Imbuing Navajo Pottery with Water Treatment Capability

A clever combination of pine tree resin and silver-based particles within traditional pottery is offering a new water filtration solution for members of the Navajo Nation, many of which still have limited access to reliable sources of clean drinking water. 

The solution is detailed in “Integrating Navajo Pottery Techniques To Improve Silver Nanoparticle-Enabled Ceramic Water Filters for Disinfection,” published in October in Environmental Science & Technology. Lead author L. Stetson Rowles III is an assistant professor at Georgia Southern University’s Department of Civil Engineering and Construction, who earned a doctorate from the University of Texas at Austin in 2021. 

The impetus behind this project goes back more than a decade, stemming from Rowles’ undergraduate experience at the University of South Carolina, when he took a course taught by Navid Saleh called “Nanotechnology in a Global Context.” In addition to exploring chemistry, engineering, and water resource management beyond the traditional methods, an ethical segment of the class explored how to implement new technologies in underserved communities. Rowles was one of a few students to visit the Navajo Nation with Saleh. 

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After seeing first-hand the effects of decades worth of uranium mining on the Nation’s land, water, and people, Rowles and Saleh decided to begin research related to water treatment for the Navajo Nation, the pair recalled. They even worked out their initial research plans on a napkin during lunch at a Subway restaurant on that trip. 

Shortly after this experience, Saleh accepted a new faculty position at the University of Texas at Austin, where he currently serves as a professor in the Fariborz Maseeh Department of Civil, Architectural and Environmental Engineering. Rowles followed along to pursue his graduate studies under Saleh. Desmond Lawler, Nassir I. Al-Rashid Chair in Civil Engineering at UT Austin, served as Rowles’ co-advisor and a co-author on the paper as well.

Other contributors included Mary Jo Kirisits, a professor in environmental and water resources engineering at UT Austin who provided insights on testing the microbial efficacy of the filters, as well as Andrei Dolocan, a research scientist at UT Austin’s Texas Materials Institute who led the surface characterization to delineate the unique properties of the coating. 
 

People-centric technology 

Traditional pottery serves as both a gateway toward building trust among the Navajo people and as a way to solve water contamination challenges with nanomaterials. 

“When we first met with Deanna Tso, a third-generation Navajo potter, she taught us about the materials and processes that she uses to produce ceramic pottery," Rowles recalled. “I remember stopping for dinner after that meeting, and a lively discussion led us to the idea of exploring if the pinyon pine tree resin could be used to embed the nanoparticles.” 

Working closely with Tso, who is a co-author on the study, Rowles and Saleh gathered the locally available resin and infused it with nano-scale silver particles. 

“The device is essentially a disc shaped ceramic filter, onto which the pine tree resin is applied, and nanoparticles are added onto the resin,” Saleh explained. “As the resin sets on the ceramic, the nanoparticles become embedded into the matrix. This allows for avoiding unnecessary loss of silver nanoparticles.” 

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This ceramic water filter creates an effective and inexpensive way to disinfect water simply by pouring water through the coated pottery. Accounting for materials and production, these pots could be made for less than $10 each.

Nano-silver particles serve as an active source of silver ions, which makes disinfection possible, but if those particles are lost, the result is a far shorter usable lifespan for the filter. This is something with which current industry filters must contend as well.

“Silver nanoparticles are oxidized in water to release silver ions, which can inactivate bacteria. These particles are commonly used for disinfection, but their release is usually not controlled,” Rowles said. “We wanted to see how we can control silver nanoparticle release, while facilitating or allowing for the antimicrobial silver ions to be released. This was the key functional role of the natural pinyon pine resin.” 

An additional benefit the resin offers is preventing the silver nanoparticle surfaces from being poisoned by chloride and sulfide ions, which are commonly found in water. 

"The poisoning occurs when aqueous chloride and sulfide react with silver and generate silver chloride and silver sulfide layers, respectively. Such layers prevent oxidation and silver ion release, and thereby reduce the efficacy of the filters,” Saleh said. 

One of the biggest challenges was figuring out how to keep the filters porous enough to allow water to flow through, while also being able to apply the pinyon pine resin and the silver nanoparticles to the ceramic water filters. 

“It was a delicate balance between applying enough resin to embed the nanoparticles, but not too much resin so that the flux of water through the filters would decrease," Rowles said. “We went through a lot of trial and error to tune the ratios of pinyon pine resin to the silver nanoparticles.” 

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Rowles and Saleh note that while ceramic water filters are commercially available, this device’s use of locally sourced materials, its low cost, and the use of something familiar like traditional pottery to help bridge the trust gap with the Navajo community gives it tremendous promise. 

“The uniqueness of this technology is its integrated knowledge of the target community and consideration of their cultural norm and ethos prior to designing a solution for them,” Saleh said. “This is one of the strengths that most technologies do not do.” 

Moving forward, the team is looking to gain a more fundamental understanding of the abilities of these natural materials for use in water treatment. Next steps will involve expanding the technology to incorporate other resins and identifying the relative roles of the respective resins for their demonstrated performance, the team explained. 

“Most importantly, the original central tenet of using pottery to overcome Navajo distrust needs to be proved. This will require a successful adoption of the technology by the Navajos,” Rowles said. “We have begun that work and are hoping for successful implementation.” 

Saleh’s lab is also focused on developing other technologies with a focus on serving other Native communities in Alaska (Inupiaqs, Yupiks, and others), Southern Mexico (Zapotecs), and Bangladesh (Chakma communities). 

“We want to make this point clear that having target community in mind at the early stages of technology development can become a key to successful adoption,” Saleh said. “This can be particularly important for Indigenous communities. People-centric technology development is becoming ever more important, as changes in nature are becoming ever more unmanageable.” 

Louise Poirier is senior editor.