The aim of the present work was to evaluate the performance of a pilot-scale BAF in terms of removal of organic matter and suspended solids to obtain a highly polished effluent. The first part of the research was the evaluation of the optimal filter media for a full scale BAF. Mechanical and biological tests were performed over four materials: glass, plastic, pozzolan and expanded clay (Arlita) and the results obtained showed that the plastic spheres and the Arlita particles were the optimal materials for both the mechanical and biological requirements. Hence, a down-flow pilot scale BAF was set up in the laboratory to treat a synthetic medium. As filter media first plastic spheres and then Arlita spheres were used. Carbon removal studies were carried out at several influent COD concentrations, specific removal efficiency and COD profiles along the height of the filter were determined and used to analyze the process. Validation and calibration of a mathematical model formulated for carbon removal, were also performed by using the experimental data obtained. The results showed that this system allows us to achieve the more strict limits on final effluent.

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