Experimental evaluation of starch utilization mechanism by activated sludge

Area of Science:

• Environmental Microbiology
• Biochemical Engineering
• Wastewater Treatment

Background:

• Activated sludge is crucial for wastewater treatment, converting organic matter.
• Understanding substrate conversion kinetics is vital for optimizing treatment processes.
• Hydrolysis of complex substrates like starch by activated sludge requires detailed investigation.

Purpose of the Study:

• To investigate the conversion processes of hydrolysable substrates, specifically native potato starch (NPS), by activated sludge.
• To compare the removal and metabolic pathways of particulate starch, soluble starch (SolS), maltose, and glucose.
• To elucidate the mechanisms of starch hydrolysis and organic carbon fate within activated sludge flocs.

Main Methods:

• Experimental data collection from a sequencing batch reactor (SBR) and parallel batch tests.
• Acclimation of activated sludge to native potato starch (NPS).
• Direct measurement of substrate, poly-glucose, and oxygen uptake rate to track organic carbon fate.

Main Results:

• Adsorption followed by intracellular enzymatic hydrolysis was the dominant starch removal mechanism.
• Starch hydrolysis predominantly produced maltose, with minimal bulk liquid enzyme activity observed.
• Native potato starch and soluble starch removal patterns resembled maltose, while glucose showed distinct behavior due to lack of biomass acclimation.

Conclusions:

• The kinetics of substrate utilization, rather than physical characteristics, should differentiate readily and slowly biodegradable chemical oxygen demand (COD).
• Activated sludge's internal enzymatic activity is key for hydrolysable substrate conversion.
• Biomass acclimation significantly influences the removal and storage patterns of different organic substrates.