Polluted water treatment method

Abstract

To provide a method for treating polluted water capable of preventing clogging of a filtration basin, and reducing the frequency of cleaning of the filtration basin, thereby, facilitating maintenance management.SOLUTION: A method for treating polluted water treats the polluted water sequentially in a floc forming basin, and, as required, in a concentration tank, a settling basin and a filtration basin, after adding a flocculant into the polluted water, and comprises: providing a mixing basin between the settling basin and the filtration basin; and providing into the mixing basin, slime-forming bodies constituted of at least one kind of a string-like material, a cotton lump-like material, and a net-like material, which are arranged oppositely, obliquely, and parallelly with respect to a water flow; further, spreading the slime-forming bodies in a zigzag manner; and furthermore, adding a flocculant in the mixing basin so as to treat the polluted water.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for treating polluted water, and more particularly to a treatment method suitable for obtaining tap water. [Background technology]

[0002] In the conventional method of treating polluted water, the polluted water is introduced into a receiving well, a coagulant is added in a mixing basin, the treated water is introduced into a flocculation basin to flocculate the pollutants, the pollutants are then removed in a settling basin, and the treated water containing the remaining pollutants is removed in a filtration basin. If necessary, the treated water from the filtration basin is chlorinated by adding a chlorine agent in a chlorine mixing basin, and then sent to a distribution reservoir as clarified water. Summary of the Invention [Problem to be solved by the invention]

[0003] However, in these conventional methods, the performance depends on the time from when the coagulant is injected until it reaches the filter basin, which places a burden on the filter media in the filter basin, and as a result, pollutants (particles) adhere to the filter media, which requires frequent cleaning. The pollutants that adhere to the filter media are difficult to remove even with cleaning, making maintenance and management difficult. Therefore, the present inventors have conducted extensive research into methods for reducing the load on the filter media in a filter basin, and as a result have completed the present invention. [Means for solving the problem]

[0004] That is, the present invention relates to a method for treating polluted water in which a coagulant is added to the polluted water and then the water is treated in a flocculation basin, and if necessary a thickening basin, a sedimentation basin and a filtration basin in succession, in which a mixing basin is provided between the sedimentation basin and the filtration basin, a slime-forming body is provided in the mixing basin, and a coagulant is further added to the mixing basin for treatment. Effect of the Invention

[0005] According to the method of the present invention, the charge of the slime-forming body and the polluting substances is rapidly neutralized by injecting a coagulant, and the polluting substances adhere to the slime-forming body. The adhered polluting substances naturally concentrate and peel off from the surface of the slime-forming body, and are deposited in high concentration on the bottom of the pond. The water treated by the slime-forming body is introduced into the filtration tank and conveyed through the distribution tank, so that the adhesion of polluting substances to the filter media of the filtration layer installed in the filtration tank is substantially small, and therefore cleaning frequency is reduced, making maintenance and management easier. [Brief description of the drawings]

[0006] [Figure 1] FIG. 2 is a flow chart showing an example of a processing flow of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a plan view of the helical string. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] This is a front view of a slime-forming body made up of spiral string-like material. [Figure 7] This is a front view of a slime-forming body made of cotton-like material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Fig. 1 is a flow diagram showing an example of a processing flow of the present invention. The present invention will be described with reference to this flow diagram. After the polluted water is introduced into the receiving well, a coagulant is added from the coagulant tank in the mixing basin, and the treated water is introduced into the flocculation basin to flocculate the pollutants.The flocculated pollutants are then removed by settling in the settling basin.The water treated in the settling basin is then introduced into the mixing basin, where a slime former is installed, and coagulant is added from the coagulant tank to mix the water.

[0008] Examples of flocculants that can be added to the mixing pond of the present invention include aluminum sulfate, ferrous sulfate, ferric sulfate, ferric chloride, sodium alginate, sodium polyacrylate, water-soluble aniline resin hydrochloride, polyvinylpyridine hydrochloride, water-soluble urea resin, polyacrylamide, gelatin, polyaluminum chloride, and polyaluminum sulfate. The concentration of the flocculant solution used is preferably 0.1 to 50% by weight. The amount of the flocculant solution added is a small amount of flocculant for low turbidity water, 0.01 to 10 mg / l, preferably 1 to 2 mg / l, but is not limited thereto.

[0009] The string-like material constituting the slime forming body 1 used in the present invention can be of various shapes, such as a straight one as shown in Fig. 2 or a spiral one as shown in Fig. 3. The shape of the string-like material can also be of various shapes, such as round, flat, rope, jute, loop, PD curl, ply, etc. Also, the material of the cotton lump-like material shown in Fig. 4 can be natural fibers or synthetic fibers such as polyester and nylon. Further, the slime forming body may be a net-like material as shown in Fig. 5. The mesh size of the net-like material is generally preferably about 20 to 40 mm. Also, a so-called curtain-like material suspended from a support as shown in Fig. 6, or a material composed of a spiral string-like material as shown in Fig. 7 may also be used. The slime-forming body of the present invention is a water-permeable structure, and is composed of the above-mentioned string-like material, cotton lump-like material, and net-like material, either alone or in appropriate combination, and is used by spreading them out in multiple layers. The method of spreading the slime-forming body can be, for example, by hanging the slime-forming body on a float in a mixing tank provided next to a settling tank, spreading them out in multiple layers so as to face, diagonally, and parallel to the water flow, and further spreading them out in a zigzag shape. Furthermore, according to the slime forming body of the present invention, the attached pollutant grows into a rod-like shape and is eventually detached from the slime forming body by the force of gravity and water current while maintaining its attached shape, allowing the pollutant to be deposited in high concentrations on the bottom of the pond.

[0010] In the present invention, in a mixing basin provided with a slime-forming body, the addition of a coagulant causes the pollutants to instantly come into contact with and adhere to the slime-forming body, which grows into a string-like aggregate through electrical neutralization, thickens, thickens, and becomes heavy, resulting in natural settling, and thus the pollutants can be recovered at a high concentration. Therefore, normal filtration blockage does not occur, and the pollutants can be recycled as an active contact filter. In other words, there is no need to wash the filter material. In addition, the method of the present invention can be used not only for low turbidity water but also for high turbidity water by providing a thickening basin having the same structure as the mixing basin provided between the above-mentioned settling basin and filtration basin in the receiving well and the next mixing basin or / and flocculation basin or / and the front, middle, and rear stages of the settling basin, thereby reducing the load on the settling basin and filtration basin to be treated next, and enabling automatic thickening and settling. In the case of high turbidity water, the capacity of the settling basin can be increased, the turbidity removal effect can be enhanced, the load on the dehydrator can be reduced, and the amount of dehydrated cake can be reduced.

[0011] The treated water from the mixing basin after the settling basin is then introduced into the filtration basin, where the remaining pollutants are separated. The treated water from the filtration basin is then introduced into the chlorine mixing basin, where chlorine is added from the chlorine tank for chlorination. The chlorinated treated water is then introduced into the distribution reservoir and sent as clear water.

[0012] Next, the present invention will be described with reference to an embodiment based on the processing flow shown in FIG. Working Example Polluted water (turbidity 9mg / L) is introduced into the receiving well at 450L / min, then into the mixing basin, where a coagulant (polyaluminum chloride) (20mg / L) is added from the coagulant tank and mixed. The treated water to which the coagulant has been added is then introduced into the flocculation basin, where the pollutants are flocculated. After this treatment, it is introduced into the settling basin, where the flocculated pollutants are separated by settling. The treated water from the settling basin is introduced into the mixing basin, where a coagulant (polyaluminum chloride) (1mg / L) is added from the coagulant tank, and fine pollutants that could not be removed in the settling basin are brought into contact with and attached to the slime forming body installed in the mixing basin, where they are attached by electrical neutralization, grow into string-like aggregates, and are removed by natural settling. The treated water from the mixing basin is then introduced into the filtration basin, and then into the chlorine mixing basin, where chlorine is added from the chlorine tank and treated, before being introduced into the distribution reservoir and sent as tap water. The turbidity of the treated water in the mixing tank after the settling tank was 0.01 mg / L.

Claims

[Claim 1] This method of treating polluted water is characterized in that after adding a coagulant to the polluted water, it is successively treated in a flocculation basin, a sedimentation basin and a filtration basin, a mixing basin is provided between the sedimentation basin and the filtration basin, slime-forming bodies consisting of at least one of string-like material, cotton-clot-like material and net-like material are hung in the mixing basin in a multi-layered manner so as to face the water flow, and a coagulant is continuously added to the mixing basin for treatment.

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