Biological nitrogen removal in a step-feed CAST with real-time control treating municipal wastewater

摘要

The performance of a 18 L step-feed cyclic activated sludge technology (CAST) combined withnreal-time control treating real municipal wastewater was evaluated. The operation strategiesnemployed pH and oxidation reduction potential (ORP) as on-line control parameters, which canncontrol the durations of oxic and anoxic phases flexibly. The obtained results showed that thenstudied process had achieved advanced and enhanced nitrogen removal by several phases ofnconsecutive oxic/anoxic periods. Total nitrogen in effluent was lower than 2 mg/L and the averagenTN removal efficiency was higher than 98%, while only requiring small amount of external carbonnsource. Unexpected characteristic points in pH and ORP profiles denoting the depletion of nitratenwere also observed during the last anoxic phase. Denitrification rate was found to be morendependent on the system temperature compared to nitrification rate. Moreover, a stable andnefficient phosphorus removal rate above 90% was achieved by using step-feed strategy whichnenabled the influent carbon source to be fully used and the favourable condition for phosphorusnreleasing to be created during the anoxic phases.