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This study investigates the use of a sodium sulfite tracer analysis to assessthe amount of gas bubbles trapped in a porous media. The objective was to contribute to thedevelopment of a new diagnostic tool to be used in waterworks to characterize andquantify air bubbles in rapid sand filters. This new method was developed and tested inlaboratory column experiments. The experimental set up was designed to reproduce the formation of bubbles in theporous media during rapid sand filtration. In this set of experiments, particle and solublecontaminant filtration was neglected and distilled water was used as inlet water. Tosimplify further the phenomenon taking place in the column during bubble formation,inlet water was saturated with oxygen. The bubbles forming in the column are thereforeoxygen bubbles.Experiments were conducted in a 63x63x313 mmsup3/sup transparent column packedwith 1 mm diameter glass beads. The porous medium (total pore volume of 522 ml) waswater saturated at the start of the experiment by flushing the column with carbon dioxideand then filling it with boiled water cooled to room temperature. Conclusions indicate that the observed conductivity breakthrough curves showed an increase of longitudinaldispersivity, in accordance with the literature, caused by the supersaturation of the inletwater. The conductivity, dissolved oxygen and pH curves evolved with time and with thepresence of oxygen bubbles in the column which were controlled by pictures andweighing of the column.The new tracer method developed in this study is useful to monitor thedevelopment of oxygen bubbles in the column; and, could therefore be a useful tool forinvestigating the presence of air bubbles in the filter bed of rapid sand filters atwaterworks. Includes 6 references, figures.

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Edition: Vol. - No. Published: 11/01/2009 Number of Pages: 5File Size: 1 file , 860 KB