Changes in phosphorus removing performance and bacterial community structure in an enhanced biological phosphorus removal reactor.

A lab-scale-enhanced biological phosphorus removal (EBPR) reactor was operated for 204 days to investigate the correlation between phosphorus removing performance and bacterial community structure. The phosphorus removing performance was good from day 1 to 92 and from day 172 to 204. However, the removal activity was in a deteriorated state from day 93 to 171. From day 69 (2 weeks before the beginning of the deterioration) to 118 (2 weeks after the beginning of the deterioration), sludge P content decreased. The amounts of ubiquinone-8 and menaquinone-8 (H(4)) decreased during this period while the amount of ubiquinone-10 increased. The comparison of these changes and the general attribution of each quinone to the bacterial phylogenetic groups suggested that beta proteobacteria and Actinobacteria contributed to EBPR positively, and that alpha proteobacteria were related to this EBPR deterioration. Glycogen accumulating organisms (GAOs) are considered to detrimentally affect EBPR ability by outcompeting the phosphorus accumulating organisms by using aerobically synthesized glycogen as the energy source to assimilate organic substrates anaerobically to form polyhydroxyalkanoates. However, in this research, there was nearly no substrate uptake during the anaerobic period at the middle of the deteriorated performance period. This suggests that the deterioration observed in this research does not agree with the GAOs inhibition model. In this research, the excess P release at the anaerobic period was concluded to cause the deterioration.