Even though it's vitally important for people in impoverished nations to check drinking water sources for pollutants, they often lack the facilities for performing such tests. A new system could help, as it uses a smartphone camera to check up on tiny aquatic organisms.
Developed by scientists at the Singapore University of Technology and Design, the setup can be used to analyze untreated water samples from lakes or rivers on the spot, within a matter of minutes.
A team led by Asst. Prof. Javier Fernandez started by observing single-celled organisms known as paramecia, which are abundant in bodies of water throughout the world. The researchers initially noted the average swimming speed of the organisms in untainted water, and then observed how much that speed decreased as different concentrations of pollutants such as heavy metals and antibiotics were introduced.
When the scientists subsequently measured the swimming speed of paramecia in water samples – utilizing a simple microscope attachment on a smartphone camera, along with object tracking algorithms – they found that they could accurately determine how polluted the water was, based on how much slower than normal the organisms were swimming.
For instance, even when heavy metals were present in concentrations considered to be half of what's safe for humans to consume, the swimming speed of the paramecia decreased by half.
"Taking a sample of water and measuring the speed of paramecia can therefore be used as a straightforward method to assess the drinkability of water without the need for specialized equipment or chemicals," says Fernandez. "Usually, you would need a different test for each pollutant, but paramecia swimming is a global measurement."
The research is described in a paper that was recently published in the journal Scientific Reports.