Henderson Lake is an urban water body of approximately 25 Ha that occupies more than half the surface area of Henderson Park in the City of Lethbridge, Alberta. The lake is approximately 100 years old and surrounded by both a public park and golf course. The only controlled source of water to the lake is from the St Mary’s Irrigation District canal system, and the only discharge from the lake is from removal to irrigate the surrounding park and golf course and a manually operated drain to the storm sewer system.
The lake is approximately 1020 m long with a maximum width of 394 m and mean width of 255 m. The maximum depth is 5.5 m; the lake is relatively shallow with a mean depth of 2.6 m. The estimated volume of water in the lake is 176,909,052 gallons.
Water circulation and aeration of the lake is accomplished with the use of 5 SolarBee units that are installed for use during the summer and are removed during the winter months.
The lake is extensively used for surface sports including a Dragon Boat Festival in July of each year. Obviously, nutrient loading is a major issue in Henderson Lake, sometimes called, “The Gem of Lethbridge,” so every person participating in the festival and every person walking by had an opinion about the lake’s unpleasant odour, its cloudiness, and its visible sludge around the rocks on the edge of the lake.
AAG treated the lake, once a week, after the water temperature reached 10 degrees Celsius. The two bioreactors were on alternating schedules allowing for treatment to happen every week until the water temperature becomes too cold (end of September, or mid way through October).
Because this lake is close to our facility, we chose to do the treatments, as you can see the blue hose below, draining the incubated product into the lake, just off the boat dock.
During three years of treatment, Henderson Lake (approximately 180,000,000 gallons) showed excellent visual and testing results in regards to sludge levels. People walking by the lake commented on their ability to see the rocks around the edges of the lake. Residents commented regularly that the “nasty” odours were gone.
In the third year of treatment, substrate testing showed a 64% level decrease from the first year of treatment (Lethbridge College and WET Environmental).