Nav: Home

Submersible sensors rapidly detect bacterial pollution in water

March 11, 2020

When it rains in San Diego, waterways such as the San Diego River and its Alvarado Creek tributary often experience bacterial pollution that is ultimately carried to the ocean. This is a public health threat for swimmers, surfers and aquatic life, and it can stem from sewer line breaks during storms, illegal discharging of wastewater into rivers, or leaky septic tanks.

Typically, coastal cities that experience frequent contamination will collect water samples and test the quality if they suspect bacterial contamination, before issuing warnings to the public and closing access to beaches. But this reactionary method involves wait times of to 18 to 24 hours, a potentially hazardous delay for the public.

Environmental engineers from San Diego State University have adapted existing sensor technology that can detect fluorescence and tweaked it to enable rapid detection of bacteria in the water. They plan to combine this technology with telemetry to transmit contamination alerts in real time, an advance with useful implications for water monitoring agencies and government authorities.

From the enamel on our teeth, to material in the clothes we wear, every object has fluorescence that is invisible to the naked eye, but can be detected by special sensors. Bacteria also have similar fluorescence these sensors can detect, which helped the researchers quickly identify contamination.

"We wanted to rapidly identify bacterial contamination, literally in seconds, and be able to watch the intensity increase in real time, using it much like a hand-held instrument," said Natalie Mladenov, water quality researcher and associate professor. "One problem many water managers are aware of is the need to have real time data, and this could be the answer."

She has long been interested in evaluating sensors as early warning alert systems for unanticipated pollution events, both in surface water and at water treatment and reuse facilities. She has previously shown how fluorescence-based sensors can indicate the presence of pollutants in treatment facilities, and this time she set out to explore whether they could be adapted for sewage pollution incidents in surface water.

In addition, "source waters for drinking water treatment plants, like lakes or reservoirs, would also be an excellent place to deploy such a sensor to warn of sewage spills or other bacterial contamination," Mladenov said.

Most sampling devices being used for this purpose have an incubation period before results are available, but the fluorescence-based sensors she tested can distinguish between bacteria in the water and organic material and plant waste, and relay that data immediately. The study will be published March 11 in the Science of the Total Environment.

Mladenov and former undergraduate engineering student Lorelay Mendoza used a portable submersible fluorometer, which comes with a choice of sensors. For bacterial wastewater tracking, they chose a sensor for tryptophan--the same amino acid that makes you sleepy after a turkey dinner--and a humic sensor for background fluorescence tracking.

Mladenov's previous research indicated the tryptophan sensor would be the most useful. For proof her team tested it both in the lab and in Alvarado Creek where they had observed the presence of fecal bacteria concentrations during storms.

Mendoza would track weather events and the night before a storm was predicted, she would place the fluorometer in the creek, tracking bacterial contamination during the storm in real time.

"The findings suggest that wastewater was discharged into Alvarado Creek because of a sanitary sewer overflow or some kind of leakage in sewer infrastructure during a storm," Mladenov said. "Sewer lines are old and many are reaching the end of their useful life."

Mendoza said the high readings were supported by high E. coli counts, and human-derived pollution was confirmed by measuring caffeine concentrations.

"We hope this research propels the deployment of fluorescence sensors to water bodies for long-term monitoring, because having data is power," Mendoza said. "I would like to see cities and water managers deploy sensors along water streams to detect vulnerabilities in water quality and to reduce the impacts of pollution events when they happen. Without early warning signals, the time between initial contamination and awareness and reaction is longer and will have negative consequences for the environment and aquatic life."

Collecting samples during storms can be challenging. That's where grad student Federick Pinongcos and colleague Alicia Kinoshita came in, to ensure that samples were collected intact and quickly brought to the laboratory. Then each sample was analyzed for markers of wastewater contamination.

"This type of multiple lines of evidence-study had previously not been undertaken," Mladenov said. "It indicates that the optical, fluorescence based approach is an effective way for future detection of sewage leaks and other spills in surface waters."

To obtain supporting biological and chemical data, Mladenov collaborated with SDSU professors Matthew Verbyla and Rick Gersberg. Next, she and geography professor Trent Biggs, are teaming up to deploy the fluorescence-based sensor together with a telemetry system to ensure the alert can be received in real time, and will conduct studies in larger water bodies including the San Diego River.

Funding for the field deployments comes from the San Diego River Conservancy. The lab research and Mendoza's stipend were covered by grants from the National Institutes of Health and SDSU's Maximizing Access to Research Careers program.
-end-


San Diego State University

Related Bacteria Articles:

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.
Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.
Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.
Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.
Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.
How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.
The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?
Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.
Bacteria uses viral weapon against other bacteria
Bacterial cells use both a virus -- traditionally thought to be an enemy -- and a prehistoric viral protein to kill other bacteria that competes with it for food according to an international team of researchers who believe this has potential implications for future infectious disease treatment.
Drug diversity in bacteria
Bacteria produce a cocktail of various bioactive natural products in order to survive in hostile environments with competing (micro)organisms.
More Bacteria News and Bacteria Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.