Biological nitrogen removal of ammonia-rich centrate in batch systems

Abstract

This study addressed the removal of ammonia from recycled centrate via biological nitrification and denitrification in batch reactors. Nitrification was successful at ammonia feed concentrations up to 400 mg/L and carbon-to-nitrogen (C/N) ratios greater than 1. The use of pre-exposed biomass to ammonia-rich centrate reduced considerably the overall time required for nitrification, which was also reflected on the corresponding specific rates. The denitrification of naturally-generated nitrates proceeded smoothly, with methanol modestly outperforming acetate as external carbon source. Furthermore, simultaneous nitrification and denitrification (SND) was induced in the presence of readily biodegradable organic carbon (i.e., methanol or acetate) under aerobic conditions. Overall, total nitrogen removal from ammonia-rich centrate by biological methods was viable under the conditions investigated.

Keywords:

• High-ammonia centrate
• nitrification
• denitrification
• carbon sources.

Acknowledgments

The authors wish to thank the staff at the Environmental Engineering Laboratory, University of Auckland for their assistance throughout this study. Funding was provided by Watercare Services Ltd, Auckland, New Zealand.