RESUMO
Creosote is an organic pollutant formed by a complex mixture of highly toxic and carcinogenic compounds and classified as a dense non-aqueous phase liquid (DNAPL). Its migration depends on media and fluid properties that control the multiphase flow in the subsurface. Residual saturation and hydraulic conductivity are essential parameters to accurately simulate fluid displacement in porous media. This work shows the behavior of creosote in porous medium for sandy and clay soils, collected in a contaminated area in the state of São Paulo, Brazil. Creosote retention was evaluated and compared to water. The retention curve parameters were obtained based on van Genuchten and Brooks and Corey models. The hydraulic conductivities of creosote and water are presented for both soils. The results show that, in the clay soil, water was more retained than creosote, while in the sandy soil, creosote retention was higher. The hydraulic conductivity values obtained in the clay soil show a difference of two orders of magnitude between creosote and water. Although creosote is a viscous fluid, it presents considerable mobility in the clay soil, which is relevant in remediation processes. This study advances our knowledge about DNAPL behavior in clay and sand, and no other study of creosote parameters in these porous media was found. A more accurate estimate of the time required for a liquid spill to reach groundwater can then be predicted, so that appropriate actions can be taken and risk management can be carried out.
Assuntos
Poluentes do Solo , Solo , Argila , Areia , Creosoto , Poluentes do Solo/análise , Monitoramento Ambiental , BrasilRESUMO
Large-scale cultivations of photoautotrophic microorganisms represent a very promising and potentially cost-effective alternative for climate change mitigation, when associated to the co-production of high value bioproducts, such as fatty acids and carotenoids, considering the growing demand for natural products. During microalgae cultivation, CO2 enrichment is a requirement to reach high productivities, although high CO2 levels are normally stressful to microalgae. On the other hand, cellular stress is a well reported strategy to induce carotenoid and fatty acids production. This work evaluated extracellular carotenoid production from the mangrove-isolated microalga Parachlorella kessleri cultivated under 5, 15 and 30% CO2 in stirred tank photobioreactors. In the 10th day of cultivation, CO2 supply was interrupted until the end of the cultivation (14th day), causing a stressful and imperative condition for microalgae cells to release the red pigment. Growth kinetics, physiological parameters and bioproducts production were evaluated. Growth kinetics were similar under all tested conditions and differences were not statistically significant, with the highest values of µmax, biomass concentration, lipid content and CO2 fixation rate of 0.77 d-1, 1.24 g L-1, 241 mg g-1 (dw) and 165 mg L-1 d-1, respectively. In contrast, total carotenoid concentrations varied significantly (p < 0.01), with the highest concentration of 0.030 µg mL-1 under 5% CO2. The produced red pigment presented antioxidant activity and characteristics of carotenoids confirmed by UV-vis and tandem mass spectrometry (MS/MS). The fatty acid profiles in the biomass varied in response to CO2 levels in the cultivations. In general, higher CO2 concentrations (15 and 30%) favored the production of saturated and mono-unsaturated fatty acids, suitable as biodiesel feedstock, while drastically decreased the production of the polyunsaturated.
Assuntos
Clorófitas , Microalgas , Biocombustíveis , Biomassa , Dióxido de Carbono , Carotenoides , Ácidos Graxos , Fotobiorreatores , Espectrometria de Massas em TandemRESUMO
RESUMO: Nesse trabalho, objetivou-se recuperar o óleo presente na borra oleosa por processo de extração, a fim de reutilizá-lo como combustível. Foram aplicados dois planejamentos experimentais: fatorial fracionado e Doehlert. Através da caracterização da borra oleosa (análises físico-químicos, elementar CHN e S, orgânicas e inorgânicas), constatou-se que a borra oleosa utilizada é constituída de 36,2% de óleo, 16,8% de cinzas, 40% de água e 7% de compostos voláteis. A eficiência média do processo de extração foi 70%. Entretanto, a análise estatística mostrou que o modelo quadrático não se ajustou bem ao processo, devido à complexidade do material estudado. Por outro lado, aplicando-se a modelagem de RNA, o coeficiente de determinação foi de 87,5%, mostrando-se bastante satisfatório.
ABSTRACT: This work aimed to recover the oil present in oily sludge by extraction process in order to reuse it as fuel. Two experimental designs were applied: fractional factorial and Doehlert. Through characterization of the oily sludge (physico-chemical analysis, CHN and S elemental, inorganic and organic), it was found that the oily sludge used consists of 36.2% oil, 16.8% ash, 40% water and 7% volatile compounds. The efficiency obtained in the oil extraction process was 70%, in average. However, statistical analysis showed that the quadratic model did not satisfactorily the process due to the complexity of the studied material. By the other hand, applying ANN the coefficient of determination became 87.5% that is quite satisfactory.
RESUMO
The photochemical degradation of agrochemicals in aqueous solution by means of advanced oxidation processes (AOPs) was studied. The photo-Fenton process was evaluated in terms of the time evolution of dissolved organic carbon (COD) and chemical oxygen demand (DOC), their total removals, and increase in biodegradability of treated wastewater. Under the experimental conditions studied, the process showed to be superior to other AOPs, at any Fe(II) and H2O2 concentrations. The results pointed towards the use of solar irradiation and low cost commercial application.