JP3811635B2 - Sludge concentration control device and sewage treatment system equipped with the sludge concentration control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is applied to a sewage treatment system that purifies sewage by biological reaction treatment in a biological reaction tank, and sludge concentration for controlling the activated sludge concentration (MLSS: Mixed liquor suspended solids) in the biological reaction tank. The present invention relates to a sewage treatment system including a control device and a sludge concentration control device thereof. In particular, the present invention relates to a measure for optimizing the activated sludge concentration.
[0002]
[Prior art]
Conventionally, a sewage treatment system disclosed in JP-A-7-185586 is known as a system for treating sewage and waste water. This kind of sewage treatment system includes a biological reaction tank, purifies raw water (sewage) by biological reaction treatment using activated sludge inside the biological reaction tank, and flows this treated water together with the sludge into a sedimentation tank. Then, the treated water and the sludge are separated by precipitating the sludge inside the settling tank. The treated water that becomes the supernatant water by this separation is discharged from the system, while the sludge that has settled in the settling tank is drawn out and returned to the biological reaction tank.
[0003]
In order to efficiently perform the biological reaction treatment in the biological reaction tank in this type of system, it is important to appropriately maintain the balance between the amount of sewage in the biological reaction tank and the activated sludge concentration.
[0004]
The applicant of this application measures the activated sludge concentration in the biological reaction tank as a sewage treatment system in view of this point, calculates the difference between the measured actual activated sludge concentration and the concentration target value, It has been proposed to control the amount of excess sludge withdrawn from the settling tank (see Japanese Patent Application Laid-Open No. 9-192686). In other words, the activated sludge concentration can be maintained at a constant target value throughout the year, so that the biological reaction treatment in the biological reaction tank can be performed efficiently.
[0005]
[Problems to be solved by the invention]
As described above, the inventor of the present invention tried to further improve the sewage treatment system capable of maintaining the activated sludge concentration at a constant target value. In other words, instead of simply maintaining the activated sludge concentration at a constant target value, we considered that it would be possible to obtain the optimum activated sludge concentration according to the environmental conditions and system usage conditions.
[0006]
And the inventor of this invention needs to fully consider the height of activity of activated sludge (microorganism), in order to maintain the balance of the amount of sewage in a biological reaction tank, and activated sludge density | concentration appropriately. I found. In other words, for example, when comparing the situation where the water temperature is high as in the summer and the situation where the water temperature is low as in the winter, the activated sludge is relatively active in the summer, whereas the activated sludge is active in the winter. Is relatively low. That is, in both cases, even if the activated sludge concentration is the same, the treatment capacity for sewage is different. Then, due to fluctuations in the treatment capacity of the activated sludge, the following problems occur when a good balance between the amount of sewage in the biological reaction tank and the activated sludge concentration is not ensured.
[0007]
In other words, when the activated sludge has a relatively high activity and there is not enough sewage in the biological reaction tank, self-digestion due to lack of nutrients in the activated sludge and scum (the dead body of microorganisms) There is a concern that the quality of the treated water will deteriorate due to the occurrence. Conversely, when the activated sludge activity is relatively low and the amount of sewage exceeding the treatment capacity exists in the biological reaction tank (when the biological load is large), the sewage can be treated sufficiently. In this case as well, there is a concern that the quality of the treated water will deteriorate. Thus, the inventor of the present invention has found that the biological reaction treatment in the biological reaction tank cannot be efficiently performed simply by maintaining the activated sludge concentration at a constant target value, and has reached the present invention. It is.
[0008]
In addition to such a seasonal change as described above, for example, in a sewage treatment system applied to a sightseeing spot or the like, the amount of sewage inflow varies greatly between the on-season and the off-season, and the use of the system. (For example, a change in the number of biological reaction tanks used in a system including a plurality of biological reaction tanks). In other words, the same problem occurs even when the balance between the concentration of activated sludge and the amount of sewage in the biological reaction tank is not ensured by these changes.
[0009]
The present invention has been made in view of such a point, and the object of the present invention is to appropriately balance the amount of sewage in the biological reaction tank and the activated sludge concentration in consideration of the height of activity of the activated sludge. Thus, the biological reaction treatment in the biological reaction tank can be performed more efficiently.
[0010]
[Means for Solving the Problems]
-Summary of invention-
In order to achieve the above object, the present invention does not maintain the activated sludge concentration in the biological reaction tank constant, but changes the target value of the activated sludge concentration according to the environmental conditions and the system usage status. The optimum activated sludge concentration is always obtained.
[0013]
-Solution-
Specifically, an apparatus for controlling the activated sludge concentration inside the biological reaction tank when the purification process of the sewage is performed by the biological reaction process of the activated sludge inside the biological reaction tank. This sludge concentration control device is provided with schedule management means and sludge concentration control means . Schedule management means is a can input a target value of the activated sludge concentration at any time to any value, is to schedule management that period and the target value. The sludge concentration control means receives the output of the schedule management means and controls the activated sludge concentration in the biological reaction tank according to the managed schedule. Furthermore, the target value of the activated sludge concentration at each of a plurality of periods can be input to the schedule management means. Then, the sludge concentration control means automatically calculates the target value of the activated sludge concentration in this intermediate period so that the activated sludge concentration is gradually changed in the intermediate period between the respective periods when these target values are set. It is configured.
[0014]
According to this specific matter, the activated sludge concentration in the biological reaction tank is controlled according to the target value of the activated sludge concentration at any time entered by the system administrator or the like. For example, in a sewage treatment system applied to a sightseeing spot or the like, a target value for activated sludge concentration is set high during the on-season, while a target value for activated sludge concentration is set low during the off-season. According to this, even if the activity of activated sludge changes, the appropriate activated sludge density | concentration according to the use condition of a sewage treatment system is obtained, and the biological reaction process in a biological reaction tank can be performed efficiently. For example, in a tourist spot that reaches the on-season in winter, the target value of the activated sludge concentration is set high in this winter. Thereby, even if the activity of activated sludge is low as the water temperature decreases, the activated sludge concentration is set high, so that the sewage treatment capacity is maintained high, and biological reaction treatment is performed efficiently. It is also possible to appropriately set the target value of the activated sludge concentration according to changes in the number of biological reaction tanks used in a system including a plurality of biological reaction tanks. Specifically, when increasing the number of biological reaction tanks to be used, the target value of the activated sludge concentration is set high before the increase. Thereby, even if the number of biological reaction tanks to be used is increased by dividing the activated sludge in one biological reaction tank, the activated sludge concentration in each biological reaction tank can be sufficiently secured. Conversely, when the number of biological reaction tanks to be used is decreased, the target value of the activated sludge concentration in each biological reaction tank is set low before the decrease. Thereby, even if the number of the biological reaction tanks used is reduced by mixing the activated sludges in a plurality of biological reaction tanks, the activated sludge concentration in the biological reaction tanks does not become too high.
[0016]
Further, since as gradually changing the concentration of activated sludge in the middle-period, without causing sudden change of the internal environment of the biological reactor, to achieve a target value of the activated sludge concentration of each time it entered be able to. If the internal environment of the bioreactor changes suddenly, there is a possibility that the activated sludge treatment capacity will be temporarily reduced. Sewage treatment with activated sludge concentration can be performed.
[0017]
Further, a target value changing means capable of changing the target value of the activated sludge concentration in the intermediate period automatically calculated by the sludge concentration control means to any value other than the target value is provided. According to this, it becomes possible to change the schedule once set in the middle according to a request from a system administrator or the like, and the convenience of the sludge concentration control device can be improved.
[0019]
Further, the sludge concentration inside the biological reaction tank is controlled by the sludge concentration control device comprising the above-mentioned means, and the biological reaction treatment is performed inside the biological reaction tank by the activated sludge whose sludge concentration is controlled. Sewage treatment systems are also within the scope of the technical idea of the present invention.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. This form demonstrates the case where this invention is applied to the sewage treatment system which performs sewage treatment by the continuous inflow intermittent aeration method. The present invention is not limited to this, and can also be applied to a sewage treatment system that performs sewage treatment such as a batch activated sludge method or an oxidation ditch method.
[0021]
FIG. 1 is a diagram showing a schematic configuration of a sewage treatment system according to the present embodiment. As shown in this figure, the sewage treatment system includes a raw water tank 1, a flow rate adjustment tank 2, a biological reaction tank 3, a precipitation tank 4, a disinfection tank 5, a sludge concentration tank 6, and a sludge storage tank 7.
[0022]
The raw water tank 1 includes a sand settling tank 11 for separating sand from the introduced raw water (sewage) and a raw water pump tank 12 into which the raw water after the sand is separated and removed in the sand settling tank 11 is introduced. . The sand settling tank 11 is provided with a first raw water pump 13 for supplying raw water to the raw water pump tank 12, and the raw water pump tank 12 is provided with a second raw water pump 14 for supplying raw water to the flow rate adjusting tank 2.
[0023]
Inside the flow rate adjusting tank 2, a stirring pump 21 for stirring the inside of the flow rate adjusting tank 2 and a flow rate adjusting pump 22 for supplying raw water from the flow rate adjusting tank 2 toward the biological reaction tank 3 are provided. ing.
[0024]
The biological reaction tank 3 is a tank equipped with an aeration / stirring device 31 inside, and the raw water is purified by a biological reaction process using activated sludge, and the treated water flows out into the sedimentation tank 4 together with the sludge. . A concentration sensor 32 for measuring the activated sludge concentration is provided inside or outside the biological reaction tank 3. The concentration sensor 32 measures the sludge concentration from a sampling solution sucked from a strainer (not shown) installed in the biological reaction tank 3 and transmits the measurement signal to the controller 9 described later.
[0025]
In the settling tank 4, sludge is precipitated in the inside thereof, thereby separating treated water and sludge. The treated water that has become the supernatant water by this separation is supplied to the sterilization tank 5 and is sterilized in the sterilization tank 5 by a chlorine sterilizer or the like and discharged. On the other hand, a part of the sludge that has settled in the settling tank 4 is pulled out of the settling tank 4 by the return sludge pump 8 and returned to the biological reaction tank 3. A return sludge valve 81a is provided in the middle of the return passage 81 connecting the settling tank 4 and the biological reaction tank 3, and the return of sludge to the biological reaction tank 3 is controlled by controlling the opening / closing operation of the valve 81a. The amount can be adjusted.
[0026]
Further, the return sludge is diverted from the downstream side of the return sludge pump 8 so that the return sludge can be stored in the sludge concentration tank 6 without being returned to the biological reaction tank 3. An excess sludge valve 82a is provided in the middle of the branch passage 82, and the amount of sludge withdrawn from the settling tank 4 can be adjusted by opening / closing control of the valve 82a.
[0027]
The sludge concentration tank 6 further separates sludge and supernatant water. After this separation, the precipitated concentrated sludge is sent to the sludge storage tank 7 by the sludge extraction pump 61 to become supernatant water. The desorbed liquid is returned to the raw water pump tank 12 by the passage 62. The passage 62 is provided with a desorbed liquid return valve 62a.
[0028]
Further, the bottom of the biological reaction tank 3 and the sludge concentration tank 6 are connected by a sludge extraction passage 33. The sludge extraction passage 33 is provided with a sludge extraction pump 34 and an extraction adjustment valve 35 for extracting sludge precipitated in the biological reaction tank 3. The amount of sludge extraction from the biological reaction tank 3 can be adjusted by opening / closing control of the extraction adjusting valve 35.
[0029]
The sewage treatment system includes a controller 9 for performing opening / closing control of the valves 62a, 81a, 82a, 35, drive control of the pumps 13, 14, 21, 22, 8, 34, and the like. The controller 9 is characterized by a sludge concentration control means 91 for controlling the concentration of activated sludge in the biological reaction tank 3 and a schedule management means 92 for managing the target value of the activated sludge concentration throughout the year. There is. Hereinafter, the control operation of the activated sludge concentration in the biological reaction tank 3 by the sludge concentration control means 91 and the schedule management means 92 will be described.
[0030]
The said sludge density | concentration control means 91 sets the target value of activated sludge density | concentration so low that the activity of the activated sludge in the biological reaction tank 3 becomes high. In other words, the target value of the activated sludge concentration is set higher as the activity of the activated sludge in the biological reaction tank 3 becomes lower.
[0031]
Specifically, the activated sludge concentration in the biological reaction tank 3 is controlled throughout the year according to the set value of the activated sludge concentration preset by the administrator of this system. As a specific adjustment operation of the activated sludge concentration, the return sludge pump 8, the return sludge valve 81a, and the excess sludge valve 82a are controlled. That is, when reducing the activated sludge concentration in the biological reaction tank 3, the return sludge pump 8 is driven, the return sludge valve 81a is closed, and the excess sludge valve 82a is opened. Thereby, the activated sludge in the biological reaction tank 3 is extracted to the sludge concentration tank 6 through the sedimentation tank 4, and thereby the activated sludge concentration in the biological reaction tank 3 is lowered. Conversely, when increasing the activated sludge concentration in the biological reaction tank 3, the closed state of the excess sludge valve 82a is maintained. As a result, the activated sludge naturally propagates in the biological reaction tank 3, whereby the activated sludge concentration in the biological reaction tank 3 gradually increases.
[0032]
Further, as another operation for adjusting the activated sludge concentration, the sludge extraction pump 34 and the extraction amount adjusting valve 35 are controlled. That is, when reducing the activated sludge concentration in the biological reaction tank 3, the sludge extraction pump 34 is driven and the extraction amount adjusting valve 35 is opened. As a result, the activated sludge precipitated in the biological reaction tank 3 is extracted into the sludge concentration tank 6, thereby reducing the activated sludge concentration in the biological reaction tank 3. On the contrary, when the activated sludge concentration in the biological reaction tank 3 is increased, the sludge extraction pump 34 is stopped and the closed state of the extraction amount adjusting valve 35 is maintained. As a result, the activated sludge naturally propagates in the biological reaction tank 3, whereby the activated sludge concentration in the biological reaction tank 3 gradually increases.
[0033]
Only one of these operations for adjusting the activated sludge concentration may be performed, or both may be performed simultaneously.
[0034]
Hereinafter, the annual schedule setting operation | movement of the activated sludge density | concentration using this system is demonstrated concretely. First, an input device such as a personal computer (hereinafter abbreviated as a personal computer) is connected to the controller 9, and an annual schedule, that is, a target value for an arbitrary activated sludge concentration is input for an arbitrary month by operating the personal computer. To do. This input value is managed by the schedule management means 92, and the schedule management means 92 automatically calculates the target value of the activated sludge concentration for each month throughout the year.
[0035]
In the present embodiment, the month in which the target value of the activated sludge concentration is desired to be highest and the target value of the activated sludge concentration in that month is input and the target value of the activated sludge concentration is desired to be the lowest among January to December. And the activated sludge concentration target value for the month is entered. FIG. 2 shows an input screen on the display of the personal computer. In this figure, the month with the highest water temperature is August, the activated sludge concentration target value for this month is 3000 mg / l, the month with the lowest water temperature is February, and the activated sludge concentration target value for this month is 4200 mg / l. It is said. These month data and target value data corresponding to the month are input to the schedule management means 92.
[0036]
The schedule management means 92 to which these data are input gradually changes the activated sludge concentration in the intermediate period (March to July, September to January) between the months when these target values are set. Thus, the target value of the activated sludge concentration in this intermediate period is automatically calculated. When each of the above values is input, the target value of the activated sludge concentration is decreased by 200 mg / l every month from February to August. Conversely, the target value of activated sludge concentration is increased monthly by 200 mg / l from August to February. The target value of the activated sludge concentration for each month calculated in this way is graphed and displayed on the annual schedule display unit 10. This graph display can improve the visibility of the administrator.
[0037]
In addition, the “target value” in FIG. 2 indicates the target value (calculated target value: 3400 mg / l) of the activated sludge concentration in the current month (October in the figure). This part can be arbitrarily changed. That is, the controller 9 is provided with target value changing means 93. By changing this “target value” by operating the personal computer, the input activated sludge concentration target value and the schedule management means 92 are changed. The target value of the activated sludge concentration automatically calculated by can be arbitrarily changed.
[0038]
As described above, the target value of the activated sludge concentration for any month (February and August) is input, and the target value of the activated sludge concentration for the intermediate month is automatically calculated based on the annual schedule. The activated sludge concentration in the biological reaction tank 3 is managed by driving the sludge concentration control means 91. That is, when it is necessary to reduce the activated sludge concentration in the biological reaction tank 3 while monitoring the activated sludge concentration in the biological reaction tank 3 by the concentration sensor 32, the activated sludge in the biological reaction tank 3 is used. Is extracted to the sludge concentration tank 6 through the sedimentation tank 4, or the activated sludge in the biological reaction tank 3 is extracted to the sludge concentration tank 6 using the sludge extraction passage 33. Conversely, when it becomes necessary to increase the activated sludge concentration in the biological reaction tank 3, the surplus sludge valve 82a and the withdrawal amount adjustment valve 35 are kept closed, and the activated sludge is naturally removed in the biological reaction tank 3. Breed. As described above, the sludge concentration control means 91, the schedule management means 92, the target value changing means 93, the return sludge pump 8, and the surplus sludge valve 82a constitute the sludge concentration control device in the present invention.
[0039]
FIG. 3 is a graph showing a change state of the activated sludge concentration in the biological reaction tank 3 in this embodiment. As shown in this figure, the input target value of activated sludge concentration in each month can be achieved without causing a sudden change in the activated sludge concentration in the biological reaction tank 3. Yes.
[0040]
As a characteristic of this graph, in the situation where the activated sludge concentration increases (period from August to February), the activated sludge naturally propagates in the biological reaction tank 3, so the passage of the period and the activated sludge concentration. Is approximately proportional. In this case, when the activated sludge is naturally propagated too much and the activated sludge concentration exceeds the target value, the surplus sludge valve 82a and the withdrawal amount adjusting valve 35 are opened, for example, to keep the inside of the biological reaction tank 3 The activated sludge is drawn into the sludge concentration tank 6 and adjusted so that the activated sludge concentration matches the target value. On the other hand, in a situation where the activated sludge concentration is decreasing (period from February to August), the activated sludge is temporarily activated by the extraction operation of the activated sludge accompanying the opening of the excess sludge valve 82a or the extraction amount adjustment valve 35. The sludge concentration is reduced to the vicinity of the target value, and thereafter, the activated sludge concentration is adjusted to be maintained at the target value by opening / closing control of the excess sludge valve 82a and the extraction amount adjusting valve 35.
[0041]
As described above, in this embodiment, the annual schedule of the activated sludge concentration in the biological reaction tank 3 is determined according to the target value of the activated sludge concentration at any time entered by the system administrator or the like, and the schedule The activated sludge concentration is controlled along the line. For this reason, it is possible to avoid the occurrence of self-digestion and scum due to lack of nutrients in the activated sludge, and avoid the situation where the amount of sewage exceeding the treatment capacity of activated sludge exists in the biological reaction tank. Biological reaction processing in the tank 3 can be performed efficiently.
[0042]
-Other embodiments-
In the above-described embodiment, the target value for each month is set and calculated in order to adjust the target value of the activated sludge concentration according to the change in season. The present invention is not limited to this, and in a sewage treatment system applied to a sightseeing spot or the like, when the sewage inflow amount changes greatly between the on-season and the off-season, the target value of the activated sludge concentration is adjusted accordingly. It may be. That is, for example, in a tourist spot that reaches the on season in winter, the target value of the activated sludge concentration is set high in this winter. Thereby, even if the activity of activated sludge is low as the water temperature decreases, the activated sludge concentration is set high, so that the sewage treatment capacity is maintained high, and biological reaction treatment is performed efficiently. That is, even if the activity of the activated sludge changes, the biological reaction treatment in the biological reaction tank 3 can be efficiently performed by obtaining an appropriate activated sludge concentration according to the use situation of the sewage treatment system. it can.
[0043]
In a system including a plurality of biological reaction tanks, when the number of biological reaction tanks to be used changes, the target value of the activated sludge concentration may be adjusted accordingly. In other words, when increasing the number of biological reaction tanks to be used, the target value of activated sludge concentration should be set high before the increase, and even if the number of biological reaction tanks to be used is increased. The activated sludge concentration in the biological reaction tank should be sufficiently secured. Conversely, when reducing the number of biological reaction tanks to be used, set the target value of the activated sludge concentration in each biological reaction tank to a low value before reducing the number of biological reaction tanks to be used. Even if it reduces, the activated sludge density | concentration in a biological reaction tank is made not to become too high. Also by this, even if the activity of activated sludge changes, the appropriate activated sludge density | concentration according to the use condition of a sewage treatment system will be obtained, and the biological reaction process in the biological reaction tank 3 can be performed efficiently. it can.
[0044]
Moreover, in the said embodiment, the target value of activated sludge density | concentration was set or calculated every month. The present invention is not limited to this, and the period for setting or calculating the target value of the activated sludge concentration is arbitrary. For example, a target value of activated sludge concentration may be set or calculated every two months or every week. Further, the target value of the activated sludge concentration to be input and set is not limited to the above-mentioned two points (February and August), and may be one point or three or more points. Furthermore, the set target value and the calculation target value of the activated sludge concentration are not limited to the above-described numerical values.
[0045]
In addition, the method for adjusting the activated sludge concentration in the biological reaction tank 3 is not limited to adjusting the amount of sludge withdrawn from the sedimentation tank 4, but the amount of sewage inflow is controlled or the volume of the biological reaction tank 3 is changed. Various methods can be employed.
[0046]
【The invention's effect】
As described above, in the present invention, the activated sludge concentration in the biological reaction tank is not maintained constant, but the target value of the activated sludge concentration is changed according to the environmental conditions and the system usage status, and this is always optimal. The activated sludge concentration is obtained. For this reason, it becomes possible to always perform the biological reaction treatment in the biological reaction tank efficiently, and it is possible to realize a sewage treatment operation capable of maintaining a good quality of the treated water.
[0047]
Further, since the activated sludge concentration is gradually changed in the intermediate period between the periods when the target value of the activated sludge concentration is set, the internal environment of the biological reaction tank is not suddenly changed. For this reason, the sewage treatment by the optimal activated sludge density | concentration is realizable, maintaining the sewage treatment capacity of activated sludge stably.
[0048]
Furthermore, if the target value of the activated sludge concentration in the interim period calculated automatically can be changed to any value other than this target value, the schedule once set can be changed depending on the request of the system administrator. Thus, the convenience of the sludge concentration control device can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a sewage treatment system according to an embodiment.
FIG. 2 is a diagram showing an input screen on a display of a personal computer when inputting a target value of activated sludge concentration.
FIG. 3 is a diagram showing a state of change in activated sludge concentration in the biological reaction tank in the embodiment.
[Explanation of symbols]
3 biological reaction tank 4 sedimentation tank 91 sludge concentration control means 92 schedule management means 93 target value changing means

Claims (3)

A device for controlling the activated sludge concentration inside the biological reaction tank when performing purification treatment of sewage by biological reaction treatment of the activated sludge inside the biological reaction tank,
A schedule management means capable of inputting the target value of the activated sludge concentration at an arbitrary time to an arbitrary value and managing the schedule of the time and the target value;
A sludge concentration control means for receiving the output of the schedule management means and controlling the activated sludge concentration in the biological reaction tank according to the managed schedule ;
While the schedule management means can input the target value of the activated sludge concentration in each of a plurality of periods,
The sludge concentration control means is configured to automatically calculate the target value of the activated sludge concentration in the intermediate period so as to gradually change the activated sludge concentration in the intermediate period between the respective periods when these target values are set. The sludge concentration control device characterized by being said . In the sludge concentration control apparatus according to claim 1 ,
A sludge concentration control device comprising target value changing means capable of changing the target value of the activated sludge concentration in the intermediate period automatically calculated by the sludge concentration control means to any value other than the target value. The sludge concentration inside the biological reaction tank is controlled by the sludge concentration control device according to claim 1 or 2 , and the biological reaction treatment is performed inside the biological reaction tank by the activated sludge whose sludge concentration is controlled. A sewage treatment system characterized by

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