defines the ratio of solids in the supernatant to the total weight of the aerobic
granules, expressed in percent (%). Integrity coefficient ranged up to 98% and
97% for aerobic granules cultivated in glucose and acetate, respectively (Tay et al.
2002b). Ghangrekar et al. (2005 ) reported that lower integrity coefficient determines
greater granule strength (Ghangrekar et al. 2005). During storage, extracellular
protein content was found to be significantly less due to more protease enzyme
(secreted by proteolytic bacteria) activity inside the granules (Adav et al. 2009).
6.4 Granule Characterization Techniques
There are several microscopic characterization techniques available for aerobic
granules like normal light microscopy, scanning electron microscope, field emission
scanning electron microscope and confocal laser scanning microscopy. Scanning
electron microscope analysis explained the dominancy of filamentous bacteria on the
outer surface of glucose-fed mature granules, whereas tightly linked microbial cells
with compact structure were found in acetate-fed granules (Tay et al. 2001b).
6.5 Factors Affecting Aerobic Granulation
There are number of conditions that should be fulfilled for microbial granular
structure formation. The factors affecting aerobic granulation are discussed in this
section.
6.5.1 Organic Loading Rate
Aerobic granulation is achievable at different organic loading rates. Moy et al.
(2002), Liu et al. (2003a) and Liu et al. (2003b) successfully achieved aerobic
granulation at high loading of 15 kg chemical oxygen demand/m
3 .day as well as
low loading of 2.5 kg chemical oxygen demand/m
3 .day organic loading rates. It
indicates that aerobic granulation is almost independent of organic loading rate
values. However, Tay et al. (2004) suggested that about 4 kg chemical oxygen
demand/m
3 .day is an optimal organic loading rate of aerobic granulation for achieving 99% of chemical oxygen demand removal efficiency.
6.5.2 Settling Time
Approximately 5 min settling time is required to achieve effective granulation.
According to literature, short settling time around 5 min helps to provide high cell
6 Aerobic Granulation in Hydrocarbon-Rich Wastewater Treatment
181
granules, expressed in percent (%). Integrity coefficient ranged up to 98% and
97% for aerobic granules cultivated in glucose and acetate, respectively (Tay et al.
2002b). Ghangrekar et al. (2005 ) reported that lower integrity coefficient determines
greater granule strength (Ghangrekar et al. 2005). During storage, extracellular
protein content was found to be significantly less due to more protease enzyme
(secreted by proteolytic bacteria) activity inside the granules (Adav et al. 2009).
6.4 Granule Characterization Techniques
There are several microscopic characterization techniques available for aerobic
granules like normal light microscopy, scanning electron microscope, field emission
scanning electron microscope and confocal laser scanning microscopy. Scanning
electron microscope analysis explained the dominancy of filamentous bacteria on the
outer surface of glucose-fed mature granules, whereas tightly linked microbial cells
with compact structure were found in acetate-fed granules (Tay et al. 2001b).
6.5 Factors Affecting Aerobic Granulation
There are number of conditions that should be fulfilled for microbial granular
structure formation. The factors affecting aerobic granulation are discussed in this
section.
6.5.1 Organic Loading Rate
Aerobic granulation is achievable at different organic loading rates. Moy et al.
(2002), Liu et al. (2003a) and Liu et al. (2003b) successfully achieved aerobic
granulation at high loading of 15 kg chemical oxygen demand/m
3 .day as well as
low loading of 2.5 kg chemical oxygen demand/m
3 .day organic loading rates. It
indicates that aerobic granulation is almost independent of organic loading rate
values. However, Tay et al. (2004) suggested that about 4 kg chemical oxygen
demand/m
3 .day is an optimal organic loading rate of aerobic granulation for achieving 99% of chemical oxygen demand removal efficiency.
6.5.2 Settling Time
Approximately 5 min settling time is required to achieve effective granulation.
According to literature, short settling time around 5 min helps to provide high cell
6 Aerobic Granulation in Hydrocarbon-Rich Wastewater Treatment
181