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Observations from many countries around the world during the past 10-20 years indicate increasing natural organic matter (NOM) concentration levels in water sources, due to issues such as global warming, changes in soil acidification, increased drought severity and more intensive rain events. In addition to the trend towards increasing NOM concentration, the character of NOM can vary with source and time (season). The great seasonal variability and the trend towards elevated NOM concentration levels impose challenges to the water industry and the water treatment facilities in terms of operational optimisation and proper process control. The aim of this investigation was to compare selected raw and conventionally treated drinking water sources from different hemispheres with regard to NOM character which may lead to better understanding of the impact of source water on water treatment. Results from the analyses of selected Norwegian and Australian water samples showed that Norwegian NOM exhibited greater humic nature, indicating a stronger bias of allochthonous versus autochthonous organic origin. Similarly, Norwegian source waters had higher average molecular weights than Australian waters. Following coagulation treatment, the organic character of the recalcitrant NOM in both countries was similar. Differences in organic character of these source waters after treatment were found to be related to treatment practice rather than origin of the source water. The characterisation techniques employed also enabled identification of the coagulation processes which were not necessarily optimised for dissolved organic carbon (DOC) removal. The reactivity with chlorine as well as trihalomethane formation potential (THMFP) of the treated waters showed differences in behaviour between Norwegian and Australian sources that appeared to be related to residual higher molecular weight organic material. By evaluation of changes in specific molecular weight regions and disinfection parameters before and after treatment, correlations were found that relate treatment strategy to chlorine demand and DBP formation. Refereed/Peer-reviewed

In this study, changes in the physical and structural properties of natural organic matter (NOM) during titanium dioxide photocatalytic oxidation process were investigated using several complementary analytical techniques. Potential of the treated water to form trihalomethanes (THMs) and haloacetic acids (HAAs) was also studied. High-performance size exclusion chromatography analysis showed that NOM with apparent molecular weights of 1-4 kDa were preferentially degraded, leading to the formation of lower molecular weight organic compounds. Resin fractionation of the treated water demonstrated that the photocatalytic oxidation changed the affinity of the bulk organic character from predominantly hydrophobic to more hydrophilic. Short chain aldehydes and ketones were identified by mass spectroscopy as one of the key degradation products. The addition of hydrogen peroxide to photocatalysis was found to increase the degradation kinetics but did not affect the reaction pathway, thus producing similar degradation end products. The amount of THMs normalized per dissolved organic carbon (specific THM) formed upon chlorination of NOM treated with photocatalytic oxidation was reduced from 56 to 10 mu g/mg. In contrast, the specific HAAs formation potential of the treated water remained relatively unchanged from the initial value of 38 mu g/mg, which could be due to the presence of hydrophilic precursor compounds that were formed as a result of the photocatalytic oxidation process. Refereed/Peer-reviewed

The photocatalytic removal of humic acid (HA) using TiO2 under UVA irradiation was examined by monitoring changes in the UV254 absorbance, dissolved organic carbon (DOC) concentration, apparent molecular weight distribution, and trihalomethane formation potentials (THMFPs) over treatment time. A resin fractionation technique in which the samples were fractionated into four components: very hydrophobic acids (VHA), slightly hydrophobic acids, hydrophilic charged (CHA) and hydrophilic neutral (NEU) was also employed to elucidate the changes in the chemical nature of the HA components during treatment. The UVA/TiO2 process was found to be effective in removing more than 80% DOC and 90% UV254 absorbance. The THMFPs of samples were decreased to below 20 mu g l(-1) after treatments, which demonstrate the potential to meet increasingly stringent regulatory level of trihalomethanes in water. Resin fractionation analysis showed that the VHA fraction was decreased considerably as a result of photocatalytic treatments, forming CHA intermediates which were further degraded with increased irradiation time. The NEU fraction, which comprised of non-UV-absorbing low molecular weight compounds, was found to be the most persistent component. Refereed/Peer-reviewed

The objective of this study was to determine if the removal of NOM in reservoir waters in conventional treatment with alum is limited by the character of the NOM. A sequential jar test procedure, which included five treatment steps was employed to study the character of the NOM which could not be removed by flocculation/sedimentation. The NOM in the raw and treated waters was characterised by techniques including dissolved organic carbon (DOC), UV absorbance (UVA), high performance size exclusion chromatography (HPSEC), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). HPSEC analysis of the reservoir waters from three sources indicated that the organic fraction remaining after alum treatment was of lower molecular weight than that in the original raw waters. Pyrolysis of freeze dried material (FDM) from one raw water source (Hope Valley Reservoir) and following treatment with a high alum dose at pH 5 (coagulated and non coagulated material) gave by-products that indicated the presence of proteins, polyhydroxyaromatics and polysaccharides.

Two South Australian drinking water treatment plants (WTPs), Happy Valley and Myponga, with different source water supplies, were selected for an 18-month natural organic matter (NOM) characterisation case study. During this study (January 2001 to July 2002), the raw water dissolved organic carbon (DOC) concentration increased near the end of 2001; however, the applied alum dose required to maintain treated water DOC concentration decreased for both WTPs. This observation linked well with the results obtained from the rapid fractionation. It was found that the increase in organic carbon at the end of the year was mainly an increase of the very hydrophobic acids (VHA) fraction. This fraction typically has the characteristic of being easily removed by alum treatment. The use of the rapid fractionation technique to study the impact of organic character on disinfection was also very successful. The chlorine demand correlated well with the VHA fraction (r2=0.75 for Happy Valley and Myponga combined) while the r2 values of chlorine demand with DOC and UV were 0.55 and 0.58, respectively.

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.