Optimizing the growth conditions of the fern Pteris vittata maximizes its ability to phytoextract arsenic from drinking water in multiple cycles

The presence of arsenic (As) in drinking water poses a significant threat to public health and results in increased costs of water purification. Water phytofiltration using the As hyperaccumulator fern Pteris vittata is a promising green technology. However, for large-scale application, a fast uptake of As and the reuse of ferns in multiple cycles is necessary for an efficient As removal from drinking water at sustainable cost. This study investigated the efficacy of P. vittata in the treatment of spring water contaminated with about 60 μg L⁻¹ of geogenic As which is usually treated using costly chemical-physical filtration systems. To enhance the efficiency and reproducibility of P. vittata -mediated As phytofiltration, different key parameters were optimized including: i) ferns age, ii) phosphate (Pi) supply during ferns propagation, iii) As removal during subsequent phytofiltration cycles. Thus, As concentration in water and ferns grown individually was monitored over time. Our results indicate that As removal using old ferns was faster than using young ferns. Pre-treating the ferns with a phosphorus (P)-free solution enhanced As uptake and using a P-free solution in conjunction with old ferns allowed 98 % of As removal within 1 day. Moreover, As uptake further increased in subsequent phytofiltration cycles, and this efficiency was maintained when growing multiple ferns in the same tank. Altogether, these results definitively show that this strategy is an effective solution for treating spring water contaminated with geogenic As and opens the way for the scalability of this plant-based As phytofiltration technology.