Sewage plant sludge often used as fertilizer may contain bacteria responsible for causing diarrhea illnesses, a Utah State University scientist believes.
Darwin L. Sorensen, research professor at the Utah Water Research Laboratory and the USU biology department, has studied the survival of the Campylobacter jejuni bacterium in sewage sludge. The bacterium has been implicated in 3 percent to 11 percent of the cases of diarrhea illness in North America."Millions of tons of sewage sludge are produced every year, and disposal is a concern," Sorensen said. "A lot is being landfilled, but if it can be treated so it can be sold or given away or used on public property as a fertilizer, then it becomes useful, rather than a liability."
But Sorensen said using sewage sludge as fertilizer may spread bacteria.
Campylobacter jejuni bacteria is borne in food and water and can cause diarrhea, especially in children and the elderly, Sorensen said. The illness it causes is widespread and is usually more severe than similar illnesses caused by viruses.
The bacteria is often transmitted in tainted poultry and can survive long periods in the environment, Sorensen said, "But we don't know how and why it survives."
Despite the bacterium's longevity in the environment, it is not easy to culture in the laboratory. Sorensen has focused on the development of a successful culturing method.
The Environmental Protection Agency has designed procedures, including composting, pasteurization and radiation sterilization, that have to be used before sewage sludge can be given away.
States also have their own regulations regarding sewage sludge disposal. In Utah, sewage sludge can be given away if it is dry and has been stored for one year. "One of our goals is to find out if the one-year storage regulation in Utah is equivalent to the EPA's procedures, especially composting," Sorensen said.