Effect of Initial Nitrate Concentrations and Heavy Metals on Autohydrogenotrohic Denitrification

Effects of initial nitrate concentrations and heavy metals on autohydrogenotrophic denitrification were investigated in batch tests to eliminate nitrate from the contaminated drinking water. Nitrate was reduced completely without nitrite accumulation at low initial concentration of nitrate (15 mg N/L), with nitrite accumulation at intermediate initial concentrations (70, and 100 mg N/L), and the denitrification of high initial nitrate concentration (150 mg N/L) was significantly inhibited at the earlier time of the reaction. However, the zero order kinetic model analysis indicated that the rates of nitrate reduction increased with the initial nitrate concentration increasing, and the rate of nitrite reduction in absence of nitrate did not change very much. The denitrification activity was significantly inhibited by Cu and Cr (VI) at the metal concentrations of more than 0.5 mg/L, whereas Zn gave no impact on the nitrate removal efficiency at all levels investigated.