JP2006255504A - Method and apparatus for treating waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for treating waste water, in which the quality of the treated waste water to be discharged to the outside can be made better/lower to satisfy the various water quality standards and consequently the waste of energy can be restrained. <P>SOLUTION: The apparatus for treating waste water has an aeration tank 10, a solid-liquid separation tank 20 and a discharge tank 30 which are arranged in this order and the adjacent ones of which are connected to each other by a flow passage. The waste water to be treated is introduced into the aeration tank 10, aerated and treated with a microbe. The aerated/treated waste water is introduced into the solid-liquid separation tank 20 and separated into sludge and treated waste water by solid-liquid separation. The treated waste water is introduced into the discharge tank 30 and then discharged to the outside from the discharge tank 30. The aeration tank 10 is connected to the discharge tank 30 by a bypass flow passage. A water quality adjusting means is arranged for adjusting the quality of the treated waste water to be discharged to the outside by supplying a part or the whole of at least one of the waste water to be introduced into the aeration tank and the waste water being aerated/treated in the aeration tank to the discharge tank 30 through the bypass flow passage and mixing the waste water supplied through the bypass flow passage with the treated waste water in the discharge tank. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wastewater treatment method and a wastewater treatment apparatus.

  Currently, in many wastewater treatment apparatuses, wastewater is purified by aerobic biological treatment. This is because the aerobic biological treatment uses the metabolic action of microorganisms, so that the treatment efficiency is high and economical. Next, the aerobic biological treatment will be described.

  First, waste water is continuously fed to the aeration tank where it comes into contact with a population of aerobic microorganisms. As a result, the wastewater substrate (BOD component) is oxidatively decomposed by the aerobic microorganism population. This population of aerobic microorganisms is commonly referred to as “activated sludge”. The wastewater treated in the aeration tank flows into the solid-liquid separation tank together with the aerobic microorganism population.

  In the solid-liquid separation tank, the aerobic microorganism population aggregates into flocs and settles. On the other hand, the supernatant (treated wastewater) is discharged to the outside. A group of aerobic microorganisms settled in the solid-liquid separation tank, that is, sludge is returned to the aeration tank via a return flow path (return sludge), and oxidative decomposition of the substrate (BOD component) is performed again.

However, since the aerobic microorganisms multiply, if all of the sludge is returned, oxygen shortage occurs in the aeration tank or solid-liquid separation becomes difficult in the solid-liquid separation tank. For this reason, the part which grew is taken out out of the system as surplus sludge (for example, refer to patent documents 1 and 2).
JP 2002-219482 A JP 2004-337811 A

  However, in the conventional wastewater treatment apparatus as described above, the quality of the treated wastewater discharged to the outside is adjusted to various water quality standards such as the quality standard of the inflow water to the sewer and the quality standard of the river discharge water. It is difficult to change, and there is a problem that energy is wasted by excessively performing processing such as aeration.

  Therefore, an object of the present invention is to adjust the water quality of the treated wastewater discharged to the outside according to various water quality standards, and as a result, it is possible to suppress waste of energy such as a blower motor used for aeration. A wastewater treatment method and a wastewater treatment apparatus are provided.

  In order to achieve the above object, the treatment method of the present invention is a wastewater treatment method, wherein an aeration process in which wastewater to be treated is introduced into an aeration tank and aerated by microorganisms, and the wastewater subjected to aeration treatment is treated. A solid-liquid separation step of introducing into the solid-liquid separation tank to separate into solid and liquid sludge and treated wastewater, and a discharge step of discharging the treated wastewater to the outside after introducing the treated wastewater into the discharge tank, Furthermore, a part or all of at least one of the waste water before the introduction of the aeration tank and the waste water during the aeration treatment is supplied to and mixed with the treated waste water in the discharge step, whereby the treated waste water to be discharged to the outside. It is the processing method which has a water quality adjustment process which adjusts water quality.

  The treatment apparatus of the present invention is a wastewater treatment apparatus, and includes at least an aeration tank, a solid-liquid separation tank, and a discharge tank, which are connected by a flow path in the order described above, and the aeration tank In the above, the waste water to be treated is introduced and aerated by microorganisms, and in the solid-liquid separation tank, the waste water subjected to aeration treatment is introduced and separated into sludge and treated waste water, and in the discharge tank, After the treatment wastewater is introduced, the treatment wastewater is discharged from the discharge tank to the outside, and the aeration tank and the discharge tank are connected by a bypass flow path. At least one or all of the waste water before introduction and the waste water during aeration treatment is supplied to the treated waste water in the discharge tank and mixed to thereby discharge the treated waste water to the outside. A processor having a water conditioning means quality of is adjusted.

  Thus, in the treatment method and the treatment apparatus of the present invention, at least one part or all of the waste water before the introduction of the aeration tank and the waste water during the aeration treatment is supplied to and mixed with the treatment waste water in the discharge step or the discharge tank. Therefore, it is possible to adjust the quality of the treated wastewater discharged to the outside. Therefore, it is possible to adjust the water quality of the treated wastewater discharged to the outside in accordance with various water quality standards, and as a result, waste of energy such as a blower motor used for aeration can be suppressed. Further, the treatment method and the treatment apparatus of the present invention can be retrofitted at low cost because it is only necessary to add a bypass channel to the existing wastewater treatment apparatus.

  In the treatment method of the present invention, the water quality adjustment index is not particularly limited. For example, suspended matter (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), n-hexane extract and the like. Among these, suspended solids (SS) and biochemical oxygen demand (BOD) are preferable. The water quality adjustment index may be one type or two or more types.

  In the treatment method of the present invention, a reference value of suspended matter (SS) and biochemical oxygen demand (BOD) of the treated wastewater discharged to the outside are set in advance, and in the treated wastewater, At least one of suspended matter (SS) and biochemical oxygen demand (BOD) is detected, and the detected value or these detected values are compared with the reference value to introduce the aeration tank in the water quality adjustment step It is preferable to determine a supply ratio of at least one of the previous waste water and the waste water during the aeration treatment.

In the treatment method of the present invention, the reference value (SS _Base ), the reference value (BOD _Base ) of the biochemical oxygen demand and the discharge flow rate (F ₂ ) are determined in advance. In the aeration step, suspended substances (MLSS) and biochemical oxygen demand (BOD1) in the wastewater in the aeration tank are detected, and in the solid-liquid separation step, the floating in the treated wastewater in the solid-liquid separation tank The substance (SS1) is detected, and in the discharge step, the biochemical oxygen demand (BOD2) in the treated wastewater in the discharge tank is detected, and the water quality adjustment step is performed using the following formulas (1) and (2) in the two supply amount of said at least one of a portion of the effluent or all in the drainage and aeration before aeration tank introduction (F _1SS, F _1BOD) seeking, among the two supply amount Adopted again how, based on the adopted feed amount, it is preferable to adjust the process wastewater quality that discharged to the outside.

_{F 1SS = {(SS Base -SS1} ) × F 2} / (MLSS-SS1) ··· (1)
F _1SS : Supply amount of drainage from aeration tank to discharge tank (m ³ / day)
MLSS: Detection value of suspended solids in waste water in aeration tank (mg / L)
SS1: Detection value (mg / L) of suspended solids in the treated wastewater in the solid-liquid separation tank
SS _Base : Pre-determined reference value (mg / L) of suspended matter in treated wastewater discharged to the outside
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.

_{F 1BOD = {(BOD Base -BOD2} ) × F 2} / (BOD1-BOD2) ··· (2)
F _1BOD : Amount of wastewater supplied from the aeration tank to the discharge tank (m ³ / day)
BOD1: Detection value of biochemical oxygen demand in waste water in aeration tank (mg / L)
BOD2: Detection value (mg / L) of biochemical oxygen demand in the treated wastewater in the discharge tank
BOD _Base : A predetermined reference value (mg / L) of biochemical oxygen demand for treated wastewater discharged to the outside.
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.

In the treatment method of the present invention, only one of the two suspended solids (MLSS, SS1) and the two biochemical oxygen demands (BOD1, BOD2) is detected, and the two supply amounts (F _1SS , F 1 _BOD ) alone may be calculated, and the quality of the treated wastewater discharged to the outside may be adjusted based on the calculated supply amount.

  In the treatment method of the present invention, the two biochemical oxygen demands (BOD1, BOD2) detect the dissolved oxygen quantity (DO) in the aeration tank and the discharge tank, and the detected value is used as the biochemical oxygen demand. It is preferably a value converted into an amount (BOD1, BOD2).

In the treatment method of the present invention, in the solid-liquid separation step, a part of the sludge is returned to the aeration step, and the remainder of the sludge is treated as surplus sludge. In the aeration step, the aeration treatment in the aeration tank is performed. By previously setting the reference value (MLSS _Base ) of the suspended matter in the waste water in the inside, and detecting the suspended matter (MLSS) in the waste water during the aeration process, and comparing this detected value with the reference value, It is preferable to determine the amount of excess sludge treated in the solid-liquid separation step.

In the treatment method of the present invention, in the aeration step, a reference value (BOD1 _Base ) of the biochemical oxygen demand in the aeration tank is set in advance, and the biochemical oxygen demand (BOD1) of the waste water during the aeration treatment is set. It is preferable to adjust the amount of aeration in the aeration step by detecting the detected value and comparing the detected value with the reference value. The aeration amount is adjusted by, for example, an output of a blower motor described later. When the amount of aeration is adjusted by the output of the blower motor, it can be adjusted by, for example, continuous operation or intermittent operation of the blower motor.

  In the treatment method of the present invention, in the aeration step, the waste water in the aeration process is divided by dividing the aeration tank into a plurality of parts, and in the water quality adjustment step, at least one of the divided aeration tanks. The waste water during the aeration process may be supplied to the treated waste water in the discharge step.

  In the treatment apparatus of the present invention, the index for adjusting the water quality is not particularly limited as described above, and for example, suspended matter (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD) ), Total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), n-hexane extract and the like. Among these, suspended solids (SS) and biochemical oxygen demand (BOD) are preferable. The water quality adjustment index may be one type or two or more types.

  In the treatment apparatus of the present invention, the discharge tank has detection means for detecting at least one of suspended matter (SS) and biochemical oxygen demand (BOD) in the treatment waste water, and the water quality adjustment means is: The detection value detected by the detection means is compared with a preset reference value of suspended matter (SS) and biochemical oxygen demand (BOD) of the treated wastewater discharged to the outside in advance, It is preferable to determine a supply ratio of at least one of the waste water before the introduction of the aeration tank and the waste water during the aeration treatment.

In the treatment apparatus of the present invention, the aeration tank has detection means for detecting suspended solids (MLSS) and biochemical oxygen demand (BOD1) in the waste water in the aeration tank, and the solid-liquid separation tank is The solid-liquid separation tank has detection means for detecting suspended solids (SS1) in the treated wastewater, and the discharge tank detects a biochemical oxygen demand (BOD2) in the treated wastewater in the discharge tank. In the same manner as described above, the water quality adjusting means includes a reference value (SS _Base ) of the suspended matter in the treated wastewater discharged to the outside and a reference value (BOD) of the biochemical oxygen demand. _Base ) and the discharge flow rate (F ₂ ) and the detected values detected by the detection means, using the following formulas (1) and (2), the drainage before the introduction of the aeration tank and the drainage during the aeration treatment Less than at least one of Ku and a part or all of the two supply amount (F _1SS, F _1BOD) sought, the two adopted smaller of the supply amount, based on the adopted supply amount, the process wastewater discharged to the outside It is preferable to adjust the water quality.

_{F 1SS = {(SS Base -SS1} ) × F 2} / (MLSS-SS1) ··· (1)
F _1SS : Supply amount of drainage from aeration tank to discharge tank (m ³ / day)
MLSS: Detection value of suspended solids in waste water in aeration tank (mg / L)
SS1: Detection value (mg / L) of suspended solids in the treated wastewater in the solid-liquid separation tank
SS _Base : Pre-determined reference value (mg / L) of suspended matter in treated wastewater discharged to the outside
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.

_{F 1BOD = {(BOD Base -BOD2} ) × F 2} / (BOD1-BOD2) ··· (2)
F _1BOD : Amount of wastewater supplied from the aeration tank to the discharge tank (m ³ / day)
BOD1: Detection value of biochemical oxygen demand in waste water in aeration tank (mg / L)
BOD2: Detection value (mg / L) of biochemical oxygen demand in the treated wastewater in the discharge tank
BOD _Base : A predetermined reference value (mg / L) of biochemical oxygen demand for treated wastewater discharged to the outside.
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.

In the treatment apparatus of the present invention, the water quality adjusting means detects only one of the two suspended substances (MLSS, SS1) and the two biochemical oxygen demands (BOD1, BOD2) as described above. Then, only one of the two supply amounts (F _1SS , F _1BOD ) may be calculated, and the quality of the treated wastewater discharged to the outside may be adjusted based on the calculated supply amount.

  In the treatment apparatus of the present invention, the two biochemical oxygen demand (BOD1, BOD2) detecting means detects the dissolved oxygen amount (DO) in the aeration tank and the discharge tank, and the detected value is biochemically detected. It is preferable to use a means for converting into the required oxygen demand (BOD1, BOD2).

  In the treatment apparatus of the present invention, a bypass flow rate adjusting valve is attached in the middle of the bypass flow path, and the water quality adjusting means supplies at least one of the waste water before the introduction of the aeration tank and the waste water during the aeration treatment. Is preferably adjusted with the bypass flow rate adjusting valve.

In the processing apparatus of the present invention, the aeration tank and the solid-liquid separation tank are also connected by a return flow path, and an excess sludge extraction flow path is connected to the solid-liquid separation tank, in the solid-liquid separation tank A part of the sludge is returned to the aeration tank by the return flow path, and the remainder of the sludge is extracted by the surplus sludge extraction flow path, and the aeration tank is a floating substance of the waste water during the aeration process. (MLSS) detecting means, and the water quality adjusting means is detected by the detection means and a reference value (MLSS _Base ) of suspended matter in the waste water during aeration processing in a preset aeration tank It is preferable to determine the amount of excess sludge to be extracted from the solid-liquid separation tank by comparing the detected value.

In the treatment apparatus of the present invention, the aeration tank has detection means for detecting the biochemical oxygen demand (BOD1) of the waste water during the aeration treatment, and the water quality adjustment means is preset in the same manner as described above. It is preferable to adjust the amount of aeration in the aeration tank by comparing the reference value (BOD1 _Base ) of the biochemical oxygen demand in the aerated tank and the detection value detected by the detection means. The aeration amount is adjusted by, for example, an output of a blower motor described later. When the amount of aeration is adjusted by the output of the blower motor, it can be adjusted by, for example, continuous operation or intermittent operation of the blower motor.

  In the treatment apparatus of the present invention, the aeration tank is divided into a plurality of parts, whereby the waste water during the aeration process is divided according to the degree of aeration treatment, and the water quality adjusting means is provided from at least one of the divided aeration tanks. You may supply the said waste_water | drain in aeration process to the said treated waste_water | drain in the said discharge tank.

  In the treatment apparatus of the present invention, the treatment apparatus further includes a measurement tank provided with means for detecting suspended solids (SS) and biochemical oxygen demand (BOD), and the waste water during the aeration process in the aeration tank is provided in the measurement tank. At least one drainage of the treated wastewater in the solid-liquid separation tank and the treated wastewater in the discharge tank is introduced, and the suspended matter (SS) of the wastewater introduced into the measurement tank by the detection means of the measurement tank ) And biochemical oxygen demand (BOD).

  Next, examples of the processing method and the processing apparatus of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.

  FIG. 1 shows an example of the configuration of the processing apparatus of the present invention. As shown in the figure, this apparatus has an aeration tank 10, a solid-liquid separation tank 20, and a discharge tank 30 as main components, which are connected by a flow path (for example, a pipe) in the above order. . The solid-liquid separation tank 20 is connected to an excess sludge extraction channel (for example, a pipe), and the excess sludge extraction channel is connected to a sludge storage tank 40. Furthermore, the aeration tank 10 and the discharge tank 30 are connected by a bypass channel (for example, a pipe). A transport pump may be attached to each of these channels. The aeration tank 10 includes dissolved oxygen detection means 11, suspended substance detection means 12, and a blower motor 80. The solid-liquid separation tank 20 has floating substance detection means 22. The discharge tank 30 includes dissolved oxygen detection means 31 and suspended substance detection means 32. A bypass flow rate adjustment valve (valve) 60 and a bypass flow rate detection means 50 are attached in the middle of the bypass flow path. An extraction sludge flow rate adjusting valve (valve) 70 is provided in the excess sludge removal flow path. The discharge tank 30 is connected to a discharge channel, and a discharge flow rate detecting means 51 is attached to the discharge channel. Various sensors can be used for each detection means according to the application. Furthermore, this apparatus has a data input unit 90, a comparison unit 100, a calculation unit 110, and an output unit 120 as water quality adjusting means. The data input unit 90 includes a suspended matter input unit 91, a dissolved oxygen input unit 92, a conversion unit 93, and a flow rate input unit 94. Next, an example of wastewater treatment using this apparatus will be described for each process.

  First, wastewater to be treated is introduced into the aeration tank 10. Here, the suspended matter (MLSS) in the waste water is detected by the suspended matter detection means 12, and the detected value is sent to the suspended matter input unit 91. Further, the dissolved oxygen amount (DO1) of the waste water is detected by the dissolved oxygen detecting means 11, and the detected value is sent to the dissolved oxygen input unit 92 and further sent to the conversion unit 93.

  In the aeration tank 10, the substrate (BOD component) in the waste water is aerated by microorganisms in the aeration tank 10 and is oxidatively decomposed. As described above, the amount of aeration in the aeration tank 10 is adjusted by the output of the blower motor 80.

  Next, the waste water that has been subjected to aeration treatment is introduced into the solid-liquid separation tank 20, where it is separated into sludge and treated waste water. The solid-liquid separation may be performed by, for example, sedimentation of the sludge, or may be performed by membrane separation. The sludge is extracted as excess sludge through the excess sludge extraction channel, and is introduced into the sludge storage tank 40. The sludge introduced into the sludge storage tank 40 is taken out of the system and processed by a predetermined means. A return flow path (for example, a pipe) that connects the aeration tank 10 and the solid-liquid separation tank 20 may be provided, and a part of the sludge may be returned to the aeration tank 10. In this case, the sludge returned to the aeration tank 10 (return sludge) is used again for the aeration process. The suspended matter (SS1) in the treated wastewater is detected by the suspended matter detection means 22 and the detection result is sent to the suspended matter input unit 91.

  Next, the treated waste water is introduced into the discharge tank 30. Here, the suspended matter (SS2) in the treated waste water is detected by the suspended matter detection means 32, and the detection result is sent to the suspended matter input unit 91. Further, the dissolved oxygen amount (DO2) of the treated waste water is detected by the dissolved oxygen detection means 31, and the detection result is sent to the dissolved oxygen input unit 92 and further sent to the conversion unit 93.

  Next, the conversion unit 93 calculates an oxygen utilization rate (Rr1) in the aeration tank from the detection value of the dissolved oxygen detection means 11 in the aeration tank. In addition, the detection by the dissolved oxygen detection means 11 of the aeration tank is performed twice with time, for example. The oxygen utilization rate (Rr1) in the aeration tank is calculated by the following equation (3).

Rr1 = (DO12−DO11) / Δt _12-11 (3)
Rr1: Oxygen utilization rate in the aeration tank (mg / L · hour)
DO11: Detection value (mg / L) of the dissolved oxygen detection means in the first aeration tank
DO12: Detection value (mg / L) of the dissolved oxygen detection means in the second aeration tank
Δt _12-11 : Time (time) between the first detection and the second detection in the aeration tank

  Further, the conversion unit 93 calculates the oxygen utilization rate (Rr2) in the discharge tank from the detection value of the dissolved oxygen detection means 31 in the discharge tank. In addition, the detection by the dissolved oxygen detection means 31 of the said discharge tank is performed twice at intervals, for example. The oxygen utilization rate (Rr2) in the discharge tank is calculated by the following formula (4).

Rr2 = (DO22−DO21) / Δt _22-21 (4)
Rr2: Oxygen utilization rate in the discharge tank (mg / L · hour)
DO21: Detection value (mg / L) of the dissolved oxygen detection means in the first discharge tank
DO22: Detection value (mg / L) of the dissolved oxygen detection means in the second discharge tank
Δt _22-21 : Time (time) between the first detection and the second detection in the discharge tank

  And in the said conversion part 93, the biochemical oxygen demand (BOD1) in the said waste_water | drain in an aeration tank is calculated from the oxygen utilization rate (Rr1) in the said aeration tank. The biochemical oxygen demand (BOD1) in the waste water in the aeration tank is calculated by the following equation (5).

BOD1 = Rr1 × α1 (5)
BOD1: Biochemical oxygen demand in waste water in aeration tank (mg / L)
Rr1: Oxygen utilization rate in the aeration tank (mg / L · hour)
α1: Constant (time)

  In the above formula (5), α1 is a constant different for each apparatus, and for example, an empirical value can be used or is obtained by experiment. Specifically, the constant α1 is measured, for example, by introducing treated wastewater having different biochemical oxygen demand (BOD) adjusted in advance into the aeration tank, and measuring the oxygen utilization rate (Rr1) in the aeration tank for each wastewater. It can be derived by obtaining the correlation between the BOD and the Rr1.

  For example, when the Rr1 is 10 mg / L · hour and the constant α1 is 150 hours, the biochemical oxygen demand (BOD1) in the waste water in the aeration tank is 1500 mg / L from the above formula (5). L.

  Further, the conversion unit 93 calculates the biochemical oxygen demand (BOD2) in the treated wastewater in the discharge tank from the oxygen utilization rate (Rr2) in the discharge tank. The biochemical oxygen demand (BOD2) in the treated waste water in the discharge tank is calculated by the following formula (6).

BOD2 = Rr2 × α2 (6)
BOD2: Biochemical oxygen demand in the treated wastewater in the discharge tank (mg / L)
Rr2: Oxygen utilization rate in the discharge tank (mg / L · hour)
α2: Constant (time)

  In the above formula (6), α2 is a constant different for each apparatus, and for example, an empirical value can be used or is obtained by experiment. Specifically, the constant α2 is, for example, that treated wastewater having different biochemical oxygen demand (BOD) adjusted in advance is introduced into the discharge tank, and the oxygen utilization rate (Rr2) in the discharge tank is set for each treated wastewater. It can be derived by measuring and calculating the correlation between the BOD and the Rr2.

  For example, when the Rr2 is 2 mg / L · hour and the constant α2 is 150 hours, the biochemical oxygen demand (BOD2) in the discharge tank is 300 mg / L from the above formula (6). .

  Here, a reference value of suspended matter (SS) and biochemical oxygen demand (BOD) of the treated wastewater discharged to the outside is set in advance, and detection by the suspended matter detection means 32 of the discharge tank is performed. When at least one of the value (SS2) and the biochemical oxygen demand (BOD2) in the treated wastewater in the discharge tank is substantially equal to the respective reference values, the opening degree of the bypass flow rate adjustment valve 60 is not changed. On the other hand, when both SS2 and BOD2 are different from the respective reference values, the opening degree of the bypass flow rate adjustment valve 60 is adjusted. Next, an example of a method for adjusting the opening degree of the bypass flow rate adjusting valve 60 will be described.

First, the reference value (SS _Base ) and the discharge flow rate (F ₂ ) of the suspended matter in the treated wastewater discharged to the outside are determined in advance, and in the suspended matter input unit 91, the reference value and the floating amount of the aeration tank are determined. The bypass flow rate (F _1SS ) is calculated from the detection value of the substance detection means 12 and the detection value of the floating substance detection means 22 of the solid-liquid separation tank. The bypass flow rate (F _1SS ) is calculated by the following equation (7).

_{F 1SS = {(SS Base -SS1} ) × F 2} / (MLSS-SS1) ··· (7)
F _1SS : Bypass flow rate (m ³ / day)
MLSS: Detection value (mg / L) of floating substance detection means in the aeration tank
SS1: Detection value (mg / L) of suspended solids detection means in the solid-liquid separation tank
SS _Base : A predetermined reference value (mg / L) of suspended solids in treated wastewater discharged to the outside.
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.

For example, when the SS _Base is 300 mg / L, the F ₂ is 100 m ³ / day, the MLSS is 3000 mg / L, and the SS1 is 0 mg / L, the bypass flow rate F _1SS is expressed by the above formula (7) Therefore, it becomes 10 m ³ / day.

The calculation result of the bypass flow rate F _1SS is sent to the comparison unit 100.

Further, a reference value (BOD _Base ) and a discharge flow rate (F ₂ ) of the biochemical oxygen demand of the treated wastewater discharged to the outside are determined in advance, and in the conversion unit 93, each reference value and the aeration tank A bypass flow rate (F _1BOD ) is calculated from the biochemical oxygen demand (BOD1) in the wastewater and the biochemical oxygen demand (BOD2) in the treated wastewater in the discharge tank. The bypass flow rate (F _1BOD ) is calculated by the following equation (8).

_{F 1BOD = {(BOD Base -BOD2} ) × F 2} / (BOD1-BOD2) ··· (8)
F _1BOD : Bypass flow rate (m ³ / day)
BOD1: Biochemical oxygen demand in waste water in aeration tank (mg / L)
BOD2: Biochemical oxygen demand in the treated wastewater in the discharge tank (mg / L)
BOD _Base : A predetermined reference value (mg / L) of biochemical oxygen demand for treated wastewater discharged to the outside.
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.

For example, when the BOD _Base is 300 mg / L, the F ₂ is 100 m ³ / day, the BOD 1 is 1500 mg / L, and the BOD 2 is 0 mg / L, the bypass flow rate F _1BOD is _expressed by the above formula (8) Therefore, it becomes 20 m ³ / day.

The calculation result of the bypass flow rate F _1BOD is sent to the comparison unit 100.

Next, the comparison unit 100 compares the two bypass flow rates F _1SS and F _1BOD that have been sent, and the smaller one is sent to the calculation unit 110.

  Next, the bypass flow rate detection means 50 detects an actual measurement value of the bypass flow rate, and the detected value is sent to the flow rate input unit 94 and further sent to the calculation unit 110.

Next, in the calculation unit 110, an appropriate opening degree of the bypass flow rate adjusting valve 60 is determined from the smaller one of the bypass flow rates F _1SS and F _1BOD and the actual measured value of the bypass flow rate by the bypass flow rate detecting means 50. The calculation result is sent to the output unit 120.

Next, output information is sent from the output unit 120 to the bypass flow rate adjustment valve 60, and the opening degree of the bypass flow rate adjustment valve 60 is adjusted. Thereby, the predetermined reference value (SS _Base ) of the suspended matter of the treated wastewater to be discharged to the outside and the predetermined reference value (BOD) of the biochemical oxygen demand of the treated wastewater to be discharged to the outside. _The waste water during the aeration process is supplied from the aeration tank 10 to the discharge tank 30 and mixed with the treated waste water by the bypass channel so that one of the values of _Base ) is obtained. As a result, wastewater treatment according to the water quality standard becomes possible. In addition, the said bypass flow path is applied not only to the said waste_water | drain during aeration process but the said waste_water | drain before introduction of an aeration tank. In this way, the treated wastewater whose water quality has been adjusted is discharged from the discharge tank 30 to the outside through the discharge channel. At this time, the amount of excess sludge extracted in the solid-liquid separation step or the solid-liquid separation tank can be reduced by the amount of floating substances contained in the wastewater supplied by the bypass channel.

Only one of the two suspended substances (MLSS, SS1) and the two biochemical oxygen demands (BOD1, BOD2) is detected, and any of the two bypass flow rates (F _1SS , F _1BOD ) is detected. By calculating only one of them, and calculating the appropriate opening degree of the bypass flow rate adjusting valve 60 from the calculated supply amount and the actual measured value of the bypass flow rate by the bypass flow rate detection means 50, the bypass flow rate adjustment The opening degree of the valve 60 may be adjusted.

In addition, when the aeration tank 10 and the solid-liquid separation tank 20 are also connected by a return channel, a reference value (MLSS _Base ) of the suspended matter in the waste water during the aeration process in the aeration tank is set in advance. In addition, when the actual measurement value (MLSS) of the suspended matter in the suspended matter detection means 12 exceeds the reference value, the extraction sludge flow rate is monitored until the reference value is reached while monitoring the actual measurement value. It is preferable to open the regulating valve 70 a little and extract excess sludge to the sludge storage tank 40 by the excess sludge removal flow path. As a result, the sludge is excessively returned to the aeration tank 10, oxygen becomes insufficient in the aeration tank 10, and the processing efficiency is lowered, or excessive sludge is excessively extracted in the sludge storage tank 40. It is possible to prevent the processing cost from increasing. In this case, it is preferable that a flow meter is provided in the surplus sludge extraction flow path, and the surplus sludge is extracted by an amount including suspended solids for the measured value exceeding the reference value. For example, when the reference value is 3000 mg / L and the actual measurement value is 3500 mg / L, if the volume of the aeration tank 10 is 10 m ³ (= 10 ⁴ L), (3500-3000) mg / L What is necessary is just to extract the said excess sludge by the quantity containing the floating substance of * 10 < ⁴ > L = 5 * 10 < ⁶ > mg. Here, if the waste water during the aeration process which is the actual measurement value (3500 mg / L) in the aeration tank 10 is concentrated twice in the solid-liquid separation tank 20, it is 5 × 10 ⁶ mg / 3500. What is necessary is just to extract the said excess sludge of x2mg / L ≒ 700L.

In addition to adjusting the opening degree of the bypass flow rate adjusting valve 60, the quality of the treated waste water discharged to the outside can be adjusted by controlling the output of the blower motor 80. That is, a reference value (BOD _Base ) is set in advance for the biochemical oxygen demand in the aeration tank, and the biochemical oxygen demand (BOD1) in the waste water in the aeration tank exceeds the reference value. Increases the output of the blower motor 80 to promote the aeration process by microorganisms in the aeration tank 10. As a result, it is possible to adjust the water quality of the treated wastewater discharged to the outside. On the other hand, when the BOD1 does not exceed the reference value, by suppressing the output of the blower motor 80, the operating cost of the blower motor 80 such as electricity bill can be suppressed.

  Next, another example of the processing apparatus of the present invention will be described with reference to FIG. In FIG. 2, the same parts as those in FIG.

  This apparatus has a measurement tank 130, and in this measurement tank 130, each dissolved oxygen amount and suspended solids are measured together. The measurement tank 130 includes dissolved oxygen detection means 131 and suspended substance measurement means 132. As shown in the figure, the waste water during the aeration process for measuring the amount of dissolved oxygen and suspended solids is introduced from the aeration tank 10 into the measurement tank 130 by the pump 133. Here, the amount of dissolved oxygen in the waste water during the aeration process is detected by the dissolved oxygen detecting means 131, and the detected value is sent to the dissolved oxygen input unit 92 and further sent to the conversion unit 93. Further, the suspended matter in the waste water during the aeration process is detected by the suspended matter detection means 132, and the detected value is sent to the suspended matter input unit 91. Similarly, the treatment tank 130 can introduce the treated wastewater for measuring the amount of dissolved oxygen and suspended solids from the solid-liquid separation tank 20 by the pump 134 and from the discharge tank 30 by the pump 135, respectively. In the measurement tank 130, the amount of dissolved oxygen and suspended substances in each of the treatment wastewaters can be measured. This makes it possible to share the dissolved oxygen detection means and suspended solids detection means, eliminating the need to provide expensive detection means for each tank. The operation and conditions of other processes are the same as those of the apparatus shown in FIG.

  In the apparatus shown in FIGS. 1 and 2, the aeration tank 10 can be divided into a plurality of pieces, for example, a configuration as shown in FIG. That is, as shown in the figure, the aeration tank 10 is divided into an upstream, a middle stream, and a downstream from the side where drainage is introduced, and a bypass flow path is drawn out from each part, and the bypass flow rate is set to each of the three bypass flow paths. An adjustment valve (61-63) is provided, and the three bypass flow paths are merged at the tip. Thereby, according to a condition, the taking-out position of the said waste_water | drain during the aeration process to a bypass flow path can be changed now. For example, when the biochemical oxygen demand (BOD2) of the treated wastewater in the discharge tank is larger than the suspended solids (SS2) in the treated wastewater in the discharge tank, the aeration treatment by the microorganism proceeds and the biochemical oxygen demand is increased. From the bypass flow rate adjustment valve 63 on the downstream side of the aeration tank 10 having a smaller amount (BOD), the waste water being subjected to the aeration process is taken into the bypass flow path that continues to the discharge tank. On the other hand, for example, when the biochemical oxygen demand (BOD2) of the treated wastewater in the discharge tank is smaller than the suspended solids (SS2) of the treated wastewater in the discharge tank, the aeration treatment with microorganisms has not progressed much. From the bypass flow rate adjustment valve 61 on the upstream side of the aeration tank 10 having a large biochemical oxygen demand (BOD), the waste water being subjected to the aeration process is taken into the bypass flow path that continues to the discharge tank. FIG. 3 shows the case where the aeration tank 10 is divided into three parts. However, the division of the aeration tank 10 is not limited to three, and it is divided into two upstream and downstream. It can also be divided into four or more.

  The use method of the wastewater treatment method and treatment apparatus of the present invention is not limited, and can be applied to the treatment of organic wastewater, for example.

FIG. 1 is a configuration diagram of an example of a processing apparatus of the present invention. FIG. 2 is a configuration diagram of another example of the processing apparatus of the present invention. FIG. 3 is a configuration diagram of an example of the aeration tank of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Aeration tank 11, 31, 131 Dissolved oxygen detection means 12, 22, 32, 132 Suspended substance detection means 20 Solid-liquid separation tank 30 Drain tank 40 Sludge storage tank 50 Bypass flow rate detection means 51 Discharge flow rate detection means 60, 61, 62 63 Bypass flow rate adjustment valve 70 Extraction sludge flow rate adjustment valve 80 Blower motor 90 Data input unit 91 Floating substance input unit 92 Dissolved oxygen input unit 93 Conversion unit 94 Flow rate input unit 100 Comparison unit 110 Calculation unit 120 Output unit 130 Measurement tank 133 , 134, 135 Pump

Claims (20)

  A wastewater treatment method, in which a wastewater to be treated is introduced into an aeration tank and aerated by microorganisms, and the aerated wastewater is introduced into a solid-liquid separation tank and solidified into sludge and treated wastewater. A solid-liquid separation step for liquid separation, and a discharge step for discharging the treated wastewater to the outside after introducing the treated wastewater into the discharge tank, and further, the wastewater before the introduction of the aeration tank and the aeration treatment A wastewater treatment method comprising a water quality adjusting step of adjusting the water quality of the treated wastewater discharged to the outside by supplying and mixing at least one part or all of the wastewater to the treated wastewater in the discharge step.   The wastewater treatment method according to claim 1, wherein the water quality adjustment index is at least one of suspended solids (SS) and biochemical oxygen demand (BOD).   A reference value for suspended solids (SS) and biochemical oxygen demand (BOD) in the treated wastewater discharged to the outside is set in advance, and in the discharge step, suspended solids (SS) in the treated wastewater and Detecting at least one of biochemical oxygen demand (BOD), comparing this detected value or these detected values with the reference value, and the drainage and aeration treatment before introducing the aeration tank in the water quality adjustment step The wastewater treatment method according to claim 1, wherein a supply ratio of at least one of the wastewater is determined. The reference value (SS _Base ), the biochemical oxygen demand reference value (BOD _Base ) and the discharge flow rate (F ₂ ) of the treated wastewater discharged to the outside are determined in advance, and in the aeration process, aeration The suspended matter (MLSS) and biochemical oxygen demand (BOD1) in the wastewater in the tank are detected, and the suspended matter (SS1) in the treated wastewater in the solid-liquid separation tank is detected in the solid-liquid separation step. In the discharge step, the biochemical oxygen demand (BOD2) in the treated wastewater in the discharge tank is detected, and from the reference values and the detection values obtained by the detection, the following formulas (1) and ( with 2), in the water conditioning process, the waste water and the two supply amount of at least one of a part or all of the waste water in the aeration treatment prior to the aeration tank introduction (F _1SS, the F _1BOD) Because, the two adopted smaller of the supply amount, based on the adopted feed rate processing method of waste water according to claim 1, wherein adjusting the quality of the wastewater to be discharged to the outside.

_{F 1SS = {(SS Base -SS1} ) × F 2} / (MLSS-SS1) ··· (1)
F _1SS : Supply amount of drainage from aeration tank to discharge tank (m ³ / day)
MLSS: Detection value of suspended solids in waste water in aeration tank (mg / L)
SS1: Detection value (mg / L) of suspended solids in the treated wastewater in the solid-liquid separation tank
SS _Base : Pre-determined reference value (mg / L) of suspended matter in treated wastewater discharged to the outside
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.

_{F 1BOD = {(BOD Base -BOD2} ) × F 2} / (BOD1-BOD2) ··· (2)
F _1BOD : Amount of wastewater supplied from the aeration tank to the discharge tank (m ³ / day)
BOD1: Detection value of biochemical oxygen demand in waste water in aeration tank (mg / L)
BOD2: Detection value (mg / L) of biochemical oxygen demand in the treated wastewater in the discharge tank
BOD _Base : A predetermined reference value (mg / L) of biochemical oxygen demand for treated wastewater discharged to the outside.
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.
Only one of the two suspended solids (MLSS, SS1) and the two biochemical oxygen demands (BOD1, BOD2) is detected, and one of the two supply amounts (F _1SS , F _1BOD ) The wastewater treatment method according to claim 4, wherein only the water quality is calculated and the quality of the treated wastewater discharged to the outside is adjusted based on the calculated supply amount.   The two biochemical oxygen demands (BOD1, BOD2) detect the dissolved oxygen quantity (DO) in the aeration tank and the discharge tank, and the detected value is converted into the biochemical oxygen demand (BOD1, BOD2). The wastewater treatment method according to claim 4, which is a converted value. In the solid-liquid separation step, a part of the sludge is returned to the aeration step, and the remainder of the sludge is treated as surplus sludge. In the aeration step, the suspended matter in the waste water during the aeration treatment in the aeration tank By setting the reference value (MLSS _Base ) of the wastewater in advance and detecting the suspended solids (MLSS) of the waste water during the aeration process, the detected value is compared with the reference value, thereby surplus in the solid-liquid separation step. The wastewater treatment method according to claim 1, wherein the amount of sludge treatment is determined. In the aeration step, a reference value (BOD1 _Base ) of the biochemical oxygen demand in the aeration tank is set in advance, and the biochemical oxygen demand (BOD1) of the waste water during the aeration treatment is detected, and this detected value The waste water treatment method according to claim 1, wherein an aeration amount in the aeration process is adjusted by comparing the reference value with the reference value.   In the aeration step, the waste water in the aeration process is divided by the aeration process by dividing the aeration tank into a plurality of parts, and in the water quality adjustment step, the waste water in the aeration process from at least one of the divided aeration tanks. The wastewater treatment method according to claim 1, wherein wastewater is supplied to the treated wastewater in the discharge step.   A wastewater treatment apparatus having at least an aeration tank, a solid-liquid separation tank, and a discharge tank, which are connected by a flow path in the order described above, and the wastewater to be treated is introduced into the aeration tank. And aeration treatment by microorganisms, in the solid-liquid separation tank, the waste water subjected to aeration treatment is introduced into solid and liquid separation into sludge and treatment waste water, and after the treatment waste water is introduced in the discharge tank, The treated waste water is discharged to the outside from the discharge tank, and the aeration tank and the discharge tank are connected by a bypass flow path, and the waste water and the aeration process before the introduction of the aeration tank are performed by the bypass flow path. A water quality control in which the quality of the treated wastewater discharged to the outside is adjusted by supplying a part or all of at least one of the wastewater to the treated wastewater in the discharge tank and mixing it. Wastewater treatment apparatus having means.   The wastewater treatment apparatus according to claim 10, wherein the index for adjusting the water quality is at least one of suspended solids (SS) and biochemical oxygen demand (BOD).   The discharge tank has detection means for detecting at least one of suspended matter (SS) and biochemical oxygen demand (BOD) in the treated wastewater, and the water quality adjustment means is detected by the detection means. Compare the detected value with the standard value of suspended matter (SS) and biochemical oxygen demand (BOD) of the treated wastewater discharged to the outside in advance, and the wastewater before introduction of the aeration tank The wastewater treatment apparatus according to claim 10, wherein a supply ratio of at least one of the wastewater during aeration treatment is determined. The aeration tank has detection means for detecting suspended solids (MLSS) and biochemical oxygen demand (BOD1) in the waste water in the aeration tank, and the solid-liquid separation tank is the treatment in the solid-liquid separation tank A detection means for detecting suspended solids (SS1) in the wastewater, wherein the discharge tank has a detection means for detecting a biochemical oxygen demand (BOD2) in the treated wastewater in the discharge tank; The adjustment means includes a preset reference value (SS _Base ), a reference value (BOD _Base ) of biochemical oxygen demand and a discharge flow rate (F ₂ ) of the suspended matter of the treated wastewater to be discharged to the outside. From the detected values detected by the detection means, using the following formulas (1) and (2), two supply amounts of a part or all of at least one of the waste water before the introduction of the aeration tank and the waste water during the aeration treatment (F _1SS, F _1BOD Look, the two adopted smaller of the supply amount, based on the adopted feed rate wastewater processing apparatus according to claim 10, wherein adjusting the process wastewater quality that discharged to the outside.

_{F 1SS = {(SS Base -SS1} ) × F 2} / (MLSS-SS1) ··· (1)
F _1SS : Supply amount of drainage from aeration tank to discharge tank (m ³ / day)
MLSS: Detection value of suspended solids in waste water in aeration tank (mg / L)
SS1: Detection value (mg / L) of suspended solids in the treated wastewater in the solid-liquid separation tank
SS _Base : Pre-determined reference value (mg / L) of suspended matter in treated wastewater discharged to the outside
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.

_{F 1BOD = {(BOD Base -BOD2} ) × F 2} / (BOD1-BOD2) ··· (2)
F _1BOD : Amount of wastewater supplied from the aeration tank to the discharge tank (m ³ / day)
BOD1: Detection value of biochemical oxygen demand in waste water in aeration tank (mg / L)
BOD2: Detection value (mg / L) of biochemical oxygen demand in the treated wastewater in the discharge tank
BOD _Base : A predetermined reference value (mg / L) of biochemical oxygen demand for treated wastewater discharged to the outside.
F ₂ : Discharge flow rate (m ³ / day) of treated wastewater to be discharged to the outside.
The water quality adjusting means detects only one of the two suspended substances (MLSS, SS1) and the two biochemical oxygen demands (BOD1, BOD2), and supplies the two supply amounts (F _1SS , F1). _14. The wastewater treatment apparatus according to claim 13, wherein only one of ( _1BOD ) is calculated, and the quality of the treated wastewater discharged to the outside is adjusted based on the calculated supply amount.   The means for detecting the two biochemical oxygen demands (BOD1, BOD2) detects the dissolved oxygen quantity (DO) in the aeration tank and the discharge tank, and the detected value is used as the biochemical oxygen demand (BOD1, The wastewater treatment apparatus according to claim 13, which is means for converting to BOD2).   A bypass flow rate adjustment valve is attached in the middle of the bypass flow path, and the water quality adjustment means determines the supply ratio of at least one of the waste water before the introduction of the aeration tank and the waste water during the aeration treatment, by the bypass flow rate adjustment valve. The wastewater treatment apparatus according to claim 10, wherein the wastewater treatment apparatus is adjusted by the step. The aeration tank and the solid-liquid separation tank are also connected by a return flow path, and the solid-liquid separation tank is connected to a discharge path for excess sludge, and in the solid-liquid separation tank, a part of the sludge is , Returned to the aeration tank by the return flow path, the remainder of the sludge is extracted by the excess sludge extraction flow path, and the aeration tank detects the suspended matter (MLSS) of the waste water during the aeration process. The water quality adjusting means compares a reference value (MLSS _Base ) of the suspended matter of the waste water during the aeration treatment in a preset aeration tank with the detection value detected by the detection means. The waste water treatment apparatus according to claim 10, wherein an amount of excess sludge withdrawn in the solid-liquid separation tank is determined. The aeration tank has a detection means for detecting the biochemical oxygen demand (BOD1) of the waste water during the aeration treatment, and the water quality adjustment means is configured to set a biochemical oxygen demand in a preset aeration tank. The waste water treatment apparatus according to claim 10, wherein the aeration amount in the aeration tank is adjusted by comparing a reference value (BOD1 _Base ) with a detection value detected by the detection means.   The aeration tank is divided into a plurality of parts, whereby the waste water during the aeration process is divided according to the degree of the aeration process, and the water quality adjusting means removes the waste water during the aeration process from at least one of the divided aeration tanks. The wastewater treatment apparatus according to claim 10, wherein the wastewater treatment apparatus supplies the treated wastewater in the discharge tank.   Furthermore, it has a measuring tank provided with a means for detecting suspended solids (SS) and biochemical oxygen demand (BOD). In this measuring tank, the waste water during the aeration process in the aeration tank, and the solid-liquid separation tank At least one wastewater of the treated wastewater and the treated wastewater in the discharge tank is introduced, and the suspended matter (SS) and biochemical oxygen demand of the wastewater introduced into the measurement tank by the detection means of the measurement tank The wastewater treatment apparatus according to claim 13, wherein at least one of the amounts (BOD) is detected.

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