JP2006084240A - Wastewater treatment measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method or apparatus for precisely and quantitatively measuring the BOD of a mixed liquid containing activated sludge and a waste liquid, the BOD of raw water, the activity of activated sludge and the like automatically in a short time as an on-line as an instrument by analyzing the measuring data of the dissolved oxygen concentration (DO), which is obtained by a measuring instrument by sampling the mixture liquid from an aeration tank to aerate it. <P>SOLUTION: The value at the point of time becoming almost constant in the concentration of dissolved oxygen by aerating the mixture liquid sampled from the aeration tank for a sufficiently long period is set to highfinal DO and, after the generalized shift factor Kabs of a substance of an aerator is calculated from a dissolved oxygen concentration change curve again obtained from the low concentration of dissolved oxygen by aeration, a reference liquid is added to calculate the decomposition speed of the reference liquid from a DO change to evaluate the activity of activated sludge. Next, raw water is added to calculate the BOD of raw water from the DO change. The reference liquid is further added to evaluate the toxity of the raw water from a change in decomposition speed. Further, when the time from the start of measurement to the acquirement of highfinal DO is required long, a sampling form is changed to shorten a measuring time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a measurement method and apparatus for a measurement apparatus that measures data necessary for operation management in wastewater treatment using aerobic microorganisms.

Activated sludge treatment is the most general method for treating organic polluted wastewater.
The basic process of wastewater treatment using aerobic microorganisms such as activated sludge is based on the use of dissolved oxygen dissolved in the mixture by aeration of a mixture of wastewater into activated sludge containing aerobic microorganisms in high concentration. This is the process by which microorganisms break down pollutants in wastewater. In general, there are various pollutants in wastewater, and various microorganisms are involved in decomposing the pollutants. The greatest feature of aerobic microbial treatment is that it can respond to various wastewater efficiently by highly concentrating the natural biological activity of acclimatizing various microorganisms corresponding to various pollutants. Because of the activity, it is extremely difficult to quantitatively understand the causal relationship between cause and result. For this reason, the activated sludge treatment will surely purify the treated water from the settling tank, but it is quantitatively determined whether the treatment is currently performed in the aeration tank and that it is normal. Is currently operating in a state that is almost unknown. The biggest reason why activated sludge treatment is in the black box state is that the raw water during operation and the aeration tank cannot be measured quickly during treatment, and the ability of activated sludge to decompose the BOD of raw water This is because there is no means for quantitatively grasping the activity).

Currently, the operation management method generally used is to replace the BOD of raw water and treated water with TOD and COD, and there is no simple means to directly evaluate the activity of activated sludge. Judgment is made indirectly based on the results of oxygen concentration, treated water, and microscopic observation of microorganisms. However, TOD and COD have a bad correlation with BOD when the raw water substrate changes, and it is very specialized to judge the activity of microorganisms from the dissolved oxygen concentration in the aeration tank, the results of treated water, and the observation of microorganisms. Even with knowledge, it can only be qualitative.
A method using a microbial electrode has been put to practical use as a method for rapidly measuring BOD, but the microorganism used for the electrode is a specific microorganism, and waste water of BOD components that can be decomposed by the microorganism can be measured. Wastewater cannot be measured accurately and is not a general-purpose method.

As methods for evaluating the activity of microorganisms, methods for measuring nucleic acids of microorganisms, methods for measuring ATP (adenosine triphosphate), etc. have been proposed, but the activity evaluation of various microbial groups such as activated sludge is proposed. As a method, it is not a general-purpose method, and at least it cannot be used for operation management.

  If the activity of activated BOD and activated sludge can be measured and quantified during the operation management of activated sludge and reflected in the operation operation, the activated sludge can be optimally operated. An effect will be obtained.

  For this reason, the present inventor measures the BOD required for activated sludge treatment in a short time by measuring the behavior of the oxygen consumption rate of the microorganism using a dissolved oxygen concentration meter and analyzing it with a computer, and also the BOD in the raw water. Proposed a method to calculate the decomposition rate of components and quantify the activity of microorganisms, specifically to acquire measurement data of dissolved oxygen concentration, to calculate BOD from the acquired data, and to analyze the decomposition rate of BOD This method is described in detail from the calculation principle (see Patent Document 1).

Based on the same calculation principle, the activated sludge device in operation is installed on the aeration tank, the mixed liquid in the aeration tank is sampled, the BOD of the mixed liquid and the sludge activity are measured, and the measurement ends. A method and apparatus that can collect data necessary for operation management of activated sludge with a frequency close to practical continuous measurement by repeating sampling → measurement is disclosed (see Patent Document 2).

If the method described in Patent Document 1 is used, an analyzer installed in a laboratory can be easily realized. However, in order to make an online instrument of an activated sludge apparatus, what timing should be sampled and what should be It is necessary to specify in detail what to measure in order, and in addition to the need to obtain measurement results in a short time more strongly than lab machines, there are various situations in actual machines, such as extremely bad processing and damage It is necessary to take measures to automatically respond to sludge that has been subjected to the treatment.

The device described in Patent Document 2 can measure the BOD and sludge activity of treated water in a short time of about 30 minutes and has been put into practical use as an automatic operation management control instrument for activated sludge. Because we have in mind, measurement is completed in a short time → a measurement method that places emphasis on the function that is reflected in the control is taken. For example, (1) When the processing is extremely bad, the BOD measurement accuracy of the sampled mixed solution decreases. (2) If the MLSS or sludge viscosity fluctuates, the measurement accuracy of the BOD and decomposition rate will decrease. (3) If the treatment is extremely bad, measure the activity and the BOD of the mixed solution. There are inadequate points such as being unable to be performed at the same time, and it is an effective method when priority is given to control, but it is not necessarily an optimal method when priority is given to measurement accuracy.
JP2001-235462 JP 10-28992 A

  Automatic measurement instruments that manage operation in wastewater treatment using aerobic microorganisms have few technologies in practical use, and even when the method of Patent Document 2 places importance on measurement accuracy, it supports various cases of actual equipment. I'm not sure. The present invention provides a method and apparatus for accurately and quantitatively measuring the BOD of treated water, the BOD of raw water, and the activity of sludge, which are essential in operating and controlling activated sludge, as an on-line instrument.

  Sampling the mixed solution from the aeration tank, charging the mixed solution to the measuring device, aeration with the aeration device, decomposing the BOD in the mixed solution by aeration, the oxygen supply rate of the aeration device and the mixing after decomposition After obtaining the dissolved oxygen concentration (this concentration is referred to as highfinalDO) at the point where the oxygen consumption rate of the liquid balances, after stopping the aeration apparatus and lowering the dissolved oxygen concentration decreased by the oxygen consumption of the mixed solution, Reactivate the aeration device, obtain the mass transfer coefficient (hereinafter referred to as Kabs) of the aeration device by calculation from the rising DO change, add the reference solution, and change the DO by the decomposition of the components by the sludge in the mixture Calculate the decomposition rate of the reference solution from the change, and if the decomposition rate of the reference solution is larger than the preset value stored in the computer, add the raw water after the decomposition of the reference solution and add the component due to sludge in the mixture of The BOD of the raw water was calculated from the DO change varies solution without smaller than the set value to perform the addition of the raw water, the measurement is completed. By repeating this sampling-measurement operation, the BOD of the mixed liquid necessary for the operation of the activated sludge, the sludge activity of the mixed liquid, and the BOD data of the raw water are measured at a frequency practically close to continuous measurement.

Also, compare the decomposition rate of the reference solution before the addition of the raw water and the decomposition rate of the reference solution after the addition of the raw water by adding the raw water and adding the reference solution again after the decomposition and measuring the decomposition rate. And evaluate the toxicity of raw water to activated sludge. Furthermore, when sampling the mixed solution from the aeration tank for repeated measurement in the above, the sampled mixed solution has a large number of unprocessed BODs after charging the mixed solution from the previous measurement to the measuring device and starting aeration. Settings that are stored in advance in the computer for the time required to obtain the dissolved oxygen concentration at the point where the oxygen supply rate of the aeration device and the oxygen consumption rate of the mixture are balanced, for example, If the value is greater than the value, after the measurement is completed, the entire measured mixture is not drained and replaced with a new mixture. The measurement time is shortened by using a mixed liquid of a measured mixed liquid and a new mixed liquid as a measurement target.

  There was no precision instrument capable of automatic and continuous measurement that can measure the activity of treated water BOD, raw water BOD, and sludge, which are essential for operation management with activated sludge. By using the instrument according to the present invention, the activity of these BOD and sludge can be accurately measured in a short time of about 2 hours. By repeating measurement and sampling, automatic measurement can be performed at a frequency close to practical continuous measurement. Moreover, it can be put to practical use as an automatic measuring device in response to various situations of actual machines. As a result, the activated sludge, which could only be handled qualitatively in the past, can be handled quantitatively, and the merit of enabling optimum operation and stable operation is very great.

Since it is necessary for the explanation of the present invention, first, a basic principle of calculation will be briefly described.
When the mixed liquid containing activated sludge and waste liquid is aerated with an aeration device, the dissolved oxygen concentration in the waste water increases with the aeration time, and the change is expressed by equation (1).

  Here, DOsat is saturated dissolved oxygen concentration [mg / l], DO is dissolved oxygen concentration in the aeration tank [mg / l], Kabs is general mass transfer coefficient [1 / min], ASact is oxygen consumption consumed by activated sludge for respiration Rate [mg / l / min], BODact is the oxygen consumption rate [mg / l / min] used by activated sludge to decompose BOD components.

The first term on the right side of equation (1) is the oxygen supply rate from the aeration device, and the second term is the oxygen consumption rate used by activated sludge for respiration and decomposition of BOD.
ASact is the rate of oxygen consumption by basic sludge respiration. Since it is a basal respiration, it is not related directly to the BOD component and is almost constant within a short time. ASact is known to be constant regardless of the DO value if the DO value is approximately 0.5 mg / l or more, and this indicates that the BOD component is almost 0 mg / l of mixed liquid and oxygen is supplied. When the change in DO is measured from a state in which the dissolved oxygen concentration is high with the state turned off, it can be easily verified by a linear decrease.

  BODact is the consumption rate of oxygen used when sludge decomposes BOD components. BODact varies depending on whether the sludge is acclimatized to the substance, the state of sludge, water temperature, pH, habitat environment such as salt concentration. When microorganisms degrade the BOD component, the reaction is carried out by an enzyme or the like corresponding to the BOD component, and each component shows a specific reaction rate. In general, in a process in which an organic substance is finally decomposed into water and carbon dioxide by a microorganism, it passes through several intermediate products, and each intermediate product has its own reaction rate. For this reason, when various BOD components are included such as raw water in wastewater treatment, the reaction process is complicated and overlapped, so it is difficult to specify one-to-one with the BOD component, but the waste liquid is a simple 1 such as methanol or acetic acid. In the case of one BOD component, a constant decomposition rate is exhibited during decomposition, and it can be easily identified one-to-one with the BOD component.

  When BODact changes during the aeration process, equation (1) cannot be easily integrated. However, when the BOD component is a mixture of almost 0 mg / l, BODact in equation (1) is almost 0 and equation (1) is It becomes as follows.

As mentioned above, ASact is almost constant at DO> 0.5mg / l, regardless of DO, so it is generally DO>
In the range of 0.5 mg / l, equation (2) can be easily integrated and expressed by equation (3).
DO = α− (α−DO ₀ ) exp (−Kabs · t) (3) where α = DOsat−ASact / Kabs
DO ₀ is an initial value when aeration is started. In addition, since the expression (3) can neglect the second term on the right side if the aeration elapsed time t becomes sufficiently large.
DO = α = DOsat−ASact / Kabs
If this value is expressed as highfinalDO, highfinalDO can be defined as the DO value that is finally reached when a mixed liquid with a BOD component of almost 0 mg / l is aerated.
DO = highfinalDO− (highfinalDO−DO ₀ ) exp (−Kabs · t) (4) can be rewritten. The change in DO according to equation (4) becomes a curve as shown by the dotted line 1 in FIG.
On the other hand, when a BOD component is present in the mixed solution, BODact has a value that cannot be ignored. Further, since the BODact value mainly changes in the BOD component to be decomposed, it changes from a large value to a small value with the aeration elapsed time t. BODact changes to almost 0 when there is no more BOD component that can be decomposed. Therefore, equation (1) cannot be simply integrated as equation (3), but the change in DO becomes a curve as shown by the solid line curve in FIG. This curve shows that in the case of simple BOD components such as methanol and acetic acid, DO is constant at a low level that balances the oxygen supply rate and the oxygen consumption rate of ASact + BODact during decomposition. It becomes a typical two-step curve as shown by the solid line in FIG. 2 that rises and becomes constant at highfinalDO.

The DO change curve expressed by equation (4) when the initial value DO ₀ at the start of aeration is the same and a mixture with almost 0 mg / l BOD component in the mixture is aerated. When the DO change curve when the mixed liquid is aerated when the BOD component is present in the mixed liquid is represented by the solid line of FIG. 2, the dotted line and the solid line at each aeration elapsed time The value obtained by multiplying the difference between the two values by Kabs represents the oxygen consumption rate used for decomposing BOD at that time = the reaction rate, and the value obtained by integrating this difference by the elapsed aeration time t is surrounded by both curves. The value corresponding to the area S, which is obtained by multiplying this value by Kabs, corresponds to the amount of oxygen used by the microorganism to decompose the BOD component. This value is different from the BOD measurement method defined by JIS, but the measurement principle itself is the same, in which the amount of oxygen required for microorganisms to decompose the BOD component is measured. JIS's BOD measurement method takes a long time of 5 days, but this measurement method uses sludge that has already been well acclimatized and also uses sludge with a high concentration of several thousand ppm, so it takes only a few tens of minutes. A value highly correlated with JIS BOD can be measured. This measurement principle itself is described in detail in Patent Document 1. Patent Document 1 further shows an operation procedure and a calculation procedure for specifically acquiring highfinalDO of the equation (4) and Kabs of the equation (1) in the measuring apparatus.

  Figure 3 shows the BOD value measured by the above measurement principle (hereinafter referred to as “measured BOD”) and the 5-day BOD value determined by JIS (hereinafter referred to as “JISBOD”) by using various waste liquids using the activated sludge. The measurement results are shown in a correlation diagram. As shown in FIG. 3, the measured BOD and JISBOD are almost in good agreement with most measured values. The measurement BOD of the measurement value group in the range of block a in FIG. 3 is smaller than JISBOD. This is the result of measurement using this block in the case where the waste liquid is a waste liquid that is toxic to the activated sludge and the sludge in which the activity of the activated sludge is clearly reduced. The measurement value group in the range of the block b is a result of measuring a special component in which the component of the waste liquid generally belongs to indegradability. In JISBOD, microorganisms cannot cope with the substance and degradation is not successful. However, since the measured BOD uses activated sludge acclimatized to the substance, it shows a greater degradation than JISBOD. In this way, BOD can be measured with high accuracy in a short time of 30 minutes to 100 minutes at most by this measurement method. This method is for measuring raw water and treated water treated with activated sludge with activated sludge, and it goes without saying that it is not possible to measure in any case, but from the viewpoint of managing activated sludge. If the sludge activity is good, it has been demonstrated that the BOD of raw water and treated water can be measured sufficiently by the method of this principle.

Next, an apparatus embodying the present invention will be described. FIG. 4 is a flow sheet of an example apparatus.
3 is an aeration container in which a mixed liquid of activated sludge is placed and aerated. 4 is a measurement container. 3 and 4 are connected by piping at the bottom. 5 is a circulation pump, and 6 is an aeration apparatus. In this apparatus example, an aspirator system is adopted, but a compressor and an air diffuser may be used. 7 is an air flow meter, and 8 is an air solenoid valve. 9 is an electrode of the dissolved oxygen meter. With the circulation pump of 5, the mixture in the apparatus is circulated in the flow of measurement container → aspirator → aeration container → measurement container, air is sucked in the aspirator, aerated in the aeration container, and transferred from the bottom to the measurement container In this way, air bubbles are separated, and the flow velocity of the electrode surface of the dissolved oxygen meter in the measurement container is ensured. 10 is a heater, and 11 is a heat exchange pipe for cooling, in which cooling water flows. 12 is a reference liquid addition pump, and 13 is a raw water addition pump. Reference numeral 14 denotes a drainage electromagnetic valve. 15 is a dissolved oxygen meter, 16 is a control panel, and 17 is a computer. A digital output / analog-to-digital conversion PC card is attached to a PCMCIA adapter and connected to a control panel, and the pump and solenoid valve of the measuring device are controlled by a command from the computer. The dissolved oxygen meter and the computer take the measured values into the computer through the serial port. The control panel is equipped with a temperature controller, and the temperature of the liquid mixture is kept constant by controlling the heater. In addition to this, a sampling device for sampling the mixed solution from the aeration tank is necessary. In this device example, a system using a vacuum pump is employed in connection with the block 3 described later. A system using a meter can also be configured. 18 is a measuring container, 19 is a vacuum pump, 20 is a vacuum solenoid valve, 21 is an air release solenoid valve, 22 is a sampling solenoid valve, and 23 is a metering container drain solenoid valve. The sampling device and the measuring device are connected by 24 communication solenoid valves. The measuring container is equipped with 25 temperature sensors and 26 pressure gauge sensors, and the measured values are taken into the computer via a PC card.

  The operation method will be described below. In order to clarify the difference from Patent Document 2, a description will be given while partially comparing. FIG. 5 is a flowchart for operating the apparatus of FIG. FIG. 1 is a pattern example showing the measurement of the DO change of the measuring apparatus by the measuring operation of the present invention.

First, the operation of the embodiment (block 1) corresponding to claim 1 will be described (except for block 2 and block 3 in the flowchart are the range of block 1).
First, at the beginning of the operation, in the step of sampling the mixed solution from the aeration tank (hereinafter referred to as Step 1), the operations of the flowcharts 1 to 2 are performed. 14 drainage electromagnetic valve is opened, and the measured mixed liquid in the measuring apparatus is drained. Next, the operation of flowchart-2 is performed. Using the sampling device from the aeration tank, sample the mixture into the measuring device. In a specific example of sampling, in the example of the apparatus, from the state that all the solenoid valves are closed, 20 vacuum solenoid valves are opened, 19 vacuum pumps are operated, and 18 measuring containers are decompressed to p1 KPa. Next, the sampling solenoid valve 22 is opened, and the mixed solution in the aeration tank is sucked into the measuring container. When the pressure inside the measuring container reaches p2KPa, the 20 sampling solenoid valves are closed. The amount of the liquid mixture sucked into the measuring container can be calculated from the total space volume V0, p1, and p2 of the measuring container. If the solenoid valve is operated from a computer so that p1 and p2 become a predetermined suction amount, an arbitrary amount of liquid mixture can be sampled. Next, 21 open-air solenoid valve is opened, 24 communication solenoid valve is opened, and the liquid mixture in the measuring container is transferred to the measuring device by a drop.

In Step 1, the present invention and Patent Document 2 are basically the same, but since the method of Patent Document 2 places importance on control, sampling is performed slightly before the aeration tank outlet, which is a point where the processing state is likely to change. On the other hand, in the present invention, it is practical to sample the mixed solution at the outlet of the aeration tank from the viewpoint of measuring the BOD of the treated water. However, the shape of the aeration tank is such that the inlet / outlet is not clear, such as a complete mixing tank type, and the case where the next to the nitrification tank is not necessarily a sedimentation tank, as in the case of biological denitrification, or like batch activated sludge. However, the sampling position is not limited to the above position because the sampling position differs depending on the form of the aeration tank, the purpose of measurement, and the like.

The next step (hereinafter referred to as Step 2) is a step of obtaining the values of highfinalDO and Kabs and measuring the BOD of the mixed solution, and is a part of flowcharts -3 to -10. Steps 2-1 to 2-3 in FIG. 1 are measurement pattern examples of DO change in this step. In this process, the supply of oxygen from the outside is refused in Patent Document 2, and the rate of decrease in dissolved oxygen due to the oxygen consumption rate of sludge is measured, and the next step (hereinafter referred to as Step 3a) is determined based on the magnitude of this oxygen decrease rate. ) Change the measurement method. In other words, if the rate of decrease is greater than the set value, the sludge is active at a high oxygen consumption rate, so the activity is sufficient, but the BOD of the mixed solution is likely to be unfinished. Select an operation to measure the BOD of the liquid. Conversely, if it is small, the sludge activity is a slow result, and it is to determine whether the sluggish cause is due to a small oxygen consumption rate with no retirement and only breathing, or a sludge is inhibited and the activity is reduced Select the operation to add the reference solution to. The basic values of highfinalDO and Kabs for calculating these measurement results are calculated using numerical values stored in a computer measured in advance. This is based on the premise that activated sludge normally operates MLSS at a constant rate and does not change during short-term operation. However, in actual machines, MLSS is changing, and physical properties such as sludge viscosity change depending on pH conditions and stress conditions on sludge toxicants, etc., and affect the efficiency of aeration devices such as aspirators. Kabs' basic figures are changing. In order to improve the measurement accuracy, it is desirable to measure each time. In the present invention, in Step 2, an operation of measuring highfinal DO and Kabs is performed. The measurement / calculation method in this step is performed by the method described in Patent Document 1. That is, the initial DO value of the sampled mixed liquid is set to DO ₀ , the circulation pump of 5 is operated, the air solenoid valve of 8 is opened, aeration by the aspirator is started, the BOD of the mixed liquid is processed, and the oxygen consumption rate becomes ASact. FIG. 1 shows a change like the DO curve 2-1 in FIG. 1 that is balanced at a position where the DO value is high. A point at which equilibrium is reached at the end of the DO curve 2-1 is defined as highfinalDO. The process so far is referred to as Step 2-1. After obtaining highfinalDO, the air solenoid valve 8 is closed to stop aeration, and the DO is reduced by the consumption of dissolved oxygen by the ASact of the mixed solution, resulting in a change as shown by the DO curve 2-2 in FIG. This process is referred to as Step 2-2. From the point of DO ₁ at which DO has sufficiently decreased, the air solenoid valve 8 is opened and aeration is resumed, and when the change in which DO increases is measured, a change as shown by DO curve 2-3 in FIG. The process so far is referred to as Step2-3. Changes in measured values of DO curve 2-3 and highfinalDO
Using the assumed Kabs, change DO ₀ in equation (4) to DO ₁ and change the value of Kabs so that the calculated value calculated from equation (4) matches the measured value. The Kabs value is obtained by regarding the matching Kabs as the Kabs of the aeration apparatus. Flow charts -7 and -9. The set value 1 and the set value 2 are for taking a sufficiently large DO calculation width so as to reduce an error when the equation (4) is calculated. In step 2-1 of the process of aeration of the sampled mixed liquid and processing of BOD of the mixed liquid, the area surrounded by the calculated value and the actual measured value calculated from equation (4) using highfinalDO and Kabs from the initial value DO ₀ The value obtained by multiplying by Kabs is the BOD of the sampled mixed solution as described in [0017]. If the sampling point is the aeration tank outlet, it is almost equivalent to the treated water BOD. That is, in Patent Document 2, the BOD of the sampling mixed solution is measured in Step 3a, whereas in the present invention, the entire measurement time is shortened by performing it in the operation process for acquiring the first highfinal DO and Kabs. .

  The next step (hereinafter referred to as Step 3-1) is a step of measuring the activity from the decomposition rate of the reference solution by adding the reference solution, and is a part of flowcharts 11 to 14. A DO curve 3-1 in FIG. 1 is an example of a measurement pattern of DO change in this step. After calculating the Kabs in Step 2-3, after reaching the complete equilibrium, 12 is operated by the command from the computer, and the reference solution addition pump is operated to add the reference solution to the measuring device. The change of DO which decomposes the reference solution by the activated sludge in the mixed solution is measured, the decomposition rate of the reference solution is measured from the measurement data, and the activity of the sludge is quantified. This process is performed for all sampling measurements. Accordingly, in Patent Document 2, the addition of the reference solution and the measurement of the BOD of the mixed solution are selected by the slope of Step 2, but in this embodiment, the reference solution is always added, so the activity is reduced but the decomposition is performed. It is possible to avoid the ambiguity of the necessity of activity measurement caused by the remaining unprocessed BOD.

  The next step (hereinafter referred to as Step 3-2) is a step of adding raw water and measuring the BOD and decomposition rate of the raw water, and is a part of flowcharts -15. To -18. A DO curve 3-2 in FIG. 1 is an example of a measurement pattern of DO change in this step.

  As a result of adding and measuring the reference solution in Step 2-1, if the activity of the sludge can be evaluated, determine the measurement method of Step 3-2 based on the activity value. Step 3-2 is originally a process of adding raw water and measuring the BOD and decomposition rate of the raw water. In order to accurately measure BOD, the sludge activity must be normal at a minimum. If the activity is in the normal range, the raw water addition pump is operated to add the raw water, and the raw water BOD and decomposition rate can be measured from the DO change measurement, and the raw water BOD and the raw water are easily decomposed. The nature of raw water, such as whether or not, can also be judged. If the sludge activity is poor, the measured BOD is smaller than JIS BOD as shown in the data of block a group in FIG. FIG. 6 is a graph showing the relationship between sludge activity and measured BOD / JISBOD. Assuming that the sludge activity is the original value, the degradation rate decreases and the time until the completion of the degradation increases while the sludge activity decrease is small, but the overall measured BOD value is maintained. The measured BOD / JISBOD value falls within the range of a little lower than 1. When the degree of decrease in activity increases, the value of the measured BOD also decreases because the decomposition stops in the middle or the decomposition rate becomes extremely slow. The degree of activity at which the BOD measurement value decreases depends on the properties of each activated sludge and raw water, but the tendency is as shown in FIG. For this reason, if the activity falls below the set value 3, measurement of the raw water BOD is omitted. The set value 3 to be determined is input to the computer in advance, but the specific numerical value depends on the need for the measurement accuracy of the raw water BOD. By incorporating such treatment, the overall measurement time can be shortened.

If the automatic measurement mode is set after completing the measurement in Step 3-2, return to Flowchart-1, drain the measured mixed solution, sample the mixed solution from the aeration tank, and perform the above measurement. repeat. In the case of normal activated sludge, if the treatment is good, the time required for the above operation is about 50 minutes for Step1, 35 minutes for Step2, 35 minutes for Step3-1, and about 60 minutes for Step3-2, totaling about 3 hours Therefore, information about the BOD of raw water, the BOD of treated water, and the activity of sludge, which are extremely important operation indexes for activated sludge, can be obtained about every 3 hours. If the method of claim 2 of Patent Document 1 is used from the raw water measurement data, the decomposition rate of the raw water can be analyzed, and even the decomposability of the raw water components can be determined. These are pieces of information that cannot be obtained with a continuous measurement TOD meter or COD meter that is currently in practical use. The above is the description of block 1.

Next, an embodiment corresponding to claim 2 will be described.
This process is referred to as Step 3-3, and is a part from -20. To -23. DO curve 3-3 in FIG. 1 is an example of a measurement pattern of DO change in this step.
In the case of the measurement pattern in which the activity is within the normal range as a result of the addition measurement of the reference solution in Step3-1 and the raw water is added in Step3-2, after the measurement of the raw water is completed, the reference solution is added again in Step3-3. To do.

  If the raw water is toxic to activated sludge, the decomposition rate of the addition measurement of the reference solution after the addition of the raw water always decreases compared to the decomposition rate of the addition measurement of the reference solution before the addition of the raw water, and the degree of toxicity The stronger the strength, the lower the degradation rate. The measurement pattern of DO curve 3-1 and DO curve 3-3 in FIG. 1 is a pattern example when raw water shows strong toxicity. The DO change of DO curve 3-3 is compared with the DO change of DO curve 3-1. The DO reduction width is small, and the flat shape as shown in the figure is long.

Toxicity is to inhibit the activity, so the toxicity intensity of the raw water can be evaluated by comparing the decomposition rate of the reference solution before and after the addition of the raw water. This is composed of various types of waste water such as chemical plant waste water, and it is very useful information for raw water composed of hardly decomposable waste water or toxic waste water alone. Of course, in the case of raw water composed only of harmless waste water such as food waste water, it may be omitted for shortening the measurement time. However, even in the case of such raw water, it is meaningful that the toxicity of the raw water can be checked if there is a possibility that a disinfectant solution may be mixed due to troubles.

  Next, an embodiment corresponding to claim 3 will be described. The present embodiment relates to the Step 1 step of sampling the mixed solution, and is a portion from -24. To -31.

  Process the BOD sampled in Step 1 and obtain highfinalDO. In Step 2-1, if the sampled mixture contains a large amount of unprocessed BOD, the time required for Step 2-1 is very long. It will be long. The incomplete treatment in the aeration tank may often occur in the actual machine due to the BOD overload of the raw water. In such a case, the time required for Step 2-1 may be significantly increased, and accordingly, the total time required for one cycle is also significantly increased, and the requirement for measuring activated sludge substantially continuously cannot be satisfied. Block 3 relates to a method to avoid this situation.

  In Step 2-1, the time ts from the start of aeration until obtaining highfinalDO in Flowchart-5 is measured in Flowchart-31. When one cycle of measurement is completed and sampling of a new mixed solution is started, if ts is smaller than the maximum measurement allowable time tc stored in the computer, the entire amount of the new mixed solution is charged in the flow of block 1, When ts is larger than tc, a part of the measured liquid mixture is left, the remaining part is replaced with a new liquid mixture, and the measuring device is charged. Flow charts -24. To -30. Show examples of replacement and mixed charge methods. The substitution rate (= new mixed liquid volume / total mixed liquid volume) is calculated by ts and tc. For example, as the simplest calculation example, measured mixed liquid volume: new mixed liquid volume = (ts−tc) : Calculated from the proportional relationship of tc. If ts is twice tc, the measured mixture is 50% and the new mixture is 50%. Since the BOD of the measured mixed liquid is almost 0 mg / l, the BOD of the charged mixed liquid is ½ of the new mixed liquid as a whole, and the decomposition time of the BOD is also halved, which is about tc. The measurement of Step2-1 is completed in time. When the measured mixed liquid amount is calculated, the measuring container is depressurized, the communication solenoid valve is opened, and the measured mixed liquid is transferred from the measuring device to the measuring container. An arbitrary amount can be transferred by manipulating the pressure of the measuring container. After the transfer, the remaining measured liquid mixture is drained, and the measured liquid mixture is returned from the measuring container to the measuring device. Thereafter, the communication solenoid valve is closed, the measuring container is depressurized, the sampling solenoid valve is opened, and a new mixed liquid is sucked into the measuring container from the aeration tank. The suction amount can be sampled in accordance with the calculated new liquid mixture amount by controlling the operation of the vacuum pump and sampling solenoid valve with a computer and operating the pressure before and after the suction of the measuring container. The measured new mixed liquid is transferred to the measuring device by opening the open-air solenoid valve and the communication solenoid valve. By doing so, the measurement in Step 2-1 can be shortened. The BOD of the new mixed solution can be obtained by calculating backward according to the substitution rate. In the activity measurement by adding the reference solution in Step 3-1, the new mixed solution is not the total amount, so if the activity has changed, the amount of change will be smaller than in the case of the total amount replacement. According to needs, this change may be used as a measured value as it is, or the amount of change can be calculated back by the substitution rate and obtained as the activity of a new mixed solution alone. In the measurement of raw water in Step 3-2, even if mixed sludge is normal, the measured value is not affected and can be measured normally. In the toxicity evaluation of raw water with the addition of the standard solution in Step 3-3, since the relative values of Step 3-1 and Step 3-3 are compared, mixed sludge has little effect on the measured value.

The reference solution added in Step 3-1 or Step 3-3 is an additive solution having a constant component composition as a reference for evaluating the ability to decompose the BOD of raw water of activated sludge. Since activated sludge generally has different properties depending on the culture environment, it is necessary to select a liquid that matches the corresponding activated sludge. The requirement that the reference solution can be used as a reference solution is
(1) There is a correlation between the change in the decomposition rate of the raw water and the change in the decomposition rate of the reference solution.
(2) There is a sufficiently large decomposition rate that can calculate the change accurately.
If the components of the raw water are not changed, the raw water itself can be used as the reference solution. If there are fluctuations in the components of the raw water, it may be possible to use a solution obtained by artificially synthesizing the main components in the raw water, and basic substances such as acetic acid that contribute to the microbial metabolic activity of activated sludge. There is a possibility that a liquid synthesized with the substance can also be used. Which of these liquids best meets the conditions (1) and (2) is selected based on actual measurement of decomposability of the reference liquid candidate and raw water by changing the conditions, and the same reference liquid is always used thereafter.

  Generally, since raw water and a reference solution are composed of a plurality of components, the decomposition rate BODact in activated sludge changes with time because the components to be decomposed change as described above. Therefore, for comparison, it is necessary to define at what time the decomposition rate is to be compared. When calculating the decomposition rate from DO change measurement data, in many cases, when decomposing some main components, depending on the decomposition rate, the oxygen supply rate by aeration is balanced through several parts where DO is constant However, the process of decomposition of the remaining components and the intermediate product of the main component rises with a gentle change with a clear step-like change, and finally the oxygen consumption rate by activated sludge by ASact and the oxygen supply rate by aeration And converge to a highfinalDO value that balances.

FIG. 7 shows a pattern example of DO change in this process. The DO measurement curve in FIG. 7 is different from the solid curve in FIG. 2 in the case where the initial value DO ₀ starts from a high highfinal DO value. Since activated sludge is an aggregate of various microorganisms, when the activity changes, the decomposition rate of all components does not always change evenly. On the other hand, since the component composition of raw water also changes, it is extremely difficult to compare each component. For this reason, a macro way of grasping is practical. For example, an average decomposition rate until 50% of the entire BOD is decomposed is used as an index. The larger the BOD decomposition rate, the more reasonable it is as an index for evaluating the decomposition power, but the measurement error also increases, and the measurement ends with a small amount of a small amount of slowly decomposable components. Since time is greatly affected, variation due to component fluctuations becomes unnecessarily large, and measurement errors also increase. On the other hand, the maximum degradation rate immediately after addition can be sensitive to changes, but the contribution of the fastest degradable component in the raw water component is very large, so the activity of only microorganisms that selectively degrade the component is limited. There is a risk of evaluation. On the other hand, the average activity of microorganisms that decompose various components in the raw water contributes until about 50% decomposition, so generally the average decomposition rate up to about 50% decomposition is an index. Is appropriate. Of course, depending on the nature of the raw water, the maximum decomposition rate may be used as an index, and when importance is attached to the decomposability of components having poor degradability, the average decomposition rate having a large decomposition rate may be used as an index.

The calculation method of the average decomposition rate from the DO measurement data to a certain decomposition rate can be calculated as follows. In the DO change curve in FIG. 7, the area surrounded by the DO change curve from the start of addition to the end of decomposition and the curve (hereinafter referred to as virtual DO curve 1) calculated by equation (4) with DO ₀ as the initial value. The value multiplied by Kabs is the total BOD value (hereinafter referred to as BODt). When the initial value DO ₀ is a highfinalDO value, the virtual DO curve becomes a straight line with the highfinalDO value. On the other hand, if the BOD decomposed by a certain time reaches 0 mg / l at that time, the DO change curve shows the highfinal DO and Kabs with the DO measurement value at that time as the initial value DO _2. It becomes a curve (hereinafter referred to as a virtual DO curve 2) calculated by the equation (4). Therefore, the value obtained by multiplying the area surrounded by the DO change curve, the virtual DO curve 1 and the virtual DO curve 2 from the start of addition to Kas by the Kabs is the BOD up to that point (hereinafter referred to as BODp). If the time when 100 × BODp / BODt reaches the relevant decomposition rate is tp, BODp / tp is the average decomposition rate up to the relevant decomposition rate. Further, claim 2 of Patent Document 1 shows a method for analyzing the decomposition rate of microorganisms as a zero-order reaction of the concentration of a substance to be decomposed, as determined only by the activity of the microorganisms for each section, regardless of the substance concentration. Can be used to compare the decomposition rate of a specific point.

  The definition of activity is the size of the ability of sludge to decompose BOD of raw water, the ability can be represented by the size of the decomposition rate, and the decomposition rate of the reference solution is correlated with the decomposition rate of the raw water. Calculate from the decomposition rate of the liquid. Although the decomposition rate is an absolute value, the activated sludge is composed of various microbial groups, and the microbial group itself may change depending on the characteristics and operating conditions of the equipment. The maximum decomposition rate of the corresponding activated sludge is This is the maximum value under certain conditions, and the maximum value may change if there are basic condition changes. Therefore, rather than quantifying activity with the absolute value of the degradation rate, it is easier to manage it as a ratio to the maximum possible degradation rate under the current basic conditions, defined as activity = degradation rate / maximum degradation rate. In this case, the activity is usually in the range of 0 to 1 and is easy to manage.

Next, a method for determining whether or not the decomposition reaction has been completed will be described. Even in the flowchart, it is necessary to determine whether or not the decomposition reaction is completed at -4, -13, -17, and -21. This determination method uses the characteristics of the microbial reaction of activated sludge. Normally, when the waste liquid is added, the decomposition reaction progresses as shown in the DO measurement curve of FIG. 7 due to the decomposition of the main components in the waste liquid. It changes almost constant around highfinalDO. Therefore, it can be determined that the reaction is completed when the DO value becomes almost constant around highfinalDO. In order to realize this on a computer, if the slope β of the regression line is calculated from several DO measurement values from several minutes before the measurement, β becomes the DO change rate, and is stored in the computer in advance. Compared with the set value 5 which is the minimum allowable value of the DO change rate,
β <set value 5 and DO ≒ highfinalDO
It can be judged under the following conditions.

Here, the meaning in the vicinity of highfinalDO is a measure for not necessarily being the same as the state of activated sludge at the time of obtaining highfinalDO. For example, although the BOD of the mixed solution is 0 mg / l at the time when highfinalDO is acquired in Step 2-1, strictly speaking, there is also the decomposition of a slow BOD component that is lower than the decomposition accuracy below the measurement accuracy. It is also a treatment that takes into account the possibility of changing the properties of sludge by adding waste liquid. In practical use, when the decomposition reaction is Kabs = 0.3 [1 / min] and highfinalDO = 6.0 [mg / l], the reaction is generally highfinDO-0.5 or higher, so the DO increase is almost sloped. if the value indicating the points DO _L in FIG. 7, it can be determined by setting such as <setpoint 5 and DO> DO _L.

  The present invention is not limited to activated sludge, but also wastewater treatment methods that utilize aerobic microorganisms such as catalytic oxidation method, biological filtration method, fluidized bed method that retains carrier microorganisms, and wastewater that partially uses suspended microorganisms. Any process can be applied.

It is an example of a pattern showing basic operation and DO change in the measurement of the present invention. It is a figure explaining the calculation principle used as the foundation of the present invention. It is a figure which compares the value of BOD by the measuring method by the calculation principle used as the foundation of this invention, and the value of BOD of JIS method. It is a flow sheet which shows the example of the measuring device of the present invention. It is a flowchart explaining the action | operation of the measuring apparatus of this invention. It is a figure which shows the relationship between the value of BOD by the measuring method of this invention, and the activity of activated sludge. It is an example of DO measurement pattern by the measuring apparatus of this invention.

Explanation of symbols

3 Aeration vessel 4 Measurement vessel 5, 12, 13 Pump 6 Aeration device 7 Air flow meter 8, 14, 20-24 Solenoid valve
9 Dissolved oxygen meter electrode 10 Heater 11 Heat exchange pipe 15 for cooling 15 Dissolved oxygen meter 16 Control panel 17 Computer 18 Measuring container 19 Vacuum pump 25 Temperature sensor 26 Pressure gauge sensor

Claims (4)

An operation evaluation method in wastewater treatment using aerobic microorganisms,
The mixed solution containing the wastewater and activated sludge sampled from the aeration tank is aerated, the change curve of dissolved oxygen concentration in the mixed solution (hereinafter referred to as DO curve 2-1) and the oxygen supply rate after BOD decomposition in the mixed solution Measure the dissolved oxygen concentration (hereinafter referred to as highfinalDO) at the balance point between the oxygen consumption rate of the liquid mixture and
Next, after aeration was stopped to reduce the dissolved oxygen concentration, a dissolved oxygen concentration change curve (hereinafter referred to as DO curve 2-3) when aeration was resumed was measured.
Calculate the mass transfer coefficient (hereinafter referred to as Kabs) in the oxygen supply means based on the DO curve 2-3 and highfinalDO, and further obtain the BOD of the mixture based on the DO curve 2-1, highfinalDO and Kabs,
Next, add a reference solution with a constant component composition to the mixture, and then obtain the activity of the activated sludge in the mixture by determining the decomposition rate of the reference solution based on the changes in dissolved oxygen concentration and highfinalDO and Kabs. And
If the activity is greater than a preset value, add raw water after the decomposition of the reference solution, calculate the BOD of the raw water based on the subsequent dissolved oxygen concentration change and highfinalDO and Kabs,
An operation evaluation method in wastewater treatment characterized by substantially continuously evaluating the BOD of a mixed solution, the activity of activated sludge in the mixed solution, and the BOD of raw water by repeating the above cycle. 2. The toxicity of raw water to activated sludge is further evaluated by adding raw water and adding the reference solution again after completion of decomposition, and comparing the decomposition rate of the reference solution before and after the addition of raw water. Wastewater treatment operation evaluation method. In Claim 1 or 2, when the time (ts) from the start of aeration to acquisition of highfinalDO in the immediately preceding cycle is greater than a predetermined maximum allowable measurement time (tc), the entire amount of the liquid to be measured is changed to a new mixed liquid. Rather than leave the measured mixed liquid in an amount corresponding to the size of ts-tc, and use the mixture of the measured mixed liquid and the new mixed liquid as the measurement target of the cycle, Wastewater treatment operation evaluation method. An operation evaluation apparatus for wastewater treatment using aerobic microorganisms,
Mixing the sampled wastewater and the activated sludge mixed solution, aeration curve of dissolved oxygen concentration in the mixed solution (hereinafter referred to as DO curve 2-1) and oxygen supply rate and mixing after decomposition of BOD in the mixed solution Means for measuring the dissolved oxygen concentration (hereinafter referred to as highfinalDO) at a balance point with the oxygen consumption rate of the liquid;
Means for measuring a dissolved oxygen concentration change curve (hereinafter referred to as DO curve 2-3) when aeration is resumed after stopping aeration and reducing the dissolved oxygen concentration;
Means for calculating a mass transfer coefficient (hereinafter referred to as Kabs) in the oxygen supply means based on the DO curve 2-3 and highfinalDO, and further obtaining a BOD of the mixed solution based on the DO curve 2-1, highfinalDO and Kabs;
Means for obtaining the activity of activated sludge in the mixed solution by adding a reference solution having a constant component composition to the mixed solution and then determining the decomposition rate of the reference solution based on the change in dissolved oxygen concentration and highfinal DO and Kabs. When,
When the activity is larger than a predetermined set value, after adding the raw water after the decomposition of the reference solution, a means for calculating the BOD of the raw water based on the subsequent dissolved oxygen concentration change and highfinalDO and Kabs;
A device for evaluating operation in wastewater treatment, comprising:

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