Key points for water quality testing operations in sewage treatment plants part four
27. What is the total solid form of water?The indicator reflecting the total solid content in water is total solids, which is divided into two parts: volatile total solids and non-volatile total solids. Total solids include suspended solids (SS) and dissolved solids (DS), each of which can also be further subdivided into volatile solids and non-volatile solids.
The measurement method of total solids is to measure the mass of the solid matter remaining after the wastewater has been evaporated at 103oC ~ 105oC. The drying time and the size of the solid particles are related to the dryer used, but in any case, the length of the drying time must be based on It is based on the complete evaporation of the water in the water sample until the mass is constant after drying.
Volatile total solids represent the solid mass reduced by burning the total solids at a high temperature of 600oC, so it is also called weight loss by burning, and can roughly represent the content of organic matter in the water. The ignition time is also like the drying time when measuring total solids. It should be burned until all the carbon in the sample has evaporated. The mass of the remaining material after burning is the fixed solid, also known as ash, which can roughly represent the content of inorganic matter in the water.
28.What are dissolved solids?
Dissolved solids are also called filterable substances. The filtrate after filtering the suspended solids is evaporated and dried at a temperature of 103oC ~ 105oC, and the mass of the residual material is measured, which is the dissolved solids. Dissolved solids include inorganic salts and organic substances dissolved in water. It can be roughly calculated by subtracting the amount of suspended solids from the total solids. The common unit is mg/L.
When sewage is reused after advanced treatment, its dissolved solids must be controlled within a certain range. Otherwise, there will be some adverse effects whether it is used for greening, toilet flushing, car washing and other miscellaneous water or as industrial circulating water. The Ministry of Construction standard "Water Quality Standard for Domestic Miscellaneous Water" CJ/T48--1999 stipulates that the dissolved solids of reused water used for greening and toilet flushing cannot exceed 1200 mg/L, and the dissolved solids of reused water used for car washing and cleaning Cannot exceed 1000 mg/L.
29.What is the salinity and salinity of water?
The salinity content of water is also called salinity, which represents the total amount of salts contained in the water. The common unit is mg/L. Since salts in water all exist in the form of ions, the salt content is the sum of the number of various anions and cations in the water.
It can be seen from the definition that the dissolved solids content of water is greater than its salt content, because the dissolved solids also contain some organic matter. When the organic matter content in the water is very low, dissolved solids can sometimes be used to approximate the salt content in the water.
30.What is the conductivity of water?
Conductivity is the reciprocal of the resistance of an aqueous solution, and its unit is μs/cm. Various soluble salts in water exist in an ionic state, and these ions have the ability to conduct electricity. The more salts dissolved in water, the greater the ion content, and the greater the conductivity of water. Therefore, depending on the conductivity, it can indirectly represent the total amount of salts in the water or the dissolved solid content of the water.
The conductivity of fresh distilled water is 0.5 to 2 μs/cm, the conductivity of ultrapure water is less than 0.1 μs/cm, and the conductivity of concentrated water discharged from softened water stations can be as high as thousands of μs/cm.
