What is the principle and efficacy of AO process?

Principle \x0d\ A/O is short for anoxia/aerobic. Its advantage is that it not only degrades organic pollutants, but also has a certain function of nitrogen and phosphorus removal. It uses anaerobic hydrolysis technology as pretreatment of activated sludge, so A/O method is an improved activated sludge method. \x0d\ A/O process connects the first anoxic stage and the second aerobic stage in series, the DO in the A stage is not more than 0.2mg/L, and the DO in the O stage is 2 ~ 4 mg/L. In the anaerobic stage, anaerobic bacteria hydrolyze suspended pollutants such as starch, fiber, carbohydrate and soluble organic matter in sewage into organic acids, so that macromolecular organic matter is decomposed into small molecular organic matter and insoluble organic matter is converted into soluble organic matter. These products after anoxic hydrolysis enter an aerobic tank for aerobic treatment, which can improve the biodegradability and oxygen efficiency of sewage. In the anoxic stage, heterotrophic bacteria ammoniate pollutants such as protein and fat (N in organic chain or amino in amino acid) and release ammonia (NH3 and NH4+). Under the condition of sufficient oxygen supply, the nitrification of autotrophic bacteria oxidizes NH3-N(NH4+) into NO3-, and returns to the A pool through reflux control. Under anoxic conditions, denitrification by heterotrophic bacteria can reduce NO3- to molecular nitrogen (.\x0d\ efficacy \x0d\ (1) efficiently. This process has a high removal effect on organic matter and ammonia nitrogen in wastewater. When the total residence time is more than 54 hours, the effluent after biological denitrification can be coagulated and precipitated, the COD value can be reduced to below 100mg/L, other indicators can meet the discharge standards, and the total nitrogen removal rate is above 70%. \x0d\ (2) Simple process, less investment and low operating cost. In this process, the organic matter in wastewater is used as the carbon source for denitrification without adding expensive carbon sources such as methanol. Especially, after the ammonia distillation tower is equipped with a device to remove fixed ammonia, the ratio of carbon to nitrogen is increased, and the alkalinity produced in the denitrification process correspondingly reduces the alkali consumption required in the nitrification process. (3) The anoxic denitrification process has high degradation efficiency for pollutants. For example, the removal rates of COD, BOD5 and SCN- in anoxic zone are 67%, 38% and 59% respectively, and the removal rates of phenol and organic matter are 62% and 36% respectively, so denitrification is the most economical and energy-saving degradation process. \x0d\ (4) High capacity load. Because the enhanced biochemistry is adopted in the nitrification stage and the high-concentration sludge membrane technology is adopted in the denitrification stage, the sludge concentration of nitrification and denitrification is effectively improved, and compared with similar processes abroad, it has a higher volume load. \x0d\ (5) The anoxic/aerobic process has strong load impact resistance. When the influent water quality fluctuates greatly or the pollutant concentration is high, the process can maintain normal operation, so the operation management is also very simple. Through the comparison of the above processes, it is not difficult to see that the biological nitrogen removal process itself is nitrogen removal, and at the same time, it also degrades organic substances such as phenol, cyanide and COD. Combined with the characteristics of water quantity and water quality, we recommend anoxic/aerobic (A/O) biological nitrogen removal.