Introduction to sewage

Sewage source:

From the point of view of the source of sewage, sewage can be defined as the liquid or water carrying waste that is discharged from residential, institutional, commercial or industrial areas and mixed with groundwater, surface water, snowstorms, etc. There are many types of sewage, and there are also many technologies and processes to reduce the environmental impact of sewage. According to the source of sewage, sewage can be divided into four categories.

Category I: Industrial effluents from manufacturing mining and industrial production activities, including runoff leachate from industrial or commercial storage, processing, and other wastewater that is not domestic sewage.

The second category: domestic sewage from residential, office buildings, organs or similar sewage; Sanitary sewage; Sewage, including industrial wastewater mixed with domestic sewage in the sewer system. Garbage, all kinds of atmospheric particles settling, etc., through the surface runoff, soil erosion, farmland drainage and other forms of water environment caused. It has the characteristics of dispersion, concealment, randomness, latent, accumulation and fuzziness, so it is difficult to monitor, difficult to quantify, and difficult to study and control. Pollutant discharge into bodies of water that causes pollution.

The third category: commercial sewage from commercial facilities and some components more than domestic sewage non-toxic, harmless sewage. Such as catering sewage. Laundry room sewage, animal feeding sewage, hair salon sewage, etc.

The fourth category: surface runoff from rain, snow, highway water, water from urban and industrial areas, etc., surface runoff does not penetrate the soil, along the streets and land into groundwater.

Causes of pollution:

Among the water pollution caused by human production activities, the water pollution caused by industry is the most serious. Such as industrial wastewater, it contains many pollutants, complex components, not only in the water is not easy to purify, but also more difficult to treat. Industrial wastewater is the most important cause of water pollution caused by industrial pollution. It accounts for most of the pollutants discharged by industry. The pollutants contained in industrial wastewater vary greatly according to different types of factories, and the quality and amount of pollutants contained in similar factories are not the same, even if the production process is different. In addition to the pollution caused by the direct injection of industrial wastewater into the water body, solid waste and exhaust gas can also pollute the water body.

Agricultural pollution is first due to farming or clearing the land surface loose, in the soil and terrain is not stable when the rainfall, a large number of sediment into the water, increasing the suspended matter in the water.

Another important reason is that the use of pesticides and fertilizers is increasing, and only a small amount of pesticides and fertilizers used are attached or absorbed, and most of the rest remain in the soil and float in the atmosphere, through rainfall, through the surface runoff scouring into the surface water and infiltration into the surface water to form pollution. Urban pollution source is caused by water pollution caused by urban population concentration, urban domestic sewage, garbage and waste gas. The main pollution of urban pollution sources to water bodies is domestic sewage, which is a mixture of various sewage produced in People's Daily life, including the sewage discharged from kitchens, washing rooms, bathrooms and toilets.

The world's urban areas alone discharge as much as 500 cubic kilometers of industrial and domestic wastewater a year, and each drop of sewage will pollute several times or even tens of times the water body.

Main pollutant sources:

Pathogen contaminant

Domestic sewage, livestock and poultry farm sewage, as well as tannery, washing, slaughterhouses and hospitals discharge wastewater, often contain a variety of pathogens, such as viruses, germs, parasites. Contamination of water bodies with pathogens can spread diseases, such as schistosomiasis, cholera, typhoid, dysentery, viral hepatitis, etc. Some of the popular plagues in history are water-borne infectious diseases. For example, in 1848 and 1854, two cholera epidemics in Britain killed more than 10,000 people; In 1892, a cholera epidemic in Hamburg, Germany, killed more than 750 people, all caused by water pollution. In the water polluted by pathogens, microorganisms proliferate, many of which are pathogenic bacteria, eggs and viruses, which often coexist with other bacteria and Escherichia coli, so it is usually prescribed that the total number of bacteria and Escherichia coli index and bacteria value number are direct indicators of pathogen contamination. The characteristics of pathogen pollution are: (1) large quantity; (2) Wide distribution; (3) Longer survival time; (4) Fast reproduction speed; (5) Easy to produce resistance, difficult to eradicate; (6) After traditional secondary biochemical wastewater treatment and chlorination, some pathogenic microorganisms and viruses can still survive in large numbers. Common coagulation, precipitation, filtration and disinfection can remove more than 99% of the virus in the water, such as when the turbidity of the water is greater than 0.5 degrees, it will still be accompanied by the penetration of the virus. Pathogen pollutants can enter the water body through a variety of ways, once the conditions are suitable, it will cause human disease.