When officials close a public beach because the water is contaminated, those announcements may not come until days after the E. coli level has reached dangerous levels – and likewise, the order to reopen a beach may not happen until days after the level has dropped.
That’s due to the fact that samples have to be sent off site for analysis, which often takes a day or two.
Not any more. Now, Rolf Deininger, a professor of Environmental Health Sciences in the University of Michigan School of Public Health, and Jiyoung Lee, a post-doctoral research fellow at the School of Public Health, have developed a fast, portable testing unit that can yield results on the spot in about 45 minutes.
Michigan Great Lakes Protection Fund helped finance the development, though now Deininger is waiting on funding for full field testing.
Deininger, who has helped design similar testing methods for drinking water and pool water, tested this new process at beaches in Michigan’s Genesee, Macomb, Monroe and Washtenaw counties. Deininger used his process to test water at the same time the county health departments conducted traditional testing to show that they both got the same results but in different time frames.
Ultimately, the goal is to have the equipment be both portable and simple enough that a lifeguard could test the water each morning before allowing the public to swim at a beach that day.
The challenge with testing beach water, as opposed to pool or drinking water, is to work through the great amount of natural debris near the shore. An effective test needs to filter out enough debris to keep it from clogging the test unit’s filter, but not do so much pre-treating as to tamper with results.
Here’s how it works: the test itself uses a process called immunomagnetic separation, which uses tiny paramagnetic beads coated with antibodies specific to E. coli. Testing involves mixing the beads with a water sample. Treated beads attach to bacteria and the beads with attached bacteria are pulled out with a magnet, and later mixed into clean water. Bacteria are lysed, or broken open, to release adenosine triphosphate, a substance known as ATP found in every living cell. Then luciferine/luciferase – the substances that make fireflies glow – are added to the clean water suspension because they light up when they interact with bacteria’s ATP. The amount of light generated is measured with a hand-held luminometer and the light reading tells whether the water sample is safe.
Equipment needed for the new test runs about $5,000, and the disposable supplies for each test are about $5, which Deininger says is comparable to existing technology.