Characterization of the microbial diversity in a biotreatment process using non-culture based methods

Molecular techniques were used to compare the microbial community of suspen ded activated sludge and attached biofilm in a biological nutrient removal process (TNCU-I) operated under various COD/total P (COD/TP) feed ratios. A nalysis of restriction fragment length polymorphism of amplified 16S rRNA g enes indicated that the microbial population structures were more closely r elated among those sludge samples taken from aerobic sludge than that taken from biofilm attached on the RBC. The use of different COD/TP feed ratios (300/2.5-300/25) had no significant effect on the change of microbial struc tures of sludge samples. The 16S rDNA clone library further indicated that at least eight and six different microbial populations were present in acti vated sludge and RBC biofilm, respectively. The phylogenetic analysis revea led that six of those eight major clones obtained from the suspended activa ted sludge were from the beta-subclass of the class Proteobacteria. In cont rast, only one clone obtained from biofilm belonged to the beta-subclass of the Proteobacteria. This difference in the microbial population structure was possibly attributed to the growth state (suspended or attached) or carb on source (autographs or heterotrophs) of the sludge samples rather than th e effect of the COD/TP ratio used.