The use of naturally generated volatile fatty acids for herbicide removal via denitrification

Abstract

This research focuses on the removal of 2, 4-D via denitrification, with a particular emphasis on the effect of adding naturally generated volatile fatty acids (VFAs) as a carbon source. These VFAs had been produced from an acid-phase anaerobic digester (mean VFA concentration of 3153 ± 801 mg/L [as acetic acid]). The first step involved developing 2, 4-D degrading bacteria in a sequencing batch reactor (SBR) fed with both sewage and 2, 4-D (30–100 mg/L). Subsequent denitrification batch tests demonstrated that the specific denitrification rate increased from 0.0119 ± 0.0039 to 0.0192 ± 0.0079 g NO₃-N/g volatile suspended solids (VSS) per day, when using 2, 4-D alone versus 2, 4-D plus natural VFAs from the digester as a carbon source. Similarly, the specific 2, 4-D consumption rate increased from 0.0016 ± 0.0009 to 0.0055 ± 0.0021 g 2,4-D/g VSS per day, when using 2, 4-D alone as compared to using 2, 4-D plus natural VFAs. Finally, a parallel increase in the percent 2, 4-D removal was observed, rising from 28.33 ± 11.88 using 2, 4-D alone to 54.17 ± 21.89 using 2, 4-D plus natural VFAs.

Keywords:

• 2,4-D degradation
• denitrification
• volatile fatty acids
• acid-phase anaerobic digester
• sequencing batch reactor

Acknowledgments

The authors would like to thank the University of Canterbury for funding this research via a doctoral scholarship (Ref 5075/2/61). Specific thanks go to David MacPherson and Peter McGuigan for their excellent technical advice and assistance in the environmental engineering laboratory.

Notes

∗As acetic acid