JP2007175686A - Anaerobic sprinkling filtration method and apparatus for organic waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new anaerobic sprinkling filtration method and apparatus which enable an anaerobic biological treatment of raw water with a thin concentration of an organic matter without heating to perform of raw water purification and methane gas generation. <P>SOLUTION: Plane members each made of synthetic fiber with a mesh pore size of 5-30 mm, in which water absorbing yarn with sludge is arranged along a three-dimensional network core material fill a treatment tank having an oxygen free atmosphere. A raw water sprinkling part is installed in the upper part of the tank, and raw water is made to flow down in a form of a liquid film along the inside of each plane member to be subjected methane fermentation. Subsequently treated water is discharged from the bottom of the treatment tank. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an anaerobic biological treatment apparatus for organic wastewater, and is effective even for raw water (BOD of about 500 to 1000 mg / l), which has been conventionally regarded as unsuitable when subjected to methane fermentation treatment, with relatively little BOD. The present invention relates to a novel methane fermentation treatment technology capable of removing BOD and generating methane gas efficiently and energy-saving.

Conventionally, the UASB method is a typical technology in the technology of methane fermentation as an anaerobic biological treatment technology. (Patent Literature 1: Patent Publication No. 11-207384: Anaerobic treatment method and apparatus)
The UASB method has a feature that the concentration of methane bacteria in the reactor can be maintained at a high concentration by granulating the methane bacteria into a granular form, and as a result, organic matter in waste water can be efficiently treated. For example, the UASB apparatus has a feature that the COD _Cr volumetric load can be efficiently operated even under an extremely large load condition of 10 to 15 (kg / m ³ .d).

However, when raw water with a low BOD (1000 mg / l or less) is applied to the UASB method, it is difficult to form and maintain methane bacteria granules, and bulking troubles easily occur during sludge acclimatization. Moreover, granule formation becomes difficult also when raw | natural water SS is high. Further, when the raw water flow rate is small, there is a disadvantage that a circulating pump is required to circulate the treated water to the raw water side to increase the upward water flow in order to fluidize the granules with the upward water flow.

Furthermore, in the case of the UASB method, when the organic load becomes high (for example, a COD volumetric load of 10 kg / m ³ .d or more), the amount of gas generated increases, but at this time, if degassing from the reactor is not performed reliably, There was also a problem that granulated sludge flowed out frequently due to blowout during gas discharge, and it was difficult to keep the granular sludge in the reactor.

On the other hand, the “submerged filter bed type methane fermentation method”, in which raw water is supplied in an upward flow to a tower packed with methane bacteria adhesion members such as Raschig rings and plastic plates without using methane bacteria granules, is also well known. is there. (Non-patent document 2: edited by Ryuichi Sudo, Biology pp176-177 for water quality conservation, published by Industrial Water Research Council, November 3, 2004)
However, this method was also not practical when the raw water BOD was dilute (approximately 1000 mg / l or less), because the methane fermentation reaction was slow.

Examples of anaerobic bacteria in organic wastewater include mesophilic anaerobic bacteria whose optimum temperature is in the medium temperature range of 30 to 35 ° C., and high temperature anaerobic bacteria whose optimum temperature is in the high temperature range of 50 to 55 ° C. However, both the UASB and the submerged filter bed method needed to heat the temperature in the tank to about 35 ° C where mesophilic methane bacteria are active, so if the raw water BOD is dilute, the heating energy can be covered by the recovered methane gas. There was also the difficulty of not.

The present invention is a technique for solving the above-mentioned problems of the prior art, and improves the conventional anaerobic treatment technique, which was unsuitable for relatively low concentration raw water of BOD, and has a BOD of 1000 mg / l or less. However, it is an object to provide a new technology capable of effectively performing methane fermentation without heating.

Means to solve the problem

In methane fermentation treatment, the amount of excess sludge generated is significantly smaller than that in aerobic treatment, but this fact means that it takes time to grow methane bacteria in large quantities. When installing a biological treatment device, it is important to ensure a sufficient amount of methane bacteria in the tank.
The present invention has devised the trickling filter method that has been applied to conventional aerobic biological treatment so that it can be effectively applied to anaerobic biological treatment, and has realized an important point of mass retention of methane bacteria.

A conventional aerobic trickling filter device is a method in which granular filter media such as Raschig rings are deposited in layers in a tank where air can circulate, and microorganisms are attached to the tank. It is a structure to take out. However, when the filter medium mass is deposited in a layered manner in this way, the space between the filter media is clogged by the grown microorganisms, and the permeation of sewage is significantly deteriorated. In addition, drift (raw water short circuit) occurs. Further, when a sponge filter medium is deposited as a filter medium, since the sponge is soft, the sponge is crushed by weight, and there is a drawback that a clogging portion is generated and a drift occurs.

The present invention is a novel anaerobic trickling filter apparatus that can sufficiently bring the entire filler into contact with raw water and enhance the decomposition treatment ability of polluted components.
When applying the water trickling filter method to the methane fermentation technology, the present inventor uses a filler having a network (three-dimensional network) structure whose strength is increased by a core material, and adheres to water-absorbing sludge in which methane-fermenting bacteria are adhered and immobilized. It has been found that it is important that the gap where the yarn is deployed is not crushed and the gap size is 3 mm or more. On the other hand, the sponge pore size is small (pore size is about 0.05 to 2 mm, and it is difficult to make it larger than this in terms of sponge manufacturing technology), as is the case with conventional sponge filter media such as polyurethane foam, SS and Anaerobic treatment cannot be effectively performed because pores are blocked by biofilm growth.

That is, the present invention fills a synthetic fiber knitted surface member having a mesh hole size of 5 to 30 mm with a water-absorbing sludge adhering yarn along a three-dimensional mesh core material in an oxygen-free atmosphere tank. An anaerobic water filter, characterized in that a raw water sprinkling section is provided at the top of the tank, and after the methane fermentation treatment is performed by flowing down the liquid inside the member, the treated water is discharged from the bottom of the processing tank. This is a treatment method, and “a synthetic fiber woven surface member having a water-absorbing sludge-attached yarn along a three-dimensional mesh-like core material and having a mesh hole size of 5 to 30 mm” in an oxygen-free tank. And a raw water sprinkling part is provided at the top of the tank so that the inside of the member flows down in the form of a liquid film, a treated water effluent surface is provided at the bottom of the processing tank, and a generated methane-containing gas discharge part is provided in the tank. It is the anaerobic watering filter apparatus characterized by having provided.

As far as the present inventor is aware, there seems to be no research example in which the watering filter method is applied to anaerobic treatment such as methane fermentation treatment. The reason for this is the “watering filter method, which is the most attractive in that aerobic biological treatment is possible without aeration by installing an aeration blower”, in principle anaerobic biological treatment that does not require aeration operation. It seems that it was because it was thought that there was no particular merit even if it was applied to.

As a result of pursuing how the water spray filter method can be effectively applied to the methane fermentation treatment, the present inventor has overcome such a fixed idea, and as a result, has adhered to anaerobic microorganisms. By optimizing the structure, hometown, and void size of the adhering material, the disadvantages of the conventional methane fermentation treatment technology as described above were solved.

The invention's effect

(1) Since the material of the present invention has a very large void size, the void portion is not blocked by the raw water SS and the biofilm growth. The sludge adsorbing yarn (BXY) has a water absorption of 5 times its own weight, has extremely good hydrophilicity and good sludge adhesion. Therefore, even with a small amount of running water, it is uniformly wet and the sludge stripping part and sludge drying part cannot be made.
Therefore, a high methane concentration, long-time SRT, and good contact effect between anaerobic organisms and raw water can be ensured, so that the methane fermentation reaction can be effectively applied even to raw water with a low BOD. Moreover, since an aeration operation like the activated sludge method is not required, the organic waste water can be purified in an extremely energy saving manner.
Moreover, even if raw water SS is high concentration, a methane fermentation process is possible, without installing SS removal process in the front | former stage. In addition, since there is no blockage of SS and / or microorganisms in the void, there is no short path (short circuit flow) of the raw water, and the set HRT (hydraulic residence time) can be secured, so that good treated water quality can be obtained stably. It is done.
(2) Since the amount of methane bacteria retained can be increased, even with raw water having a water temperature of less than 30 ° C. (about 15 to 25 ° C.), the decrease in reaction rate due to a decrease in water temperature can be offset. Therefore, methane fermentation can be performed without heating raw water, no heating energy is required, and no heating equipment is required. Therefore, combined with the aeration unnecessary effect, the organic waste water can be purified in a very energy-saving manner.
(3) Since the amount of excess sludge generated is very small, sludge treatment and disposal is very easy.
(4) Unlike UASB, there is no need to grow and grow methane bacteria granules, and naturally there is no need to fluidize the granules, so a treated water circulation pump is unnecessary.
(5) Compared with the anaerobic treatment method in which the filter bed is submerged in the tank, water pressure is not applied to the tank wall, so the construction cost of the outer wall structure of the filter bed is low.

An embodiment of the present invention will be described with reference to FIG.
In the anaerobic tank 1 that blocks air from entering, there are a large number of “three-dimensional mesh structure members made of water-absorbing synthetic fibers and having a gap size of 5 to 30 mm” 2, pipe frames used for scaffolding etc. at the building construction site, etc. A plurality of three-dimensional mesh structure member surfaces (one thickness of about 20 mm) are overlapped on the mold, and the mold is fixed so that the mesh surface is in the height direction of the anaerobic tank 1. Since the mesh-structured filler is made to function as an anaerobic trickling filter bed, the filler is naturally not in a submerged state but positioned in the gas phase in the anaerobic tank 1.

According to the present invention, “a three-dimensional network member made of a water-absorbing synthetic fiber and having a gap size of 5 to 30 mm” is very suitable as a bioadhesive material disclosed in (Patent Document: JP-A-2002-136986). (Trade name: biofix; symbol BX: product of NIT Co., Ltd.).

This contact material has a three-dimensional net-like core material 1 as shown in FIG. 2-1 and this enlarged view 2-2, and anaerobic microorganisms (acid fermentation) along the net-like core material 1. Bacteria, methane bacteria, sulfate-reducing bacteria) 2 sludge adhesion yarns are arranged. The sludge-attached yarn 2 is formed of “water-absorbing” yarn with good adhesion of microbial sludge such as acrylic high bulk fiber. The monofilament 3 constituting the core material 1 is formed to be thicker than the monofilament 3 and can occupy a three-dimensional space formed by the core material 1 at a predetermined volume ratio.

The core material 1 is composed of, for example, a strong monofilament 3 made of synthetic resin. As shown in FIG. 3, the monofilament 3 is composed of a continuous yarn in which a plurality of Ω-shaped portions and inverted Ω-shaped portions are alternately arranged in an uneven shape. In the core material 1, a plurality of monofilaments 3, 3,... Are arranged in parallel, and Ω-shaped portions of adjacent monofilaments 3, 3, that is, convex portions or inverted Ω-shaped portions, that is, concave portions. Are connected to each other by the connecting thread 4 to form a three-dimensional net as described above. For this reason, it can expand and contract in the direction of the arrow.

The “mesh hole size” referred to in the present invention means the gap length between adjacent connecting yarns 4 in FIG. In order to change the mesh hole size, the mesh structure member may be expanded and contracted in the direction of the arrow in FIG.
One of the gist of the present invention is that the mesh size is set to a large pore size of 5 mm or more. As a result, there is an important effect that the blockage by the raw water SS and the blockage of the void due to anaerobic microorganism growth do not occur. (As described above, in the technique using a sponge as a filler, since the gap size of the sponge is small, clogging with SS or microorganisms is unavoidable.) When the mesh size is set to 30 mm or more, the adhesion area of anaerobic bacteria is increased. Since it decreases considerably, it is not preferable.

Next, the “water absorption” of the filler fiber, which is the second point of the present invention, is defined as the property that moisture is absorbed between the fibers.
That is, even if the fiber itself is not hygroscopic, if the gap is appropriate when the surface is wet, water penetrates into the gap of the entire fiber by capillary action. For example, acrylic fiber is mainly composed of acrylonitrile, and the fiber itself has a low hygroscopic property. However, when a large number of acrylic fiber yarns are twisted into a high bulk shape, a capillary structure is formed and has a large water absorption. This phenomenon is water absorption. Water absorption is greatly influenced by the aggregate state of the fibers. The amount of water absorption is greatly influenced not only by the type of fiber but also by the twist of the yarn, the structure of the fabric, and the finishing process, and the water absorption is often evaluated by the water absorption rate in addition to the water absorption amount.
The water absorption rate greatly depends on the interfacial chemical wetting resistance of the fiber itself and the porosity (porosity) of the fiber assembly. Polyester, polypropylene, wool products, etc., which are difficult to wet the fibers themselves, do not change the water absorption amount even if the porosity is changed, but other fiber products such as acrylic fibers have the maximum water absorption amount of 75% or 85%.

The filler of the present invention having such a configuration / structure is a configuration in which “water-absorbing anaerobic microbial sludge adhering yarn 2” is arranged along the three-dimensional mesh-like core material 1, and has a thickness. A knitted fabric structure is formed, and “water-absorbing anaerobic sludge adhering yarn 2” occupies a predetermined volume ratio in a three-dimensional space based on the predetermined thickness.

The filling method of the water-absorbing filler having a large gap size used in the present invention and having the structure of the nate workpiece has a large number of sheets so that the mesh surface of FIG. 2-1 is in the height direction of the anaerobic tank 1. A method of filling adjacently is preferable. Although the method of filling the mesh surface so as to be in the horizontal direction of the anaerobic tank 1 is possible, it is more practical to install the BX surface in the vertical direction because there is a restriction on the expansion and contraction direction of the BX. .

Organic waste water (raw water) 3 is fed into the upper part of the filler 2 and sprinkled from a water sprinkling member 6 such as a perforated tube to flow down in the space of the filler in which a large amount of anaerobic microorganisms are retained. The raw water sprayed from the top (liquid to be treated) spreads evenly in the individual voids of the network structure without short-circuiting, slowly flowing down, and evenly contacting the methane-fermenting bacteria adhering to the sludge-attached yarn, making it anaerobic Biological reaction proceeds. Since it is a sealed type, bad odors do not leak to the outside, odor control is easy, and there is no problem with filter bed.
The water sprinkling member 6 is disposed horizontally in the upper part of the tank 1, is fixed to a rotating shaft that penetrates through the central portion thereof, and is configured to be rotatable. A sprinkler may be used for watering the raw water. There is a water surface 4 at the lower part of the anaerobic tank 1, and the treated water 5 flows out. 7 is an anaerobic gas (mixed gas of methane gas, carbon dioxide gas, hydrogen sulfide, etc.) generated from raw water by methane fermentation treatment.

When the water-absorbing filler of the present invention is used for an anaerobic trickling filter bed, the raw water does not flow down at a stretch through the void portion of the three-dimensionally arranged “methane fermentation bacteria sludge adhering yarn 2”. It travels along the methane-fermenting fungus sludge adhering yarn 2 ”and drops in the form of a liquid film, and then slowly flows down. As a result, the contact probability and contact time of BOD to the raw water and the methane-fermenting bacteria sludge adhering yarn 2 can be increased, and the methane fermentation reaction proceeds smoothly.
If fibers with low water absorption (for example, vinylidene chloride) are used for the sludge-attached yarn 2, adhesion of anaerobic microorganisms such as methane bacteria hardly occurs, and the amount of methane bacteria retained becomes poor. In addition, the sprinkled raw water is difficult to get wet with the filler and does not flow slowly but falls to the bottom of the tank in a short time, so the contact time with methane bacteria is insufficient, and the methane production reaction does not proceed sufficiently Causes a fatal problem.

As a result, the BOD component in the raw water is subjected to a highly anaerobic treatment and flows out as treated water 5 with less BOD. For example, when the flow rate of the filter bed is increased to remove excess sludge, a part of the treated water 5 may be circulated to the water spray part of the anaerobic water filter bed.
In addition, what is necessary is just to perform aerobic biological treatments, such as an aerobic trickling filter treatment, an aerobic biofilm treatment, and activated sludge treatment, when removing BOD highly. Further, when the treated water 5 is not subjected to an aerobic treatment, when the SS in the treated water 5 is large, it may be discharged after removing the SS in the sedimentation tank.

The effect of the present invention was verified using a small test apparatus having the structure shown in FIG.

1. Test equipment specifications

Comparative example

In order to compare the performance of the filter medium filled in the apparatus shown in FIG. 1, instead of the biofix shown in Table 1, a 13-diameter granular polyurethane foam sponge (cube with a side of 30 mm, sponge pore size of 0.8 mm) was used. A sprinkling filter device filled with liters was installed and a parallel test was conducted. Polyurethane foam is hydrophobic and difficult to wet with water.

2. Raw water quality <br/> Water temperature: 20C
CODCr: 500 mg / l
Raw water composition: sucrose, sodium acetate, propionic acid, yeast extract, trace inorganic salts (acid potassium, calcium chloride, magnesium chloride, iron chloride, manganese sulfate)

3. Process and results Before start of operation, 10L of anaerobic digested sludge was collected from the anaerobic digestion facility of sewage sludge and supplied from the upper part of the test apparatus with a monopump at a flow rate of 1L / hr for 10 hours. Then, it was planted in the water-absorbing fiber part of the filler. Then, the air in a tank was substituted with nitrogen gas, the raw water of Table 2 was sprinkled from the tank upper part, and experiment was started.
The HRT (abbreviated symbol for hydraulic residence time, the value obtained by dividing the apparent volume of the packed portion by the raw water flow rate (L / hr), the unit is hr) was set as follows depending on the number of operating days.
That is, from the operation start date to 60 days, 24 hours, 61 days to 90 days were HRT 12 hours, 91 days to 120 days were 6 hours, and 121 days to 150 days were 3 hours.
The COD load per filter bed volume is 4 (kg / m ³ · d) for HRT 3 hours and 1 (kg / m ³ · d) for HRT 12 hours.

Water quality analysis was started 30 days after the start of operation.
The treated water was sampled once a week, CODcr was measured, and the COD removal rate was determined.
In addition, the amount of produced gas and the methane gas concentration were analyzed once a week, and the methane recovery rate based on the raw water CODcr was calculated. Methane recovery rate = defined as methane generation / theoretical methane generation. (Theoretically, 0.35 liters of methane gas can be obtained from 1 g of removed CODcr.)

しかも、ＨＲＴが３時間というきわめてＣＯＤ負荷（４Ｋｇ／ｍ^３・ｄ）の条件においても、ＣＯＤ除去率は約６０％が得られた。このことは、本発明生物保持材のメタン菌の保持量が非常に大きいことを意味している。実際に試験終了後に、生物保持材を取り出して、保持されていた汚泥量を測定した結果、３８ｇ／Ｌ保持材という高濃度であった。The results are shown in Table 1. The results in parentheses are the results when the comparative granular sponge is used. From the results shown in Table 1, COD removal by the anaerobic trickling filter of the present invention is performed at a water temperature of 20 ° C. and COD of 500 mg / l, even though the raw water has a remarkably low water temperature and low concentration compared to the ordinary methane fermentation method. The effect was very good.

Moreover, the COD removal rate of about 60% was obtained even under extremely COD load conditions (4 kg / m ³ · d) of HRT of 3 hours. This means that the amount of methane bacterium retained in the biological support material of the present invention is very large. After the test was actually completed, the biological retaining material was taken out and the amount of retained sludge was measured. As a result, the concentration was as high as 38 g / L retaining material.

The granular sponge of the comparative example was significantly inferior in the treated water COD removal rate compared to the present invention in the present invention, the raw water, and the HRT. This is because the pores of the sponge are as small as 0.8 mm and the sponge pores are blocked by anaerobic biological sludge, and only the organisms attached to the sponge surface are used for purification of raw water and are hydrophobic. It was. Further, after 90 days from the start of operation, the sponge packed layer was partially clogged to form “Mimizumi”, and a short circuit of raw water occurred. This was also the cause of the deterioration of the COD removal rate.

Main structure of the apparatus of the present invention Fig. 2-1 Example of filler of the present invention Fig. 2-2 Enlarged view of Fig. 2-1 Detail detail of filler

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core material 2 Sludge adhesion thread 3 Monofilament 4 Connecting thread 5 Open part 6 Anaerobic water spray filter device 7 Three-dimensional mesh structure filler 8 Raw water 9 Treated water surface 10 Treated water 11 Raw water sprinkling dispersion plate 12 Contains methane Gas outlet 13 Water seal

Claims (1)

1. Filled with a “synthetic fiber planar member having a mesh hole size of 5 to 30 mm by arranging a water-absorbing sludge adhering yarn along a three-dimensional mesh-like core material” in an oxygen-free atmosphere tank, An anaerobic sprinkling filter treatment method characterized by providing a raw water sprinkling section, allowing a methane fermentation treatment to flow down in the form of a liquid film inside the member, and then allowing the treated water to flow out from the bottom of the treatment tank.
2. Filled with a “synthetic fiber planar member having a mesh hole size of 5 to 30 mm by arranging a water-absorbing sludge-attached yarn along a three-dimensional mesh-like core material” in an oxygen-free atmosphere tank, A raw water sprinkling part is provided to flow down in a liquid film form inside the member, a treated water outflow surface is provided at the bottom of the treatment tank, and a generated methane-containing gas discharge part is provided in the tank. Anaerobic sprinkling filter equipment.

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