Francisca Pessôa de França

A review of the technological solutions for the treatment of oily sludges from petroleum refineries

The activities of the oil industry have several impacts on the environment due to the large amounts of oily wastes that are generated. The oily sludges are a semi-solid material composed by a mixture of clay, silica and iron oxides contaminated with oil, produced water and the chemicals used in the production of oil. Nowadays both the treatment and management of these waste materials is essential to promote sustainable management of exploration and exploitation of natural resources. Biological, physical and chemical processes can be used to reduce environmental contamination by petroleum hydrocarbons to acceptable levels. The choice of treatment method depends on the physical and chemical properties of the waste as well as the availability of facilities to process these wastes. Literature provides some operations for treatment of oily sludges, such as landfilling, incineration, co-processing in clinkerization furnaces, microwave liquefaction, centrifugation, destructive distillation, thermal plasma, low-temperature conversion, incorporation in ceramic materials, development of impermeable materials, encapsulation and biodegradation in land farming, biopiles and bioreactors. The management of the technology to be applied for the treatment of oily wastes is essential to promote proper environmental management, and provide alternative methods to reduce, reuse and recycle the wastes.

Biodegradation of crude oil in sandy sediment

The bioremediation of light Arabian oil in sandy sediment by the mixed culture designated ND, obtained from landfarming, associated to indigenous microorganisms resulted in 42.9% reduction of the heavy fraction of oil in 28 days when a phosphate and a nitrate source were provided. Tests performed only in the presence of native flora, have achieved 11.9% removal of these compounds. These results have demonstrated the importance of utilizing cultures adapted to pollutants to enhance eAciency and productivity of the bioremediation process. # 1999 Elsevier Science Ltd. All rights reserved.

Lipopeptide Surfactant Production by Bacillus subtilis Grown on Low-Cost Raw Materials

The production of biosurfactant by Bacillus subtilis ATCC 6633 was investigated using commercial sugar, sugarcane juice and cane molasses, sugarcane juice alcohol stillage, glycerol, mannitol, and soybean oil. Commercial sugar generated the minimum values of surface tension, with the best results (28.7 mN/m, (relative critical micelle concentration [CMC−1] of 78.6) being achieved with 10 g of substrate/L in 48 h. At a pH between 7.0 and 8.0, a higher production of surface-active compounds and a greater emulsifier activity was also observed. Enrichment of the culture medium with trace minerals and EDTA showed maximum yields, whereas supplementation with yeast extract stimulated only cell growth. The kinetic studies revealed that biosurfactant production is a cell growth-associated process; surface tension, CMC, and emulsification index values of 29.6 dyn/cm, 82.3, and 57%, respectively, were achieved, thus indicating that it is feasible to produce biosurfactants from a renewable and low-cost carbon source.

Optimization of culture conditions for exopolysaccharides production in Rhizobium sp. using the response surface method

The combined effects of the processing parameters for exopolysaccharides production by Rhizobium sp. was studied using the experimental design and response surface methodology. The experiments were carried out using a fermenter with 20 L capacity, as the reactor. All processing parameters were online monitored. The temperature [(30 ± 1)oC] and pH value (7.0 ± 0.1) were kept constant throughout the experimental time. As statistical tools, a complete 2 3 factorial planning with central point and response surface were used to study the interactions among three relevant variables of the fermentation process: calcium carbonate concentration, aeration and agitation. The processing parameters setup for reaching a maximum response for exopolysaccharides production was obtained when applying the highest values for calcium carbonate concentration (1.1 g/L), aeration (1.3 vvm) and agitation (800 rpm). In addition, the combination of these optimum processing parameters yielded Y P/S (g/g) = 0.35.

Cadmium Uptake by Biosorbent Seaweeds: Adsorption Isotherms and Some Process Conditions

Abstract Cadmium biosorption was evaluated in 15 samples of heat-inactivated seaweeds collected from the coast of Rio de Janeiro State, Brazil. The classical Langmuir and Freundlich sorption models were fitted to the results in order to test whether these equations could appropriately describe the process of passive biosorption uptake. Depending on the algal sample and on some assumptions, both models could be applied to this study. The possible ion-exchange mechanism associated with the adsorption process was also investigated, as well as the effect of pH on biosorption and re-use of the different biomasses through several biosorption/ desorption cycles.

Biosorption of lead by the brown seaweed Sargassum filipendula -batch and continuous pilot studies

The biosorption of lead by the brown alga Sargassum filipendula was studied. pH 4.0 was the optimum value for the biosorption of lead. Isotherms indicated that for solutions containing 0.03 ± 0.001 up to 3.27 ± 0.04 mmol/L of lead, 2.0g/L was the optimum biomass concentration. The Langmuir model was fitted to represent the experimental data, and the kinetics of biosorption presented equilibrium in 30 min. The continuous system operated for 56 hrs presenting a 100% binding of ionic lead, which corresponds to an accumulation of 168 g lead, equivalent to a load of 1.7 mmol ionic lead/g Sargassum filipendula. The results that were obtained in a continuous system showed a gradual saturation of the biomass in the reactors.

Calcium interference with continuous biosorption of zinc by Sargassum sp. (Phaeophyceae) in tubular laboratory reactors

Abstract The zinc biosorptive capacity of the brown seaweed Sargassum sp. (Phaeophyceae) was studied in the presence or absence of competing calcium ions, using a continuous system with tubular fixed-bed reactors. In order to detect the effect of calcium on zinc biosorption, a 130 mg/l zinc solution was used, and calcium was added at 50–340 mg/l. The potential zinc biosorptive capacity of the biomass was markedly influenced by the presence of ionic calcium. Zinc sorption decreased with increasing calcium concentrations, as expressed by zinc uptake rates. Calcium was effectively recovered only during the initial stages of the process, as expressed by the decrease in its uptake rates. Calcium uptake rates were also much higher than zinc uptake rates, indicating that calcium was preferentially recovered when compared to zinc.

The behaviour of the microalgae Tetraselmis chuii in cadmium-contaminated solutions

The accumulation of cadmium by living and dead cells of the green microalgae Tetraselmis chuii was studied both in cell suspensions and in growing conditions. Microalgal cell suspensions accumulated a maximum of 292.60 (23.09) and 210.54 (16.05) mg Cd (g biomass)-1 when living and dried cells were used, respectively. After biosorption, the total cadmium accumulated was efficiently desorbed with concentrated EDTA solution, indicating that cadmium accumulation took place through surface structural components. During cell growth in cadmium-contaminated medium, the toxic effect of the metal proved to be higher for increasing metal concentrations in the medium. This increasing toxicity had a marked influence upon cell productivity. Cadmium was not incorporated during growth of T. chuii cells.The accumulation of cadmium by living and dead cells of the green microalgae Tetraselmis chuii was studied both in cell suspensions and in growing conditions. Microalgal cell suspensions accumulated a maximum of 292.60 (23.09) and 210.54 (16.05) mg Cd (g biomass)-1 when living and dried cells were used, respectively. After biosorption, the total cadmium accumulated was efficiently desorbed with concentrated EDTA solution, indicating that cadmium accumulation took place through surface structural components. During cell growth in cadmium-contaminated medium, the toxic effect of the metal proved to be higher for increasing metal concentrations in the medium. This increasing toxicity had a marked influence upon cell productivity. Cadmium was not incorporated during growth of T. chuii cells.

The release of light metals from a brown seaweed (Sargassum sp.) during zinc biosorption in a continuous system

The biosorption of zinc and calcium was investigated with a biomass of Sargassum sp., a brown seaweed, in a continuous system consisting of three serial tubular fixed-bed laboratory reactors. Results indicated that zinc was efficiently recovered by the biomass. After treatment of 9.0 liters of a mixed solution containing 130.0 mg/l zinc and 260.0 mg/l calcium, the first column of the system saturated with zinc; the remaining columns did not saturate with zinc as a result of the pre treatment performed by the first reactor. Calcium was also efficiently biosorbed by the biomass, saturating the system much faster than zinc. X-ray fluorescence spectrum indicated the presence of various elements in the structure of the Sargassum sp. biomass, especially alkaline and alkaline-earth elements. Alkaline and alkaline earth elements played a key role in the biosorption of zinc, being responsible for ion-exchange reactions performed during zinc biosorption.

Cadmium Interaction with Microalgal Cells, Cyanobacterial Cells, and Seaweeds; Toxicology and Biotechnological Potential for Wastewater Treatment

The accumulation of cadmium (Cd) by Tetraselmis chuii and Spirulina maxima was studied with dead and growing cells. Results indicated that the 2 microorganisms accumulated Cd by 2 different means according to the mechanisms involved—metabolism-dependent or metabolism-independent sorption. The mechanism involved in Cd accumulation on Tetraselmis chuii was restricted to surface phenomena, while in Spirulina maxima, Cd was accumulated on different layers of the cyanobacterium surface. In order to select a suitable immobilization support for the cells, several seaweeds were tested. Two types of seaweed were selected for experiments, using a small continuous pilot unit: Sargassum sp., a strong Cd adsorber, and Ulva sp., a poor one. The column reactors of the continuous system were filled with the algal supports and covered with dense microbial biofilms of Tetraselmis chuii or Spirulina maxima. The results obtained proved the success of the association between living microbial cells and dead seaweeds for operation of the continuous system.