JP6643086B2 - Monitoring and control system using activated sludge method - Google Patents

Description

  The present invention relates to a monitoring and control system for sewage treatment equipment by an activated sludge method, and more particularly to a monitoring and control system for a combined sewerage system in which an inflow sewage flow rate increases in rainy weather.

  Sewerage systems widely introduced in Japan and abroad are broadly classified into combined sewers and split sewers from the viewpoint of handling rainwater. The one where the rainwater removal line is connected to the sewage collection line is called a merged type, and the one that is not connected and is removed by another line is called a split type. In Japan, the former merger ceremony has been introduced mainly in large urban areas where sewerage infrastructure development was implemented in advance. The characteristic of the combined sewer is that rainwater is mixed into the sewage, so that the amount of sewage flowing into the sewage treatment plant during rainy weather is greatly increased. If the amount of rainfall is large, the amount of inflowed sewage including rainwater exceeds the planned treatment amount (Qsh: maximum hourly sewage amount) in the facility design of the sewage treatment plant, and the entire amount cannot be properly treated. There is a problem. In the standard activated sludge process, which is most widely introduced as a sewage treatment process, only the simple treatment by the sedimentation basin is performed for the inflow sewage that exceeds the maximum amount of wastewater Qsh, and the biological reaction in the subsequent stage In general, simple discharge was performed without flowing into the tank. For this reason, simple effluent with insufficient water quality is discharged into public water bodies such as rivers and lakes, which has become a major cause of water pollution.

  On the other hand, as a means for reducing the simple discharge, for example, the introduction of an activated sludge method in rainy weather, which is described in Technical Document 1 described below, has been advanced. This method adopts a method in which the inflow sewage of up to twice the amount of Qsh is step-inflowed to the latter stage of the biological reaction tank of the activated sludge process without simply discharging the amount exceeding the time maximum wastewater amount Qsh. The inflowed sewage flowed in step is inferior in water quality to the water treated from the inlet of the biological reaction tank and usually treated, but the pollutants (mainly organic matter) Is removed, and the quality of treated water can be improved as compared with the case of simple treatment. It is stated that this makes it possible to reduce the simple discharge flow rate and reduce the water pollution load on the discharge destination.

Takahiro Yamamoto et al., Improvement of combined sewerage using existing facilities in Osaka City, Journal of the Society of Environmental System Measurement and Control, Vol. 10, No. 2, 2006

  In the case of the activated sludge method in rainy weather, the amount of excess wastewater exceeding the time maximum wastewater amount Qsh can be step-flowed into the latter stage of the biological reaction tank, so that the simple discharge amount can be reduced. In the operation control method disclosed in the above-mentioned Non-Patent Document 1, the sewage amount Qfront flowing from the biological reaction tank inlet is constant at the time maximum sewage amount Qsh, and the sewage is flowed stepwise into the latter stage of the biological reaction tank. The flow rate Qback is up to 2 × Qsh. However, these flow rates Qfront and Qback should originally be optimized to reflect the amount of pollutants in the incoming sewage and the state of activated sludge in the biological reactor at each treatment point. For example, if the amount of pollutants in the inflowing sewage is larger than usual, the amount of biological adsorption by activated sludge will exceed the upper limit, which may cause a case where the quality of treated water is significantly deteriorated. In addition, there is a problem that a similar case cannot be avoided even when the amount of activated sludge in the biological reaction tank is small.

  The present invention has been made in view of such problems, and fluctuates in the amount of pollutants in influent sewage and the amount of activated sludge in a biological reaction tank, which are practical problems of the activated sludge method in rainy weather. The purpose of the present invention is to suppress the deterioration of treated water quality when there is a problem by appropriate control based on a rational index.

The monitoring control system according to the present invention, in the monitoring control system based on the activated sludge method, calculates a measuring means for measuring the flow rate and the water quality of the inflow sewage, and calculates the upper limit of the amount of bioadsorption that can be bioadsorbed in the latter stage of the bioreactor. calculation means, on the basis of the said biosorption amount upper limit value calculated by the calculating means and the inflow sewage water measured by the measuring means, and control means for determining a sewage supply amount to the step flow into the front and rear stages bioreactor, It is characterized by having.

  According to the present invention, the amount of living organisms adsorbed by the activated sludge in the biological reaction tank is estimated, and based on this, by appropriately controlling the flow rate of the sewage supplied to the biological reaction tank inlet and the latter stage of the biological reaction tank, the inflow sewage is reduced. It is possible to suppress the deterioration of the treated water quality even when there is a change in the pollutant load and the state of the activated sludge in the biological reaction tank. As a result, it becomes possible to reduce the pollution load on the public water area to which the treated sewage is discharged.

It is a figure explaining a control method of a sewage treatment process by the present invention. FIG. 3 is a diagram illustrating a configuration of a control module. FIG. 6 is a diagram illustrating a processing flow of a control unit. It is a figure which shows an example of the correlation between the activated sludge density | concentration of a biological reaction tank, and the maximum value of the amount of biological adsorption.

  The treated water quality by the activated sludge method in rainy weather is greatly affected by the biological adsorption phenomenon at the latter stage of the biological reaction tank. For this reason, in order to maintain the treated water quality at a predetermined level, the step inflow amount to the latter stage of the biological reaction tank is determined within a range that does not exceed the upper limit of the amount of bioadsorption that changes according to the state at each treatment time. There is a need.

  In the present invention, the upper limit of the amount of biosorption is calculated by a simulation based on the activated sludge model. The activated sludge model is a model in which the phenomenon of biosorption and metabolic decomposition of pollutants is formulated by a numerical model. In order to perform a simulation in the operation control scene of a sewage treatment process, an activated sludge model based on water quality items that can be continuously measured or analyzed periodically is applied. Specifically, the amount of activated sludge is evaluated by the suspended solids concentration (MLSS; mixed liquid suspended solids concentration) in the biological reaction tank. In addition, the state (biological activity) of the activated sludge is evaluated by a function such as water temperature. The upper limit of the amount of bioadsorption calculated in such a model is not exceeded, and the step inflow in a range not exceeding this is the amount of pollutants in the inflowing sewage, for example, organic matter concentration (BOD; biochemical oxygen demand) or its Calculated based on alternative water quality items. Thus, the above-described problem is solved by appropriately controlling the step inflow amount so that the pollutant load supplied in the step inflow to the latter stage of the biological reaction tank does not become excessive. The present invention includes a plurality of realizing means, one example of which is described below.

(Example)
Hereinafter, embodiments will be described with reference to the drawings.

  In the present embodiment, an example of a control method and a system for an activated sludge method in rainy weather corresponding to a combined sewerage system in which the amount of inflowed sewage increases in rainy weather among activated sludge processes will be described.

  FIG. 1 is a diagram illustrating a configuration of an activated sludge process that is an object of the present embodiment and a method of controlling a sewage treatment facility 100 by a monitoring control system 200. The main components of the sewage treatment equipment 100 to be controlled are a first settling tank 150, a biological reaction tank 160, and a final settling tank 170. The sewage 101 to be treated here is assumed to be sewage mixed with rainwater. The sewage 101 to be treated first flows into the sedimentation basin 150, and then flows into the biological reaction tank 160 after suspended substances having a large specific gravity are removed by settling. Activated sludge is used in the biological reaction tank 160, and has a function of purifying sewage by metabolizing and decomposing a soluble pollutant (mainly, an organic substance, etc.) contained in the water to be treated 101 after biological adsorption. . The treated sewage 101 that has been treated in the biological reaction tank 160 for a predetermined residence time flows into the final sedimentation basin 170, where the supernatant from which the activated sludge has been removed is the treated water 107. A part of the activated sludge settled in the final sedimentation tank 170 is removed out of the system as surplus sludge, but the remaining activated sludge is returned to the preceding stage of the biological reaction tank 109 as returned sludge 109.

  In the rainy day activated sludge method, when the sewage to be treated 101 exceeds a planned treatment amount (Qsh: hourly maximum sewage amount) in the facility design of the sewage treatment equipment 100, the flow rate of the upstream supply water 103 is set to Qsh, In general, an operation is performed in which the remainder is flown into the subsequent stage of the biological reaction tank 160 as the latter stage feedwater 105, but in the present invention, the flow rates of the former stage feedwater 103 and the latter stage feedwater 105 are reduced. Appropriate control is performed according to the situation at each processing point by a control logic described later. Excess of the processing capacity in the biological reaction tank 160 is discharged as simple discharge water 106 to the outside of the system such as a public water body. The control of these flow rates is performed by adjusting the opening of the flow control valve 120. The flow rate control can be realized by adjusting the flow rate of a pump body (not shown), in addition to the method of adjusting the opening of the flow rate control valve 120 described above.

  The monitoring and control system 200 performs the above-mentioned calculation necessary for the flow rate control by the activated sludge model simulator 210 and the control module 250 based on the measured value 302 by the water quality meter 110 and the flow meter 115 installed in the sewage treatment equipment 100, It has a function of outputting the control signal 301 to operate the flow control valve 120 and the like. The water quality meter 110 here measures a pollutant contained in the sewage 101 to be treated, and specifically, biochemical oxygen demand (BOD), chemical oxygen demand (COD), or BOD And other water quality items that can indirectly estimate COD, such as ultraviolet absorbance, turbidity, and suspended solids (SS).

  FIG. 2 is a diagram illustrating the configuration of the monitoring control system 200 including the control module 250 which is a feature of the present invention. The monitoring and control system 200 includes an activated sludge model simulator 210 and a control module 250 as main components, and further includes a display unit 201 such as a display and a keyboard 202, and has a function of input / output to a user. ing.

  The activated sludge model simulator 210 can calculate the behavior of the activated sludge in the biological reaction tank 160 according to a calculation instruction from the control module 250. The model database 220 stores an activated sludge model. This model can calculate the amount of bioadsorption in the bioreactor required for the control according to the present invention. The calculation target of the amount of biosorption here is an organic substance such as BOD which is a water quality regulation item of the treated water 107, and it is desirable that a model that also targets nitrogen and phosphorus is included if necessary. The form of the activated sludge model is a mathematical expression or a numerical table (discrete numerical data set). The model engine 230 has a function of executing the activated sludge model stored in the model database 220 using the measured value 302 and outputting a calculation result to the control module 250.

  The control module 250, which is another main component of the monitoring and control system 200, includes a signal output unit 255, a signal input unit 260, a control unit 270, and a control database 290. The control output unit 255 has a function of outputting a signal for operating the flow regulating valve 120 and the like based on the control instruction value calculated by the control unit 270 and stored in the control database 290. Further, the signal input means 260 has a function of receiving measurement data from a measuring instrument installed in the sewage treatment facility 100 in addition to the water quality meter 110 and the flow meter 115 and storing the measurement data in the control database 290.

  The control means 270 determines the flow rates of the first-stage supply water 103 and the second-stage supply water 105 in accordance with a processing flow described later for each predetermined control cycle. The calculation here is performed by activating the activated sludge model simulator 210, and the calculation result is stored in the control database 290. The control cycle and various parameters for control refer to data stored in the control database 290.

  FIG. 3 shows an example of a processing flow of the control means 270. While exchanging data with the control database 290, a start instruction is given to the model engine 230, and the flow rates of the upstream supply water 103 and the downstream supply water 105 to be controlled here are calculated. In the first data reading step 272, various measurement data at the present time of the sewage treatment equipment 100, for example, the flow rate and water quality data of the sewage 101 to be treated are read from the control database 290, and the data can be used for calculation in the next step. And

  In the next bioadsorption amount calculation step 274, the model engine 230 is activated to calculate a pollution load amount (Lmax: bioadsorption amount upper limit value) at which biosorption can be performed at a stage subsequent to the bioreaction layer 160 at this time. The pollution load here is generally an organic matter amount (for example, BOD). In addition, when there is a water quality item (for example, nitrogen, phosphorus, etc.) to be noted other than the BOD, the calculated pollution load may be the nitrogen amount and the phosphorus amount. The calculation of Lmax is performed by the model engine 230 using the activated sludge model stored in the model database 220.

  FIG. 4 shows an example of the correlation between Lmax calculated by the activated sludge model and its influencing factors. Influencing factors in this example are the activated sludge concentration (MLSS: amount of suspended solids in the mixed liquid) and the water temperature in the biological reaction tank 160. The horizontal axis shows the relative value of MLSS, and the vertical axis shows the relative value of Lmax. In general, the higher the MLSS, that is, the greater the amount of activated sludge cells per unit volume, the higher the biosorption ability and the larger the Lmax. In addition, when the water temperature is in a range up to a predetermined value, the higher the water temperature, the higher the activity of the bacteria generally, the higher the ability of biosorption, and the higher the Lmax. Using the activated sludge model capable of calculating such a correlation and the current MLSS and water temperature measurement data stored in the control database 290, the Lmax relative value can be calculated. By storing in advance the standard absolute value of Lmax under standard conditions (for example, MLSS = 2000 mg / L, water temperature of 20 ° C.), the absolute value of Lmax corresponding to the current condition can be obtained. In this example, the influence factors are described as the MLSS and the water temperature. However, the influence factors are not limited to these, and other influence factors may be adjusted according to the actual situation of the target sewage treatment equipment 100 and the contents of related knowledge. It is also possible to consider

  In the sewage flow rate check step 276, it is determined whether or not the flow rate Qin of the sewage 101 to be treated exceeds the time maximum sewage amount Qsh with reference to the control database 290. If not exceeded, the process proceeds to the non-rainy weather calculation step 278. If it has exceeded, the process proceeds to the rainy weather calculation step 280. In the non-rainy weather calculation step 278, the flow rate Qw of the downstream supply water 105 and the simple discharge water 106 is set to 0 (zero), and the upstream supply water 103 is set to be the same as the flow rate of the sewage 101 to be treated.

  On the other hand, in the rainy day calculation step 280, since the flow rate of the sewage 101 to be treated exceeds Qsh, the flow rate Qback of the post-supply water 105 to be flown into the post-stage of the biological reaction tank 160 is calculated. Qback is set to a value obtained by dividing Lmax by the pollutant concentration Cin measured by the water quality meter 110. In addition, the flow rate Qfront of the upstream supply water 103 is set to a value obtained by dividing Qback from Qin, and Qw is set to 0. However, when Qfront exceeds Qsh, Qfront is set to be the same as Qsh, and Qw is set to a value obtained by dividing Qin by the sum of Qfront and Qback.

  In the last control output step 282, the set values of Qfront, Qback, and Qw calculated in the non-rainy weather calculation step 278 or the rainy weather calculation step 280 are output to the control database 290, and the processing flow for one time is ended. . This processing flow is repeated at a predetermined control cycle, and each time, the flow rate is controlled based on the set value stored in the control database 290.

  In addition to the functions described above, it is desirable to have a means for visualizing the operating state and the control state as a function for assisting the driver of the sewage treatment facility 100. Specifically, the water quality and flow rate data measured by the water quality meter 110 and the flow meter 115, and various flow rate set values calculated by the control module 250 are displayed on the display unit 201 of the monitoring control system 200. . As a result, it is expected that the current operation state and control state can be accurately grasped, and necessary measures can be easily taken.

  The above is a description of a typical embodiment relating to the function and operation of the control unit 270 which is a feature of the present invention.

101 Sewage to be treated 103 Biological reaction tank upstream supply water 105 Biological reaction tank downstream supply water 107 Treated water 108 Simple discharge water 100 Sewage treatment equipment 110 Water quality meter 115 Flow meter 120 Flow control valve 150 First sedimentation tank 160 Biological reaction tank 170 First sedimentation Pond 200 Monitoring control system 201 Display means 202 Keyboard 210 Activated sludge model simulator 220 Model database 230 Model engine 250 Control module 255 Signal output means 260 Signal input means 270 Control means 290 Control database 301 Control signal 302 Measured value

Claims (4)

In the monitoring and control system by the activated sludge method,
Measuring means for measuring the inflow sewage flow rate and water quality,
Calculating means for calculating an upper limit of the amount of bioadsorption that can be bioadsorbed in the latter stage of the bioreactor,
Wherein based on the biosorption amount upper limit value calculated in the inflow sewage water measured by the measuring means and said calculating means, and control means for determining a sewage supply amount to the step flow into the front and rear stages bioreactor,
A supervisory control system comprising: 2. The monitoring control system according to claim 1, wherein said measuring means includes a water quality measuring means for measuring at least polluted organic matter in the inflow sewage. According to claim 1, estimated before Kisei was adsorbed amount upper limit value, the monitoring control system, which comprises using a biological adsorption, the activated sludge model representing at least the activated sludge concentration or temperature, the relationship. 2. The apparatus according to claim 1, further comprising a display unit, wherein the display unit supplies the flow rate and the water quality of the inflow sewage measured by the measuring unit and the amount of sewage supplied to the biological reaction tank before and after the biological reaction tank determined by the control unit. A supervisory control system characterized by visualizing information.

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