With more than 500 dairy operations, Alberta is Canada’s fourth-largest milk-producing province. Many of these farms rely on irrigation water to grow feed crops to sustain their cattle herds, but drought and water shortages in recent years have made that more difficult to do.
A team of researchers from Agriculture and Agri-Food Canada (AAFC) and Canadian universities want to help solve this problem, and they’re looking for a dairy farmer in Alberta to lend a hand.
Audrey Murray, an AAFC research scientist based in Charlottetown, is collaborating with Marico Arlos from the University of Alberta and Anne Laarman from the University of Waterloo in Ontario on a five-year study, which started this spring. The researchers are examining how wastewater from dairy operations can be naturally treated through constructed wetlands to produce water for irrigating cattle feed crops.
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To do this, Murray has assembled a series of pilot-scale wetlands at the Harrington research farm in P.E.I. to test different design variables for a dairy wastewater treatment system that can be put into practice on dairy farms.
Murray is currently seeking a volunteer dairy farmer in Alberta to partner with her team so a full-scale version of the system can be set up in that province later on in the project.
“We hope to find one as soon as possible, partly because we want it to be a co-development project. We would also like input from the producer, so they can let us know what they want. We want something that works for farmers, not just something that works technically. If it doesn’t work in a way that is helping them to run their farm, then it doesn’t necessarily meet our goals,” says Murray.
Once the project is completed, it’s hoped progressive early-adopters interested in this technology will have a tried-and-tested model for building such a system on their own dairy farms.
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Murray and her team hope to have an Alberta producer-partner recruited by next summer, so they can begin initial work on wastewater lagoon sampling and wetland design.
The researchers hope to hear from producers with 100 to 150 head of cattle and who also irrigate and grow feed crops, and they are getting the word out through farm conferences in Alberta and through Alberta Milk, the province’s dairy producers’ association. Those interested in participating in the study can contact AAFC at 1-855-773-0241 or by email.
Murray’s replicated experiments in P.E.I. are aimed at ironing out design parameters for effective wastewater treatment before a full-scale version of the system is set up in Alberta.
Once that’s up and running, likely by the third year of the project, farmers will be encouraged to check it out and familiarize themselves with this nature-based solution to water shortages.
“We’ve had calls from farmers in different parts of Canada who are thinking about wetlands on their property. Farmers are smart people, and a lot of them read research or are interested in this type of thing already. We’re basically just providing an opportunity,” Murray says.
She adds the goal is to provide dairy producers in Alberta with a clear roadmap for treating wastewater naturally and provide them with an extra irrigation source at a time when it’s most needed.
“This is what farmers are looking for. They need some direction,” Murray says. “One of our deliverables is to produce design guidance for this specific purpose in Alberta (and) find something that works well.”
She notes one reason researchers chose Alberta for the project was because that’s where they saw the greatest need for this kind of water treatment and re-use solution. “It’s important especially in an Alberta agricultural context. It might be a slightly harder sell in P.E.I., I think.
“They have water shortages in Alberta, and at the time we wrote this proposal, they were experiencing severe drought and had been told that they would get half the water allotments they usually get. If you’re a farmer in that position, you have to then find ways to make the best use of the water that you have, and water re-use could be a part of that.”
Murray has conducted other wetland studies in P.E.I., researching how constructed wetlands on potato farms can naturally filter water from field runoff before it enters nearby streams and rivers. As she points out, wetlands also provide natural habitats for many species of plants, animals and insects, and they can even help capture carbon and reduce greenhouse gas emissions.
Murray views her current wetlands project as one more application of her previous research, which she maintains hasn’t been explored for dairy farms in Canada up to now.
The middle layer
Here’s how the plan is envisioned to work in Alberta. Many dairy farms there have holding lagoons where wastewater from manure, used animal bedding and dairy production practices such as milk-house rinsing is stored. Farmers will often mix the contents of the lagoon in the spring, producing a nutrient-rich slurry that can be applied to crop fields as a natural fertilizer before planting.
Prior to mixing, the wastewater in these holding lagoons separates into layers, with a top layer that is thick and fatty and a bottom layer where much of the solids settle. There’s also a middle layer that contains the cleanest liquid — which is the basis of Murray’s constructed wetlands research. The treatment system starts with extracting this middle layer of liquid from unstirred holding lagoons.
“The ideal scenario is to build a wetland sightly downhill from the holding lagoon. A pipe is placed into the right location of the holding lagoon, connecting it to the wetland, and then gravity does the rest. This engineering solution is very common in municipal wastewater treatment plants,” Murray says.
As the water flows through the wetland, its quality is improved through physical and biological processes. It then enters a final mixing pond, where it is diluted with clean pond water and brought to quality standards required for use as a supplementary source of irrigation water.
“The wastewater is produced on site and the irrigation infrastructure is already there, so it’s just about tapping into that extra water source. It’s very efficient,” Murray says. She adds the end product may contain a bit more nutrients than regular pond water, but stresses it’s not meant to be used for fertigation purposes.
Murray is building her mini-version of this system using wastewater provided by local P.E.I. dairy farmers and mesocosms — that is, controlled outdoor experiments designed to simulate natural ecosystems. Various mesocosms consisting of different wetland soils and plants are being used to determine which are most effective in treating the wastewater.
Researchers are testing the output water quality from each mesocosm, and determining the ideal design concept and projected cost for the entire system, before moving forward with the full-scale design in Alberta.
Murray sees more possibilities for treating waste streams from other agricultural operations such as hog barns or feedlots this way, and she says she’d be interested in continuing her wastewater treatment and re-use research in this area.
“This is beyond the scope of this project, but I can see that there are many potential applications and a lack of clear design guidance for farmers who are interested in these technologies,” Murray says. “Hopefully there’ll be a continued appetite for this kind of research in the future. I think there might be.”
