The role of ozonation and activated carbon filtration in the natural organic matter removal from drinking water

Aquatic natural organic matter is one of the most important problems in the drinking water treatment process design and development. In this study, the removal of the natural organic matter was followed both in the full-scale drinking water treatment process and in the pilot-scale studies. The full-scale process consisted of coagulation, flocculation and flotation, sand filtration, ozonation, activated carbon filtration and disinfection. The aim of the pilot study was to investigate the influence of the dose and contact time of ozonation, and also the impact of activated carbon filtration, on the removal efficiency of organic matter. Several methods, including high-performance size-exclusion chromatography, total organic carbon content and assimilable organic carbon content measurements were used to characterize the behaviour of organic matter and its removal efficiency. On the full-scale process, total organic carbon was removed by over 90 %. According to size-exclusion measurements, chemical coagulation removed the high molar mass organic matter with an efficiency of 98 %. The ozonation further removed the smaller molar mass fraction compounds by about 27%, while residual higher molar mass matter remained quite unaltered. Activated carbon filtration removed primarily intermediate and low molar mass organic matter. In the pilot-tests, conducted with sand filtered water from the full-scale process, it was noticed, that the ozonation removed primarily smaller organic compounds. The amount of assimilable organic carbon increased with increasing ozone dose, up to 0.4 mg l(-1) with the highest ozone dose of 4.0 mg V. The activated carbon filtration removed the assimilable organic carbon. Total organic carbon content was not reduced in ozonation.