[Spatial distribution of nitrifying bacteria communities in suspended carrier biofilm]

Spatial distributions of ammonia oxidizing bacteria (AOB) and nitrobacteria in a renovated suspended carrier biofilm reactor (SCBR) were investigated by using fluorescence in situ hybridization (FISH) with 16S rRNA oligonucleotide probes in combination with confocal laser scanning microscopy (CLSM). Three bench-scale structurally identical SCBR reactors were operated under different ratios of COD to NH4(+) -N in influents, 5, 10 and 15, respectively. Each SCBR reactor was consisted of a 6 L of aeration basin and a 2L of clarifier, with the hydraulic retention time (HRT) of 1.0h. The monitoring results showed that the thickness of biofilm in the SCBR was about 80 to 120 micron. Both the total amount of AOB and nitrobacteria decreased with depth in biofilm, most of the nitrification bacteria communities lied in the upper layer of biofilm, about 20 to 30 micron. The proportion of AOB to all bacteria in biofilm decreased when the ratio of COD to NH4(+) -N increased.