2.1On April 22nd, 970, DennisHayes, a student of Harvard University in the United States, initiated and organized environmental protection activities, which received enthusiastic response from environmental protection organizations. About 20 million people from all over the United States took part in this massive demonstration and rally, aiming to arouse people's awareness of environmental protection and urge the US government to take some measures to control environmental pollution. Later, this activity was approved by the United Nations. Up to now, April 22nd every year has been designated as "Earth Day".
3. Wastewater treatment: Wastewater treatment refers to the treatment of wastewater by physical, chemical and biological methods, so as to achieve the purpose of purifying wastewater, reducing pollution, recycling wastewater and making full use of water resources.
4. Waste gas treatment: Waste gas treatment is also called waste gas purification. Waste gas treatment refers to the pretreatment of waste gas produced in industrial sites and factory workshops before discharge, so that it meets the national waste gas discharge standards. General waste gas treatment includes organic waste gas treatment, dust waste gas treatment, acid-base waste gas treatment, malodorous waste gas treatment and air disinfection and purification.