The impact of optimised coagulation on membrane fouling for coagulation/ultrafiltration process

Abstract

This work aimed to demonstrate the effect of optimised coagulation on minimise fouling for coagulation–ultrafiltration process. Coagulation as pretreatment has the potential to mitigate fouling and enhance flux. Operating parameters were tested by a matrix of experiments for various mixing conditions and coagulant doses. In coagulation experiments, varied shear forces were applied to generate different floc characteristics in order to assess the effect on membrane fouling. Floc properties were investigated with an optical monitoring technique to identify structure, size and growth of flocs. It was shown that stronger flocs are of advantage for fouling mitigation and that the coagulant dosage is crucial for the performance of filtration. The impact of water quality was assessed using general water quality parameters and organic characterisation techniques to investigate the performance of each treatment step. The treatment efficiency was further assessed based on comparing the molecular size fractions of the organic matter before and after coagulation using a size exclusion chromatography technique. The result confirmed the significance of organic character on treatment performance.

Keywords:

• Coagulation
• Flocculation
• Natural organic matter
• Photometric dispersion analyser
• Ultrafiltration

Acknowledgements

This work is supported by the South Australian Premiers’ Science and Research Project “Development of materials engineering solutions for treatment of Murray-Darling Basin sourced water supplies”. The authors also like to thank Dr. Alice Antony, UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering, The University of New South Wales for her support on LC–OCD analysis.