Quantifying Filter Layer Porosity: A Comparative Study of X-ray Microtomography, Fluid Injection and Fluid Saturation Techniques

Wastewater filtration for reuse is a practice applied to conserve water resources. However, its effectiveness is directly related to the permeability of the filter, which can be compromised by clogging processes due to the retention of suspended particles or by precipitated materials during the process of removing chemical contaminants. This study investigates the porous structure of filter layers by different techniques. The study explores porosity in porous media, emphasizing the importance of pores and the interconnected matrix. To evaluate the porosity, fluid injection techniques, fluid saturation techniques and XR-?CT were employed for porosity determination. It hypothesizes that fluid injection techniques, volumetric measurements, and imaging methods differ in their ability to accurately determine porosity. Nine reference columns of three different porous arrangements were mounted in an acrylic cylinder to study the sensitivity of the techniques to different sizes of matrix arrangements. Finally, the porosity results were compared statistically to determine the error. Fluid injection and saturation techniques are cost-effective methods for determining effective layer porosity. However, experimental studies show that water-based techniques often yield higher porosity values than helium gas porosimetry. This discrepancy may be attributed to operational errors inherent to the experimental method, leading to an overestimation of porosity. XR-?CT and gas porosimetry have been shown to be more suitable for quantifying smaller pores. Furthermore, XR-?CT allows for a deeper characterization of the porous medium, such as the determination of local porosity, and the application of fluid simulation techniques to observe the permeability and tortuosity of the medium.