New Low-Cost Method Can Detect Sewage Pollution in Streams, Rivers

A team of scientists at the University of Sheffield, UK, has developed and tested a promising novel method that uses inexpensive samplers (cotton tampons) to identify where wastewater is polluting our streams and rivers.

New Low-Cost Method Can Detect Sewage Pollution in Streams, Rivers

Pasig River, Manila, Philippines. Image credit: Bar Fabella / CC BY 2.0
“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,” said Prof David Lerner of the University of Sheffield’s Department of Civil and Structural Engineering, the senior author of the paper published in the Water and Environment Journal .
“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.”
Prof Lerner and his colleague, Dr Dave Mark Chandler, have 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.
The team carried out lab experiments 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 5 sec into a solution containing 0.01 ml of detergent per liter of water, the optical brighteners could be identified immediately and continued to be visible for the next 30 days.
The method was then tested in the field by suspending tampons for 3 days in 16 surface water outlets running into streams and rivers in Sheffield, UK, and then testing the tampons under UV light. Nine of the tampons glowed, confirming the presence of optical brighteners – and therefore sewage pollution.
The scientists then followed the pipe network back from four of the nine polluted outlets they’d identified, dipping a tampon in at each manhole to see where the sewage was entering the system.
They were able to successfully isolate the sections of each network where the sewage originated, narrowing down the households which would need to be inspected in more detail. A visual inspection in one area immediately revealed a house where both a sink and soil stack were connected to the wrong sewer.