Anaerobic ammonium oxidation improvement via a novel capsule bioreactor

Abstract

This study developed a capsule bioreactor made from polyvinyl alcohol (PVA) to entrap anaerobic ammonium oxidation (ANAMMOX) bacteria for the removal of nitrogen from synthetic wastewater. Experimental results demonstrate that the ANAMMOX bacteria were entrapped inside the capsule and not washed out from the bioreactor. This method also avoids damaging the ANAMMOX bacteria during immobilization. The proposed bioreactor also has a shorter start-up period. The diffusion rate of ammonium and nitrite from the bulk solution through the capsule determined the rate of the ANAMMOX reaction. The optimal ratio of was approximately 1 for the bioreactor. In addition, the capsule protected the ANAMMOX bacteria from nitrite inhibition. The bioreactor achieved a high stable nitrogen removal rate (5.8 Kg-N m⁻³ day⁻¹) at high nitrite levels (up to 600 mg-N L⁻¹ in the influent). Therefore, the proposed capsule bioreactor has considerable potential for actual nitrogen removal applications.

Keywords:

• ANAMMOX
• nitrogen removal
• bio-capsule
• bioreactor
• polyvinyl alcohol

Acknowledgements

The authors would like to thank the National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract No. NSC 95-2211-E-236-011.