Catalytic wet peroxide oxidation to remove natural organic matter from real surface waters at urban and rural drinking water treatment plants

Abstract

Al/Fe-pillared-clay-activated catalytic wet peroxide oxidation (CWPO) of dissolved natural organic matter (NOM) in real surface water streams at both urban drinking water treatment plants (DWTPs) and rural plants (R) was investigated. The clay-catalyst prepared from technical-grade reagents exhibited textural properties quite comparable to those of the one obtained from analytical-grade, costly reagents. The mineralization of dissolved organic carbon (DOC) was improved to around 90 % under ambient conditions of temperature (10–19 °C) and pH (6.07–8.12), and not governed by adsorption of the complex on the catalyst’s surface. Optimal dose of hydrogen peroxide per unit mass of DOC and Fe in the solid was found to be 0.037 mg H2O2/mg C.mg Fe. The maximal efficiency of hydrogen peroxide consumption in the degradation of a synthetic surrogate of NOM (0.437 mg C/mg H2O2) was significantly enhanced in comparison with recent studies on phenol spiked solutions (≤0.124 mg C/mg H2O2), but also when real water samples were treated (0.176 mg C/mg H2O2), while the selectivity to DOC mineralization remained close to 90 %. Sulfates and chlorides in real surface waters showed the most detrimental effect on the DOC mineralization. The more cost-effective couplings of the Al/Fe-PILC-catalyzed CWPO treatment to improve urban drinking water treatment plants by promoting both DOC mineralization and improved H2O2 consumption as a function of the input SUVA254 were (raw water → CWPO → physicochemical treatment) for values < 2.0 dm3/mg DOC.m, and (raw water → physicochemical treatment → CWPO) for values > 2.0 dm3/mg DOC.m.