A ceramic water filter (CWF) with curved (ovoid) walls has been developed by Potters without Borders, a nonprofit that provides technical assistance to CWF factories. Here, a modified version of the USEPA testing method was used to evaluate the performance of ovoid CWFs, which have yet to be studied in the literature. Filters with/without silver nanoparticles (AgNPs) were evaluated for bacterial removal, turbidity removal, flow rate, and silver leaching. Log removal values (LRVs) for Escherichia coli for AgNP coated CWFs were 9.5–10.9 LRV while uncoated achieved 8.0–9.8 LRV. All the CWFs tested here had flow rates between 0.8 and 1.3 L h⁻¹. The turbidity of the influent was reduced by the filters throughout the general and challenge water conditions with removal of 9.1–90.9% and 99.3–99.8%, respectively. Silver-coated CWFs had a higher total effluent silver concentration compared to uncoated (coated CWFs had 74% more total silver leaching on average) and had an increased silver release during the challenge phase (35 ppb) compared to the general phase (13 ppb). The exterior wall coated with AgNPs was shown to leach silver off the ceramic using X-ray photoelectron spectroscopy, providing evidence that supports the recommendation to coat only the interior wall of CWFs with AgNPs. The procedure demonstrated utility as a reproducible performance testing technique. X-ray diffraction and mercury intrusion porosimetry were used to study the ceramic structure.

Ceramic water filters (CWFs) are point-of-use drinking water treatment systems that are manufactured and used in under-served communities around the world. The clayey material (CM) used to manufacture CWFs is a locally sourced mixture of clay, sand, slit and amorphous material (usually dug near the CWF factory). CM varies in composition and purity depending on the geographical location and geological setting. In this study, a set of 13 CM samples collected from around the world were analyzed using grain size analysis, as well as liquid and plastic limit tests. Mineralogical composition was determined using X-ray diffraction. A selection of three CM samples (Guatemala, Canada, and Guinea Bissau) with a range of compositions were used to study biofilm growth on CM before and after firing. Biofilm coverage was studied on CM (before firing) and CWF material (after firing) using Pseudomonas fluorescens Migula. The average biofilm coverages for Guatemala, Canada, and Guinea Bissau CM were 20.03 ± 2.80%, 19.28 ± 0.91%, and 9.88 ± 4.02%, respectively. The average biofilm formation coverages for Guatemala, Canada, and Guinea Bissau CWF were 13.08 ± 1.74%, 10.36 ± 3.41%, and 8.66 ± 0.13%, respectively. The results presented here suggest that CM can be manipulated to manufacture better performing CWFs by engineering the soil characteristics, such as grain size, liquid and plastic limits, and mineralogy. This could improve the durability and biofilm resistance of CWFs.

This review critically analyzes the most recent literature on parameters affecting the performance of ceramic water filters and compares proposed standardization testing as quality control tools.

Bacterial growth stage plays an important role in how bacteria interact with nanoparticles, but the effect that two-dimensional nanomaterials may have on this interaction has yet to be rigorously studied. The goal of this study is to explore the role of the growth stage (non-growing, exponential, transitional, and stationary) of Escherichia coli (E. coli) in its response to graphene oxide (GO), MoS₂, and MoSe₂ colloidal nanosheets (ranging 0.00–2.52 μg GO–TOC, MoS₂–Mo, or MoSe₂–Mo mL⁻¹). This study is the first to comprehensively examine the response of E. coli at its various growth stages to two-dimensional nanomaterials. We also examine bacterial response to novel two-dimensional nanomaterials (MoS₂ and MoSe₂) compared to an extensively studied material (GO). The bacterial responses were quantified in terms of respiration and growth rate and membrane permeability. A novel, high throughput technique was applied to rapidly reveal the range of biological responses that occurred. E. coli response to nanosheet exposure was dependent on the concentration and type of nanomaterial, and the bacterial growth stage. GO at 2.27 μg GO–TOC mL⁻¹ led to a 17% reduction in respiration rate. Reductions in growth rate for this condition during the transitional and stationary stages were 9% and 87% respectively, compared to the 0.00 μg GO–TOC mL⁻¹ control condition growth rate. When rapidly growing E. coli in a nutrient-rich environment is exposed to GO, the growth rate increased (up to 22% for the 2.27 μg GO–TOC mL⁻¹ sample). Under these conditions, E. coli can use GO as a scaffold for cellular growth, leading to an increase in growth rate. MoS₂ and MoSe₂ have little impact on the growth and respiration of E. coli regardless of the environment. The membrane permeability assay shows that the Mo nanosheets lead to a greater increase in membrane permeability in E. coli compared to GO. Our characterization of the Mo materials shows that they are smaller and stiffer compared to GO, so they are more likely to puncture the membrane. This study demonstrates that microorganisms have a range of responses to nanosheets and that the physiological condition of the bacteria and the nanosheet type play important roles in their response.