Automatic adjustment of cycle length and aeration time for improved nitrogen removal in an alternating activated sludge process

The paper examines the nitrogen dynamics in the alternating BIODENITRO and BIODENIPHO processes with a focus on two control handles influencing now scheduling and aeration: the cycle length and the ammonia concentration at which a nitrifying period is terminated. A steady state analysis examining the combined effect of both control handles reveals three conditions which characterize when nitrogen removal is maximized. A dynamic analysis shows that these conditions also apply for a changing ammonia load. This then allows an automatic control strategy for maximizing nitrogen removal to be based on a cycle by cycle single variable optimization rather than a more difficult multivariable optimization over a longer time horizon. Copyright (C) 1996 IAWQ.