Tratamento biológico de solo contaminado por biodiesel bruto

Abstract

During the exploration, refining, transportation and storage operations of fuel and / or its derivatives may occur accidental spills causing contamination of soils, rivers, atmosphere (Andrade et al., 2010). A strategy for the elimination of fuel in the soil is the bioremediation. Its a process that transforms from the biological activity, contaminants in inert substances. This feature is limited by factors such as lack of micro-organisms or environmental conditions unfavorable to them. The aim of this study proposed the treatment of soil contaminated by crude biodiesel (CB) using mixed culture arising site contaminated by petroleum products. After adaptation of this crop to the CB was proposed to use three types of bioreactors: a) bioreactors tray open, b) bioreactor with trays closed system with controlled environment, as the temperature , moisture, nutrients (N and P) c) rotary reactor simple system with efficient stirring. These bioreactors were studied the following conditions: tray and rotary bioreactor with varying temperature and concentration of crude biodiesel (CD), and bioreactor tray with variation in the C: N and C: P.These bioreactors have as main purpose to increase the removal of the pollutant load (Crude Biodiesel- CB) and reduce the time bioremediation. Initially at the work was adapted a mixed culture into medium containing increasing concentrations of contaminants. In the sequence culture was adapted to contaminated soil. Preliminary tests were also conducted to identify the best working conditions for the concentration of initial inoculum and the amount of crude biodiesel supported by mixed culture. After preliminary tests were performed Delineation of Central Composite (DCC) ascertaining the tracks of study variables in the best conditions. Finally evaluations were carried out, these being tests with the best conditions obtained in the DCC. Throughout the study obtained as a result, the concentration of 8% v / v contaminant was the maximum supported by this culture. At this concentration was obtained by a removal of total organic carbon (TOC) content of 65% with a final cell concentration of 1010 CFU / mL. The mixed culture when passed to ground for adapting to the environment, showed a significant increase, reaching the end of the 56 days of the process at a cell concentration of approximately 1010 CFU / ml for bacteria and fungi. The first preliminary tests had the option of 25% (w / w) was chosen to obtain a desired amount of microorganisms (in the order of 1015 CFU / mL) and satisfactory results from removal of contaminants compared with other tests. The mixculture endured the same amount of contaminants in the liquid medium had when passed to the soil (80,000 mg CB.kg -1 soil). In the experimental design, each specific features presented, where the amount of removal CB ranged from 33.9 to 100%, 19 to 100% and 25 to 100%, in DCC1, DCC2 and DCC3, respectively. During the assessments, the microorganisms showed a good removal capacity, being well adapted and efficient, probably due to these microorganisms are already adapted. In the case of concentrations of 50,000 and 70,000 mg CB. kg-1 soil, the bioremediation time was 21 days (less time than shown in the experimental design), while the concentrations of 100,000 and 120,000 mg CB. kg-1 soil, the time was 42 days (these values of concentration are higher than these biodiesel concentration used in the experimental design).