Impact of UV/H2O2 advanced oxidation treatment on molecular weight distribution of NOM and biostability of water

The presence of natural organic matter (NOM) poses several challenges to the commercial practice of UV/H2O2 process for micropollutant removal. During the commercial application of UV/H2O2 advanced oxidation treatment, NOM is broken down into smaller species potentially affecting biostability by increasing Assimilable Organic Carbon (AOC) and Biodegradable Organic Carbon (BDOC) of water. This work investigated the potential impact of UV/H2O2 treatment on the molecular weight distribution of NOM and biostability of different water sources. A recently developed flow cytometric method for enumeration of bacteria was utilized to assess biological stability of the treated water at various stages through measurement of AOC. BDOC was also assessed for comparison and to better study the biostability of water. Both AOC and BDOC increased by about 3–4 times over the course of treatment, indicating the reduction of biological stability. Initial TOC and the source of NOM were found to be influencing the biostability profile of the treated water. Using high performance size exclusion chromatography, a wide range of organic molecule weights were found responsible for AOC increase; however, low molecular weight organics seemed to contribute more. Positive and meaningful correlations were observed between BDOC and AOC of different waters that underwent different treatments.

► Impact of UV-H2O2 advanced oxidation treatment on biostability of water was investigated.
► Changes in molecular weight distribution of organics were monitored and linked to biostability.
► AOC and BDOC were compared as two parameters demonstrating biostability of water.
► Flow cytometric method was utilized for enumeration of bacteria in the AOC assay.
► Positive correlations were observed between BDOC and AOC of different waters.