JP7754142B2 - Wastewater treatment method - Google Patents

Description

The present invention relates to a wastewater treatment method that estimates the wastewater load at the wastewater treatment inlet, allocates high-load wastewater to a separate storage tank based on the estimated wastewater load to prevent the wastewater treatment from failing, and delivers high-load wastewater at times when the wastewater load is low, thereby stabilizing the wastewater treatment.

The concentration and volume of wastewater discharged from beverage, food, and other manufacturing plants often fluctuate greatly depending on the product, production volume, and the elapsed time since the production line was cleaned. The optimal operating conditions for wastewater treatment often vary depending on the wastewater load, and large fluctuations in wastewater load can affect the treatment status.

Organic wastewater in particular is typically treated using biological processes such as aerobic and anaerobic treatment, but if the wastewater load is large, the biological treatment may fail due to the organisms exceeding their processing capacity, resulting in problems such as a deterioration in the quality of the treated water.

Furthermore, even in treatments using physical and chemical processes such as the Fenton reaction or adsorption, the amount of chemicals or adsorbents required to be added changes, so it is important to understand the fluctuations in the load of wastewater flowing into the treatment facility.

Conventionally, operators would regularly collect and analyze wastewater samples to determine the wastewater load at the inlet of the wastewater treatment plant. When high-load wastewater flowed in, they would manually take measures such as emergency evacuation to another tank, dilution, or reducing the amount of wastewater entering the treatment plant. However, because this method requires constant manual work, continuous measurement is not possible, and the inflow of high-load wastewater could be overlooked or measures delayed, leading to a breakdown in the wastewater treatment system and a deterioration in the quality of the treated water. Therefore, it is extremely important to continuously monitor the load of inflowing wastewater and take prompt measures to prevent the wastewater treatment system from breaking down.

Patent Document 1 discloses a wastewater treatment device that stabilizes wastewater treatment by allocating treatment processes according to concentration. Specifically, wastewater is divided into high-concentration and low-concentration wastewater based on the measured electrical conductivity of the wastewater. However, the electrical conductivity measured by this method makes it difficult to adequately evaluate pollutants with low conductivity. In addition, high-concentration and low-concentration wastewater are distinguished by comparing the two, and are not limited by numerical values. With this method, the determination of whether the wastewater is high or low in concentration varies depending on the water quality of the wastewater. For example, if high-concentration wastewater continues for a long period of time, there is a concern that wastewater with a concentration that would affect subsequent wastewater treatment may be classified as low-concentration wastewater.

Japanese Patent Application Laid-Open No. 2002-282889

The objective of the present invention is to provide a wastewater treatment method that can stably treat wastewater.

[1] A wastewater treatment method in which wastewater flows into an adjustment tank and is sent from the adjustment tank to wastewater treatment equipment,
Water quality items or operational management items related to wastewater loads are measured continuously or periodically, and the wastewater load at the wastewater inlet (wastewater treatment inlet) to the wastewater treatment facility is estimated using a predetermined calculation formula based on the measured values;
If the estimated wastewater load is less than a predetermined threshold, the wastewater is supplied to the adjustment tank;
When the estimated wastewater load is equal to or greater than the threshold value, the wastewater is branched at a wastewater branch position upstream of the adjustment tank and stored in a high-load adjustment tank.

[2] The wastewater treatment method of [1], wherein the water quality items or operational management items related to the wastewater load include the pollution load of the wastewater or items correlated with the pollution load, and the wastewater flow rate flowing into the wastewater treatment facility.

[3] A wastewater treatment method according to [1] or [2], in which if the wastewater load when water is sent from the high-load adjustment tank and joined downstream of the wastewater branch position is below a predetermined threshold, water is sent from the high-load adjustment tank.

[4] A wastewater treatment method according to [3], in which water is pumped from the high-load adjustment tank and merges downstream of the adjustment tank.

[5] The wastewater treatment method of [3], in which water is pumped from the high-load adjustment tank to the adjustment tank.

According to the present invention, wastewater treatment can be carried out stably.

FIG. 1 is a schematic configuration diagram of a wastewater treatment system according to a reference technology. FIG. 1 is a schematic configuration diagram of a wastewater treatment system according to a reference technology. FIG. 1 is a schematic configuration diagram of a wastewater treatment system according to a reference technology. 1 is a schematic configuration diagram of a wastewater treatment system according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the wastewater treatment system according to the embodiment. FIG. 1 is a schematic configuration diagram of a wastewater treatment system according to a reference technology. 1 is a schematic configuration diagram of a wastewater treatment system according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the wastewater treatment system according to the embodiment. FIG. 2 is a schematic configuration diagram of the wastewater treatment system according to the embodiment. FIG. 2 is a schematic configuration diagram of the wastewater treatment system according to the embodiment. FIG. 1 is a schematic configuration diagram of a wastewater treatment system according to a reference technology. FIG. 1 is a schematic configuration diagram of a wastewater treatment system according to a reference technology. 1 is a schematic configuration diagram of a wastewater treatment system according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the wastewater treatment system according to the embodiment.

A wastewater treatment system according to an embodiment of the present invention receives wastewater in an equalization tank and delivers it from the equalization tank to a wastewater treatment facility. It measures the pollution load upstream of the equalization tank, the flow rate of wastewater flowing into the equalization tank, and the flow rate of wastewater flowing into the wastewater treatment facility, and uses these to estimate the wastewater load at the inlet of the wastewater treatment facility (hereinafter also referred to as the "wastewater treatment inlet"). Furthermore, based on the estimated wastewater load, high-load wastewater is allocated to a separate storage tank to prevent the wastewater treatment from failing, and high-load wastewater is delivered when the wastewater load is low, thereby stabilizing the wastewater treatment.

One or more equalization tanks are provided, and as described below, multiple equalization tanks 1 may be arranged in parallel or in series. Specifications such as the volume of the equalization tank are not particularly limited. Furthermore, the treatment method and number of systems in the wastewater treatment facility are not particularly limited. Treatment methods include, for example, so-called biological treatment, including aerobic and anaerobic treatment, and physicochemical treatments such as Fenton treatment and activated carbon treatment.

Next, we will explain how to estimate the wastewater load at the wastewater treatment inlet using the drawings.

As shown in Figure 1, when a wastewater treatment system includes an equalization tank 1 and wastewater treatment equipment 3 installed downstream of the equalization tank 1, the pollutant load of the wastewater is measured using a pollution load measuring unit 4 installed upstream of the equalization tank 1. In addition, a first flow rate measuring unit 5 is used to measure the flow rate of wastewater flowing into the equalization tank 1, and a second flow rate measuring unit 10 is used to measure the flow rate of wastewater flowing into the wastewater treatment equipment 3.

The adjustment tank 1 has an HRT (hydraulic retention time) of 30 minutes or more in order to regulate and mitigate fluctuations in water quality and quantity.

In this embodiment, an example will be described in which TOC concentration is measured as the pollution load, but the measurement item is not limited to TOC concentration, and other indicators of pollution load, such as COD concentration or SS concentration, may also be used. Furthermore, the pollution load measurement unit 4 may measure items that are correlated with pollution load, such as electrical conductivity or Brix sugar content.

The first flow rate measuring unit 5 can be a flow meter. If the adjustment tank 1 is a batch-flow tank, the first flow rate measuring unit 5 may calculate the flow rate of wastewater flowing into the adjustment tank 1 from the increase in water level per unit time in the adjustment tank 1. Alternatively, if the adjustment tank 1 is a continuous flow tank, the flow rate of wastewater flowing into the adjustment tank 1 may be calculated from the sum of the change in the storage volume of the adjustment tank 1 and the discharge flow rate from the adjustment tank.

The second flow rate measuring unit 10 can be a flow meter. If the adjustment tank 1 is a batch water supply tank, the second flow rate measuring unit 10 may calculate the flow rate of wastewater flowing into the wastewater treatment equipment 3 from the amount of decrease in water level per unit time in the adjustment tank 1.

The pollution load measuring unit 4, first flow rate measuring unit 5, and second flow rate measuring unit 10 continuously or periodically measure the pollution load or related items, which are water quality items or operational management items related to wastewater load, the flow rate of wastewater flowing into the balancing tank 1, and the flow rate of wastewater flowing into the wastewater treatment system, either continuously or at relatively short time intervals.

The calculation unit 6 estimates the TOC concentration at the wastewater treatment inlet (outlet of the equalization tank 1) using the TOC concentration measured by the pollution load measurement unit 4 and the flow rate measured by the first flow rate measurement unit 5. The calculation unit 6 also estimates the wastewater treatment inlet load (kg-TOC/day) using the estimated TOC concentration and the flow rate measured by the second flow rate measurement unit 10.

The TOC concentration at the wastewater treatment inlet can be estimated using the TOC concentration measured by the pollution load measurement unit 4 and the flow rate measured by the first flow rate measurement unit 5 using various proposed concentration calculation models for retention tanks. However, depending on whether the equalization tank 1 is a continuous or batch flow tank, for example, different estimation methods can be used, such as those described below.

<When water is flowing continuously>
Estimation method (1)-1
The TOC concentration (mg/L) at the inlet of the wastewater treatment plant is estimated by taking a moving average of the TOC concentration measured upstream of the adjustment tank 1 over a time period close to the residence time in the adjustment tank 1. For example, if the residence time in the adjustment tank 1 is 50 minutes, the average of the TOC concentration measurement results from the present to 50 minutes ago can be considered to be the TOC concentration at the inlet of the wastewater treatment plant (discharged from the adjustment tank 1).

Estimation method (2)-1
From the TOC concentration and flow rate measured upstream of the adjustment tank 1, the change in the concentration of wastewater flowing into the adjustment tank 1 is estimated using a complete mixing tank model, and the TOC concentration (mg/L) at the wastewater treatment inlet is estimated.

<When passing water through a batch>
Estimation method (3)-1
The TOC concentration (mg/L) at the wastewater treatment inlet is estimated by dividing the total TOC weight (g) that flowed into the adjustment tank 1 by the total water volume (m ³ ) that flowed into the adjustment tank 1. In order to accurately determine the total TOC weight and total water volume that flowed into the adjustment tank 1, it is desirable to obtain an adjustment tank inlet valve open/close signal or a pump start/stop signal, and calculate the load by integrating the TOC concentration and water volume from the inlet valve "open" to "close" or while the pump is operating. If it is difficult to obtain a valve open/close signal or a pump start/stop signal, the timing at which wastewater is flowing into the adjustment tank 1 can be determined from changes in the water level in the adjustment tank 1.

The calculation unit 6 estimates the wastewater load (kg-TOC/day) using the following formula 1 from the TOC concentration at the wastewater treatment inlet estimated using one of the above estimation methods (1)-1, (2)-1, or (3)-1, and the flow rate at the wastewater treatment inlet measured by the second flow rate measurement unit 10.

Equation 1: Wastewater load (kg-TOC/day)=TOC concentration at inlet of wastewater treatment (mg/L)×flow rate at inlet of wastewater treatment (m ³ /h)×24h/1000

As shown in Figure 2, when an adjustment tank 2 is installed in series with the adjustment tank 1 between the adjustment tank 1 and the wastewater treatment equipment 3, the TOC concentration (estimated value A) at the outlet of the adjustment tank 1 is first estimated. One or more adjustment tanks 2 may be installed, and as described below, multiple adjustment tanks 2 may be arranged in parallel. Specifications such as the volume of the adjustment tank 2 are not particularly limited. As with Figure 1, the estimation method differs depending on whether the adjustment tank 1 is a continuous or batch-flow system. In the case of continuous flow, the TOC concentration (estimated value A) at the outlet of the adjustment tank 1 is estimated using the above estimation method (1)-1 or (2)-1, and in the case of batch-flow, estimation method (3)-1.

Next, the TOC concentration (estimated value B) at the wastewater treatment inlet (outlet of adjustment tank 2) is estimated from the TOC concentration (estimated value A) at the outlet of adjustment tank 1 determined as described above and the flow rate of wastewater flowing into adjustment tank 2 measured by third flow measurement unit 8. Here again, the estimation method differs depending on whether adjustment tank 2 is a continuous or batch flow system. In the case of continuous flow, the TOC concentration (estimated value B) at the wastewater treatment inlet is estimated using estimation method (1)-2 or (2)-2 below, and in the case of batch flow, estimation method (3)-2.

Estimation method (1)-2
The TOC concentration (estimated value A) is averaged over a period of time close to the residence time in the adjusting tank 2 to estimate the TOC concentration (mg/L) at the inlet of the wastewater treatment plant.

Estimation method (2)-2
From the TOC concentration (estimated value A) and the flow rate flowing into the adjustment tank 2, the change in the concentration of wastewater flowing into the adjustment tank 2 is estimated using a complete mixing tank model, and the TOC concentration (mg/L) at the wastewater treatment inlet is estimated.

Estimation method (3)-2
The total TOC weight (g) flowing into the adjustment tank 2 is divided by the total amount of water (m ³ ) flowing into the adjustment tank 2 to estimate the TOC concentration (mg/L) at the inlet of the wastewater treatment.

The third flow rate measuring unit 8, which measures the flow rate of wastewater flowing into the equalization tank 2, may be a flow meter, or, if the equalization tank 2 is a batch-flow tank, it may be calculated from the increase in water level per unit time in the equalization tank 2. Alternatively, if the equalization tank 2 is a continuous-flow tank, the flow rate of wastewater flowing into the equalization tank 2 may be calculated from the sum of the change in storage volume in the equalization tank 2 and the discharge flow rate from the equalization tank.

The wastewater load (kg-TOC/day) is estimated using the above formula 1 from the TOC concentration (estimated value B) at the wastewater treatment inlet determined in this way and the flow rate at the wastewater treatment inlet measured by the second flow rate measurement unit 10.

Next, as shown in Figure 3, consider the case where equalization tanks 2A and 2B are installed in parallel between equalization tank 1 and wastewater treatment equipment 3, and wastewater is returned from equalization tank 2B to equalization tank 1. Wastewater flowing out of equalization tank 1 flows into equalization tank 2A or 2B. Wastewater flowing out of equalization tank 2A flows into wastewater treatment equipment 3. Wastewater flowing out of equalization tank 2B is returned to equalization tank 1.

The fourth flow rate measurement unit 13 measures the flow rate of wastewater flowing into the adjustment tank 2B, and may be measured using a flow meter or calculated from the increase in water level per unit time in the adjustment tank 2B. The fifth flow rate measurement unit 15 measures the flow rate of wastewater returned from the adjustment tank 2B to the adjustment tank 1, and may be measured using a flow meter or calculated from the decrease in water level per unit time in the adjustment tank 2B.

In this case, the condition is that the adjustment tank 2B, which returns wastewater to the adjustment tank 1, is a batch water supply tank, and the adjustment tank 1 and adjustment tank 2A may be either continuous water supply tanks or batch water supply tanks. One or more adjustment tanks 2A may be provided, and multiple adjustment tanks 2A may be arranged in parallel.

First, the TOC concentration (estimated value C) of the wastewater in the equalization tank 2B is estimated using the following estimation method (3)-3 from the TOC concentration measured upstream of the equalization tank 1 and the flow rate measured by the fourth flow rate measurement unit 13.

Estimation method (3)-3
The TOC concentration (mg/L) in the adjustment tank 2B is estimated by dividing the total TOC weight (g) flowing into the adjustment tank 2B by the total amount of water (m ³ ) flowing into the adjustment tank 2B.

Next, the TOC concentration at the outlet of the adjustment tank 1 (estimated value D) is estimated from the TOC concentration in the adjustment tank 2B obtained as described above (estimated value C), the flow rate measured by the fifth flow rate measurement unit 15, and the TOC concentration and flow rate measured upstream of the adjustment tank 1. If the adjustment tank 1 is continuously flowing, estimation method (2)-3 is used; if the adjustment tank 1 is batch-flowing, estimation method (3)-4 is used.

Estimation method (2)-3
Using the TOC concentration and flow rate measured upstream of the adjustment tank 1, the TOC concentration (estimated value C) in the adjustment tank 2B, and the flow rate flowing from the adjustment tank 2B into the adjustment tank 1, the change in the concentration of the wastewater flowing into the adjustment tank 1 is estimated using a complete mixing tank model, and the TOC concentration (mg/L) at the outlet of the adjustment tank 1 is estimated.

Estimation method (3)-4
The TOC concentration (mg/L) at the outlet of adjustment tank 1 is estimated by dividing the total TOC weight (g) that flowed into adjustment tank 1 by the total water volume (m ³ ) that flowed into adjustment tank 1. The total TOC weight and total water volume are calculated by adding the TOC weight and water volume measured upstream of adjustment tank 1 to the TOC weight and water volume returned from adjustment tank 2B, respectively.

Next, the TOC concentration (estimated value E) at the wastewater treatment inlet (outlet of adjustment tank 2A) is estimated from the TOC concentration (estimated value D) at the outlet of adjustment tank 1 obtained as described above and the flow rate into adjustment tank 2A. If adjustment tank 2A is continuously flowing, the TOC concentration (estimated value E) at the wastewater treatment inlet is estimated using estimation method (1)-3 or (2)-4; if it is batch flow, estimation method (3)-5.

Estimation method (1)-3
The TOC concentration (estimated value D) is averaged over a period close to the residence time in the adjustment tank 2A to estimate the TOC concentration (mg/L) at the inlet of the wastewater treatment system.

Estimation method (2)-4
From the TOC concentration (estimated value D) and the flow rate flowing into the adjustment tank 2A, the change in the concentration of the wastewater flowing into the adjustment tank 2A is estimated using a complete mixing tank model, and the TOC concentration (mg/L) at the wastewater treatment inlet is estimated.

Estimation method (3)-5
The TOC concentration (mg/L) at the wastewater treatment inlet is estimated by dividing the total TOC weight (g) flowing into the adjustment tank 2A by the total amount of water (m ³ ) flowing into the adjustment tank 2A.

The wastewater load (kg-TOC/day) is estimated using the above formula 1 from the TOC concentration (estimated value E) at the wastewater treatment inlet determined in this way and the flow rate at the wastewater treatment inlet measured by the second flow rate measurement unit 10.

In this embodiment, the pollution load (or items correlated with the pollution load) upstream of the adjustment tank 1, the flow rate of wastewater flowing into the adjustment tank, and the flow rate of wastewater flowing into the wastewater treatment facility are measured, and these are used to estimate the wastewater load at the wastewater treatment inlet. Based on these estimated values, the amount of inflow to the wastewater treatment facility can be controlled, or high-load wastewater can be allocated to a high-load adjustment tank (see Figures 4 to 14), thereby stabilizing wastewater treatment.

A threshold is set for the estimated wastewater load, and if the wastewater load is above the threshold, it is distributed to a high-load adjustment tank, and if it is below the threshold, it is distributed to a normal adjustment tank. The threshold is set under conditions that will prevent wastewater treatment from failing, such as being below the design standard value of the downstream wastewater treatment equipment. In addition to the current wastewater load, the wastewater load of wastewater that passed through several hours ago can also be used to determine the threshold. For example, if the current wastewater load is above set threshold A and the wastewater load from several hours ago was above set threshold B, it may be distributed to the high-load adjustment tank. It is desirable to set thresholds in advance to suit the situation on site.

When water is sent from the high-load adjustment tank to be mixed with wastewater, if the wastewater load at the wastewater treatment inlet is added to the wastewater load sent from the high-load adjustment tank and the combined load is below the set threshold, water will be sent from the high-load adjustment tank. Conversely, if the combined load exceeds the threshold, the water will not be sent and will remain stored in the high-load adjustment tank.

Specific examples of how water is distributed to the high-load adjustment tank and how it is sent from the high-load adjustment tank are explained below.

Figure 4 shows a configuration in which a high-load adjustment tank 12 is installed in the wastewater treatment system shown in Figure 1. In the configuration shown in Figure 4, the high-load adjustment tank 12 is arranged in parallel with the adjustment tank 1. The wastewater delivered by the transfer pump 11 branches upstream of the adjustment tank 1, and by controlling the opening and closing of valves 17A and 17B, it is possible to switch whether the wastewater flows into the adjustment tank 1 or the high-load adjustment tank 12.

The calculation unit 6 acquires the TOC concentration measured by the pollution load measurement unit 4 and the flow rate measured by the first flow rate measurement unit 5, and estimates the TOC concentration at the wastewater treatment inlet using one of the estimation methods (1)-1, (2)-1, or (3)-1 described above. The calculation unit 6 also uses the estimated TOC concentration and the flow rate measured by the second flow rate measurement unit 10 to estimate the wastewater load at the wastewater treatment inlet, and determines whether it is safe for the wastewater to flow into the wastewater treatment facility 3.

Under normal circumstances, wastewater flows into adjustment tank 1. If the calculation unit 6 determines that the estimated wastewater load is above a predetermined threshold and that the wastewater treatment may fail, it closes valve 17A and opens valve 17B, and distributes the wastewater to high-load adjustment tank 12. Even after the wastewater inflow destination is switched to high-load adjustment tank 12, the transfer pump 20 continues to transport the wastewater from adjustment tank 1 to wastewater treatment equipment 3, and the calculation unit 6 continues to estimate the TOC concentration at the wastewater treatment inlet and the wastewater load.

After that, when the estimated wastewater load falls below the threshold, the wastewater inflow destination is switched from the high-load adjustment tank 12 to the adjustment tank 1. The calculation unit 6 also controls the transfer pump 19 to adjust the timing of sending high-load wastewater from the high-load adjustment tank 12 to the wastewater treatment equipment 3 so as not to cause the wastewater treatment to fail. If the wastewater load when the wastewater from the high-load adjustment tank 12 is mixed (confluent) with the wastewater from the adjustment tank 1 downstream of the adjustment tank 1 falls below a predetermined threshold, the calculation unit 6 sends water from the high-load adjustment tank 12. If the wastewater load after mixing is equal to or greater than the threshold, the water is not sent from the high-load adjustment tank 12 and remains stored.

The calculation unit 6 may display the opening and closing timing of valves 17A and 17B on a monitor screen or the like, and an operator may manually control the opening and closing of valves 17A and 17B in accordance with the display. Similarly, the calculation unit 6 may display the water supply timing of transfer pumps 19 and 20 on a monitor screen or the like so that the operator can see the timing, and an operator may manually operate the pumps in accordance with the display. Alternatively, instead of transfer pumps 19 and 20, a transfer pump may be installed downstream of the confluence, and a switching valve may be provided just before the confluence of wastewater from adjustment tank 1 and the high-load adjustment tank, allowing operation with a single transfer pump.

In the configuration shown in Figure 4, the wastewater in the high-load adjustment tank 12 is sent to the wastewater treatment equipment 3, but as shown in Figure 5, the wastewater in the high-load adjustment tank 12 may also be sent to the adjustment tank 1.

In the configuration shown in Figure 6, wastewater is sent to adjustment tank 1 and adjustment tank 1' at will without considering the wastewater pollution load. When sending wastewater to adjustment tank 2, valve 7A is opened and valve 7B is closed. When sending wastewater to adjustment tank 2', valve 7A is closed and valve 7B is opened. In addition, of adjustment tanks 2 and 2', wastewater is sent to wastewater treatment equipment 3 from the adjustment tank that is not sending wastewater. If the calculation unit 6 determines that the wastewater load is high and the wastewater treatment may fail, it controls transfer pumps 19' and 20' to adjust the flow rate of wastewater sent from adjustment tank 1 and adjustment tank 1' so that the wastewater load (TOC concentration x flow rate) is such that the wastewater treatment will not fail. The calculation unit 6 displays the water supply rates of transfer pumps 19' and 20' on a monitor screen or the like, so that operators can operate the pumps manually according to the display. Alternatively, instead of transfer pumps 19' and 20', a transfer pump can be installed downstream of the confluence, and a switching valve can be installed just before the wastewater from adjustment tank 1 and high-load adjustment tank 12 join, allowing operation with a single transfer pump.

Figure 7 shows a configuration in which a high-load adjustment tank 12 is installed in parallel with the adjustment tank 2 of the wastewater treatment system shown in Figure 2. By controlling the opening and closing of valves 7A and 7B, it is possible to switch whether the wastewater delivered from adjustment tank 1 flows into adjustment tank 2 or high-load adjustment tank 12.

The calculation unit 6 acquires the TOC concentration measured by the pollution load measurement unit 4 and the flow rate measured by the first flow rate measurement unit 5, and estimates the TOC concentration at the outlet of the equalization tank 1 using one of the above estimation methods (1)-1, (2)-1, or (3)-1.

The calculation unit 6 estimates the TOC concentration at the wastewater treatment inlet using one of the estimation methods (1)-2, (2)-2, or (3)-2 above, using the estimated TOC concentration at the outlet of the equalization tank 1 and the flow rate of wastewater flowing into the equalization tank 2 measured by the third flow rate measurement unit 8. The calculation unit 6 also estimates the wastewater load at the wastewater treatment inlet using Equation 1 above, based on the estimated TOC concentration at the wastewater treatment inlet and the flow rate at the wastewater treatment inlet measured by the second flow rate measurement unit 10.

Under normal circumstances, wastewater from adjustment tank 1 flows into adjustment tank 2. If the calculation unit 6 determines that the estimated wastewater load is above a predetermined threshold and that the wastewater treatment may fail, it closes valve 7A and opens valve 7B, allowing the wastewater delivered from adjustment tank 1 to flow into high-load adjustment tank 12. Even after the wastewater inflow destination is switched to high-load adjustment tank 12, the transfer pump 20 continues to deliver the wastewater from adjustment tank 2 to wastewater treatment equipment 3, and the calculation unit 6 continues to estimate the TOC concentration at the outlet of adjustment tank 1, the TOC concentration at the wastewater treatment inlet, and the wastewater load.

After that, when the estimated wastewater load falls below the threshold, the wastewater inflow destination is switched from the high-load adjustment tank 12 to the adjustment tank 2. The calculation unit 6 also controls the transfer pump 19 to adjust the timing of sending high-load wastewater from the high-load adjustment tank 12 to the wastewater treatment equipment 3 so as not to cause the wastewater treatment to fail. If the wastewater load when the wastewater from the adjustment tank 2 is mixed with the wastewater from the high-load adjustment tank 12 is below a predetermined threshold, the calculation unit 6 sends water from the high-load adjustment tank 12. If the wastewater load after mixing is equal to or greater than the threshold, the water is not sent from the high-load adjustment tank 12 and remains stored.

In the configuration shown in Figure 7, the opening and closing of valves 7A and 7B was controlled to switch the destination of the wastewater delivered from adjustment tank 1. However, as shown in Figure 8, a transfer pump 18A that delivers water from adjustment tank 1 to adjustment tank 2 and a transfer pump 18B that delivers water from adjustment tank 1 to high-load adjustment tank 12 may be provided, and the on/off of transfer pumps 18A and 18B may be controlled to switch whether the wastewater is delivered to adjustment tank 2 or high-load adjustment tank 12. The calculation unit 6 may display the start/stop timing of transfer pumps 18A and 18B on a monitor screen or the like so that the operator can see the timing, and the operator may manually operate the pumps according to the display.

In the configuration shown in Figure 7, the wastewater in the high-load adjustment tank 12 is sent to the wastewater treatment equipment 3 when the wastewater load decreases, but as shown in Figure 9, the wastewater in the high-load adjustment tank 12 may also be sent to the adjustment tank 2.

In the configuration shown in Figure 9, the opening and closing of valves 7A and 7B was controlled to switch the destination of the wastewater delivered from adjustment tank 1. However, as shown in Figure 10, a transfer pump 18A that delivers water from adjustment tank 1 to adjustment tank 2 and a transfer pump 18B that delivers water from adjustment tank 1 to high-load adjustment tank 12 may be provided, and the start and stop of transfer pumps 18A and 18B may be controlled to switch whether the wastewater from adjustment tank 1 flows into adjustment tank 2 or high-load adjustment tank 12.

In the configurations shown in Figures 7 to 10, wastewater branching occurs downstream of the adjustment tank 1, and is distributed to the high-load adjustment tank 12, which is placed in parallel with the adjustment tank 2, when the wastewater load is estimated to exceed a predetermined value. If the wastewater branching occurs upstream of the adjustment tank 1 and is distributed to the high-load adjustment tank 12, the quality of the wastewater will fluctuate greatly and distribution to the high-load adjustment tank 12 will be frequent. This can place a burden on the operation of opening and closing valves and starting and stopping the transfer pump, especially when performed manually. Therefore, in order to simplify the distribution operation, it is preferable to distribute the wastewater to the high-load adjustment tank 12 downstream of the adjustment tank 1.

Note that the HRT of the adjustment tank 1 in Figures 7 to 10 is preferably between 30 and 60 minutes. At an HRT of 60 minutes or less, the ability of the adjustment tank 1 to level out water quality is low, and it is thought that there will be little difference in the frequency or effectiveness of distribution regardless of whether the water is branched to the high-load adjustment tank 12 upstream or downstream of the adjustment tank 1. Therefore, in this case, it is desirable to branch off downstream of the adjustment tank 1 and install the adjustment tank 2 and high-load adjustment tank in parallel to level out water quality and distribute high-load wastewater.

Furthermore, it is preferable that the HRT of the adjustment tank 2 is approximately 60 minutes to 30 hours. If the HRT is 60 minutes or more, it is believed that the water quality will be sufficiently equalized, but if it is estimated that the wastewater load will exceed a predetermined value despite equalization, the wastewater treatment can be stabilized by allocating the wastewater to the high-load adjustment tank 12 in advance. On the other hand, if the HRT is more than 30 hours, it is unlikely that the wastewater load will exceed the predetermined value, and it is believed that there is no need to allocate the wastewater to the high-load adjustment tank 12.

In the configuration shown in Figure 11, wastewater is sent to adjustment tank 2 and adjustment tank 2' at will without considering the wastewater pollution load. When sending wastewater to adjustment tank 2, valve 7A is opened and valve 7B is closed. When sending wastewater to adjustment tank 2', valve 7A is closed and valve 7B is opened. Furthermore, of adjustment tanks 2 and 2', wastewater is sent to the wastewater treatment equipment 3 from the adjustment tank that is not sending wastewater. Alternatively, as shown in Figure 12, transfer pump 18A that sends water from adjustment tank 1 to adjustment tank 2 and transfer pump 18B that sends water from adjustment tank 2 to adjustment tank 2' may be provided, and the pumps may be started and stopped separately. If calculation unit 6 determines that the wastewater load is high and that wastewater treatment may fail, it controls transfer pumps 19' and 20' to adjust the flow rate of wastewater sent from adjustment tank 2 and adjustment tank 2' so that the wastewater load (TOC concentration x flow rate) is such that wastewater treatment will not fail.

Figure 13 shows a configuration in which the adjustment tanks 2A and 2B of the wastewater treatment system shown in Figure 3 have been replaced with adjustment tank 2 and high-load adjustment tank 12, respectively. By controlling the opening and closing of valves 7A and 7B, it is possible to switch whether wastewater delivered from adjustment tank 1 flows into adjustment tank 2 or high-load adjustment tank 12.

The calculation unit 6 acquires the TOC concentration measured by the pollution load measurement unit 4 and the flow rate of wastewater flowing into the high-load adjustment tank 12 measured by the fourth flow rate measurement unit 13, and estimates the TOC concentration in the high-load adjustment tank 12 using the estimation method (3)-3 described above.

The calculation unit 6 uses the estimated TOC concentration in the high-load adjustment tank 12, the flow rate measured by the fifth flow rate measurement unit 15, the TOC concentration measured by the pollution load measurement unit 4, and the flow rate measured by the first flow rate measurement unit 5 to estimate the TOC concentration at the outlet of the adjustment tank 1 using the estimation method (2)-3 or (3)-4 described above.

Next, the calculation unit 6 uses the estimated TOC concentration at the outlet of the equalization tank 1 and the flow rate of the wastewater flowing into the equalization tank 2 measured by the third flow rate measurement unit 8 to estimate the TOC concentration at the wastewater treatment inlet (outlet of the equalization tank 2) using one of the above estimation methods (1)-3, (2)-4, or (3)-5.

Then, the calculation unit 6 estimates the wastewater load using the above formula 1 from the estimated TOC concentration at the wastewater treatment inlet and the flow rate at the wastewater treatment inlet measured by the second flow rate measurement unit 10.

Under normal conditions, wastewater from adjustment tank 1 flows into adjustment tank 2. If calculation unit 6 determines that the estimated wastewater load is above a predetermined threshold and that wastewater treatment may fail, it closes valve 7A and opens valve 7B, allowing the wastewater delivered from adjustment tank 1 to flow into high-load adjustment tank 12. Even after the wastewater inflow destination is switched to high-load adjustment tank 12, transfer pump 20 continues to deliver wastewater from adjustment tank 2 to wastewater treatment equipment 3, and calculation unit 6 continues to estimate the wastewater load.

After that, when the estimated wastewater load falls below the threshold, the wastewater inflow destination is switched from the high-load adjustment tank 12 to the adjustment tank 2. The calculation unit 6 also controls the transfer pump 19 to adjust the timing of sending high-load wastewater from the high-load adjustment tank 12 to the adjustment tank 1 so as not to cause the wastewater treatment to fail. If the wastewater load when the wastewater from the high-load adjustment tank 12 is returned to the adjustment tank 1 is below a predetermined threshold, the calculation unit 6 sends water from the high-load adjustment tank 12 to the adjustment tank 1. If the wastewater load becomes equal to or exceeds the threshold due to the return, the water is not sent from the high-load adjustment tank 12 and remains stored.

In the configuration shown in Figure 13, the opening and closing of valves 7A and 7B was controlled to switch the destination of the wastewater sent from adjustment tank 1. However, as shown in Figure 14, a transfer pump 18A is provided to send water from adjustment tank 1 to adjustment tank 2, and a transfer pump 18B is provided to send water from adjustment tank 1 to high-load adjustment tank 12. By controlling the start and stop of transfer pumps 18A and 18B, it is possible to switch whether the wastewater from adjustment tank 1 flows into adjustment tank 2 or high-load adjustment tank 12.

In this embodiment configured as described above, high-load wastewater above a preset threshold is diverted to the high-load adjustment tank, preventing the wastewater load in the subsequent wastewater treatment stage from exceeding the set value. By mixing the wastewater diverted to the high-load adjustment tank with raw water so that it does not exceed the set threshold, it can be treated while preventing the wastewater load in the subsequent wastewater treatment stage from exceeding the set value. This is expected to stabilize wastewater treatment.

In the above embodiment, a configuration was described in which the calculation unit 6 performs calculations such as estimating the pollution load at the inlet of the wastewater treatment plant and estimating the wastewater load at the inlet of the wastewater treatment plant. However, the calculation unit 6 may be configured as a single computer, or may perform distributed processing across multiple computers.

The present invention is not limited to the above-described embodiments, and can be embodied by modifying the components within the scope of the spirit of the invention when implemented. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined.

1, 2, 2' Adjustment tank 3 Wastewater treatment equipment 4 Pollutant load measurement unit 5 First flow rate measurement unit 6 Calculation unit 8 Third flow rate measurement unit 10 Second flow rate measurement unit 11, 19, 19', 20, 20' Transfer pump 12 High load adjustment tank 13 Fourth flow rate measurement unit 15 Fifth flow rate measurement unit

Claims (5)

A wastewater treatment method in which wastewater flows into an adjustment tank and is sent from the adjustment tank to wastewater treatment equipment,
The water quality items related to the wastewater load, the flow rate of the wastewater flowing into the adjustment tank, and the flow rate of the wastewater flowing into the wastewater treatment facility are continuously or periodically measured, and the wastewater load at the wastewater inlet (wastewater treatment inlet) to the wastewater treatment facility is estimated using a predetermined calculation formula based on the measured values;
If the estimated wastewater load is less than a predetermined threshold, the wastewater is supplied to the adjustment tank;
When the estimated wastewater load is equal to or greater than the threshold value, the wastewater is branched at a wastewater branch position upstream of the adjustment tank and stored in a high-load adjustment tank. The wastewater treatment method according to claim 1 , wherein the water quality items related to the wastewater load include a pollution load of the wastewater or an item correlated with the pollution load, and the pollution load includes any one of a TOC concentration, a COD concentration, and an SS concentration . The wastewater treatment method of claim 1, wherein water is fed from the high-load adjustment tank if the wastewater load when fed from the high-load adjustment tank and joined downstream of the wastewater branch position is equal to or less than a predetermined threshold. The wastewater treatment method described in claim 3, wherein water is conveyed from the high-load adjustment tank and merged downstream of the adjustment tank. The wastewater treatment method described in claim 3, wherein water is pumped from the high-load adjustment tank to the adjustment tank.