NITROGEN REMOVAL FROM URBAN WASTEWATER BY ACTIVATED SLUDGE PROCESS OPERATED OVER THE CONVENTIONAL CARBON LOADING RATE LIMIT AT LOW TEMPERTATURE

This study deals with nitrogen removal from urban wastewater employing the activated sludge process at low temperature. It aims at determining the performances and rates of nitrification, and characterising the autotrophic biomass (concentration and kinetic parameters) at 11°C and for F/M ratios higher than the conventional maximum value of 0.1 kg BOD5·kg MLVSS-1·d-1 (i.e. SRT around 15 d). To reach this objective, a study of a continuous activated sludge pilot plant operated under controlled conditions was undertaken for five months. Two methods were used: • A combination of nitrogen mass balance on the continuous reactor and weekly tests in a separate batch reactor • The use of the Activated Sludge Model No 1 (ASM1) calibrated and validated with 6 intensive sampling test runs in the aeration tank of the pilot plant.