Substrate-to-biomass ratio as a process control parameter in heterogeneous populations growing on complex substrates

Area of Science:

• Environmental microbiology
• Biotechnology
• Wastewater treatment

Background:

• Activated sludge systems are crucial for wastewater treatment.
• Understanding substrate removal dynamics is key to optimizing these systems.
• Bovine serum albumin (BSA) serves as a complex model substrate.

Purpose of the Study:

• To investigate the removal of bovine serum albumin (BSA) by activated sludge.
• To determine the relationship between substrate adsorption, removal rate, and exoprotease induction.
• To evaluate the efficacy of substrate per unit biomass (S/B) ratio versus substrate per unit volume for modeling.

Main Methods:

• Assessing initial BSA adsorption onto activated sludge.
• Measuring the rate of BSA removal.
• Quantifying exoprotease activity in sludge matrix and supernatant.
• Analyzing correlations using substrate per unit biomass (S/B) and substrate per unit volume.

Main Results:

• A higher correlation was found when using the substrate per biomass (S/B) ratio.
• Exoprotease activity was observed both on the sludge matrix and in the supernatant.
• The interaction between sludge and substrate concentrations complicates direct application of pure culture models.

Conclusions:

• The substrate per biomass (S/B) ratio offers a more robust basis for empirical activated sludge models compared to substrate concentration alone.
• The findings suggest that models for pure cultures may not be directly applicable to complex activated sludge systems.
• Optimizing wastewater treatment requires considering the interplay of substrate and biomass concentrations.