JPH0735741A - Bod measuring equipment - Google Patents

Abstract

PURPOSE:To allow independent measurement of C-BOD (biochemical oxygen demand) due to oxidation of organic substance and N-BOD based on nitrification while eliminating the clogging of piping system. CONSTITUTION:A biosenscr 31 measuring C-BOD using microorganisms eating organic substances is combined with a biosensor 32 measuring N-BOD using nitrified bacterium eating ammonia nitrogen and further provided with a pretreatment unit 2 and a suspesoid removing unit 33 thus allowing independent measurement of C-BOD and N-BOD and more detailed analysis of water quality. Even if suspesoid or suspended matters remain in the sample water passed through the pretreatment unit 2, they scarcely cause clogging of piping system and thereby the maintenance frequency can be decreased while enhancing the measurement accuracy.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the biochemical oxygen demand (BOD) in water in wastewater from sewage treatment plants, factories, business establishments, and in environmental waters such as rivers and lakes. The present invention relates to an apparatus that independently measures (C-BOD) and BOD (N-BOD) based on the nitrification action of nitrogen compounds, and particularly to a BOD measurement apparatus that can be simply and accurately measured using a biosensor.

[0002]

BOD is the dissolved oxygen content in water consumed by aerobic microorganisms at 20 ° C. for 5 days, expressed in mg / l, and is extremely important as the most representative water pollution index. BOD is usually Japanese Industrial Standard (JIS)
Factory drainage test method (JIS K 0102:
It is measured as an official method by the Industrial Wastewater Testing Method), but this official method requires (a) a long time of 5 days until the measurement results are obtained, which is important for managing wastewater treatment processes. Therefore, the measurement result cannot be utilized promptly.

(B) For example, determination of the dilution ratio of the sample, p
H removal and interference removal operations, nitrification suppression,
Measurement operations such as planting are very complicated and require skill. (C) Since it is a manual analysis, automatic measurement cannot be performed. In recent years, the BOD measurement method using a biosensor (microorganism sensor) that applies an immobilized microbial membrane has been
It is described in Japanese Examined Patent Publication No. 61-7258.

The above-mentioned BOD measuring method using a biosensor is an effective BOD measuring method capable of measuring BOD in wastewater in about 20 to 40 minutes, and its apparatus was introduced in 1990 in Japan. Industrial standard (JIS K 3602: Biochemical oxygen consumption "BOD _S " measuring instrument with microbial electrode)
Came to be adopted as. However, since the pores of the immobilized microbial membrane are usually as small as 0.22 to 0.45 μm, the immobilized microorganisms should directly utilize the soluble organic substances that pass through the pores. However, suspended organic substances that cannot pass through the pores cannot be assimilated. In addition, the suspended organic matter causes clogging in the liquid delivery system (pump), the piping system (tube), etc. of the BOD measurement device, which is a serious problem in terms of measurement accuracy and maintenance. Further, this type of biosensor used for BOD measurement changes the pH value inside the immobilized microbial membrane due to the organic acid generated when the soluble organic matter in the sample water is assimilated, and the sensor output fluctuates. Therefore, in order to prevent this, a buffer solution is used, and the sample solution is mixed with the buffer solution and diluted before the measurement. Therefore, when continuously monitoring the BOD in the sample water, the consumption of the buffer solution increases, which causes problems in maintenance and running cost of the measuring device.

On the other hand, the present inventors solubilized suspended substances in sample water with a pretreatment device, and B derived from a suspending organic substance, which was impossible with the conventional biosensor methods.
From the same applicant, a practical BOD measuring device capable of measuring the OD measuring device and saving the buffer solution is disclosed in Japanese Patent Application Laid-Open No. 2-3.
This is disclosed in Japanese Patent No. 1153. The outline is described below.

FIG. 4 is a BOD filed by the inventors of the present invention.
It is a schematic diagram which showed the flow direction of the sample water with the arrow about the structure of a measuring device. In FIG. 4, the water sampling device 1 includes a raw water pump 1a for sampling waste water, a sample water storage tank 1b sampled by overflow, and pipes. The pretreatment device 2 crushes suspended matter in the sample water sampled by the water sampling pump 3 and solubilizes it, and uses an ultrasonic homogenizer, an ozonizer, or the same applicant as the applicant. It is composed of an enzyme reaction tank and a semiconductor photoreaction tank in Japanese Patent Application No. 5-47035. The measuring device is the water sampling device 1 , the pretreatment device 2 , the biosensor 5 provided in the constant temperature tank 4, the standard solution tank 6, the dilution water tank 7,
A liquid sending device including valves 8, 9, 10, 11 and a pump 12 and a pipe, a buffer solution circulating device 15 including a buffer solution tank 13, a pump 14 and a pipe, and an arithmetic process of an output signal of the biosensor 5. The measurement / control circuit 16 controls the operation of the measuring apparatus. As the buffer solution, for example, a phosphate buffer solution of 0.05 to 0.1 M and pH 7.0 is used. As the standard solution, for example, two kinds of equal-volume mixed solutions of glucose and glutamic acid are used, and used for preparing the calibration curve of the biosensor 5 . The dilution water is, for example, a standard solution of BOD 0 mg / l, and is used each time for measurement in order to wash the piping path and dilute the sample water.

FIG. 5 is a schematic sectional view showing the structure of the biosensor 5 . In FIG. 5, the biosensor 5 is composed of a flow cell 18 to which an immobilized microbial membrane 17 is attached and a dissolved oxygen detector 19, and the thermostat 4 shown in FIG.
Can be stored in and kept at the measured temperature. It should be noted that the sample water and the buffer solution are also placed inside the constant temperature bath 4 in the heat exchangers 20, 21.
Is maintained at the measurement temperature by passing through. The biosensor 5 uses the dissolved oxygen detector 19 as a current value signal to show the amount of decrease in dissolved oxygen consumed when the soluble organic matter is assimilated by the microorganisms immobilized in the immobilized microbial film 17. Output. The amount of decrease in dissolved oxygen is proportional to the concentration of the dissolved organic matter dissolved in the sample water,
The value of the soluble C-BOD can be calculated by the calculation / control circuit 16 from the output signal current value.

The BOD measurement by the biosensor 5 is carried out for the current value of the output signal when a preset time of about 5 to 15 minutes has passed since the sample water was supplied into the flow cell 18. Referring again to FIG. 4, the output signal from the biosensor 5 is calculated / controlled by the calculation / control circuit.
Digitalized by 16 A / D converters 22
3, the formula of the calibration curve and the BOD value of the sample water are calculated and recorded according to a predetermined calculation formula. The calculated BOD value is output from the output device 24, or the valves 8, 9, 10, 11 are switched and the operation control signals of the water sampling pump 3 and the pretreatment device 2 are output according to a preset order and time. Output. As shown in FIG. 5, the buffer solution flows in from the buffer solution inlet 27 and flows out from the buffer solution outlet 28 in the biosensor 5 , and is always transferred by the buffer solution circulation device 15 at, for example, 1 to 3 ml / min. It passes through the heat exchanger 21 and is circulated while being kept at the measurement temperature. As the buffer solution, a phosphate buffer solution of 0.05 to 0.1 M and pH 7.0 as described above may be used, and a solution containing a trace amount of nutrient added thereto may also be used.

First, in accordance with the switching command of the output device 24, only the dilution water in the dilution water tank 7 passes through the valve 10 and the heat exchanger 20 by the pump 12 to be kept at the measurement temperature and flow from the liquid inlet 29. Then, it is sent into the biosensor 5 and discharged from the liquid outlet 30 to the outside of the system. Biosensor 5
After the output signal of is stabilized, the valves 8 and 9.10 are sequentially switched according to a preset order, a calibration curve is created by the BOD standard solution, and the BOD calculation formula is stored in the memory 25. Next, at the time of calibration of the biosensor 5 , the sample water sampled at the same time by the water sampling pump 3 and solubilized by the pretreatment device 2 passes through the heat exchanger 20 by the pump 12 through the valve 11 and the measured temperature. And the BOD value is measured by being sent to the biosensor 5 . The biosensor 5 is calibrated several times a day, and the BOD measurement of the sample water can be repeated at regular time intervals.

[0010]

According to recent research,
It seems that organic matter was sufficiently removed by biological treatment.
As a result of measuring BOD by manual analysis, the treated water was originally organic.
BOD (C-BOD) due to oxidation of products should be measured
However, BOD (N-BOD) due to nitrification is simultaneously
Unexpectedly high BOD as it will be measured
However, for example, according to Hattori et al., Magazines, water and wastewater:34
(5) Described and pointed out in 397 (1992), etc.
It

Under such circumstances, B described in the above-mentioned Japanese Patent Laid-Open No. 2-31153 using a biosensor.
The OD measuring device is equipped with a pretreatment device that oxidizes and decomposes suspended organic matter and lowers the molecular weight of soluble organic matter, and in order to measure C-BOD derived from organic matter, many Although it has advantages, it is difficult to measure N-BOD based on nitrification. In addition, a suspended substance or a suspended matter that has not been completely processed in the sample pretreatment device causes clogging of the piping system, which causes a problem in measurement accuracy and maintenance of the device.

The present invention has been made by paying attention to the above points, and the purpose thereof is to provide C-BOD by oxidation of organic substances.
And N-BOD based on nitrification can be measured independently to perform a more detailed water quality analysis, and further, it is possible to eliminate suspended substances and suspended substances that clog the piping system. It is another object of the present invention to provide a biosensor application BOD measuring device having a suspended substance removing device having an automatic backwashing mechanism.

[0013]

In order to solve the above problems, the BOD measuring apparatus of the present invention uses a biosensor for C-BOD measurement using a microorganism that assimilates an organic substance, and assimilates ammoniacal nitrogen. The biosensor for N-BOD measurement using nitrifying bacteria is used in combination with a pretreatment device and a suspended substance removing device.

[0014]

Since the BOD measuring device of the present invention is constructed as described above, it is possible to measure C-BOD and N-BOD independently of each other, which enables more detailed water quality analysis. Even if there are suspended solids or suspended solids that have not been completely processed in the sample water that has passed through the processing unit, the system is equipped with a suspended substance removal unit that eliminates them. Clogging is less likely to occur, less maintenance is required, and measurement accuracy is high.

[0015]

EXAMPLES The present invention will be described below based on examples. FIG. 1 is a schematic diagram showing a configuration of a main part of a BOD measuring device according to the present invention and a liquid feeding system for sample water, and the same reference numerals are used for the same parts as those in FIG. The basic structure of the apparatus of FIG. 1 according to the present invention is almost the same as that of the apparatus shown in FIG. 4, and the portion surrounded by a dotted line is C-B.
It is represented as an OD measuring biosensor 31 .

There are two differences between FIG. 1 and FIG. 4, and one is
The device of FIG. 1 includes a biosensor for N-BOD measurement.32To
Added, specifically, fixed in the immobilized microbial membrane.
Nitrite is produced by the microorganisms and the standard solution for calibration.
Change with bacteria, eg to concentrations of 0.2 and 0.4 mg / l
The biosensor for N-BOD measurement32
Is structurally a biosensor for C-BOD measurement31And totally
Is the same. In addition, the N-BOD measurement should be performed in advance.
The relationship between the ammoniacal nitrogen concentration and N-BOD was calculated by the official method.
From the ammonia nitrogen concentration based on the conversion value obtained by measurement
Calculate and determine N-BOD.

The second difference between FIG. 1 and FIG. 4 is that a suspension substance removing device 33 is added. From the above, only the suspension substance removing device 33 will be described here. FIG. 2 is a schematic diagram showing a configuration of a main part of the suspended substance removing device 33 by enclosing it with a dotted line. In FIG. 2, the sample water that has passed through the pretreatment device 2 is sent from the valve 35 to the pump 12 after the suspended substance is removed by the storage tank 34. Bal <br/> Bed 35 has a valve to a normally open valve 35a, the two opposite operations each other normally closed valve 35b, the porous filter 36 is normally open valve 35
a and a normally closed valve 35b are connected to an air pump 37. At the time of measurement, the porous filter 36 uses the normally closed valve 35b for pump 12
Send sample water from the measuring system to the measuring system, and when not measuring, air pump 37
The air can be sent through the normally open valve 35a, and the backwash can be automatically performed by using the valves 35 that operate in reverse with each other. Further, the pressure indicated by the pressure gauge 38 is sent as a signal to the arithmetic / control circuit 16, and when the pressure exceeds a certain value, for example, 0.5 Kg / cm ³ , it is displayed on the output device 24 as the filter replacement time.

FIG. 3 shows the use of the BOD measuring device of the present invention.
It is a bar graph which shows the result obtained by measuring three kinds of secondary treated water. In Figure 3, manual analysis BOD and C- respectively.
The BOD sensor measurement value, the N-BOD sensor measurement value, and the (C + N) -BOD value are shown. From the results of FIG. 3, Total BOD, that is, (C + N) -BOD, can obtain a value close to BOD ₅ of the official method (manual analysis), and C-BOD and N-BOD can be known as a breakdown thereof. .

[0019]

[Effects of the Invention] B in water in wastewater from sewage treatment plants, factories, business establishments, and in environmental waters such as rivers and lakes.
When OD is measured by a BOD measuring device using a biosensor, BOD (C-
BOD) should be measured, but B due to nitrification
Since the OD (N-BOD) is measured at the same time, it is pointed out that the BOD value is surprisingly high. By using the BOD measuring device of the present invention made to solve this, as described in the embodiment, C-BOD and N-
Since BOD and BOD can be measured independently at the same time, more detailed water quality analysis can be performed, and effective information can be obtained regarding the discharged water quality of the sewage treatment process. It will be possible.

Further, in the past, the suspended substance component in the sample water caused the clogging of the piping system of the measuring device, which was a problem in terms of measurement accuracy and frequency of maintenance of the device. According to the above, since a suspended substance removing device is provided in the device system, the suspended substance that has not been completely processed by the pretreatment device is removed, and then the measurement is performed. The frequency of the BOD measurement is reduced, and a highly practical BOD measurement device can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a main part of a BOD measuring device of the present invention.

FIG. 2 is a schematic diagram showing a main part configuration of a suspended substance removing apparatus used in the BOD measuring apparatus of the present invention.

FIG. 3 is a bar diagram showing the measurement results of the BOD measuring device of the present invention.

FIG. 4 is a schematic diagram showing a configuration of a conventional BOD measuring device.

FIG. 5 is a schematic diagram showing the configuration of a biosensor.

[Explanation of symbols] 1 water sampling device 1a raw water pump 1b storage tank 2 pretreatment device 3 water sampling pump 4 constant temperature tank 5 biosensor 6 standard solution tank 7 dilution water tank 8 valve 9 valve 10 valve 11 valve 12 pump 13 buffer solution tank 14 Pump 15 Buffer Solution Circulation Device 16 Operation / Control Circuit 17 Immobilized Microbial Membrane 18 Flow Cell 19 Dissolved Oxygen Detector 20 Heat Exchanger 21 Heat Exchanger 22 A / D Converter 23 Computing Device 24 Output Device 25 Memory 27 Buffer Solution Inlet 28 Buffer Solution Outlet 29 Liquid Inlet 30 Liquid Outlet 31 Biosensor for C-BOD Measurement 32 Biosensor for N-BOD Measurement 33 Suspended Substance Removal Device 34 Storage Tank 35 Valve 35a Normal Open Valve 35b Normal Closed Valve 36 Porous Filter 37 Air pump 38 Pressure gauge

Claims (4)

[Claims] 1. A water sampling device for collecting and storing sample water, a pretreatment device for solubilizing suspended matter, and a suspended substance removing device,
A BOD measuring device comprising a biosensor for measuring BOD derived from an organic substance and a biosensor for measuring BOD derived from ammoniacal nitrogen. 2. The BOD measuring device according to claim 1,
A biosensor for measuring BOD derived from an organic substance comprises a. A biosensor combining an immobilized microbial membrane on which microorganisms that utilize organic substances are immobilized and a dissolved oxygen detector, b. A liquid sending device for sending reagents, washing water, and sample water to a dissolved oxygen detector, c. A buffer solution circulation device for circulating a buffer solution through the dissolved oxygen detector, d. A heat exchanger that is placed in a constant temperature bath to keep the sample water and the buffer solution at the measurement temperature, e. A BOD measuring device having an arithmetic / control circuit for performing arithmetic processing of an output signal of a biosensor and operation control. 3. The BOD measuring device according to claim 1 or 2, wherein the biosensor for measuring BOD derived from ammoniacal nitrogen is a. A biosensor combining an immobilized microbial membrane on which nitrifying bacteria that selectively utilize ammoniacal nitrogen are immobilized and a dissolved oxygen detector, b. A liquid sending device for sending reagents, washing water, and sample water to a dissolved oxygen detector, c. A buffer solution circulation device for circulating a buffer solution through the dissolved oxygen detector, d. A heat exchanger that is placed in a constant temperature bath to keep the sample water and the buffer solution at the measurement temperature, e. A BOD measuring device having an arithmetic / control circuit for performing arithmetic processing of an output signal of a biosensor and operation control. 4. The BOD measuring device according to any one of claims 1 to 3, wherein the suspended substance removing device comprises an air pump, a porous filter, two valves that operate in reverse, and a pressure gauge, and the biosensor according to a predetermined sequence. A BOD measuring device having a backwashing mechanism that operates when calibrating the pressure gauge or when the pressure exceeds the set pressure of the pressure gauge.