Activated sludge tank - Quantifying nitrous oxide emissions combining CFD and biokinetics

Quantifying nitrous oxide emissions in WWTP with detailed hydrodynamic modelling

Greenhouse gas emissions from wastewater treatment plants (WWTP) are a matter of growing concern. Nitrous oxide production within wastewater treatment processes depends largely on the local dissolved oxygen concentrations, which are highly dependent on the extent of mixing in large bioreactors. Current modeling techniques using systemic models do not take local mixing into account and thus average out local variations in predicting concentrations. CFD modelling integrated with biokinetic models for predicting nitrous oxide emissions was performed to get te needed insights.

Major findings

• N2O concentrations vary along the length and width of the reactor
• Higher nitrous oxide concentrations are observed where local DO concentration is low and vice versa
• N2O emissions also vary with changing process conditions (different scenarios tested)

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