Use of solar water heating system for oil contaminated soil treatment

Bioremediation is one of the most efficient and widely applied methods of biotechnology, which also plays an important role in cleaning the environment from pollution by oil and oil products as well as rehabilitating the soil. Time is a limiting factor which prevents the effective use of biological treatment method, since the biodegradation of oil products is highly dependent on the season of a year and takes place only during the warm period, when the microorganisms act as active decomposers. Biodegradation of oil and its products takes about 9 months in a temperate climate zone. By properly organizing the modern biological systems of treatment of soil polluted by oil products, considerably better result can be achieved compared to previously used methods. Soil heating is one of ways to increase the intensity of biodegradation process of oil products. For this purpose the solar energy, one of the alternative energy sources, was used. Changes of diesel fuel and heavy fuel oil concentrations in soil during cold and warm season were studied. In order to determine the heat transfer process in soil, the modeling of the part of defined solar system had been done. The modeling realized using FEM (Finite Element Method) computer software constituted on numerical solution of heat equation. Simulation results indicate the dependency of contaminated soil temperature from the outer air temperature as well as comparing the physical experiments with the modeling results. To summarize the results we can state, that the outcome of biological treatment of samples using solar-based heating system during cold and warm seasons was better in both cases of pollutants. Heat produced by solar collector intensified the process of degradation of pollutants: in samples with solar-based water heating system, the diesel fuel removal level reached 70 %, in case of heavy fuel oil - 46 %, and in control samples it was 54 % for diesel fuel and 26% for heavy fuel oil. The treatment time of soil contaminated with oil products decreased accordingly. The obtained results allow to propose new technological principles of remediation of polluted soil, which decrease the treatment time, and thus the cost, and extends the area of application of alternative energy sources.