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a b s t r a c tThe biodegradation kinetics of BTEX (benzene, toluene, ethylbenzene and xylene isomers) compounds were studied individually and as mixtures by using models with different levels of sophistication. In order to evaluate the performances of the unstructured models we used experimental data from literature. The system description was based on the material balances of key components for batch operations, where Monod and Andrews models were applied for the biodegradation of individual substrates. To simulate the biodegradation kinetics of substrate mixtures, models of competitive, noncompetitive and uncompetitive inhibition were applied along with the sum kinetics with interaction parameters (SKIP) models. The kinetic parameters were estimated via a global search method known as Particle Swarm Optimization (PSO). The main result of this study shows that the sophisticated biodegradation kinetics of BTEX mixtures can be successfully described by applying a SKIP model, with the main advantage being the consideration of the substrate interactions.

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In this work, the potential removal of Cd, Cu, and Zn ions by non-living macrophytes Egeria densa has been studied. The adsorption kinetic and equilibrium experiments of these three metals on E. densa were performed in batch systems with controlled temperature and constant shaking. It was observed that all metal adsorption rates have increased when the pH was increasing. A pH threshold of 5 was established for use in adsorption experiments in order to avoid the metal precipitation. For adsorption kinetic tests, the equilibrium times for all metals were around 45 to 60 min. The equilibrium data at pH 5 were better described by the Langmuir isotherm than the Freundlich one, with the adsorption rate and maximum metal content values of 0.43 L g −1 and 1.25 mequiv g −1 for Cd, 4.11 L g -−1 and 1.43 mequiv g −1 for Cu, and 0.83 L g −1 and 0.93 mequiv g −1 for Zn. These adsorption parameters for E. densa resemble or are better than those for other biosorbents already studied, suggesting that the macrophytes E. densa as a biosorbent has a good metal removal potential for applications in effluent treatment systems.

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Concentrations of trace metallic element as well as macronutrients were measured in water and plants from pond water. The aquatic macrophyte Salvinia sp. was evaluated for its trace metals removal potential in river water under laboratory conditions. The experiment were performed using several healthy acclimatized plants Salvinia sp. The water and grown plants were collected from ponds. For the trace element removals test, 30-35 grams of fresh aquatic plants were grown in river water into a greenhouse for ten weeks. Control plants were also grown during the experiment. Every two weeks, both plants and water samples were collected. After the end of each experiment, the growth rate was calculated. Trace element concentrations in plants and pond water were obtained using TXRF techniques. Values for the elements (K, Ca, Ti, Fe, Cr, Mn, Cu, Zn and Sr) concentrations in plant dry weight have been obtained after deducting metal contents of control plants. For each trace element, the aquatic Salvinia sp. plant showed to possess different affinity for the incorporation of the metals in its biomass. Results suggest the use of aquatic macrophytes Salvinia sp. for metal abatement in dilute wastewaters.

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