An Experimental Investigation of Nitrogen Removal via Heterotrophic Nitrification and Aerobic Denitrification (HNAD) Pathway

Abstract

Nitrogen removal from wastewater is critical due to increasing eutrophication concerns and its associated ecological hazards. Heterotrophic nitrification aerobic denitrification (HNAD) bacteria offer a feasible single reactor system for managing diverse nitrogenous contaminants, which are present in wastewater. However, the process scale-up is often limited due to the inability of strains in tolerating the changes in temperature and other operational conditions. There is a huge need for bioprospecting novel strains capable of sustaining at real-time conditions. Thus, the present study aimed to isolate and identify native HNAD strains from the sewage treatment plant of Thapar Institute of Engineering and Technology, Patiala through biochemical and molecular characterization. Initial visualization and microscopic identification showed the bacterial strains to form opaque, red, and yellow colonies with characteristic rod-shaped and gram-positive nature. Phylogenetic analysis through 16S rRNA sequencing identified the strains as Rhodococcus ruber and Cellulosimicrobium cellulans. Shake flask experiments showed a significant growth rate in simultaneous nitrification and denitrification (SND) medium with doubling time of consortia 131 min.