Scientists reveal key insights into emerging water purification technology — @ColoradoStateU

Left represents an omniphobic membrane, and right represents a conventional hydrophobic membrane with increased water-air interfacial areas (green lines). Credit: Kota lab

Here’s the release from Colorado State University (Anne Manning):

With water scarcity a critical challenge across the globe, scientists and engineers are pursuing new ways to harvest purified water from unconventional sources, like seawater or even wastewater.

One of those researchers is Tiezheng Tong, an assistant professor in the Department of Civil and Environmental Engineering, whose lab is studying an emerging technology called membrane distillation.

Membrane distillation involves a thin, water-repellant membrane that exploits vapor pressure differences between hotter impure liquid, called “feedwater,” and colder purified water, called “permeate.” During the process, water vapor passes through the membrane and is separated from the salty or dirty feedwater. According to Tong, membrane distillation works better than other technologies like reverse osmosis, which can’t treat extremely salty water such as desalination brines or produced water from hydraulic fracturing.

While it holds promise, membrane distillation doesn’t work perfectly. A key challenge is designing membranes to purify water efficiently while ensuring zero contamination of the clean water.

Tong and materials scientist Arun Kota in the Department of Mechanical Engineering joined forces to get at the fundamental science behind designing that perfect membrane. In new experiments they describe in Nature Communications, the CSU engineers offer new information into why certain membrane designs used in membrane distillation work better than others.

“The fundamental knowledge from our paper improves mechanistic understanding on the water-vapor transport within microporous substrates and has the potential to guide the future design of membranes used in membrane distillation,” Tong said.

How it works

In membrane distillation, the feedwater is heated, separating the pure and impure components by differences in volatility. The micro-porous membrane is a key component to the setup because it allows water vapor through, but not the entire impure liquid. Typically, the membrane is made of a “hydrophobic,” or water-repellant, material in order to let only the water vapor pass through but maintain a barrier for the feedwater.

However, these hydrophobic membranes can fail, because the feedwater, such as shale oil-produced water, can have low surface tension. This low surface tension allows the feedwater to leak through the membrane pores, contaminating the pure water on the other side – a phenomenon called membrane wetting.

Previous research had unveiled that using “omniphobic” membranes – membranes that repel all liquids, including water and low surface tension liquids – keep the vapor/water separation intact. But, omniphobic membranes typically slow down the rate and amount of water vapor passing through the membrane, dramatically reducing the efficiency of the entire process.

The CSU researchers set out to discover why this tradeoff between hydrophobic vs. omniphobic membranes exists. Through systematic experiments in the lab led by postdoctoral researchers Wei Wang in Kota’s lab, and Tong’s graduate student Xuewei Du, they found that conventional hydrophobic membranes create a larger liquid-vapor interfacial area. This increases the amount of evaporation taking place. With the omniphobic membranes, they saw a much smaller liquid-vapor interface. This explains the difference between the membranes’ performances.

The omniphobic membranes used in the experiments were made without depositing extra particles. Thus the researchers were able to determine that their observations weren’t the result of structural changes to the membranes.

Cross-sectional view of a conventional hydrophobic membrane used in membrane distillation. The blue represents water. Credit: Tong and Kota labs

Solving the tradeoff problem

While they didn’t offer a solution to the tradeoff, their insights reveal the core challenge around making membrane distillation a successful technology. “If you understand the problem thoroughly, then there is scope for solving it,” Kota said. “We have identified the mechanism; now we have to solve the tradeoff problem.”

For example, smart membranes with exceptional omniphobicity and simultaneously large liquid-vapor interfacial area can render membrane distillation a robust and cost-effective process for water purification. More collaborative research has been initiated by the team to design such smart membranes, with the goal of increasing efficiency of membrane distillation.

Tong added that the research happened at the interface of two disciplines: surface science and membrane technology.

“Arun and I utilized our complementary expertise to systematically conduct this work,” Tong said. “It is an example of good interdisciplinary collaboration across campus.”

Graduate students Hamed Vahabi in mechanical engineering and Yiming Yin in civil and environmental engineering also contributed to this work.

“This is an example of #climatechange in our own backyard. The reasons there are more algal blooms is because the temperatures are slightly warmer every year” — Ed Hall #ActOnClimate

Cyanobacteria. By NASA – http://microbes.arc.nasa.gov/images/content/gallery/lightms/publication/unicells.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5084332

From 9News.com (Marc Sallinger):

The City of Greeley said algae is to blame for bad-tasting drinking water in the city.

Recent hot weather caused algae blooms in two lakes where Greeley gets its water.

Lake Loveland and Boyd Lake provide more than 20 million gallons of drinking water to the City of Greeley every day. The algae bloom left that water tasting like dirt and metal.

“People don’t like water that tastes dirty,” said Ed Hall, Assistant Professor Department of Ecosystem Science and Sustainability at Colorado State University.

The blooms happen when there are nutrients in the water, hot days and not much wind…

Algae releases byproducts that cause the water to taste and smell strange. Right now, Greeley’s water department said the byproducts released from the algae are 250 times stronger than usual.

“This is an example of climate change in our own backyard. The reasons there are more algal blooms is because the temperatures are slightly warmer every year,” said Hall. “This isn’t going to go away. We really need to start thinking about how to protect ourselves and live with these as the earth becomes warmer every year.”

[…]

The city said they are now treating the water to try and get all the taste and smell from the algae out of the water. They said it should be almost back to normal by the time it gets to your sink.

From The Greeley Tribune (Cuyler Meade):

When the roughly 40 million gallons per day of potable — or drinkable — water consumed by Greeley residents started tasting and smelling noticeably different last week, the Water Department didn’t wait long to react. The department believes its swift response last weekend has effectively solved the problem, and Greeley water should now taste better.

The problem: Concurrent algae blooms in both Boyd Lake and Lake Loveland, the major peak-months water sources from which the department draws and treats the water delivered to Greeley…

That meant, Chambers said, that the option of turning off sourcing from one of Boyd Lake or Lake Loveland — from which much of the area’s water is drawn during the “peak” summer months — was not sufficient. While the department did end up turning off its delivery from Lake Loveland, where Chambers said it was determined the algae situation was “about four times” as bad as it was in Boyd Lake, the water coming from Boyd Lake was still affected with an unappealing taste and smell…

The solution, then: Increase the activated carbon used to treat the water at the Boyd Lake treatment plant.

“Activated carbon is a good way to remove (the poor taste and smell),” Chambers said. “It’s also very expensive, and it’s hard to get the dosage exactly right for the amount that we’re measuring, which is in parts per billion. Tiny, tiny molecules that have a fair amount of influence on taste and odor…

Normally, activated carbon is used to treat the water in the 25 to 27 milligrams per liter range, Chambers said. But this dual algae bloom required more.

“Last Friday, we turned off our Lake Loveland supply, which allowed our activated carbon dosage to do a better job pulling those odor-causing molecules out,” Chambers said. “Then we upped the dosage, as well.”

Chambers said they began treating the water with about 35 milligrams per liter, up about 40% from the normal dosage. The department is continuing to use that increased dosage for the time being.

“Our internal sampling has led us to believe that’s perfectly adequate for removing what’s needed,” Chambers said.

The more southerly lakes become critical sources of water in the high-usage summer months, but the “workhorse” treatment plant is actually at the Poudre River Basin in Bellvue.

“We treat our water at those two locations near the foothills where you can grab higher-quality source water than you can find in Greeley and deliver the water to Greeley,” Chambers said. “Visionary system that was developed in the early 1900s up at Bellvue.”

Chambers emphasized the fact that even before treatment, while the water may have tasted differently, it was at no time unsafe to drink.

#PFAS: Widefield aquifer cleanup update

Widefield aquifer via the Colorado Water Institute.

From Colorado Public Radio (Dan Boyce):

The Environmental Protection Agency issued a health advisory in 2016 that warned of the connection between PFAS and certain types of cancer.

After the advisory and the discovery of widespread groundwater and soil contamination near Peterson Airforce Base, the Pikes Peak Community Foundation shut down organic vegetable production at the Venetucci farm. They opted to instead raise lower-priced feedstock for horses.

It’s one example of the financial burden this region still bears from the pollution, despite the $50 million the Air Force has spent on cleanup around Peterson.

“There are 60,000 stories just like this and they’re happening at the kitchen sink in every Fountain, Widefield and Security home,” Clark said of the communities whose water was tainted by the foam.

The foundation, as well as the nearby Security Water District, have sued the Air Force over the chemicals. District general manager Roy Heald said they had to find a new source of water for their customers, a complicated process which involved the construction of a mile-long pipeline to buy water from Colorado Springs. The cost of the pipeline and the first two years of water set the district back $6 million…

In 2018, the Air Force stepped in to cover the district’s water costs until the construction of a new treatment facility was completed. The Air Force will also pay for the facility. Still, Heald said it’s unclear what the ongoing long-term costs will be for the district when it comes to the new facility. It will be needed as long as the contamination remains in the groundwater, which could essentially be forever…

As of this June, $357 million has been spent on PFAS cleanup around 22 Air Force installations nationwide. It’s a lot of money that many who live near the sites say barely touches on the full problem…

There’s disagreement even between government agencies about what concentration of PFAS is safe for humans. A division of the Centers for Disease Control and Prevention found that levels should be set seven to 10 times lower than the EPA’s health advisory.

Genna Reed, the lead PFAS researcher for the Union of Concerned Scientists, has said the Department of Defense “misrepresented the scope of this issue in order to avoid having to pay.”

The Air Force would not grant an interview for this story, but states on the PFAS website it established that “protecting human health is our priority.”

Reed said the Department of Defense has limited which PFAS chemicals it tests for in groundwater and only releases data when the results are above the higher EPA threshold.

“Community members who have been exposed to this chemical and were not told of its release are being the ones left with the burden of paying for this contamination and paying to find out how much is in their water and also to find out how much is in their blood,” Reed said.

Rosenbaum said the full blood panel to test for PFAS chemicals costs about $700 — out of reach for many living near Peterson AFB.

Rosenbaum has organized a local clean water coalition to go after grants to test residents’ blood and water. She’s frustrated they have to do that work themselves.

“There’s absolutely no reason for our communities to go into debt over another water contamination that we didn’t cause,” she said.

Twenty-four water systems across the Arkansas Valley are in violation of the Clean Water Act — The La Junta Tribune-Democrat

Arkansas Valley Conduit Comanche North route via Reclamation

From The La Junta Tribune-Democrat (Christian Burney):

Twenty-four water systems across the Arkansas Valley are in violation of the Clean Water Act due to the levels of radioactive contaminants – some of them naturally occurring – in the water, according to data from the Colorado Department of Public Health and Environment.

The systems deemed to be in open health-based violation are located in or near La Junta, Cheraw, Rocky Ford, Manzanola, Swink and Wiley, and the water produced by those facilities is high in radioactive elements, radium and uranium and, in fewer instances, gross alpha radiation.

Colorado Sen. Larry Crowder (R-Dist.35) told the La Junta Tribune-Democrat that other municipalities – such as Fowler, Ordway, Sugar City, Las Animas, Eads and Hasty – could also be affected.

While those towns were not identified by the CDPHE to be in open violation of clean water standards, various contaminants such as selenium were measured by some of their water systems, he said.

The fact that radioactive contaminants exist in some water systems is not itself a new development. As Lower Arkansas Valley Water Conservation District Manager Jay Winner put it, communities in the region have been dealing with them for years…

But the CDPHE’s findings reveal that radium levels in some Arkansas Valley water systems is up to 63 times higher than levels at the Pueblo Reservoir, and the amount of uranium is up to 12 times higher, Crowder said.

What does that mean if you’re born and raised here and have been drinking the contaminated water your entire life?

Maybe nothing, but the potential does exist for health problems if the impurities in drinking water regularly exceed the maximum contaminant level (MCL) recommended by the EPA and if there is long-term exposure.

For instance, the EPA says prolonged exposure to levels of nitrate (measured as nitrogen) – which is in fertilizer and which makes its way into groundwater and aquifers via runoff – exceeding the MCL could result in serious illness and, potentially, death in infants below 6 months of age.

Long-term exposure to selenium that exceeds the MCL could result in hair or fingernail loss, numbness in fingers or toes and other circulatory problems.

Several water systems tested positive for radium 226 and 228 (combined), which the EPA says could result in an increased risk of cancer, if the exposure is prolonged and above the recommended MCL. Radium appears in groundwater through the erosion of natural deposits…

Crowder requested the water quality tests in preparation for another push to get federal funding for the long overdue Arkansas Valley Conduit, which would deliver water from the Pueblo Reservoir up to about 130 miles downstream, bypassing the sources of contamination and providing cleaner water to communities in the Arkansas Valley.

Soldier Canyon Water Treatment Authority embarks on $38.9 million expansion

The Soldier Canyon Dam is located on the east shore of Horsetooth Reservoir, 3.5 miles west of Fort Collins, Colorado. The zoned earthfill dam has an outlet works consisting of a concrete conduit through the base of the dam, controlled by two 72-inch hollow-jet valves. The foundation is limey shales and sandstones overlain with silty, sandy clay. Photo credit Reclamation.

From The North Forty News (Annika Deming):

Soldier Canyon Water Treatment Authority recently broke ground on a $38.9 million expansion to the water treatment plant in Fort Collins, Colorado. Fort Collins-Loveland Water District (FCLWD) receives the majority of the water it provides to 45,000 people in parts of Fort Collins, Loveland, Timnath, Windsor and Larimer County from the Soldier Canyon Filter Plant. Slated for a 2021 completion, the project will allow Soldier Canyon to meet peak summer capacity demands without relying on any other plants. It will also improve water quality with the construction of additional taste and odor facilities.

FCLWD currently receives raw water from the North Poudre Irrigation Company, Colorado-Big Thompson (C-BT) project, Josh Ames, Divide Canal and Reservoir Company, and Windsor Reservoir Company. Raw Water sources must be treated before being delivered to customers. Most of the water delivered to customers for household usage comes from the Soldier Canyon Filter Plant, which pulls from the Poudre River and Horsetooth Reservoir. The plant has some of the highest quality water in the area, which is measured and reported on quarterly for the plant, and years for FCLWD. The remainder of the water comes from the City of Fort Collins Water Treatment Facility and the City of Loveland Water Treatment Plant.

After the Soldier Canyon plant expansion is complete staff will be able to treat 60 million gallons of water per day. They will also have more treatment tools available for taste and odor removal, additional flocculation and sedimentation facilities, and additional contact time for chlorine to inactivate viruses and other pathogens. The expansion will be constructed offline, meaning minimal impact to FCLWD customers. At the end of the project, it will be connected to the existing facility.

“Our mission has always been to provide high quality, secure, reliable and affordable water to our customers,” says Chris Matkins, FCLWD general manager. “As the district continues to expand, we need to ensure we can continue to provide the highest quality water in the area water to customers. We are always planning for the future and this expansion is part of a multi-prong plan to meet demand and maintain infrastructure.”

Soldier Canyon Filter Plant, located at the base of Horsetooth Reservoir, treats and distributes water for three local entities: Fort Collins-Loveland Water District, North Weld County Water District and East Larimer County Water District.

FCLWD has provided water services to businesses and citizens since 1961. The District serves approximately 45,000 people in an area that encompasses approximately 60 square miles in parts of Fort Collins, Loveland, Timnath, Windsor and Larimer County. Governed by separately elected Boards of Directors, the Districts provide the full spectrum of high-quality and dependable water treatment and delivery as well as water reclamation services. For additional information about Fort Collins-Loveland Water District, its services and project visit http://www.fclwd.com or follow us on Facebook.

For additional information and updated on the expansion as well as tips for water conservation and efficiency visit FCLWD’s Facebook page, http://www.facebook.com/fclwd.

Fountain is about to turn dirt on new groundwater treatment facility using USAF dough

PFAS contamination in the U.S. via ewg.org

From KOAA.com (Tyler Dumas):

A [new] groundwater treatment facility is going to be built just north of the existing one.

The facility will be paid for by the Air Force and will be built by the Army Corps of Engineers. The project is part of the agreement reached to protect Fountain’s water from contamination from Peterson Air Force Base in 2016.

@USBR awards $5.1 million in research for new ways to desalinate and treat water

Desalination and water purification research, like this being undertaken at the Brackish Groundwater National Desalination Research Facility in Alamogordo, New Mexico, will help communities treat impaired or otherwise unusable water. Photo credit: Bureau of Reclamation

Here’s the release from the Bureau of Reclamation (Peter Soeth):

The Bureau of Reclamation announced that 30 projects will receive $5.1 million from the Desalination and Water Purification Research Program to develop improved and inexpensive ways to desalinate and treat impaired water.

“We are awarding grants to a diverse group of projects to reduce the cost, energy consumption and environmental impacts of treating impaired or otherwise unusable water for local communities across the country,” said Reclamation Commissioner Brenda Burman. “This funding is a direct result of the Trump Administration’s commitment to increase water supply and delivery through improved technology.” Twenty-five awards are for laboratory-scale projects, which are typically bench scale studies involving small flow rates. They are used to determine the viability of a novel process, new materials or process modifications. Awards are limited to $150,000.

Five projects are selected as pilot-scale proposals, which test a novel process at a sufficiently large-scale to determine the technical, practical and economic viability of the process. Awards are limited to $400,000 and no more than $200,000 per year.

Types of projects funded include modeling, testing new materials such as nanomaterials, and improvements on known technologies such as distillation and electrodialysis. Projects are funded in the following states:

More detail on each project is available at http://www.usbr.gov/research/dwpr.