MSE Research Project Database

Gas Generation in Biologically-Active Sediments

Project Leader: Anthony Stickland
Staff: Peter Scales
Collaborators: Daniel Lester (RMIT University) Nicky Eshtiaghi (RMIT University)
Sponsors: Australian Research Council, Melbourne Water, Barwon Water
Primary Contact: Anthony Stickland (
Disciplines: Chemical & Biomolecular Engineering
Research Centre: Particulate Fluids Processing Centre (PFPC)

Anaerobic lagoons and ponds are used in many industries to biologically digest large volumes of wastewater, with biogas a useful by-product. However, lagoon design is inadequate due to limited capacity to model the complex multi-phase hydrodynamic and biological behaviour.  A part of improving our understanding lies with the transport of gas through the system. 

Gas is generated in the sludge layer at the lagoon bottom. The sludge has a yield stress such that bubbles movement is limited.  Instead, the gas diffuses through the liquid in the sludge. Near the top of the sludge, buoyancy overcomes the bed strength and bubbles are released.  As they rise through the liquid region, the bubbles either swarm or coalesce.  Solid particles can attach to bubbles and be carried to the top of the lagoon, forming a foamy scum layer at the top of the lagoon that can inhibit biogas capture and damage the lagoon covers.

The PhD student will investigate the mechanisms for gas transport in anaerobic lagoons.  The student will perform theoretical calculations on bubble growth, bubble rise through the sediment and the rate of gas diffusion through the sediment. Experiments of gas generation in well-controlled systems will be used to validate the predictions.

This topic is broad with multiple avenues of investigation.  The project requires a Chemical Engineering graduate strong in both experiment and theory.  The student needs to be curiosity-driven to design appropriate experiments, and self-motivated to plan and execute experiments.

Schematic of Anaerobic Lagoon