JP2005177628A - Wastewater treatment method and wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment method and a wastewater treatment apparatus which enable operation by keeping activated sludge hard to clog a separation membrane under an aerobic condition for sufficient BOD oxidation and nitrification of nitrogen when wastewater after biological treatment is subjected to solid-liquid separation using the separation membrane. <P>SOLUTION: (1) In the wastewater treatment method, the activated sludge is collected from an activated sludge treatment tank to measure the amount of filtrate obtained by filtering the above activated sludge with a filter paper having a pore size of 0.4-2 μm and to measure the SS concentration in filtrate obtained by filtering the activated sludge with a filter paper having a pore size of 6-10 μm, and the treatment condition in the activated sludge treatment tank is controlled from the above measured filtrate amount and SS concentration. (2) The wastewater treatment apparatus carries out the above method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention belongs to a technical field related to a wastewater treatment method and a wastewater treatment apparatus, and more specifically, relates to a wastewater treatment method and a wastewater treatment apparatus that biologically treats wastewater and separates the treated water using a separation membrane. Belongs to the field.

  Membrane separation is used as a solid-liquid separation (separating activated sludge and treated water) means in a wastewater treatment apparatus that uses the action of microorganisms (activated sludge). In membrane separation, it is important to prevent clogging of the membrane as much as possible, and various apparatus structures and operation methods for that purpose have been devised (Japanese Patent Laid-Open Nos. 2-86893 and 1-293103, JP-A-5-277345). However, even if the device structure and operation method are optimized to prevent clogging of the membrane, the clogging of the membrane is greatly affected by changes in the properties of the activated sludge. It was difficult to maintain a good separation performance.

  In order to solve the above problems, a method has been proposed in which the membrane is less likely to be clogged by controlling the properties of activated sludge (Japanese Patent Laid-Open No. 10-151494). The feature of this method is that filamentous bacteria grow preferentially in the activated sludge in the biological reaction tank, making it difficult for clogging of the membrane, but to make filamentous bacteria dominant species The bioreactor should not be kept in a normal aerobic state, but must be kept slightly aerobic with a dissolved oxygen concentration (DO) of 1 mg / liter (hereinafter also referred to as L). However, under such microaerobic conditions, oxidation of organic matter (BOD) and nitrification of nitrogen are not performed efficiently, so that the processing time is long, foaming is likely to occur in a biological reaction tank, There is a problem that a biofilm floating on the liquid surface of the biological reaction tank is likely to occur.

  More specifically, the above devised or proposed technology is as follows. That is, the technique described in Japanese Patent Application Laid-Open No. 2-86893 can efficiently peel the membrane surface cake layer with a simple structure by surrounding the membrane module and the diffuser tube with a rectangular box shape that is open on both sides. It can be done. In the technique described in Japanese Patent Laid-Open No. 1-293103, the suction means for sucking the treated water take-out side is intermittently operated to increase or decrease the negative pressure applied to the film surface, and the cake layer is accumulated on the film surface. Can be effectively prevented. The technique described in Japanese Patent Laid-Open No. 5-277345 can increase the filtration area by setting the interval between the filtration elements to 6 to 10 mm and the casing length under the membrane surface to 500 to 2000 mm, and the gas-liquid two-phase flow is The parallel flow can prevent the generation of dead space and can uniformly clean the entire film surface.

  The technology described in Japanese Patent Laid-Open No. 10-151494 is based on the condition that filamentous bacteria become a priority species in a wastewater treatment apparatus equipped with a membrane separation device as a solid-liquid separation means of a biological reaction tank that performs biological treatment of sewage wastewater. It is characterized by driving at. With this technology, the high purification ability of filamentous bacteria can be used effectively, and the membrane is less likely to be clogged. In order to make filamentous bacteria the dominant species, it is necessary to keep the biological reaction tank microaerobic (dissolved oxygen concentration: 0 to 1 mg / L).

In order to control the properties of activated sludge so as to facilitate membrane separation, an appropriate operation management index is required. As an index of membrane filtration properties of activated sludge, there is an index called “filter paper filtration amount”, which is generally known. Specifically, it is a method in which a filter paper obtained by folding a flat flat membrane filter paper having a pore diameter of 1 μm is set in a funnel, 50 ml of activated sludge is added, and the filtration amount for 5 minutes is measured. Thereby, it is said that it can be evaluated whether the activated sludge is a property suitable for membrane separation. However, this method has a problem of lack of accuracy due to a large measurement error. In addition, this index alone is not sufficient for use as an actual management index because the state of activated sludge cannot be sufficiently grasped.
JP-A-2-86893 JP-A-1-293103 JP-A-5-277345 JP-A-10-151494

  The present invention has been made paying attention to such circumstances, and its purpose is to biologically treat the wastewater, and to separate the treated water into solid and liquid using a separation membrane for wastewater treatment. It is an object of the present invention to provide a wastewater treatment method and a wastewater treatment apparatus that can be operated while maintaining activated sludge in a condition in which the separation membrane is not easily clogged under aerobic conditions in which nitrification of nitrogen can be sufficiently performed.

  In order to achieve the above object, the present inventors have intensively studied, and as a result, completed the present invention. According to the present invention, the above object can be achieved.

  The present invention thus completed and capable of achieving the above object relates to a wastewater treatment method and a wastewater treatment apparatus, and is directed to a wastewater treatment method according to claims 1 to 4 (first to fourth inventions). The waste water treatment method according to claim 5) and the waste water treatment device according to claim 5 (the waste water treatment device according to the fifth invention), which has the following configuration.

  That is, the wastewater treatment method according to claim 1 includes a step of biologically treating the wastewater in an activated sludge treatment tank and a step of solid-liquid separation of treated water obtained by biological treatment in the step using a separation membrane. A wastewater treatment method comprising collecting activated sludge from the activated sludge treatment tank, measuring the amount of filtrate when the activated sludge is filtered with a filter paper having a pore diameter of 0.4 to 2 μm, and treating the activated sludge with a pore diameter of 6 Measure the SS concentration of the filtrate when filtered with ~ 10 μm filter paper, and control the treatment conditions in the activated sludge treatment tank based on the measured filtrate amount and SS concentration value A wastewater treatment method [first invention].

  The waste water treatment method according to claim 2 is the waste water treatment method according to claim 1, wherein a cylindrical filter paper is used as the filter paper having a pore diameter of 0.4 to 2 μm, and a cylindrical filter paper is used as the filter paper having the pore diameter of 6 to 10 μm. .

  The wastewater treatment method according to claim 3 is the wastewater treatment method according to claim 1, wherein a filter paper having a pore diameter of 1 μm is used as the filter paper having a pore diameter of 0.4 to 2 μm, and a filter paper having a pore diameter of 8 μm is used as the filter paper having a pore diameter of 6 to 10 μm. There is [third invention].

  In the wastewater treatment method according to claim 4, in the measurement of the filtrate amount and the SS concentration, 50 ml of activated sludge is filtered under the condition of filtering for 5 minutes, and the measured filtrate amount and SS concentration are expressed as follows (1) The wastewater treatment method according to any one of claims 1 to 3, wherein the wastewater treatment method is classified into four cases (4) to control treatment conditions in the activated sludge treatment tank according to each classification [fourth invention]. .

[Case 1] Measured filtrate volume: 10 ml or more, Measured SS concentration: 40 mg / L or less [Case 2] Measured filtrate volume: 10 ml or more, Measured SS concentration: more than 40 mg / L [Case 3] Measured filtrate volume: less than 10 ml, measured SS concentration: 40 mg / L or less [Case 4] Measured filtrate volume: less than 10 ml, measured SS concentration: more than 40 mg / L

  The wastewater treatment apparatus according to claim 5, comprising an activated sludge treatment tank for biologically treating the wastewater, and means for solid-liquid separation of treated water obtained by treatment in the treatment tank using a separation membrane. The sludge collection means for collecting activated sludge from the activated sludge treatment tank, the first filtration means for filtering the activated sludge collected by the sludge collection means, and the amount of filtrate filtered by the first filtration means A filtrate amount measuring means for measuring the concentration, a second filtration means for filtering the activated sludge collected by the sludge collecting means, and an SS concentration for measuring the SS concentration of the filtrate obtained by filtration by the second filtration means A wastewater treatment apparatus comprising a measuring means [fifth invention].

  According to the wastewater treatment method according to the present invention, when the wastewater is biologically treated and the treated water is subjected to solid-liquid separation using a separation membrane for wastewater treatment, aerobic conditions that can sufficiently perform BOD oxidation and nitrification of nitrogen content. In this case, the activated sludge can be kept in a state where the separation membrane is not easily clogged.

  According to the waste water treatment apparatus according to the present invention, the above-described waste water treatment method according to the present invention can be performed, and as a result, the above-described effects can be achieved.

  As a result of intensive studies to achieve the above object, the inventors of the present invention combined the following two indices (index A and index B) to control the operating conditions, thereby causing the separation membrane to clog the membrane. I found that it was difficult to drive.

  Index A: The amount of filtrate when activated sludge in an activated sludge treatment tank is filtered through a filter paper having a pore diameter of 0.4-2 μm

  Index B: SS (suspended substance) concentration of filtrate when activated sludge is filtered through filter paper with a pore size of 6 to 10 μm

  The present invention has been completed based on such knowledge, and a wastewater treatment method according to the present invention includes a step of biologically treating wastewater in an activated sludge treatment tank, and a treatment obtained by biological treatment in the step. A wastewater treatment method comprising a step of separating water into a solid and a liquid using a separation membrane, wherein activated sludge is collected from the activated sludge treatment tank, and the activated sludge is filtered through a filter paper having a pore diameter of 0.4 to 2 μm. The liquid amount is measured, and the SS concentration of the filtrate when the activated sludge is filtered through a filter paper having a pore diameter of 6 to 10 μm is measured. Based on the measured filtrate amount and SS concentration value, the activated sludge is measured. The wastewater treatment method is characterized by controlling treatment conditions in the treatment tank.

  According to the wastewater treatment method of the present invention, as can be seen from the above knowledge, BOD oxidation and nitrification of nitrogen content are performed when the wastewater is biologically treated, and the treated water is separated into solid and liquid using a separation membrane for wastewater treatment. Therefore, it is possible to operate with the activated sludge maintained in a property in which the separation membrane is not easily clogged under aerobic conditions where the above can be sufficiently performed.

  It is desirable to use a cylindrical filter paper as the filter paper having a pore diameter of 0.4 to 2 μm, and a cylindrical filter paper as the filter paper having a pore diameter of 6 to 10 μm [second invention]. If cylindrical filter paper is used in this way, analysis with a measurement error smaller than that of a general filter paper filtration amount measurement method becomes possible.

  The amount of filtrate is, for example, filtered under the condition that 50 ml of activated sludge is filtered for 5 minutes to obtain the measured filtrate amount. As the cylindrical filter paper, for example, a cylindrical filter paper (for example, ADVANTEC No. 86R) having a pore diameter of 1 μm is used.

  As the SS (suspended substance) concentration, for example, 50 ml of activated sludge is filtered under the condition of filtering for 5 minutes to obtain the measured SS concentration of the filtrate. As the filter paper in this filtration, for example, cylindrical filter paper (for example, ADVANTEC No. 84) having a pore diameter of 8 μm is used. The SS concentration is measured according to a general method such as a sewage test method. If the relationship between the SS concentration and the turbidity is examined in advance, the turbidity can be used instead of the SS concentration. Turbidity is measured, for example, with a turbidimeter 2100N type (manufactured by HACH).

  Embodiments of the present invention are shown in FIGS. FIG. 1 is a schematic configuration diagram showing an example of a wastewater treatment apparatus according to the present invention. FIG. 2 is a schematic diagram showing a method for measuring the index A and the index B according to the present invention.

  The wastewater treatment apparatus shown in FIG. 1 performs wastewater treatment by an activated sludge method, and purifies wastewater in a biological reaction tank 13 equipped with a membrane separation device 11 and an aeration device 12. The raw waste water flows into the biological reaction tank 13 through the pipe 14 and is purified. After that, the treated water is filtered by the membrane separator 11 and sucked and discharged by the pump 16 provided in the pipe 15. In addition, air supplied from the pipe 17 is aerated through the diffuser 12 to the biological reaction tank 13, and the biological reaction tank 13 is maintained in an aerobic state. The biological reaction tank 13 corresponds to an activated sludge treatment tank, and the membrane separation device 11 corresponds to a means for solid-liquid separation.

  The membrane used in the membrane separation device 11 is generally a precision membrane (MF membrane), an ultrafiltration membrane (UF membrane), etc., but a microorganism cake layer is formed on a coarse membrane such as a nonwoven fabric during membrane separation. It is also possible to use so-called dynamic filtration, in which filtration is performed.

  When measuring the index A (that is, measuring the amount of filtrate when the activated sludge in the activated sludge treatment tank is filtered through a filter paper having a pore diameter of 0.4 to 2 μm), the filter paper having a pore diameter of 0.4 to 2 μm is used. If a filter paper with a pore size smaller than 0.4 μm is used, the amount of filtration will be small for any sample. Therefore, differences due to differences in sludge properties are unlikely to occur, and if a filter paper with a pore size larger than 2 μm is used, it will be filtered for any sample. This is because the excess amount increases, so that differences due to differences in sludge properties are less likely to occur. Among filter papers having a pore diameter of 0.4 to 2 μm, it is preferable to use a filter paper having a pore diameter of 1 μm [third invention]. When such a filter paper having a pore diameter of 1 μm is used, a difference due to a difference in sludge properties is likely to occur.

  When measuring the index B (that is, measuring SS (suspended substance) concentration of the filtrate when activated sludge is filtered through a filter paper having a pore size of 6 to 10 μm), filter paper having a pore size of 6 to 10 μm is used. The reason is that if a filter paper with a pore size smaller than 6 μm is used, the fine SS component in the activated sludge is difficult to pass through the filter paper. This is because the filter paper passes through a relatively large SS component in the sludge, so that differences due to differences in sludge properties are less likely to occur. Among the filter papers having a pore diameter of 6 to 10 μm, it is preferable to use a filter paper having a pore diameter of 8 μm [third invention]. When such a filter paper having a pore diameter of 8 μm is used, a difference due to a difference in sludge properties is likely to occur.

  When measuring index A, filter paper with a pore size of 1 μm is filtered under the condition that 50 ml of activated sludge is filtered for 5 minutes. When measuring index B, filter paper with a pore diameter of 8 μm is used and filtered with the condition of filtering 50 ml of activated sludge for 5 minutes. In this case, if the index A is 10 ml or more and the index B is 40 mg / L or less, it can be determined that the activated sludge has good properties that facilitate membrane separation. Furthermore, if the index A is 15 ml or more and the index B is 20 mg / L or less, the properties are even better.

  On the other hand, if the index A is less than 10 ml or / and the index B is greater than 40 mg / L, it can be determined that the activated sludge has become unsuitable for membrane separation, and the countermeasures described later (see the table below). 2) is necessary.

  In order to keep the activated sludge in the biological reaction tank 3 in a state where it can be easily membrane-separated, basically, the activated sludge concentration, aeration amount, treatment time, etc. are adjusted so as to maintain the conditions shown in Table 1. While driving. The operating condition is preferably within the optimum range shown in Table 1, but if it is difficult to maintain the optimum range due to the restrictions of the apparatus, the type of drainage, etc., the operation may be performed within the appropriate range shown in Table 1.

  Basically, by keeping the conditions shown in Table 1, activated sludge can be kept in a good condition that prevents membrane clogging. However, changes in the components and concentration of the inflowing wastewater, changes in temperature, and other equipment problems For example, the sludge properties may change, and the membrane may be easily clogged.

  In order to prevent this, it is necessary to monitor the two indices (index A and index B), grasp the state of activated sludge, and take appropriate measures according to the situation. This is summarized in Table 2.

  Since case 1 is activated sludge having good properties suitable for membrane separation, it is sufficient to perform the operation for maintaining the current state.

  Case 2 shows that the bacteria in the activated sludge grow in a dispersed state and the fine suspension is increasing. In this case, any one of the countermeasures (1) to (5) in Table 2 One or more are performed to control the dispersal growth of bacteria.

  Case 3 indicates that the activated sludge floc has been dismantled and the floc has become smaller. In this case, any one or more of the measures (1) to (5) in Table 2 are implemented to activate activated sludge. The operation which suppresses the dismantling of is performed.

  Case 4 indicates that the properties of activated sludge deteriorated further from Case 2 or Case 3 and changed to properties that are not suitable for membrane separation, and the dispersal growth of bacteria or the dismantling of activated sludge flocs is significant. It can be judged that there is. When the case 2 is reached through the case 2, the countermeasure for the case 2 is carried out, and when the case 4 is reached through the case 3, the countermeasure for the case 3 is carried out so that the activated sludge can be easily separated from the membrane. Let me recover.

  To change the operating conditions in each measure, first increase or decrease the operating value of each item in the current operating conditions at a rate of 5 to 20%. If no improvement effect is seen, the operating conditions at a higher rate To change.

  The indicators A and B may be monitored at an appropriate interval according to the driving situation, but in practice, monitoring every 8 to 24 hours is recommended.

  An example of the monitoring device for the indicators A and B is shown in FIG. In the case of this apparatus, a certain amount of activated sludge is sent from the biological treatment tank through line 2 or line 3 by pump 1. The activated sludge having passed through the line 2 is filtered with a filter paper 4 having a pore diameter of 0.4 to 2 μm, and after a certain time, the weight of the filtrate is measured and recorded by the weight measuring unit 5 (index A). On the other hand, the activated sludge passing through the line 3 is filtered with a filter paper 6 having a pore diameter of 6 to 10 μm, and after a certain time, the turbidity of the filtrate is measured and recorded by the turbidity measuring unit 7 (index B). The filter paper is exchanged by the filter paper exchange device 8 at every measurement.

  An example of the process incorporating the monitoring device is shown in FIG. In the case of this process, a fixed amount of activated sludge is sent from the biological treatment tank 21 (see FIG. 2) of the membrane separation activated sludge apparatus to the monitoring apparatus 23 (see FIG. 3) at regular intervals by the sludge transfer pump 22. The monitoring device 23 automatically measures and records the indicators A and B according to the present invention. The operation is performed by the method of the present invention based on the measurement result. When the operation control is automatically performed, the measurement result of the monitoring device 23 is transmitted as an electric signal 24 to the control panel 25, and the operation control is automatically performed by the control panel 25 based on the electric signal.

  The waste water treatment method according to the fourth aspect of the present invention is configured to take appropriate measures according to the case as described above. This waste water treatment method is the waste water treatment method according to the present invention described above, and when measuring the filtrate amount and the SS concentration, 50 ml of activated sludge is filtered for 5 minutes, and the filtrate amount and the SS concentration measured. Are classified into the following four cases 1 to 4, and the treatment conditions in the activated sludge treatment tank are controlled according to each classification.

[Case 1] Measured filtrate volume: 10 ml or more, Measured SS concentration: 40 mg / L or less [Case 2] Measured filtrate volume: 10 ml or more, Measured SS concentration: more than 40 mg / L [Case 3] Measured filtrate volume: less than 10 ml, measured SS concentration: 40 mg / L or less [Case 4] Measured filtrate volume: less than 10 ml, measured SS concentration: more than 40 mg / L

  That is, when measuring the index A and the index B, 50 ml of activated sludge is filtered for 5 minutes, and the measured values (index A and index B) are classified into the following four cases 1 to 4, The treatment conditions in the activated sludge treatment tank are controlled according to each classification.

[Case 1] Indicator A: 10 ml or more, Indicator B: 40 mg / L or less [Case 2] Indicator A: 10 ml or more, Indicator B: More than 40 mg / L [Case 3] Indicator A: Less than 10 ml, Indicator B: 40 mg / L [Case 4] Indicator A: Less than 10 ml, Indicator B: More than 40 mg / L

  Control of the treatment conditions in the activated sludge treatment tank is performed as shown in Table 2, for example.

  According to the above wastewater treatment method, as can be seen from the above-mentioned Table 2 and the like, an appropriate response can be taken according to the case, so that the activated sludge can be more reliably maintained in a property that the separation membrane is not easily clogged. [4th invention].

  As described above, the wastewater treatment apparatus according to the present invention comprises an activated sludge treatment tank for biologically treating wastewater, and means for solid-liquid separation of treated water obtained by treatment in the treatment tank using a separation membrane. A wastewater treatment apparatus having sludge collection means for collecting activated sludge from the activated sludge treatment tank, first filtration means for filtering activated sludge collected by the sludge collection means, and filtration by the first filtration means A filtrate amount measuring means for measuring the filtrate amount, a second filtration means for filtering the activated sludge collected by the sludge collecting means, and an SS concentration of the filtrate obtained by filtration by the second filtration means. The waste water treatment apparatus includes an SS concentration measuring means for measuring.

  According to the above wastewater treatment apparatus, the activated sludge is collected from the activated sludge treatment tank by the sludge collecting means, the collected activated sludge is filtered by the first filtration means, and the filtrate amount is filtered by the filtrate amount measuring means. The activated sludge that has been measured and collected is filtered by the second filtration means, and the SS concentration of the filtrate obtained by filtration can be measured by the SS concentration measurement means. At this time, by using a filter paper having a pore diameter of 0.4 to 2 μm as the filter paper in the first filtration means and using a filter paper having a pore diameter of 6 to 10 μm as the filter paper in the second filtration means, the activated sludge is filtered with a filter paper having a pore diameter of 0.4 to 2 μm. And the SS concentration of the filtrate when the activated sludge is filtered through a filter paper having a pore diameter of 6 to 10 μm can be measured. And based on the value of this filtrate amount and SS density | concentration, the process conditions in an activated sludge processing tank can be controlled.

  Therefore, according to the waste water treatment apparatus according to the present invention, the waste water treatment method according to the present invention can be performed, and as a result, the same operational effects as in the case of the waste water treatment method can be achieved.

  As said 1st filtration means, what was shown in above-mentioned FIG. 2 can be used, for example. As said 2nd filtration means, what was shown in above-mentioned FIG. 2 can be used, for example. The thing shown in this FIG. 2 can be shared as a 1st filtration means and a 2nd filtration means.

  Examples of the present invention and comparative examples will be described below. The present invention is not limited to this embodiment, and can be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention, all of which are within the technical scope of the present invention. include.

[Example 1]
Membrane separation activated sludge treatment equipment that continuously treats general municipal sewage (active sludge treatment tank for biological treatment and means for solid-liquid separation of treated water obtained by treatment in the treatment tank using a separation membrane; Activated sludge is collected three times on different days from each other, and the first sample is sample a, the second sample is sample b, and the third sample is sample c. A sample of the above sample was crumpled using a cylindrical filter paper (ADVANTEC No. 86R, pore diameter 1 μm) and a circular flat membrane filter paper (ADVANTEC 5C, pore diameter 1 μm), and the amount of filter paper filtered (filtered liquid when filtered) Amount) (ml / 5 min) was measured. The results are shown in Table 3. The MLSS concentration of the collected activated sludge is 10000 to 11000 mg / L.

  When the cylindrical filter paper is used, it can be seen that the standard deviation is small, that is, the measurement error is small. On the other hand, it can be seen that the standard deviation is large, that is, the measurement error is large when a fold filter paper that is generally used is used. Therefore, if cylindrical filter paper is used, highly reliable data can be obtained by a single measurement.

[Example 2]
Operation according to the present invention in a membrane separation activated sludge method for general municipal sewage (a wastewater treatment method in which wastewater is biologically treated in an activated sludge treatment tank and then the treated water is separated into solid and liquid using a separation membrane) The results with and without control are shown in FIGS. That is, the activated sludge is collected from the activated sludge treatment tank, and when the activated sludge is filtered through a cylindrical filter paper having a pore diameter of 1 μm, the amount of filtrate (index A) is measured, and this activated sludge is filtered through a cylindrical filter paper having a pore diameter of 8 μm. The SS concentration (indicator B) of the filtrate was measured, and the processing conditions in the activated sludge treatment tank were controlled based on the measured filtrate amount (index A) and SS concentration (index B). FIG. 5 shows the results when the operation was performed as described above [Embodiment 1 of the present invention]. Neither the measurement of the index A nor the measurement of the index B, nor the control of the activated sludge treatment tank treatment conditions based on the index A and the index B, except for these points, is the same as the above case (in the case of FIG. 5). FIG. 6 shows the result of the operation under the above conditions [Comparative Example 1].

  In the membrane separation activated sludge method, since the membrane is gradually blocked, if the transmembrane pressure difference exceeds a certain level, it is necessary to stop the operation and perform cleaning. In this example (Example 1, Comparative Example 1), membrane cleaning was performed when the transmembrane pressure difference became 20 kPa higher than the initial value.

  In the case of Example 1 of the present invention, the activated sludge can be controlled so that it can be easily separated from the membrane, so that the increase in the transmembrane pressure difference is gradual, and 120 days of operation is possible with only one membrane cleaning. there were. On the other hand, in the case of Comparative Example 1, since the rate of increase in the transmembrane pressure difference was large, it was necessary to clean the membrane 4 times during 120 days, which took time and cost.

[Example 3]
In a membrane separation activated sludge process that treats general municipal sewage, the activated sludge with good properties (sample A ₁ ) when operating smoothly and the transmembrane pressure difference rise to 20 kPa or more in about one week. Using such activated sludge (sample B ₁ ), index A and index B were measured using filter paper with various pore sizes. The measurement results of this index A are shown in Table 4, and the measurement results of index B are shown in Table 5.

In the measurement of the index A, when filter paper having a pore diameter of 0.4 to 2 μm, particularly 1 μm, is used, the difference between the sample A ₁ and the sample B ₁ [filter paper filtration amount, ie, difference in filtrate amount (index A)] most large, it can be seen clearly distinguishable differences in properties of sample a ₁ and the sample B ₁ (Table 4).

In the measurement of the index B, the difference between the sample A ₁ and the sample B ₁ [difference in SS concentration of the filtrate (index B)] is largest and clear when filter paper having a pore diameter of 6 to 10 μm, especially 8 μm is used. it can be seen that can distinguish between properties of a sample a ₁ and the sample B ₁ in (Table 5).

  According to the wastewater treatment method and the wastewater treatment apparatus according to the present invention, BOD oxidation and nitrification of nitrogen content are sufficient when the wastewater is biologically treated and the treated water is separated into solid and liquid using a separation membrane for wastewater treatment. Since the activated sludge can be kept in a state where the separation membrane does not easily clog under the aerobic conditions that can be performed, it can be suitably used as a wastewater treatment method and a wastewater treatment apparatus.

It is a schematic diagram which shows an example of the waste water treatment apparatus which concerns on this invention. It is a schematic diagram which shows an example of the means for measuring the parameter | index which concerns on this invention. It is a schematic diagram which shows an example of the monitoring apparatus of the parameter | index which concerns on this invention. It is a schematic diagram which shows an example of the waste water treatment apparatus incorporating the monitoring apparatus of the parameter | index which concerns on this invention. It is a driving | operation result in the case of Example 1 of this invention, Comprising: It is a figure which shows the relationship between a driving | running day and transmembrane differential pressure. It is a driving | operation result in the case of the comparative example 1, Comprising: It is a figure which shows the relationship between a driving | running day and transmembrane pressure difference.

Explanation of symbols

  1--pump, 2--line, 3--line, 4--filter paper, 5--weight measuring unit, 6--filter paper, 7--turbidity measuring unit, 8--filter paper changing device, 11-- Membrane separator, 12--Air diffuser, 13--Bioreaction tank, 14--Piping, 15--Piping, 16--Pump, 17--Piping, 21--Biological treatment tank, 22--Sludge transfer Pump, 23--Monitoring device, 24--Electric signal, 25--Control panel.

Claims (5)

  A wastewater treatment method comprising a step of biologically treating wastewater in an activated sludge treatment tank and a step of solid-liquid separation of treated water obtained by biological treatment in the step using a separation membrane, wherein the activated sludge treatment Collect activated sludge from the tank, measure the amount of filtrate when the activated sludge is filtered through a filter paper with a pore diameter of 0.4-2 μm, and filter the filtrate when the activated sludge is filtered through a filter paper with a pore diameter of 6-10 μm. A wastewater treatment method characterized by measuring SS concentration and controlling treatment conditions in the activated sludge treatment tank based on the measured filtrate amount and SS concentration value.   The wastewater treatment method according to claim 1, wherein a cylindrical filter paper is used as the filter paper having a pore diameter of 0.4 to 2 µm, and a cylindrical filter paper is used as the filter paper having the pore diameter of 6 to 10 µm.   The waste water treatment method according to claim 1 or 2, wherein a filter paper having a pore diameter of 1 µm is used as the filter paper having a pore diameter of 0.4 to 2 µm, and a filter paper having a pore diameter of 8 µm is used as the filter paper having a pore diameter of 6 to 10 µm. When measuring the filtrate amount and SS concentration, 50 ml of activated sludge is filtered under the condition of filtering for 5 minutes, and the measured filtrate amount and SS concentration are classified into the following four cases 1 to 4, respectively. The waste water treatment method in any one of Claims 1-3 which controls the process conditions in an activated sludge process tank according to.
[Case 1] Measured filtrate volume: 10 ml or more, Measured SS concentration: 40 mg / L or less [Case 2] Measured filtrate volume: 10 ml or more, Measured SS concentration: more than 40 mg / L [Case 3] Measured filtrate volume: less than 10 ml, measured SS concentration: 40 mg / L or less [Case 4] Measured filtrate volume: less than 10 ml, measured SS concentration: more than 40 mg / L A wastewater treatment apparatus having an activated sludge treatment tank for biologically treating wastewater, and means for solid-liquid separation of treated water obtained by treatment in the treatment tank using a separation membrane, from the activated sludge treatment tank Sludge collection means for collecting activated sludge, first filtration means for filtering activated sludge collected by the sludge collection means, filtrate amount measurement means for measuring the amount of filtrate filtered by the first filtration means, It has 2nd filtration means which filters the activated sludge collected by the said sludge collection means, and SS concentration measurement means which measures SS concentration of the filtrate obtained by filtering by said 2nd filtration means, It is characterized by the above-mentioned. Wastewater treatment equipment.

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