JP4784539B2 - Inclined settling device - Google Patents

Description

  The present invention relates to an inclined settling device used for separating solids from sludge in various treatments such as clean water, industrial water, sewage, human waste, and industrial wastewater.

  As a conventional example of a sedimentation apparatus used in various water treatments, there is an inclined sedimentation apparatus disclosed in JP-A-4-338202. In this device, a large number of inclined sedimentation accelerators such as inclined plates or inclined pipes are installed in the tank to increase the sedimentation area and improve the sedimentation efficiency. To improve processing efficiency.

  This device has a remarkable effect of promoting the sedimentation of suspended solids by inclined plates and inclined tubes, etc., but sludge deposited on the inclined plate surface and algae grown by sunlight slide down to the lower part. It's not easy to do. As a result, problems such as deterioration of the quality of treated water occur due to the clogging of the gaps between the inclined plates due to accumulated sludge and algae and the decay of sludge. A large amount of equipment and labor are required for the regular cleaning of such accumulated sludge and algae, and this tendency is particularly remarkable in an activated sludge settling apparatus used for wastewater treatment.

  As a countermeasure, the apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-187302 uses a gradient sedimentation accelerator made of FRP, smoothes the surface, and contains silver (Ag) having an antibacterial action on the surface. A biofouling prevention gel coat is formed. According to this device, generation and reproduction of algae and bacteria can be suppressed or killed by the action of Ag having antibacterial properties.

The latter apparatus has a smaller amount of sludge attached than the former apparatus, and is considerably improved in terms of sludge downhill. However, in the activated sludge settling apparatus used for wastewater treatment, the effect of preventing the adhesion of sludge is not sufficient, and the sludge accumulates on the inclined plate over time, so regular cleaning is required.
JP-A-4-338202 JP 2001-187302 A

  The present invention was made in view of the problems in the conventional inclined sedimentation apparatus as described above, and the object of the present invention is excellent in the sedimentation promoting effect by preventing the adhesion of sludge to the inclined sedimentation promoting body. Another object of the present invention is to provide an inclined settling device.

The inclined sedimentation device of the present invention is
In the inclined sedimentation apparatus comprising a sedimentation tank and an inclined sedimentation accelerator arranged in the sedimentation tank,
The inclined sedimentation accelerator has a hydrophilic treatment layer on the surface thereof.

  According to the present invention, since the hydrophilic treatment layer is provided on the surface of the inclined sedimentation promoting body, a thin water film is formed on the surface of the inclined sedimentation promoting body in the precipitation tank. This water film prevents the protein in the sludge from binding to the surface of the inclined sedimentation promoting body, and accordingly, prevents the phenomenon that sludge, bacteria, etc. are deposited on the surface of the inclined sedimentation promoting body.

  The inclined sedimentation accelerator is generally made of a non-corrosive material, and examples thereof include stainless steel, titanium alloy or resin, and a hydrophilic treatment layer is provided on the surface of the base material. The applied one is used.

  Preferably, the hydrophilic treatment layer has hydrophilicity with a contact angle with water of 40 ° or less.

  The hydrophilic treatment layer will be further described.

  In the case of a resin, since it is composed of a polymer, it is difficult to form a complete crystal, and a structure in which a crystal part and an amorphous part are mixed is easily obtained. For this reason, it has the fault that the surface is easy to be damaged, and sludge will enter there if it is damaged. As shown in FIG. 5, the sludge adhering to the surface penetrates into the polymer of the resin, and the sludge is integrated with the resin on the surface of the resin, so that the sludge does not slide down on the inclined plate and easily accumulates. Become.

  As shown in FIG. 6, the solid matter of sewage sludge contains a large amount of high molecular weight polysaccharides and proteins, and dissociative hydrophilic properties such as amino groups, carboxyl groups, sulfonic acid groups, and hydroxyl groups in the polymer structure. I have a lot of groups. Since these hydrophilic groups form a stable hydrophilic layer, the solid matter of sewage sludge is surrounded by a water film. Here, by performing a hydrophilic treatment on the surface of the inclined sedimentation promoting body, a thin water film is formed on the surface of the inclined sedimentation promoting body as shown in FIG. Since the sludge itself is also surrounded by a thin water film, it does not come into direct contact with the inclined plate surface, and the sludge does not easily adhere to the inclined plate. In the case of stainless steel (or titanium alloy) as well, the sludge hardly adheres to the inclined plate by forming the hydrophilic layer in the same manner as the hydrophilic layer of the resin.

  As described above, due to the presence of the water film between the surface of the inclined sedimentation accelerator and the sludge, the sludge components are not bonded to the surface, and the surface is kept smooth. Also, the sludge component that has reached the surface easily slides down because the frictional force between the surface of the inclined sedimentation promoting body is small due to the presence of the water film. This makes it difficult for sludge to adhere, prevents a decrease in sedimentation efficiency due to sludge accumulation, prevents clogging of gaps, and the like, and maintains an excellent sedimentation promoting function.

  According to the present invention, it is possible to prevent sludge from adhering to the inclined sedimentation promoting body and improve the downhill acceleration effect. Moreover, since no harmful substances are contained in the treated water, there are no restrictions on the use of the treated water. Moreover, the inclined sedimentation apparatus based on this invention can be applied, without selecting the kind of treated water, and also can be used regardless of indoor and outdoor.

An example of an inclined settling device according to the present invention will be described with reference to the drawings.
FIG. 1 is a partially omitted vertical cross-sectional view of an inclined settling device, and FIG. 2 is a transverse cross-sectional view of an inclined plate (inclined settling accelerator) used in this device. As shown in FIG. 1, this inclined settling device has a settling tank 1, and an inclined plate 2 is arranged in the settling tank 1. A suspension rod 4 is attached to the gantry 3 provided on the upper part of the settling tank 1, and a net-like support frame 5 is suspended from these suspension rods 4 via a suspension angle. The inclined plate 2 is supported by the support frame 5 at both ends and upper and lower sides, and is disposed in the sedimentation tank 1 in an inclined state. In the figure, 8 indicates the water surface. FIG. 1 shows only one side, and there is a similar support frame 5 on the heel side to support the inclined plate 2.

  Next, the inclined sedimentation promoting body of the present invention will be described. As shown in FIG. 2, the inclined plate 2 has a laminated body 2a made of metal or resin, and a hydrophilic treatment layer 2b is formed on the surface of the laminated body 2a.

  3 and 4 show examples of other forms of the inclined sedimentation promoting body. FIG. 3 is a perspective view showing a part of the inclined plate with fins, and FIG. 4 is a perspective view showing a part of the honeycomb-like inclined tube. The finned inclined plate 6 shown in FIG. 3 and the honeycomb-like inclined tube 7 shown in FIG. 4 can be used in place of the inclined plate 2 shown in FIG. 3 is formed on the surface of the inclined plate 6 and on the inner surface of each inclined tube 7 in FIG.

Next, the hydrophilic treatment of the surface of the inclined sedimentation promoting body (inclined plate 2, inclined plate 6 with fins, honeycomb-shaped inclined tube 7) will be described.
First, a method in which the inclined plate is made of metal and the metal base material is subjected to a hydrophilic treatment will be described. Formation of the hydrophilic treatment layer on the metal surface can be realized by acid treatment of the metal surface. When a metal material such as stainless steel or titanium alloy comes into contact with air in the manufacturing process, an oxide film is formed on the surface immediately. Here, since organic substances or cutting oil in the air adheres to the surface, a non-uniform oxide film is formed. Although the oxide film is hydrophilic, for the reasons described above, when a metal material is used for the inclined sedimentation accelerator, the hydrophilicity of the surface is biased. For this reason, sludge adheres from a portion having a low degree of hydrophilicity, and eventually the sludge adheres to the entire surface of the promoting body.

Therefore, once the oxide film is removed with a reducing acid such as hydrochloric acid or hydrofluoric acid, the cleaned metal surface is exposed, and then a dense and uniform oxide film is formed on the metal surface with an oxidizing acid such as nitric acid or sulfuric acid. By making it, a hydrophilic treatment layer can be formed. Although the acid treatment conditions differ depending on the combination of the metal material and the acid used, for example, Table 1 shows an example of conditions for acid treatment of stainless steel or a titanium alloy.

  In the apparatus according to the present invention, it is important to form a uniform hydrophilic treatment layer without unevenness on the entire surface of the inclined sedimentation accelerator, and for this purpose, the reaction time (immersion time) between the metal base material and the acid Must be long enough.

  Usually, the wettability (hydrophilicity) between a solid and a liquid is expressed by a contact angle, and in the apparatus according to the present invention, it is desirable that the contact angle of the hydrophilic treatment layer is less than 40 degrees. When the contact angle is 40 degrees or more, the hydrophilicity of the inclined sedimentation promoting body surface becomes insufficient, and the sludge adheres easily. Therefore, as long as the contact angle of the hydrophilic treatment layer after the acid treatment satisfies the above condition of less than 40 degrees, the treatment condition is not limited to Table 1.

Next, when the material of the inclined plate is resin, as a method of hydrophilizing the resin surface,
(A) A method by melting and solidification for improving the substrate surface by bringing the substrate into contact with the resin surface and heating to melt the resin portion in contact with the substrate and then removing the substrate;
(B) Surface modification method by ultraviolet irradiation;
(C) a method of modifying a resin surface by grafting reaction to a monomer;
(D) a method of forming a thin film containing inorganic particles on the resin surface;
Etc.

In the method of melting and solidifying in (a), the use of a material having a high surface energy (for example, metal) as the substrate increases the density of functional groups on the resin surface, that is, the degree of crystallinity on the surface, and makes it more hydrophilic. This is desirable because it increases. Examples of the hydrophilization treatment (b) include, for example, hydrophilization in which a low-pressure mercury lamp is used to irradiate the surface of polypropylene with ultraviolet rays to form a hydroxyl group that is a hydrophilic group. Examples of hydrophilization by graft polymerization of (c) include graft polymerization by acting acrylamide as a monomer on the surface of low density polyethylene or oriented polypropylene, or N-vinylpyrrolidone or acrylic acid as a monomer on the surface of oriented polypropylene. It is known that the hydrophilicity of the resin surface is remarkably improved by the action of graft polymerization. As a method of forming the hydrophilic thin film of (d), a method of forming a thin film containing titanium oxide and silica particles (Patent No. 2756474; International Publication WO96 / 29375 pamphlet), polymerization with an acrylic monomer And a method of forming a thin film containing a reactive silane coupling agent and colloidal silica on the surface of the resin by emulsion polymerization (JP 07-233270 A).

  Each specimen was immersed in an immersion tank in which sludge extracted from the final sedimentation basin of the sewage treatment plant was circulated for 60 days, and tested for algae generation and sludge adhesion. In the column of immersion liquid in Table 2, SS indicates suspended matter, MLSS indicates activated sludge suspended matter, MLVSS indicates activated sludge organic suspended matter, and SVI indicates active capacity index.

  In Table 3, the evaluation of the sludge adhesion amount is as follows: ◯ indicates the adhesion surface area ratio of sludge or algae: 10% or less, Δ indicates more than 10 to less than 50%, and X indicates 50% or more. As can be seen from Table 3, the specimen in which the hydrophilized layer was formed has a small sludge adhesion surface area ratio and algae adhesion surface area ratio, and it is understood that the amount of sludge adhesion is small compared to the comparative specimen.

As described above, since the hydrophilization treatment layer is formed on the surface of the inclined sedimentation accelerator, the precipitation apparatus according to the present invention has the following useful effects:
(A) Due to the presence of the hydrophilic layer formed on the surface, a thin water film is formed on the inclined plate surface, the protein in the sludge is prevented from binding with the inclined sedimentation accelerator, and the friction coefficient of the inclined sedimentation accelerator surface is increased. small. As a result, sludge easily slides down and has an excellent sedimentation promoting effect;
(B) It can be used in a wide range both indoors and outdoors.

FIG. 2 is a partially omitted longitudinal sectional view showing an example of an inclined sedimentation apparatus according to the present invention. It is a cross-sectional view of an inclined plate used in the inclined settling device. It is a perspective view which shows a part of other example (inclined board with a fin) of the inclination board used with an inclination sedimentation apparatus. It is a perspective view which shows a part of other example (honeycomb-like inclination pipe) of the inclination board used with an inclination sedimentation apparatus. The figure explaining the adhesion situation of the sludge on the resin surface. The figure explaining the microbial structure model in sludge. The figure explaining the adhesion situation of the sludge of the resin fiber surface made hydrophilic.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Sedimentation tank, 2 ... Inclined plate, 2a ... Laminated body, 2b ... Hydrophilic treatment layer, 3 ... Mount, 4 ... Hanging rod, 5 ... Support frame, 6 ... inclined plate with fins, 7 ... honeycomb inclined tube, 8 ... water surface.

Claims (2)

In the inclined sedimentation apparatus comprising a sedimentation tank and an inclined sedimentation accelerator arranged in the sedimentation tank,
The inclined sedimentation promoting body has a hydrophilic treatment layer having hydrophilicity with a contact angle with water of 40 ° or less on the surface thereof,
This hydrophilic treatment layer is obtained by immersing a stainless steel base material in 5 to 15 wt% hydrochloric acid for 5 to 20 minutes to remove the oxide film on the surface, and then in 5 to 20 wt% nitric acid. It is composed of an oxide film formed by immersion for 20 minutes,
Inclined sedimentation device characterized by. In the inclined sedimentation apparatus comprising a sedimentation tank and an inclined sedimentation accelerator arranged in the sedimentation tank,
The inclined sedimentation promoting body has a hydrophilic treatment layer having hydrophilicity with a contact angle with water of 40 ° or less on the surface thereof,
This hydrophilic treatment layer is obtained by immersing a titanium base material in 5 to 20 wt% hydrochloric acid for 5 to 30 minutes to remove the oxide film on the surface, and then 5 to 30 wt% in nitric acid of 5 to 20 wt%. It is composed of an oxide film formed by partial immersion,
Inclined sedimentation device characterized by.

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