Effects of Operation Parameters on Nitrification in Up-Flow Biological Aerated Filter Coupled with Zeolite Media at Low Temperature

A lab scale biological aerated fiter(BAF) reactor with an effective volume of 12.1 L and zeolite as media is operated at 7°C treating synthetic sewage continuously. The nitrification properties and the impacts of different operation parameters such as HRT, effluent recirculation and COD/NH₃N(C/N) on this process are studied respectively. The results suggest that the HRT has a great influence on the ammonia removal. The ammonia removal is above 80% at the operation HRT of 4 hours with an obvious comparison of decrease to 37% at 1 hour. Correspondingly, appropriate recirculation can enhance the system performance; an improvement of 13% and 21% ammonia removal can be achieved with 100% and 200% at 2 hours respectively, but only 10% evaluation at 1 hour even with 200% recirculation for the washout of nitrifier in a deduction of reaction time. Experiments with different C/N ratios indicate that as C/N ratios increase, ammonia removal decreases linearly because of the competition in the oxygen uptake between the heterotrophs and nitrifier.