Nutrient biological removal in an up-flow sludge bed reactor under intermittent aeration using glycerol as the sole carbon source

Abstract

This work evaluated the feasibility of glycerol as the sole carbon source for nutrient biological removal in an intermittently aerated bioreactor. The reactor operation was divided into two phases: the first one aimed only at removing nitrogen; and the second one aimed at removing nitrogen and phosphorus. In the first operational phase, three C/N (Carbon / Nitrogen) ratios were tested: 1.2, 1.5 and 1.8. For a C/N ratio of 1.8, higher denitrification efficiency was achieved (91 ± 8%). During the second phase, the reactor was subjected to periods of aeration and non-aeration of 2 h and 4 h, respectively, for a C/P (Carbon / Phosphorus) ratio of 10. The biological phosphorus removal in this phase was not significant (12 ± 9%), indicating that there was no development of PAO (Phosphorus Accumulating Organisms), since phosphate release did not occur during the anaerobic phase. This can be explained by the lack of VFA (Volatile Fatty Acids), which should come from the anaerobic degradation of the remaining amount of glycerol after denitrification was completed. The optical microscopy analysis indicated the presence of filamentous bacteria similar to the genus Beggiatoa, which could also have consumed part of the substrates from the glycerol fermentation.