flow rate of the filter is about LV10~20m/hr, and the ratio of washing water to treated water is 10~20%.
It is.

In this way, when raw water is introduced from the raw water pipe 39 into the overtank 29 and the overbody 28 is rotated at 5 to 20 rpm,
Due to the difference in head between the overwater tank 29 and the overwater tank 35, the water in the overwater tank 29 passes through the long blanket 32, and the overwater flows from inside the overbody 28 to the overwater outlet 33, overwater pipe 34, and overwater tank 35 for treatment. It flows out from the water pipe 40. Since the long woolen blanket 32 has long hairs three-dimensionally overlapping to form a superlayer, it can effectively filter through even highly concentrated turbid water and capture a large amount of solid matter. A normal strainer has a SS limit of 100ppm, but a long blanket can pass up to about 2000ppm, making it suitable for surplus water treatment.

When the captured solid content reaches the lower end due to the rotation of the overbody 28, it is transferred to the overwater chamber 35 and the sludge drain pipe 38.
Due to the difference in heads, it is backwashed with excess water and peeled off.
At this time, the long hairs become fluffed as the water passes through the long blanket, and the cake is effectively peeled off, and the long blanket is regenerated and returns to the overband. The separated solid content becomes slurry and flows out from the mud drain pipe 38.
Even with a long blanket of 2 denier (approximately 10μ), which is the minimum thickness that can be manufactured, it is difficult to capture suspended solids with a particle size of 5μ, so in order to capture particles smaller than this, superimposed materials such as asbestos are used. Coagulation may be carried out by precoating an auxiliary agent, body-feeding a auxiliary agent such as clay mineral, or adding a flocculant to raw water. It is particularly preferable to carry out flocculation because it aggregates the suspended particles to a large particle size due to floc formation and improves the turbidity. In this case, as the flocculant, an inorganic flocculant or a polymer flocculant can be used alone, but by using both in combination, a floc with better permeability can be produced. The flocculant may be added to the extent that it increases the particle size, and if it is added in a large amount to produce large flocs as in ordinary flocculation, it may cause clogging or sedimentation, which is undesirable.

Now, returning to Figure 1, the residual water flowing out from the sedimentation zone 1 has a relatively low concentration in the early stage of the sedimentation treatment because of its long residence time in the sedimentation zone, and the particle size of the suspended solids contained therein is often small. As the precipitation process progresses, the concentration of suspended solids increases and the number of large particles increases.

The surplus water of SS5000~10000ppm enters the inclined plate sedimentation device 11 from the pipe 9, and separates the suspended matter with large particle size.
Water with low turbidity of SS 500 to 2000 ppm flows out from the pipe 14 and enters the thick long-hair filter 12. Suspended substances are further separated in the thick long-hair filter 12.
It becomes turbid water with SS500ppm or less and flows into pipe 15.
Enter the thin long hair filter machine 13. Thin long hair filter machine 13
, small particle size suspensions are separated, SS10~20ppm
The treated water is discharged from the treated water pipe 16.
As mentioned above, if a flocculant is injected into the raw water entering the inclined plate settling device 11, the thick long-hair filter 12, and the thin long-hair filter 13 to perform coagulation sedimentation or coagulation, the separation efficiency can be further improved. Inclined plate precipitation device 11
Depending on the turbidity of the effluent water, either the thick long-hair filter 12 or the thin long-hair filter 13 may be omitted.

Inclined plate sedimentation device 11, thick long hair filter 12,
The suspension separated and concentrated by the thin long-hair filter 13 is
The sludge enters the thickener 20 through the drainage pipes 17, 18, and 19 and is separated by sedimentation, and the supernatant water enters the pipe 9 and returns to the inclined plate settling device 11 along with the surplus water.
The solids return to settling zone 1.

According to the inventor's tests, the height of the fin plate is 5 cm, the interval is 5 cm, and the distance between the tip of the fin plate and the opposing inclined plate.
A tilted plate sedimentation device with a diameter of 2.5 cm, an inclined plate angle of 45°, and 3 stages (however, blocks made of stacked tilted plates were arranged to form a rectangular parallelepiped) was used.
When SS8000ppm of surplus water was passed between the fin plate ridge and the upper inclined plate at a flow rate of 180cm/min, SS1800
of treated water was obtained. When 50 ppm of inorganic coagulant (PAC) was added to raw water, the treated water had an SS of 700 ppm. In addition to the latter treated water
PAC 15ppm and polyacrylamide partial hydrolyzate 1ppm were added and fed to an acrylic fiber long-hair filtration machine with 2 denier, pile length 55mm, and fabric weight 1500, and filtration was carried out at a rotation speed of 12.5 rpm.
Treated water with SS5ppm was obtained.

If the height of the fin plate exceeds 12 cm, the SS of the treated water will
SS may exceed 2000ppm, and when the height of the fin plate is less than 2 cm, the effect of the fin plate becomes less, and the SS exceeds 2000pm.

Another embodiment of the invention is additionally shown in dotted lines in FIG. In this embodiment, the suspended matter separator is a combination of a circular or cross-flow type settling device 42 and a sand filtering device 43 instead of a long-hair filter, and these are connected to an inclined plate type settling device by pipes 44 and 45. 11 in series.
The circular or cross-flow type sedimentation device 42 is of the type that settles and separates suspended matter while the raw water flows upward or downward in the case of a circular type, or while the raw water flows in a horizontal direction in the case of the cross-flow type. It is. A sand filter device has a bed filled with granular sand, and after the bed becomes clogged, it is regenerated by backwashing. Sludge removal pipes 46 and 47 of the cross-flow settling device 42 and the sand filter device 43 are connected to the thickener 2.
Contacting 0. 48 is a treated water pipe.

In the above configuration, surplus water enters the inclined plate settling device 11 from the pipe 9 and undergoes treatment, and the treated water enters the circular or cross-flow settling device 42 from the pipe 44 to precipitate and separate suspended matter, resulting in SS of 50 to 100 ppm. The low turbidity water enters the sand filter unit 43 from the pipe 45, where it is filtered and becomes treated water with SS10 to 20 ppm.
The water is discharged from the treated water pipe 48. The separated and concentrated suspended matter enters the thickener 20 through the mud removal pipes 46 and 47 and is treated as described above.

According to the inventor's tests, when the treated water from the above-mentioned inclined plate type sedimentation device was subjected to precipitation separation in a circular sedimentation device with a diameter of 1.5 m in an upward flow at a flow rate of 1.5 m/min, the treated water had a raw water SS of 1800 ppm. In the case of
In the case of SS70ppm and raw water SS700ppm, it was 40ppm. When this treated water is passed through a sand filter device filled with sand with an effective diameter of 0.5 mm and a uniformity factor of 1.3 to a height of 60 cm, the treated water will be
15ppm, and in the case of raw water SS40ppm, it was 10ppm.

As described above, according to the present invention, it is possible to perform solid-liquid separation of dredging slurry or landfill slurry with a simple device and operation, and high-quality water treatment with efficient solid-liquid separation of outflowing surplus water. It will not be released as water and pollute the environment. In the present invention, a tilted plate sedimentation device that effectively treats surplus water whose concentration changes is used in combination with a plurality of other suspended matter separation devices, so solids are concentrated to a high concentration in the sedimentation area and accumulated as they are. be able to. Therefore, the reclaimed area can be used as it is as a sedimentation area, and even when using earth carriers, it can be transported as a highly concentrated solid content. In addition, solid-liquid separation can be efficiently performed even for leftover water with an increased solid content concentration. Furthermore, in the present invention, the suspended matter separated and concentrated by the inclined plate sedimentation device and other suspended matter separation devices is precipitated and separated by a thickener, separated into supernatant water and solids, and returned to appropriate parts of the processing line. The sludge can be efficiently treated without being discharged and effectively used for landfilling, and the overall treatment system can perform efficient treatment. In the present invention, solid-liquid separation of surplus water is particularly preferred by a combination of an inclined plate type sedimentation device and a long-hair sieve, and the inclined plate type sedimentation device allows treatment by a long-hair sieve even if the quality of the leftover water changes.
Since water with an SS of less than 2000ppm can be obtained, the long hair filter can be operated continuously and efficiently. In particular, both the inclined plate sedimentation device and the long-hair filter are small and require a small installation area, making it easy to transport them from one dredging location to another as needed, and making operational management easier. In addition, by using a long-hair filtration machine and making it a continuous rotation type, continuous processing is possible.
It is no longer necessary to interrupt the process for backwashing as is the case with ordinary filters. By adding a flocculant to perform coagulation-sedimentation or coagulation during sedimentation separation or filtration, it is possible to improve the quality of treated water and treatment efficiency, and if the discharged slurry is returned to the sedimentation zone, solid-liquid separation in the sedimentation zone can be achieved. This is preferable because it helps. In the embodiment, the reclaimed area was used as it is as the sedimentation area, but it is also possible to use a sedimentation pond such as an earth carrier. Although dredged slurry is used as the slurry to be treated, it is also possible to use other slurries such as mountain soil as the slurry for reclamation.

[Brief explanation of the drawing]

The drawings show an embodiment, and FIG. 1 is a system diagram, FIG. 2 is a perspective view of an inclined plate sedimentation device, and FIG. 3 is a sectional view of a long-hair filter, in which 1 is a sedimentation area, 2 is an enclosure, and 3 is a sectional view of a long-hair filter.
1 is a dredging area, 4 is a dredger, 11 is an inclined plate sedimentation device, 12 is a thick long-hair filter, 13 is a thin long-hair filter, 20 is a thickener, 23 is a fin plate, 24 is an inclined plate, 25 is a tank, and 28 is a filter. Body, 29 is hypertank,
32 is a long blanket, 34 is an overwater pipe, 35 is an overwater chamber, 36 is a roller, 37 is a mud collecting hopper, 38
is a sludge drainage pipe, 42 is a circular or cross-flow settling device,
43 is a sand filter device.

Claims (1)

[Claims] 1. In a method for solid-liquid separation of dredging slurry or landfill slurry, the slurry is introduced into a sedimentation zone, the solid content is concentrated and accumulated in the sedimentation zone through sedimentation treatment, and the separated surplus water is a) Water is passed through an inclined plate sedimentation device in which inclined plates with multiple fin plates arranged in an inclined direction are lined up at intervals for treatment, and then (b) Water is passed sequentially to other suspended matter separation devices. (c) The suspended matter separated and concentrated in the inclined plate settling device and a plurality of other suspension separators is precipitated and separated in a thickener, and the supernatant water is returned to the inclined plate settling device together with the remaining water. , a solid-liquid separation method for dredging and landfill slurry, characterized by returning the solids to the settling zone. 2. The method according to claim 1, wherein the height of the fin plate is 2 to 12 cm. 3. The method according to claim 1 or 2, wherein the other suspension separation device is a long-bed filtration device. 4. The method according to claim 3, wherein the long blanket type sieving device is a sieving device using a thick long blanket and/or a sieving device using a thin long blanket. 5. The method according to claim 1 or 2, wherein the other suspension separation devices are circular or cross-flow settling devices and sand filters. 6. The method according to any one of claims 1 to 5, in which solid-liquid separation is performed by adding a flocculant to raw water supplied to an inclined plate sedimentation device and other suspended matter separation devices.