CINCINNATI -- Just a year ago, people in Toledo couldn't drink their tap water because toxins from blue-green algae had made their way into that city's drinking water supply.
So now, with algae covering a 500-mile stretch of the Ohio River -- from West Virginia to beyond Louisville -- why isn't Cincinnati's tap water dangerous, too?
"We have a lot more advance treatment here in Cincinnati than they do in Toledo," said Jeff Swertfeger, superintendent of water quality and treatment for Greater Cincinnati Water Works.
It's a simple answer with a lot of history behind it, going back at least 40 years.
Cincinnati Gets a Wake-Up Call
In the 1970s, Swertfeger said, a few chemical spills upstream brought bigger attention to all the river's risks: some chemicals from the spills made their way through the treatment plants and into the city's drinking water. Understandably, people were "very alarmed."
"We are vulnerable to chemicals on the Ohio River," he said. "Just look up and down the Ohio River -- we need to have a barrier for chemicals."
Water Works, along with the U.S. Environmental Protection Agency, looked at the best ways to remove those chemicals and found that granular activated carbon -- the same stuff that's in, say, a Brita filter -- was incredibly useful.
People in ancient Egypt used charcoal to purify water; much later, in the 19th century, bone char was used to refine sugar. But modern activated charcoal didn't come into widespread use until World War I, when it was used in gas masks.
"Millions of pores in GAC capture...organic substances, removing them from the water," according to GCWW's website. "Most spills in the Ohio River are organics."
To get an idea of how many pores there are, consider this: A cup of granular activated carbon has the surface area of about 25 football fields.
Water Works' granular activated carbon facility, one of the largest in the United States, opened in 1992 and has been filtering Cincinnati's drinking water ever since.
Toledo? It only uses activated carbon as needed because of the expense. Adding to the problems, that city's water treatment plant was plagued by a huge backlog of repairs, leaving it in what The Blade called a state of "silent deterioration."
"Historically, people (in Cincinnati) have been very supportive of water infrastructure," Swertfeger said. "They know the importance of clean drinking water. They funded the construction of that barrier -- they saw the benefit, they were willing to pay for it."
But granular activated carbon is just one step in a process to clean out contaminants, and, according to Swertfeger, toxins from the blue-green algae aren't even making it that far down the line.
What We're Seeing
Blue-green algae isn't a true algae per se, but rather a kind of bacteria called cyanobacteria -- literally, "blue bacteria." It's always around in our water, but under the right conditions -- specifically, clear water, warm temperatures and lots of phosphorus and nitrogen -- it can explode in numbers, forming huge blooms that look like thick mats or scum. The blooms might also look like spilled paint.
On Aug. 31, the Kentucky Department of Water received a report of an algal bloom on the Ohio River near Greenup, Kentucky. Subsequent sampling of the river indicated higher levels of microcystin toxins existed in some areas of the Ohio River from Ashland, Kentucky to the Meldahl Dam.
Since then, conditions favorable for the development of blue-green algae blooms have persisted throughout the river basin, and more formed downstream. A recreational advisory for people boating or swimming in the river now extends to Cannelton, Indiana, southwest of Louisville.
Although there was a blue-green algae bloom downstream from Cincinnati in 2008, Swertfeger said, it only lasted about a week.
"Nobody's seen or heard anything this bad or this long," Swertfeger said.
Not all types of blue-green algae are poisonous, but some produce toxins called microcystins. That's what forced Toledo to issue a "do not drink" advisory for three days in August 2014.
The Early Warning Toledo Didn't Have
Water Works is part of an eight-state network of utilities along the Ohio River, stretching from New York to Illinois. With 13 monitoring stations, the Ohio River Valley Water Sanitation Commission checks for pollution so that downstream members know when trouble might be headed their way.
"When they see an algal bloom upstream, they report it to the network," Swertfeger said. "So we actually had several weeks' notice this was coming down."
Toledo only recently put an early detection system in place, with buoys in Lake Erie, after last summer's scare there.
Water Works also does its own checks for contamination before water enters the utility's Richard Miller Treatment Plant, in the city's California neighborhood. So scientists knew when the algae arrived.
"When it first got here, we did shut down for a day so we could take a look, see what's happening, be sure we had response plans in place, be sure we would be able to treat for it," Swertfeger said. "That's always the knee-jerk reaction -- we'd rather shut down and see what we're dealing with."
(You probably didn't notice, because Water Works has enough water stored to keep the taps flowing even when its river intakes are closed.)
What Water Works scientists found, Swertfeger said, was that toxins were getting removed early in the filtration process -- where sediment is filtered out, treated with powdered activated carbon and put through sand filters.
Treatment granular activated carbon happens near the end, just before the water is treated with ultraviolet light and chlorine, both of which should take out pretty much anything that survived the earlier steps.
The UV treatment is a relatively new addition to Water Works' treatment process, completed in 2013 at a cost of $30 million and designed to kill virtually any germs that make it through the conventional filtration process.
And if you're worried something might slip through the system, consider this: Water Works runs about 600 tests on its water, and there are online monitors that are constantly checking the quality. Staff are at the utility's two treatment plants -- the other treats water from an aquifer that accounts for about 10 percent of Water Works' finished product -- around the clock ever day.
"The safety of the water is always our biggest concern," Swertfeger said. "I drink it, my family drinks it, so we not only have professional interest but also personal interest in being sure it's safe."
When Will River Clear Up?
So far, scientists aren't totally sure why there's so much blue-green algae over such a large area of the Ohio. A wet early summer might have dumped more phosphorus and nitrogen from agriculture into the water. And the river's been running more slowly than normal, making it clearer and letting in more sunlight -- which blue-green algae loves.
But the conditions haven't really been out of the ordinary.
"Researchers are scratching their heads a bit," Swertfeger said.
He thinks it will take a change in the seasons to clear up the algal blooms, but there are already some encouraging signs upriver, near Ironton, Ohio.
"We actually saw reports...saying the water is clearing," Swertfeger said.