Governing factors for bacterial adhesion and aggregation in activated sludge and their effect on wastewater treatment

Start date 01/01/2009
End date The project is closed: 31/03/2014

​Wastewater treatment generally relies on a consortium of microorganisms, mainly bacteria, contained within an engineered environment used to remove organic substances and nutrients from the wastewater. When the treatment is performed by the commonly used activated sludge process the microorganisms grow suspended. Apart from performing biochemical conversions, the microorganisms should also form aggregates (flocs) that can be removed from the treated water in an efficient way. The process of microbial aggregation is the least understood and it is often the capacity limiting factor of the whole process. Poor floc formation leads to increased concentrations of suspended solids in the effluent and operational problems such as decreased secondary settler capacity. The aggregates are complex ecosystems with intriguing chemical and physical interactions.

The aim of this project is to increase the understanding of the factors that regulate aggregation and dissociation of the microorganisms in activated sludge and the implications it has for the operation efficiency of the treatment plant. By using advanced molecular tools these processes can be studied at high resolution at the cell level.


The project is carried out at the Division of Water Environment Technology.

Keywords: Activated sludge, floc formation, molecular biology, population dynamics, microbial composition

Project members

Britt-Marie Wilén

Project members 
Britt-Marie Wilén
Johan Fredriksson

Britt-Marie Wilén
External partners at the project
​Gothenburg University, Department of Chemistry and Molecular Biology
Chalmers Areas of Advance
​Built Environment
​FORMAS, Gryaab AB, Chalmers

Page manager Published: Mon 28 Oct 2013.