Electrodialysis Identified as Potential Way to Remove Salt from Fracking Waste Water

Fracking is a highly controversial and divisive issue. Proponents argue that it could be the biggest energy boom since the Arabian oil fields were opened almost 80 years ago, but this comes at a serious cost to the environment. Among the detrimental effects of the process is that the waste water it produces is over five times saltier than seawater, which is, to put it mildly, not good. A research team led by MIT that has found an economical way of removing salt from fracking waste water that promises to not only reduce pollution, but conserve water as well.

Hydraulic fracturing, or fracking uses water pressure to shatter oil shale formations, releasing oil and natural gas from deposits that would otherwise be uneconomical to exploit. One of the major problems with this process is that as the water is pumped through the oil shale, it picks up salt, and by the time it’s pumped back to the surface, it’s extremely salty – in the order of 192,000 parts per million (ppm). In contrast, seawater is only 35,000 ppm. This makes it not only too salty to be disposed of without reprocessing, but it’s also too salty to be reused in fracking.

The MIT research team sought to find the most cost effective means of desalinating fracking water. They found that electrodialysis is not only a promising way of cleaning up fracking waste water, but could also provide oil explorers with a closed-loop system that places less demand on local water supplies.

Diagram of the MIT desalinating process (Image: Jose-Luis Olivares/MIT)

Electrodialysis is not a new technology. It was developed half a century ago and is currently used to desalinate brackish water and seawater, for small-scale drinking water plants, in food processing, greenhouses, hydroponics, and desalinating various chemicals.

In electrodialysis, a series of membranes divide streams of water of different salinity into stacks. An electric current on either side of the stack draws the sodium and chlorine ions of the salt across the membranes, leaving the water behind. The end result is a very salty stream of water, and a relatively pure stream.

According to MIT, electrodialysis has been overlooked as a way of treating fracking waste water until now because the process was thought to only be effective on water that wasn't of such high salinity. However, the team’s research found that electrodialysis is not only practical, but economically viable – not the least because water conducts electricity better as it gets saltier, therefore the electrodialysis process works better.

The team found that the key was to desalinate the water in stages and rather than making the water potable, it only had to be cleaned up enough to be pumped back into a fracking well and used again. This not only has the potential to reduce the costs, but also alleviate pressure on local water supplies and minimize the need for disposal of contaminated water.

In addition, the process described by MIT is extremely flexible, allowing engineers to "dial" the saline output. This is important, because reusing the water will mean finding the most effective level of salinity for fracking, which is a question still to be answered.

According to the team, there’s still a lot of work to be done before the process is practical. In addition to tweaking the electrodialysis design, laboratory work needs to be done on removing oil, gas, and mineral contaminants that may clog the membranes, and new equipment needs to be designed, built, and tested to apply the new technology.

Rivers Recover Natural Conditions Quickly Following Dam Removal

A study of the removal of two dams in Oregon suggests that rivers can return surprisingly fast to a condition close to their natural state, both physically and biologically, and that the biological recovery might outpace the physical recovery.

The analysis, published by researchers from Oregon State University in the journal PLOS One, examined portions of two rivers -- the Calapooia River and Rogue River. It illustrated how rapidly rivers can recover, both from the long-term impact of the dam and from the short-term impact of releasing stored sediment when the dam is removed.

Most dams have decades of accumulated sediment behind them, and a primary concern has been whether the sudden release of all that sediment could cause significant damage to river ecology or infrastructure.

However, this study concluded that the continued presence of a dam on the river constituted more of a sustained and significant alteration of river status than did the sediment pulse caused by dam removal.

"The processes of ecological and physical recovery of river systems following dam removal are important, because thousands of dams are being removed all over the world," said Desirée Tullos, an associate professor in the OSU Department of Biological and Ecological Engineering.

"Dams are a significant element in our nation's aging infrastructure," she said. "In many cases, the dams haven't been adequately maintained and they are literally falling apart. Depending on the benefits provided by the dam, it's often cheaper to remove them than to repair them."

According to the American Society of Civil Engineers, the United States has 84,000 dams with an average age of 52 years. Almost 2,000 are now considered both deficient and "high hazard," and it would take $21 billion to repair them. Rehabilitating all dams would cost $57 billion. Thus, the removal of older dams that generate only modest benefits is happening at an increasing rate.

In this study, the scientists examined the two rivers both before and after removal of the Brownsville Dam on the Calapooia River and the Savage Rapids Dam on the Rogue River. Within about one year after dam removal, the river ecology at both sites, as assessed by aquatic insect populations, was similar to the conditions upstream where there had been no dam impact.

Recovery of the physical structure of the river took a little longer. Following dam removal, some river pools downstream weren't as deep as they used to be, some bars became thicker and larger, and the grain size of river beds changed. But those geomorphic changes diminished quickly as periodic floods flushed the river system, scientists said.

Within about two years, surveys indicated that the river was returning to the pre-removal structure, indicating that the impacts of the sediment released with dam removal were temporary and didn't appear to do any long-term damage.

Instead, it was the presence of the dam that appeared to have the most persistent impact on the river biology and structure -- what scientists call a "press" disturbance that will remain in place so long as the dam is there.

This press disturbance of dams can increase water temperatures, change sediment flow, and alter the types of fish, plants and insects that live in portions of rivers. But the river also recovered rapidly from those impacts once the dam was gone.

It's likely, the researchers said, that the rapid recovery found at these sites will mirror recovery on rivers with much larger dams, but more studies are needed.

For example, large scale and rapid changes are now taking place on the Elwha River in Washington state, following the largest dam removal project in the world. The ecological recovery there appears to be occurring rapidly as well. In 2014, Chinook salmon were observed in the area formerly occupied by one of the reservoirs, the first salmon to see that spot in 102 years.

"Disturbance is a natural river process," Tullos said. "In the end, most of these large pulses of sediment aren't that big of a deal, and there's often no need to panic. The most surprising finding to us was that indicators of the biological recovery appeared to happen faster than our indicators of the physical recovery."

The rates of recovery will vary across sites, though. Rivers with steeper gradients, more energetic flow patterns, and non-cohesive sediments will recover more quickly than flatter rivers with cohesive sediments, researchers said.

This research was supported by the Oregon Watershed Enhancement Board, the National Oceanic and Atmospheric Association and the National Marine Fisheries Service. It was a collaboration of researchers from the OSU College of Agricultural Sciences, College of Engineering, and College of Science.

Source: Oregon State University.

Small Spills at Gas Stations Could Cause Significant Public Health Risks Over Time

Source: Johns Hopkins Bloomberg School of Public Health
Summary: A new study suggests that drops of fuel spilled at gas stations - which occur frequently with fill-ups - could cumulatively be causing long-term environmental damage to soil and groundwater in residential areas in close proximity to the stations.

Few studies have considered the potential environmental impact of routine gasoline spills and instead have focused on problems associated with large-scale leaks. Researchers with the Johns Hopkins Bloomberg School of Public Health, publishing online Sept. 19 in the Journal of Contaminant Hydrology, developed a mathematical model and conducted experiments suggesting these small spills may be a larger issue than previously thought.

"Gas station owners have worked very hard to prevent gasoline from leaking out of underground storage tanks," says study leader Markus Hilpert, PhD, a senior scientist in the Department of Environmental Health Sciences in the Johns Hopkins Bloomberg School of Public Health. "But our research shows we should also be paying attention to the small spills that routinely occur when you refill your vehicle's tank."

Over the lifespan of a gas station, Hilpert says, concrete pads underneath the pumps can accumulate significant amounts of gasoline, which can eventually penetrate the concrete and escape into underlying soil and groundwater, potentially impacting the health of those who use wells as a water source. Conservatively, the researchers estimate, roughly 1,500 liters of gasoline are spilled at a typical gas station each decade.

"Even if only a small percentage reaches the ground, this could be problematic because gasoline contains harmful chemicals including benzene, a known human carcinogen," Hilpert says. Hilpert and Patrick N. Breysse, PhD, a professor in the Department of Environmental Health Sciences, developed a mathematical model to measure the amount of gasoline that permeates through the concrete of the gas-dispensing stations and the amount of gasoline that vaporizes into the air.

The model demonstrates that spilled gasoline droplets remain on concrete surfaces for minutes or longer, and a significant fraction of spilled gasoline droplets infiltrate into the pavement, as concrete is not impervious.

"When gasoline spills onto concrete, the droplet will eventually disappear from the surface. If no stain is left behind, there has been a belief that no gasoline infiltrated the pavement, and all of it evaporated," Hilpert says. "According to our laboratory-based research and supported by our mathematical model, this assumption is incorrect. Our experiments suggest that even the smallest gasoline spills can have a lasting impact."

Since the health effects of living near gasoline stations have not been well studied, Breysse says there is an urgency to look more closely, especially since the new trend is to build larger filling stations with many more pumps. These stations continue to be located near residential areas where soil and groundwater could be affected.

"The environmental and public health impacts of chronic gasoline spills are poorly understood," says Breysse. "Chronic gasoline spills could well become significant public health issues since the gas station industry is currently trending away from small-scale service stations that typically dispense around 100,000 gallons per month to high-volume retailers that dispense more than 10 times this amount."

"In a perfect world, it would be ideal to avoid chronic spills," Hilpert says. "However, if these spills do occur, it is also important to prevent rainwater from flowing over the concrete pads underneath the pumps. Otherwise, storm runoff gets contaminated with benzene and other harmful chemicals and can infiltrate into adjacent soil patches or form stormwater that may end up in natural bodies of water."

Story Source: The above story is based on materials provided by Johns Hopkins Bloomberg School of Public Health.

Surfactants, Such as Soaps and Detergents, Do Not Harm the Environment, Study Suggests

Source: Aarhus University
Summary: What happens to soap and detergent surfactants when they run down the drain? Do they seep into the groundwater, lakes and streams, where they could pose a risk to fish and frogs? Not likely. This is shown in a new and very comprehensive report of the potential impact on the environment of the enormous amounts of common surfactants used day in and day out by consumers all over the world.

Senior researcher Hans Sanderson keeps an eye on laboratory technician Pia Petersen as she pours soapsuds down the drain with a clear conscience. They are both employed at the Department of Environmental Science, AU Roskilde.
Credit: Steen Voigt, Aarhus University

You can brush your teeth, and wash yourself and your clothes with a clear conscience. The most common soaps, shampoos and detergents actually pose a minimal risk to the environment. This is the conclusion of a comprehensive survey that covers more than 250 scientific studies over several decades.

When you take a shower and rinse the soap and shampoo off your body, the foam conveniently disappears between your toes and down the drain. Have you ever thought about what happens to the surfactants afterwards? Whether they seep into the groundwater, lakes and streams, where they could pose a risk to fish and frogs?

Not likely. This is shown in a new and very comprehensive report of the potential impact on the environment of the enormous amounts of common surfactants used day in and day out by consumers all over the world.

"We humans use several million tons of surfactants a year on a global scale. It amounts to billions of kilos, so these are substances that you really don't want to release into the environment unless you're thoroughly familiar with them," says senior researcher Hans Sanderson, Department of Environmental Science, Aarhus University, who is one of the authors of the report.

More Than 250 Studies

For the purpose of promoting the sustainable use of surfactants, the researchers analysed their findings regarding the use, disposal, treatment and risk to the aquatic environment of the most important surfactant ingredients in North America. Although the studies are based in North America, they nevertheless apply on a global scale because they are more or less identical all over the world.

The result is a 100-page virtually encyclopaedic list that sums up more than 250 scientific studies spanning forty to fifty years, at an overall cost of approximately USD 30 million.

"It's the most comprehensive and definitive report to date regarding the environmental properties of detergent substances in soap products -- in other words, personal care and cleaning products," says Hans Sanderson.

Soap is Rapidly Degraded

The report shows that when the substances are used correctly and responsibly, and once they have been through a proper treatment plant, the risk to the surrounding environment is very low.

"The substances are made so that they degrade rapidly and thus don't pose a risk to the environment. I can't think of any other substances released into the environment in such large amounts via everyday use by all of us. It's the most commonly used substances of all that go directly into the wastewater, so it's important to keep track of them and ensure that there are no unpleasant surprises in the treatment plants or in the environment," says Hans Sanderson.

How Do Surfactants Work?

Surfactants have a special ability to dissolve fat while at the same time being water soluble. This is because they consist of components that have a hydrophilic head and a hydrophobic tail. The hydrophobic tails repel water but are fond of fat. This means that the tails are the ones that dissolve the fat when we wash ourselves with soap. The surfactant's hydrophilic heads ensure that the fat is carried away in the rinse water.

Story Source: The above story is based on materials provided by Aarhus University.