JP4643365B2 - Sewage disinfection system - Google Patents

Description

The present invention relates to a disinfection system under water that apply to combined sewer facilities.

  The combined sewer system drains wastewater from ordinary households and various factories together with rainwater, and normally, after a predetermined water treatment is performed at a sewage treatment plant, it is discharged into a river or the like. On the other hand, during rain, the amount of sewage increases due to the addition of rainwater, and when it exceeds the capacity of the sewage treatment plant, it is directly discharged by a storm drainage facility such as an overflow weir or pump station. Yes. In this case, since rainwater does not pass through the sewage treatment plant, it is necessary to disinfect with a disinfectant so that no problem occurs even if it is discharged.

  That is, the main purpose of the disinfecting facility in the combined sewer is to inject an amount of disinfectant into the inflowing sewage so that the disinfecting process can be performed so that the treated water satisfies the predetermined conditions. The defined condition is generally recognized as “3000 coli / mL or less in the treated water”. Increasing the injection amount of disinfectant increases the disinfection effect and reduces coliform bacteria in the treated water, but injecting more disinfectant than necessary causes the unreacted disinfectant to be discharged along with the treated water, affecting the discharge water environment. There are concerns. For this reason, it is desirable that the injection amount of the disinfectant is a necessary and sufficient amount that can satisfy the conditions for the treated water.

In a combined sewer system, the difficulty in determining the appropriate amount of disinfectant to be injected is that the amount of rain and rainwater that flows into the confluence pipe in rainy weather is much more variable than the sewage in fine weather. Disinfection of sewage at times is to cope with fluctuations in water volume and quality. As a method of determining the amount of disinfectant injected in a combined sewer disinfection facility, a method of measuring the amount of inflow sewage water and the quality of the disinfection facility and calculating the amount of disinfectant injection based on the measured water amount and water quality (For example, refer to Patent Document 1 and Patent Document 2).
JP 2003-260470 A JP 2003-1256 A

  These inventions are one effective method for determining the amount of disinfectant injected into sewage, but there are various factors related to disinfectant injection in rainy weather, and indicators that represent them are specified. It is desired to perform more accurate disinfectant injection control.

An object of the present invention, when disinfected by injecting chlorine against sewage, found an index for determining the chlorine injection rate, disinfection systems feasible sewage adequate disinfection against sewage in rainy weather Is to provide.

The sewage disinfection system according to the present invention is a sewage sterilization system for disinfecting chlorine by injecting chlorine into the sewage. A characteristic value detection means for detecting the characteristic value from the sewage, a characteristic value detected by the characteristic value input means, and a chlorine corresponding to the inputted characteristic value. Chlorine consumption calculation means for extracting consumption from the database, and chlorine injection based on the chlorine consumption calculated by the chlorine consumption calculation means, adding an injection quantity within the range that does not exceed the allowable residual chlorine concentration of discharged water determining the rate, characterized in that a disinfecting equipment for injecting chlorine into the sewage by chlorine injection rate this determined.

  In this sewage disinfection system, the database includes, as characteristic values representing sewage characteristics, the organic matter concentration of sewage, the contact time between sewage and chlorine, and the chlorine consumption corresponding to these multiple values. As the characteristic value detecting means, it is preferable to use an organic substance concentration detecting means and a contact time calculating means for calculating the contact time from the measured sewage flow rate.

  Further, the sewage disinfection system according to the present invention comprises a contact time calculating means for calculating a contact time between sewage and chlorine based on the flow rate measured by the organic matter concentration detecting means and the flow rate measuring means of the sewage, Based on the chlorine consumption calculation means for obtaining the chlorine consumption by a predetermined calculation model formula using the organic matter concentration of the sewage and the contact time between the sewage and chlorine, and the chlorine consumption calculated by the chlorine consumption calculation means, A configuration may be provided that includes a disinfection facility that determines the chlorine injection rate by adding an injection amount in a range that does not exceed the allowable residual chlorine concentration of the discharged water, and injects chlorine into the sewage at the determined chlorine injection rate.

  Furthermore, the sewage disinfection system according to the present invention inputs weather data of a specific area, predicts the amount of sewage inflow into a plurality of sterilization facilities into which the sewage flows into the specific area, Inflow prediction calculation means for predicting the organic matter concentration and contact time of the sewage to be sterilized in each sterilization equipment based on each, and using the organic matter concentration and contact time in each sterilization equipment predicted by this inflow prediction calculation means, Chlorine consumption calculation means for obtaining a predicted value of chlorine consumption, and transmission means for transmitting the predicted value of chlorine consumption of each sterilization facility obtained by the chlorine consumption calculation means to the corresponding sterilization facility via a communication line; In each disinfection facility, the chlorine injection rate is determined by adding the injection amount within the range that does not exceed the allowable residual chlorine concentration of the effluent based on the transmitted chlorine consumption. It may be configured to inject chlorine into sewage in the chlorine injection rate.

  According to the present invention, as a result of investigating an appropriate chlorine injection rate for disinfection for a plurality of sewage having different water qualities and amounts, an index representative of a plurality of factors in which chlorine consumption affects the disinfection effect on sewage As a result, it was found that there is little residual chlorine, and effective disinfection that reduces the number of coliforms to a predetermined number or less was made possible by determining the chlorine injection rate based on this chlorine consumption.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, as a result of investigating the appropriate chlorine injection rate for disinfection in a sewage disinfection system that disinfects chlorine by injecting chlorine into the sewage, the chlorine consumption represents several factors that affect the disinfection effect on the sewage Explain that it was found to be an indicator.

  In general, the amount of water and quality of sewage that flows into a pumping station during rainy weather is extremely large, and there is a lack of knowledge to obtain an appropriate chlorine injection rate. Therefore, when sterilizing coliform bacteria in sewage by injecting chlorine into the combined sewage, determine the chlorine injection rate according to important factors that affect the chlorine injection rate (organic concentration of sewage, contact time with chlorine). We examined whether it was possible and tried to formulate it. Therefore, the following experiment was conducted.

  Raw water was prepared by adjusting the water quality by adding pure water to sewage or sewage. Sodium hypochlorite solution was used as a disinfectant. The raw water was taken in a beaker, and the sodium hypochlorite solution was poured in a predetermined small amount range while stirring at a normal temperature while stirring at a normal temperature. After stirring and mixing for a predetermined time, residual chlorine (free chlorine and combined chlorine) was measured immediately, and coliform bacteria were measured.

  Thus, when chlorine is injected into sewage, the coliform group and residual chlorine in the sewage have a relationship as shown in FIG. 6, for example, with respect to the chlorine injection rate. In FIG. 6, the coliform group generally decreases exponentially with respect to the chlorine injection rate. This is expressed as the following equation (1). That is, when the coliform group is plotted on the logarithmic axis, it is shown as a straight line.

y _c = b ₁ · a ₁ ^x (1)
x: Chlorine injection rate (mg / L)
y _c : coliform group (pieces / mL)
a ₁ : Constant (-)
b ₁ : Constant (pieces / mL)
Residual chlorine changes to around 0 mg / L to a certain extent, but increases thereafter in proportion to the chlorine injection rate due to the increase in bound chlorine. This proportionally increasing region can be approximated by a straight line and is expressed by the following equation (2).

y _r = a ₂ · x + b ₂ (2)
x: Chlorine injection rate (mg / L)
_yr : Residual chlorine (mg / L)
a ₂ : Constant (-)
b ₂ : Constant (mg / L)
If the chlorine consumption r _0.1 is defined as the chlorine injection rate at which the residual chlorine is 0.1 mg / L, the chlorine consumption r _0.1 can be calculated using the equation (2). And (1) can be obtained coliforms in chlorine consumption yc _{(x = r 0.1)} with. r _0.1 are defined as equivalent to the chlorine amount consumed by organic substances or the like contained in raw water. yc (x = r _0.1 ) is defined as indicating the coliform group in the treated water in which the minimum residual chlorine was detected.

The above experiment was conducted by changing the organic substance concentration (hereinafter referred to as COD) of sewage and the contact time between sewage and chlorine as parameters, and changing these values to large, medium, and small. The above six constants (a ₁ , b ₁ , a ₂ , b ₂ , r _0.1 , yc (r _0.1 )). Since these experiments use COD and contact time as parameters, as described above, finding a significant relationship between these two parameters and the above constants, based on the two parameters, It is possible to determine an appropriate chlorine injection rate in consideration of coliform bacteria and residual chlorine.

  As a result of the experiment, we will look at two parameters.

  When COD was increased, the residual chlorine increase line in FIG. 6 shifted to the right as COD increased. In addition, the inclination became smaller. The decrease in coliforms became milder as COD increased. This means that the sterilizing effect of chlorine is reduced. That is, it is considered that the raw water with high COD contains more chlorine consuming substances, so that the injected chlorine is consumed by reacting with the chlorine consuming substances, and the amount of chlorine effective for sterilization is reduced.

  As for the contact time, as the contact time decreased, the residual chlorine increase line in FIG. 6 moved to the left, and the slope increased. The amount of coliform bacteria decreased as the contact time was shortened. That is, the bactericidal effect of chlorine decreased. This is thought to be due to the fact that the reaction time between chlorine-consuming substances and coliform bacteria contained in the raw water and chlorine is short, so that the coliform bacteria are not reduced despite an increase in residual chlorine.

  Next, for each constant, the relationship with respect to changes in the COD and the contact time, which are the parameters, has been clarified, but is omitted here.

From the result of the above experiment, in the function y _r = a ₂ · x + b ₂ (2) in the increase region of residual chlorine, the relationship between the COD and the contact time is related to the chlorine consumption (r _{0.1 in} FIG. 6). It was seen. The constant b _{2 in the} expression (2) is simply an arithmetic constant and has no meaning. Therefore, the expression (2) should be expressed as y _r = a ₂ · (x−r _0.1 ) +0.1. Good.

Also, COD, relationship between the contact time is observed in _{a 2.} Thus, it is possible to predict residual chlorine based on COD and contact time. In particular, the chlorine consumption r _0.1 is an important index for determining the chlorine injection rate for sewage containing a large amount of chlorine consuming substances. Generally, the alarm value for residual chlorine concentration in sewage effluent is set to a very small amount. As a method for determining the chlorine injection rate that can most effectively obtain the bactericidal effect of Escherichia coli under such constraint conditions, it has been found that chlorine is added in an amount of chlorine consumption r _0.1 plus an alarm value of residual chlorine concentration, The present invention has been reached.

  That is, the method of the present invention obtains a chlorine consumption from the chlorine injection amount for sewage and its residual chlorine, and adds a chlorine injection amount within a range not exceeding the allowable residual chlorine concentration of effluent water based on this chlorine consumption to add chlorine. It is to determine the injection rate.

By this method, it becomes possible to inject a maximum amount of chlorine in which the residual chlorine concentration of the sterilized water is suppressed to an alarm value (allowable value) or less. As a result, the measured values of coliform chlorine consumption r _0.1, by injecting chlorine in an amount obtained by adding the warning value of the residual chlorine concentration in the chlorine consumption r _0.1, is Coliforms 3000 It can be surely sterilized to be less than 1 piece / mL.

  As described above, as a result of investigating an appropriate chlorine injection rate for sterilization of sewage having different water quality and water volume, chlorine consumption can be an index representing a plurality of factors affecting the disinfection effect on sewage. I found out. Therefore, in the present invention, as a method of disinfecting sewage, the chlorine consumption is determined from the amount of chlorine injected into the sewage and the residual chlorine. Based on the amount of chlorine consumed, the amount of chlorine injected within a range not exceeding the allowable residual chlorine concentration of the discharged water. In addition, by determining the chlorine injection rate, it is possible to effectively disinfect by reducing the number of coliforms to a predetermined number or less with little residual chlorine.

  Here, in the present invention, when determining the chlorine consumption, as described above, the COD, which is a characteristic of sewage, and the contact time are used as parameters, and how to determine these will be described below.

  For COD, an organic matter concentration calculation model is used. That is, a high correlation is expected between the turbidity of sewage measured by a turbidimeter and COD, and the organic matter concentration calculation model formula is the following formula (3).

C _COD = a ₃ · C _Turb + b ₃ ··· (3)
C _COD : Organic matter concentration of influent sewage (COD) (mg / L)
C _Turb : Turbidity of incoming sewage (degree)
a ₃ : Constant b ₃ : Constant For the contact time, a contact time calculation model is used. This contact time calculation model outputs the contact time T _rct based on the sewage flow rate Q _pump . That is, the flow rate Q _pump and the water channel volume V _rct are _simply calculated by the following contact time calculation model equation (4).

T _rct = V _rct ÷ Q _pump × 60 (4)
T _rct : Contact time (min)
V _rct : Channel volume (m ³ )
Q _pump : Flow rate (m ³ / h)
Chlorine consumption of sewage is determined by the chlorine consumption calculation model equation (5) shown below.

r _0.1 = (a ₄ · C _COD ) · (a ₅ · T _rct + b ₅ ) (5)
r _0.1 : Chlorine consumption (mg / L)
C _COD : Organic matter concentration of influent sewage (as COD) (mg / L)
T _rct : Contact time (min)
a _4: Constants a _5: Constant b _5: chlorine injection rate for disinfection for constant sewage focuses on chlorine consumption _{r 0.1,} warning of the residual chlorine concentration in the chlorine consumption _{r 0.1} (or (Allowable value) The value is _obtained by adding _{Cres_Cl} . The chlorine injection rate target value calculation model formula is (6) below.

R _Cl = r _0.1 + C _{res_Cl} (6)
R _Cl : Chlorine injection rate target value (mg / L)
r _0.1 : Chlorine consumption (mg / L)
C _{res_Cl} : Residual chlorine concentration reference value (constant) (mg / L) of treated water
Next, an embodiment of a sewage disinfection system according to the present invention will be described in detail with reference to FIG.

  In FIG. 1, reference numeral 11 denotes a treatment tank for sewage disinfection, in which chlorine is injected from the disinfection facility 12 into the inflow sewage from the left side in the figure, and then discharged as treated water on the right side in the figure. The discharged treated water is discharged into rivers. Reference numeral 13 denotes a water collection tank for measuring the chlorine consumption of sewage, and a predetermined amount of sewage is collected from the treatment tank 11 by a water collection pump 14 into the water collection tank 13. Chlorine is added to the water collection tank 13 by a chlorine injector 15 at various injection rates. A residual chlorine meter 16 detects residual chlorine in the water sampling tank 13. That is, as described above, chlorine is added to the water collection tank 13 at various injection rates by the chlorine injector 15, and residual chlorine after a predetermined time from chlorine injection at each injection rate is measured.

  17 is a chlorine consumption calculation means, which inputs the sampling flow rate by the sampling pump 14, the chlorine injection amount by the chlorine injector 15, and the residual chlorine concentration measured by the residual chlorine meter 16, respectively, and calculates the chlorine consumption of the sewage. calculate.

The chlorine consumption calculation means 17 is input with various injection rates of chlorine injected into the sewage in the water sampling tank 13 by the chlorine injector 15 and residual chlorine after a predetermined time has elapsed from the injection. The graph shown in FIG. 2 is made using these values. Then, an approximate curve (straight line a) is obtained from data in a region where residual chlorine increases before reaching a discontinuous point in this graph, and the extrapolated curve is used to obtain the chlorine consumption (point b). This is the same as the _{r 0.1} described in FIG.

  The sewage chlorine consumption thus obtained is output to the disinfection facility 12. In the disinfection facility 12, the chlorine injection rate is determined by adding the injection amount within a range not exceeding the allowable residual chlorine concentration of the discharged water based on the input chlorine consumption of the sewage, and the sewage is discharged to the sewage at the determined chlorine injection rate. Inject chlorine. That is, the chlorine injection rate is determined by the above-described chlorine injection rate target value calculation model equation (6), and chlorine is injected into the sewage in the treatment tank 11 with constant injection rate control.

  As a result, the amount of residual chlorine in the treated water (discharged water) is small, and effective disinfection that reliably reduces the number of coliforms to a predetermined number or less is possible.

  Next, the embodiment shown in FIG. 3 will be described. In this embodiment, the relationship between the characteristic value that affects the chlorine consumption of sewage and the chlorine consumption when this characteristic value is changed is obtained in advance as an actual measurement value and compiled as a database. The chlorine consumption in actual sewage is calculated using the source.

  In this embodiment, the organic substance concentration (COD) of sewage and the contact time between sewage and chlorine are used as the characteristic values. In order to obtain these characteristic values, as shown in FIG. 3, the flow rate and turbidity of sewage flowing into the treatment tank 11 for sewage disinfection are measured by a flow meter 21 and a turbidimeter 22, respectively. The measured sewage flow rate is input to the contact time calculation means 23, and the turbidity is also input to the COD calculation means 24. The contact time calculation means 23 simply calculates the contact time by using, for example, the contact time calculation model equation (4) described above, using the input flow rate and the preset channel volume or constant of the treated water. . Further, the COD calculating means 24 calculates the COD by the organic substance concentration calculating model equation (3) described above using the input sewage turbidity and a preset constant.

A database 25 holds the relationship between the characteristic values described above and the chlorine consumption when the characteristic values are changed. The data structure is as shown in Table 1.

  That is, in the database 25, the chlorine consumption determined in advance corresponding to the COD values x1, x2, and x3 as one characteristic value and the contact time values y1, y2, and y3 as the other characteristic values. Values of the quantities z1 to z33 are set.

  Chlorine consumption calculation means 27 receives the contact time from contact time calculation means 23, receives COD from COD calculation means 24, extracts the chlorine consumption corresponding to these values from database 25, and outputs it.

  The sewage chlorine consumption thus obtained is output to the disinfection facility 12. In the disinfection facility 12, the chlorine injection rate is determined by adding an injection amount within a range not exceeding the allowable residual chlorine concentration of the discharged water based on the input chlorine consumption of the sewage, and the injection rate for the sewage in the treatment tank 11. Inject chlorine with constant control.

  As a result, the amount of residual chlorine in the treated water (discharged water) is small, and effective disinfection that reliably reduces the number of coliforms to a predetermined number or less is possible.

  Next, the embodiment shown in FIG. 4 will be described. In this embodiment, as in the embodiment shown in FIG. 3, COD and contact time based on turbidity and flow rate measured from sewage are used as characteristic values that affect the chlorine consumption of sewage. However, the database 25 in FIG. 3 is not used, and the chlorine consumption is calculated each time by the chlorine consumption calculation means 29 using the turbidity and the contact time. Other portions are the same as those in FIG. 3, and corresponding reference numerals are given, and detailed description thereof is omitted.

  In FIG. 4, the chlorine consumption calculation means 29 has the chlorine consumption calculation model formula (5) described above. Then, based on the flow rate and turbidity measured from the flow meter 21 and turbidimeter 22 from the sewage, the COD and contact time calculated by the contact time calculating means 23 and COD calculating means 24 are input, and preset constants. Is used to calculate the chlorine consumption according to the chlorine consumption calculation model equation (5).

  The sewage chlorine consumption thus obtained is output to the disinfection facility 12. In the disinfection facility 12, the chlorine injection rate is determined by adding an injection amount within a range not exceeding the allowable residual chlorine concentration of the discharged water based on the input chlorine consumption of the sewage, and the injection rate for the sewage in the treatment tank 11. Inject chlorine with constant control.

  As a result, the amount of residual chlorine in the treated water (discharged water) is small, and effective disinfection that reliably reduces the number of coliforms to a predetermined number or less is possible.

  Next, the embodiment shown in FIG. 5 will be described. In this embodiment, the meteorological data of a specific area is used to predict each sewage inflow amount to a plurality of sterilization facilities into which sewage flows in this specific area, and each sterilization facility is based on the predicted sewage inflow amount. The predicted value of the chlorine consumption amount is obtained, and the obtained predicted value of the chlorine consumption amount is transmitted to a corresponding disinfection facility through a communication line.

  In FIG. 5, 31A, 31B,..., 31N are a plurality of treatment facilities into which sewage from a specific area flows, and treatment tanks 11A, 11B,. ,..., 12N, which injects chlorine into the sewage flowing in from the responsible basin and discharges it as treated water. 32 is an inflow amount predicting calculation means for predicting the inflow sewage amount and water quality to each of the treatment facilities 31A, 31B,..., 31N based on the meteorological data relating to the specific area. That is, it is predicted when and how much rainfall there is in the specific area by weather information. The inflow amount prediction means 32 inputs this weather information and determines the degree of rainfall in the specific area. Then, the inflow sewage amount to each of the treatment facilities 31A, 31B,..., 31N that flows in due to rainfall to the specific area is calculated by a known inflow amount prediction method such as the RRL method. Moreover, since the turbidity of this inflowing sewage can also be predicted from this predicted amount of inflowing sewage, this turbidity is also predicted.

  The chlorine consumption calculation means 33 inputs the inflow sewage amount and turbidity for each processing equipment 31A, 31B,..., 31N from the inflow prediction calculation means 32, and each processing equipment 31A, 31B,. , 31N is calculated and predicted for chlorine consumption. That is, the chlorine consumption amount calculating means 33 simply calculates the contact time based on the above-described contact time calculation model equation (4) based on the inflow sewage amount. Further, the COD is calculated by the above-mentioned organic substance concentration calculation model formula (3) based on the input sewage turbidity. Based on the contact time and COD, the chlorine consumption is calculated for each of the treatment facilities 31A, 31B,..., 31N by the chlorine consumption calculation model equation (5) described above.

  The chlorine consumption for each of the treatment facilities 31A, 31B,..., 31N thus obtained is sent to the corresponding disinfection facilities 12A, 12B,..., 12N via a communication line 34 such as the Internet. Sent. Each disinfection facility 12A, 12B,..., 12N receives the corresponding chlorine consumption, and adds chlorine injection based on the chlorine consumption, adding an injection amount that does not exceed the allowable residual chlorine concentration of the discharged water. Determine the rate. And chlorine is inject | poured by the injection rate fixed control with respect to the sewage in corresponding processing tank 11A, 11B, ..., 11N.

  As a result, the amount of residual chlorine in the treated water (discharged water) is small, and effective disinfection that reliably reduces the number of coliforms to a predetermined number or less is possible.

  Thus, based on the local weather information, the chlorine consumption for each of the plurality of sterilization facilities 31A, 31B,... And the chlorine consumption calculation means 33 concentrates and predicts the calculation, and the chlorine consumption of each processing equipment 31A, 31B,..., 31N obtained as a result is obtained via a communication line 34 such as the Internet. Since it transmits to corresponding disinfection equipment 12A, 12B, ..., 12N, it is not necessary for each processing equipment 31A, 31B, ..., 31N to have chlorine consumption calculation means, respectively, and it can improve equipment efficiency. I can do it.

It is a system configuration figure showing one embodiment of a sewage disinfection system by the present invention. It is a graph used for calculating the potato sewage oil fertilizer in embodiment same as the above. It is a system configuration figure explaining an embodiment using a database of the present invention. It is a system block diagram explaining embodiment which calculates chlorine consumption each time by the chlorine consumption calculating means of this invention. It is a system block diagram explaining embodiment which concentrates and calculates the chlorine consumption for every processing facility by the chlorine consumption calculating means provided in the center side of this invention. It is a graph which shows the relationship between the residual chlorine accompanying chlorine injection, and coliform bacteria.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Treatment tank 12 Disinfection equipment 17,27,29,33 Chlorine consumption calculation means 23 Contact time calculation means 24 COD calculation means 25 Database

Claims (4)

A sewage disinfection system that disinfects sewage by injecting chlorine,
A database storing a plurality of characteristic values of sewage captured in advance and the relationship between chlorine consumption in each characteristic value;
Characteristic value detecting means for detecting the characteristic value from the sewage,
Chlorine consumption calculating means for inputting the characteristic value detected by the characteristic value input means and extracting the chlorine consumption corresponding to the inputted characteristic value from the database;
Based on the chlorine consumption calculated by this chlorine consumption calculation means, the chlorine injection rate is determined by adding the injection amount in the range that does not exceed the permissible residual chlorine concentration of the discharged water, and the sewage is discharged at this determined chlorine injection rate. A sewage disinfection system comprising a disinfection facility for injecting chlorine. The database stores the organic matter concentration of sewage, the contact time between sewage and chlorine, and the chlorine consumption corresponding to these multiple values as characteristic values representing the characteristics of sewage in advance. And
The sewage disinfection system according to claim 1, wherein the characteristic value detection means includes an organic substance concentration detection means and a contact time calculation means for calculating a contact time from the measured flow rate of sewage. A sewage disinfection system that disinfects sewage by injecting chlorine,
Contact time calculating means for calculating the contact time between sewage and chlorine based on the flow rate measured by the sewage organic matter concentration detecting means and the flow rate measuring means of the sewage, contact between the organic matter concentration of the sewage, and contact between the sewage and chlorine Chlorine consumption calculation means for obtaining chlorine consumption by a predetermined calculation model formula using time;
Based on the chlorine consumption calculated by this chlorine consumption calculation means, the chlorine injection rate is determined by adding the injection amount in the range that does not exceed the permissible residual chlorine concentration of the discharged water, and the sewage is discharged at this determined chlorine injection rate. A sewage disinfection system comprising a disinfection facility for injecting chlorine. A sewage disinfection system that disinfects sewage by injecting chlorine,
Input weather data of a specific area, predict the amount of sewage inflow into multiple sterilization facilities where sewage flows into this specific area, and based on the predicted amount of sewage inflow, organic matter of sewage to be disinfected in each sterilization facility Inflow prediction calculation means for predicting the concentration and the contact time respectively;
Chlorine consumption calculation means for obtaining a predicted value of chlorine consumption of each disinfection facility using the organic substance concentration and contact time in each disinfection facility predicted by this inflow prediction calculation means;
Transmission means for transmitting the predicted value of chlorine consumption of each sterilization facility obtained by this chlorine consumption calculation means to the corresponding sterilization facility via a communication line,
At each disinfection facility, the chlorine injection rate is determined by adding an injection amount that does not exceed the allowable residual chlorine concentration of the effluent based on the chlorine consumption that has been transmitted. Sewage disinfection system characterized by injecting.

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