JP7437144B2 - water treatment plant - Google Patents

Description

The present invention relates to water treatment plants.

The biological reaction treatment method for sewage is shown below. The activated sludge method is a biological reaction treatment method for sewage that uses a reaction tank in which aggregates of microorganisms called activated sludge are suspended. The process of removing pollutants using the conventional activated sludge method, which does not use a separation membrane, involves removing pollutants using activated sludge in a reaction tank (adsorption, uptake, oxidation, assimilation, etc.) and solid-liquid separation of activated sludge in a final settling tank. It can be summarized as follows. A part of the activated sludge separated into solid and liquid is sent to a reaction tank as return sludge, mixed with sewage, and used again for sewage treatment. The remainder is treated as surplus sludge.

The main components of pollutants removed by the activated sludge method are organic matter, nitrogen, phosphorus, etc. Note that in addition to the removal of organic matter, the removal of nitrogen, phosphorus, etc. is called advanced treatment. The higher the concentration of activated sludge (higher MLSS concentration), the higher the ability to remove pollutants. On the other hand, the lower the activated sludge concentration (lower MLSS concentration), the higher the solid-liquid separation ability is.

A tilted plate sedimentation device (added to the final sedimentation tank) is a technology that enhances solid-liquid separation performance. Among the types of activated sludge method, there is a rainy weather activated sludge method (3W method) that copes with large flow inflows during rainy weather. In this 3W method, 1Qsh out of 3Qsh (1Qsh is the maximum amount of wastewater per hour) is treated in the front stage of the reaction tank in the same way as the conventional method, and the remaining 2Qsh, which was previously discharged directly, is processed in the rear stage of the reaction tank. Step input and processing.

Membrane separation activated sludge method (MBR) is a process in which activated sludge is used to perform biological reaction treatment on sewage, and then treated water and activated sludge are separated using a separation membrane such as an ultrafiltration membrane or a microfiltration membrane. This is a method to separate and remove activated sludge from treated water. Since activated sludge is separated by external force using a separation membrane, it is possible to set a high activated sludge concentration in the reaction tank during treatment.

Hybrid MBR is a treatment method (water treatment plant) that combines MBR and other treatment methods. When introducing MBR in the renovation and renewal of a medium-sized or large-scale sewage treatment plant that includes multiple water treatment lines, the configuration may be such that the existing lines and MBR lines are used together. Therefore, by emphasizing the merits of the combination of both systems, the overall water treatment can be optimized.

In Patent Document 1, in a hybrid MBR, the capacity of the MBR system can be reduced by burdening the conventional activated sludge process system to deal with large flow inflows (peak inflow water amount), and as a whole, it is possible to reduce the capacity of the MBR system, which is expensive. Techniques have been described that can reduce the number.

Japanese Patent Application Publication No. 2017-113722

In the conventional activated sludge method, in order to achieve both a high MLSS concentration for advanced treatment and a low MLSS concentration for solid-liquid separation, if priority is given to advanced treatment (high MLSS concentration), for example, sludge sedimentation during rainy weather or winter may be reduced. During periods of deterioration, sludge from the final settling tank may leak. On the other hand, when lowering the MLSS concentration to temporarily improve the solid-liquid separation performance during rainwater or a period when sludge settling property deteriorates, the ability to remove organic matter, nitrogen, phosphorus, etc. decreases.

Therefore, in the conventional activated sludge method, a technology is desired that can effectively change the high MLSS concentration for advanced treatment and the low MLSS concentration for solid-liquid separation depending on the situation.

One aspect of the present invention provides a first water treatment system including a first biological reaction tank and a settling tank that separates water from the first biological reaction tank into activated sludge and treated water; a second water treatment line including a second biological reaction tank installed with a separation membrane that separates the treated water from the activated sludge between the first water treatment line and the second biological reaction tank; are mutually fed, and the amount of the activated sludge fed in at least one direction between the first water treatment line and the second biological reaction tank can be adjusted.

According to one aspect of the present invention, in the conventional activated sludge method, the high MLSS concentration for advanced treatment and the low MLSS concentration for solid-liquid separation can be effectively changed depending on the situation.

1 shows a schematic flow of a water treatment plant according to an example. A detailed flow of a water treatment plant according to an example is shown. An example of a mechanism for mutually feeding mud between reaction tanks is shown. This figure shows the cross-sectional structure of the trough and the gate weir installed in the trough. This shows the flow of water when the amount of sewage flowing into the primary settling tank is greater than a predetermined value, such as during rainy weather. Another example of the flow of water when the amount of sewage flowing into the initial settling tank is greater than a predetermined value, such as during rainy weather, will be shown. Another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line is shown. Another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line is shown. Another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line is shown. Another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line is shown. Another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line is shown. Another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line is shown.

Embodiments will be described below with reference to the accompanying drawings. It should be noted that this embodiment is merely an example for implementing the present invention, and does not limit the technical scope of the present invention.

<Outline of water treatment plan>
FIG. 1 shows a schematic flow of a water treatment plant according to an example. The water treatment plant is a hybrid type that includes different types of water treatment lines, including a pre-treatment facility 10 into which sewage, which is water to be treated, flows, and a first water treatment line 11 provided downstream of the pre-treatment facility. and a second water treatment line 12. Water treatment plant control system 14 controls the operation of the water treatment plant.

Sewage flows into pretreatment equipment 10 . Pretreatment equipment 10 physically removes solids from sewage. The pretreatment equipment 10 can use, for example, a precipitation separation, a flotation separation, or a solid-liquid separator.

Water from the pretreatment facility 10 flows into the first water treatment line 11 . The water treatment plant includes a plurality of modes; in one mode, water from the pretreatment facility 10 flows into the first water treatment train 11 without entering the second water treatment train 12. In another mode, water from the pretreatment facility 10 flows into the second water treatment train 12 in addition to the first water treatment train 11 . For example, the control system 14 switches the operating mode depending on the expected inflow amount of sewage, and controls the flow of water from the pretreatment facility 10 depending on the selected mode. In another example, the water from the pretreatment facility 10 may always flow into two water treatment trains 11, 12.

The first water treatment line 11 performs biological reaction treatment of sewage, specifically, advanced treatment (removal of nitrogen, phosphorus, etc. in addition to organic matter removal) using a conventional activated sludge method. The first water treatment line 11 includes a conventional activated sludge method water treatment facility 111, a final settling tank 112 installed downstream of the conventional activated sludge method water treatment facility 111, and a final settling tank 112 installed downstream of the final settling tank 112. This includes disinfection equipment 13 in the latter stage.

The conventional activated sludge method water treatment equipment 111 removes pollutants such as organic matter, nitrogen, and phosphorus through biological reaction treatment using activated sludge. The final settling tank 112 separates water flowing from the conventional activated sludge method water treatment equipment 111 into a supernatant liquid and activated sludge by gravity settling. The supernatant liquid after sedimentation separation is sent to disinfection equipment 13. A part of the activated sludge that has been sedimented and separated is returned to the conventional activated sludge method water treatment facility 111 as return sludge (not shown in FIG. 1).

The disinfection equipment 13 disinfects the supernatant from the final settling tank 112 by bringing a disinfectant (sodium hypochlorite solution, liquefied chlorine, etc.) into contact with the supernatant. The treated water flowing out of the disinfection equipment 13 is discharged into public water bodies such as rivers.

The second water treatment line 12 includes membrane separation activated sludge (MBR) water treatment equipment 121 . The MBR water treatment equipment 121 performs biological reaction treatment of sewage using activated sludge, and performs membrane separation treatment of treated water and activated sludge using a separation membrane such as an ultrafiltration membrane or a microfiltration membrane, thereby removing water from the treated water. Separate and remove activated sludge. The treated water from the MBR water treatment facility 121 is used as reclaimed water or the like, or is discharged into public water bodies such as rivers together with the treated water from the first water treatment line 11.

In the water treatment plant shown in FIG. 1, activated sludge is transferred between a first water treatment line 11 and a second water treatment line 12. One or both of the sludge feeding amounts can be adjusted, and by adjusting the sludge feeding amount, the activated sludge concentration (MLSS concentration) in the first water treatment line 11 that uses the conventional activated sludge method can be adjusted depending on the situation. It can be adjusted to the desired value.

For example, when improving the processing capacity of the advanced treatment of the first water treatment line 11, the water treatment plant increases the amount of mud sent from the second water treatment line 12 to the first water treatment line 11. The amount is increased relative to the amount of mud sent from the to the second water treatment line 12. As a result, the first water treatment line 11 has a high MLSS concentration. As will be described later, the MLSS concentration of the activated sludge sent from the second water treatment line 12 using MBR is higher than the MLSS concentration in the conventional activated sludge method water treatment facility 111.

The high MLSS concentration in the first water treatment line 11 can compensate for the decrease in biological phosphorus removal capacity due to the decrease in substrate concentration in sewage, and eliminates or reduces the need for flocculants for solid-liquid separation. be able to. In addition, by increasing the MLSS concentration, it is possible to suppress the introduction of oxygen into the anaerobic part due to excessive aeration that inhibits biological phosphorus removal.

For example, when temporarily improving the solid-liquid separation performance of the final settling tank 112 during rainy weather, the water treatment plant changes the amount of mud sent from the first water treatment line 11 to the second water treatment line 12 to the second water treatment line 112. 12 to the first water treatment line 11. As a result, the first water treatment line 11 has a low MLSS concentration.

In one example, when the amount of inflowing sewage is normal, the water treatment plant does not allow the water from the pretreatment equipment 1 to flow directly into the second water treatment train 12, but allows the entire amount to flow into the first water treatment train 11. . The second water treatment line 12 mainly uses membrane separation treatment, and the first water treatment line 11 mainly uses biological treatment. If the amount of inflowing sewage exceeds the amount of water that can be treated, for example, the water treatment plant causes the water from the pretreatment facility 1 okara to also directly flow into the second water treatment line 12 .

In MBR, high MLSS concentration causes a decrease in oxygen dissolution efficiency. Therefore, the amount of air (energy consumption) required for biological reaction treatment (removal of organic matter, nitrogen, etc.) is greater than in conventional activated sludge methods. As mentioned above, during normal times, the first water treatment line 11, which conventionally uses the activated sludge method, performs biological treatment with higher oxygen dissolution efficiency than the second water treatment line 12, which uses MBR, so energy can be saved. . Furthermore, by operating the MBR intermittently at a fixed rate, the amount of aeration cleaning of the separation membrane unit can be reduced, resulting in energy savings.

In addition, a hybrid water treatment plant that includes an MBR water treatment line and a water treatment line that uses a settling tank increases the amount of water that can be treated in the same space, and allows for renovations and upgrades in a limited space. , business continuity can be ensured.

Although FIG. 1 shows one first water treatment line 11 and one second water treatment line 12, the water treatment plant may include a plurality of first water treatment lines and a plurality of second water treatment lines. I can do it. One second water treatment line mutually transports activated sludge with one or more first water treatment lines.

<Details of water treatment plant>
FIG. 2 shows a detailed flow of the water treatment plant according to the example. The water treatment plant includes a first settling tank 201, a first reaction tank (first biological reaction tank) 239, and a final settling tank 257, in order from the inflow side (upstream side) of sewage, which is water to be treated. The water treatment plant further includes a second reaction tank (second biological reaction tank) 207. The first reaction tank 239 and the final settling tank 257 constitute a first water treatment train using a conventional activated sludge method, and the second reaction tank 207 constitutes a second water treatment train using MBR. In FIG. 2, the control system 14 is omitted.

The first sedimentation tank 201 includes an inflow channel 203 into which sewage flows, and a subsequent sedimentation tank 205. Sewage flows into the settling basin 205 through the inflow waterway 203, and in the settling basin 205, the solid content contained in the sewage is first sedimented and separated as settling basin sludge by gravity settling. The initial sedimentation tank sludge is transferred to sludge treatment through a pump (not shown).

The water to be treated (sewage) from which the solid content has been removed in the first settling tank 201 flows into the first reaction tank 239 . Although not shown in FIG. 2, pretreatment equipment for removing fibrous substances (hair, etc.) that cause membrane clogging (entanglement) is generally installed between the first settling tank 201 and the first reaction tank 239. (It is installed downstream of the discharge of simple treated water). Alternatively, instead of the first settling tank 201, a pretreatment facility having the above function and the function of the first settling tank may be provided.

In the example of FIG. 2, the first reaction tank 239 performs advanced treatment of the water to be treated using an anaerobic, anoxic, and aerobic method. The first reaction tank 239 includes, from the upstream side, an inflow waterway 241, an anaerobic tank 243, an anoxic tank 245, and an aerobic tank 247. The anaerobic anoxic aerobic method utilizes excessive phosphorous uptake by activated sludge and nitrification-denitrification reactions.

Water to be treated from the final settling tank 257 and return sludge 267 from the final settling tank 257, which will be described later, flow into the inflow waterway 241. The mixed water of the water to be treated and the returned sludge flows into the anaerobic tank 243 from the inflow waterway 241 . Further, a part of the mixed water in the anoxic tank 245 at the latter stage is supplied to the anaerobic tank 243 by the pump 249 . Oxygen is not supplied to the anaerobic tank 243, and the activated sludge is in an anaerobic state. Microorganisms in the activated sludge ingest organic matter in the mixed water and release phosphorus.

The mixed water from the anaerobic tank 243 flows into the anoxic tank 245 at the subsequent stage. Oxygen is not supplied to the anoxic tank 245. Microorganisms in the activated sludge reduce nitrate nitrogen and nitrite nitrogen in the mixed water to nitrogen gas. Nitrogen gas is released into the air. In this way, nitrogen is removed in the anoxic tank 245. Note that part of the mixed water may be circulated from the aerobic tank 247 in the latter stage to the anoxic tank 245. Thereby, denitrification efficiency can be increased.

The mixed water from the anoxic tank 245 flows into the subsequent aerobic tank 247. An air diffuser 251 is installed inside the aerobic tank 247. Blower 253 supplies air containing oxygen to air diffuser 251 via piping 255. The air diffuser 251 provides air bubbles to the mixed water in the aerobic tank 247 .

In the aerobic tank 247, microorganisms in the activated sludge breathe with the supplied oxygen. In aerobic conditions, microorganisms decompose organic matter and ingest more phosphorus than released in the anaerobic tank 243. This removes phosphorus from the sewage. Furthermore, the microorganism converts organic nitrogen in the mixed water into ammonia nitrogen, and further converts ammonia nitrogen into nitrate nitrogen or nitrite nitrogen (nitrification).

The mixed water containing activated sludge from the aerobic tank 247 flows into the final settling tank 257 . The final settling tank 257 separates activated sludge and supernatant liquid (solid-liquid separation). The final sedimentation tank 257 includes an inflow channel 259 and a sedimentation tank 261 on the downstream side thereof. Water from the aerobic tank 247 flows into the settling tank 261 via the inflow waterway 259. In the settling tank 261, the activated sludge is separated from the supernatant by gravity settling.

The supernatant liquid is discharged as treated water after being disinfected if necessary. A portion of the separated activated sludge is transferred as surplus sludge 265 to sludge treatment via pump 263. Another part of the separated activated sludge is returned to the inflow waterway 241 as return sludge 267 via the pump 263. Returned sludge 267 is reused for biological reaction treatment of sewage. The second reaction tank 207 includes a membrane separation tank 213. In the configuration example of FIG. 2, the second reaction tank 207 is configured only with a membrane separation tank 213.

Mutual feeding of activated sludge is performed between the second reaction tank 207 and the first reaction tank 239. In this specification, in mutual sludge feeding between the platforms of the first water treatment train and the second water treatment train, the part from which activated sludge flows out is referred to as the sludge transport stage, and the part into which activated sludge flows is referred to as the sludge receiving stage. do.

In the example of FIG. 2, mixed water 271 containing activated sludge flows from the aerobic tank 247 (sludge feeding stage) of the first reaction tank 239 into the membrane separation tank 213 (sludge receiving stage). Further, the mixed water 273 from the membrane separation tank 213 (sludge feeding stage) flows into the anoxic tank 245 (sludge receiving stage) of the first reaction tank 239. By sending slurry from the membrane separation tank 213 to the stage before the aerobic tank 247, the MLSS concentration in the first reaction tank 239 can be adjusted more appropriately, and further, by sending the slurry to the anoxic tank 245, the oxygen concentration etc. in the anaerobic tank 243 can be adjusted. A decrease in phosphorus release due to an increase in phosphorus can be avoided.

A separation membrane unit 223 is installed inside the membrane separation tank 213. The separation membrane unit 223 includes, for example, one or more separation membranes such as an ultrafiltration membrane or a microfiltration membrane, and a pipe that holds the separation membranes and transports treated water separated by the separation membranes. For example, treated water that has been sucked in by a pump (not shown) and passed through a separation membrane is reused or discharged through a pipe. Due to the membrane separation process, the activated sludge concentration (MLSS concentration) in the membrane separation tank 213 increases. That is, mixed water (activated sludge) with a high MLSS concentration is sent from the second reaction tank 207 to the first reaction tank 239 .

In the membrane separation tank 213, an air diffuser 219 is installed below the separation membrane unit 223. The other diffuser 221 is installed at a position away from the separation membrane unit 223. Blower 225 supplies air containing oxygen to air diffuser 219 via piping 229. Blower 227 supplies air containing oxygen to air diffuser 221 via piping 231.

The air diffuser 219 emits air bubbles into water (diffuses air) mainly for aeration cleaning of the separation membrane unit 223. The air bubbles and upward flow from the air diffuser 219 prevent the surface of the separation membrane from being covered with activated sludge. The aeration device 221 mainly diffuses air in order to equalize the activated sludge concentration (MLSS concentration) of the mixed water in the membrane separation tank 213. The air diffusers 219 and 221 perform intermittent air diffusion, for example.

Since the water in the membrane separation tank 213 contains activated sludge and is supplied with oxygen, nitrification and phosphorus uptake by microorganisms are performed similarly to the aerobic tank 247 of the first reaction tank 239. In a configuration in which the second reaction tank 207 (membrane separation tank 213) mainly performs membrane separation treatment and the first reaction tank 239 mainly performs biological reaction treatment, oxygen is supplied to the membrane separation tank 213 for biological reaction treatment. There's no need. By reducing the amount of air diffused from the air diffusers 219 and 221, energy consumption can be reduced. Moreover, it is possible to prevent the oxygen concentration of the mixed water in the membrane separation tank 213 from becoming too high.

The control system 14 controls the mutual feeding amount between the first reaction tank 239 and the second reaction tank 207 automatically or in response to instructions from an operator. Thereby, the MLSS concentration in the first water treatment series is controlled to a desired value.

For example, in order to increase the processing capacity by increasing the MLSS concentration in the first reaction tank 239, the control system 14 sends sludge from the aerobic tank 247 of the first reaction tank 239 to the membrane separation tank 213 of the second reaction tank 207. The amount of mud sent from the membrane separation tank 213 to the anoxic tank 245 of the first reaction tank 239 is increased.

Further, for example, in order to improve the solid-liquid separation performance of the final sedimentation tank 257 by reducing the MLSS concentration of the mixed water from the aerobic tank 247 that flows into the final sedimentation tank 257, the control system 14 controls the first reaction tank 239. The amount of mud sent from the aerobic tank 247 to the membrane separation tank 213 of the second reaction tank 207 is increased, and the amount of mud sent from the membrane separation tank 213 to the anoxic tank 245 of the first reaction tank 239 is decreased. Note that in order to adjust the MLSS concentration in the first reaction tank 239, the control system 14 may adjust only one of the mud feeding amounts.

An example of a method of controlling the amount of mutually fed mud by the control system 14 will be described. Various sensors are installed at many locations in a water treatment plant to monitor the status of the water treatment plant. By obtaining the measured values from these sensors, the control system 14 can determine the inflow amount, inflow water quality (current value and predicted value), status of reaction tanks 2 and 239 (MLSS concentration, dissolved oxygen concentration, pH, etc.), and processing. Water quality (SS (suspended solids) concentration, organic matter, nitrogen, phosphorus, etc.) can be monitored.

For example, the control system 14 uses predicted values of the amount of sewage inflow and the quality of inflow water to optimize the MLSS from the viewpoint of biological reaction treatment in the first reaction tank 239 and solid-liquid separation in the final settling tank 257. Determine the concentration, and use that value as a target to determine the amount of mutually transferred mud.

The control system 14 obtains past actual measurement data from, for example, the flow rate measurement value of a flow meter installed upstream of the first settling tank 201 and the amount of rainfall in the treatment area measured by a rain gauge in the treatment area. Refer to this to predict future sewage inflow.

The control system 14 calculates the upper limit MLSS concentration for the amount of flow into the final settling tank 257 under conditions in which sludge does not flow out from the final settling tank 257. The control system 14 can calculate the upper limit MLSS concentration for the inflow from the analytical model of the final settling tank 257. Many analytical models are known, any of which may be used.

For example, the control system 14 determines, based on the relationship between the sludge interface depth (distance from the water surface) at the outlet of the final settling tank 257 and the outlet depth of the final settling tank 257, the maximum sludge at which sludge does not flow out from the final settling tank 257. The interface height can be determined. Furthermore, the upper limit MLSS concentration corresponding to the maximum sludge interface height is determined according to a preset analytical model.

Many models are known that show the relationship between sludge interface height and MLSS concentration, any of which can be used. For example, the descending velocity V of the sludge interface can be expressed as a function of water temperature, MLSS concentration, and sludge volume index. In addition, the sludge interface depth D1 at the distance L1 from the inlet of the final settling tank is a function of, for example, the descending speed V, the depth of the final settling tank, the surface area of the final settling tank, the total length of the final settling tank, the inflow amount, etc. It can be expressed as

The control system 14 further determines the amount of sewage inflow to the first reaction tank 239 that can achieve the target treated water quality (SS, organic matter, nitrogen, phosphorus, etc.) from the amount of inflow to the final settling tank 257 and the upper limit MLSS concentration. , calculated from a preset formula. The control system 14 determines the target MLSS concentration, also taking into consideration energy saving (pump power, blower power). The control system 14 determines the mutual feed amount from the target MLSS concentration and the amount of sewage flowing into the first reaction tank 239. Note that the amount of sewage that exceeds the determined amount of sewage flowing into the first reaction tank 239 is, for example, simply discharged.

The control system 14 monitors the above-mentioned various values of the water treatment plant, and periodically or when an unsteady state such as a typhoon is predicted, or if there is a sign of abnormality in the monitored values (for example, when a predetermined monitoring value is (exceeding a predetermined value), it is determined whether the target MLSS concentration is appropriate, and if necessary, the target MLSS concentration is recalculated and reflected in the amount of mutual mud feeding.

In one example, the amount of mud sent from the aerobic tank 247 to the membrane separation tank 213 is such that the hydraulic retention time (HRT) of the membrane separation tank 213 is 3 hours or more in order to prevent residual organic matter, residual nitrogen, etc. As in, controlled. Furthermore, the amount of activated sludge sent from the membrane separation tank 213 to the anoxic tank 245 is basically equivalent to the amount of excess sludge generated in the membrane separation tank 213.

The control system 14 may automatically control the mutual pumping (circulation) between different water treatment trains of activated sludge, or display the information necessary for controlling the mutual pumping, for example in a display device. This may assist operators in managing the operation of the water treatment plant. This makes it easier to reduce the risk of sludge outflow in the final settling tank and achieve the target treated water quality in the complicated operational management of water treatment plants that use different treatment methods.

Next, an example of a mechanism for mutually feeding mud between the first reaction tank 239 and the second reaction tank 207 will be described. In one example, mutual feeding is performed by a water level difference between the two reaction tanks 207, 239. By not using a pump, energy consumption can be reduced. FIG. 3A shows an example of a mutual pumping mechanism between reaction tanks 207 and 239. In the example of FIG. 3A, the membrane separation tank 213 of the second reaction tank 207 in the center is sandwiched between two first reaction tanks 239 on both sides.

A plurality of troughs 281 extend between the anoxic tanks 245 of the first reaction tanks 239 on both sides and the membrane separation tank 213 in the center. The activated sludge (mixed water) in the central membrane separation tank 213 passes through these troughs 281 and flows into the anoxic tanks 245 on both sides. Similarly, a plurality of troughs 281 extend between the aerobic tanks 247 of the first reaction tanks 239 on both sides and the membrane separation tank 213 in the center. The activated sludge (mixed water) in the aerobic tanks 247 on both sides passes through these troughs 281 and flows into the membrane separation tank 213 in the center. The activated sludge in one tank flows into the other reaction tank through the trough 281 due to the water level difference between the tanks.

FIG. 3B shows a cross-sectional structure of the trough 281 and the gate weir 283 installed in the trough 281. The gate weir 283 is installed in each tank, and changes the opening area of the inlet and outlet of the trough 281 by moving up and down. The control system 14 can control the amount of mud sent from one tank to the other tank by controlling the height of the gate weir 283.

The mutual control of the amount of mud fed between different water treatment systems is not limited to the combination of troughs and gate weirs, and any mechanism can be used. For example, automatic control of valve opening adjustment, pump flow rate control, etc. Can be used. For example, activated sludge is sent from the membrane separation tank 213 to the first reaction tank 239 by the above method, and final sedimentation is sent from the first reaction tank 239 to the membrane separation tank 213. By closing the outflow gate to pond 257, activated sludge may be pumped through the trough. This point is the same in the examples described later with reference to FIGS. 8 to 10.

In the above example, the water to be treated flows directly from the initial settling tank 201 only into the first reaction tank 239, but does not flow directly into the second reaction tank 207. In another example, the control system 14 may cause a portion of the treated water from the first settling tank 201 to also flow into the second reaction tank 207 when the amount of incoming sewage is large. Thereby, a decrease in the biological reaction processing capacity of the first reaction tank 239 can be suppressed.

FIG. 4A shows the flow of water when the required treatment capacity (amount of water to be treated) is greater than a predetermined value, such as during rainy weather or when other treatment equipment (not shown) in the water treatment plant is stopped. The differences from FIG. 2 will be explained. There is an inflow 301 of water to be treated from the first settling tank 201 to the first reaction tank 239, and an inflow 302 of water to be treated to the second reaction tank 207. Further, the water to be treated that cannot be treated in the first and second reaction tanks 239 and 207 is discharged as simply treated water 303. Note that when the water to be treated is directly flowed into the membrane separation tank 213 in this way, there is no difference in water level between the membrane separation tank 213 and the first reaction tank 239, so a pump is used to mutually feed mud.

FIG. 4B shows another example of water flow when the required treatment capacity (amount of water to be treated) is greater than a predetermined value, such as during rainy weather or when other treatment equipment (not shown) in the water treatment plant is stopped. show. In this example, instead of discharging the simple treated water shown in FIG. 4A, a wet-weather activated sludge method (3W method) is applied to the example shown in FIG. 2. The control system 14 supplies 1Qsh (311) of 3Qsh (1Qsh is the maximum hourly amount of wastewater) to the inflow waterway 241 of the first reaction tank 239, and supplies the remaining 2Qsh (313) to the aerobic tank 247. Similar to the example shown in FIG. 4A, there is also an inflow 315 of the water to be treated into the second reaction tank 207.

When the water to be treated flows from the initial settling tank 201 to the membrane separation tank 213 as described with reference to FIG. 4A or 4B, the control system 14 automatically or in response to an operator's instructions controls the flow of the water into the membrane separation tank 213. By controlling the aeration in the membrane separation tank 213, the biological treatment capacity in the membrane separation tank 213 may be increased. By controlling the amount of air diffused (including the frequency of air diffusion) from the air diffusers 219 and 221, an anaerobic region and/or anoxic region is formed on the upstream side in the membrane separation tank 213, and a preferable region is formed on the downstream side. It is possible to form an air region. For example, the amount of air diffused by the upstream air diffuser is reduced, and the amount of air diffused by the downstream air diffuser is increased.

Furthermore, by installing a circulation pump in the membrane separation tank 213 and returning (circulating) some of the mixed water from the downstream side to the upstream side, the biological reaction treatment can be made more efficient. In addition, in FIG. 4A, two air diffusers 219 and 221 are shown as an example, but it is possible to install more air diffusers in the membrane separation tank 213, and air diffusers from these can be installed. By controlling the amount, an anaerobic region, anoxic region, or an aerobic region can be formed more effectively.

If the water to be treated increases, the control system 14 may further adjust the mutual sludge between the first reaction tank 239 and the second reaction tank 207. For example, the feeding of slurry from the aerobic tank 247 of the first reaction tank 239 to the membrane separation tank 213 is stopped, and the slurry is fed from the anoxic tank 245 or the anaerobic tank 243 of the first reaction tank 239 to the membrane separation tank 213. Thereby, the biological reaction treatment in the membrane separation tank 213 can be enhanced.

As mentioned above, by mutually feeding activated sludge between the first reaction tank 239, which uses the conventional activated sludge method, and the membrane separation tank 213, the first reaction tank 239 can be adjusted appropriately depending on the situation. MLSS concentration can be controlled.

Note that the configurations of the water treatment plans shown in FIGS. 2 to 4B are merely examples, and other configurations are possible. For example, an inclined plate settling device (not shown) may be installed in the settling tank 261 to improve the solid-liquid separation ability of the final settling tank. In addition, in order to cope with the phenomenon of inhibition of biological phosphorus removal (phosphorus release and uptake) due to a decrease in substrate concentration during rainy weather, etc., flocculant addition equipment may be added, and the flocculant is aerobically removed. May be added in tank.

The anaerobic section, anoxic section, and aerobic section in the reaction tank may be separated into different tanks as in the above example, or may be separated within one tank. In addition to the anaerobic anoxic aerobic method, the first reaction tank may use an anaerobic aerobic activated sludge method, a circulating nitrification endogenous denitrification method, an anaerobic nitrification endogenous denitrification method, or the like.

<Other Examples>
Other configuration examples of the hybrid MBR water treatment plant will be described below. FIG. 5 shows another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line. In the following, differences from FIG. 2 will be mainly explained. In the configuration example shown in FIG. 5, mixed water 401 containing activated sludge flows from the anoxic tank 245 of the first reaction tank 239 into the membrane separation tank 213. Further, the mixed water 403 from the membrane separation tank 213 flows into the anaerobic tank 243 of the first reaction tank 239. In this way, by sending the mixed water from the anoxic tank 245 to the membrane separation tank 213, it is possible to avoid overaeration of the mixed water.

The mutual mud feeding shown in FIG. 5 and the mutual mud feeding shown in FIG. 2 may be switchable. For example, the operator selects an appropriate activated sludge circulation path ( (Piping). For example, in the case of overaeration (high dissolved oxygen concentration), the circulation path shown in FIG. 5 is selected, and in the case of insufficient biological reaction treatment (high residual nitrogen concentration, etc.), the circulation path shown in FIG. 2 is selected. The control system 14 may automatically switch the circulation path. Further, the flow path control described with reference to FIG. 4A or FIG. 4B can be applied to the configuration shown in FIG. 5.

FIG. 6 shows another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line. In the following, differences from FIG. 2 will be mainly explained. In the configuration example shown in FIG. 6, the first reaction tank 239 uses an anaerobic and aerobic method, and the anoxic tank 245 is omitted.

Figure 6 shows two circulation paths for activated sludge. In one circulation path, mixed water 411 containing activated sludge flows into membrane separation tank 213 from aerobic tank 247 of first reaction tank 239 . Further, the mixed water 413 from the membrane separation tank 213 flows into the anaerobic tank 243 of the first reaction tank 239. In another circulation path, mixed water 415 containing activated sludge flows into membrane separation tank 213 from anaerobic tank 243 of first reaction tank 239 . Further, the mixed water 413 from the membrane separation tank 213 flows into the anaerobic tank 243 of the first reaction tank 239.

Only one of the circulation paths shown in FIG. 6 may be provided, or both circulation paths may be provided and switchable. For example, in the case of over-aeration (high dissolved oxygen concentration), the mixed water 415 from the anaerobic tank 243 is selected, and when the biological reaction treatment is insufficient (high residual nitrogen concentration, etc.), the mixed water from the aerobic tank 247 is selected. Select 411. The control system 14 may automatically switch the circulation path. Further, the flow path control described with reference to FIG. 4A or FIG. 4B can be applied to the configuration shown in FIG. 6.

FIG. 7 shows another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line. In the following, differences from FIG. 2 will be mainly explained. In the configuration example shown in FIG. 7, mixed water 421 containing activated sludge flows from the aerobic tank 247 of the first reaction tank 239 into the membrane separation tank 213. Further, the mixed water 423 from the membrane separation tank 213 flows into the inflow channel 241 of the first reaction tank 239. When a plurality of first reaction tanks branch from the inflow waterway 241, activated sludge can be sent to the plurality of first reaction tanks simultaneously by sending activated sludge to the shared inflow waterway.

In the configuration example of FIG. 7, the pump 425 sends a part of the mixed water (activated sludge) drawn from the membrane separation tank 213 to the sludge treatment as excess sludge 427, and sends the other part to the mixed water (activated sludge) 423. It is sent to the inflow waterway 241 of the first reaction tank 239 as a liquid. By adjusting the amount of mutual sludge, the amount of excess sludge 265 extracted from the final settling tank 257 of the first water treatment line is reduced, and by increasing the amount of excess sludge 427 extracted from the membrane separation tank 213, the concentration of excess sludge 427 can be reduced. can be increased. Thereby, the processing efficiency of excess sludge 427 can be improved.

By sharing the pump 425 for the mutual feeding of activated sludge and the transfer of excess sludge between the water treatment lines, the equipment configuration can be simplified. Note that the flow path control described with reference to FIG. 4A or FIG. 4B can be applied to the configuration shown in FIG. 7.

FIG. 8 shows another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line. In the following, differences from FIG. 2 will be mainly explained. In the configuration example shown in FIG. 8, activated sludge 435 that has been subjected to solid-liquid separation in the final settling tank 257 of the first water treatment system is sent from the settling tank 261 to the membrane separation tank 213. Further, the mixed water 423 from the membrane separation tank 213 is sent to both the anaerobic tank 243 and the anoxic tank 245 of the first reaction tank 239.

In the configuration example of FIG. 8, the pump 263 sends a part of the activated sludge extracted from the settling tank 261 to the sludge treatment as surplus sludge 265, and sends the other part as return sludge 267 to the first reaction tank 239. The other part 435 is sent to the waterway 241 and the other part 435 is sent to the membrane separation tank 213. In addition, the pump 437 sends a part of the mixed water (activated sludge) drawn from the membrane separation tank 213 to the sludge treatment as surplus sludge 439, and sends the other part to the first reaction tank as the mixed water (activated sludge) 431. 239 to an anoxic tank 245, and the other part is sent to an anaerobic tank 243 as mixed water (activated sludge) 433.

In this way, by mutually feeding activated sludge between the water treatment systems using a pump, the amount of sludge being fed can be easily controlled. Furthermore, the equipment configuration can be simplified by using one pump to send sludge to multiple pipes. Note that the flow path control described with reference to FIG. 4A or FIG. 4B can be applied to the configuration shown in FIG. 8.

FIG. 9 shows another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line. In the following, differences from FIG. 2 will be mainly explained. In the configuration example shown in FIG. 9, activated sludge 443 subjected to solid-liquid separation in the final settling tank 257 of the first water treatment system is sent from the settling tank 261 to the membrane separation tank 213. Further, mixed water 441 from the membrane separation tank 213 is sent to the inflow waterway 241 of the first reaction tank 239.

In the configuration example of FIG. 9, the pump 263 sends a part of the activated sludge extracted from the settling tank 261 to the sludge treatment as surplus sludge 265, and sends the other part as return sludge 267 to the first reaction tank 239. The other part 443 is sent to the waterway 241 and the other part 443 is sent to the membrane separation tank 213. In addition, the pump 445 sends a part of the mixed water (activated sludge) drawn from the membrane separation tank 213 to the sludge treatment as surplus sludge 447, and sends the other part to the first reaction tank as the mixed water (activated sludge) 441. 239 to the inflow waterway 241.

In this way, by mutually feeding activated sludge between the water treatment systems using a pump, the amount of sludge being fed can be easily controlled. Furthermore, the equipment configuration can be simplified by using one pump to send sludge to multiple pipes. Note that the flow path control described with reference to FIG. 4A or FIG. 4B can be applied to the configuration shown in FIG. 9.

FIG. 10 shows another example of mutual feeding of activated sludge between the first water treatment line and the second water treatment line. In the following, differences from FIG. 2 will be mainly explained. In the configuration example shown in FIG. 10, the second reaction tank 207 includes, from the upstream side, an inflow waterway 209, an anaerobic tank 211, an anoxic tank 217, and a membrane separation tank (aerobic tank) 213. A pump 215 is installed inside the anoxic tank 217 to send a portion of the water from the anoxic tank 217 to the anaerobic tank 211.

The second reaction tank 207, like the first reaction tank 239, performs advanced treatment using activated sludge. The water to be treated directly flows from the first settling tank 201 into the second reaction tank 207 . By performing advanced treatment in the second reaction tank 207, the processing capacity of the water treatment plant can be increased.

In the configuration example of FIG. 10, the pump 263 sends a part of the activated sludge extracted from the settling tank 261 to the sludge treatment as surplus sludge 265, and sends the other part as return sludge 267 to the first reaction tank 239. The other part 451 is sent to the water channel 241 and the other part 451 is sent to the inflow water channel 209 of the second reaction tank 207.

In addition, the pump 455 sends a part of the mixed water (activated sludge) drawn from the membrane separation tank 213 to the sludge treatment as excess sludge 457, returns the other part to the anoxic tank 217 as return sludge 459, and returns the other part to the anoxic tank 217 as return sludge 459. A part of the mixed water (activated sludge) 453 is sent to the inflow waterway 241 of the first reaction tank 239. By returning the returned sludge 459 to the anoxic tank 217 and sending part of the water in the anoxic tank 217 to the anaerobic tank 211, a decrease in phosphorus release in the anaerobic tank 211 is suppressed.

In this way, by mutually feeding activated sludge between the water treatment systems using a pump, the amount of sludge being fed can be easily controlled. Furthermore, the equipment configuration can be simplified by using one pump to send sludge to multiple pipes. Note that the flow path control described with reference to FIG. 4B can be applied to the configuration shown in FIG. 10.

Note that the present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above have been described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace some of the configurations of each embodiment with other configurations.

Further, each of the configurations, functions, processing units, etc. described above may be partially or entirely realized in hardware by designing an integrated circuit, for example. Furthermore, each of the above configurations, functions, etc. may be realized by software by a processor interpreting and executing a program for realizing each function. Information such as programs, tables, files, etc. that implement each function can be stored in a memory, a recording device such as a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card or an SD card. In addition, control lines and information lines are shown that are considered necessary for explanation, and not all control lines and information lines are necessarily shown in the product. In reality, almost all configurations may be considered interconnected.

10 Pretreatment equipment, 11 First water treatment line, 12 Second water treatment line, 13 Disinfection equipment, 14 Control system, 111 Conventional activated sludge method water treatment equipment, 112 Final sedimentation tank, 121 MBR water treatment equipment, 201 First sedimentation Pond, 203, 209, 241, 259 Inflow channel, 205, 261 Sedimentation tank, 207 Second reaction tank, 211, 243 Anaerobic tank, 213 Membrane separation tank, 217, 245 Anoxic tank, 219, 221, 251 Aeration device , 223 Separation membrane unit, 225, 227, 253 Blower, 229, 231, 255 Piping, 239 First reaction tank, 247 Aerobic tank, 257 Final sedimentation tank, 281 Trough, 283 Gate weir, 215, 249, 263, 425 , 437, 445, 455 pump

Claims (3)

a first water treatment system including a first biological reaction tank and a settling tank that separates water from the first biological reaction tank into activated sludge and treated water;
a second water treatment line including a second biological reaction tank equipped with a separation membrane that separates activated sludge and treated water;
a control system;
Activated sludge is mutually fed between the first water treatment line and the second biological reaction tank,
Between the first water treatment line and the second biological reaction tank, the amount of activated sludge sent in at least one direction is adjustable;
The control system determines the MLSS concentration in the first water treatment train based on the measured value in the first water treatment train, and determines the amount of activated sludge sent in at least one direction based on the MLSS concentration,
The first biological reaction tank includes an anaerobic section, an anoxic section downstream from the anaerobic section, and an aerobic section downstream from the anoxic section,
A portion of the water in the anoxic section is returned to the anaerobic section,
The sludge receiving stage through which the activated sludge is fed from the second biological reaction tank is the anoxic section, and the sludge feeding stage through which the activated sludge is sent to the second biological reaction tank is the aerobic section. ,
In a first mode, sewage is allowed to flow into the first water treatment train without flowing into the second water treatment train;
In a second mode, a part of the sewage flows into the first water treatment train, and another part of the sewage flows into the second water treatment train,
In the second mode, the amount of aeration on the upstream side of the second biological reaction tank is lowered and the amount of aeration on the downstream side is increased than in the first mode. A water treatment plant that increases biological reaction treatment capacity in biological reaction tanks . The water treatment plant according to claim 1,
A water treatment plant, wherein at least one direction of mutual feeding of the activated sludge is performed by a water level difference. The water treatment plant according to claim 1,
A water treatment plant, wherein surplus sludge is transferred from each of the first water treatment line and the second water treatment line for treatment.

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