groundwatertreatment using the fenton process: changes in natural organicmattercharacteristics andarsenic removal

this work investigates the use of fenton’s process (ph 5.5 and 6; 0.10-0.50 mm fe(ii); molarratios fe(ii) to h2o2 of 1:5-1:20) combined with flocculation for the treatment of groundwater which is richin natural organic matter (nom) (10.6±0.37 mg c/l) and arsenic (110±6.7 μg/l). changes to the character ofthe residual nom fractions were followed, as well as the removal efficiencies of nom and arsenic. underoptimal reaction conditions at ph 5.5, 55% of thedissolvedorganic carbon (doc) was removed, whilst removalsof specific disinfection by-product precursors of trihalomethanes (thm), haloacetic acids (haa) andhaloacetonitriles (han) were 80%, 75% and 98%, respectively. total arsenic concentrations were reduced tobelow 5 μg/l under all investigated experimental conditions. after the fenton treatment, the percentage of thehydrophobic nomfraction (humic acid and fulvic acid fraction) decreased, and the percentage of the hydrophilicfraction (acidic and non-acidic fractions) increased. the hydrophilic fraction, which was the most abundant inthe treated water, was also the most reactive fraction towards thm and haa formation, whereas the residualfulvic acid fraction contributed the most to the formation of han.