Monitoring and treatment of St. George lake to mitigate Cyanobacterial Harmful Algal Blooms (cyano-HABs)

This study aimed to monitor St. George Lake, located in the Athalassa National Forest Park of Cyprus, in order to correlate its trophic condition with its water quality characteristics and identify the key environmental variables driving cyanobacteria blooming and their cyanotoxicity. The monitoring lasted for 12 continues months, between January and December 2019, and samples were analyzed for several physicochemical parameters, cyanobacterial and green algae content, and cyanotoxins concentration. The actual blooming period was between May to September 2019, and 99% of the phytoplankton biovolume was attributed to a single picocyanobacterial species, the Merismopedia sp. Besides monitoring the lake, cyanobacterial contaminated water was also used to test novel oxidants that release hydrogen peroxide as a mitigation process. During the blooming period, water was collected and used for bench-scale experiments in order to compare different oxidation processes in terms of efficiency and targeted treatment, while taking into consideration the environmental impact of the treatment. Liquid hydrogen peroxide, calcium peroxide and magnesium peroxide granules were applied as mitigation processes for treating toxic cyanobacteria. The oxidants exhibited different efficiencies as the release of active hydrogen peroxide varied, with calcium peroxide being the most promising one for this dense bloom.