JPS62106894A - Filter material for anaerobic treatment of sanitary sewage - Google Patents

Abstract

PURPOSE:To make it possible to properly secure the contact of waste water with anaerobic microbes, by superposing a large number of vertical sheets having the same shape in such a state that said sheets are allowed to mutually make a half turn on a plane and adhering the contact parts of the sheets to form a block shaped filter material. CONSTITUTION:The filter material 1 allowed to fill a biological treatment tank is formed by a method wherein sheets 15, 16, 17... made of plastic are allowed to alternately make a half turn on a plane to be superposed and the contact parts thereof are adhered to constitute a block. Each sheet is formed by a method wherein a vinyl chloride resin plate obtained by extrusion molding is molded under vacuum so that said plate is continuously bent in a horizontal cross-section and sludge temporarily collecting recessed parts 20, 21... each having an almost L-shaped vertical cross-section are formed on the bent surfaces 18, 19... so as to provide intervals in the oblique direction. The waste water flowing in an anaerobic filter bed 2 receives cross mixing by the bent surfaces 18, 19... of the sheets 15, 16... to be divided into many streams which are, in turn, contacted with anaerobic microbes and high treatment efficiency is obtained.

Description

[Detailed description of the invention] (b) Industrial application fields 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 single material used in an anaerobic method for purifying wastewater by biological treatment.

(B) Prior art and problems to be solved by the present invention Biological treatment of wastewater is broadly divided 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 very small-scale treatment, 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. The end products of anaerobic treatment are methane and carbon dioxide,
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 is mainly used to treat wastewater such as industrial wastewater, sewage, human waste, or combined treatment with domestic wastewater, but contact aeration tanks using aerobic bacteria are used. Recently, a method has been used to reduce the load on the contact aeration tank and improve the purification capacity by placing a sedimentation separation tank or an anaerobic filter bed in front of the contact aeration tank. Precipitation ionization tanks have a simple processing equipment structure and are easy to maintain, but the reaction rate of anaerobic microorganisms is slow, so it is necessary to have a long residence time. In addition to making connections and increasing the tank capacity, there are problems such as large fluctuations in flow and collapse will wash out anaerobic bacteria and significantly reduce purification ability. Therefore, the current structure only serves to separate solids from wastewater. On the other hand, the anaerobic bed method, which is filled with a filter bed, allows a large number of anaerobic bacteria to inhabit 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. Advantages of this method include (1) Since the biological treatment tank is filled with contact filter media, 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 capture 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 mesh and string bodies are suitable as aerobic one-bed filter media, anaerobic filter beds have the following problems because they do not require aeration and agitation by aeration.

■ Poor ability to trap bacteria (microorganisms).

■ The structure obstructs the flow of wastewater in the tank, resulting in poor agitation effect.

■ It is easy to get clogged with sludge.

■ Net-like materials require containers and frames to be filled, and string-like materials require frames to be stretched above and below, which requires time and effort in 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. Since the adhesion force was weak, there was a problem in that the capture efficiency was significantly reduced.

(c) Means for solving the problem and its effect This invention consists of stacking a large number of substantially vertical sheets of the same shape alternately by half a turn on a plane, and bonding the contacting parts to form a block. Each of the sheets is continuously bent in a horizontal section, each bent surface is inclined to one side with respect to the vertical as a whole, and each inclined bent surface has an abbreviated shape in the vertical section. For anaerobic sewage treatment, the recesses for temporarily trapping sludge are formed at intervals in the inclination direction, and the bottom surface of the recesses is inclined in the width direction, and is further provided with protrusions for resisting sludge flow in the depth direction. It is a filter medium.

That is, in this invention, each sheet has a specific ftj oblique bending surface connected to each other, and is alternately inverted and plied together, so that the sewage that descends from above at an angle is mixed in a crosswise manner. At the same time, the intersection causes a swirling flow as a whole, and furthermore, the mixed swirling flow is repeatedly divided 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.
This prevents the sludge (including anaerobic microorganisms) from falling in one direction, ensuring enough contact time between wastewater and anaerobic microorganisms.

Examples of 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 sheets of vinyl chloride resin, and other metal plates that are formed into irregularities. Can be used. First, when extrusion-molded seams 1- are vacuum formed, the wall thickness of the recesses for temporarily trapping sludge is reduced, so the buoyancy caused by general structural materials, methane, and carbon dioxide gas is reduced. 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 slope of the curved surface formed on this d-light sea is 50 to 70 degrees to the horizontal in order to moderate the capture and shedding of sludge.
About 60 degrees is even more desirable.

(d) Examples This invention will be described in detail below based on examples shown in the figures. Note that this invention is not limited to this.

First, in Figure 3, J'3 is a filter medium for anaerobic wastewater treatment (1
) is used immersed in the anaerobic filter bed (2) which is the pre-treatment tank of the wastewater treatment device (H), (3) is the wastewater inflow channel, and (4)
(5) is a gas vent pipe, and (5) is a sludge discharge path.

In addition, (6) is the contact aeration tank, (the sword is the contact tank between this tank and the anaerobic filter bed (2), (8) is its aerobic contact material, (9)
) is a diffuser pipe. 00) is the attached tank for final treatment, [1
1) is the excess sludge discharge path, and ('+21) is the treated water extraction path.

Therefore, the filter medium for anaerobic wastewater treatment (1) is particularly suitable for the first to second
In the figure, a number of identically shaped and vertical sheets O5) 0
6) Alternately rotate a7)....... on a plane by half a turn (1
80°), and the contact portions are glued to form a block shape.

The sheet (151 is a vacuum-formed vinyl chloride resin plate obtained by extrusion molding, and is continuously bent in the horizontal section, and each bent surface (181 (191...) is vertical as a whole. In addition, each of those curved surfaces (2)e, which are inclined to one side with respect to
... are formed at intervals in the inclination direction, and the bottom of the recess is inclined in the width direction (for example, about 30
Furthermore, a protruding strip 94) (c) for resisting sludge flow is formed that extends within the vertical surface portion approximately at right angles to the depth direction (that is, the downward inclination direction). Note that the sheet 1-(151) has exactly the same shape as the sheet 1-(151), so a description thereof will be omitted.

By the way, these sheets (151 ■ ribs...) are
When overlapping, use an appropriate adhesive (for example, sheet material dissolved in a solvent consisting of 70% by volume of tetrahydrofuran and 30% by volume of methyl ethyl ketone (MEK)) on the contact areas of adjacent sheets. It is firmly attached.

Thus, wastewater (e.g. industrial wastewater or sewerage) flowing into the anaerobic filter bed (2) flows through the adjacent sheets (15).
[Bending surface portion of 31] Due to the illusion..., the water is cross-mixed, and the water is divided by the contacting portion 88 and repeatedly descends. Also, adjacent sheets (1
5) Each curved surface (I8) [F] of 06) (
Since the two sides are facing each other, the wastewater becomes a swirling flow and descends.

Such swirling flow and cross-merging/diverging flow allow sufficient contact between anaerobic microorganisms and wastewater, prevent excessive adhesion of sludge to the sheet, and prevent retention of gases such as methane and carbon dioxide. It can be prevented. Incidentally, the ill distillation of gas is dangerous because it imparts a large buoyancy to the entire block-shaped filter medium for anaerobic wastewater treatment (1).

Furthermore, the wastewater falling through the filter medium (1) for anaerobic sewage treatment forms sludge (including anaerobic microorganisms) due to contact with anaerobic microorganisms, and the sludge gradually descends to form excess sludge. It is appropriately discharged from the discharge path (5). 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 a concave part (21) for temporarily trapping sludge, and also has convex stripes () (c) for resisting sludge flow formed on its inner surface. Therefore, the bottom of the recess and the convex strip (241) appropriately limit the fall of sludge in the wastewater, ensuring sufficient contact time between the anaerobic microorganisms in the sludge and the wastewater, and improving the efficiency of wastewater pretreatment. In short, the filter medium for anaerobic sewage treatment (1) easily attracts anaerobic microorganisms, and it alternately captures and sheds moderate amounts of excess sludge that has grown and easily falls off, allowing new anaerobic microorganisms to adhere. Fresh sludge is regenerated by repeating the process, and the treatment rate increases.

In addition, since the spaces between the sheets are connected without being separated (the spaces between the sheets are separated by curved ridges), it is easy for methane gas, carbon dioxide gas, etc. generated in the filter bed to escape, especially as mentioned above. The buoyancy force applied to the filter medium for anaerobic wastewater treatment can be reduced.

Unlike the above embodiments, a large number of small holes (for example, holes of 10 to 50 mmφ) may be distributed in each sheet constituting the filter medium for anaerobic wastewater treatment to make the distribution of wastewater more uniform. can. Furthermore, in order to secure a sufficient bonding area when stacking and bonding each sheet, for example, a flat circular part for bonding may be formed at the corresponding 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 will be given.

[Example of general dimension specifications]

(A) Bottom part of concave part for temporary sludge capture Depth: 5 to 15 mm, Width: 40 to b Vertical part Height: 15 to 45 mm, Width: 40 to 120 m
m (B) Convex strips for resisting sludge flow Height: 1 to 3 mm Width: 1 to 3 mm Number of strips: 2 to 5 [Experimental example] (△) Filter material for anaerobic sewage treatment - product of the present invention> Vertical, horizontal, Height: 500x 500x 500 (m
m) Constituent sheet: Vacuum-formed vinyl chloride resin extrusion molded plate (plate thickness approximately 0.5 mm), bent bidge:
200mm Pitch between constituent sheets (1 cycle of waves): 0mm Bending height, total height of waves): 80mm Bottom of recess for temporary sludge capture Depth: 10mm, width 80mm Vertical surface Height: 30mm, width 80mm Resistance to sludge flow Convex strip height: 2 Body width: 2 mm Number of strips = 2 (comparison quantity) Commercial product manufactured by Dainippon Plastic ■: Taleo Packing (registered trademark) PW80 Length, width, height + 500 x 500 x 480 (m
m) Pinch between two constituent sheets same as the present invention: 80mm Bending and touching (wave cycle): 125mm bending height, total height of waves): 50mm Ensure pitch between sheets and bond both sheets together It forms a flat boss and a flat receiver for receiving the boss.

(B) Anaerobic bacteria Anaerobic bacteria with MLssm degree of approximately 20,000 - obtained from sewage (water temperature 24°C) (C) Experimental equipment water tank Length/width/height 1 x IX 2 (m) Height approx. 5
A filter medium for anaerobic sewage treatment was placed on a 00 mm stand with a water level of 1.3 m (D) Experimental method Anaerobic bacteria were gradually introduced into the water tank using a vacuum car (approx. 1.3 m'). This sample 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 sapwood was measured, and the amount of bacteria held on the filter medium per m3 was changed.

(E) Test results Aerobic treatment, typified by methane fermentation, is a treatment method that utilizes the growth and metabolic activity of anaerobic microorganisms, and the treatment effect is correspondingly greater as the amount of bacterial cells retained is greater. The results show that the filter medium of the invention had about 10 times the amount of bacterial cells retained as compared to 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 one 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 configuration showing an example of a wastewater treatment device incorporating the same. It is an explanatory diagram. (1)・・・Wire rod for anaerobic sewage treatment, fly)
06) (171... Sheet, (1810'3
...Bending surface, N (2++...Concavity for temporary sludge trapping, 241 Solid...Convex strip 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 portions are adhered to form a block shape, and each sheet has the following features: The horizontal cross section is continuously bent, and each of the curved surfaces is inclined to one side with respect to the vertical direction, and a recess for temporarily trapping sludge having an approximately L-shaped vertical section is formed in each of the inclined curved 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.