Spatial distribution of ammonia-oxidizing bacteria in the biofilm and suspended growth biomass of the full- and partial-bed biological aerated filtersA paper submitted to the Journal of Environmental Engineering and Science.

The extent of comparable nitrogen removal in the full- and partial-bed biological aerated reactors needs further microbiological evidence, specifically the existence of ammonia-oxidizing bacteria (AOB). The nitrogen removal process in such systems is typically initiated by chemoliautotrophic ammonia-oxidizing bacteria converting ammonia to nitrite and traces of oxidized nitrogen gases. The formation of a dense biofilm as a result of higher turbulence would account for the higher number of AOB cells enumerated in the biofilm samples from the partial-bed reactor (4.3 × 105 ± 1.9 × 105No. of AOB cells/mL sample) as compared with those from the full-bed reactor (1.5 × 105 ± 8.0 × 104No. of AOB cells/mL sample).