Application of a novel polarity method for the characterization of natural organic matter during water treatment

The changes in polarity of natural organic matter (NOM) across a pilot-scale conventional water treatment plant with pre-ozonation and biofiltration were analyzed using the polarity rapid assessment method (PRAM). PRAM is a novel method developed for the characterization of the polarity of NOM in environmental samples. Characterization was accomplished by monitoring UV absorbance (UVA) at 254 nm. Under ambient conditions, the NOM was characterized as highly anionic (>50%), with limited hydrophobic (10–25%) and hydrophilic (0–10%) domains. Results showed temporal variations in the polarity of NOM entering the pilot plant. These differences were ascribed to changes in water blend and variability in NOM characteristics. Changes in NOM chemistry were also observed as the organics passed through the treatment process. Ozonation decreased the hydrophobicity and increased the polarity of NOM, confirming results from previous research utilizing resin fractionation methods. Coagulation, flocculation and biofiltration resulted in the decrease of the hydrophobic and hydrophilic character of the chromophoric NOM. However, these polarity changes varied during the pilot plant run, suggesting a more precise evaluation of NOM through unit operations is warranted.