However, the mean granule diameter was almost similar in both cases. The removal
rate of nitrogen, phosphorous and organic matter were 75%, 93% and 85%, respectively in 100% floc sequencing batch reactor, while in 90% floc sequencing batch
reactor the removal rates were found to be 84%, 99% and 80%, respectively (Coma
et al. 2012).
6.5.7 Food to Microorganism Ratio
In most of the cases, high food-to-microorganism ratio accelerates faster and larger
granulation, and a low food-to-microorganism ratio results into slower and smaller
granule formation. Moreover, a high food-to-microorganism ratio enhances granule
stability and size (Lobos et al. 2008). But Moy et al. (2002) reported that large and
compact granules suffer from air diffusion limitations. Hence, food-to-microorganism ratios should keep changing at different phases of sequencing batch reactor
operation to achieve proper granulation. Li et al. (2011) suggested high food-tomicroorganism ratio in the initial phase and low food-to-microorganism ratio in the
final phase as optimum criteria for aerobic granulation.
6.5.8 Height-to-Diameter Ratio
Height-to-diameter ratio of an aerobic granular reactor column is the major controlling parameter for granular shape and microbial structure formation. Zhu et al.
(2008) observed that when the height-to-diameter ratio is very high in an aerobic
granular reactor, internal flow patterns helped in strong granule formation. In
contrast, Kong et al. (2009) reported that in aerobic granular reactor, height-todiameter ratio and granule settling velocity had no significant effect on granulation.
6.5.9 Hydraulic Retention Time
Hydraulic retention time determines the average time duration for a soluble compound remains in a bioreactor. For sequencing batch reactor performance optimization, an effective hydraulic retention time should be carefully selected (Fang and Yu
2000, 2001). Beun et al. (1999) observed that shorter hydraulic retention times
promote stable granulation. However, a very short hydraulic retention time can
suppress the biomass growth due to excessive washout of the flocculent biomass
from the reactors.
6 Aerobic Granulation in Hydrocarbon-Rich Wastewater Treatment
183
rate of nitrogen, phosphorous and organic matter were 75%, 93% and 85%, respectively in 100% floc sequencing batch reactor, while in 90% floc sequencing batch
reactor the removal rates were found to be 84%, 99% and 80%, respectively (Coma
et al. 2012).
6.5.7 Food to Microorganism Ratio
In most of the cases, high food-to-microorganism ratio accelerates faster and larger
granulation, and a low food-to-microorganism ratio results into slower and smaller
granule formation. Moreover, a high food-to-microorganism ratio enhances granule
stability and size (Lobos et al. 2008). But Moy et al. (2002) reported that large and
compact granules suffer from air diffusion limitations. Hence, food-to-microorganism ratios should keep changing at different phases of sequencing batch reactor
operation to achieve proper granulation. Li et al. (2011) suggested high food-tomicroorganism ratio in the initial phase and low food-to-microorganism ratio in the
final phase as optimum criteria for aerobic granulation.
6.5.8 Height-to-Diameter Ratio
Height-to-diameter ratio of an aerobic granular reactor column is the major controlling parameter for granular shape and microbial structure formation. Zhu et al.
(2008) observed that when the height-to-diameter ratio is very high in an aerobic
granular reactor, internal flow patterns helped in strong granule formation. In
contrast, Kong et al. (2009) reported that in aerobic granular reactor, height-todiameter ratio and granule settling velocity had no significant effect on granulation.
6.5.9 Hydraulic Retention Time
Hydraulic retention time determines the average time duration for a soluble compound remains in a bioreactor. For sequencing batch reactor performance optimization, an effective hydraulic retention time should be carefully selected (Fang and Yu
2000, 2001). Beun et al. (1999) observed that shorter hydraulic retention times
promote stable granulation. However, a very short hydraulic retention time can
suppress the biomass growth due to excessive washout of the flocculent biomass
from the reactors.
6 Aerobic Granulation in Hydrocarbon-Rich Wastewater Treatment
183