JP2006043563A - Wastewater treatment method and wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment method and apparatus which can prevent the flow out of activated sludge from a final settling basin due to the deterioration of activated sludge settling properties when wastewater is treated with the activated sludge. <P>SOLUTION: (1) In the waste water treatment method using the activated sludge, the kinds and number of protozoa in the activated sludge are measured, a diversity index is calculated from the results, and the settling properties of the activated sludge are predicted based on the value of the diversity index to judge whether prevention of flow out of the activated sludge from the final settling basin is necessary or not. (2) In the above waste water treatment method, the calculation of the diversity index is performed with Shannon's equation for obtaining a diversity index. (3) In the above waste water treatment method, preventative measures against the flow out of the activated sludge from the final settling basin are taken when the value of the diversity index calculated with the above equation is below the predetermined value (for example, 0.4-0.6). (4) The wastewater treatment apparatus is used for such a wastewater treatment method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to a technical field related to a wastewater treatment method and a wastewater treatment apparatus, and more specifically to a technical field related to a wastewater treatment method and a wastewater treatment apparatus using activated sludge.

  In the wastewater treatment method using the action of microorganisms (activated sludge), the wastewater treatment equipment used for it generally consists of a first sedimentation tank, a biological treatment tank (aeration tank), and a final sedimentation tank. The pollutant is taken into microorganisms (activated sludge) by biological treatment, and water and activated sludge (hereinafter also referred to as sludge) are separated into solid and liquid in the final sedimentation basin. Part of the sludge settled in the final sedimentation basin is discarded as surplus sludge, and part of it is returned to the wastewater treatment facility and used again in the biological treatment tank. On the other hand, the supernatant liquid separated into solid and liquid is discharged from the upper part of the final sedimentation basin as treated water.

  Therefore, in wastewater treatment using activated sludge, good solid-liquid separation in the final sedimentation basin is important.If solid-liquid separation cannot be performed well, that is, activated sludge does not settle well, activated sludge This will cause a fatal situation for wastewater treatment in which the quality of treated water deteriorates due to the outflow with treated water.

  Generally, in wastewater treatment using activated sludge, operation is often dependent on experience, and the problem of sludge spillage is mostly dealt with empirically after sedimentation actually begins to deteriorate. However, there is a problem that sludge flows out after a delay.

  There are SV30 and SVI as general indicators of sedimentation of activated sludge. However, this indicator can be used to determine whether sedimentation has already deteriorated, but it cannot predict what will happen in the future. These SV30 and SVI are indicators such as (1) and (2) below.

(1) SV30:
Put 1 L of activated sludge into a 1 L (liter) measuring cylinder and let it stand for 30 minutes, then read the scale at the sludge interface and check the sludge volume V (ml). Calculate SV30 from the following equation (3). It is judged that the sludge has better sedimentation as this value is smaller ["Sewage test method", Japan Sewerage Association, 1997, p. 271-272 (Non-Patent Document 1)].
SV30 (%) = 100 x V / 1000 --------------------- Equation (3)

(2) SVI:
Using the above SV30 value and sludge concentration (MLSS; mg / L), calculate by the following formula (4). It is judged that the sludge has better sedimentation as this value is smaller ["Sewage test method", Japan Sewerage Association, 1997, p. 272 (Non-Patent Document 2)].
SVI (ml / g) = SV30 × 10000 / MLSS ------------- Formula (4)

  Abnormal growth of filamentous bacteria is well known as a cause of the deterioration of sedimentation of activated sludge. Since the density of filamentous bacteria is low, if the filamentous bacteria grow abnormally, these hyphae are entangled with the activated sludge and the sedimentation property of the activated sludge deteriorates. Therefore, if the amount of filamentous bacteria is periodically checked with a microscopic observation as a biological indicator, sludge sedimentation caused by filamentous bacteria can be predicted. Driving may be performed. In order to reduce filamentous bacteria, there is a method of introducing a drug that inactivates filamentous bacteria.

  However, there are many unknown causes of sludge sedimentation deterioration, and there is often a problem that sludge sedimentation deteriorates and sludge flows out even in an environment where filamentous bacteria do not grow.

  If such sludge sedimentation deterioration can be predicted in advance, measures such as adding a flocculant at an early stage can be taken.

However, at present, there is no effective means for predicting in advance such sludge sedimentation deterioration, which is a means not based on filamentous bacteria.
"Sewage test method", Japan Sewerage Association, 1997, p. 271-272 "Sewage test method", Japan Sewerage Association, 1997, p. 272

  The present invention has been made paying attention to such circumstances, and its purpose is to prevent activated sludge outflow from the final sedimentation basin due to deterioration of activated sludge sedimentation when treating wastewater using activated sludge. It is an object of the present invention to provide a wastewater treatment method and a wastewater treatment apparatus that can perform the above.

  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 relates to a wastewater treatment method according to claims 1-7 (the wastewater treatment method according to the first to seventh inventions). ), A wastewater treatment apparatus according to claim 8 (a wastewater treatment apparatus according to the eighth invention), which has the following configuration.

  That is, the wastewater treatment method according to claim 1 is a wastewater treatment method using activated sludge, which quantifies the type and number of protozoa in the activated sludge, calculates a diversity index from the results, This is a wastewater treatment method characterized in that the settling property of activated sludge is predicted based on the value, and it is judged whether or not it is necessary to take measures to prevent activated sludge outflow from the final settling basin [first invention].

The wastewater treatment method according to claim 2 is the wastewater treatment method according to claim 1, wherein the diversity index is calculated using the following formula (1) [second invention]. However, in the following formula (1), DI is a diversity index, P _i is a value determined based on the following equation (2). In the following formula (2), N is the total number of protozoa, and N _i is the number of the i-th protozoa.

P _i = N _i / N --------------------- Equation (2)

  The waste water treatment method according to claim 3 takes measures to prevent activated sludge from flowing out from the final sedimentation basin when the diversity index becomes a predetermined value or less from the point of sedimentation of activated sludge. It is a waste water treatment method as described in [3rd invention].

  The waste water treatment method according to claim 4 is the waste water treatment method according to claim 3, wherein the predetermined value is 0.4 to 0.6 [fourth invention].

  The waste water treatment method according to claim 5 is the waste water treatment method according to claim 3, wherein the predetermined value is 0.6 [fifth invention].

  The wastewater treatment method according to claim 6, when taking preventive measures against activated sludge outflow from the final sedimentation basin, as this preventive measure, a method by adding a flocculant, a method by adding an inorganic substance, an activity from the final sedimentation basin The method according to any one of claims 1 to 5, wherein one or more of a method by increasing the amount of sludge extraction, a method by lowering the inflow of wastewater, and a method by injecting wastewater without first passing through the settling basin are used. It is a wastewater treatment method as described in [6th invention].

  The wastewater treatment method according to claim 7, when quantifying the type and number of protozoa in the activated sludge, automatically samples the activated sludge, and automatically measures the type and number of protozoa in the activated sludge by image analysis. The wastewater treatment method according to any one of claims 1 to 6, wherein the quantification is performed and the diversity index is calculated from the result, and is calculated by automatic calculation [Seventh Invention].

  The waste water treatment apparatus according to claim 8, wherein in the waste water treatment apparatus using activated sludge, means for automatically sampling activated sludge, and the type and number of protozoa in activated sludge automatically sampled thereby are automatically measured by image analysis. And a means for automatically calculating a diversity index from the result of the quantification, which is a wastewater treatment apparatus [8th invention].

  According to the wastewater treatment method of the present invention, when wastewater treatment is performed using activated sludge, activated sludge outflow from the final sedimentation basin due to deterioration of activated sludge settling can be prevented. According to the wastewater treatment apparatus according to the present invention, such a wastewater treatment method can be suitably performed.

  The present inventors have found that it is possible to predict the deterioration of sedimentation of activated sludge by examining the diversity of protozoa in activated sludge, and have completed the present invention. That is, the present inventors have found that the sedimentation property of activated sludge can be predicted from the value of the diversity index obtained by quantifying the type and number of protozoa in activated sludge. The present invention has been completed based on such knowledge, and is a wastewater treatment method having the above-described configuration.

  The wastewater treatment method according to the present invention thus completed is a wastewater treatment method using activated sludge, quantifies the type and number of protozoa in the activated sludge, calculates a diversity index from this result, It is a wastewater treatment method characterized by predicting the settling property of activated sludge based on the value of the diversity index, and determining whether it is necessary to take measures to prevent activated sludge outflow from the final settling basin [first invention ].

  Thus, if the kind and number of the protozoa in activated sludge are quantified and a diversity index is computed from this result, the sedimentation property of activated sludge can be predicted based on the value of this diversity index. Then, it is possible to determine whether or not it is necessary to take preventive measures against activated sludge outflow from the final sedimentation basin (hereinafter also referred to as sludge outflow preventive measures). If it does so, the prevention measure of the sludge outflow from the final sedimentation basin can be taken at an appropriate timing.

  Therefore, in the wastewater treatment method according to the present invention, as described above, the type and number of protozoa in the activated sludge are quantified, and a diversity index is calculated from the results, and based on the value of this diversity index. The sedimentation of activated sludge is predicted, and it is determined whether it is necessary to take measures to prevent activated sludge from flowing out from the final sedimentation basin. For this reason, sludge spill prevention measures (sludge spill spill prevention measures from the final sedimentation basin) can be taken at an appropriate timing.

  Therefore, according to the wastewater treatment method according to the present invention, activated sludge can be prevented from flowing out from the final sedimentation basin due to the deterioration of activated sludge sedimentation when wastewater is treated using activated sludge.

  Tens of thousands of protozoa are known in total, and it is said that more than 100 protozoa appear in activated sludge. Protozoa appearing in the activated sludge are broadly divided into flagellates, fleshly worms, and ciliates, and further classified into genus.

  By collecting activated sludge and observing under a microscope, the species of protozoa present per unit sludge volume, that is, per unit mass of sludge or per unit volume (for example, per ml) is identified to the genus, and the number of each is determined. It can be quantified. Therefore, the diversity of protozoa can be obtained from the type and number of protozoa per unit sludge amount.

A representative index of biological diversity is Shannon's diversity index, which is calculated by the following equation (5). However, in the following formula (5), DI is a diversity index, P _i is a value determined according to the following equation (6). In the following formula (6), N is the total number of individuals, N _i is the number of i-th individuals.

P _i = N _i / N --------------------- Equation (6)

The above formulas (5) to (6) can be applied to the diversity of protozoa in the activated sludge. That is, the diversity index of protozoa in activated sludge can be calculated using the following formula (1) [second invention]. In the following formula (1), DI is a protozoan diversity index, and _Pi is a value obtained based on the following formula (2). In the following formula (2), N is the total number of protozoa, and N _i is the number of the i-th protozoa. These N and _Ni are both the number of sludges per unit volume, and the unit is individual / unit volume (sludge), for example, individual / ml (sludge).

P _i = N _i / N --------------------- Equation (2)

Measures to prevent sludge spillage (activated sludge from the final sedimentation basin) when the diversity index calculated using the above formulas (1) to (2) falls below a predetermined value from the standpoint of sedimentation of activated sludge (Third invention). More specifically, this value is the upper limit of the diversity index (DI _eul ) when it is expected that sludge spill prevention measures need to be taken, that is, the diversity index is less than this value (DI _eul ). It is a value (DI _eul ) that is expected to take measures to prevent sludge spillage when it becomes, and is determined in advance (before wastewater treatment). This value is determined based on, for example, the result of past wastewater treatment, or is determined based on the result of conducting a wastewater treatment test in advance.

  If it does in this way, the sludge outflow prevention measure can be taken more easily. That is, it is possible to determine the time point at which sludge spill prevention measures are taken, and since it is determined, the time point at which the sludge spill prevention measures are taken is not complicated and simple. In addition, it is possible to take measures to prevent sludge outflow at a more appropriate timing, and more reliably prevent activated sludge outflow from the final sedimentation basin due to deterioration of activated sludge settling.

  As a result of the study by the present inventors, the activated sludge having a diversity index calculated using the above formulas (1) to (2) of greater than 0.6 is unlikely to deteriorate the settling property. It was found that activated sludge of 0.4 to 0.6 or less (0.4 to 0.6 or less) has a high possibility of deterioration of sedimentation. The standard of the diversity index when the sedimentation of activated sludge begins to deteriorate is around 0.5, but this value is not constant depending on the nature of the wastewater treatment and the operation method, and ranges from 0.4 to 0.6. Have. In other words, the diversity index when activated sludge sedimentation begins to deteriorate is 0.4 to 0.6. From a safety perspective, it is possible that sedimentation may deteriorate if the diversity index is 0.6 or less.

  Therefore, the predetermined value is preferably set to 0.4 to 0.6 [fourth invention]. That is, when the diversity index calculated using the above formulas (1) and (2) is 0.4 to 0.6 or less (0.4 to 0.6 or less), sludge spill prevention measures (active sludge spill from the final sedimentation basin) Preventive measures) should be taken. If it does in this way, the sludge outflow prevention measure can be taken at a more appropriate timing, and by extension, the activated sludge outflow from the final sedimentation basin due to the activated sludge sedimentation deterioration can be more reliably prevented.

  Further, the predetermined value may be set to 0.6 [fifth invention]. That is, when the diversity index calculated using the above formulas (1) to (2) is 0.6 or less, it is recommended to take measures to prevent sludge outflow. If it does in this way, activated sludge outflow from the final sedimentation basin by activated sludge sedimentation deterioration can be prevented more reliably than the above case.

  If such a diversity index is regularly monitored, it is possible to predict the deterioration of sedimentation of sludge, and it is possible to cope with the deterioration of sedimentation at an appropriate early timing.

  When taking measures to prevent sludge outflow, various methods generally used in the field of wastewater treatment can be used as the prevention measures. That is, a method by adding a flocculant, a method by adding an inorganic substance, a method by increasing the amount of activated sludge withdrawn from the final settling basin, a method by reducing the inflow of wastewater, and letting the wastewater flow through the first settling basin One kind or two or more kinds of methods may be used [sixth invention]. In addition, the inflow of wastewater without going through the first settling basin is a measure to prevent sludge spillage, so there is no settling in the first settling basin. This is because the sludge settleability in the pond is large (sludge is likely to settle).

  Even if these preventive measures are implemented after sludge settling has deteriorated, the wastewater treatment method according to the present invention, which can predict sludge settling in advance, is effective. Can prevent sludge outflow.

  When quantifying the type and number of protozoa in activated sludge by microscopic observation, for example, take an arbitrary amount of activated sludge collected from a biological treatment tank, for example, about 0.05 ml, place it on a slide glass, cover After placing the glass, set in a microscope and observe at a magnification that is easy to observe, for example, 100 to 200 times, and count the number and type of protozoa. Based on the result of this counting, the number per 1 ml of activated sludge is calculated. Observation may be performed once, but in order to increase the accuracy of counting, the average is repeated several times.

  Table 1 shows the results of quantification of types and numbers of protozoa in activated sludge by microscopic observation. In the case of Table 1, ten kinds of protozoa are observed, and the number of each is represented by N (pieces / ml). When the diversity index (DI) is calculated using the above formulas (1) to (2), DI = −0.86. DI is calculated in this way.

  It is desirable to measure the DI (diversity index) of protozoa in sludge as soon as possible so that the deterioration of sludge sedimentation can be predicted earlier. Since the sex does not deteriorate, in practice, it may be measured at a frequency of about once every 2 to 10 days.

  The DI value is usually around 1.0, but if it falls to 0.4 to 0.6 or less (0.4 to 0.6 or less), then the sedimentation of the sludge deteriorates and there is a risk of sludge spillage from the final sedimentation basin. There is sex. Therefore, when DI falls below 0.4 to 0.6, it is recommended to take measures to prevent sludge outflow. Note that the DI value when activated sludge sedimentation begins to deteriorate depends on the properties of the influent wastewater and the operation method in each wastewater treatment, so set a DI value suitable for each wastewater treatment as the operation continues. Measures to prevent sludge spillage should be taken when the value falls below this DI value. At this time, it is better to take measures to prevent sludge spillage when this DI value or a slightly lower DI value is reached. Furthermore, when setting to the safe side, it is only necessary to take measures to prevent sludge spillage when the DI value is 0.6.

  DI (diversity index) can be measured by a method of automatic measurement by image analysis in addition to a method of human observation by a microscope. Since protozoa can be classified according to their shape, a database relating to the shape and size of protozoa is incorporated into the image analysis apparatus, and the type and number can be automatically counted by automatically analyzing the image. DI can be automatically calculated from the type and number of protozoa. The activated sludge to be measured can be automatically sampled.

  Therefore, when quantifying the type and number of protozoa in the activated sludge, the activated sludge is automatically sampled, and the type and number of protozoa in the activated sludge are automatically measured and quantified by image analysis. When calculating the sex index, a method of calculating by automatic calculation can also be used [Seventh Invention].

  An exemplary embodiment for carrying out such a method is shown in FIG. The activated sludge is sampled by the automatic sampling device 13 from the waste water treatment facility 11 through the pipe 12. The sampled activated sludge is sent to the image analyzer 14, where the type and number of protozoa are automatically counted, and DI is automatically calculated. This data is sent as a signal to the control device 15, and the control device 15 determines the operation method. A signal from the control device 15 is sent to the wastewater treatment facility 11 to automatically control the operation.

  In this way, all may be automatically operated, or a part may be manually operated. For example, if the process up to image analysis is made automatic and an alarm is issued when DI becomes 0.6 or less, it is possible to perform a method such as manually controlling the operation by watching the alarm.

  As can be seen from such embodiments, the apparatus for performing the wastewater treatment method according to the present invention includes means for automatically sampling activated sludge, and the types of protozoa in the activated sludge automatically sampled thereby. It is preferable to use a device characterized in that it has a means for automatically measuring and quantifying the number by image analysis and calculating a diversity index from the result of this quantification by automatic calculation. The treatment method can be suitably carried out [8th invention]. That is, when activated sludge is sampled, this can be done automatically, saving labor, and when quantifying the type and number of protozoa in activated sludge, this can be done automatically, saving labor. In addition, the measurement (quantitative) accuracy is prevented from being reduced due to human error. Furthermore, when calculating the diversity index from the result of this quantitative measurement, this can be done automatically, saving labor and reducing human error. This prevents the calculation accuracy from being reduced.

  As shown in FIG. 2, the waste water treatment facility as described above is generally one having a first sedimentation basin, a biological treatment tank, and a final sedimentation basin, and the present invention is applied when such waste water treatment facility is used. However, the present invention can also be applied to a case where there is no initial sedimentation tank and a biological treatment tank and a final sedimentation tank are used.

  When measuring the diversity index of protozoa in activated sludge, the activated sludge in the biological treatment tank is usually sampled and used as the measurement sample, but it is sampled from the final sedimentation basin and used as the measurement sample. You can also.

  In the field of wastewater treatment, it is known that it is possible to evaluate whether the organic matter decomposing ability of activated sludge is stable using the diversity of microorganisms in activated sludge as an index. That is, the diversity index is used as an index for determining whether or not the microbial population can be satisfactorily treated with pollutants. However, the diversity index in this case is merely for judging the treatment status of the pollutant, and the relationship between the sludge settling property and the diversity index has not been known. That is, it has not been known so far that the sedimentation property of activated sludge can be predicted from the diversity index of protozoa in activated sludge as in the case of the present invention. It is an important matter.

  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.

[1] Example 1, Comparative Example 1
The wastewater treatment apparatus used in Example 1 and Comparative Example 1 is shown in FIG. This apparatus is a general waste water treatment apparatus and has the following configuration. That is, the waste water flows into the first settling basin 2 through the pipe 1, and the sediment is discarded through the pipe 3 as surplus sludge in the first settling pond 2. The supernatant water of the first sedimentation basin 2 flows into the biological treatment tank 5 through the pipe 4 and is biologically treated with activated sludge. The activated sludge after treatment flows into the final sedimentation basin 7 through the pipe 6, the sludge settled in the final sedimentation basin 7 is withdrawn through the pipe 8, a part of it is discarded as excess sludge, and a part is returned. It returns to the biological treatment tank 5 as sludge. On the other hand, the supernatant water of the final sedimentation basin 7 is discharged as treated water through the pipe 9.

  An experiment of wastewater treatment using the wastewater treatment apparatus was performed as follows. In other words, the general municipal sewage is used as the inflow wastewater to the sedimentation basin 2 and the operation is performed so that the activated sludge concentration (MLSS) in the biological treatment tank 5 is about 2,500 mg / L. The activated sludge is sampled from the tank 5 and the type and number of protozoa in the activated sludge are quantified. From this result, the diversity index (DI) of the protozoa in the activated sludge is expressed by the above formulas (1) to (2). And calculated. At the same time, a part of the treated water obtained from the final sedimentation tank 7 via the pipe 9 was sampled, and the treated water SS concentration (solid content concentration in the treated water) was measured. The treated water SS concentration is usually about 10 mg / L or less, but when sludge spill occurs, the activated sludge flows out together with the treated water, so the treated water SS concentration becomes high.

(1) Example 1
In the case of Example 1, measures for preventing sludge spillage (measures for preventing activated sludge spillage through the pipe 9 from the final sedimentation basin 7) were taken using the protozoan diversity index (DI) as an index. In other words, as shown in Fig. 3, sludge spill prevention measures (addition of aluminum flocculant) were implemented on the 95th day when DI became 0.6 or less (about 0.52), and DI recovered to over 0.6 (about 0.61). On the 130th day, the sludge prevention measures were completed. As a result, the treated water SS concentration was suppressed to 10 mg / L or less, and sludge outflow could be prevented.

(2) Comparative Example 1
In the case of the comparative example, sludge outflow prevention measures were taken after discovering sedimentation deterioration (increase in treated water SS concentration). That is, as shown in Fig. 4, the sludge spill prevention measures were not implemented even on the 125th day when the DI became 0.6 or less (about 0.55), and the treated water SS concentration increased to 20mg / L on the 145th day. Measures to prevent sludge outflow (addition of aluminum flocculant) were implemented. As a result, the treated water SS concentration reached a maximum of 500 mg / L or more, and sludge outflow could not be prevented.

  As can be seen from Fig. 4, the treated water SS concentration is almost zero even on the 125th day when DI is judged to be 0.6 or less (about 0.55) and it is necessary to take measures to prevent sludge spillage. On the 145th day when the DI decreased to about 0.5, a change (increase) in the concentration of treated water SS was detected for the first time. Therefore, although the treated water SS concentration can be used as an index to determine whether or not the sedimentation property has already deteriorated, it cannot be predicted in the future, and the sludge sedimentation property cannot be predicted in advance. For this reason, it can only be dealt with empirically after the sedimentation actually begins to deteriorate, and there is a high possibility that sludge will flow out with a delay in the response. The case where SV30 or SVI is used as an index is the same as the case where the treated water SS concentration is used as an index.

  On the other hand, as can be seen from Fig. 3, the protozoan diversity index (DI) is changing (decreasing) even when the concentration of treated water SS does not increase so much and it is not necessary to immediately take measures to prevent sludge spillage. In addition, deterioration of sludge sedimentation can be predicted in advance. For this reason, sludge spill prevention measures can be taken at an appropriate timing, and sludge spill can be prevented.

[2] Examination of the relationship between DI and the degree (frequency) of sludge spillage Using the wastewater treatment system shown in Fig. 2, the diversity index of protozoa in activated sludge (DI) in the same manner as in Example 1 ) Was measured for wastewater treatment. However, even if DI decreased, it was operated without implementing sludge spill prevention measures and it was confirmed whether sludge spill would occur.

  The results are shown in Table 2. In the case where DI did not drop to 0.6 (there were three times), sludge outflow was not observed in all three cases (in any of the three cases). In the case where DI decreased to 0.6 or less (0.6 to 0.55) (there were two times), sludge outflow was observed in one of the two times. In the case where DI decreased to 0.5 or less (0.5 to 0.45) (there were 3 times), sludge outflow was observed in 2 out of 3 times. In the case where DI decreased to 0.4 or less (0.4 to 0.2) (2 times), sludge outflow was observed twice.

  The wastewater treatment method according to the present invention can prevent activated sludge outflow from the final sedimentation basin due to the activated sludge sedimentation deterioration when wastewater treatment is performed using activated sludge. It can be suitably used without causing a situation. The wastewater treatment apparatus according to the present invention can be suitably used for such a wastewater treatment method.

It is a schematic diagram which shows the example of the apparatus for enforcing the wastewater treatment method which concerns on this invention. It is a schematic diagram which shows the waste water treatment apparatus used for the waste water treatment which concerns on Example 1 and Comparative Example 1. FIG. It is a figure which shows the relationship between the operation days of a wastewater treatment which concerns on Example 1, a diversity index (DI), and a treated water SS density | concentration. It is a figure which shows the relationship between the operation days of a wastewater treatment which concerns on the comparative example 1, a diversity index (DI), and a treated water SS density | concentration.

Explanation of symbols

1--piping, 2--first sedimentation basin, 3--piping, 4--piping, 5--biological treatment tank, 6--piping,
7--Final sedimentation basin, 8--Piping, 9--Piping,
11--Wastewater treatment equipment, 12--Piping, 13--Automatic sampling device, 14--Image analysis device,
15--Control device.

Claims (8)

  In the wastewater treatment method using activated sludge, the type and number of protozoa in the activated sludge are quantified, the diversity index is calculated from the results, and the sedimentation of the activated sludge is predicted based on the value of the diversity index. A wastewater treatment method characterized by determining whether it is necessary to take measures to prevent activated sludge spillage from the final sedimentation basin. The wastewater treatment method according to claim 1, wherein the diversity index is calculated using the following formula (1).

However, in the above formula (1), DI is a diversity index, P _i is a value determined based on the following equation (2).
P _i = N _i / N --------------------- Equation (2)
In the above formula (2), N is the total number of protozoa and N _i is the number of the i-th protozoa.   The wastewater treatment method according to claim 2, wherein measures for preventing activated sludge outflow from the final sedimentation basin are taken when the diversity index becomes equal to or less than a predetermined value in terms of sedimentation of activated sludge.   The wastewater treatment method according to claim 3, wherein the determined value is 0.4 to 0.6.   The wastewater treatment method according to claim 3, wherein the predetermined value is 0.6.   When taking preventive measures against activated sludge outflow from the final sedimentation basin, the preventive measures include a method by adding a flocculant, a method by adding an inorganic substance, a method by increasing the amount of activated sludge withdrawn from the final sedimentation basin, wastewater The wastewater treatment method according to any one of claims 1 to 5, wherein one or more of a method based on a decrease in inflow and a method based on inflowing wastewater without first passing through a settling basin are used.   When quantifying the types and number of protozoa in the activated sludge, the activated sludge is automatically sampled, and the types and number of protozoa in the activated sludge are automatically measured and quantified by image analysis. The wastewater treatment method according to any one of claims 1 to 6, wherein the index is calculated by automatic calculation when calculating the index. In wastewater treatment equipment using activated sludge, means for automatically sampling activated sludge, and the type and number of protozoa in the automatically sampled activated sludge are automatically measured and quantified by image analysis. A wastewater treatment apparatus having means for automatically calculating a diversity index.

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