Sheffield researchers used tampons under a black light to find misconnected sewers

In a WIRED piece by Gwen Pearson, Prof. David Lerner of the University of Sheffield describes a project that placed tampons in streams and sewers around Yorkshire. Storm sewers are meant to carry only rain and runoff to natural waterways, but misconnected plumbing or deliberate dumping sends washing-machine and dishwasher water into them.

Existing detection was costly. Fibre optic cables could be run through sewers at up to 9 pounds ($13) per metre, and spectrophotometers need training and calibration. The target was a method ordinary citizens could use. Lerner and his collaborator adapted a US EPA technique that used cotton pads for detecting optical brighteners, which are added to detergents and glow under UV, and swapped the pads for tampons, which are smaller, portable and come with a string.

Lab tests showed tampons picked up brighteners at very low concentrations. In the field, tampons were tied to bamboo poles in 16 surface water sewers and retrieved after 3 days. Under UV light the result was a clear positive or negative, and the researchers estimated the cost at about 20 pence (30 US cents) per tampon including the black light.

Use a tampon as a cheap cotton sponge that catches detergent brighteners and glows under a black light.

Optical brighteners do not occur naturally in rivers, so any glow signals human grey water.

Brighteners stick strongly to cotton, so a short soak concentrates them enough to see.

A string on a tampon makes it easy to tether in a sewer.

A black light from a party store replaces a spectrophotometer, so volunteers need little training.

When a measurement needs expensive kit, look for an everyday object whose physical properties already do the sampling, then let amateurs run the test.

The method was published as a low cost method to detect polluted surface water outfalls and misconnected drainage in Water and Environment Journal (2015). Lerner said the next step was to recruit volunteers to dip tampons at as many points as possible across their watershed and map which stretches of river might be polluted. The article reports no rollout results yet.