When Algae Collide: Unveiling the Causes of Odor Risks from Thioether Release in Drinking Water Sources

Taste and odor (T&O) issues in drinking water sources are common sensory concerns, with thioethers being major contributors to septic odors. Although algal metabolism is a known source of these odors, the mechanisms driving thioether production remain insufficiently explored. This study systematically analyzed the primary thioethers present in a reservoir-based drinking water source in southeastern China. Multiple algal species were cultured under near-natural conditions, both individually and in combination, to investigate the mechanisms of thioether release. The results revealed that dimethyl sulfide (DMS), reaching concentrations up to 2.54 μg/L, was primarily produced by Cyclotella (diatom). Dimethyl trisulfide (DMTS), with a peak concentration of 0.26 μg/L─exceeding its odor threshold by 26-fold─posed the highest odor risk and was mainly produced by Microcystis aeruginosa (cyanobacteria) and Cyclotella. Cyclotella emerged as the primary thioether-producing algae, particularly when coexisting with Microcystis aeruginosa. As the biomass of Microcystis aeruginosa increased, the growth of Cyclotella was inhibited and its proliferative capacity declined, resulting in a 32–54% increase in thioether release, whereas thioether production by Microcystis aeruginosa decreased by 17–76%. This study provides novel insights into algal interactions driving thioether release, guiding odor risk management in water sources.