1. Classification of biological sewage treatment technology and its advantages and disadvantages: The biological treatment method of sewage is usually divided into the activated sludge method for suspension growth and the biofilm method for attachment growth. The advantages of the activated sludge method are that the process is mature, the process parameters are easy to adjust, and the effluent quality is good, and most sewage treatment plants use the activated sludge method, and the disadvantages are that the volume of the reaction structure is relatively large, the remaining sludge is more, and the sludge is easy to swell.
The advantages of the biofilm method are strong resistance to load impact, the reactor volume is small, the sludge expansion will not occur, and the remaining sludge is less, and the disadvantage is that the effluent water quality is slightly poor, especially when the water quality and quantity change greatly, the biofilm is largely decapitated, and the water quality fluctuates greatly.
2. Traditional A/O or A2/O biological denitrification theory: the ammonia nitrogen in domestic sewage is converted into nitrate and nitrite by autotrophic nitrifying bacteria with oxygen as electron acceptor during the nitrification process, and then the nitrate and nitrite are reduced to gas by heterotrophic denitrifying bacteria to denitrify the sewage. Because nitrifying bacteria have strong aerobic properties, the nitrification process must be aerobic, while traditional denitrifying bacteria use oxygen as the electron acceptor to carry out aerobic respiration under aerobic conditions, and only in the anaerobic state do they use nitrate or nitrite as the electron acceptor to obtain the energy to synthesize the cell body, so the traditional denitrifying bacteria can only carry out denitrification in the anoxic environment. The traditional biological denitrification process developed according to the above theory separates the anaerobic (facultative) tank from the aerobic tank, which leads to process shortcomings such as long process flow, high infrastructure investment, complex system operation and operation, and the need to supplement carbon sources to the denitrification tank.
3. MBBR technology: MBBR is a new type of high-efficiency reactor that combines the advantages of activated sludge method and biofilm method, and overcomes the shortcomings of the two, and its core technology is: select a suspended biological carrier with excellent performance and add aerobic denitrification bacteria in the aeration area, so as to realize aerobic nitrification and denitrification in time and space, and break through the traditional A/O or A2/O biological denitrification theory and technology.