The harm of wastewater to the earth! Urgent! ! ! !

With the rapid development of industrialization and urbanization, the discharge of industrial wastewater and urban domestic sewage has also increased correspondingly, and the nature and composition of wastewater have become more and more complicated. Wastewater discharged directly into natural water without any treatment will inevitably cause serious pollution of water body. After water is polluted, it can sometimes be directly detected, for example, the color change of water, turbidity, the emission of unpleasant gases, the decrease or death of some biological populations, the appearance and sharp increase of another biological population and so on. However, some water pollution cannot be directly observed, and it is necessary to directly monitor and analyze some indicators and pollutants in order to judge the degree of water pollution. The harm of water pollution is mainly manifested in the following aspects.

(1) Wastewater containing color, smell and taste.

High chroma wastewater not only affects the appearance of water body. It will also affect the color and product quality, and obviously reduce the quality of printing, dyeing and papermaking products in industrial products. Colored wastewater mainly contains various inorganic and organic soluble colorants, such as chromate (yellow), chromium salt (green), copper salt (cyan), nickel salt (yellow), ferrous salt (brown) and so on. Some wastewater is colorless when discharged, but it can react with other dissolved substances to generate color after entering the water body, such as wastewater containing iron ions and tannins. You can see black and so on. When water contains hydrogen sulfide and phenolic compounds, it will make the water stink. Aquatic organisms are affected by this foul-smelling wastewater, which not only reduces the quality of fish and shellfish, but also makes them inedible.

(2) Organic pollution

Municipal domestic wastewater, food industry wastewater, papermaking wastewater, etc. , contains a lot of organic matter, which will become the nutrient source of microorganisms after being discharged into the water body, so that the organic matter can be decomposed and digested. In the process of decomposition, a large amount of dissolved oxygen is consumed in water, once the water body lacks oxygen supply; Oxidation will stop. It causes anaerobic fermentation of organic matter, decomposes methane, hydrogen, hydrogen sulfide, mercaptan, ammonia and other malodorous gases, emits malodor, pollutes the environment and poisons aquatic organisms. Due to the floating of gas, organic deposits are also brought to the water surface, which not only worsens the water surface, but also prevents air from entering the water body. These organic wastewater containing various components are extremely complex mixed pollutants and the most important aspect of water pollution.

(3) Inorganic pollution

The pollution of acid, alkali and inorganic salt to water body first changes the PH value of water body, destroys its natural buffering effect, eliminates or inhibits the growth of bacteria and microorganisms, and hinders the self-purification of water body; At the same time, it will greatly increase the hardness of inorganic salts and water in water, which will bring unfavorable factors to industrial and domestic water; Moreover, irrigating farmland with water with high salt content will cause soil salinization.

(4) Toxic substance pollution

The composition of toxic substances is very complicated. When the wastewater contains a large number of toxic substances such as phenols, cyanide, mercury, cadmium, lead, arsenic and other metal elements, organic pesticides and pesticides. When it is discharged into natural water, at high concentration, it will poison and kill aquatic organisms; At low concentration, it can be enriched in organisms and gradually concentrated through the food chain, thus ultimately affecting human health. Minamata disease, a public hazard in Japan; It is because the factory discharges mercury-containing wastewater into the bay, which is enriched repeatedly through the food chain through biological methylation, and people eat aquatic products with high organic mercury concentration for a long time. Bone pain is also the result of cadmium accumulation in human body after drinking cadmium-containing water and eating cadmium-containing food for a long time.

(e) Eutrophication pollution

Wastewater containing plant nutrients enters the natural water body, causing eutrophication, algae proliferation, consuming dissolved oxygen in the water, suffocating fish in the water and destroying aquatic resources. The increase of nitrogen compounds in water is very harmful to human and animal health. Nitrite reacts with hemoglobin in human body to produce methemoglobin, which makes hemoglobin lose its oxygen transmission ability and make people poisoned. Nitrate and nitrite are substances that form nitrosamines, which are carcinogens and can induce esophageal cancer and gastric cancer in human digestive system.

(vi) Oil pollution

Oil exploitation, tanker transportation, wastewater discharge from oil refining industry in coastal and estuary areas, etc. , will make water bodies polluted by oil, especially in estuaries and offshore waters, and this pollution has been very prominent in recent years.

The pollution of oil is not only harmful to the utilization of water, but also harmful to living things because the oil forms an oil film on the water surface. The oil film floating on the water is also easy to fill the gills of fish and suffocate them. The oil layer floating on the water surface can also spread to far places with the influence of current and wind, leading to the deterioration of beaches, the destruction of resorts and scenic spots, and the harm to birds' lives.

(7) Thermal pollution

The cooling water of thermal power plant is the main source of thermal pollution. If it is directly discharged into natural water, it will cause the water temperature to rise. The increase of water temperature will reduce the dissolved oxygen in water, even to zero, and increase the toxicity of some poisons in water. The increase of water temperature has the greatest impact on fish, even causing the death of fish or the change of aquatic population.

(8) Pathogenic microorganism sewage

Domestic sewage, hospital sewage and meat processing sewage contain various pathogenic microorganisms, such as germs, viruses and parasites. When it flows into natural water, it will spread various diseases. When water is used to irrigate farmland, it will lead to the epidemic of diseases in polluted areas.

In a word, with the continuous development of economy, environmental pollution must also be paid full attention to. In terms of water quality, the water quality of major rivers, lakes and reservoirs has declined to varying degrees due to the pollution of a large number of industrial wastewater, domestic sewage and other toxic wastes in China. According to the investigation of surface water pollution in China in recent years, the pollution is developing, which has caused great harm to people's water use, fishery and irrigation. Among the 53,000-kilometer river sections surveyed, fish and shrimp have disappeared, and there are 2,400 kilometers of river sections that have become "stagnant water". About 23.3% of the water pollution can not be used for irrigation, and only 14 of the water meets the water quality standards for drinking water and fishery water. Water pollution further reduces the available water resources, thus aggravating the shortage of water resources in China and causing huge economic losses. Therefore, controlling water pollution and protecting water resources is an important task of environmental protection.