JP4334718B2 - Method and apparatus for treating silver-containing wastewater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for treating silver-containing wastewater generated during the production of a photosensitive material such as a photographic film.
[0002]
[Prior art]
When producing photosensitive materials such as photographic film, wastewater containing silver components such as silver chloride (hereinafter referred to as “silver-containing wastewater”) is generated. Various methods have been conventionally used to treat such silver-containing wastewater. Are known. For example, in JP-A-11-80850, a silver component is incorporated by sequentially adding a polymer flocculant having a cationic structure containing an N-vinylacrylamidine salt unit and an anionic polymer flocculant to silver-containing wastewater. A method for separating the silver component in the silver-containing wastewater by generating floc and precipitating and separating the floc in a coagulating sedimentation tank is disclosed. Clarification of the silver containing waste water is achieved by this method.
[0003]
[Problems to be solved by the invention]
However, according to the silver-containing wastewater treatment method described in the above-mentioned conventional publication, the first reaction tank to which the N-vinylacrylamidine salt unit-containing polymer flocculant is usually added, and the anionic polymer flocculant Three tanks, a second reaction tank to which is added and a coagulation sedimentation tank, are required. Here, in the coagulation sedimentation tank, it cannot be said that the sedimentation rate of flocs formed in the introduced silver-containing wastewater is sufficiently high. For this reason, in order to ensure the processing amount of the silver containing waste water in a coagulation sedimentation tank, it is necessary to enlarge a coagulation sedimentation tank. Therefore, the silver-containing wastewater treatment apparatus becomes larger as a whole, and a large installation space is required.
[0004]
On the other hand, if an attempt is made to reduce the size of the coagulation sedimentation tank while maintaining the treatment amount of the silver-containing wastewater, the silver component flows into the treated water in the coagulation sedimentation tank because the sedimentation speed of the floc formed in the second reaction tank is small. There is a fear.
[0005]
Then, an object of this invention is to provide the processing method and processing apparatus of silver containing waste_water | drain which can fully prevent the outflow of the silver component to processing water while reducing the processing apparatus of silver containing waste_water | drain.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a cation addition step of adding a cationic polymer flocculant to silver-containing wastewater, and a feed supply in which the wastewater to which the cationic polymer flocculant is added is disposed in a precipitation tank. An introduction process for introducing into the pipe, an anion addition process for adding an anionic polymer flocculant to the waste water from a plurality of locations, agitation of the waste water in the feed supply pipe, and flocs generated in the waste water being fed into the feed supply pipe And a separation step of separating the silver component in the silver-containing wastewater by being discharged through a plurality of jets of a distributor extending radially from the nozzle and trapped in the aggregation flock layer in the settling tank.
[0007]
According to this method, the cationic polymer flocculant is added to the silver-containing wastewater, the wastewater is introduced into the feed supply pipe, and the anionic polymer flocculant is added to the wastewater in the feed supply pipe and stirred. A floc that incorporates a silver component in the supply pipe grows. At this time, since the anionic polymer flocculant is added from a plurality of locations, flocs grow efficiently in the feed supply pipe even in a small feed supply pipe. The grown flocs are sprayed from a plurality of outlets of the distributor, and the flocs are captured by the aggregated floc layer inside the settling tank. Since the flock incorporates the silver component, the silver component is sufficiently separated from the silver-containing wastewater. In addition, since the aggregated floc layer has high uniformity and is composed of a coarse and dense aggregated floc, the floc is sufficiently captured by the aggregated floc layer. Therefore, it is possible to increase the ascending flow rate in the settling tank, and it is possible to greatly reduce the size of the settling tank.
[0008]
In the cation addition step, it is preferable to use a polycondensate of dicyandiamide and formaldehyde as the cationic polymer flocculant.
[0009]
The polycondensate of dicyandiamide and formaldehyde can efficiently agglomerate the silver component with gentle stirring, so there is less air generation than when rapid stirring is performed, which prevents the floc from rising due to air. In addition, when a stirrer is used for stirring, the power is small.
[0010]
The present invention also adds a cationic polymer flocculant to the silver-containing wastewater, and adds an anionic polymer flocculant to the wastewater to which the cationic polymer flocculant is added to separate the silver components in the silver-containing wastewater. A treatment apparatus for silver-containing wastewater, comprising a precipitation tank, a feed supply pipe disposed in the precipitation tank for receiving wastewater to which a cationic polymer flocculant is added, and wastewater to which a cationic polymer flocculant is added. Supply means for supplying into the feed supply pipe, anion addition means for adding anionic polymer flocculant to the waste water in the feed supply pipe from a plurality of locations, a mixer for stirring the waste water in the feed supply pipe, and radial from the feed supply pipe And a distributor having a plurality of injection ports.
[0011]
According to this apparatus, the invention of the above method can be effectively implemented.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or equivalent components are denoted by the same reference numerals.
[0013]
FIG. 1 is a schematic cross-sectional view showing a main part of an embodiment of a silver-containing wastewater treatment apparatus (hereinafter referred to as “drainage treatment apparatus”) according to the present invention. As shown in FIG. 1, the waste water treatment apparatus 10 has a reaction tank 2, and silver-containing waste water discharged from a film manufacturing factory or the like is introduced into the reaction tank 2 through a line L 1. The wastewater treatment apparatus 10 also has a tank 3 that adjusts and stores the cationic polymer flocculant to a concentration suitable for dispersing the cationic polymer flocculant in the wastewater. It is designed to be added to silver-containing wastewater. Further, in the reaction tank 2, a stirring device 5 for stirring the waste water in the reaction tank 2 is provided from the viewpoint of promoting the generation of flocs.
[0014]
The wastewater treatment device 10 also includes a coagulating sedimentation device 4 that coagulates and precipitates silver components in the wastewater discharged from the reaction tank 2 as flocs. The coagulating sedimentation apparatus 4 has a cylindrical sedimentation tank 6, and an overflow part 7 is provided on the top of the sedimentation tank 6. A feed supply pipe 8 is provided upright in the center of the settling tank 6, and the feed supply pipe 8 is rotatable. And the waste_water | drain discharged | emitted from the reaction tank 2 through the line L2 flows in into the feed supply pipe | tube 8. FIG.
[0015]
A stirring rotating shaft 12 is provided concentrically in the feed supply pipe 8, and a plurality of stirring blades 14 are attached to the outer periphery of the stirring rotating shaft 12. A drive unit 16 that rotates the rotary shaft 12 is connected to the upper end of the stirring rotary shaft 12. Therefore, when the rotating shaft 12 is rotated by the drive unit 16, the waste water in the feed supply pipe 8 is stirred by the stirring blade 14.
[0016]
In the feed supply pipe 8, a plurality of inlets 18 are arranged in the feed supply pipe 8 in order to add the anionic polymer flocculant from a plurality of locations. In this case, as shown in FIG. 1, for example, a plurality of (two in FIG. 1) supply pipes 20 are connected to the tank 22, branch pipes are extended from each supply pipe 20, and a plurality of inlets 18 are connected to the feed supply pipe 8. What is necessary is just to arrange | position in. The supply pipe 20 and the tank 22 constitute an anion addition means.
[0017]
A plurality of tubular distributors 24 extending radially from the feed supply pipe 8 are provided at the lower end of the feed supply pipe 8, and each distributor 24 is formed with a plurality of injection ports 24a that open downward. Yes.
[0018]
Further, a sludge scraping shaft 26 is suspended from the lower end portion of the distributor 24, and a rake arm 28 for scraping the sludge accumulated at the bottom of the sedimentation tank 6 to the central portion of the sedimentation tank 6 is disposed at the lower end of the scraping shaft 26. Is provided. The sludge scraped to the center is pulled out by the pump 30 and stored in the sludge storage tank 32, and the stored sludge is dehydrated by the dehydrator 34.
[0019]
FIG. 2 is a flowchart showing the entire waste water treatment apparatus 10 of FIG. As shown in FIG. 2, in the wastewater treatment apparatus 10, it is preferable that a vacuum degassing tank 36 is installed on the upstream side of the reaction tank 2. Thereby, since silver containing waste_water | drain is deaerated previously, it can prevent that a flock takes in air in the process of silver containing waste_water | drain, or a flock is levitated by air. Furthermore, it is preferable that a biological denitrification device 38 is installed on the upstream side of the vacuum degassing tank 36. In this case, when the silver-containing wastewater contains nitrate nitrogen and nitrite nitrogen, the organic matter in the silver-containing wastewater can be decomposed and released as nitrogen gas. Nitrogen gas can be taken in and flocs can be prevented from being floated by nitrogen gas. The biological denitrification device 38 returns the silver-containing wastewater in the first adjustment tank 40, the second adjustment tank 42, and the second adjustment tank 42 that stirs the silver-containing wastewater under anaerobic conditions to the first adjustment tank 40, for example. And a return line 44.
[0020]
Next, the processing method of the silver containing waste_water | drain using the waste water treatment apparatus 10 mentioned above is demonstrated.
[0021]
First, the silver-containing waste water is sequentially introduced into the biological denitrification device 38 and the vacuum degassing tank 36 to perform denitrification and deaeration. Thereby, gases such as nitrogen gas and air in the silver-containing wastewater are sufficiently removed. Therefore, floating of the floc due to these gases is sufficiently prevented in the reaction tank 2 or the feed supply pipe 8. Subsequently, the silver containing waste_water | drain discharged | emitted from the vacuum deaeration tank 36 is introduce | transduced in the reaction tank 2 through the line L1. Then, a cationic polymer flocculant is added from the tank 3 to the reaction tank 2 in order to generate fine floc (cation addition step). Thereafter, the waste water to which the cationic polymer flocculant in the reaction tank 2 is added is stirred using the stirring device 5. Thereby, fine flocs are efficiently generated in the reaction tank 2.
[0022]
As the above cationic polymer flocculant, a strong cationic polymer flocculant is preferable from the viewpoint of efficiently neutralizing the surface charge of fine particles containing silver dispersed in waste water. As the flocculant, for example, polydicyandiamide-based, polydiallylamine-based, polyamine-based copolymers, and polycondensates of dicyandiamide and formaldehyde are used. Of these, it is particularly preferable to use a polycondensate of dicyandiamide and formaldehyde. This is because the polycondensate of dicyandiamide and formaldehyde can efficiently agglomerate the silver component with gentle stirring, so there is less air generation than when rapidly stirring, and the fine flocs float due to air. This is because the power of the stirring device 5 can be reduced.
[0023]
Subsequently, the waste water discharged from the reaction tank 2 is introduced into the feed supply pipe 8 of the coagulating sedimentation apparatus 4 through the line L2 (introduction step). Then, after anionic polymer flocculant is added to the waste water in the feed supply pipe 8 from the plurality of inlets 18 (anion addition step), the stirring rotary shaft 12 is rotated and the waste water is stirred by the stirring blade 14. Examples of the anionic polymer flocculant include acrylamide and sodium acrylate copolymer. At this time, since the anionic polymer flocculant is added from the plurality of inlets 18, even if the feed feed pipe 8 is small, flocs grow efficiently in the feed feed pipe 8.
[0024]
The flocs thus grown are guided to the distributors 24 in a state of being mixed with the waste water, and are ejected downward from the ejection ports 24a. Here, since the distributor 24 provided in the feed supply pipe 8 rotates in the settling tank 6, the floc is sprayed uniformly over the entire surface of the settling tank 6. Then, the injected flocs collide with each other to form an agglomerated floc layer 46 composed of a coarse and dense agglomerated floc with high uniformity (see FIG. 1). Accordingly, the flocs ejected from the distributor 24 are sufficiently captured by the aggregated floc layer 46. For this reason, in the coagulation sedimentation apparatus 4, the ascending flow rate or the surface area load can be increased, and the sedimentation tank 6 itself can be greatly reduced in size. Therefore, the whole waste water treatment apparatus 10 can be reduced in size, and installation space can be saved significantly. Further, since the flocs captured by the aggregated floc layer 46 have taken in the silver component, the silver component in the silver-containing wastewater is sufficiently separated (separation step). Therefore, a clarified layer 48 made of clarified treated water from which the floc has been removed is formed on the aggregated flock layer 46, and the outflow of the silver component to the treated water is sufficiently prevented. The treated water flows out at the overflow section 7.
[0025]
On the other hand, flocs captured by the aggregated floc layer 46 gradually grow and settle due to their own weight, thereby forming a concentrated sludge layer 50. Then, the concentrated sludge is scraped to the center of the settling tank 6 by rotating the rake arm 28 via the sludge scraping shaft 26. Then, this sludge is appropriately extracted by the pump 30, stored in the sludge storage tank 32, and dehydrated by the dehydrator 34. The operation of the pump 30 is controlled so that the height of the upper surface of the aggregated floc layer 46 is in an appropriate range, that is, the floc does not flow into the treated water and the concentrated sludge concentration is sufficiently high. Here, since this sludge is extracted from the concentrated sludge layer 50, the sludge concentration is high. Accordingly, the sludge is easily dehydrated by the dehydrator 34 and the burden on the dehydrator 34 is reduced.
[0026]
In addition, this invention is not limited to embodiment mentioned above. For example, the waste water treatment device 10 preferably includes a pH adjusting device on the upstream side of the reaction tank 2. Such a waste water treatment apparatus is effective when a large amount of carbonate ions are contained in the silver-containing waste water. That is, when a large amount of carbonate ion is contained in the silver-containing wastewater, the pH can be lowered to about 4 using a pH adjuster and removed as carbon dioxide gas, thereby preventing the flock from rising due to the carbon dioxide gas. In this case, it is preferable that a neutralization facility is provided on the downstream side of the pH adjusting device. Moreover, the waste water treatment apparatus 10 provided with the pH adjusting device is also effective when the silver-containing waste water is acidic or alkaline. In this case, the silver-containing wastewater can be neutralized using a pH adjusting device, and the treated water can be directly led to a post-treatment activated sludge treatment device or a public sewer.
[0027]
Furthermore, the waste water treatment apparatus 10 may include a return means for returning a part or all of the sludge extracted by the pump 30 or a part or all of the sludge in the sludge storage tank 32 to the reaction tank 2 or the feed supply pipe 8. . In this case, even if there is a water quality change such that the concentration of silver components and suspended solids in the silver-containing wastewater decreases, the water quality fluctuation can be suppressed by returning the sludge using the return means. The performance can be stabilized.
[0028]
Depending on the composition of the waste water, the vacuum degassing tank 36, the biological denitrification device 38, and the pH adjustment device may be omitted.
[0029]
【The invention's effect】
As described above, according to the silver-containing wastewater treatment method and treatment apparatus of the present invention, since the floc is sufficiently captured by the coagulation floc layer, it is possible to increase the ascending flow rate, that is, the surface area load in the precipitation tank. Therefore, it is possible to reduce the size of the sedimentation tank, and thus the entire processing apparatus can be reduced in size. Moreover, since the floc which took in the silver component is fully capture | acquired by the aggregation floc layer, the outflow of the silver component from a silver containing waste_water | drain to a treated water can fully be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a main part of an embodiment of a silver-containing wastewater treatment apparatus of the present invention.
FIG. 2 is a flowchart showing the entire silver-containing waste water treatment apparatus of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 ... Reaction tank, 10 ... Silver-containing waste water processing apparatus, 6 ... Precipitation tank, 8 ... Feed supply pipe, L2 ... Line (supply means), 12 ... Rotating shaft (mixer) for stirring, 14 ... Stirring blade (mixer) , 16 ... drive unit (mixer), 18 ... inlet (anion supply means), 20 ... supply pipe (anion addition means), 21 ... branch pipe (anion addition means), 22 ... tank (anion addition means), 24 ... Distributor, 24a.

Claims (3)

A cation addition step of adding a cationic polymer flocculant to the silver-containing wastewater;
An introduction step of introducing the waste water added with the cationic polymer flocculant into a feed supply pipe disposed in the precipitation tank;
An anion addition step of adding an anionic polymer flocculant to the waste water from a plurality of locations;
The waste water in the feed supply pipe is agitated, and the flocs generated in the waste water are discharged through a plurality of outlets of a distributor extending radially from the feed supply pipe and are captured by the coagulation flock layer in the settling tank. Separating the silver component in the silver-containing waste water by,
The processing method of the silver containing waste_water | drain characterized by including. The method for treating silver-containing wastewater according to claim 1, wherein, in the cation addition step, a polycondensate of dicyandiamide and formaldehyde is used as the cationic polymer flocculant. A silver-containing wastewater in which a cationic polymer flocculant is added to silver-containing wastewater, and an anionic polymer flocculant is added to the wastewater to which the cationic polymer flocculant is added to separate silver components in the silver-containing wastewater. A processing device,
A settling tank;
A feed supply pipe disposed in the settling tank and receiving waste water to which the cationic polymer flocculant is added;
Supply means for supplying wastewater to which the cationic polymer flocculant is added into the feed supply pipe;
Anion addition means for adding the anionic polymer flocculant from a plurality of locations to the waste water in the feed supply pipe;
A mixer for stirring the wastewater in the feed supply pipe;
A distributor extending radially from the feed supply tube and having a plurality of jets;
An apparatus for treating silver-containing wastewater.

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