Influence of wastewater organic carbon form on biological kinetics: Case of nitrogen removal by activated sludge
Résumé
The aim of this work is to compare the effects of the use of a synthetic feed instead of a real domestic wastewater on the nitrogen removal efficiency of an activated sludge process. The comparison is based on the comparison of the operating key parameters like sludge production, sludge retention time, nitrification rate, autotrophic growth rate. An activated sludge pilot plant was supplied firstly with a synthetic feed free of suspended solids, and secondly with a real urban wastewater. The observed sludge production yield and the maximum nitrification rate were measured every week; then the autotrophic biomass concentration and its maximum growth rate were determined. It is demonstrated that the synthetic feed induces 1.5 to 2 times lower sludge production values, and 2 to 3 times lower maximum nitrification rates compared to the value obtained with the real wastewater. The difference observed on sludge production are due to the lack of nonbiodegradable organic suspended solids. The lower maximum nitrification rates are only due to the difference on µA, maxi values because the autotrophic biomass concentration is similar for both cases. These results demonstrate that the use of this synthetic feed, rather than the real wastewater, leads to much more favorable conditions of growth for autotrophic biomass.