Ciprofloxacin adsorption to magnetite-pine bark biosorbents as affected by preconditioning with distinct microbiomes

Biosorbents from agricultural and forestry waste are low-cost, eco-friendly, and biodegradable, offering abundant availability, reusability, and a low risk of secondary pollution. However, factors such as microbial colonisation can change their surface properties and affect adsorption efficiency. This study investigated how biosorbent loading with microorganisms affected the adsorption efficiency of pharmaceuticals. The adsorption efficiency of ciprofloxacin (CIP) on magnetite-pine bark (MPB) biosorbent was evaluated after preconditioning with either a population of specific bacterial cells (Aeromonas rivipollensis strain isolated from municipal wastewater) or hospital wastewater effluent harbouring a complex microbial community. The removal efficiency trends after exposure to pure culture bacteria at three timepoints of 3 h, 24 h, and 48 h showed more decline (5.1-56.6%) in performance compared to those (3.7-42.9%) observed after exposure to wastewater effluent at three timepoints of 3 h, 24 h, and 1 week. In most cases, 24-h bacterial or wastewater colonisation reduced adsorption efficiency to (18.2-56.6%) and (3.7-21.3%) in the order at contact times 10-360 min. According to 16S rRNA gene amplicon sequencing, Pseudomonas was the most abundant genus at all three distinct colonisation times (24 h, 48 h, and 1 week). Microbial diversity on the MPB increased progressively over time after being exposed to hospital wastewater over 24 h to 1 week colonisation times and bacteria from the hospital wastewater colonised the biosorbent. Collectively, these findings suggest that complex microbial communities in wastewater contribute both positively and negatively to adsorption performance.