Everyone knows that water is the source of life. However, with the development of industry, water pollution has become increasingly serious. Let's look at the latest news first.

News background

Anhui Tianchang a "cancer village", local villagers and they may raise cancer related to drinking well water, authorities said recently organized an expert on-site well water dam village group of sampling tests to see if the well water contained in the end what The composition will be further investigated based on the test results. We sincerely hope that the experts can publish the test results as soon as possible, preferably not related to water quality.

As early as 2007 , the results of the water pollution survey in Anhui showed that the development of the highly polluting industry became the largest original sin. In fact, water pollution including drinking water not only occurred in Anhui, but some experts said that various signs indicate that rivers, rivers, The water crisis of residents caused by the pollution of lakes and sea has reached a “ hurdle ” . “The development of resource-robbing industries with black rivers, odors, lakes and green algae, high levels of cancer processing, low added value, and high pollution, local governments have a strong view of investment indicators, economic indicators, and officials’ distorted political achievements. Almost all companies are madly robbed, and the basic principle is ' not to be rejected ' . " This is the biggest original sin of pollution in Anhui. "

Frequent water pollution incidents remind people that they have to face such harsh reality: China has already entered the stage of intensive water pollution explosion. Because of this, related water quality detectors have been promoted and known.

The principle of water quality detector

1 、The working principle of pH meter

The pH of the water depends on the amount of dissolved material, so the pH can be a sensitive indicator of changes in water quality. The change of pH value has a great influence on the reproduction and survival of organisms, and it also seriously affects the biochemical action of activated sludge, which affects the treatment effect. The pH value of sewage is generally controlled between 6.5 and 7 . Water is chemically neutral, and some water molecules spontaneously decompose according to the following formula: H2O=H++OH- , ie, decompose into hydrogen ions and hydroxide ions. In the neutral solution, the concentrations of hydrogen ion H+ and hydroxide ion OH- are both 10 to 7 mol/l , and the pH is the negative number of the logarithm of the hydrogen ion concentration at the base of 10 : pH = -log , so neutral The pH of the solution is equal to 7 . If there is an excess of hydrogen ions, the pH is less than 7 and the solution is acidic ; conversely, if the hydroxide ion is excessive, the solution is alkaline.

The pH value is usually measured by the potentiometric method. Usually, a constant potential reference electrode and a measuring electrode are used to form a primary battery. The electromotive force of the primary battery depends on the concentration of hydrogen ions and also depends on the pH of the solution. The plant uses a CPS11 pH sensor and a CPM151 pH transmitter. There is a special glass probe with sensitive pH response on the measuring electrode. It is made of special glass that can conduct electricity and can penetrate hydrogen ions. It has the characteristics of high measurement accuracy and good anti-interference. When the glass probe is in contact with hydrogen ions, a potential is generated. The potential is measured by a silver control reference electrode suspended in a silver chloride solution. different pH values, not the same corresponding to the potential generated by the transmitter to convert it into a standard 4 ~ 20mA output.

2. How does the dissolved oxygen analyzer work?

The oxygen content in the water can fully show the degree of water self-purification. For a biological treatment plant using activated sludge, it is very important to know the oxygen content of the aeration tank and the oxidation ditch. The increase of dissolved oxygen in the sewage will promote biological activities other than anaerobic microorganisms, thus enabling the removal of volatile substances and ease of use. Naturally oxidized ions purify sewage. There are three main methods for determining oxygen content: automatic colorimetric analysis and chemical analysis measurement, paramagnetic measurement, and electrochemical measurement. Dissolved oxygen in water is generally measured electrochemically. The plant uses COS4 dissolved oxygen sensor and COM252 dissolved oxygen transmitter. Oxygen is soluble in water and the solubility depends on the temperature, the total pressure on the surface of the water, the partial pressure, and the dissolved salts in the water. The higher the atmospheric pressure, the greater the ability of the water dissolved oxygen, which relationship is determined by Henry (Henry) and Dalton's law (Dalton) Law, Henry's Law solubility of the gas that is proportional to its partial pressure.

Moisture meter working principle:

The principle is based on the fact that iodine is reduced by sulphur dioxide in the presence of water, and in the presence of pyridine and methanol, pyridine iodide and methyl hydrogen sulphate are produced. The reaction formula is as follows: H2O+I2+SO2+3C5H5N→2C5H5N•HI+C5H5N•SO3

C5H5N•SO3+CH3OH→C5H5N•HSO4CH3

In the electrolysis process , the electrode reactions are as follows :

Anode : 2I--2e→I2

Cathode : I2+2e→2I-

2H++2e→H2↑

The iodine produced reacts with the water in the sample to form hydroiodic acid until all the water has reacted. The endpoint of the reaction is indicated by a pair of platinum electrode detection units. In the whole process, sulfur dioxide is consumed, and its consumption is equal to the number of moles of water.

Explanation of the 35 indicators of the national water quality standards

First, sensory traits and general chemical indicators

1 , color

Natural water often shows a variety of different colors, and the color of water is usually from the plant kingdom. Pollution of industrial waste water can make the water body produce a variety of colors. The color of surface water varies greatly, and it is related to the soil and vegetation of the catchment. Water color can be divided into two kinds of true color and appearance. The color that appears when the suspended solids in the water are completely removed is called true color, and it is mainly composed of rot and water organisms dissolved in water. The presence of various organic or inorganic impurities in the water, such as the leaves of plants, roots and some of the substances in the soil, sediment, minerals, etc., are called appearance colors, or false colors, false colors.

2 , turbidity

The turbidity of water refers to the degree of obstruction caused by suspended solids and colloidal impurities in water. It is related to impurity content in water, particle size, shape and surface reflectivity. The method for measuring turbidity is relatively simple, and it is generally used to indirectly reflect the amount of suspended and colloidal impurities in water. The degree of turbidity produced when 1 liter of water contains 1 milliliter of kaolin ( or kaolin ) is called 1 degree or 1 milligram per liter. Turbidity is one of the important signs to measure the degree of water pollution. It is related to the nature of the river bank, the speed of the examination bar, and the pollution of industrial wastewater, and changes with the climate and seasonal changes.

3 , smell and taste

Clean water is odorless and odorless. Contaminated water produces smell and taste. Some of the algae plankton, organic matter, dissolved gases, minerals, industrial wastewater pollution, chlorine disinfection, water temperature, dissolved oxygen content in water, etc. will make the water with smell and taste. The lower the water temperature is, the more muddy the river water is, and the muddy earth is often smelly and astringent ; the dissolved oxygen is more, and the taste is slightly sweeter ; the blue-green algae protozoa emit grassy stench and so on.

4 , visible to the naked eye

Drinking water should not contain sediments, macroscopic aquatic organisms, and odious substances.

5 , PH value

The pH value represents the concentration of activated hydrogen ions in the water to replace the activity of hydrogen ions.

6 , the total hardness

The hardness of water refers to the degree of precipitation of soap, which causes the soap to precipitate, mainly due to the presence of calcium and magnesium salts in natural water. The hardness of groundwater is often relatively high. The hardness of surface water varies with geographical and geological conditions. The hardness of groundwater is generally not too high. In addition, the hardness of the water is too high to form scale in the water distribution system and consume excess soap.