Beginning sometime in late-June of this year, customers of the City of Ithaca drinking water supply system started reporting that their water was discolored. After suggesting several possible reasons for the discolored water and trying several solutions, the City has determined that the cause of the discoloration was high levels of manganese, and the problem is successfully being addressed.
Manganese is present in high concentrations in the earth and in sediments in the reservoir. It dissolves into the water, especially when it gets warm or when there is little rain. Dissolved manganese has no color, but when chlorine is added to water with high levels of manganese, the manganese solidifies and the water turns color, at first yellow and eventually brown.
It takes time for this to occur, so even though the water was clear or mostly clear at the water plant, it turned brown while it was in the water mains that carry water throughout the city. The manganese can solidify so much that it forms flakes that look like rust.
The City’s water treatment plant cannot remove manganese when it is dissolved, so the City started adding a chemical oxidant to the intake pipe at the reservoir to make the manganese solidify before it reaches the water plant. At first not enough of the oxidant was added and most of the dissolved manganese was still getting through. But by early August the right amount of oxidant was being added, and most of the manganese was solidifying early and being removed by the treatment plant. At that point, the reports of brown water almost completely stopped.
Since early July, the City has taken weekly samples from several locations throughout the water system. These samples are tested for several things, including the concentration of manganese and turbidity (cloudiness) of the water. The tests for manganese have to be sent to a private lab, and because the lab is very busy, it has taken four or more weeks to get back some of the results.
On July 11 the manganese concentration at the water plant was 0.59 milligrams per liter, and on July 19 it was 0.98 milligrams per liter. Both readings are above the maximum concentration limit for New York of 0.3 milligrams per liter. This is classified as a “Tier 3” violation, which is the least serious and requires that the public be notified within 12 months, typically as part of the annual water quality report.
Other samples taken on those same days at other locations in the water system all showed concentrations below 0.3 milligrams per liter. This indicates that the concentration that most water users were getting at their taps was lower than what was recorded at the water plant.
The City received results from more recent samples taken on August 16 (after reports of brown water had subsided), which showed so little manganese leaving the water plant that it was below detectable limits, and the levels of manganese throughout the water system met state water quality standards. The most recent results were expedited, but the City is still awaiting the results of additional tests taken before August 16. The City expects that those tests may also show elevated levels of manganese, because they were taken before the manganese was effectively being removed at the water plant.
Tests for turbidity (cloudiness) of the water showed that for the month of July the average turbidity at the water plant holding tanks was above the water quality limit. This was not unexpected given the discoloration that was being reported. However, it is considered a “Tier 2” water quality standard violation, one that requires water users be notified within 30 days.
Turbidity is regulated because it can be associated with bacteria and other microbes. However, the City monitors bacteria levels closely, and none of the 30 tests taken each month by the water department has shown any microbial contamination of the water supply.
The City worked with the County Health Department to develop a combined official notice of both violations. That notice is now available on the City’s website.
To prevent similar problems in the future, the City will maintain and operate a permanent system for adding the chemical oxidant at the reservoir. The City will monitor water temperature and stream flow and will use these to signal the right time to take manganese samples from the raw water and to begin adding the oxidant to help remove the manganese.
Cloudy and discolored water can also be caused by events such as water main breaks, like the one on August 17 when a large water main broke near Wegmans and caused brown water throughout the City system. Much of the brown color was likely the manganese that had settled to the bottom of the pipes over the previous month.
The water main has been repaired and most of the system has been flushed. However, pockets of discolored water can sometimes linger in the system. If you experience discolored water at your tap, please notify the water and sewer department at 272-1717 during business hours or 273-4680 after hours, and someone will come to flush the hydrants near your address.
If you have questions about the information contained in this summary, please contact Chief of Staff Dan Cogan at (607) 274-6512, or at dcogan@cityofithaca.org.
