JP6327306B2 - Membrane separation methane fermentation treatment apparatus and membrane separation methane fermentation treatment method - Google Patents

Description

  The present invention relates to a membrane-separated methane fermentation treatment apparatus and a membrane-separated methane fermentation treatment method for treating an organic substance in a waste liquid by methane fermentation.

  It is known to perform membrane-separated methane fermentation using methane fermentation and membrane filtration in combination with wastewater containing organic substances such as septic tank sludge, sewage sludge, human waste, garbage, and food waste. (For example, patent documents 1-4).

  In the membrane separation methane fermentation process, solid-liquid separation is performed using a filtration membrane. As the filtration process is continued, the solid matter (SS) to be separated remains on the membrane surface and inside the membrane, and filtration is performed by blocking or narrowing the membrane pores. Performance may be reduced.

  The cause of such clogging (fouling) of the filtration membrane is that SS is deposited on the membrane surface, or inorganic components in the liquid to be treated used for the filtration treatment form insoluble substances. It may be precipitated in the film (pores). Known inorganic components that are likely to precipitate in the liquid to be treated include metal sulfides such as iron sulfide and magnesium ammonium phosphate (MAP).

  For the deposition of SS on the membrane surface, an air diffuser is provided below the filter membrane, and the upward flow generated by the air lift action of the air bubbles diffused from the air diffuser is used as a sweeping flow between the membranes of the filter membrane. The membrane surface is washed by cross-flow through the flow path (for example, Patent Documents 1 and 2).

  On the other hand, for precipitation of inorganic components into the membrane, filter membranes can be removed by periodically washing the membrane with chemicals or by injecting organic acids that form complexes with inorganic components into the liquid to be treated. Washing (for example, Patent Document 3).

JP 2001-170631 A JP 2010-207762 A JP 2000-61274 A JP 2010-207700 A

  However, in order to periodically wash the filtration membrane with a chemical, the filtration operation must be stopped at the time of washing, which may reduce the operating rate of the membrane separation methane fermentation treatment apparatus. Moreover, when inject | pouring the chemical | medical agent which forms a complex, there exists a possibility that maintenance cost, such as a chemical | medical agent cost and chemical | medical agent injection | pouring operation | work, may increase.

  In view of the above circumstances, an object of the present invention is to provide a technique that contributes to suppression of clogging of a filtration membrane in membrane separation methane fermentation treatment.

  One aspect of the membrane separation methane fermentation treatment apparatus of the present invention that achieves the above object is a methane fermentation tank for performing methane fermentation and a membrane for separating the filtrate from the treatment liquid supplied with the treatment liquid of the methane fermentation tank. A membrane separation methane fermentation treatment apparatus having a filtration tank is characterized in that the liquid to be treated is heated to a temperature higher than the set temperature of the methane fermentation tank and then supplied to the membrane filtration tank.

  Further, the membrane separation methane fermentation treatment method of the present invention that achieves the above object is a methane fermentation tank for performing methane fermentation and a membrane filtration for separating the filtrate from the liquid to be treated, which is supplied with the liquid to be treated in the methane fermentation tank. A membrane separation methane fermentation treatment method using a membrane separation methane fermentation treatment apparatus having a tank, wherein the liquid to be treated is heated to a temperature higher than the set temperature of the methane fermentation tank and then supplied to the membrane filtration tank It is characterized by.

  According to the above invention, it can contribute to suppression of clogging of the filtration membrane in the membrane separation methane fermentation treatment.

It is the schematic of the membrane separation methane fermentation processing apparatus which concerns on Embodiment 1 of this invention. It is the schematic of the membrane separation methane fermentation processing apparatus which concerns on Embodiment 2 of this invention. It is the schematic of the membrane separation methane fermentation processing apparatus which concerns on Embodiment 3 of this invention. It is the schematic of the membrane separation methane fermentation processing apparatus which concerns on a reference example. It is a characteristic view which shows a time-dependent change of the film differential pressure | voltage of a ceramic flat film in case the temperature of a to-be-processed liquid is 20 degreeC. It is a characteristic view which shows a time-dependent change of the film differential pressure | voltage of a ceramic flat film in case the temperature of a to-be-processed liquid is 40 degreeC.

  A membrane separation methane fermentation treatment apparatus and a membrane separation methane fermentation treatment method according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Embodiment 1]
FIG. 1 is a schematic diagram of a membrane separation methane fermentation treatment apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, the membrane separation methane fermentation treatment apparatus 1 according to Embodiment 1 includes a methane fermentation tank 2, a membrane filtration tank 3, and a heat exchanger 4.

  The methane fermentation tank 2 performs methane fermentation with methane bacteria. The methane fermentation tank 2 is provided with a pipe 5 to which the liquid to be treated is supplied and a supply pipe 6 for supplying a part of the liquid to be treated circulating through the methane fermentation tank 2 to the membrane filtration tank 3. The supply pipe 6 is provided with a circulation pump 7 and a heat exchanger 4. The pipe 5 is provided with a heat exchanger (not shown) as necessary, and the liquid to be treated supplied to the methane fermentation tank 2 is heated.

  As a fermentation method in the methane fermentation tank 2, there are, for example, a medium temperature fermentation method in which fermentation is performed at 36 to 38 ° C and a high temperature fermentation method in which fermentation is performed at 50 to 60 ° C. In the high-temperature fermentation method, the high-temperature methane bacteria have 2-3 times the activity as compared with the medium-temperature methane bacteria whose activity increases at 36 to 38 ° C., and the decomposition rate is achieved by performing methane fermentation with the high-temperature methane bacteria. Can be improved and digestibility can be improved. Thus, since the high temperature fermentation method has high decomposition efficiency of organic matter, the methane fermentation tank 2 can be made small. The high-temperature fermentation method is capable of high-speed treatment, but usually, the higher the temperature, the higher the killing speed of the methane bacteria, and particularly when the temperature exceeds 60 ° C. on the high temperature side, the methane bacteria will be markedly killed. For this reason, in the high temperature fermentation method, the temperature in the methane fermentation tank 2 is always managed within a certain range to prevent the death of methane bacteria due to high temperature.

  The heat exchanger 4 warms the liquid to be processed supplied to the membrane filtration tank 3. As the heat exchanger 4, for example, a spiral heat exchanger that performs heat exchange by circulating hot water is used. As the heat exchanger 4, a well-known heat exchanger that can heat the liquid to be treated is selected and used, and in particular, a heat exchanger 4 that is not easily clogged and excellent in corrosion resistance is preferable.

  The membrane filtration tank 3 is supplied with a part of the liquid to be treated that circulates in the methane fermentation tank 2, and performs filtration of the liquid to be treated. In the lower part of the membrane filtration tank 3, a supply pipe 6 for supplying the liquid to be treated is provided. In the upper part of the membrane filtration tank 3, the gas for scrubbing with the liquid to be treated overflowing from the membrane filtration tank 3 is subjected to methane fermentation. A return pipe 8 for returning to the tank 2 is provided. Moreover, the membrane 9 is provided by being immersed in the liquid to be treated in the membrane filtration tank 3, and the air diffuser 10 is provided below the membrane 9.

  The filtration membrane 9 filters the liquid to be treated in the membrane filtration tank 3. The filtration membrane 9 is provided with a discharge pipe 11 through which the filtrate filtered through suction is discharged. That is, the suction pipe 11 is provided with a suction pump (not shown), and the suction membrane filtered by the suction pump is used to suck the filtrate filtered by the filtration membrane 9. Through the system. The filtration area of the filtration membrane 9 is appropriately set based on the design filtration flow rate. The filtration membrane 9 is a ceramic flat membrane, for example. When multiple ceramic flat membranes are provided, each ceramic flat membrane is provided in parallel with the membrane surfaces facing each other, and the ceramic flat membrane is subjected to membrane filtration so that the liquid to be treated flows between the ceramic flat membranes provided in parallel. Arranged in the tank 3. The filtration membrane 9 is not limited to a ceramic flat membrane, and an organic hollow fiber membrane, an organic flat membrane, an inorganic flat membrane, an inorganic single tube membrane, or the like can be used. Examples of the material of the filtration membrane 9 include cellulose, polyolefin, polysulfone, PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene) and the like in addition to ceramic. Moreover, the pore diameter formed in the filtration membrane 9 is selected according to the particle diameter of the substance to be subjected to solid-liquid separation. For example, if it is used for solid-liquid separation of activated sludge, a filtration membrane having a pore size of 0.5 μm or less is used, and when sterilization is required, such as filtration of purified water, a pore size of 0.1 μm or less is used. A filtration membrane 9 is used.

  The air diffuser 10 is provided below the filtration membrane 9 and scrubs the filtration membrane 9. As the air diffuser 10, for example, a pipe in which air diffused holes are formed at an appropriate interval is used, and the gas generated in the methane fermentation tank 2 is supplied by the aeration blower 12. As the diffuser 10, any known diffuser may be used as long as it can supply the scrubbing gas to the filtration membrane 9. However, the liquid to be treated in the membrane filtration tank 3 has a high organic matter concentration and viscosity. It is preferable to use an air diffuser that is less likely to clog the air holes and reduce the amount of air diffused.

  In the membrane separation methane fermentation treatment apparatus 1 according to the first embodiment, the liquid to be treated circulating in the methane fermentation tank 2 is heated and supplied from the lower part of the membrane filtration tank 3. The liquid to be treated supplied to the membrane filtration tank 3 rides on the upward flow generated by scrubbing the air diffuser 10 and passes through the filtration membrane 9, where the liquid to be treated is separated into solid and liquid. The overflow of the liquid to be treated after passing through the filtration membrane 9 is returned to the methane fermentation tank 2 through the return pipe 8 together with the scrubbing gas recovered at the upper part of the membrane filtration tank 3. The return pipe 8 is dedicated to returning the overflow of the liquid to be treated, and the gas for scrubbing to the methane fermentation tank 2 is returned by separately providing a communication pipe in the methane fermentation tank 2 and the membrane filtration tank 3. Also good.

[Temperature control of membrane separation methane fermentation treatment equipment]
Here, the temperature control method of the membrane separation methane fermentation treatment apparatus 1 according to Embodiment 1 will be described.

In the membrane separation methane fermentation treatment apparatus 1, the temperatures of the methane fermentation tank 2, the heat exchanger 4, and the membrane filtration tank 3 are controlled. The set temperature inside the methane fermentation tank 2 is T ₁ (° C.), and the volume of the methane fermentation tank 2 is V ₁ (m ³ ). The control temperature of the heat exchanger 4 is T ₂ (° C.), the heat energy supplied by the heat exchanger 4 is J (J / hr), and the circulation amount of the heat exchanger 4 is Q (m ³ / hr). . Then, the control temperature of the membrane filtration tank 3 and T ₃ (° C.). Since the liquid to be treated heated by the heat exchanger 4 is supplied to the membrane filtration tank 3, T ₃ ≈T ₂ .

When performing intermediate temperature fermentation in the methane fermentation tank 2, the temperature in the methane fermentation tank 2 is controlled to be in the range of 36 to 38 ° C. For example, as the set temperatures T ₁ and 37 ° C., warming control for the setting temperature T ₁ of the heat exchanger 4 and the management target is executed. Moreover, when performing high temperature fermentation with the methane fermenter 2, it controls so that the temperature in the methane fermenter 2 may be in the range of 50-60 degreeC. For example, as the set temperatures T ₁ and 55 ° C., warming control of the heat exchanger 4 is made to this setting temperatures T ₁ as the management target.

  When the heat energy required to maintain the fermentation temperature in the methane fermentation tank 2 is supplied from the heat exchanger 4, the supplied heat energy J supplied from the heat exchanger 4 is supplied to the methane fermentation tank 2. It is determined from the energy balance such as the loss of heat energy due to the heating energy of the treatment liquid and the filtrate flowing out from the membrane filtration tank 3, and the loss due to heat dissipation that varies depending on the ambient temperature (from the outer walls and piping of each tank). The

Then, the circulation rate (Q / V ₁ ) that is the replacement rate of the liquid to be treated in the methane fermentation tank 2 determined by the volume V _{1 of} the methane fermentation tank 2 and the circulation amount Q is appropriately controlled (the circulation amount Q is appropriately adjusted). Control) to maintain the temperature difference (ΔT = T ₂ −T ₁ ) between the set temperature T ₁ in the methane fermentation tank 2 and the control temperature T ₂ of the heat exchanger 4. . For example, ΔT can be set to about 5 ° C.

In general, the solubility of a compound increases as the liquid temperature increases (solubility). Therefore, as ΔT is increased, there is an effect of suppressing crystals (crystals of inorganic components such as phosphorus components) deposited on the filtration membrane. . Control temperature T ₂ is maintenance cycle and methane bacteria can survive temperatures of the membrane 9 (e.g., within a period not exceeding 60 ° C.) is set in consideration of the.

However, when the circulation amount Q decreases and the circulation ratio decreases, in order to keep the supplied heat energy J constant, it is necessary to set the control temperature T ₂ of the heat exchanger 4 higher and increase ΔT. . As a result, when the temperature of the liquid to be processed after passing through the heat exchanger 4 exceeds 60 ° C., the methane bacteria are remarkably killed. In the case of the high-temperature fermentation method, it is assumed that the control temperature T ₂ exceeds the temperature at which the methane bacterium can survive, but the growth rate of the methane bacterium significantly increases as the temperature of the liquid to be treated increases. Therefore, when the circulation ratio (Q / V ₁ ) is small and methane fermentation is performed by a high temperature fermentation method, the control temperature T ₂ can be set to 60 ° C. or higher, and the rate at which methane bacteria are killed and the growth of methane bacteria ΔT is determined in consideration of the balance with the speed.

  In the membrane separation methane fermentation treatment apparatus 1, the circulation amount Q may be set within a range that does not hinder filtrate removal in the membrane filtration tank 3, and all the necessary supply heat energy J is transferred to the heat exchanger 4. Need not be supplied. Therefore, a heat exchanger dedicated to heating is separately provided, the methane fermentation tank 2 is heated by a plurality of heat exchangers, and the heat energy supplied by the heat exchanger 4 is compensated for the amount of heat energy that is insufficient. Also good.

  As mentioned above, according to the membrane separation methane fermentation processing apparatus 1 which concerns on Embodiment 1, it heats the to-be-processed liquid supplied to the membrane filtration tank 3 so that it may become temperature higher than the preset temperature of the methane fermentation tank 2. FIG. By doing so, it can suppress that the crystal | crystallization of inorganic substances, such as a phosphorus component, deposits on the filtration membrane 9, and the water permeability of the filtration membrane 9 can be maintained.

  By suppressing clogging of the filtration membrane 9, it is possible to lengthen the period of performing the washing step for washing the inorganic substance deposited on the filtration membrane 9, and the operation rate of the membrane separation methane fermentation treatment apparatus 1 is improved. Furthermore, the cost of the chemical | medical agent which wash | cleans the filtration membrane 9, and maintenance costs, such as chemical | medical agent injection | pouring operation | work, can be reduced.

  Moreover, the temperature control in the membrane filtration tank 3 can be easily performed by supplying the liquid to be treated to the membrane filtration tank 3.

[Embodiment 2]
FIG. 2 is a schematic diagram of a membrane separation methane fermentation treatment apparatus 13 according to Embodiment 2 of the present invention. The membrane separation methane fermentation treatment apparatus 13 according to Embodiment 2 relates to Embodiment 1 except that a gas for scrubbing the filtration membrane 9 is mixed with the liquid to be treated supplied from the methane fermentation tank 2 to the membrane filtration tank 3. It is the same as the membrane separation methane fermentation treatment apparatus 1. Therefore, about the same structure as the membrane separation methane fermentation processing apparatus 1 which concerns on Embodiment 1, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.

  As shown in FIG. 2, the membrane separation methane fermentation treatment apparatus 13 according to Embodiment 2 includes a methane fermentation tank 2, a membrane filtration tank 3, and a heat exchanger 4.

  A circulation pipe 7 and a heat exchanger 4 are provided in the supply pipe 6 that supplies a part of the liquid to be treated circulating in the methane fermentation tank 2 to the membrane filtration tank 3. A gas supply pipe 14 is connected to the supply pipe 6, and the gas generated in the methane fermentation tank 2 is supplied to the supply pipe 6 by the aeration blower 12. And the gas-liquid mixture which mixed the liquid to be processed and the scrubbing gas is supplied from the lower part of the membrane filtration tank 3.

  The membrane filtration tank 3 is provided with a filtration membrane 9, and a diffuser plate 15 is provided below the filtration membrane 9. The diffuser plate 15 disperses the gas-liquid mixture supplied from the supply pipe 6. Since the gas-liquid mixture is dispersed by the dispersion plate 15, the liquid to be processed and the scrubbing gas supplied from the supply pipe 6 are supplied uniformly by the filtration membrane 9.

  As described above, according to the membrane separation methane fermentation treatment apparatus 13 according to the second embodiment, the scrubbing gas is mixed with the liquid to be treated supplied to the membrane filtration tank 3, thereby performing the membrane separation according to the first embodiment. In addition to the effect of the methane fermentation treatment apparatus 1, the membrane filtration tank 3 is sufficiently stirred, and the membrane surface flow velocity that circulates through the surface of the filtration membrane 9 can be secured.

[Embodiment 3]
FIG. 3 is a schematic view of a membrane separation methane fermentation treatment apparatus 16 according to Embodiment 3 of the present invention. The membrane separation methane fermentation treatment apparatus 16 according to Embodiment 3 is according to Embodiment 2 except that the gas-liquid mixture supplied from the supply pipe 6 to the membrane filtration tank 3 is supplied to the membrane filtration tank 3 after heating. This is the same as the membrane separation methane fermentation treatment apparatus 13. Therefore, about the same structure as the membrane separation methane fermentation processing apparatus 13 which concerns on Embodiment 2, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.

  As shown in FIG. 3, the membrane separation methane fermentation treatment apparatus 16 according to the third embodiment includes a methane fermentation tank 2, a membrane filtration tank 3, and a heat exchanger 4.

  A gas supply pipe 14 is connected to the supply pipe 6 for supplying a part of the liquid to be treated circulating in the methane fermentation tank 2 to the membrane filtration tank 3, and the gas generated in the methane fermentation tank 2 is supplied by the aeration blower 12 to the supply pipe 6. To be supplied. The supply pipe 6 is provided with a circulation pump 7 and a heat exchanger 4. The heat exchanger 4 is provided downstream from a connection portion (mixing point) to which the gas supply pipe 14 is connected.

  That is, after the liquid to be processed and the scrubbing gas supplied from the methane fermentation tank 2 to the membrane filtration tank 3 are mixed at the connection portion of the supply pipe 6 and this gas-liquid mixture is heated in the heat exchanger 4, It is supplied from the lower part of the membrane filtration tank 3.

  The membrane filtration tank 3 is provided with a filtration membrane 9, and a diffuser plate 15 is provided below the filtration membrane 9. The diffuser plate 15 disperses the gas-liquid mixture supplied from the supply pipe 6, and the liquid to be processed and the scrubbing gas are supplied uniformly to the filtration membrane 9.

  As described above, according to the membrane separation methane fermentation treatment apparatus 16 according to the third embodiment, since the gas-liquid mixture whose temperature is controlled by the heat exchanger 4 is supplied to the membrane filtration tank 3, the liquid to be treated and the scrubbing The gas-liquid mixture controlled to a predetermined temperature can be supplied to the membrane filtration tank 3 without being affected by the temperature difference from the other gas. As a result, in addition to the effect of the membrane separation methane fermentation treatment apparatus 13 according to the second embodiment, a stable filtration operation can be performed.

[Reference example]
The inventors conducted a membrane filtration test using digested sludge from an actual sewage treatment plant using the membrane separation methane fermentation treatment apparatus 17 according to the reference example shown in FIG. 4, and the liquid temperature of the liquid to be treated and the membrane of the ceramic flat membrane 23. The relationship with differential pressure was examined.

  The membrane separation methane fermentation treatment apparatus 17 includes a stock solution tank 18, a membrane filtration tank 19, and a filtered water tank 20.

  A cooler and a heater controlled by a temperature controller were immersed in the liquid to be processed in the stock solution tank 18, and the temperature was controlled so that the temperature of the liquid to be processed was 20 ° C. (or 40 ° C.). The liquid to be treated in the stock solution tank 18 is supplied to the membrane filtration tank 19 at 4.5 to 1.0 m / d by the stock solution supply pump 21, and overflow from the membrane filtration tank 19 is returned to the stock solution tank 18 through the return pipe 22. did.

The membrane filtration tank 19 was made of acrylic, and used one having a width of 100 mm, a depth of 50 mm, and a height of 500 mm (effective volume 2.5 L). A ceramic flat membrane 23 was provided by immersing in the liquid to be treated in the membrane filtration tank 19, and a diffuser tube 24 for aeration of scrubbing air was provided below the ceramic flat membrane 23. The air pump 25 supplies air to the diffuser tube 24 to scrub the ceramic flat membrane 23, the ceramic flat membrane 23 is sucked by the filtration suction pump 26, and the liquid to be treated is filtered at a filtration flow rate of 0.3 to 1.0 m / d. Filtration was performed. The film area of the ceramic flat film 23 is 0.036 m ² , and its specifications are shown in Table 1.

  The differential pressure of the ceramic flat membrane 23 is measured with a pressure gauge PI (manufactured by Nagano Keiki Co., Ltd., model GC61-174), and the filtration flow rate of the ceramic flat membrane 23 is measured by a flow meter FI (manufactured by Keyence Corporation, model FD- SS02A).

  Digested sludge used for the test was collected from the digestion tank outlet of the sewage treatment plant that treats municipal sewage, passed through a slit with a mesh opening of 2 mm to remove impurities, and used as the test sludge in the stock solution tank 18. Supplied. Table 2 shows the properties of the test sludge. Table 3 shows the properties of the liquid to be treated supplied from the stock solution tank 18 to the membrane filtration tank 19 and the filtrate filtered through the ceramic flat membrane 23 (filtrate of the filtered water tank 20).

  Symbols in the items of Table 2 and Table 3 are respectively COD: chemical oxygen demand, BOD: biochemical oxygen demand, TN: total nitrogen content, TP: total phosphorus content, TS: total solid Quantity, VS: Incineration loss.

  In the filtration process in the ceramic flat membrane 23, the raw liquid supply pump 21 is operated to supply the liquid to be processed to the membrane filtration tank 19, and the air pump 25 supplies air to the diffuser tube 24 to scrub the ceramic flat membrane 23 (25 to 25). 100 m / d), the filtration suction pump 26 was operated. Every time the filtration treatment was performed for 10 minutes, the back washing process of the ceramic flat membrane 23 was performed for 1 minute. In the back washing process, the filtration suction pump 26 is stopped from the state at the time of operation, and the return pump 27 returns the filtrate in the filtered water tank 20 to the ceramic flat membrane 23 (0.3 to 1.0 m / d). I went.

  FIG. 5 is a characteristic diagram showing the relationship between the pressure difference of the ceramic flat membrane 23 and the temperature of the liquid to be treated in the membrane filtration tank 19 with respect to the filtration time when the temperature of the stock solution tank 18 is set to 20 ° C. FIG. 6 is a characteristic diagram showing the relationship between the membrane differential pressure of the ceramic flat membrane 23 and the temperature of the liquid to be treated in the membrane filtration tank 19 with respect to the filtration time when the temperature of the stock solution tank 18 is set to 40 ° C. . In FIGS. 5 and 6, the film differential pressure of the ceramic flat film 23 periodically decreases. This is the film differential pressure after the ceramic flat film 23 is back-washed.

  As shown in FIG. 5, when the temperature of the stock solution tank 18 is set to 20 ° C., the membrane differential pressure of the ceramic flat membrane 23 gradually increases from 18 kPa, and finally (filtration operation duration time is about 240 minutes). It rose to 87 kPa. And the fluctuation | variation of the film | membrane differential pressure | voltage of the ceramic flat film 23 was violently unstable in 11 minutes of the filtration process process-backwashing process period. Moreover, the temperature of the membrane filtration tank 19 was around 20 ° C., which is the same as the control temperature of the stock solution tank 18.

  Thus, when the filtration treatment is performed at a temperature lower than the medium temperature fermentation temperature (37 ° C.) of the actual methane fermenter, the influence of the back washing process of the ceramic flat membrane 23 is large, and the ceramic is obtained by performing the back washing process. The membrane differential pressure of the flat membrane 23 is greatly reduced.

  On the other hand, as shown in FIG. 6, when the temperature of the stock solution tank 18 was set to 40 ° C., the membrane differential pressure of the ceramic flat membrane 23 was 4 kPa and was almost constant (filtering operation duration time was about 240 minutes) and was stable. And the temperature of the membrane filtration tank 19 was 40 degreeC substantially the same as the control temperature of the stock solution tank 18. FIG.

  Thus, when the filtration process is performed at the same temperature as the intermediate temperature fermentation temperature (37 ° C.) of the actual methane fermenter, the increase in the membrane differential pressure of the ceramic flat membrane 23 due to the filtration process is small, and the back washing process is performed. Thus, the film differential pressure of the ceramic flat film 23 hardly changes.

  As shown in FIG. 5 and FIG. 6, the behavior of the membrane differential pressure of the ceramic flat membrane 23 with respect to the filtration processing duration varies greatly depending on the temperature difference in the membrane filtration tank 19.

  As a factor affecting the behavior of the membrane differential pressure, the effect of the viscosity of the liquid to be treated is assumed. In general, the viscosity of a liquid decreases with increasing temperature. That is, the higher the temperature in the membrane filtration tank 19, the lower the viscosity of the liquid to be treated and the higher the Reynolds number. However, the change in the value of the Reynolds number was not so significant as to the change in the film differential pressure of the ceramic flat film 23.

  As shown in Table 2, it is known that sewage sludge and the like contain a large amount of phosphorus, and research and development of recovery and utilization of phosphorus from sewage and sewage sludge is being promoted. Moreover, as shown in Table 3, the filtrate in the filtered water tank 20 also contains high concentration of phosphorus. Therefore, it is thought that the factor which reduces the water permeability of the ceramic flat membrane 23 is the blockage of the ceramic flat membrane 23 by the phosphorus component contained in a to-be-processed liquid.

  Therefore, it is considered that the increase in the film differential pressure of the ceramic flat film 23 can be suppressed by reducing the blockage of the ceramic flat film 23 due to the precipitation of inorganic components such as phosphorus components.

  These inorganic components can be removed using a drug. However, when an inorganic component such as a phosphorus component is removed with a chemical, the attached inorganic component crystals can be removed, but the inorganic component crystals cannot be prevented from adhering to the ceramic flat film 23. The inorganic component adhering to the ceramic flat film 23 becomes the nucleus of crystal growth, increases the growth rate of crystals of the inorganic component, and promotes the blockage of the ceramic flat film 23.

  On the other hand, since the membrane separation methane fermentation processing apparatus 1,13,16 which concerns on embodiment of this invention is heating the to-be-processed liquid supplied to the filtration membrane 9, it uses for filtration of the filtration membrane 9. The solubility of the inorganic component in the liquid to be treated is increased. As a result, not only the inorganic component can be prevented from depositing on the filtration membrane 9 but also the inorganic component crystals can be prevented from adhering to the filtration membrane 9. That is, an increase in the membrane differential pressure of the filtration membrane 9 can be further reduced.

DESCRIPTION OF SYMBOLS 1,13,16,17 ... Membrane separation methane fermentation processing apparatus 2,18 ... Methane fermentation tank 3,19 ... Membrane filtration tank 4 ... Heat exchanger (heating means)
DESCRIPTION OF SYMBOLS 5 ... Pipe 6 ... Supply pipe 7 ... Circulation pumps 8, 22 ... Return pipe 9 ... Filtration membrane 10 ... Air diffuser 11 ... Exhaust pipe 12 ... Aeration blower 14 ... Gas supply pipe 15 ... Diffuser plate 20 ... Filtration water tank 21 ... Stock solution supply pump 23 ... Ceramic flat membrane 24 ... Aeration pipe 25 ... Air pump 26 ... Filtering suction pump 27 ... Return pump

Claims (8)

A methane fermentation tank for methane fermentation,
A membrane filtration tank that is supplied with the liquid to be treated of the methane fermentation tank and separates the filtrate from the liquid to be treated;
A heating means for heating the liquid to be treated supplied to the membrane filtration tank to a temperature higher than the set temperature of the methane fermentation tank;
A cleaning means for cleaning the filtration membrane provided in the membrane filtration tank;
A return pipe for returning the liquid to be treated of the membrane filtration tank to the methane fermentation tank;
Have
Membrane separation methane fermentation process characterized in that the heating means supplies all of the amount of heat necessary for temperature control of the methane fermentation tank before the membrane filtration tank to control the temperature of the methane fermentation tank apparatus. The to-be-processed liquid heated by the said heating means is supplied to the said membrane filtration tank, without being mixed with the to-be-processed liquid discharged | emitted from the said membrane filtration tank. Membrane separation methane fermentation treatment equipment. The cleaning means has an aeration blower for scrubbing the filtration membrane, and a gas for scrubbing the filtration membrane is mixed with a liquid to be treated supplied to the membrane filtration tank, and this gas-liquid mixture is mixed with the membrane. The membrane separation methane fermentation treatment apparatus according to claim 1, wherein the apparatus is supplied to a filtration tank. The membrane separation methane fermentation treatment apparatus according to claim 3, wherein the heating means warms the gas-liquid mixture and supplies the mixture to the membrane filtration tank. The membrane-separated methane fermentation treatment apparatus according to claim 3 or 4, wherein the cleaning unit further includes a reverse cleaning unit that performs reverse cleaning of the filtration membrane in addition to the aeration blower. A methane fermentation tank for performing methane fermentation, a treatment liquid of the methane fermentation tank, a membrane filtration tank for separating the filtrate from the treatment liquid, and a treatment liquid supplied to the membrane filtration tank are heated. Membrane separation methane fermentation having heating means for cleaning, cleaning means for cleaning the filtration membrane provided in the membrane filtration tank, and a return pipe for returning the liquid to be treated of the membrane filtration tank to the methane fermentation tank A membrane separation methane fermentation treatment method using a treatment device,
From the heating means, supply all the amount of heat necessary for temperature control of the methane fermentation tank in the previous stage of the membrane filtration tank, and the liquid to be treated supplied to the membrane filtration tank from the set temperature of the methane fermentation tank A membrane-separated methane fermentation treatment method, wherein the temperature of the methane fermentation tank is controlled by heating to a higher temperature. 7. The membrane according to claim 6, wherein the liquid to be treated heated by the heating means is supplied to the membrane filtration tank without being mixed with the liquid to be treated discharged from the membrane filtration tank. Separate methane fermentation treatment method. The said membrane filtration tank repeats the filtration process process and the backwashing process which performs the backwashing of the filtration membrane provided in the said membrane filtration tank with a predetermined period, The Claim 6 or Claim 7 characterized by the above-mentioned. Membrane separation methane fermentation treatment method.

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