Nitrogen Recovery through Dissimilatory Nitrate Reduction to Ammonium: Impact of Environmental Factors

The application of the bacterial dissimilatory nitrate reduction to ammonium (DNRA) process for treating nitrate-rich wastewater offers an environmentally friendly and resource-efficient strategy with significant potential for ammonium nitrogen recovery. This study investigates the impact of carbon sources, C/N ratios, pH, and temperature on the DNRA efficiency of Pseudomonas sp. strain LZ-1 (strain LZ-1). The results revealed that sodium citrate is the most favorable carbon source among sodium formate, sodium acetate, sodium propionate, and sodium citrate for enhancing DNRA in strain LZ-1. Ammonia production by strain LZ-1 peaks at a C/N of 8 within the range of 3 to 20, increasing before and decreasing thereafter. Furthermore, neutral to alkaline conditions (pH 7–10) are favorable for the DNRA process, with an optimal initial pH of 9. Temperature studies indicate a similar trend of initial increase followed by a decline in DNRA efficiency as temperatures rise from 20 to 35 °C, with peak ammonia production at 30 °C. The presence of sulfur ions inhibits the DNRA process in the strain LZ-1. However, this inhibitory effect diminished as the S/N ratio increased from 1/4 to 1. These insights contribute to a deeper understanding of the impact of environmental factors on DNRA and serve as a valuable reference for the utilization of strain LZ-1 in nitrogen recovery from nitrate-rich wastewaters.