Engineers at the University of Sheffield in the United Kingdom have been using the seemingly unconventional method of tracking glowing tampons in a water body to identify areas of pollution from wastewater. Often, tampons soak up the optical brighteners, chemicals added to detergents and other cleaners to enhance whites and bright colors - the same stuff that makes your white t-shirt glow in the black light of a bowling alley. The tampons then glow under ultraviolet light. Because the natural, untreated cotton in tampons readily absorbs the chemicals, they have the potential to be a convenient and inexpensive indicator of pollution in rivers and streams.
The engineers on the project have shown that it takes a very small about of detergent to provide enough optical brighteners to make tampons glow. At nearly 300 times more dilute than expected, laboratory trials from the study showed that after submerging a tampon in a concentration of 0.01 milligrams of detergent per liter for just five seconds, the tampon was visible and identifiable for a full thirty days.
Professor David Lerner who led the study, described the need for such a system, “More than a million homes have their wastewater incorrectly connected into the surface water network, which means their sewage is being discharged into a river, rather than going to a treatment plant. Unfortunately, it’s very difficult to detect where this is happening, as the discharge is intermittent, can’t always be seen with the naked eye and existing tests are complex and expensive. The main difficulty with detecting sewage pollution by searching for optical brighteners is finding cotton that does not already contain these chemicals. 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."
The study also tested tampons in the field. Researchers suspended tampons in each of sixteen surface water outlets in Sheffield for three days before returning to the lab and placing them under UV light. The researchers were able to identify nine areas of sewage pollution thanks to glowing tampons. With the help of the local utility, they were able to pinpoint where the sewage originated.
According to Lerner, “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. A visual inspection in one area immediately revealed a house where both a sink and soil stack were connected to the wrong sewer. 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.”
The next step in research for Professor Lerner and his associates is implementing a larger scale trial in the city of Bradford.
Sources: University of Sheffield