Análise de eficiência da remediação por sistema extração multifásica em postos de combustíveis

Abstract

Gas stations are the primary source of soil and underground water contamination with BTEX compounds, such as Benzene, Toluene, Ethyl-Benzene and Xylene. This kind of contamination is due leaks in the storage system and also from bad operational workflow. To solve the problem, the areas are decontaminated with remediation techniques. MPE (Multi-phase Extraction) has been pointed as most effective, safe and low cost operation for toxic compounds removal, therefore is the most used process in this kind of situations. In this study we evaluated the effectiveness of MPE remediation in three fuel vendors, one in each south federative territory of Brazil. The evaluation was based in comparison between the physical features of the place where it was built, the contamination level and the local law. It was found that the MPE is an excellent technique because it could decontaminate if not totally, a great percentage of the toxic compounds found in the ground. It has been observed that some factors were critical for the success of the remediation, like the extension of the contamination and the good application of the technique and like it was expected, the largest area of contaminated soil demanded a larger time of process. The determination of risk analyses and of the targeted levels of contamination caused great impact in the timeline of the decontamination of dissolved hydrocarbon compounds. In all of the three cases in study, the legislation had no influence in the process, once that the goal levels of contamination were not defined by local law, but by each establishment. It was observed as well that the contamination plume has shrunken and did not exhibit any sign of movement, not even in direction of underground water flow. That implies that the vacuum used in the process was effective in pushing the water flow to extraction wells, proving that hydraulic gradient and flow speed of underground water had no influence in the remediation in any of the three observed processes.