NORMAN — Treated water from Lake Thunderbird will soon be aluminum free, according to Norman utilities officials.
“We’re switching from aluminum sulfate to ferric sulfate, and it’s working great,” Water Plant Manager Chris Mattingly said. “We’re going to switch (to ferric sulfate). We’ve already switched one clarifier, and we’re waiting for the opportunity to switch to the other big clarifier.”
Right now, about one-third of the lake water is being treated with the ferric sulfate. The remaining two-thirds of the lake water is still being treated with aluminum sulfate.
When that aluminum sulfate is used up, the city will transition to ferric sulfate for all treatment. During the trial period, the water treated with ferric sulfate was tested for iron content, and none was detected in the finished water.
The city will use up the rest of its aluminum sulfate to not to be wasteful, and the changeover should be complete by the end of the month.
Iron is a primary contaminant, so city officials wanted to verify that using ferric sulfate would not put iron into the water.
Iron causes more staining and corrosion to equipment, Water Treatment Plant supervisor Bryan Hapke told The Transcript earlier this year. Both factors increase maintenance, and corrosion can shorten equipment life.
Norman’s current lake water treatment method resulted in an aluminum content of about 1.0 to 1.2 parts per million in the finished water. That’s at least five times the recommended limit.
Whether aluminum is a health issue is debatable. A study as early as 1989 linked Alzheimer’s to the aluminum content of drinking water. However, results from a variety of studies since then have had conflicting results, and the debate about aluminum has become notorious in scientific circles.
Aluminum does affect taste and odor.
“EPA sets a recommended limit of 0.05 to 0.2 parts per million as a secondary contaminant,” Hapke said. “Secondary contaminants are not considered to represent a risk to human health but cause aesthetic problems.
“Aluminum is a secondary contaminant because there were no clear health effects from the presence of aluminum when this limit was set. Secondary contaminant limits are not enforced but only recommended.”
The Food and Drug Administration limits aluminum in bottled water to the recommended 0.2 milligrams per liter (equivalent to 0.2 parts per million).
Norman’s well water is not tested for aluminum.
The change to ferric sulfate has been in the works for about a year but was delayed because of an ozone pilot project, Mattingly said.
In 2007, city council members decided to use ozone in future water treatment. That project is being completed in two phases. Currently, the city is entering the design stage for Phase 2.