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62 Acre Lake Sludge Reduction

Updated: Feb 5

Who would have thought natural soil bacteria could reduce sludge by over 60% and increase oxygen substantially in a 62 acre lake?

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. It as known as the "hub" of Lethbridge.

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. Nutrient loading is a major issue in Henderson Lake, 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.

The Solution

AdvancedWater landed a 3 year tender to treat the lake for sludge reduction, which included once-a-week dosages of sludge digesting bacteria. This can only be done once the water temperature reached 10 degrees Celsius. 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).

The Results

During three years of treatment, Henderson Lake showed excellent visual and testing results in regards to sludge and oxygen 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).

64% reduction in organic sludge

Furthermore, oxygen levels were carefully monitored in the lake throughout the months of June - September. As you can see in the graphs below, prior to AdvancedWater treatment in 2011, oxygen levels dipped dangerously low in the months of July - August, reaching 0 mg/l.

During the very first year of treatment with AdvancedWater biologicals, oxygen levels remained constant and never reached 0 mg/l. Which is a testament to efficient nutrient cycling and sludge digestion promoted by the bacteria.

O2 levels in the lake in 2011. Zero O2 at 5m

Much healthier O2 levels in the lake in 2012

Water clarity was incredible during the last year of treatment

Dr. John Derksen, the owner of WET Environmental and also the Chair of the Aquaculture Centre of Excellence (Lethbridge College) spearheaded the research project, after having 15 years of baseline data prior to AdvancedAg's treatment.

Some information about Dr. John Derksen:

John is well known for his work in aquatic environments, as he has over 30 years’ experience in the fisheries and aquatic field, working for both provincial and federal governments, academia and the private sector. He is currently chair of the Aquaculture Centre of Excellence (ACE) at Lethbridge College and half time faculty and researcher. John has been with the College for 20 years, teaching courses in Aquatic Ecology, Fish Habitat, Fisheries Techniques, Fisheries Science, Water Quality, Limnology, Fish Culture and Senior Project. John is also involved with developing aquaponics curriculum. From a research perspective, aquaponics, aquatic ecosystem health, fish culture science and fish health are areas of research strength and experience. The science and ecology behind what makes aquaponics systems function is of particular interest to John as the potential of this growing technique for future generations is huge.

John maintains active involvement in his field through conferences and memberships (American Fisheries Society, North American Lake Management Society, Alberta Lake Management Society, Oldman River Watershed Council) and through managing is own environmental aquatic consultancy (WET Environmental Inc.). John has a B.Sc. in Fisheries Biology and a M.Sc. in Fish Pathology, both from the University of Guelph, Ont.

Below is a video of Dr. John Derksen talking about AdvancedAg's treatment on Henderson Lake, as well as some of the other treatment strategies used on the lake.

For a full report on the Henderson Lake Treatment Program, contact an AdvancedWater representative.

Want to hear Dr. John Derksen speak in person? RSVP to the Natural Lake & Pond Solutions Seminar below:

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