FLOCCULATION AND SEDIMENTATION FOR CONTROL OF FLORIDA RED TIDE AND OTHER HARMFUL ALGAL BLOOMS

The worldwide proliferation of HABs in aquatic systems results in severe environmental, economic, and human health effects. These impacts emphasize the need for effective strategies to reduce the effects of HABs on coastal resources and communities, while causing minimal environmental impact. Strategies for flocculation and sedimentation of cells are at the forefront of HAB control technologies, with regular application in marine and freshwater systems in some parts of the world. This technology is achieved using combinations of clays, polymers, coagulants and other materials, sometimes with other chemicals acting as algaecides or contributing to toxin breakdown. Through multiple projects, we have examined the efficacy of several compounds, including mineral clays, polyaluminum chloride (PAC), activated carbon, calcium peroxide (CaO₂) and polyphenolic compounds, individually and in combination, for the destruction and removal of Karenia brevis cells and toxins. PAC-modified kaolinite clay rapidly removed cells from the water column (>90% in ≤6hrs at clay loadings ≥0.3g/L), although cells remained viable in floc for >48hrs and toxin removal was ≤50%. The addition of 5% curcumin with clay resulted in 100% cell death within 6hrs. PAC without clay but with 150mg/L CaO₂ resulted in 100% cell death within 2hrs. 0.5g L^-1 activated carbon with luteolin resulted in ~90% cell removal at 24hrs and >97% removal within 72hrs. This presentation will overview these studies, summarize results and consider the feasibility of applying these approaches as bloom control strategies.

Primary Presenter: Vincent Lovko, Mote Marine Laboratory (vlovko@mote.org)

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