Source water odor in one reservoir in hot and humid areas of southern China: occurrence, diagnosis and possible mitigation measures

Identifying typical odor-causing compounds is essential for odor problem control in drinking water. In this study, aiming at a major water source reservoir in hot and humid areas in southern China, which encountered seasonable odor problems in recent years, an integrated approach including comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC–TOFMS), flavor profile analysis (FPA) and quantitative real-time polymerase chain reaction (qPCR) was adopted to investigate the odor occurrence. The results indicated that earthy–musty odor is blamed to the seasonable odor problems, and it is consistent with the complaints results from consumers. Fifty-four typical odor compounds were investigated in the reservoir and twelve were detected, of which, 2-methylisoborneol (2-MIB) was significantly increased during the odor event. Pseudanabaena sp. is the dominant species in the reservoir, which can be further represented by the number of mic gene with qPCR method (R2 = 0.746, P < 0.001). Oxygen consumption (CODMn) and dissolved organic carbon (DOC) have great influence on growth of Pseudanabaena sp., and the release of 2-MIB from the Pseudanabaena sp. cells is affected by temperature and light. Our findings demonstrated that 2-MIB is the odor-caused substance in the reservoir and Pseudanabaena sp. is the main 2-MIB producer, which was confirmed as a benthic filamentous algae. Due to CODMn and DOC have great influence on Pseudanabaena sp. growth, further measures to reduce the CODMn and DOC input should be performed. We also demonstrated that the 2-MIB release is affected by temperature and light. The risk of sudden increase of 2-MIB will be reduced by raising the depth of water in the reservoir. Our study will improve the understanding of T&O problems in this city, as well as in other hot and humid area.