JP2007198869A - Biofilm monitoring method of aqueous system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biofilm monitoring method which enables grasping of the adhesion state of the biofilm of an aqueous system in an accurate, rapid and easy manner. <P>SOLUTION: In this method, a predetermined amount of a predetermined compound is added to the target aqueous system, and the water of the target aqueous system is sampled at each predetermined time by analyzing the concentration of the added compound; and from the extent of the reduced amount of the added compound, the biofilm formed in the aqueous system is monitored. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for monitoring a biofilm generated in an aqueous system.

It is known that when microorganisms are present in various water systems such as cooling water for various processes and air conditioning and circulating water in the manufacturing process in the paper industry, they cause problems.
As one of the problems, there are obstacles such as clogging of pipes due to biofilms produced by microorganisms, reduction of heat transfer efficiency in heat exchangers, corrosion of metal parts of pipes, or contamination of products due to biofilms.

  In order to prevent such obstacles, a treatment for adding a bactericidal agent to the aqueous system is performed, or depending on the situation, in order to remove the biofilm generated in the aqueous system, the biofilm is washed with a release agent or the like. A removal process is performed.

  In order to appropriately and efficiently perform the above treatment, it is necessary to accurately grasp the state of biofilm formation in the aqueous system.

As a method for monitoring the biofilm in the aqueous system, a method of immersing an adhesive plate such as a rubber plate or a glass plate in the aqueous system and periodically measuring the amount of the biofilm adhering thereto (Non-patent Document 1) , A method of knowing the tendency of adhesion from the differential pressure change in the tube due to dirt adhesion (Non-patent Document 2), measuring the change in natural potential of stainless steel due to the adhesion of microorganisms A known method (Patent Document 1), a method for knowing the adhesion state (Patent Document 2), etc. are known from the degree of decrease in light transmittance due to the adhesion of microorganisms to transparent materials such as acrylic plates and acrylic tubes.
Introduction to microbial corrosion for engineers NACE Standard RP0189-2002 On-Line Monitoring of Cooling Waters (2002) Japanese Patent Laid-Open No. 2001-4590 JP-A-9-236546

  However, the method of immersing the adherent plate in the aqueous system changes the amount of attachment depending on where the adherent plate is installed in the aqueous system, and it is difficult to grasp the biofilm adhesion amount of the entire aqueous system. When pulling up from the water system, there is a possibility that the biofilm may fall off, and there is a risk that the obtained result may be inaccurate. Also, it takes time from the installation of the adhesive plate to the formation of the biofilm. And there is a problem that the result cannot be immediately known.

  Also, regarding the method for measuring the change in differential pressure, the method for measuring the change in the natural potential of stainless steel, and the method for measuring the decrease in light transmittance, the biofilm should be placed on the measurement part of the device after installation. It takes time to form and understand the situation, and many devices take a bypass from the water system and guide the water to the device and measure in the device. It is merely an indirect measurement of the adhesion status, and it is difficult to say that the situation of the entire water system is accurately grasped. Also, there is a problem with the space where the device is installed, and maintenance of the device after installation. There are problems such as the need for maintenance and the time-consuming maintenance and the cost of the device itself.

  Accordingly, an object of the present invention is to provide a biofilm monitoring method capable of accurately, quickly and easily grasping the state of attachment of an aqueous biofilm.

  The present invention adds a predetermined amount of a predetermined compound to the target aqueous system, collects the water every predetermined time, and analyzes the concentration of the added compound. The present invention provides a method for monitoring the biofilm produced in the next step.

  In the present invention, the compound added to the aqueous system is a low-molecular compound soluble in water that can be used by microorganisms, and these compounds are preferably organic acids, amino compounds, ammonium salts, and saccharides. Specifically, the organic acid is formic acid, acetic acid, propionic acid, butyric acid, lactic acid, malonic acid, malic acid, citric acid, succinic acid, oxalic acid, pyruvic acid, and the amino compound is alanine, arginine, asparagine, Aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, urea, ammonium salts are ammonium chloride, ammonium sulfate, ammonium nitrate, acetic acid It is ammonium, and saccharides are glucose, fructose, galactose, mannose, maltose, sucrose, and lactose.

  According to the present invention, a predetermined compound is added to the target aqueous system, the water is collected at predetermined time intervals, and the concentration of the added compound is analyzed. A method of monitoring the produced biofilm is provided.

  According to the present invention, the state of biofilm production in the water system can be monitored by a simple method of collecting and analyzing the water without installing a new adhesion plate or measuring device in the water system of interest. In particular, the problem of securing the installation location and the maintenance problem after installation are not caused unlike the apparatus.

  In addition, in the method in which the attachment plate and the measurement device are installed in the water system, the biofilm is newly attached to the measurement unit of the attachment plate and the device, and the measurement is performed. Although it took time until it was newly generated and it took time to make a determination, in the present invention, since it is a method of directly measuring a biofilm already generated in the aqueous system, it takes a short time. You can know the result.

  Furthermore, in the method of installing the adherence plate or device in the water system, it is a method of measuring only the newly produced biofilm on the measurement unit of the attached adherence plate or device, and measuring the entire biofilm in the water system. I can't do that. In the present invention, since a predetermined compound is added to the aqueous system and the degree of decrease is measured, the biofilm production status of the entire aqueous system can be accurately monitored.

  In carrying out the present invention, a predetermined amount of a predetermined compound is added to the aqueous system to be measured. The form of the compound to be added is not particularly problematic if used in any form, but it is desirable to use it in the form of an aqueous solution preparation. It is also preferable for rapid dissolution and homogenization. Then, after the addition of the compound, the water is collected every predetermined time. The collection of the water is repeated over time, and analysis is performed by a method suitable for the compound to which they are added to determine the concentration of the compound. In this way, the concentration change with time of the added compound in the target aqueous system is determined.

  When there is almost no decrease over time in the compound or the degree of decrease over time is very small, it can be determined that the amount of biofilm in the aqueous system is small, and the larger the slope of decrease, the larger the amount of biofilm. Is determined.

  The present invention will be specifically described by the following test examples, but the present invention is not limited to these test examples.

Test example 1

Carbon steel (size 30 mm x 75 mm, thickness 0.35 mm) is installed as a test piece in the water tank, and activated sludge collected from the sewage treatment plant is used as a microbial source.
A mixed solution diluted 100 times with a solution having a composition of NaHCO ₃ 15 mg / l and KH ₂ PO ₄ 15 mg / l was placed in the above water tank and circulated at a circulation flow rate of 800 ml / min for 7 days. In this way, a biofilm was formed on the surface of the test piece.

  The test piece to which the biofilm thus obtained was attached was transferred to another water tank, and an aqueous solution in which the compound shown in Table 1 was dissolved to 20 mg / l was put in each water tank. The time when the aqueous solution was put in the water tank was set to 0 hour, and thereafter the aqueous solution was collected every 3 hours, and the concentration of each compound was measured. Each compound was performed by the method shown in Table 1. The test results are shown in Table 2. Compounds other than (1) to (6) shown in Table 1, namely fructose, galactose, mannose, maltose, and sucrose are (1) glucose and (2) saccharides that are the same sugars as lactose and can be easily utilized by microorganisms. Since it is a low-molecular compound that is soluble in water, it was omitted from the test examples. For the same reason, alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tyrosine, valine, urea, ammonium chloride, ammonium sulfate, ammonium nitrate, Ammonium acetate is a compound having the same amino group as (3) glycine and (4) tryptophan, and formic acid, propionic acid, butyric acid, malonic acid, malic acid, citric acid, succinic acid, oxalic acid, and pyruvic acid are (5 ) Acetic acid and (6) Lactic acid, which are the same organic acids, and omitted from the test examples.

  As is clear from the test examples, it was confirmed that each added compound was consumed by the biofilm attached to the test piece.

Test example 2

The model cooling tower apparatus was used to consume the compound by biofilm.
The outline of the apparatus is shown in Table 3.

  Sodium lactate was added to the above model cooling water system that had not been washed for about one year as 10 mg / l as lactic acid ions, and the time of addition was set to 0 hour, and the cooling was circulated to 8 hours over time. Water was collected. This operation results in the consumption of lactic acid by bacteria attached as biofilm + the consumption of lactic acid by bacteria dispersed in cooling water + the amount of physical lactic acid loss due to cooling water blowing or evaporation. is there. (= Measurement of lactic acid consumption rate of the whole cooling water system)

  In addition, in order to investigate only the consumption rate of lactic acid by microorganisms dispersed in the circulating cooling water, 1 L of cooling water was sampled in another container, and similarly, 10 mg / 1 was added, and the time of addition was set to 0 hour, and the circulating cooling water was collected over time until 8 hours thereafter. For each of the collected cooling waters, the concentration of lactic acid was measured by high performance liquid chromatography, and the consumption rate was determined. (Measurement of lactic acid consumption rate by bacteria dispersed in cooling water)

  By subtracting (lactic acid consumption rate of bacteria dispersed in cooling water) and (evaporation loss of cooling water, physical lactic acid loss due to blow) from (cooling water system overall lactate consumption rate) The deposition rate of lactic acid by the biofilm adhered in the aqueous system was determined. The test results are shown in Table 4.

  The above operation was performed twice (1) before cooling water system cleaning and (2) after cooling water system cleaning, and the test results were compared. The cooling water system was washed with hydrogen peroxide to confirm complete removal of the biofilm. After washing, the inside of the apparatus was thoroughly washed with water, and then (2) the test was performed. Moreover, a part of piping of this apparatus was opened at the time of washing | cleaning, and it was confirmed how much biofilm had adhered. A biofilm of about 200 cc in wet volume could be collected in a pipe having a diameter of 20 mm and a length of 1200 mm. The other parts of the device were open due to the structure and could not be confirmed. However, it was assumed that a considerable amount of biofilm had adhered before the cleaning of the device inferred from the state of attachment of the previous part. It was.

  A clear difference was observed in the lactic acid consumption rate before washing of the cooling water system, that is, in the state where the biofilm was present in the cooling water system, and after washing, that is, in the state where there was no biofilm.

Claims (7)

  By adding a predetermined amount of a predetermined compound to the target water system, collecting the water every predetermined time, and analyzing the concentration of the added compound, the biofilm generated in the water system from the degree of the decrease How to monitor.   The method for monitoring a biofilm according to claim 1, wherein the compound added to the target aqueous system is a low-molecular compound soluble in water that can be used by microorganisms.   The method for monitoring a biofilm according to claim 2, wherein the water-soluble low molecular weight compound that can be used for a microorganism is an organic acid, an amino compound, an ammonium salt, or a saccharide.   The method for monitoring a biofilm according to claim 3, wherein the organic acid is formic acid, acetic acid, propionic acid, butyric acid, lactic acid, malonic acid, malic acid, citric acid, succinic acid, oxalic acid, and pyruvic acid.   The amino compound is alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, urea 4. The method for monitoring a biofilm according to 3.   The biofilm monitoring method according to claim 3, wherein the ammonium salt is ammonium chloride, ammonium sulfate, ammonium nitrate, or ammonium acetate. The method for monitoring a biofilm according to claim 3, wherein the saccharide is glucose, fructose, galactose, mannose, maltose, sucrose, or lactose.