JP5052081B2 - Sewage treatment equipment - Google Patents

Description

  The present invention relates to a wastewater treatment apparatus and relates to a technique for treating wastewater containing nitrogen-containing contaminants.

  Conventionally, as this kind of wastewater treatment method, for example, there is a wastewater treatment method described in Patent Document 1. This is a continuous supply of influent sewage, which is sequentially led to an anaerobic tank, an intermittent aeration tank, and a membrane separation tank. The liquid mixture in the tank is returned to the anaerobic tank only during non-aeration, and the membrane filtrate separated by solid-liquid separation by the membrane separator immersed in the membrane separation tank is taken out as treated water. In the anaerobic tank, non-aerated from the intermittent aeration tank By returning the mixed liquid in the tank only at the time, DO (dissolved oxygen) is prevented from being brought in, and reliable dephosphorization is performed, and intermittent aeration is performed by adjusting the cycle of intermittent aeration according to changes in the quality of influent wastewater. Denitrification is appropriately performed by adjusting DO (dissolved oxygen) in the tank and the membrane separation tank.

  In addition, there is a wastewater treatment method described in Patent Document 2. This is because the water to be treated is continuously supplied to the first treatment tank and intermittent aeration treatment is performed, and the water in the first treatment tank is guided to the second treatment tank in which the separation membrane is disposed, and continuous aeration is performed. And a process of suction filtration through the separation membrane and discharging the permeated water out of the system, and a step of returning a part of the water in the second treatment tank to the first treatment tank. ing.

  Then, the process water is quantitatively fed to the first treatment tank by the raw water pump, the intermittent aeration process in the first treatment tank, the continuous aeration process in the second treatment tank, and the second The water to be treated is continuously treated by simultaneously performing a step of returning a part of the water in the treatment tank to the first treatment tank.

This treatment eliminates the need for nitrification time in the first treatment tank as compared to the intermittent aeration method, so that the formation of an anaerobic state in the first treatment tank is guaranteed, and denitrification is performed reliably. It is.
Other prior art documents include Patent Documents 3 and 4.
JP 2005- 211728 A Japanese Patent No. 3150506 JP-A-11-216493 Japanese Patent Application Laid-Open No. 7-116691

  However, in the conventional configuration, since the sewage flowing into the system is continuously processed, in Patent Document 1, the liquid mixture in the tank is constantly circulated between the intermittent aeration tank and the membrane separation tank. Since the nitrification liquid containing dissolved oxygen flows from the membrane separation tank even during non-aeration in the denitrification process in the aeration tank, it is sometimes difficult to stabilize the denitrification efficiency.

  In addition, since sewage flows into the intermittent aeration tank through the anaerobic tank, a sufficient BOD is not always ensured during the denitrification process in the intermittent aeration tank. Sometimes it becomes difficult.

  Also in Patent Document 2, the mixed liquid in the tank is constantly circulated between the first treatment tank and the second treatment tank, and dissolved oxygen is also removed during non-aeration in which denitrification treatment is performed in the first treatment tank. Since the containing nitrification liquid flows from the second treatment tank, it is sometimes difficult to stabilize the denitrification efficiency.

  The present invention solves the above problems, and provides a sewage treatment apparatus that exhibits excellent nitrogen removal performance under stable denitrification efficiency when sewage containing nitrogen-containing contaminants is nitrified and denitrified. The purpose is to do.

  In order to solve the above-mentioned problems, the wastewater treatment apparatus of the present invention denitrifies during non-aeration when the front tank aeration apparatus in the tank is intermittently operated and the front tank aeration apparatus is stopped for a predetermined stop time. The membrane is separated by the membrane separator in the tank by continuously operating the front tank that performs nitrification during aeration and the rear tank diffuser in the tank. A rear tank that performs treatment and nitrification, a raw water supply system that supplies raw water to the front tank, a feed transfer system that feeds and transfers the liquid mixture in the tank from the front tank to the rear tank, and mixing in the tank from the rear tank to the front tank A return transfer system for returning and transferring the liquid, and supplying the raw water from the raw water supply system to the non-aerated front tank for a predetermined supply time in synchronization with the stop of the front tank aeration apparatus. The transfer of the liquid mixture in the tank by the transfer system is started in synchronization with the operation of the front tank diffuser. Of synchronization with the stop, wherein the stop.

  The sewage treatment apparatus of the present invention intermittently operates the front tank diffuser in the tank, performs a denitrification process during non-aeration to stop the front tank diffuser for a predetermined stop time, The front tank that performs nitrification during aeration when the apparatus is operated for a predetermined operating time, and the rear tank that performs membrane separation processing and nitrification processing by the membrane separation device in the tank by continuously operating the rear tank diffuser in the tank A raw water supply system for supplying raw water to the front tank, a feed transfer system for sending and transferring the liquid mixture in the tank from the front tank to the rear tank, and a return transfer system for returning and transferring the liquid mixture in the tank from the rear tank to the front tank The raw water is supplied over a predetermined supply time from the raw water supply system to the non-aerated front tank in synchronization with the stop of the front tank diffuser, and the transfer of the mixed liquid in the tank by the feed transfer system is performed in the front tank. This is performed continuously when the air diffuser is stopped and operating, and the liquid mixture in the tank is transferred by the return transfer system. Start in synchronism with the operation of the apparatus, characterized by stopping in synchronization with the stop of the front tank air diffuser.

  The sewage treatment apparatus of the present invention intermittently operates the front tank diffuser in the tank, performs a denitrification process during non-aeration to stop the front tank diffuser for a predetermined stop time, The front tank that performs nitrification during aeration when the apparatus is operated for a predetermined operating time, and the rear tank that performs membrane separation processing and nitrification processing by the membrane separation device in the tank by continuously operating the rear tank diffuser in the tank A raw water supply system for supplying raw water to the front tank, a feed transfer system for sending and transferring the liquid mixture in the tank from the front tank to the rear tank, and a return transfer system for returning and transferring the liquid mixture in the tank from the rear tank to the front tank The raw water is supplied over a predetermined supply time from the raw water supply system to the non-aerated front tank in synchronization with the stop of the front tank diffuser, and the mixed liquid in the tank by the feed transfer system and the return transfer system is supplied. Transfer starts after operation of the front tank diffuser after a predetermined interval after stopping the flow of raw water , Wherein the stop in synchronism with the stop of the front tank air diffuser.

  The sewage treatment apparatus of the present invention intermittently operates the front tank diffuser in the tank, performs a denitrification process during non-aeration to stop the front tank diffuser for a predetermined stop time, The front tank that performs nitrification during aeration when the apparatus is operated for a predetermined operating time, and the rear tank that performs membrane separation processing and nitrification processing by the membrane separation device in the tank by continuously operating the rear tank diffuser in the tank A raw water supply system for supplying raw water to the front tank, a feed transfer system for sending and transferring the liquid mixture in the tank from the front tank to the rear tank, and a return transfer system for returning and transferring the liquid mixture in the tank from the rear tank to the front tank The raw water is supplied over a predetermined supply time from the raw water supply system to the non-aerated front tank in synchronization with the stop of the front tank diffuser, and the transfer of the mixed liquid in the tank by the feed transfer system is performed in the front tank. This is performed continuously when the air diffuser is stopped and in operation, and the mixed liquid in the tank is transferred to the raw water by the return transfer system. After a predetermined interval time after the inflow stop it started before the operation of the front tank air diffuser, wherein the stop in synchronism with the stop of the front tank air diffuser.

  Further, a measuring means for measuring at least one of an anaerobic index value indicating anaerobic response performance and an aerobic index value indicating aerobic response performance in the front tank, and an anaerobic index value and an aerobic index value measured by the measuring means Control means for performing cycle adjustment control based on at least one of the measured values, and in the cycle adjustment control, the control means is an intermittent consisting of an operation time and a stop time of the front tank aeration device based on the measurement value of the measurement means. The unit cycle time of the operation cycle is increased or decreased, or the ratio between the stop time and the operation time in the intermittent operation cycle is changed and adjusted.

  Further, a measuring means for measuring at least one of an anaerobic index value indicating anaerobic response performance and an aerobic index value indicating aerobic response performance in the front tank, and an anaerobic index value and an aerobic index value measured by the measuring means Control means for performing interval time adjustment control based on at least one of the measured values, and in the interval time adjustment control, the control means increases or decreases the interval time after stopping the inflow of raw water based on the measurement value of the measurement means. It is characterized by that.

  As described above, according to the present invention, nitrification / denitrification treatment is performed batchwise in the front tank, and nitrification treatment and membrane separation treatment are continuously performed in the rear tank, and the raw water is intermittently supplied and membrane separated. Realizes continuous removal of treated water.

  For this reason, the liquid mixture in the tank is not always circulated between the front tank and the rear tank, but the oxygen-rich nitrification liquid is supplied from the rear tank to the front tank only when the front tank is aerated. When non-aeration is performed, only raw water is supplied from the raw water supply system, and denitrification is performed in an oxygen-free state, so that nitrification and denitrification of sewage containing nitrogen-containing contaminants is excellent under stable denitrification efficiency. Nitrogen removal ability can be exhibited.

  In addition, by performing cycle adjustment control or interval time adjustment control using at least one of an anaerobic index value indicating anaerobic response performance and an aerobic index value indicating aerobic response performance in the front tank as an operation control index, Can be operated. The anaerobic index value includes, for example, the DO reduction rate (in other words, the time required for anaerobicization until the dissolved oxygen concentration reaches O, or the amount of decrease in DO within a predetermined time) when raw water is added. The value includes, for example, a DO increase rate at the start of aeration (in other words, a time required for aerobicization until the dissolved oxygen concentration reaches a predetermined value, or an increase amount of DO within a predetermined time).

  Other examples of the anaerobic index value and the aerobic index value include a decrease rate and an increase rate of ORP. Correlation between DO increase rate or decrease rate and BOD load of raw water, correlation between ORP increase rate or decrease rate and BOD load of raw water, especially DO decrease rate or ORP decrease rate immediately after raw water is added By measuring and evaluating the relationship with the BOD load of the raw water in advance and obtaining the correlation, the evaluation value of the BOD load of the raw water can be determined using the measurement value of the measuring means as an index.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, the sewage treatment apparatus includes a front tank 1 for batch nitrification / denitrification treatment and a rear tank 2 for continuous nitrification treatment and membrane separation treatment, The continuous removal of the treated water after membrane separation is realized.

  The front tank 1 includes a front tank air diffuser 3 in the tank, and the front tank air diffuser 3 includes an air diffuser 4 installed in the tank and a blower 5 connected to the air diffuser 4. The front tank 1 operates the front tank diffuser 3 intermittently, thereby performing a denitrification process when the front tank diffuser 3 stops for a predetermined stop time, and the front tank diffuser 3 is predetermined. Nitrification is performed during aeration during the operation time.

  In addition, a stirrer 6 and a measuring device 7 are installed in the front tank 1, and the measuring device 7 measures a DO meter that measures DO (dissolved oxygen) in the mixed liquid in the tank or an ORP (oxidation-reduction potential). It comprises an ORP meter, and constitutes a measuring means for measuring the DO increasing rate, decreasing rate or ORP increasing rate and decreasing rate with a control device to be described later.

  Furthermore, the raw water supply system 8 provided with the raw water supply pump 8a communicates with the front tank 1, and the raw water supply system 8 supplies the front tank 1 with sewage containing nitrogen-containing contaminants as raw water. The raw water supply pump 8a can be replaced by a valve.

  The rear tank 2 includes a rear tank air diffuser 9 and a submerged membrane separation device 10 disposed above the rear tank air diffuser 9 in the tank, and the rear tank air diffuser 9 is installed in the tank. 11 and a blower 12 connected to the air diffuser 11. The rear tank 2 performs a membrane separation process and a nitrification process by the submerged membrane separator 10 while the rear tank diffuser 9 is continuously operated.

  The submerged membrane separation apparatus 10 includes a plurality of membrane cartridges 14 arranged in parallel inside a casing 13, and a vertical flow path is formed between the membrane cartridges 14 adjacent to each other. Each membrane cartridge 14 has filtration membranes disposed on the front and back surfaces of the filter plate, and the permeate flow path between the filter plate and the filtration membrane communicates with the water collecting pipe 15 via a tube or the like. A suction pump 17 is interposed in the middle of the discharge pipe 16 following the water collection pipe 15, and the suction pressure of the suction pump 17 acts on each membrane cartridge 14 as a driving pressure. In the present embodiment, the suction pressure of the suction pump 17 is the driving pressure, but gravity filtration can also be performed using the water head in the tank as the driving pressure.

  Between the front tank 1 and the rear tank 2, a feed transfer system 19 having a feed transfer pump 18 and a return transfer system 21 having a return transfer pump 20 are provided. The feed transfer system 19 feeds and transfers the mixed liquid in the tank from the front tank 1 to the rear tank 2, and the return transfer system 21 returns and transfers the mixed liquid in the tank from the rear tank 2 to the front tank 1. The return transfer system 21 may be configured such that a valve is interposed in a communication pipe that communicates the front tank 1 and the rear tank 2.

  Connected to the control device 22 are the blower 5, the stirrer 6, the measuring device 7, the raw water supply pump 8, the suction pump 17 of the submerged membrane separation device 10, the feed transfer pump 18, and the return transfer pump 20. The control device 22 controls each device based on the measurement value of the measurement device 7. The control will be described later.

The operation of the sewage treatment apparatus having the above configuration will be described below.
Driving example 1
2 (a) and 2 (b) show the operation state in the first half of the operation cycle, FIGS. 2 (c) and 2 (d) show the operation state in the second half of the operation cycle, and FIG. 6 shows a timing chart of each device. ing.

  As shown in FIGS. 2A and 2B, the denitrification process is performed in an oxygen-free state in the front tank 1 in the first half of the operation cycle. For this reason, the blower 5 of the front tank aeration apparatus 3 is stopped for a predetermined stop time, the stirrer 6 is driven during this time, and the raw water supply pump 8a is operated to supply the raw water from the raw water supply system 8 to the front tank 1. .

  The agitator 6 and the raw water supply pump 8 are activated in synchronization with the stop of the blower 5 of the front tank aeration apparatus 3 at the end of the previous operation cycle, and a predetermined supply from the raw water supply system 9 to the front tank 1 in a non-aerated state. Feed raw water over time (T0-T1). By this supply of raw water, the front tank 1 reaches the highest water level.

  In the rear tank 2 in the first half of the operation cycle, nitrification and membrane separation are performed in an oxygen-rich state. Therefore, the suction pump 17 of the submerged membrane separation apparatus 10 is operated to separate the mixed liquid in the tank through the membrane cartridge 14, and the membrane permeate is taken out of the system through the water collection pipe 15, the discharge pipe 16 and the suction pump 17. .

  Further, the blower 12 of the rear tank aeration device 9 is operated, the air supplied from the blower 12 is diffused as the film cleaning air from the diffusion pipe 11, the film surface of the film cartridge 14 is cleaned, and the mixed liquid in the tank Aeration is performed to supply oxygen.

Next, after the inflow of raw water is stopped (T1), it passes through a predetermined interval time (T1 to T3) and becomes the second half of the operation cycle. At this time, the rear tank 2 is at the lowest water level.
As shown in FIGS. 2 (c) and 2 (d), the nitrification treatment is performed in an oxygen-rich state in the front tank 1 in the later stage of the operation cycle. For this reason, the agitator 6 is stopped, the blower 5 of the front tank aeration apparatus 3 is continuously operated for a predetermined operation time, and the operation of the front tank aeration apparatus 3 is stopped at the initial stage (-T0) of the next operation cycle. To do.

In the rear tank 2 in the later stage of the operation cycle, the nitrification treatment and the membrane separation treatment are performed in an oxygen-rich state following the previous period.
Then, the feed transfer pump 18 and the return transfer pump 20 are activated in synchronization with the start of the operation of the front tank diffuser 3 (T3), and the mixed liquid in the tank is transferred from the front tank 1 to the rear tank 2 by the feed transfer system 19. It is fed and transferred, and the mixed liquid in the tank is returned and transferred from the rear tank 2 to the front tank 1 by the return transfer system 21, and the mixed liquid (nitrification liquid and activated sludge) is circulated between the front tank 1 and the rear tank 2. The operation of the feed transfer pump 18 and the return transfer pump 20 is continued until the initial (−T0) of the next operation cycle, and the tank by the feed transfer system 19 and the return transfer system 21 is synchronized with the stop of the front tank aeration device 3. Stop the transfer of the inner liquid mixture.

  In the operation described above, the mixed liquid in the tank flows into the rear tank from the front tank when the front tank is in an aerated state, so that nitrification treatment of ammonia nitrogen can be performed under perfect aerobic conditions, By circulating the mixed liquid in the tank between the front tank 1 and the rear tank 2 in the later stage of the operation cycle, the activated sludge concentrated by the submerged membrane separation device 10 of the rear tank 2 flows into the front tank 1, and the front tank The sludge concentration of 1 increases to a high concentration.

  In this state, the mixed liquid in the tank is not circulated between the front tank 1 and the rear tank 2 in the first half of the operation cycle, and the front tank 1 subjected to nitrification treatment in the latter stage of the previous operation cycle is in a non-aerated state. Only raw water is supplied from the raw water supply system 8 and denitrification is performed in an oxygen-free state.

  As a result, when sewage containing nitrogen-containing contaminants is nitrified and denitrified, the BOD source of the flowing raw water is used as a BOD source for denitrification, and the nitrogen removal ability is excellent under stable denitrification efficiency in anoxic conditions. Can be demonstrated.

  In addition, environmental conditions can be adjusted by dividing the front tank 1 into the denitrification priority process in the previous period and the nitrification priority process in the latter period, and the rear tank 2 can be adjusted to complete aerobic conditions. Stable and increased denitrification efficiency.

  FIG. 13 shows the change in the nitrogen concentration in the front tank 1. TKN (total Kjelder nitrogen) is constant without decreasing during the previous period, decreases due to nitrification in the latter period, and nitrate nitrogen decreases in the previous period. However, it increases in the latter period.

  FIG. 14 shows the change in the nitrogen concentration in the rear tank 2. TKN (total Kjelder nitrogen) is nitrified during the previous period and maintains 0, and the raw water flows from the front tank 1 in the latter period at a time. Nitrate nitrogen is maintained at a sufficient value so that it has sufficient capacity for nitrification in the first period and flows out into the front tank 1 in the second period, and shows a slight decrease in one period.

  By the way, the amount of raw water input per unit time is constant with respect to the tank capacity, and the amount of raw water supplied per operation cycle is proportional to the amount of raw water supplied per operation cycle. The dilution factor is inversely proportional. At this time, shortening the cycle time of the operation cycle including the first period and the latter period increases the dilution ratio of the raw water with respect to the nitrification liquid. Further, the increase in nitric acid concentration due to the late nitrification treatment is proportional to the length of the aeration operation time. Therefore, the nitric acid concentration does not increase if the cycle time is shortened. As described above, since the nitric acid concentration does not increase and the nitrogen removal rate increases by shortening the operation cycle, it is desirable to shorten the operation cycle.

However, as shown in FIG. 10, the behavior of dissolved oxygen concentration and oxidation-reduction potential in the front tank 1, the oxidation-reduction potential is optimal for denitrification when the operation cycle time is about 50 minutes. Although it decreases to the range of −100 (mV), as shown in FIG. 11, when the operation cycle time is about 25 minutes under the same processing conditions, the oxidation-reduction potential in the front tank 1 is optimized for denitrification −50 It does not drop to the range of -100 (mV).

  As a reference for comparison, as shown in FIG. 12, in the case where the mixed liquid in the tank is continuously circulated throughout the first and second periods and the raw water is continuously charged, the amount of raw water charged per operation cycle time is the same as in FIG. In order to reduce the oxidation-reduction potential in the front tank 1 to the range of −50 to −100 (mV) which is optimal for denitrification, about 100 minutes are required as the operation cycle time.

  For this reason, as in the present embodiment, in the front tank 1 for batch nitrification / denitrification treatment and the rear tank 2 for continuous nitrification treatment and membrane separation treatment, the previous denitrification priority step, By adjusting the environmental conditions separately in the later nitrification priority process, it is possible to realize the environmental condition of the oxidation-reduction potential that is optimal for denitrification in a short operation cycle time.

  However, in order to establish an oxygen-free condition suitable for denitrification in the front tank 1, it is necessary to secure a time for consuming dissolved oxygen and a time required for a denitrification reaction. It is necessary to secure the time required for the reaction. For this reason, making the operation cycle time too short makes it difficult to reliably establish the environmental conditions of the first and second periods.

  For this reason, there is an appropriate value for the operation cycle time, and it is desirable to consume dissolved oxygen at an early stage after charging raw water. In the present embodiment, since the activated sludge concentrated from the rear tank 2 to the front tank 1 is circulated in the latter period to increase the sludge concentration in the front tank when the raw water is charged, the consumption rate of dissolved oxygen is high once. The dissolved oxygen can be consumed at an early stage by adding raw water for the operating cycle in a short time.

  By the way, the correlation between the DO increase rate or decrease rate in the front tank 1 and the BOD load of the raw water, the correlation between the ORP increase rate or decrease rate and the BOD load of the raw water, especially the DO decrease rate immediately after the raw water is added. Alternatively, the evaluation value of the raw water BOD load can be determined using the measured value of the measuring device 7 as an index by measuring and evaluating the relationship between the ORP reduction rate and the raw water BOD load in advance.

  For this reason, the control device 22 calculates the DO increase rate, the decrease rate or the ORP increase rate and the decrease rate based on the measurement value of the measurement device 7, and calculates the DO increase rate, the decrease rate or the ORP increase rate, Based on the decreasing speed, each of the blower 5, the stirrer 6, the measuring device 7, the raw water supply pump 8, the suction pump 17 of the submerged membrane separator 10, the feed transfer pump 18, and the return transfer pump 20 of the front tank aeration device 3. Control the equipment.

  For example, when the raw water is unstable in nature with time variation of the BOD load, the control device 22 determines whether or not based on the measured DO increase rate, decrease rate or ORP increase rate, decrease rate. The unit cycle time of the intermittent operation cycle consisting of the operation time and the stop time of the air diffuser 3 is increased or decreased, or the ratio of the stop time and the operation time in the intermittent operation cycle is changed and adjusted. This makes it possible to exhibit excellent nitrogen removal ability under stable denitrification efficiency.

  Alternatively, the interval until the controller 22 starts the feed transfer pump 18 and the return transfer pump 21 after the inflow of the raw water stops (T1) based on the DO increase rate, the decrease rate or the ORP increase rate, and the decrease rate. Increase or decrease the time.

By the way, when nitrification denitrification treatment is rate-determined by nitrification reaction, that is, there is a case where ammonia nitrogen remains due to insufficient time for nitrification treatment in the operation cycle. The correspondence will be described below. Driving example 2
In the first half of the operation cycle, the water level in the rear tank 2 becomes the lowest water level at the end of the operation cycle. In this state, the membrane surface cleaning effect of the membrane cartridge 14 by the cleaning air is the lowest, so that the water level of the front tank 1 is as high as possible throughout the first and second stages of the operation cycle, and the water levels of the front tank 1 and the rear tank 2 remain the same. It is desirable to do.

  Therefore, as shown in FIGS. 3 (a), 3 (b) and FIG. 8, the raw water supply system 8 is supplied to the front tank 1 in the non-aerated state in synchronization with the stop of the front tank diffuser 3 in the first half of the operation cycle. The raw water is supplied over a predetermined supply time (T0 to T2), the stirrer 6 is driven, the raw water supply pump 8a is operated, and the raw water is supplied from the raw water supply system 8 to the front tank 1. The feed transfer pump 18 of the feed transfer system 19 is operated to transfer the mixed liquid in the tank from the front tank 1 to the rear tank 2.

  The transfer of the liquid mixture in the tank by the feed transfer system 19 is continuously performed when the front tank aeration apparatus 3 is stopped and during operation. During this time, the blower 5 of the front tank diffuser 3 is stopped for a predetermined stop time in the front tank 1, and during this time, denitrification is performed in an oxygen-free state, and in the rear tank 2 nitrification and membrane separation are performed in an oxygen-rich state. Process.

  And after the inflow of raw water stops (T2), it becomes the latter half of an operation cycle through predetermined interval time (T2-T3). As shown in FIGS. 3C and 3D, the nitrification treatment is performed in an oxygen-rich state in the front tank 1 in the later stage of the operation cycle. For this reason, the agitator 6 is stopped, the blower 5 of the front tank aeration apparatus 3 is continuously operated for a predetermined operation time, and the operation of the front tank aeration apparatus 3 is stopped at the initial stage (-T0) of the next operation cycle. To do. The transfer of the liquid mixture in the tank by the return transfer system 19 is started by starting the feed transfer pump 18 in synchronization with the operation of the front tank diffuser 3, and the feed transfer pump in synchronization with the stop of the front tank diffuser 3. Stop 18 and finish.

In the rear tank 2 in the later stage of the operation cycle, the nitrification treatment and the membrane separation treatment are performed in an oxygen-rich state following the previous period.
Driving example 3
As shown in FIGS. 4 (a), (b) and FIG. 7, in order to perform the denitrification process in the oxygen-free state in the front tank 1 in the first half of the operation cycle, During the stop time, the agitator 6 is driven, and the raw water supply pump 8a is operated to supply raw water from the raw water supply system 8 to the front tank 1.

  The agitator 6 and the raw water supply pump 8 are activated in synchronization with the stop of the blower 5 of the front tank aeration apparatus 3 at the end of the previous operation cycle, and a predetermined supply from the raw water supply system 9 to the front tank 1 in a non-aerated state. Feed raw water over time (T0-T1). By this supply of raw water, the front tank 1 reaches the highest water level.

  In the rear tank 2 in the first half of the operation cycle, nitrification and membrane separation are performed in an oxygen-rich state. Therefore, the suction pump 17 of the submerged membrane separation apparatus 10 is operated to separate the mixed liquid in the tank with the membrane cartridge 14, and the membrane permeate is taken out of the system through the water collection pipe 15, the discharge pipe 16 and the suction pump 17. .

  Further, the blower 12 of the rear tank aeration device 9 is operated, the air supplied from the blower 12 is diffused as the film cleaning air from the diffusion pipe 11, the film surface of the film cartridge 14 is cleaned, and the mixed liquid in the tank Aeration is performed to supply oxygen.

  Next, as shown in FIGS. 4 (c) and 4 (d), after the inflow of the raw water stops (T 1), after a predetermined interval time (T 1 to T 2), and before entering the second half of the operation cycle When the rear tank 2 reaches the lowest water level in the middle stage, the feed transfer pump 18 and the return transfer pump 20 are activated, and the feed liquid in the tank is fed from the front tank 1 to the rear tank 2 by the feed transfer system 19 and transferred. The mixed liquid in the tank is returned and transferred from the rear tank 2 to the front tank 1 by the return transfer system 21, and the mixed liquid (nitrification liquid and activated sludge) is circulated between the front tank 1 and the rear tank 2.

  In this middle period, by supplying the mixed liquid in the front tank 1 to the rear tank 2, a part of the ammonia nitrogen in the front tank 1 is preliminarily stored in the rear tank 2 prior to nitrification in the latter stage of the operation cycle. Nitrification is ensured and the nitrification treatment time is ensured substantially longer. For this reason, the load in the nitrification process in the later stage of the operation cycle, which will be described later, that is, ammonia nitrogen in the front tank 1 is reduced, and the nitrification process can be completed within the later operation time.

  In addition, the nitrification liquid nitrified in the rear tank 2 returns to the non-aerated oxygen-free front tank 1 and is denitrified, so that nitric acid that should be denitrified in the first stage of the next operation cycle is also removed. Since the nitriding treatment is performed, the denitrification treatment is substantially accelerated.

The interval time (T1 to T2) needs to be set within a range where the anaerobic condition of the front tank 1 is not broken.
Then, after the feed transfer pump 18 and the return transfer pump 20 are started, that is, the feed mixture 19 starts feeding and transferring the liquid mixture in the tank from the front tank 1 to the rear tank 2, and the return transfer system 21 starts the rear tank 2. From the start to the front tank 1, the mixed liquid in the tank is returned and started to be transferred, and then after the predetermined interval time (T2 to T3), the latter stage of the operation cycle.

  As shown in FIGS. 4E and 4F, the nitrification treatment is performed in an oxygen-rich state in the front tank 1 in the later stage of the operation cycle. For this reason, the agitator 6 is stopped, the blower 5 of the front tank aeration apparatus 3 is continuously operated for a predetermined operation time, and the operation of the front tank aeration apparatus 3 is stopped at the initial stage (-T0) of the next operation cycle. To do. The feed transfer pump 18 and the return transfer pump 20 continue to operate until the initial stage (−T0) of the next operation cycle, and the tank by the feed transfer system 19 and the return transfer system 21 is synchronized with the stop of the front tank aeration device 3. Stop the transfer of the inner liquid mixture.

In the rear tank 2 in the later stage of the operation cycle, the nitrification treatment and the membrane separation treatment are performed in an oxygen-rich state following the previous period.
Further, the control device 22 calculates the DO increase rate, the decrease rate or the ORP increase rate and the decrease rate based on the measurement value of the measurement device 7, and the calculated DO increase rate, the decrease rate or the ORP increase rate and the decrease. Based on the speed, the blower 5, the stirrer 6, the measuring device 7, the raw water supply pump 8, the suction pump 17 of the submerged membrane separation device 10, the feed transfer pump 18, and the return transfer pump 20 based on the speed. Control, adjust the interval time after stopping the inflow of raw water, and delay or speed up the timing to start the feed transfer pump 18 and the return transfer pump 20, excellent under stable denitrification efficiency Nitrogen removal ability can be demonstrated.
Driving example 4
Also in the above-described operation, it is desirable that the water level of the front tank 1 is as high as possible throughout the first and second stages of the operation cycle, and that the water levels of the front tank 1 and the rear tank 2 change equally.

  For this reason, as shown in FIGS. 5A, 5B, and 9, the raw water supply system 8 is supplied to the front tank 1 in the non-aerated state in synchronization with the stop of the front tank diffuser 3 in the first half of the operation cycle. The raw water is supplied over a predetermined supply time (T0 to T2), the stirrer 6 is driven, the raw water supply pump 8a is operated, and the raw water is supplied from the raw water supply system 8 to the front tank 1. The feed transfer pump 18 of the feed transfer system 19 is operated to transfer the mixed liquid in the tank from the front tank 1 to the rear tank 2.

  The transfer of the liquid mixture in the tank by the feed transfer system 19 is continuously performed when the front tank aeration apparatus 3 is stopped and during operation. During this time, the blower 5 of the front tank diffuser 3 is stopped for a predetermined stop time in the front tank 1, and during this time, denitrification is performed in an oxygen-free state, and in the rear tank 2 nitrification and membrane separation are performed in an oxygen-rich state. Process.

Then, as shown in FIGS. 5 (a) and 5 (b), when the inflow of raw water stops (T2) and in the middle period before the latter half of the operation cycle, the return transfer pump 20 is started and the return transfer is started. The mixed liquid in the tank is returned and transferred from the rear tank 2 to the front tank 1 by the system 21, and the mixed liquid (nitrification liquid and activated sludge) is circulated between the front tank 1 and the rear tank 2. The subsequent operation and effect are the same as those of the operation example 3, and the description is omitted.
Example 5
In the operation example 1 described above, the DO increase rate, the decrease rate or the ORP increase rate, the decrease rate are adopted as the anaerobic index value and the aerobic index value that are the indexes of the operation control of the present invention, and the DO increase rate, the decrease rate are reduced. Cycle adjustment control or interval time adjustment control was performed based on the rate or the rate of increase or decrease in ORP. That is, in the cycle adjustment control, the unit cycle time is adjusted to increase or decrease, or the ratio between the stop time and the operation time in the intermittent operation cycle is changed and adjusted. In the interval time adjustment control, the interval time after stopping the inflow of raw water was increased or decreased.

  By the way, for an anaerobic index value which is an index of operation control in the present invention, that is, an anaerobic response performance in the front tank 1, as another example, DO reduction rate (in other words, dissolved oxygen concentration at the time of charging raw water) It is also possible to adopt the DO increase rate at the start of aeration as another example for the aerobic index value, that is, the response performance of aerobicization. It is.

Then, based on the anaerobic index value and the aerobic index value, cycle adjustment control or interval time adjustment control or cycle adjustment control and interval time adjustment control are combined.
Cycle adjustment control Cycle adjustment control increases or decreases the unit cycle time of the intermittent operation cycle consisting of the operation time and stop time of the front tank diffuser 3, or changes the ratio of the stop time and operation time in the intermittent operation cycle To be adjusted. This is intended to adjust the flow rate, concentration, etc., and when the raw water load is low, especially when the raw water flow rate is low, the anaerobic response performance deteriorates. If the time required for anaerobicization until the concentration reaches O becomes 5 minutes or more and becomes extremely slow, the cycle time is extended.

  FIG. 19 shows BOD load, cycle time, time until DO becomes 0, and return start time when control is not performed. FIG. 18 shows BOD load, cycle time, DO when cycle adjustment control is performed. This shows the time until the value of 0 and the return start time.

表１に示すように、サイクルの嫌気開始時におけるＤＯ減少速度がサイクルを重ねるにつれて遅くなり、サイクルの好気化開始時におけるＤＯ増加速度がサイクルを重ねるにつれて速くなる場合には、設計最大流量よりも原水の流量が減っていることが要因であると判断し、サイクル調整制御においてサイクル時間を長くすることで脱窒時間を確保して、制御を行なわない場合に増加するＮＯｘを抑制する。

As shown in Table 1, when the DO decrease rate at the start of the anaerobic cycle becomes slower as the cycle is repeated and the DO increase rate at the start of the aerobic cycle becomes faster as the cycle is repeated, Judging that the flow rate of the raw water is a factor, the cycle time is increased in the cycle adjustment control to secure the denitrification time, and the NOx that increases when the control is not performed is suppressed.

  Also, if the DO decrease rate at the start of anaerobic cycle increases as the cycle repeats and the DO increase rate at the start of cycle aerobic decreases as the cycle repeats, the flow rate of raw water gradually increases Is determined as a factor, and in the cycle adjustment control, the cycle time is shortened to increase the dilution rate, and the TKN that increases when the control is not performed is suppressed.

あるいは表２に示すように、サイクルの嫌気開始時におけるＤＯ減少速度がサイクルを重ねるにつれて遅くなり、サイクルの好気化開始時におけるＤＯ増加速度がサイクルを重ねるにつれて速くなる場合には、原水濃度が平均濃度よりも減っていることが要因であると判断し、サイクル調整制御においてサイクル時間を長くすることで脱窒時間を確保して、制御を行なわない場合に増加するＮＯｘを抑制する。

Alternatively, as shown in Table 2, when the DO decrease rate at the start of anaerobic cycle becomes slower as the cycle is repeated, and the DO increase rate at the start of cycle aerobicization becomes faster as the cycle is repeated, the raw water concentration is averaged. It is determined that the concentration is lower than the concentration, and by increasing the cycle time in the cycle adjustment control, the denitrification time is secured, and NOx that increases when the control is not performed is suppressed.

Also, if the DO decrease rate at the start of anaerobic cycle increases as the cycle repeats and the DO increase rate at the start of cycle aerobic rate decreases as the cycle repeats, the raw water concentration increases from the average concentration, or It is determined that the increase in the MLSS concentration is a factor, and in the cycle adjustment control, the cycle time is shortened to increase the dilution rate, and the NOx that increases when the control is not performed is suppressed.
Interval time adjustment control The interval time adjustment control is to increase or decrease the interval time after stopping the inflow of raw water. This is for the purpose of adjusting the concentration, etc. When the load due to the raw water increases, oxygen is consumed due to residual ammonia, etc., and the aerobic response performance deteriorates. When the DO increase rate becomes slow, the interval time is shortened.

  For example, as shown in Table 3, when the DO decrease rate at the start of the anaerobic cycle becomes faster as the cycle is repeated and the DO increase rate at the start of the aerobic cycle becomes slower as the cycle is repeated, However, it is judged that the increase in the raw water concentration or the increase in MLSS concentration is the cause, and the interval time is shortened and the feed time is shortened in the interval time adjustment control. TKN which increases when performing is suppressed.

  Also, when the load of raw water is larger than the original planned load and the response performance of anaerobic is excessive, the time required for anaerobic until the dissolved oxygen concentration becomes O when the raw water is charged is too short, and aerobic When the DO response speed deteriorates, that is, when the DO increase rate at the start of air diffusion slows, cycle adjustment control and interval time adjustment control are combined.

  FIG. 17 shows changes in load, cycle time, time until DO becomes 0, and return start time when cycle adjustment control and interval time adjustment control are performed in combination.

例えば、表３に示すように、サイクルの嫌気開始時におけるＤＯ減少速度がサイクルを重ねるにつれて速くなり、サイクルの好気化開始時におけるＤＯ増加速度がサイクルを重ねるにつれて遅くなる場合には、平均濃度よりも原水濃度が増え、あるいはＭＬＳＳ濃度が増えたことが要因であると判断し、インターバル時間調整制御においてインターバル時間を短くして、送り時間を早めるとともに、サイクル調整制御においてサイクル時間を短くすることで、ＮＯｘおよびＴＫＮの増加を抑制する。

For example, as shown in Table 3, when the DO decrease rate at the start of the anaerobic cycle becomes faster as the cycle is repeated and the DO increase rate at the start of the aerobic cycle becomes slower as the cycle is repeated, In addition, it is judged that the increase in raw water concentration or the increase in MLSS concentration is the cause, shortening the interval time in the interval time adjustment control, shortening the feed time, and shortening the cycle time in the cycle adjustment control , NOx and TKN increase are suppressed.

  As a result, as shown in FIG. 20, when the control is not performed, when the load increases, here, when the number of cycles is about 20 times, the nitrogen concentration tends to increase. By combining the adjustment control and the interval time adjustment control, the nitrogen concentration can always be suppressed to a low concentration.

  Even if the cycle time (dilution ratio) adjustment or interval time adjustment is not successful, there may be factors such as a load exceeding the plan or an unexpected oxygen consumption substance. In this case, it is effective to change the ratio of the intermittent aeration stop time and the operation time as control for preventing a significant deterioration in nitrogen removal. For example, if oxygen consumption increases at a higher MLSS than expected, it appears as an increase in the DO reduction rate, but if this is not solved easily by adjusting the cycle time (dilution factor) or adjusting the interval time, it is unexpected. It is determined that the situation is in effect, and the oxygen supply amount is increased by decreasing the intermittent aeration stop time ratio and increasing the operation time ratio. There is also an opposite situation, in which case the oxygen supply amount is reduced by increasing the intermittent aeration stop time ratio and decreasing the operation time ratio.

The flow sheet figure which shows the wastewater treatment apparatus in embodiment of this invention Schematic showing Operation Example 1 of the sewage treatment apparatus Schematic showing Operation Example 2 of the sewage treatment apparatus Schematic showing Operation Example 3 of the sewage treatment apparatus Schematic showing Operation Example 4 of the wastewater treatment apparatus Timing chart in operation example 1 of the sewage treatment apparatus Timing chart in operation example 3 of the sewage treatment apparatus Timing chart in operation example 2 of the sewage treatment apparatus Timing chart in operation example 4 of the sewage treatment apparatus Graph showing changes in dissolved ozone concentration and oxidation-reduction potential in the operation cycle of the wastewater treatment device Graph showing changes in dissolved ozone concentration and oxidation-reduction potential in the operation cycle of the wastewater treatment device Graph showing changes in dissolved ozone concentration and oxidation-reduction potential in the operation cycle of the wastewater treatment device The graph which shows the change of TKN and NOx in the front tank in the operation example 1 of the wastewater treatment apparatus The graph which shows the change of TKN and NOx in the rear tank in the operation example 1 of the wastewater treatment apparatus The graph which shows the change of TKN and NOx in the front tank in the operation example 1 of the wastewater treatment apparatus The graph which shows the change of TKN and NOx in the rear tank in the operation example 1 of the wastewater treatment apparatus The figure which shows the change in load, cycle time, time until DO becomes 0, and return start time in the case of performing in combination with cycle adjustment control and interval time adjustment control in Operation Example 5 of the wastewater treatment apparatus The figure which shows the load in the case of performing the cycle adjustment control, the cycle time, the time until DO becomes 0, and the return start time in the operation example 5 of the wastewater treatment apparatus The figure which shows the change in load, cycle time, time until DO becomes 0, and return start time in the case of not performing control in the operation example 5 of the sewage treatment apparatus. The figure which shows the change of nitrogen concentration when not performing control, when performing cycle adjustment control, and when performing cycle adjustment control and interval time adjustment control in combination

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front tank 2 Rear tank 3 Front tank air diffuser 4 Air diffuser pipe 5 Blower 6 Stirrer 7 Measuring device 8 Raw water supply system 8a Raw water supply pump 9 Rear tank air diffuser 10 Submerged membrane separator 11 Air diffuser 12 Blower 13 Casing 14 Membrane cartridge 15 Water collection pipe 16 Discharge pipe 17 Suction pump 18 Feed transfer pump 19 Feed transfer system 20 Return transfer pump 21 Return transfer system 22 Controller

Claims (6)

Operate the front tank diffuser in the tank intermittently, perform denitrification treatment during non-aeration when the front tank diffuser stops for a predetermined stop time, and operate the front tank diffuser for a predetermined operation time Supply the raw water to the front tank that performs nitrification during aeration, the rear tank aeration apparatus in the tank, and the membrane separation and nitrification treatment by the membrane separator in the tank, and the front tank A front tank aeration apparatus comprising a raw water supply system, a feed transfer system for sending and transferring the mixed liquid in the tank from the front tank to the rear tank, and a return transfer system for returning and transferring the mixed liquid in the tank from the rear tank to the front tank. The raw water is supplied from the raw water supply system to the non-aerated front tank for a predetermined supply time in synchronization with the stop of the operation, and the mixed liquid in the tank is transferred by the feed transfer system and the return transfer system. The sewage treatment is characterized by starting in synchronization with the stop and stopping in synchronization with the stop of the front tank diffuser Location. Operate the front tank diffuser in the tank intermittently, perform denitrification treatment during non-aeration when the front tank diffuser stops for a predetermined stop time, and operate the front tank diffuser for a predetermined operation time Supply the raw water to the front tank that performs nitrification during aeration, the rear tank aeration apparatus in the tank, and the membrane separation and nitrification treatment by the membrane separator in the tank, and the front tank A front tank aeration apparatus comprising a raw water supply system, a feed transfer system for sending and transferring the mixed liquid in the tank from the front tank to the rear tank, and a return transfer system for returning and transferring the mixed liquid in the tank from the rear tank to the front tank. The raw water is supplied from the raw water supply system to the non-aerated front tank for a predetermined supply time in synchronization with the stoppage of the tank, and the transfer of the mixed liquid in the tank by the feed transfer system is stopped when the front tank aeration device is stopped and in operation. It is performed continuously, and the transfer of the mixed liquid in the tank by the return transfer system is started in synchronization with the operation of the front tank diffuser. , Sewage treatment apparatus characterized by stopping in synchronization with the stop of the front tank air diffuser. The front tank diffuser in the tank is operated intermittently, the degassing process is performed during non-aeration when the front tank diffuser is stopped for a predetermined stop time, and the front tank diffuser is operated for a predetermined operation time. Supply the raw water to the front tank that performs nitrification during aeration, the rear tank aeration apparatus in the tank, and the membrane separation and nitrification treatment by the membrane separator in the tank, and the front tank A front tank aeration apparatus comprising a raw water supply system, a feed transfer system for sending and transferring the mixed liquid in the tank from the front tank to the rear tank, and a return transfer system for returning and transferring the mixed liquid in the tank from the rear tank to the front tank. The raw water is supplied from the raw water supply system to the non-aerated front tank for a predetermined supply time in synchronization with the stoppage of the tank, and the transfer of the mixed liquid in the tank by the feed transfer system and the return transfer system is stopped after the flow of the raw water is stopped. It starts before the operation of the front tank diffuser after an interval time and is the same as the stop of the front tank diffuser. Sewage treatment apparatus characterized by stops. The front tank diffuser in the tank is operated intermittently, the degassing process is performed during non-aeration when the front tank diffuser is stopped for a predetermined stop time, and the front tank diffuser is operated for a predetermined operation time. Supply the raw water to the front tank that performs nitrification during aeration, the rear tank aeration apparatus in the tank, and the membrane separation and nitrification treatment by the membrane separator in the tank, and the front tank A front tank aeration apparatus comprising a raw water supply system, a feed transfer system for sending and transferring the mixed liquid in the tank from the front tank to the rear tank, and a return transfer system for returning and transferring the mixed liquid in the tank from the rear tank to the front tank. The raw water is supplied from the raw water supply system to the non-aerated front tank for a predetermined supply time in synchronization with the stoppage of the tank, and the transfer of the mixed liquid in the tank by the feed transfer system is stopped when the front tank aeration device is stopped and in operation. Continuously transfer the liquid mixture in the tank by the return transfer system after stopping the inflow of raw water. Started before the operation of the front tank air diffuser through the interval time, before tank air diffuser for sewage treatment apparatus characterized by stopping in synchronization with the stop. Measuring means for measuring at least one of an anaerobic index value indicating anaerobic response performance and an aerobic index value indicating aerobic response performance in the front tank, and at least an anaerobic index value and an aerobic index value measured by the measuring means Control means for performing cycle adjustment control based on one measurement value,
In the cycle adjustment control, the control means adjusts the unit cycle time of the intermittent operation cycle consisting of the operation time and the stop time of the front tank diffuser based on the measurement value of the measurement means, or the stop time in the intermittent operation cycle The wastewater treatment apparatus according to any one of claims 1 to 4, wherein the proportion of the operation time is changed and adjusted. Measuring means for measuring at least one of an anaerobic index value indicating anaerobic response performance and an aerobic index value indicating aerobic response performance in the front tank, and at least an anaerobic index value and an aerobic index value measured by the measuring means Control means for performing interval time adjustment control based on one measurement value,
5. The wastewater treatment apparatus according to claim 3, wherein in the interval time adjustment control, the control unit adjusts the interval time after stopping the inflow of the raw water based on the measurement value of the measurement unit.

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