Hydroxyl Radical-Mediated System for Effective Geosmin Mineralization and <i>Anabaena</i> sp. Inactivation for the Decontamination of Drinking Water

Hydroxyl radical (^•OH)-based decontamination approach is considered an efficient and eco-friendly technology, which can be a competitive solution to odor pollution. Geosmin (GSM) is an odor metabolite produced by the cyanobacterium <i>Anabaena</i> sp., which can seriously compromise the drinking water source quality. The independently developed ^•OH equipment based on strong ionization discharge produced ^•OH solution with high concentration, which was identified using electron spin resonance spectroscopy. Complete inactivation on <i>Anabaena</i> sp. and efficient degradation on GSM (to 4.26 ng/L, which is below the odor threshold of 10 ng/L) by ^•OH occurred concurrently within 12 s at a total reactive oxidant (TRO) concentration of 1.1 mg/L. The scanning electron microscopy results revealed that <i>Anabaena</i> sp. cells kept their physical integrity during ^•OH inactivation. The intracellular GSM barely released from the cells. The results of gas chromatograph/mass spectrometer analyses showed that the chromatogram converged to the baseline with a TRO concentration of 3 mg/L in 12 s, demonstrating that GSM was mineralized. ^•OH can open the ring structures to finally form CO₂, H₂O, and inorganic ions. While O₃ and ClO₂ failed to mineralize GSM when the reaction times are 10 and 60 min. Hence, ^•OH can inactivate <i>Anabaena</i> sp. without cell integrity loss and mineralize GSM simultaneously, the results of which support that the ^•OH technology may serve as the next-generation drinking water treatment to control algal odor problems.