Development of Effective and Fast-Flow Ceramic Porous Media for Point-of-Use Water Treatment: Effect of Pore Size Distribution

Abstract

Ceramic filters are widely used for sustainable point-of-use water treatment in developing countries. It has remained a great challenge, however, for ceramic filters to simultaneously achieve high flow rate and effective bacterial removal. In this work, we reported the use of recycled paper fiber (greenfiber) as combustible material for the development of effective and fast-flow ceramic filters and compared their performance to filters that were fabricated using starch and rice husk, two common combustible materials used in previous studies. The clean ceramic filters made using 15% greenfiber achieved >4 log removal of bacteria (>99.99% removal) and an equivalent flow rate of 5.9 L/h (37.5 L/m2-h); the filters made using 20% greenfiber exhibited a fast flow rate of 13.9 L/h (87.1 L/m2-h) while maintaining a log microbial removal efficiency of >2 (>99% removal of bacterial cells). The two flow rates were ∼100% and >300% higher than the flow rates of mainline ceramic filters currently in use. The filters were characterized using mercury intrusion porosimetry, scanning electron microscopy, X-ray fluorescence analysis, and Fourier transform infrared spectroscopy. Our results suggested that the pore size distribution pattern played critical roles in the microbial removal efficiency. A mathematical framework was developed to provide a semiquantitative analysis of the relationship between filter bacterial removal efficiency and pore size distribution.

Ceramic water filter for point-of-use water treatment in developing countries: Principles, challenges and opportunities

“…Table 2 summarizes the flow rate and microbial removal efficiency of CWFs reported in previous laboratory-and field-scale investigations. To allow for the comparison of CWFs made in different shapes, the reported flow rates were converted to the "equivalent" flow rates of a full-size ceramic pot filter with a frustum shape, based on the hydraulic method used in our previous study (Yang et al, 2020). So far, the ceramic pot filter design (Fig.…”

“…Pore size of CWFs is considered a critical parameter that can affect both flow rate and microbial removal efficiency (Soppe et al, 2015;Youmoue et al, 2017). CWFs were prepared using three combustible materials that include irregularly shaped rice husk, spherical/oval shaped starch and tubular shaped recycled paper fiber in our recent study (Yang et al, 2020). Because of the different shapes of combustible materials, the fabricated CWFs had varied pore size distribution patterns, resulting in substantially different flow rates and bacterial removal efficiencies.…”

“…An improved understanding of key factors that affect and control the pore size distribution can provide important insights into guiding the design of CWFs with both high flow rate and bacterial removal. In an initial attempt, a semiquantitative model was developed to explain the role of pore size distribution on the design of optimal CWFs that can balance effective microbial removal and adequate flow rate (Yang et al, 2020). With further information of pore network within porous ceramic using advanced characterization and 3-dimensional imaging techniques, development of more sophisticated pore-scale mathematical and numeric models in the future can be beneficial to direct the design of ceramic filters with controlled pore size distribution and improved performance.…”

“…1(c)). Detail for adjustment can be found in Yang et al (2020); b) LRV, log reduction value;c) Average pore diameter was obtained by the pore size distribution data measured by mercury intrusion porosimetry (MIP); d) Pottery for peace, a US-based non-profit working on ceramic water filter; e) Resource Development International-Cambodia, a non-profit working on ceramic water filter.…”

A review of the impact of testing conditions on the performance and quality control of locally manufactured, point-of-use ceramic water filters

“…76,77,92,93 In both cell-to-cell and cell-to-surface interactions, increasing the ionic strength of the solution compresses the electric double layer (EDL), which promotes adhesion. 75–77 Adhesion of cells can lead to the formation of flocs, which are larger and therefore easier to retain in a CWF. 76 Increasing the ionic strength of the testing solution will also promote the adhesion of bacterial cells to quartz, which is the primary mineral in the CWF ceramic matrix.…”