Effects of ion exchange resin pre-treatment on GAC adsorption

Abstract

In Italian drinking water treatment plants (DWTP), the problem of chlorination by-products control is very important as the Italian drinking water regulations (Dlgs. 31/2001, as enactment of the CEU directive 98/83) set very strict limits for these compounds. A possible strategy for controlling the concentrations of DBPs (disinfection by-products) is the application of treatment processes able to reduce the concentration of dissolved organic matter, the main precursor of DBPs, before the dosage of chlorine-based disinfectants. Recently, ion exchange resins for the removal of dissolved organics have shown several applications in drinking water treatment. In this experimental study, the treatment with ion exchange resins MIEX®DOC and the treatment with GAC (granular activated carbon) were evaluated for the removal of dissolved organics. Moreover, the effects of MIEX® pre-treatment on the subsequent GAC filtration phase were evaluated, with particular attention to the effects on the life-time of the GAC filter. The GAC filter operation was simulated by rapid small scale column tests (RSSCT), which allow the evaluation of the GAC breakthrough curve in a shorter time with respect to a full plant and pilot plant trials. On the basis of the experimental results, the ion exchange process was very efficient in dissolved organics removal (60–70% UV254 removal). Moreover, the results indicated that the application of ion exchange resins as pre-treatment in a conventional drinking water treatment train could increase the filter life-time in the subsequent GAC adsorption phase (about 200%) resulting in potentially important cost benefits for the overall treatment process.