The current "Health Standards for Drinking Water" (GB5749-2006) stipulates strict hygiene requirements for drinking water quality, namely: ①Good sensory properties: transparent, colorless, no peculiar smell and odor, and no visible objects; ② Epidemiologically safe: it does not contain pathogenic microorganisms and parasite eggs; ③The chemical composition is harmless to humans: the chemical substances contained in the water do not cause acute, chronic and long-term harm to the human body.

Ground water refers to the water that occurs in the rock voids below the ground, and in a narrow sense refers to the water in the saturated aquifer below the ground water surface. In the national standard "Hydrogeology Terminology" (GB/T 14157-93), groundwater refers to various forms of gravity water buried below the surface. Foreign scholars believe that there are three definitions of groundwater: one refers to all the water buried in groundwater that is significantly different from surface water, especially the part of the water in the saturated zone in the aquifer; the other refers to downward flow or penetration to make soil and rocks It is saturated and replenishes the water of springs and wells; the third is the water stored in the rock cavities underground and in the voids that make up the crustal material. Groundwater is an important part of water resources. Because of its stable water volume and good water quality, it is one of the important water sources for agricultural irri

Domestic sewage is the waste water discharged in the daily life of residents. It mainly comes from residential buildings and public buildings, such as houses, offices, schools, hospitals, shops, public places and industrial enterprises toilets. The pollutants contained in domestic sewage are mainly organic matter (such as protein, carbohydrate, fat, urea, ammonia nitrogen, etc.) and a large number of pathogenic microorganisms (such as parasite eggs and intestinal infectious virus, etc.). The organic matter in domestic sewage is extremely unstable and easily decomposes to produce foul smell. Bacteria and pathogens multiply by taking organic matter in domestic sewage as nutrients, which can lead to the spread of infectious diseases. Therefore, domestic sewage must be treated before it is discharged. In the process of sewage treatment, firstly it is necessary to detect and analyze the quality of sewage, mainly by detecting the data of SS, COD, BOD, etc. in the water.