JPH026592B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a filter medium used in a sewage treatment tank.
More specifically, the present invention relates to the structure of a filter medium used in an anaerobic filter bed for purifying wastewater by biological treatment. (b) Prior art and problems to be solved by the present invention Biological treatment of wastewater is broadly classified into aerobic treatment using aerobic bacteria and anaerobic treatment using anaerobic bacteria. Since aerobic treatment requires a short reaction time and provides good treated water quality, wastewater has generally been treated by aerobic treatment, typified by the activated sludge method and the biological simulation method. On the other hand, although anaerobic treatment was adopted as a small-scale pretreatment, it was mostly used only for part of the treatment of human waste and sludge. However, recently, as energy conservation has been promoted in wastewater treatment, anaerobic treatment has been reconsidered. In other words, aerobic treatment requires constant supply of oxygen through aeration, which requires large power costs for this equipment. In contrast, anaerobic treatment not only does not require the supply of oxygen, but on the contrary, the presence of oxygen inhibits the reaction. Since no aeration operation is required in this way, power costs are significantly reduced, resulting in energy savings. Furthermore, the end products of anaerobic treatment are methane and carbon dioxide gas, and the former methane can be recovered as an energy source, and pathogenic microorganisms and parasite eggs in wastewater are quickly killed. Although anaerobic treatment has these advantages, it has disadvantages such as slow reaction rate, poor quality of treated water, and poor contact efficiency between microorganisms and pollutants. By the way, specifically, biological treatment using aerobic bacteria has become popular and mainstream for the treatment of industrial wastewater, sewage, human waste, etc., or the combined treatment with domestic wastewater, but contact aeration tank treatment using aerobic bacteria has become mainstream. Recently, methods have been used to reduce the load on the contact aeration tank and improve the purification capacity by arranging a sedimentation separation tank or an anaerobic filter bed in front of the contact aeration tank. Sedimentation separation tanks have a simple structure and are easy to maintain and manage, but the reaction rate of anaerobic microorganisms is slow, so it is necessary to have a long residence time. In addition to having to connect the tank or increasing the tank capacity, there are also problems such as large fluctuations in the flow rate will wash out anaerobic bacteria and significantly reduce the purification ability. Therefore, the current structure only serves to separate solids from wastewater. On the other hand, the anaerobic filter bed method, in which a filter bed is filled, allows a large number of anaerobic bacteria to live and can be expected to decompose a considerable amount of organic matter in wastewater, so it has recently been put into practical use as a pretreatment method for combined septic tanks. is being advanced. The advantage of this method is that the biological treatment tank is filled with contact filter media, so there is no need to return the sludge and maintenance is easy. The amount of sludge produced is small and the sludge settles well. Aeration, which requires a large amount of electricity, is not required at all. etc. However, on the other hand, the adhesion of anaerobic bacteria to the membrane is generally weak, making it difficult to trap them. Thus, most of the filter media used in anaerobic filter beds are three-dimensional mesh bodies or string-like contact materials, and in some cases, plate-like contact materials used for aerobic bacteria are also used.
Although net-like bodies and string-like bodies are suitable as filter media for aerobic filter beds, anaerobic filter beds have the following problems as they do not require aeration and agitation by air ration. It does not have good ability to trap bacteria (microorganisms). The structure obstructs the flow of wastewater in the tank, and the stirring effect is poor. It tends to become clogged and cause sludge blockage. The net-like material requires a container and frame to be filled, and the string-like material requires a frame to be stretched above and below, which requires time and effort for equipment and filling work, resulting in high construction costs. On the other hand, if a flat contact material used for aerobic bacteria (for example, see Japanese Patent Publication No. 47-7301) or a contact material that is bent in horizontal section but each curved surface is vertical is used, anaerobic bacteria will not be attracted to it. There was a problem in that the trapping efficiency was significantly reduced due to the weak adhesion. (C) Means for solving the problems and their effects This invention involves stacking a large number of substantially vertical sheets of the same shape on a plane by alternately rotating them half a turn, and bonding the contacting parts to form a block. Each of the sheets is continuously bent in a horizontal cross section, each bent surface is inclined to one side with respect to the vertical as a whole, and each inclined bent surface has a substantially L-shaped vertical section. anaerobic sewage comprising recesses for temporarily trapping sludge formed at intervals in the inclination direction, the bottom surface of the recesses being inclined in the width direction, and further provided with protrusions for resisting sludge flow in the depth direction. It is a filter medium for processing. That is, in this invention, each sheet has a specific inclined curved surface in succession, and is alternately reversed and overlapped, so that the sewage that descends from above at an angle can be mixed in a crosswise manner. , their intersection generates a swirling flow as a whole, and furthermore, the mixed swirling flow is repeatedly split at the contact portions of adjacent sheets. In addition, this invention has a specific recess for temporarily trapping sludge, and a protrusion for resisting sludge flow is formed in the recess, so that the unilateral descent of sludge (including anaerobic microorganisms) is prevented. This ensures sufficient contact time between wastewater and anaerobic microorganisms. The sheets that can be used in this invention include plastics, such as extrusion molded sheets of vinyl chloride resin that are formed by vacuum forming, injection molded vinyl chloride resin sheets, and other metal plates that are molded with concave and convex shapes. can. In particular, when extruded sheets are vacuum-formed, the wall thickness of the recesses for temporary sludge collection must be reduced, so the buoyancy generated by general structural materials, methane, and carbon dioxide gas is Formation of protrusions for resistance to sludge flow is suitable for use as a structural material that can withstand high temperatures, as it increases strength. The inclination of the bent surface formed in the sheet of the present invention is preferably 50 to 70 degrees, more preferably about 60 degrees with respect to the horizontal, in order to moderate the capture and shedding of sludge. (d) Examples This invention will be described in detail based on examples shown in the figures below. Note that this invention is not limited to this. First, in FIG. 3, a filter medium 1 for anaerobic wastewater treatment is used by immersing it in an anaerobic filter bed 2 which is a pre-treatment tank of a wastewater treatment device H, 3 is a wastewater inflow channel, 4 is a gas vent pipe, and 5 is the sludge discharge channel. In addition, 6 is a contact aeration tank, 7 is a connection path between this tank and the anaerobic filter bed 2, 8 is its aerobic contact material, and 9 is an aeration pipe. 10 is an attached tank for final treatment, 11
12 is the excess sludge discharge path, and 12 is the treated water extraction path. Therefore, the filter medium 1 for anaerobic wastewater treatment is particularly suitable for the first filter medium 1.
In Figures 1 to 2, a large number of vertical sheets 15, 16, 17, etc. having the same shape are stacked on top of each other by alternately turning half a turn (180 degrees) on a plane, and the contact portions are glued to form a block shape. The sheet 15 is formed by vacuum forming a vinyl chloride resin plate obtained by extrusion molding, and is continuously bent in a horizontal cross section, and each of its bent surfaces 18, 19... is inclined to one side with respect to the overall vertical direction. There is. Further, in each of the bent surfaces 18, 19..., sludge temporary trapping recesses 20, 21... having a substantially L-shaped vertical section are provided.
are formed at intervals in the inclination direction, and the bottom surface part 22 of the recess is inclined in the width direction (for example, about 30 degrees with respect to the horizontal), and furthermore, the bottom part 22 of the recess is inclined in the depth direction, that is, in the inclination direction (downward). Sludge flow resistance protrusions 24 and 25 extending at right angles to the vertical surface portion 23 are formed. It should be noted that the sheets 16 and 17 have exactly the same shape as the sheet 15, so a description thereof will be omitted. By the way, these sheets 15, 16, 17...
When overlapping, apply an appropriate adhesive [e.g., 70% by volume of tetrahydrofuran and 30% by volume of methyl ethyl ketone (MEK) to the contact areas of adjacent sheets.
The sheet material is dissolved in a solvent consisting of the following: Thus, wastewater (for example, industrial wastewater or sewerage) flowing into the anaerobic filter bed 2 is cross-mixed and bonded by the bent surfaces 18, 19, . . . 26, 27 of the adjacent sheets 15, 16. The flow is divided by the flow and these are repeatedly descended. In addition, each bent surface 18, 19...2 of the adjacent sheets 15, 16
6, 27... are facing each other, so the waste water becomes a swirling flow and descends. Such swirling flow and cross-mixing branch flow allow sufficient contact between anaerobic microorganisms and wastewater, and prevent unnecessary adhesion of sludge to the sheet.
In addition, retention of gases such as methane and carbon dioxide can be prevented. Note that gas retention is dangerous because it imparts a large buoyancy to the entire block-shaped filter medium 1 for anaerobic wastewater treatment. Furthermore, the wastewater that descends in the filter medium 1 for anaerobic sewage treatment forms sludge (including anaerobic microorganisms) through contact with anaerobic microorganisms, and the sludge gradually descends into the excess sludge discharge channel. 5 is discharged as appropriate. However, due to their nature, anaerobic microorganisms and sludge containing them generally have extremely poor adhesion to the sheet surface compared to aerobic microorganisms, and furthermore, the treatment time is long. Therefore, the wastewater imparted with the above-mentioned high fluidity descends into sludge in a short period of time, and there is a risk that the treatment by anaerobic microorganisms will be insufficient. However, the filter medium 1 for anaerobic sewage treatment has recesses 20, 21 for temporarily trapping sludge, and has protrusions 24, 25 for resisting sludge flow formed on the inner surface thereof, so that the bottom surface of the recess 22 and the protrusions 24 and 25 appropriately limit the fall of sludge in the wastewater, ensuring sufficient contact time between the anaerobic microorganisms in the sludge and the wastewater,
The efficiency of wastewater pretreatment can be improved. in short,
The filter medium 1 for anaerobic sewage treatment easily attracts anaerobic microorganisms, and furthermore, the excess sludge that has proliferated easily falls off and new anaerobic microorganisms adhere to it. Fresh sludge is regenerated, increasing treatment efficiency. In addition, since the spaces between the sheets are connected without being separated (the spaces between the sheets are not separated by curved ridges), the methane gas generated in the filter bed,
Carbon dioxide gas etc. can escape easily, and in particular, as mentioned above, the buoyancy force applied to the filter medium for anaerobic wastewater treatment can be reduced. Unlike the above embodiments, each sheet constituting the filter medium for anaerobic wastewater treatment has a large number of small holes (for example, 10 to 10 holes).
The flow rate distribution of wastewater can be made more uniform by distributing the holes (50mmφ). Furthermore, in order to ensure a sufficient bonding area when stacking and bonding each sheet, a flat adhesive circular part may be formed at the reaction contact point of the curved ridge of each curved surface (for example, a flat circular part for bonding may be formed on each sheet). form a flat boss and a circular flat receiver that receives the boss). Here, for reference, examples of general dimensional specifications and experimental examples of recesses for temporarily trapping sludge formed in a sheet constituting a filter medium for anaerobic sewage treatment and protrusions for resisting sludge flow within the recesses are listed. [Example of general dimensional specifications] (A) Recess for temporary sludge capture Bottom part Depth: 5 to 15 mm, Width: 40 to 120 mm Vertical part Height: 15 to 45 mm, Width: 40 to 120 mm (B) For sludge flow resistance Convex strips Height: 1 to 3 mm Width: 1 to 3 mm Number of strips: 2 to 5 [Experiment example] (A) Filter medium for anaerobic sewage treatment (product of the present invention) Length, width, and height: 500 x 500 x 500 (mm) Constituent sheet: Vacuum formed from a vinyl chloride resin extrusion molded plate (plate thickness approx. 0.5mm), Bending pitch: 200mm Bitch between constituent sheets (1 cycle of waves): 80
mm Bending height (total height of waves): 80mm Concave part for temporary sludge capture Bottom part Depth: 10mm, Width: 80mm Vertical part Height: 30mm, Width: 80mm Convex strip for resisting sludge flow Height: 2mm Width: 2mm Number of threads: 2 (comparative product) Commercial product manufactured by Dainippon Plastics Co., Ltd.: Kleopatzkin (registered trademark) PW80 Length/width/height: 500 x 500 x 480 (mm) Composition sheet: Same composition as the present invention Pitch between sheets: 80mm Bending pitch (wave cycle): 125mm Bending height (total height of waves): 50mm A flat boss to secure the pitch between sheets and to bond both sheets, and a flat receiver to receive the boss. and is formed. (B) Anaerobic bacteria Anaerobic bacteria with a MLSS concentration of approximately 20,000 ppm obtained from sewage (water temperature 24°C) (C) Experimental equipment Water tank Length/width/height 1 x 1 x 2 (m) On a pedestal with a height of approximately 500 mm A filter medium for anaerobic sewage treatment was placed in the water tank. Water level: 1.3 m (D) Experimental method Anaerobic bacteria were gradually introduced into the tank using a vacuum cleaner (approximately 1.3 m ³ ). After this, it was left to stand for 48 hours, and then the anaerobic bacteria in the aquarium were extracted, and after being left for one week, the weight of the bacteria adhering to the filter medium was measured, and the amount of bacteria held by the filter medium per m ³ was calculated. (E) Test results

[Table] Anaerobic treatment, typified by methane fermentation, is a treatment method that utilizes the growth and metabolic activity of anaerobic microorganisms, but the treatment effect is greater as the amount of bacteria retained increases. In the present results, the filter medium of the invention was able to retain approximately 10 times more bacterial cells than the comparative product. (E) Effects of the Invention According to the present invention, it is possible to ensure appropriate contact between wastewater and anaerobic microorganisms, to obtain high treatment efficiency, and to obtain sufficient strength as a structural material.

[Brief explanation of drawings]

Fig. 1 is a partial explanatory perspective view showing an embodiment of the present invention, Fig. 2 is a vertical cross-sectional view of the recess for temporarily trapping sludge, and Fig. 3 is a structural explanation showing an example of a wastewater treatment device incorporating the same. It is a diagram. 1... Filter medium for anaerobic sewage treatment, 15, 16, 1
7... Sheet, 18, 19... Bent surface, 20, 2
1... Concavities for temporary sludge trapping, 24, 25... Convex lines for resisting sludge flow.

Claims (1)

[Scope of Claims] 1. A large number of substantially vertical sheets of the same shape are stacked on top of each other by alternately turning half a turn on a plane, and the contact parts are glued together to form a block shape, and each sheet has a horizontal The cross section is continuously bent, and each of the bent surfaces is inclined to one side with respect to the vertical direction, and a sludge temporary trapping recess with a substantially L-shaped vertical section is formed in each of the inclined bending surfaces in the inclined direction. A filter medium for anaerobic sewage treatment, which is formed with intervals, the bottom surface of the recessed portion is inclined in the width direction, and further provided with protrusions for resisting sludge flow in the depth direction.