JP2016007576A - Water treatment plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment plant which attains water quality improvement of treated water discharged to a public water area, energy saving, and maintenance improvement by exploiting ICT in a sewage treatment plant.SOLUTION: The water treatment plant is provided which comprises influent 100 which is water to be treated, an aerobic tank 3 for oxidizing the influent 100, a blower 5 for feeding air to the aerobic tank 3, a flowing down flow rate estimation part for estimating a flowing down flow velocity in the aerobic tank 3, an influent quality estimation part 11 for estimating quality of the influent, a blower air flow rate measurement part 13 for measuring an air flow rate of the blower, a blower air flow rate calculation part 20 for calculating an air flow rate of the blower. In the water treatment plant, the water quality estimated by the influent quality estimation part 11 is water quality varying caused by blowing oxygen 106 from the blower, the blower air flow rate calculation part 20 includes a necessary air flow rate calculation function for calculating a relationship between the water quality estimated by the influent quality estimation part 11 and the necessary air flow rate, and the blower air flow rate calculation part 20 calculates blower air flow rate 106 using an air flow rate 106 obtained by calculating with a value of water quality at a present time estimated by the influent quality estimation part 11 and an air flow rate 106 obtained by calculating with a value at a past time.

Description

The present invention relates to a water treatment plant mainly equipped with a water treatment control system for controlling the quality of treated water at a sewage treatment plant.

  Now that environmental issues and cost reductions have become essential, sewage treatment plants are also required to improve the quality of treated water discharged into public water areas, further reduce energy consumption, and improve maintainability using ICT. .

  In sewage treatment plants, organic matter and nitrogen in sewage are removed with a microbial suspension called activated sludge. A reaction tank that blows air into activated sludge by a blower is called an aerobic tank. In the aerobic tank, organic substances are ingested and consumed by assimilation and catabolism by microorganisms and removed. Most of the nitrogen in the incoming sewage is contained in the form of ammoniacal nitrogen, which is oxidized to nitrate nitrogen by nitrifying bacteria in the presence of oxygen. Part of this nitrate nitrogen remains in the return sludge and is returned upstream. At that time, a denitrification reaction that reduces to nitrogen gas occurs, and the nitrogen component is removed. On the other hand, if ammonia nitrogen remains in the effluent due to insufficient nitrification, there are concerns about the impact on aquatic organisms in the effluent water area and the consumption of dissolved oxygen (DO). Management is required. For that purpose, it is necessary to appropriately control the air volume supply by the blower which consumes a lot of electric power. If the air supply is not sufficient, it will cause adverse environmental effects due to insufficient nitrification. Alternatively, if the air volume supply amount is excessive, the air volume is wasted even after the completion of nitrification, increasing the power consumption.

  The control of sewage treatment includes DO control using DO of a DO meter installed at the downstream end of the aerobic tank as a control index. By controlling the blower air volume so as to keep the terminal DO on the downstream side of the aerobic tank constant, the activity of microorganisms is maintained, and organic matter removal and nitrification reaction are controlled (for example, [Non-Patent Document 1]).

  In recent years, the accuracy of ammonia meters that measure the concentration of ammoniacal nitrogen in activated sludge and the controllability of small-capacity blowers suitable for individual biological reaction tanks have improved. A control method using an ammonia meter has been studied for the control ([Non-Patent Document 2], [Non-Patent Document 3]).

  In the method of [Patent Document 1], each aerobic tank set in advance from the flow rate of sewage flowing into the biological reaction tank, the air volume to each aerobic tank, and the measured value of the ammonia meter installed in each aerobic tank. Calculate the air flow to each aerobic tank necessary for the amount of nitrification in the meantime, and proceed with nitrification with the air flow without excess or deficiency.

JP 2012-170883 A

"Sewerage facility planning and design guidelines and explanation" 2009 edition, Japan Sewerage Association Endo Kazuhiro: Development of air flow control system using ammonia meter and DO meter, pp.918-920 (2010) Oku Daisuke: Reduction of Electricity by Efficient Aeration Control-2nd Report, Verification of Effectiveness in Real Facilities, Proceedings of the 50th Sewerage Research Conference, pp.799-802 (2013)

  In the method of [Non-Patent Document 1], DO is a parameter related to the reaction activity of microorganisms, but it is not ammoniacal nitrogen itself to be considered in the nitrification reaction. For this reason, there was a problem that the quality of treated water deteriorated due to insufficient air flow or excessive air flow due to fluctuations in inflow flow rate and inflow water quality.

  Next, problems in the case of control using an ammonia meter will be described. In general, an ion electrode type ammonia meter is installed not in the last stage of the aerobic tank but in the middle stage slightly upstream because the life of the consumable electrode is shortened when the ammonia concentration is lowered.

  The method of [Non-Patent Document 2] is cascade-type feedback (FB) control in which a target value of the DO value at the rear stage of the aerobic tank is set based on an ammonia meter installed at the middle stage of the aerobic tank. Because of the control based on the quality of the treated or treated water, if the influent water quality fluctuates, the fluctuation is not taken into account until the effect reaches the sensor position. there were. More specifically, for example, when the daily fluctuation is large or when sewage in which ammonia is temporarily diluted flows due to sudden rain. If the concentration measured with the middle ammonia meter is large, the total air volume will increase. At this time, the diluted upstream side is excessively treated, and the target value of the treated water may be reached before reaching the downstream side. As a result, there is a possibility that excessive processing will occur due to excessive processing even under the minimum air volume on the downstream side after flowing down. Once it deviates significantly from the target value at the middle ammonia meter position, the air volume may vibrate thereafter and the processing may not be stable. Another issue is related to maintenance. The relational expression between the ammonia concentration at the middle stage used for control and the target value of DO must be adjusted by the operator on a trial and error basis according to the treatment characteristics and continuously according to the seasonal variation of the activated sludge properties. Maintenance is not always easy.

  In the method of [Non-Patent Document 3], an ammonia meter is installed in the inflow side and the middle stage of the aerobic tank, and feedforward (FF) control by the inflow side ammonia meter is added to the FB control by the ammonia meter in the middle stage of the aerobic tank. In this way, the follow-up to fluctuations in water quality load is enhanced. However, the ammonia concentration measured with the ammonia meter on the inflow side is a value only at the current time, and is different from the ammonia concentration at the time of inflow in the fluid that has already flowed into the aerobic tank (past inflow ammonia concentration). The value used to calculate the air volume of the entire aerobic tank is not sufficient, and it is not always possible to ensure followability to fluctuations in the water quality load, and there has been a problem that the treated water quality deteriorates due to the air volume shortage or excessive air volume.

  In the methods of [Non-patent document 1], [Non-patent document 2], and [Non-patent document 3], parameters for control are manually given. Since the characteristics of activated sludge change with time, it is necessary to adjust the parameters by trial and error, and there is a problem that the labor for maintenance increases.

In the method of [Patent Document 1], by installing an ammonia meter in each aerobic tank, the relationship between the ammonia concentration processed between each reaction tank and the air volume is measured, and the necessary air volume is calculated based on the processing performance. To do. This is a connection of FF control that calculates the required air volume from the measured value of the ammonia concentration on the upstream side, and in order to ensure the stability of the control, ammonia meters are installed in all reaction tanks as in [Patent Document 1]. There is a need. In addition to the DO meter at the end of the aerobic tank, which is recommended to be installed in a normal treatment plant, installing expensive ammonia meters in all the reaction tanks is disadvantageous in terms of cost and increases its maintenance. There was a problem.

  In order to achieve the above-described problems, the present invention provides inflow water that is treated water, an aerobic tank that oxidizes the inflow water, a blower that sends air to the aerobic tank, and the aerobic tank. Downstream flow rate estimation unit for estimating downflow velocity, inflow water quality estimation unit for estimating water quality of the inflow water, blower air volume measurement unit for measuring the air volume of the blower, and blower air volume calculation unit for calculating the air volume of the blower The water quality estimated by the inflow water quality estimation unit is a water quality that varies by blowing oxygen from the blower, and the blower air volume calculation unit is estimated by at least the previous inflow water quality estimation unit Equipped with a required air volume calculation function that describes the relationship between water quality and required air volume, and the required air volume calculated based on the current time value of the water quality estimated by the inflow water quality estimation unit in the previous term Must The blower air volume is calculated using the required air volume.

  Furthermore, the present invention is characterized in that, in a water treatment plant, the water quality estimated by the influent water quality estimation unit is an ammoniacal nitrogen concentration.

  The water treatment plant further includes an aerobic tank water quality estimation unit installed in the aerobic tank, and the water quality estimated by the aerobic tank water quality estimation unit blows oxygen from the blower. With the fluctuating water quality, the blower air volume calculating unit calculates the blower air volume so that the water quality value estimated by the aerobic tank water quality estimating unit in the previous period becomes a set value.

  Furthermore, in the water treatment plant, the present invention is characterized in that the water quality estimated by the aerobic tank water quality estimation unit is an ammoniacal nitrogen concentration.

  Furthermore, the present invention is characterized in that, in the water treatment plant, a second aerobic tank water quality estimation unit for estimating the dissolved oxygen concentration is provided in addition to the aerobic tank water quality estimation unit to be estimated.

  Further, in the water treatment plant according to the present invention, the blower air volume calculation unit is configured to perform the required air volume calculation function based on the necessary air volume calculated by the inflow water quality estimation unit, the aerobic tank water quality estimation unit, and the required air volume calculation function. It is characterized by updating the water quality-necessary air volume relationship.

Furthermore, the present invention is characterized in that in the water treatment plant, a treatment characteristic display unit for displaying the treatment characteristic information extracted from the water quality-necessary air volume relationship in time series is provided.

According to the present invention, it is possible to improve maintainability and suppress energy consumption while appropriately controlling the quality of sewage treatment.

Configuration diagram of water treatment plant of Example 1 Relationship between flow rate and target value of aerobic tank ammonia concentration Upstream air volume calculation with virtual fluid mass Processing characteristic function Update of processing characteristic function Temporal change of extracted processing characteristics

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of Embodiment 1 of the present invention.

  The present embodiment is an example in which a sewage treatment control system is applied to a sewage treatment plant of a circulation type nitrification denitrification method. From the upstream side, the first sedimentation tank 1, the anoxic tank 2, the aerobic tank 3, and the final sedimentation tank 4 communicate with each other, and the aerobic tank 3 communicates with the blower 5. In the first sedimentation basin 1, the inflowing sewage 100 is separated by gravity sedimentation into first sedimentation water 101 as a supernatant and primary sedimentation sludge as a sediment. In the final sedimentation basin 4, the activated sludge 102 that flows in is separated into treated water 103 that is a supernatant and return sludge 104 that is a sediment. The return sludge 104 is mixed with the first subsidence flowing water 101 and flows into the anoxic tank 2 as the activated sludge 102. From the end of the aerobic tank 3, a part of the activated sludge 102 circulates as a circulating liquid 105 to the anoxic tank 2. Air 106 is sent from the blower 5 to the aerobic tank 3.

  The anaerobic tank 3 is provided with a downstream flow meter 10 as a downstream flow rate estimation unit and an inflow ammonia meter 11 as an inflow water quality estimation unit, and measures the flow rate and ammonia concentration of the inflow water flowing into the aerobic tank 3. The ammonia concentration here is a water quality that varies as oxygen is blown from a blower in the same manner as dissolved oxygen. The aerobic tank 3 is provided with an aerobic tank ammonia meter 12 which is an aerobic tank water quality estimation unit, and measures the ammonia concentration in the aerobic tank 3. An air flow meter 13 which is a blower air flow measuring unit is installed in a pipe communicating the blower 5 and the aerobic tank 3 to measure the air flow of the air sent to the aerobic tank 3.

  The values measured by the flow down flow meter 10, the inflow ammonia meter 11, the aerobic tank ammonia meter 12, and the air flow meter 13 are transmitted to the blower air flow calculation unit 20. The calculation result of the blower air volume calculation unit 20 is transmitted to the blower air volume control unit 21, and the air volume of the blower 5 is controlled to the air volume calculated by the blower air volume calculation unit 20.

  The air volume calculation method in Example 1 is demonstrated. In Example 1, an aerobic tank upstream of the aerobic tank ammonia meter 12 in the aerobic tank 3 is an upstream aerobic tank, and a downstream aerobic tank is a downstream aerobic tank.

  In the first embodiment, the upstream air volume necessary for the upstream aerobic tank is calculated by feedforward calculation using the measured value such as the inflow ammonia concentration and the processing characteristic function which is the water quality-necessary air volume relationship, and the aerobic tank ammonia meter is calculated. The downstream air volume required for the downstream aerobic tank is calculated by feedback calculation based on the measured values. Below, it demonstrates in order of downstream air volume calculation and upstream air volume calculation.

If the individual air volume cannot be applied to the upstream and downstream aerobic tanks, D _up [-] is applied to the entire aerobic tank for the total air volume Q _B (t) [m ³ / h] at time t. as the distribution ratio of the volume of air to the upstream side aerobic tank, the air volume Q _Bup to upstream aerobic tank (t), the air volume Q _Bdwn the downstream aerobic tank (t) is expressed by equation (1).
Downstream air volume calculation is the target value NH _{md_tgt} (t) [mg-N / L] for the aerobic tank ammonia concentration and the measured value NH _md (t) [mg-N / L] for the aerobic tank ammonia concentration Execute feedback calculation by PI control. NH _{md_tgt} (t) is calculated from a graph with respect to the flowing-down flow rate Q [m ³ / h] as shown in FIG. 2, for example. Here, NH _{out_tgt} [mg-N / L] is the target value of the treated water ammonia concentration, which is the water quality desired by the administrator, and is 1.0 mg-N / L in this example. When the flow rate Q is increased, the residence time is shortened, so that the amount of ammonia that can be treated with the same air volume is reduced. Therefore, when the _downstream flow rate Q is large, the target value NH _{md_tgt} of the aerobic tank ammonia concentration is reduced, so that the target value NH _{out_tgt} of the treated water ammonia concentration can be achieved.

From FIG. 2, the target value NH _{md_tgt} (t) of the aerobic tank ammonia concentration is calculated as a value having a fluctuation range as a function of the changing flow rate Q. The downstream air volume Q _Bdwn (t + Δt) [m ³ / h] at time t + Δt calculated based on this target value is shown in equation (2). Δt [h] is a control cycle.
C _par (Z) is the transfer function of a discrete-time parallel PI controller, expressed by equation (3) with P as the proportional term parameter, I as the integral term parameter, and T _s [min] (= 60Δt) as the sampling time. Is done.
The flow-down flow rate here is a flow rate flowing down the biological reaction tank. In this embodiment, since the circulation type nitrification denitrification method is targeted, the flow down flow is the total value of the inflow flow rate, the circulation flow rate, and the return flow rate.

In the upstream air volume calculation, a virtual fluid mass that flows one-dimensionally into the calculation system (in this case, the biological reaction tank from the upstream ammonia meter to the intermediate ammonia meter) at a constant control period Δt is considered. Follow Lagrange. A conceptual diagram is shown in FIG. The virtual fluid mass shown in gray flows into the calculation system at time t ₀ and reaches the rear end of the calculation system at time t _N. The size of the virtual fluid mass varies depending on the flow rate Q _in (t). _{Assuming that} the position of the i-th virtual fluid mass i from the upstream side at time t is X _{vc, i} (t) [m], X _{vc, 1} (t) and X _{vc, i} (t + Δt) are expressed as ) (5)
Here, S [m ² ] is a cross-sectional area in the downward direction of the biological reaction tank. Each virtual fluid mass flows down while maintaining a unique value measured and calculated at the time of inflow. When the measured value of ammonia concentration at the inflow is NH _in (t) [mg-N / L], the inflow ammonia concentration NH _{in, i} (t) [mg-N / L] corresponding to the virtual fluid mass i is It is expressed by equation (6).
The required cumulative air volume V _{B — tgt, i} [m ³ ] _, which is the required air volume for controlling the virtual fluid mass i to the target water quality, is calculated from the processing characteristic function of FIG. 4 and Equation (7).
The processing characteristic function is constructed from the information of the virtual fluid mass reaching the upstream aerobic tank end. ΔNH _tgt (t) [mg-N / L] is the target treatment ammonia concentration.

T _{0, i} is the time when the virtual fluid mass i flows into the calculation system, and Q _Bup (t) [m ³ / h] is the aeration air volume into the upstream aerobic tank (aerobic tank up to the ammonia meter at the midpoint) When the air volume distribution density at position X _i (t) is D (X _i (t)) [-], the cumulative air volume V _{B, i} (t) [m ³ ] to the virtual fluid mass i at time t is It is expressed by equation (8).
Here, the air volume distribution density D (X _i (t)) is a function representing the distribution ratio of the aeration air volume to each upstream aerobic tank, and the average of the distribution ratio in the entire upstream aerobic tank is 1. V _{rt, i} (t) [−] is a volume ratio of the virtual fluid mass i to the total volume V _all [m ³ ] of the upstream aerobic tank, and is expressed by the equation (9).
Since the virtual fluid mass i has the necessary accumulated air volume V _{B_tgt, i} obtained in FIG. 4, the value obtained by dividing the difference from the accumulated air volume V _{B, i} (t) by the remaining residence time is the air volume necessary for the fluid mass i. Become. Therefore, _assuming that the calculation system is filled with N virtual fluid masses, the calculated value Q _Bup (t + Δt) [m ³ / h] of the upstream air volume at time t + Δt is expressed by equation (10). .
L _all [m] is the total length of the upstream aerobic tank. The amount of aeration required for the fluid mass i is in the curly brackets, but by setting the upper limit value and the lower limit value according to the operation of the implementation facility, it is possible to avoid an excessive value or a negative value due to a small denominator.

Here, i = 1 is a value obtained based on the inflow ammonia concentration at the current time t, and i ≧ 2 is a value obtained based on the past inflow ammonia concentration. In other words, the calculated value Q _Bup (t + Δt) of the upstream air volume at time t + Δt is calculated based on the required air volume calculated based on the current time value of the inflow ammonia concentration, which is the water quality estimated by the inflow water quality estimation section in the previous period, and the past This is the blower air volume calculated using the required air volume calculated based on the value.

By using the total air volume Q _B (t + Δt) obtained by adding the upstream air volume and downstream air volume at time t + Δt obtained by calculation, the air volume that can achieve energy conservation with stable tracking of the water quality target value Can be requested. In the present embodiment, the upstream air volume and the downstream air volume are added together, but the weight may be changed as required, for example, by placing importance on the downstream feedback element. Further, the amount of air sent individually to the upstream / downstream aerobic tank may be controlled by controlling a plurality of blowers and valves communicating with the upstream / downstream aerobic tank. In this case, it is not necessary to distribute the total air volume according to the equation (1) to the upstream / downstream air volume, and the upstream air volume and the downstream air volume may be calculated by the method of this embodiment.

  In the present embodiment, the processing characteristics visualized as the processing characteristics function vary with the seasonal variation of the activated sludge properties. However, the updating method of the processing characteristics function is important for improving the maintainability. By actual operation of the present embodiment, the inflow ammonia concentration, the aerobic tank ammonia concentration, and the accumulated air volume based on the actually measured values are accumulated in the virtual fluid mass that has reached the end of the upstream aerobic tank. Based on this information, the current value of the processing characteristic function can be updated statistically. In addition, the change in time accelerates the awareness of abnormal times. In development control, control accuracy is ensured by automatically updating control parameters based on actual values, and at the same time, maintenance can be improved.

FIG. 5 shows the update. Each time control is performed using the function before the update, information on the actual value is accumulated from the inflow ammonia concentration, the aerobic tank ammonia concentration, and the cumulative air volume. The processing characteristic function based on the actual value can be updated by drawing an approximate curve by, for example, regression analysis from the actual value group at an arbitrary timing (may be a fixed feeling or an operator's judgment). The approximate curve here may be a monomial represented by the positive or negative power of x, such as y = ax + b or y = ax ^-1 + b, or a combination of these if it is a curve that accurately approximates the measured value. It may be a polynomial. Also, combinations with mathematical functions such as exponents, logarithms, and trigonometric functions may be used. Moreover, it is not necessarily a function, and a discontinuous and stepwise correspondence table may be used. In that case, the processing characteristic function may be updated with a correspondence prepared based on a database prepared in advance or the operator's judgment.

  For example, the time change of the index obtained from the process characteristic function of FIG. 6 may be displayed on the operation screen. In FIG. 6, as an index, the air volume required for treating 25 kg of ammonia concentration was selected, and the change with time was plotted. In general, the nitrification reaction rate decreases in the low temperature period, but the influence of temperature is removed here. From this, it is presumed that there was some change such as a decrease in the amount of nitrifying bacteria because the air volume suddenly increased in October at the A treatment plant. By visualizing the processing characteristics and monitoring them continuously, this anomaly can be immediately detected, and as shown in FIG. In addition, the B treatment plant requires a larger air volume than the A treatment plant throughout the year. This indicates that the A treatment plant is operating more efficiently than the B treatment plant, suggesting that operational improvements should be considered with reference to the operation of the A treatment plant.

  From the above, by applying the control system by the sewage treatment plant of the present embodiment, it is possible to stabilize the quality of the treated water, save energy, and improve the maintainability.

  In this embodiment, the flow-down flow meter 10 installed in the aerobic tank is used. However, since it is sufficient to know the flow velocity flowing down the biological reaction tank in the region to be controlled, as an alternative to the flow-down flow meter, for example, inflow sewage It is good also as a total value of the flow rate measured with the flowmeter, the return sludge flowmeter, and the circulation flowmeter.

  In this example, the circulation type nitrification denitrification method was taken up as an application example, but nitrification is carried out in an aerobic tank such as a standard method, AO method, A2O method, semi-advanced treatment method, and a method in which step feed is applied to these methods. Any method can be applied. In that case, for example, in the standard method or the AO method, the flow rate is the sum of the inflow sewage flow rate and the return sludge flow rate. Therefore, the total value of the inflow sewage flow meter and the return sludge flow meter may be used instead of the flow rate flow meter 10. .

  In this embodiment, the ammonia concentration by the inflow ammonia meter 11 is used for the feedforward control in the upstream aerobic tank, but the ammonia meter or UV meter installed in the sewage 100 or the first subsidence water 101 part is correlated. Other alternative means for estimating the ammonia concentration from the relationship or the like may be used. Alternatively, an estimated value of ammonia concentration from flow rate fluctuation, daily fluctuation, and seasonal fluctuation may be used. In these cases, when obtaining the ammonia concentration flowing into the aerobic tank, the sewage flow rate, the return sludge flow rate, the circulation flow rate, and the ammonia by the aerobic tank ammonia meter 12 with respect to the ammonia concentration of the sewage 100 and the first overflow water 101. The inflow ammonia concentration may be estimated using the return sludge estimated from the concentration and the ammonia concentration contained in the circulating fluid.

  In this embodiment, PI control is used as the calculation of the downstream air volume, but PID control and other feedback control methods may be used.

  In this example, feedback control was performed using an aerobic tank ammonia meter, but in actual operation, a lower limit value was set for DO on the downstream side of the aerobic tank based on the empirical operating policy of the facility, and downstream of the aerobic tank. When the DO value by the installed DO meter is below the lower limit value, DO control with the lower limit value as the target may be used.

  In this embodiment, an ammonia meter is used as the aerobic tank water quality estimation unit, but a DO meter may be used. In that case, equation (2) may be feedback control such as PI control based on the target DO value. The target DO value here may be a constant set value, or may be changed according to time, season, flow rate, or the like. In the case of time, it is conceivable to increase the DO setting value during the daytime when the load is large, and decrease the DO setting value during the nighttime when the load is small. In the case of the season, it is possible to increase the DO setting value in winter when the water temperature is low and the reaction speed is low, and to decrease the DO setting value in the large summer season. In the case of a flow rate, it is conceivable that the DO set value is increased during a period when the flow rate is large and the residence time is short, and the DO set value is decreased during a period where the residence time is long.

In this embodiment, an ammonia meter is used as the aerobic tank water quality estimation unit, but a DO meter may be installed as a second aerobic tank water quality measurement unit on the downstream side thereof. In that case, equation (2) may be feedback control such as PI control based on the target DO value. The target DO value here may be cascade control corresponding to the measured value NH _md (t) of the aerobic tank ammonia concentration. For example, if the measured value NH _md (t) of the aerobic tank ammonia concentration is large, the difference to the target value NH _{out_tgt} of the treated water ammonia concentration is large, so the DO setting value is increased and the measured value of the aerobic tank ammonia concentration When NH _md (t) is small, it is conceivable to decrease the DO setting value.

In this embodiment, the first settling basin 1 is installed, but a configuration excluding the first settling basin 1 may be used. As an alternative to the final sedimentation basin 4, a membrane separation activated sludge method activated sludge method using a membrane for separation of activated sludge and treated water may be used. In that case, for example, the membrane may be immersed in the aerobic tank 3.
In this embodiment, sewage was treated as sewage and ammonia nitrogen was taken as an example of water quality to be estimated based on the quality of the influent water. However, the present invention is not limited thereto, and water treatment provided with a control system for controlling the blower air volume As an invention relating to the plant, the water quality estimated by the influent water quality estimation unit may be any water quality that varies due to oxidation or the like by blowing oxygen from the blower.

1. First sedimentation basin 2. 2. Anoxic tank Aerobic tank 4. 4. Final sedimentation basin Blower 100. Sewage 101. First subsidence water 102. Activated sludge 103. Treated water 104. Return sludge Circulating fluid 106. Air 10. 10. Inflow flow meter Inflow ammonia meter 12. Aerobic tank ammonia meter13. Air flow meter20. Blower air volume calculation unit 21. Blower air volume control unit

Claims (7)

Inflow water to be treated,
An aerobic tank for oxidizing the inflow water;
A blower for sending air to the aerobic tank;
A flow rate estimator for estimating a flow velocity in the aerobic tank;
An influent water quality estimation unit for estimating the quality of the influent water;
A blower air volume measuring unit for measuring the air volume of the blower;
In a water treatment plant comprising a blower air volume calculating unit that calculates the air volume of the blower,
The water quality estimated by the inflow water quality estimation unit is a water quality that varies by blowing oxygen from the blower,
The blower air volume calculating unit has a necessary air volume calculating function that describes a water quality-necessary air volume relationship related to the water quality and the required air volume estimated at least by the inflow water quality estimating unit in the previous period,
A water treatment plant characterized in that a blower air volume is calculated using a required air volume calculated based on a current time value of water quality estimated by an inflow water quality estimation unit in the previous period and a required air volume calculated based on past values.
The water treatment plant of claim 1,
The water quality estimated by the said influent water quality estimation part is ammonia nitrogen concentration, The water treatment plant characterized by the above-mentioned.
In one water treatment plant according to claim 1 or 2,
An aerobic tank water quality estimation unit installed in the aerobic tank,
The water quality estimated by the aerobic tank water quality estimation unit is a water quality that fluctuates when oxygen is blown from the blower, and the water quality value estimated by the aerobic tank water quality estimation unit in the previous period is the set value. A water treatment plant characterized by calculating the blower air volume.
The water treatment plant of claim 3,
A water treatment plant characterized in that the water quality estimated by the aerobic tank water quality estimation unit is an ammoniacal nitrogen concentration.
The water treatment plant of claim 4,
A water treatment plant comprising a second aerobic tank water quality estimation unit for estimating a dissolved oxygen concentration in addition to the aerobic tank water quality estimation unit to be estimated.
In one water treatment plant of claims 3-5,
The blower air volume calculation unit updates the water quality-required air volume relationship in the required air volume calculation function based on the required air volume calculated by the inflow water quality estimation unit, the aerobic tank water quality estimation unit, and the required air volume calculation function. A characteristic water treatment plant.
The water treatment plant of claim 6,
A water treatment plant comprising a treatment characteristic display unit for displaying treatment characteristic information extracted from the water quality-necessary air volume relationship in time series.