KR19980082125A - Method and apparatus for measuring organic pollutants in effluents - Google Patents

Abstract

The present invention relates to a method and apparatus for measuring organic contaminants in effluent using ultraviolet absorbance, wherein the effluent is irradiated with ultraviolet light to measure absorbance, the effluent is filtered, and the filtered effluent is irradiated with ultraviolet light to measure absorbance before and after filtration. A method for measuring the concentration of organic contaminants in a sample by obtaining a corrected absorbance value using the values, a sampling pump, a suspended solids filtration unit connected to the sampling pump, an ultraviolet absorbent unit connected to the suspended solids filtration unit, and measuring ultraviolet absorbance, The organic contaminant measuring device in the effluent includes a conduit and valve connecting the sampling pump and the ultraviolet absorbing unit and a microprocessor connected to each unit to process electrical signals and control the pump and the valve. High value of reliability and suspended solids Because of the high correlation between absorbance and organic pollutant concentration in the samples contained, it is difficult to measure daily BOD daily, such as individual sewage treatment or small sewage / wastewater treatment plants using septic tanks, and to monitor organic pollutant emissions in areas where pollutant emissions are difficult to monitor. It is suitable for applications where it is mainly used to continuously monitor the concentration of BOD or organic contaminants.

Description

Method and apparatus for measuring organic pollutants in effluents

[Industrial use]

The present invention relates to a method and apparatus for measuring organic contaminants in effluent using ultraviolet absorbance, and more particularly, is included in septic effluent and includes BOD (biochemical oxygen demand) or COD (chemical oxygen demand). The present invention relates to a method and apparatus that can be applied to a system capable of continuously measuring organic contaminants by measuring organic contaminants represented by using ultraviolet absorbance.

[Prior art]

Wastewater discharged from households is treated mainly by centralized treatment by large sewage treatment plants. However, wastewater in areas with low population densities such as mountainous areas and coastal areas is expensive to install into sewage pipes to the sewage treatment plant. It is suitable. Individual sewage treatment is mainly composed of septic tank and sand filter. In septic tank, decay or oxidation by microorganisms in domestic sewage occurs and suspended solids are filtered out in sand filter. The individual sewage treatment method can be a very good treatment method compared to the central treatment method when managed efficiently, but there is a problem that it is very difficult to efficiently manage or monitor the pollutant. The main reason why monitoring pollutants is difficult is that no equipment has been developed to continuously and efficiently measure organic contaminants in effluents.

The 5 days BOD is widely used for the measurement of organic contaminants contained in the effluent, but the 5 days BOD measurement method is difficult to measure the organic contaminants continuously because it is time consuming, inconvenient, and inaccurate. Recently, a method for measuring BOD within a rapid time period has been developed to compensate for the shortcomings of the 5-day BOD measurement method. As the BOD measurement method, a method using the biofilm electrode method of US Pat. No. 5,356,792, US Pat. No. 5,518,893 And the method using the ultraviolet absorber of US Pat. No. 5,420,432.

Among them, the biofilm electrode method is a method of thinly coating microorganisms on an ultrafiltration membrane film and then bonding the coating film with an oxygen electrode. When a sample is passed through the biofilm electrode, microorganisms fixed on the film consume oxygen by metabolism of organic matter. The oxygen concentration gradient is formed inside and outside the film, and it is converted into a current signal to predict the organic concentration and convert it to BOD. In addition, the method using a bioreactor is introduced into the bioreactor cultured microorganisms and then measured the change in oxygen concentration over time with a dissolved oxygen (DO) meter to calculate the amount of oxygen consumed at this time to the BOD It is equivalent. The biofilm electrode method or the bioreactor method is similar to the 5-day BOD, which is a method of measuring organic matter that can be biologically decomposed by microorganisms, and has a high correlation with the 5-day BOD value. Since it occurs within about 30 minutes, organic pollutants that are slowly decomposed are not measured, and thus the measured value has a lower value than the 5-day BOD.

On the other hand, BOD or organic substance concentration measurement method using the ultraviolet absorbance is a method using an organic compound containing a benzene ring or an organic substance having a conjugated double bond absorbs ultraviolet rays of 254nm wavelength. In other words, when the ultraviolet light is irradiated onto the sample, the light intensity decreases in proportion to the concentration of the organic material absorbing the ultraviolet light, thereby detecting the reduced light intensity to predict the concentration of BOD or organic matter. This method is very simple, has a very short measurement time of less than 10 seconds, has a high reproducibility for a single sample, and is more economical than the biofilm electrode method or bioreactor method. It is a suitable system where organic pollutant measuring equipment which is inexpensive and easy to operate is required such as individual sewage treatment monitoring. However, the ultraviolet absorbance method has a problem in that a large amount of suspended solids in the sample affects the measured value. That is, since the suspended solids absorb ultraviolet rays or scatter light, when the suspended solids are large in the sample, the decrease in intensity of irradiated ultraviolet rays is large, and thus the BOD concentration is higher than the actual value.

In order to solve this problem, the existing ultraviolet absorbance method uses a method of indirectly measuring the concentration of suspended solids and correcting the ultraviolet absorbance value. have. The use of visible light absorbance is one in which visible light in a yellow region is correlated with the absorbance of suspended solids. The concentration of organic contaminants is determined by correcting the ultraviolet absorbance value to the visible light absorbance. The method of using the scattering degree of light is to determine the concentration of organic pollutants by detecting the intensity of scattered light when the sample is irradiated with visible light and correcting the ultraviolet absorbance. However, because not only suspended solids but also soluble organics absorb visible light, it is difficult to accurately predict suspended solids using visible light absorbance, and scattered light because the degree of light scattering varies according to the type of suspended solids. It is not possible to accurately determine the concentration of suspended solids in a sample by using the method of determining the strength of. Therefore, when determining the concentration of BOD or organic matter in the above manner, there is a problem in that it shows a significant difference from the actual 5 days BOD value or organic pollutant concentration.

The present invention is to solve the problems of the prior art as described above, the present invention is a method for measuring organic contaminants suitable for areas where it is difficult to monitor pollutant discharge, such as a small-scale treatment plant or individual septic tank, the organic pollutants in the effluent continuously and efficiently It is an object of the present invention to provide a method and apparatus for measuring organic contaminants that can be measured in a short time and minimized errors in the concentration of organic contaminants due to suspended solids present in the effluent.

1 is a process flowchart of an organic pollutant measuring device according to an embodiment of the present invention.

Figure 2a is a cross-sectional view of the suspended solids filtration unit according to an embodiment of the present invention.

Figure 2b is a hollow fiber membrane filtration process inside the suspended solids filtration unit according to an embodiment of the present invention.

3 is a cross-sectional view of the ultraviolet absorbing unit according to an embodiment of the present invention.

4A is a graph showing 5-day BOD predicted against actual 5-day BOD according to one embodiment of the invention.

4B is a graph showing the 5 day BOD predicted by 254 nm ultraviolet absorbance with respect to the 5 day measured BOD.

[Means for solving the problem]

In order to achieve the above object, the present invention is to measure the first absorbance by irradiating the effluent with ultraviolet light, the step of filtering the effluent, measuring the second absorbance by irradiating the filtered effluent with ultraviolet light and the first absorbance The method provides a method for measuring organic contaminants in effluent, including correcting the value to a second absorbance value to measure the concentration of organic contaminants in a sample.

In addition, the present invention is a sampling pump for supplying a sample, a suspended solids filtration unit connected to the sampling pump and the first conduit to filter the suspended solids in the sample, the first installed in the first conduit to control the flow of the sample 1 a solenoid valve, an ultraviolet absorbing unit connected to a second conduit provided with a second solenoid valve on the suspended solids filtration unit to measure ultraviolet absorbance of a sample, a third conduit connecting the sampling pump and the ultraviolet absorbing unit, the A third solenoid valve installed in a third conduit and connected to the sampling pump, the first, second and third solenoid valves, the suspended solids filtration unit and the ultraviolet absorbing unit to control the flow of the sample, and process the electrical signal; Device for measuring organic contaminants in effluent including a microprocessor for controlling pumps and valves The ball.

Hereinafter, the present invention will be described in detail.

The organic pollutant measuring method of the present invention is a method suitable for a place requiring an organic pollutant measuring equipment which is inexpensive and easy to operate, such as monitoring individual sewage treatment. This is done by four steps: That is, after irradiating ultraviolet light to the sample to measure the first absorbance, microfiltration the sample, irradiating the ultraviolet light to the filtered sample to measure the second absorbance, and then the first absorbance value to the second absorbance value. Calibrate to determine the concentration of organic contaminants in the sample.

In the present invention, the method for determining the concentration of organic contaminants in the effluent is a method using ultraviolet absorbance, and the absorbance of the finely filtered sample instead of the visible light absorbance or scattering value used to overcome the interference effect of the suspended solids contained in the organic contaminants. It characterized by using. The ultraviolet region which can be used in the present invention is 200-300 nm, and most preferably ultraviolet light having a wavelength of 254 nm is used.

In the filtration step, microfiltration is performed using a filtration membrane having a pore size of 0.1-1 μm, and when the sample is precisely filtered, solids having a particle size of 0.1 to 1 μm or more are filtered so that light is scattered when the sample is irradiated with ultraviolet rays. Almost all of the suspended solids can be removed. The sample from which the suspended solids were removed contains only soluble organics, and the second absorbance is correlated with the concentration of soluble organics. The difference between the first absorbance and the second absorbance is due to absorption and scattering of ultraviolet rays by the suspended solids except soluble organics. Absorbance and correlate with the concentration of suspended solids.

Therefore, the organic substance concentration is determined by correcting the second absorbance to the absorbance value generated as the suspended solids. If the suspended solids are not organic, the concentration of the organics is determined by the second absorbance only.If the organics occupy a portion of the suspended solids, the difference between the first absorbance and the second absorbance is multiplied by a correction factor and then summed with the second absorbance. Determine the organic concentration. The correction factor is determined according to the type of wastewater, and the value is obtained experimentally and used by inputting it to the measuring device.

The correction value obtained experimentally is determined by calculating the ratio of volatile solids and nonvolatile solids among the solids contained in the waste water. The advantage of this method of determining BOD or organic matter concentration is that it directly measures the difference in the UV absorbance values due to the suspended solids, so that the organic matter concentration can be determined very closely regardless of how many or small the suspended solids are.

The apparatus for measuring the BOD or organic contaminants in the effluent according to the above method is a sampling pump 50, suspended solids filtration unit 10, ultraviolet absorption unit 20, micro It consists of a processor (not shown), conduits (40, 42, 44, 46, 48) connecting each unit, and various valves (30, 32, 34, 36, 38), and a septic tank and a small sewage and wastewater treatment plant. It is mainly used for monitoring pollutants.

Sampling pump 50 is a peristaltic pump (peristaltic pump) to take the sample periodically to supply the sample at fixed pressure, static pressure so that the ultraviolet absorption unit 20 and the suspended solids filtration unit 10 can operate normally Do it. A sampling tube is connected to the sampling pump 50 to collect a sample, and the sampling tube connected to the sampling pump uses a flexible hose that does not deform to temperature changes or acids or alkalis. In order to prevent contamination or blockage of the absorption unit 20, a mesh of 18 mesh size capable of removing 1 mm solids is installed. The sample collected by the sampling pump 50 is supplied to the suspended solids filtration unit 10 and the ultraviolet absorbing unit 20 through the first conduit 40 and the third conduit 44, respectively, and the flow of the sample Is controlled by a first solenoid valve 30 and a third solenoid valve 34 installed over each conduit.

The suspended solids filtration unit 10 is a precision filtration device that excludes suspended solids that affect ultraviolet absorbance. A hollow fiber membrane capable of filtering suspended solids is included inside the filter and is configured to be backwashed with tap water after filtration. . The suspended solids filtration unit 10 has a hollow fiber membrane 14, a support plate 15 for supporting it, a sample inlet 11 through which a sample is introduced, and a filtrate outlet 13 through which a sample is discharged, as shown in FIG. 2A. It consists of. The hollow fiber membrane 14 is usually made of polysulfone, polyethylene, polypropylene, polyacrylonitrile, and the hollow fiber membrane 14 having a hollow shape is fixed by the support plate 15. The hollow fiber membrane 14 has a pore size of 0.1-1 mu m, so that suspended solids of 0.1-1 mu m or more can not pass therethrough, and soluble organic substances can pass therethrough as shown in Fig. 2B. The filtration process is a process in which the sample is introduced through the sample inlet 11 and the suspended solids are filtered through the hollow fiber membrane 14, and then the sample from which the suspended solids are excluded flows into the filtrate outlet 13, and the suspended solids are filtered. The collected filtrate is supplied to the ultraviolet absorbing unit 20 through the second conduit 42, where the flow of the filtrate is controlled by the second solenoid valve 32. In addition, the suspended solids filtration unit 10 is installed in the fourth conduit 46, the fourth conduit 46 for introducing the washing water for cleaning, as shown in Figure 1 for adjusting the flow of the washing water A selenoid valve 36, a washing water outlet 12 through which the washing water for cleaning the hollow fiber membrane is discharged, and a fifth conduit 48 connected to the washing water outlet 12 and provided with a fifth solenoid valve 38; .

In the ultraviolet absorbing unit 20 measures the ultraviolet absorbance of the sample that is not removed from the suspended solids and the sample filtered through the suspended solids filtering unit (10). The ultraviolet range which can be used at this time is 200-300 nm, It is most preferable to use the ultraviolet-ray of 254 nm wavelength. UV absorbing unit 20 is a low pressure mercury lamp 21 as a light source, a lens 22 for collimating light, a quartz cell 23 through which a sample passes, a reflector 24 for diffracting light, and light. It consists of a detector 25 for sensing. The light intensity signal measured by the detector 25 passes through a signal amplifier (not shown) and is converted into absorbance in a microprocessor (not shown). Absorbance measurement follows the method of determining the relative absorbance value of the sample by setting the absorbance of distilled water to 0 and the value of the standard solution to the span value. Therefore, when the instrument is first set up or periodically calibrated, use distilled water and standard solution. Perform facial expressions on the device.

The microprocessor (not shown) may be configured to process electrical signals measured by the ultraviolet absorption unit 20, calculate electrical signals for quantifying organic matter, control the sampling pump 50 and various valves, input measurement cycles, and measurement values. Is responsible for the output of

Operation of the organic contaminant measuring apparatus of the present invention can be divided into three stages: ultraviolet absorbance measurement of the sample which is not largely filtered, absorbance measurement of the filtered sample, and washing of the suspended solids filtration unit. This will be described with reference to FIG. 1.

The ultraviolet absorbance measurement of the unfiltered sample is performed in the order that the third solenoid valve 34 is opened and the sampling pump 50 is operated to measure the ultraviolet absorbance at the ultraviolet absorption unit 20. The second, fourth, and fifth solenoid valves 30, 32, 36, 38 are all in a closed state.

The absorbance measurement of the filtration sample is performed by opening the first solenoid valve 30 and the second solenoid valve 32, operating the sampling pump 50, closing the fifth solenoid valve 38, and filtering the sample. It moves to the ultraviolet absorption unit 20, and it consists of the order of measuring the ultraviolet absorbance of a soluble organic substance. At this time, all of the third, fourth, and fifth solenoid valves 34, 36, and 38 are in a closed state.

The washing of the suspended solids filtration unit is performed in the order of opening the fourth solenoid valve 36 and the fifth solenoid valve 38 installed in the fourth conduit 46 and the fifth conduit 48, respectively. The second and third solenoid valves 30, 32, and 34 are all in a closed state. In this case, the tap water flows through the washing water outlet 12 through the sample inlet 11 of the suspended solids filtration unit 10, at which time the suspended solids adhered to the surface of the hollow fiber membrane 14 fall. At this time, the gate valve 52 and the pressure regulator 54 are installed in front of the fourth solenoid valve 36 in order to maintain a constant flow rate and pressure of the incoming tap water.

In order to convert the absorbance of the sample measured according to the above method and apparatus into the concentration of organic contaminants in the sample, the value of the UV absorbance of the sample was corrected to the absorbance of the filter sample and the 5-day BOD or COD value obtained through the water analysis. After returning, the linear equation of the linear equation between the corrected absorbance values and the BOD or COD values is obtained. At this time, the corrected absorbance value is the difference between the ultraviolet absorbance (second absorbance) of the sample in which the suspended solids are filtered, the absorbance (first absorbance) of the sample in which the suspended solids are not filtered, and the absorbance (second absorbance) of the filtered sample; It is determined by the calculation of the experimentally obtained suspended solids correction coefficient value, it is determined by the following equation (1). The linear linear first-order equation of the 5-day BOD or COD obtained in this manner is input to the microprocessor to convert the corrected absorbance value for the sample entering the device into the 5-day BOD or COD value.

[Equation 1]

Corrected absorbance value = second absorbance + (first absorbance-second absorbance) × correction coefficient

EXAMPLE

The following presents preferred examples and comparative examples to aid in understanding the invention. However, the following examples are provided only to more easily understand the present invention, and the present invention is not limited to the following examples.

Example

The BOD was measured by using a sample of primary wastewater (cold matter removal, gravity sedimentation) of wastewater consisting of food, manure, and bath water. After measuring the absorbance of the sample at 254 nm, the suspended solids of the sample were filtered by a precision filtration device equipped with a filtration membrane having a pore size of 0.1-1 μm, and the absorbance of the filtered sample was measured at 254 nm. The corrected absorbance of the sample was obtained by using the absorbance of the filtered sample, the difference between the absorbances of the non-filtered sample and the filtered sample, and the experimentally obtained suspended solids correction coefficient values. After plotting the predicted BOD value obtained by this method with respect to the measured 5 day BOD value, a regression linear equation was obtained to predict the correlation of ultraviolet absorbance, which is shown in FIG. 4A.

Comparative example

The experiment was performed in the same manner as in Example, except that the absorbed values obtained using only 254 nm ultraviolet absorbance were used to obtain the corrected absorbance instead of measuring the absorbance of the sample filtering the suspended solids. The results of are shown in Figure 4b.

In the case of FIG. 4A in which the ultra-violet absorbance is corrected by performing microfiltration, the predicted BOD is shown to be very close to the measured BOD because the effect of absorbance due to the suspended solids is excluded. On the other hand, in the results of FIG. 4B, the larger the BOD value of 5 days, the more severe the deviation of the predicted BOD, which is determined to have an influence on the absorbance due to the scattering of the ultraviolet solids. In terms of accuracy, when the correlation between the measured BOD and the predicted BOD is corrected by performing fine filtration to correct the absorbance, FIG. 4A shows a high correlation with 0.94, while FIG. 4B shows a low correlation with 0.85.

The method and apparatus of the present invention have a very short measurement time of about 10 seconds, can be manufactured at a very low price compared to conventional continuous BOD measuring equipment, and have high reliability because of the high measurement value. It is suitable for monitoring organic pollutant emissions in areas where it is difficult to measure 5-day BOD daily, such as wastewater treatment plants, and where pollutant emissions are difficult to monitor, and it is mainly applied to monitoring the concentration of BOD or organic pollutants continuously. In particular, it is possible to measure organic contaminants in place of 5-day BOD because it is difficult to regulate by measuring 5-day BOD, and the measured value stored in the microprocessor can be monitored from a long distance because data communication is possible through modem or dedicated line. And when an abnormality is found, it can respond quickly.

In addition, the method of the present invention can significantly increase the correlation between the absorbance and the organic contaminant concentration in the sample containing the suspended solids, compared to the method of determining the concentration of organic contaminants only by the ultraviolet absorbance, and the difference in the ultraviolet absorbance due to the suspended solids In the visible light correction method and the scattered light correction method for correction, the correlation coefficient of organic matter concentration is about 0.6 to 0.9, while the method of the present invention can increase the correlation coefficient to about 0.8 to 0.95.

Claims (10)

Irradiating the effluent with ultraviolet light to measure a first absorbance; Filtering the effluent; Irradiating ultraviolet light to the filtered effluent to measure a second absorbance; And Measuring the organic contaminant concentration of the sample by correcting the first absorbance value to the second absorbance value; Organic pollutants measuring method in the effluent containing. The method of claim 1, wherein the wavelength of the ultraviolet ray is 200 to 300 nm. The method of claim 1, wherein the filtration is microfiltration using a filtration membrane having a pore size of 0.1 to 1 μm. According to claim 1, The organic contaminant concentration measurement is obtained by using the experimentally measured correction coefficient obtained in the absorbance value corrected by Equation 1 below, the obtained absorbance value and 5 days BOD obtained through water analysis or Obtaining the regression line of the first equation as the COD value to convert the corrected absorbance value of the sample into a 5 day BOD or COD value. [Equation 1] Corrected absorbance value = second absorbance + (first absorbance-second absorbance) × correction coefficient A sampling pump for supplying a sample; A suspended solids filtration unit connected to the sampling pump and a first conduit to filter suspended solids in the sample; A first solenoid valve installed in the first conduit to control a flow of a sample; An ultraviolet absorbing unit connected to the suspended solids filtering unit by a second conduit provided with a second solenoid valve to measure ultraviolet absorbance of the sample; A third conduit connecting said sampling pump and said ultraviolet absorbing unit; A third solenoid valve installed in the third conduit to control the flow of the sample; And A microprocessor connected to the sampling pump, the first, second, and third solenoid valves, the suspended solids filtration unit, and the ultraviolet absorption unit to process an electrical signal and to control the pump and the valve; Organic pollutant measuring device in the effluent containing. The apparatus of claim 5, wherein the suspended solids filtration unit comprises a sample inlet through which a sample is introduced, a hollow fiber membrane through which the sample is introduced, and a filtrate outlet through which the sample passed through the hollow fiber membrane is discharged. The apparatus of claim 6, wherein the hollow fiber membrane has a pore size of 0.1-1 μm. The device of claim 6, wherein the hollow fiber membrane is selected from the group consisting of polysulfone, polyethylene, polypropylene, and polyacrylonitrile. According to claim 5 or 6, wherein the suspended solids filtration unit is a fourth conduit for introducing the washing water, a fourth selenoid valve installed in the fourth conduit to control the flow of the washing water, the hollow fiber membrane to clean the And a fifth conduit connected to said wash water outlet, said fifth conduit connected to said wash water outlet, and having a fifth solenoid valve installed. 6. An apparatus according to claim 5, wherein the wavelength of ultraviolet rays in said ultraviolet absorption unit is 200-300 nm.