6.3.2 Chemical Parameters
Specific Oxygen Utilization Rate
Specific oxygen utilization rate denotes the activity of microorganisms expressed as
milligrams of oxygen consumed by a milligram of cellular proteins per hour. In a
case study, specific oxygen utilization rate values in glucose-fed and acetate-fed
granules ranged between 55.9 to 69.4 mg O 2 /g mixed liquor volatile suspended
solids/h (Tay et al. 2002b).
Extracellular Polymeric Substances
Extracellular polymeric substances are metabolic polymers secreted by aerobic
granules which help in granule formation. Extracellular polymeric substances
mainly contain β-polysaccharides and proteins. In aerobic granules proteins/polysaccharides ratios are generally found between 3.4 to 6.2 which is 0.9 time higher
than flocculent-activated sludge (Adav and Lee 2008). Relatively high protein
fractions are required as an important feature for matured aerobic granule formation
(McSwain et al. 2005).
6.3.3 Biological Parameters
Different light and electronic micrograms like light microscopy, scanning electron
microscopy, field emission scanning electron microscopy, fluorescence in situ
hybridization along with confocal laser scanning microscopy are mainly employed
to reveal aerobic granular structures (Lemaire et al. 2008). Dominancy of ammonia
oxidizing bacteria was generally observed on the granule surfaces (Jang et al. 2003).
De Kreuk et al. (2005) observed a mixture of heterotrophic phosphate accumulating
organisms and autotrophic nitrifiers prevailing in the outer granule layers and
phosphate accumulating organisms in the core of granules by using fluorescence
in situ hybridization analysis of aerobic granule.
6.3.4 Granule Stability and Storage
Excessive growth of filamentous organisms is the major cause for granule instability
during reactor operation. Long solid retention time, dissolved oxygen and nutrient
deficiency along with low substrate concentration are the possible reasons behind
filamentous outgrowth in aerobic granules (Liu and Liu 2006). Integrity coefficient
is a parameter which is used to denote granule physical strength. Integrity coefficient
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S. Ghosh and S. Chakraborty
Specific Oxygen Utilization Rate
Specific oxygen utilization rate denotes the activity of microorganisms expressed as
milligrams of oxygen consumed by a milligram of cellular proteins per hour. In a
case study, specific oxygen utilization rate values in glucose-fed and acetate-fed
granules ranged between 55.9 to 69.4 mg O 2 /g mixed liquor volatile suspended
solids/h (Tay et al. 2002b).
Extracellular Polymeric Substances
Extracellular polymeric substances are metabolic polymers secreted by aerobic
granules which help in granule formation. Extracellular polymeric substances
mainly contain β-polysaccharides and proteins. In aerobic granules proteins/polysaccharides ratios are generally found between 3.4 to 6.2 which is 0.9 time higher
than flocculent-activated sludge (Adav and Lee 2008). Relatively high protein
fractions are required as an important feature for matured aerobic granule formation
(McSwain et al. 2005).
6.3.3 Biological Parameters
Different light and electronic micrograms like light microscopy, scanning electron
microscopy, field emission scanning electron microscopy, fluorescence in situ
hybridization along with confocal laser scanning microscopy are mainly employed
to reveal aerobic granular structures (Lemaire et al. 2008). Dominancy of ammonia
oxidizing bacteria was generally observed on the granule surfaces (Jang et al. 2003).
De Kreuk et al. (2005) observed a mixture of heterotrophic phosphate accumulating
organisms and autotrophic nitrifiers prevailing in the outer granule layers and
phosphate accumulating organisms in the core of granules by using fluorescence
in situ hybridization analysis of aerobic granule.
6.3.4 Granule Stability and Storage
Excessive growth of filamentous organisms is the major cause for granule instability
during reactor operation. Long solid retention time, dissolved oxygen and nutrient
deficiency along with low substrate concentration are the possible reasons behind
filamentous outgrowth in aerobic granules (Liu and Liu 2006). Integrity coefficient
is a parameter which is used to denote granule physical strength. Integrity coefficient
180
S. Ghosh and S. Chakraborty