Follow up use of Lake Guard Blue™ at Lev-HaNegev Reservoir, “Mekorot”
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 acre) 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 – 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 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.
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 (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 BlueTM. 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 in 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 in relative to previous treatment!
- 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 a 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 costs savings 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 to 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 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.