Influência do teor de biodiesel no processo de degradação microbiana do óleo diesel e utilização de radiação ultravioleta como controle microbiológico

Abstract

Currently in Brazil the addition of biodiesel to diesel oil is 10%, with an increase to 15% already established. The mixture is possible due to its miscibility with diesel oil, which promotes environmental benefits, but the mixture becomes susceptible to degradation, where biodiesel contributes to water absorption, facilitating the contamination and proliferation of microorganisms. In view of this, this work aims to evaluate the influence of biodiesel content on the microbiological contamination of different blends of commercial diesel fuel B, and to verify the effect of ultraviolet radiation as a control method for the inactivation of microorganisms present. Samples of commercial diesel oil (B11) and pure biodiesel (B100) were collected, and blends with 25, 50, and 75% biodiesel contents were prepared and the influence of water content was evaluated at 1000 and 2500 ppm, values above the allowed by the legislation. After the blends preparation, the samples are stored for 10 days, characterized and after this period, taken to the ultraviolet radiation reactor, composed of a germicidal UVC lamp (55 W, 253 nm). The tests lasted 360 minutes, with collections every 60 minutes to perform the microbiological analysis and physicochemical analysis, before the process and after the 360 minutes. The microbiological characterization consisted of spectrophotometric quantification methods, Gram staining and molecular identification of the microorganisms. In the physical-chemical characterization of the fuel, the following analyses were performed: temperature, specific mass at 20° C, kinematic viscosity at 20° C, and water content. After the tests with ultraviolet radiation, the samples are stored for 10, 20 and 30 days, and at these times, aliquots are collected to perform the quantification of microorganisms, in order to verify the efficiency and time of action of ultraviolet radiation. The results showed that the initial storage period of 10 days favored the proliferation of microorganisms in some samples with added water. For the ultraviolet radiation tests, all samples had a reduction in the concentration of microorganisms above 50%, and the samples B11-C, B25-1000 and B50-C had a reduction percentage above 80%. It was possible to identify different microorganisms present in the diesel and biodiesel samples, such as: Solobacillus spp., Exiguobacterium scetylicum and Pantoea spp. For the physical-chemical properties evaluated, the addition of biodiesel and water promoted changes, but after the exposure period to ultraviolet radiation the values returned to those stipulated by the standardization. For the physical-chemical properties evaluated, the addition of biodiesel and water caused changes, but after the period of exposure to ultraviolet radiation the values returned to those stipulated by the standardization. For experimental storage of the fuel after exposure to ultraviolet radiation it was concluded that the action of radiation remains active for up to 10 days, and after this period it is necessary to perform the treatment again. With all the correlated data, it is concluded that the use of ultraviolet radiation was efficient to eliminate and/or reduce the load of microorganisms present in diesel oil and biodiesel.