| Sequential batch reactors (SBRs) were fed with either glucose- or acetate-containing synthetic wastewaters to evaluate microbial population dynamics using a fatty acid methyl esters (FAMEs) profile analysis. The FAMEs profile was found to be an effective means of monitoring the microbial population change in an activated sludge system. PAOs grown from the glucose-fed SBR were significantly different, in terms of metabolic behavior and FAMEs profile, from the acetate-fed SBR. ‘G bacteria’, a group of microorganisms capable of competing with PAOs for organic substrate in an anaerobic-aerobic activated sludge system co-existed with PAOs even in a well-developed BPR process. However, the growth rate for PAOs was always greater than ‘G bacteria’ at various acetate or glucose concentrations, indicating that ‘G bacteria’ were not able to compete with PAOs for limited substrate in the mixed system. Results have demonstrated the danger in over-designing the anaerobic and aerobic zones of a BPR system. Both acetate-fed and glucose-fed PAOs were found to have denitrification capability. The PAOs preferred to denitrify when nitrate was present, rather than to release phosphorus. Therefore, when there is more organic substrate in wastewater than required for denitrification, PAOs will perform BPR even in the presence of the nitrate. |
