What are the common water quality testing methods?

Water quality testing is generally divided into drinking water testing, sewage testing, surface water testing, etc., and the parameters that generally need to be tested are different according to the different water quality tested.

Drinking water main testing:There are 17 items, including color, turbidity, odor and taste, visible to the naked eye, pH, aluminum, iron, manganese, copper, zinc, chloride, sulfate, total dissolved solids, total hardness, oxygen consumption, volatile phenols, and anionic synthetic detergents.

Sewage main detection:Conductivity, pH, hardness, alkalinity, inorganic acidity, etc., inorganic indicators: toxic metals, toxic metalloids, nitrates, nitrites, phosphates, etc.

Surface water is mainly tested:pH value detection, SS (suspended solids) detection, ammonia nitrogen detection, BOD detection, COD detection.

Water quality testing instruments are mainly used to detect water quality parameters, such as: COD detector, BOD detector, suspended solids detector, etc.

COD detector.

The scope of water quality testing includes: sewage, pure water, seawater, fishery water, swimming pool water, reclaimed water, bottled pure water, drinking natural mineral water, cooling water, farmland irrigation water, landscape water, domestic drinking water, groundwater, boiler water, surface water, industrial water, test water, etc.

The test items include: temperature, color, turbidity, pH value, conductivity, suspended solids, dissolved oxygen, chemical oxygen demand and biochemical oxygen demand, etc., as well as some toxic substances, such as phenol, cyanide, arsenic, lead, chromium, cadmium, mercury and organic pesticides.

Water quality testing mainly considers the impact on human health and the environment, and its water quality standards include microbial quality assurance in addition to physical and chemical indicators.

Water is an indispensable resource for the survival of all animals, plants and human beings, but nowadays due to a series of reasons such as overuse of resources and environmental damage, water pollution is also aggravating and deteriorating, so a series of water quality testing standards have been formulated.

Water quality test method:

1.The turbidity of the water.

The turbidity of water is caused by the presence of suspended substances such as sediment, clay, organic matter, inorganic matter, plankton and microorganisms in the water, which can scatter or absorb light, and natural water is treated with coagulation, precipitation and filtration to make the water clear. Generally, the turbidity of drinking water should not exceed 1NTU.

2.The smell of water.

The odor substances in water are divided into two categories: inorganic odor substances and organic odor substances. A few gases such as NO2, NH3, SO2 and H2S have strong odors, while most volatile organic compounds have odors, and organic odor substances are mainly aliphatic hydrocarbon oxygen-containing derivatives, sulfur-containing compounds, nitrogen-containing compounds and aromatic compounds.

3.Acidity and alkalinity of water.

The negative value of the logarithm of the concentration of hydrogen ions in the water indicates the pH of the water, that is, the pH value of the water, less than 7 is acidic, equal to 7 is neutral, and greater than 7 is alkaline. The optimal pH for optimal drinking water is:

4.The chromaticity of water.

Chromaticity is one of the sensory indicators of water. Water is a colorless, odorless, tasteless transparent liquid, when there are certain substances in the water (such as some soluble organic matter, some inorganic ions and colored suspended particles, etc.), it may make the water colored, that is, the water will appear a certain color, that is, chromaticity.

5.The hardness of the water.

The hardness of water refers to the content of salts dissolved in water, that is, the content of calcium salt and magnesium salt, China's "Sanitary Standard for Domestic Water" stipulates that the total hardness of drinking water does not exceed 450mg L. Hard water usually does not pose a direct health hazard, but because hard water contains more calcium salts, the kettle we use to boil water is particularly prone to limescale.

6.Electrical conductivity of water.

The conductivity of water is the reciprocal of the resistance of water, and the standard for drinking water does not specify the conductivity index, but there are total dissolved solids and total hardness indicators in the standard, and the conductivity can be roughly estimated to be about 2 times of the total dissolved solids, that is, about 2000us cm. So the conductivity of water is usually used to indicate the purity of water.

Water quality test method:

1. Visual: Some water quality can be seen with the naked eye that the water body is turbid, containing muddy water, clay, organic matter, inorganic matter, and some plankton, this water quality must have been polluted, and it needs to be filtered and disinfected to make the water clear and can be used for a second time.

2. Smell: The water body is polluted, in addition to visual inspection, the water body can also be found to be polluted by smelling, because a few gases such as NO2, NH3, and H2S in the inorganic matter have a strong odor, and some have a foul smell, so the water body needs to add bleaching powder or other chemicals for chemical reduction to remove the odor.

3. Select water quality testing instruments: use water quality testing instruments to detect whether the water body is polluted, and carry out water quality transformation according to the test results.

Water quality testing instruments.

What is the specific content of the water quality testing method, the following Zhongda Consulting will answer for you.

Colorimetry. In response to the worsening water pollution problem, the waterworks have adopted a method of adding large amounts of chlorine (bleaching powder) that exceed the standard to disinfect and sterilize. Although chlorination can kill various germs in the water, once it is combined with the organic matter in the water, it will produce a large amount of organic chloride (such as chloroform, dibromochloromethane) due to the effect of residual chlorine or bleaching powder, which is harmful to human health.

Organochlorides have been identified as carcinogens in animal tests. Most people think that simply boiling tap water can kill bacteria, but in fact, boiling water for 20 minutes is enough to remove harmful bacteria or viruses. During the boiling process, chlorine in the water will intensify the combination with organic matter, resulting in the formation of a large number of carcinogens such as trihalomethanes, especially in the period of 100.

To remove chlorine, it is necessary to boil for more than 30 minutes and open the lid of the pot to allow the chlorine to evaporate with the steam. Otherwise, the trihalomethanes synthesized from chlorine will remain in the water and pose a chronic health hazard.

TDS pen. The electrical conductivity of water has a certain relationship with the amount of inorganic acids, alkalis and salts it contains. When their concentration is low, the conductivity increases with increasing concentration, so this metric is often used to estimate the total concentration or salt content of ions in water.

Different types of water have different electrical conductivity. The conductivity of freshly distilled water is 2—4 s cm due to the absorption of CO2 after a period of time. The conductivity of ultrapure water is less than.

The conductivity of natural water is mostly between 50-500 s cm, and mineralized water can reach 500-1000 s cm. The conductivity of industrial wastewater containing acids, alkalis, and salts often exceeds 10,000 s cm. The electrical conductivity of seawater is about 30000 s cm.

Conductivity is an important indicator of the purity of pure water, reflecting the purity of pure water and the control of the production process. The national standard stipulates that the electrical conductivity in purified water shall not be higher than 10 s cm.

1. Connect the water quality detector to the tap water faucet, and observe whether there is a significant change in the cotton in the water quality detector after two to days, and the worse the water quality, the greater the change.

2. Take two clean cups, one for Jianlu tap water, and the other for purified water filtered by a water purifier. Turn on the DS pen switch to test the PM value of the purified water, read the value and record it after the value is stable, return the data of the DS pen to zero after registration, and then test the tap water value.

3. Take two clean and transparent cups, one cup is connected to tap water, and the other cup is connected to purified water. The same dose of residual chlorine reagent was dropped into two cups of water to observe the color change.

4. Put the RO membrane into the filter bottle, pour tap water into the sewage tank, drip in an appropriate amount of ink and stir well, plug in the power supply to start the RO demonstration machine. After the machine is started, you can see the pure water flowing out of the water purification port.

5. Take two clean and transparent cups, one with tap water and the other with purified water. Put the iron and aluminum rods from the two water electrolyzers into two cups of water at the same time, plug in the power supply for about 30 seconds to see the color change. The darker the color, the more impurities and ions there are in the water.

The scope includes sewage, pure water, seawater, fishery water, swimming pool water, reclaimed water, bottled pure water, drinking natural mineral water, cooling water, farmland irrigation water, landscape water, domestic drinking water, groundwater, boiler water, surface water, industrial water, test water, etc.

Water quality testing indicators:

1. Chromaticity: Most people can detect the color of drinking water when it is greater than 15 degrees, and people feel disgusted when it is greater than 30 degrees. The standard stipulates that the color of drinking water should not exceed 15 degrees.

2. Turbidity: It is an expression of the optical properties of water samples, which is used to indicate the degree of clarity and turbidity of water, which is one of the most important indicators to measure the good degree of water quality, and is also an important basis for assessing the purification efficiency of water treatment equipment and evaluating the status of water treatment technology.

The reduction of turbidity means that the content of organic matter, bacteria, viruses and other microorganisms in the water body is reduced, which can not only improve the disinfection and sterilization effect, but also help reduce the amount of halogenated organic matter.

3. Odor and taste: The production of water odor is mainly the presence of organic matter, which may be caused by the manifestation of increased biological activity or industrial pollution. A change in the normal odor of a public water supply can be a sign of a change in the quality of the raw water or inadequate water treatment.

4. Visible to the naked eye: mainly refers to particles or other suspended substances existing in water that can be observed with the naked eye.

5. Residual chlorine: Residual chlorine refers to the amount of chlorine remaining in the water after chlorination and disinfection. It has a continuous sterilization ability in the water to prevent the self-contamination of the water supply pipeline and ensure the quality of the water supply.

6. Chemical oxygen demand: refers to the oxygen required by chemical oxidants to oxidize organic pollutants in water. The higher the chemical oxygen demand, the more organic pollutants there are in the water.

Organic pollutants in water are mainly produced by the discharge of domestic sewage or industrial wastewater, and the decomposition of animals and plants.

7. Total number of bacteria: The bacteria contained in the water, ** in the air, soil, sewage, garbage and the corpses of animals and plants, the types of bacteria in the water are diverse, including pathogenic bacteria. In China, the standard for drinking water is that the total number of bacteria in 1ml of water does not exceed 100.

8. Total coliform bacteria: It is an indicator of fecal contamination, and the situation detected from it can indicate whether there is fecal contamination in the water and its degree of pollution. In the process of water purification, if the total coliform index can meet the requirements of drinking water standards after disinfection, it means that other pathogens and protobacteria have also been basically killed.

The standard is no more than 3 L's in the test.

9. Heat-resistant coliform bacteria: It more appropriately reflects the degree of food contamination by human and animal feces than coliform bacteria, and is also an indicator bacteria of fecal pollution in water bodies.