With each issue, Trib+Water brings you an interview with experts on water-related issues. Here is this week's subject:
Navid Saleh is an assistant professor in the Department of Civil, Architectural and Environmental Engineering at the University of Texas at Austin. He created the Saleh Research Group, which is working to develop ceramic water filters embedded with silver nano particles for the Navajo Nation.
Editor's note: This interview has been edited for length and clarity.
Trib+Water: Could you explain a little bit about how ceramic works as a filter for contaminated water?
Navid Saleh: Essentially, ceramic filters have been in use to remove bacteria and viruses. Viruses are small, they get through the ceramic pores and bacteria can be removed. But, recently, I would say it has been two to three years now, there’s a group at the University of Virginia who have been working with silver nano particles with ceramic so they embed the silver nano particles in the ceramic and the silver nano particles work to kill the bacteria. So, typically, ceramic filters remove the bacteria physically, but when you have the silver nano particles in the ceramic filter, those can actually kill the bacteria, not just retain the bacteria like a filter. So that is the process by which it works.
Trib+Water: So how are the ceramic filters you're making with the Navajo community different than the ones with the silver particles?
Saleh: Well, to be clear on a couple of things, one is that I can not give you much details on the material type because we are working on a patent and we haven’t published it yet, but I will tell you what exactly the idea is.
So the project with Navajo Nation started a year and a half ago with one of my students, [Stetson Rowles], who joined me. He’s a potter, so essentially he wrote the proposal to NSF, National Science Foundation, to actually work with pottery where he’s going to incorporate nano materials to disinfect.
So the first difference is that the University of Virginia filters have to be made somewhere in a factory. Then you give those filters to a community, and they can use them. That’s how they work. As you may imagine — particularly in the indigenous population either in the U.S. or in Africa, China or Asia — a technology you can make anywhere you want, whatever the strength of the technology, when you give it to community, particularly if it is indigenous, there is an inherent resistance to use that technology, because they are not familiar with it.
There has been a lot of literature out there talking about embeddedness of technology. When you develop a technology, if you have a community in mind, the community that you are targeting the technology for, you can work with them. That will allow the technology to be accepted in that social setting a lot more easily and a lot more efficiently.
So what we have done is we are working with Navajo Nation. Particularly we are working with a potter in the Navajo Nation. Her name is Deanna Tso. So what we are doing is we are making filters, but we are making filters with bare technology, bare technique — centuries-old technique that they use, which is not identical to the ceramic filters that are made in a factory. So the materials are local. They’re not ceramic powder that they buy. These are clay material that is in New Mexico, in big sort of mountains that they go out and collect them. They are called Mesa. The material that we are working with now is called Red Mesa. So these materials are collected locally.
The primary difference is that we are working with them from the very, very beginning, from the get go, to incorporate their knowledge of the techniques with ours.
Also we are not doing disk filters — disk shaped ceramic filters that are made in a factory. Rather we are incorporating the nano materials in a glaze, in a coating around a filter that is a candle filter, it looks like a candle. It goes in the middle of a bucket, and then the water is interacting with the candle on the outside and then the filter nano particles, and the other nano particles that I will mention in a second can disinfect the water. So essentially it’s a different technique. It’s not in the filter; it’s applied as a coating on the filter.
The benefits are that if you use disk filters it has to be made somewhere else, that means local populations are not going to be able to make them on their own. Second if you use pot filters the way the Virginia group had been working on ... those pot filters have also been researched on with silver nano particles in our EWRE program. Dr. Desmond Lawler actually had a student who had worked on this and essentially developed these pot filters, but they have issues. They break. She did a study in Tanzania and if you take these big pots around from one village to another on Tanzania, half of them break. You lose the material that way.
So what we are doing, by making these ceramic candles that are small we can pack them better, they can serve equally well and we are not putting a ton of material in the ceramic. We are putting these materials as a coating on the outside. These are the key differences in the technique.
Trib+Water: Why did you narrow in on the Navajo community for this project?
Saleh: I have been in touch with them since 2012 through another NSF grant, so I took a few of my students there. So what we did is we looked at their water quality and we found out that their groundwater supply is heavily contaminated with uranium, arsenic and other heavy metals. So these are occurring in their water primarily because of uranium mining that had happened between 1940 and 1980. There’s a lot mine tailings that were left behind and from that, kind of a long-term effect is occurring now, and that’s how the groundwater is getting contaminated.
The surface water, which is water in the lakes and ponds and rivers, those are relatively less contaminated than the groundwater in some areas because groundwater has most of the minerals. But the problem is, in surface water, you have bacteria and viruses that you don’t have as much in groundwater. So surface water needs to be decontaminated to kill the bacteria and viruses, that’s why we are working with the Navajo Nation, because we have an established relationship, they consider clay as a integral part of their life. It’s not something like a piece of art they put up on their shelves. They actually work with clay and make pottery on a day-to-day basis.
Trib+Water: Could you see this water purification technology working in areas of Texas that also have limited access to water?
Saleh: I did mention to you the other technology that I said I could not disclose as much information about details. So the similar technology, using ceramic pot filters, we are developing another nano particle — we already have developed a shown proof of concept, and right now we are working on a manuscript — where we have shown that you can put that filter in the bucket, you can put your water in that bucket with your nano filter that we made. You can then put that bucket in a microwave oven, like a kitchen microwave.
If you microwave it at a low intensity for 10 seconds, you’re going to kill 99.9 percent of bacteria. So it’s extremely effective. So as you can imagine, in Texas or in other rural communities in the U.S., this will be highly applicable to treat surface water because most of the communities have a kitchen microwave in their disposal. So they can do it in a community setting.
I think the microwave technology will be more appropriate and more safe compared to the silver nano particles the University of Virginia had worked on before.
Trib+Water: What do you think is the biggest threat to clean water access in the state?
Saleh: I believe that in most of the towns were you have centralized water distribution systems, I believe that if the quantity produced for clean water is adequate, the cost is the only limiting factor. In most of the modern cities and towns, water in the central distribution system and the way we treat water is very well established. It’s almost a century old now. We’re still working on improving technologies, but I don’t think that’s a limiting factor — it’s cost for people.
But I believe what the limiting factor would be in small towns, rather rural settings, where people have to rely on their local wells, be it groundwater or surface water. Then it becomes the issue of how do they make sure the water they are using is safe. They might think that the groundwater looks clean, and that doesn’t necessarily mean that it is safe. There are a lot of dissolved contaminants, bacteria that you don’t see, but it’s still in your water. I think the limiting factor in that case is to really develop robust point of use technologies for communities that don’t have access to centralized water distribution systems. That way, they can have better access to water.
However, for California and for the Central Plains, there are areas, like the Ogallala aquifer, receding. So water management can also play a big role where central distribution systems are adequate, sometimes local wells for small towns dry up, because your aquifer is going down. In those cases, you need better management practices for water, which is now being studied quite a bit for urban infrastructures.
Trib+Water: What would you like to do with this technology from here?
Saleh: I believe that the microwave technology that I mentioned in particular has a lot of potential. There are three primary strengths for that. One, it can be used in point of use set up, for communities, for families, in a small town. It’s very robust. It’s cheap. It’s long lasting. It’s relatively safe — we are working on all of those aspects. So that’s good.
The second strength is that you can treat dirty water, turbid water, but you cannot treat with conventional treatment technologies. These days, ultraviolet rays are used for disinfection. You cannot disinfect dirty water with ultraviolet rays as well because it needs a clear pathway for light. A microwave doesn’t need a clear pathway for light. As you know, you can warm up your food in a dark, black bowl. It doesn’t need the light to penetrate through because it’s penetrated heat.
The third advantage is that you can actually scale up this method for large-scale water treatment units. I think it can work for both water waste, water treatment facilities for disinfection and also can work for hatcheries, for food industry, where water disinfection sometimes becomes the key, limiting factor for production in fishes, in production for other agricultural products that need water.
The only other thing I would like to note is that the technologies we are working on, it’s still quite in the preliminary stage. We need to be quite aware that it’s not in a stage that we can commercialize it, that we can take it to ground to test in communities tomorrow. It’s going to be at least five years' worth of work, if not longer to be able to make completely sure that it’s effective and it’s safe for people.