JP2008168199A - Membrane separation activated sludge apparatus and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a membrane separation activated sludge apparatus operation method which can prevent a decrease in the particle size of activated sludge to suppress an increase in a transmembrane pressure difference due to the clogging of fine activated sludge. <P>SOLUTION: A membrane separation activated sludge apparatus comprises a biological reaction tank 1 that receives water to be treated and treats organic matter in it with activated sludge, a filtration membrane 2 that performs solid-liquid separation of the activated sludge in the biological reaction tank 1, a suction device 3 that is connected to the filtration membrane 2 and sucks treated water, a pressure gauge 4 for measuring the transmembrane pressure difference of the filtration membrane 2, an activated sludge concentration meter 7 that measures the concentration of the activated sludge, and a control device 9 that adds an injection amount of a coagulant from the measured value of the activated sludge concentration meter 7 when the measured value of the pressure gauge 4 is equal to or larger than a setting value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a membrane-separated activated sludge apparatus that uses a biological treatment that removes organic substances in wastewater with activated sludge and uses a filtration membrane for solid-liquid separation between activated sludge and treated water, and an operating method thereof.

  One of the wastewater treatment methods is the membrane separation activated sludge method. The membrane-separated activated sludge method has advantages such as an improved removal rate and downsizing of the apparatus because the activated sludge concentration in the biological reaction tank can be made higher than the conventional standard activated sludge method. The membrane-separated activated sludge method has a problem of preventing clogging of the membrane because the solid-liquid separation of activated sludge and treated water is performed by a filtration membrane. So far, as a countermeasure against clogging of the membrane, a method of cleaning the membrane surface with bubbles used for supplying oxygen to the activated sludge and a method of cleaning with a brush have been proposed.

  However, if an excessive aeration amount or a decrease in inflow load occurs, the activated sludge is dismantled and the particle size of the activated sludge is reduced, which may cause clogging of the membrane. In order to increase the particle size, as described in [Patent Document 1], there is a method in which a flocculant is injected so that the molar ratio of aluminum to phosphorus is within a range of 0.1 to 1.0. A method of injecting a flocculant such as polyaluminum chloride into the biological reaction tank is known as one of phosphorus removal methods. In this method, phosphorus and aluminum in the wastewater react to generate an insoluble salt such as aluminum phosphate, and the phosphorus in the wastewater is removed by solid-liquid separation of the salt.

  Also, as described in [Patent Document 2], there is an apparatus in which an MLSS meter is installed in an aerobic tank, a true alkalinity obtained by correcting an increase in the MLSS concentration is obtained, and a condensing agent injection amount is adjusted. In addition, as described in [Patent Document 3], an inorganic flocculant is added, an amphoteric organic polymer flocculant is added to organic wastewater having a pH value of 5 to 8, and solidified by a separation membrane in the aeration tank. Some perform liquid separation.

JP 2003-170185 A JP 2002-221518 A Japanese Patent Laid-Open No. 9-38680

  Although the treatment method described in [Patent Document 1] controls the injection amount of the flocculant by the molar ratio of aluminum and phosphorus, there is a fear that the activated sludge particle size cannot be optimized by the molar ratio using phosphorus as an index. There is. In addition, the water treatment process control device described in [Patent Document 2] does not perform solid-liquid separation by a separation membrane, but adjusts the pH value of the aerobic tank to optimize the particle size of the activated sludge. There is no consideration for doing. In addition, the wastewater treatment method described in [Patent Document 3] is to add an amphoteric organic polymer flocculant to form a relatively large and high-strength floc. It is not considered that the activated sludge is dismantled and the particle size of the activated sludge becomes small.

  The objective of this invention is providing the membrane separation activated sludge apparatus which can control the particle size of activated sludge appropriately, and can suppress the raise of the membrane differential pressure by clogging of fine activated sludge, and its operating method.

  In order to solve the above problems, a membrane separation activated sludge apparatus and an operation method thereof according to the present invention introduce water to be treated into a biological reaction tank, treat organic matter in the water to be treated with activated sludge, and remove the activated sludge from a filtration membrane. A solid-liquid separation is performed to obtain treated water, and a pressure gauge for measuring a membrane differential pressure of the filtration membrane and an activated sludge concentration meter for measuring the concentration of the activated sludge are provided, and measurement of the pressure gauge The value is equal to or greater than the set value, and the flocculant injection amount is added based on the measured value of the activated sludge densitometer.

  Further, a sludge particle size measuring means for measuring the particle size of the activated sludge is provided, and the measured value of the sludge particle size measuring means is a predetermined value or less, and a flocculant is added.

  A chemical washing process for backwashing the filtration membrane with filtered water to which a chemical has been added, and a coagulant injection process for injecting a coagulant after the chemical washing process are provided. Moreover, the activated sludge concentration meter which measures the density | concentration of activated sludge is provided, and the coagulant injection | pouring amount is added based on the measured value of the said activated sludge concentration meter in the said coagulant | flocculant injection | pouring process. Further, a pH meter for measuring the pH of the reaction solution in the biological reaction tank is provided, and the flocculant is injected so that the measured value of the pH meter becomes a set value in the flocculant injection step.

  At least one of a pressure gauge for measuring a membrane differential pressure of the filtration membrane and a sludge particle size measuring device for measuring a particle size of the activated sludge is provided, and the measured value of the pressure gauge is equal to or greater than a predetermined value, the sludge At least one of the measured values of the particle diameter measuring means is a predetermined value or less, and particles having a set particle diameter are added.

  According to the present invention, when detecting the clogging of the membrane, the flocculant can be injected according to the amount of activated sludge in the biological reaction tank, so that the particle size of the activated sludge can be prevented and the clogged fine activated sludge is clogged. The increase in the membrane differential pressure due to the pressure can be suppressed, and the operating cost of the membrane separation activated sludge method can be reduced.

  Embodiments 1 to 3 of the present invention will be described with reference to the drawings.

  1 is a configuration diagram of a membrane separation activated sludge treatment apparatus of Example 1. FIG. A filtration membrane 2 is installed in a biological reaction tank 1 filled with activated sludge. A diffuser tube 5 is disposed below the filtration membrane 2, and an air supply device 6 such as a blower is connected to the diffuser tube 5. The air supplied by the air supply device 6 is supplied from the diffuser pipe 5 into the biological reaction tank 1, oxygen is supplied to the activated sludge by the supplied air, and the membrane surface of the filtration membrane 2 is washed by bubbles. .

  A suction device 3 such as a pump is connected to the secondary side of the filtration membrane 2, that is, the filtration side, and the treated water filtered by the filtration membrane 2 is sucked and taken out as filtered water. The piping connecting the filtration membrane 2 and the suction device 3 is provided with a pressure gauge 4, and the biological reaction tank 1 is provided with an activated sludge concentration meter 7. The pressure gauge 4 and the activated sludge concentration meter 7 are controlled. It is connected to the device 9. The activated sludge concentration meter 7 installed in the biological reaction tank 1 measures the concentration of activated sludge in the biological reaction tank 1.

  The control device 9 is connected to the flocculant supply device 8, feeds back the measured values of the pressure gauge 4 and the activated sludge concentration meter 7 to control the flocculant supply device 8, and injects the flocculant into the biological reaction tank 1. The amount of injection is controlled. The flocculant supply device 8 injects a flocculant such as polyaluminum chloride into the biological reaction tank 1.

  Raw water is introduced into the biological reaction tank 1, and the treated water is sucked into the suction device 3 from the filtration membrane 2 and drained. The pressure of the pipe sucked by the suction device 3 is measured by the pressure gauge 4, and atmospheric pressure is acting on the biological reaction tank 1, so the pressure of the pipe connecting the filtration membrane 2 and the suction device 3 is measured. Thus, the membrane pressure difference of the filtration membrane 2 can be measured. The position for injecting the flocculant into the biological reaction tank 1 is provided on the upstream side of the filtration membrane 2 in order to ensure the time for the activated sludge to aggregate due to the injection of the flocculant.

  The operation method of the present embodiment will be described. The control device 9 obtains the membrane differential pressure P of the filtration membrane 2 from the measured value of the pressure gauge 4. When the membrane differential pressure P reaches the upper limit value P1 of the membrane differential pressure, the control device 9 injects the flocculant with the flocculant supply device 8. The upper limit value P1 is set to the membrane differential pressure value when the suction pressure is about 10 to 20 kPa larger than the initial value of the membrane differential pressure P.

  The flocculant injection amount of the flocculant supply device 8 is calculated by the control device 9 from the measured value of the activated sludge concentration meter 7 and the information of the volume of the biological reaction tank 1 and the type and concentration of the flocculant input in advance.

  When the flocculant is an aluminum type such as polyaluminum chloride or aluminum sulfate, the amount of flocculant injected is controlled by the flocculant supply device 8 so that the amount of flocculant per unit weight of activated sludge is α. Here, α is set to 0.5 to 2.0%.

  Since polyaluminum chloride and aluminum sulfate are acidic, a pH meter is installed in the biological reaction tank 1 when they are used, and when the pH reaches the lower limit, the injection of the flocculant is stopped. The lower limit of pH is controlled to be about 6. In this way, excessive injection of the flocculant can be prevented.

  The cause of the increase in the membrane differential pressure is not only due to the decrease in the particle size of the activated sludge. Repeatedly, the injection amount of the flocculant may be excessive. As an example of the countermeasure, the control interval for injecting the flocculant is optimized, and the flocculant injection interval is determined based on the SRT that is an indicator of the residence time of the activated sludge in the biological reaction tank 1. The frequency of flocculant injection by the controller 9 is determined to be about 1/2 to 1/10 of the SRT.

  If the effect of suppressing the membrane differential pressure does not appear even after a predetermined period of time has passed after the flocculant is injected, the amount of air supplied from the backwashing, chemical cleaning, intermittent operation, and air supply device 6 is increasing. Implement at least one of the following. The same applies to the other embodiments.

  According to the present embodiment, the amount of flocculant injected can be controlled according to the amount of activated sludge in the biological reaction tank 1, so that the decrease in the particle size of activated sludge can be prevented, and the membrane differential pressure due to clogging of fine activated sludge. Can be suppressed, and the operating cost of the membrane separation activated sludge process can be reduced.

  FIG. 2 shows a second embodiment of the present invention. This embodiment is configured in the same manner as in the first embodiment, but in this embodiment, a sludge particle size measuring device 12 is installed instead of the activated sludge concentration meter 7. The sludge particle size measuring instrument 12 measures the particle size of the activated sludge in the biological reaction tank 1 and sends the measured value to the control device 9.

  The operation method of the present embodiment will be described. The control device 9 obtains the membrane differential pressure P of the filtration membrane 2 from the measured value of the pressure gauge 4. When the membrane differential pressure P reaches the upper limit value P1 of the membrane differential pressure, the control device 9 injects the flocculant with the flocculant supply device 8. The upper limit value P1 is set to the membrane differential pressure value when the suction pressure is about 10 to 20 kPa larger than the initial value of the membrane differential pressure P.

The control device 9 controls injection start of the flocculant from the flocculant supply device 8 and receives a measurement value signal from the sludge particle size measuring device 12. By injecting the flocculant, the activated sludge in the biological reaction tank 1 is agglomerated and its particle size is increased. The control device 9 stops the flocculant injection when the measured value of the sludge particle size measuring device 12 reaches the set value. The set value of the activated sludge particle size is set to about 100 μm.

  Further, the injection of the flocculant from the flocculant supply device 8 may be started when it is detected that the measured value of the sludge particle size measuring instrument 12 has reached the lower limit value. The lower limit is preferably set to about 100 μm.

  According to this example, since the injection amount of the flocculant can be controlled in accordance with the activated sludge particle size of the biological reaction tank 1, the activated sludge particle size can be maintained at a set value or more, and the membrane due to clogging of the fine activated sludge The increase in differential pressure can be suppressed, and the operating cost of the membrane separation activated sludge process can be reduced.

  FIG. 3 shows a third embodiment of the present invention. This embodiment is configured in the same manner as in Embodiment 1, but in this embodiment, a pH meter 11 is provided in the biological reaction tank 1 in addition to the activated sludge concentration meter 7, and the biological reaction tank 1 is provided by the chemical cleaning device 10. The cleaning water is supplied to the piping between the suction device 3 and the suction device 3.

  The pH meter 11 measures the pH of the biological reaction tank 1. The control device 9 allows the cleaning water to pass through the filtration membrane 2 from the secondary side in the chemical cleaning step. Washing water is obtained by adding sodium hypochlorite or the like to filtered water. By carrying out the chemical cleaning step, the organic substance adhering to the filtration membrane 2 can be removed, and the membrane differential pressure can be recovered.

  In this embodiment, when the measured value of the pressure gauge 4 reaches a preset upper limit value or when a set period has elapsed, the control device 9 starts the chemical cleaning process. The control device 9 is set to execute the coagulant injection process after the chemical cleaning process, and after allowing the cleaning water to permeate in the chemical cleaning process, starts the coagulant injection process after the set time has elapsed. To do. The interval between the chemical cleaning step and the flocculant injection step may be set to several hours.

  In the membrane separation activated sludge method, organic substances, nitrogen, phosphorus, and the like are removed by the action of microorganisms called activated sludge, and therefore it is necessary to maintain the inside of the biological reaction tank 1 at a pH appropriate for the activity of microorganisms. A sodium hypochlorite solution is generally used as an additive agent used in washing water. For this reason, the washing water becomes alkaline, and the pH in the biological reaction tank 1 may be alkalized. Commonly used flocculants are polyaluminum chloride, aluminum sulfate, ferric chloride and the like are acidic substances. Therefore, the alkalinization in the biological reaction tank 1 can be prevented by providing the flocculant injection step after the chemical cleaning step.

  A method of controlling the flocculant injection amount by the control device 9 will be described. When the pH meter 11 is not installed, the control device 9 determines the flocculant injection amount based on the measured value of the activated sludge concentration meter 7 as described above. In the case where the flocculant is an aluminum system such as polyaluminum chloride or aluminum sulfate, the flocculant supply device 8 is controlled so that the flocculant amount α per unit weight of the activated sludge is 0.5 to 2.0%. . Here, the value of α is preferably set so that the pH at the time when the coagulant injection step is completed is near neutral.

  When using the measured value of the pH meter 11, an operation method will be described. The control device 9 determines the amount of flocculant injected in the flocculant injection step so that the measured value of the pH meter 11 falls within the set range. Since the target value of the pH meter 11 is neutral, the pH is set between 6 and 8.

  In this example, it is possible to prevent alkalinization after the chemical cleaning step and decrease in the particle size of the activated sludge, suppress an increase in the membrane differential pressure due to clogging of the fine activated sludge, and reduce the operating cost of the membrane separation activated sludge method. Can be reduced.

  FIG. 4 shows a fourth embodiment of the present invention. The present embodiment is configured in the same manner as in the first embodiment, but in this embodiment, the particle adding device 13 is arranged instead of the flocculant supply device 8, and the sludge particle diameter is replaced instead of the activated sludge concentration meter 7. A measuring instrument 12 is arranged. The sludge particle size measuring instrument 12 is the same as that of the second embodiment. The sludge particle size measuring instrument 12 measures the particle size of the activated sludge in the biological reaction tank 1 and sends the measured value to the control device 9. The particle adding device 13 adds particles having a particle diameter set by a signal from the control device 9 into the biological reaction tank 1. The particles to be added are carriers such as activated carbon, first sedimentation basin sludge, and plastic.

  The method for adding particles in this example will be described. The control device 9 obtains the membrane differential pressure P of the filtration membrane 2 from the measured value of the pressure gauge 4. When the film differential pressure P reaches the upper limit value P <b> 1 of the film differential pressure, the control device 9 adds particles using the particle adding device 13. The upper limit value P1 is set to the membrane differential pressure value when the suction pressure is about 10 to 20 kPa larger than the initial value of the membrane differential pressure P.

  Moreover, the control apparatus 9 may control the particle | grain addition apparatus 13 using the measured value of the sludge particle size measuring device 12, and it will start when the measured value of the sludge particle size measuring device 12 detects a lower limit. Anyway. The lower limit is preferably set to about 100 μm.

  Thus, when the membrane differential pressure increases or the activated sludge particle size decreases, the control device 9 adds a set amount of particles from the particle addition device 13 into the biological reaction tank 1. The amount of added particles is preferably about 1% to 10% of the volume of the biological reaction tank 1. By adding particles, it is possible to increase the average particle size, clean the membrane surface by flowing particles, and adsorb the activated sludge having a small particle size to the particles. For this reason, in a present Example, the raise of the membrane differential pressure by the clogging of fine activated sludge can be suppressed, and the operating cost of a membrane separation activated sludge method can be reduced.

  As described above, according to the present embodiment, when the clogging of the membrane is detected, the flocculant can be injected according to the amount of activated sludge in the biological reaction tank. The increase in membrane differential pressure due to clogged activated sludge can be suppressed, and the operating cost of the membrane separation activated sludge method can be reduced. In addition, after washing the filter membrane with an alkaline agent such as sodium hypochlorite, an acidic flocculant is injected to prevent a decrease in the particle size of the activated sludge. Can be prevented.

It is a block diagram of the membrane filtration apparatus which is Example 1 of this invention. It is a block diagram of the membrane filtration apparatus which is Example 2 of this invention. It is a block diagram of the membrane filtration apparatus which is Example 3 of this invention. It is a block diagram of the membrane filtration apparatus which is Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biological reaction tank 2 Filtration membrane 3 Suction apparatus 4 Pressure gauge 5 Aeration pipe 6 Air supply apparatus 7 Activated sludge concentration meter 8 Coagulant supply apparatus 9 Control apparatus 10 Chemical washing apparatus 11 pH meter 12 Sludge particle size measuring instrument 13 Particle addition apparatus

Claims (11)

  A biological reaction tank for introducing treated water and treating organic matter of the treated water with activated sludge, a filtration membrane for solid-liquid separation of activated sludge in the biological reaction tank, and suction of treated water connected to the filtration membrane A suction device, a pressure gauge for measuring the membrane differential pressure of the filtration membrane, an activated sludge concentration meter for measuring the concentration of the activated sludge, and a measured value of the pressure gauge is not less than a set value, A membrane separation activated sludge apparatus provided with a control device for adding a flocculant injection amount based on a measured value of an activated sludge concentration meter.   A biological reaction tank for introducing treated water and treating organic matter of the treated water with activated sludge, a filtration membrane for solid-liquid separation of activated sludge in the biological reaction tank, and suction of treated water connected to the filtration membrane A pressure device for measuring the membrane differential pressure of the filtration membrane, a sludge particle size measuring device for measuring the particle size of the activated sludge, and a measured value of the pressure meter is not less than a set value. A membrane separation activated sludge apparatus comprising a control device for injecting a flocculant and stopping the injection of the flocculant when the measured value of the sludge particle size measuring device is equal to or greater than a set value.   A biological reaction tank for introducing treated water and treating organic matter of the treated water with activated sludge, a filtration membrane for solid-liquid separation of activated sludge in the biological reaction tank, and suction of treated water connected to the filtration membrane A sludge particle size measuring device that measures the particle size of the activated sludge, and a control device that starts the injection of the flocculant when the measured value of the sludge particle size measuring device is not more than a set value. Membrane separation activated sludge equipment.   A pH meter for measuring the pH of the biological reaction tank; and a chemical cleaning device for allowing cleaning water to permeate the filtration membrane from the secondary side in the chemical cleaning step, and the control device injects the coagulant in the coagulant injection step. The membrane separation activated sludge apparatus according to claim 1, wherein the amount is controlled so that the measured value of the pH meter falls within a set range.   An operation method of a membrane separation activated sludge apparatus for introducing treated water, treating the organic matter of the treated water with activated sludge in a biological reaction tank, solid-liquid separating the activated sludge with a filtration membrane, and obtaining treated water. Measure the membrane differential pressure of the filtration membrane with a pressure gauge, measure the concentration of the activated sludge with an activated sludge concentration meter, and measure the activated sludge concentration meter above the set value of the pressure gauge. The operation method of the membrane separation activated sludge apparatus which adds the coagulant | flocculant injection amount based on a value.   An operation method of a membrane separation activated sludge apparatus for introducing treated water, treating the organic matter of the treated water with activated sludge in a biological reaction tank, solid-liquid separating the activated sludge with a filtration membrane, and obtaining treated water. , Measure the membrane differential pressure of the filtration membrane with a pressure gauge, measure the particle size of the activated sludge with a sludge particle size measuring instrument, and inject the flocculant at a value more than the value set by the pressure gauge, The operation method of the membrane separation activated sludge apparatus which stops injection | pouring of the said coagulant | flocculant when the measured value of the said sludge particle size measuring device is more than the set value.   An operation method of a membrane separation activated sludge apparatus for introducing treated water, treating the organic matter of the treated water with activated sludge in a biological reaction tank, solid-liquid separating the activated sludge with a filtration membrane, and obtaining treated water. The operation method of the membrane separation activated sludge apparatus which measures the particle size of the activated sludge with a sludge particle size measuring device and starts the injection of the flocculant when the measured value of the sludge particle size measuring device is not more than a set value.   An operation method of a membrane separation activated sludge apparatus for introducing treated water, treating organic matter in the treated water with activated sludge in a biological reaction tank, and separating the activated sludge by solid-liquid separation with a filtration membrane to obtain treated water, A method for operating a membrane separation activated sludge apparatus, comprising: a chemical washing step for backwashing a filtration membrane with filtered water to which a chemical is added; and a flocculant injection step for injecting a flocculant after the chemical washing step.   The activated sludge concentration meter for measuring the concentration of the activated sludge is provided, and the flocculant injection amount is added based on the measured value of the activated sludge concentration meter in the flocculant injection step. How to operate the device.   The pH meter for measuring the pH of the reaction liquid in the biological reaction tank is provided, and the flocculant is injected so that the measured value of the pH meter becomes a set value in the flocculant injection step. The operation method of the membrane separation activated sludge apparatus as described.   The operation method of the membrane separation activated sludge apparatus according to any one of claims 5 to 10, wherein an injection position of the flocculant is provided on the upstream side of the filtration membrane.

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