Stimulating Biological Nitrification via Electrolytic Oxygenation

The feasibility of electric current prompted aerobic biodegradation of ${\mathrm{NH}}_4^{+}–\mathrm{N}$ in an attached growth bioreactor system is demonstrated. Nitrification was induced at electric current densities of 1.25 and $2.5\mathrm{mA}∕{\mathrm{cm}}^2$ and with pure oxygen supplied at a rate equivalent to $1.25\mathrm{mA}∕{\mathrm{cm}}^2$ when the bioreactor was operated in batch mode at 6 days detention time. About 84% $(27\mathrm{mg}∕\mathrm{L}){\mathrm{NH}}_4^{+}–\mathrm{N}$ loss was observed at the end of each detention period during all three experimental conditions, indicating that the electric current did not negatively impact the rate of nitrification. Nitrite accumulation was observed during the initial stages of nitrification experiments with $1.25\mathrm{mA}∕{\mathrm{cm}}^2$ current intensity, but nitrite did not accumulate during the other two sets of nitrification experiments. A mathematical model formulated to obtain the rates of biological reactions showed that rates of ${\mathrm{NH}}_4^{+}–\mathrm{N}$ removal are similar for all aeration conditions. Abiotic experiments showed that ${\mathrm{NH}}_4^{+}–\mathrm{N}$ was not removed electrolytically and via stripping, confirming that ${\mathrm{NH}}_4^{+}–\mathrm{N}$ disappearance is due to biological activity.