Abstract: The experiment of high concentration domestic sewage treatment was carried out by using predenitrification biological aerated filter (BAF) and polyurethane filler.Under the conditions of the hydraulic loading is 0.64 m³/(m²·h) and reflux ratio is 1∶1,the treatment effect of different ratios of air to water was studied.Results show that the treatment effect of the device is good and stable.When the aerobic section of the gas-water ratio is 20∶1,the effect of pollutants removal is the best,with obvious features of simultaneous nitrification and denitrification,significant nitrogen removal ratio of 82.96%,and effluent concentration less than 10 mg/L.Sampling along the layer on the aerobic,results show that the total nitrogen removal mainly occurs at the bottom of the reactor between 0 and 0.6 m,demonstrating when ρ(DO) is between 1.5 and 2 mg/L,the simultaneous nitrification and denitrification is obvious,and the TN removal rate is remained more than 80%.By simultaneously monitoring changes in ORP values along the layer,the ORP during the simultaneous nitrification and denitrification process can send control signal and respond stably and sensitively.According to the change of ORP,the aeration can be adjusted to save energy efficiently.