By Peter Chawaga, Associate Editor, Water Online
In the rare instances that an outbreak of harmful bacteria affects public water supplies, it can mean a real-life nightmare for utilities.
Such a nightmare took place in Walkerton, Ontario in 2000 when an E. coli outbreak contaminated drinking water, killing seven people and sickening thousands. To avoid a worst-case scenario like that, utilities typically disinfect contaminated water using chlorination, ozonation, or other methods specifically tailored to the contaminant in question. But made-to-order elimination of the outbreak can come at a significant expense, and that’s assuming it will work.
“Outbreaks of specific biohazards can be costly to water treatment facilities because they necessitate modification to the treatment system and may not even eliminate the hazard, which creates significant problems for consumers,” said David Wendell, an associate professor at the University of Cincinnati’s College of Engineering and Applied Sciences.
While studying a strong-binding protein, Wendell and his fellow researchers developed a photocatalytic protein that is capable of generating hydrogen peroxide and eliminating E. coli, Listeria, and Cryptosporidium from water supplies. He sees the discovery as a better way for water utilities to avoid contamination outbreaks.
“By creating a selective photocatalyst, we can supply an alternative disinfectant which is compatible with consumption and can be added at the setting stage — if exposed to the sun — or anywhere blue LEDs can be introduced,” he said.
The protein, called StrepMiniSog (SMS), converts blue light into a high-energy form of oxygen called singlet oxygen. Antibodies then combine water with the singlet oxygen to form hydrogen peroxide. These antibodies also seek out the contaminants in question.
“So, the full catalyst has SMS attached to antibodies, which both target the catalyst to specific pathogens and locally generate hydrogen peroxide when exposed to light,” said Wendell. “I think this will be most useful for potable water treatment, specifically for sporadic outbreaks, since the catalyst is selective and less disinfectant is required. Currently there are little to no selective disinfectants for commercial-scale applications.”
Wendell imagines the protein being useful against Cryptosporidium outbreaks, cyanotoxin blooms, or when biohazard events occur on a potable water network. He doesn’t see it as a replacement for traditional disinfection, but a potentially cheaper, simpler, and more effective alternative in emergencies.
“I do not think this technology will replace existing disinfectants like chlorine,” he said. “We see this as a new tool in the treatment arsenal that is useful for specific treatment situations.”
It also carries another advantage to typical treatment methods: it’s greener.
“I would say this disinfectant is better in many ways than conventional oxidants in that it is selective, it does not produce the harmful DBPs [disinfection byproducts] that chlorine can, it can be renewably sourced, and it is compatible with human consumption,” said Wendell.
The research team is working on scaling up the production of SMS. It’s currently working on a way for a bacterial producer to secrete the photocatalyst, which would make it easy and inexpensive to collect and manufacture. Wendell sees it being available within the next five years and, hopefully, outbreak nightmares remain at bay for at least that long.
Image credit: "Microscopic," danicodesign © 2010, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/