KR100638158B1 - Sewage treatment system - Google Patents

Abstract

This invention makes it a subject to implement appropriate water quality control according to the situation, even if the situation where the water quality in a biological reactor cannot reach | attain the target value level generate | occur | produced.

The water quality control target value determination means 24 determines whether or not the water quality control target value input from the water quality control target value setter 22 is reachable, and the measurement data from the inflow flow meter 27 and the total nitrogen concentration meter 28; Judgment is made based on the estimated bacterial concentration. The determination result execution means 25 changes the target value set in the water quality control target value setter 22 to a level that can be reached when the determination result is unreachable, or when it cannot change, the controller 23. ) The amount of operation of the blower 13 is kept below a predetermined level.

Sewage treatment system, water quality control.

Description

Sewage Treatment System {SEWAGE TREATMENT SYSTEM}

1 is a configuration diagram of a sewage treatment system according to a first embodiment of the present invention.

2 is a configuration diagram of a sewage treatment system according to a second embodiment of the present invention.

3 is a configuration diagram of a sewage treatment system according to a third embodiment of the present invention.

FIG. 4 is an explanatory view of data stored in the inflow water quality database 33 in FIG. 3, FIG. 4A is a chart showing an example of conservation data, and FIG. 4B is based on this conservation data example. The characteristic diagram which shows the pattern example of the inflow total nitrogen concentration obtained.

5 is a configuration diagram of a sewage treatment system according to a fourth embodiment of the present invention.

FIG. 6 is an explanatory view of the configuration of the main part of FIG. 5, FIG. 6 (a) is a characteristic diagram showing a pattern example of the inflow nitrogen load estimated by the inflow load prediction means 36, and FIG. 6 (b) is the target value planning means. Explanatory drawing about target value plan which 37 made.

7 is a block diagram of a conventional sewage treatment system.

Explanation of the sign

1: inlet valve

2: first settler

3: bioreactor

4: anaerobic tank

5: anaerobic tank

6: aerobic

7: final settler

8: bypass valve

9: carbon source storage tank

10: carbon source injection pump

11: flocculant storage tank

12: flocculant injection pump

13: blower

14: diffuser

15: return pump

16: conveying pump

17: Initial settling drawing pump

18: surplus pump

19: Sludge tank

20: ammonia nitrogen concentration meter

21: monitoring device

21A: Surveillance Device

21B: Surveillance Device

21C: Surveillance Device

21D: Surveillance

22: water quality control target setter

23: controller

24: water quality control target value determination means

25: determination result execution means

26: display unit

27: inflow meter

28: total nitrogen concentration meter

29: circulating flowmeter

30: nitrate nitrogen concentration meter

31: nitrate nitrogen concentration meter

32: treated water total nitrogen concentration meter

33: influent water quality database

34: Inflow water quality prediction means

35: Influent Load Database

36: inflow load prediction means

37: target planner

The present invention relates to a sewage treatment system for treating municipal sewage, industrial wastewater and the like.

The water treated by the sewage treatment system is finally discharged to rivers and the like, but due to the discharged treated water, so-called "eutrophication" has been a problem in the closed waters of lakes, swamps and bays in recent years. . "Nutriation phenomenon" is a phenomenon in which large amounts of phytoplankton occur due to the nutrients of nitrogen and phosphorus contained in the drainage, which is a type of environmental pollution causing adverse effects on water pollution, bad smell, or fish and shellfish.

In order to prevent the occurrence of such eutrophication, it is necessary to suppress the outflow of nitrogen and phosphorus as the causative substances from the sewage treatment system to the closed water. On the other hand, in the conventional conventional sewage treatment system, only organic matter is removed by a process called an activated sludge process, but nitrogen and phosphorus are not effectively removed by such an activated sludge process. Therefore, in recent sewage treatment systems, as disclosed in, for example, Japanese Patent Laid-Open Nos. 9-248596 and 11-244894, removal can be performed not only for organic matter but also for nitrogen and phosphorus. In many cases, an advanced processing system is adopted.

7 is a configuration diagram of a conventional sewage treatment system employing the above advanced treatment system. In FIG. 7, inflow sewage from the immersion paper (not shown) is sent to the initial immersion battery 2 through the inflow valve 1, where small sand, dust, and the like which cannot be removed from the immersion paper are removed. have.

The sewage having passed through the initial settler 2 is then sent to the bioreactor 3. This bioreactor 3 is of a type which carries out a process treatment called "coagulant injection A2O method", and is comprised by the anaerobic tank 4, the anaerobic tank 5, and the aerobic tank 6. As shown in FIG. In this bioreactor 3, organic matters are removed by aerobic microorganisms contained in activated sludge, and nitrogen and phosphorus are simultaneously removed.

The treated water subjected to the treatment in the bioreactor 3 is then sent to the final settler 7 where it is separated into activated sludge and supernatant, and the supernatant is disinfected in a chlorine mixed paper (not shown) and discharged into a river or the like. It is supposed to be.

The bypass valve 8 is used for directly supplying organic substances contained in the influent sewage in order to activate the phosphorus accumulation bacteria present in the anaerobic tank 4.

The carbon source injection pump 10 is for injecting carbon sources such as methanol, ethanol, acetic acid, spent acetic acid, glucose, and the like stored in the carbon source storage tank 9 to activate the accumulation bacteria present in the anaerobic tank 4.

The coagulant injection pump 12 supplies the coagulant (PAC) for precipitating phosphorus components such as polyaluminum chloride, aluminum sulfate and iron sulfate stored in the coagulant storage tank 11 to the aerobic tank 6.

A blower 13 as an aeration device is attached to the bottom of the aerobic tank 6, and air from the blower 13 is activated in the sludge through the diffuser 14 disposed in the aerobic tank 6. It is intended to be supplied to aerobic microorganisms. The water in the aerobic tank 6 is agitated by aeration to be completely mixed, and the aerobic microorganisms are activated by the air supplied in this state to promote decomposition and magnetization of organic matter.

A part of the water in the aerobic tank 6 is circulated to the anoxic tank 5 by the circulation pump 15. In addition, the activated sludge drawn out from the bottom of the final settler 7 is conveyed to the inlet of the anaerobic tank 4 by the transfer pump 16.

In addition, the surplus sludge collected at the bottom of the initial settler 2 is drawn by the initial settling drawing pump 17 and sent to the sludge storage tank 19 to be collected at the bottom of the final settler 7 to the anaerobic tank by the transfer pump 16. The surplus sludge that has not been completely returned to the (4) side is also sent to the sludge storage tank 19.

An ammonia nitrogen concentration meter 20 is arranged in the aerobic tank 6, and the concentration of ammonia nitrogen (NH ₄ -N) is measured. Moreover, the monitoring apparatus 21 has the water quality control target value setter 22, and the target value with respect to the ammonia nitrogen concentration in the aerobic tank 6 is output. The controller 23 controls the blower 13 so that the ammonia nitrogen concentration measured by the ammonia nitrogen concentration meter 20 coincides with the target value set by the water quality control target value setter 22.

Next, the operation regarding nitrogen removal and phosphorus removal in the configuration of FIG. 7 will be described. First, the nitrogen removal will be described. In the aerobic tank 6, the nitrifying bacteria replace ammonia nitrogen (NH ₄ -N) with nitrite nitrogen (NO ₂ -N) using oxygen supplied by the blower 13. And oxidize with nitric acid nitrogen (NO ₃ -N). In addition, nitrite nitrogen (NO ₂ -N) and nitrate nitrogen (NO ₃ -N) transferred from the aerobic tank (6) to the anoxic tank (5) by the circulation pump (15) make organic matter a nutrient source under anoxic conditions. It is reduced to nitrogen gas (N ₂ ) by nitric acid breathing or nitrite breathing by denitrifying bacteria and is removed out of the system.

In this case, good nitrogen removal is not performed unless the organic substance necessary for denitrification is sufficiently supplied. As a measure for replenishing this organic matter, the bypass valve 8 is opened to bypass the initial settler and supply inflow sewage to the anaerobic tank 4, or methanol, ethanol, acetic acid, waste acetic acid and glucose collected in the carbon source storage tank 9. Injecting a carbon source such as the same into the anaerobic tank 4, or injecting a draw sludge generated in the final settler (7) into the anaerobic tank (4).

Here, the nitrogen removal reaction is represented by the following formula. That is, nitriding reaction becomes like Formula (1) and Formula (2).

^{_{NH 4 + + 2O 2 → NO}} 2 - + 2H 2 O ... … Formula (1)

NO₂                             ^-+ 1 / 2O₂ → NO₃                             ^-                              … … Formula (2)

In the denitrification reaction, the reaction in the case where methanol is used as the organic substance is described as Formula (3).

6NO₃                             ^-+ 5CH₃0H → 3N₂+ 5CO₂+ 7H₂O + 6OH^-                              … … Formula (3)

The controller 23 rotates the blower 13 based on the input of the measurement data from the ammonia nitrogen concentration meter 20 and the target value from the water quality control target value setter 22 so that the above reaction is promoted. To control.

Next, the phosphorus removal will be described. In the anaerobic tank 4, the accumulation bacteria in the activated sludge accumulate organic acids such as acetic acid in the body and excessively release phosphoric acid (PO ₄ ). Phosphorus in the form of excessively released phosphoric acid is sent to the aerobic tank (6), but in the aerobic tank (6), the phosphorus in the form of more than the phosphoric acid released from the anaerobic tank (4) is activated by the use of the phosphorus excess intake action of the accumulation bacteria Is absorbed in. Thereby, phosphorus removal is performed.

In order to advance the above reaction, an organic acid such as acetic acid is required as the hydrogen donor. However, at the time of rainwater inflow, the concentration of organic acid is diminished and the organic matter available to the accumulation bacteria decreases, so that the discharge reaction of phosphorus is not sufficiently performed, and the subsequent excess intake reaction of phosphorus is also insufficient.

In order to supplement this, a carbon source necessary for phosphorus removal is secured in the same manner as in the case of nitrogen removal, or a coagulant (PAC) such as polyaluminum chloride, aluminum sulfate, or iron sulfate stored in the coagulant storage tank 11 is injected to make aluminum phosphate. Or phosphorus by precipitating the phosphorus component in the form of iron phosphate.

A1 ³⁺ + PO ₄ ^3- → AlP0 ₄ ... … Formula (4)

Removal of nitrogen contained in the influent sewage and removal of phosphorus are performed using the above-described biological reactions, and the controller 23 controls each process device so that the nitrogen concentration and the phosphorus concentration reach a target value (fixed value). have.

However, the inflow of inflow sewage is greatly varied (e.g. during rainfall), so that the nitrogen concentration and phosphorus concentration contained in the sewage may fluctuate greatly. Here, regarding the phosphorus concentration, even if the amount of sewage inflow increases rapidly during rainfall, the target value level is easily maintained by increasing the amount of injected flocculant, carbon source or the like, so that there is almost no problem.

On the other hand, with regard to the nitrogen concentration, when the inflow amount of a certain level or more increases, it is impossible to reach the target water quality due to the residence time of the treated water in the bioreactor 3 and the bioreaction rate. In this case, the controller 23 increases the aeration volume of the blower 13 to the maximum level even though it is impossible to reach the target nitrogen concentration, but such control leads to waste of power and waste. It causes a rise in power costs.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sewage treatment system capable of performing appropriate water quality control according to the situation even when a situation in which the water quality in the biological reactor cannot reach the target level is generated. Doing.

As a means for solving the said subject, the invention of Claim 1 is equipped with the sewage treatment process containing an initial settler, a bioreactor, and a last settler, and controls the operation amount of the predetermined process apparatus provided in these sewage treatment processes. Thus, in the sewage treatment system which performs water quality control so that the water quality in the said bioreactor reaches a predetermined water quality control target value, the water quality limit prediction value is based on either or both of predetermined measurement data and prediction data. Water quality control target value determination means for calculating whether or not the water quality control target value is reachable based on a comparison between the water quality limit prediction value and the water quality control target value, and determining that the water quality control target value determination means is unreachable. In that case, we inform the judgment result and the water quality And determination result execution means for changing the control target value to a level attainable or fixing the operation amount of the predetermined process device.

In the invention according to claim 2, in the invention according to claim 1, the water quality in the bioreactor is ammonia nitrogen concentration in an aerobic tank constituting a part of the bioreactor, and is a predetermined process provided in the sewage treatment process. The operation amount of the device is characterized in that the aeration air volume of the blower installed in the exhalation tank.

In the invention according to claim 3, in the invention according to claim 1, the water quality in the bioreactor is an anoxic tank of an aerobic tank front end that constitutes a part of the bioreactor, or a quality in an anaerobic tank of the anoxic tank front end. The acid nitrogen concentration, and the operation amount of the predetermined process equipment provided in the sewage treatment process is characterized in that the carbon source injection amount of the carbon source injection pump to the anoxic tank or anaerobic tank.

In the invention according to claim 4, in the invention according to any one of claims 1 to 3, the water quality control target value determination means performs the determination based only on the predetermined measurement data, and the measurement The data is characterized by including the flow rate and total nitrogen concentration of the sewage entering the sewage treatment process.

The invention according to claim 5 is the invention according to any one of claims 1 to 3, wherein the water quality control target value determination means performs the determination based on both of the predetermined measurement data and the prediction data. The measurement data is the flow rate of sewage flowing into the sewage treatment process, and the prediction data is historical time series data on the total nitrogen concentration of the incoming sewage.

The invention according to claim 6, wherein the invention according to claim 1 includes target value planning means for creating a target value plan based on the predetermined prediction data and setting the created target value plan as the water quality control target value. It features.

In the invention according to claim 7, the water quality control target value determination means performs the determination based only on the predetermined measurement data, and the measurement data is based on the flow rate of the sewage flowing into the sewage treatment process, and the aerobic tank. It characterized in that it comprises a circulating flow rate and the nitrate nitrogen concentration for the treated water circulated to an anoxic tank.

The invention according to claim 8 is, in the invention according to claim 3, the amount of operation of a predetermined process device installed in the sewage treatment process is replaced with the amount of carbon source injection into the anoxic tank or anaerobic tank of the carbon source injection pump. It is characterized by setting it as the step inflow amount of each sewage to the said anaerobic tank, the said anoxic tank, and the said aerobic tank which comprise a reaction tank.

The invention according to claim 9 is, in the invention according to claim 3, the amount of operation of a predetermined process device installed in the sewage treatment process is replaced with the amount of carbon source injection into the oxygen-free tank or anaerobic tank of the carbon source injection pump. Bypassing the settling basin characterized in that the first settling bypass flow rate flowing into the bioreactor.

In the invention according to claim 10, in the invention according to claim 3, the anaerobic tank is replaced with an operation amount of a predetermined process device installed in the sewage treatment process, instead of the carbon source injection amount for the anoxic tank or the anaerobic tank of the carbon source injection pump. Or inputting raw sludge from the bottom of the initial settler to the anoxic bath, or inputting raw sludge into the anaerobic tank of fermentation product produced by fermenting the raw sludge from the bottom of the initial settler. do.

In the invention according to claim 11, the invention according to any one of claims 1 to 10, wherein the water quality control target value determining means is a substance resin for calculating a resin of a substance for determining the water quality in the bioreactor. And a statistical model for outputting historical data of the resin calculation result of the substance.

In the invention according to claim 12, in the invention according to any one of claims 1 to 11, the water quality control target value determining means calculates the water quality limit predicted value into a plurality of steps and at the same time. According to the difference between each predicted value of the and said water quality control target value, it is characterized by making a said determination every several steps.

The invention according to claim 13 is provided with a display unit for displaying the determination result for each of the plurality of steps by the water quality control target value determination means according to the invention according to claim 12.

EMBODIMENT OF THE INVENTION Hereinafter, each embodiment of this invention is described based on drawing. However, the same components as shown in Fig. 7 are denoted by the same reference numerals and redundant description thereof will be omitted. In addition, in each of the following embodiments, only the removal of nitrogen is a problem, and therefore, the injection destination of the carbon source injection pump 10 is not the anaerobic tank 4 but the anoxic tank 5, but in the present invention, the injection destination is the anaerobic tank. (4) and any one of the structure which made the injection destination both the anaerobic tank 4 and the anaerobic tank 5 is included.

1 is a configuration diagram of a sewage treatment system according to a first embodiment of the present invention. 1 differs from FIG. 7 in that the monitoring device 21 is a monitoring device 21A in addition to the injection destination of the carbon source injection pump 10 described above, and the total nitrogen concentration meter at the inlet side of the anaerobic tank 4. (28) is provided. In addition to the water quality control target value setter 22, the monitoring device 21A includes water quality control target value determination means 24, determination result execution means 25, and a display unit 26.

The water quality control target value determination means 24 determines whether the water quality control target value input from the water quality control target value setter 22, that is, whether ammonia nitrogen concentration is reachable, is the inflow flow meter 27 and the total nitrogen concentration meter 28. The determination is made based on the measurement data from and the nitride bacterium concentration estimate estimated by an arbitrary method (for example, a test or a simulation). In addition, although the period of the determination operation which the water quality control target value determination means 24 performs can be set to arbitrary time, it is assumed in this embodiment that a determination operation is performed about every 1 hour.

When the determination result of the water quality control target value determination means 24 is unreachable, the determination result execution means 25 displays on the display unit 26 that the unreachability is not reached and prompts the operator's attention. . In this case, the determination result execution means 25 changes the target value set in the water quality control target value setter 22 to a level that can be reached, or when the controller 23 cannot change to a level that can be reached. To control the operation amount with respect to the blower 13, and to control so that the aeration air volume of the blower 13 may not become above a predetermined level.

Next, the effect | action of 1st Embodiment comprised as mentioned above is demonstrated. The measured value of the ammonia nitrogen concentration meter 20 attached to the aerobic tank 6 is sent to the controller 23, and the controller 23 is close to the ammonia nitrogen concentration target value set in the water quality control target value setter 22. The amount of aeration air of the blower 13 is calculated.

Since the nitriding reaction does not proceed in the state of lack of oxygen, if the ammonia nitrogen concentration is higher than or equal to the target value, the aeration air volume is increased, and if it is lower than or equal to the target value, the aeration amount can be controlled appropriately without excess or deficiency.

The aeration air flow rate calculation equation is expressed in the form of equation (1.1), for example, when the controller is a PI controller. Qair (t) is the target value of aeration air volume [m ³ / min] at time t, Qair ₀ is the initial value of aeration air volume [m ³ / min], and Kp is proportional gain [m ⁶ / g · min]. Where T _I is the integral constant [min], Δt is the control period [min], e (t) is the deviation [mg / L], SV _NH4 (t) is the ammonia nitrogen concentration target value [mg / L], PV _NH4 (t) is an ammonia nitrogen concentration meter measurement [mg / L].

When the aeration air flow rate controller is a PI controller represented by the form as shown in the formula (1.1), when the ammonia nitrogen concentration measurement value PV _NH4 is larger than the target value SV _NH4 , the aeration air volume increases in the direction of increasing the ammonia than the target value SV _NH4. When the measured nitrogen concentration concentration PV _NH4 is small, the aeration air weight target value is calculated in the direction of decreasing the aeration air volume.

In the aerobic tank 6, it is preferable that the nitriding is promoted so that the ammonia nitrogen concentration does not remain as long as possible, and therefore, a target value of ammonia nitrogen concentration of 0.5 to 1 [mg / L] is usually set near the end of the aerobic tank 6. do. However, in the case where the inflow load, which is the product of the inflow flow rate and the inflow total nitrogen concentration, is large, there may be a situation in which ammonia nitrogen cannot be removed even if the airflow is increased to some extent.

In this case, if control is performed while the target value is fixed, the air volume increases up to the maximum aeration air volume and the air volume becomes excessive. By the way, the water quality control target value determination means 24 determines whether this control target value is achievable.

In Fig. 1, assuming that the anaerobic tank 4, the anaerobic tank 5, and the aerobic tank 6 are completely mixed tanks, nitrification does not basically occur in the anaerobic tank 4 and the anaerobic tank 5, and the liquid There is only the elution of the nitrogen component accompanying the mixing and hydrolysis of.

Here, when the mass balance of ammonia nitrogen in the anaerobic tank 4 is calculated, it becomes as Formula (1.2). Where Snh4 (1) is anaerobic ammonia nitrogen concentration [mg / L], Qin is the inflow flow rate [m ³ / day], Snh4in is the influent ammonia nitrogen concentration [mg / L], and Qret is the return flow rate [m ³ / day], Snh4 (4) is the sedimentation basin ammonia nitrogen concentration [mg / L], V (1) is the anaerobic tank volume [m ³ ], and Δx1 is the elution rate of ammonia nitrogen accompanying anaerobic bath hydrolysis [g / day].

Similarly, the mass balance of ammonia nitrogen in the oxygen-free tank 5 is calculated as shown in equation (1.3). However, Snh4 (2) is anoxic crude ammonia nitrogen concentration [mg / L], Qin is the inflow flow rate [m ³ / day], Qcir is the circulation flow rate [m ³ / day], and Snh4 (3) is the aerobic bath ammonia nitrogen concentration [Mg / L], V (2) is the anoxic bath volume [m ³ ], and [Delta] x2 is the elution rate of ammonia nitrogen accompanying the anoxic bath hydrolysis [g / day].

In determining whether the target value is achievable, it may be considered in a steady state. Thus, when the left side of Equation (1.2) and (1.3) is set to 0, Equation (1.4) is obtained. However, a1 and a2 are integers.

In addition, considering the mass balance of the ammonia nitrogen concentration in the aerobic tank it is as shown in equation (1.5). Where Snh4 (3) is the aerobic ammonia nitrogen concentration [mg / L], V (3) is the aerobic tank volume [m ³ ], and Δx3 is the aerobic bath hydrolysis and elution rate of ammonia nitrogen with organic matter removal [g / day], Rnh4 is the reduction rate [g / day] of ammonia nitrogen accompanying the growth of nitride bacteria.

The reduction rate of ammonia nitrogen accompanying the growth of nitride bacteria is represented by equation (1.6). Where μaut is the maximum specific growth rate of nitride bacteria, Yaut is the yield of nitride bacteria, SO2 (3) is the aerobic dissolved oxygen concentration [mg / L], Salk (3) is the aerobic alkalinity [mg / L], and Xaut is the nitride Bacterial concentration [mg / L], K02, Knh4, and Kalk are half-saturation constants.

In a condition where nitriding is not inhibited by dissolved oxygen and alkalinity (a condition where nitriding occurs at maximum efficiency), equation (1.6) becomes as shown in equation (1.7).

If the right side of equation (1.5) is set to 0, the ammonia concentration at steady state can be calculated. Substituting equation (1.4) and equation (1.7) into equation (1.5) and making the right side = 0, equation (1.8) is obtained.

Here, since nitrate nitrogen and nitrite nitrogen in the influent are considered to be hardly present, ammonia nitrogen generated by hydrolysis or the like is considered to be almost attributable to the organic nitrogen in the influent. Therefore, equation (1.8) can be rewritten as in equation (1.9). Here, ST-Nin is the total nitrogen concentration (mg / L) of inflow water. In addition, solving the equation (1.9) and deriving the correct solution gives the equation (1.10).

,

단,

,

only,

Snh4 (3) lim is the lower limit of the aerobic ammonia nitrogen concentration.

μaut is a parameter depending on the water temperature T (° C), and μaut = 1.12 ^(T-20) , Yaut = 0.24, and Knh4 = 1. Equation (1.10) is a solution obtained by a condition without nitriding inhibition (a condition in which nitriding occurs at maximum efficiency), and thus the limit value of ammonia nitrogen concentration is obtained.

Since ST-Nin is measured by the total nitrogen concentration meter 28 and Qin by the inflow flow meter 27, when the value of Xaut (3) is known, it can be determined by the discriminant of Equation (1.10) whether the target value can be controlled. Can be.

Since it is difficult to measure Xaut (3) (nitride bacteria concentration) directly, it is necessary to estimate it by the method of the nitriding rate test at that time, or by any method, such as simulation using an active sludge model.

When obtained by simulation, Xaut (3) changes depending on how long the residence time A-SRT of the solid in the aeration tank is to be taken, so that the previous operating conditions (about one week), the inflow water quality, and the inflow flow rate (time series data) If not, it is good to use the average data) as input and perform simulation to set the value where Xaut (3) falls in the steady state. Usually, it is thought that this will fall to a value of about 50-100. This value needs to be updated at a frequency of about once a week to about once a month.

In this way, if Xaut (nitride bacterium concentration) can be estimated, by inputting the nitride bacterium concentration estimation value to the water quality control target value determination means 24, it is possible to determine whether the target value can be achieved by using Equation (1.1O). have.

For example, as the first condition, Xaut (3) = 80 [mg / L], ST-Nin = 30 [mg / L], water temperature 20 [° C], Snh4ref = 1 [mg / L], V3 = When 1000 [m ³ ] and Qin = 4000 [m ³ / day], the solution (limit value) obtained by the formula (1.10) satisfies the equation of 0.54 [mg / L]. If there is no inhibition of nitriding by, control is possible.

Further, as the second condition, Xaut (3) = 80 [mg / L], ST-Nin = 30 [mg / L], water temperature 20 [° C], Snh4ref = 1 [mg / L], V3 = 1000 [ m ³ ], when Qin = 8000 [m ³ / day], the solution (limit value) obtained in Eq. (1.10) is 2.03 [mg / L], and this target value is related to the residence time regardless of how much aeration air is blown. It can be seen that the phase cannot be controlled.

In the case of the second condition, the operator is informed that the target value control is impossible, or the inverse operation of the target value that can be achieved at the same time as the notification is performed (the expression (1.10) is performed). Since the operation is performed based on the condition that can be removed to the maximum, the calculation operation is not performed as the control target value as it is, but rather a value larger than that is set as the control target value.

That is, if DELTA Snh4 is a bias value (about 0.5) and Snh4ref (auto) is a target value automatic calculation value, equation (1.11) is obtained. In this case, since the answer is 2.03 [mg / L], it is possible to control when bias is set to about 3 as the control target value.

According to the first embodiment described above, the following effects can be obtained. First, since the target value that can be achieved is automatically calculated, the air volume compared with the PI control using the conventional ammonia nitrogen concentration meter in the case where the inflow load is high. Can be reduced. Secondly, the inflow water quality is measured at the overflow part of the initial settling, so that the nitrogen component flowing into the aeration tank can be accurately identified, so that a more accurate target value can be determined.

In addition to the above-described embodiment, the first embodiment also broadly includes the following forms.

(1) The position of the inflow flowmeter 27 and the total nitrogen concentration meter 28 may be anywhere upstream of the anaerobic tank 4, for example, the upstream side of the initial settler 2 or the inflow valve ( The upstream side of 1) may be sufficient.

(2) The measured values of the inflow flowmeter 27, the total nitrogen concentration meter 28, and the ammonia nitrogen concentration meter 20 may be filtered by the equation (1.12) or equation (1.13). However, PV (t) is a sensor measurement value at time t, FT is a filter coefficient of 0-1, and n is an integer.

(3) The ammonia nitrogen concentration limit prediction value is not limited to the formula (1.1O), and any model may be used as long as the model outputs a limit concentration such as a model or a statistical model that handles the mass balance in more detail or simply. For example, from the inflow water quality data and the flow rate data, the ammonia nitrogen concentration limit value of the aerobic tank 6 may be predicted by an equation (1.14).

Where a and b are integers, ST-Nin is the influent total nitrogen concentration (mg / L), and Qin is the influent flow rate (m ³ / day).

(4) The method of measuring Xaut (3) in Equation (1.10) is not limited to the method calculated by simulation, and the amount of Xaut (3) may be estimated from the results of the actual nitriding rate test. It may be obtained by other means.

(5) The bioreactor 3 in the first embodiment was of a type that performs a process treatment called a "coagulant A2O method", but is not necessarily limited thereto. In addition, the AO process and cyclic nitriding denitrification A sewage treatment process such as a process may be performed, or alternatively, various A ₂ O methods such as a carrier injection, a coagulant combination type, or an AOAO method may be used.

(6) The controller 23 for controlling the blower 13 is not limited to the PI controller, and may be any type as long as the controller 23 performs calculation based on a deviation between a target value and a measured value such as a PID controller.

(7) When the determination result execution means 25 determines that the target value currently set by the water quality control target value determination means is unreachable, even if the target value is not changed to a predetermined level reachable, Only the notification of the effect may be performed and the operation amount of the blower 13 may be fixed.

(8) Although the above calculation is based on the condition that there is no restriction of dissolved oxygen, in practice, the capacity of the blower 13 to perform aeration is determined, and even if the maximum air volume is blown, the dissolved oxygen concentration DO does not rise, Nitriding may not occur. By the way, the maximum supplyable aeration air volume is Qair, max, and the mass balance of dissolved oxygen concentration DO in the aerobic tank 6 is taken to obtain the equation (1.15). Where Kla is the overall capacity factor, Qair, max is the maximum aeration volume [m ³ / day], S _{O 2} , sat is the saturated dissolved oxygen concentration [mg / L], and R _COD is the rate of oxygen consumption by heterotrophic bacteria [ [G / m ³ ] / day]. This equation (1.15) may be used to determine the ammonia concentration limit.

That is, even if the right side of Equation (1.15) is set to 0, S02 (3) is solved, the DO (S02max, (3)) at the maximum air volume is calculated, and the ammonia concentration limit Snh4lim is obtained by Equation (1.14). good. In addition, the calculation of DO (SO2max, (3)) at the maximum air flow rate is not limited to the equation (1.14), and may be predicted by the same calculation formula as the equation (1.16) based on past statistics and the like. A and b are integers.

SO2max, (3) = aQair, max + b... … Formula (1.16)

(9) Since the limit concentration prediction model is considered to have an error, it is divided into three outputs, for example, "an absolutely impossible target value", "a difficult target value", and "a barely achievable target value". Three lines may be displayed on the monitoring screen.

Next, 2nd Embodiment of this invention is described based on the block diagram of FIG. 2 is different from FIG. 1 in that the input / output of the controller 23 is different, and the input of the water quality control target value determination means 24 at the monitoring device 21B is different.

That is, in the present embodiment, the water quality to be controlled is the nitrate nitrogen concentration in the anoxic tank 5, and the controller 23 has the nitrate nitrogen concentration measured by the nitrate nitrogen concentration meter 31 in the water quality control target value. The injection amount of the carbon source injection pump 10 is controlled to match the target value set by the setter 22.

Further, the water quality control target value determination means 24 determines whether the water quality control target value input from the water quality control target value setter 22, that is, whether the nitrate nitrogen concentration is reachable, is the inflow flowmeter 27 and the circulation flowmeter 29. ) And the measurement data from the nitrate nitrogen concentration meter 30 are determined based on the estimated value of denitrifying bacteria concentration estimated by any method (for example, test or simulation).

Next, the operation of the second embodiment having the above-described configuration will be described. Since the denitrification reaction does not proceed in a state where the organic matter is insufficient, when the nitrate nitrogen concentration remains above the target value, the controller 23 increases the injection amount of the carbon source injection pump 10, and on the other hand, the nitrate nitrogen concentration When is lower than the target value, if the carbon source injection amount is reduced, it becomes possible to control the appropriate carbon source input amount without excess and deficiency.

The carbon source input formula is expressed in the form of formula (2.1), for example, when the controller is a PI controller. Qcar (t) is the target value of carbon source injection amount [m ³ / min] at time t, Qair _o is the initial value of carbon source injection amount [m ³ / min], Kp is proportional gain [m ⁶ / g · min], and T _I is Integral constant [min], Δt are control periods [min], e (t) is deviation [mg / L], SV _NO3 (t) is the nitrate nitrogen concentration target value [mg / L], PV _NO3 (t) is It is an anoxic-nitrogen nitrate nitrogen concentration meter measurement [mg / L].

When the controller is a PI controller represented by the form as shown in Equation (2.1), when the nitrate nitrogen concentration measurement value PV _NO3 is larger than the target value SV _NO3 , the carbon source injection amount is increased, and conversely, the nitrate nitrogen is higher than the target value SV _NO3. When the concentration measurement value PV _NO3 is small, the carbon source injection amount target value is calculated in a direction in which the carbon source injection amount decreases.

In the oxygen-free tank 5, since it is good in water quality that denitrification is accelerated | stimulated and nitrate nitrogen concentration does not remain as much as possible, it is usually 0.1-0.5 [mg / L] nitric acid vicinity in the vicinity of the terminal of the aerobic tank 6. The nitrogen concentration target is set. However, when the nitrate nitrogen load flowing into the oxygen-free tank 5 is large, there may arise a situation in which nitrogen cannot be removed even if a carbon source is injected to some extent, for example.

In this case, if control is performed while the target value is fixed, the injection amount increases up to the maximum carbon source injection amount even though the denitrification reaction cannot be promoted, and excessive carbon source injection is performed. By the way, the water quality control target value determination means 24 determines the target value.

In Fig. 2, assuming that the anaerobic tank 4, the anaerobic tank 5, and the aerobic tank 6 are completely mixed tanks, it is considered that there is almost no nitrate nitrogen in the influent and little in the anaerobic tank 4. Also good. Therefore, it can be considered that nitrate nitrogen flowing into the oxygen-free tank 5 only circulates from the aerobic tank 6 by the circulation pump 15.

When the mass balance of nitrate nitrogen in the anoxic tank is calculated, it is as in Formula (2.2). However, Sno3 (2) is anoxic crude nitrate nitrogen concentration [mg / L], Qin is the inflow flow rate [m ³ / day], Sno3 (3) is the aerobic nitric acid concentration [mg / L], and Qret is the return flow rate [ m ³ / day], Qcir is the circulation flow rate [m ³ / day], V (2) is the anaerobic bath volume [m ³ ], and Rno ³ is the decrease in nitrate nitrogen [g / day] accompanying the growth of denitrification bacteria.

The rate of decrease of nitrate nitrogen accompanying the growth of denitrification bacteria is represented by equation (2.3). However, μH is the maximum specific growth rate of heterotrophic bacteria (denitrifying bacteria), YH is the yield of heterotrophic bacteria (denitrifying bacteria), SO2 (2) is anoxic dissolved oxygen concentration [mg / L], and Sno3 (2) is anoxic. Nitrate nitrogen concentration [mg / L], Scod (2) is anoxic crude organic concentration [mg / L], and Xh (2) is anoxic crude heterotrophic concentration [mg / L].

Since the carbon source is replenished, the carbon source does not become a rate determination of the present reaction. Assuming that no dissolved oxygen enters the aerobic tank 6, the maximum removal rate Rno3 of the nitrate nitrogen in the anoxic tank 5 is represented by equation (2.4).

If the right side of equation (2.2) is set to 0, the nitrate nitrogen concentration in the steady state can be calculated. Substituting equation (2.4) into equation (2.2) and making the right side = 0, equation (2.5) is obtained. If at least this condition is not satisfied, control to the target value is impossible.

Sno3 (2) obtained by solving the equation (2.5) is the limit target value (Sno31im) of the nitrate nitrogen concentration. In addition, the flow volume of Qcir, Qin, Qret, etc. is measured by the flowmeter (not shown), and Sno3 (3) is measured by the nitrate nitrogen concentration meter 30. As shown in FIG. In addition, since V (2) is the volume of an anoxic tank, it is already known.

=0.8, Kno3=0.5로 된다. 따라서, Xh(2)(종속영양균 농도)의 값이 알려지면, 목표치가 도달 가능한 것인지의 여부를, 식(2.5)의 판별식에 의거하여 판정할 수 있다.μH is a parameter depending on the water temperature T (° C), and referring to the parameter value of the international standard model ASM2d, μH = 6.0 · 1.07 ^(T-20) , and YH = 0.63,

= 0.8 and Kno3 = 0.5. Therefore, if the value of Xh (2) (dependent nutrient concentration) is known, whether or not the target value can be reached can be determined based on the discriminant of Equation (2.5).

Since it is difficult to measure Xh (2) directly, it is necessary to estimate it by any method, such as estimating by simulation using an active sludge model, substituting it by the conversion coefficient from MLSS, or substituting for MLVSS. Since MLVSS is an indicator of the amount of microorganisms, and most of the microorganisms contained in the sludge are heterotrophic bacteria, an approximate value can be obtained by setting Xh (2) = 0.9 x MLVSS. This estimate needs to be updated at a frequency of about once a week to about once a month.

If it is possible to estimate the heterotrophic concentration, that is, the denitrifying bacterium concentration Xh (2) by any of the above methods, it is possible to determine whether or not the target value can be reached by using Equation (2.6).

Sno3ref (auto) = ｛-b + (b ² -4a.c)｝ / 2a + ΔSno3... … Equation (2.6)

DELTA Sno3 is a bias value (about 0.1), and Sno3ref (auto) is a target value automatic calculation value. In addition, a, b, and c are defined as follows.

a = Qcir / V (2)

ㆍμHㆍ(1-YH)/2.86YHㆍXh(2)+(Qin+Qret+Qcir)ㆍKno3/V(2)-Qcir/V(2)ㆍSno3(3)b =

ΜH (1-YH) /2.86YHXh (2) + (Qin + Qret + Qcir) Kno3 / V (2) -Qcir / V (2) Sno3 (3)

c = QcirKno3 / V (2)

If the water quality control target value determination means 24 determines that the target value set in the water quality control target value setter 22 is difficult to reach, from the limit target value determined by equation (2.6), the determination result execution means 25 Inform).

The determination result execution means 25 notifies the operator via the display unit 26 that the control to the target value is impossible, and inversely computes the target value that can be achieved, and sets the new set value of the water quality control target value setter 22. Change to Since this calculation is based on the nitrogen load which can be removed to the maximum, the reverse calculation value is not used as the control target value, but rather a larger value is set as the control target value.

According to the second embodiment described above, the following effects can be obtained. First, in the case where the nitrate nitrogen inflow load into the anoxic tank is high, the attainable target value is automatically calculated, so that control using a normal nitrate nitrogen concentration meter is performed. Compared with this, the amount of carbon source injected can be reduced. Second, since the nitrate nitrogen concentration meter flowing into the anoxic tank is provided on the circulation pipe, the nitrate nitrogen load flowing into the oxygen chamber can be directly calculated, so that a more accurate target value determination can be made.

In addition to the above-described embodiment, the second embodiment also broadly includes the following forms. In addition, the forms of (5), (6), (7), and (9) described at the end of the first embodiment are similarly included in this second embodiment.

(1) When the nitrate nitrogen concentration meter 30 cannot be disposed on the circulation pipe, the treated water nitrogen concentration meter 32 disposed on either one of the outlet side or the inlet side of the final settler 7 and the aerobic tank The nitrate nitrogen concentration to be circulated may be calculated on the basis of the difference in each measured value between the ammonia nitrogen concentration meters 20 disposed in (6).

(2) The measured values of the inflow flowmeter 27, the circulation flowmeter 27, the nitrate nitrogen concentration meter 30, and 31 may be filtered. The calculation formula used in this case is the same as the formula (1.12) or formula (1.13) described in the first embodiment.

(3) It is not limited to the determination formula (2.5) used for determination of a target value, Any model may be used as long as it outputs limit concentrations, such as a model which handled the substance balance in detail or simply, and a statistical model using past data. good.

Next, a third embodiment of the present invention will be described based on the configuration diagram of FIG. 3. The main point in which FIG. 3 differs from FIG. 1 is the inflow water quality database 33 and the inflow water quality prediction in the monitoring apparatus 21C. The means 34 is provided, and the total nitrogen concentration meter 28 is omitted.

That is, in this embodiment, the inflow water quality prediction means 34 searches the inflow water quality database 33 to predict the total nitrogen concentration on a similar day on the operation day. In addition, the water quality control target value determination means 24 determines the water quality control target value from this predicted value, the measured value from the inflow flowmeter 27, and the nitride bacterium concentration estimated value.

4 is an explanatory diagram of data stored in the inflow water quality database 33, (a) is a table showing an example of preservation data, and (b) is an inflow total nitrogen concentration obtained based on this example of preservation data. It is a characteristic diagram which shows a pattern example.

In the storage data of FIG. 4A, data such as inflow total nitrogen amount, inflow flow rate, and rainfall on one day, that is, August 1, 2003 (Tuesday), are described for each sampling period of one hour. In the inflow water quality database 33, such data is registered over a plurality of days. This registration data may be input by the operator by the result of the manual analysis, or may be anything, such as the input of the data measured using the water quality sensor.

The inflow water quality prediction means 34 extracts the registration data according to the day most similar to the day when the operation of the sewage treatment control is performed from the registration data stored in the inflow water quality database 33, and extracts the extracted data. It outputs to the water quality control target value determination means 24 as an inflow water quality prediction value.

The characteristic diagram of FIG. 4B shows the extracted stored data in time series. As shown in this figure, normally, when there is no rainfall, the peak point is a waveform of a mountain shape existing at daytime and evening.

The water quality control target value determination means 24 of the present embodiment inputs the predicted value from the inflow water quality predicting means 34 in place of the measured value from the total nitrogen concentration meter 28 (FIG. 1), and is similar to the first embodiment. , The measured value from the inflow flowmeter 27, and the nitride bacterium concentration estimation value are input. Further, based on these inputs, a determination is made as to whether or not the target value set in the water quality control target value setter 22 is reachable.

In the third embodiment described above, since the inflow total nitrogen concentration is predicted from past trend data, an expensive all nitrogen concentration meter can be omitted, and the aeration volume control can be efficiently performed. Therefore, it can contribute to the cost reduction of a system.

In addition, in the example shown in FIG. 3, the inflow total nitrogen concentration is predicted based on the data stored in the database, but the method of performing such a prediction is not necessarily limited to the method using the database. For example, in addition to the inflow flow meter 27, a water quality sensor such as a UV system or an SS system may be used to predict the inflow total nitrogen concentration P _TN based on the formula (3.1). Qin is the inflow flow rate, SS is the inflow SS measurement value, UVin is the inflow UV measurement value, and a, b, c, and d are integers.

P _TN = a Qin + b SSin + c UVin + d. … Formula (3 · 1)

Note that the forms of (1) to (9) described at the end of the first embodiment are also included in the third embodiment.

Next, 4th Embodiment of this invention is described based on FIG. 5 is different from FIG. 1 in that the inflow load database 35, the inflow load estimation means 36, and the target value planning means 37 are attached to the monitoring apparatus 21D, and the total nitrogen concentration meter ( 28) is omitted.

That is, in the present embodiment, the inflow load predicting means 36 searches the inflow load database 35 to extract the inflow water quality pattern and the inflow flow rate pattern on similar days on the operation day, and predict the product of these as the inflow load. It is supposed to be done. The contents of the data stored in the inflow load amount database 35 are the same as those shown in Fig. 4A.

Fig. 6A is a characteristic diagram showing a pattern example of the inflow nitrogen load amount predicted by the inflow load amount prediction means 36. Figs. Normally, if there is no rainfall, the peak point becomes a mountain-shaped waveform present at daytime and evening, but since both peak points of flow rate and all nitrogen exist during the day and evening, the water quality shown in FIG. 4 (b) Compared to the fluctuation of the bay, the fluctuation of the load is larger.

The target value planning means 37 prepares a target value plan for the ammonia nitrogen concentration in the aerobic tank 6 as shown in FIG. 6B based on the inflow load estimated by the inflow load prediction means 36. . The target value plan created by the target value planning means 37 is output to the water quality control target value setter 22, and the target value plan value is set in the water quality control target value setter 22 as the water quality control target value. In addition, the water quality control target value determination means 24 inputs the prediction value of the inflow load amount from the inflow load amount prediction means 36. Therefore, after the target value created by the target value planning means 37 is set in the water quality control target value setter 22, the same operation as in the first embodiment is performed.

In the fourth embodiment described above, the inflow load amount represented by the product of the inflow flow rate and the inflow water quality is predicted from the past trend data. Thus, as in the third embodiment, an expensive all nitrogen concentration meter can be omitted, and the efficiency Aeration volume control can be performed favorably. Therefore, it can contribute to the cost reduction of the system.

Note that the forms of (1) to (9) described at the end of the first embodiment are also included in the fourth embodiment.

According to the said structure, even if the situation where it is impossible to reach the target quality level of the water quality in a biological reaction tank generate | occur | produces, it becomes possible to perform appropriate water quality control according to the situation.

Claims (13)

Water quality in the bioreactor (nitric acidity) is provided by having a sewage treatment process including an initial settler, a bioreactor, and a last settler, and controlling an operation amount (aeration amount of air or a carbon source injection amount) of the process equipment installed in these sewage treatment processes. In the sewage treatment system which performs water quality control so that a nitrogen concentration or ammonia nitrogen concentration) may reach the water quality control target value preset, Measurement data (flow and total nitrogen concentration of influent sewage, or circulating flow rate and nitrate nitrogen concentration for treated water circulated from an aerobic tank to anoxic tank) and predictive data (past time series data for total nitrogen concentration of influent sewage) Water quality control target value determination means for calculating a water quality limit prediction value based on either or both inputs, and determining whether the water quality control target value is reachable based on a comparison of the water quality prediction value and the water quality control target value. and, When it is determined that the water quality control target value determination means is unreachable, the determination result execution means for notifying the determination result and changing the water quality control target value to a level that can be achieved or fixing the operation amount of the process device. Sewage treatment system characterized in that provided. The method of claim 1, The water quality in the bioreactor is the ammonia nitrogen concentration in the aerobic tank constituting a part of the bioreactor, The amount of operation of the process apparatus provided in the sewage treatment process is the amount of aeration air of the blower provided in the exhalation tank. The method of claim 1, The water quality in the bioreactor is the anoxic tank at the front of the aerobic tank that forms part of the bioreactor, or the nitrate nitrogen concentration in the anaerobic tank at the front of the anaerobic tank, The amount of operation of the process apparatus installed in the sewage treatment process is a carbon source injection amount to the anoxic tank or anaerobic tank of a carbon source injection pump. The method of claim 1, The water quality control target value determination means performs the determination based only on the measurement data, and the measurement data includes the flow rate of the sewage flowing into the sewage treatment process and the total nitrogen concentration. . The method of claim 1, The water quality control target value determination means performs the determination based on both the measurement data and the prediction data. The measurement data is the flow rate of the sewage flowing into the sewage treatment process, The predictive data is historical time series data on the total nitrogen concentration of the incoming sewage. The method of claim 1, And a target value planning means for creating a target value plan based on the predicted data and setting the created target value plan as the water quality control target value. The method of claim 3, The water quality control target value determination means performs the determination based only on the measurement data, The measurement data includes a flow rate of the sewage flowing into the sewage treatment process, and a circulating flow rate and a nitrate nitrogen concentration for the treated water circulated from the aerobic tank to the anoxic tank. The method of claim 3, The amount of each sewage to the anaerobic tank, the anoxic tank, and the aerobic tank which constitutes the bioreactor is replaced with the amount of operation of the process equipment installed in the sewage treatment process, instead of the carbon source injection amount to the anoxic tank or the anaerobic tank of the carbon source injection pump. The sewage treatment system characterized by the step amount of inflow. The method of claim 3, The amount of operation of the process equipment installed in the sewage treatment process is replaced with the amount of carbon source injection into the anoxic or anaerobic tank of the carbon source injection pump, and bypasses the initial settler and flows into the initial settler bypass flow flowing into the bioreactor. Sewage treatment system. The method of claim 3, The operating amount of the process equipment installed in the sewage treatment process is a fresh sludge input from the bottom of the initial settler to the anaerobic tank or the anaerobic tank instead of the carbon source injection amount to the anaerobic tank or the anaerobic tank of the carbon source injection pump. Or or a raw sludge fermentation product input to the anaerobic tank of a fermentation product produced by fermenting fresh sludge from the bottom of the initial settler. The method of claim 1, The water quality control target value determination means is constituted by a mass balance model for calculating a resin of a substance for determining the water quality in the bioreactor, or a statistical model for outputting historical data of the resin calculation result of the substance. Sewage treatment system. The method of claim 1, The water quality control target value determining means calculates the water quality limit prediction value by dividing the water quality limit prediction value into a plurality of stages, and performs the determination for each of the plurality of stages according to the difference between the predicted values of the plurality of stages and the water quality control target value. Sewage treatment system. The method of claim 12, And a display unit for displaying the determination result for each of the plurality of steps by the water quality control target value determination unit.

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