Solar Bees
During 2005 the Steilacoom Lake Board of Directors entered into a one year agreement with Solar Bee to install and maintain solar powered equipment designed to prevent toxic blue-green algae blooms. Deployment of the Solar Bee equipment was the first full scale implementation of this technology within the Pacific Northwest region.
In December 2005 nine 10,000 gallon/minute SolarBee circulators were purchased by the Lake Steilacoom Improvement Club and installed at various locations throughout, Lake Steilacoom. Their purpose was to (1) suppress the growth of undesirable blue-green algae through habitat disturbance, by artificial circulation of the upper layer of warm water, (2) create conditions that would result in the growth of desirable forms of algae and (3) to eliminate toxic blue-green blooms that have plagued the lake on a yearly basis. During the period December 2005 through October 2006 the lake was extensively monitored to obtain data on the lake’s physical and biological response to SolarBee performance. Monitoring included biweekly sampling at seven locations lake-wide consisting of dissolved oxygen, conductivity, pH, temperature, secchi disk and turbidity. Phytoplankton sampling was also conducted and analyzed to determine concentrations and speciation identification.
Beginning in August 2006 and lasting through October the blue-green algae counts at Lake Steilacoom exceeded, many times over, the World Health Organization’s human health hazard limit of 100,000 cells per ml, in spite of SolarBee circulation of the lake.
During 2006, the units failed to suppress toxic algae bloom conditions. Blue-green algae species were noticeable in the water column during the mid summer months (July) and steadily increased in intensity through October.
Criteria established to evaluate Solar Bee performance
Prior to installation, specific performance criteria were established to assist the home owners association in evaluating the units operation. Performance criteria consisted of the following elements:
-
No toxic algae bloom as declared by the Pierce County Health Department.
-
No shoreline or mid basin floating green scums consisting of blue-green algae species.
-
Blue-green algae counts were not to exceed 25% of the total composition of samples taken.
-
Secchi disc readings where not to be less then 6 feet.
-
Blue-green algae counts were not to exceed the WHO standard for non-potable water bodies.
-
Unit performance would shift algae composition from one dominated by blue-green species to one consisting of green species and zooplankton.
-
Units would operate twenty four hours a day.
Solar Bee units failed to meet six of the seven established performance criteria. Of the seven criteria the units were only able to produce lake water quality that met the secchi disk standard of six feet. SolarBee circulation of Lake Steilacoom did not suppress undesirable blue-green algae populations and toxic blooms, did not create conditions that favored increases in desirable algae populations, did not produce lake waters that were free of surface scums consisting of blue-green species, did not produce lake water quality that was below Pierce County Health standards warranting lake closure associated with toxic algae conditions and the units did not operate continuously on a daily basis. There was no observed difference in the lake’s water quality during 2006 when compared to past years. Historical data supports the conclusion.
Why SolarBee Units Failed (opinion of Doug Dorling)
SolarBee unit circulation does not address the most important factor in suppressing toxic blue-green algae populations, which is reducing the concentration of their essential nutrient, i.e., soluble phosphorus. Circulation of the water column can be effective provided the blue-green algae cells are carried by induced water currents below the (sun) lighted zone of a lake, which is not possible in a shallow lake like Lake Steilacoom. (This is the main premise and science behind aeration systems. Algae must pass through a zone where photosynthesis does not take place so the algae will die.)
In a Memorandum dated March 18, 2005 addressed to SolarBee, personnel Dr. Chris Knud –Hansen stated: “Experience has shown that SolarBees will not be effective for blue-green bloom control if the photic (lighted) zone extends significantly below the intake hose depth. The photic zone in Lake Steilacoom extends to the bottom of the lake in the northern basin and extends below the thermocline in the southern basin. Solar Bee circulation was limited to above the thermocline in the southern basin and to within one foot of the bottom substrate in the northern basin.