【Daily Question No. 40】February 9, 2021

Error. Generally speaking, wastewater treatment can be divided into three levels: primary, secondary, and tertiary. Primary wastewater treatment relies mainly on physical methods, while secondary treatment involves biological methods and similar approaches. Tertiary treatment represents an additional step of deeper processing after the secondary stage. In today’s society, water that has undergone secondary treatment can meet the lowest emission standards and can also be used for agricultural irrigation. There are various methods for secondary wastewater treatment. The first one is the activated sludge method, which has a history of over 100 years. Its principle involves mixing wastewater with certain microorganisms under conditions of high artificial oxygen supply to cultivate active sludge; then, the biological processes occurring within this sludge are utilized to break down the organic pollutants present in the wastewater. The activated sludge process includes various techniques such as the oxidation ditch, SBR intermittent activated sludge process, and A-A-O simultaneous nitrogen and phosphorus removal process. Second, the biofilm method: This approach requires certain conditions – specific microorganisms in the water must be allowed to attach to a filler surface and grow there, thereby forming a biofilm. This biofilm can effectively break down solid and colloidal organic pollutants present in wastewater. The biofilm process is more efficient than the activated sludge process, requires less space, is very convenient to use, and is currently a widely employed technology. The biofilm process mainly includes technologies such as biological filters, biological rotating disks, and biological contact oxidation tanks. Third, anaerobic biological treatment: Just as people have different preferences, microorganisms do as well; some bacteria prefer oxygen while others do not. Based on these anaerobic microorganisms, we have developed a wastewater treatment method using anaerobic biological treatment. This method requires low amounts of materials and energy, generates less sludge, and can also produce biogas; it is an excellent approach that is widely used in today’s society. One of the methods involved is the UASB upflow anaerobic sludge bed treatment technology, which allows wastewater to be treated in a very small tank, thus achieving high efficiency. Fourth, natural biological treatment methods. This method is likely familiar to everyone; it involves making use of nature’s own purification capabilities, with people also creating artificial wetlands such as oxidation ponds based on these natural purification abilities. These wetlands can improve water quality while also enhancing the environment – it’s a win-win situation.