Integrating Navajo Pottery Techniques To Improve Silver Nanoparticle-Enabled Ceramic Water Filters for Disinfection.

Point-of-use treatment technologies can increase access to safe drinking water in rural areas. Sustained use of these technologies is uncommon due to oversight of community needs, user-perceived risks, long-term maintenance, and conflict with traditional practices. Nanosilver-enabled ceramic water filters are unique due to the use of locally sourced materials available at or near the target community; however, technical limitations persist (e.g., nanosilver's uncontrolled release and passivation from sulfide or chloride). This work aims to overcome these limitations by impregnating nanosilver onto ceramics with a Navajo pottery rosin, collected from pinyon trees with a third-generation artisan. Here, we investigate this sustainable and novel material for drinking water treatment; the study ranges from a proof of concept to testing under realistic conditions. Results show that when embedded in a thin film, the biopolymer controlled ionic silver dissolution and prevented silver passivation from sulfide and chloride. When applied to ceramic filters, the biopolymer effectively immobilized nanosilver in a range of waters. Over a 25 day study to emulate household-use conditions, this coating method sustained disinfection of a coculture of Gram-positive and Gram-negative bacteria while controlling biofouling. Overall, the use of this Navajo pottery material can facilitate adoption while providing the needed technological advancement to these widely used treatment devices.

An improved protocol for extracting extracellular polymeric substances from granular filter media.

Extracellular polymeric substances (EPS) are an important parameter in drinking-water biofilters, and, to date, this is the first study to compare protocols from the literature for extracting EPS from granular filter media. Five extraction protocols were compared, and one was improved by varying the type of initial physical treatment and the shaking intensity, temperature, and time of incubation. Extracting EPS from granular filter media in triplicate by combining 2 g (wet weight) of filter media with 10 mL of extraction buffer (10 mM Tris, 10 mM EDTA, 2.5% NaCl, pH 8), vortexing for 1 min, and incubating for 4 h at 35 °C with shaking at 200 rpm yielded significantly higher EPS polysaccharide and/or protein concentrations than did protocols from the literature. This improved protocol extracted a significant fraction of the biofilm attached to sand but was less effective on biofilm attached to anthracite or granular activated carbon (GAC). A survey of 11 full-scale biofilters from the U.S. and Canada revealed that EPS polysaccharide and protein concentrations can vary over one order of magnitude, from 0.02 to 0.60 mg glucose/g total solids (TS) and 0.27 to 3.38 mg bovine serum albumin/g TS, respectively. Backwashing significantly lowered the biomass and EPS polysaccharide concentrations, but the majority of the biofilm remained attached to the filter media after backwashing, as expected. The fraction of EPS polysaccharides and proteins removed during backwashing did not differ between anthracite and GAC biofilters. The improved EPS extraction protocol can be utilized to investigate the role of EPS in biofilter performance.