A pilot plant study of the processes of filtration and adsorption of drinking water through granular activated carbons: a comparative study

This study reports a procedure for the evaluation and comparison of the adsorption and filtration capacities of commercial activated carbons in the treatment of drinking water and the design and operation of a pilot plant to simulate the behavior of fast open filters made of granular activated carbon. The milestone of this experimental work was to determine the adsorption and filtration capacities and the physicochemical properties of five commercial activated carbons with a view to determining which activated carbon might replace the open sand filters of the drinking water treatment plant (DWTP) of the city of Salamanca (western Spain). Compliance with the requirements and physicochemical characteristics stipulated in the EN 12915 European standard for the different activated carbons tested was analyzed, and studies of the prewashing and behavior of the carbons operating in the filters were performed. In this sense, filtration tests to study the saturation of the bed, the variations in pressure drop and the performance of the removal of organic matter in suspension were carried out. Furthermore, the optimal time and rate of the countercurrent washing of the filters and the expansion of the filter bed were evaluated. In the adsorption assays, the specific surface area, porosity, useful lifetime and capacity of adsorption of the dissolved organic matter –especially humic acids, the major precursors of water chlorination by-products – of the activated carbons were determined. The results not only provided an overview of the actual behavior of different types of commercial activated carbons from their initial installation up to the end of their useful life, but also permitted optimization of the filtration and adsorption processes that could lead to the corresponding economic savings and energy reduction in the use of such activated carbon filter-adsorbers.