Place: Lev Hanegev Reservoir, Israel
Date: May 2017
The “Lev Hanegev” reservoir is managed by Mekorot, Israel’s national water company, supplying reclaimed wastewater for irrigation purposes. The reservoir is prone to repeated algal blooms (diatoms or Chlorella-like sp) which clog irrigation pipes and mandate regular treatment.
Mekorot is currently treating the reservoir periodically with ~25-50 kg (50-100 lb.) of copper sulfate. The application requires two workers and takes approx. half a day.
The Lev Hanegev reservoir holds ~12,000 m2 (3 acres) of surface water. Being a man-made wastewater reservoir, approaching the water is only permitted from a single designated location at its northern end. This predetermined application location limits the operator’s ability to optimally apply the Lake Guard™ upwind – in accordance with the flow of the currents. At the time of application, wind and currents rendered the application point suboptimal, carrying the floating granules sideways (Western wind, see picture below), rather than deep into and across over the reservoir. Furthermore, intensive pumping during the treatment resulted in a rapid recession of water levels.
At the time of application, the water in the reservoir was infested with a bloom of green algae, Chlorella-like sp., that dominated the entire water column.
Based on the conditions in the reservoir, it was determined to treat the water with 12 kg (24 lb., theoretical concentration of ~0.35 ppm) of Lake Guard Blue™, which is 25-50% of the usual dose applied during regular treatments .
Measurements were taken at the surface of the water as well as at a pumping location at the intake [2-3m (~6-9f) deep]. Each measurement comprised of 3 biological replicates and included: temperature, pH, %DO, specific conductivity, phycocyanin concentration, chlorophyll-a concentration, total copper concentration as well as filter-clogging time.
The treatment was applied at the Northern access point of the reservoir, the only place to approach the water. The entire dose was applied manually from the shore within 5 min. Immediately after application, the floating granules were dispersed by a western wind.
Measurements were taken before treatment, as well as 24 hours and 48 hours after treatment.