[Pharmwaste] ultrasound to destroy pharms in water
Laurie.Tenace at dep.state.fl.us
Mon Dec 12 11:35:23 EST 2011
Every time we flush the toilet, some of the compounds and medicines we take every day end up in our streams, rivers and lakes.
These "emerging contaminants" include antibiotics, birth-control drugs, antidepressants and caffeine.
As scientists better understand the threat these pollutants pose to wildlife and people, Ohio State University researchers are developing a method to destroy them before they cause harm.
A process that fires high-frequency sound waves through water holds great promise, said Linda Weavers, an OSU environmental engineer.
The idea is based on a similar technique she helped develop that uses ultrasound to clean mercury from lake and stream bottoms. " It works reasonably fast," Weavers said. "You flip a switch, it works, and you don't have to use a lot of chemicals."
For years, environmental studies have detected a host of drugs, chemicals and compounds in waterways across the United States.
An October 2010 U.S. Geological Survey study of the Scioto River system found 12 antibiotics in the water. The study also found three antibiotics in Columbus' treated drinking water.
Other studies have found that at least 17 pollutants, including caffeine and the mosquito repellant DEET, also are present in the city's drinking water.
In each case, the concentration of a specific drug or compound was at a level 1,000 to 10,000 times lower than other, more-commonly detected pollutants.
There are no government limits for these pollutants in streams or drinking water. Scientists who study them say they don't know whether limits are necessary.
Jeffrey Reutter, director of the OSU Sea Grant Program and Stone Laboratory on Lake Erie, said that even at small concentrations, fish and aquatic wildlife are constantly exposed to the chemicals and drugs we flush daily.
"There's no way they can get out of it," Reutter said.
Past studies have detected antidepressants in fish brains. Others suggest a link between human birth-control drugs and fish reproductive problems. That's why Ohio Sea Grant has spent about $97,000 over the past two years to help fund Weavers' research.
Here's how her method works: Weavers shoots sound waves through water contaminated with prescription antibiotics.
The pressure created by each sound wave helps form microscopic bubbles in the water. When the bubbles collapse, the heat of the implosion destroys some of the compounds. The implosions also create oxygen and oxygen-hydrogen radicals that chemically react with and break down the compounds.
In earlier experiments, Weavers used ultrasound bubbles to break up mercury, a potent neurotoxin from mud found in lake and stream bottoms, so it could be absorbed by genetically engineered algae.
Where drugs, caffeine and other compounds are concerned, algae are unnecessary; the bubbles break down the chemicals by themselves.
For example, the ultrasound treatment removed half the concentration of ibuprofen from water in less than two minutes. Half the antibiotic ciprofloxacin was removed in 5.5 minutes, Weavers said.
In another experiment that added bits of organic material from a swamp to the water, the ultrasound treatment took 10 minutes to 2 hours to achieve the same results. The higher the concentration of organic material, the longer the process took, Weavers said.
She said a third round of experiments will use wastewater from the discharge of a sewage-treatment plant. Much of the emerging contaminants found in streams pass through sewage treatment.
Weavers said she wants to see how compounds from treated sewage affect the ultrasound process. She said the experiments also will test different ultrasound frequencies.
Weavers said the process could be used to help treat sewage and drinking water.
She said the method could be superior to other drinking-water treatment systems that rely on membranes or carbon filters to screen pollutants. They have to be replaced.
Columbus officials said that, until there are government standards requiring the removal of drugs and other compounds, cities probably won't look into adopting such a treatment.
"I think first we would have to have a reason to look at it," said Lynn Kelly, the city's water-supply and treatment coordinator. "Then we would have to look at the reliability, effectiveness and expense of the process."
That doesn't mean the city isn't concerned about emerging contaminants. The water division paid $125,000 to help fund the Geological Survey's Scioto River research.
Environmental Specialist III
Waste Reduction Section
Florida Department of Environmental Protection
2600 Blair Stone Rd., MS 4555
Tallahassee FL 32399-2400
Laurie.Tenace at dep.state.fl.us
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