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Improvement of autohydrogenotrophic nitrite reduction rate through optimization of pH and sodium bicarbonate dose in batch experiments

Paper ID Volume ID Publish Year Pages File Format Full-Text
22260 43264 2009 6 PDF Available
Title
Improvement of autohydrogenotrophic nitrite reduction rate through optimization of pH and sodium bicarbonate dose in batch experiments
Abstract

Accumulation of nitrite intermediate in autohydrogenotrophic denitrification process has been a challenging difficulty to tackle. This study showed that further growth of “true denitrifying” bacteria and adaptation to nitrite led to a faster reduction of nitrite than nitrate as a solution to circumvent nitrite accumulation. Moreover, two effective parameters namely pH and bicarbonate dose were optimized in order to achieve a better reduction rate. Sodium bicarbonate dose ranging from 20 to 2000 mg/L and pH in the range of 6.5–8.5 was selected to be examined employing 0.2 g MLVSS/L of reacclimatized denitrifying bacteria. Eleven runs of experiments were designed considering the interactive effect of these two operative parameters. A fairly close reduction time less than 4.5 h (> 22.22 mg NO2−–N/g MLVSS/h) was gained for the pH range between 7 and 8. The highest specific nitrite reduction rate at 25 mg NO2−–N/g MLVSS/h was achieved applying 1000 mg NaHCO3/L at pH 7.5 and 8. The pH was found to be the leading parameter and bicarbonate as the less effective parameter on nitrite reduction removal. Central composite design (CCD) and response surface design (RSM) were employed to develop a model as well as define the optimum condition. Using the experimental data, the developed quadratic model predicted optimum condition at pH 7.8 and sodium bicarbonate dose 1070 mg/L upon which denitrifiers managed to accomplish reduction within 3.5 h and attained the specific degradation rate of 28.57 mg NO2−–N/g MLVSS/h.

Keywords
Autohydrogenotrophic; Denitrification; Nitrite; Optimization; pH; Bicarbonate
First Page Preview
Improvement of autohydrogenotrophic nitrite reduction rate through optimization of pH and sodium bicarbonate dose in batch experiments
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Bioscience and Bioengineering - Volume 107, Issue 3, March 2009, Pages 275–280
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering