Baby bluegill and perch gobble their favorite zooplankton. Reeds, canary grass and other aquatic plants rise from wetlands and wave in the breeze.
Is this any way to run a municipal water plant?
A group of engineers and biologists from Notre Dame and Goshen College thinks so.
The novel water treatment system they've devised puts tanks of small-fry perch, walleye and other angler's favorites to work removing excess nitrogen and phosphorous from city waste water. At the same time, reeds and other plants growing in miniature, man-made wetlands soak up and recycle trace metals and other water-borne undesirables.
The system is the idea of Notre Dame's Lloyd H. Ketchum Jr., associate professor of civil engineering and geological sciences, and doctoral candidate Art K. Umble. They're collaborating with a biology professor and students at Goshen College and the operators of the City of Elkhart Wastewater Treatment Facility.
Ketchum says smaller cities like Elkhart, east of South Bend, are having trouble meeting increasingly stringent water quality standards because they can't afford the equipment, chemicals and expertise needed to remove certain pollutants.
One person's trash is often another's treasure, however, and such is the case with water. Some of the substances that regulators label pollutants -- including nitrogen and phosphorus -- are also effective fertilizers. They nourish algae, the plants at the bottom of the aquatic food chain.
Ketchum and his colleagues want to use the nitrogen and phosphorous that remains in municipal water even after conventional treatment and grow algae. The algae would then feed certain types of zooplankton that are the favorite meals of young walleye, perch, bluegill and other sport fish.
In the other part of their system -- the artificial wetlands -- common reeds and other native aquatic plant species would be used to recycle other nutrients/pollutants through their roots and take up any nitrogen and phosphorous not needed for algae-plankton-fish production.
Ketchum says the key to using waste water to culture fish is pinpointing the right amount of "fertilizer." With too low a concentration of nitrogen and phosphorous, the fish starve. But use too much, and the algae overbloom, consuming the water's oxygen and suffocating the young fish. Down the road, biologists would also want to test fish regularly to make sure substances like mercury aren't accumulating in their tissues. That would make the fish dangerous to eat.
The experimental system has been in operation about three years but is still in the pilot stage, Umble says. It currently treats approximately 3,000 gallons a day, compared with the more than 15 million gallons a day processed daily at the Elkhart plant by conventional means and released into the Saint Joseph River.