Abstract:
This reserch studied residence time distribution (RTD) of the upflow partially aerated biofilm reactor. The RTD were observe with and without plastic media under various hydraulic retention time (HRT) with a 100% recirculation rate. Tracer curves of two collecting points, anaerobic zone, and effluent, were analyzed using the mathematic model. The curve of all conditions shows that the flow patterns were plug flow in anaerobic zone and completely mix in aerobic zone because of aeration and recirculation. Reductions of HRT were increased with 84.1% of expected HRT. An upflow partially aerated biofilm reactor was developed to study the removal of COD and nitrogen from synthetic wastewater (COD 400 mg/l. and NH3 -N 40 mg-N/l). The studied HRT were of 2, 4, 8, and 12 h, achieving COD removal efficiencies of 91.9%, 91.6%, 92.1%, and 98.7%, respectively. The highest COD removal rate was 171 mg/l/h. When HRT were 12 and 8 h, the reactor attained a good performance of denitrification and nitrification processes and the NH3-N removal efficiency reached 99% while total nitrogen (TN) reached 37.3% and 52.5%, respectively. The average nitrification rate was 0.0659±0.0107 gN/m2/d. For 2 and 4 h HRT, NH3-N in effluent were 30.2±3.99and 34.4±0.910 mg/l, respectively with little nitrite or nitrate production. The results demonstrated that the upflow partially aerated biofilm reactor can be operated at HRT of 2, 4, 8, and 12 h with more than 90% COD removal efficiency and at HRT of 12 h and 8 h for more than 99% of NH3-N removal and 40% for TN removal.