Water pollution is mainly caused by pollutants produced by human activities. It includes industrial pollution sources, agricultural pollution sources and domestic pollution sources.
Industrial wastewater is an important source of pollution in waters. It has the characteristics of large volume, wide area, complex composition, high toxicity, difficult purification, and difficult treatment. According to the 1998 China Water Resources Bulletin, the total amount of waste water discharged in this year was 53.9 billion tons (excluding direct current cooling water), of which industrial waste water discharged 40.9 billion tons, accounting for 75.88%. In fact, the amount of sewage discharged far exceeds this number because it is difficult to count the industrial sewage discharge of many township enterprises.
Agricultural pollution sources include livestock manure, pesticides, and fertilizers. In pesticide sewage, one is high in organic matter, plant nutrients and pathogenic microorganisms, and the other is high in pesticides and fertilizers. China does not carry out agricultural monitoring. According to relevant data, 1.1049 million tons of pesticides are used annually on 100 million hectares of arable land and 2.2 million hectares of grassland. China is one of the countries with the most serious soil erosion in the world. The annual topsoil loss is about 5 billion tons, causing a large amount of pesticides and fertilizers to flow into rivers, rivers, lakes, and reservoirs with the topsoil, and the loss of nitrogen, phosphorus, and potassium nutrients. Two-thirds of the lakes are endangered by eutrophication pollution of varying degrees, causing abnormal reproduction of algae and other organisms, causing changes in water transparency and dissolved oxygen, and worsening water quality.
The main sources of domestic pollution are various detergents and sewage, garbage, feces, etc. used in urban life, mostly non-toxic inorganic salts. Domestic sewage contains many nitrogen, phosphorus, and sulfur, and many pathogenic bacteria. According to the survey, China’s domestic sewage discharge in 1998 was 18.4 billion tons.
Every year, about 1/3 of industrial wastewater and more than 90% of domestic sewage are discharged into waters without treatment. Among the more than 1,200 rivers monitored nationwide, more than 850 are polluted, and more than 90% of urban waters are also Pollution has caused the extinction of fish and shrimps in many river sections, and only 32.2% of rivers meet the national first and second water quality standards. Pollution is developing from shallow to deep. Groundwater and sea water in the offshore area are also being polluted. The water we can drink and use is unknowingly decreasing.
Increasing water pollution has posed a major threat to human survival and safety, and has become a major obstacle to human health, economic and social sustainable development. According to a survey by a world authoritative organization, in developing countries, 80% of various diseases are spread by drinking unsanitary water. Drinking unsanitary water causes at least 20 million deaths worldwide every year. Therefore, water pollution is called "The world's number one killer".
Water pollution affects industrial production, increases equipment corrosion, affects product quality, and even makes production impossible. Water pollution also affects people's lives, destroys ecology, directly endangers human health, and causes great damage.