Quantitative Characterization of Microfiltration Membrane Fouling Using Optical Coherence Tomography with Optimized...

Area of Science:

• Membrane Science and Technology
• Biomedical Optics
• Environmental Engineering

Background:

• Membrane fouling significantly impairs water treatment efficiency, necessitating accurate diagnostic tools.
• Current methods for assessing fouling are often destructive and require time-consuming offline analysis.
• Optical Coherence Tomography (OCT) offers in situ, real-time visualization but quantitative analysis of thin foulant layers is challenging.

Purpose of the Study:

• To develop and validate a reproducible, automated image analysis workflow for quantitative OCT-based membrane fouling diagnostics.
• To benchmark various image processing algorithms for accurate segmentation of foulant layers.
• To enable real-time monitoring of fouling layer thickness and its correlation with membrane performance.

Main Methods:

• Developed an OCT image analysis workflow combining band-pass filtering, Gaussian smoothing, unsharp masking, and dual-threshold subtraction.
• Benchmarked 17 global thresholding algorithms against Scanning Electron Microscopy (SEM) data for cake thickness.
• Applied the optimized workflow to quantify fouling layer thickness for humic acid, kaolin, and sodium alginate foulants.

Main Results:

• The Triangle-Moments thresholding algorithm combined with the developed workflow demonstrated robust performance, closely agreeing with SEM measurements (14.23 ± 1.18 µm vs. 15.29 ± 1.54 µm for humic acid).
• The method successfully quantified fouling thickness evolution and correlated it with flux decline for various foulants.
• Observed instances where flux decline persisted without significant thickness increase, indicating compaction or permeability changes.

Conclusions:

• The proposed OCT image analysis framework enables quantitative, real-time fouling diagnostics, moving beyond qualitative visualization.
• This approach supports mechanistic interpretation of fouling processes and can lead to improved operational control of membrane systems.
• The automated workflow enhances the utility of OCT for in situ monitoring and management of membrane performance.