The pollution of water resources, the causes of water pollution

China is a country with severe water shortages. The seven major river systems of the Hai River, the Liao River, the Huai River, the Yellow River, the Songhua River, the Yangtze River and the Pearl River are all polluted to varying degrees.

The situation in the sea is also not optimistic, and the red tide is coming every year as scheduled. In the beautiful Bohai Bay, turbid currents are splashing, and the oil floating on the sea surface is like a black torch about to burn the life in the ocean.

A large amount of freshwater resources are concentrated in the south, and the freshwater resources in the north are only 1 4 of the water resources in the south. In addition to water shortage, water pollution is also a prominent problem. According to the cross-sectional monitoring of China's seven major water systems in 2001, only 44% of the water quality of the three categories of water quality can enter the waterworks, while the inferior water quality of the five categories is as high as 44%; In addition, the pollution of shallow groundwater resources in China is relatively common, about 50% of the shallow groundwater in the country is polluted to a certain extent, and about half of the groundwater pollution in urban areas is relatively serious.

Due to the wanton discharge of industrial wastewater, more than 80% of surface water and groundwater are polluted. At present, China's urban water supply is mainly surface water or groundwater, or the two water sources are mixed, and some areas of China have overdrawn groundwater for a long time, resulting in the decline of regional groundwater level, and finally forming a falling funnel of regional groundwater level. At present, more than 100 regional groundwater landing funnels have been formed in the country, covering an area of 150,000 square kilometers, and some cities have formed large funnels of several hundred square kilometers, causing seawater to pour back dozens of kilometers.

Our country is also a country with serious water shortages. The total amount of freshwater resources is 2.8 trillion cubic meters, accounting for 6% of the world's water resources, second only to Brazil, Russia and Canada, ranking fourth in the world, but only 2,300 cubic meters per capita, only 1 4 of the world average, 1 5 of the United States, ranking 121st in the world, and one of the 13 countries with the poorest per capita water resources in the world. After deducting the hard-to-use flood runoff and groundwater resources scattered in remote areas, the actual amount of available freshwater resources in China is even less, only about 1.1 trillion cubic meters, and the per capita water resources are about 900 cubic meters, and their distribution is extremely uneven.

By the end of the 20 th century, more than 400 of the more than 600 cities in the country had the problem of insufficient water supply, of which 110 cities had serious water shortages, and the total water shortage in cities across the country was 6 billion cubic meters. According to monitoring, the groundwater in most cities in the country is polluted to a certain extent by points and surfaces, and there is a trend of increasing year by year. The increasingly serious water pollution not only reduces the use function of water bodies, further aggravates the contradiction of water shortage, and has a serious impact on the sustainable development strategy being implemented in China, but also seriously threatens the drinking water safety of urban residents and the health of the people.

Ministry of Water Resources**, the Chinese population will reach 1.6 billion in 2030, when the per capita water resources will be only 1,750 cubic meters. Under the condition of fully considering water conservation, it is estimated that the total water consumption will be 700 billion to 800 billion cubic meters, and the water supply capacity will be increased by 130 billion to 230 billion cubic meters compared with the current level.

The current status of water pollution is as follows:

With the increase of population, rapid social and economic development, and the acceleration of urbanization, the problem of water pollution in China is becoming more and more serious. China's per capita water resources are only 1.4 of the world's per capita water resources, and about half of the country's cities are short of water, but the deterioration of water quality has made the problem of water shortage even worse.

China's rivers and lakes are generally polluted, and most of the lakes have varying degrees of eutrophication.

The main water system is obviously polluted.

Among the seven major water systems in the country (Pearl River water system, Yangtze River water system, Yellow River water system, Huai River.

water system, Liaohe River water system.

The Haihe River and Songhua River are involved, and there are more than 2,000 kinds of pollutants involved, and the number of pollutants in the water is still increasing. Among them, the Huai River, the Yellow River and the Haihe River have the worst water environment quality, with 70 sections of the river being polluted.

The interruption of the flow in the middle and lower reaches of the Yellow River, Huaihe River and Haihe River has led to serious siltation of the estuary. Many small and medium-sized rivers have become sewage rivers due to the excessive discharge of sewage from urban industries, and cannot be used by human beings.

Water pollution is mainly due to industrial wastewater, agricultural wastewater, and domestic sewage.

and others. With the rapid development of social economy, wastewater and its discharge continue to increase, according to statistics, the increase rate of these wastewater and its discharge is 1.8 billion m3 per year, China's industrial production of wastewater and people's daily sewage discharge of about 100 million m3.

Eighty percent of the wastewater discharged from the upstream tribe is untreated, and the arbitrary discharge of these urban domestic and industrial wastewater pollutes the rivers and underground water sources around the city, and some organic pollutants such as trihalomethanes.

The high levels of chloroacetic acid and heavy metals increase the risk of teratogenicity and mutagenicity of water quality, which seriously affects people's health.

However, there is still a deep well water intake chain mode in rural water, which has poor water source fluidity, which is more likely to cause heavy metal enrichment and harm the nervous, urinary, reproductive and other systems of the human body. Ke Sui Xiaoxiao saw that the current water pollution situation in China has been very common, and there is a trend of becoming more and more serious, and the water pollution control work has a long way to go.

There are two main forms of water pollution: one is natural pollution, which is formed by the dissolution of geology, the erosion of precipitation on the atmosphere, the washing of the ground, and the flow of various pollutants into the water body; the second is man-made pollution, i.e., industrial wastewater, domestic sewage, pesticides and fertilizers; The third is water pollution caused by human activities, that is, the inflow of various harmful substances, chemicals, minerals and toxic substances in water bodies, resulting in the inability of water bodies to be effectively utilized, and the sustainable development of polluted environments is seriously threatened. There are seven main sources of water pollution, namely pathogen pollution, aerobic substance pollution, organic matter and heavy metal pollution, and plant nutrient pollution.

the use of harmful substances such as pesticides and fertilizers; industrial wastewater; domestic sewage; Hospital sewage, etc., enters water bodies and exceeds their self-purification capacity, causing physical and chemical changes in natural water bodies. There are two main forms of water pollution: one is natural pollution

Due to geological dissolution, precipitation washes the atmosphere and the ground, bringing various pollutants into the water body. The second is man-made pollution, that is, the pollution of water bodies by industrial wastewater, domestic sewage, pesticides and fertilizers. The latter is more serious, but manageable. There are seven main sources of water pollution:

That is, pathogen pollution, aerobic substance pollution, plant nutrient pollution, thermal pollution, radioactive pollution, salt pollution, organic matter and heavy metal pollution, etc.

Water pollution, also known as water pollution, is water that pollutes the environment by reducing or losing the value of water caused by harmful chemicals. Acids, alkalis, oxidants, as well as compounds such as copper, cadmium, mercury, arsenic, benzene, dichloroethane, ethylene glycol and other organic poisons in sewage will poison aquatic organisms and affect drinking water sources and scenic landscapes.

After the dissolved oxygen in the water is exhausted, the organic matter is decomposed by the oxidation, producing hydrogen sulfide, mercaptan and other unpleasant gases, which further deteriorates the water quality, and various pollutants enter the water body, and its quantity exceeds the self-purification capacity of the water body.

Water pollution refers to the phenomenon that the chemical, physical, biological or radioactive characteristics of the water body are changed due to the intervention of a certain substance, thereby affecting the effective use of water, endangering human health or destroying the ecological environment, and causing the deterioration of water quality.

In short, the phenomenon of water quality change and deterioration of water quality under the influence of human activities is collectively referred to as water pollution. Regardless of whether it affects the degree of use, as long as Mu Danmin occurs, it is pollution.

Industrial wastewater is an important source of pollution in waters, which has the characteristics of large quantity, wide area, complex composition, difficult to purify, and difficult to treat. Agricultural sources of pollution include livestock manure, pesticides, fertilizers, etc. In pesticide sewage, one is high in organic matter, plant nutrients and pathogenic microorganisms, and the other is high in pesticides and fertilizers.

The main sources of domestic pollution are all kinds of detergents and sewage, garbage, feces, etc. used in urban life, most of which are non-toxic inorganic salts, and domestic sewage contains more nitrogen, phosphorus, sulfur, and more pathogenic bacteria. Water pollution is mainly caused by the pollutants caused by human activities, which includes three major parts: industrial pollution sources, agricultural pollution sources and domestic pollution sources.

The earth's surface2 3 is covered by water, but only freshwater resources, and the freshwater available to humans accounts for only the total amount of global water, and the whole world can only take fresh water from rivers and lakes.

China's total water resources are about 12 to the power of the 12th (including 800 billion m of groundwater), ranking sixth in the world, but according to the per capita occupancy of about 2200m, only 1 4 of the world's per capita occupancy, equivalent to 1 5 of the United States, 1 7 of Russia, ranking 100th in the world. (Therefore, China has been included in the list of water-poor countries in the world.) ）

PS: It is estimated that 400 500 billion m of sewage is discharged worldwide every year, accounting for more than 14% of global runoff. It has been argued that when the world's population grows to 8.3 billion by 2025, 1 2 percent of the population will suffer from moderate or high water scarcity if water resources are not developed and used irrationally.

Handmade, excerpted from the first section of the first chapter of "Water Treatment Engineering" published by South China University of Technology Press