JP2003260484A - Wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment apparatus wherein the SS, turbidity or see-through degree and pH of wastewater and the MLSS and pH of a mixed liquid in a reaction tank are measured using the same sampling device, and the control of a necessary air amount, the load control of BOD/SS and SRT control are more simply realized on the basis of the correlation of SS, BOD and Kjeldahl nitrogen. <P>SOLUTION: A flowmeter 3 is provided in a wastewater flow channel 2 while a sampling device 4 with an internal automatic washing function having an SS meter 6 and a pH meter 7 arranged therein is provided in a water tank 5. A sample extraction passage 11 communicating with the wastewater flow channel 2 and a sample extraction passage 12 communicating with the reaction tank 1 are provided to the sampling device 4 to enable the selective communication of either one of both sample extraction passages. The measuring data from the flowmeter 3 and the measuring data from the SS meter 6 and the pH meter 7 are sent to an operation control unit 32. The amount of aeration air, the draw-out amounts of the return sludge and the excess sludge or the draw-out times of them are calculated in the operation control unit 32 to issue output commands to respective drive devices. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for treating wastewater such as domestic wastewater, kitchen wastewater and hot spring wastewater.

[0002]

2. Description of the Related Art Air is sent to a reaction tank (aeration tank) by calculating the amount of air to be aerated, and wastewater and activated sludge flowing into the reaction tank are aerated to biochemically remove pollutants in the wastewater by activated sludge. At the same time, a part of the sludge settled in the settling tank is returned to the reaction tank, and the rest is discharged as surplus sludge. The degree or transparency and pH were measured separately from the MLSS and pH of the mixed solution in the reaction tank.

For this reason, a plurality of measuring devices are required, which requires extra cost and requires a large installation space. Further, when the measurement is performed separately, an error may occur between the sensors.

[0004] Regarding the technology for controlling the aeration air volume,
A method of controlling the amount of aerated air in proportion to the amount of inflow water,
Although a typical aeration control method such as a method of controlling the aeration intensity so as to keep the reaction tank DO constant already exists, the former does not consider the endogenous respiration of microorganisms and the change in concentration of inflowing pollutants. Oxygen cannot be supplied accurately. The latter has a delay in responding to a sudden change in the inflow load.

[0005] In order to achieve a certain effluent quality, BOD
・ SS load control is important. In the conventional BOD / SS load control method, the means for measuring the inflow BOD is a complicated and time-consuming manual analysis, or an expensive sensor that requires a lot of maintenance, and thus lacks practicality.

[0006] SRT control is an important concept for controlling the residence time of microorganisms for ensuring the growth of nitrifying bacteria in a reaction tank. However, in the conventional method, M
Practicality is lacking because three parameters of LSS, excess sludge concentration, and excess sludge withdrawal amount must be measured.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems when a plurality of measuring devices are required, and has been developed in consideration of SS, turbidity or transparency and pH of wastewater flowing into a reaction tank. A wastewater treatment apparatus capable of measuring the MLSS and pH of a mixed solution in a reaction tank by using the same apparatus, thereby eliminating all the problems of the conventional apparatus. It will not be provided.

[0008] In order to solve the above problems of the aeration control method, the present invention measures the above-mentioned BOD and BOD by measuring the SS which can be easily measured by utilizing the correlation between SS and BOD and Kjeldahl nitrogen in the inflowing sewage. Determine the Kjeldahl nitrogen, add the amount of inflow water to the amount of inflow load, calculate the amount of aeration for the inflow load, measure the MLSS, calculate the amount of aeration for endogenous respiration, and calculate the total amount of aeration. An apparatus for controlling is also provided. Thereby, an accurate and timely aeration method can be realized.

In addition, in order to solve the problem of the above-mentioned BOD / SS load control method, the present invention measures the above-mentioned BOD by measuring the SS which can be easily measured by using the correlation between the SS and the BOD in the inflowed sewage. The amount of influent water is combined with the amount of inflow BOD load, and based on this, the BO
An apparatus for performing D / SS load control is also provided.
Furthermore, since the SS meter is installed in a sampling device with an internal automatic cleaning function, it is hardly contaminated and has excellent maintainability.

Furthermore, in order to solve the above-mentioned problem of the SRT control, the present invention also provides an apparatus for measuring an increase amount of a reaction tank MLSS during a predetermined period and performing a simple SRT control based on the measured amount. is there.

[0011]

Means for Solving the Problems The gist of the present invention is as follows. (1) Calculate the amount of air to be aerated and send air to the reaction tank to aerate the wastewater and activated sludge flowing into the reaction tank to biochemically remove pollutants in the wastewater with activated sludge and settle the wastewater in the sedimentation tank. A part of the sludge is returned to the reaction tank, and the rest is discharged as surplus sludge. In a wastewater treatment device, the amount of inflow water is measured in a flow passage of inflow wastewater or a flow passage of treated water to be discharged. Provide a flow meter, while
An SS meter for measuring the concentration of suspended solids in the water tank, a sampling device with an internal automatic washing function provided with a turbidity meter or a fluorometer and a pH meter are provided, and the sampling device is further provided with:
Providing a sample extraction path leading to the wastewater flow path and a sample extraction path leading to the reaction tank, making it possible to selectively communicate either of these sample extraction paths, and a signal of measurement data from the flow meter. The signal of the measurement data from the SS meter, the turbidity meter or the fluorometer and the pH meter is sent to an arithmetic and control unit that outputs data input / calculation and operation control commands. A wastewater treatment apparatus characterized in that the amount or time of withdrawal of returned sludge and excess sludge is calculated and an output command is issued to each operating device.

(2) Water flow rate F Measuring means for measuring the _inflow and the inflow SS and the reaction vessel MLSS;
Necessary aeration air volume Qair by equation (2) A wastewater treatment apparatus comprising: a calculating means for calculating _total; and an operation control means for controlling an aeration air volume. Qair _total = k _Inflow x F _Inflow + k _Endogenous × MLSS (1) k _Inflow = f (SS) (2) where k _Inflow is the aeration coefficient due to the inflow load and is a function of the inflow SS. k _Endogenous is the aeration coefficient due to endogenous respiration of microorganisms.

(3) Flow rate of water F _The measuring means for measuring the _inflow and the inflow SS, and the BOD by the following equations (3) and (4)
-A wastewater treatment apparatus comprising: a calculation unit that calculates a target value of the MLSS based on the SS load set value; and an operation control unit that controls the MLSS. MLSS = F _Inflow × BOD / ( _{LBOD / X} × V) (3) BOD = g (SS) (4) Here, _{LBOD / X} is the BOD · SS load, and V is the volume of the reaction tank. Inflow BOD is a function of inflow SS.

(4) Measuring means for measuring the increase amount MLSS of the MLSS during a predetermined period Δt, calculating means for calculating the target MLSS from the following equation (5), and operation control means for controlling the MLSS. SRT characterized by the following:
(Solids Retention Time) Control type wastewater treatment equipment. MLSS = SRT × (△ MLSS / △ t) (5)

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of the configuration of the first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a reaction tank, and 2 denotes a flow passage of wastewater to the reaction tank 1. Reference numeral 3 denotes a flow meter provided in the waste water flow passage 2 for measuring the amount of inflow water. In this embodiment, the flow meter is provided in the flow path of the waste water, but may be provided in the flow path of the treated water to be discharged.

Reference numeral 4 denotes a sampling device having an internal automatic washing function, which comprises a water tank 5, an SS meter 6 and a pH meter 7 installed inside the water tank. In addition, the sampling device 4 discharges the internal sample at appropriate times based on a command from the arithmetic and control unit described later, and performs cleaning by squirting cleaning water each time. In addition, 8 is a pipe for washing water, 9 is a valve, and 10 is washing water. Further, the SS meter 6 and the pH meter 7 send signals of measurement data to the arithmetic and control unit described later.

Further, the sampling device 4 is provided with a sample extraction path 11 leading to the waste water flow path 2 and a sample extraction path 12 leading to the reaction tank 1. Communication is selectively possible. Reference numeral 13 denotes the sample extraction paths 11 and 12
Is connected to the water tank 5 of the sampling device 4,
A pump 14 is provided on the way. The sample extraction paths 11 and 12 are also provided with valves 15 and 16 in the middle thereof, respectively. And these pumps 14, valves 15, 1
Numeral 6 operates based on a command from the arithmetic and control unit described later.

Reference numeral 17 denotes the pump 1 in the passage 13.
This is a sample discharge passage connecting the reaction tank 1 with a middle part between the sampler 4 and the sampling device 4, and a valve 18 is provided in the middle part. Further, the valve 18 operates based on a command from the arithmetic and control unit described later. Reference numeral 19 denotes a sample discharge passage connecting the water tank 5 of the sampling device 4 and the reaction tank 1. Reference numeral 20 denotes the D installed in the reaction tank 1.
This is an O meter, which sends the measured data to the arithmetic and control unit described later.

Reference numeral 21 denotes a sedimentation tank, 22 denotes a passage connecting the reaction tank 1 and the sedimentation tank 21, and 23 denotes a passage for discharging the supernatant water of the sedimentation tank 21. Reference numeral 24 denotes a sludge return path connecting the bottom of the settling tank 21 and the reaction tank 1, and reference numeral 25 denotes a sludge discharge path connected to an intermediate part of the sludge return path 24. Then, the connection portion of the sludge discharge passage 25 in the sludge return passage 24 and the settling tank 21
A pump 26 is provided in the middle between the two. Furthermore, valves 27 and 28 are respectively provided in the middle of the sludge discharge path 25 and the sludge discharge path 25 in the sludge return path 24, closer to the reaction tank 1 than the connection part. The pump 26 and the valves 27 and 28 operate based on a command from the arithmetic and control unit described later.

Numeral 29 denotes an air passage for discharging the air sent from the blower 30 into the reaction tank 1 for aeration, and the air is discharged from a diffuser plate 31 at the bottom of the reaction tank 1. The blower 30 operates based on a command from the arithmetic and control unit described later.

Numeral 32 denotes an arithmetic and control unit for outputting data input / calculation and operation control commands. The arithmetic and control unit 32 also receives a signal of measurement data from the flow meter 3 and a signal of measurement data of the SS meter 6 and the pH meter 7,
It calculates the amount of aeration air and the amount or time of withdrawal of returned sludge and excess sludge, and issues an operation command to each of the operating devices such as the sampling device 4, the blower 30, the pump, and the valve.

Next, a method of calculating the amount of aerated air and the amount of excess sludge withdrawn in the apparatus of the present invention will be described. The principle is as follows. Aeration air volume Qair If the aeration volume required to maintain the dissolved oxygen concentration is ignored, the aeration air volume required for removal of inflow load and endogenous respiration of microorganisms is as follows. Qair _total = Qair _{Inflow load} + Qair _{Endogenous respiration} (6) Here, Qair is the aeration air volume.

Indirect measurement of inflow load by SS meter and calculation of aeration air volume corresponding thereto _{Inflow load} = Qair _BOD + Qair _Kje-N = F _Inflow × (k1 × BOD + k2 × Kje-N) (7) Here, F is a flow rate of water, and k1 and k2 are aeration coefficients.
BOD and Kje-N are the BOD flowing into the reactor and the Kjeldahl nitrogen concentration. As shown in FIGS. 3 and 4, in many wastewater treatment plants, there is a correlation between the inflow BOD, Kje-N and the inflow SS. Therefore, if the SS is measured, the inflow load can be grasped. Equation (7) can be simplified as equation (8). Qair _{Inflow load} = k _Inflow x F _Inflow (8) k _Inflow = f (SS) (9) where k _Inflow is the aeration coefficient due to the inflow load and is a function of the inflow SS.

Measurement of MLSS by SS meter and calculation of aeration air volume corresponding thereto _{Endogenous respiration} = k _Endogenous × MLSS (10) where k _Endogenous is the aeration coefficient. MLSS is the activated sludge concentration in the reactor. The activated sludge concentration MLSS of the reaction tank is measured using the SS meter 6 or the turbidity meter or the translucence meter installed in the sampling device 4, and the air amount required for endogenous respiration can be calculated. Therefore, it is possible to calculate the total aeration air volume corresponding to both the inflow load and the microbial volume as in equation (11). Qair _total = k _Inflow x F _Inflow + k _Endogenous × MLSS (11)

Amount of surplus sludge generated The amount of surplus sludge generated per unit time is expressed by the following equation. △ W _ds = Y × F _Inflow x SS (12) When surplus sludge is intermittently withdrawn, the amount of MLSS should be increased. ΔMLSS / Δt = ΔW _ds / V = Y × F _Inflow × SS / V (13) Here, ＳＳMLSS is an increase amount of MLSS, and △ t is △ ML.
Time corresponding to SS, $ W _ds is the amount of excess sludge generated per unit time, Y is the conversion ratio of activated sludge to the inflow SS, SS is the inflow SS, and V is the volume of the reaction tank. Inflow S
By measuring S, the amount of surplus sludge withdrawn can be calculated. If the excess sludge concentration is measured, the amount to be extracted can be easily calculated, and the extraction of the excess sludge can be controlled.

Excessive Sludge Withdrawal Control Method There are the following methods for controlling the amount of excess sludge withdrawal so that the MLSS has a set concentration. -1 Control while continuously measuring MLSS online. -2 If continuous online measurement of MLSS is not possible, use the measured value
The amount of excess sludge withdrawn is calculated and controlled based on the conversion ratio of activated sludge to the sludge. Depending on the case, one of these two control methods can be selected.

BOD / SS load L _{BOD / X} = F _Inflow × BOD / (MLSS × V) (14) Here, _{LBOD / X} is a BOD · SS load. Since the discharge water quality changes depending on the BOD / SS load, it is necessary to control the BOD / SS load to achieve a constant discharge water quality. Here, the BOD is calculated based on the measured inflow SS. The BOD value uses an average value during a certain period. By calculating the MLSS according to the above equation (14), the BOD / SS load can be controlled. By transforming equation (14), MLSS = F _Inflow × BOD / ( _{LBOD / X} × V) (15) Further, since the inflow BOD is a function of the inflow SS, BOD = g (SS) (16) MLSS = F _Inflow × g (SS) / ( _{LBOD / X} × V) (17) By measuring the inflow SS, the BOD / SS load control becomes the MLSS control based on the equation (17).

SRT Generally, SRT is defined by the following equation. SRT = MLSS × V / W _ex = MLSS × V / (Q _ex x SS _ex ) (18) where W _ex is the amount of excess sludge withdrawn, Q _ex is excess sludge withdrawal flow rate, SS _ex is the excess sludge concentration. In order to remove the inflowing organic nitrogen and ammonia nitrogen, it is necessary to secure a sludge residence time SRT of a certain value or more. However, in equation (18), MLSS or Q _ex and SS _It is necessary to measure _ex and it is difficult to put it to practical use. On the other hand, when surplus sludge is intermittently extracted, W _ex = △ MLSS × V / △ t (19) That is, SRT = MLSS × V / (△ MLSS × V / △ t) = MLSS / (△ MLSS / △ t) (20) Therefore, the SRT can be calculated by measuring the MLSS and the increase amount of the MLSS for a certain period (Δt). Further (20)
By transforming the equation, MLSS = SRT × (△ MLSS / △ t) (21) Therefore, the SRT control becomes the MLSS control.

Relationship Between NO ₃ —N Concentration in Treated Water and pH As shown in FIG. 5, the nitrate nitrogen concentration of treated water has a correlation with the pH of the reaction tank. The nitrification reaction can be controlled by adjusting the aeration air volume and the MLSS. Specific control method, DO control, as shown in FIG. 6, the set value of the control parameters such as proportional control (target value of the dissolved oxygen concentration DO ^*, aeration factor k_ _influx, k _Endogenous, etc.)
Adjust automatically.

Next, a second embodiment of the present invention shown in FIG. 2 will be described. The difference between the present embodiment and the first embodiment is that, in the first embodiment, a diffused aeration system using a blower and a diffuser plate is used.
This embodiment uses a reaction tank 33 of an endless water channel provided with a partition wall 33a at the center and an aeration rotor 34, generates a water flow by the aeration rotor 34, and circulates and stirs wastewater and activated sludge containing air. It is a mechanical stirring type aeration system. The aeration rotor 34 operates based on a command from the arithmetic and control unit 32, and controls the supply amount of air (oxygen) by controlling the number of revolutions. still,
Other configurations and operations are the same as those of the first embodiment, and therefore, the same members are denoted by the same reference numerals and detailed description thereof will be omitted.

[0032]

The present invention has the above-described structure and operation, and
SS, turbidity or transparency and pH of wastewater flowing into the reactor
And the MLSS and pH of the mixed solution in the reaction tank are measured by using the same sampling device. Therefore, the cost can be reduced and the installation space can be reduced because only one measuring device is required. In addition, there is a possibility that an error may occur between sensors when measurement is performed separately as in the related art, but such a problem does not occur in the case of the present invention. Furthermore, since all the sensors are installed in the sampling device with the internal automatic cleaning function, they are hardly soiled and have excellent maintainability.

In addition, according to the present invention, the inflow SS is measured, and based on the correlation between SS and BOD and Kjeldahl nitrogen, air (oxygen) required amount control, BOD / SS load control SRT which is extremely important in the activated sludge treatment plant Control can be realized more easily.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory diagram of a first embodiment of the present invention.

FIG. 2 is a configuration explanatory diagram of a second embodiment of the present invention.

FIG. 3 is a graph showing a correlation between inflow BOD and SS.

FIG. 4 is a graph showing the correlation between inflow Kjeldahl nitrogen and SS.

FIG. 5 is a graph showing a correlation between treated water NO ₃ —N and pH.

FIG. 6 is a DO control configuration diagram for automatically adjusting a target value DO.

[Explanation of symbols]

1 Reaction tank 2 Wastewater passage 3 Flow meter 4 Sampling device 5 aquarium 6 SS total 7 pH meter 11, 12 Sample drainage channel 13 passage 14 pump 15, 16 valve 17 Sample discharge passage 18 Valve 19 Sample discharge passage 21 Settling tank 24 Sludge return route 25 Sludge discharge channel 26 pump 27, 28 valve 29 Ventilation path 30 Blower 32 arithmetic and control unit

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Shoichi Shinozaki             363 Yagioka, Moka City, Tochigi Prefecture (72) Inventor Shigehito Ishiyama             148 Aramachi, Moka City, Tochigi Prefecture (72) Inventor Takaaki Otsuka             359-1 Yagioka, Moka City, Tochigi Prefecture (72) Inventor Akinori Ueno             1006-1 Yabe-cho, Totsuka-ku, Yokohama-shi, Kanagawa             IF PLAZA Totsuka 306 F term (reference) 4D028 BB03 BC18 BC24 BD11 BD16                       CA09 CA11 CA12 CB03 CC05                       CC11 CD00 CD01 CE03

Claims (4)

[Claims] 1. A method for calculating the amount of air to be aerated, sending air into a reaction tank, aerating wastewater and activated sludge flowing into the reaction tank, and removing contaminants in the wastewater biochemically with activated sludge. A part of the sludge settled in the wastewater is returned to the reaction tank, and the rest is discharged as surplus sludge. Provide a flow meter to measure, and on the other hand, provided a sampling device with an internal automatic washing function equipped with an SS meter to measure the concentration of suspended solids in the water tank, a turbidity meter or a fluorometer and a pH meter, The sampling device is provided with a sample extraction path leading to the wastewater flow path and a sample extraction path leading to the reaction tank, so that either of these two sample extraction paths can be selectively communicated with each other. Measurement data Data signals and signals of measurement data from the SS meter, the turbidimeter or the fluorometer and the pH meter are sent to an arithmetic and control unit for inputting and calculating data and outputting operation control commands. A wastewater treatment apparatus characterized in that the apparatus calculates an aeration air flow rate and a withdrawal amount or a withdrawal time of returned sludge and excess sludge, and outputs an output command to each operating device. 2. Flow rate F of water Measuring means for measuring the _inflow and inflow SS and the reaction tank MLSS, calculating means for calculating the required aeration air flow Qair _total by the following equations (1) and (2), and operation control means for controlling the aeration air flow Wastewater treatment device characterized by the above-mentioned. Qair _total = k _inflow × F _inflow + k _endogenous × MLSS (1) k _inflow = f (SS) (2) where k _inflow is the aeration coefficient due to inflow load and is a function of inflow SS. k _Endogenous is the aeration coefficient due to endogenous respiration of microorganisms. 3. A measuring means for measuring a flow rate F _inflow and an inflow SS of water, and BOD · S by the following equations (3) and (4).
A wastewater treatment apparatus comprising: a calculation unit that calculates an MLSS target value based on an S load set value; and an operation control unit that controls the MLSS. MLSS = F _Inflow × BOD / ( _{LBOD / X} × V) (3) BOD = g (SS) (4) Here, _{LBOD / X} is the BOD · SS load, and V is the volume of the reaction tank. Inflow BOD is a function of inflow SS. 4. A measuring means for measuring an increase amount MLSS of the MLSS during a predetermined period Δt, a calculating means for calculating a target MLSS from the following equation (5), and an operation control means for controlling the MLSS. SRT (So
(Lids Retention Time) control type wastewater treatment equipment. MLSS = SRT × (△ MLSS / △ t) (5)