JP2019111480A - Organic wastewater treatment system and method for starting the same - Google Patents

Abstract

To provide an organic wastewater treatment system and a method for starting an organic wastewater treatment possible to improve a biogas recovery rate in an anaerobic wastewater treatment and shorten a processing start-up time.SOLUTION: An organic wastewater treatment system includes: an anaerobic reaction tank 1 having an endless channel 2 in which sludge containing methane bacteria and raw water are accommodated; a cover member 5 covering an upper opening of the endless channel 2; a finishing tank 20 for retaining water to be treated that has flowed out from the endless channel 2; a settling tank 25 which separates sludge from the water to be treated which flowed out from the finishing tank 20; a sludge return line 27 extending from the settling tank 25 to the endless channel and configured to return the sludge containing methane bacteria from the settling tank 25 to the endless channel 2; and a scum crusher 30 configured to recover scum floating on a surface of the endless channel 2, crush the recovered scum, and return the crushed scum to the endless channel 2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an organic wastewater treatment apparatus that performs methane fermentation under anaerobic conditions in a closed endless channel. The present invention also relates to a method of starting up an organic wastewater treatment apparatus.

  Methods of treating organic wastewater using microorganisms include aerobic biological treatment and anaerobic biological treatment. Among anaerobic biological treatments, methane fermentation treatment uses the metabolic reaction of anaerobic microorganisms grown in an anaerobic environment without oxygen to decompose organic matter in organic wastewater into methane gas or carbon dioxide by methane fermentation. Biological treatment method.

  The conventional organic wastewater treatment is a treatment method using microorganisms, such as activated sludge treatment under aerobic conditions and methane fermentation treatment under anaerobic conditions. Compared with activated sludge treatment, methane fermentation treatment has the advantage of generating less excess sludge and eliminating the need for electricity costs such as blowers (aeration), which has the advantage of not requiring running costs, and can effectively utilize the generated methane gas Because of its merits, it has drawn particular attention as a method for treating organic wastewater.

  Lagoon treatment is a method of treating organic wastewater over a long period with a pond of simple structure such as undigging. The lagoon treatment facility can be constructed at low cost compared to other treatment methods and is easy to maintain and manage, but it requires a large site. Therefore, lagoon treatment is not common in Japan, but it is a common treatment method in areas with large sites such as Southeast Asia.

  Lagoon treatment includes aerobic lagoon treatment, anaerobic lagoon treatment, and treatment combining these, depending on the presence or absence of oxygen utilization. Anaerobic lagoon treatment can not recover methane gas generated by the treatment because the water surface is open, and not only can not effectively use methane gas, but also releases greenhouse gas methane gas to the atmosphere. Contributing to the

  In particular, in warm regions such as Indonesia and Malaysia, palm oil squeezed waste liquid (POME; Palm Oil Mill Effluent) containing a high concentration of lipids and fatty acids from a plant that produces palm oil, the world's most-produced vegetable oil Are being discharged, and their treatment and effective use have become major issues. The conventional general POME treatment is an anaerobic lagoon treatment in which palm oil squeezed waste liquor is treated anaerobically over a long period of time in an open pond.

  In order to recover methane gas generated by anaerobic lagoon treatment, Covered lagoon treatment is developed in which the lagoon is sealed with a cover such as rubber. However, in the lagoon where the stirring device is not installed, the contact efficiency between wastewater and microorganisms such as methane-fermenting bacteria present in the lagoon is poor, and the processing stability is lacking. .

  Wastewater containing fats and oils such as POME is prone to scum during treatment. In the fully mixed anaerobic digester, the scum can be crushed by forcibly circulating the waste water through the draft tube etc. However, in the anaerobic lagoon, the scum accumulates on the water surface, making the treatment unstable or becoming a gas line. There is a defect that causes troubles such as mixing.

  Anaerobic lagoons can not retain high concentrations of methane-fermenting bacteria as compared to Upflow Anaerobic Sludge Blankets (UASB) using self-granulated granular sludge. For this reason, in order to treat low concentration waste water stably, it is necessary to make organic substance load to sludge below in a fixed value, and it was necessary to enlarge the capacity of the lagoon sufficiently.

  In addition, generally, it is said that the start of methane fermentation treatment takes a long time of about 3 to 6 months, and the start of methane fermentation treatment in a short period has been requested.

Patent No. 5372845 gazette Patent No. 3524004 gazette JP, 2009-582, A Japanese Patent Laid-Open No. 2002-273490 Patent No. 6122232 JP, 2017-18929, A JP 2004-41933 A JP, 2002-18476, A JP 10-43787 A JP-A-9-141289 JP 9-141288 A JP-A-9-108694 JP-A-9-1137 JP-A-8-155446 Japanese Patent Application Laid-Open No. 8-1184 JP, 2014-133210, A

Sludge holding means In Patent Document 1, a fixed bed is installed to hold the methane fermentation microorganism group, but not only equipment cost is required, but the fixed bed resists the water flow of the endless channel. Therefore, there is a concern that processing performance may deteriorate due to deterioration of fluidity or clogging of the fixed bed gap.
In patent document 2, solid-liquid separation using a filtration membrane is performed as a sludge holding means, and the average pore diameter of 0.1-0.5 micrometer of a filtration membrane is said to be preferable. However, although this treatment system has a very high solid-liquid separation function, not only the facility cost becomes very expensive, but also the power required for the pump operation to pass the waste liquid through the filtration membrane is also great. There is a drawback that
In Patent Document 10, solid-liquid separation is performed using a settling tank as a sludge holding means. However, the biological reaction tank is not anaerobic and is operated under aerobic conditions, and a finishing tank and a scum crusher are not provided.
In Patent Document 16, a finishing tank and a settling tank are provided as the sludge holding means. However, the methane fermenter is not an endless channel, and no scum crusher is provided.

-Stirring method In patent document 1, it does not show in particular about the stirring method of an anaerobic endless channel.
In Patent Document 3, the stirring method of the oxidation ditch, which is an aerobic endless channel, includes a propeller agitator driven outside the tank and a bottom flow velocity of 0.1 m / sec or more so that activated sludge does not precipitate in the channel. Although it is described that it is required, specific stirrer conditions are not described.
Although patent document 7 describes that the stirring apparatus of the oxidation ditch which is an aerobic non-terminated water channel is equipped with the stirring apparatus which consists of a submersible propulsion apparatus etc., it is also equipped with the aerator which aerates while stirring. .

Scum Crushing Mechanism In Patent Document 1, no scum crusher is particularly provided. Generally, in the waste water treatment including fats and oils and the like, higher fatty acids are generated as the lipids are decomposed to foam and scum is generated. The scum that has risen to the surface of the water does not come in contact with the methane-fermenting bacteria in the water, so the decomposition efficiency decreases. Furthermore, if a large amount of scum is generated, it may cause equipment failure due to the inflow to the gas line.
Patent Document 6 describes removing scum in an endless channel, but does not describe a scum crusher.
Patent Document 14 describes removal in an endless channel, but does not describe breaking up the recovered scum and returning it to the endless channel.

-Process start-up method It is generally said that start-up of methane fermentation process requires a long period of 3 to 6 months.
Although patent document 4 describes that an easily degradable raw material is introduced into the wastewater at the time of start-up of operation, there is no description about a method of starting up with only the wastewater to be treated. Moreover, although it is known that start-up can be performed in a short period by throwing seed sludge, it does not clearly describe about the conditions of a seed sludge specifically.

  The present invention has been made in view of the above-mentioned conventional problems, and the object of the present invention is to improve the recovery rate of biogas in anaerobic wastewater treatment and to reduce the time required for the treatment of organic wastewater. An apparatus and method of setting up an organic wastewater treatment.

  One aspect of the present invention is an anaerobic reaction tank having an endless channel containing sludge containing methane bacteria and raw water, a cover member for recovering biogas by covering the upper opening of the endless channel, and It is connected to an endless channel, is connected to the finishing tank which makes the to-be-processed water which flowed out from the said endless channel stay, and discharges the non-decomposed organic substance in the to-be-treated water as biogas, A settling tank for separating sludge from the treated water that has flowed out and obtaining sludge containing methane bacteria, extending from the settling tank to the endless channel, and returning sludge containing methane bacteria from the settling tank to the endless channel Sludge returning means, and a scum crusher for recovering scum floating on the surface of the endless channel, shredding the recovered scum, and returning the crushed scum to the endless channel It is organic waste water treatment apparatus according to claim.

In a preferred aspect of the present invention, the scum crusher comprises: a scum recovery device disposed on a water surface of the endless water channel; a scum storage tank for storing scum recovered by the scum recovery device; And a scum return line extending from the scum reservoir to the endless water channel, the scum pump being connected to the scum return line.
A preferred embodiment of the present invention is characterized by further comprising a cover member for recovering biogas by covering the upper opening of the finishing tank.
The preferable aspect of this invention is characterized by further having piping and a blower which introduce | transduce the biogas produced | generated with the said endless channel and the said finishing tank to a power generator.
A preferred embodiment of the present invention further comprises a plurality of agitators disposed in the endless channel and circulating the raw water in the endless channel, and the total required power of the plurality of agitators corresponds to that of the endless channel. The stirring power obtained by dividing by volume is characterized by being 0.1 W / m ³ or more and 10 W / m ³ or less.

  One embodiment of the present invention is the above-mentioned organic wastewater treatment apparatus, wherein seed sludge containing activated methane fermentation bacteria obtained from an anaerobic reaction tank other than the above-mentioned endless channel is fed into the above-mentioned endless channel A method of setting up an organic waste water treatment apparatus characterized by:

The organic waste water treatment apparatus according to the present invention can improve the biogas recovery rate by combining the finishing tank and the scum crushing apparatus with the anaerobic reaction tank.
In the method for starting up the organic waste water treatment apparatus according to the present invention, seed sludge containing activated methane fermentation bacteria obtained from an anaerobic reaction tank separate from the endless water channel is introduced into the endless water channel. This makes it possible to shorten the start-up time.

It is a top view which shows typically one embodiment of the organic waste water treatment equipment of the present invention. It is a schematic diagram of an organic wastewater treatment device. It is a figure which shows the shape of a round endless channel. It is a figure which shows the shape of a rectangular endless channel. It is a figure which shows the shape of a return type | mold endless water channel. It is a figure which shows a water stirrer. It is sectional drawing of the trough as a scum collection | recovery apparatus. FIG. 7 illustrates an embodiment in which the finishing tank is configured integral with the non-terminating water channel. FIG. 7 shows another embodiment in which the finishing tank is configured integrally with the endless channel. It is a table | surface which shows the experimental result implemented on various conditions. It is a table | surface which shows the experimental result which investigated the relationship between the stirring power of a water stirrer and the flow velocity of raw water. It is a figure which shows a time-dependent change of biogas integrated generation amount.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a plan view schematically showing an embodiment of the organic waste water treatment apparatus of the present invention, and FIG. 2 is a schematic view of the organic waste water treatment apparatus. The present invention can be applied to anaerobic treatment in all temperature ranges such as mesophilic methane fermentation treatment with 30 ° C to 40 ° C as optimum temperature and high temperature methane fermentation treatment with 50 ° C to 60 ° C as optimum temperature it can.

  As shown in FIG. 1 and FIG. 2, the organic waste water treatment apparatus according to the present invention comprises an anaerobic reaction tank 1, a finishing tank 20, and a settling tank having an endless channel 2 in which sludge containing methane bacteria and raw water are stored. 25 and a scum crusher 30 are provided as main components. The endless channel 2 of the present embodiment is a track channel having an oval shape. The upper opening of the endless channel 2 is covered with a cover member 5 for recovering biogas, and a closed endless channel 2 is formed in the anaerobic reaction tank 1. The top opening of the finishing tank 20 is also covered by the covering member 40. The covering members 5 and 40 are, for example, high density polyethylene sheets. The biogas (methane gas) generated from the endless water channel 2 and the finishing tank 20 is collected by the cover members 5 and 40 and transferred to the blower B through the pipes 44 and 45. The blower B transfers the biogas to the desulfurizer 7 through the pipe 46 and further to the power generator 8 through the pipe 47. The biogas is used as a fuel for the power generation device 8.

  Raw water is supplied into the anaerobic reaction tank 1 through the inflow line 10. Raw water to be treated is an organic wastewater containing components that can be decomposed by methanogens. Examples of organic wastewater include wastewater discharged when producing agricultural products such as POME. The raw water may contain solids, but since inorganic substances with high specific gravity such as sand and silt accumulate in the endless channel 2, it is preferable not to allow inorganic substances with high specific gravity to flow into the endless channel 2.

  The endless channel 2 includes a sidewall 2a formed by a circumferential circuit including two straight portions and two curved portions connecting them, and a center wall 2b surrounded by the sidewalls 2a. The material, size, and depth of the endless channel 2 are not particularly limited. For example, the endless channel 2 may be formed of concrete, or an impermeable sheet may be coated on the green channel.

  A curved guide wall 2 c is installed in the flow path of the endless channel 2. The material of the guide wall 2c is not particularly limited. For example, the guide wall 2c may be made of the same concrete as the endless channel 2, or may be made of plastic or metal. The installation position of the guide wall 2c is installed so that the straightening effect of the endless channel 2 is generated. When the endless channel 2 has a track shape, it is effective to install along the curved portion of the sidewall 2a. The endless channel 2 of this embodiment is a track type, but may have any shape as long as it forms a circulating channel, for example, a circle shown in FIG. 3, a rectangle shown in FIG. It may be a folded type as shown in FIG.

As shown in FIGS. 1 and 2, the organic wastewater treatment apparatus includes a plurality of agitators 12 disposed in the endless channel 2. The agitator 12 has a motive power capable of securing a raw water flow velocity of 0.1 m / sec or more at the bottom of the non-terminated water channel 2. The stirring power per unit water volume of the endless channel 2 is 0.1 W / m ³ or more and 10 W / m ³ or less. The stirring power can be obtained by dividing the sum of the required powers of the plurality of agitators 12 by the volume of the endless channel 2.

  FIG. 6 is a schematic view showing the stirrer 12. In the present embodiment, the stirrer 12 includes a stirring impeller 12a and an electric motor 12b for rotating the stirring impeller 12a. The agitator 12 is attached to a guide rail 14 extending in the vertical direction, and can move up and down along the guide rail 14. By installing such a guide rail 14, it is possible to easily check and manage the stirrer 12 from the maintenance bridge 15 provided on the upper end of the non-terminated water channel 2.

  As shown in FIG. 1 and FIG. 2, the organic wastewater treatment system comprises a finishing tank 20 connected to the endless channel 2 via a first transfer line 17 and a finishing tank 20 via a second transfer line 22. It further comprises a connected settling tank 25 and a sludge return line (sludge return means) 27 extending from the settling tank 25 to the endless channel 2. Raw water, which is organic wastewater supplied through the inflow line 10, circulates in the endless channel 2 and is methane-fermented by the microorganisms retained in the endless channel 2. The treated water containing the microorganisms is transferred to the finishing tank 20 through the first transfer line 17 and retained for a certain period of time. Further, the water to be treated is sent from the finishing tank 20 to the settling tank 25 through the second transfer line 22. The sludge in the water to be treated precipitates in the settling tank 25. A portion of the sludge containing microorganisms is returned to the endless water passage 2 through the sludge return line 27 by a sludge return pump 29 disposed in the settling tank 25.

Agitation power In the aerobic condition oxidation ditch, since air is blown in using a blower such as a diffuser for supplying oxygen, it is possible to stir by a strong upflow with air.
On the other hand, in methane fermentation which is an anaerobic condition, the agitation by the upflow of the methane gas generated by the decomposition of the organic matter is weaker in the entire water channel as compared with the air agitation in the oxidation ditch. Therefore, it is necessary to eliminate stagnation by flowing raw water horizontally (downward direction) in the water channel with an appropriate stirring power. Moreover, it becomes possible to send a scum to a scum crushing apparatus, without making the scum produced | generated by making it flow into a downflow direction accumulate | store in the anaerobic reaction tank.

Scum Crusher Two anaerobic scum crushers 30 are provided in the anaerobic reaction tank 1. Each scum crusher 30 includes a trough 31 as a scum recovery device for collecting scum that is floating on the surface of the endless water channel 2, a scum storage tank 33 for storing scum, and a scum pump disposed in the scum storage tank 33. A scum transfer line 38 connecting the trough 31 and the scum storage tank 33 and a scum return line 39 connecting the scum storage tank 33 and the anaerobic reaction tank 1 are provided. The trough 31 is disposed at substantially the same height as the water surface in the endless channel 2 and is disposed to cross the endless channel 2. In the embodiment shown in FIG. 1, two scum crushers 30 are provided, but only one scum crusher 30 may be provided.

  FIG. 7 is a cross-sectional view of the trough 31. The scum floating on the surface of the raw water flowing through the endless water channel 2 flows into the trough 31 and is transferred to the scum storage tank 33 through the scum transfer line 38. The scum is stored in the scum storage tank 33. As shown in FIG. 2, a scum pump 36 is disposed in the scum storage tank 33, and the scum pump 36 is connected to a scum return line 39.

Generally, scum consists of higher fatty acids produced in the process of decomposition of lipids contained in raw water. This scum comes to the surface of the water by holding fine bubbles of biogas generated in the process of methane fermentation inside.
The scum floating on the surface of the endless channel is collected by the trough 31, and the collected scum is temporarily stored in the scum storage tank 33. The scum in the scum storage tank 33 is sucked into the scum pump 36 and broken by passing through the scum pump 36. The crushed scum is returned to the endless water channel 2 through the scum return line 39 by the scum pump 36. Thus, by returning the scum in the scum storage tank 33 to the endless water channel 2 while crushing the scum in the scum pump 36, the fine air bubbles contained in the scum are separated, and the scum is dissolved in the raw water in the endless water channel 2. It can be done. As a result, the contact between the methane fermenting bacteria in the raw water and the scum is improved, the decomposition of the scum proceeds, and the amount of biogas generation can be increased.

-Finishing tank The finishing tank 20 is disposed between the endless channel 2 and the settling tank 25. The water to be treated that has flowed out of the endless water channel 2 is transferred to the finishing tank 20 and further transferred to the settling tank 25. If the residence time of the treated water in the finishing tank 20 is too short, biogas recovery in the finishing tank 20 becomes insufficient, and the recovery rate of biogas decreases, and sludge due to biogas generation in the subsequent settling tank 25 Ascension takes place. On the other hand, when the residence time of the water to be treated in the finishing tank 20 is too long, it becomes an excessive facility. Therefore, the residence time of the water to be treated in the finishing tank 20 is preferably 2 hours or more and 24 hours or less, and more preferably 4 hours or more and 12 hours or less.

  The structure of the finishing tank 20 is not particularly limited as long as an effective residence time is secured, and may be a complete mixing type equipped with a stirrer, or a water channel type not equipped with a stirrer. As shown in FIG. 2, the biogas recovery rate can be improved by covering the finishing tank 20 with the covering member 40 in the same manner as the endless channel 2, but the covering member 40 can be omitted.

  The finishing tank 20 is disposed apart from the endless channel 2 and connected to the endless channel 2 by a first transfer line 17. In one embodiment, as shown in FIG. 8, the finishing tank 20 may be configured integrally with the endless channel 2. In the embodiment shown in FIG. 8, the finishing tank 20 is in contact with the endless channel 2 and the first transfer line 17 is not provided. An opening 41 is formed in the side wall 2 a constituting the non-terminated water channel 2, and the finishing tank 20 communicates with the non-terminated water channel 2 via the opening 41. As shown in FIG. 9, in place of the opening 41, the overflow portion 42 may be formed in the sidewall 2 a that constitutes the endless channel 2. The overflow portion 42 is, for example, a recess formed at the upper end of the sidewall 2 a.

  When the scum flows into the finishing tank 20, the gas separation property is deteriorated, so it is necessary not to flow the scum into the finishing tank 20. Therefore, the first transfer line 17 (see FIG. 2) and the opening 41 (see FIG. 8) are provided below the water surface of the endless water channel 2 so that the scum does not flow into the finishing tank 20. In the embodiment of FIG. 9 in which the water to be treated overflows from the endless channel 2, the finishing tank 20 is disposed at a position where no scum exists in the endless channel 2. As a position where there is no scum in the endless channel 2, a region downstream of the trough 31 which is a scum recovery device, specifically, a region within 25% of the circumferential length of the endless channel 2 from the trough 31 can be mentioned.

The water to be treated which has flowed out of the endless water channel 2 contains dissolved methane, and a certain percentage of undegraded organic matter remains. Therefore, by holding the water to be treated in the finishing tank 20, it is possible to release and recover the undegraded organic substance as biogas.
Moreover, by letting the water to be treated flow into the settling tank 25 after releasing the biogas, it is possible to suppress the sludge floating and improve the sedimentation.

  If scum crushing is not performed, scum will be generated in the finishing tank and settling tank installed at the rear stage of the endless channel, and the water surface of the finishing tank will be covered to lower the residual gas recovery rate or solid / liquid in the sedimentation tank. A separation failure occurs. On the other hand, according to the present embodiment in which the scum crusher 30 is installed, the organic matter contained in the scum can be returned to the endless channel 2 and can be disassembled in the endless channel 2. Since there is no inflow of scum into the finishing tank 20, it is possible to suppress the sludge floating in the settling tank 25.

The settling tank 25 may be rectangular or circular, and may be of any shape as long as the sludge can be separated from the water. In order to improve the sludge separation, it is desirable to install a comb-like picket fence (not shown) in the settling tank 25. When the settling tank 25 is circular, the sludge separation can be improved by rotating the picket fence. The picket fence may be fixed to the settling tank 25 if it is a lateral flow settling tank 25.

・ Stable, high-load treatment by sludge return By combining the non-stop water channel 2 and the settling tank 25, it is possible to increase the sludge concentration in the non-flow channel 2 and higher-load processing becomes possible, making the device compact Can be
Furthermore, by providing the finishing tank 20 between the endless channel 2 and the settling tank 25, not only the solid-liquid separation performance can be improved, but also the biogas recovery rate can be improved.

  The sludge containing methane bacteria collected in the settling tank 25 is returned to the endless channel 2 through the sludge return line 27 by the sludge return pump 29 installed in the settling tank 25. The return amount of the sludge is set in accordance with the target value of the sludge concentration in the endless channel 2. As a result, the endless channel 2 can maintain the necessary sludge load by holding sufficient methane bacteria, and stable operation becomes possible. In particular, when the organic matter concentration of the raw water is low, the sludge load can be maintained even if the hydraulic retention time (HRT) is shortened, so that the organic wastewater treatment apparatus can be miniaturized.

-Starting method of organic waste water treatment The solid matter concentration (TS; Total Sludge) in the endless channel 2 is 0.5% or more and 5% or less for seed sludge collected from other lagoons already installed It injects into the endless water channel 2 so that it may become. The solid concentration TS is preferably measured by an official method, but an analysis result using an infrared moisture meter may be used.
Seed sludge is preferably sludge collected from an anaerobic lagoon, and more preferably sludge collected from an existing anaerobic lagoon that processes the same raw water.
Seed sludge is collected in the area corresponding to 5 to 40 days by HRT in the flow-down direction from the raw water input of the anaerobic lagoon. If the HRT is less than 5 days, the percentage of undegraded organic matter contained in the sludge is high, and if the HRT exceeds 40 days, the amount of non-activated sludge is large. In the sludge collected in the area of 5 to 40 days by HRT, methane fermenting bacteria necessary for the anaerobic reaction are retained in a highly active state.

・ Reduction of the start-up period The sludge accumulated in the existing anaerobic lagoon that is processing raw water is collected from an appropriate position and fed as seed sludge to the non-terminal water channel newly installed. It becomes possible to complete the start-up operation which requires ~ 6 months in 45 days or less.
Here, the start-up operation refers to the operation until the design condition is reached or the operation until all the raw water is received.
In addition, as a method of operation management at start-up, the methane concentration in biogas is measured, and load adjustment is performed so that the methane concentration is maintained at 60% or more. The load is an organic substance load, and is calculated by multiplying the concentration of the organic substance in the raw water by the flow rate of the raw water. The load adjustment described above is performed by adjusting the flow rate of the raw water flowing into the endless water channel 2. If it is difficult to measure the methane concentration, load adjustment is performed so that the carbon dioxide concentration in the biogas is maintained at 40% or less based on the composition of the biogas becoming almost 100% of methane and carbon dioxide. May be

  If an overload state occurs during startup, low-molecular volatile organic acids (VFA; volatile fatty acid) such as acetic acid and propionic acid may remain in the endless water channel 2. Since the HRT of the endless channel 2 is more than a few dozen days, and the load amount is small particularly at the start-up, the HRT may reach several tens of days. For this reason, even if the organic matter derived from the raw water remains, it is diluted in the endless channel 2, so it takes a considerable time for the water quality change such as pH drop or VFA residue to appear.

  On the other hand, when VFA remains, there is a characteristic that the concentration of methane in biogas decreases and the concentration of carbon dioxide increases. The residence time of the biogas collected in the covering member 5 covering the upper opening of the endless water channel 2 is about several hours to one day. Therefore, it is possible to detect change of methane concentration in biogas promptly compared with change of water quality. Furthermore, by installing a small volume gas trap for gas detection on the water surface of the endless channel 2, it is also possible to detect a more rapid change in methane concentration.

Examples of the present invention will be specifically described below with reference to the table shown in FIG. 10, but the present invention is not limited by these examples.
In the following comparative examples and examples, POME with COD _Cr (oxygen demand by potassium dichromate; Chemical Oxygen Demand) of about 75,000 mg / L was used as raw water. POME was naturally cooled to 40 to 50 ° C. so that the water temperature in the reaction vessel became a condition suitable for mesophilic methane fermentation, and then charged into the reaction vessel. The flow rate of raw water flowing into the reactor starts from 160m ³ / day, and every five days 240m ³ / day, 320m ³ / day, 400m ³ / day, 480m ³ / day, 560m ³ / day, and finally designed It was 635 m ³ / day on the 31st day of the condition.

Comparative Example 1
The reaction vessel used in Comparative Example 1 was an anaerobic lagoon without a cover member generally prevailing. The reactor volume was 32,000 m ³ and the hydraulic retention time at design conditions was 50 days. The construction cost is low because the structure is similar to bare digging, but the generated biogas is released to the atmosphere and energy recovery is not performed.
The scum crusher, finishing tank and settling tank were not installed.
Seed sludge is sludge collected from the entire surface of another anaerobic lagoon, and the seed sludge was introduced into the reaction tank so that the solid concentration in the reaction tank became 1%.
The average COD _Cr removal rate from the 31st day to the 45th day when the raw water flowed under design conditions was 55%. A scum had surfaced over the entire surface of the reaction tank.

Comparative Example 2
The reaction vessel used in Comparative Example 2 was a 12,000 m ³ track-type endless channel. The top opening of the endless channel was covered with a cover for biogas recovery and methane fermentation was performed under anaerobic conditions. A plurality of low power agitators were installed in the endless channel to circulate the raw water in the endless channel. The stirring power obtained by dividing the sum of the required powers of the plurality of low power stirrers by the volume of the non-terminated water channel was 5 W / m ³ .
No scum crusher and finishing tank were installed.
The effluent water from the endless channel was sent directly to the settling tank, the sludge was separated from the water in the settling tank, and part of the separated sludge was returned to the endless channel.
Seed sludge is sludge collected from the entire surface of another existing anaerobic lagoon, and the seed sludge was introduced into the endless channel so that the solid concentration in the endless channel 2 was 2%.
The average COD _Cr removal rate from day 31 to day 45 when raw water was introduced under design conditions was 72%. The methane recovery per removed COD _Cr was 85%. A scum had floated on the entire surface of the endless channel 2.

Example 1
The reaction vessel used in Example 1 was a 12,000 m ³ track-type endless channel 2 shown in FIGS. 1 and 2. The upper opening of the endless channel 2 was covered with a cover member 5 for biogas recovery, and methane fermentation was performed under anaerobic conditions. A plurality of low power agitators 12 were installed in the endless channel, and the raw water was circulated in the endless channel 2. The stirring power of the plurality of stirrers 12 was 5 W / m ³ .
A trough 31 as a scum recovery device is provided on the water surface of the endless channel 2, and the recovered scum is guided to the scum storage tank 33, crushed by the scum pump 36, and returned to the endless channel 2.
The finishing tank 20 was not provided, and the effluent water from the endless channel 2 was sent directly to the settling tank 25. The sludge was separated from the water in a settling tank, and a part of the separated sludge was returned to the endless channel 2.
Seed sludge is sludge collected from the entire surface of another existing anaerobic lagoon, and the seed sludge was introduced into the endless channel 2 so that the solid concentration in the endless channel 2 was 2%.
The average COD _Cr removal rate from the 31st day to the 45th day when raw water was introduced under design conditions was 81%. The methane recovery per removed COD _Cr was 92%. No scum was found on the surface of the endless channel 2.

Example 2
In Example 2, the organic waste water treatment apparatus shown in FIGS. 1 and 2 was used. The reaction vessel used in Example 2 was a 12,000 m ³ track-type endless channel 2 shown in FIGS. 1 and 2.
The upper opening of the endless channel 2 was covered with a cover member 5 for biogas recovery, and methane fermentation was performed under anaerobic conditions. A plurality of low power agitators 12 were installed in the endless channel, and the raw water was circulated in the endless channel 2. The stirring power of the plurality of stirrers 12 was 5 W / m ³ .
A trough 31 as a scum recovery device is provided on the water surface of the endless channel 2, and the recovered scum is guided to the scum storage tank 33, crushed by the scum pump 36, and returned to the endless channel 2.
Effluent water from the endless channel 2 was sent to the settling tank 25 via the finishing tank 20. The volume of the finishing tank 20 was 100 m ³ , and the retention time of water in the finishing tank 20 was 4 hours. The sludge was separated from the water in the settling tank 25, and a part of the separated sludge was returned to the endless channel 2.
Seed sludge is sludge collected from the entire surface of another existing anaerobic lagoon, and the seed sludge was introduced into the endless channel 2 so that the solid concentration in the endless channel 2 was 2%.
The average COD _Cr removal rate was 85% from day 31 to day 45 when raw water was introduced under design conditions. The methane recovery per removed COD _Cr was 99%. No scum was found on the surface of the endless channel 2.

Example 3
In Example 3, the organic waste water treatment apparatus shown in FIGS. 1 and 2 was used. The reaction vessel used in Example 2 was a 12,000 m ³ track-type endless channel 2 shown in FIGS. 1 and 2.
The upper opening of the endless channel 2 was covered with a cover member 5 for biogas recovery, and methane fermentation was performed under anaerobic conditions. A plurality of low power agitators 12 were installed in the endless channel, and the raw water was circulated in the endless channel 2. The stirring power of the plurality of stirrers 12 was 5 W / m ³ .
A trough 31 as a scum recovery device is provided on the water surface of the endless channel 2, and the recovered scum is guided to the scum storage tank 33, crushed by the scum pump 36, and returned to the endless channel 2.
Effluent water from the endless channel 2 was sent to the settling tank 25 via the finishing tank 20. The capacity of the finishing tank 20 was 150 m ³ , and the retention time of water in the finishing tank 20 was 6 hours. The sludge was separated from the water in the settling tank 25, and a part of the separated sludge was returned to the endless channel 2.
Seed sludge is sludge collected from the area equivalent to 10 to 30 days by HRT of other existing anaerobic lagoons, and no seed sludge is used so that the solid concentration in the endless channel 2 is 2%. The water was introduced into the end channel 2.
The average COD _Cr removal rate from day 31 to day 45 when raw water was introduced under design conditions was 90%. The methane recovery per removed COD _Cr was 99%. No scum was found on the surface of the endless channel 2.

Flow Evaluation for Stirring Power FIG. 11 is a table showing the results of an experiment in which the relationship between the stirring power of the water stirrer 12 and the flow rate of the raw water was investigated using the organic waste water treatment apparatus of FIG. 1 and FIG. In this experiment, the flow velocity of the raw water at the bottom of the endless water channel 2 was measured while changing the stirring power of the water stirrer 12, and the flow condition of the water was observed visually. The stirring power of the water stirrer 12 was converted from the rotation speed of the water stirrer 12.

At a stirring power of 0.05 W / m ³ , the flow velocity measured at a position 0.1 m above the bottom of the endless channel 2 was 0.06 m / s. According to the “Sewerage Facility Planning and Design Guidelines and Comments” (Japan Sewerage Association), the bottom flow velocity to control sludge deposition in the oxidation ditch is 0.1 m / s. Since the flow velocity 0.06 m / s is lower than 0.1 m / s, stagnation occurs in the curved portion of the endless channel 2 and there is a risk of sludge accumulation.

When the stirring power was 0.1 W / m ³ or more and 10 W / m ³ or less, the bottom flow rate was 0.1 m / s or more, and the flow condition by visual observation was also good. On the other hand, at the stirring power of 15 W / m ³ , wave was generated on the water surface, and although the flow was good, it was judged that the stirring power was excessive.

-Example of operation control method at the time of start-up The volatile organic acid (VFA) in the water to be treated is measured at the start-up of the organic waste water treatment apparatus of FIG. 1 and FIG. The methane concentration of the biogas collected from the sample valve installed in the member 5 was measured. The POME input amount is made constant when the control standard of the treatment is deviated, and the number of days until recovery to a methane concentration of 60% or more in biogas is shown in the table of FIG.
Recovery took 18 days when VFA in the treated water exceeded 500 mg / L. When the concentration of biogas methane was less than 55%, the recovery period was 12 days. When the biogas methane concentration was less than 58%, the recovery time was 5 days. When the concentration of biogas methane was less than 60%, the recovery period was 3 days.

-Example of HRT of finishing tank 800 mL of effluent water from the endless channel 2 was put in a plastic bottle, and the plastic bottle was immersed in a 35 ° C constant temperature water tank to confirm the time-dependent change of the biogas integrated generation amount. The generation of biogas was confirmed immediately after the start, and after 12 hours, the slope of the integrated amount of biogas generation decreased, and hardly generated after 24 hours.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and, of course, may be implemented in various different forms within the scope of the technical idea thereof.

DESCRIPTION OF SYMBOLS 1 Anaerobic reaction tank 2 Endless water channel 2a Side wall 2b Center wall 2c Guide wall 5 Cover member 7 Desulfurization device 8 Power generation device 10 Inflow line 12 Stirrer 12a Agitating impeller 12b Electric motor 14 Guide rail 15 Maintenance bridge 17 1st transfer line 20 finishing tank 22 second transfer line 25 settling tank 27 sludge return line (sludge return means)
29 Sludge return pump 30 Scum crusher 31 Trough (scum recovery device)
33 scum reservoir 36 scum pump 38 scum transfer line 39 scum return line 40 cover member 41 opening 42 overflow section

Claims (6)

Anaerobic reaction tank having an endless channel in which sludge containing methane bacteria and raw water are stored,
A cover member for recovering biogas by covering the upper opening of the endless channel;
A finishing tank connected to the endless channel and retaining the treated water flowing out from the endless channel and releasing undegraded organic matter in the treated water as biogas;
A settling tank connected to the finishing tank to separate sludge from the water to be treated which has flowed out of the finishing tank, to obtain sludge containing methane bacteria;
Sludge return means extending from the settling tank to the endless channel and returning sludge containing methane bacteria from the settling tank to the endless channel;
A scum crushing apparatus for collecting scum floating on the water surface of the endless channel, crushing the recovered scum, and returning the crushed scum to the endless channel;
An organic wastewater treatment apparatus comprising: The organic wastewater treatment apparatus according to claim 1,
The scum crusher includes the scum recovery device disposed on the surface of the endless channel, a scum storage tank for storing the scum recovered by the scum recovery device, and the scum in the scum reservoir by suctioning the scum. An organic wastewater treatment apparatus comprising: a scum pump for crushing scum; and a scum return line extending from the scum storage tank to the endless water channel, wherein the scum pump is connected to the scum return line. The organic waste water treatment apparatus according to claim 1 or 2
An organic wastewater treatment apparatus, further comprising a cover member for recovering biogas by covering an upper opening of the finishing tank. In the organic waste water treatment apparatus according to the third aspect,
An organic wastewater treatment apparatus, further comprising a pipe and a blower for introducing the biogas generated in the endless water channel and the finishing tank into a power generation apparatus. The organic wastewater treatment apparatus according to claim 1,
The system further comprises a plurality of agitators installed in the endless channel and circulating the raw water in the endless channel,
The organic wastewater characterized in that the stirring power obtained by dividing the sum of the required powers of the plurality of stirrers by the volume of the endless channel is 0.1 W / m ³ or more and 10 W / m ³ or less Processing unit. The organic wastewater treatment apparatus according to claim 1, wherein
A method for setting up an organic wastewater treatment apparatus, comprising: feeding seed sludge containing activated methane fermentation bacteria obtained from an anaerobic reaction tank different from the non-terminated water channel into the non-terminated water channel.

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