I took some time out and went to visit the Management of Rietvlei Dam to find out what those floating structures were in the water and what their function is. I was referred to Leanne Coetzee who is a Director at the Water Treatment Works just below the dam wall. I arrived unannounced and a big thank you to Leanne for seeing me and this is the article that she sent to me regarding the Solarbee's.
Solarbee Technology – October 2009[/b]
The Rietvlei Dam has been used by the City since 1934 for the production of drinking water and produces about 36 million litres of drinking water per day, 365 days a year. This is approximately 6% of the city’s drinking water requirements. The WTW and the Rietvlei Dam are surrounded by the 4000 hectare Rietvlei Nature Reserve, set up to protect this valuable resource and home to a large variety of game including buffalo, rhino, hippo and cheetah.
The Rietvlei Dam has become severely eutrophic (nitrogen and phosphate enrichment) and, like many dams in South Africa, is plagued with cyanobacterial (blue-green) algae blooms especially during the warmer months. This enrichment causes excessive growth of undesirable aquatic plants especially cyanobacteria. These organisms cause tastes and odors as well as toxin release into the water. These compounds are difficult to remove and require expensive treatment at Rietvlei WTW, including ozone and activated carbon.
The City of Tshwane has been working in conjunction with the Department of Water Affairs and the Harties[/i] Metsi a Me[/i] project to find solutions for algal blooms, a problem in many South African impoundments. .Until now, there have not been any dam management approaches that have efficiently improved the water quality of eutrophic dams. Habitat disturbance is known to eliminate algal blooms by impairing the cyanobacteria’s ability to out-compete non cyanobacteria and not by limiting their nutrient availability. This method of lake management can now be utilized, since the development of the SolarBee, a solar powered water circulation machine, developed in the USA
SolarBee’s are up-flow pumps with a flexible intake hose that draws water from any set depth and distributes the water outwards, thereby creating laminar flow. One SolarBee is capable of producing 40 000 litres of flow per minute and treats up to 14 hectares of dam surface. In this way, the upper waters where the cyanobacteria grow are put into a slow but continuous motion, which creates an unfavorable habitat for these organisms. This decreases the cyanobacterial growth allowing the ecosystem to return to a more natural state by enabling the growth of green algae. These green algae are consumed and this allows the improvement of the entire food chain including oxygenating the water column, improved water clarity and increasing fish spawning and biodiversity in the dam.
There are 6 SolarBees being installed in the dam and we expect reduction of cyanobacterial numbers, improved oxygenation of the water and increased water clarity as well as a healthier ecosystem without stagnant waters. This should also improve the treatability of the water for drinking purposes with a cost benefit to the City. To date, this technology has been implemented in nearly 200 lakes in North America including 80 drinking water supply dams, with excellent results.
• Control of harmful algal blooms
• Reduction / elimination of odors
• Improved water clarity
• Reduction / elimination of seasonal fish kills
• Improvement in spawning, zooplankton no’s ↑
• Dissolved oxygen levels ↑ pH ↓ ammonia ↓
• Reduction of heavy metals released into water
• Substantial economic savings in chemicals, H2O, energy
• Enhances food web -improvement in species diversity
Our latest results indicate that the Secchi Depth (a measure of water clarity) is improving. A black and white disc is lowered into the water until just before it disappears and the depth is noted. Significant increases in water clarity have been noted compared to last year this time.
As development continues to encroach upon our natural resources, it becomes increasingly important that algal blooms are controlled and catchment and lake management is prioritized. This technology is the “greenest†most energy efficient and ecologically sustainable tool in the dam management toolbox to address this global problem.
[/b]
Solarbee Technology – October 2009[/b]
The Rietvlei Dam has been used by the City since 1934 for the production of drinking water and produces about 36 million litres of drinking water per day, 365 days a year. This is approximately 6% of the city’s drinking water requirements. The WTW and the Rietvlei Dam are surrounded by the 4000 hectare Rietvlei Nature Reserve, set up to protect this valuable resource and home to a large variety of game including buffalo, rhino, hippo and cheetah.
The Rietvlei Dam has become severely eutrophic (nitrogen and phosphate enrichment) and, like many dams in South Africa, is plagued with cyanobacterial (blue-green) algae blooms especially during the warmer months. This enrichment causes excessive growth of undesirable aquatic plants especially cyanobacteria. These organisms cause tastes and odors as well as toxin release into the water. These compounds are difficult to remove and require expensive treatment at Rietvlei WTW, including ozone and activated carbon.
The City of Tshwane has been working in conjunction with the Department of Water Affairs and the Harties[/i] Metsi a Me[/i] project to find solutions for algal blooms, a problem in many South African impoundments. .Until now, there have not been any dam management approaches that have efficiently improved the water quality of eutrophic dams. Habitat disturbance is known to eliminate algal blooms by impairing the cyanobacteria’s ability to out-compete non cyanobacteria and not by limiting their nutrient availability. This method of lake management can now be utilized, since the development of the SolarBee, a solar powered water circulation machine, developed in the USA
SolarBee’s are up-flow pumps with a flexible intake hose that draws water from any set depth and distributes the water outwards, thereby creating laminar flow. One SolarBee is capable of producing 40 000 litres of flow per minute and treats up to 14 hectares of dam surface. In this way, the upper waters where the cyanobacteria grow are put into a slow but continuous motion, which creates an unfavorable habitat for these organisms. This decreases the cyanobacterial growth allowing the ecosystem to return to a more natural state by enabling the growth of green algae. These green algae are consumed and this allows the improvement of the entire food chain including oxygenating the water column, improved water clarity and increasing fish spawning and biodiversity in the dam.
There are 6 SolarBees being installed in the dam and we expect reduction of cyanobacterial numbers, improved oxygenation of the water and increased water clarity as well as a healthier ecosystem without stagnant waters. This should also improve the treatability of the water for drinking purposes with a cost benefit to the City. To date, this technology has been implemented in nearly 200 lakes in North America including 80 drinking water supply dams, with excellent results.
• Control of harmful algal blooms
• Reduction / elimination of odors
• Improved water clarity
• Reduction / elimination of seasonal fish kills
• Improvement in spawning, zooplankton no’s ↑
• Dissolved oxygen levels ↑ pH ↓ ammonia ↓
• Reduction of heavy metals released into water
• Substantial economic savings in chemicals, H2O, energy
• Enhances food web -improvement in species diversity
Our latest results indicate that the Secchi Depth (a measure of water clarity) is improving. A black and white disc is lowered into the water until just before it disappears and the depth is noted. Significant increases in water clarity have been noted compared to last year this time.
As development continues to encroach upon our natural resources, it becomes increasingly important that algal blooms are controlled and catchment and lake management is prioritized. This technology is the “greenest†most energy efficient and ecologically sustainable tool in the dam management toolbox to address this global problem.
[/b]