Dénitrification par l'utilisation de la souche Enterobacter Hormaechei

Abstract

The work that we present in this thesis consists of a study of the nitrate degradation reaction of wastewater by the use of a biological process. Heterotrophic denitrification is one of the most selective and advanced method for nitrate removal, it is usually inhibited by insufficient carbon sources. This process requires the use of a final electron acceptor, often it is a hydrocarbon such as methanol, glucose, fructose .... In our case we tested at 35 ° C in a suitable nutrient medium, sodium succinate and methanol, in a first step by the use of a mixed culture taken from the wastewater treatment plant (WWTP) Ibn Ziad, Constantine , Algeria. In a second step by five bacterial strains that have been isolated but only the N5 and N6 strains that have been identified. five bacterial strains were isolated but only the strains N5 and N6 were identified. The strains were preliminarily identified using biochemical, Gram staining and by API 20 E system, tests and then a method based on the similarity of the PCR-16S rRNA. 16S rRNA gene sequence analysis indicated that both strains were most closely related to Enterobacter hormaechei with sequence similarities of 99%. Both strains showed an excellent capability to remove nitrate and to transform carbon substances namely methanol and sodium-succinate to carbon dioxide. This process was accompanied by a slight rise in pH with a simultaneous production of nitrogen gas as the end product at 35°C. Nitrate was removed after 48 h of incubation. Thus, the anaerobic denitrification ability of strains N5 and N6 has been proved. Sodium-succcinate is the most favorable carbon source for denitrification by both strains (N5 and N6). Furthermore, strains N5 and N6 could effectively remove nitrate at low C/N ratios and under conditions where the temperature is elevated, which would benefit nitrate removal from the wastewater.