Biological nitrogen removal from wastewater by Paracoccus denitrificans ISTOD1: optimization of process parameters using response surface methodology

Abstract

In freshwater ecosystems, the vital biogenic constituent is nitrogen and the increasing nutrient load discharge from wastewaters has turned into a more grievous issue. A previously demonstrated bacterial strain Paracoccus denitrificans ISTOD1 was studied for the bioremoval of nitrogen in the form ammoniaN from synthetic wastewater media. A high concentration of NH4+-N of 100 mg/L was used to study the behavioral pattern of the bacterial strain during the utilization process. Pre-optimization experiments with different culture conditions for the strain ISTOD1 exhibited high ammonia removal efficiency of 83.9 %, 75.7% and 76.23% in presence of glucose as C-source, pH 7 and temperature of 30°C respectively. Optimization of process parameters for enhancing the heterotrophic nitrification and denitrification process in synthetic wastewater done using the Response Surface Methodology (RSM) showed 98.2% and 91.8% reduction in the concentration of ammonia and nitrate, respectively as compared to the preoptimized conditions. Nitrogen balance analysis revealed that approximately 67 % of NH4+-N was removed as gas products and 32.4% was transformed into biomass. This study helps in developing a biodegradation treatment method under aerobic conditions suitable for purification of ammonia-rich
wastewater and eliminating the by-product such as NO3-N involved in polluting the receiving waters.