University proves glow in the dark tampons detect sewage pollution
Engineers at the University of Sheffield have been using tampons to identify where wastewater from baths, washing machines, sinks and showers is polluting rivers and streams
The natural, untreated cotton in tampons readily absorbs chemicals commonly used in toilet paper, laundry detergents and shampoos. These chemicals, known as optical brighteners, are used to enhance whites and brighten colours and show up under ultraviolet (UV) light.
Using a mixture of laboratory tests and field trials, a team from the university's Faculty of Engineering has shown that when tampons are suspended in water contaminated by even very small amounts of detergents or sewage, they will pick up optical brighteners and glow under UV light.
Professor David Lerner, who led the study, said: “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.”
Funded through the Engineering and Physical Sciences Research Council, the study used laboratory trials to determine how much detergent would need to be in the water to be picked up by the tampon test. When a tampon was dipped for just five seconds into a solution containing 0.01ml of detergent per litre of water – more than 300 times more dilute than would be expected in a surface water pipe – the optical brighteners could be identified immediately and continued to be visible for the next 30 days.
The technique was trialled in the field by suspending tampons for three days in 16 surface water outlets running into streams and rivers in Sheffield and then testing them under UV light. Nine glowed, confirming the presence of optical brighteners, and therefore sewage pollution.
With the help of Yorkshire Water, the team followed the pipe network back from four of the nine polluted outlets identified, dipping a tampon in at each manhole to see where the sewage was entering the system.
They successfully isolated the sections of each network where the sewage originated, narrowing down the households that would need to be inspected in more detail.
Prof Lerner now hopes to trial the scheme at a larger scale to identify all the sources of sewage pollution on the Bradford Beck, the river which runs through the Bradford.
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