Autotrophic denitrification using hydrogen generated from metallic iron corrosion

Hydrogenotrophic denitrification was demonstrated using hydrogen generated from anoxic corrosion of metallic iron. For this purpose, a mixture of hydrogenated water and nitrate solution was used as reactor feed. A semi-batch reactor with nitrate loading of 2000 mg m−3 d−1 and hydraulic retention time (HRT) of 50 days produced effluent with nitrate concentration of 0.27 mg N L−1 (99% nitrate removal). A continuous flow reactor with nitrate loading of 28.9 mg m−3 d−1 and HRT of 15.6 days produced effluent with nitrate concentration of ∼0.025 mg N L−1 (95% nitrate removal). In both cases, the concentration of nitrate degradation by-products, viz., ammonia and nitrite, were below detection limits. The rate of denitrification in the reactors was controlled by hydrogen availability, and hence to operate such reactors at higher nitrate loading rates and/or lower HRT than reported in the present study, hydrogen concentration in the hydrogenated water must be significantly increased.