Study author David Lerner checks one of the submerged tampons. Photo by Lerner/University of Sheffield
SHEFFIELD, England, March 31 (UPI) -- Researchers at the University of Sheffield have found a novel use for tampons. They're begun employing them in the fight against pollution -- or more specifically, as a method for identifying where wastewater is leaking into streams and rivers.
Most tampons are made of natural, untreated cotton, a material that readily absorbs a class of chemicals called optical brighteners. Optical brightening agents (OBAs), which have a "whitening effect" and also enhance color brightness, are used in toilet paper, detergents and shampoos. That makes them an ideal indicator of the presence of wastewater -- from baths, washing machines, sinks and showers.
As engineers at Sheffield have shown, even the smallest trace of an optical brightener can be picked up and absorbed by a tampon suspended in the pool of a stream. Placed under a UV light, the tampon will glow if it has absorbed the chemicals.
"The main difficulty with detecting sewage pollution by searching for optical brighteners is finding cotton that does not already contain these chemicals," lead study author David Lerner, a professor of engineering at Sheffield, said in a press release. "That's why tampons, being explicitly untreated, provide such a neat solution. Our new method may be unconventional -- but it's cheap and it works."
After proving the remarkable sensitivity of tampons to OBAs in the lab, Lerner and his colleagues used them to find sewage contamination in local streams. They placed the tampons at 16 locations where surface water pipes feed runoff into the stream. After three days in the water, the tampons were inspected -- 9 of the 16 showed the presence of sewage.
Researchers were then able to use the same technique to trace the wastewater leaks back to the houses that had been hooked up to the wrong sewage lines.
"Often the only way to be sure a house is misconnected is through a dye test -- putting dye down a sink or toilet and seeing where the colored water appears in the sewer," Lerner explained. "It's clearly impractical for water companies to do this for all the households they supply, but by working back from where pollution is identified and narrowing it down to a particular section of the network, the final step of identifying the source then becomes feasible."
OBAs are just one of several types of contaminants in wastewater that can damage freshwater ecosystems -- altering the microbial makeup of streams and damaging invertebrate species. Wastewater's presence can also encourage pollution-tolerant species and enable the growth of a slimy residue called "sewage fungus."
The new study was published this week in the Water and Environment Journal.