MBR-21: Characterisation of model fluids used for hydrodynamic investigations in MBRs
RWTH |
07/2009 - 12/2009 |
Background and motivation: A fundamental understanding of cake layer formation and removal mechanisms governing the overall MBR process is required to further optimise both the membrane module design and by that the overall filtration performance of the system. However, these insights are difficult to get due to significant changes in the chemical composition of the wastewater and the biological properties of the activated sludge. Therefore, it is intended to establish an appropriate model fluid representing the rheological characteristics of activated sludge properly. In this regard, already available model substances such as xanthan gum solution containing SiO2 particles are suffering from high fouling propensities as well as low removal efficiencies of the xanthan molecules and in turn non-realistic permeate viscosities. Hence, this 6 month research work within the MBR-TRAIN Project aims at the characterisation of microgel-based model suspensions and the evaluation of the limitations to model activated sludge.
Objectives: Characterisation of particle size distribution, surface charge, rheological properties as well as cross-flow and submerged filtration properties of different microgel suspensions. Depending on the quality of results, future activities in the framework of fundamental research projects in the field of membranes in water and wastewater treatment will benefit from the outcomes of this study.
Approach and work tasks: The fellow will characterise different suspensions as a function of process parameters such as pH, temperature and ionic strength in lab-scale experiments. Measurements will be performed to compare the rheology of the micro gels with that of activated sludge. Subsequently, filtration tests will be conducted to analyse the filterability of the suspension and the interaction of the membrane under different operating parameters. These experiments will be performed in close collaboration with another project partner at RWTH Aachen University with respect to the microgel preparation and the particle size and surface charge characterisation. Finally, general conclusions will be drawn concerning the applicability of microgels as model substances for both cross-flow and submerged filtration studies.