A boil water advisory for New Orleans’ east bank was lifted Thursday after a second round of tap water samples tested negative for total coliform, a bacteria already present in earlier samples.
The warning was in effect for a second day after two samples in the first round of testing – one in the Hollygrove neighborhood and the other in the Tulane/Gravier area – tested positive for the bacteria. Although total coliform is not typically harmful by itself, S&WB officials said the warning was extended out of an “abundance of caution” because the presence of the bacteria could indicate that other, more harmful bacteria have entered the water system. A warning for the West Bank was lifted early Thursday afternoon when all samples were found to be safe.
A second round of testing was conducted on samples from the east bank taken several hours after the first round and sent to the Louisiana Department of Health late Tuesday. The tests were negative, meaning bacteria that entered the system after the city’s water pressure fell below safe levels were successfully flushed out after pressure returned to normal.
The boil water advisory – the first citywide advisory in years – was triggered by a Mylar balloon that struck a power line near S&WB’s Carrollton water plant. An S&WB employee was injured while trying to restart the pumps.
When the city’s drinking water pumps operate normally, they keep pressure in the system high enough to prevent contaminants from entering. The S&WB has about 40 minutes to flip the switch and restore power to the pumps before water pressure drops below the recommended boil water level. However, because of the employee’s accident, it took workers 50 minutes to restore power.
This pressure drop allowed contaminants to enter the system.
The second round of tests was likely negative because the drop in pressure was short-lived, says Tiong Gim Aw, a microbiologist at Tulane University’s School of Public Health.
“Once power is restored and the sewage treatment plant is functioning, most of these pollutants can usually be removed and clean drinking water produced,” he said.
In general, it is rare for tests for coliform bacteria to be positive.
“This does not happen very often because with our current water treatment technologies we should be able to produce clean drinking water and remove most of these contaminants, including bacteria,” he said.
S&WB has occasionally taken samples that have tested positive for coliform bacteria near water mains undergoing repairs, leading to local boil water advisories, said S&WB spokeswoman Grace Birch. But a positive coliform test that would have led to a widespread boil water advisory had not occurred recently before this week, she said.
At a press conference on Wednesday afternoon, S&WB Managing Director Ghassan Korban said the incident showed how vulnerable the utility company was to supplying its drinking water system with electricity from the city’s households.
A plan by local officials to strengthen that system suffered a major setback when a political dispute caused the city to lose $29 million in state funding for a proposed new complex. The $300 million project, which involves a new electrical substation owned by Entergy New Orleans, would connect to both the pumps that drain the city and those that supply drinking water.
However, without these additional resources, the substation can only supply electricity to the sewage pumps. The drinking water pumps therefore have to rely on the same energy sources as today.
“I see no alternative but to continue looking for means to complete the project,” Korban said.
