Water quality testing method
National Standard Material Resource Platform : In the environment of water shortage, we must cherish water resources, and the testing department should do a good job in testing and provide protection for the health of the people. Water testing is a major event concerning people's livelihood. It should not be underestimated. This is its significance.
Water quality testing Under normal circumstances, bacteriological indicators and sensory traits are listed as mandatory items, and other indicators can be selected according to local water quality and needs. A full analysis is performed monthly for source water, factory water, and some representative pipe network tip water. The sampling points, sampling times and inspection items of self-contained water supply and rural centralized water supply quality inspection can be determined according to the specific conditions according to the above requirements.
First, the simple water quality test method:
1. Look: Use a glass with a high transparency to be filled with a glass of water. Look at the light to see if there are fine substances suspended in the water? Allow to stand for three hours, then observe the bottom of the cup for sediment? If there is, it indicates that the suspended impurities in the water are seriously exceeding the standard;
2. Smell: Use a glass to pick up a glass of water as far as possible from the faucet, and then smell it with your nose. Is there any smell of bleach (chlorine)? If you can smell the bleaching powder (chlorine), it means that the residual chlorine in the tap water is excessive;
3. Taste: Drink hot boiled water, have the taste of bleaching powder (chlorine), if you can smell the bleaching powder (chlorine), it means that the residual chlorine in the tap water is too high! It is also necessary to use a water purifier for terminal processing;
4. View: Use tap water to make tea. After the night, observe whether the tea is black? If the tea turns black, it indicates that the iron and manganese in the tap water are seriously exceeding the standard, and the water purifier equipped with the iron and manganese filter should be used for terminal treatment;
5. Product: Tasting the boiled water, does the taste feel innocent? If yes, the hardness of the water is too high;
6. Check: Check the water heater at home, open the kettle, and whether there is a layer of yellow scale on the inner wall? If there is, it also indicates that the hardness of the water is too high (the calcium and magnesium salts are too high), and should be softened as soon as possible! Note: Water with too high hardness can easily cause scaling of the water heater pipe, which is caused by poor heat exchange; long-term consumption of water with too high hardness can easily lead to various stones.
Second, water quality testing methods:
(I) Determination of Chloride Ion in Water 1. Principle Method This method uses potassium chromate as an indicator and titrates with a silver nitrate standard solution in the range of pH 5 to 9.5. The silver nitrate reacts with the chloride to form a white silver chloride precipitate. When an excessive amount of silver nitrate is present, it reacts with the potassium chromate indicator to form a brick red silver chromate, indicating that the reaction reaches the end point.
The reaction formula is:
Ag++ Cl-→ AgCl↓ (white)
2Ag++ CrO42- → Ag2CrO4↓ (brick red)
2. Analysis step 3. Results The chloride ion content is calculated as the mass concentration Ï1, and the value is expressed in mg/L. The calculation formula is as follows:
Where: c--concentration of silver nitrate standard titration solution, mol / L;
V1: blank test consumes the amount of silver nitrate standard titration solution, mL;
V2: the amount of silver nitrate standard titration solution consumed by water sample, mL;
V3: water sample volume, mL.
(Reagent: acid solution: 1+300; sodium hydroxide solution: 2g/L; silver nitrate standard titration solution: 0.01mol/L potassium chromate indicator: 50g/L; phenolphthalein indicator: 10g/L ethanol solution)
(II) Determination of CODCr 1. Principle method In a strong acidic solution, the reducing substance in the sample is oxidized with potassium dichromate, and the excess potassium dichromate is tested with ferrous ferrous sulfate solution by using ferrous ferrous sulfate as an indicator. The chemical oxygen demand in the sample can be calculated from the consumed ammonium ferrous sulfate solution.
2. Analysis step: using distilled water as blank and sample analysis together 3. Results Calculation of chemical oxygen demand CODCr (O2, mg / L) is calculated by the following formula:
CODCr=where: c--the actual concentration of ammonium ferrous sulfate standard solution, mol / L;
V0: titration blank consumption volume of [FeSO4(NH4)2SO4·6H2O] standard solution, mL;
V1: titration sample consumption [FeSO4(NH4)2SO4·6H2O] standard solution volume, mL;
V2: sample volume, mL;
8: molar mass of oxygen (O2), g/moL.
4. Precautions (1) Chloride ion interferes with this method. If the chloride ion concentration is less than 1000mg/L, HgSO4 can be added. If the chloride ion concentration is high, add mercury sulfate to make it and the chloride ion weight ratio is 10:1. A small amount of precipitation did not affect the determination.
(2) For water samples with a chemical oxygen demand of less than 50 mg/L, a 0.025 mol/L K2Cr2O7 standard solution should be used instead. A 0.01 mol/L [FeSO4(NH4)2SO4·6H2O] solution was used for the back drop.
Reagents: HgSO4 solution Ag2SO4-H2SO4 solution (6.7g+500mL), test ferritic indicator K2Cr2O7 standard solution (0.25N), ammonium ferrous sulfate [FeSO4(NH4)2SO4·6H2O] standard solution (0.0125mol/L)
(III) Determination of water color chromaticity 1. Principle method A series of standard solutions of potassium chloroplatinate and cobalt chloride standard solution were determined by spectrophotometer. The color was measured by spectrophotometer when the sample was detected.
2. The glassware that is sampled and sampled in contact with the sample should be cleaned with hydrochloric acid or a surfactant solution, and finally washed and drained with distilled or deionized water.
Samples were sampled in glass vials with a volume of at least 1 L and assayed as soon as possible after sampling. If necessary, store the sample in the dark. In some cases, avoid contact with the sample. Also avoid temperature changes.
3. How to improve the detection accuracy rate to ensure the accuracy of water quality inspection and analysis data, while we strive to improve the water quality inspection technology, we must continuously strengthen the management of inspection data, such as inspection of original records, selection of valid figures, inspection report preparation, water quality analysis. Evaluation results and so on. On the other hand, it is necessary to make scientific and reasonable data analysis methods and establish a sound data management system.
Such as the establishment of water quality testing data management system, the development of water quality sharing platform, the establishment of a water quality supervisor system, the promotion of research and management around the control of water quality, timely understanding of water quality changes, regular assessment of water quality, water quality assessment report In order to check the water quality data at any time, the management work has a very smooth information channel, so that it can be arranged in an orderly manner. Scientifically conducting comprehensive analysis of water quality inspection data and strengthening inspection data management are issues that must be addressed and should be effectively addressed by water quality inspections in the future.
The National Standard Material Resource Platform ( biobw.com ) lists the national standard materials and the standards, reference materials and chemical reagents developed by the company, which facilitates the customer's inquiry of standard substances and chemical reagents! All the orders received were changed from door-to-door to express delivery, which not only speeded up the use of products by foreign customers, but also standardized the internal warehouse structure! Make the purchase of one-stop standard materials more precise and efficient!
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National Standard Material Resource Platform : In the environment of water shortage, we must cherish water resources, and the testing department should do a good job in testing and provide protection for the health of the people. Water testing is a major event concerning people's livelihood. It should not be underestimated. This is its significance.
Water quality testing Under normal circumstances, bacteriological indicators and sensory traits are listed as mandatory items, and other indicators can be selected according to local water quality and needs. A full analysis is performed monthly for source water, factory water, and some representative pipe network tip water. The sampling points, sampling times and inspection items of self-contained water supply and rural centralized water supply quality inspection can be determined according to the specific conditions according to the above requirements.
First, the simple water quality test method:
1. Look: Use a glass with a high transparency to be filled with a glass of water. Look at the light to see if there are fine substances suspended in the water? Allow to stand for three hours, then observe the bottom of the cup for sediment? If there is, it indicates that the suspended impurities in the water are seriously exceeding the standard;
2. Smell: Use a glass to pick up a glass of water as far as possible from the faucet, and then smell it with your nose. Is there any smell of bleach (chlorine)? If you can smell the bleaching powder (chlorine), it means that the residual chlorine in the tap water is excessive;
3. Taste: Drink hot boiled water, have the taste of bleaching powder (chlorine), if you can smell the bleaching powder (chlorine), it means that the residual chlorine in the tap water is too high! It is also necessary to use a water purifier for terminal processing;
4. View: Use tap water to make tea. After the night, observe whether the tea is black? If the tea turns black, it indicates that the iron and manganese in the tap water are seriously exceeding the standard, and the water purifier equipped with the iron and manganese filter should be used for terminal treatment;
5. Product: Tasting the boiled water, does the taste feel innocent? If yes, the hardness of the water is too high;
6. Check: Check the water heater at home, open the kettle, and whether there is a layer of yellow scale on the inner wall? If there is, it also indicates that the hardness of the water is too high (the calcium and magnesium salts are too high), and should be softened as soon as possible! Note: Water with too high hardness can easily cause scaling of the water heater pipe, which is caused by poor heat exchange; long-term consumption of water with too high hardness can easily lead to various stones.
Second, water quality testing methods:
(I) Determination of Chloride Ion in Water 1. Principle Method This method uses potassium chromate as an indicator and titrates with a silver nitrate standard solution in the range of pH 5 to 9.5. The silver nitrate reacts with the chloride to form a white silver chloride precipitate. When an excessive amount of silver nitrate is present, it reacts with the potassium chromate indicator to form a brick red silver chromate, indicating that the reaction reaches the end point.
The reaction formula is:
Ag++ Cl-→ AgCl↓ (white)
2Ag++ CrO42- → Ag2CrO4↓ (brick red)
2. Analysis step 3. Results The chloride ion content is calculated as the mass concentration Ï1, and the value is expressed in mg/L. The calculation formula is as follows:
Where: c--concentration of silver nitrate standard titration solution, mol / L;
V1: blank test consumes the amount of silver nitrate standard titration solution, mL;
V2: the amount of silver nitrate standard titration solution consumed by water sample, mL;
V3: water sample volume, mL.
(Reagent: acid solution: 1+300; sodium hydroxide solution: 2g/L; silver nitrate standard titration solution: 0.01mol/L potassium chromate indicator: 50g/L; phenolphthalein indicator: 10g/L ethanol solution)
(II) Determination of CODCr 1. Principle method In a strong acidic solution, the reducing substance in the sample is oxidized with potassium dichromate, and the excess potassium dichromate is tested with ferrous ferrous sulfate solution by using ferrous ferrous sulfate as an indicator. The chemical oxygen demand in the sample can be calculated from the consumed ammonium ferrous sulfate solution.
2. Analysis step: using distilled water as blank and sample analysis together 3. Results Calculation of chemical oxygen demand CODCr (O2, mg / L) is calculated by the following formula:
CODCr=where: c--the actual concentration of ammonium ferrous sulfate standard solution, mol / L;
V0: titration blank consumption volume of [FeSO4(NH4)2SO4·6H2O] standard solution, mL;
V1: titration sample consumption [FeSO4(NH4)2SO4·6H2O] standard solution volume, mL;
V2: sample volume, mL;
8: molar mass of oxygen (O2), g/moL.
4. Precautions (1) Chloride ion interferes with this method. If the chloride ion concentration is less than 1000mg/L, HgSO4 can be added. If the chloride ion concentration is high, add mercury sulfate to make it and the chloride ion weight ratio is 10:1. A small amount of precipitation did not affect the determination.
(2) For water samples with a chemical oxygen demand of less than 50 mg/L, a 0.025 mol/L K2Cr2O7 standard solution should be used instead. A 0.01 mol/L [FeSO4(NH4)2SO4·6H2O] solution was used for the back drop.
Reagents: HgSO4 solution Ag2SO4-H2SO4 solution (6.7g+500mL), test ferritic indicator K2Cr2O7 standard solution (0.25N), ammonium ferrous sulfate [FeSO4(NH4)2SO4·6H2O] standard solution (0.0125mol/L)
(III) Determination of water color chromaticity 1. Principle method A series of standard solutions of potassium chloroplatinate and cobalt chloride standard solution were determined by spectrophotometer. The color was measured by spectrophotometer when the sample was detected.
2. The glassware that is sampled and sampled in contact with the sample should be cleaned with hydrochloric acid or a surfactant solution, and finally washed and drained with distilled or deionized water.
Samples were sampled in glass vials with a volume of at least 1 L and assayed as soon as possible after sampling. If necessary, store the sample in the dark. In some cases, avoid contact with the sample. Also avoid temperature changes.
3. How to improve the detection accuracy rate to ensure the accuracy of water quality inspection and analysis data, while we strive to improve the water quality inspection technology, we must continuously strengthen the management of inspection data, such as inspection of original records, selection of valid figures, inspection report preparation, water quality analysis. Evaluation results and so on. On the other hand, it is necessary to make scientific and reasonable data analysis methods and establish a sound data management system.
Such as the establishment of water quality testing data management system, the development of water quality sharing platform, the establishment of a water quality supervisor system, the promotion of research and management around the control of water quality, timely understanding of water quality changes, regular assessment of water quality, water quality assessment report In order to check the water quality data at any time, the management work has a very smooth information channel, so that it can be arranged in an orderly manner. Scientifically conducting comprehensive analysis of water quality inspection data and strengthening inspection data management are issues that must be addressed and should be effectively addressed by water quality inspections in the future.
The National Standard Material Resource Platform ( biobw.com ) lists the national standard materials and the standards, reference materials and chemical reagents developed by the company, which facilitates the customer's inquiry of standard substances and chemical reagents! All the orders received were changed from door-to-door to express delivery, which not only speeded up the use of products by foreign customers, but also standardized the internal warehouse structure! Make the purchase of one-stop standard materials more precise and efficient!
Http://
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