Molecular-level characterization of biodegradable organic matter causing microbial regrowth in drinking water by non-target screening using Orbitrap mass spectrometry

Abstract

Biodegradable organic matter (BOM), which can be partially evaluated by assimilable organic carbon (AOC), can deteriorate the biological stability of drinking water, causing microbial regrowth in premise plumbing. However, little information is available about the compounds consisting of BOM or AOC. In this study, non-target screening analysis using high-resolution Orbitrap mass spectrometry (Orbitrap MS) was applied to resolve the BOM candidates in drinking water. The ozonated water was incubated with a microbial community in the effluent from biological activated carbon (BAC) filtration. Changes in the molecular-level composition of dissolved organic matter before and after incubation were assessed by Orbitrap MS. In the ozonated water, 14 components were extracted as BOM candidates. On the other hand, 22 BOM candidates were screened in the finished drinking water incubated with an indigenous microbial community proliferating in drinking water. Comparison of these candidates showed that the ozonated water and finished drinking water had different BOM compositions. A chlorine disinfection experiment demonstrated that most of the 22 BOM candidates in the finished drinking water were generated as chlorine disinfection byproducts. Although BAC filtration effectively removed BOM candidates generated by ozonation, different types of BOM were generated by the final chlorine disinfection. Chlorine disinfection is indispensable for microbial risk control, but it also influences the residual BOM composition in drinking water causing microbial regrowth.