LONDON, Ont. -- They’re called slag bags and they may be another step toward cleaner waterways.

Slag is waste material, a by-product of the steel making industry, but it may have value in the effort to clean up our waterways.

The Upper Thames River Conservation Authority launched a three-year pilot project Tuesday morning near Lucan which uses slag bundled in bags to draw phosphorus from farm run-off.

Phosphorus has an attraction to iron ore and slag is filled with the ore.

Michael Funk is an agricultural soil and water quality technician with the conservation authority.

He says a the pilot will include two- and three-foot diameter pipes with a system that will push water from farm drainage tiles up through the slag.

"As the water comes up and passes through this slag it will actually remove some of the phosphorus by binding to it as the water passes through."

Phosphorus has contributed to algae blooms in Lake Erie, impacting native fish species and other aquatic life.

UTRCA staff say most land owners have already taken significant steps to reduce phosphorus entering waterways.

Conservation Services Manager Brad Glasman says this could be an added level of protection, “This pilot’s a three-year pilot through the Great Lakes Stewardship Initiative and we'll be testing starting this fall and through the next three years."

Another goal was to limit economic impacts on the farmer. Because it's a waste product, the slag comes free from steel makers, but there is a cost for transportation.

The filters would also have to be changed periodically.

All those impacts will be part of the pilot program evaluation