Phosphorus removal project in the Holland Marsh delayed for more testing

Monday, February 28, 2011

A type of clay developed in Australia may provide a temporary solution to phosphorus finding its way into the Holland River. But growers have some questions about its possible effects on their fields

by MARY BAXTER

When the Lake Simcoe Region Conservation Authority delayed a pilot program to remove phosphorus along a portion of the Holland Marsh's interior canals until more testing could be done, Alex Makarenko was among those who expressed relief.
"There are too many questions," says this carrot, celery and onion grower, who is also chair of the Holland Marsh Growers' Association.

The conservation authority, working with local and provincial partners, had launched the project in 2008. It proposed using engineered clay to remove phosphorus that had found its way into the Holland River from the former marsh. The goal was to explore the product's effectiveness.

The area falls under the provincial Lake Simcoe phosphorus reduction strategy that aims to reduce the amount of phosphorus released into Lake Simcoe to 44 tonnes per year. Currently, 72 tonnes is released annually into the lake. Runoff from agriculture within the Holland Marsh accounts for about four per cent of this load; agriculture within the entire watershed accounts for about 25 per cent. Runoff from urban development and airborne discharges are other major sources.

Mike Walters, general manager of the authority's watershed management program, says area authorities have been exploring ways to reduce phosphorus runoff from farming of the Holland Marsh's rich organic soils since the 1980s. "None of them have met our criteria," he says.

The clay, Phoslock, checked all the right boxes. It was safe for the environment and people, and cost significantly less per kilogram of phosphorus removed than a storm water pond or sewage treatment plant. It is envisioned as a temporary solution. The permanent solution would be best management practices to reduce fertilizer applications, Walters says.

Invented by Australia's national research council, Phoslock is a clay-like granular material that contains the naturally occurring earth element lanthanum. It is mixed with water to form slurry before being applied to a body of water.

As the granules sink to the bottom, phosphorus binds with the lanthanum. Once they reach bottom, the granules form a paper-thin layer that prevents the release of phosphorus from the waterbed's soil. The product has been commercialized by Phoslock Water Solutions Limited, which claims it has been used successfully to treat phosphorus problems in water bodies in Europe, the United States, China and Australia. "It's very effective," says Walters.

The authority had wanted to test the product at the point where the Holland Marsh's inner canal emptied into the Holland River during spring runoff. A pump house there controls water levels in the former marsh's canals and provides an opportunity to take accurate measurements. "We can get a really accurate picture of . . . how much phosphorus is discharged into the lake from the marsh every year," Walters explains.

But early on, Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) representatives questioned what effect treated water used for agricultural irrigation would have on crops. No one knew.

The growers' association became concerned. "We're not saying yes, we're not saying no; we're sort of saying no right now until we get more information," says Makarenko. He recognizes the location would provide access to precise measurements, but notes that the Holland Marsh is a tiny part of Lake Simcoe's phosphorus problem. Locating the pilot farther downstream, where one of the canals on the marsh's perimeter meets the river would make more sense "because then it covers a bigger area."

The authority revised its plans and first tested the product in a storm water pond and a reservoir. It didn't see any negative impacts, Walters says.

Meanwhile, the OMAFRA and the University of Guelph researched Phoslock's effect on crops. Preliminary results indicate there is no impact; final results have not yet been released. The authority is now searching for a consultant to co-ordinate the design of a test at the original location.

Jamie Reaume, the growers' association executive director, says the farmers still have some concerns, such as the interaction between Phoslock's clay base and the muck soils if sediment dredged from a treated canal ends up on fields. Yet it's a small pilot, he stresses. "They're not going to be going in and doing seven kilometres of Holland Marsh canals; they're going to be doing 150 to 200 yards."

He also credits the authority for taking the farmers' concerns into account. "I think we're far better off doing a smaller pilot and getting the results from the water than we are to just throw everything in and do it carte blanche." BF