JPH05264537A - Method and apparatus for measuring concentration of organic acid and ammonia for digested sludge - Google Patents

Abstract

PURPOSE:To provide a method and an apparatus which enables handy measurement of the concentration of organic acid and ammonia in a liquid containing ammonia of a high concentration like a digested sludge. CONSTITUTION:After the injection of a non-phosphor soluble reagent 2b and a coagulant 2a into a sample to be measured extracted and separated from a digested sludge, a fixed amount of a liquid passing through a filter film of an ultrafilter 16 is transferred to a titration tank 17 for measuring organic acid and a titration tank 18 for measuring ammonia to acidify and a nitrogen gas is passed through both the titration tanks to volatilize dissolving carbonic acid. A titration is performed using an alkali solution to calculate the total concentration of organic acid in the sample to be measured from the amount of the alkali solution required for neutral titration of the sample in the titration tank 17 for measuring the organic acid. The titration is further continued for the titration tank 18 for measuring ammonia to calculate the total concentration of ammonia of the sample to be measured from the titration quantity of alkali required until ammonia ions in the titration tank 18 for measuring the ammonia turns to isolated ammonia.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the organic acid concentration and ammonia concentration of digested sludge while monitoring the internal condition of the digestion tank in the sludge treatment process.

[0002]

2. Description of the Related Art Conventionally, when monitoring the internal condition of a sludge digestion tank or a methane fermentation tank, the organic acid concentration and ammonia concentration in the liquid phase in the tank have been important monitoring items.
As a method for measuring the above organic acid concentration, the following 5
One means is known.

(1) Steam distillation method ... The sample is put in a centrifuge, and sulfuric acid (1 + 1) is added to the supernatant to adjust the pH to 3-4.
Acidified to this, magnesium sulfate and copper sulfate aqueous solution were added thereto, then steam distillation was carried out, 2 to 3 drops of phenolphthalein indicator were added to the distillate, and neutralization titration was carried out with N / 10 sodium hydroxide solution. Determine the amount (ml) of sodium hydroxide solution required. Further, a predetermined amount of N / 10 sodium hydroxide solution is added, and then barium chloride is immediately added to the container and the container is tightly sealed. The mixture is left for 5 minutes while shaking. Then N / 10
The salt is titrated until the red color disappears, and the volatile organic acid concentration is calculated from the required amount of N / 10 hydrochloric acid and the amount of sodium hydroxide (see the sewage test method, 1984 version).

(2) Direct titration method: The sample is put in a centrifuge, and sulfuric acid (1 + 1) is added to the supernatant to acidify it to pH 3.5. Then, the mixture was boiled for 5 minutes on a hot plate with a reflux condenser to remove carbon dioxide, cooled to room temperature, and adjusted to pH 4.0 with a N / 10 sodium hydroxide solution. Further, neutralization titration was performed with a N / 10 sodium hydroxide solution until the pH reached 7.0, and the pH was adjusted to 4.
From the amount of N / 10 sodium hydroxide solution (ml) required from 0 to 7.0, the concentration of volatile organic acid was calculated as m of acetic acid.
Calculate as g / l (see 1974 version of Sewage Test Method).

(3) Direct distillation method: The sample is put in a centrifuge, sulfuric acid (1 + 1) is added to the supernatant to acidify it, and it is directly distilled at a distillation rate of 5 to 6 ml / min, and this distillate is distilled off. A phenolphthalein indicator is added to the solution, and the solution is neutralized and titrated with a N / 10 sodium hydroxide solution. Then, from the required amount of the sodium hydroxide solution (ml), the volatile organic acid concentration was adjusted to
(See the 1974 version of the sewage test method).

(4) Gas chromatographic method: A fatty acid, for example, 5 ml of acetic acid is dissolved in water to make 1 liter to prepare a fatty acid standard solution. The concentration of this standard solution is standardized each time it is used. Then, centrifuge the sample and add 11 to the supernatant.
A sodium hydroxide solution is added until it becomes, and the solution is concentrated and cooled. Then, hydrochloric acid (1 + 2) is added to the concentrated solution to adjust the pH to 4 or less, 10 ml of formic acid is further added, and water is added to prepare a sample solution. This sample solution was injected into a fatty acid standard solution to record a gas chromatogram, the peak area at a position corresponding to the retention time of the fatty acid was measured, and the amount of the fatty acid was calculated from the calibration curve.
The volatile fatty acid concentration (mg / l) in the sample is calculated (see the 1984 version of the Sewage Test Method).

(5) Ion chromatographic method: a chromatographic method using ions as a mobile phase (the basic means is common to that of a gas chromatograph, and detailed description thereof is omitted).

Among the above-mentioned five means, the steam distillation method (1), which is relatively high in accuracy, is generally adopted, but this steam distillation method has a drawback that the operation is complicated and the measurement time is long. Further, in the case of the gas chromatograph method, the operation is rather complicated, and the concentration of formic acid cannot be measured. Since it involves operations that are difficult to automate, such as collecting the supernatant with a centrifuge or removing carbon dioxide by boiling with a reflux condenser on a hot plate, (1),
The automatic measuring device for organic acid using each of the means (2), (3), and (4) has not yet been put into practical use.

In addition to the above-mentioned means, an organic acid measuring device utilizing an ion selective electrode method or a dilute conductivity method has been developed. However, in addition to the complexity of the operation, the measurement accuracy can be sufficiently satisfied. Has not reached.

Therefore, recently, the operation is relatively simple,
An ion chromatographic method capable of separately measuring various organic acids for each type is becoming widespread, and an organic acid automatic apparatus combining an ultrafiltration apparatus and an ion chromatographic method is commercially available.

On the other hand, as a method for measuring the ammonia concentration,
For example, the sewage test method (1984 edition) describes indophenol blue absorptiometry, neutralization titration method, and ion electrode method. Each of these methods will be briefly described as follows: (6) Indophenol blue absorptiometric method: The sample is made alkaline, and the ammonia distilled during heating distillation is absorbed by the boric acid solution, A method for quantifying ammonium nitrogen by measuring the absorbance of a blue color (indophenol blue) produced by the reaction of ammonium ions with phenol and sodium hypochlorite. Quantitative range is 0.0
05-0.05 mg / l.

(7) Neutralization titration method: The sample is made alkaline, ammonia distilled during heating and distillation is absorbed in a saturated boric acid solution, and ammonium ion in the distillate is measured by neutralization titration. Method to quantify ammonium nitrogen. The quantitative range is 0.7 to 10 mg / l.

(8) Ion electrode method: The sample is made alkaline, ammonia distilled during heating and distillation is absorbed by sulfuric acid, and the distillate is adjusted to pH 11 to 13 to change ammonium ion to ammonia. A method of measuring this ammonia using an ion electrode (ammonia electrode) to quantify ammonium nitrogen. The quantitative range is 0.1 to 100 mg NH ₄ ⁺ / l as ammonium ion.

On the other hand, an automatic measuring method and device (digestion tank monitor device) for simultaneously quantifying the total organic acid concentration, total ammonia concentration and total inorganic carbon concentration of digested sludge by using a measurement principle completely different from the above-mentioned existing analysis method. Is proposed. This method is a method of calculating organic acid, ammonia, and inorganic carbon concentrations from titration amounts of acids and bases necessary for adjusting digested sludge to a constant pH based on the acid-base equilibrium theory. It is a method that is relatively easy and highly feasible to automate.

The present inventors have previously developed a new measuring method which is introduced with the statistical analysis method of optimizing the above-mentioned acid / base titration method. That is, the simplex method is used with initial values such as total organic acid concentration, total ammonia concentration and total inorganic carbon concentration calculated by multiple regression analysis of a formula derived from a chemical equilibrium equation and a charge balance equation using a pH titration curve. This is a method for performing optimization processing. Here, the evaluation function of the optimization process is
The total organic acid concentration, the total ammonia concentration and the total inorganic carbon concentration that give this minimum value were calculated as the sum of the squares of the measured and calculated values of each pH and used as the measured values by the titration method (Japanese Patent Application No.
No. 301455 and Japanese Patent Application No. 3-340549). By this method, the total value of organic acid, total ammonia and total inorganic carbon is within the error range of 10 to 20% in the concentration range of 500 to 1000 mg / l. Satisfactory measurement accuracy is obtained.

The outline of the above automatic measuring device will be briefly described with reference to FIG. 4. The digested sludge is first received in the sludge receiving tank 1 having a capacity sufficient to secure the extract, and then in the coagulating tank 2, The molecular aggregating agent 2a is added to agglomerate the fine particle component. Next, after solid-liquid separation in the precipitating tank 3, the supernatant of the precipitating tank 3 is filtered using the filter 4 to obtain a filtrate having a target ss concentration or less, and the filtrate is collected in the filtrate tank 5 Stored in. When glass beads or an ultrafiltration device is used as the filter 4, solid matter that could not be removed by precipitation in the clarification tank 3 is removed. Then, a fixed amount of the filtrate is sampled and sent to the acid titration tank 6 and the alkali titration tank 7, where HCl and NaOH as titration reagents are dispensed by the dispenser 8.
a, 8b and an electric burette are added for titration, and the sequence in which the titer, the pH value measured by the pH meter 9 and the temperature value measured by the thermometer 10 constitute the control unit 11 The total organic acid, which is a measurement item, is sent to the controller 12 and the personal computer 13 to perform arithmetic processing based on a number of formulas created by substituting the obtained data into the acid-alkali equilibrium theory and the charge balance formula. The concentration (A), the total ammonia concentration (N), the total inorganic carbon concentration (T), etc. are monitored. The thermometer 10
The value measured at is used for temperature coefficient correction during data processing in the control unit 11.

When carrying out the continuous monitoring based on the acid-alkali equilibrium theory, all the steps are carried out fully automatically based on a program previously incorporated in the sequence controller 12 or the personal computer 13 constituting the control section 11. It is characterized by The measurement result is displayed on a CRT screen which is an output device of the personal computer 13. In order to increase the reliability of this measurement result, the multiple regression analysis or the optimization process using the simplex method is performed.

[0018]

However, both the conventional organic acid concentration measuring apparatus utilizing the steam distillation method and the ammonia concentration measuring apparatus utilizing the indophenol blue absorptiometry method are complicated in operation. There is a problem that it takes time to measure and it is difficult to automate the measuring operation.

That is, each of the means (1), (2), and (3) requires a centrifuge operation, a heating reflux operation, and a steam distillation operation for a sample, but it is technically technical to automate these operations. Have difficulty. Further, in the means of (1) and (3), N / 1 is added to the distillate containing the organic acid obtained by steam distillation.
Since the neutralization titration is performed using a 0 sodium hydroxide solution, the measurement accuracy is high, but there is a drawback that steam distillation requires a long time.

In the means (2), steam distillation is not carried out. Instead, the sample is boiled by using a reflux condenser to remove soluble carbon dioxide, and then N / 10 sodium hydroxide is added. Since neutralization titration using a solution is performed, there is an advantage that measurement can be performed in a relatively short time.
If carbon dioxide or hydrogen sulfide remains in the sample, or if there is a non-volatile alkali consuming substance such as nitrite or sulfite or phosphate, it gives a positive error to the measurement result, Particularly, there is a problem that the measurement accuracy may be lowered in the low concentration region of the organic acid.

Further, in order to automate each operation in the gas chromatograph method or the ion chromatograph method, which is the means of the above (4) and (5), a high level of technology is required. Therefore, the ultrafiltration device and the ion chromatograph method described above are required. The organic acid automatic device in which the above and the above are combined has a drawback that it becomes extremely expensive.

On the other hand, in the ammonia concentration measuring methods described in (6), (7) and (8) above, in addition to the complexity of the operation, a decrease in measurement accuracy due to dilution of the sample is likely to occur, and the measurement There is a problem that it is difficult to automate the operation. In particular, using each of the above-mentioned measurement methods, the concentration of ammoniacal nitrogen in digested sludge is in the range of hundreds to thousands of mg / l.
Although it is necessary to dilute the sample when measuring a sample having a high concentration, it is generally known that when the sample is diluted, the higher the dilution ratio, the lower the measurement accuracy. Therefore, in the case of measuring a sample having a high ammonia concentration, the ion electrode method (8), which has a relatively wide quantitative range and a low degree of dilution, is generally adopted among the above methods.

However, even if the ion electrode method is used, there is room for improvement in terms of measurement accuracy and measurement operation, such as a repeated measurement error of 5 to 20% for the same sample and a long distillation operation. Also, taking the case of measuring ammonia for the purpose of maintenance of the digestion tank as an example, the measurement accuracy may be at the same level as the current ion electrode method or a little inferior, but the measurement time is shortened automatically. The situation is such that development of a measuring device is desired.

Further, an automatic measuring device utilizing the above-mentioned acid and base titration method is currently under development, but the concentration of total ammonia and total inorganic carbon in the digested sludge is 500 to 1000.
Since the concentration is often in the range of mg / l, practically sufficient measurement accuracy can be obtained, but with respect to total organic acid, the concentration range in the digested sludge is wide from 0 to several thousand mg / l, and the digestion state is 100 mg / l or less when it is good, so 100
It is necessary to have such a measurement accuracy that it is possible to distinguish whether the concentration is higher or lower than this concentration with mg / l as the boundary. On the other hand, in the case of the above-mentioned automatic measuring device, considering the measurement principle, ± 1 mm
It is expected that a measurement error of about ole / l, that is, about ± 60 mg / l will occur. Furthermore, the price of a measuring device consisting of a solid-liquid separation device for digested sludge sample, an acid / base titrator, and a control device such as a personal computer is extremely expensive. If there is a shortened measuring method, it is considered to be practically useful even if the measuring accuracy is comparable to or slightly inferior to that of the ion electrode method.

Therefore, according to the present invention, the total organic acid concentration and the total ammonia concentration can be measured at the same time, the measurement accuracy is maintained in good condition, the operation is simplified, the measurement time can be shortened, and the price is increased. It is an object of the present invention to provide an organic acid concentration / ammonia concentration measuring method and an apparatus thereof, which enables automation of the measuring operation without being accompanied.

[0026]

In order to achieve the above-mentioned object, the present invention injects a phosphorus insolubilizing reagent into a sample to be measured extracted and separated from digested sludge to make a phosphate ion into an insoluble salt, and to agglomerate it. A step of injecting an agent to form a fine particle component, a step of removing the salt, suspended matter component and protein in the liquid by subjecting the sample to an ultrafiltration device, and a fixed amount of the sample as a titration tank for measuring an organic acid. A step of acidifying the samples in both titration tanks after transfer to the titration tank for ammonia measurement, and aeration of nitrogen gas or carbon dioxide in both titration tanks for a certain period of time to dissolve soluble carbonic acid in the samples The step of volatilizing and performing titration using an alkaline solution for both titration tanks, and the total organic acid concentration in the sample to be measured from the amount of alkali solution required for neutralization titration of the sample in the titration tank for measuring organic acid And the ammonia measurement To continue the titration against use drop Joso,
And a method for measuring the organic acid and ammonia concentration of digested sludge, comprising the step of calculating the total ammonia concentration of the sample to be measured from the titration amount of alkali required until the ammonium ions in the ammonia measurement titration tank become free ammonia. It has the structure of the device.

The sample to be measured is a liquid obtained by subjecting the supernatant of the digested sludge to a centrifugal separation treatment, and the sample of the alkali required until the ammonium ion in the titration tank for ammonia measurement becomes free ammonia. The titer of the sample is 7
The amount of alkali required to reach from 1 to 11.5.

Further, one titration tank is used as both the titration tank for organic acid measurement and the titration tank for ammonia measurement, and the organic acid concentration is calculated by alkali titration to this titration tank, and then the titration is continued. The measurement method and device are used to calculate the ammonia concentration.

[0029]

According to such an organic acid and ammonia concentration measuring method and device, after phosphorus in a sample to be measured extracted from digested sludge is insolubilized and fine particle components are aggregated,
By subjecting the sample to an ultrafiltration device, suspended matter components and proteins in the liquid as interfering substances are removed and the positive error on the ammonia readings is reduced.

The soluble carbonic acid is volatilized by aerating the air from which nitrogen gas or carbon dioxide is removed, and then titration is performed using an alkaline solution, and the amount of the alkaline solution required for the neutralization titration is used to determine the sample to be measured. The total amount of organic acids in the solution was calculated, and the titration amount of alkali required until the ammonium ions in the solution became free ammonia, that is, the alkali titration amount required for the pH to change from 7 to 11.5, The total ammonia concentration is calculated from the difference from the data of the blank sample by an arithmetic expression.

Therefore, according to the present invention, the total organic acid concentration and the total ammonia concentration can be measured at the same time, and the operation is simplified and the measurement time can be shortened. A method and apparatus for measuring ammonia concentration can be obtained.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the organic acid and ammonia concentration measuring apparatus for digested sludge according to the present invention will be described in detail below with the same components as those of the above-mentioned conventional components given the same reference numerals.

The configuration of this embodiment will be described with reference to FIG. In this embodiment, the overall configuration is roughly divided into a sample pretreatment unit 30, an alkali titration processing unit 40, a measurement result calculation processing unit 50, and a cleaning processing unit 60 as shown in the figure.

First, the structure of the sample pretreatment unit 30 will be described. 1 is a mud receiving tank, and the mud receiving tank 1 has a capacity capable of sufficiently securing an extract of digested sludge. 2 is a flocculation tank, 3 is a precipitation tank, 16 is an ultrafiltration device, and 5 is a filtrate tank. The flocculation tank 2 is filled with a polymer flocculant 2a and a phosphorus insolubilizing reagent 2b, and a motor and blades. An agitation mechanism 2c configured by is attached. Further, the supernatant of the sedimentation tank 3 is filtered by the ultrafiltration device 16 in association with the action of the pump P ₁ , and this filtrate is stored in the filtrate tank 5.

Next, the structure of the alkali titration processing section 40 will be described. That is, 17 is a titration tank for measuring organic acid (hereinafter abbreviated as A titration tank), and 18 is a titration tank for measuring ammonia (hereinafter N titration tank).
(Abbreviated as a titration tank), a fixed amount of the filtrate is sampled and sent from the filtrate tank 5 to the A titration tank 17 and the N titration tank 18. Reference numeral 9 is a pH meter connected to a pH electrode immersed in both titration tanks 17 and 18.

The A titration tank 17 is provided with an alkali titration dispenser 19 and an acid dispenser 20, and the N titration tank 18 is similarly provided with an alkali titration dispenser 21 and an acid dispenser. 22 and 22 are deployed. Reference numeral 23 denotes a nitrogen gas supply device, from which the A titration tank 17 and the N titration tank 18 are connected.
Nitrogen gas is sent to.

Next, the configuration of the measurement result calculation processing section 50 will be described. That is, 12 is a sequence controller and 13 is a personal computer.
1 is configured.

Next, the structure of the cleaning processing unit 60 will be described.
Reference numeral 25 denotes a wash water storage tank. The wash water stored in the wash water storage tank 25 is supplied to the mud receiving tank 1 by a pump P ₂ and the A titration tank 17 and N by a pump P _3.
Cleaning water is also supplied to the titration tank 18.

In the present embodiment, the measurement of the organic acid concentration by the A titration tank and the measurement of the ammonia concentration by the N titration tank are based on a program previously incorporated in the sequence controller 12 or the personal computer 13 constituting the control unit 11. It is characterized by being carried out fully automatically. The measurement result is displayed on a CRT screen which is an output device of the personal computer 13.

Next, the operation of the device of the present invention will be described with reference to FIGS. First, in step 101, digested sludge extracted and separated from a digestion tank (not shown) by a centrifugal separation method or the like is weighed as a sample, put into the mud receiving tank 1, temporarily stored, and then transferred to the coagulation tank 2. Next, in step 102, the phosphorus insolubilizing reagent 2b is injected into the sample and stirred by the stirring mechanism 2c.

As a reason for adding the phosphorus insolubilizing reagent in step 102, it is considered that the digested sludge usually contains a considerable amount of phosphate, and this phosphate gives a positive error to the measurement result. To be done. Therefore, in this embodiment, as the phosphorus insolubilizing reagent, for example, 2 ml of calcium chloride solution (1.1 W / V%), potassium hydroxide solution (1 W / V%) and sodium carbonate solution (1.3
By adding 1 ml of an equal volume mixture of W / V%) and stirring and mixing by using the stirring mechanism 2c, the phosphate ion is removed as an insoluble salt.

Next, in step 103, the polymer coagulant is injected into the coagulation tank 2 and stirred to coagulate the fine particle components. In step 104, the stirring is stopped, and after standing for a certain period of time, the separated liquid is transferred to the precipitation tank 3. In step 105, the separated liquid is applied to the ultrafiltration device 16 by operating the pump P ₁ , and the sample that has passed through the filtration membrane of the ultrafiltration device 16 is transferred to the filtrate tank 5. The liquid that does not pass through the filtration membrane is returned to the clarification tank 3 and repeatedly applied to the ultrafiltration device 16.

The reason why the ultrafiltration device is used in step 105 is to eliminate suspended substances (ss component) in water and proteins having a buffering property to eliminate interfering substances at the time of ammonia concentration measurement and to eliminate measurement error. To reduce.

Next, at step 106, a fixed amount of sample is transferred from the filtrate tank 5 to the A titration tank 17 and the N titration tank 18. Then, in step 107, (1 + 1) sulfuric acid is dropped from the acid dispensers 20, 22 to both titration tanks 17, 18.
The pH of both titration tanks 17 and 18 is set to 3 or less. Next, at step 108, both titration tanks 17, 18 are fed from the nitrogen gas supply device 23.
Nitrogen gas is fed into the chamber and bubbled for 20 to 30 minutes to remove soluble carbonic acid in the sample. It is also possible to use air from which carbon dioxide has been removed, instead of the nitrogen gas N ₂ .

Next, in step 109, both titration tanks 17,
18 from alkaline titration dispensers 19, 21 to 0.
1N NaOH or 1N NaOH solution is dispensed. Then, the pH meter 9 connected to the pH electrode immersed in both titration tanks 17 and 18 measures the acidity in both titration tanks 17 and 18, and the measured pH value constitutes the controller 11 of the sequence controller. It is sent to 12.

Then, from step 109 to step 110, the concentration of the organic acid in the A titration tank 17 is calculated, while from step 109 to step 117, the concentration of ammonia in the N titration tank 18 is calculated.

That is, in step 110 shown in FIG. 3, titration is performed until the pH in the A titration tank 17 is changed from pH 4 to pH 7, and the amount of 0.1N sodium hydroxide solution ml required for this titration is used in step 111. The acid concentration is calculated using an arithmetic expression.

Next, in step 112, the titrated pH prepared in advance is used.
After correcting the titration pH range by the correction table, step 113
The titration amount in the titration pH range corrected by is measured, and after inputting the data of the titration amount of the blank test similarly performed using distilled water in step 114, the total organic acid concentration is calculated in step 115, and the step 116 is performed. The result is displayed on the CRT.

Then, from the amount a of the alkaline solution required for the pH to change from pH 4 to pH 7 to the total amount of the organic acid in the sample,

[0050]

## EQU1 ## Total organic acid (mg / l) = aF × (1000 / sample ml) × 6.01 (1) (F is a factor of alkaline solution) Calculated by the formula. (Refer to Japanese Patent Application No. 3-216818 for the details of the steps relating to the organic acid concentration and the arithmetic expression).

On the other hand, the process proceeds from step 109 to step 117, and the pH in the N titration tank 18 is changed from pH 7 to pH 1.
Titration is carried out until it reaches 1.5, the data of the titration amount by the blank test is input in step 118, the total ammonia concentration is calculated based on the arithmetic expression described later in step 119, and the result is displayed on the CRT in step 116. It Incidentally, in order to obtain the blank titration data in step 118, it is necessary to carry out a blank test using distilled water or the like, but since the results of the blank test are in a substantially constant range,
It suffices to substitute a blank value measured by manual analysis in advance into the above-mentioned arithmetic expression, and it is not necessary to separately carry out a blank test.

Titration pH of the N titration tank in step 117
The reason why the range is changed from 7 to 11.5 is as follows. That is, due to the relationship between the existing form of ammonia in a normal solution and pH, the ammonia mostly exists as ammonium ions in the vicinity of neutrality, but becomes almost free ammonia at pH 11.5. Therefore, at pH 11.5 and above, there is no change of ammonium ion to free ammonia,
Since hydrogen ions are not released, it can be regarded as the end point in this titration.

Further, the calculation formula for calculating the total ammonia concentration from the alkali titration amount in step 119 can be expressed as the following formula.

[0054]

## EQU00002 ## Total ammonia (mg.N / l) = (ab) F.times. (1000 / sample ml) .times.14.times.1.3 (2) where a; titration pH range of sample ( Titration amount corresponding to 7 to 11.5) b; Titration amount corresponding to the titration pH range (7 to 11.5) by blank test F; Factor of 1N sodium hydroxide solution (2) where 14 is the concentration conversion coefficient and 1.3 is phosphorus This is a conversion factor that takes into consideration the dilution due to the addition of the phosphorus insolubilizing reagent when the insolubilization treatment is performed. When 0.1N NaOH is used as the alkali, the coefficient is multiplied by 0.1.

After measuring the total organic acid concentration and the total ammonia concentration of the sample to be measured in this way, a cleaning operation is performed in step 120. In this cleaning operation, the pump P ₂ is operated to clean the inner wall surface of the mud receiving tank 1 with the cleaning water in the cleaning water storage tank 25, and the pump P ₃ is operated to similarly perform both titration tanks 17 and 18. Clean the inner wall of the. After completion of the washing operation, the process returns to step 101, and the same operation is repeated.

In the sample pretreatment unit 30 shown in FIG. 1, when the phosphate insolubilizing reagent 2b is injected to make the phosphate ion in the sample an insoluble salt, the sample is injected by the reagent. It is necessary to correct the concentration in consideration of the dilution of. In this example, by performing ultrafiltration after insolubilizing phosphoric acid in the pretreatment stage, most of the causative substances that give a positive error such as the ss component can be removed, and ammonia and organic acid It is possible to improve the measurement accuracy in the low concentration region.

In this embodiment, the two titration tanks 17 and 18 are used as the alkali titration processing section 40, but one titration tank can be used as the two titration tanks. In this case, after the organic acid concentration is first measured by the titration tank, the alkali concentration can be continuously measured to measure the ammonia concentration.

Furthermore, it is also possible to change the pretreatment operation of the sample to be measured and the reagent, and perform titration using an acid such as hydrochloric acid instead of alkali. In this case, the step of removing the phosphorus insolubilizing reagent or the soluble carbonic acid can be omitted, and the alkalinity is calculated from the titration amount until the pH reaches 4.8 by performing titration using 1N HCl. The total inorganic carbon concentration can be estimated by multiplying the alkalinity by a coefficient.

[0059]

As described in detail above, according to the method for measuring the organic acid and ammonia concentration of digested sludge and the apparatus therefor according to the present invention, the organic acid concentration and the ammonia concentration can be measured almost simultaneously, and The measurement operation can be automated. Especially, compared to the conventional organic acid concentration measuring device using the steam distillation method or the ammonia concentration measuring device using the indophenol blue absorptiometry method, the operation is simplified and the measurement time is shortened. In addition, there is an effect that the measurement accuracy does not decrease due to the dilution of the sample. Moreover, even when measuring a sample with a high concentration of ammonia nitrogen of several hundred to several thousand mg / l, such as digested sludge, it is not necessary to dilute the sample, and the same sample is repeatedly measured. It is possible to make the error within an allowable range.

In the practice, the sample to be measured has a function of volatilizing and removing soluble carbonic acid and sulfide ions in the air by aerating with nitrogen under an acidic condition. The organic acid concentration and the total ammonia concentration can be calculated. Further, by changing the concentration of the alkali for titration, it is possible to measure a wide range of organic acid concentration and ammonia concentration from low concentration to high concentration without diluting the sample.

Further, a method for measuring the concentration of ammonia is provided, which can obtain a practically satisfactory measurement accuracy without using a solid-liquid separation device for a digested sludge sample or an expensive control device such as a personal computer, and can automate the measurement operation. You can do it.

Further, by using a phosphorus insolubilizing reagent as a pretreatment of the sample to be measured and removing the phosphate ion having a pH buffering action as an insoluble salt, the positive error given to the measured value of the ammonia concentration is reduced, Further, by applying an ultrafiltration device as a pre-sample to remove the acid-soluble solid sulfides and proteins in the ss component that also have a pH buffering action, positive errors due to interfering substances can be eliminated.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the measurement principle of the device of the present invention.

FIG. 2 is a chart illustrating the operation of the device of the present invention.

FIG. 3 is a chart illustrating the operation of the device of the present invention.

FIG. 4 is a schematic diagram showing an example of a device for calculating organic acid, ammonia, and inorganic carbon concentrations based on the acid-base equilibrium theory.

Claims (6)

[Claims] 1. A step of injecting a phosphorus insolubilizing reagent into a sample to be measured extracted and separated from digested sludge to convert phosphate ions into an insoluble salt, and injecting a flocculant to form a fine particle component, and the sample. Applying an ultrafiltration device to remove salts, suspended matter components and proteins in the liquid, and after transferring a certain amount of sample to the organic acid measurement titration tank and the ammonia measurement titration tank, the samples in both titration tanks are removed. A step of acidifying, aeration of air from which nitrogen gas or carbon dioxide has been removed in both titration tanks for a certain period of time to volatilize the soluble carbonic acid in the sample, and using an alkaline solution for both titration tanks. Perform the titration and calculate the total organic acid concentration in the sample to be measured from the amount of the alkaline solution required for the neutralization titration of the sample in the organic acid measurement titration tank, and continue the titration for the ammonia measurement titration tank. hand,
And a step of calculating the total ammonia concentration of the sample to be measured from the titration amount of alkali required until the ammonium ion in the ammonia measuring titration tank becomes free ammonia, and an organic acid of digested sludge, Ammonia concentration measurement method. 2. The method for measuring the organic acid and ammonia concentrations of digested sludge according to claim 1, wherein the sample to be measured is a liquid obtained by subjecting a supernatant of the digested sludge to a centrifugal separation treatment. 3. The titration amount of alkali required for the ammonium ions in the ammonia titration tank to become free ammonia is the amount of alkali required for the pH of the sample to change from 7 to 11.5. 1. The method for measuring the organic acid and ammonia concentrations of digested sludge according to 1. 4. The organic acid measuring titration tank and the ammonia measuring titration tank are combined into one titration tank, and the organic acid concentration is calculated by alkali titration to the titration tank, and then the titration is continued. A method for measuring the organic acid and ammonia concentration of digested sludge, which comprises calculating the ammonia concentration by means of a method. 5. A mud receiving tank for receiving a sample to be measured extracted and separated from digested sludge, and a phosphorus insolubilizing reagent and an aggregating agent are injected into the sample to be measured to convert phosphate ions into an insoluble salt and form a fine particle component. A coagulation tank, an ultrafiltration device for removing salts, suspended matter components and proteins in the sample, a titration tank for measuring an organic acid and a titration tank for measuring ammonia, to which a fixed amount of sample is transferred, and both titration tanks An acid dispenser that acidifies the sample inside, a nitrogen gas supply device that aerates nitrogen gas in both titration tanks, and an alkali titration dispenser that titrates the alkaline solution with respect to the samples in both titration tanks , PH provided in both titration tanks
Based on the measured value of the meter, while controlling the operation of the acid dispenser and the dispenser for alkali titration, the amount of the alkaline solution required for neutralization titration of the sample in the titration tank for measuring organic acid Measurement result calculation unit that calculates the total organic acid concentration in the sample, while calculating the total ammonia concentration in the sample to be measured from the titration amount of alkali required until the ammonium ions in the ammonia measurement titration tank become free ammonia An apparatus for measuring organic acid and ammonia concentrations in digested sludge, which comprises: 6. The digested sludge according to claim 5, further comprising a cleaning treatment unit for supplying cleaning water to the mud receiving tank, the organic acid measuring titration tank and the alkali measuring titration tank after the measurement is completed. Organic acid and ammonia concentration measuring device.