GroundwaterTreatment using the Fenton process: Changes in Natural OrganicMatterCharacteristics andArsenic Removal

Abstract

This work investigates the use of Fenton's process (pH 5.5 and 6; 0.10-0.50 mM Fe(II); molar<br />ratios Fe(II) to H2O2 of 1:5-1:20) combined with flocculation for the treatment of groundwater which is rich<br />in natural organic matter (NOM) (10.6±0.37 mg C/L) and arsenic (110±6.7 μg/L). Changes to the character of<br />the residual NOM fractions were followed, as well as the removal efficiencies of NOM and arsenic. Under<br />optimal reaction conditions at pH 5.5, 55% of theDissolvedOrganic Carbon (DOC) was removed, whilst removals<br />of specific disinfection by-product precursors of trihalomethanes (THM), haloacetic acids (HAA) and<br />haloacetonitriles (HAN) were 80%, 75% and 98%, respectively. Total arsenic concentrations were reduced to<br />below 5 μg/L under all investigated experimental conditions. After the Fenton treatment, the percentage of the<br />hydrophobic NOMfraction (humic acid and fulvic acid fraction) decreased, and the percentage of the hydrophilic<br />fraction (acidic and non-acidic fractions) increased. The hydrophilic fraction, which was the most abundant in<br />the treated water, was also the most reactive fraction towards THM and HAA formation, whereas the residual<br />fulvic acid fraction contributed the most to the formation of HAN.