Based on the commissioning of the modified inverted A2/O process in a wastewater treatment plant in Jiading District of Shanghai,its optimal operation mode and parameters under different treatment conditions were determined by analog simulation to achieve the aims of up-to-standard discharge,energy saving and consumption reduction.

It shows that modified A~2/O process has not only the very efficiency in the removal of organics,nitrogen and phosphorus,but also the advantage of operation steadiness,high resistance to the loading impulsion.

The effects of the return sludge ratio and the return mixed liquid ratio on the removal of nitrogen and phosphorus were studied in the modified A2/O process.

The characteristics and operation situation of the modified A2/O process used in Xi an Wastewater Treatment Plant are introduced.

Combined with the practical operation of reversed A2/O process of a large municipal wastewater treatment plant in Beijing,the mathematical simulation of the plant working conditions was conducted using TUD model and the default parameters.

In reversed A2/O process an anaerobic tank is put before anoxic tank and design dividual point infall in aerobic tank after anoxic tank.

The effect of temperature on biological nitrogen and phosphorus removal by reversed A2/O process system was studied under the condition of low temperature to seek for the critical temperature to make the nitrification effect in the water studied get poor.