(446c) Removal of Red Tide Cells (Karenia brevis) and Toxins By Modified Biochar Flocculation.

Frequent Harmful Algal Bloom (HAB) events are causing significant destruction to marine ecosystems and posing serious public health concern as microscopic algae releases toxins into seawater. Karenia brevis also known as red tide has consistently threatened Florida waters, including Gulf of Mexico, and the southwestern coasts. Neurotoxin like Brevetoxin is commonly produced from Karenia brevis, which leads to fish killings, and distressing diarrhetic, neurologic, and respiratory symptoms. This upsurge creates a negative impact on socioeconomic factors. To address this issue, this study investigates the use of biochar derived coagulants for the remediation of both intra-cellular and extra-cellular Karenia brevis cells. Corn stover biomass was pretreated with Poly aluminum Chloride (PAC) at varied weight dosages (1:2, 1:4, 1:8 and 1:10) and then pyrolyzed at 600 °C. Material characterization was performed on the PAC treated biochar, including Ultimate, and Proximate analysis, Thermogravimetric analysis, Brunauer-Emmett-Teller (BET) analysis, X-ray powder diffraction (XRD), Point of zero charge (pH_PZC), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Fourier transformation infrared spectroscopy (FTIR) and Ion Chromatography (IC). These results revealed that the procured coagulants are positively charged, low porosity, thermally stable, with a dense carbon core and aluminum surface. Flocculation experiments were conducted using these coagulants dispersed over the Karenia brevis cells exploring varying conditions such as dosage amount of coagulant (0.1 – 0.3 g/L), Low bloom concentration (5 × 10⁶ cells/L) and High Bloom concentration (10 × 10⁶ cells/L) all with respect to time. Intra-cellular cells were enumerated by using cell counting, while extra-cellular cells were quantified by Liquid Chromatography Mass Spectroscopy (LC-MS). The investigated biochar coagulants demonstrated versatility in mitigating Red Tide blooms and their adverse effects on the Karenia brevis cells and the dissolved Brevetoxin.