Natural organic matter: Characterization and removal by AOPs to assist drinking water facilities

Abstract

The water sources of drinking water generally contain natural organic matter (NOM) as a result of the interactions between the hydrologic cycle and the environment. The amount, character, and properties of NOM vary considerably according to the origins of the waters and depend on the biogeochemical cycles of their surrounding environments. NOM can negatively influence water quality in drinking water supply systems, and it can significantly influence the performance of drinking water treatment processes. Hence, NOM removal is an important issue in order to optimize drinking water treatment operation and to reduce the risks of water alteration in the distribution systems. Several treatment processes can be applied for NOM removal depending on water quality, the nature of NOM, and the treatments already existing in the supply system. Among the most effective conventional solutions coagulation/flocculation, filtration, and carbon adsorption are available. An interest has recently increased toward nonconventional solutions based on membrane filtration and advanced oxidation processes (AOPs). An overview on the AOPs will be presented and discussed. Moreover, the AOP with ozone and UV radiation, with two low pressure UV lamps, at 254 and 185 nm wavelength, was experimented on a surface water in order to study the removal of odorous and pesticide, organic compounds (UV absorbance and THMs precursors) and bromate formation. Different batch tests were performed with ozone concentration up to 10 mg L−1, UV dose up to 14,000 J m−2, and a maximum contact time of 10 min. The main results show that metolachlor can be efficiently removed with ozone alone while for geosmin and MIB a complete removal can be obtained with the advanced oxidation of ozone, with concentration of 1.5–3 mg L−1 and contact time of 2–3 min, with UV radiation (with doses of 5,000–6,000 J m−2). As concerns the influence of the organic precursors, all the experimented processes show a medium removal of about 20–40% for UV absorbance and 15–30% for THMFP (trihalomethane formation potential).