In a room in Mason Laboratory, a team of Yale researchers are finding ways to deal with the nation's sewage.
Kyle Bibby GRD '12 and Chris Ziemba GRD '11 study pathogens in sewage sludge and ways to effectively kill them. Professor Jordan Peccia, who advises the pair, said their research could help the Environmental Protection Agency reevaluate regulations on the use of treated sewage sludge.
"We want to provide unbiased science in an argument in which almost everyone has a dog in the fight," Peccia said.
Building on Peccia's work in the field, Bibby is analyzing sludge samples from municipal sewage treatment plants across the United States to identify the main pathogens in sludge, including the Legionella bacterium and the Adenovirus, both of which cause minor respiratory diseases.
While sewage treatment plants primarily monitor the amount of E. coli bacteria in treated sludge, Bibby said there can be other pathogens in the sludge even if the treatment process killed many of the harmful organisms.
Ziemba's research focuses on the relationship between the killing rate of bacteria and temperature. His data has indicated that cooking sewage sludge at 60 degrees Celsius may be the most energy efficient process for killing bacteria.
Treatment plants currently kill many of the pathogens and break down the solids in sewage sludge by cooking it at 37 degrees Celsius for about 30 days. But 37 degrees Celsius, which is around body temperature, is not warm enough to kill most pathogens, so some plants treat the sludge at 50 to 55 degrees Celsius, Ziemba said. But 60 degrees Celsius may be optimum temperature, Peccia said.
At this temperature, there is a huge increase in the rate of bacteria death, Ziemba said. While the extra heat requires more energy, Ziemba said the cooking time can be decreased, which may indicate that sewage treatment plants can kill more bacteria while maintaining current costs.
Yale Researchers Say that Sludge Isn't Heated High Enough to Kill Pathogens
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Seeking solutions in sludge
By Carol Hsin
Yale Daily News, Feb 3, 2010
Straight to the Source
