NITROGEN REMOVAL UPGRADE OF A WASTE-WATER TREATMENT-PLANT WITHIN EXISTING REACTOR VOLUMES - A SIMULATION SUPPORTED SCENARIO ANALYSIS

A simulation supported scenario analysis for the upgrading of a munici pal WWTP Hoogstraten (Belgium) with nitrogen removal is presented. The most cost-effective solution is to create optimal aerobic and anoxic conditions within the existing reactor volumes. The IAWQ-model No.1 wa s used for the simulation of the biological reactor. A measuring campa ign and some specific respirometric tests provided the necessary infor mation for calibration and verification of the biological model. The s tudy consisted of two parts : 1) increase of the denitrification capac ity, and 2) optimisation of operation. First, the impact of three meas ures, i.e. creation of anoxic zones, implementation of step feeding an d introduction of internal recirculation, was evaluated by means of si mulation. For this purpose a standard time variant influent was define d based on the measuring campaign. This approach made it easy to compa re the different scenarios. In the second part of the study some speci fic problems were handled. To avoid high nitrate concentrations during weekends three possible control actions were simulated. The simulatio n study also evaluated the usefulness-of the primary clarifier in the upgraded design and the effect on the biological process of first flus h during intensive rainfall. Copyright (C) 1996 IAWQ. Published by Els evier Science Ltd.