Color removal in granular activated carbon columns for improvement of fime installation effluent as a function of the rate of application

Abstract

The presence of humic substances in the water of supply has received attention of several researchers in the last decades, because it can generate by-products when exposed to oxidants and disinfectants. The multistage filtration (FiME) is an alternative considered to achieve water treatment for small size rural communities, however, the efficiency with relationship to the removal of true color associated to dissolved organic carbon or to humic substances, has been questioned or reported as low. Slow filtration with pre-ozonation is being used, since the ozone acted in the molecules of the organic matter of high molecular weight, increasing its biodegradability and by-products disappear soon after the application. The combined application of ozone and hydrogen peroxide has the objective of producing species with free radicals, of short-lived, that are highly reagents and can oxidize most of the present substances in the natural water. The present research evaluated the removal of humic substances in slow sand filtration, using for that evaluation indirect parameters as true color, absorbance 254 nm and dissolved organic carbon. Five experiments were realized using four slow filters, being two with layer of granulate activated carbon (GAC), in that several pre-oxidation alternatives were rehearsed with ozone and hydrogen peroxide. It was obtained, as main conclusion that the slow filters with GAC proceeded of oxidation with ozone and hydrogen peroxide, in appropriate doses, presented medium removal of true color of 64% of the initial color. It was also concludes that the hydrogen peroxide interferes in the development of the biological layer, interfering in the development of the loss of head, in the turbidity removal and in the removal of humic substances.