Doctoral thesis of Philosophy: Characterisation and mitigation of the fouling of ceramic microfiltration membranes caused by algal organic matter released from cyanobacteria

Characterisation and Mitigation of the Fouling of Ceramic Microfiltration Membranes Caused by Algal Organic Matter Released from Cyanobacteria

Author: Xiaolei Zhang

Field: Environmental Engineering, Water Treatment

Document Summary:

This doctoral thesis investigates the fouling of ceramic microfiltration (MF) membranes caused by soluble algal organic matter (AOM) released from cyanobacteria, specifically Microcystis aeruginosa. Ceramic MF membranes are increasingly used in water treatment due to their advantages over conventional polymeric membranes, but membrane fouling remains a significant challenge. AOM, often present in water catchments due to algal blooms, can severely impact treatment efficiency. This study aims to understand the factors contributing to AOM fouling on ceramic MF membranes, analyze the characteristics of AOM and its impact on membrane performance, and evaluate feedwater pre-treatment methods, including chemical coagulation and UV/H₂O₂ oxidation, for mitigating fouling. The research characterizes AOM at different growth stages of Microcystis aeruginosa and examines the influence of feed solution chemistry and operating conditions on fouling. It also explores the interaction between AOM and humic substances and their combined effect on fouling. The findings provide insights into the mechanisms of AOM fouling and offer potential strategies for effective membrane system design and operation in water treatment.

Detailed Table of Contents:

• Declaration
• Acknowledgements
• List of Publications
• Nomenclature
• Summary
• Chapter 1: Introduction
  • 1.1 Project Background
  • 1.2 Objectives
  • 1.3 Thesis Outline
• Chapter 2: Literature Review
  • 2.1 Natural Organics in Waters
    • 2.1.1 Natural organic matter
    • 2.1.2 Algal organic matter (AOM)
    • 2.1.3 Characterisation of aquatic organic matter
  • 2.2 Membrane Process in Water Treatment
    • 2.2.1 Membrane materials and structures
    • 2.2.2 Membrane fouling and causes
    • 2.2.3 Strategies for membrane fouling mitigation
  • 2.3 Summary
• Chapter 3: Materials and Methods
  • 3.1 Cultivation of Algae and AOM Extraction
  • 3.2 Preparation of MF Feed Solutions
  • 3.3 Feedwater Pre-treatment by Coagulation
  • 3.4 Feedwater Pre-treatment by UV/H₂O₂
  • 3.5 Background Water
  • 3.6 Analytical Methods
  • 3.7 Membrane Filtration Tests
• Chapter 4: Influence of the Characteristics of Soluble AOM Released from Microcystis Aeruginosa on the Fouling of a Ceramic MF Membrane
  • 4.1 Growth Pattern of M. Aeruginosa in MLA Medium
  • 4.2 Influence of AOM from Different Phases of M. Aeruginosa Growth
  • 4.3 Influence of AOM Pre-filtration
  • 4.4 Influence of Calcium Ion
  • 4.5 Summary
• Chapter 5: Impact of the Feed Solution Chemistry and Operating Condition on the Fouling of a Ceramic MF Membrane by Soluble AOM
  • 5.1 Influence of AOM Concentration
  • 5.2 Influence of Solution pH
  • 5.3 Influence of Solution Ionic Strength
  • 5.4 Influence of TMP
  • 5.5 Summary
• Chapter 6: Understanding the Fouling of a Ceramic MF Membrane Caused by the AOM
  • 6.1 Contribution of the Fouling Layers to the Flux Decline and Filtration Resistance
  • 6.2 Characterisation of Feed, Permeate and Membrane Foulant
  • 6.3 Discussion
  • 6.4 Summary
• Chapter 7: Impact of the Interaction Between Aquatic Humic Substances and AOM on the Fouling of a Ceramic MF Membrane
  • 7.1 MF of the Solutions Containing Individual and Mixed Compounds
  • 7.2 DOC and UVA254 Rejection
  • 7.3 Characterisation of Feed Solutions
  • 7.4 Discussion
  • 7.5 Summary
• Chapter 8: Feedwater Coagulation to Mitigate the Fouling of a Ceramic MF Membrane Caused by AOM
  • 8.1 Optimum Coagulant Dosages
  • 8.2 Microfiltration Tests
  • 8.3 Characterising the Effect of Coagulation by EEM Spectra
  • 8.4 Effect of Coagulation on Molecular Weight of AOM
  • 8.5 Effect of Coagulation on Carbohydrate and Protein Removal
  • 8.6 Characterising the Effect of Coagulation by Organic Matter Fractionation
  • 8.7 Membrane Fouling Analysis
  • 8.8 Summary
• Chapter 9: Impact of UV/H₂O₂ Feed Pre-treatment on Mitigation of the Fouling of a Ceramic MF Membrane Caused by AOM
  • 9.1 Multi-cycle MF Tests
  • 9.2 Characterising the Effect of UV/H₂O₂ and Coagulation Feed Pre-treatment on MF Performance
  • 9.3 Fate of Algal Toxin During UV/H₂O₂-MF and Coagulation-MF Process
  • 9.4 Summary
• Chapter 10: Conclusions, Implications and Recommendations
  • 10.1 Influence of AOM Characteristics and Process Variables on the Fouling of the Ceramic MF Membrane
  • 10.2 Contribution of the AOM Components to the Membrane Fouling
  • 10.3 Impact of the Interaction Between Aquatic Humic Substances and AOM on the Fouling
  • 10.4 Effect of the Coagulation Feed Water Pre-treatment
  • 10.5 Effect of the UV/H₂O₂ Feedwater Pre-treatment
  • 10.6 Implications
  • 10.7 Recommendations for Future Work
• References
• Appendix A. MLA Nutrient Medium Preparation
• Appendix B. Relationship Between OD684 and Algal Cell Concentration
• Appendix C. Characteristics of the Ceramic Membranes
• Appendix D. Example of Data Processing for a Filtration Experiment