O refers to good treatment, A refers to anaerobic treatment or anoxic treatment
The previous level is the O section of the AO process. The previous level is AO, which is the activated sludge process. The following contact oxidation method belongs to the biofilm method
The main reason for this design is that the pollutant load of sewage is relatively high, that is, the content of pollutants is high. Only through the AO process, organic matter cannot be effectively degraded and the water quality can be improved. Therefore, the cascade process is used to achieve the standard. The cascade process is a series combination of several or one process