Ceramic Water Filter for Point-Of-Use Water Treatment in Developing Countries: Principles, Challenges and Opportunities

Drinking water source contamination poses a great threat to human health in developing countries. Point-of-use (POU) water treatment techniques, which improve drinking water quality at the household level, offer an affordable and convenient way to obtain safe drinking water and thus can reduce the outbreaks of waterborne diseases. Ceramic water filters (CWFs), fabricated from locally sourced materials and manufactured by local labor, are one of the most socially acceptable POU water treatment technologies because of their effectiveness, low-cost and ease of use. This review concisely summarizes the critical factors that influence the performance of CWFs, including (1) CWF manufacturing process (raw material selection, firing process, silver impregnation), and (2) source water quality. Then, an in-depth discussion is presented with emphasis on key research efforts to address two major challenges of conventional CWFs, including (1) simultaneous increase of filter flow rate and bacterial removal efficiency, and (2) removal of various concerning pollutants, such as viruses and metal(loid)s. To promote the application of CWFs, future research directions can focus on: (1) investigation of pore size distribution and pore structure to achieve higher flow rates and effective pathogen removal by elucidating pathogen transport in porous ceramic and adjusting manufacture parameters; and (2) exploration of new surface modification approaches with enhanced interaction between a variety of contaminants and ceramic surfaces

Understanding the microbiological, organic and inorganic contaminant removal capacity of ceramic water filters doped with different silver nanoparticles

Pathogen removal efficacy of ceramic water filters (CWF) impregnated with silver nanoparticles (nAg) has been well studied, however scarce information is available about the impact of nAg surface functionalization and removal of inorganic and organic pollutants. In this study, we examined the effect of nAg functionalized with casein, maltose and phyto-extracts on the microbiological (Escherichia coli), organic (polycyclic aromatic hydrocarbon, PAH) and inorganic (heavy metals) simultaneous removal using disks manufactured in the laboratory. Results showed that the mass of nAg retained on each disk varied depending on the nanoparticles used (casein-nAg: 80%, maltose-nAg: 93%, and rosemary-nAg: 95%). Untreated CWF disks had a bacterial mass rejection (Rmass) of 95.97%, while nAg impregnated showed values above 99%. Bacteria log removal values (LRV) varied with the type of nanoparticle applied to the disks, rosemary-nAg impregnated disks attained the highest value among all the nAgs tested. In terms of lead removal, non-impregnated Red Art disks had a Rmass of 61%, while the nAg impregnated filters removed 74%, 72%, and 69%, for disks impregnated with casein-nAg, rosemary-nAg, and maltose-nAg, respectively. PAH removal was most effective in unmodified clay (72%), while modified disks had removal of 72% for casein-nAg, 67% for rosemary-nAg, and 69% for maltose-nAg. Mass removal rates of fluorene were determined at 73.38% for unmodified disks, while 74% for casein-nAg, 69% in rosemary-nAg, and 72% in maltose-nAg modified disks. nAg treated disks exhibited no statistical difference in PAH removal when compared to untreated. Application of nAg reduced the amount of culturable bacteria extracted from the surface an interior of the disks compared with unmodified disks. Results show that nAg impregnation increased the removal rates of E. coli and lead in the disks and that nAg average size and size distribution is an important factor in the removal rate of bacteria and lead in CWF

Enhancement of surface runoff quality using modified sorbents

The objective of this study was to develop and test nanoparticle-and polymer-based bioactive amended sorbents to enhance stormwater runoff treatment in best management practices (BMPs). Red cedar wood and expanded shale were the sorbents tested. Red cedar wood chips (RC) were modified with 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride (TPA) and silver nanoparticles (AgNPs) at different mass loadings (0.36 mg/g, 0.67 mg/g, and 0.93 mg/g for TPA and 0.33 mg/g and 0.68 mg/g for AgNPs) to simultaneously improve the sorption of organic and inorganic contaminants and pathogenic deactivation in BMPs treating stormwater runoff. Unmodified expanded shale is often used as a filter material for stormwater treatment and was used as a base comparison. The results showed that TPA and AgNPs loading onto red cedar increased the Langmuir maximum sorption coefficient (Q) for polycyclic aromatic hydrocarbons, up to 35 fold and 29 fold, respectively, compared to unmodified red cedar. In the case of heavy metals, Q for lead increased with increased loading of TPA and AgNPs, whereas no significant change in the Q value for cadmium was observed, while zinc and nickel sorption slightly decreased. The Langmuir maximum sorption coefficient of copper was higher for modified red cedar; however, no correlation was observed with TPA or AgNP loadings. The log reduction value (LRV) for Escherichia coli using unmodified red cedar was \u3c1 log, while modified red cedar exhibited LRV up to 2.90 ± 0.50 log for 0.67 mg/g TPA-RC and up to 2.10 ± 0.90 log for 0.68 mg/g AgNP-RC. Although AgNP-modified red cedar shows a comparable performance to TPA-RC, the high cost of production may limit the use of AgNP-amended materials. While TPA-modified red cedar has advantages of lower cost and lower toxicity, the fate, transport, and environmental implications of TPA in natural environments has not been fully evaluated. The findings from this study show that if BMPs were to incorporate the modified red cedar, stormwater treatment of PAH and E. coli could be enhanced, and the quality of the treated water will improve. © 2014 American Chemical Society