Modelling of activated sludge acclimisation to a non-ionic surfactant

Area of Science:

• Environmental microbiology
• Biochemical engineering
• Wastewater treatment technologies

Background:

• Activated sludge is crucial for wastewater treatment.
• Acclimatisation allows microorganisms to degrade novel compounds.
• Non-ionic surfactants pose challenges in biodegradation.

Purpose of the Study:

• To develop and validate a mathematical model for activated sludge acclimatisation to a non-ionic surfactant.
• To understand the microbial degradation pathways and kinetics involved.
• To assess the model's performance under varying operational conditions.

Main Methods:

• Utilized a sequencing-batch reactor (SBR) with non-acclimatised sludge.
• Employed WEST software for automated model calibration and parameter estimation.
• Assumed a three-COD fraction degradation model with specific kinetic assumptions (hydrolysis, Haldane, first-order).

Main Results:

• The best-fit model described sequential degradation of three COD fractions.
• Primary degradation occurred via hydrolysis without growth.
• Microbial growth on intermediate metabolites followed Haldane and first-order kinetics.
• The model accurately fitted four consecutive acclimatisation assays using Brij 30.
• Observed a decrease in self-inhibition of growth on the second COD fraction during acclimatisation.

Conclusions:

• The proposed model successfully describes activated sludge acclimatisation to non-ionic surfactants.
• Kinetic parameters indicate evolving microbial community dynamics during acclimatisation.
• The model provides insights into biodegradation processes and microbial inhibition.