[Hydrogenotrophic denitrification for the removal of nitrate in drinking water]

Autotrophic denitrification with hydrogen as the electron donor for the removal of nitrate in drinking water was investigated by using a bench-scale sequencing batch reactor in an attached growth system. Gas permeable membrane was employed as the hydrogen diffuser to improve the hydrogen mass transfer and decrease the explosion risk. The results showed that nitrate could be removed efficiently with this technology. The removal rates of NO3(-)-N and TN could achieve 6.45 mg/(L h) and 4.89 mg/(L h) respectively, with the highest accumulation of NO2(-)-N 11.58 mg/L. pH increased to 10.56 and DOC increased 0.91 mg/L. A zero order kinetic model was proposed for NO3(-) and NO2(-) reduction, with the kinetic coefficients in the ranges of 0.33 - 0.60 g/(g d) and 0.37 - 0.45 g/(g d) respectively, The removal rates of NO3(-)-N and TN were not affected with the hydrogen pressure higher than 40 kPa, with the values (5.97 +/- 0.08) mg/(L h) and (4.25 +/- 0.04) mg/(L h) respectively, while decreased remarkably when the hydrogen pressure was 25 kPa. The denitrification reaction was inhibited at pH 6 with the removal rate of NO3(-)-N 1.83 mg/( L h); pH higher than 8 was the favorable condition for denitrification with the removal rate of NO3(-)-N 3.13 mg/(L h).