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Fri April 26, 2013
Local Scientist Discovers Rapid Water Quality Testing Method
We talk to a local scientist who developed a new method of rapidly detecting polluted water that’s likely to become the standard in the United States.
For information on current swimming advisories, chick [here].
The biggest danger you may encounter at the beach this year may not have fins. North Carolina Division of Marine Fisheries Shellfish Sanitation and Recreational Water Quality Division tests 240 ocean beaches and estuarine swimming areas for harmful bacteria. In 2012, there were 22 swimming advisories issued due to contaminated waters in Beaufort, Brunswick, Carteret, Dare, New Hanover, and Pamlico Counties.
A scientist in eastern North Carolina recently developed a new technique that relies on a technology called PCR to test water samples in a faster, more efficient way. PCR is a term you might be familiar with from watching crime scene investigation shows like NCIS or CSI.
“Mack, there’s a DNA test that test HIV. It shortens the window which means I would get an immediate answer. I was hoping that you would authorize getting a PCR kit that is needed to run the test.”
Professor at the University of North Carolina’s Institute of Marine Sciences in Morehead City Dr. Rachel Noble came up with the improved technique that’s quickly becoming the new standard for water quality testing in the United States. She says the traditional way of testing takes 18 to 96 hours from sample to result. Dr. Nobel explains how the process has worked for many years.
“They bring back the sample to the laboratory and they process the sample to put it into a filter or some similar matrix and then they place that material that filter on to some media or in a petri dish often that allows the bacteria to grow.”
With the older method, Noble says beachgoers could be swimming in a contaminated area while the test results are being analyzed.
“This delay is basically causing you problems with accuracy. And along with that you can quickly see that a method that takes 5 minutes or 10 minutes would be preferable.”
While that technology isn’t available yet, Noble has identified a process that dramatically decreases the wait time for results to just a few hours.
“The bottom line is that these are methods to allow you to take small samples whether it be a blood sample, a skin sample, or a water sample in our case and they allow you to target a very specific type of DNA in the sample and make millions and millions of copies of it.”
When testing water to determine if a beach should remain open or be closed, researchers are looking for the presence of a bacteria called enterococcus. Noble uses a machine that causes the bacteria to replicate at a faster rate than what naturally occurs in a petri dish, yielding much faster results. All tests begin with the DNA of a single enterococcus cell.
“After one PCR cycle, or one polymerase chain reaction cycle. You end up with two copies. But the next cycle, you end up with four copies. And with the next cycle, eight copies. The next cycle, 16 copies and so on and so forth. So we’re running 30 to 40 cycles of PCR and those reactions in the cycles are very fast. These reactions are occurring in the order of seconds to minutes. And this machine is amplifying the DNA to a point where you can actually the quantity that you have. And so after 30 to 40 cycles, you could have millions of copies of enterococcus DNA in your sample.”
The final amplified material can be compared against known standards to figure out if the concentration of enterococcus bacteria is at an unsafe level. In addition to testing water at beaches, Noble has made the PCR water quality testing applicable to a variety of water types.
“we’ve examined it and how it functions in all kinds of waters from storm water runoff, which means a creek or river coming towards the ocean. We actually use it in estuaries to do test on oysters for certain types of bacteria that can be present in oysters that can also make people sick. We use the same technique in wastewater samples which basically means it’s coming from a waste water treatment plant. Drinking water, groundwater.”
Because rapid testing is not the standard, for now, the cost is relatively expensive. To fully outfit a lab with the equipment to run the test would be upwards of 60 thousand dollars. And for each sample, 10 to 25 dollars. That’s compared to the traditional method of testing which ranges in cost from 6 to 20 dollars. Noble says her aim is to make the process user friendly and affordable so that more beach water testing can be done and the results known sooner.
“We’d really really like them to be either equal in cost or lower so that you don’t have any increase in expenditures for this ability to protect the public.”
Several eastern North Carolina groups including the State’s Division of Marine Fisheries Shellfish Sanitation and Recreational Water Quality section participated in the training on the new, rapid water quality process. They currently have three people qualified to conduct the testing. The last workshop held by the Institute of Marine Science’s Molecular Training Facility was held in March. Another workshop is planned for Nov. 3 thru the 8th where scientist from around the country will learn the new technique and implement where they live. Noble says making scientists aware of this technology and teaching them how to conduct the rapid testing will decrease the chances that beachgoers are exposed to polluted water.
“If we take a water sample between six and eight o clock in the morning, certainly before noon as people are coming to the beach and putting their beach blankets down and beginning to recreate in the water. You’ve already been able to put a sign up if there’s any kind of contamination of the water.”
Noble plans to continue to improve the technology, making it faster and easier to conduct a water quality sample. Her goal is to create a “dipstick” approach, similar to the way a lifeguard tests pool water sample, that can yield results in just a few minutes.
For more information on swimming advisories along the North Carolina coast, go to the Division of Marine Fisheries website. We've provided a link on our homepage, publicradioeast.org. I'm Jared Brumbaugh.
Information on current swimming advisories: http://portal.ncdenr.org/web/mf/rwq-swim-advisories-current