JP2005349327A - Method for treating waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a microbe such as white rot fungi function effectively when a persistent substance is treated by using the microbe such as white rot fungi or molds. <P>SOLUTION: This system for treating waste water comprises the steps of: adjusting each of the nitrogen concentration and carbon concentration of waste water 14 beforehand within a preset range in a pretreatment tank 12; subjecting the waste water 14 having the adjusted nitrogen concentration and carbon concentration to membrane treatment using a filtration membrane 15 so that a solid component of the waste water 14 is removed by the filtration membrane 15 and the waste water 30 permeated through the filtration membrane 15 is supplied to a microbe-used treatment tank 26; and treating the waste water 30 with the microbe such as white rot fungi or molds in the microbe-used treatment tank 26. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for treating wastewater such as industrial wastewater, sewage and human waste. More specifically, the present invention relates to a method for decomposing hardly decomposable substances (for example, exogenous endocrine disrupting substances such as dioxins, environmental hormones, coloring causative substances, agricultural chemicals, etc.) contained in wastewater using white rot fungi.
In the present specification, the term “white rot fungus” means a microorganism having a strong oxidative degradation action, and not only a white rot fungus in the original sense but also other oxidative degradation action equivalent to that of a white rot fungus. Used to include filamentous fungi.

Microorganisms such as white-rot fungi release enzymes having a strong oxidizing action (for example, lignin peroxidase, manganese peroxidase, laccase, etc.). For this reason, a technique for oxidizing and decomposing hardly degradable substances such as dioxins and environmental hormones using these microorganisms has been studied (for example, Patent Document 1).
In the technique described in Patent Document 1, a carrier on which a microorganism strain such as white rot fungus is fixed is disposed in a microorganism treatment tank (bioreactor). Wastewater is supplied to the microorganism treatment tank, and the hardly decomposable substance in the wastewater is decomposed into carbon dioxide gas and an easily decomposable substance (low molecular compound) by the microorganisms. The treated water discharged from the microorganism treatment tank is supplied to the membrane filtration device. Among the substances separated by the membrane filtration device, the polymer component and the solid component are returned to the microorganism treatment tank. On the other hand, the treated water which permeate | transmitted the membrane filtration apparatus is supplied to an easily decomposable substance processing tank (for example, activated sludge tank, biofilm processing tank). In the easily decomposable substance treatment tank, the easily decomposable substance contained in the treated water is decomposed.
JP2003-126883A

  However, whether or not microorganisms such as white rot bacteria function well depends greatly on the environment in which these microorganisms are placed (the environment of the microorganism treatment tank). That is, depending on the environment of the microbial treatment tank, almost no effective enzyme is released from white rot fungi and the like, and thus hardly decomposable substances in the waste water can be decomposed. The above-mentioned prior art is a technique (so-called post-treatment technique) for further treating the treated water treated with white rot fungi, and is the most important before the microorganisms such as white rot fungi function effectively. There has been no study on treatment, and development of a pretreatment technique for effectively functioning white rot fungi is desired.

  The present invention has been made in view of such circumstances, and its purpose is to effectively function microorganisms such as white rot fungi when treating hardly decomposable substances using microorganisms such as white rot fungi. It is to provide a pre-processing technique for making it happen.

In order for the present inventors to effectively function microorganisms such as white rot fungi, it is important to control the nitrogen concentration and carbon concentration of the wastewater, and to make a substantially aseptic state in which no other microorganisms exist. And the present invention has been reached. That is, the treatment method of the present invention includes a pretreatment step of adjusting the nitrogen concentration and carbon concentration in wastewater within a preset concentration range, and wastewater whose nitrogen concentration and carbon concentration are adjusted by the pretreatment step is membrane filtered. A membrane filtration step, and a microbial treatment step of treating waste water that has passed through the membrane in the membrane filtration step with white rot fungi.
In this treatment method, the nitrogen concentration and carbon concentration in the wastewater are adjusted by pretreatment, and separated into solids and permeate by membrane filtration. Therefore, since the microorganisms contained in the wastewater are removed by the filtration membrane, the permeated water that has permeated the filtration membrane becomes substantially aseptic. For this reason, the nitrogen concentration and the carbon concentration are adjusted, and the waste water that has become substantially aseptic is treated with microorganisms such as white rot fungi. According to this treatment method, the nitrogen and carbon concentrations are adjusted, and the wastewater that has become substantially aseptic is treated with microorganisms such as white rot fungi. The hard-to-decompose substance is effectively decomposed.

In the pretreatment step, the treatment is preferably performed so that the nitrogen concentration in the wastewater is low, and further, the treatment is preferably performed so that the carbon concentration in the wastewater is an appropriate concentration. By adjusting the carbon concentration and nitrogen concentration in the wastewater to appropriate concentrations, the white rot fungus functions more effectively, and the degradation rate of the hardly decomposable substance in the wastewater can be improved.
The pretreatment step can be performed by various methods that can control the carbon concentration and the nitrogen concentration and can be combined with the membrane treatment. For example, the pretreatment step is preferably performed by an activated sludge method. Pretreatment of the wastewater by the activated sludge method causes the solids in the wastewater to aggregate, so that it is easy to collect the solids (microorganisms) in the wastewater by subsequent membrane filtration.

  Moreover, it is preferable that the hole diameter of the filtration membrane used at a membrane filtration process is the range of 1-20 micrometers. If the pore diameter exceeds 100 μm, microorganisms in the wastewater cannot be removed well, and if it is less than 1 μm, the frequency of clogging of the filtration membrane increases.

  A wastewater treatment system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a wastewater treatment system according to the present embodiment. As shown in FIG. 1, the wastewater treatment system according to this embodiment includes a pretreatment tank 12 for pretreating wastewater, and a microorganism treatment tank 26 for microbially treating the wastewater treated in the pretreatment tank 12.

  Waste water 10 is supplied to the pretreatment tank 12. The waste water 10 is waste water such as industrial waste water, sewage and human waste, and the waste water 10 contains a hardly decomposable substance. Examples of the hardly decomposable substances contained in the waste water 10 include dioxins and environmental hormones. Dioxins are a general term for polychlorinated dibenzopararadixin, polychlorinated dibenzofuran, and the like, and are treated as concepts including coplanar PCBs that exhibit the same toxicity as these substances. PCB is polychlorinated biphenyl, and coplanar PCB means PCB having a flat structure. The environmental hormone means an exogenous substance that affects the normal hormonal action in the living body when taken into the living body of the animal. For example, dioxins, PCBs, polybrominated biphenyls (PBB), hexachlorobenzene (HCB), pentachlorophenol (PCP), amitrol and the like are said to be environmental hormones.

Further, the waste water 10 supplied to the pretreatment tank 12 can be colored waste water. Despite the fact that colored wastewater can be easily detected and subject to complaints as well as bad odors, no effective countermeasure technology has been developed. The present wastewater treatment system can effectively decompose a colored component (hardly decomposable substance) contained in the wastewater to make it colorless.
Examples of colored wastewater include human waste secondary treatment water, dyeing industrial wastewater, molasses wastewater, and heat treatment separation liquid. Secondary treatment water for human waste is waste water that has been treated at a human waste treatment plant. Dyeing industrial wastewater is used in offices where synthetic dyes are used (for example, textiles, paper, stationery, cosmetics, foods, liquid crystals, color filter pigments, etc. Wastewater discharged from the manufacturing plant). Molasses wastewater is black-brown wastewater after sugar content is separated from molasses, which is a secondary product produced in sugar mills, and the heat treatment separation liquid is brown dewatering that occurs during the dewatering process of excess sludge generated at sewage treatment plants. It is a liquid.

  In the pretreatment tank 12, a process of adjusting the nitrogen concentration and the carbon concentration of the supplied waste water 10 within a preset concentration range is performed. That is, the nitrogen component and the carbon component contained in the waste water 10 are removed, the nitrogen concentration is low, and the carbon concentration is set to an appropriate value. The nitrogen concentration is preferably adjusted to 200 mg / l or less, and the carbon concentration is preferably adjusted within the range of 500 to 2000 mg / l. This is because when the nitrogen concentration is higher than this value, the degradation performance of white rot fungi is significantly reduced. Moreover, when the carbon concentration is higher than this range, the quality of the treated water is deteriorated, and when the carbon concentration is lower than this range, the degradation performance of the white rot fungus is lowered.

  For the treatment of the pretreatment tank 12, an activated sludge method, an immobilized microorganism method, a biofilm treatment method, or the like can be used. When the activated sludge method is adopted, the solid components in the wastewater 10 are aggregated, and the solid components are easily removed by subsequent membrane treatment, which is preferable. In addition, when the activated sludge method is employed, easily decomposable organic substances in the wastewater 10 can be decomposed and removed. In addition, when employ | adopting a biofilm processing method, various methods, such as a trickling filter method, a contact aeration method, and a rotating disc method, can be used.

When the activated sludge method is adopted as the treatment of the pretreatment tank 12, it is preferable to arrange the aeration apparatus 20 near the bottom surface of the pretreatment tank 12. The aeration apparatus 20 is connected to the blower 16 through the air supply pipe 18a. When the blower 16 is activated, micro air bubbles are sent from the aeration device 20 to the waste water 14 in the pretreatment tank 12. Thereby, oxygen is supplied to the activated sludge (microorganisms) in the pretreatment tank 12 and activated, and the waste water 14 can be stirred. Since the amount of oxygen in the wastewater 14 plays an important role in activating activated sludge (microorganisms), a dissolved oxygen meter (DO meter) that measures the amount of dissolved oxygen in the wastewater 14 (the amount of oxygen dissolved in the wastewater 14) is used. It may be equipped and the aeration apparatus 20 may be controlled based on the measured value of the dissolved oxygen meter. Moreover, you may make it produce the anaerobic state intentionally by performing the operation | movement by the aeration apparatus 20 intermittently, and may make it reduce the nitrogen in the wastewater 14 (denitrification effect).
In addition, as an operation method of the activated sludge method, any one of a batch activated sludge method and a continuous activated sludge method can be used. Further, a flocculant (for example, polyacrylamide, PAC (polyaluminum chloride), etc.) may be introduced into the pretreatment tank 12 to agglomerate solid components contained in the waste water 14.

  The wastewater 14 whose nitrogen concentration and carbon concentration are adjusted by the pretreatment described above is subjected to membrane separation treatment by the filtration membrane 15. That is, the filtration membrane 15 is disposed in the pretreatment tank 12, and the waste water 14 in the pretreatment tank 12 is sucked into the filtration membrane 15. Solid components (including microorganisms and the like) in the waste water 14 cannot pass through the filtration membrane 15, and the solid components are removed by the filtration membrane 15. On the other hand, the waste water 30 that has passed through the filtration membrane 15 is supplied to the microorganism treatment tank 26. Therefore, the waste water 30 supplied to the microorganism treatment tank 26 is in a substantially aseptic state in which solid substances such as microorganisms are removed by the filtration membrane 15. In particular, when the activated sludge method is used for the pretreatment, the microorganisms in the wastewater 14 are aggregated and increased in diameter, and therefore can be easily removed by the filtration membrane 15.

  The shape and material of the filtration membrane 15 can be appropriately determined according to the water quality of the waste water 14. Therefore, any shape such as a flat membrane, a spiral type, and a hollow fiber shape can be adopted as the filtration membrane 15. Moreover, it is preferable to make the hole diameter of the filtration membrane 15 into the range of 1-20 micrometers. This is because if the pore size of the filtration membrane 15 exceeds 100 μm, microorganisms in the waste water 14 are not sufficiently removed, and if the pore size is less than 1 μm, clogging of the membrane frequently occurs. As the filtration membrane 15, for example, a microfiltration membrane (such as a porous hollow filtration membrane) can be suitably used. In the above-described embodiment, the filtration membrane 15 is immersed in the pretreatment tank 12, but the filtration membrane (membrane filtration device) can also be installed outside the pretreatment tank 12.

  In the microorganism treatment tank 26 to which the waste water 30 that has passed through the filtration membrane 15 is supplied, a hardly decomposable substance-degrading bacterium such as a white rot fungus is arranged in a floating state or fixed to a carrier. For example, a hardly decomposable substance-degrading bacterium may be fixed on a fine carrier (textile, etc.) and the carrier may be suspended in the waste water 28, or a carrier on which the hardly degradable substance degrading bacterium is fixed may be a microorganism. You may arrange | position in the processing tank 26 so that a movement is impossible.

Here, white rot fungi generally belong to basidiomycetes and are basidiomycetes having the ability to strongly decompose lignin among basidiomycetes that decay wood. Examples include the genus Trametes and the genus Phanerochaete. Enzymes released by these white rot fungi include manganese peroxidase, lignin peroxidase, laccase and the like. Manganese peroxidase and lignin peroxidase are oxidized by hydrogen peroxide to become active, and oxidize and decompose dioxins, environmental hormones, chromatic components, and other indegradable substances. Laccase is an enzyme that oxidizes phenolic hydroxyl groups, and oxidizes, for example, hydroquinone, polyphenol, p-phenylenediamine, ascorbic acid, dianine dye and the like. By this oxidation action, benzenes can be cleaved and decomposed. Therefore, it exerts a remarkable decomposition effect on dioxins composed of benzene rings.
There are fungi other than white rot fungi that have similar properties. Among them, Penicillium and Cladosporium filamentous fungi strongly decompose difficult-to-decompose substances such as chromaticity components. Can be used in the present processing system.

Further, since the white rot fungus is an aerobic bacterium, it is preferable that the aeration apparatus 24 is disposed in the vicinity of the bottom surface of the microorganism treatment tank 26. The aeration device 24 can be connected to the blower 16 via the filter 22 and the air supply pipe 18b. When the blower 16 is operated, the air sent from the blower 16 is blown into the microorganism treatment tank 26 as micro air bubbles from the aeration device 24. As a result, oxygen is supplied to the aerobic hardly decomposable substance-degrading bacteria and activated, and the hardly decomposable substance contained in the waste water 28 is decomposed. Since dust and the like are removed from the air supplied from the aeration device 24 by the filter 22, the waste water 28 in the microorganism treatment tank 26 is not contaminated by this air.
In order to activate the hardly decomposable substance-degrading bacteria, it is preferable to maintain the dissolved oxygen concentration of the waste water 28 in the microorganism treatment tank 26 at 0.5 mg / l or more. Moreover, the water temperature of the waste water 28 in the microorganism treatment tank 26 is maintained at 15 to 30 ° C, preferably 25 to 30 ° C. At this temperature, the activity of the microorganism is increased, and the degradation efficiency can be increased by effectively producing a degrading enzyme.

  Moreover, you may make it throw into the waste water 28 in the microorganism treatment tank 26 the organic substance used as the nutrient source of a hardly degradable substance decomposing | disassembling bacteria as needed. As the organic substance to be added, it is desirable to add a predetermined amount of sugars such as glucose, sucrose, and fructose, alcohols, and organic acids. Furthermore, in order to prevent the propagation of other germs, a pH adjuster that sets the wastewater 28 to be acidic may be added. A wide range of acids such as strong acids such as hydrochloric acid and organic acids such as acetic acid can be used as the pH adjuster.

  The waste water 28 decomposed by the above-described hardly decomposable substance-degrading bacteria is discharged out of the microorganism treatment tank 26 as treated water 32. The treated water 32 is regenerated water having a hydrophilic water level that can be touched by humans because the easily decomposable substance is decomposed in the pretreatment tank 12 and the hardly decomposed substance is decomposed in the microorganism treatment tank 26. Can do. Moreover, you may make it process the treated water 32 further as needed.

Colored wastewater was treated using the wastewater treatment system described above. In the microorganism treatment tank 26, white rot fungi (Trametes versicolor IFO-30340 strain) were placed, and melanoidin-containing wastewater was used as the colored wastewater. Melanoidin is a coloring cause substance contained in various colored wastewaters such as molasses wastewater, thermal decomposition treatment liquid, livestock wastewater and the like, and is a hardly decomposable substance that is extremely difficult to treat with ordinary microorganisms.
In the experiment, first, the melanoidin-containing wastewater was adjusted in the pretreatment tank 12 to a nitrogen content of 100 mg / l and a carbon content of 2000 mg / l. An activated sludge method was used for the treatment of the pretreatment layer 12. Next, the wastewater whose nitrogen concentration and carbon concentration were adjusted was membrane-separated with a filtration membrane, and the wastewater that permeated the filtration membrane was treated with white rot fungi. The decolorization rate was calculated from the change in chromaticity of the treated water after being treated with white rot fungi.
In addition, as a comparative example, waste water (nitrogen content 900 mg / l, carbon content 3000 mg / l) which was only subjected to membrane treatment without a pretreatment was treated with white rot fungi, and the decolorization rate was calculated. (Comparative Example 1). Furthermore, the wastewater which has not been subjected to pretreatment and membrane treatment was directly treated with white rot fungi, and the decolorization rate was calculated (Comparative Example 2). The results of the experiment are shown in Table 1.

  As is apparent from Table 1, according to the wastewater treatment system of this embodiment, a high decolorization rate can be obtained, and it was confirmed that the treatment system of this embodiment is effective for the treatment of colored wastewater.

  As is clear from the above description, in the wastewater treatment system of this embodiment, the nitrogen concentration and carbon concentration of the wastewater are adjusted before the wastewater is treated with microorganisms such as white rot fungi, and further the microorganisms of the wastewater are removed. It is almost aseptic. For this reason, microorganisms can actively act, and thereby, the hardly decomposable substance contained in the wastewater can be efficiently decomposed. Therefore, according to the wastewater treatment system of the present embodiment, it is possible to obtain hydrophilic water-level reclaimed water that can be touched by humans even with wastewater containing a hardly decomposable substance. Can be promoted. Moreover, since the ability of microorganisms is utilized, it can process at low cost compared with the chemical or physicochemical processing method.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The figure which shows the whole structure of the wastewater treatment system which concerns on one Embodiment of this invention.

Explanation of symbols

10 .. Waste water 12 ... Pretreatment tank 14 ... Waste water 15 ... Filtration membrane 16 ... Blower 20 ... Aeration device 22 ... Filter 24 ... Aeration device 26 ... Microorganism treatment tank

Claims (5)

A pretreatment step of adjusting the nitrogen concentration and carbon concentration in the wastewater within a preset concentration range;
A membrane filtration step for membrane filtration of wastewater whose nitrogen concentration and carbon concentration are adjusted by the pretreatment step;
A wastewater treatment method comprising treating the wastewater that has passed through the membrane in the membrane filtration step with a white rot fungus.   The wastewater treatment method according to claim 1, wherein in the pretreatment step, the treatment is performed so that the nitrogen concentration in the wastewater is low.   The wastewater treatment method according to claim 2, wherein in the pretreatment step, the treatment is further performed such that the carbon concentration in the wastewater falls within a predetermined concentration range.   The wastewater treatment method according to claim 2 or 3, wherein the pretreatment step is performed by an activated sludge method.   The wastewater treatment method according to claim 4, wherein the pore size of the filtration membrane used in the membrane filtration step is in the range of 1 to 20 µm.

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