Comparison of OH and NaClO on geosmin degradation in the process of algae colonies inactivation at a drinking water treatment plant

Abstract

• OH equipment was developed to install in drinking water system of 12000 m 3 /day. • OH degraded GSM in the process of algae colonies inactivation within 20 s. • OH inactivated algae colonies to individual intact ones without IOM release. • OH mineralized GSM through the crucial ring opening reactions. • All water quality and DBP indexes satisfied the limits of Chinese Standards. Excessive proliferation of cyanobacteria blooms resulting in metabolic musty-earthy odor materials such as geosmin (GSM) pose potential risks to aquatic ecosystems and human health. In this paper, a high-yield OH equipment was developed to be installed in drinking water treatment system with a capacity of 12,000 m 3 /day in the Xiang’an Water Plant, Xiamen, China, and the comparison of OH and NaClO on GSM degradation in the process of algae colonies inactivation were studied. The results showed that with OH inactivation at 1.0 mg/L within 20 s algae colonies were scattered to individual algae that still had intact shape, while with the NaClO inactivation at 2 h algae still mainly existed as colonies form but were deformed and ruptured due to extensive damage of cell membrane. After the coagulation sedimentation with injection of OH at 1.0 mg/L and the sand filtration at 0.5 mg/L, the GSM were both degraded to below 10 ng/L (Chinese standard limit) within only 20 s, while the NaClO degraded GSM slightly until 2 h later. Based on the intermediates analyses with mass spectra database, pathways of GSM degradation by OH or NaClO were obtained. With OH disinfection at 0.5 mg/L, all water quality and disinfection by-product indexes satisfied the limits of Chinese Standards. Therefore, the OH method based on the strong ionization discharge showed great prospect for large-scale industrial application in inactivation of algae colonies meanwhile degradation of odorous material GSM.