Treatment of Synthetic Wastewater in a Pre-Denitrification Biofilm Reactor Packed with Polyurethane Media

In the experiment, a pre-denitrification biofilm reactor with polyurethane as media was used to treat synthetic wastewater, and the influence of air-liquid ratio(A/L), hydraulic loading and reflux ratio on the performance of the reactor was investigated. The experimental results indicate that, when the influent concentration of COD was 270-300 mg/L, NH4+-N was 33-35 mg/L and TN was 35-40 mg/L, under the operating condition of the air-liquid ratio being 8:1, the hydraulic loading being 0.96m/h(HRT of 1.5 h), and reflux ratio being 150%, the removal efficiency of COD, NH4+-N and TN attained to 86%, 94% and 64%, respectively. The effluent quality satisfied the discharging standard of integrated wastewater of Liaoning (DB 21/1627-2008). In the pre-denitrification biofilm reactor, COD and TN removal was mainly realized in the anoxic zone, while NH4+-N removal was mainly achieved in the oxic zone. In order to guarantee the good quality of the effluent, the COD, NH4+-N and TN loading should be controlled below 6.42, 0.71 and 0.58 kg/(m3·d), respectively, and the influent COD/TN ratio should be greater than 6.