A Novel Full-Scale Approach to Indirect Potable Reuse - with Eng. Rafael Zarate, SAPAL, Mexico

[00:00:00] Piers Clark: Welcome to the Exec Exchange 15-minute podcast, in which a leader from the water sector shares a story to inspire, inform, and educate other water sector leaders from around the globe.
[00:00:11] Piers Clark: My name is Piers Clark, and my guest today is Engineer Rafael Zarate, President for the Center of Innovation at SAPAL in Mexico.
[00:00:21] Piers Clark: Engineer Rafael, wonderful to have you with me.
[00:00:24] Rafael Zarate: Thank you very much, Piers. It's an honor to be here.
[00:00:28] Piers Clark: You know how we start. We always want to know a bit about our speakers. So, tell me, what were you doing before you got into this role as president of the Center for Innovation?
[00:00:40] Rafael Zarate: I studied civil engineering at the University of Guanajuato, Mexico, and later I went to Spain where I earned the Master of Science Degree from the Polytechnic University of Madrid, and I also completed a specialization in water treatment at the same university.
[00:00:57] Rafael Zarate: I've been always passionate about water management treatment and especially reuse. I have been working in water reuse since 35 years. I am a certified water resource engineer of the American Academy of Water Engineering. I was also president of the National Chamber of Consulting and President of the Board of the Water Utility of the city of Guanajuato.
[00:01:21] Rafael Zarate: And right now, I'm president of the Center of Innovation in Water Technology.
[00:01:26] Piers Clark: Did I hear that right, 35 years in water?
[00:01:28] Rafael Zarate: Yeah. I focus in water reuse which was something weird at that moment but right now it's an urgent need all around the world.
[00:01:38] Piers Clark: People listening to this, don't get to see the video, but I get to see you and I can see if you've got 35 years’ experience. I've got 35 years’ experience, so we must be about the same age. We must be in our mid-fifties. Yet you look a lot younger than me. This must be the Mexican sunshine and the Mexican diet!
[00:01:54] Rafael Zarate: We look the same and yeah, I'm 60.
[00:01:56] Piers Clark: Now you are just making this worse. You are five years older than me and you have this full head of hair and, oh, anyway, let's not go there.
[00:02:03] Piers Clark: Now, tell me about SAPAL.
[00:02:07] Rafael Zarate: SAPAL is the water utility of the city of León, the fifth largest city in Mexico and we in León, we're going through one of the most severe water crisis in the history. Right now, 61% of the state is under extreme drought and rainfall has dropped by nearly 49% between 2015 and 2022.
[00:02:31] Rafael Zarate: So, this situation threatens not only water availability for citizens, but also for all industrial developments. We need to look to a alternative water source different from groundwater and surface water.
[00:02:47] Piers Clark: In preparing for this interview, I was reading a bit about the City of León and I found the fascinating fact that it seems to be regarded as the most environmental city in Mexico. Mainly because of, it's got lots of cyclists is what it seemed to tell me. But that also, in 2012, it was given a City Champion Water Award by the government because of the work it had done in sanitation and water reuse, which serves as a wonderful segue into the activities that you've been doing in indirect potable reuse.
[00:03:18] Piers Clark: So, let's start by going back to, when did you start doing indirect potable reuse?
[00:03:24] Rafael Zarate: That's very interesting question because this is not a new project. We started planning it 10 years ago and it became a reality five years ago.
[00:03:34] Rafael Zarate: We start piloting with a very, very small facility, then we scale and in this process, we weren't alone. We were searching all the cities in which potable water use is made like in California, in Texas.
[00:03:51] Rafael Zarate: We joined experts like the NEWT which is the Nano-Enabled Water Treatment, which includes Yale University, Rice University, Arizona State University. We also approach the University Polytechnique of Catalonia in Barcelona.
[00:04:10] Piers Clark: You really did go around the world. You went and picked everybody's brains.
[00:04:14] Rafael Zarate: Yes, because this is a new project. We cannot afford the technology that they are using in countries like the United States, for example, California and Texas. They apply Reverse Osmosis as a process, which is a warranty, but it's too expensive for us.
[00:04:32] Rafael Zarate: So we went searching about alternative technologies. And in the Rice University, which is pioneer of nanotechnology, they told us about the option of nano filtration instead of reverse osmosis following by advanced oxidation.
[00:04:51] Rafael Zarate: So we started this promising solution in the indirect potable use. We start making pilots and we found hollow fiber nano filtration which is sensitive to the PFAS because there are some nano filtration membranes that are sensitive to salts but in our case, we don't want to remove the good salts because we are going to need them later.
[00:05:15] Piers Clark: So you've got nano filtration with a follow on step, but the nano filtration means that you can do the membrane treatment much cheaper than you would if you were doing RO. But even with the nano filtration, you still needed some innovation inside there, preserving the nutrients and the salts inside the water.
[00:05:32] Rafael Zarate: Yeah, we found the best results with the hollow fiber nanofiltration. In our case, we work with the NX Filtration. After that we have a six stages process: oxidation with ozone, activated carbon filtration, UV, chlorine. We have found that we were able to remove practically a hundred percent of the contaminants of emerging concern.
[00:05:59] Rafael Zarate: And another challenge we faced is that our regulation was kind of weak so we adopt the Texas regulation and I can tell you that after five years of piloting of analysis, we have been working in this process also with KWR, Water research Institute of the Netherlands, and they have certified that we are able to remove just with the nano filtration 94% of the PFAS.
[00:06:30] Piers Clark: I do think this is incredible because I love that bit where you weren't comfortable with the national regulations and so you actually adopted Texan regulations. You set yourself a very high bar and then NX Filtration, the company that you mentioned whose membranes you're using, they're based in the Netherlands and the Dutch are obviously very well known for exporting leading technology around water treatment. They also have the internationally renowned laboratory, KWR, who you've then brought them in to sort of mark your homework to check that you actually were compliant with the regulations that you were aspiring to comply with.
[00:07:07] Rafael Zarate: Yes, because this project not only is going to be the first one in all Latin America for indirect portable use, but it's going to be the first one all around the world without the use of reverse osmosis.
[00:07:20] Piers Clark: It is an absolutely groundbreaking project. Which leads me to my next question, when did you do these tests and what scale were these tests?
[00:07:28] Rafael Zarate: We started with a single membrane in a very small field testing. And we found results acceptable in terms of TDS, total dissolved solids. And we said, okay, something's happening because filtration couldn't remove any of the solids. So, we came later to a larger five Liters per second facility in which we got the same results. Then we went to 10 Liters per second, and finally we went to 40 Liters per second. So we bet on that technology and we found that, we were able to achieve our goals.
[00:08:05] Rafael Zarate: I recently came from Chicago at the WEFTEC and they told me, why are you doing that? Nobody's doing it. We are going to be the first, but we have the results. It's something that we tested for five years and we have found that we are fulfilling the regulation.
[00:08:22] Piers Clark: Obviously you are happy that it's cleaning the water to the level that you want to clean it for indirect potable reuse. So it's interesting that you went down nanofiber because it was supposedly cheaper than using RO.
[00:08:36] Piers Clark: Do you now have robust data that confirms that it was cheaper? And is it cheaper on the CapEx or on the OpEx or both?
[00:08:43] Rafael Zarate: Both CapEx and OpEx. And I can tell you in CapEx it's like half and in the OpEx is a third.
[00:08:50] Rafael Zarate: I know technology has an evolution and always the products are cheaper and are more efficient, but at this time, we are at half of price of the investment we need to do.
[00:09:04] Piers Clark: Those figures seem incredible bearing in mind the NX Filtration, hollow fiber membrane is itself very innovative. So you'd imagine that being one of the first adopters, it would've still been at a premium cost. And yet it's still making that impact.
[00:09:18] Rafael Zarate: Yeah. And even considering that the membranes need to be replaced every five years. That's part of the cost and we can afford that. It's also cheaper than the reverse osmosis.
[00:09:31] Piers Clark: Now, how's the public taken to indirect potable reuse?
[00:09:35] Rafael Zarate: That's the most important part of the project, the social acceptance.
[00:09:40] Rafael Zarate: In this case, this reservoir we're using, it's inside the city. It's a recreational area. People is aware that it's getting dry. And now let me tell you, two years ago it was totally dry.
[00:09:51] Rafael Zarate: So people is concerned and they said, yeah, let's do that. We are showing the results. This is the water analysis coming from our Water Research Institute of KWR in Netherlands. And everybody's happy because, they saw it's different and that has helped that the people of León has conscience of the situation and that's helping with the acceptance.
[00:10:16] Piers Clark: This sounds like it's a full-scale installation, 40 Liters per second.
[00:10:20] Piers Clark: Will you roll out other plants? What happens next?
[00:10:23] Rafael Zarate: The final stage is going to be a 400 liters per second it's to supply about 20% of the city. And we are now working in the facilities we have already acquired all the equipment, including the membranes.
[00:10:37] Rafael Zarate: We hope that early 2026, we're going to release the first 200 Liters per second. And by the May of next year, we're going to operate in a full capacity of 400 Liters per second.
[00:10:53] Rafael Zarate: We are working also with the federal authorities because we need permissions. They have been very supportive with the project.
[00:11:01] Piers Clark: Rafael, I'm very impressed. A world first of doing nano treatment at scale for indirect potable reuse.
[00:11:08] Piers Clark: Unfortunately, we're running out of time and we do always finish with a slightly cheeky question.
[00:11:14] Piers Clark: If we could go back to a 20-year-old Rafael Zarate, what advice would you give him?
[00:11:20] Rafael Zarate: Okay. I will say there will be a big difference if everybody can go back forty years and tell climate change is going to be a reality. And if you save water now, the situation will be different. So I think we are 24 years far from that, but we are also 24 years from the future.
[00:11:41] Rafael Zarate: And we must do something right now in terms of saving water, taking care of the environment because, if not, our children will have to pay the price.
[00:11:52] Piers Clark: You have been listening to the Exec Exchange with me Piers Clark, and my guest today has been Engineer Rafael Zarate, from SAPAL.
[00:12:00] Piers Clark: And we've been talking about indirect portable reuse being done with Nano Hollow fiber nano filter membranes. I hope you can join us next time. Thank you.