The technological performance and social acceptance of ceramic water filters impregnated with silver nanoparticles for point-of-use water treatment were investigated in the laboratory and in the field in the Guatemalan highland community of San Mateo Ixtatán. In the laboratory, filters were constructed with clay and sawdust collected from the Guatemalan community and were tested to determine the effects of percent sawdust and silver nanoparticle treatment on the transport and removal of E. coli. For ceramic filters without silver treatment, size-exclusion and/or sorption is the mechanism of removal and a lower mass-percent sawdust corresponds to greater bacteria removal. The addition of silver nanoparticles to the ceramic filters improved the performance for all mass percentages of sawdust relative to filter media without nanoparticle treatment. Filters with higher porosity achieved higher bacteria removal than those with lower porosity, suggesting an increase in burnable material percentage is advantageous, assuming structural integrity is not compromised. Subsequent to laboratory testing, ceramic filters were manufactured with local materials and labor in San Mateo Ixtatán, Guatemala, and distributed to 62 households in this peri-urban community. The study participants were randomly divided into two groups, and filters were tested periodically over 23 months or 12 months. Filtered effluent samples were tested for turbidity reduction, bacteria removal, and silver leaching. Over the course of the study, the average percent reduction in total coliforms and E. coli was 87% and 92%, respectively. The average effluent turbidity was 0.18 nephelometric turbidity units (NTUs) and average effluent concentration of ionic silver was $0.02\mathrm{mg}/\mathrm{L}$ (below the U.S. EPA standard of $0.1\mathrm{mg}/\mathrm{L}$ ). Filters distributed to the second study group consistently performed better than the first study group as manufacturing techniques improved and contact with researchers increased. Overall, users were satisfied with the filters, citing them as easy to use and maintain while improving water quality. The findings of this study suggest that locally manufactured ceramic filters can significantly improve the microbiological quality of water when used as a point-of-use water-treatment technology.

Background: Silver nanoparticles (AgNPs) have attracted great attention due to their outstanding electrical, optical, magnetic, catalytic, and antimicrobial properties. However, there is a need for alternative production methods that use less toxic precursors and reduce their undesirable by-products. Phyto-extracts from the leaves of olive and rosemary plants can be used as reducing agents and (in conjunction with Tollens’ reagent) can even enhance AgNP antimicrobial activity. Methods: Conditions for the proposed hybrid synthesis method were optimized for olive leaf extracts (OLEs) and rosemary leaf extracts (RLEs). The resultant AgNPs were characterized using UV–visible spectroscopy, an environmental scanning electron microscope, and Dynamic Light Scattering analysis. An atomic absorption spectrophotometer was used to measure AgNP concentration. Fourier transform infrared spectroscopy (FTIR) was used to determine the specific functional groups responsible for the reduction of both silver nitrate and capping agents in the leaf extract. Additionally, the antimicrobial properties of the synthesized AgNPs were assessed against Gram-negative bacteria (Escherichia coli and Salmonella enterica) and Gram-positive bacteria (Staphylococcus aureus), by using both the Kirby–Bauer and broth microdilution methods on Mueller–Hinton (MH) agar plates. Results and Discussion: A simple, feasible, and rapid method has been successfully developed for silver nanoparticle synthesis by reducing Tollens’ reagent using leaf extracts from olive and rosemary plants (widely available in Jordan). Scanning electron microscopy images showed that the method produces AgNPs with a spherical shape and average core sizes of 45 ± 2 and 38 ± 3 nm for OLE and RLE, respectively. A negative zeta potential (ζ) of −43.15 ± 3.65 mV for OLE-AgNPs and −33.65 ± 2.88mV for RLE-AgNPs proved the stability of silver nanoparticles. FTIR spectra for AgNPs and leaf extracts indicated that the compounds present in the leaf extracts play an important role in the coating/capping of synthesized nanoparticles. The manufactured AgNPs exhibited an antibacterial effect against Escherichia coli and Staphylococcus aureus with minimum inhibitory concentrations (MIC) of 9.38 and 4.69 μl/ml for OLE-AgNPs and RLE-AgNPs, respectively. The MIC for Salmonella enterica were 18.75 μl/ml for both OLE-AgNPs and RLE-AgNPs. Furthermore, our results indicated that the RLE-AgNPs exhibited a stronger antibacterial effect than OLE-AgNPs against different bacteria species. These results contribute to the body of knowledge on nanoparticle production using plant-mediated synthesis and performance. They also offer insights into the potential for scaling up this production process for commercial implementation.