A control system with the objective of improving nitrogen removal has
been installed in a 60,000 p.e. communal wastewater treatment plant. T
he system controls the biological stage of the activated sludge plant
employing mass balances for evaluating the control measures. The contr
ol resulted in an overall reduction of the nitrogen output by half and
one third in warm and cold periods respectively, compared to an uncon
trolled reference train. Violating effluent standards could be avoided
through the application of the control system. (C) 1998 Published by
Elsevier Science Ltd. All rights reserved.