Oxidation of geosmin and 2-methylisoborneol by the photo-Fenton process: Kinetics, degradation intermediates, and the removal of microcystin-LR and trihalomethane from Nak-Dong River water, South Korea

- The photo-Fenton process is effective method to remove taste and odor compounds.
- Degradation intermediates are related with dehydration and ring opening pathways.
- Degradation efficiency of GSM and MIB was mainly affected by pH.
- The photo-Fenton process also removes THMs and MC-LR in Nak-Dong River water.

Due to the increased intensity and frequency of cyanobacterial blooms, taste and odor (T&O) causing compounds, geosmin (GSM) and 2-methylisoborneol (MIB), have become a cause for great concern in drinking water treatment plants (DWTPs). Advanced oxidation processes (AOPs) have been studied for the removal of GSM and MIB. However, in this work, a photo-Fenton treatment was investigated for the first time for the degradation of GSM and MIB in both synthetic and Nak-Dong River water from DWTPs. Synthetic water-based experiments were performed to investigate the optimal operation conditions for the removal of GSM and MIB, and the effects of water quality parameters of the photo-Fenton process, including the Fe(II)/H2O2 concentration, reaction time, pH, organic matter, and initial concentration of GSM and MIB. Degradation intermediates of dehydration and ring-opening were observed during the photo-Fenton process. The optimal conditions were determined to be 2 mg/L Fe(II) and 20 mg/L H2O2 at pH 5 considering both efficiency and cost. The degradation efficiency was lower than that of DI water, mainly because of the pH (7.2-7.6). Nevertheless, the photo-Fenton process meets the guideline levels (20 ng/L) in South Korea when the initial concentration in the river water is below 50 ng/L. In addition, trihalomethanes (THMs) and microcystin-LR (MC-LR), derived from cyanobacterial blooms and another cause for concern, were degraded effectively using the photo-Fenton process on the river water.

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