Welcome to the blog that is going to keep you informed about water issues! Political, social, economic, human health, land use… you name it! It has been my personal goal to educate the public to the need to understand that our water health is dependent on our actions and inaction.
Your community CANprotect your water!
Exploring real world environmental concerns must also include social, economic, political, human health, and natural resource implications. This allows for a comprehensive understanding of complicated environmental matters that do not stop at man-made state lines, or international lines of delineation. Water, genetically modified organisms (GMOs), waste, industrial farming, disaster relief, air quality, carbon sequestration, energy production, and fishing industries, to name a few, all encompass multiple disciplines in both its onset and its potential solutions. Educating the public to environmental sciences as a single discipline, taught from a text, within a classroom, whose antithesis is business, does not convey the entire picture.
The GET WET! Project addresses residential water needs by collaborating with local universities, government representatives, businesses, conservation commissions, ENGOs, parents, and community volunteers to assure all interested parties are heard. Focusing on local environmental issues through school-centered, community-based curriculum increases participation and opens a dialogue regarding local resources, jobs, human health, politics, and economics. Allowing the community to decide which of the concerns they feel deserves the most attention provides an autonomy that may be more palatable.
Engineers at the University of Bath have shown that it’s possible to capture and use energy created by the natural reactions occurring in microorganisms within soil.
A team of chemical and electrical engineers has demonstrated the potential of cheap, simple ‘soil microbial fuel cells’ (SMFCs), buried in the earth to power an electrochemical reactor that purifies water.
The proof-of-concept design was demonstrated during field testing in North-East Brazil that took place in 2019 and showed that SMFCs can purify about three litres of water per day- enough to cover a person’s daily water needs.
The project is a collaboration with a team of geographers from Universidade Federal do Ceará and a team of chemists from Universidade Federal do Rio Grande do Norte.
Testing took place in Icapuí, a fishing village located in a remote semi-arid location where the main source of drinking water is rainwater and access to a reliable power network is scarce.
Rainwater must be chlorinated to be drinkable, and in addition to causing bad taste and odour, uncontrolled chlorination is dangerous to human health — so safe methods to treat water are essential.
Soil microbial fuel cells shown to work in the field
SMFCs generate energy from the metabolic activity of specific microorganisms (electrigens) naturally present in soil, which are able to transfer electrons outside their cells.
The system, developed by staff from Bath’s Department of Chemical Engineering and Department of Electronic & Electrical Engineering, consists of two carbon-based electrodes positioned at a fixed distance apart (4cm) and connected to an external circuit. One electrode, the anode, is buried inside the soil, while the other, the cathode, is exposed to air on the soil surface.
Electrigens populate the surface of the anode and as they ‘consume’ the organic compounds present in soil, they generate electrons. These electrons are transferred to the anode and travel to the cathode via the external circuit, generating electricity.
By building a stack of several SMFCs, and by connecting this to a battery it is possible to harvest and store this energy, and use it to power an electrochemical reactor for water treatment.
A single SMFC unit costs just a few pounds, which could be further reduced with mass production and with the use of local resources for the electrode fabrication.
Cheap and sustainable solution for a chlorination problem
The need for sustainable water purification in the area stems from the fact that the main supply of water is from precipitation, which needs to be chlorinated to be drinkable.
The technology, installed at the EEF Professora Mizinha of Icapuí primary school, creates a small amount of power, which can be used to purify up to three litres of water in about a day. Further research is needed to scale-up its capacity.
The team is aiming to refine the design of the equipment and its efficiency to allow one piece of equipment to purify the water needed by a family in a day. This presents three challenges: generating enough energy; collecting and storing that energy effectively; and treating the water efficiently to ensure quality and drinkability.
Dr Mirella Di Lorenzo, who led the project said: “Using soil microbial fuel cell technology to treat a family’s daily water needs is already achievable in laboratory conditions, but doing so outdoors and with a system that requires minimal maintenance is much trickier, and this has previously proven a barrier to microbial fuel cells being considered effective. This project shows that SMFCs have true potential as a sustainable, low-energy energy source.”
She added: “We’re addressing the issue of water scarcity and energy security in North-East Brazil, which is a semi-arid area. We sought a sustainable way to treat water effectively and make it drinkable. Rainwater is the main source of drinking water in the area, but this is not sterile — our approach in this work points to a way we could solve the issue.
“Another important element of our project is education around sustainable technologies. The field work was performed together with primary school pupils and their teachers. They were trained on the system’s working principles, installation and maintenance.”
During the fieldwork, which took place in 2019, a system was installed at the primary school, where it was tested to ensure it could replicate results previously seen in the lab.
The Brazilian leader of the project, Dr. Adryane Gorayeb, from Federal University of Ceará (UFC), said: “The application of the technology, as well as the educational element of the project, provided a transformative experience to the pupils, that have broadened their world view.
“The pupils helped with the soil microbial fuel cells fabrication and have learned how to handle the technology. They also participated in a dedicated workshop to raise environmental awareness, based on the United Nations Sustainable Development Goals.”make a difference: sponsored opportunity
Jakub Dziegielowski, Benjamin Metcalfe, Paola Villegas-Guzman, Carlos A. Martínez-Huitle, Adryane Gorayeb, Jannis Wenk, Mirella Di Lorenzo. Development of a functional stack of soil microbial fuel cells to power a water treatment reactor: From the lab to field trials in North East Brazil. Applied Energy, 2020; 278: 115680 DOI: 10.1016/j.apenergy.2020.115680
FOR MORE INFORMATION: University of Bath. “Soil-powered fuel cell promises cheap, sustainable water purification: Soil microbial fuel cells proven to be capable of creating energy to filter a person’s daily drinking water in Brazil test.” ScienceDaily. ScienceDaily, 28 October 2020. <www.sciencedaily.com/releases/2020/10/201028082944.htm>.
Microplastics (plastics <5mm) and their negative health impacts have been studied in oceans, rivers, and even soils, and scientists are beginning to grapple with the myriad human health impacts their presence might have. One understudied, but critical, link in the cycle is groundwater, which is often a source of drinking water.
While microplastics in groundwater likely affect human health, only a handful of studies have examined the abundance and movement of microplastics in groundwater. This gap means the potential for adverse health effects remains largely unknown.
At the Geological Society of America’s 2020 Annual Meeting today at 1:30, Teresa Baraza Piazuelo, a Ph.D. candidate at Saint Louis University, will help fill that knowledge gap by presenting new research on groundwater microplastics in a karst aquifer. “There hasn’t been that much research looking at [micro]plastics and groundwater,” Baraza says. “It’s a very new topic. There’s been a boom of research on microplastics in the ocean, even in soils… but to fully understand something, you have to explore it in all its aspects.”
Microplastics pose multiple physical and chemical risks to the ecosystems where they’re present, and those risks are exacerbated by plastics’ longevity in natural environments. “Since they’re plastic, they’re very durable,” Baraza says, “which is why plastic is great. But it doesn’t degrade easily.” Microplastics’ ability to linger in their environments for decades or longer likely has cumulative detrimental effects on both the organisms and quality of the ecosystem. Their chemical threat stems largely from their ability to transport harmful compounds on their surfaces; when organisms at the base of the food chain ingest microplastics, they ingest the toxins, too. As larger organisms consume the smaller ones, the toxins can build up (a process called bioaccumulation), eventually resulting in responses like organ dysfunction, genetic mutation, or death. “Cave ecosystems are known for being super fragile to begin with,” she explains. “All the cave organisms — salamanders, blind fish — are sensitive, so any contaminants that are introduced could damage those ecosystems.”
Groundwater can stay in the same aquifer for tens to hundreds of years, or even longer. Combining that long residence time with plastics’ resistance to degradation means that those chemical effects could effectively build up in the water and in any organisms within it, increasing the likelihood of toxic bioaccumulation. Together, these could result in long-term contamination of water sources with poorly-understood health effects and ecosystem damage.
To understand where microplastics in groundwater come from and how they move through aquifers, Baraza and her Ph.D. advisor have been sampling groundwater from a Missouri cave weekly, all year long, and analyzing its chemistry and microplastics load. Because previous groundwater-microplastics studies have been limited to low-rainfall conditions, they’re also studying how flooding events affect microplastics concentrations in groundwater.
So far, they’ve found that while microplastics do increase in groundwater during a flood event, there’s also a second peak in microplastics after the flooding has begun to wane. Their explanation is that there are two sources of microplastics for groundwater: those that are already in the subsurface, and those that are newly delivered from the surface. “Finding so much plastic later on in the flood, thinking that it could be coming from the surface… is important to understand the sourcing of microplastics in the groundwater,” Baraza says. “Knowing where the plastic is coming from could help mitigate future contamination.”
Their current flood results are only based on one event, but Baraza will continue sampling through the rest of the year — weather permitting. “Flood sampling is hard,” she says, “especially in St. Louis, where the weather is so unpredictable. Sometimes we think it’s going to rain and then it doesn’t rain, and then sometimes it doesn’t seem like it’s going to rain, but it does… we caught a flood a week ago, and we are expecting to catch a couple more floods.” The effort is worth it to determine if flooding events — which are becoming more common under climate change — are highly-effective deliverers of microplastics in groundwater reservoirs.make a difference: sponsored opportunity
FOR MORE INFORMATION: Geological Society of America. “Microplastics in groundwater (and our drinking water) present unknown risk: Presentation at the 2020 Annual Meeting of the Geological Society of America.” ScienceDaily. ScienceDaily, 26 October 2020. <www.sciencedaily.com/releases/2020/10/201026153939.htm>.
Like a baseball slugger whose home run totals rise despite missing more curveballs each season, the U.S. Corn Belt’s prodigious output conceals a growing vulnerability. A new Stanford study reveals that while yields have increased overall — likely due to new technologies and management approaches — the staple crop has become significantly more sensitive to drought conditions. The research, published Oct. 26 in Nature Food, uses a novel approach based on wide differences in the moisture-holding capabilities among soils. The analysis could help lay the groundwork for speeding development of approaches to increase agricultural resilience to climate change.
“The good news is that new technologies are really helping to raise yields, in all types of weather conditions,” said study lead author David Lobell, the Gloria and Richard Kushel Director of the Center on Food Security and the Environment. “The bad news is that these technologies, which include some specifically designed to withstand drought, are so helpful in good conditions that the cost of bad conditions are rising. So there’s no sign yet that they will help reduce the cost of climate change.”
Corn production in the U.S. is a seemingly unstoppable juggernaut. Despite concerns about resistant weeds, climate change and many other factors, the industry has set record yields in five of the last seven years. Likely drivers of these bumper crops include changes in planting and harvesting practices, such as adoption of drought-tolerant varieties, and changes in environmental conditions, such as reduced ozone levels and increased atmospheric carbon dioxide concentrations that generally improve the water-use efficiency of crops.
As climate change intensifies, however, the cost to maintain crop yields will likely increase.
Using county soil maps and satellite-based yield estimates, among other data, the researchers examined fields in the Corn Belt, a nine-state region of the Midwest that accounts for about two-thirds of U.S. corn production. By comparing fields along gradients of drought stress each year, they could identify how sensitivity to drought is changing over time.
Even within a single county, they found a wide range of soil moisture retention, with some soils able to hold twice as much water as others. As might be expected, there were generally higher yields for soils that held more water. They found yield sensitivity to soil water storage in the region increased by 55 percent on average between 1999 and 2018, with larger increases in drier states.
The results made clear soil’s ability to hold water was the primary reason for yield loss. In some cases, soil’s ability to hold an increased amount of moisture was three times more effective at increasing yields than an equivalent increase in precipitation.
So, why have yields become more sensitive to drought? A variety of factors, such as increased crop water needs due to increased plant sowing density may be at play. What is clear is that despite robust corn yields, the cost of drought and global demand for corn are rising simultaneously.
To better understand how climate impacts to corn are evolving over time, the researchers call for increased access to field-level yield data that are measured independently of weather data, such as government insurance data that were previously available to the public but no longer are.
“This study shows the power of satellite data, and if needed we can try to track things from space alone. That’s exciting,” Lobell said. “But knowing if farmers are adapting well to climate stress, and which practices are most helpful, are key questions for our nation. In today’s world there’s really no good reason that researchers shouldn’t have access to all the best available data to answer these questions.”
Lobell is also a professor of Earth System Science in Stanford’s School of Earth, Energy & Environmental Sciences; the William Wrigley Senior Fellow at the Stanford Woods Institute for the Environment and a senior fellow at the Freeman Spogli Institute for International Studies and the Stanford Institute for Economic Policy Research. Study co-authors include Jillian Deines, a postdoctoral research fellow in Stanford’s School of Earth, Energy & Environmental Sciences, and Stefania Di Tommaso, a research data analyst at the Center on Food Security and the Environment.make a difference: sponsored opportunity
Ancient Maya in the once-bustling city of Tikal built sophisticated water filters using natural materials they imported from miles away, according to the University of Cincinnati.
UC researchers discovered evidence of a filter system at the Corriental reservoir, an important source of drinking water for the ancient Maya in what is now northern Guatemala.
A multidisciplinary team of UC anthropologists, geographers and biologists identified crystalline quartz and zeolite imported miles from the city. The quartz found in the coarse sand along with zeolite, a crystalline compound consisting of silicon and aluminum, create a natural molecular sieve. Both minerals are used in modern water filtration.
The filters would have removed harmful microbes, nitrogen-rich compounds, heavy metals such as mercury and other toxins from the water, said Kenneth Barnett Tankersley, associate professor of anthropology and lead author of the study.
“What’s interesting is this system would still be effective today and the Maya discovered it more than 2,000 years ago,” Tankersley said.
UC’s discovery was published in the journal Scientific Reports.
The Maya created this water filtration system nearly 2,000 years before similar systems were used in Europe, making it one of the oldest water treatment systems of its kind in the world, Tankersley said.
Researchers from UC’s College of Arts and Sciences traced the zeolite and quartz to steep ridges around the Bajo de Azúcar about 18 miles northeast of Tikal. They used X-ray diffraction analysis to identify zeolite and crystalline quartz in the reservoir sediments.
At Tikal, zeolite was found exclusively in the Corriental reservoir.
For the ancient Maya, finding ways to collect and store clean water was of critical importance. Tikal and other Maya cities were built atop porous limestone that made ready access to drinking water difficult to obtain for much of the year during seasonal droughts.
UC geography professor and co-author Nicholas Dunning, who has studied ancient civilizations most of his career, found a likely source of the quartz and zeolite about 10 years ago while conducting fieldwork in Guatemala.
“It was an exposed, weathered volcanic tuff of quartz grains and zeolite. It was bleeding water at a good rate,” he said. “Workers refilled their water bottles with it. It was locally famous for how clean and sweet the water was.”
Dunning took samples of the material. UC researchers later determined the quartz and zeolite closely matched the minerals found at Tikal.
UC assistant research professor Christopher Carr, an expert in geographic information system mapping, also conducted work on the UC projects at Bajo de Azúcar and Corriental.
“It was probably through very clever empirical observation that the ancient Maya saw this particular material was associated with clean water and made some effort to carry it back,” Dunning said.
UC anthropology professor emeritus Vernon Scarborough, another co-author, said most research on ancient water management has tried to explain how civilizations conserved, collected or diverted water.
“The quality of water put to potable ends has remained difficult to address,” Scarborough said. “This study by our UC team has opened the research agenda by way of identifying the quality of a water source and how that might have been established and maintained.”
Of course, reconstructing the lives, habits and motivations of a civilization 1,000 years ago is tricky.
“We don’t have absolute proof, but we have strong circumstantial evidence,” Dunning said. “Our explanation makes logical sense.”
“This is what you have to do as an archaeologist,” UC biologist and co-author David Lentz said. “You have to put together a puzzle with some of the pieces missing.”
Lentz said the filtration system would have protected the ancient Maya from harmful cyanobacteria and other toxins that might otherwise have made people who drank from the reservoir sick.
“The ancient Maya figured out that this material produced pools of clear water,” he said.
Complex water filtration systems have been observed in other ancient civilizations from Greece to Egypt to South Asia, but this is the first observed in the ancient New World, Tankersley said.
“The ancient Maya lived in a tropical environment and had to be innovators. This is a remarkable innovation,” Tankersley said. “A lot of people look at Native Americans in the Western Hemisphere as not having the same engineering or technological muscle of places like Greece, Rome, India or China. But when it comes to water management, the Maya were millennia ahead.”make a difference: sponsored opportunity
Kenneth Barnett Tankersley, Nicholas P. Dunning, Christopher Carr, David L. Lentz, Vernon L. Scarborough. Zeolite water purification at Tikal, an ancient Maya city in Guatemala. Scientific Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-75023-7
Mexico has reached a deal to settle its water debts with the US despite widespread protests by Mexican farmers, some of which turned violent.
A bilateral treaty signed in 1944 says the two countries must share water sources along their arid border.
Mexican farmers say they need the water themselves, in what has been one of the driest years in decades.
But the US says Mexico has recently not been fulfilling the agreement and owed almost a year’s worth of water.
Last month, hundreds of Mexican farmers seized La Boquilla dam in Chihuahua state to stop water being diverted to the US, leading to violent clashes with Mexico’s National Guard.
A woman was shot dead in the unrest, in what the National Guard called “a regrettable accident”.
Farmers in the US have been putting pressure on the Trump administration to make Mexico meet its obligations.
Mexican President Andres Manuel Lopez Obrador said Mexico would now make up its shortfall.
“If we need water for human consumption they will provide it and if we have a severe drought they will help us,” he told reporters.
“I want to take the opportunity to thank the United States government for its understanding and solidarity.”
Mexican farmers have been growing crops that use greater volumes of water from the Conchos river, which flows north into the US. It has taken 71% of the water despite only being allowed to use 62% under the treaty and letting the rest flow into the Rio Bravo, which is also known as the Rio Grande, AP reported last month.
The abstract benefits of biochar for long-term storage of carbon and nitrogen on American farms are clear, and now new research from Rice University shows a short-term, concrete bonus for farmers as well.
That would be money. To be precise, money not spent on irrigation.
In the best-case scenarios for some regions, extensive use of biochar could save farmers a little more than 50% of the water they now use to grow crops. That represents a significant immediate savings to go with the established environmental benefits of biochar.
The open-access study appears in the journal GCB-Bioenergy.
Biochar is basically charcoal produced through pyrolysis, the high-temperature decomposition of biomass, including straw, wood, shells, grass and other materials. It has been the subject of extensive study at Rice and elsewhere as the agriculture industry seeks ways to enhance productivity, sequester carbon and preserve soil.
The new model built by Rice researchers explores a different benefit, using less water.
“There’s a lot of biochar research that focuses mostly on its carbon benefits, but there’s fairly little on how it could help stakeholders on a more commercial level,” said lead author and Rice alumna Jennifer Kroeger, now a fellow at the Science and Technology Policy Institute in Washington, D.C. “It’s still an emerging field.”
The study co-led by Rice biogeochemist Caroline Masiello and economist Kenneth Medlock provides formulas to help farmers estimate irrigation cost savings from increased water-holding capacity (WHC) with biochar amendment.
The researchers used their formulas to reveal that regions of the country with sandy soils would see the most benefit, and thus the most potential irrigation savings, with biochar amendment, areas primarily in the southeast, far north, northeast and western United States.
The study analyzes the relationship between biochar properties, application rates and changes in WHC for various soils detailed in 16 existing studies to judge their ability to curtail irrigation.
The researchers defined WHC as the amount of water that remains after allowing saturated soil to drain for a set period, typically 30 minutes. Clay soils have a higher WHC than sandy soils, but sandy soils combined with biochar open more pore space for water, making them more efficient.
WHC is also determined by pore space in the biochar particles themselves, with the best results from grassy feedstocks, according to their analysis.
In one comprehensively studied plot of sandy soil operated by the University of Nebraska-Lincoln’s Agricultural Water Management Network, Kroeger calculated a specific water savings of 37.9% for soil amended with biochar. Her figures included average rainfall and irrigation levels for the summer of 2019.
The researchers noted that lab experiments typically pack more biochar into a soil sample than would be used in the field, so farmers’ results may vary. But they hope their formula will be a worthy guide to those looking to structure future research or maximize their use of biochar.
More comprehensive data for clay soils, along with better characterization of a range of biochar types, will help the researchers build models for use in other parts of the country, they wrote.
“This study draws attention to the value of biochar amendment especially in sandy soils, but it’s important to note that the reason we are calling out sandy soils here is because of a lack of data on finer-textured soils,” Masiello said. “It’s possible that there are also significant financial benefits on other soil types as well; the data just weren’t available to constrain our model under those conditions.”
“Nature-based solutions are gaining traction at federal, state and international levels,” Medlock added, noting the recently introduced Growing Climate Solutions Act as one example. “Biochar soil amendment can enhance soil carbon sequestration while providing significant co-benefits, such as nitrogen remediation, improved water retention and higher agricultural productivity. The suite of potential benefits raises the attractiveness for commercial action in the agriculture sector as well as supportive policy frameworks.”make a difference: sponsored opportunity
J.E. Kroeger, G Pourhashem, K.B Medlock, C.A Masiello. Water Cost Savings from Soil Biochar Amendment: A Spatial Analysis. GCB Bioenergy, 2020; DOI: 10.1111/gcbb.12765
FOR MORE INFORMATION: Rice University. “Biochar helps hold water, saves money: Rice study shows sandy soils benefit most by retaining water, cutting irrigation needs.” ScienceDaily. ScienceDaily, 19 October 2020. <www.sciencedaily.com/releases/2020/10/201019125519.htm>.
Southwest Research Institute developed an integrated hydrologic computer model to evaluate the impact of different types of wastewater disposal facilities on the Edwards Aquifer, the primary water source for San Antonio and its surrounding communities. The research results will guide authorities on what actions to take to protect the quality and quantity of water entering the aquifer.
The two-year study, which concluded in July, was funded through the City of San Antonio’s Edwards Aquifer Protection Plan (EAPP) under the direction of the San Antonio River Authority. The tax-funded EAPP identifies and protects land and water crucial to the well-being of the aquifer. SwRI researchers selected the nearly 25-square-mile Helotes Creek Watershed in northwest Bexar County as the study area. They combined surface and groundwater data, including streamflow and groundwater elevations, along with climate, soil and topographic input to create an integrated model of the watershed.
“We chose the Helotes Creek Watershed because it is entirely in the contributing and recharge zones of the Edwards Aquifer. Rainfall and bodies of water over these key zones replenish the aquifer,” said SwRI’s Mauricio Flores, who helped lead the project. “Our findings are intended to provide insight on which wastewater practices offer the best protection for the aquifer when considering new development in these critical zones.”
SwRI’s Water Resources group constructed a base case model, replicating what is happening now with septic systems already located in the watershed area. Starting with that data, they evaluated what would happen if they added wastewater disposal facilities to the region. Scenarios evaluated included additional septic or onsite sewage systems, facilities that reuse wastewater for irrigation and systems that dispose of wastewater in nearby creeks or rivers.
“We considered a range of hypothetical scenarios. The size and capacity of the hypothesized wastewater facilities were consistent with possible residential development in the Helotes Creek Watershed area,” said Dr. Ronald Green, SwRI technical advisor and project manager. “Our results predicted that installing additional wastewater systems in the region, regardless of type, would increase the amount of wastewater discharged to the environment and significantly degrade the watershed and the quality of water recharging the Edwards Aquifer.”
The Helotes Creek Watershed study was the first of its kind in this area. The findings are applicable to most watersheds in the aquifer’s contributing and recharge zones. However, SwRI researchers recommend expanding the study to outside of Bexar County to demonstrate how development and increased wastewater disposal would impact these areas.
“The results of the study not only highlight the impact development could have on the aquifer, but can also be used to prioritize protection of land, rivers and streams that recharge the aquifer,” said Flores. “Our findings show this type of research is vital to protecting important water resources.”
The City of San Antonio is conducting additional EAPP-funded research aimed at protecting the aquifer. An official city report, which will include the SwRI study, is expected in 2023.make a difference: sponsored opportunity
A study led by Brown University researchers sheds new light on how pollutants found in firefighting foams are distributed in water and surface soil at release sites. The findings could help researchers to better predict how pollutants in these foams spread from the spill or release sites — fire training areas or airplane crash sites, for example — into drinking water supplies.
Firefighting foams, also known as aqueous film forming foams (AFFF), are often used to combat fires involving highly flammable liquids like jet fuel. The foams contain a wide range of per- and polyfluoroalkyl substances (PFAS) including PFOA, PFOS and FOSA. Many of these compounds have been linked to cancer, developmental problems and other conditions in adults and children. PFAS are sometimes referred to as “forever chemicals” because they are difficult to break down in the environment and can lead to long-term contamination of soil and water supplies.
“We’re interested in what’s referred to as the fate and transport of these chemicals,” said Kurt Pennell, a professor in Brown’s School of Engineering and co-author of the research. “When these foams get into the soil, we want to be able to predict how long it’s going to take to reach a water body or a drinking water well, and how long the water will need to be treated to remove the contaminants.”
It had been shown previously that PFAS compounds tend to accumulate at interfaces between water and other substances. Near the surface, for example, PFAS tend to collect at the air-water interface — the moist but unsaturated soil at the top of an aquifer. However, prior experiments showing this interface activity were conducted only with individual PFAS compounds, not with complex mixtures of compounds like firefighting foams.
“You can’t assume that PFOS or PFOA alone are going to act the same way as a mixture with other compounds,” said Pennell, who is also a fellow at the Institute at Brown for Environment and Society. “So this was an effort to try to tease out the differences between the individual compounds, and to see how they behave in these more complex mixtures like firefighting foams.”
Using a series of laboratory experiments described in the journal Environmental Science and Technology, Pennell and his colleagues showed that the firefighting foam mixture does indeed behave much differently than individual compounds. The research showed that the foams had a far greater affinity for the air-water interface than individual compounds. The foams had more than twice the interface activity of PFOS alone, for example.
Pennell says that insights like these can help researchers to model how PFAS compounds migrate from contaminated sites.
“We want to come up with the basic equations that describe the behavior of these compounds in the lab, then incorporate those equations into models that can be applied in field,” Pennell said. “This work is the beginning of that process, and we’ll scale it up from here.”
Ultimately, the hope is that a better understanding of the fate and transport of these compounds could help to identify wells and waterways at risk for contamination, and aid in cleaning those sites up.make a difference: sponsored opportunity
jed costanza, Linda M. Abriola, Kurt D Pennell. Aqueous film-forming foams exhibit greater interfacial activity than PFOA, PFOS, or FOSA. Environmental Science & Technology, 2020; DOI: 10.1021/acs.est.0c03117
Researchers at MIT and elsewhere have significantly boosted the output from a system that can extract drinkable water directly from the air even in dry regions, using heat from the sun or another source.
The system, which builds on a design initially developed three years ago at MIT by members of the same team, brings the process closer to something that could become a practical water source for remote regions with limited access to water and electricity. The findings are described today in the journal Joule, in a paper by Professor Evelyn Wang, who is head of MIT’s Department of Mechanical Engineering; graduate student Alina LaPotin; and six others at MIT and in Korea and Utah.
The earlier device demonstrated by Wang and her co-workers provided a proof of concept for the system, which harnesses a temperature difference within the device to allow an adsorbent material — which collects liquid on its surface — to draw in moisture from the air at night and release it the next day. When the material is heated by sunlight, the difference in temperature between the heated top and the shaded underside makes the water release back out of the adsorbent material. The water then gets condensed on a collection plate.
But that device required the use of specialized materials called metal organic frameworks, or MOFs, which are expensive and limited in supply, and the system’s water output was not sufficient for a practical system. Now, by incorporating a second stage of desorption and condensation, and by using a readily available adsorbent material, the device’s output has been significantly increased, and its scalability as a potentially widespread product is greatly improved, the researchers say.
Wang says the team felt that “It’s great to have a small prototype, but how can we get it into a more scalable form?” The new advances in design and materials have now led to progress in that direction.
Instead of the MOFs, the new design uses an adsorbent material called a zeolite, which in this case is composed of a microporous iron aluminophosphate. The material is widely available, stable, and has the right adsorbent properties to provide an efficient water production system based just on typical day-night temperature fluctuations and heating with sunlight.
The two-stage design developed by LaPotin makes clever use of the heat that is generated whenever water changes phase. The sun’s heat is collected by a solar absorber plate at the top of the box-like system and warms the zeolite, releasing the moisture the material has captured overnight. That vapor condenses on a collector plate — a process that releases heat as well. The collector plate is a copper sheet directly above and in contact with the second zeolite layer, where the heat of condensation is used to release the vapor from that subsequent layer. Droplets of water collected from each of the two layers can be funneled together into a collecting tank.
In the process, the overall productivity of the system, in terms of its potential liters per day per square meter of solar collecting area (LMD), is approximately doubled compared to the earlier version, though exact rates depend on local temperature variations, solar flux, and humidity levels. In the initial prototype of the new system, tested on a rooftop at MIT before the pandemic restrictions, the device produced water at a rate “orders of magnitude” greater that the earlier version, Wang says.
While similar two-stage systems have been used for other applications such as desalination, Wang says, “I think no one has really pursued this avenue” of using such a system for atmospheric water harvesting (AWH), as such technologies are known.
Existing AWH approaches include fog harvesting and dew harvesting, but both have significant limitations. Fog harvesting only works with 100 percent relative humidity, and is currently used only in a few coastal deserts, while dew harvesting requires energy-intensive refrigeration to provide cold surfaces for moisture to condense on — and still requires humidity of at least 50 percent, depending on the ambient temperature.
By contrast, the new system can work at humidity levels as low as 20 percent and requires no energy input other than sunlight or any other available source of low-grade heat.
LaPotin says that the key is this two-stage architecture; now that its effectiveness has been shown, people can search for even better adsorbent materials that could further drive up the production rates. The present production rate of about 0.8 liters of water per square meter per day may be adequate for some applications, but if this rate can be improved with some further fine-tuning and materials choices, this could become practical on a large scale, she says. Already, materials are in development that have an adsorption about five times greater than this particular zeolite and could lead to a corresponding increase in water output, according to Wang.
The team continues work on refining the materials and design of the device and adapting it to specific applications, such as a portable version for military field operations. The two-stage system could also be adapted to other kinds of water harvesting approaches that use multiple thermal cycles per day, fed by a different heat source rather than sunlight, and thus could produce higher daily outputs.make a difference: sponsored opportunity
Alina LaPotin, Yang Zhong, Lenan Zhang, Lin Zhao, Arny Leroy, Hyunho Kim, Sameer R. Rao, Evelyn N. Wang. Dual-Stage Atmospheric Water Harvesting Device for Scalable Solar-Driven Water Production. Joule, 2020; DOI: 10.1016/j.joule.2020.09.008
FOR MORE INFORMATION: Massachusetts Institute of Technology. “Solar-powered system extracts drinkable water from ‘dry’ air: Engineers have made their initial design more practical, efficient, and scalable.” ScienceDaily. ScienceDaily, 14 October 2020. <www.sciencedaily.com/releases/2020/10/201014114648.htm>.
Located within the most isolated archipelago in the world, Hawai’i is critically dependent on a clean, ample supply of fresh water. New research led by University of Hawai’i at M?noa scientists indicates that rain brought to the islands by hurricanes and Kona storms can often be the most important precipitation for re-supplying groundwater in many regions of the island of O’ahu.
“The majority of Hawai’i’s freshwater comes from groundwater,” said Daniel Dores, lead author and groundwater and geothermal researcher in the UH M?noa School of Ocean and Earth Science and Technology. “In this study, we investigated the relationship between trade wind showers, major rainfall events like Kona storms, and groundwater.”
Dores and a team of scientists from SOEST and the Hawai’i Department of Health collected rainfall around the island of Oahu and analyzed the stable isotopes of rainwater, chemical signatures in the water molecules. They compared the chemical signatures in rainwater to those of groundwater to determine the source of water in the aquifers — event-based rainfall or trade wind-related rain.
“Because windward and mauka showers are so common, it is easy to assume that is the main source of our drinking water,” said Dores. “Also, large rainfall events such as Kona storms result in significant runoff into the oceans. However, our research found that a lot of the rain from Kona storms makes it into our groundwater aquifers and is an important source of our drinking water.”
Hawai’i is experiencing substantial changes in trade wind weather patterns, and precipitation events could become more extreme. Some of the study co-authors will continue research to understand more about local and regional groundwater recharge and water quality.
“By better understanding how our groundwater is impacted by these extreme precipitation events, we can better protect the resource itself,” said Dores.make a difference: sponsored opportunity
Daniel Dores, Craig R. Glenn, Giuseppe Torri, Robert B. Whittier, Brian N. Popp. Implications for groundwater recharge from stable isotopic composition of precipitation in Hawai’i during the 2017–2018 La Niña. Hydrological Processes, 2020; DOI: 10.1002/hyp.13907