Follow-Up Treatment Using Lake Guard® Blue - Lev-HaNegev Reservoir, “Mekorot”, Israel
June 25, 2017
Place: Lev Hanegev Reservoir, Israel
Date: June 2017
A second, follow-up pilot was performed 3 weeks after the previous treatment, designed to demonstrate the superiority of the Lake Guard Blue® in the field. The treatment was applied at the request of Mekorot, Israel’s national water company. Based on the accumulated experience, the reservoir’s water level was reduced to form a ~6000 m2 (1.5 acres) surface area in order to examine whether a much smaller dose of Lake Guard® Blue can achieve the same successful results.
Pilot Protocol and Application:
Based on the conditions in the reservoir (an intensive green algae bloom), the water was dosed with 1 g/m2 – a total of 6 kg (12 lb.) of Lake Guard® Blue. This was 50% off the previous dose applied 3 weeks before and ~12.5% off the usual dose applied in regular treatments.
Measurements were taken at the surface of the water. Each measurement comprised 3 biological replicates and included: temperature, pH, %DO, specific conductivity, phycocyanin concentration, chlorophyll-a concentration, total copper concentration as well as filter-clogging time.
Treatment was applied, again, from the only access point at the northern part of the reservoir (Fig. 1A). Wind regime at the time of treatment was N-S.
Application time took ~5 min. The compound moved towards the southern part of the reservoir as expected (Fig. 1B).
Fig. 1. (A) time 0: Application of 6 kg (12 lb). Lake Guard® Blue. Wind regime at the time of application was N-S. (B) Time 10 min: floating granules of the algaecide move with the currents towards the southern end of the reservoir.
Measurements taken before treatment indicated the existence of a dominant bloom of green algae with an averaged Chl-A concentration of 58 µg/l (triple the concentration measured prior to the previous treatment, 3 weeks before). Within 24h these concentrations dropped by 82% to 10 µg/l – the same results in absolute terms as achieved in the previous treatment (Fig. 2A).
Phycocyanin levels (a proxy for cyanobacteria) dropped by 90%.
Total copper ions concentration in the water before treatment was below detection levels. Total copper averaged concentration 24h post-treatment was 0.05 ppm.
Filter-clogging time indicated an improvement of 110% in the quality of the water 24h following treatment (Fig. 2B).
A significant drop in pH from 8.07 to pH 7.7 within 24 hours indicated a massive lysis of the photosynthetic microorganisms and a heterotrophic bacterial activity over the lysed cells.
A drop in 44% of DO was also observed, from an average of 191% to 123%, and was probably the result of the same mechanism described above.
All other parameters (temp. and specific conductivity) did not vary significantly within the 24 hours from treatment.
Fig. 2. Measurements of (A) Chl-a concentrations, and (B) filter clogging time before and after treatment with Lake Guard® Blue. Arrows signal the time of treatment. n=3.
Efficacy of the Treatment with Lake Guard® Blue: the treatment proved to be efficacious in all relevant parameters within 24 hours from treatment.
Further Reduction of Effective Dose: the treatment achieved its goals of treating a bloom while using ~12.5% of the dose usually applied at this reservoir.
When taking into account that Chl-a levels tripled their levels compared with previous treatment while algicide quantities were halved, it can be concluded that this new operational methodology was 6-fold more efficacious relative to previous treatment!
The convenience of work and ability to operate prophylactically rather than in response to a bloom: As suggested in the previous report [LINK] total algaecide quantities were reduced significantly, from the regular treatment of ~50 kg to 6 kg, whilst achieving a dramatic and long-lasting effect.
Prevention of harmful algal blooms in the reservoir, avoidance of undesired suspension of operations throughout the season and reduction in complaints from end users.
Time and cost savings: dramatically reducing the dose and the time needed to effectively treat the reservoir.
Incidental cost savings are associated with reducing the amounts of needed chlorine needed at the intake; pesticides needed for treating subsequent crustaceans' nuisance; as well as reducing filters’ backwash.
Safety: the proposed treatment with Lake Guard® Blue reduces dramatically the safety hazards associated with the current treatment regime for the field operators. This routine includes:
exposure to high quantities of pesticides;
preparing them for treatment;
dangerous movement along the reservoir’s circumference in the attempt to spread the pesticides as evenly as possible.
As mentioned before, the application of the Lake Guard® Blue:
requires no preparation;
allows the use of minute quantities in comparison with the alternative;
can be applied from one point in the reservoir, even if suboptimal, while leaving the remainder of the spatial distribution of the compound in the water to winds and currents.
has a superior Environmental outcome, given the reduced copper levels and subsequent accumulation in the environment in absolute terms.
Protocol Fine Tuning: The excellent results of this pilot demonstrate the versatility that can be achieved through treatment with the Lake Guard®. Given its ease of use and the negligible operational costs associated with its application, operators can easily and cost-effectively “tailor” a treatment protocol to each and every reservoir. Such an approach can allow them to eliminate the tremendous trouble and high costs associated with handling blooms and replace them with a simple and cheap routine.
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