Changes and Packing (Reflections from El Paso, Post 3)

Things got a bit hectic during the last few weeks in Honduras and it has taken me a while to get situated at home again. I do want to take the time to finish up on our activities, so this is the third of at least three that will summarize what we did in September and what we are planning to do in the future.

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We turned off the desalination system on 8 September and kept the evaporation system running until 9 September. Then we started packing. To be honest, it was kind of sad. We have worked with a great bunch of people and got to work in a wonderful country. This post will show the packing process, how the site has changed over the last few months, and will include my attempt at showing the joy that a fun team can bring to life.

The field where we put the PV panels was originally covered with trash and many plants had been there, but the UPi crew did a lot of work to make the site usable for a pilot. During the last few weeks of operation, we noticed that a lot of plants had been growing between the PV panels and along the walls. As we started removing panels, the degree of growth became much more apparent. Plants had intertwined themselves around our wiring, making removal an interesting task. I thought it would be fun to show how things looked during the course of the last few months. Disclaimer: I live (and am from) the desert. Green things are somewhat abnormal - even after two months in a very green place.

[Pictures came from multiple sources including Clara Borrego, Victoria Amador, and Victor Zepeda]

View from the front of the field.
The first picture shows how barren the land was (after the UPi crew had cleaned it)
The middle picture shows how the field looked with the panels installed towards the beginning of the pilot
The final picture shows the field after we removed the panels

View from the back of the field.
(LOOK AT ALL THE PLANTS!)

So, back to the packing process. One lesson learned from shipping the system to Honduras was that we wanted to protect the PV panels better. We thought that we had secured the panels very well for shipment, but we hadn't built any structure to hold them in place (other than ratchet straps and pallets). So, we decided to build boxes to provide more structural support (we hope!). The next parts involved packing from the back of the container to the front. It got a little tight towards the end.

Clara and Mr. Rusbel devised a plan for the boxes using the pallets we used to ship from El Paso.
We had to build the bases first, then load them into the container.

For some reason, using power tools using solar power always made me smile.
(I'm not good with saws, thankfully Clara and Rusbel are)

The completed boxes & the straps
Each box had L-brackets to secure the sides to each other, the base, and the the top. We used ratchet straps to secure everything to the floor of the container.

The next step involved taking the array apart and dismantling the desalination system. Similar to when we packed the system in El Paso, we had as many people as possible to save our backs and make the work go faster. But, in Tegucigalpa, UPi brought a grill and made delicious tacos for all! 

Each of the blocks weighs about 25 pounds. We had over a hundred of these to remove, stack, then load into the container.

Clara is always smiling.

I didn't realize we'd have such a perfect stack of blocks!

Jonathan Eveline helped get some of the L-braces onto the PV panel boxes.

It takes a group of us to get everything loaded. (Sorry for my bad picture skills, Victoria!) 

The final pieces. By this time, we were having to crawl over things and squeeze through small spaces.

The container was shipped to UPi for storage until we can find funding for the next adventure. Let me know if you'd like to be part of it. We will need partners, funding, and possibly volunteers.

The desalination container gets some rest at UPi. (what a view!)
[Photo credit: Victoria Amador; great shot, thank you!]

What a fun team. The UPi-UTEP crew will work together and have fun again. Thank you to all that made this possible.

...Stay Tuned

Hindsight is 20/20: Some preliminary conclusions (Reflections from El Paso, Post 2)

Things got a bit hectic during the last few weeks in Honduras and it has taken me a while to get situated at home again. I do want to take the time to finish up on our activities, so this is the second of at least three that will summarize what we did in September and what we are planning to do in the future.

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After having a few weeks to think about what we have learned, I keep thinking "If I only did this..." or "If I just would have started with..." or many other things that are only obvious after time has passed and one has learned from experience, mistakes, and observations. This post will be my way of organizing what we learned from the pilot from a technical point of view. This will be a long post, but I will put some pictures here and there to balance the text.

It is probably helpful to review what our initial objectives were for our pilot demonstration in Tegucigalpa. A few months ago, I summarized how we were using ZDD to desalinate brackish water using energy from the sun. We received funding from USAID to:

• Demonstrate that high efficiency and zero liquid discharge are possible using ZDD powered by renewable energy
• Transfer knowledge to our partners at UPi
• Provide training for Honduras farmers about water quality and desalination technology (including ZDD, of course!)
• Assess the commercial potential for ZDD in Honduras

Just in case you forgot - Here's our pilot site, located at the East end of Morazán Blvd
The PV panels were on the ground in the left. The desalination equipment is in the container in the middle of the picture. The salt recovery and enhanced evaporation system was behind the wall with the interesting art on the right of the picture.

In addition to these general objectives, we were also produce 8,000 liters per day of irrigation water and 250 liters per day of drinking water with certain water quality parameters that were set by the Desal Prize judges. The drinking water requirements were relatively simple, in that the salinity had to contain no more than 600 parts per million of dissolved salts (and meet other World Health Organization water quality requirements). Most reverse osmosis and some nanofiltration membranes can meet these requirements. The irrigation water quality requirements were more challenging. The salinity requirement was slightly lower (no more than 550 parts per million of dissolved salts), but other requirements included a sodium absorption ratio less than 3 (this requirement generally ensures better water infiltration into the soil), a calcium to magnesium ratio greater than 1, pH less than 8, and boron no higher than 0.5 parts per million. [If you would like to learn more about how water quality can affect soil quality and crop health, here are some resources from Texas A&M, Colorado State University, and North Carolina State University.] 

Relationship between SAR and Conductivity.
High SAR (high sodium relative to calcium and magnesium) generally reduces infiltration, however it depends also on the salinity (measured using conductivity) also. Some groundwater may have the same SAR, but the one with higher conductivity is more acceptable for irrigation (For more info: Montana State University). 

Most reverse osmosis membranes produce very high quality water from a salinity perspective, however, because the membranes are very good at rejecting large ions and large dissolved species, the concentration of calcium and magnesium in the product water is very low. This means that the water is generally unacceptable for irrigation without adding some minerals back to the water. Our team usually uses a blend of "loose" reverse osmosis and nanofiltration membranes to achieve suitable water quality. The number and orientation of membranes is chosen based on the amount of silica in the water. All of the waste stream from the RO/NF is fed to another system, called EDM, that removes some of the species that limit desalination efficiency using RO or NF alone (read more here). However, EDM does not remove uncharged species like silica, so the concentration will build up between the RO/NF and EDM systems unless the silica has another place to go. Using loose membranes allows us to have the silica pass into the product water. However, there is a balance: as more silica is allowed to pass into the product water, more of other dissolved species also pass into the product water. This means that the product (irrigation water) will have higher salinity. This means we balance the product water quality and silica concentration. If the silica (and/or other sparingly soluble species) reach levels above saturation, they will precipitate on the RO/NF membranes. Sometimes the precipitated salts (sometimes called "scale") can be removed with a chemical cleaning. Sometimes the precipitation is permanent and reduces the membrane performance.

Hindsight lesson #1: Bring more field testing kits and monitor silica more often. We knew silica in the brackish water had the potential to be problematic. However, previous pilot experience had led me to think I could monitor things well enough without having a full analytical laboratory. I. Was. Wrong. We scaled up the first set of membranes permanently, mostly because we weren't adding antiscalant, which mitigates scale formation in the membranes (we added checking on the pump to our regular monitoring to make sure this didn't happen again). We loaded new membranes and we thought they were doing well. But, as it turns out we scaled them up again. I need some more time to do some calculations, but the RO/NF membrane combination seemed to remove more silica than expected, which led to more silica in the RO/NF loop. We ended up installing a bleed line to ensure the silica stayed below a safe concentration. However, the scale was permanent and affected our production. We did a cleaning, but it seemed to affect the salt rejection, so our product water quality wasn't as great. Had we started with the bleed, we probably would never have had the silica problem in the system (good old hindsight...).

Lesson Learned: Measure silica regularly (and check antiscalant addition)

Hindsight Lesson #2: Use acid for pre-treatment of the brackish groundwater (i.e. trust  intuition and past experience). The Desal Prize judging rules penalized teams for using chemicals, like acid, as part of the desalination process. So, we decided to try to operate without acid, even though the alkalinity present in the Los Almendros well was higher than any other groundwater the team had ever worked with in past pilot tests (I wrote about this here). Alkalinity present in the RO/NF concentrate ends up in the EDM's Mixed Na stream at a much higher concentration. Because the compounds formed (mostly sodium bicarbonate, but also some sodium carbonate) could eventually be supersaturated and precipitate, the stream is eventually diluted with a very low salinity water. Finding the setpoint for dilutions without an alkalinity test kit involves trial and error, and some indirect measurements. We operated for the first few weeks this way, but eventually decided to install an acid feed line on the brackish feed. Had we done this from the beginning, this could have been incorporated into the automatic controls. I chose not to do this partially for budgetary reasons, but also because I really wanted to see how the system would perform without acid. In previous pilots I have been able to find the appropriate setpoint without needing to do a lot of field tests, however, field tests ended up being necessary. We thought we would have access to a laboratory with alkalinity test capabilities for the pilot, so we didn't bring reagents with us. After receiving a test kit that was sent from UTEP, we were able to monitor alkalinity in the RO/NF and EDM systems and were able to get mostly stable operation. While the process was not smooth, we did find a pH setpoint that seemed to work for both the RO/NF and EDM systems. Thankfully, we had UPi students available to help with the field tests.

Monitoring Alkalinity.
Top Left: Using the trial & error method involves testing various concentrations in the Mixed Na stream. If the concentration is too high, scale forms in the Mixed Na compartments. We could confirm that the scale was carbonate-based by adding acid and seeing if it bubbled.
Bottom Left: Indirect measurements involved taking a sample from the various streams with suspected supersaturated alkalinity. If precipitation was visible, we had gone too far.
Right: Measure alkalinity analytically. Here, UPi student Victoria Amador is performing the alkalinity test

Hindsight Lesson 3: Prepare for the worst in terms of particle removal when you only have one water sample to base a design from. Another thing that most water engineers know is that you can't base a design off of a single water sample. But, that was all we had, so we did. Also, we didn't know a lot about the well design before arriving in Honduras (another bad idea, in terms of design). One thing we found out when we got here is that the well produces much more water than we need, and the well isn't currently used, so the well was cycled on & off several times during the day to fill a storage tank that we pumped from for the pilot. Each time a well is turned on, particles are brought to the surface. This is usually not a problem, since wells are not normally operated in this manner. Also, many desalination plants will install a strainer to filter out sand and other particles from the well. We did have cartridge filters ahead of our pilot equipment, but we initially had filters with too large of pores installed. Even the smallest pore size filters we had (1 micron) still allowed some particles to leak by. These particles caused fouling of the membranes and are suspected to have also contributed to the precipitation issues found in the RO/NF. We didn't have enough budget to install additional particle removal equipment on this project, but it will be included with the system for further work so that better results can be expected.

Particle Removal.
Left: RO/NF feed tank after 20-micron cartridge filters
Middle: Cartridge filters after one week, one day, and no use (clean)
Right: RO/NF feed tank after 1-micron cartridge filters (there was a vast improvement, but particles were still leaking past the filters)

Bottom Line: We worked hard to be successful

So, what did we learn? And did we meet our stated goals and objectives? I think so. 

Between competing in the Desal Prize and operating in Honduras, we reduced our energy needs by 40%! This means that a smaller PV system could be purchased or that the extra energy could be used for farmers' homes (or possibly sold to recover additional costs). Further energy savings are possible if more of the AC load can be moved to the DC side.

We were able to achieve very high desalination efficiency (94%) with a very challenging brackish water source and only used power produced from our PV system. We produced solid gypsum (the first sample sent to our UTEP lab indicated about 98% purity) and liquid sodium chloride using a salt recovery and enhanced evaporation system. We weren't able to concentrate the sodium chloride enough prior to evaporating it, but previous experiments suggest that we can achieve good enough purity for use in the EDM. Before the RO/NF membranes scaled, we were able to meet the water quality objectives, as estimated from the field analyses. We have identified conservative operational setpoints for how a ZDD system could operate at the Los Almendros location.

And, while we weren't able to demonstrate everything running at the same time, our enhanced evaporation system seems to be capable of evaporating enough of the waste stream to maintain zero liquid waste discharge. With a fan installed and oeprating, we were able to evaporate almost a gallon per hour, which is about double the combined waste flow. 

This project was so much more than the technical objectives. We started the process of transferring knowledge to our UPi partners and to various groups in Honduras. Over the course of two months, we held three training sessions and a public tour at the end of the piloting, we met various UPi professors and students, and we had a chance to meet with Mr. James Watson, the USAID Mission Director Honduras. I am grateful for the opportunity to visit the good people of Honduras and hope that we will be able to continue this work.

Developing Desalination in Honduras. From Left to Right: Clara Borrego, Chancellor Jance Carolina Funes (UPi), Mr. James Watson (USAID), Malynda Cappelle, Ing. Luis Eveline, and Isaac Ferrera (USAID)

We got some great press (Reflections from El Paso, Post 1)

Things got a bit hectic during the last few weeks in Honduras and it has taken me a while to get situated at home again. I do want to take the time to finish up on our activities, so this is the first of at least three that will summarize what we did in September and what we are planning to do in the future.

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The first few days of September were pretty eventful. Our UTEP-UPi team had the opportunity to be on TV and in the newspaper. On September 1, Clara and I received word that we would be picked up in the morning to go to Televisión Educativa Nacional, TEN Canal 10 along with Luis Eveline to talk about our project. This was pretty exciting nerve-wracking for us (or maybe only nerve-wracking for me since I don't speak Spanish). The show we were on is live and unscripted. So, even though I had some prepared remarks that I was fully capable of reading, it didn't matter. 

Clara and Me - Waiting outside the TV station

We arrived with a few minutes to spare for our appointment. After waiting for a while, we were told that we would have to come back another day because there was an important political event that was being covered live and they weren't going to do the regular show. While this was disappointing, it was somewhat relieving because that would mean that I could practice with Clara a bit more and be more comfortable. 

We asked to go to the restroom and were led through a room where a movie or TV scene was about to be filmed. I really wish that I had a camera to take a picture. The actors were dressed up kind of like the actors in the 10 commandments movie and the green screen setup looked like the desert someplace. I was having fun watching the monitors, which showed how the actors and scene were combined. I have no idea what they were filming. Too bad.

After a bit more waiting, we were told that the show would go on and we were escorted upstairs. My heart was racing. The final bits of the political event were still live, so while we were getting our microphones and places, we got to hear the speech from one of the candidates for president. She was pretty interesting to listen to. I'll be curious to watch how the elections go. Then, we went live. Things moved very fast. It was cool to watch how they went from the offsite event, to weather, to announcements, and then to us. It was a crazy time. I forgot all Spanish. Watching the video now, without cameras, I understand more, but at the time I forgot every word I know. Clara did very well. I struggled with whether I would include the link because of my embarrassment, but it was a good opportunity and so I am including it here for you.

We had a few minutes, so why not take a selfie with one of the anchors? (photo credit: Clara Borrego)

On September 2, we hosted a group of important players in Honduras water and agriculture at our pilot site. This included representatives from the USAID Honduras Mission, SANAA, Fundación Para el Desarrollo Municipal, Federación Nacional de Agricultores y Ganaderos de Honduras, Secretaría de Agricultura y Ganadería Honduras, Asociación de Municipios de Honduras, Programa de Agua del Banco Mundial, and others invited by Ing. Luis Eveline.

The event was held on a day where we (thankfully) had no rain, but also, we had full sun and very little cloud cover, so it was HOT. The event started with Ing. Luis providing a warm welcome to the visitors and introductions of the key people present. Also present was Ari Herrera, who is part of our project team. Ari and Dr. Shane Walker went to graduate school together at UT-Austin and he (Ari) is the connection we (UTEP) had to UPi and Honduras. Ari is originally from Honduras and has extensive experience in water and wastewater treatment. Ari is also very skilled at acting as a translator. He stood by me and translated key portions of comments made by participants and also translated what I said to the group. (note to self: learn more Spanish...). 

Group picture with me talking (photo credit: Victor Zepeda)

Everyone loves our recovered gypsum!
(I think Victor took this photo, but I don't remember...)

After a round robin of comments, we took the group to the well, then provided tours of the desalination and enhanced evaporation/salt recovery systems. La Tribuna, a Honduras newspaper, arrived towards the end of the tours and they interviewed our team and took some great pictures. Their article appeared in the paper the next day. They did a nice job covering the event and I am pleased that we could get such great national coverage to present our project to Honduras.

Here's a link to the article, Honduras ya cuenta con proyecto piloto de desalineación de agua (desalination was misspelled, but that's OK. It can be desalinación or desalinización, I prefer the former since I don't like desalinization in English either).