Microplastics (MPs) pose significant risks to aquatic life and human health. Conventional water treatment is ineffective in removing MPs, demanding alternative technologies. Biochar exhibits a potential for removing MPs through adsorption and filtration. The efficiency of biochar derived from macadamia (Macadamia Integrifolia) nutshells on MP removal from contaminated water was assessed in fixed-bed column tests at environmentally relevant MP concentrations in upward flowing regime. Fragmental polyethylene MPs (50-100 and 100-300 μm) were tested on the effects of the operating conditions, the relative MP-biochar size ratios (0.05-0.14 and 0.13-0.36 for small and large MPs), and biofilm formation on their retention in the biochar bed. The interactions between MPs and biochar are apparently electrostatically repulsive. Small biochar demonstrated >
78% removal of the MPs at flow rates of 2.78 × 10