Cofre, C., Campos, J. L., Valenzuela-Heredia, D., Pavissich, J. P., Camus, N., Belmonte, M., et al. (2018). Novel system configuration with activated sludge like-geometry to develop aerobic granular biomass under continuous flow. Bioresour. Technol., 267, 778–781.
Abstract: A novel continuous flow system with “flat geometry” composed by two completely mixed aerobic tanks in series and a settler was used to promote the formation of aerobic granular sludge. Making similarities of this system with a typical sequencing batch reactor (SBR), for aerobic granules cultivation, the value of the tank 1/tank 2 vol ratio and the biomass recirculation rate would correspond with the feast/famine length ratio and the length of the operational cycle, respectively, while the settler upflow liquid velocity imposed would be related to the settling time. From the three experiments performed the best results were obtained when the tank 1/tank 2 vol ratio was of 0.28, the sludge recycling ratio of 0.25 and the settler upflow velocity of 2.5 m/h. At these conditions the aggregates had settling velocities between 29 and 113 m/h, sludge volume index at 10 min (SVI10) of 70 mL/g TSS and diameters between 1.0 and 5.0 mm.
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Pavissich, J. P., Camus, N., Campos, J. L., Franchi, O., Pedrouso, A., Carrera, P., et al. (2021). Monitoring the stability of aerobic granular sludge using fractal dimension analysis. Environ. Sci-Wat Res., 7(4), 706–713.
Abstract: Cyclic episodes of granules formation and disintegration took place in two lab-scale aerobic granular sludge sequencing batch reactors, one fed with synthetic wastewater (COD: 0.6 g L-1 and NH4+-N: 0.06 g L-1) and operated at a constant organic loading rate (2.5 g COD per L d), and the other fed with real wastewater (soluble COD: 0.27-1.37 and NH4+-N: 0.02-0.16 g L-1) and with a variable loading rate (between 1.1 and 5.5 g CODsoluble per L d). The sludge volume index, density and diameter (mean value and relative standard deviation) of the granular biomass showed great fluctuations, without any clear tendency during the operational period. However, changes in granules fractal dimension values (both mean and relative standard deviation) matched with the formation and disintegration dynamics of the granular biomass. Statistical data analysis showed that the relative standard deviation of the granules fractal dimension could be a useful parameter for monitoring the granules status. Indeed, an increase of its value during the maturation or steady-state granulation stages is an early warning of disintegration episodes. A control strategy to maintain granules integrity based on this parameter is proposed.
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