The disappearance of water- borne bacteria from Clearwater’s municipal water system is just the latest, albeit welcome, twist in an ongoing mystery.
Since September, when routine testing detected an unusual spike in the amount of E. coli bacteria at a variety of locations throughout the city, a team of scientists has been trying to figure out how the microscopic organisms apparently infiltrated the system.
“It’s a large puzzle that we are piecing together,” said Andy Neff, the city’s public utilities director.
The cause of the mysterious contamination could range from damaged pipes to people connecting irrigation wells into their home water systems to mistakes made in the sample collection and testing process.
Even hurricanes could be to blame, Neff said. “The hits followed the hurricanes, and that is something we are looking at,” he said. During hurricanes, “certain things are shut off” and water is processed differently, Neff said.
The city’s drinking water supply was never in danger, and the three boil-water advisories issued for specific neighborhoods in September were only precautionary, Neff said.
“Water is not antiseptic,” he said.
E. coli bacteria is not, in and of itself, a danger to humans. It is a subspecies of coliform bacteria, both of which can be indicative of the presence of life- threatening diseases. The city tests water at 220 sites throughout the system, usually once every 60 days, so that 110 samples are examined in any given month. After the September tests began coming back as positive for coliform and E. coli, more samples were taken in an unsuccessful effort to pinpoint the problem, Neff said.
A total of 1,509 samples were taken, with 56 positive findings of coliform and 16 of E. coli, Neff said. In August, there had been no positive readings.
The numbers fell dramatically in October, when 220 samples yielded seven positive hits for coliform, four of which also contained E. coli, Neff said. In November, with the testing program back to normal, 110 tests yielded four coliform findings, of which two contained E. coli.
December’s tests all came back clean. At no time did results exceed a federal standard for safe water set at 5 percent positive results, Neff said.
“To date, we haven’t found a fingerprint of a suspect,” he said.