Effects of influent composition on biological activity, acclimation time and microbial community profile of activated sludge

Background: The performance and stability of activated sludge (AS) processes are strongly related to influent wastewater characteristics. Objective: To investigate the influence of different chemical compositions of influent wastewater, in terms of source of carbon, on activated sludge. Methods: Response was measured in oxygen uptake rate (OUR), volatile suspended solids in the mixed liquor (MVLSS), chemical oxygen demand (COD), and microbial community profile, obtained using Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS). Results: Results showed that the microbial community profile obtained in both reactors is consistent with those reported for full-scale AS bioreactors treating sewage. However, when the source of carbon is less bioavailable (bioreactor 1), there was a statistically significant difference (p-value<0.05, 95% confidence) in the biological activity of the biomass, both in terms of MLVSS growth and OUR in comparison with the reactor with source of carbon more bioavailable (bioreactor 2). This difference also impacted the time required for complete acclimation: it could be considered completed in 15 days in bioreactor 2, whereas in bioreactor 1, acclimation required more than 120 days to be completed, as during this period there was no net biomass growth even though there was high COD removal.