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What does an Alberta dairy farm and a Prince Edward Island research scientist have in common? They both want to get moving on efficient water use. It’s all part of a new 5-year research project with Agriculture and Agri-Food Canada (AAFC) Research Scientist, Dr. Audrey Murray, in collaboration with researchers from the University of Alberta and the University of Waterloo in Ontario. The project is funded by Alberta Innovates and Results Driven Agricultural Research.
“I’ve always had an interest in water reuse. Water is a limited resource and drought conditions in Alberta have increased the need to improve water use efficiency. Certain natural climate solutions can provide many ecosystem benefits like high-quality water.”
- Dr. Audrey Murray, Research Scientist, Agriculture and Agri-Food Canada
Dairy farms often rely on irrigation to grow cattle feed. Water in Southern Alberta runs from farm to farm through an extensive network of ditches. Each farm has their own water holding pond used for household and cattle needs, as well as for irrigating crops. With drought and water shortages becoming more common in recent years, farmers have less water to use on crops as they prioritize water use toward cattle and household needs.
Farms in the region also have holding lagoons which store the wastewater from dairy production, like milk house rinsing water, used bedding straw, manure, and more. Currently, farmers mix the contents of the lagoon in the spring, to produce a nutrient-rich slurry that can be applied to crop fields as a naturale fertilizer before planting. Dr. Murray and her collaborators are studying a way to extract some of the wastewater from unstirred holding lagoons. This water can then be treated and used for irrigating crops throughout the growing season with a little engineering and a larger natural climate solution.
Treating wastewater with constructed wetlands
For several years, as part of Living Lab – Prince Edward Island, Dr. Murray studied constructed wetlands on farms to see how they can naturally filter water from farm field runoff before it enters receiving waterways such as rivers and streams. Wetlands also provide habitats for many species, such as plants, insects, amphibians, birds, waterfowl, and other wildlife. They can even help capture carbon and reduce greenhouse gas emissions.
Like cream mixed with milk, over time, wastewater in holding lagoons will also separate into layers – the top layer is thick and fatty, the bottom layer is where much of the solids settle, with the middle layer containing the cleanest liquid. It could be liquid gold, according to Dr. Murray, once Newton’s law can be applied to move the middle layer into a constructed wetland for further polishing.
“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.”
- Dr. Audrey Murray, Research Scientist, Agriculture and Agri-Food Canada
Similar to a sewage treatment plant design, the effectiveness of farm wastewater treatment improves water quality with each additional stage — making it a numbers game where more steps lead to better results. The holding lagoon provides pre-treatment through settling and anaerobic digestion, a natural process where microorganisms break down organic matter. The wetland continues to improve the water quality through physical and biological processes. A mixing pond will serve as the final treatment stage where treated water is diluted with clean pond water to meet quality standards providing a supplementary irrigation source for irrigating crops.
Applying this unique concept to dairy farms is one that hasn’t been explored in Canada until now, and Dr. Murray is on the hunt for a volunteer farmer in Alberta to participate. But before the wetland and mixing pond can be constructed on a farm, Dr. Murray is creating a scaled-down model to prove the concept.
Wading in with mesocosms
At the Harrington Research Farm on Prince Edward Island, Dr. Murray is building her own wastewater treatment plant on a much smaller scale by using mesocosms and wastewater from local dairy farmers. A mesocosm is a controlled outdoor experiment system designed to simulate a natural ecosystem, in this case.
Each mesocosm will be comprised of various wetland materials, such as various plants and soils, to see which ones are most effective in treating the wastewater. Other research results indicate that constructed wetlands paired with mixing ponds can effectively treat wastewater over periods ranging from approximately 3 days to 2 weeks depending on environmental circumstances. Dr. Murray will test the output water quality from each mesocosm, as well as determine the ideal design concept, and cost for the entire system, before moving forward with the full-scale design in Alberta.
Once the project is finished the team hopes to have a clear roadmap to help dairy farmers treat their own wastewater naturally and provide an extra irrigation source at a time when it’s most needed. Dr. Murray hopes that dairy farmers will soon be able to milk it for all it’s worth.
Key benefits and discoveries
- Dairy farms often rely on irrigation to grow cattle feed. With drought and water shortages becoming more common in recent years, farmers have less water to use on crops as they prioritize water use toward cattle and household needs.
- AAFC scientist Dr. Audrey Murray and other researchers began a 5-year project to study a way to naturally treat dairy wastewater with a constructed wetland and mixing pond, so water can be used for irrigating cattle feed crops throughout the growing season.
- At the Harrington Research Farm on Prince Edward Island, Dr. Murray is building her own wastewater treatment plant on a much smaller scale by using mesocosms and wastewater from local dairy farmers.
- Dr. Murray will test the quality of the water from each mesocosm, as well as determine the ideal design concept, and cost for the entire system, before moving forward with the full-scale design in Alberta.
- The team is currently recruiting an Alberta farmer to participate in the research project.
Photo gallery
Dr. Audrey Murray is researching wetlands constructed on farms on Prince Edward Island and hopes they can be used to treat dairy wastewater in Alberta.
Before developing a full-scale wetland in Alberta, Dr. Murray is testing the concept in mesocosms, shown above, at the Harrington Research Farm.