MICROBIOLOGICAL CONVERSIONS IN NITROGEN REMOVAL

Nitrogen conversion processes are essential for most wastewater treatm ent systems. Due to the many possible conversions, and the complexity of analysing the reactions under actual conditions, there is much room for confusion. This review provides an overview of the possible micro biological nitrogen conversions described in literature. The relevance of these conversions with respect to wastewater treatment processes i s discussed. Rates described for aerobic denitrification or denitrific ation by autotrophic nitrifiers are so low that these conversions prob ably do not play a significant role under practical conditions. Hetero trophic nitrification may be of relevance only when the wastewater con tains a high COD/N ratio (>10). Anaerobic ammonium oxidation can occur in fully autotrophic systems with very long sludge retention times or biofilm systems. This conversion offers great opportunities since it allows us to denitrify with ammonium as electron donor, i.e. no organi c substrate is needed in the nitrogen removal process. (C) 1998 Publis hed by Elsevier Science Ltd. All rights reserved.