Gizmorama - September 3, 2018
How do you remove contaminants from storm water? With sand, of course! Well, engineered mineral-coated sand. Before you go to the beach check this out...
Learn about this and more interesting stories from the scientific community in today's issue.
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*-- Engineered sand removes contaminants from stormwater --*
Scientists have engineered mineral-coated sand to remove contaminants from storm water. In places where water resources are strained, engineered sand could transform storm water into a valuable asset.
"The way we treat storm water, especially in California, is broken. We think of it as a pollutant, but we should be thinking about it as a solution," Joseph Charbonnet, a graduate student in civil and environmental engineering at the University of California, Berkeley, said in a news release. "We have developed a technology that can remove contamination before we put it in our drinking water in a passive, low-cost, non-invasive way using naturally-occurring minerals."
Afraid of the toxic chemicals and pollutants picked up as storm water runs across herbicide-soaked lawns, down oil-soaked streets and past overflowing sewers, most cities do their best to divert runoff away from water reservoirs and into rivers and streams.
The latest research -- published Thursday in the journal Environmental Science and Technology -- suggests this unwanted storm water, if treated properly, could provide a lifeline to water-strapped cities like Los Angeles.
Charbonnet and his researcher adviser, David Sedlak, are currently working with a local community in the Sun Valley neighborhood of Los Angeles to turn a 46-acre gravel pit into a wetland outfitted with a water filtration system.
The project, a scaled-up version of a rain garden, will see storm water diverted to the wetland where it will pass through layers of the mineral-coated sand before seeping back into underground aquifers.
"Before we built the buildings, roads and parking lots that comprise our cities, rainwater would percolate into the ground and recharge groundwater aquifers," said Sedlak, a professor of civil and environmental engineering at UC Berkeley. "As utilities in water stressed regions try to figure out how to get urban storm water back into the ground, the issue of water quality has become a major concern. Our coated sands represent an inexpensive, new approach that can remove many of the contaminants that pose risks to groundwater systems where storm water is being infiltrated."
In the lab, Charbonnet mixed sand with two types of manganese, which react to form manganese oxide. The mineral coating binds and reacts with organic toxins, including herbicides, pesticides and harmful chemicals like bisphenol-A, breaking them down into smaller, less toxic molecules that are more easily biodegraded.
While engineered sand can't totally purify contaminated water, it can be combined with other water treatments to turn storm water into a safe source of drinking water.
In tests, Charbonnet found the sand effectively removed almost all of the BPA from a contaminated water. However, the sand's decontamination abilities diminished over time. To recharge the sand's ability to clean water, he exposed the sand to a solution containing a low concentration of chlorine. The solution boosted the mineral coating's reactivity.
"If you have to come in every year or two and dig up this sand and replace it, that is incredibly labor intensive, so in order to make this useful for community stakeholders it's really important that this stuff can be regenerated in place," Charbonnet said.
Even in places where water isn't in short supply, improved stormwater filtration systems could improve the ecological health of local water ways. In the Pacific Northwest, studies have shown contaminated storm water is harming local salmon populations. Elsewhere, storm water runoff has been blamed for fueling toxic algae blooms that threaten fish stocks and endangered species.
*-- Opportunity rover expected to call home as Martian dust storm clears --*
The weeks-long Martian dust storm is waning, and Opportunity rover can finally see clearly. NASA scientists think the rover will soon receive enough sunlight to recharge its batteries and resume its science mission.
"The sun is breaking through the haze over Perseverance Valley," John Callas, Opportunity project manager at NASA's Jet Propulsion Laboratory, said in a news release.
Mars' tau level is the measure of the concentration of particulate matter in the Martian atmosphere. Once the tau level surrounding Opportunity dips below 1.5, scientists will attempt to resume communication with the rover.
Scientists haven't traded messages with Opportunity since June 10.
While Mars' massive dust storms, which crop up every several years, can disrupt on-the-ground scientific missions, they also offer scientists a unique opportunity to study Mars' atmosphere and weather patterns.
Planetary scientists still don't entirely understand how and why Martian dust storms form and grow. But with each new storm, scientists gain a new dataset to aid analysis and modeling efforts.
Scientists have been tracking the progress of the storm and estimating tau levels using photographs captured by the NASA's Mars Reconnaissance Orbiter and its Mars Color Imager.
"The dust haze produced by the Martian global dust storm of 2018 is one of the most extensive on record," said MRO scientist Rich Zurek. "MARCI images of the Opportunity site have shown no active dust storms for some time within 3,000 kilometers [about 1,900 miles] of the rover site."
Even though the skies are clearing, scientists can't be certain of the health of Opportunity's operation systems. It's possible the dust storm caused damage.
"In a situation like this you hope for the best but plan for all eventualities," said Callas. "We are pulling for our tenacious rover to pull her feet from the fire one more time. And if she does, we will be there to hear her."
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