Screening and Cultivation of Oligotrophic Aerobic Denitrifying Bacteria

Abstract

During the past few decades, more and more people have poured nitrogen into the fresh water ecosystem, leading to serious environmental problems, such as eutrophication, algal bloom, and unsafe water, especially in drinking water reservoirs. Nitrogen removal in freshwater ecosystems is important for water utilization processes. Physical (air stripping) and chemical techniques (chemical precipitation) are widely used to remove nitrogen from wastewater, as the traditional biological method (nitrification by autotrophs under aerobic conditions and denitrification by heterotrophs under anaerobic conditions) is impractical. Conventional biological denitrification only occurs under anaerobic or anoxic conditions with the reduction from nitrate to nitrogen gas. Oxygen inhibits the reaction steps, which makes them impractical in natural waters, especially in reservoirs. However, few studies have focused on aerobic denitrifiers’ characteristics for removing nitrogen from oligotrophic drinking water reservoirs. To end this, we isolated several strains using enrichment and screening processes. We found that some strains have perfect performance on nitrogen removal in aerobic conditions with low pollutant concentration. Therefore, the objectives of the present work were to determine the taxonomic status using the 16S rRNA method, and to determine nitrogen removal performance in nutrient medium. The results can be useful for applications of aerobic denitrifiers for micropollution reservoir bioremediation. There are two parts in this chapter: (1) Screening and isolation of oligotrophic aerobic denitrifying bacteria; (2) Denitrification performance in pure culture conditions. The results of this part demonstrated that oligotrophic aerobic denitrifying bacterial species had aerobic denitrification ability, and resist a low carbon to nitrogen ratio, therefore, provided the scientific evidence for micropolluted source water bioremediation processes in situ.