JP2019025438A - Organic waste water treatment apparatus and organic wastewater treatment method - Google Patents

Abstract

To provide an organic waste water treatment apparatus and an organic wastewater treatment method capable of reducing energy consumption and generation of surplus activated sludge.SOLUTION: An organic wastewater treatment apparatus 1 according to the present invention comprises first treatment means 20 for methane fermentation of organic wastewater containing organic matter and nitrogen component under anaerobic conditions and membrane filtration to obtain membrane filtrate water, and second treatment means 30 for denitrifying the nitrogen component contained in the membrane filtrate water by anaerobic ammonium oxidation reaction. The organic waste water treatment method according to the present invention comprises first treatment step S1 for methane fermentation of organic wastewater containing organic matter and nitrogen component under anaerobic conditions and membrane filtration to obtain membrane filtrate water, and second treatment step S2 of denitrifying the nitrogen component contained in the membrane filtrate water by anaerobic ammonium oxidation reaction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an organic wastewater treatment apparatus and an organic wastewater treatment apparatus for highly treating organic wastewater containing organic matter and nitrogen components such as domestic wastewater, industrial wastewater, sewage, or wastewater mixed using at least one of them. The present invention relates to a wastewater treatment method.

  Currently, organic wastewater containing organic matter and nitrogen components, such as domestic wastewater, industrial wastewater, sewage, or wastewater mixed using at least one of these (hereinafter referred to simply as “organic wastewater”) Are often treated by a system using aerobic microorganisms typified by the activated sludge process. As described in Non-Patent Document 1, the activated sludge method is a method of using microorganisms suspended in water. Activated sludge is one in which various microorganisms are propagated by using organic substances in organic wastewater by blowing air into organic wastewater and stirring to form cohesive flocs. The activated sludge contains non-biological inorganic substances and organic substances in addition to microorganisms such as bacteria, protozoa and metazoans.

  About 100 years have passed since sewage treatment (organic wastewater treatment) by the activated sludge method has been put into practical use, and various methods such as a standard activated sludge method and a circulating nitrification denitrification method have been developed. FIG. 6 is an explanatory view showing an outline of an organic wastewater treatment facility according to a circulation type nitrification denitrification method which is one of the activated sludge methods and has an excellent ability to remove nitrogen components in organic wastewater.

  As shown in FIG. 6, the organic wastewater treatment facility related to the circulation type nitrification denitrification method includes a sedimentation basin 601, an initial sedimentation basin 602, an oxygen-free tank (denitrification tank) 603, and an aerobic tank (nitrification tank) 604. And a final sedimentation basin 605, and in the case of digesting the generated sludge, it has a concentration facility 606, a digestion facility 607, and a dehydration facility 608.

  The sand basin 601 is a pond for precipitating and removing earth and sand in organic waste water (sewage). The first sedimentation basin 602 is equipment for precipitating and removing SS having a large specific gravity mainly composed of organic substances floating in organic waste water. In the anaerobic tank 603, only agitation is performed, and in the aerobic tank 604, aeration is performed. The anoxic tank 603 first supplies organic matter necessary for the denitrification reaction from the settling tank 602, and denitrifies nitrate nitrogen in the organic wastewater by the action of denitrifying bacteria to convert it into nitrogen gas. The aerobic tank 604 converts organic nitrogen or ammonia nitrogen in the organic waste water into nitrite nitrogen by the action of ammonia oxidizing bacteria, and nitrate nitrogen by the action of nitrite oxidizing bacteria. Convert to The organic wastewater containing nitrate nitrogen treated in the aerobic tank 604 is circulated to the anoxic tank 603 to denitrify nitrate nitrogen by the action of denitrifying bacteria as described above. It is converted into nitrogen gas and can be removed from the organic wastewater into the air. The final sedimentation tank 605 is a facility for precipitating activated sludge and discharging clean water (treated water) of the supernatant. In the concentration facility 606, the excess activated sludge collected by collection in the final settling tank 605 and the first settling sludge (raw sludge) collected from the first settling tank 602 are concentrated by settling and separating. In the digestion facility 607, the concentrated activated sludge and the like are digested by the action of methane-producing archaea, and methane is generated and recovered. In the dehydration facility 608, the digested sludge after the methane production is dehydrated with a centrifuge or the like. And dehydrated digested sludge (dehydrated sludge) is conveyed outside. Since the dehydrated filtrate obtained by dehydration may contain high-concentration nitrogen components and BOD components, they may be returned to the sand basin 601 for the purpose of denitrification again.

Japan Sewerage Association, “Sewerage Facility Planning and Design Guidelines and Explanation 2009, Second Part”, published by Japan Sewerage Association, October 2009, p. 12-p. 20

However, the conventional activated sludge method, for example, the above-described circulation type nitrification denitrification method, requires aeration using a large amount of air and power in the aerobic tank 604 and has a problem that a great deal of energy is required. there were.
The denitrifying bacterium that performs denitrification in the anoxic tank 603 is a heterotrophic bacterium that uses an organic substance as an electron donor for the denitrification reaction and grows using the organic substance. Therefore, when denitrification was performed using denitrifying bacteria, there was a problem that a large amount of excess activated sludge was inevitably generated.

  This invention is made | formed in view of the said condition, and makes it a subject to provide the organic waste water treatment apparatus and the organic waste water treatment method which can reduce energy consumption and the generation amount of excess activated sludge.

  The organic wastewater treatment apparatus according to the present invention that has solved the above-described problems is a first treatment means for performing membrane filtration on organic wastewater containing organic matter and a nitrogen component under anaerobic conditions to obtain membrane filtrate. Second treatment means for denitrifying a nitrogen component contained in the membrane filtrate by an anaerobic ammonia oxidation reaction.

  The organic wastewater treatment method according to the present invention that has solved the above problems includes a first treatment step of obtaining membrane filtered water by subjecting an organic wastewater containing an organic matter and a nitrogen component to methane fermentation under anaerobic conditions and membrane filtration. A second treatment step of denitrifying a nitrogen component contained in the membrane filtrate by an anaerobic ammonia oxidation reaction.

  The organic wastewater treatment apparatus and the organic wastewater treatment method according to the present invention can reduce the energy consumption and the amount of surplus activated sludge generated.

It is explanatory drawing which shows the outline | summary of the organic waste water treatment apparatus which concerns on this embodiment. It is a schematic block diagram which shows the specific structure of the organic waste water treatment apparatus which concerns on this embodiment. It is a perspective view which shows a support | carrier. It is a flowchart explaining the content of the organic drainage method which concerns on this embodiment. It is explanatory drawing which shows a mode that the organic waste water treatment equipment which concerns on Example 3 was provided in the organic waste water treatment facility which concerns on the circulation type nitrification denitrification method which is one of the circulation type activated sludge methods. It is explanatory drawing which shows the outline | summary of the organic waste water treatment facility which concerns on a circulation type nitrification denitrification method.

Hereinafter, an embodiment of an organic wastewater treatment apparatus and an organic wastewater treatment method according to the present invention will be described in detail with reference to the drawings as appropriate.
[Organic wastewater treatment equipment]
FIG. 1 is an explanatory diagram for explaining an outline of an organic wastewater treatment apparatus 1 according to the present embodiment. FIG. 2 is a schematic configuration diagram illustrating the configuration of the organic wastewater treatment apparatus 1 according to the present embodiment.
The organic wastewater treatment apparatus 1 according to the present embodiment highly processes organic wastewater containing organic matter and nitrogen components such as domestic wastewater, industrial wastewater, sewage, or wastewater mixed using at least one of them. It is a device to do.
As shown in FIG. 1, the organic waste water treatment apparatus 1 according to this embodiment includes a first treatment unit 20 and a second treatment unit 30.

Here, the domestic wastewater refers to water that is generated and discharged along with general human life such as cooking, washing, and bathing. Domestic wastewater may contain human waste and rainwater.
Industrial wastewater refers to wastewater from agriculture, forestry and fisheries (primary industry) and mining and manufacturing (secondary industry).
Sewage refers to wastewater mainly composed of domestic wastewater, and industrial wastewater and, in some cases, rainwater.
In addition, in this specification, the leachate from a landfill site can also be handled as organic waste water.
An organic substance is also called an organic compound, and refers to a compound that is configured on the basis of a covalent bond between carbon atoms.
As nitrogen components, free ammonia (NH ₃ ), ammonium ions (NH ₄ ⁺ ), ammoniacal nitrogen (NH ₄ -N), nitrite nitrogen (NO ₂ -N), nitrate nitrogen (NO ₃ -N) Is mentioned. Ammonia nitrogen refers to nitrogen in the form of ammonia, nitrite nitrogen refers to nitrogen in the form of nitrous acid, and nitrate nitrogen refers to nitrogen in the form of nitric acid. Say.
High treatment means removal (denitrification) of the nitrogen component described above in addition to removal of the organic matter.
Since the organic wastewater treatment apparatus 1 according to the present embodiment has means described later, it can be processed regardless of the concentration of organic matter in the organic wastewater and the concentration of the nitrogen component.

(Flow adjustment tank 10)
The organic waste water treatment apparatus 1 can be provided with a flow rate adjusting tank 10 that adjusts the amount of inflow of organic waste water into the first treatment means 20 before the first treatment means 20. The flow rate adjusting tank 10 can be provided as necessary, and need not be provided.
As shown in FIG. 2, the adjustment of the inflow amount of the organic waste water from the flow rate adjusting tank 10 to the first processing means 20 is performed, for example, between the flow rate adjusting tank 10 and the first processing means 20. This can be done by adjusting the output of the pump P2. The inflow of the organic wastewater into the flow rate adjusting tank 10 can be performed by a pump P1 provided between the organic wastewater treatment plant facility. The flow rate adjustment tank 10 may include a stirrer 11 for stirring the organic waste water. In the present embodiment, a sand basin (not shown) can be provided in the previous stage of the flow rate adjustment tank 10 to precipitate and remove earth and sand in the organic waste water.

(First processing means 20)
In the 1st processing means 20, while carrying out methane fermentation of the above-mentioned organic wastewater on anaerobic conditions, membrane filtration is performed and membrane filtration water is obtained. That is, the first treatment means 20 can decompose most of the organic substances contained in the organic waste water, and can generate methane. Methane fermentation is a general term for the decomposition reaction of organic substances by various microorganisms and the reaction in which methanogenic archaea finally produces methane. In addition, the methane produced | generated by the 1st process means 20 is collect | recovered as biogas, and is used for the production | generation of electricity or heat. Moreover, since membrane filtration is performed, suspended matter is not contained in membrane filtration water. Organic matter and suspended solids become the source of activated sludge in the second treatment means 30. That is, activated sludge is likely to occur when the second treatment means 30 contains denitrifying bacteria. For this reason, it is preferable to decompose or remove as much organic matter and suspended solids as possible with the first processing means 20.

Methane is produced by the action of methanogenic archaea (methane producing archaea). Methanogenic archaea is a general term for a group of microorganisms that produce methane under anaerobic conditions, all of which are classified as archaea. Under anaerobic conditions, methanogenic archaea produce methane using as a substrate hydrogen, carbon dioxide, formic acid, acetic acid, methylamines, and the like produced by the complete decomposition of organic matter by multiple types of microorganisms. A plurality of processes for producing methane have been proposed, but the following two are listed as processes that may produce a large amount of methane in nature.
CH ₃ COO ⁻ + H ⁺ + OH ⁻ → CH ₄ + CO ₂ + OH ⁻
CO ₂ + 8H ⁺ + 8e ⁻ → CH ₄ + 2H ₂ O

  In the present embodiment, hydrogen-utilizing methanogenic archaea, acetic acid-assimilating methanogenic archaea, and the like can be used. Examples of methanogenic archaea that can be used in the present embodiment include, Examples include the genus Methanosarcina, the genus Methanosbus, the genus Methanococcoides, the genus Methanothrix (Methanosaeta), the genus Methanoregula, the genus Methanolinea, the genus Methanohalophilus, the genus Methanohalobium, and the genus Methanocorpusculum. In addition, in this embodiment, it will not be limited to these, What kind of bacteria can be used if it can produce | generate methane. Methanogenic archaea and various microorganisms that decompose the organic matter can be easily obtained from existing digestion tanks.

As the 1st process means 20, it is preferable to use the membrane separation methane fermentation tank 20a provided with the membrane module 22 which performs membrane filtration. If it does in this way, the organic waste water treatment equipment 1 can be made compact compared with the apparatus which concerns on the conventional activated sludge process, and construction cost can be reduced. Moreover, since it is not necessary to aerate with a large amount of oxygen (air) unlike the activated sludge method, energy consumption can be reduced and running cost can be reduced.
The membrane separation methane fermentation tank can be a methane fermentation tank holding suspended anaerobic bacteria (including methanogenic archaea) or a methane fermentation tank holding anaerobic granule sludge. The suspended anaerobic bacterium means an anaerobic bacterium that does not form granules.

  Anaerobic bacteria can be retained in the former methane fermentation tank by simply suspending the anaerobic bacteria in organic waste water or using a polyethylene glycol (PEG) -based prepolymer. It can be performed by attaching an anaerobic bacterium to the gel carrier prepared in the above step. When attached and fixed, fouling to the membrane can be made difficult to occur in membrane filtration.

  Moreover, the anaerobic granular sludge in the latter methane fermenter means the granulated sludge formed using the property of anaerobic bacteria self-aggregation and granulation. The granule contained in the anaerobic granule sludge generally refers to a particle having a particle size of 0.2 mm or more, but is not limited to this in this embodiment. Can be handled as granules if a granulated body is formed. Even in the case of anaerobic granule sludge, fouling to the membrane can be made difficult to occur in membrane filtration.

Anaerobic conditions can be created by performing treatment using a sealed tank in which air does not flow from the outside. In order to achieve anaerobic conditions, carbon dioxide (CO ₂ ), nitrogen (N ₂ ) gas, or the like may be introduced into the gas phase (head space) of the tank as necessary. Here CO ₂ and N ₂ gas to be introduced, it is possible to use those produced by the organic waste water treatment apparatus 1.

  The membrane filtration uses at least one of a microfiltration (MF) membrane, an ultrafiltration (UF) membrane, a nanofiltration (NF) membrane, and a reverse osmosis (RO) membrane. It can be carried out. In this way, since organic substances of a predetermined size cannot permeate, the amount of activated sludge generated in the second treatment means 30 described later can be reduced. In the present embodiment, among the above, it is preferable to use an MF film or a UF film. When filtration is performed using an MF membrane or a UF membrane, not only solid organic matter but also organic waste water (membrane filtered water) not containing microorganisms such as methanogenic archaea can be supplied to the second processing means 30 described later. . That is, by using the MF membrane or the UF membrane, the organic waste water treatment apparatus 1 prevents the methanogenic archaea from flowing out of the first treatment means 20, and the living cells of the methanogenic archaea in the first treatment means 20. The number can be kept high. In the present embodiment, it is more preferable to use an MF membrane having a pore diameter of 1 μm or less. If it does in this way, the power of the membrane filtration pump P4 used for filtration can be suppressed compared with the case where an NF membrane or an RO membrane is used.

  As a membrane used for membrane filtration, a membrane formed of chlorinated vinyl resin (CPVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or the like can be used. As the form of the membrane used for membrane filtration, any of a flat membrane, a tubular membrane, and a hollow fiber membrane (a tubular membrane having an inner diameter of 5 mm or less, preferably 3 mm or less) can be adopted.

  Examples of the membrane separation methane fermentation tank used as the first processing means 20 described above include, for example, a cross-flow type anaerobic membrane bioreactor (MBR), an immersion type anaerobic MBR (bath tank type), and an immersion type. Anaerobic MBR (integrated type) or the like can be used. FIG. 2 illustrates an immersion type anaerobic MBR (integrated type) 21.

The cross-flow type anaerobic MBR has a methane fermentation tank for methane fermentation and a membrane separation device that separates sludge with a membrane, and applies high pressure inside the membrane module of the membrane separation device to flow the sludge. Perform membrane filtration.
The submerged anaerobic MBR (tank separate type) and the submerged anaerobic MBR (integrated type) 21 perform membrane separation, that is, membrane filtration, by suction with a membrane filtration pump P4. The submerged anaerobic MBR (separate tank type) is a methane fermentation tank and a membrane separator installed independently, and the submerged anaerobic MBR (integrated type) 21 is a membrane separator in the methane fermenter. Is installed.

  In the present embodiment, any of the above-described membrane-separated methane fermenters can be employed, but it is preferable to employ a submerged anaerobic MBR (integrated) 21 as shown in FIG. When the immersion type anaerobic MBR (integrated type) 21 is employed, the membrane module 22 is accommodated in the tank, so that the installation area is reduced and the apparatus can be made more compact. Moreover, when the immersion type anaerobic MBR (integrated type) 21 is employed, the number of installed pumps (flow rate adjusting tank pump P2 and membrane filtration pump P4) can be reduced. Therefore, the organic waste water treatment apparatus 1 can reduce construction costs and running costs, and can further save energy. In addition, when the immersion type anaerobic MBR (tank separate type) is adopted, the film can be easily cleaned as compared with the immersion type anaerobic MBR (integrated type) 21.

As shown in FIG. 2, the first processing means 20 preferably includes third processing means 25 that removes CO ₂ generated by the first processing means 20. For example, when organic wastewater such as domestic wastewater and organic wastewater having a low concentration of nitrogen component are methane-fermented to produce CO ₂ , the pH of the organic wastewater may be lowered. However, such a fear can be prevented by operating at all times or in a timely manner to remove CO ₂ . That is, since the CO ₂ is removed by the third processing means 25, it is possible to make it difficult to lower the pH of the organic waste water. Therefore, it becomes easy to adjust the pH of the obtained membrane filtrate to a range of 7 to 8.5 suitable for the anammox reaction performed by the second treatment means 30 in the subsequent stage. Note that there are organic wastewaters with a high concentration of organic matter and a low concentration of nitrogen component (NH ₄ -N), but the same effect can be obtained with such organic wastewater.

For example, as shown in FIG. 2, the third processing unit 25 is connected to a membrane cleaning blower B1 that prevents fouling to the membrane by circulating the gas in the head space of the third processing unit 25, For example, a CO ₂ removal device that uses a container 26 of a predetermined size containing water 27 and absorbs and removes CO ₂ in the water 27 can be used.

In the case of a large apparatus, for example, using a continuous continuous absorption tower, the biogas generated in methane fermentation is allowed to flow in an upward flow, while water is sprinkled in a downward flow to cause gas-liquid contact, thereby bringing the biogas into contact. A device that removes CO ₂ contained in water by absorbing it can be employed. Further, as the CO ₂ removing agent, it can be employed an apparatus packed column type using a particulate slaked lime.

Examples of the third processing means 25 include a discharge mechanism (not shown) that removes CO ₂ by discharging it out of the apparatus. Examples of such a discharge mechanism include a CO ₂ permselective membrane (facilitated transport membrane). The CO ₂ permselective membrane is a dendrimer membrane (dendritic polymer having a structure that is regularly branched from the center), for example, produced using polyethylene glycol (PEG), polyvinyl alcohol (PVA), or polyamidoamine (PAMAM). Film). In the case of using such a CO ₂ selective permeation membrane may prompt the transport of CO ₂ from the tank using a suction pump.
The third processing unit 25 is not limited to the above-described one, and any device can be used as long as it can remove CO ₂ .

  For the first treatment means 20, for the purpose of maintaining the activity of methanogenic archaea, calcium, magnesium, iron, nickel, cobalt, potassium, sodium, zinc, selenium, tungsten, molybdenum, copper, manganese, aluminum, etc. An apparatus (not shown) for adding the inorganic salt (metal) can be provided. Moreover, the 1st process means 20 can be provided with the heating apparatus (not shown) for adjusting water temperature. The heating device can use heat and electricity obtained by burning the methane gas obtained by the first processing means 20. The first processing means 20 can be provided with a sensor Sr1 such as a pH meter, a dissolved carbon dioxide meter, or a thermometer. Although the sensor Sr1 is provided for each measurement object, only one sensor Sr1 is shown in FIG.

(Second processing means 30)
In the 2nd process means 30, the nitrogen component contained in the membrane filtered water obtained by the 1st process means 20 is denitrified by anaerobic ammonia oxidation (anaerobic ammonium oxidation; Anammox). The anammox reaction is a reaction in which anammox bacteria produce N ₂ using NH ₄ —N and NO ₂ —N as substrates under anaerobic conditions, and the following reaction formula 1 is shown.

[Reaction Formula 1]
1.0 NH ₄ ⁺ +1.32 NO ₂ ⁻ +0.066 HCO ₃ ⁻ + 0.13H ⁺ →
1.02N ₂ + 0.26NO ₃ ⁻ + 0.066CH ₂ O _0.5 N _0.15 + 2.03H ₂ O

  As the anammox bacterium, a bacterium belonging to the order of the Bacteria genus Planctomycetes genus Brocadiales can be used. Since anammox bacteria are not currently purely cultured, all phylogenetic classifications are labeled “Candidatus”. Specific examples of anammox bacteria that can be used in this embodiment include Candidatus Brocadia, Candidatus Kuenenia, Candidatus Jettenia, Candidatus Anammoxoglobus, Candidatus Scalindua, and Candidatus Anammoximicrobium. In addition, in this embodiment, it is not limited to a classification name or a scientific name, but any bacteria can be used as long as it can perform an anammox reaction. Anammox bacteria can be obtained by cultivating activated sludge collected from existing wastewater treatment equipment or surplus activated sludge as seed sludge and culturing for a long time in organic wastewater such as medium containing ammonia nitrogen and nitrite nitrogen or sewage. Can do. The anammox bacteria can also be obtained by culturing the seed sludge described above in an anammox medium having the following composition.

[Composition of Anammox medium]
· NaNO _2: 0~300mg / L
· _NH 4 Cl or _{(NH 4) 2 SO 4:} 0~300mg / L
・ KH ₂ PO ₄ : 54 mg / L
・ KHCO ₃ : 125 mg / L
・ Micro Fe / EDTA ^{# 1} : 1mL / L
(Composition of # 1: FeSO ₄ · 7H ₂ O 9 g, EDTA · 2Na 5 g)

As shown in Reaction Formula 1, the molar ratio of NH ₄ —N and NO ₂ —N contained in the membrane filtrate that performs the anammox reaction is about 1: 1 to 1: 1.5. Preferably, it is about 1: 1.32. However, although depending on the state of organic wastewater or membrane filtration water as raw water, the content of NH ₄ -N in membrane filtration water is high, while the content of NO ₂ -N is often low. Is often not the one described above. Therefore, it is preferable that a part of NH ₄ -N contained in the membrane filtered water is oxidized with nitrifying bacteria (ammonia oxidizing bacteria) to generate NO ₂ -N. This is referred to as “partial nitritation” or the like because part of NH ₄ —N in the membrane filtrate is converted to NO ₂ —N. That is, in this embodiment, an “anaerobic” ammonia oxidation reaction (anammox reaction) is performed, but it is not necessary to make the membrane filtrate contain no oxygen at all. In the present embodiment, a part of NH ₄ -N contained in the membrane filtered water can contain oxygen necessary for the ammonia oxidizing bacteria to convert to NO ₂ -N. That is, the above-mentioned “anaerobic” does not mean that the second processing means 30 is completely anaerobic, but the conditions under which the anammox reaction is simply performed (that is, the anammox reaction is limited). This indicates that a certain range) may be under anaerobic conditions. Therefore, when the membrane filtered water in the second treatment means 30 does not contain sufficient oxygen to perform partial nitritation, aeration can be performed using the blower B2, as shown in FIG. . The oxygen concentration of the membrane filtered water in the second processing means 30 can be measured with a dissolved oxygen meter DOS.

In principle, partial nitritation requires only about half of NH ₄ —N to be converted to NO ₂ —N, and therefore, the reaction of nitrifying the entire amount of NH ₄ —N to NO ₂ —N in the conventional activated sludge process In comparison, the amount of contacted air can be halved. Therefore, in this embodiment, when aeration power is used to nitrify NH ₄ —N to NO ₂ —N, the required aeration power can be reduced by half compared to the conventional activated sludge method. Therefore, energy consumption such as the amount of electricity in such a case can be reduced to about half.

  Examples of ammonia-oxidizing bacteria include, but are not limited to, bacteria belonging to the genus Nitrosomonas, Nitrosococcus, Nitrosospira, Nitrosolobus, Nitrosovibrio and the like.

The generation of NO ₂ —N may be performed in the same tank as the tank in which the anammox reaction is performed, or may be performed in another tank. In addition, NO is called the one-pot type anammox tank performs 2 production and anammox reaction _-N same bath, those carried out in a separate tank of double-chamber type anammox tank.
In this embodiment, as shown in FIG. 2, it is preferable to use a single tank type anammox tank 31. When the single tank type anammox tank 31 is used, it is possible to save space and reduce the construction cost as compared with the case of the two tank type anammox tank (not shown).
When the two-tank anammox tank is used, the anammox bacteria and the ammonia-oxidizing bacteria can be managed in separate tanks, so that each bacteria can be easily managed and the reaction can be controlled. In addition, when a two-tank anammox tank is used, it can be introduced into a tank for performing an anammox reaction by adjusting the NO ₂ ^- concentration and flow rate of membrane filtrate containing NO ₂ -N produced by ammonia-oxidizing bacteria. The molar ratio of NH ₄ —N and NO ₂ —N is likely to be as described above.

As shown in the above-mentioned reaction formula 1, a small amount of NO ₃ —N is produced in the anammox reaction. Therefore, it is preferable that the second treatment means 30 includes denitrifying bacteria that reduce the produced NO ₃ —N to N ₂ . In this way, by the final anammox bacteria and denitrifying bacteria, most of NH ₄ ⁺ and NH 4 _-N contained in the organic waste water can be converted into N ₂ with no harm to the environment.

  Examples of denitrifying bacteria include, but are not limited to, Pseudomonas denitrificans, Pseudomonas aeruginosa, Pseudomonas stutzeri, Pseudomonas mendocina, Comamonas testosteroni, Paracoccus denitrificans, Alcaligenes faecalis, and the like. The treatment with the denitrifying bacteria may be performed by means (tank) different from the second treatment means 30.

In addition, ammonia oxidizing bacteria and denitrifying bacteria can be easily obtained from activated sludge or surplus activated sludge collected from an existing wastewater treatment apparatus.
Since anammox bacteria and ammonia-oxidizing bacteria are autotrophic bacteria that do not use organic substances for growth, even if soluble organic substances are contained in the membrane filtration water, they do not grow in large quantities. Therefore, in this embodiment, the production amount of activated sludge derived from anammox bacteria and ammonia oxidizing bacteria can be reduced.
On the other hand, a denitrifying bacterium is a heterotrophic bacterium that uses an organic substance as an electron donor to convert NO ₃ -N to N ₂ but grows using the organic substance. Therefore, in this embodiment, although activated sludge derived from denitrifying bacteria is generated, most of the organic matter has already been decomposed into methane by the first treatment means 20 described above, and remains in the membrane filtered water. The concentration of organic matter is low. Therefore, in this embodiment, compared with the conventional activated sludge method, the production amount of the activated sludge which a denitrifying bacterium grows can be reduced. Moreover, in this embodiment, since the growth of heterotrophic bacteria including denitrifying bacteria is suppressed in the second processing means 30, dominance of anammox bacteria can be achieved. Therefore, high concentration of anammox bacteria and efficient anammox reaction can be performed. In the present embodiment, organic substances other than methanol can be added in order to sufficiently convert NO ₃ ⁻ to N ₂ by denitrifying bacteria.

  The single tank type anammox tank 31 preferably includes a carrier 32 having an inner diameter of 3 to 30 mm, a length of 3 to 30 mm, and a hollow cylinder having both ends opened. The perspective view of FIG. 3 shows this carrier 32. If the carrier 32 is included, ammonia oxidizing bacteria are held on the outer side 32a of the carrier 32, so that dissolved oxygen derived from the air or the like ventilated in the one-tank anammox tank 31 is consumed. For this reason, the inner side 32b of the carrier 32 is likely to be in an anaerobic condition. Therefore, the inside 32b of the carrier 32 is easy to grow and hold anammox bacteria. Moreover, the inner side 32b of the support | carrier 32 can perform the anaerobic ammonia oxidation reaction by an anammox bacteria suitably. In the present embodiment, the inner diameter of the hollow cylindrical carrier 32 is preferably 5 to 15 mm from the viewpoint of performing more suitable growth and retention of anammox bacteria and anaerobic ammonia oxidation reaction by anammox bacteria. Is preferably 5 to 15 mm. The hollow cylinder is preferably cylindrical, but can be any shape such as a triangular prism or a quadrangular prism. The carrier 32 can be formed of any resin such as polypropylene (PP) resin, polyethylene terephthalate (PET) resin, polyvinyl chloride (PVC) resin. The outer diameter of the carrier 32 is not particularly limited. The dose of the carrier 32 can be, for example, 10 to 20%, preferably 15%, but not limited to the volume ratio of the anammox tank 31.

In addition, the single tank anammox tank 31 charged with the carrier 32 stirs the liquid in the tank supplied with the membrane filtered water by at least one of air blowing and mechanical stirring, and the dissolved oxygen concentration of the liquid in the tank is determined. It is preferable to control to 0.5 mg / L or less. In this way, O ₂ can be supplied to the ammonia oxidizing bacteria held outside the carrier 32 at an appropriate concentration from the necessary minimum, and partial nitritation can be performed. Further, as described above, in this embodiment, O ₂ is consumed by the ammonia oxidizing bacteria held on the surface of the carrier 32. Therefore, in this embodiment, anaerobic conditions can be maintained for the anammox bacteria held on the inner side 32b of the carrier 32, and an anammox reaction can be performed. That is, by controlling the dissolved oxygen concentration as described above, partial nitritation by ammonia-oxidizing bacteria can be performed without significantly affecting the anammox reaction by anammox bacteria. In addition, in order to acquire the above-mentioned effect more reliably, it is more preferable to control the dissolved oxygen concentration of the liquid in a tank to 0.3 mg / L or less.

  The second treatment means 30 includes calcium, magnesium, iron, nickel, cobalt, potassium, sodium, zinc, selenium, tungsten, molybdenum for the purpose of maintaining the activity of anammox bacteria, ammonia oxidizing bacteria, denitrifying bacteria, and the like. An apparatus (not shown) for adding an inorganic salt (metal) such as copper, manganese, or aluminum can be provided. Further, the second processing means 30 can be provided with a heating device (not shown) for adjusting the water temperature. The heating device can use heat and electricity obtained by burning the methane gas obtained by the first processing means 20. The second processing means 30 can be provided with a sensor Sr2 such as a pH meter, a dissolved oxygen meter DOS, an ammonia sensor, a nitric acid sensor, and a thermometer. The sensor Sr2 is provided for each measurement object, but only one sensor Sr2 is illustrated in FIG.

  The second treatment means 30 may be provided with a sedimentation zone 33 for precipitating excess activated sludge after the treatment in the tank. In addition, this precipitation zone 33 can be provided arbitrarily and does not need to be provided. The sedimentation zone 33 can be provided by dividing the inside of the tank with a metal fence or the like having an opening that does not allow the carrier 32 to permeate. When this sedimentation zone 33 is provided, the sedimentation basin 50 described later can be omitted.

(Other facilities in the organic wastewater treatment equipment 1)
As shown in FIGS. 1 and 2, the organic waste water treatment apparatus 1 according to the present embodiment may include a dehydration facility 40 that dehydrates sludge collected from the first treatment means 20. As the dehydration equipment 40, for example, a centrifugal separator, a belt press dehydrator, a screw press dehydrator, or the like can be used. The dewatered sludge dehydrated by the dewatering equipment 40 is carried out and appropriately treated, such as being incinerated or used for landfilling at the final disposal site. As shown in FIG. 2, the conveyance of the sludge from the 1st process means 20 to the spin-drying | dehydration equipment 40 can be performed with the pump P3 provided between these.

  Further, as shown in FIG. 2, an anaerobic water tank 23 may be provided between the first processing means 20 and the second processing means 30. In this case, the anaerobic treatment water tank 23 is preferably provided with a membrane filtration pump P4 for transferring the membrane filtrate water between the first treatment means 20 and the membrane filtration water is transferred between the second treatment means 30. It is preferable that a pump P5 is provided. When the anaerobic treatment water tank 23 is provided in this way, the membrane filtrate is temporarily stored in the anaerobic treatment water tank 23, and the inflow amount of the membrane filtrate to be introduced into the second treatment means 30 can be arbitrarily adjusted.

  As shown in FIG. 2, in the subsequent stage of the second treatment means 30, the sludge in the treated water treated by the second treatment means 30 is settled and separated, and the precipitated sludge and the supernatant clean water (treated water) are separated. A settling basin 50 that separates and discharges the clean water (treated water) may be provided. The sedimentation basin 50 also has a function of storing treated water.

  Further, a water seal 61 for preventing the inflow of air from the opening of the gas pipe can be provided in the gas pipe for discharging the biogas (methane) generated from the first processing means 20 to the outside. Furthermore, the gas pipe can be provided with a gas meter 62 for measuring the amount of biogas produced. The gas pipe can be provided with a desulfurization tower 63 for removing hydrogen sulfide contained in the biogas. As the water sealer 61, the gas meter 62, and the desulfurization tower 63, commercially available ones can be used.

  Since the organic waste water treatment apparatus 1 according to the present embodiment has the first treatment means 20 and the second treatment means 30 even when the flow adjustment tank 10 and the dehydration equipment 40 are provided. The installation area, cost, and the like can be reduced as compared with the conventional activated sludge method (for example, circulation type nitrification denitrification method) (see FIG. 6).

As described above, the organic wastewater treatment apparatus 1 according to the present embodiment described above can methane-ferment the organic matter by the first treatment means 20 and perform membrane filtration to obtain membrane filtrate. Since the organic matter is decomposed by methane fermentation to become methane and CO ₂ , the concentration of the organic matter contained in the membrane filtered water can be lowered. Note that almost all organic substances contained in the membrane filtered water are soluble. Moreover, since it filters by membrane filtration, it will be in the state which does not contain a suspended substance at all. Therefore, the second treatment means 30 at the latter stage can reduce the amount of surplus activated sludge generated by the membrane filtrate. On the other hand, the membrane filtered water treated by the first treatment means 20 often contains a large amount of NH ₄ -N, but the second treatment means 30 partially nitrites NH ₄ -N to form NH ₄ -N. it can be converted to about a half of the the _NO 2 -N. By the second processing means 30 anammox bacteria, it can produce _{N 2} and a _NH 4 -N and _NO 2 -N. The organic waste water treatment apparatus 1 can reduce the amount of air used in partial nitritation to about half compared with the reaction in which the total amount of NH ₄ —N in the conventional activated sludge process is nitrified to NO ₂ —N. Therefore, in the present embodiment, the aeration power and the amount of electricity necessary for nitrifying NH ₄ —N to NO ₂ —N can be reduced to about half. Therefore, the organic waste water treatment apparatus 1 can reduce energy consumption. Further, as described above, since the membrane filtrate treated by the first treatment means 20 contains almost no organic matter or suspended solids, the denitrification bacteria that are heterotrophic bacteria in the second treatment means 30 also have these. Therefore, it is difficult to multiply and the amount of surplus activated sludge generated can be reduced.

[Organic wastewater treatment method]
Next, the organic waste water treatment method according to this embodiment will be described.
The organic wastewater treatment method according to this embodiment highly treats organic wastewater containing organic matter and nitrogen components such as domestic wastewater, industrial wastewater, sewage, or wastewater mixed using at least one of these wastewater. Is the method. Since the organic wastewater treatment method according to the present embodiment can be suitably implemented by the organic wastewater treatment apparatus 1 according to the present embodiment described above, the following description will be given by taking the organic wastewater treatment apparatus 1 as an example. . Therefore, the same code | symbol is attached | subjected about the component which is common in the organic waste water treatment method which concerns on this embodiment, and the organic waste water treatment apparatus 1 which concerns on this embodiment, and detailed description is abbreviate | omitted.

FIG. 4 is a flowchart for explaining the contents of the organic wastewater treatment method according to this embodiment.
As shown in FIG. 4, the organic waste water treatment method according to the present embodiment includes a first treatment step S1 and a second treatment step S2, and these steps are performed in this order.

(First processing step S1)
The first treatment step S1 is a step of obtaining membrane filtrate by performing methane fermentation of the organic waste water under anaerobic conditions and performing membrane filtration. This first treatment step S1 can be performed by the first treatment means 20 in the organic wastewater treatment apparatus 1. Therefore, the membrane filtrate treated in the first treatment step S1 has a low concentration of organic matter and does not contain suspended substances. Therefore, in the second processing step S2 at the latter stage, the amount of surplus activated sludge generated by the membrane filtrate can be reduced.

  The first treatment step S1 is preferably performed in the membrane separation methane fermentation tank 20a. If it does in this way, in this embodiment, compared with the conventional activated sludge method, the apparatus used by 1st process process S1 can be reduced in size, and construction cost can be reduced. Further, since it is not necessary to aerate with a large amount of oxygen (air) unlike the activated sludge method, the running cost can be reduced. The membrane separation methane fermentation tank 20a can be a methane fermentation tank holding suspended anaerobic bacteria (including methane-producing archaea) or a methane fermentation tank holding anaerobic granule sludge.

Incidentally, the first processing step S1 is preferably includes a third processing step S3 of removing the CO ₂ generated. This third treatment step S3 can be performed by the third treatment means 25 in the organic waste water treatment apparatus 1. Accordingly, the third treatment step S3 is performed to remove CO ₂ , so that the pH in the first treatment step S1 (methane fermentation) is prevented from being lowered to 6.5 or less, and the pH of the membrane filtration water is hardly lowered. can do. Therefore, it becomes easy to adjust the pH of the obtained membrane filtrate to a range of 7 to 8.5 suitable for the anammox reaction performed in the second treatment step S2 in the subsequent stage.

(Second processing step S2)
The second treatment step S2 is a step of denitrifying a nitrogen component contained in the membrane filtrate by an anaerobic ammonia oxidation reaction (anammox reaction). This second treatment step S2 can be performed by the second treatment means 30 in the organic wastewater treatment apparatus 1. At this time, if necessary, a part of NH ₄ -N contained in the membrane filtrate can be oxidized by ammonia oxidizing bacteria to produce NO ₂ -N. In this embodiment, it is only necessary to convert about half of NH ₄ —N to NO ₂ —N, so that the total amount of NH ₄ —N in the conventional activated sludge process is compared with the reaction of nitrifying to NO ₂ —N. Thus, the amount of air to be contacted can be halved. Therefore, as described above, in the present embodiment, the aeration power and the amount of electricity necessary for nitrifying NH ₄ —N to NO ₂ —N can be reduced by about half.

The second treatment step S2 is preferably performed in the single tank type anammox tank 31. When the single tank type anammox tank 31 is used, it is possible to save space and reduce the construction cost as compared with the two tank type anammox tank.
Moreover, it is preferable that the single tank type anammox tank 31 includes a carrier 32 having an inner diameter of 3 to 30 mm, a length of 3 to 30 mm, and a hollow cylinder having both ends opened. In this way, since ammonia-oxidizing bacteria are held outside the carrier 32, dissolved oxygen derived from the air or the like ventilated in the one-tank anammox tank 31 is consumed. Therefore, the inside of the carrier 32 tends to be anaerobic conditions. Therefore, the inside 32b of the carrier 32 is easy to grow and hold anammox bacteria. Moreover, the inner side 32b of the support | carrier 32 can perform the anaerobic ammonia oxidation reaction by an anammox bacteria suitably.

Further, the one-tank anammox tank 31 into which the carrier 32 is charged stirs the liquid in the tank supplied with the membrane filtered water by at least one of air blowing and mechanical stirring, and the dissolved oxygen concentration of the liquid in the tank is reduced. It is preferable to control to 0.5 mg / L or less. In this way, O ₂ can be supplied to the ammonia oxidizing bacteria held outside the carrier 32 at an appropriate concentration from the necessary minimum, and partial nitritation can be performed. As described above, O ₂ is consumed by the ammonia-oxidizing bacteria held on the surface of the carrier 32. Therefore, anaerobic conditions can be maintained for the anammox bacteria held on the inner side 32b of the carrier 32. The reaction can be performed. In addition, in order to acquire the above-mentioned effect more reliably, it is more preferable to control the dissolved oxygen concentration of the liquid in a tank to 0.3 mg / L or less.

As described above, the organic wastewater treatment method according to the present embodiment described above can methane-ferment the organic matter in the first treatment step S1 and perform membrane filtration to obtain membrane filtrate. Since the organic matter is decomposed by methane fermentation to become methane and CO ₂ , the concentration of the organic matter contained in the membrane filtered water can be lowered. In addition, since it filters by membrane filtration, it will be in the state which is not contained at all about a floating substance. Therefore, in the second processing step S2 in the subsequent stage, the amount of surplus activated sludge generated by the membrane filtrate can be reduced. On the other hand, the membrane filtrate treated in the first treatment step S1 often contains a large amount of NH ₄ —N, but in the second treatment step S 2, NH ₄ —N is partially nitrified to form NH ₄ —N. it can be converted to about a half of the the _NO 2 -N. In the second treatment step S2, N ₂ is generated from NH ₄ —N and NO ₂ —N by anammox bacteria. The organic wastewater treatment method according to this embodiment reduces the amount of air used in partial nitritation to about half compared to the reaction in which the total amount of NH ₄ —N in conventional activated sludge process is nitrified to NO ₂ —N. it can. Therefore, in the present embodiment, the aeration power, the amount of electricity and the like necessary for nitrifying NH ₄ —N to NO ₂ —N can be reduced to about half. That is, according to the organic wastewater treatment method according to the present embodiment, the energy consumption can be reduced. Further, as described above, since the membrane filtrate treated in the first treatment step S1 contains almost no organic matter or suspended solids, the denitrifying bacteria that are heterotrophic bacteria in the second treatment step S2 also have these. And the amount of surplus activated sludge generated can be reduced.

  Next, the effect of the present invention will be specifically described by comparing an example that satisfies the requirements of the present invention with a comparative example that is not.

[Example 1]
Sewage was treated using the organic waste water treatment apparatus 1 having the configuration shown in FIG. As shown in FIG. 2, the organic waste water treatment apparatus 1 uses a membrane separation methane fermentation tank as the first treatment means 20, and a single tank anammox tank 31 (hereinafter simply referred to as “anammox tank 31) as the second treatment means 30. ") Was used. Specifically, a submerged anaerobic MBR (integrated type) 21 (hereinafter simply referred to as “anaerobic MBR21”) was used as the membrane separation methane fermentation tank. A flow rate adjusting tank 10 is provided in front of the anaerobic MBR 21 via a pump P1 for transferring sewage. In the flow control tank 10, an excessive amount of sewage was pumped from a sand basin (not shown) and overflowed at all times, so that fresh sewage was always supplied to the anaerobic MBR 21.
The quality of the organic waste water supplied from the flow rate adjusting tank 10 to the anaerobic MBR 21 is as follows. Here, SS represents the amount of suspended solids, COD _cr represents the oxygen demand by potassium dichromate, BOD represents the biochemical oxygen demand, TN represents the total nitrogen content, TP Represents the total amount of phosphorus.

<Water quality of sewage>
-PH: 7.1-7.8 (average 7.4)
SS: 150-310 mg / L (average 200 mg / L)
COD _cr : 310-510 mg / L (average 400 mg / L)
-BOD: 110-250 mg / L (average 165 mg / L)
-TN: 25-50 mg / L (average 35 mg / L)
TP: 2.0 to 6.5 mg / L (average 4.0 mg / L)

The anaerobic MBR 21 is provided with a CO ₂ removal device in which water is put in a container of a predetermined size as the third processing means 25 in order to remove the generated CO ₂ . This CO ₂ removal device is connected to a membrane cleaning blower B1 that cleans the membrane of the anaerobic MBR 21, and gas is supplied to the anaerobic MBR 21, the membrane cleaning blower B1, and the CO ₂ removal device by the air feeding force of the membrane cleaning blower B1. It can be circulated. The CO ₂ removal device was activated to remove CO ₂ when the pH of sewage or sludge in the anaerobic MBR 21 was 6.5 or less.

In addition, an anaerobic treatment water tank 23 was provided between the anaerobic MBR 21 and the anammox tank 31 via a membrane filtration pump P4 for transferring the membrane filtrate. Membrane filtrate was temporarily stored in this anaerobic water tank 23, and the amount of the membrane filtrate water flowing into the anammox tank 31 was adjusted using the pump P5.
The anaerobic MBR 21 and the anammox tank 31 were each treated at 25 ° C. by passing 25 ° C. warm water through the jacket.

In anaerobic MBR21, the digested sludge of an existing anaerobic digester that anaerobically digests sewage sludge was added as seed sludge so that the MLSS (active sludge suspended solids) concentration was 5000 mg / L. And the supply amount of the sewage supplied to anaerobic MBR21 was increased in steps.
The anammox tank 31 was previously supplied with artificial waste water containing 250 mg N / L (N indicates nitrogen content) as a single nitrogen source at a NH ₄ -N concentration. By doing so, aerobic ammonia-oxidizing bacteria are attached to the outer surface of the carrier 32 made of polypropylene resin (hollow cylinder having an inner diameter of about 5 mm and a length of about 5 mm), and anammox bacteria are attached to the inner surface. I let you.

  The carrier 32 thus obtained was introduced at a volume ratio of 15% with respect to the volume of the anammox tank 31, and the supply amount of membrane filtrate treated with the anaerobic MBR 21 was increased stepwise.

Anaerobic MBR21 has an effective liquid capacity of 20 L, and ^two hollow fiber membrane elements (membrane module 22) made of PVDF having a membrane surface area of 0.07 m ² / sheet are held in a state of being immersed in the liquid in the tank. Yes. The liquid in the tank is sucked by the membrane filtration pump P4 and filtered by the hollow fiber membrane element. The hollow fiber membrane element is configured so that anaerobic MBR21 gas is aerated from below. This prevented sludge from adhering to the membrane surface of the hollow fiber membrane element.

  The anammox tank 31 had an effective liquid capacity of 6.7 L, and was subjected to air aeration so that the dissolved oxygen concentration was 0.3 ppm or less.

The amount of sewage treatment starts from 20L / day, the BOD removal rate in anaerobic MBR21 (BOD concentration of membrane filtrate filtered with anaerobic MBR21), the BOD concentration of treated water treated in anammox tank 31, and TN Concentration and NH ₄ -N concentration were measured and the amount of sewage treatment was increased step by step while confirming.

The final treatment conditions were a sewage treatment rate of 80 L / day, an anaerobic MBR residence time of 6 hours, an anammox tank residence time of 2 hours (retention time of the entire apparatus of 8 hours), and a treatment water temperature of 25 ° C.
As a result, the quality of the membrane filtered water filtered by the anaerobic MBR 21 and the quality of the treated water treated by the anammox tank 31 were as follows. Incidentally, the water quality was measured SS, BOD, T-N, a _NH 4 -N.

The sludge concentration (MLSS) in the anaerobic MBR 21 treated under the above-described final treatment conditions was 8000 to 10,000 mg / L. The amount of biogas generated from anaerobic MBR21 was 6.08 L / day (from 6.08 L / 80 L-sewage, 76 L / m ³ -sewage), and the CH ₄ concentration in the biogas was 60%. That is, the amount of CH ₄ gas generated from the anaerobic MBR 21 was 3.65 L / day (from 3.65 L / 80 L-sewage, 45.6 L / m ³ -sewage). Note that when the CO ₂ removal apparatus was operated, the CH ₄ concentration in the biogas was 80% or more.

In the conventional nitrification denitrification method, which is a conventional sewage treatment method, the BOD of treated water is treated at <10 mg / L and TN at <10 mg / L by treating in a large reaction tank with a residence time of 14 to 18 hours. It was.
On the other hand, in Example 1, in the reaction tank having a residence time of 8 hours (about half of the conventional method), the treated water having a water quality superior to that of the conventional method (BOD of treated water is <5 mg / L, T- N was <10 mg / L).

  In the conventional method, biogas can be obtained only by collecting generated sludge and providing an anaerobic digester for sludge treatment. In Example 1, an anaerobic digester for treating sludge is provided. It was confirmed that biogas can be obtained without it.

  Furthermore, in the conventional method, a large amount of surplus activated sludge was generated when the same amount of organic wastewater was treated (11400 to 12000 mg / 80 L-sewage), but in Example 1, the surplus activated sludge was generated. It was confirmed that there was little (4800 mg / 80L-sewage).

The bacteria present in the anaerobic MBR 21 and the single tank anammox tank 31 were investigated by sampling the sludge in each tank, extracting DNA from these sludges, and analyzing 16S rDNA.
In the anaerobic MBR21, the genus Methanosaeta, Methanoregula, Metahnobacterium, Methanospirillum, and Methanolinea are detected as methanogenic archaea. -7, Acidobacteria, Verrucomicrobia, Chlorobi, and Planctomycetes were detected.
Candidatus Kuenenia and Candidatus Brocadia were detected as anammox bacteria, and Nitrosomonas genus, Nitrobacter genus and Nitrospira genus were detected as ammonia oxidizing bacteria in the single tank anammox tank 31.

[Example 2]
The suspension of the food waste was processed by the organic waste water treatment apparatus 1 having the configuration shown in FIG.
In Example 2, the flow rate adjustment tank 10 (effective liquid capacity: 1 m ³ ), anaerobic MBR 21 (effective liquid capacity: 6 m ³ , MLSS: 6000 to 8000 mg / L), anammox tank 31 (effective liquid capacity: 1 m ³ ) The sedimentation basin 50 (effective liquid volume: about 100 L) was used.
In addition, although the anaerobic MBR 21 in Example 2 was provided with a stirring blade for stirring the liquid in the tank and a motor for rotating the same (none of which is shown), a CO ₂ removal device was provided. There wasn't.
In addition, the processing steps from the flow rate adjusting tank 10 to the sedimentation basin 50 were substantially maintained at a liquid temperature of 30 ° C. When heating was necessary, hot water at 50 ° C. was allowed to flow through the heat exchanger installed in each tank described above.

In Example 2, 1 m ³ / day of the suspension obtained by crushing food waste with a disposer was introduced into the flow rate adjustment tank 10. That is, in Example 2, the flow rate adjusting tank 10 was used as a tank (raw material storage tank) for storing raw materials. In the flow control tank 10, the food waste proceeded with acid fermentation during the residence time of 1 day.
The properties of the suspension of food waste in the flow rate adjusting tank 10 are as follows. Here, BOD, TN, and TP are the same as described above, TS represents total solids (evaporation residue), and VS represents volatile solids (ignition loss). VS is a substance that volatilizes when the evaporation residue is ashed at 600 ± 25 ° C. for 30 to 40 minutes, and is mainly a measure of the amount of organic substances.

<Properties of food waste suspension>
-PH: 3.8-4.5 (average 4.0)
TS: 18000 to 22000 mg / L (average 20000 mg / L)
VS: 16200-19800 mg / L (average 18000 mg / L)
・ BOD: 11700-14300mg / L (average 13000mg / L)
-TN: 600-800 mg / L (average 700 mg / L)
* TP: 69-85 mg / L (average 77 mg / L)

  The food waste slurry having undergone acid fermentation was supplied from the flow rate adjustment tank 10 to the anaerobic MBR 21 and methane fermentation was performed in the anaerobic MBR 21 for a residence time of 5 days. In addition, the sludge was extracted and maintained so that the sludge density | concentration in the tank of anaerobic MBR21 might be set to 10000-15000 mg / L.

A hollow fiber membrane element having a membrane area of 2.5 m ² is immersed in the anaerobic MBR 21. Membrane filtrate obtained by filtering the suspension of food waste subjected to methane fermentation with the hollow fiber membrane element was supplied to the anammox tank 31.
From anaerobic MBR21, 12.5 m ³ N / day of biogas having a methane concentration of about 62% and a CO ₂ concentration of about 38% was generated.
The quality of the membrane filtered water in Example 2 is as follows. Here, TS, VS, BOD, TN, NH ₄ -N, and TP are the same as described above.

<Water quality of membrane filtration water>
-PH: 7.3 to 7.7 (average 7.5)
TS: 5100-6300 mg / L (average 5700 mg / L)
VS: 3200 to 4000 mg / L (average 3600 mg / L)
-BOD: 550-750 mg / L (average 650 mg / L)
-TN: 600-700 mg / L (average 650 mg / L)
NH ₄ -N: 400 to 500 mg / L (average 450 mg / L)
-TP: 60-80 mg / L (average 70 mg / L)

  In the anammox tank 31, a polypropylene carrier 32 having an inner diameter of about 10 mm and a length of about 10 mm was introduced at a volume ratio of 15% with respect to the volume of the anammox tank 31. And the anammox tank 31 controlled the amount of aeration air so that DO might be 0.3 ppm (0.3 mg / L) or less.

  When the anammox tank 31 is treated with a residence time of 1 day, brown aerobic ammonia-oxidizing bacteria and the like propagate on the outer surface of the carrier 32, and red-brown anammox bacteria grow on the inner surface of the carrier 32. The BOD component (various organic substances) and the nitrogen component remaining in the membrane filtered water were treated.

In the anammox tank 31, the overflow water in the subsequent settling basin 50 was returned in the same supply amount as the supply amount of the membrane filtration water.
As the sedimentation basin 50, a container having a diameter of 35 cm, a straight body height of 1 m, and a capacity of about 100 L was used, and sludge flowing into the sedimentation basin 50 was settled and separated.
The water quality of the overflow water of the settling basin 50 (treated water treated by the organic waste water treatment apparatus 1 according to Example 2) is as follows. Here, SS, BOD, TN, and TP are the same as described above.

<Water quality of overflow water in sedimentation basin 50>
-PH: 7.1-7.3 (average 7.2)
SS: 10-20 mg / L (average 15 mg / L)
-BOD: 10-20 mg / L (average 15 mg / L)
-TN: 130-170 mg / L (average 150 mg / L)
-TP: 55-65 mg / L (average 60 mg / L)

  It was confirmed that the TP of the overflow water (treated water) can be reduced to 20 mg / L or less by introducing a required amount of polyaluminum chloride (PAC) into the sedimentation basin 50 as necessary.

Example 3
FIG. 5 is an explanatory diagram showing a state in which the organic waste water treatment apparatus 1 according to Example 3 is provided in an organic waste water (sewage) treatment facility according to a circulation type nitrification denitrification method which is one of activated sludge methods.
FIG. 6 is an explanatory diagram showing an outline of an organic wastewater (sewage) treatment facility according to the circulatory nitrification denitrification method as described above, and is referred to as Comparative Example 1 here.

  As shown in FIG. 6, in Comparative Example 1, the raw sludge collected in the first settling basin 602 and the surplus activated sludge collected in the final settling basin 605 are concentrated in a concentration facility 606, for example, to a solids concentration of 3 to 4%. Concentrate. Then, as described above, the concentrated raw sludge and surplus activated sludge are put into the digestion facility 607, and the organic matter in the sludge is decomposed by anaerobic bacteria at medium temperature (35 to 38 ° C) or high temperature (52 to 56 ° C). The gas is converted to digestion gas (methane gas) to reduce the volume of sludge. The surplus activated sludge and the like that have been reduced in volume are then dehydrated by the dehydration equipment 608. Since the dehydrated filtrate obtained by dehydration may contain high-concentration nitrogen components and BOD components, they may be returned to the sand basin 601 for the purpose of denitrification again. In this case, since the nitrogen concentration of the sewage to which the dehydrated filtrate is supplied becomes high, it is necessary to increase the amount of aerated air in the aerobic tank 604, and a great amount of power is required.

Therefore, as shown in FIG. 5, anaerobic MBR 21 and a path returning from the dehydration facility 608 to the sand basin 601 are removed in order to remove nitrogen components and BOD components contained in the dehydrated filtrate and reduce the load on water treatment. An organic wastewater treatment apparatus 1 having an anammox tank 31 is provided as Example 3 and tested. The anaerobic MBR 21 and the anammox tank 31 according to Example 3 were each treated at 30 ° C. by passing warm water of 30 ° C. through the jacket. The water quality of the dehydrated filtrate used in the test is as follows. Here, BOD, TN, NH ₄ -N, and TP are the same as described above.

<Water quality of dehydrated filtrate>
-PH: 7.5-8.5 (average 8.0)
-BOD: 100-300 mg / L (average 200 mg / L)
-TN: 700-1000 mg / L (average 800 mg / L)
_{· NH 4 -N: 630~900mg / L} ( mean 730 mg / L)
-TP: 50-90 mg / L (average 70 mg / L)

The effective liquid volume of the anaerobic MBR21 according to Example 3 was 40 L, and the treatment was performed with MLSS: 6000 to 8000 mg / L and residence time: 8 hours. The biogas generation amount of the anaerobic MBR21 according to Example 3 was 9 L / day (methane concentration 65%). The anaerobic MBR 21 was equipped with six microfiltration membrane (MF) elements having a membrane area of 0.07 m ² and a membrane pore diameter of 0.05 μm. The anaerobic MBR 21 circulated the gas in the head space of the anaerobic MBR 21 and bubbled from the lower part of the MF element to prevent fouling and clogging of the film. The quality of the membrane filtrate treated by anaerobic MBR21 is as follows. Here, BOD, TN, NH ₄ -N, and TP are the same as described above.

<Water quality of membrane filtration water>
-PH: 7.3 to 7.7 (average 7.5)
-BOD: 10-30 mg / L (average 20 mg / L)
-TN: 650-850 mg / L (average 760 mg / L)
_{· NH 4 -N: 600~800mg / L} ( mean 700 mg / L)
-TP: 50-70 mg / L (average 60 mg / L)

  The obtained membrane filtrate was supplied to the anammox tank 31 for processing. The effective liquid volume of the anammox tank 31 was 60 L, and the residence time was 12 hours. In the anammox tank 31, a polypropylene carrier 32 (not shown in FIG. 6) having an inner diameter of 5 mm and a length of 5 mm was introduced at a volume ratio of 15% with respect to the volume of the anammox tank 31. The carrier 32 is grown by attaching anammox bacteria and aerobic ammonia-oxidizing bacteria with synthetic ammonia wastewater (ammonia concentration 600 mg / L).

The supply amount of the dehydrated filtrate to the organic waste water treatment apparatus 1 according to Example 3 was gradually increased from 40 L / day, and finally a stable operation was performed at 120 L / day.
The anammox tank 31 was processed by controlling the amount of aerated air so that the dissolved oxygen concentration was 0.3 ppm or less.
The spilled water (treated water) from the anammox tank 31 was subjected to sedimentation separation of SS in the sedimentation basin 50, and the obtained overflow water was supplied to the sand basin 601. The quality of the overflow water obtained in this way is as follows. Here, BOD, TN, NH ₄ -N, and TP are the same as described above.

<Water quality of overflow water>
-PH: 7.1-7.5 (average 7.3)
-BOD: 5-10 mg / L (average 7 mg / L)
-TN: 150-250 mg / L (average 200 mg / L)
_{· NH 4 -N: 100~200mg / L} ( mean 150 mg / L)
TP: 40-60 mg / L (average 50 mg / L)

  As described above, by treating the dehydrated filtrate with the organic waste water treatment apparatus 1 according to Example 3, the BOD component and the nitrogen component can be efficiently removed, and the load on water treatment can be greatly reduced. Was confirmed.

Example 4
Next, the energy consumption in the organic wastewater (sewage) treatment facility (Comparative Example 2) according to the conventional circulation nitrification denitrification method, and the energy consumption in the organic wastewater treatment apparatus 1 (Example 4) according to the present invention The amount was compared. In addition, the energy consumption in Example 4 is a trial calculation assuming the case (refer to the following) which treats sewage with the processing amount comparable as the apparatus which concerns on the comparative example 2. FIG.

<Assumed throughput>
・ Sewage treatment amount: 10000 m ³ / day <assumed treatment performance>
・ BOD: 200mg / L → 20mg / L
・ SS: 200mg / L → 20mg / L
-TN: 33 mg / L → 10 mg / L

  As shown in FIG. 6, the configuration of the apparatus according to Comparative Example 2 includes a sand basin 601, an initial sedimentation basin 602, an anaerobic tank (denitrification tank) 603, an aerobic tank (nitrification tank) 604, and a final sedimentation. In addition to having a pond 605, it has a concentration facility 606, a digestion facility 607, and a dehydration facility 608. The sedimentation basin 601, the first sedimentation basin 602, the anoxic tank 603, the aerobic tank 604, and the final sedimentation basin 605 perform water treatment, and the concentration facility 606, digestion facility 607, and dehydration facility 608 perform sludge treatment. is there. The energy consumption of Comparative Example 2 is shown in Table 2.

  The configuration of the apparatus according to the fourth embodiment includes a flow rate adjusting tank 10, an anaerobic MBR 21, an anammox tank 31, and a sedimentation tank 50, and a dehydrating facility 40. The flow rate adjusting tank 10, the anaerobic MBR 21, the anammox tank 31, and the sedimentation basin 50 perform water treatment, and the dehydration facility 40 performs sludge treatment. The energy consumption of Example 4 is shown in Table 3.

As shown in Table 2, the apparatus according to Comparative Example 2 required a total amount of 4150.51 kWh / day, and the unit power consumption was 0.415 kWh / m ³ .
On the other hand, as shown in Table 3, the apparatus according to Example 4 required a total amount of power of 27773.56 kWh / day, and the unit power consumption was 0.277 kWh / m ³ .
That is, the energy consumption of the device according to Example 4 was calculated to be about 67% of the energy consumption of the device according to Comparative Example 2. Therefore, it was confirmed that the organic wastewater (sewage) treatment apparatus and the organic wastewater (sewage) treatment method according to the present invention can reduce the energy consumption as compared with the conventional method.

DESCRIPTION OF SYMBOLS 1 Organic waste water treatment apparatus 10 Flow control tank 20 1st process means 25 3rd process means 30 2nd process means 31 One tank type anammox tank (Anamox tank)
32 Carrier 40 Dehydration equipment S1 First treatment step S2 Second treatment step S3 Third treatment step

Claims (12)

A first treatment means for subjecting an organic wastewater containing organic matter and a nitrogen component to methane fermentation under anaerobic conditions and performing membrane filtration to obtain membrane filtered water;
A second treatment means for denitrifying a nitrogen component contained in the membrane filtrate by an anaerobic ammonia oxidation reaction;
An organic wastewater treatment apparatus characterized by comprising:   The organic wastewater treatment apparatus according to claim 1, wherein the first treatment means includes third treatment means for removing generated carbon dioxide.   The organic wastewater treatment apparatus according to claim 1 or 2, wherein the first treatment means is a membrane separation methane fermentation tank and the second treatment means is a single tank anammox tank.   The organic waste water treatment according to claim 3, wherein the membrane separation methane fermentation tank is a methane fermentation tank holding suspended anaerobic bacteria, or a methane fermentation tank holding anaerobic granular sludge. apparatus.   The organic drainage according to claim 3 or 4, wherein the one-tank anammox tank includes a carrier made of a hollow cylinder having an inner diameter of 3 to 30 mm and a length of 3 to 30 mm and having both ends opened. Processing equipment.   In the single tank type anammox tank charged with the carrier, the liquid in the tank is stirred by at least one of air blowing and mechanical stirring, and the dissolved oxygen concentration of the liquid in the tank is controlled to 0.5 mg / L or less. The organic waste water treatment apparatus according to claim 5. A first treatment step of subjecting an organic wastewater containing organic matter and a nitrogen component to methane fermentation under anaerobic conditions and performing membrane filtration to obtain membrane filtered water;
A second treatment step of denitrifying a nitrogen component contained in the membrane filtrate by an anaerobic ammonia oxidation reaction;
An organic wastewater treatment method comprising:   The organic wastewater treatment method according to claim 7, wherein the first treatment step includes a third treatment step of removing generated carbon dioxide.   The organic wastewater treatment method according to claim 7 or 8, wherein the first treatment step is performed in a membrane separation methane fermentation tank, and the second treatment step is performed in a one-tank anammox tank.   The organic effluent treatment according to claim 9, wherein the membrane separation methane fermentation tank is a methane fermentation tank holding suspended anaerobic bacteria or a methane fermentation tank holding anaerobic granular sludge. Method.   The organic drainage according to claim 9 or 10, wherein the one-tank anammox tank includes a carrier made of a hollow cylinder having an inner diameter of 3 to 30 mm and a length of 3 to 30 mm and having both ends opened. Processing method.   In the single tank type anammox tank charged with the carrier, the liquid in the tank is stirred by at least one of air blowing and mechanical stirring, and the dissolved oxygen concentration of the liquid in the tank is controlled to 0.5 mg / L or less. The organic waste water treatment method according to claim 11.

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