AUSTIN (KXAN) — The reason all of Austin is under a boil water notice and unable to safely drink tap water can be summed up like this — the water headed into treatment plants is too murky.
More specifically, its turbidity, which measures how light is impacted by particles in the water, is 100 times higher than normal.
Typically the turbidity in Austin’s water intake is measured at about four nephelometric turbidity units. Currently, it’s coming in at about 400 NTU.
Some perspective / geek 🤓 insight on Austin’s water:
-Normal intake is 4 NTU (measures turbidity, AKA how cloudy the water is)
-Current intake is 400 NTU (100X more than normal)
-Need to get output below federal standard of 0.3NTU (Austin is worried it wont meet this) pic.twitter.com/Do3IeYIFXk— Tom Miller (@TomMillerKXAN) October 22, 2018
Dr. Lynn Katz runs the UT Center for Water and the Environment and spent Monday morning consulting with Austin Environmental Engineers, many of whom she taught as students.
She said Austin’s water plants are not designed to handle such murky water, with high levels of dirt and silt, over a sustained period of time.
“If it happened for a few minutes or a few hours, a plant could probably handle it pretty well,” Katz said. “When it’s going on for days, that’s where the challenge comes in for the treatment plants.”
City water officials said the turbidity caused problems at all three of its water treatment plants.
Filters are getting clogged much quicker, and it’s difficult to find the right chemical balance to remove the particles.
From inside her lab, Katz demonstrated how iron and lime compounds can be used to expand and clump together particles in the water.
Once big enough, the particles sink to the bottom of the jar and become what’s known as sludge. The clean water is then taken from the top and moved into the filtration process.
However, after pouring in enough sentiment to reach 400 NTU, Katz and her lab assistants struggled to find the right formula to create sludge.
“If all of a sudden you said, ‘well here’s a completely new water, and I’m going to give you 20 minutes to figure out what to do,’ that would be a challenge, that’s the analogy,” Katz said. “I would be like, ‘well I can start here, and then I can try it again, and maybe that’s not enough, then I can try again,’and in a jar that’s pretty easy.”
It becomes significantly harder when you’re dealing with more than 100 million gallons of water each day, and unpredictable conditions, like Austin environmental engineers, are.
While the city hasn’t failed any tests yet, water officials worry they soon won’t be able to meet the federal standard of a 0.3 turbidity reading in 95% of tests over the course of a month, hence the boil water notice.