Heavy metals, especially Pb (lead), are generally toxic to living things. Pb can contaminate organisms in the water through the food chain. The purpose of this study is to enhance water quality by using Salvinia molesta to phytoremediate Pb-polluted water. This study aims to evaluate the ability of S. molesta as a Pb phytoremediator. We evaluated total protein, free amino acids produced by the plant, and plant growth (dry biomass). S. molesta was grown in a hydroponic system exposed to Pb at dosages of 0, 5, 10, and 15 ppm for 7 and 14 days. Pb level was analyzed using Atomic Absorption Spectrophotometer and amino acids were analyzed using High-Pressure Liquid Chromatography. Data were statistically analyzed using analysis of variance (ANOVA) followed by Tukey’s test (α < 0.05). Results showed a significant change in Pb content in the roots and leaves of Pb-exposed S. molesta Mitch compared to control. In Pb-exposed plants, total protein and amino acids, especially cysteine, were lowered. S. molesta could be used as a Pb phytoremediator due to its high potential to survive Pb exposure and its ability to absorb Pb.

The higher areal productivity and lipid content of microalgae and aquatic weed makes them the best alternative feedstocks for biodiesel production. Hence, an efficient and economic method of extracting lipid or oil from aquatic weed, Salvinia molesta is an important step towards biodiesel production. Since Salvinia molesta is an unexplored feedstock, its total lipid content was first measured as 16 % using Bligh and Dyer’s method which was quite sufficient for further investigation. For extracting more amount of lipid from Salvinia molesta, methanol: chloroform in the ratio 2:1 v/v was identified as the most suitable solvent system using Soxhlet apparatus. Based on the literature and the preliminary experimentations, parameters such as solvent to biomass ratio, temperature, and time were identified as significant for lipid extraction. These parameters were then optimized using response surface methodology with central composite design, where experiments were performed using twenty combinations of these extraction parameters with Minitab-17 software. A lipid yield of 92.4 % from Salvinia molesta was obtained with Soxhlet apparatus using methanol and chloroform (2:1 v/v) as solvent system, at the optimized conditions of temperature (85 °C), solvent to biomass ratio (20:1), and time (137 min), whereas a predicted lipid yield of 93.5 % with regression model. Fatty acid methyl ester (FAME) analysis of S. molesta lipid using gas chromatograph mass spectroscopy (GCMS) with flame ionization detector showed that fatty acids such as C16:0, C16:1, C18:1, and C18:2 contributed more than 9 % weight of total fatty acids. FAME consisted of 56.32, 28.08, and 15.59 % weight of monounsaturated, saturated, and polyunsaturated fatty acids, respectively. Higher cetane number and superior oxidation stability of S. molesta FAME could be attributed to its higher monounsaturated content and lower polyunsaturated content as compared to biodiesels produced from C. vulgaris, Sunflower, and Jatropha.

Utilization of Salvinia molesta, an aquatic weed which is notorious for its allelopathy and invasiveness, has been explored by its vermicomposting. Fourier transform infrared spectroscopy (FT-IR) and plant bioassay tests were conducted to analyze the composition and fertilizer value of S .molesta vermicompost. Germination and seedling growth tests were performed in soil supplemented with vermicompost at levels ranging from 0.75 to 40% by weight of the soil on three common food plants, ladies finger (Abelmoschus esculentus), cucumber (Cucumis sativus), and green gram (Vigna radiata). The influence of S. molesta’s vermicompost on some of the physicochemical and biological attributes of the soil was also studied. FT-IR analysis revealed that S. molesta loses its allelopathy, as the chemical compounds that are responsible for it are largely destroyed, in the course of its vermicomposting. There is also an indication that a portion of lignin content of S. molesta is degraded. Vermicompost enhanced the germination success and promoted the morphological growth and biochemical content of the plant species studied. It also bestowed plant friendly physicochemical and biological attributes to the soil. The findings raise the prospect that billions of tons of S. molesta biomass―which not only goes to waste at present but is also a cause of serious harm to the environment―may become utilizable in organic agriculture.

Aquaculture is an activity with economic and social importance since it generates food, employment, and income. However, like other human activities, it negatively impacts the environment, in this respect mainly due to the production of effluents rich in sedimentable solids, organic matter, phosphorus, and nitrogen. These last two are responsible for the eutrophication of water courses, causing changes in the aquatic biota. Hence, there is a need to adopt strategies to improve the efficiency of wastewater reuse. In this sense, the objective of this work was to evaluate the efficiency of using the floating aquatic macrophytes Eichhornia crassipes, Pistia stratiotes, and Salvinia molesta for the treatment of aquaculture effluents. The experiment was conducted in a completely randomized design, with seven treatments and three repetitions; the treatments were the following: T1, without plant, treated only with sedimentation; T2, Eichhornia crassipes; T3, Pistia stratiotes; T4, Salvinia molesta; T5, Eichhornia crassipes and Pistia stratiotes; T6, Eichhornia crassipes and Salvinia molesta; and T7, Pistia stratiotes and Salvinia molesta. The treatments were evaluated for a period of 168 h: the first collection of effluent allowed analysis of the raw effluent; the second occurred 24 h after the first collection and the others, on alternate days with 72, 120, and 168 h, totaling five collections in each experimental unit. The effluent used came from breeding tanks of Nile Tilapia (Oreochromis niloticus). The quality of the effluent was evaluated by the rate of removal of nutrients N-total, N-nitrite, N-nitrate, N-ammoniacal and Ptotal, temperature, pH, turbidity, dissolved oxygen, electrical conductivity, total alkalinity, BDO, and CDO. After the effluent was treated, the values of the parameters were compared with the maximum admissible values (MAVs), as specified by Brazil’s National Environmental Council (CONAMA) in Resolutions 430/2011 and 357/2005. With the use of floating aquatic macrophytes, the concentrations of all evaluated limnology parameters improved significantly. There was also an improvement in the physical aspect of the effluent (transparency and turbidity). Thus, it can be concluded that the use of the macrophytes Eichhornia crassipes, Pistia stratiotes, and Salvinia molesta is effective in the treatment of effluents from fish farming.