Lots of people enjoy watching and feeding the ducks at Davenport's Vander Veer Botanical Park lagoon.
But as ducks eliminate their waste and as food products disintegrate, the resulting "fertilizer" promotes the growth of algae. The green yucky stuff lowers water quality in the lagoon by using up the oxygen.
Fountains in the one-acre lagoon keep water moving but they don't filter, so they don't do much to reduce the algae, said Jennifer Meyer, lead outdoor horticulture technician.
To fix this, the Davenport parks department hit on a relatively new, high-tech solution called a BioHaven floating island, a product made since 2005 by a Montana-based company.
Made of plastic but planted with real plants with long roots that extend down into the water, the islands mimic natural floating islands, or wetlands, that remove nitrate, phosphate and ammonia from the water. They also are effective in reducing suspended solids and dissolved organic carbon and are pretty to look at, because the plants bloom with flowers on top.
A $2,500 environmental grant from Iowa American Water, Davenport, will pay for a medium-sized, 7½-foot-by-9½-foot island that has room for 149 plants, Meyer said. It isn't the plant roots themselves that break down nutrients and other pollutants, but tiny microbes. The plants' role is to create a surface for them to stick to, creating a biofilm, she said. Nutrients circulating in the water come into contact with the biofilms and are consumed.
This is nature's way of cleaning water; the company that makes them was inspired by the floating peat bogs of northern Wisconsin.
In addition to cleaning water, the Vander Veer project is meant to educate people about this new practice and how it might be used in other applications.
One challenge at Vander Veer will be to keep the ducks and geese off the island, Meyer said. Putting up a fence would detract from the island's looks, so she is hoping to use what she describes as "a big, upside down wire basket."
The grant will pay for the island, expected to come in by September, but soil and plants will cost somewhere less than $1,000, Meyer said.