(142a) Removal of Red Tide Cells (Karenia brevis) and Toxins By Modified Biochar Flocculation

With frequent Harmful Algal Blooms (HABs) events occurring destruction to marine ecosystems, and public health is of serious concern as microscopic algae lyze lethal toxins into freshwater and seawater. Karenia brevis also known as red tide has posed consistent threat to Florida waters such as Gulf of Mexico, and the southwestern coasts. Neurotoxin such as Brevetoxin are commonly produced from Karenia brevis, which causes fish kills, and distressing diarrhetic, neurologic, and respiratory symptoms. Thus, this upsurge adversely creates a negative impact on socioeconomic factors. This study navigates the use of biochar mixed with coagulant, polyaluminum chloride (PAC) to remove both the intra-cellular and extra-cellular (ruptured) brevetoxin cells. The modified biochar coagulants were synthesized via pyrolysis of at 500 °C for 1 h with varying biochar to PAC (0.5 mol/L) ratio of 1:5, 1:10 and 1:15. As biochar : PAC ratio is varied, observations on the material characterization were performed namely, ultimate and proximate analysis, thermogravimetric analysis, Brunauer-Emmett-Teller (BET) analysis, X-ray powder diffraction (XRD), point of zero charge (pH_PZC) and, Boehm titration analysis, and Fourier transformation infrared (FTIR) spectroscopy. Flocculation experiments were performed using slurry concentration of biochar coagulant (0.5 g/L) dispersed over known initial cell count of Karenia brevis. For this study, slurry concentrations were concocted by suspending biochar coagulant with deionized water. Ultimately, a 24 h study was performed to observe the behavior of Karenia brevis cells once interacted with the varying modified biochar coagulants. Analysis of remaining cells and ruptured toxins were identified by cell-counting and High-Performance Liquid Chromatography (HPLC) respectively. For the ruptured cells, microscopic examination were performed to confirm lysing of the cells. As a result, the investigated biochar coagulants showed versatility in mitigating Red Tide blooms ensuing adverse effects on the Karenia brevis cells and the dissolved brevetoxins.