Performance of Lemna gibba bioreactor for nitrogen and phosphorus retention, and biomass production in Mediterranean climate

Lemna gibba (Lemnaceae) had been experimented in Morocco to develop macrophyte-based wastewater treatment systems adapted to the local climatic and socio-economic circumstances. This species growing on pre-treated urban wastewater, in a lagoon (Lemna bioreactor) operating in fed-batch, generates a net productivity of 28.39 t dw.ha^-1.yr^-1, through regular harvest of the biomass produced. In wet seasons the roots of this macrophyte generally exceed 10 cm. The Lemna lagoon clearly reduces plankton production, especially during the vegetative period, when compared to the bioreactor without macrophytes (lagoon; chlorophyll-a concentration of 86.4 ± 168 μg. l^-1). The Lemna bioreactor also removes more particulate nitrogen (N) and phosphorus (P), and shows a highly significant total P and significant non-particulate P retention, in comparison with the lagoon. L. gibba can export daily the equivalent of 13.2% of N and 19.9% of P entering the bioreactor. The algal flora is dominated throughout the year by phytoplanktonic populations of Euglenophyceae and Chlorophyceae. Branchiopoda (Daphniidae), Insecta (Dytiscidae Chironomidae, Culicidae and Heteroptera), and Gastropoda are the main taxa of animalia developing in the Lemna bioreactor. In the Mediterranean climate, the L. gibba bioreactors would be more profitable in the tertiary wastewater treatment, especially P removal, provided regularly collect of the biomass produced.

The potential of Lemna gibba L. and Lemna minor L. to remove Cu, Pb, Zn, and As in gallery water in a mining area in Keban, Turkey

This study was designed to investigate removal efficiencies of Cu, Pb, Zn, and As in gallery water in a mining area in Keban, Turkey by Lemna gibba L. and Lemna minor L. These plants were placed in the gallery water of Keban Pb-Zn ore deposits and adapted individually fed to the reactors. During the study period (8 days), the plant and water samples were collected daily and the temperature, pH, and electric conductivity of the gallery water were measured daily. The plants were washed, dried, and burned at 300 °C for 24 h in a drying oven. These ash and water samples were analyzed by ICP-MS to determine the amounts of Cu, Pb, Zn, and As. The Cu, Pb, Zn and As concentrations in the gallery water of the study area detected 67, 7.5, 7230, and 96 μg L(-1), respectively. According to the results, the obtained efficiencies in L. minor L. and L. gibba L. are: 87% at day 2 and 36% at day 3 for Cu; 1259% at day 2 and 1015% at day 2 for Pb; 628% at day 3 and 382% at day 3 for Zn; and 7070% at day 3 and 19,709% at day 2 for As, respectively. The present study revealed that both L. minor L. and L. gibba L. had very high potential to remove Cu, Pb, Zn, and As in gallery water contaminated by different ores.