The harm of domestic sewage

Sewage hazards:

Pathogen contamination

It mainly comes from urban domestic sewage, hospital sewage, garbage and ground runoff. The characteristics of pathogenic microorganisms are: (1) large quantity; ② Widely distributed; ③ the survival time is longer; ④ the reproduction speed is fast; ⑤ easy to produce resistance, difficult to eliminate; After traditional secondary biochemical sewage treatment and chlorination, some pathogenic microorganisms and viruses can still survive in large numbers; Such pollutants actually enter the human body through a variety of ways, and survive in the body, causing human disease.

Aerobic organic pollution

The common feature of organic matter is that these substances directly into the water body, through the biochemical action of microorganisms and decomposition into simple inorganic substances carbon dioxide and water, in the decomposition process need to consume dissolved oxygen in the water, in the hypoxic conditions of pollutants occur corruption decomposition, deterioration of water quality, often called these organic matter as aerobic organic matter. The more aerobic organic matter in the water body, the more oxygen consumption, the worse the water quality, indicating that the water pollution is more serious.

Eutrophication pollution

It is a kind of water pollution phenomenon caused by excessive content of plant nutrients such as nitrogen and phosphorus. Eutrophication of aquatic ecosystems can occur in two ways through chemical pollutants: one is through the increase of the amount of inorganic nutrients limited to plants under normal circumstances; The other is through the increase of organic matter as a decomposer.

stench

Stench is a common pollution hazard, it also occurs in polluted water. People can smell more than 4,000 kinds of stench, and there are dozens of harmful ones. The harm of odor is as follows: ① hinder normal respiratory function and reduce digestive function; Mental irritability, work efficiency decreased, judgment, memory decreased; Working and living in a malodorous environment for a long time will cause olfactory disorders and damage the excitatory and regulatory functions of central nervous system and cerebral cortex. ② Some aquatic products are infected with a foul smell and cannot be eaten or sold; (3) Fetid water can not be used for swimming, fish farming, drinking, and destroy the use and value of water; ④ can also produce hydrogen sulfide, formaldehyde and other toxic hazards.

Acid, alkali, salt pollution

Acid and alkali pollution make the pH of the water body change, destroy its buffering effect, eliminate or inhibit the growth of microorganisms, hinder the self-purification of the water body, and can also corrode Bridges, ships, fishing gear. Acid and base often enter the same water body at the same time, after the neutralization can produce some salts, from the point of view of pH value, acid and alkali pollution due to the neutralization and self-purification, but produce a variety of salts, and become new pollutants in the water body. Because the increase of inorganic salt can increase the osmotic pressure of water, it has a bad effect on the growth of freshwater organisms and plants, and in salinized areas, the salt in surface water and groundwater will further harm the soil quality.

Groundwater hardness increase

The harm of high hard water, especially high permanent hardness water, is manifested in many aspects: difficult to drink; Can cause digestive tract dysfunction, diarrhea, pregnant animals abortion; For people daily inconvenience; High energy consumption; Affect the life of kettle and boiler; Boiler water fouling, easy to cause explosion; It is necessary to soften and purify, and the loss of acid, alkali and salt to the environment will cause the groundwater hardness to rise, forming a vicious circle.

Toxic pollution

Toxic substances pollution is a particularly important category of water pollution, there are many kinds, but the common feature is the toxic harm to biological organisms.

Sewage treatment:

Current situation and future

The development and progress of China's sewage treatment industry is relatively late, since the founding of the country to the reform and opening up, China's sewage treatment needs are mainly based on the cutting-edge use of industry and national defense. After the reform and opening up, the rapid development of the national economy and the significant improvement of people's living standards have driven the demand for sewage treatment. After entering the 1990s, China's sewage treatment industry has entered a period of rapid development, and the growth rate of sewage treatment demand is much higher than the global level.

Since 1990, the global apparent consumption of sewage treatment has increased at an average annual rate of 6%, and in the decade of 1990s, the average annual growth rate of China's apparent consumption of sewage treatment has reached 17.73%, which is 2.9 times the average annual growth rate of the world. Entering the 21st century, China's sewage treatment industry has grown rapidly. From 2000 to 2004, China's sewage treatment consumption increased from 1.88 million tons to 4.47 million tons, an increase of 2.3 times, with an average annual growth rate of more than 27%. Among them, in 2001, China's apparent consumption of sewage treatment reached 2.25 million tons, surpassing the United States to become the world's first sewage treatment consumer. At the same time, sewage treatment imports have also increased significantly. In 1998, China imported 1 million tons of sewage treatment, thus becoming the world's largest importer of sewage treatment. In 2004, compared with 1998, the annual growth rate of sewage treatment imports reached 27.14%. It is expected that in 2005, China's apparent consumption of sewage treatment will reach 5 million tons, and imports will remain at about 3 million tons.