Fog-o-ponic cultivation of duckweed ( Lemna minor L.): an innovative technique for phytoremediation

Multitiered duckweed bioreactors have been developed but have limitations due to the weight of the water column. It was hypothesized that fog-o-ponic growth systems can enable space efficient duckweed culturing by facilitating stacked cultivation systems with multiple thin layers of duckweed, in the absence of a heavy water column. In this study, the growth was assessed of Lemna minor suspended on a fabric textile under a nutrient-rich medium provided as a fog. The best growth of L. minor was a relative growth rate (RGR) of 0.24 d⁻¹ with a maximum quantum efficiency (Fv/Fm) and light-adapted quantum yield (Y(II)) of around 0.8 and 0.5, respectively, which are values comparable to those achieved on traditional liquid medium under otherwise similar conditions. These results reveal that L. minor not only survives under fog-o-ponics culture conditions, but it thrives both in short and longer trials. Consistent with good growth, removal of nutrients by L. minor was considerably (e.g.,500 mg total nitrogen (TN) m⁻²day⁻¹) under fog-o-ponics conditions. It is concluded the innovative way of duckweed culturing comprises a promising, multi-stacked, high capacity, phytoremediation system.