A rapid characterisation technique for natural organic matter (NOM), specifically designed to study water treatment processes, is reported. The organic carbon concentrations of four NOM fractions, very hydrophobic acids (VHA), slightly hydrophobic acids (SHA), hydrophilic charged (CHA) and hydrophilic neutral (NEU), were determined.

Raw water and alum treated samples were analysed using this technique. A wide alum dose range (30–180 mg l−1 alum) was selected to simulate the situation of underdosing, conventional alum treatment, enhanced coagulation and extreme overdosing. The variation of the residual dissolved organic carbon (DOC) concentration of each fraction was used to interpret the removal mechanism under different situations. The results showed that the NEU fraction was hardly removed by alum treatment. The CHA fraction was readily removed in the underdosing and extreme overdosing situations. In the alum dose range covering the conventional to enhanced coagulation, both the SHA fraction and the VHA fraction were preferably removed. This technique could be applied in the operation of the treatment plant and could potentially guide treatment operators to control and monitor the treatment processes in the most effective way for NOM removal.