Assessment of Nitrate Reduction by Microbes in Artificial Groundwater Medium

Abstract

There are significant reasons for nitrate contamination in groundwater (Delhi, India): sewage, runoff from landfill sites, nitrogenous chemical fertilisers, and pesticides from agricultural lands. The highest recorded concentration of nitrate in Delhi’s groundwater is reported to be 1500 mg/l. Consumption of high nitrate through water may pose serious health problems in humans, especially children (below five years). The study’s primary objective was to isolate and identify nitrate-remediating microbes from the nitrate-contaminated site Okhla Barrage, located on the Yamuna River in Delhi, India. A total of 11 different strains were isolated from this site. Among these four strains exhibited 40%–50% remediation efficiency at a nitrate concentration of 1000 mg/l. Molecular characterisation revealed that these four strains, Enterobacter aerogenes, E. coli K12, <i>Klebsiella oxytoca</i> and <i>Lelliottia amnigena</i>, belong to the Enterobacteriaceae family. This study assessed the nitrate remediation potential of isolated microbes in groundwater with 1000 and 1500 mg/l nitrate concentrations. By using a 2% inoculum, the microbes were incubated anaerobically at room temperature for ten days. Nitrate concentrations were monitored every 48 hours. <i>Lelliottia</i>, <i>E. coli</i>, and <i>Enterobacter</i> reduced nitrate (1500 mg/l) by approximately 42%, 24%, and 29%, respectively, while <i>K. oxytoca</i> showed minimal reduction. <i>L. amnigena</i> exhibited superior nitrate removal efficiency compared to other strains. According to the reported data, these strains are known to reduce nitrate concentrations of 620 mg/l. However, our findings demonstrate a remarkable nitrate remediation capacity of 1500 mg/l, showcasing a novel contribution to this study. Further detailed analysis for condition optimisation and association of microbe-microbe could be more helpful.