More than two years of testing has researchers convinced they have a faster way to detect untreated sewage in the Tijuana River.
The new tools are called fluorescence monitors. San Diego State University (SDSU) scientists have submerged several of them beneath a platform in the mouth of the Tijuana River. They’re measuring pollution in a river estuary that’s notorious for fecal contamination.
The sensors emit UV light that’s reflected by the chemicals in wastewater that give it a unique optical signature.
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Environmental engineering professor Natalie Mladenov has partnered with geography professor Trent Biggs, also at SDSU, on the two-and-a-half year project. They’ve published a paper in the journal ScienceDirect.
Mladenov said the technology is working and fluorescent testing on site is a lot faster than testing water samples in a lab.
"A sensor might be able to cut that work in half. And still provide a good indication of when the water quality is fine … to 'Okay, now something is wrong and we should check,'" Mladenov said.
She added they have checked the results of the submerged monitors against lab results, which showed the same results.
“We had to collect real samples as well, and we analyzed them the old fashioned way, which was to take the sample to the lab and look at the chemical parameters and biological parameters,” she said.
The fluorescence monitors have their limitations. Untreated sewage in the Tijuana River flows into the ocean, forcing the closure of beaches nearby, but testing ocean waters for signs of sewage is less reliable because the wastewater becomes very diluted.
Meanwhile, Mladenov said it performed very well in the Tijuana River.
“The estuary setting was actually a perfect setting,” she said. “Unfortunately, it’s because there's a lot of pollution that was making its way into the estuary. And so when pollution levels are higher these sensors work better.
Mladenov said their testing in 2022 showed water quality in the estuary was pretty good. For the past year-and-a-half its been polluted almost every day.
