Investigations into the impact of storage conditions and filtration on the analysis of natural organic matter in water

Abstract

When treating water for drinking water purposes, it is crucial to consider the composition of natural organic matter (NOM). NOM is a complex mixture of organic compounds influencing water quality and treatment processes. To ensure accurate reporting of analytical results, suitable sample storage and preparation are essential for maintaining sample integrity. This study investigated the effects of different storage conditions on water samples collected from Africa's largest bulk water provider, which sources its water from the Upper Vaal Catchment area. Samples were stored for varying durations under different temperature and light conditions to assess their impact on dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm (UV254). The results showed that storing water samples for 34 days in the dark, at room temperature or at 5 oC did not significantly alter the DOC and UV254 measurements compared to the initial sample measurements. The pre-washing of filters from different brands with ultrapure water indicated that there were retained UV-active contaminants in the filter materials, of which 81% to 91% were removed after washing with 25 mL of ultrapure water. Furthermore, the portable, battery-operated UV254 Go! analyser is a cost-effective tool for direct field measurements of NOM aromaticity.