Because of its shallow depths, its large nutrient loads, and its importance as a water supply for more than 10 million people, western Lake Erie is North America’s top hotspot for cyanobacteria harmful algal blooms (CHABs)—a distinction reinforced by the August 2014 Toledo water crisis.

CHABs aren’t Lake Erie’s only problem. The lake was famously declared “dead” in the 60s when hypoxic conditions led to fish kills. Water quality regulations and restoration efforts have improved conditions, but invasive species and other problems still impact the lake

CHABs remain a persistent and perhaps growing problem, however, and is the target of legislation and regional and binational agreements. In the recently updated U.S.-Canadian Great Lakes Water Quality Agreement, both governments have agreed to reduce phosphorus input—thought to be the main driver of CHABs—by 40 percent. And in 2015, Ohio, Michigan, and Ontario signed a similar agreement for Lake Erie; and the state of Ohio enacted a new law regulating how and when farmers in the Maumee River watershed can apply fertilizer and manure.

But even with these efforts, reducing nutrient pollution in Lake Erie will take decades to yield real improvements. To live with CHABs, NOAA and other research outfits are providing increasingly precise modeling and forecasts of the blooms, while water utilities, with funding and support from the state and federal EPA, look to improve water quality testing and treatment.

Photo Credit: NOAA

Improving monitoring and modeling

The NOAA Great Lakes Environmental Research Laboratory (NOAA-GLERL) and collaborating organizations have run a monitoring program for about a decade based on weekly sampling at eight sites near the intakes for municipal water utilities. NOAA-GLERL also uses remote sensing data from satellites and aircraft to forecast the locations and intensity of cyanobacteria blooms three to five days in advance.

“We can give water intake managers a couple days warning for when really dense blooms might be advected into their area,” said Tom Johengen, associate director with the Cooperative Institute for Limnology and Ecosystems Research at University of Michigan. “Our models can also predict where the algae will be distributed within the water column. Most water intakes are four to five meters below the surface, and there are often times when, based on the amount of wind and wave mixing, the algae will just be on the surface.”

Doug Wagner, superintendent of water treatment for Toledo’s neighboring town Oregon, Ohio, says he and his colleagues rely on the NOAA forecasts so they can be ready to adjust water treatment should a CHAB manifest near their intake. “Those forecasts that get emailed to us a couple times a week are very beneficial in knowing what the bloom is doing,” he said.

Soon, NOAA-GLERL will deploy a $500,000 in situ Environmental Sample Processor (ESP) to do real-time monitoring at the Toledo water intake. The first such device to be used in fresh water, Johengen says the instrument will allow tracking of toxin concentrations multiple times a day.

Photo Credit: NOAA

Improving testing and treatment

Photo Credit: NOAA

Small utility opts for ozone treatment

That loan fund is paying about 5% of the $14 million that Oregon, a small town of about 20,000 near Toledo, will spend on a new ozone treatment system and associated biofiltration system. A $1.4 million grant from the Ohio Public Works Commission also supports the project, with the balance financed through water rate increases of $2 to $3 per month.

Oregon got through the August 2014 bloom without a “do not drink” order—not by shutting down its intake pumps but by ramping up treatment after being alerted to the bloom by NOAA warnings and a heads-up from Toledo.

“On that and other occasions when we see a bloom at the intake, we crank up all the chemicals to make sure we take care of the problem,” said Wagner. “Potassium permaganate oxidizes microcystin. Powder-activated carbon absorbs extra-cellular toxins. Our coagulant aluminium sulfate helps settle out the algal cells before they can emit toxins. And anything that slipped through was treated with chlorine.”

But Toledo’s experience helped convince town leaders that an additional layer of protection was needed. “Ozone destroys microcystin and organics in milliseconds versus hours for other treatments,” said Wagner. “The ozone system will enable the utility to cut back on chemical inputs, but those savings aren’t estimated yet.”

Aside from the capital cost, “there really are no disadvantages,” said Wagner. “It will improve the taste and odor of the water, eliminate a lot of the organics and destroy any microsystin that gets into our system.”

Ozone treatment is still rare in U.S. water utilities, even among those drawing water from western Lake Erie. For its part, Toledo has upgraded its treatment options by increasing its ability to feed powdered activated carbon at its Collins Park treatment station and potassium permanganate at its intake crib and low service pump station, according to the city’s report. New chlorine disinfection facilities were also built at the Collins Park plant.

While existing and contemplated testing and treatment technologies will likely prove effective against CHAB toxins, water utility managers like Oregon’s Wagner can’t help but look upstream and wish that more would be done to reduce  or at least stabilize nutrient runoff from farmland. “I see more and more field tiles going in all the time,” Wagner said of the farm drainage systems that effectively transport dissolved reactive phosphorus to waterways. “It almost seems like there’s a race to get the fields tiled before someone tells them they can’t do it anymore.”

The resulting increase in runoff is apparent to Wagner when he drives over the Portage River southeast of Oregon. “It used to be that when it rained, it took two or three days for the river to rise. Now it seems like it rises on the same day or day after. Runoff water is definitely getting to the lake faster, and the faster it gets there, the more nutrients it’s going to carry.”

© Ecology and Environment, Inc.    All Rights Reserved

© Ecology and Environment, Inc.    All Rights Reserved

Living with Toxic Algal Blooms: Lake Erie