Electrolytic stimulation of denitrification in sand columns

Denitrification in two sand columns inoculated with a mixed culture of denitrifying microorganisms was stimulated when an electric current was passed using electrodes inserted within the columns. An average nitrogen removal efficiency of 49% was achieved at a current of 20 mA. Abiotic column experiments showed an average nitrogen removal efficiency of 20% at a current of 20 mA, indicating that the direct electrochemical reduction of nitrate on the cathode was occurring. Statistical analysis showed that at a 95% confidence level, the performance of the two columns with respect to the nitrogen removal efficiency was similar, the increase in nitrogen removal efficiency with an increase in passed current was significant and the difference in the performance between the abiotic and biologically active columns was significant. At a current of 20 mA, the 95% confidence interval for the contribution of biological activity to denitrification in the column is 18 to 69%.