The United Nations has designated June 5th each year as World Environment Day and issued a warning of "There is only one earth" to draw people's attention to global environmental issues and remind people to protect the environment and the earth. Environmental protection and ecological balance have become a worldwide social issue that governments and people around the world pay close attention to. It is closely related to people's physical health and living standards, economic and social development, and the happiness of future generations.

Since the 1950s, with the development of the economy, the people have developed a large number of industries, and large factories have sprung up. The production and living environments in many parts of the world have been increasingly polluted and destroyed. According to statistics, for every ton of raw leather processed and produced in my country, the longevity of wastewater is about 50-150 tons. The tanning industry discharges more than 8 million tons of wastewater into the environment each year, accounting for about 0.3 of my country’s total industrial wastewater discharge. %; The leather industry's emissions per 10,000 yuan of output value ranks third in the light industry, second only to the papermaking and brewing industries.

Nowadays, environmental pollution has become a serious social hazard. The sky is full of smog; the inland waters are dirty and dirty; the vast sea has become a garbage dump, etc., which greatly threaten the health and lives of the people. In an era when environmental problems have become so severe, the leather industry, known for being dirty, messy, smelly, and tired, has faced unprecedented pressure.

Harm of Wastewater from Tanning Industry

1. In the process of leather processing, animal fur needs to be dyed. Therefore, leather wastewater will contain a lot of dyes, but the sewage has a high color. If it is discharged directly without treatment, it will affect the surface water quality.

2. The animal skin needs to be dehaired during leather processing. The depilatory solution contains a large amount of sulfide. When sulfur-containing waste liquid encounters acid, it is easy to produce H2S gas, and sulfur-containing sludge will also be released under anaerobic conditions. H2S gas is extremely harmful to water bodies and people.

3. A large amount of lime, caustic soda and Na2S will be used in the peeling process, which will cause the sewage to become alkaline. High alkalinity without treatment will affect the pH value of surface water and crop growth.

4. Chloride and sulfate are used in the preservation, pickling and tanning process of the original hides, and when the sulfate content exceeds 100mg/L, the water taste will become bitter, and diarrhea will easily occur after drinking.

5. Due to the high content of protein and other organic matter in leather wastewater and certain reducing substances, both COD and BOD are high. If it is discharged directly without treatment, it will cause water pollution and promote bacterial growth. The dissolved oxygen in the water body is consumed. When the dissolved oxygen in the water body is lower than 4 mg/L, the respiration of fish and other aquatic organisms will become difficult or even die.

According to incomplete statistics, there are more than 500 industrial-scale leather factories in China, more than 15,000 small leather factories, and countless small workshops that cannot be counted. The annual processing capacity is more than 10 million pieces of cowhide, 75 million pieces of pigskin and 10 million pieces of sheepskin. There are nearly 150 domestic tanneries that have environmental protection facilities, but few of them meet national emission standards and operate normally. Most of them cannot operate normally because of unreasonable treatment processes, high operating costs, and troublesome operation management. Most tannery wastewater is discharged directly into rivers or lakes without treatment or after simple precipitation, and some are even discharged in seepage pits.

In view of the actual situation of enterprises in various regions, we must seriously consider, study, and conduct full demonstrations. Based on the principle of saving investment, occupying less land, and low operating costs, we will draw up sewage treatment plans for experts to demonstrate.