Cleaning Agricultural Water Naturally
By Adeline Panamaroff
Floating islands, metal-framed rafts stuffed with water-loving plants, strung across sloughs and storm ponds, are all part of the research that Olds College in Alberta is doing to clean water runoff from commercial feedlots.
How effective are these human-made islands? What maintenance do they require?
Filtering water for safe use in agricultural settings by natural means creates a very satisfying closed-loop cycle – from industrial waste runoff, to clean drinking or irrigation water – all on-site for one farmer.
Tannas Conservation Services, who have patented the design of the floating islands that Olds College are testing, have put these islands in use in diverse industrial settings.
These floating islands are now in Phase 3 of agricultural testing through Olds College’s Floating Island Technology for Livestock Water Remediation research project. They have also been used in coal mining tailings ponds to clear out heavy metals and in urban storm ponds to mitigate the runoff of fertilizers, herbicides and other chemicals used in city parks. This project focuses on cleaning the storm ponds of the excess nutrients that run off from adjacent feedlots.
Utilizing only plants that would naturally be found in Alberta’s wetlands, Phase 1, conducted in 2018, consisted of controlled greenhouse trials. Large tubs of water spiked with measured amounts of nutrients had a small-scale floating island installed on top.
Various plants were tested in this controlled environment, such as sedges, rushes, cattail and smartweed, which performed well in absorbing the excess nutrients. Phase 2, also a controlled greenhouse trial, differed from Phase 1 in that the water used in the tubs actually came from the college feedlot. Results from this phase showed that the plants removed 45 to 84 percent of nutrients, depending on the species.
Use of some plants ended once the project entered Phase 3 because “we’ve got environmental factors like wind and whatnot, and growing cattails on these big islands and big open areas is probably not practical because they are too large a plant,” says Daniel Karran, ecohydrologist and instructor at the Werklund School of Agriculture Technology, Olds College.
Phase 3 began in 2021 as a three-year data collection survey of four ponds near feedlots in the Linden, Alta. area.
The first year consisted of collecting baseline data on the levels of contaminants in the ponds. This was measured with instrumentation like H-Flumes, In-Situ Aqua TROLL 600 Sondes, and YSI ProDSS – all instruments that periodically test a wide array of water quality parameters. Weather stations were also used to measure wind, temperature and precipitation.
Larger islands on two of the ponds were installed in 2022, using two other ponds as controls.
“We have 41 islands in one pond, and we have 14 in the other pond. We were shooting for five per cent coverage of the ponds,” says Karran. The islands are “about 4.5 x 8.0' in size. Then inside it, there’s a soil medium. It’s a peat moss medium that’s in there. Then there’s a plastic membrane between the soil and the medium that allows the roots to grow through the plastic membrane into the contaminated water below.”
Testing with a mix of Baltic rush, sedges and chives, the islands were let loose for the growing season, with the most obvious sign of success being the growth of the plants.
Lab analysis includes weekly water samples from each pond to measure any reduction in contamination and tissue samples taken from both the roots and shoots of the plants to quantify the level of nutrient uptake.
Last year was the first season for plant growth on the islands. Early results showed that some plants, like chives, did not grow and so their use has been abandoned. While the root zones for the sedges and Baltic rush were not as large as hoped for, they did do well with their surface growth. With one more year of growth to go, it is hoped that those root zones will reach deeper into the ponds as they get more established.
Installation of the islands is easy. Strung together with carabiners, and secured to the pond’s edge with ropes, a line of floating islands can span the width of a storm pond and be moved as a unit or pulled off the water as needed.
As for maintenance, Karran’s advice is to “harvest the plant material every year, actually remove it, but in the case of nutrients, I think we’re assuming that that biomass is going to regenerate every year and then decompose in the soil media in the islands itself.”
If the floating islands turn out to be successful at cleaning storm pond water to a safe level to be used for cattle or for irrigation, it would be another low-cost tool for producers to increase their sustainability.
Having experienced a drought that has lasted a few years, access to as much clean water as is available can only be a good thing.
Funded by industry stakeholders such as Alberta Real Estate Foundation, Henry Heuver (founder of Foothills Landscaping), High Plains Industrial Park, RDAR, and UFA, this project hopes to have the technical report ready by mid 2025.
Long-term monitoring of the test ponds is the plan, but will depend on the availability of renewed funding.
“This knowledge is very much transferable to a lot of different sectors. We’re hoping to generate this knowledge for not only the ag sector, but for the floating islands itself, and for anyone who might consider it as a remediation tool,” explains Karran. BF
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