Effects of operational parameters on the treatment of nitrate‐rich wastewater by autohydrogenotrophic denitrifying bacteria

The effects of the C / N ratio, as well as hydrogen gas and substrate concentrations, on the treatment of nitrate‐rich wastewater by autohydrogenotrophic denitrifying bacteria in sequencing batch reactors were investigated. Among the various C / N ratios applied in this study, a C / N ratio of 4 was found to be the most suitable ratio that resulted in faster growth and adaptation. The denitrification rate improved with less accumulation of nitrite with increasing H 2 sparging time. Moreover, an increase in nitrate concentration resulted in high nitrite accumulation. The nitrite accumulated to 601 mg/L NO 2 ‐ N when the nitrate concentration was 1000 mg/L NO 3 – ‐ N . The specific degradation rates for nitrate and nitrite were found to be 27.8 mg NO 3 − ‐ N /g MLVSS /d and 50 mg NO 2 − ‐ N /g MLVSS /d, respectively, when the C / N ratio was 2, and H 2 as electron donor was sparged for 1 min with 2 h interval.