This animation illustrates how a standard Polychem chain and flight scraper system is assembled and installed.
The Department of Natural Resources has rescinded an order for people in the northeastern part of Madison, Wis., to boil their water after further tests showed no presence of E. coli.
Samples analyzed Friday by the State Board of Hygiene showed some of the bacteria, leading state and city officials to advise people in part of Madison to boil their water as a precaution, said Tom Stunkard, public water supply engineer with the DNR's South Central District. Samples analyzed Saturday did not show any signs of the E. coli, he said.
"Based on the sample results we got today, it looks like the water is safe," Stunkard said.
The change in the results could have been due to additional chlorine that was added to the water supply Friday, he added. "If there is anything out there, it's being addressed through the increased chlorination."
Another possibility for the improved results was that the samples received Friday were contaminated between the time they were taken and when they were analyzed, said David Denig-Chakroff, Madison Water Utility manager.
No cases of illness were linked with the problem, although the presence of E. coli can be a red flag that something is wrong with the water supply, including the existence of pathogens that cause disease. Illness symptoms may include diarrhea, cramps, nausea, jaundice, headaches and fatigue.
Officials warned people to boil their water just in case there was an illness-causing bacteria in the water. That is no longer necessary, they said.
"We went ahead and issued the boil water notice as a precautionary measure, although we didn't know what the situation was and whether it was an actual problem with the water supply," Denig-Chakroff said.